全 文 ：第 19 卷 第 2 期
Vol. 19 No. 2
草 地 学 报
ACTA AGRESTIA SINICA
2011 年 3 月
M ar. 2011
Study on the Cenozoic Flora and Flora Evolution of the Loess
Plateau of Northern Shaanxi Province
LI Deng-wu1, 2 , ZHA NG Wen-hui1, 2 , GOU Xiao-dong3 , WA NG Dong-mei1
( 1. C ol lege of Forest ry, Northw est A& F University, Yangling, Sh aanxi Provin ce 712100, C hina;
2. Key Laboratory of West Environm ent and Ecology of Educat ion Minist ry, NWAFU , Yangling, Shaanxi Province 712100, Ch ina;
3. Col lege of Economics and Management , Northw est A& F U niversi ty, Yan gl ing, Shaanx i Province 712100, China)
Abstract: Flora study is basic to the understanding of the int rinsic att ributes of regional vegetation and its
zoning , management, and ut ilizat ion. T herefore, studies on the f lora geog raphy o f the Loess Plateau of
Northern Shaanx i Province w ill be important no t only for the Loess P lateau Flora zoning, but also for the
flo ra studies of Wester n China, lo cal planning o f it s ag riculture, forest ry and animal husbandry industr ies.
It w il l also have reference value for the ut ility and protect ion of lo cal plant resources. In shor t, the study
of the flo ra geog raphy w ill have eco logical, econom ic and social importance in the eco logical improvement
and natural resources protect ion. Comparat iv e analysis o f material betw een paleobo tany and pr esent-day
flo ra of the Loess P lateau of N orthern Shaanxi Province ( LPNS) show s the evolut ion and sources of the
LPNS. s flora. The evolutions of flora over stages since the Cretaceous period are discussed. From the flora
evolution and the spo re and pollen compar ison betw een the modern and the Cenozoic period, it is believ ed
that the f lora of the LPNS can be dated back to four major sources: ¹ the local and neighbo ring f lor a in the
late Cretaeous period and Paleogene, w ith some herbaceous plants and hygrophytes or ig inat ing in the Neo-
gene and the hardy and drought enduring plants in the Quaternary period; º the M editerranean, Central
Asia and the Eurasian Steppe; » the No rtheast Asia, the temperate and cold area o f Siber ia; ¼the South-
w est China, Nor thw est China, North China, and the Qinling Mts. and Central China.
Key words: Flor a; Evo lut ion; Orig in; Cenozo ic; Loess Plateau o f Northern Shaanx i Province ( LPNS)
陕北黄土高原植物区系的演变及新生代植物区系分析
李登武1, 2 , 张文辉1, 2 , 苟小东3, 王冬梅1
( 1. 西北农林科技大学林学院,陕西 杨凌 712100; 2. 西北农林科技大学西部环境与生态教育部重点实验室,
陕西 杨凌 712100; 3. 西北农林科技大学经管学院, 陕西 杨凌 712100)
摘要: 运用植物区系地理学的研究方法,根据古植物学资料及与现代植物区系的对比分析,对陕北黄土高原植物区
系的演变及新生代植物区系进行了研究,对深入了解陕北黄土高原植物区系、植被的起源和发展具有重要意义, 同
时为指导本区目前实施的退耕还林还草、植被恢复等生态环境建设方面可以提供参考。文中论述了自白垩纪以来
各时期陕北黄土高原植物区系的演变发展过程, 对陕北黄土高原植物区系的演变和现代与新生代孢粉植物群进行
了比较分析,认为本区植物区系主要来源于 4个方面: 一是起源于本地及邻近地区晚白垩纪- 早第三纪植物群, 一
些草本植物和湿生植物主要发生于晚第三纪,耐寒和耐旱的种类主要发生于第四纪; 二是来源于地中海区- 中亚
和欧亚草原;三是来源于东北亚、西伯利亚温- 寒地区;四是来源于我国西南、西北、华北及秦岭、华中地区。
关键词:植物区系; 起源;来源; 新生代;陕北黄土高原
中图分类号: Q948. 5 文献标识码: A 文章编号: 1007-0435( 2011) 02-0181-10
Species evo lut ion is not only closely related to
heredity mechanism o f species, but also to environ-
mental changes, part icular ly geolog ical historical
-the changes of the w orld. and the changes o f the
paleo-climate. There are many repor ts on the pale-
obotany and paleo-geogr aphy in China, and their
achievements discuss impo rtant r efer ence value to
the study o f the f lora evlut ion and sources o f the
收稿日期: 2009-11-25;修回日期: 2010- 11-23
基金项目:中科院知识创新项目( KZCX1-06) ;国家自然科学基金( 30671672) ;西北农林科技大学青年学术骨干支持计划( 01140304)资助
作者简介:李登武( 1968- ) ,男,宁夏固原人, 副教授,博士,研究方向为生物多样性保护与利用、植物生物地理学和植被恢复与保持等,
E-mail: dengw uli@163. com
草 地 学 报 第 19卷
LPNS.
The LPNS, like the Loess P lateau, r esulted
from the Quaternary ice age and the interglacial
ag e. T his is a reg ion o f ancient cultur al prosperity,
w here most of the land has been reclaimed, and
serious soil erosion, nat ive vegetat ion is almost
non-ex istence, w ith a unique natura-l cultural land-
scape. Consequent ly extensive at tent ion has been
paid to the sustainable development of the LPNS.
There are major inter ests on the forest steppe w ith
flo ra evo lut ion of the LPN S has much interest .
Therefore, in or der to f ind out the evo lut ion and
sources o f the Loess Plateaus F lora and of fer po s-
sible suggest ions fo r sustainable development o f
the Loess P lateau, part icularly cur rent projects o f
Returning Farmland to Fo rest and Grassland,
Vegetat ion Restorat ion, both flo ra evolut ion and
the Ceno zoic f lora o f the LPN S are studied.
