全 文 ：Received 1 Jul. 2003 Accepted 17 Nov. 2003
Supported by the China Ministry of Science and Technology (G1999043507), the National Natural Science Foundation of China (90102009,
30270263, 30370251) and the Knowledge Innovation Program of The Chinese Academy of Sciences (KZCX1-10-05).
* Author for correspondence. Tel: +86 (0)10 62591431 ext. 6273; Email: .
http://www.chineseplantscience.com
Acta Botanica Sinica
植 物 学 报 2004, 46 (4): 379-391
Northeast China Transect (NECT):
Ten-Year Synthesis and Future Challenges
NI Jian1, 2*, WANG Guo-Hong 1
(1. Laboratory of Quantitative Vegetation Ecology, Institute of Botany, The Chinese Academy of Sciences, Beijing 100093, China;
2. Max Planck Institute for Biogeochemistry, Jena 07701, Germany)
Abstract : Northeast China Transect (NECT), one of the fifteen International Biosphere-Geosphere
Programme (IGBP) terrestrial transects, has been established for 10 years by Prof. Zhang Xin-Shi, through
a core project of the IGBP — the Global Change and Terrestrial Ecosystems (GCTE). This transect is
located in the mid-latitude semi-arid region, ranging 42-46°N latitude and 110-132°E longitude. The
primary driving force for global change is precipitation and the secondary one is land use intensity.
Research progresses have been performed during the past decade in the following aspects: ecological
database development, climate and its variability, ecophysiological response of plants to environments,
vegetation and landscape changes, biodiversity patterns and their changes, plant functional types and traits
with relation to climatic gradient, productivity and carbon dynamics, pollen-vegetation relationship, trace
gas emissions, land use and land cover changes, as well as biogeographical and biogeochemical modelling. In
order to achieve the higher level of integrated research, the NECT needs the consistent basic data sets
within the same framework, fu rther field exper iments and observations, integrated simulat ions of
vegetation structure, process and function from patch, landscape to biome scales, intercomparisons of
results and simulations within the transect and to other IGBP transects, mu ltidisciplinary research,
national and international co-ordinates, and full scientific plan and implementation strategy.
Key words: biodiversity; carbon cycle; climate change; CO2; land use change; vegetation modeling;
precipitation gradient; plant functional types; vegetation pattern and dynamics
Trans ect stud ies for many decades have played very
important roles in the context of ecological researches. This
approach was adopted recen tly for large-s cale global
change studies, and the so-called “Terrestrial Transect” is
proved to be a valuab le too l (Koch et al., 1995; Steffen,
1995; Steffen et al., 1999; Canadell et al., 2002). In the glo-
bal change context, trans ect studies: (1) facilitate the im-
portant scale t ransition from local process study through
landscape effects to reg ional and global understand ing;
(2) promote interdisciplinary research through sharing of
sites and resources; (3) provide ideal “ground-truth” test
beds for both remotely sensed data and global models; (4)
facilitate application of global change research to more im-
mediate resource management problems; and (5) promote
efficien t use of s care research resources (Steffen et al.,
1999).
The International Biosphere-Geosphere Programme
(IGBP) Terrestrial Transect approach aims at clarifying the
spatial variability of ecosystem processes and their inte-
gration at larger scales, addres sing the effects of global
change on ecosystems from regional to global scales, which
are the major issues in one of the IGBP core p rogrammes:
Global Change and Terrestrial Ecosystems (GCTE). The
transects were initially suggested along major gradients of
temperature, precipitation and land use change which rep-
res ent the major climat ic regions of the world and allow
repeated observations at the same time (Koch et al., 1995;
see also the Chinese Translation: Ni and Zhang, 1996). So
far there are 15 IGBP Terrestrial Transects (Canadell et al.,
2002) located in the boreal regions (East and West Siberia,
Europe, Canada, Alas ka), the temperate reg ions (China,
USA, Argent ina), the semi-arid tropics (Australia, South
Africa, West Africa) and the humid t ropics (SE Asia,
Miombo, Amazon). China has two transects which have
been accepted by the GCTE. The first transect is the North-
east China Transect (NECT) which was established in 1993
by Prof. Zhang Xin-Shi (GCTE, 1994), and another one is
the North-South Transect of Eastern China (NSTEC) which
was established in 1999 (Peng and Ren, 2000).
The NECT represents a mid-latitude semi-arid gradient
(Koch et al., 1995; Zhang et al., 1997a; Steffen et al., 1999;
Ni and Zhang, 2000). The t ransect , ranging 42-46° N
.Review.
Acta Botanica Sinica 植物学报 Vol.46 No.4 2004380
latitude and 110-132° E longitude, extends from temperate
conifer-broadleaf mixed forests in the east through meadow
steppes and agricultural lands in the middle to steppes and
desert grasslands in the west (Zhang et al., 1997a; Steffen
et al., 1999; Ni and Zhang, 2000). The transect demonstrates
a large precipitation/moisture gradient, with rainfall rang-
ing from 600 to 1 000 mm at the east end, from 300 to 600 mm
in the middle and from 100 to 300 mm at the west end. Sec-
ondary driving gradient is land use intensity from forestry
in the east, agriculture in the middle to pastoral in the west
(Ni and Zhang, 2000).
There are three long-term ecological research stations
on the NECT (Zhang et al., 1997a), i.e., the Changbai Moun-
tain Forest Ecosystem Research Station in the forest area
of eastern transect, the Nei Mongol Grassland Ecosystem
Research Station in the steppe area of western trans ect,
and the Changling Grassland Ecosystem Research Station
in the meadow part of the middle transect. Multidisciplinary
and long-term researches have been carried out in this re-
gion for more than 20 years. More research interests among
eco logis ts were re-activated since 1993 when the NECT
was identified as an IGBP Terrestrial Transect by the GCTE
(1994). Since then, both experimental and theoretical works
have been intensively conducted on the NECT by scien-
tists from both domestic and international communities.
In total five field surveys were conducted during the
last decade along the NECT. The first two were conducted
in 1994 and 1997, respectively (led by Prof. Zhang Xin-Shi,
Inst itute of Botany, The Chinese Academy of Sciences).
The third was carried out in 1998, extending from the grass-
land part of the transect to southeastern Mongolia (led by
Dr. Dennis Ojima, Natural Resource Eco logy Laboratory,
Colorado State University). Two recent field surveys were
conducted in 1999 and 2001 respectively throughout the
whole transect (led by Prof. Zhou Guang-Sheng, Institute
of Botany, The Chinese Academy of Sciences). On the other
hand, site-based field experiments were also conducted in
different area with different ecosystem properties along the
NECT, focusing on ecosystem structure and functioning,
pho tos ynthes is p roperty o f dominan t s pecies , s oil
respiration, and gas emission and exchange.
