Download Restoration of degraded hill land in South China

Pathways and determinants of early spontaneous vegetation succession in
degraded lowland of South China
Wen-Jun DUAN1, 2, Hai REN1*, Sheng-Lei FU1, Qin-Feng GUO3, Jun WANG1,2
(1. Heshan Hilly Land Interdisciplinary Experimental Station, South China Botanical
Garden, the Chinese Academy of Sciences, Guangzhou 510650, China;
2. Graduate School of the Chinese Academy of Sciences, Beijing 100039, China;
3. USDA – Southern Research Station, Asheville, NC 28804, USA))
Tel 020-37252916; Fax: 020-37252916;
Email:[email protected]
Handling editor: Jian-Xin Sun
Received : 12 Sept. 2006 Accepted: 20 Mar. 2007
Category: Ecology
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Abstract:
Continuous and prolonged human disturbances have caused severe degradation of a
large portion of lowland in South China and how to restore such degraded ecosystems
becomes an increasing concern. The process and mechanisms of the spontaneous
succession, which plays an important role in vegetation restoration, have not been
adequately examined. To identify the pathways of early spontaneous vegetation
succession, 41 plots representing plant communities abandoned over different times
were established and investigated. The communities and indicator species of the
vegetation were classified by analyzing the important values of plant species using
multivariate analyses. The results indicated that the plant species could be classified
into 9 plant communities representing 6 succession stages. The pathway and species
composition also changed in the process of succession. We also measured 13
environmental variables of microtopography, soil structure and soil nutrition in each
plot to examine the driving forces of succession and the vegetation-environment
relationships. Our results showed that the environmental variables changed in diverse
directions, and the soil bulk density, soil water capacity and soil acidity were
considered to be the most important factors.
Keywords: Degraded lowland; ecological restoration; soil; spontaneous succession
Supported by the National Natural Science Foundation of China (No. 30200035) and Field
Station Project of the Chinese Academy of Sciences (CAS) to Heshan Hilly land
Interdisciplinary Field Station, CAS
*Author for correspondence.
Tel +86 (0)20 37252916;
Fax: +86 (0)20 37252916;
Email :< [email protected]>.
2
Ecological restoration is intended to initiate or accelerate the recovery of an
ecosystem in terms of its health, integrity and sustainability (SER 2004). Restoration
is often closely related to the reconstruction of the structure, biological interactions,
and related processes of the ecosystem (Hobbs & Norton 1996; Reay & Norton 1999;
Ren & Peng 2001; Ren 2004). The traditional approach to reclaim degraded lowland
in South China has been to plant fast-growing trees to minimize financial and human
resource expenditures (Yu & Peng 1996). Since plantations could achieve short-term
socioeconomic goals by protecting the soil surface from erosion, by facilitating native
species, and by accelerating the recovery of genetic diversity. However, spontaneous
vegetation succession or natural recovery as an alternative approach to restoration has
gained increasing attention (Bradshaw 1997; Pensa et al.2004). Plant community
succession is becoming one of the important aspects of restoration ecology and forms
a large body of ecological research (Zhang 2005).
Most studies on terrestrial vegetation succession were focused on the restoration of
abandoned mine land (Martinez 2005; Dutta 2005; Pensa 2004), degraded grassland
(Peintinger 2006; Bornkamm 2006; Scholes 1997; Callaway 1993), forest land after
deforestation or fire disturbance (Choung 2006; Karlo 2006; Shimizu 2005; Hooper
2005; Calvo 2005; Turner 1997). However, the pathways and determining factors of
vegetation succession in degraded lowland are unclear, and little information is
available.