Due to the par ticular geolo gical and phy sio-
g raphical features of the Loess P lateau and the suc-
cessiv e and excessive exploitat ion and ut ilizat ion
over a long t ime, the natural vegetat ion and f lora
have been seriously af fected. Consequently , ser-i
ous soil and w ater loss fo llow ed, w hich has draw n
ex tensiv e academic at tent ion. The Chinese Acade-
my of Sciences has org anized large-sized vegetat ion
surveys and plant collect ions in LPNS w ith ex ten-
sive research on the vegetat ion, f lora, community
funct ions and ut ilization. These results and related
ar ticles [ 1~ 6] provide support ing informat ion for
vegetat ion restor at ion and ut ilizat ion.
1 Materials and methods
1. 1 Study area
The LPN S is t radit ionally farmland. It is a
long reg ion f rom south to north. It lies in the cen-
tral part of the Loess Plateau in China( E106b30c~
111b15c and N34b33c~ 39b35c) and is bo rdered by
Guanzhong Plain, Shanx i, Ningx ia, and Inner
Mongolia on its south, east , w est and no rth. T he
altitude of the region is w ithin 500 ~ 2400 m,
most ly w ithin 900~ 1500 m. T he region stretches
over the m id- temper ate and w arm temperate zones
from no rth to south and its temperature and pre-
cipitation are very seasonal as it falls in the cont-i
nental temperate monsoon climate in the east o f the
Euro-Asia Cont inent . The aver age annual tempera-
tur e is 7 ~ 13 e , w ith the average temperature
being - 4~ 9 e in January and 20~ 24 e in July.
T he ex t reme high temperature of the region is 36~
41 e and ext reme low temper ature - 25. 4 e . The
act ive accumulated temperature \10 e is 2 600~ 3
500 e . T he f rost- f ree period of the region is about
170~ 200 days. T he annual precipitation is 400~
700 mm. T he varied land surface, tog ether w ith
the differ ent climate condit ions in LPNS, deter-
mines the spat ial dist ribut ion, characterist ics,
str ucture and evo lut ion of the f lora in the reg ion,
and the vegetat ion t ransit ion f rom forest , fo rest
g rassland, dry gr assland to sand land from south
to north. Important ly, endemic f lora components
of both ancient and young species evo lve in this
special environment .
1. 2 Methods
1. 2. 1 Establishment of the presen-t day seed plants
databank
T ho rough investig at ion has been reported fo r
the main communit ies of the key areas of the region
through plots and along special r outes. Detailed
studies w er e also done in the Herbarium of NWA-
FU ( the former Herbarium of Nor thw est Inst itue
of Bo tany) . Further, the present-day seed plants
dir ectory of the reg ion w as compiled and databank
established.
1. 2. 2 Flo ra area-l type classif ication
Accor ding to the classif ication methods by
WU Zhengyi[ 7] , area-l type stat ist ics applied to the
seed plants of the reg ion at g enus level.
1. 2. 3 The Evo lut ion and Sour ces of the Flor a
Accor ding to the compar at ive analysis of the
material betw een paleobo tany and present-day f lora
of the LPNS, related references w ere studied
[ 8~ 20]
.
2 Results
2. 1 Present day flora in the LPNS
Accor ding to finding s in the Loess Plateau of
Nothern Shaanx i, there are 1413 species ( including
infraspecif ic tax on) , 574 genera in 140 families of
vascular plants, of w hich 63 species, 32 genera in
17 fam ilies are, and 14 species, 7 genera in 5 fam-i
lies are g ymnosperm plants, and 1336 species, 535
182
第 2期 李登武等:陕北黄土高原植物区系的演变及新生代植物区系分析
genera in 118 families are angiosperm plants. T he
later include 1105 species, 425 genera in 101 fam-i
l ies of dico tyledon plants and 231 species, 110 gen-
era in 17 families o f monocotyledon plants.
In terms o f family size, ther e are only families
w ith over 100 species in the LPN S: Compositae,
Gr am ineae, Rosaceae and Legumino sae, w hich ac-
counts only for 3. 3% of the total fam ily number.
Yet these 4 fam ilies, all cosmopolitan w ith over
1000 species, include 162 gener a, 486 species, re-
spectively 29. 9% and 36. 0% of the total genera
and species number in this region. T he f irst 3 fam-
ilies ar e w idely dist ributed in the temperate zone
and the last one in both temperate and tropic zone
in the w orld. T he larg e numbers of g enera and
species of these 4 families show that they are no
doubt the main components in the fam ily categ ories
of the seed plants in LPNS.
There are 7 families w ith 30~ 99 species, 5.
5% of the to tal families number. T hey are Ranun-
culaceae, Chenopodiaceae, Labiatae, Cyperaceae,
Poly gonaceae, L iliaceae and Cruciferae and they
comprise 97 genera and 270 species, w hich are re-
spectively 17. 9% and 20. 0% of the total genera
and species number. T herefore, these 7 families
also play an important role in the seed flo ra o f the
region.
2. 2 Flora evolution
2. 2. 1 T he Cretaceous period
According to paleobotany, the Jurassic and
the early stage of the Cretaceous period w as w hen
gymnosperm thrived and fern plants remained up-
grow ing. H uge changes took place f rom the m iddle
of the Cretaceous period w hen ferns and gymno-
sperms decr eased shar ply, replaced by angiosperm
plants, which quickly developed during the late
Cr etaceous period and dom inated later in the T er t-i
ary period. T he f lora evolution of LPNS generally
fo llow ed this rule in the Cretaceous period.
According to Wang Hesheng
[ 8]
, fer n plants
dom inated the f lora, follow ed by gymnosperm in
the early Cretaceous per iod in the LPNS, when it
w as under the arid tr opic and sub- tropic climate
condit ion. T hen gymnosperms started to dom inate
in the late Cretaceous per iod.
