全 文 ：第 26卷第 5期
2006年 5月
生 态 学 报
AC I．A EC0LOGICA SINICA
Vo1．26，No．5
May，2006
切枝对三峡库区两种榕属乔木
生物量积累和枝供给的影响
曾 波，张小萍，钟章成
(西南大学三峡库区生态环境教育部重点实验室，重庆 400715；西南大学生命科学学院，重庆 400715)
摘要 ：榕 (Ficu~microcarpa L．)和黄桷树 (Ficus virens Ait．var．sub／anceo／ata(Miq．)Comer)是在三峡库 区广泛栽植 的优 良绿 化树
种。在三峡库区诸多公路、铁路修建和移民搬迁城镇建设等工程建设后的生态恢复和环境改善中，需要大量的榕和黄桷树。榕
和黄桷树的繁殖通常采用切枝扦插的营养繁殖方式进行。因种苗培育的需要，对榕和黄桷树进行切枝时常发生，并且为了尽快
获得大的种苗，通常切取榕和黄桷树植冠下部的大枝条用于种苗培育。切枝导致植株大量光合叶组织损失，对榕和黄桷树的总
体光合生产和生物量积累会发生影响，同时，也会影响新枝的生长和发生数量以及植株再次提供切枝的能力。为了明确切枝对
榕和黄桷树生长的影响，对切枝后榕和黄桷树的生物量积累和枝供给进行了研究，目的在于阐明在三峡库区亚热带气候条件
下，生长速度比较快的榕和黄桷树是否可以在每年 1次的切枝后很好恢复，从而能够可持续地提供切枝用于种苗培育。实验中
对榕和黄桷树 1a切枝 1次，连续进行了 3a。实验共设置了 4个切枝强度(从植冠下部开始 ，分别切去植冠长度 0％(对照)、
20％、50％和 70％范围内的所有枝条)和两个切枝处理季节(春季切枝和秋季切枝)。实验结果表明，切枝会减少榕和黄桷树地
上部分生物量增量，生物量增量减少的程度与切枝强度呈正相关 ；并且，每年连续进行的切枝使地上部分生物量增量减少加剧。
实验发现，在 20％、50％和 70％ 的 3个切枝强度中，高切枝强度可以保证在第 1次切枝处理中获得高的枝收获量，但并不能保
证在第 2次和第 3次切枝处理中也能获得高的枝收获量。与春季切枝处理相 比，秋季切枝处理使榕和黄桷树获得更高的地上
部分生物量增量，从而获得更高的枝收获量。就植株地上部分生物量增量和枝收获量而言，切枝强度对二者的影响并不因切枝
季节不同而表现出差异。研究表明，对于本实验研究中采用的榕和黄桷树植株，当切枝强度高于20％时，每年 1次的切枝不能
使榕与黄桷树植株的生长完全恢复。如果切枝每年进行 1次，为保证能够可持续地获得切枝并且对植株的生长不造成过大影
响 ，对于本研究 中所采用 的榕 和黄桷树植株而言 ，最适的切枝强度应低于 20％。
关键词 ：切枝；枝供给；生物量积累；榕；黄桷树；三峡库区
文章编号 ：1000．0933(2006)05．1382．08 中图分类号 ：Q143，Q948 文献标识码 ：A
Efects of branch removal on biomass production and branch availability of two fig
tree species in Three Gorges reservoir region of China
ZENG Bo，ZHANG Xiao—Ping，ZHONG Zhang—Cheng (Key Lab。ratory of Eco-envlr0n m in Th e GD增 胍 e 如咖n， D，
Edacation，Southwest China University，Chongqing 400715，China Faculty of Life Science，Southwest China University，Chongqing 400715。China )．Acta
Ecolo~qca~nica。20O6，26(5)：1382—1389．
Abstract：In Three Gorges reservoir region of China，many roads，highways，railways，buildings and even new towns and cities
have been constructed or are under construction．In this region，fig tree species F／cus microcarpa and F／cus virens are extensively
planted for the ecological restoration and environmental improvement．Using branch cutings to vegetatively cultivate saplings is a
基金项目：荷兰国家自然科学基金资助项目(WB84—411)；国家教育部资助项 目(2002—247)；重庆市科技资助项目(2002—7471)
收稿 日期：2005—09—18；修订日期：2006—02—19
作者简介：曾波(1972一)，男，重庆人，博士，教授，主要从事植物生态学和环境生物学研究．E—mail：bzeng@swu．edu．ca
Foundation item：The Project was supported by Netherlands Foundation for the Advancement of Tropical Research(No．WB84．41 1)，Chinese Ministry of Education
(No．2002-247)and Chongqing Science and Technology Commission(No．2002-7471)
Received date：2005-09-18；Accepted da te ：2006-02-19
Biography：ZENG Bo，Ph．D．，Profos~r，mainly engaged in plan t ecology and environmental biology．E-mail：bzeng@ swu．edu．ca
Acknowledgements：We thank Prof．Marinus Werger and Dr．Heinjo During for valuable comments on previous version of the manuscript
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5期 曾波 等：切枝对三峡库区两种榕属乔木生物量积累和枝供给的影响 l383
chief way of tree propagation for these two species in Three Gorges reservoir region，annual branch removal from trees of the two
species for obtaining branch cuttings are common in the region．To evaluate the efects of annual branch removal on plant growth
and subsequent harvest of branch cutings，a branch removal experiment with four relTIOVal intensities(0％ ，20％ ，50％ ，and
70％)，two removal seasons(spring and autumn)was carried out．Branch removal was conducted in three successive years．
Aboveground biomass production of branch-removed F／cus microcarpa and F／cus virens trees decreased following treatment，and
this reduction was correlated with branch—removal intensity．Annually repeated branch removal aggravated the decrease of
aboveground biomass production．Among removal intensities of 20％ ，50％ ，and 70％ ，higher removal intensities led to larger
branch harvests in all species at the first pruning，but did not necessarily lead to larger branch harvests at the second and the third
treatment．Trees subjected to branch removal in autumn produced higher aboveground biomass production，and resulted in a larger
branch harvest than trees subjected to branch removal in spring．However，with respect to the aboveground biomass production and
branch harvest，no interactions were found between treatment seasons and relTlOVal intensities．The results indicate that，in Three
Gorges reservoir region，the annual branch removal regime can not provide enough time for these two堍 trees to fully recoverfrom
removal intensities higher than 20％ ．The optimal removal intensity which ensures the largest sustainable harvest of branch cuttings