Environmental degradation is especially serious in China. It is estimated that the
total area under soil erosion is about 3.56×106 km2, accounting for 37.1% of the
national land (SEPA, 2006). As a traditional approach, plantation may sometimes
quickly increase forest coverage and rehabilitate degraded ecosystem. Most previous
studies of ecological restoration focused on the selection of the pioneer species and
the development of engineering technology. However, few studies have examined the
feasibility of restoration through spontaneous vegetation succession (Qian 1994; Ren
& Peng 2001; Peng 2003). With rapid economic development, many farmers are
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abandoning the agricultural fields and shifting to manufacturing. Consequently，many
croplands are left untended. Moreover, large forestlands are degraded into grasslands
because of intensive logging and poor management. In South China, more than 3.74
×106ha (Zhang, 1994) lowlands were degraded. In order to increase forest coverage
and mitigate soil erosion, the national and local governments have devoted
considerable amount of human and financial resource to extend the plantation. The
fast growing species such as Eucalypt (Eucalyptus citriodora; Eucalyptus exserta;
Eucalyptus robusta) and pines (Pinus elliotii; Pinus massoniana) or nitrogen fixing
species such as Acacia auriculaeformis have been widely used as pioneer species.
However, negative effects such as biodiversity loss (Rawinder 1990; Lisanework
1993), soil nutrient depletion (Madeira 1989), and soil acidification also occur but are
largely overlooked. To avoid these problems, we must understand the processes and
mechanisms of vegetation succession in degraded lowland of South China.
The major objective of this study is to identify the pathways and mechanisms of
vegetation succession associated with restoration processes in South China.
Specifically, we address the following issues: (1) what are the early succession series
of plant communities in South China? (2) Which environmental factor are the key
‘filters’ to determine the vegetation composition and structure in succession; and (3)
what are the most effective approaches to accelerate the vegetation succession and to
reach the ‘futuristic’ restoration goal?
Results
Classification of succession stages
Based on TWINSPAN analysis, 60 species were classified into 9 groups,
representing 6 succession stages (Figure1).
Stage I (0-3 years after abandonment): This stage was the primary period of recovery.
The plant coverage was low (10%) and the community composition was very simple.
Plant species was exiguous (less than 5) and mainly comprised decumbent and
profuse root system species.
Stage II (3-5 years): This stage included two different community types (II-I:
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Imperata cylindrica and II-II: Lycopodium cernuum). Most of the plant species were
gramineous species, which could tolerate the drought and infertile soils. Some
leguminous species also appeared.
Stage III (5-12 years): This stage had two different community types (III-I:
Glochidion
eriocarpum+Panax
stipuleanatus
and
III-II:
Neyraudia
neyraudiana+Miscanthus.sinensi). Most of the species were annual herbs. Many
shrub species also appeared in the communities. The vegetation was generally
dwarfish. This was the transition stage when many grasses species were gradually
replaced by shrub species.
Stage IV (12-17 years): This stage can be divided into two community types.
IV-I: Eurya chinensis+Rhaphiolepis indica
At the beginning of this stage, the dominant species was Dicranopteris linearis.
Some shrub species such as Gerdenia sootepensis and Rhaphiolepis indica were
scattered in the community. However, at the end of this stage, the community
structure changed dramatically and some shrub species, such as sychotria rubra,
Eurya chinensis, Litsea rotundifolia. oblongifolia colonized the community.
IV-II: Litsea cubeba+Litsea gluinosa
In contrast to IV-I, some gramineous species also appeared in this community. At
the end of this stage, many broad-leaved species emerged.
Stage V (17-23 years): The dominance of shrubs over grasses became evident and
many herbaceous species disappeared. Moreover, the coverage of vegetation greatly
increased (about 80%).
Stage VI (23-30 years): The total vegetation cover reached 95%, and the herb
species were highly restricted and their coverage was less than 20% due to the
limitation of light. Both tree and shrub species were dominant. The community
structure of this stage was relatively steady which could resist some extents of
disturbance, reassembling “climax” community under natural conditions.
TWINSPAN analyses showed that, on the same substrate, there was a
combination-separation-combination process of vegetation succession in degraded
lowland, indicating two parallel paths in stage II, III, IV finally combined in stage V
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(Figure 1).