Based on the long-term ecological studies, field surveys,
statistic analyses and model simulations, most of the works
are available in recent publications covering several as-
pects of the IGBP researches, e .g., GCTE (e.g ., Li, 1995;
Zhou and Zhang, 1995; Zhang et al., 1997a; 1997b; 1998;
Jiang et al., 1999; Ni et a l., 1999; Tang, 1999; Tang and
Zhang, 1999a; 1999b; Tang et al., 1999; Yue et al., 1999;
Chen et al., 2000; 2003a; 2003b; Jiang and Dong, 2000; Li,
2000; Ni and Zhang, 2000; Su et al., 2000; Wang et al., 2000;
Wang and Zhou, 2000a; 2000b; 2001; Chen, 2001; Zhou et
al., 2001a; 2001b; Song et al., 2002; Wang, 2002; Wang et
al., 2002; Zhou, 2002; Zhou et al., 2002c; Ni, 2003; Wang
and Gao, 2003; Wang et al., 2003), PAGES— Past Global
Changes (e.g., Li et al., 2000a; 2000b), IGAC— In terna-
tional Global Atmospheric Chemistry (e.g., Chen et al., 1999;
Cui et al., 2000; Dong et al., 2000; 2001), LUCC— Land
Use and Land Cover Change (e.g., Kang et al., 2000; Tang,
2000; Yang et al., 2001; Zhou et al., 2002a) and GAIM—
Global Analysis, Integration and Modelling (e.g., Gao and
Zhang, 1997; Gao and Yu, 1998; Tang et al., 1998; Chen and
Wang, 2000; Gao et al., 2000; Ni, 2000; Chen and Li, 2003).
A synthesis book (Zhou, 2002) and a review paper (Zhou et
al., 2002b) were recently published, in order to improve the
unders tanding o f how climate change, especially the
ariditification and land use practices impact on the grass-
land ecosystems on the NECT.
In this paper, we seek to summarize the major advances
over the last decade in describing the response of ecosys-
tems to global change along the NECT, to move beyond
the details of specific scientific research, and to define the
major challenges in the future.
1 Research Progress and Assessment
Stud ies on the NECT mainly aimed at elucidating the
relationsh ips among env ironments, ecosystems and hu-
man beings, and one central theme is: how does water avail-
ability influence the composition of plant functional types,
soil organic matter, net primary productivity, trace gas flux
and land-use distribution (Koch et al., 1995)? Studies on
this issue can be sorted into s everal procedures encom-
pass ing ecological database development, analyses and
s yn thes is o f field measurements , and eco log ical
simulations.
1.1 Databases
Several kinds of ecological databases have been devel-
oped based on studies from both long-term ecological re-
search sites and investigations along the whole NECT
(Zhou et al., 2001b). These are bas ic and important scien-
tific resources in the transect studies.
·Trace gas flux (daily CO2, CH4 and N2O flux, seasonal
and inter-annual CO2 flux)
·Seasonal soil respiration flux
·Plant leaf physiology (photosynthesis and respiration)
·Doubled CO2 experiments (dominant tree species in
the Changbai Mountain)
·Temperature and precipitation sensitivity experiments
·Multi-year and mult i-biome biomass and net primary
NI Jian et al.: Northeast China Transect (NECT): Ten-Year Synthesis and Future Challenges 381
productivity (NPP) measurements (grassland, forest, crop)
and NPP derived from the national forest and g rassland
inventories
·Digitized vegetation map (1:1 million scale)
·Pollen records (160 surface samples and 29 profiles)
·Digitized soil texture map (1:1 million scale)
·Soil organic carbon measurements
·Historical climate records (temperature, precipitation,
cloudiness , evaporation, wind velocity) and microclimate
gradient observations
·Land use/land cover change investigations
·Remote sensing data (the Normalized Difference Veg-
etation Index, NDVI)
Among these databases, their spatial scales are quite
diverse. Some of them are site-based data, while others are
whole t ransect-based data. In addition , databas es were
elaborated also based on different temporal scales, i.e., short-
term measurements and long-term measurements. These
temporal-spatial d ifferences of data were mainly derived
from the differences either in research history, research tar-
get and aim or in fund limitation in the past two decades.
Since 1997 when the first synthesis paper was pub lished
(Zhang et al ., 1997a), s uch kind of differences were
weakened, but we still need to stretch the temporal scale as
long as possible and to extend the spatial scale as wide as
possible for getting more comprehensive databases.
1.2 Climate characteristics and climate variability
Along the NECT, temperature does not show any no-
ticeable trend due to its small latitude span (2°). In contrast,
precipitation along this transect demonstrates a steep gra-
dient due to its huge longitude span of 24° (Zhang et al.,
1997a). As a result , precipitation was s upposed to be a
major global change d riving force along the NECT. And
further, an explicit precipitation gradient was identified, i.e.,
ranging from 600-1 000 mm in the east, 300-600 mm in the
middle, and 100-300 mm in the west (Zhang et al., 1997a;
Ni and Zhang, 2000). In fact, mos t previous studies con-
ducted on the NECT frequently take the precipitation gra-
dien t as a surrogate o f the ultimate env ironment driving
force to interpret the underlying mechanisms of ecosystem
responding to global change. On the other hand, the sub-
stantial inter-annual fluctuations and inner-annual changes
of precipitation is also one of the most notable features of
the NECT. Temporal climatic patterns, and the inter-annual
and inner-annual variability are also high and this temporal
variability is the highest in the driest and coldest portions
of the NECT (Ni and Zhang, 2000).
As a major driving factor, precipitation is therefore fre-
quently used in the context of ecological gradient analysis
on the NECT in the previous studies (Zhang et al., 1997a;
Ni and Zhang, 2000). Nonetheless, further climatic data is
needed, such as long-term daily and monthly rainfall, snow
cover, and evaporation, etc., to dig more detailed pattern of
precip itation grad ient as well as aridity index or humidity
index. Furthermore, different soil types or location with re-
spect to the water table may also have significant effects,
thus, such kind of datasets is obv iously critical to con-
struct a robust model o f environmental grad ient on the
NECT.
1.3 Ecophysiological response of plants to environments
In s ites o f gras s land reg ion , res pons es o f leaf
photosynthesis , stomatal conductance and respiration to
environmental factors (Wang and Zhou, 2000a; 2000b; 2001),
and responses of plant d13C value and water use efficiency
to environmental gradien t (Su et a l., 2000) have been
investigated. Response of tree eco-physiology to CO2 e l-
evation has been studied by field experiments (Wang et al.,
2000) and poten tial response of forest dynamic to climate
change has been simulated by forest gap model (Chen and
Wang, 2000) in sites of forest region.
It is worthy noting the implications of s uch kinds of
studies are very limited in the transect study due mainly to
the limited temporal-spatial scales. For example, most of
them were conducted at only a few experimental sites in
either grassland or forest regions. Long-term observations
on plant ecophysiological responses in typical ecosystem
to changing env ironments as well as the spatial trends
(patterns) of ecophysiological characteristics on the whole
NECT are therefore needed in the future. On the other hand,
we need to dis tinguish what are the major ecophysiologi-
cal factors that may take key roles in the context of plant
responses to environmental stress.
1.4 Vegetation patterns
Vegetation pattern and dynamics are central iss ues in
the studies conducted on the NECT during the last decade.
Zhang et al. (1997a; 1997b; 1998), Ni et al. (1999), Ni and
Zhang (2000) and Chen et al. (2000; 2003b) described the
general characteristics of vegetat ion patterns in terms of
vegetation distribution, floristic composition and plant func-
tional types (PFTs ) as well as the correlations with major
environmental factors, such as topography, so il, climate
and land use. However, the vegetation dynamics and
changes of landscape patterns have not been considered
(Zhang et al., 1997a; Ni et al., 1999). Although Chen et al.