from these trees under annual removal regime should be less than 20％ ．
Key words：branch cutting；branch supply；Ficus mierocarpa；Fieus virens；Th ree Go rges reservoir region；tree growth
Owing to the largest dam construction of the world at Three Gorges in China，the Th ree Go rges reservoir region is on
its way of fast development．Many roads， highways，railways，buildings and even new towns and cities have been
constructed or are under construction．To restore the damaged vegetation and to improve the environmental quality in this
region，a lot of trees are needed．F／cus microcarpa L．and F／cus virens Air．var．sublanceolata (Miq．) Cornor
(Moraceae)are two fig species which are naturaly distributed in this region．Trees of these two species have shapely
crowns and are able to grow on poor soils．Due to these advantages，they are widely planted in Th ree Go rges reservoir
region，especialy in cities，towns and along roads．For the two species，vegetative multiplication is the chief means of tree
propagation，in which branch cutings are used to cultivate saplings．Generally，the common mode local people apply to
get branch cuttings is to remove branches from the lower crown annually，leaving the upper parts of trees intact．
Branch removal leads to a reduction in leaf area，and this supposedly results in an overall decrease in the assimilate
production of the trees．Th e higher the removal intensity，the smaller the assimilate production．While removal takes away
branches and leaves，the stem and root systems are retained．Th us，a large proportion of the assimilates produced by the
residual leaf tissue after removal(especially under intensive remova1)has to be used for the maintenance of a relatively
large mass of remaining unproductive，live support tissue．As a result，assimilate investments in future photosynthetic
production become smaller，and the regrowth of trees may be reduced consequently．
However，whether or not tree growth is affected by leaf loss is dependent on the degree of leaf loss and the time the
treated trees possess to grow following leaf loss．At a certain degree of leaf loss，if there is a sufficiently long time period
after damage．【he immediate reduction in regrowth following leaf loss wil gradually decrease to zero¨ ～ and treated trees
may resume their normal growing states ．Under the circumstances，branch removal results in obtainment of branch
cuttings without impairng tree growth．On the contrary，if branch removal is repeated before the full recovery of damaged
trees，a steady reduction in the growth of the damaged trees should be the result and therefore the potential supply of
branch cuttings over the years may turn out to be smaller．Some studies showed that in areas with mild climate，tree growth
may not be affected by moderate leaf loss．Studies on Eucalyptus nitens in south Australia revealed that the rates of CO2
assimilation of three-year—old Eucalyptus nitens increased by up to 175％ over a 16一month period folowing 50％ crown
pruning ]。
． Moreover， the stem dry mass increment of Eucalyptus nitens trees was not reduced after 50％ crown
pruning ．In a defoliation study carried out in Three Gorges reservoir region，Cornelissen found that 50％ defoliated
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1384 生 态 学 报 26卷
saplings of Castanopsis fargesi，an evergreen broad·leaved tree species，achieved the same plant biomass as control
saplings within ca．eight months after the treatment ．In Three Gorges reservoir region，the favourable period for plant
growth is relatively long，about nine months 引
． It is likely that in this region there exists an intensity of branch removal
up to which annually repeated branch removal does not impair tree growth and branch cutings can be obtained for tree
propagation．
In Three Gorges reservoir region，tree growth is seasona1．Trees grow fast in spring and summer，and grow slow or
even do not grow in winter[。，9。
． Furthermore，even in fast．growing seasons，the season of maximal growth difers between
evergreen an d deciduous tree species[9。
． It is possible that branch removal conducted in diferent seasons may afect the
growth of trees diferently．
Th is paper is to investigate the efects of annual branch removal on aboveground biomass production an d branch
supply of two fig trees in Three Gorges reservoir region．Four branch removal intensities and two treatment seasons were
adopted in the experiment．Th e folowing questions are specifcally addressed：