It w as f rom the late Cretaceous period that an-
giosperm plants f lourished. During this period, the
predom inant families, Lauraceae, Fagaceae, Mag-
noliaceae of the sub- tropic forest in the south of
China, and the deciduous t rees such as Tilliaceae,
U lmaceae already existed, w hile in the no rth of
China ( including the LPNS) , Fagaceae, Proteace-
ae and o ther ang io sperms appear ed. The zonality
of the g round plants also started to show .
2. 2. 2 The tert iary per iod
T he ter tiary period featured great development
of ang io sperms. Tao Junrong[ 9] believed that the
per iod from the late Cretaceous to paleo-gene w as
the second stage, the golden age of ang io sperm
plants. Due to the H imalayan M ovement and the
format ion of monsoon climate, the paleo-geog ra-
phy framew ork of No rth China w as formed. The
temperature continued to decrease, and conse-
quent ly the f lora and vegetat ion changed immense-
ly. T he ang io sperm cont inued its g row th and pre-
dominance. A larg e number of temperate plants
appear ed and herbage and hydrophy tic plants mu-l
t iplied quickly coming in the third evolut ion stage
of angiosperm, i. e. , prime period of herbage
plants.
2. 2. 2. 1 Paleogene
Compared w ith the Cretaceous period, f lora
elements in the T er tiary period changed tremen-
dously, i. e. the fern plants that boomed in the
M esozo ic period decreased great ly, gymnosperm
plants like Br achyphy llum, Potoz amites and Wel-
w i tschia mir abil i s died out, Cycas r evolute and
Ginkgo biloba dropped on a large scale, w hile the
Pinaceae, the T axodiaceae and the Podocar pus
M acr ophy llus g rew in number. T he P inus tabu-
laef ormis in part icular, w er e already flourishing in
the LPNS and even the No rth China f rom the Eo-
cene to the early Oligocene epoch ( According to
T ao Junrong, et al .
[ 10]
) . The more impo rtant
change w as the pr edominance o f angiosperm in this
per iod. A rbo r t rees const ituted most of the many
angiosperm plants, of w hich ament plants like
J uglans, Pter ocar va, B etula, Quer cus were im-
portant g enera of the f lora. Some typical t ropic and
sub- tr opic plants also g rew in the flo ra. M ore than
half the components of these fam ilies and genera
are now dist ributed in the area south to the line of
Huai River-Qinling-Bailong river. T he co-existence
183
草 地 学 报 第 19卷
of bo th temperate and sub- tropic components
pro ves that the f lora are mainly o f ament plants
and o rig inated f rom the everg reen and deciduous
bro adleaf m ixed fo rest of the Southern A ngar aland
and Northern Cathaysian land.
The H imalayan movement startedduring the
Tert iar y period. The Old Mediterranean gradually
died out , the w arm sea shr ank, and the Eurasian
cont inent gradually formed. With the evolut ion o f
the H imalayas, the Kunlun M ts. , the Gandese,
the Altai and the T ian M ts. started to influence at-
mospher ic circulat ion, w hich resulted in the hu-
m idity change in Central A sia. T he No rthw est and
North China became ext remely dry. Part icularly in
the late Paleogene per iod, the g round sur face tem-
perature began to decrease, Frig id Zone compo-
nents appeared in the w hole Norther n Hem-i
sphere, w hich conf ined the prevalent dist ribut ion
of the tr opic species and gener a. T he vegetat ion in
North China w as most ly deciduous br oadleaf f lora
w ith aments, i. e. , mainly Ulmus, Cel ti s, Betula,
Cor y lus, Quercus. T he P inus and her bage dicoty-
ledon w er e mor e common in the Paleogene period.
2. 2. 2. 2 Neogene Period
The climate zones of the Neogene period w er e
very much like the current climate zones. The arid
zone in the N orth Hemispher e extends f rom SWW
to NEE. The Westerly belt w as formed.
In the late Tert iar y, the climate in N orth Ch-i
na w as both dry and warm , forests decreased
great ly. T he t ropic and sub- tropic components like
Cycadaceae, Taxodiaceae, M yrtaceae of the Paleo-
gene either died out or became relict plants gradu-
ally . Further , plants of g rassland types, such as
Chenopodiaceae, Compositae, Plantag inaceae, Le-
gum inosae, Cyper aceae and Gramineae emerged.
Shrubs w ere also developed, such as Ericaceae,
Rhamnaceae, Oleaceae, Ro saceae. The arbor
plants w er e mainly dr ought endurance oak plants,
in addit ion to Ulmus, Br oussonetia. Due to the in-
creased drought in the inner Old Asian Cont inent
and control of the subtropical high in the Tert iar y,
the sub- tropic sparse for est, g rassland and desert
in the hot and dry area o f the Southern Xinjiang
and Qinghai w ere intensified. Gansu, Ningx ia and
Northern Shaanx i w ere also inf luenced; forest
shrank while her bage increased. The south of the
LPNS and Guanzhong Basin w ere featured w ith
continental sem-i ar id and temperate climate w ith
plants components rather poor, similar to the pres-
ent st ructur e, except for Ginkgo, Cry p tomer ia.
2. 2. 3 The Quaternary period
T he H imalayan movement was st ronger in the
Quaternary per iod as the mountain cont inued to
rise and the global climate f luctuated w ith alterna-
t ions o f drought and f lood, cold and heat . A num-
ber of ice ages and interglacial periods emerged.
T he East Asia Monsoon w as formed and further
developed. Consequent ly the fauna and f lora
changed dr ast ically. It w as during the dry and cold
ice age that the Quaternar y loess accumulat ion e-
merged. T he ice age and the dr y and cold climate
also st imulated the development of living beings.