(2000; 2003b) analyzed the changes of geographical
distribution, frequency and dominance pattern and the spa-
tial correlation of 16 tree species at landscape scale along
the forest part of the NECT between 1986 and 1994, under
Acta Botanica Sinica 植物学报 Vol.46 No.4 2004382
the predictable global change scenario, issues such as at
what extent the major vegetation types on the NECT would
be rep laced as well as what is the underlying mechanism
causing these s hifts , are still remaining uncertain. More
explicit studies coupling with vegetation dynamics, human
activity and environmental gradient are obviously urgently
needed. In such studies, data from remote sensing and from
long-term vegetation survey would be very useful. Simula-
tion from ecological model such as regional vegetat ion
dynamic model would als o be a very useful approach in
vegetation dynamic studies on the NECT (see below 1.11).
1.5 Biodiversity
The relat ionship between b iodiversity and ecosystem
functioning has emerged as central issue in ecological and
environmental sciences during the last decade (Loreau et
al., 2001). Due to the steep precipitation gradient, diverse
vegetation types and rich species diversity, the NECT is
obviously a suitable platform to test hypothesis related to
biodivers ity pat terns associated with the p recipitation
gradient. Biodiversity studies conducted on the NECT can
be sorted into several types belonging to different aspects
in the con text o f biodiversity theory. First, most studies
focus ed on the spatial pattern of species d iversity along
the NECT. In this context, the correlations between species
richness and the major environmental gradients were posed
as major issues. For example, based on the field measure-
ments on vegetation composition and major environmental
elements obtained from the 1997 field survey, statistic and
theoretic analys es on species divers ity pattern were
performed, and the result showed that on the NECT plant
diversity decreased from forest to meadow, steppe and
desert (Tang and Zhang, 1999b; Yue et al., 1999; Li, 2000).
On the other hand, the complexity and diversity of typical
plant communities along the NECT is higher in the lightly
grazed grassland than that in the heavily grazed grassland
(Li, 2000). Plan t life form diversity was relatively higher in
the eastern fo rests and the ecotone between typical
vegetations, while lower in the meadow grasslands and
typical steppes (Wang et al., 2002).
The second issue was whether or not the observed di-
versity pattern influenced by different plant regenerative
strategy. According to Song et al. (2002), phalanx clonal
plants were more abundant in communities of the western
portion of NECT where the altitude was h igher and both
the soil nitrogen contents and precipitation were relatively
lower. Whereas guerilla clonal plants were more abundant
in the midd le of the NECT where the precipitation, mean
annual temperature and photosynthet ically active radia-
t ion were relat ively h igher. In the more p roductive
temperate typical steppe, plant species diversity was cor-
related negatively with the importance of phalanx clonal
plants and positively with the importance of guerilla clonal
plants. In more unproductive temperate desert steppe, plant
species diversity was positively correlated with the impor-
tance of both phalanx and guerilla clonal plants (Song et
al., 2002).
Relationship between diversity and productivity was
the third major issue in the biodiversity studies of NECT.
To elucidate the correlations among resource productivity,
species richness, plant trait richness and aboveground net
primary productivity (ANPP) at regional scale as well as
how the observed species richness-p roductivity pat tern
varied with scale, a field experiment in herb dominated com-
munities on the NECT was designed (Wang and Ni, unpub-
lished data). Results indicated that at the whole NECT scale,
species richness increases with increased precipitation and
ANPP, and meanwhile precipitation poses a major influence
on the pattern of species richness. At smaller scale, species
richness increases with increased precipitation, while spe-
cies richness and ANPP demonstrated a unimodal pattern.
Temporal s cale variation o f species divers ity on the
NECT was also an important issue. As reported by Chen
(2001), the relat ive abundance o f d ifferent tree s pecies
changed differently between 1986 and 1994 based on analy-
sis from 287 plots. From 1986 to 1994, tree d iversity in the
areas with high and medium tree diversity decreased, while
in the areas of low tree diversity it increas ed. Chen (2001)
suggested that the change of relative abundance of the
moisture-sensitive tree species, such as Quercus mongolica
and Larix olgensis, could be used as a surrogate to detect
climate change in this region.
Furthermore, fores t management-related and climatic
change-related s imulat ions of t ree divers ity in mixed
broadleaved Korean pine forest in Northeast China (Chen
and Li, 2003; Chen et al ., 2003a) ind icated that t ree
biodiversity would change (increase or decrease) in future
50-100 years, and these changes are closely related to the
introduction and removal of different tree species.
It s hould be noted that, of all the s tudies concerning
diversity patterns on the NECT mentioned above, impacts
of the interactions among biotic or abiotic factors on diver-
sity pattern have not been explicitly interpreted. To answer
questions such as what is a general pattern between spe-
cies richness and ANPP at regional scales, some more spe-
cific manipulated experiments with controlled conditions in
terms of both species richness and resource productivity
(such as a manipulated precipitation gradient) are there-
fore needed. This kind of gradient study would inevitably
NI Jian et al.: Northeast China Transect (NECT): Ten-Year Synthesis and Future Challenges 383
contribute more to the current biodiversity theories. On the
other hand, NECT is located in the highly human-disturbed
regions, hence any biod iversity s tudies should link with
disturbance regimes such as land use / land cover changes
(grassland grazing, forest harvest, conversion of grassland
to farmland etc.) in space and in time.
1.6 Plant Functional Types (PFTs) and traits
The concept of PFTs has received new attention as one
possible framework for predicting ecosystem response to
human—induced global changes (Smith et al., 1996; Diaz
and Cab ido, 1997; Craine et al., 2001). Studies on PFTs
along the NECT so far mainly focused on the identification
of specific PFTs as well as the correlations between PFTs
and the environmental gradient (Jiang et al., 1999; Tang,
1999; Tang and Zhang, 1999; Tang et al., 1999; Jiang and
Dong, 2000; Wang, 2002; Ni, 2003).
Tang et al. (1999), Tang and Zhang (1999) and Wang
(2002) studied the spatial pattern of plants with different
photosynthetic pathway (C3 and C4) and its relationship
with the major environmental grad ient. Res ults indicated
that from east to west along the NECT, the ratio of C4 vs. C3
plants showed two low and two high trends and their dis-
tribution was mainly influenced by annual mean tempera-
ture and precipitation (Tang et al., 1999; Tang and Zhang,
1999). The number of C4 s pecies in Songnen meadow
(western part of NECT) was 70%-80 % greater than that in
Xilingol steppe (middle part of NECT) and Hunshandak
desert grassland (west end of NECT) and the distribution
of C4 species is also related to precipitation, but that for C3
species did not differ significantly among the three grass-
land types (Wang, 2002).
In order to disclose the underlying mechanism with re-
spect to the response of plant to the environmental gradi-
ent along the NECT, Jiang et al. (1999) and Jiang and Dong
(2000) conducted a field obs ervation focused on the mea-
surement o f some physiolog ical p ropert ies of p lants
(grouped into PFTs) as well as the correlation to major en-
v ironmental g radient . A dataset encompas s ing net
photosynthesis, trans piration, stomatal conductance, in-
ternal CO2 concentration and water use efficiency o f 215
plant species along the NECT was elaborated (Jiang et al.,
1999; Jiang and Dong, 2000). Eight PFTs (forest g ras s,
meadow steppe grass, typical steppe grass, des ert grass,
forest s hrub, steppe s hrub, desert s hrub, and forest tree)
were identified based on their life forms (Jiang et al., 1999)
and two PFTs (clonal and non-clonal) based on reproduc-
tive features (Jiang and Dong, 2000). Results from these
studies indicated that net photosynthesis and water use
efficiency appeared to be lower in the east and west ends
of NECT, with peaks in the middle. Transpiration was found
to be higher in the west end where most temperate desert
plants were the dominant species. The meadow steppe and
typical steppe grasses showed higher values of physiologi-
cal variables than that of the forest or the desert species.