(1)Can branch·removed trees gain the same aboveground biomass production as intact trees after annually repeated
branch removal?Is aboveground biomass production affected by removal intensity?
(2)Is there a linear relation between branch removal intensity and branch harvest at any annually repeated treatment?
(3)Does branch removal in diferent seasons afect aboveground biomass production and branch harvest differently?
1 Materials and methods
1．1 Species and study area
F／cus microcarpa and F／cus virens are broad·leaved tree species with entire leaves；the former is evergreen and the
latter is deciduous．Individuals of both species can reach a height of 20 meters⋯
． In the Three Gorges reservoir region．
trees of these two species start growth in early March，and new leaves an d shoots can occur during the whole growing
season．No apparent growth in these species can be observed during winter．Th e two species can be found everywhere in
Three Gorges reservoir region，and Ficus virens is regarded as the“civic tree”of Chongqing city．Due to the high
prope nsity of cut branches to root，it is quite easy to vegetatively propagate these two species and vegetative reproduction is
nearly the only applied method for tree muhiplication of these two species in Three Gorges reservoir region．
Th e field where trees of these two species were planted for study is situated at the fot of the Nature Reserve of Jinyun
Mountain(29。50 N and 106。26 E)，ca．40 km north of the city of Chongqing，China．The substrate is quartziferous
stone．Soils are acidic and yellowish．The climax vegetation of this region is evergreen broad·leaved forest．The climate in
this region is monsoonal，resulting in hot，humid summers and chily but mostly frost free winters．Details of the
monsoonal climate of this region are given by Comelissen ，Fliervoet et a1． ，and Li et a1． ．
1．2 Experimental design
In early 1996，300 small trees(saplings with height ranging from 1．1 to 1．4 meters)of each of F／cus microcarpa and
Ficus virens were planted in an experimental garden at the foot of Mt．Jinyun．F／cus microcarpa and Ficus virens trees had
branched when they were planted．Trees of each species were planted in a separate plot，with enough spacing between
individuals to avoid mutual shading during the whole experiment．Weeding，watering，and insecticide spraying were
applied to all trees when needed．
In early 1997，after one year growth for acclimation，for each species，20 ran domized blocks were established for
branch．removal treatment．Environmenta1 conditions were visually homogeneous within and between blocks．Each block
contained nine trees．These nine trees were subjected to one of the following treatments：20％，50％，70％ branch·
removal in spring；20％ ，50％ ，70％ branch·removal in autumn；one tree was set as control，and the remaining two trees
were harvested in the spring or the autumn of 1997．Trees were assigned to treatments randomly．
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5期 曾波 等：切枝对三峡库区两种榕属乔木生物量积累和枝供给的影响 1385
Branch iemoval was conducted in the spring(mid May)of 1997，1998，and 1999 and in the autumn(early October)
of 1997 and 1998．At the first spring branch-remova1．the mean heights of F／cts microcarpa and Ficus vil~n$trees were 1．
5 and 1．8 meters，respectively．At the first autumn branch-removal，the mean tree heights of two spe cies were 2．0 and 2．
3 meters， respectively． Branch-removal was done by removing branches an d associated leaves from the lower crown，
leaving the top of the crown of each tree intact(Fig．1)．卟is implied that the crown depth(defined as the distance from
the apical meristem of a tree to the insertion point of the lowest branch of the tre)of each tre was reduced by 0％。
20％ ，50％ ，and 70％ ，respectively．The second and the third treatment of branch removal in 1998 and 1999 were
performed in the same way，after removing sprouted branches on the pruned lower stem parts of some trees．
1．3 Biomass measurements
At each branch-removal treatment，removed branches and leaves of each tree were weighed separately in the field．
Their dry weights(regarded as the branch supply or branch availability)were determined based on the subsamples
analysed in the laboratory (oven-dried at 70％ for 96h)．For each tree，the stem length and basal diameter(ca．10 cm
above the soil surface)，and the length and basal diameter
(ca．1 cm from the base)0f all first．order branches were
measured．Th e number of leaves was counted．Based on
