Botanical Studies (2006) 47: 185-190.

*

Corresponding author: Tel: 86+020-37252996; Fax:

86+020-37252981; E-mail: why@scbg.ac.cn

Effects of periodic cutting on the structure of the

Mikania micrantha community

Juyu LIAN

1

, Wanhui YE

1,

*, Honglin CAO

1

, Zhimin LAI

1

, and Shiping LIU

2

1

South China Botanical Garden, The Chinese Academy of Sciences, Guangzhou 510650, The People¡¦s Republic of China

2

Dongguan Botanical Garden, Dongguan, 523079, The People¡¦s Republic of China

(Received August 12, 2004; Accepted December 5, 2005)

ABSTRACT.

Mikania micrantha H.B.K., an aggressive exotic climber, has caused significant damage to

many ecosystems in the Guangdong province in recent years. To study the plant community dynamics and

develop methods for control of this weed, we investigated in the effects of periodic-cutting on M. micrantha

in Dongguan, Guangdong province, in south China. We harvested the aboveground biomass of our cut treat-

ment and control plots of M. micrantha once every two months for a year. Results show that periodic-cutting

reduced the competitiveness of M. micrantha, changed the composition of its community, and promoted

growth of native and other non-native species, especially those of Compositae species. Considering costs of

time and labor, resilience of M. micrantha is too high strong that too high to control completely by periodic-

cutting once every two months,

but periodic-cutting is an effective, safe, and easy method to put into practice

for forests and plantation crops.

Keywords: Community structure; Exotic species; Invasion; Mikania micrantha; Periodic-cutting; Species

diversity.

INTRODUCTION

Invasion of exotic species into native plant communi-

ties is pervasive and widespread, and it has substantial

negative effects on native community structure and func-

tion (Heywood, 1989; Macdonald et al., 1991; Timmins

and Williams, 1991; D¡¦Antonio and Vitousek, 1992;

Berger, 1993; Hobbs and Humphries, 1994; Cronk and

Fuller, 1995; Higgins et al., 1999). We have not found an

effective method that can be used to control all harmful

alien plant species, because of differences in biological

and ecological traits among these species. To control them,

mechanical, chemical, and biological methods, or some

combinations of these, are commonly used (Berger, 1993;

Maffei and Marin, 1999; Peng and Xiang, 1999; Li and

Xie, 2002).

Mikania micrantha H.B.K. (Compositae), a climbing

perennial weed that originated from South and Central

America (Hills, 1999; Maffei and Marin, 1999). Since its

introduction to China in 1919, M. micrantha has spread

extensively. It has been called a plant-killer since it causes

native species to disappear (Zhang et al., 2004). The

species is destructive to forests and plantation crops, such

as tea, teak, rubber, and oil palm, and it causes economic

losses and decline in native biodiversity. Since the 1960s,

various efforts to control M. micrantha have been report-

ed, such as mechanical, biological, and chemical control

(Bogidarmanti, 1989). Herbicides are very effective in

controlling this weed (Zhang et al., 2004), but they cause

serious environmental problems. Removing M. micrantha

manually is the best way to control this weed since her-

bicides and mechanical removal have undesirable effects

on the community. Cutting M. micrantha vines near the

ground once a month can eliminate 90% of them at the

individual level (Kuo et al., 2002). In the growing season

for M. micrantha in 2000, the Shenzhen government hired

thousands of citizens to hand pull the weed. This was quite

effective, and many dying trees damaged by M. micrantha

recovered (Feng et al., 2002). To control M. micrantha

by cutting on the community of M. micrantha in natural

environment in South China, we need to understand how

M. micrantha community is affected by this manipulation.

Therefore, we initiated this project to study the effects of

cutting M. micrantha on plant community dynamics dur-

ing one growing season under a low subtropical climate.