2. 2. 3. 1 T he Pleistocene
2. 2. 3. 1. 1 The early Pleistocene
Due to the climatic alterat ion fr om w arm and
coo-l dry and temperate-humid coo l in the early
P leisto cene, the vegetat ion of the south o f the
LPNS also evolv ed f rom the coniferous for est dom-
inance in the ear ly stage, to the mixed fo rest of
broadleaf and conifer , w ith r ather w ell developed
g rassland plants in the middle stage, to the conifer
predom inance in the late stage. Of the diver se
components dom inated by w oody plants, the most
predom inant w ere Abies lanceolata , Picea asp era-
ta, Pinus, Ulmus , Cunninghamia, T suga lanceo-
lata etc, fo llow ed by Quer cus sp . , Car p inus tur c-
z aninow i i , B etula sp . , Ti l ia sp . , Ginkgo biloba,
P seudolarix kaemp f eri , L iquidambar f ormosa-
na , P ter ocar ya stenop ter a, Cr yp tomeria f ortunei ,
Car ya cathay ensis . Her bs mainly consisted of Ar-
temisia and Chenopodiaceae Plants. It w as colder
in the no rth of the LPNS than in the south, so the
vegetat ion in the north of the reg ion w as mainly
forest steppe-sem-i arid steppe and for est steppe.
2. 2. 3. 1. 2 The M id-Pleistocene
T here w ere thr ee alterat ions of dry ing and
w et ting in N orthern China during the M id Pleisto-
cene period. T here w ere ero sions during the w et-
t ing per iod ( Tongchuan per iod) and loess accumu-
lat ion during the dr ying per iod ( The new Shek pe-
riod) . Due to the climat ic difference betw een the
ice age and interg lacial ag e, plants species w ere
rather poor. Fo rests in the south of the LPNS and
184
第 2期 李登武等:陕北黄土高原植物区系的演变及新生代植物区系分析
Guang zhong area degr aded while her bs such as
Plantago, A r tem isia, Gr amineae, Cyp eraceae,
Chenopodiaceae, Cary ophy l laceae, Cr ucif er ae
thrived. T he w oody plants only consisted o f
Platy cladus, Pinus, Juglans, B etula, Car p inus,
Broussonet ia and Rosaceae. Because of the co ld
and arid environment , the North LPNS plants died
and ret reated to the south, leaving a desert land-
scape.
2. 2. 3. 1. 3 T he late Pleistocene
There w er e tw o ice ages dur ing the late Pleis-
to cene period in China, the Lushan Ice Age and the
Dali Ice Age. T he low temperature, part icularly
during the Dali Ice Age, produced a serious influ-
ence on Shaanx i. Af ter the ice ages, cont inental
climate started to form as the temperature in-
creased w ith a fur ther loess accumulat ion of the
Malan Stage. According to L i Bingcheng and Sun
Jianzhong. s[ 11~ 12] study on the spo re and pollen o f
Luochuan and Fux ian in Shaanx i, more than 150
families and genera w ere able to gr ow in the LPNS
during the late Pleistocene, of w hich 48 w ere ar-
bors, 24 shrubberies, 61 herbages, 17 fern spores
and 3 freshw ater alg ae, most o f w hich are the
present temperate plants in Loess P lateau. T he ar-
bor plants mainly included P icea, A bies, Pinus,
Pinaceae, Quer cus, B etula, Carp inus, Cor y lus,
Ulmus , Celt is, Ai lanthus, Castanea, Alnus,
Salix , J ug lans, Ti l ia, Fr ax inus, Aceae, Oleace-
ae etc. , the shrubberies included Ep hedra, Rosa-
ceae, Eup telea, Rhamnus, E laeagnus, N itr ar ia,
Sambucus, the herb plants included A r tem isia,
Compositae, Chenopodiaceae, Gramineae, Ranun-
culaceae, T hal ictr um, Rubiaceae, Scrophulariace-
ae, Cruciferae, Polygonum, Leguminosae, H u-
mulus, Car yophy llaceae, Cyperaceae, Typ ha, the
fern spor e plants included, Po lypodiaceae, Selag i-
nel la ( e. g. Selaginel la sinensis ) , Pter idium, H i-
criop ter is, L y copodium, A diantum. The minority
w ere plants that g rew in bo th the temperate and
tr opic zones, such as, Koel r euter ia, Rhus, Ptero-
car ya, Cor nus, Pistacia etc. in addit ion to a small
number of t ropic plants, such as T sug a, P laty-
car ya, Carya, L iquidambar , Eng ethar dt ia. Ad-i
t ionally there w ere f reshw ater alg ae such as Con-
centr icy stes, Zygnema, Ped iastr um.
Also in the mid and late Quaternary per iod the
Yellow River, north to the Q inling Mounts, un-
derw ent dry and w indy climate w ith fr equent haze
intensifying the loess accumulat ion process. The
Nor th of Shaanx i w as most ly affected by the dry
climate so that some broadleaf arbor plants started
to retr eat to the southeast. T he components o f the
dry desert steppe of cent ral A sia intr uded into
Nor th Shaanx i, some even to the Qinling M ounts.
T his movement line probably star ted f rom Kash-
gar, through Qinghai, Gansu, Inner Mongolia,
Ningx ia to Nor th Shaanx i. T he ancestor s o f the
present ly ex ist ing N itraria, K alidium, Zigo-
phy llum in this area came to Shaanx i at that
t ime[ 12] . As the loess grains o f the Plateau become
smaller f rom NW to SE, it is believ ed that the lo-
ess came from the movement by cold northw est
w inds. It w as then much drier and colder in North
Shaanx i than in Guanzhong , w hich resulted in the
southw est ret reat or even ext inct ion of broad-
leaved species. Of course some finally go t adapted
to the env ir onment and survived. T he paleosoil of
the old loess, namely the br ow n forest soil, o r e-
ven the typical brow n soil w ere fo rmed under rath-
er w arm and humid climate, w ho se vegetat ion usu-
ally w ere summer gr een forest or forest steppe.