Most clonal species have higher values of net photosyn-
thesis and physiological variables than non-clonal species,
suggesting that clonal species might have advantages over
non-clonal species in utilizing environmental resources such
as light, CO2, and especially water.
Using data from three field surveys along the grassland
part of the NECT and its extension to SE Mongolia, the
geograph ic pat terns o f s ix broad PFTs: C3 s pecies, C4
species, grass es, shrubs, forbs and succulents and their
relationships with climate were analyzed (Ni, 2003). Differ-
ent PFTs from different regions and in grassland types dem-
onstrated different spatial patterns. Species richness in each
PFT als o has d ifferen t relations h ips with climate
(significantly or not). Generally, the richness of C3 species,
C4 species, grasses and forbs has positive relationships,
shrubs have negative relationship and succulents have no
relationship with precipitation and aridity. Shrubs, grasses
and forbs have stronger relationships with precipitation
than C3 and C4 species do. The relationships between C3
species, forbs and aridity are more s ignificant than with
precip itation. On a regional basis, the combined effect of
precip itation and temperature, the aridity , is more signifi-
cant ly correlated with the distribution o f C3 species and
forbs, which are more dominant in the study area, than with
C4 species, grasses and succulents.
The role of different plant traits or trait combination in
the context of vegetation response to the environmental
gradient on the NECT was also distinguis hed (Wang and
Ni, unpublished data). They stated that plant functional
classification do have phylogenic implications, while plant
traits may be also differentiated from each other with re-
spect to their evolutionary background. Plant trait s such
as vegetat ive, phenology and plant photosynthetic traits
were strong ly cons trained by the precipitation gradient,
while most regenerative traits and sys temat ic trait s eem
less affected by the same environmental gradients, and they
might be associated with some more profound factors, es-
pecially those during the process of plant phylogeny.
The gradients in PFTs can help us to understand how
plants will respond to environments and further global cli-
mate changes. PFTs can also help us to shorten the com-
plex behavior of plant species in modeling vegetation struc-
ture and dynamics at large spatial scale. From these points
of view, NECT precipitation gradient analysis of PFTs (both
Acta Botanica Sinica 植物学报 Vol.46 No.4 2004384
broad and narrow classificat ions) is of importance. How-
ever the recogn ition of PFTs cannot require that environ-
mental res pons es o f all taxa be determined by direct
experiment. Much research on PFTs has therefore focused
on the identificat ion o f “traits” (here emphasizing plant
characteristics that can be observed directly, or by simple
measurements or assays) that can be shown to be reliably
associated with plant responses to environment. PFTs study
was prosperous on the NECT, bu t trait s s tudy is just
starting. Therefore NECT needs more measurements of traits
and more analyses o f relations hips between plant traits
and environmental factors such as climate and land use.
1.7 Productivity and carbon dynamics
Spatial and temporal patterns of p roductivity and car-
bon are important issue for global change study on the
NECT. Biomass measurements and productivity estimations
have been invest igated fo r a long time at s ome s pecific
sites on the NECT such as the grassland research station
of Xilingo l and the fo rest research s tation o f Changbai
Mountains, but carbon dynamics of any vegetation types
have not reported in the early NECT s tudies. Moreover,
due to the difficulties to measure b iomass (especially the
fine root biomass) and CO2 flux in the field, studies linking
productivity and carbon dynamics to climate change on
the whole transect were scarce in the past decade. Recently,
a field experiment was conducted to examine the effects of
large-scale climatic changes on biomass and biomass allo-
cation (Wang et al. 2003), especially the shoot density and
shoot biomass (Wang and Gao, 2003) in Leymus chinensis.
Results suggested that the total biomass, vegetative shoot
biomas s and reproductive shoot biomass of the plant in-
creased from the west to the east with the decrease of arid-
ity or the increase of precipitation, but that of rhizome bio-
mass decreased in sites ranging from 116-120° E. Vegeta-
tive shoot biomass allocation increased from the west to
the east along the gradient; rhizome allocations, however,
dropped significantly. Unlike those of rhizome and vegeta-
tive shoot, reproductive shoot biomass allocations at the
two ends were remarkably lower than that in the middle of
the gradient. In general, the total and component biomass
and their allocations showed strong correlation with pre-
cip itation or aridity index along the grad ient (Wang and
Gao, 2003; Wang et al., 2003).
Based on the field measurements of CO2 flux in the Stipa
grandis steppe (400 m ´ 400 m plo t), Zhou et al. (2001a)
reported that the annual carbon flow is 45.1 ton carbon (C)
for plant photosynthesis, 18 ton for plant respiration, 10.1
ton for litter, and 14.1 ton for soil and litter respiration. The
C sto rage is 24.9 ton in the atmosphere, 45.8 ton in plant
biomass and 820.4 ton in soil organic matter. The C budget
is 13 ton C Per year fo r th is s teppe, indicating that this
vegetation is a C sink. However, the soil C budget is –4 ton
C Per year, indicating a soil carbon source. A further calcu-
lation of carbon balance in different vegetation types, land-
use practices and temporal scales was given more recently
on NECT (Zhou et al., 2002c). Results indicated that mean
annual C budget is the largest for the mixed coniferous-
broadleaved forest ecosystem (503.2 g C.m-2.a-1), followed
by the meadow steppe ecosystem (227.1 g C.m-2.a-1), and
the lowest being the typical steppe ecosystem (175.8 g C.
m-2.a-1).
Net primary productivity (NPP) and C are two key vari-
ables in our understanding on ecosystem functioning and
their responses to global climate change. NECT is a good
platform for s tudying regional NPP spatial pattern and C
dynamics. Further funding is needed to support more ex-
tensive biomass and CO2 concentration field measurements,
in order to evaluate how water availability influence on
NPP and C at these regional and gradient scales. Meanwhile,
biogeochemical model could play a very important role in
NPP and C studies on NECT (see below 1.11).
1.8 Pollen-vegetation relationship
The relationship between surface po llen and vegeta-
tion would contribute to the reconstruction of past vegeta-
tion by us ing pollen records dated s uch as to the mid-
Holocene (6 000 14C years ago) and last glacial maximum
(18 000 14C years ago). Based on regression and correlation
analyses of surface pollen samples with modern vegeta-
tion composition along the NECT, Li et al. (2000a; 2000b)
suggested that there is a close relationship between veg-
etation and s urface pollen taxa (Pinus, Betu la, Quercus,
Tilia, Acer, Ulmus, Artemisia, Chenopodiaceae, Gramineae
and Cyperaceae) and the similarity between pollen assem-
b lage and plan t community was more than 50%.
Unfortunately, this is not a representative research topic in
the NECT study . However, if linking surface pollen —
modern vegetation relationship to precipitation grad ient
and land use change, it would be a n ice resu lt to be
expected.