MATERIALS AND METHODS

Study site

We set up experiments in an abandoned litchi garden in

a hilly area between main road Dongguan and Dongguan

Avenue, west of Dongguan city center (113¢X31¡¦~114¢X15¡¦E,

22¢X39¡¦~23¢X09¡¦N). The climate is typical subtropical with

ECOLOGY

186

Botanical Studies, Vol. 47, 2006

marine monsoon. It is warm and humid with mild winters,

long hot and humid summers, and lots of sunshine. The

rainy season is from April to September. Soil samples

from the 0-10 cm mineral horizon were collected from our

experimental plots at the beginning in June 2002. In recent

years, human activities have badly destroyed the natural

vegetation in this area, which has resulted in favorable

conditions for alien species invasion. Our study site was

dominated by M. micrantha, with coverage of over 80%.

The other dominant plant species in the M. micrantha

community were the non-native Ageratum conyzoides and

Bidens pilosa and the native Urena lobata.

Experimental design

To examine the influence of periodic cutting on M.

micrantha, we set up 10 1 m ¡Ñ 1 m plots. Once every two

months from June of 2002 to June of 2003, we harvested

the aboveground plant biomass by clipping from each of

these plots and from the other 10 uncut control plots each

time. That is, there were 10 cutting plots and 70 control

ones. Then, all plant material was sorted by species as it

was harvested. Biomass was dried at 80

o

C for 48 h and

weighed to obtain biomass.

Measure of diversity

To assess the species diversity of the different control

treatments, we calculated the effective species richness

(e

H¡¦

) (Dukes, 2002), where,

H ¡¦ = - . p

i

In p

i

and p

i

is the biomass proportion of species i to the total

biomass in a plot at a harvest. Effective species richness

measures the number of equally abundant species

necessary to obtain a given H¡¦.

Statistical analyses

All tests were carried out at a P<0.05 significance level

using SPSS (version 12.0). All variables were analyzed by

a 2-way ANOVA with harvest time and cutting treatment

as main factors. When the interaction was significant, the

treatment effects were tested by a t-test for each harvest

time. As harvest time was not our main interest, we did

not use multiple range tests to compare all the means of

the interaction. Since the interaction was significant for all

variables tested, we will not present its results individually.

RESULTS

Influence of periodic cutting on biomass in M.

micrantha community

Influence of cutting on aboveground community

biomass. Periodic cutting resulted in significantly de-

creases in aboveground biomass of M. micrantha com-

munity on all of our harvest days (Figure 1). In June

2003, the mean total M. micrantha community biomass

in plots with periodic cutting was 46.0% less than of the

uncut plots (215.2¡Ó30.9 g/m

2

vs. 398.2¡Ó51.6 g/m

2

). In the

control, aboveground biomass of the M. micrantha com-

munity varied with time of year, with the highest in June,

which was about 2.8 times that of the lowest in February.

During the growing season from June to October 2002 and

from April to June 2003, the biomass of cut plots was only

about half of that of uncut plots (54.0% in August, 52.3%

in October 2002, and 54.0% in June 2003). It is also

clear that the M. micrantha community has great ability

to recover from cutting (Figure 1). In the 2002 growing

season, the ratio of the community aboveground biomass

between June and August was 49.0%, 64.3% between Au-

gust and October. In the non-growing season, the ratio was

28.0% between October and December 2002, and 21.7%

between December and February 2003.

Influence of periodic cutting on biomass of M. micran-

tha. Periodic cutting significantly reduced the biomass of

M. micrantha on all the harvest days (Figure 2a). In June

2003, the mean M. micrantha biomass in the infected plots

was 75.3% less than of the control plots (86.0¡Ó24.2 g/m

2

vs. 348.1¡Ó51.6 g/m

2

). The mean aboveground biomass of

M. micrantha per plot varies with time (Figure 2a). In con-

trol plots, the maximum biomass was in August 2002 and

the minimum in February 2003 (Figure 2a). Community

biomass in the control was dominated by M. micrantha,

and the proportion of M. micrantha biomass to the total

was about 90%, except for June 2002 and April 2003 when

it was about 60% (Figure 2b). In cutting plots, M. micran-

tha biomass proportion decreased almost linearly from

August 2002 to February 2003 (Figure 2b). From Febru-

ary to June 2003, the proportion of M. micrantha biomass

increased almost linearly (Figure 2b), and it was less than

40%. It is clear that cutting decreased the proportion of M.