T here w ere differ ences betw een no rth Shaanxi and
Guanzhong f rom the internal dif ferences o f so il.
T he deciduous broadleaf fo rest dominated the
southeast area, nor th to Qinling M ts. , w hile the
forest steppe and steppe got the predom inance in
the Northw est. Par ticularly in the late Quaternary
per iod, the paleo soil in Malan Loess w as found to
be Heilu soil, w hich further pr oves that the vege-
tation dur ing that t ime w ere the co ld and ar id
steppe o r meadow and scrub.
Nor th to the line of the Great W all, w hich
w as a concave belt w ith lar ge lake ar ea and suff-i
cient w ater, the vegetation evolut ion in the late
P leisto cene w as obv ious though it w as different
f rom other areas. Accor ding to the study on the
ancient botany o f the Salaw usu River area w here
the Hetao M an fossil was found, conifer w as pre-
dominant during the late Pleistocene, w hich mostly
consisted of the p inus, fo llow ed by P icea, Ce-
dr us, T suga and T axodiaceae. T he bro adleaf ac-
counted for a relat iv ely smal l percentag e, mainly
included Betula, Quer cus, Car p inus, Ulmus,
185
草 地 学 报 第 19卷
Salix , Fag us, P ter ocar ya atc. , and Juglandaceae
some plants. T he shrubberies included Rhamnace-
ae and Cory lus a few plants. The herbage mainly
consisted of Chenopodiaceae, A rtemisia and Com-
positae, follow ed by Ep hedra, Ranunculaceae,
Cr uciferae and Po lypodiaceae some plants. As the
climate g radually became dry in the late Pleisto-
cene, some w arm th and hum idity requiring plants
such as T axodiaceae, Jug landaceae, Pter ocar ya,
Carp inus, B etula, Ulmus , Fagus, Cor y lus, Po-l
ypodiaceae died out and the for est steppe landscape
dom inated by Pinus were formed.
2. 2. 3. 2 The Ho locene epoch
When human beings emerged in the Ho locene
period, in order to sur vive, they participated in va-
r ious product ion andlivelihood act ivities, conse-
quently the env ir onment w as altered, w hich inev-i
tably af fected plants and vegetation. In the beg in-
ning human g rew some of the plants that had value
fo r human being s to collect and harvest , so consid-
erable area of forest w as cut dow n for farm land. In
order to cook, get heat , build houses, fire bricks
and t iles, make furniture and w ares, it w as neces-
sary to enlar ge the forest to chop down and cult-i
v ate. A s refugees f rom political suppression, w ar,
and econom ic explo itat ion cult ivated new land, the
farm land g rew . The natural vegetation w as thus
damaged, w hich resulted in soil and w ater loss,
decreased precipitat ion, drought, dr ought endur-
ing plants invaded while the shade requir ing plants
reduced. Shaanx i has a long civilized histor y.
How ever, the environmental damage and vegeta-
t ion dest ruct ion should not be under estimated. Of
course, it should be noted that a lot of plants w ith
economic value w er e also int roduced in this cultiva-
t ion process w ith the development of civilization.
2. 2. 3. 2. 1 T he early Ho locene
From the late P leistocene to early Holo cene,
the temperature dr opped, at a smaller degree com-
pared w ith pr evious coo ling-downs though. As a
result, coniferous fo rest consisted mainly of P i-
nus, P icea and A bies was formed on the Plateau,
w ith the number of P inus probably more than the
Picea and Abies.
2. 2. 3. 2. 2 T he Mid Holo cene
It w as w arm and humid in the mid Holo cene,
about 2~ 3 e than the curr ent, and the vegetat ion
and biolog ical categ ory w as very complex[ 12, 14] .
Sub- tropic components f requent ly intr uded into the
forest of LPNS and Guang zhong Plain. According
to the spore and po llen study by Zhu Zhicheng[ 15]
and historical documents[ 12, 16, 17] , the forest plants
consisted o f Quer cus, Betula, Carp inus, Ulmus,
Cel ti s, J uglans, Car ya, A ilanthus, S al ix , Cas-
tanea, Rhus, P laty car ya, Oleaceae, Diosp y r os,
T amarix , Mor us mongol ica, Cudr ania tr iouap i-
dala, Populus, T il ia, Catalpa, Chimonanthus,
P runus sal icina, Py r us, H emip telea dav idi i ,
Castanop sis, Quercus baroni i , Tr achy car pus,
Bambusoideae, Br oussonet ia, P ter ocel ti s tar turi-
now i i , M elia, Acer, Morus, Puer ar ia p seudohir-
suta . Pinus, Platy cladus developed ex tensively.
T he ar bor categ ory mainly consisted of the w arm-
temperate species and genera, w hile some of the
sub- tropic components, like P laty carv a, Rhus,
T rachy car pus, P ter ocel t is tartur inow ii etc. ,
though not many, w ere distr ibuted to the far
Nor th [ 14, 15] . The known shrubberies and herbage
w ere most ly w arm-temperate species and genera,
w ith a small number of intr uded sub- tropical com-
ponents, e. g. the famous herb medicine L igust ic-
um chuanx iong grew even in the area north to 38bN
alt itude in Mid Holo cene, growing in Sichuan,
Yunnan and Guizhou now aday s, moved about 10~
13 altitude degrees south. Generally, the middle
and south of LPNS in the M id Ho locene w as cov-
ered w ith deciduous bro adleaf fo rest w ith mino rity
sub- tropic components and warm th requiring conif-
erous and broadleaf fo rest mainly consisted of Pi-
nus, Quercus, Ulmus , Cel t is. The existence of
Castanop sis, Castanea, Tr achy car pus proves that
the climate w as much w armer and wet ter than to-
day, sim ilar to the Southern areas to Qinling Mts.
today . T his w as also the period w ith most f lour-
ishing vegetat ion f rom the Pliocene up to today.