1.9 Trace gas emission
Based on the measurement of the CO2-release rate of
soil respiration and litter decomposition in S. grandis steppe,
Chen et al. (1999) and Cui et al. (2000) analyzed the sea-
sonal dynamic pattern of soil respiration and litter decom-
position and their relations to the aboveground biomass,
belowground biomass and environmental factors. The sea-
sonal dynamic pattern fit nearly a trapezoidal curve and the
highest CO2-release rate appearing in the late August. The
NI Jian et al.: Northeast China Transect (NECT): Ten-Year Synthesis and Future Challenges 385
seasonal dynamic pattern of CO2-release rate was gener-
ally consistent with that of the aboveground biomass, es-
pecially with the green aboveground biomass, but was not
consistent with or even contrary to that of the belowground
biomass . The litter layer on the soil surface cou ld s low
down the emission of CO2 from soil to atmosphere. The soil
moisture was highly correlated with the CO2-release rate.
Using a dark enclosed chamber technique, the fluxes of
CO2, N2O and CH4 from natu ral and disturbed grasslands
were also meas ured in the grassland section of the NECT
(Dong et al., 2000; 2001). Results showed that the dynam-
ics of the fluxes of CO2, N2O and CH4 were strongly influ-
enced by the annual rainfall gradient. In addition, human
activities, such as grazing and reclamation are also critical
factors affecting the fluxes of these gases from grassland.
The measured annual mean emission of N2O from different
gras slands with different treatment of fertilizer enhance-
ment (chemical N fertilizer and chemical N fertilizer com-
bined with organic manure) were 52.8 and 61.4 mug N2O.
m-2.h-1, respect ively. A relatively low annual mean emis-
sion of 2.2 mug N2 O.m-2.h-1 was measured in soils that
had not been fertilized for 12 years. The results indicated
that o rganic manure also had a significant effect on N2 O
emissions, combined with the effects of chemical N fertilizer;
N2O emissions would increase 20% per year.
Due mainly to the fund limitation, such kinds of trace
gas studies were mostly conducted in small plots with rela-
tive short times. Broader spatial scale and longer temporal
series trace gases meas urements are therefo re further
needed, with relations to topography , climate, soils, veg-
etation types and land use regimes on the NECT.
1.10 Land use change as well as their impacts on ecosys-
tem
Kang et al. (2000) reported that great changes have taken
place with respect to the land use pattern on the NECT
during 1984 to 1996, and furthermore, these changes are at
large extent induced by human activities. On the other hand,
changes of land use pattern would pose profound impacts
on ecosystem. Yang et al. (2001) reported that in grassland,
different grazing disturbance would lead to different plant
diversity pattern. In detail, plant diversity (Shannon index)
was higher in the moderate/heavy-grazing stages and lower
in light-grazing and over-grazing. A general discussion on
the sustainable land use patterns on the NECT was also
addressed (Tang, 2000). More recently, Zhou et al. (2002a)
discussed the correlations among species richness, soil C,
soil N and aboveground biomass with land-use practices
(grassland fencing, mowing and grazing) in the west part
of NECT. The resu lts indicated that (1) the above-ground
biomass of grassland communities has a linear relationship
with precip itat ion under three land-use p ract ices , while
species richnes s, soil C, and total soil N have linear rela-
tionships with precip itation under fencing and mowing;
under grazing the relationships are non-linear; (2) species
richness, soil C and total soil N have strong linear relation-
ships with above-ground biomass under both fencing and
mowing, while they seem to have non-linear relationships
under grazing; (3) land-use p ractices along the precipita-
tion gradient result not only in changes in grassland com-
munities but also in qualitative changes of their structure
and function; (4) grasslands are more vulnerable to changes
in climate under mowing than under fencing, and are more
capable to store C in so il and plants ; and (5) at a given
precipitation level, number of plant species, above-ground
biomass, and soil C are higher under low to medium inten-
sity of human activities (mowing and grazing).
Land use intensity is the second driving factor of global
change on the NECT. However, studies on land use/land
cover change on the NECT during the past decade are rela-
tively poor due to the lack of an integrated research plan. In
order to get a better unders tanding with respect to how
different intensities of human activities will affect the struc-
tures and functions of ecosystems on the NECT, we need
further researches on both the dynamics of land use pat-
terns and their mechan isms , as well as the correlations
among ecosystem functioning and major driving forces of
environmental change and human activities. In addit ion,
coupling political, economical and social concerns with land
use changes may be one of the critical steps to exam the
potential influences of land use on ecosystem functioning.
1.11 Biogeographical and biogeochemical simulations
Ecological modeling is a good approach for understand-
ing ecosystem patterns, processes and dynamics from leaf
to biome levels, specifically at the regional to global scales.
During the pas t two decades, the large-scaled vegetation
models have been developed from the biogeography and
biogeochemistry models to the coupled biogeography and
biogeochemistry models, as well as the Dynamic Global
Vegetation Models (DGVMs). The NECT is a good testing
bed for these kinds of global models, to simulate and pre-
dict biogeographical patterns and b iogeochemical pro-
cesses on the water gradient.
The first model predicting vegetation pattern along the
NECT was developed at the early stage o f the transect
study (Li, 1995). According to a decision rule system of
vegetation classificat ion established by statistical analy-
sis of environment-vegetation relationships, elevation and
quaternary geology were applied as indices of topography
Acta Botanica Sinica 植物学报 Vol.46 No.4 2004386
and parent materials, along with climatic index of moisture,
to classify vegetation and then predicted the response of
vegetation in the NECT to climate change (Li, 1995). The
model is statistical and the results are coarse, but this is the
first attempt to model the NECT vegetation. A general bio-
geochemical model that is also a statistic model was devel-
oped at the same stage (Zhou and Zhang, 1995). This model
was applied to simulate the NPP patterns along this transect.
Based on the Holdridge Life Zone Classification, b iomes
along the NECT were classified and their responses to a
simple temperature and precipitation scenarios were also
predicted (Tang et al., 1998).
Using a coupled biogeographical and biogeochemical
vegetation model BIOME3, Ni (2000) modeled the potential
vegetation, annual NPP and leaf area index (LAI) under the
present climate along the NECT. The simulated vegetation
was basically in good agreement with potential vegetation
map based on a numerical comparison. Predicted NPP and
LAI increase g radually from western desert and steppe,
midd le grass land to eastern forests along the increasing
precipitation g radient. The effects of climate change and
CO2 enrichment on vegetation were derived from a coupled
ocean-atmosphere general circulat ion model– HadCM2.
The climate change and CO2 increase produced a general
pole-ward shift of all forest biomes, westward shift o f all
grassland biomes and disappearance of desert, as well as
reduction/increase of vegetation areas. The changes led to
increase or decreas e of NPP and LAI under changed cli-
mate and doubled CO2 along the NECT.
However, above studies were performed at the ecosys-
tem/biome level. A landscape level study together with the
ecological simulation is also needed on the NECT. Gao and
Zhang (1997) established a remote sensing-derived model
to simulate the spatiotemporal variations of vegetation bio-
mass in the NECT. The s imulation showed that with the
present climate conditions, doubling atmospheric CO2 con-
centration led approximately to a 20.3% increase in green
biomass, 11.0% increase in non-green biomass, 19.0% in-
crease in green NPP, 12.8% increase in non-green NPP, and
24.9% increase in overall average NPP at s teady state. A
dynamic regional vegetation model was also developed to
addres s problems of responses of regional vegetat ion to
elevated ambient CO2 and climatic change (Gao and Yu,
1998). The model takes into consideration both local eco-
system processes within a patch or grid cell and mass and
energy flow across adjacen t grid cells. The resu lts indi-
cated that with doubled CO2 concentration, a 20% increase
in precipitation and a 4 °C increase in temperature, the model
predicted that NPP of Larix forests, conifer-broadleaf mixed
forests, Leymus chinensis steppes, S. grandis steppes, and
wetland and salty meadows would decrease by 15% to 20%.