micrantha biomass in the community, except from June

to August 2002 (ANOVA, F=11.766, P=0.006) (Figure

2b). The proportion of M. micrantha biomass of the first

cutting increased from 61.6% to 86.8% though biomass

of community and of M. micrantha decreased from June

to August 2002 (biomass of community from 476.3¡Ó37.2

g/m

2

to 233.3¡Ó38.5 g/m

2

; biomass of M. micrantha from

0

100

200

300

400

500

Jun-

02

Aug-

02

Oct -

02

Dec-

02

Feb-

03

Apr-

03

Jun-

03

*

*

*

*

*

**

*

**

*

**

*

**

Figure 1. Total community aboveground biomass (mean¡ÓSE,

n=10) in cutting (¡³) and control (¡´) plots. The asterisks indicate

significant difference between treatments (*P<0.05, ** P<0.01,

*** P<0.001) at individual harvest days.

LIAN et al. ¡X Effects of periodic cutting on the structure of the

Mikania micrantha

community

187

293.6¡Ó66.9 g/m

2

to 202.5¡Ó29.5 g/m

2

). This indicates that

the ability of M. micrantha to recover is high, so the rate

of the re-growth is high after the first cutting.

Influence of cutting on biomass of companion species.

In control plots, proportions of biomass in both native and

non-native species were about 10% during our experiment

(Figure 3a, 3b). These species were overgrown by M. mi-

crantha (Figure 2b). In the cutting treatment, the biomass

proportion of other invasive species increased from 16.9%

in June 2002 to 65.9% in April 2003. Biomass proportion

of native species was lower than 20%, except in February

2003 (Figure 3b). In February 2003, biomass proportion

of native species was >40%.

In our experimental plots, the main Compositae spe-

cies were Ageratum conyzoides, Bidens pilosa, and Conyz

abonariensis. Their biomass proportions were increased

by cutting (Figure 3c), and they were much higher than

those of the control treatment, except in June and August

2002 (Figure 3c). All three Compositae species are exot-

ics. Their relative biomass increased to 65.0% in April

2003 in the cut plots.

Influence of cutting on litter biomass. Litter biomass

of periodically cut plots was stable and negligible, and the

amount was much lower than that of control (ANOVA,

F=63.886, P<0.001) (Figure 4). Also, litter biomass of

control plots fluctuated with time.

Figure 2. Mean plot biomass (mean¡ÓSE, n=10). (a) and relative

biomass (mean¡ÓSE, n=10); (b) of M. micrantha in cutting (¡³)

and control (¡´) plots. Refer to Figure 1 for the definitions of the

asterisks.

Figure 3. Me an rel at iv e bi om as s (m e an ¡ÓS E , n= 10) o f

companion species in cutting plots (¡³) and control plots (¡´). a,

nonnative species; b, native species; c, Compositae species. Re-

fer to Figure 1 for the definitions of the asterisks.

Figure 4. Mean amount of litter (mean¡ÓSE, n=10) in cutting

plots (¡³) and control plots (¡´). Refer to Figure 1 for the defini-

tions of the asterisks.

188

Botanical Studies, Vol. 47, 2006

Influence of periodic cutting on structure of the

M. micrantha community

Influence on number of species. Periodic cutting

resulted in increasing in number of species, according

calculating of the total number of species in 10¡Ñ2 plots,

and increases in native species were more pronounced

than in exotic species (Figure 5). In control plots, species

were in both fluctuation and stable states. That is, number

of species in the community was the same on given dates

between years, but it changed with the season. This was

true for both native and non-native species; native species

were in the same dynamic state as all the species. At the

end of our experiment, there were 6 native species while 3

exotic ones.

Compared to control, periodic cutting promoted inva-

sion of non-native species. In cut plots number of species

increased from 7 to 23, as about 3 times the numbering as

the control plots, which was 9. At the end of our experi-

ment, there were totaling 16 native and 7 exotic species.