T he north o f LPNS w as for est steppe consisted
mainly of P inus.
2. 2. 3. 2. 3 The Late Holocene
T he late Holocene w as about 2 500 ~ 1 200
years ago. The climate during this period turned to
drier and cooler, about 1~ 2 e low er than the M id
Ho locene. T he broadleaf fo rest in the north of
LPNS star ted to ret reat fr om NW to SE. The open
forest landscape of short Xero-mesophy te arbo r
186
第 2期 李登武等:陕北黄土高原植物区系的演变及新生代植物区系分析
started to show , such as Pr unus ansu, Ulmus
macr ocar p a, U. p umila, U. glaucescens, Py r us
betulaef ol ia, Pr unus d avidiana, Populus simo-
ni i , P . hop eiensi s[ 12] . The P inus tabulaef ormis ,
Platy cladus or iental is and Junip erus r igida in the
east w ere also components of open forest . T he
shrub and herbage were most ly Xer o-mesophy te,
w ith a small number of int ruded steppe Xer ophytes
such as S tipa bungeana, S . g randis, T hymus
mongmd icus and A rtemisia f rigida. T he forest
community in the south ex tended to the forest
steppe along valley s. On ridges and top of hills
w as shr ub steppe as the pr ecipitat ion w as low . Dry
steppe communit ies even emerged in the ex tr eme
dry areas. T he shrub steppe w as composed typica-l
ly of few M eso-xerophy te species in Car agana such
as C. gansuensi s, C. micr ophy l la, C. opulens
while the herbage w ere dom inated by species w ith
st rong Xer ophyte features such as S tipa bun-
geana, S tipa gr andis, Poa sp hond y lodes, Cleis-
togenes squar rosa, A r temisia f r ig ida . This w as a
clear dist inct ion f rom the arbor open forest. T he a-
bove show s that the forest in the south ex tended
no rthw ard along valleys w hile the steppe in the
no rth st retched southw ard along the dry r idges and
hill tops and short ar bor open for est gr ew on the
expansive slope under the topog raphical condit ions
of gullies and hills and the redistribution of mois-
ture and heat by air movement . Those w ere the
features of the fo rest steppe of the hills and gullies
of the Loess Plateau.
In addit ion, according to the spo re and pollen
study o f the Holo cene f lora by Zhou Kunshu, et
al . [ 18] in Fuping of the south the LPNS and Huang
Cixuan
[ 19]
in Jingbian on the north verge of the
LPNS, all the three stag es of Holocene w er e dom-i
nated by her bage, accounting for 80~ 90% of the
to tal po llen amount . T he species w er e rather sim-
ple, mainly composed of Ar temisia powder, fo-l
low ed by Chenopodium, Ep hedra, and Cyperace-
ae, Gentianaceae, U mbelliferae and Polygonaceae.
The arbor plants w ere mainly composed o f Pinus,
Quer cus and Betula, and supplemented by Salix ,
Alnus cr emastogyne and H ippop hae. The T suga
and T ypha found in the spor e po llen of the Ho-l
o cene in Fuping indicated that the climate tur ned
w armer af ter the ice ages of Pleistocene. So during
the H olocene the vegetation changed from fo rest
steppe to steppe, and the steppe featur e w as even
str engthened fr om Mid to Late Ho locene and from
the south to the north.
2. 2. 4 The Neoteric
As a r esult of the cont inuous populat ion
g row th, most land o f the area has been cult ivated
in the near past, only small areas o f forest, mainly
broadleaf for est composed of Quercus, Pop ulus,
Betula and conifer ous fo rest composed of Pinus
and P laty cladus, w ere preserved in the southern
mountainous regions ( Guan Mt. , Huanglong
M t. , Ziwu Range and so on ) . T he vegetat ion
north to Yan. an w as mostly damaged w ith land ex-
posed. Only in the abandoned farmland, the river
and field banks did some secondary drought endur-
ing herbaceous communit ies and the shrubberies
remain, such as Gly cy r rhiz a uralensis , A neur ole-
p idium dasy stachy s , Pennisetum f laccidum ,
T hymus quinquecostatus var. p r z ew alski i, Cara-
gana micr ophy lla, Bothriochloa i schaemum , So-
phora davidi i , Rosa xanthina , Ziz y phus j uj uba
var. sp inosa, Ostry op si s dav idiana. Accor ding to
the primar y study by Zhu zhicheng[ 20] on the vege-
tation condit ions in the north LPNS from the r em-
nant communities and individuals and the textual
research of the botanical place names, the areas
north to Yan. an, due to the moisture and heat de-
cr ease from SE to NW, featured spatial vegetat ion
alterat ion order of for est, fo rest steppe f rom
southeast to northw est . Because the ir regular sep-
aration by the hil ls and gullies, the mo istur e, heat
and air movement varied even in the same area,
w hich resulted in m iscellaneous living conditions.
T his made it possible fo r plants o f very different
eco- types gr ow ing tog ether in the same area.
T herefore, the for est and steppe format ion fea-
tur es can be generalized as: the steppe areas most-
ly w er e on the top of hills , ridg es of highland and
w atersheds, w hile forest w ere most ly in gul lies,
valleys and other comparat ively w et areas, as a re-
sult , the fo rest and steppe w ere separated f rom
each other into blocks; besides, due to the climat-
ic, topog raphic and hydraulic dist ribution factors,
the forest steppe in the southeast dif ferentiated
f rom the w est of the LPNS; the lat ter w as featur ed
w ith shrubbery steppe landscape, w ith fo rest
187
草 地 学 报 第 19卷
shrunk and shrubberies enlarg ed in gullies. T he
predominant component that consisted the flo ra o f
the steppe ar ea w as Bothr iochloa i schaemum , Pen-
nisetum f laccid um and some other Xero-meso-
phytes w hile the superiority of St ip a and other
components of dry steppe increased only in w est o f
the ar ea. T he typical arbor t rees of the forest in
this area ar e Ulmus sp . , Pinus tabulaef ormis ,
Armeniaca sibir ica, P laty cladus or iental is , fo-l
low ed by Populus sp . , Salix sp . , Py rus betulae-
f ol ia etc. The P inus and Platy cladus are mor e
seen in the east while A rmeniaca sibi ri ca and
Py r us betulaef ol ia more in the w est. A lthough
the oak and other components of the summer
bro ad- leaved forest have ex tended to the no rth
along w ith the gul lies o f the forest steppe, their
propor tions are rather smal l.