However, NPP of deciduous b roadleaf forests, woodland
and shrubs, Stipa baicalensis meadow steppes, and desert
grasslands would increase by 20% to 115%, as predicted
by the model for the same climatic scenario. The average
NPP of natural vegetation over the whole transect would
decreas e slightly, largely because of the compensat ion
between the positive effects of increased CO2 and precipi-
tation and the negative effect of increased evapotranspira-
tion induced by increased temperature. Gao et al. (2000)
analyzed the quantitative relationship between spatial veg-
etation type distribution and NPP in the NECT based on a
spatial simulation model of vegetation dynamics. The analy-
sis indicated that relative increases in NPP due to variation
of vegetation type distribution were significantly related to
two spatial pattern indices; that variation of vegetation type
distribution had significant effects on NPP for all prescribed
climatic scenarios. Specifically vegetation diversity and
spatially disperse distribution of vegetation types were in
favor of primary production and helped regional ecosys-
tems to resist degradation and to maintain primary produc-
tivity under severe climatic conditions. A more severe envi-
ronmental condition rendered regional productivity more
dependent on spatial vegetation structure.
On the other hand, a mechanistic and adapted model
MIGRATE was constructed to simulate the shift of range
for tree species of Betula costata and Juglans mandshurica
(Chen, 2002). It was found that Gaussian dispersal function
could well describe the shift of range and abundance pat-
tern of these two species at the short time scale. The events
of wind-dispersal and animal-dispersal are considered, but
the modeled results are invalid.
By using models, e.g. from statistic models to process-
based models and dynamic models, from biogeographical
models to coupled biogeograph ical and biogeochemical
models, and from climate-driven models to remote sens-
ing-driven models , the NECT vegetat ion st ructure and
functioning have been well s imulated in the past decade.
However, mechanis ms o f vegetation modeling in d iffer-
en t models and vegetat ion classification used in those
models are quite diverse. A more comprehensive and more
standard regional vegetation model is needed to simu-
late vegetation changes in terms of both st ructure and
function under curren t climate and CO2 concen tration
as well as under futu re climate and CO2 s cenarios . Hu-
man disturbances such as land us e regimes and natural
dis turbances s uch as fire regimes should be introduced to
those models.
NI Jian et al.: Northeast China Transect (NECT): Ten-Year Synthesis and Future Challenges 387
1.12 Summary of research advances
The IGBP Terrestrial Transect is a group of large-scale
env ironmental gradients (temperature, precipitation and
land use intensity) worldwide. The Northeast China Transect
is a precipitat ion g radien t in temperate semi-arid region.
Along this gradient from east forests through middle mead-
ows and agricultural fields to west steppes and deserts, its
ecological characteristics such as climate variability, eco-
physiological property of plants, vegetation composition
and p lant funct ional types, species diversity, vegetation
productivity, C dynamics , trace gas emissions, and land
cover are basically and no s urprisingly gradual changes
with the decrease of precipitation, based on results from
field meas urements , s tatis t ic analys es and model
simulations. A few exceptions only occur in some specific
areas/sites, due probably to the influence of topography
and elevations. However, there is no clear and final answer
to the general question “how does water availability influ-
ence the composit ion of plant funct ional types, s oil or-
ganic matter, net primary productivity, trace gas flux and
land-use distribu tion? ”, because most previous studies
were mainly confined within specific sites or regions. Stud-
ies across the whole transect are basically scarce, thus to
get a comprehensive answer is still a major challenge in the
future.
2 Future Challenges
The individual IGBP Terrestrial Transects are making
ra p id p ro gre s s t owa rd b eco min g fa cil it ies f o r
interdisciplinary, integrative global change research (Steffen
et al., 1999). The NECT is foraging ahead toward the aims
of IGBP Terrestrial Transects, but is raising more questions,
uncertainties and limitations. To reach its fu ll potential as
other IGBP Transects, it needs to be implemented as a co-
ordinated international set, y ielding even further insights
into global change interactions with terres trial ecosystem
functioning, composition and structure (Steffen et al., 1999).
To achieve this higher level of integration, the future NECT
study needs generally:
Consistent basic data sets The transect needs to have
a general database in sites and a Geographical Information
System (GIS) database in grid cells containing basic transect
information such as vegetation composition, biogeochemi-
cal characteristics (biomass, net primary productivity, leaf
area index, nu trien t), PFTs and trait s, so il type and
characteristics, climate (present meteorology and fu ture
scenarios, both monthly and yearly), and land use and land
cover, etc. Ideally, the NECT should use the same grid cell
size, same classifications of soil, vegetation and land-use/
cover types (or perhaps a regionally preferred classifica-
tion that can be translated into an international standard),
and common climate scenarios, as other IGBP transects. In
the last five years we build up many pieces of data in this
transect, from field, remote sensing, computer modeling and
literature, but we have not narrowed them down in a stan-
dard way.
Further experimental and observational researches
Examples include measuring ecos ystem res ponse to pre-
cipitation and its interannual and seasonal variability; litter
chemis try and decomposition; biomass (specifically root
biomass), NPP, net ecosystem production (NEP) and net
b iome product ion (NBP); C s to rage, C cycle and
constraints; C, water, and energy fluxes and their controls
between the biosphere and atmosphere; plant traits, PFTs
and their bioclimatic controls; trace gas flux; and land use
and vegetation change, etc. These measurements should
use the same methodologies, instruments and techniques as
other IGBP t rans ects. Where s uch commonality is not
possible, different measurement systems should be carefully
intercompared so that appropriate correction factors can be
applied (Steffen et al., 1999). The measurement is not only in
some specific sites, but also along the whole gradient.
Integrated model ing of vegetation structure, process
and function from patch, landscape to biome scales Ac-
cording to past and future ecological data of above topics,
the existing biogeographical, biogeochemical and dynamic
vegetation models , vegetation s tructure and function at
different scales should be simulated. These include short-
term and long-term models of ecosystem structure and func-
tion (specifically the carbon dynamics), response of veg-
etation to land use and disturbance (such as fire) both in
grassland and forest sections, and response of vegetation
to climate processes and CO2 concentrations. The scaling
changes should be tested in the NECT, specifically in the
semi-arid gras sland section. The models need to be vali-
dated by remote sensing data.
Intercomparison of results and simulations The NECT
studies should be compared with other transects in the
mid-latitude semi-arid regions, such as the North American
Mid-Latitude Transect (NAMER) and Argentina Transect,
on some general and specific topics (e.g., water and energy
exchange). The use of models developed on one transect
to simulate the same process on a companion transect, and
then comparison to measurements, is an especially power-
ful technique for building robust simulation tools (Steffen
et al., 1999).
Multidisciplinary researches The past and ongoing
NECT studies focused mostly on the ecological processes
Acta Botanica Sinica 植物学报 Vol.46 No.4 2004388
and related iss ues. However, the IGBP trans ect as an
in ter p ro ject s tudy (Ano nymous , 1996) req u ires
multidiscipline researches, not only ecology, but also geo-
graphic science and atmospheric science. Further, we must
take this transect as a part of Earth System into account.