Influence on species diversity. Periodic cutting resulted

in higher species diversity and in greater variation in (Fig-

ure 6). In control treatment, the diversity index changed

Figure 6. Species diversity in cutting (¡³) and control plots (¡´).

Figure 5. Number of species in cutting (¡³) and control plots

(¡´). a, all the companion species; b, native species; c, other non-

native species.

very little from June 2002 of 1.9 to April 2003 and then

increased to 2.7 in June 2003. In periodic cutting, diversity

was reached a maximum of 10.0 in February 2003, and

then it decreased to 4.1 in June 2003.

DISCUSSION

Our results indicate that periodic cutting has consider-

able influence on species richness of the M. micrantha

community. Cutting reduced the biomass of M. micrantha

and increased species diversity of the community. These

results supported the intermediate disturbance hypothesis

(Connell, 1978). Connell proposed that species diversity

was maximized under intermediate levels of disturbance.

Thus, bimonthly cutting was likely intermediate distur-

bance for the M. micrantha community. The process of

regrowth showed that dominance of M. micrantha was re-

duced by periodic cutting, which created opportunities for

other species to establish in the community. This is why

the number of species, the index of species diversity, and

biomass ratio of other species increased more in the cut-

ting treatment than it did in the control.

Disturbance by frequent cutting of the M. micrantha

community caused invasion by other non-native and of

native species. These results are in accord with the com-

petitive mechanisms responsible for invader superiority

(Petren et al., 1993). That is, disturbance enhanced com-

munity invasibility. Elton (1958) suggested that low com-

munity diversity caused greater invasion. Our result agrees

with this concept, though some opinions differ from those

of Elton (Robinson et al., 1995; Palmer and Maurer, 1997;

Higgins et al., 1999). After invasion by M. micrantha, the

community accorded with the negative theory of com-

munity diversity to invasibility. In a year of bimonthly

cutting, number of native and other non-native species

increased as did their biomass proportion.

Periodic cutting increased the relative biomass of other

Compositae species. With decrease of the M. micrantha

population, biomass percentages Ageratum conyzoides,

Bidens pilosa and Conyz abonariensis, increased continu-

ously. This result agrees that of with Bao et al. (2003),

who also found that Compositae species increased un-

LIAN et al. ¡X Effects of periodic cutting on the structure of the

Mikania micrantha

community

189

der different mowing regime for 19 years in the steppe

dominated by Leymus chinensis.

Periodic cutting effectively controlled M. micrantha

and promoted recovery of native species. However, M.

micrantha has a great ability to recover following cutting.

The proportion of M. micrantha biomass increased after

the first cut. Its relative biomass in the growing season

was still >40% during the bimonthly cuttings, and it was

increasing after senescence in February. It seems that cut-

ting at intervals of less than two months would be more

effective than the 2-month cutting interval. Although cost

of periodic cutting is high, herbicide and mechanical re-

moval can have undesirable affects on non-target species

and on the environment. Thus, for forests and plantation

crops, cutting is an effective, safe, and easy method to put

into practice for controlling M. micrantha.

Acknowledgements. We thank Dr. Wang Zhangming for

advice on data analysis and English language revision, Fu

Qiang, Deng Xiong, Yang Qihe, Shen Hao and Hong Lan

for their reliable assistance with measurements and help

in setting up the experiment, and Cai Chuxiong and Ye

Wanhe for help with harvests. This work was supported

by the State Key Basic Research and Development Plan of

China (No. G2000046803), Guangdong provincial Natu-

ral Science Foundation of China (No. 021536 and No.

05200701) and the National Natural Science Foundation

of China (No. 30530160).

LITERATURE CITED

Bao, Q.H., Y.T. Bao, Q.L. Yan, and Y.P. Ao. 2003. The com-

parison study on community characteristics under mowing

treatments in the steppe of Leymus chinensis. Acta Scien-

tiarum Naturalium Universitatis NeiMongol 34: 74-78 (in

Chinese with English abstract).

Berger, J.J. 1993. Ecological restoration and non-indigenous

plant species: a review. Restor. Ecol. 1: 74-82.