these measurements，the dry weights of the stem，residual
branches and residual leaves(viz．residual aboveground
mass totally)of each tree after branch-removal treatment
were estimated non—destructively(see below)．卟e sum of
removed mass and residual aboveground mass was regarded
as total aboveground mass．In the autumn of 1999，the
aboveground parts of all trees of all species were harvested．
Dry weights of the stem，branches，and leaves of each tree
were determined．
Inform ation for non．destructive determination of the
biomass of bran ch．removed trees were obtained from
harvested trees．
In the spring of 1997，the aboveground parts of 20
trees(one from each of the 20 blocks)of each species were
harvested．For each tree，stem，branches，and leaves were
weighed in the field．Length and basal diameter(ca。10
cm above the soil)of the stem，and length and basal
diameter of each first．order branch were measured．Th e
numb er of leaves was determined．Stem，branch，and leaf
dry weights were determ ined based on the biomass
subsamples analysed in the laboratory (oven-dried at 70％
for 96h)．Regression formulas were constructed for two tre
species for stem dry weight on the product of stem length
times squared stem basal diameter，and for total branch dry
weight on the sum of the product of length times squared
basal diameter of al first．order branches ( rable 1)．
Table 1 Regression form ulas constructed for stem dry weight and total
branch dry weight of F．microcarpa and F．p~ens trees
Regression formulas for stem dry weight(Y：stem dry weight(g)； ：
product of stem length times squared stem basal diameter(cm2))and total
branch dry weight(Y：total branch dry weight(g)； ：sum ofthe product of
length times squared basal diameters of all first—order branches(cm2))of F．
microcarpa and F．v／rens were constructed．For each species．20 trees weTe
harvested in the spring and autumn of 1997，respectively，and 35 trees were
harvested ；it the autumn 0f l 998
O 70％
Fig．1 Ilustration of branch removal intensities
See text for details of the branch—removal treatment
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1386 生 态 学 报 26卷
Average dry weight per leaf was determined for both F／cus microcarpa and Ficus virens species．With this information．the
dry weights of the stem，residual branches and leaves of each spring—treated tree after the first spring branch—removal were
determined．Average dry weight per leaf was also used to estimate the total dry weight of residual leaves of each spring—
treated tree in the spring of 1998 and 1999．
Similarly，in the autumn of 1997，another 20 trees(from 20 blocks)of each species were harvested and analysed in
the same way．With the information from harvested trees，the dry weights of the stem，residual branches an d leaves of each
autumn —treated tree after the first autumn branch—removal treatment were estimated．Constructed regression formulas for
stem dry weight and branch dry weight based on the harvested trees were also used to estimate stem dry weights and branch
dry weights of treated trees in the spring of 1998(Table 1)．Average dry weight per leaf based on harvested trees was used
to estima te the dry weight of residual leaves in each autumn—treated tree in the autumn of 1998．
In the autumn of 1998．5 blocks out of 20 were randomly selected and trees in these five blocks were harvested．With
these harvested trees，regresion formulas for stem dry weight and branch dry weight were constructed(Table 1)．The dry
weights of stem and branches of each treated tree of two species in the autumn of 1998 and the spring of 1999 were
estima ted，using these regression form ulas ．
1．4 Data analysis
Aboveground biomass production per tree was defined as the diference between the aboveground mass one year after
treatment and the residual aboveground mass instantaneously觚 er treatment．
For each treatment season，efects of branch—removal intensity and treatment year on the amounts of removed branch
and leaf mass(branch supply)and biomass production were evaluated for each species by using two—way ANOVAs．
Diferences between branch—removal intensities in each treatment year and diferences between treatment years were
checked by applying Duncan’s multiple range test．Data of year 1999 were excluded when the efects of treatment season
and branch—removal intensity on biomass production and branch supply were explored by using two—way ANOVAs，since no