Due to the vegetat ion dest ruct ions by human
being s, the climate tends to be drier and the steppe
is pushing against the forest . N ot only is the forest
in the area north to Yan. an turning into secondary
steppe, steppe islands also emerged in the summer
green br oadleaf forest south to Yan. an. M any spe-
cies and genera in the summer gr een broadleaf for-
est , such as Quercus, Rhus, T i l ia, Betula, Cory-
lus have retr eated from the far nor th regions of
Baiyushan Mount , H engshan and the areas north
to Jianx ian to the regions south to Yan. an. While
the fo rest components ar e ret reat ing, some steppe
families and genera have cont inued to increase and
expand, such as St ip a bungeana, Stipa gr andis,
Cryp sis aculeate , A grop y ron cr i statum, Aneurol-
ep id ium dasy stachy s , A r temisia f r ig ida , A rtemi-
sia mongolica, Ar temisia g ir aldi i , Potenti l la
mul ti caul is , Car agana kor shinski i , Caragana mi-
cr ophy lla, Car ag ana pygmaea and Car agana op-
ulens . N ot only have they become the components
of the local f lora, but also formed the predominant
communities, and cont inued to move south-
w ards [ 13] .
2. 3 Analysis of the Cenozoic flora of the LPNS
2. 3. 1 Composit ion o f the ex ist ing Cenozoic sper-
matophy te flo ra of the LPNS
T o summar ize the above and related docu-
ments, stat ist ics on the Cenozo ic spermatophyte
f lora of the LPNS ( table 1) .
Table 1 Statistics of Cenozoic flora of the LPNS
Taxa
Tert iary era Quaternary period Exist in g s eed plants in the LPNS Exist ing seed plants in th e w orld
Family Genus Family Genu s Family Genus Fam ily Genus
Gymnosperm 7 14 6 13 5 5 10 22
Angiosperm ( 47) ( 73) ( 59) ( 91) ( 59) ( 81) ( 83) ( 125)
Dicotyledon 41 46 52 84 54 76 74 118
Monocotyledon 6 6 7 7 5 5 9 7
T otal 54 87 65 104 64 86 93 147
T able 1 show s that there exist now 93 fam-i
l ies, 147 genera of seed plants, o f w hich 10 fam-i
l ies, 22 genera are gymnosperm plants, 83 fam-i
l ies, 125 genera are ang iosperm plants. There ar e
64 fam ilies, 86 genera in the LPNS, accounting for
68. 8% and 58. 5% of the w orld ex ist ing totals
respectively.
For the exist ing 5 families, 5 genera of gym-
nosperm plants o f the LPNS are Pinaceae, Cupres-
saceae, T axaceae, Cephalotaxaceae, Ephedraceae
and Pinus, Platy cladus, Cephalotaxus, T axus,
Ephedr a. T here exist 59 families, 81 genera of an-
g iosperm plants on the LPN S.
2. 3. 2 T he area-l types of the exist ing Cenozoic
seed plants of the LPNS
2. 3. 2. 1 Family ar ea-l types
Of the ex ist ing Cenozoic spermatophyte fam-i
lies of the LPNS, 16 families are cosmopolitan, ac-
count ing fo r 25. 0% of the total, includingCompos-
itae, Leguminosae, Chenopodiaceae, Rosaceae,
Rhamnaceae, Caryophyllaceae, Labiatae, Convo-l
vulaceae, Scrophulariaceae, P lantaginaceae, Cera-
tophy llaceae, Typhaceae, Cyperaceae, Gramineae,
Potamogetonaceae and Liliaceae.
T here are 24 families o f t ropical dist ribut ion,
account ing for 37. 5% of the total, most o f w hich
are pan- tropic types, includingUlmaceae, Fagace-
ae, M oraceae, Lauraceae, Rutaceae, Zygophy lla-
ceae, Meliaceae, Anacardiaceae, Ebenaceae, Eu-
pho rdiaceae, Celastr aceae, Sapindaceae, Sima-
188
第 2期 李登武等:陕北黄土高原植物区系的演变及新生代植物区系分析
r ubaceae, V erbenaceae, Rubiaceae, Symplocaceae,
Vitaceae, Sabiaceae, Oleaceae, A lang iaceae, and
Araliaceae. The t ropical Asia and tropical America
disjuncted include 2 families: Magno liaceae and
Tiliaceae.
There are 24 families of temperate dist ribu-
t ion, 37. 5% of the total fam ily number, of w hich
19 families are No rth temper ate and its subtypes,
i. e. Pinaceae, Cupressaceae, Taxaceae, Ephed-
r aceae, Betulacea, Jug landaceae, Salicaceae, A-
ceraceae, Elaeagnaceae, Caprifoliaceae, Ranunculaceae,
Poly gonaceae, Cruciferae, Cornaceae, Hamamel-i
daceae, Gent ianaceae, Umbelliferae, Plumbag-i
naceae and Berberidaceae etc. T he East Asian dis-
tribution include 3 families: Eupteleaceae, Cerc-i
diphyllaceae and Cephalo tax aceae. T here is only
one family of E A sian and N. American disjunc-
ted: Schisandraceae. T he Old wo rld dist ribut ion
only concludes one fam ily, Tamaricaceae.