Bogidarmanti, R. 1989. Impact of Mikania spp. on forestry and

agriculture land (in Indonesian). Buletin Penelitian Hutan

511: 29-40.

Connell, J.H. 1978. Diversity in tropical rain forests and coral

reefs. Science 199: 1302-1310.

Cronk, Q.C.B. and J.L. Fuller (eds.). 1995. Plant Invaders .

Chapman and Hall, London, UK.

D¡¦Antonio, C.M. and P.M. Vitousek. 1992. Biological invasions

by exotic grasses, the grass/fire cycle, and global change.

Annu. Rev. Ecol. Syst. 23: 63-87.

Dukes, J.S. 2002. Species composition and diversity affect

grassland s usceptibility and response to invasion. Ecol.

Appl. 12: 602-617.

Elton, C. (eds.) 1958. The Ecology of Invasion by Animals and

Plants. Methuen: London, UK

Feng, H.L., H.L. Cao, X.D. Liang, X. Zhou, and W.H. Ye. 2002.

The distribution and harmful effect on Mikania micrantha

in Guangdong. J. Trop. Subtrop. Bot. 10: 263-270 (in Chi-

nese with English abstract).

Heywood, V.H. 1989. Pattern, extent and modes of invasions by

terrestrial plants. In J.A. Drake, H.A. Mooney, F.D. Castri

et al. (eds.), Biological Invasions: A Global Perspective.

Wiley, Chichester: New York, pp. 31-60.

Higgins , S .I., D.M. R ichards on, R.M. Cowli ng, a nd T.H.

Trinde r-S m ith. 1999. P redic ting t he la ndsc ape -s ca le

distribution of alien plants and their threat to plant diversity.

Conserv. Biol. 13: 303-313.

Hills, L. 1999. Mile-a-minute, Agnote 535. URL http://www.

Nt.gov.au/dpif/pubcat/agntes/535.htm.

Hobbs, R.J. and S.E. Humphries. 1994. An integrated approach

to the ecology and management of plant invasions. Conserv.

Biol. 9: 761-770.

Kuo, Y.L., T.Y. Chen, and C.C. Lin. 2002. Using a periodic-

cutting method and allelopathy to control the invasive

vine, Mikania micrantha H. B. K. Taiwan J. For. Sci. 17:

171-181 (in Chinese with English abstract).

Li, Z.Y. and Y. Xie (eds.). 2002. Invasive Alien Species in Chi-

na. China Forestry Publishing House, Beijing (in Chinese).

Macdonald, I.A.W., C. Thebaud, W.A. Strahm, and D. Strasberg.

1991. Effects of alien plant invasions on native vegeta-

tion remnants on La Reunion (Mascarene Islands, Indian

Ocean). Environ. Conserv. 18: 51-61.

Maffei, E.M.D. and M.M.A. Marin. 1999. Chromosomal poly-

morphism in 12 populations of Mikania micrantha (com-

positae). Genetics Mol. Biol. 22: 433-444.

P alm er, M.W. and T. Maurer. 1997. Doe s dive rsi ty beget

diversity. A case study of crops and weeds. J. Veg. Sci. 8:

235-240.

Peng, S.L. and Y.C. Xiang. 1999. The invasion of exotic plants

and effects of ecosystems. Acta Ecol. Sin. 19: 560-568 (in

Chinese with English abstract).

Petren, K., D.T. Bolger, and T.J. Case. 1993. Mechanisms in

the competitive success of invading sexual gecko over an

asexual native. Science 259: 354-358.

Robinson, G.R., J.F. Quinn, and M.L. Stanton. 1995. Invasibility

of experimental habitat islands in a California winter annual

grassland. Ecology 76: 786-794.

Timmins, S.M. and P.A. Williams. 1991. Weed numbers in New

Zealand¡¦s forest and scrub reserves. New Zealand J. Ecol.

15: 153-162.

Zhang, L.Y, W.H. Ye, H.L. Cao, and H.L. Feng. 2004. Mikania

micrantha H. B. K. in China ¡V an overview. Weed Res. 44:

42-49.

190

Botanical Studies, Vol. 47, 2006