National and international coordinates T he
multidiscipline studies need the national and international
cooperation in the NECT. In the past five years the Chinese
scientists have built up a scientific team in the base of the
Laborato ry of Quant itative Vegetat ion Ecology (LQVE),
Institute of Botany, The Chinese Academy of Sciences in
Beijing . The in ternational research groups carry ing out
collaborative research on the NECT are increasing, but the
cooperation was only in short time and informal. We need
robust and long-term coordination in the NECT with inter-
national scientists who are interested in the IGBP transect
study and who are interested in the NECT and the East and
Mid-Asia regions.
Full scientific plan and implementation strategy To
achieve the integration of the NECT, we need a five-to-ten-
year scientific plan and implementation strategy, which pre-
sents the topic issues of the future NECT studies and how
to implement the research plan. This would pose a major
challenge for those who either have studied on the NECT
for a long time or are new faces and will do some research
for the NECT.
References:
Anony mous. 1996. The interproject: a new concept for IGBP
research. Global Change Newslett, 26:6.
Canadell J G, Steffen W L, White P S. 2002. IGBP/GCTE terres-
trial transects: dynamics of terrestrial ecosystems under envi-
ronmental change. J Veg Sci, 13:298-300.
Chen S-Q, Cui X-Y, Zhou G-S, Li L-H. 1999. Study on the CO2-
release rate of soil respiration and litter decomposition in Stipa
grandis Steppe in Xilin River Basin, Inner Mongolia. Act Bot
Sin , 41:645-650. (in Chinese with English abstract)
Chen X-W, Wang F-Y. 2000. Simulation of the potential responses
of the communities of mixed coniferous and broadleaf Korean
pine to climatic change by BKPF forest gap model. Act
Phytoecol Sin , 24:327-331. (in Chinese with English abstract)
Chen X-W, Zhang X-S, Zhou G-S, Chen J-Z. 2000. Spatial char-
acterist ics and change for tree species (genera) along North-
east China Transect (NECT). Act Bot Sin, 42:1075-1081.
Chen X W, Zhou G S, Zhang X S. 2003b. Spatial characteristics
and change for tree species along the North East China Transect
(NECT). Plant Ecol, 164:65-74.
Chen X W. 2001. Change of tree diversity on Northeast China
Transect (NECT). Biodiv Conserv, 10:1087-1096.
Chen X W. 2002. Simulation of shift of range for Betula costata
Trautv. and Juglans mandshur ica Maxim. along Northeast
China Transect (NECT). Polish J Ecol, 50:397-402.
Chen X W, Li B L. 2003a. Effect of global climate change and
human disturbances on tree diversity of the forest regenerat-
ing from clear-cuts of mixed broadleaved Korean pine forest in
Northeast China. Chemosphere, 51:215-226.
Chen X W, Li B L, Lin Z S. 2003. The acceleration of succession
for the restoration of the mixed-broadleaved Korean pine for-
ests in Northeast China. Forest Ecol Manag, 177:503-514.
Craine J M, Froehle J, Tilman D G, Wedin D A, Chapin Ⅲ F S.
2001. The relationships among root and leaf traits of 76 grass-
land species and relative abundance along fertility and distur-
bance gradients. Oikos, 93:274-285.
Cui X-Y , Chen S-Q, Chen Z-Z. 2000. CO2 emission of Stipa
grandis steppe. Chin J Appl Ecol , 11:390-394. (in Chinese
with English abstract)
Diaz S, Cabido M. 1997. Plant functional types and ecosystem
function in relation to global change. J Veg Sci, 8:463-473.
Dong Y S, Scharffe D, Qi Y C, Peng G B. 2001. Nitrous oxide
emissions from cultivated soils in the North China Plain. Tellus-
B, 53:1-9.
Dong Y S, Zhang S, Qi Y C, Chen Z Z, Geng Y B. 2000. Fluxes of
CO2, N2O and CH4 from typical temperate grassland in Inner
Mongolia and its daily variation. Chin Sci Bull, 45:1590-
1594.
Gao Q, Yu M, Yang X S. 2000. A simulation analys is of t he
relationship between regional primary production and vegeta-
tion structure under climatic change scenarios . Ecol Mod,
131:33-45.
Gao Q, Yu M. 1998. A model of regional vegetation dynamics and
it s ap plication to the study of Northeast China Transect
(NECT) responses to global change. Global Biogeochem Cy,
12:329-344.
Gao Q, Zhang X S. 1997. A simulation study of responses of the
Northeast China Transect to elevated CO2 and climate change.
Ecol Appl, 7:470-483.
Global Change and Terrestrial Ecosystems (GCTE). 1994. GCTE
core research: 1993 annual report. Canberra: Global Change
and Terres trial Ecosys tems Int ernat ional Project Office
(GCTE-IPC). 135.
Jiang G-M, Dong M . 2000. A comparative study on photosyn-
thesis and water use efficiency between clonal and non-clonal
plant species along the Northeast China Transect (NECT).
Act Bot Sin , 42:855-863.
Jiang G M , Tang H P, Yu M , Dong M, Z hang X S. 1999. Re-
NI Jian et al.: Northeast China Transect (NECT): Ten-Year Synthesis and Future Challenges 389
sponse of photosynthesis of different plant functional types
to environmental changes along Northeast China Transect.
Trees, 14:72-82.
Kang M-Y, Jiang Y , Shi R-X. 2000. A preliminary analys is on
land use change in NECT during 1984-1996. Sci Geogr Sin ,
20:115-120. (in Chinese with English abstract)
Koch G W, Scholes R J, Steffen W L, Vitousek P M, Walker B H.
1995. The IGBP Terrest rial T ransects : Science P lan .
Stockholm: International Biosphere-Geosphere Programme
(IGBP). 61.
Li X. 1995. Modelling the response of vegetation in North-East
China transect to global change. J Biogeogr, 22:515-522.
Li Y-Y, Zhang X-S, Zhou G-S, Ni J . 2000b. Quant itative rela-
tionships between vegetation and several pollen taxa in sur-
face soil from North China. Chin Sci Bull, 45:761-765. (in
Chinese)
Li Y-Y , Zhang X-S, Z hou G-S . 2000a. Study of quantitat ive
relationships between vegetation and pollen in surface samples
in the eastern forest area of Northeast China Transect. Act Bot
Sin, 42:81-88. (in Chinese with English abstract)
Li Z-Q . 2000. The complexity and diversity of typical plant
communities along t he Northeast China Transect (NECT).
Act Bot Sin, 42:971-978. (in Chinese with English abstract)
Loreau M, Naeem S, Inchausti P, Bengtsson J, Grime J P, Hector
A, Hooper D U, Huston M A, Raffaelli D, Schmid B, Tilman
D, Wardle, D A. Ecology-biodivers it y and ecosys tem
functioning: current knowledge and future challenges. Science,
294:804-808.
Ni J , Li Y-Y , Zhang X-S. 1999. The scientific significance of the
Northeast China Transect (NECT) to global change study by
its ecogeographic characteristics. Act Ecol Sin , 19:622-629.
(in Chinese with English abstract)
Ni J, Zhang X-S. 1996. The IGBP Terrestrial Transects: Science
Plan (Chinese Translation). Stockholm: International Bio-
sphere-Geosphere Programme (IGBP). 59. (in Chinese)
Ni J, Zhang X S. 2000. Climate variability, ecological gradient and
the Northeast China Transect (NECT). J Arid Environ, 46:
313-325.
Ni J . 2000. Modelling veget ation distribut ion and net primary
production along a precipitation gradient, the Northeast China
Transect (NECT). Ekologia-Bratislava, 19:375-386.