branch—removal treatment was conducted in the autumn of 1999．Logarithmic transformation was conducted to equalize
variances if necessary 。
2 Results
2．1 Aboveground biomass production
Branch removal reduced aboveground biomass production of F／cus microcarpa and F／cus virens in both spring—and
autumn—treated trees(Fig．2)．Generally，after each annual treatment of branch removal，aboveground biomass production
declined with increasing removal intensities for two species．
Annually produced biomass increased in undamaged trees with the years．But，in most cases，the biomass increase in
repeatedly damaged trees was greatly reduced，which resulted in a steadily increasing diference in annual aboveground
biomass production between non—branch—removed and branch—removed trees(see the interaction of treatment year and
branch—removal intensity in Fig．2)．
In either of year 1997 and 1998，autumn —treated trees had higher aboveground biomass production than spring—treated
trees(Table 2，Fig．2)．However，as regards the patterns of aboveground biomass production versus removal intensity，
spring—treated trees were not diferent from autumn —treated trees(Fig．2)．No interactions between treatment season and
removal intensity on aboveground biomass production were found for all species(Table 2)．
2．2 Branch harvest
At the first branch—removal conducted in 1997，the harvests of branches were larger as the intensity of removal was
higher(Fig．3)．However，at the second branch—removal，70％ crown damage did not always yield higher harvests of
branches than the lower removal intensities．F／cus microcarpa and spring-treated trees of F／cus virens showed no diference
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5期 曾波 等：切枝对三峡库区两种榕属乔木生物量积累和枝供给的影响 l387
l2
l0
8
6
4
2
0
l2
l0
8
6
4
2
0
Springbranch removal
Spring 97 Spring 98 Spring 99
Spring97 Spring98
l2
l0
8
6
4
2
0
v~ens
l2
l0
AImlmn branch removal
Autumn97 Antumn 98
Spring99 一 Autumn 97 Autumn 98
口 Con~ol 囝 20％ 50％ ■ 70％
Fig·2 Aboveground biomas production(mean士se)of two fig tree species one year after each spring or autumn treatment．Branch removal treatment w8s
done in the spring of 1997，1998，1999 and in the autumn of 1997，1998 for two species
． Removal intensities were 0％ (contro1)，20％ ，50％。ald 70％ ．
For eachremovaltreatment of each species ，meRl~ which sharethe s帅 elower-ca8edletters 8
．re not significantly differentfrom one another
． F0r eachtreatment
sea8on of each species，diferent pper。cased leters are used to indicate diferences in overail inean aboveground bi0rlass produeti0n(n0t shown in the ilSu~)
between years
in the harvest of branches between branch removal intensities at the second treatment
．
At the third spring treatment，the branch harvests in the 20％ removal treatments were not lower than those in the
50％ and 70％ removal treatments(Fig．3)．For the Ficus virens trees，20％ removal led to a higher harvest than 50％
removal，and for Ficus microcarpa trees，50％ removal led to a higher harvest than 70％ remova1
． The interactions on
harvest of branches between damage intensity and treatment year were significant in both two species(Fig．3)．In either of
year 1997 and 1998，autumn treatment led to higher harvests of branches in all species(Table 2，Fig．3)．Treatment
season did not change the paterns of branch harvest versus removal intensity．No interactions between treatment season and
removal intensity on branch harvests were found for these two species(Table 2)．
3 Discussion
Basicaly．the reduction in tree growth caused by the loss of photosynthetic structures is related to the length of the
time period for regrowth．If the time period is long enough， Table 2 The efects of branch．reⅢovai鼬l踟 n蛆d the intencdo璐
damaged trees are able to recover and eventuallv no si即 of be‘ween branch’remoⅧ season蚰d rem val inte ty佃 abovegrouad
the damage remains[J一3．J
．
The results 0f this study clearlv bioma．~producti0n蛆d brancb lIarveSl 0f tw。fig‘ree。pecies·Data 0f
’
year 1999 were exduded when two-way ANOVAs were applied to
show that annual branch removal reduced aboveground e
valuate the ef 啮 0f treatment ason 柚 d the inten c廿。璐 between
biomass production of F／cus microcarpa and F／cus virens treatment season and branch．removal intensity
(Fig．2)．In this study，the branch．removal intensities Aboveground biomass production Branch harvest
Species ———’。。。———————’—。。。。————————。’。。。‘——— ———。。—— ——’。。。。 ——— ——’’。。。 —————’。。。‘——— ————
were 20％，50％，and 70％．It is evident that for removal 兰竺! !竺!竺! ! !竺竺 !