The area-l types of the families show that the
temperate and tropic distr ibuted fam ilies account
fo r half of the total number. How ever , the gener a
and species of the t ropical dist ributed families ar e
most ly the ex tended ones or the r emnant variet ies,
w hich at least indicate the historical inter- relation-
ship betw een the local f lora and tropic f lora.
2. 3. 2. 2 T he generic area-l types
T able 2 show s the ar ea-l types of the ex ist ing
86 genera of the Cenozoic seed plants of the
LPNS
[ 7]
. The temperate types ( 8-14) , including
54 genera and account ing fo r 74. 0% o f the total
g enera number, have the absolute advantag e, of
w hich the N. T emperate area-l type is the riches,
w ith 28 genera and 37. 3% of the total, fol low ed
by the Old Wor ld T emperate, E A sia and N Amer-
ican disjuncted, composed of 7 and 6 gener a re-
spect ively. There are 5 genera of E Asian Distr ibu-
t ion and 4 genera of the Mediterranean and Central
Asia dist ribution.
Secondly, the T ropic Area-l types include 17
genera, 23. 3% of the total, of w hich 10 or 13. 7%
are the Pan- tropic distr ibut ion. Seven genera are
other t ropic area-l types. In addition, 2 genera
( 2. 7% ) are endemic to China and 13 genera belong
to the World distr ibution.
T he above analysis show s that the geog raph-
ical dist ribut ion o f the exist ing seed plants o f the
LPNS in the Cenozoic period on the level o f g enera
is basically the same as that of today.
Table 2 Area-l types of the existing Cenozoic seed plants genera in the LPNS
Area-l types Genera No. % Main genera
1. Cosmopolitan 13 - T yp ha, L emna, P otamog eton, Rhamnu s, P olyg onum, Chenop o-
d ium, S op hora, Ny mph oide s, Convolvulus, Cer atop hyl lum, G en-
t iana, L imonium, P lantag o
2. Pant ropic 10 13. 7 Ce lt is, Zizip hus, S ymp ly oc os, Celastr us, Euonymu s, Diospy ros,
Vi te x , Zanthoxy lum, E ph ed ra, Eup horbia
3. Tr op. Asia and t rop. Am erica disjun cted 2 2. 7 Me liosma, L i tsea
4. Old w orld t ropical dist ribut ion 1 1. 4 A langium
5. Tr op. Asia to T rop. Oceania 2 2. 7 A i lanthus, Toona
7. Tr op. Asia 2 2. 7 B roussonet ia, P uer aria
8. N. T em p. 28 38. 4 P inu s, T axu s, Ulmus , Quercus, Ti l ia, Betula, Cor ylus, Car pi-
nu s, Be rberi s, J ug lan s, P op ulus, Sal ix, R osa, Sp i raea, Cr atae-
gus, Cotoneast er, Fr axinus, J unip erus, St ipa, Mor us, H umulus,
A cer, Cornus, Ar temisia, L onicera, Viburnum, P runus, E laeagnus
9. E. Asia & N. Amer. dis juncted 6 8. 2 L e sp ed ez a, Magnol ia, Wiste ria, G ledi t sia, S chi sandr a, T ox ico-
d endr on
10. Old World Temp. 7 9. 6 Ze lkova, P yr us, A mygdalus, H ip p op hae, Th ymus, T amarix ,
Clei stog enes
11. Temp. Asia 4 5. 5 Car agana, Camp ylot rop is, Ar meniaca, Ex och or da
12. Medit .- C. Asia 4 5. 5 P istacia, K alid ium, N itrar ia, Zigop hyl lum
14. E. Asia 5 6. 8 Cer cidip hyl lum, K oel reute ria, P laty cla dus, Cep halotax us,
A canthop anax
15. Endem ic to China 2 2. 7 X anthocer as, Ost ry op si s
Total 86 100
189
草 地 学 报 第 19卷
3 Discussion and conclusion
In general, the T ert iary w as the periodw hen
the gymnosperm declined and the ang io sperm g rew
rapidly and the f lora of LPNS formed, w hile the
Quaternary w as the period w hen the f lor a o f the
LPNS re-assembled, moved and cont inued to
evolve o r dif ferent iated.
During the geolog ical period and early histor-i
cal times, climate had been the dom inat ing factor
fo r the changes o f the f lora and vegetation, w ith
the change of climate changes in the co ld and w arm
and dry and w et . As human act iv ity intensified,
climate w as no longer the unique factor for the f lo-
r a and vegetat ion changes. Human act ivity has
played a more evident role to the f lor a and vegeta-
t ion changes.
According to the existing spore and pollen re-
cords, it can be inferr ed that the present-day f lora
of the LPNS is much r icher than it used to be,
there are 1413 species, 574 genera in 140 families
of v ascular plants. A summarization of the above
and related documents may help us to see the
connect ions and differ ences of the flo ra betw een
the present-day and the Cenozo ic.
From the flo ra evolut ion and the spore and
po llen comparison betw een the modern and the Ce-
nozoic period, it is believ ed that the flo ra of the
LPNS can be dated back to four major sources.
The sour ces of the present-day f lora of the LPNS,
like north China
[ 8]
, may be recognized as taking
four paths. It is mainly o f autochthonous ( A lso
spread to neighboring areas of many species) or ig in
w ith evolut ion f rom the Paleogene to the present
like various ancient w oodplants, temperate and
subtropical or t ropical elements. H erbs occurred
most ly since the Neogene. Besides, some species
ar e from subtropica-l t ropical reg ions o f southw est
China, especially from Henduan M ts. . Some ar e
from the Central Asia-Mediterranean and Europe-
Asia steppe as w el l as northeast A sia and the Sibe-
r ian temperate-cold ar eas due to the expansion o f
steppe as the climate became co ld during the Neo-
gene and the Pleisto cene.
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