Ni J. 2003. Plant functional types and climate along a precipita-
tion gradient in temp erate grasslands , Northeast China and
Southeast Mongolia. J Arid Environ, 53:501-516.
Peng S L, Ren H. 2000. The North-South T ransect of Eas tern
China (NSTEC) for global change studies. GCTE News, 16:6.
Smith T M, Shugart H H, Woodward F I. 1996. Plant Functional
Types. Cambridge: Cambridge University Press. 369.
Song M H, Dong M, J iang G M. 2002. Importance of clonal
plants and p lant species divers ity in the Northeas t China
Transect. Ecol Res, 17:705-716.
Steffen W L, Scholes R J, Valentin C, Zhang X S, Menaut J C.
1999. The IGBP terrestrial transects. Walker B H, Steffen W
L, Canadell J, Ingram J S I. The Terrestrial Biosphere and
Global Change: Imp lications for Natural and Managed
Ecosy stems. Cambridge: Cambridge Univers ity Press . 66-
87.
Steffen W L. 1995. Rapid progress in IGBP Transects. Global
Change Newslett, 24:15-16.
Su B, Han X-G, Li L-H , Huang J-H, Bai Y-F, Qu C-M. 2000.
Responses of plant d13C value and wat er use efficiency to
environmental gradient in the grassland region of the North-
east China Transect. Act Phytoecol Sin, 24:648-655. (in Chi-
nese with English abstract)
Tang H-P, Chen X-D , Zhang X-S. 1998. A preliminary study on
the biome classification and the response of biomes to global
change along Northeast China transect (NECT). Act Phytoecol
Sin, 22:428-433. (in Chinese with English abstract)
Tang H-P, Jiang G-M , Zhang X-S. 1999. Application of discrimi-
nant analysis in distinguishing plant photosynthetic types: a
case study in Northeast China Transect (NECT) area. Act Bot
Sin, 41:1132-1138. (in Chinese with English abstract)
Tang H P, Zhang X S. 1999a. A new approach to dist inguishing
phot osynthetic typ es of p lants: a case study in Northeast
China Transect (NECT) platform. Photosynthetica, 37:97-
106.
Tang H-P, Zhang X-S. 1999b. A study on the ecosystem diver-
sity gradient along NECT and its relationship with environ-
mental factors . Quat Sci , 5:499. (in Chinese with English
abstract)
Tang H P. 1999. Distribution of C4 plants along the Northeast
China Transect and its correlation to the environmental factors.
Chin Sci Bull, 44:1316-1320.
Tang H-P. 2000. On the sustainable land use patterns in North-
east China Transect. China Postdoctors, 3:35-37. (in Chi-
nese with English abstract)
Wang M, Dai L-M , Han S-J , Ji L-Z , Li Q-R . 2000. Effect of
elevated atmospheric CO2 concentration on ecophysiological
characteristics of major tree species in mixed broad-leaved and
Pinus koraiensis forest, the Changbai Mountain. Chin J Appl
Ecol, 11:675-679. (in Chinese with English abstract)
Wang R Z, Gao Q. 2003. Climate-driven changes in shoot density
and shoot biomass in Leymus chinensis (Poaceae) on the North-
east China Transect (NECT). Global Ecol Biogeogr, 12:249-
Acta Botanica Sinica 植物学报 Vol.46 No.4 2004390
259.
Wang R Z, Gao Q, Chen Q S. 2003. Effects of climatic change on
biomass and biomass allocation in Leymus chinensis (Poaceae)
along the Northeast China Transect (NECT). J Arid Environ,
54:653-665.
Wang R Z, Gao Q, Tang H P. 2002. Variations of plant life form
diversity along the Northeast China Transect and its direct
gradient analysis. J Environ Sci-China, 14:547-551.
Wang R-Z . 2002. Photosynthetic pathways and life forms in
different grassland types from North China. Photosynthetica,
40:243-250.
Wang Y-H, Zhou G-S. 2000a. Comparison of characterist ics of
Leymus chinensis on two soil types. Chin J Grasslands , 8:
1-8. (in Chinese with English abstract)
Wang Y-H, Zhou G-S. 2000b. Simulation of response of stomatal
conductance of Leymus chinensis to environmental factors.
Act Phytoecol Sin , 24:739-743. (in Chinese with English
abstract)
Wang Y-H, Zhou G-S. 2001. The analysis on ecophysiological
characteristics of leaf photosynthesis of Leymus chinensis in
Songnen grassland. Chin J Appl Ecol , 12:75-79. (in Chinese
with English abstract)
Yang L-M , Han M, Li J-D. 2001. The plant diversity change of
grassland communities along grazing disturbance gradient in
Northeast China Transect. Act Phytoecol Sin, 25:110-114. (in
Chinese with English abstract)
Yue T-X , Zhou C-H, Li Z-Q, Ni J. 1999. A theoretical analysis on
models for biological diversity. Geo-Inform Sci , 1:19-25. (in
Chinese with English abstract)
Zhang X-S, Gao Q, Yang D-A , Zhou G-S , Ni J, Wang Q, Tang H-
P. 1998. A gradient analysis and modeling of the Nort heast
China Transect (NECT) for global change study. Bull Chin
Acad Sci, 12:15-21. (in Chinese with English abstract)
Zhang X-S, Gao Q, Yang D-A, Zhou G-S, Ni J, Wang Q. 1997a. A
gradient analy sis and p redict ion on the Nort heast China
Transect (NECT) for global change study. Act Bot Sin, 39:
785-799. (in Chinese with English abstract)
Zhang X-S, Zhou G-S, Gao Q, Yang D-A, Ni J, Tang H-P. 1997b.
Northeast China Transect (NECT) for global change studies.
Earth Sci Front, 4:145-151. (in Chinese with English abstract)
Zhou G S, Wang Y H, Wang S. 2002a. Resp onses of grass land
ecosystems to precipitation and land use along the Northeast
China Transect. J Veg Sci, 13:361-368.
Zhou G S, Wang Y H, Jiang Y L, Chen X W, Yang Z Y. 2001b.
Synthesis of the IGBP-Northeast China Transect (NECT).
Zhou G S. Abstracts of the XII GCTE-SSC M eeting and
Chinese-GCTE Global Change Conference. Beijing: Institute
of Botany, The Chinese Academy of Sciences. 120-121.
Zhou G S, Wang Y H, Jiang Y L. 2001a. Carbon dynamics along
the IGBP-Northeast China Transect (NECT). Canadell J G.
Land Use Change and the Terrestrial Carbon Cycle in Asia.
Kobe: The Asia-Pacific Network for Global Change Research
(APN). 30-31.
Zhou G-S , Wang Y-H , Jiang Y-L. 2002b. Global change and the
Northeast China Transect (NECT). Earth Sci Front , 9:198-
215. (in Chinese with English abstract)
Zhou G S, Zhang X S. 1995. A new NPP model. Ye D Z. China
Contribution to Global Change Studies. Beijing: Science Press.
197-202.
Zhou G-S. 2002. The Northeast China Transect (NECT) and
Global Change: Aridification, Human Act ivit ies and
Ecosy stems. Beijing: Meteorological Press House. 415. (in
Chinese)
Zhou G S, Wang Y H, Jiang Y L, Xu Z Z. 2002c. Carbon balance
along the Northeast China Transect (NECT-IGBP). Sci Chin
(Ser C), 45 (suppl.):18-29.
(Managing editor: HAN Ya-Qin)