intensities largerthan 20％ cmwn depth reduction， one 唧 68·65丑 O·76 2Ol·62 O·3l
* * * ” ns * * * ns
year was not suficient for the treated trees to gain ful F．virens 62．51 1．06 96．23 1．91
recovery and achieve the same biomass increments丑Ls intact 二二二 竺 ：：： 竺
trees，even though these trees had a relatively long growth ：F al 。。．b：sig“击 an 。leve1。：ns：Not。j m 鲫 ； p一
* p<0．01： * * p <0．001
∞^ 董。茸。_I3Ⅱ=蛋 事 a
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l388 生 态 学 报 26卷
Spring branch removal
Spring 97 Spring 98 Spring 99
Spring97 Spring98 Spring99
团 20％
1500
1200
900
600
300
0
virens
l800
1500
1200
900
600
300
0
50％
Autumn branch removal
Autllml 97 Autllmn 98
Autllmn97 Autllmn98
■ 70％
Fig．3 Amount of branch harvest(mean±se)of two fig tree species at each spring and autumn removal treatment
Removal intensities were 20％ ，50％ ，and 70％ ，and removal was done in the spring of 1997，1998，1999 and in the autumn of 1997，1998 for all species．
For each removal treatment of each species，means which share the Same lower-eased letters are not significan tly diferent from one another．For each treatment
seson of each species，diferent upper-cased leters are used to indicate diferences in overal metal branch harvests(not shown in the figure)between years
period per year in Three Gorges reservoir region[8l9]
． Compared to untouched trees． branch harvest of annually branch—
removed trees decreased increasingly due to their insufficient recovery．Th is resulted in the fact that branch harvests in this
study were correlated with removal intensities at the first treatment，but not correlated with removal intensities at the second
and the third treatment(Fig．3)．In this study，an annual removal intensity of 70％ was too high for the studied species
to continually provide high harvest of branches．Comparatively，removal intensities of 20％ and 50％ appeared to be better
than 70％ in terms of obtainment of branches cutings．However，since the aboveground biomass production of the
investigated trees was decreased at removal intensities larger than 20％ ，the optimal removal intensity which ensures the
largest sustainable branch harvest from these trees under annual removal regime should be less than 20％．
In this study，generaly，autumn—treated trees realized higher aboveground biomass production than spring—treated
trees(Table 2，Fig．2)，and autumn removal resulted in a larger harvest of branches than spring removal (Table 2，Fig．
3)．However，no interactions were detected between treatment season and removal intensity for these two variables(Table
2)．It seems that the paterns of aboveground biomass production and branch harvest associated with removal intensity
could not be influenced by treatment season．In the experiment，the investigated F．microcarpa and F．virens have
different leaf habits，the form er is evergreen，and the latter is deciduous．Based on the experimental results，it was found
that F．microcarpa and F．virens had the similar paterns of aboveground biomass production and branch harvest folowing
removal treatment(Figs．2，3，Table 2)，which implies that in regard to the general tendency of biomass production and
branch harvest as affected by bran ch removal treatment，leaf habit did not make significant difference．
To conclude，in Three Gorges reservoir region，one year was not enough for Ficus mieroearpa and Ficus virens trees
to fully recover from branch removal higher than intensity of 20％．Under annual removal regime，removal intensities
which may not decrease aboveground biomass production of these trees should be less than 20％ ．Due to the continuous
reduction in biomass production caused by annual branch removal，for removal intensities larger than 20％ ，higher removal
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5期 曾波 等：切枝对三峡库区两种榕属乔木生物量积累和枝供给的影响 1389
intensities could only lead to larger harvests of branches at the first pruning，but were not able to result in larger harvests
later on．In order to get sustainable supply of branch cuttings without impairing tree growth，it would be better to increase
the time interval between branch removal events to a period of longer than one year ．As far as the efects on biomass
production and branch harvest were concemed，it is found that removal treatment in spring did not difer from treatment in
autumn．
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