Ordination analysis of succession
In the two-dimensional DCA scatter diagram (Figure 2), the axis 1 most likely
represented the time course. From right to left, the succession periods became longer
and the community composition and structure vary greatly. In the stages I and II, there
were few species and most of them rarely appeared at the adjacent areas, the
community boundary was clear. However, from stages III to IV, with the
improvement of environment, species number increased. Accordingly, the community
boundary became unclear. This was also embodied in the diagrams. Compared with
stage I and II, the shapes of stages III, IV, V were abnormal. Moreover, there were
many transitional species which distributed in the middle position of these 3 stages. In
the end, an obvious change of plant diversity was observed in the Figure 2. From
stage I to stage VI, there was an increasing-decreasing process of the plant diversity.
This diagram shows plots of the same succession stages with similar ordination
scores. Compare with Figure 3, we found the ordination of quadrats at the same stages
had similar position in these two diagrams. It indicated that the environmental factors
of the community changed significantly from one stage to the next, and the species
composition varied with the environment changes.
Changes of species number and composition
During succession, the number of species and species composition changed over
time (Figure 5). Since the succession stages were the inchoate phases in the whole
process of vegetation restoration, the fluctuation of species number was obvious.
Moreover, during all 6 succession stages, the species number of different life forms
changed in different ways. Overall, the temporal pattern of herb and shrub species
was parallel to that of total species number. However, the change of shrubs lagged
behind the herbs. In stage V and IV, the herbs decreased rapidly but shrubs were still
increasing. The species number of lianes changed randomly at all 6 succession stages,
probably because the lianes could better adapt to the environment, and species
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number was small. The tree species increased evidently at the last three stages.
In general, pioneer species at the study site were heliophytes which could endure
drought and leanness. During the first two stages, pioneer species dominated the
community. However, as succession progressed, the microenvironment was
meliorated and the proportion of the pioneer species decreased. This trend was more
obvious in the last two stages. In these two stages, trees and tall shrubs dominated the
communities while many heliophytes, especially herbs and shrubs were shaded out
and a few mesophytes and shade-tolerant species colonized understory. In the first
two stages, most species had very small but large number of seeds mainly dispersed
by wind. In the late stages, however, more species had larger seeds that were mainly
dispersed by animals.
Changes of environmental factors
There was a steady-going degressive direction of soil bulk density during the 6
succession stages, suggesting that the soil structure would be meliorated during
succession process. Moreover, the degressive direction was more obvious in the first 4
stages. It was because that the vegetation coverage increased dramatically in these
stages and it played an important role in water and soil conservation. The changing
pattern of soil saturation moisture (SSM) and soil capillary moisture (SCM) was
completely contrary to soil bulk density (SBD). This indicated that SBD played an
important role in the increase of soil moisture. The pH decreased slowly during the
succession possibly because the acidity of laterite substrate was relatively high. At the
beginning of succession, surface soil was eroded and the soil substrate became
exposed because of low vegetation cover. The pH would decrease due to the effects of
following pedogenic process. Soil organic matter greatly increased during the
succession, especially in the late stages probably due to the increase of plant biomass
and litter. At the first 3 stages, there was little hydrolyzed nitrogen accumulated in the
soil, however, this situation changed at the late stages. Available phosphorus and
exchangeable kalium in the soil showed an increase at the beginning and a decrease
afterwards during the succession, which was possibly resulted from the complex
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interactions between the changes in pH and soil organic matter along the successional
process (Fig. 7).
Analysis of determining environmental factor
The length of lines in the CCA ordination diagram indicates the strength of the
correlation between plant community and the environment, and the angle between two
lines represents their relativity. Figure 8 shows that soil bulk density, soil moisture, N,
pH were the most important factors in vegetation restoration. The soil of our sites was
laterite, acidic, with the pH ranging from 3.6 to 5. Soil pH can affect vegetation
succession in several ways.. First, it could filter out certain species thus change the
community composition.. Second, many essential elements such as P, Ca and Mg are
fixed. For example, Figures 8 showed that these elements were positively correlated
with pH, suggesting that pH could also affect vegetation restoration by restricting the
effectiveness of some soil elements. Third, pH can affect the quantity and activity of
soil microorganisms which play important roles in vegetation succession. The two
CCA ordination diagrams also indicated soil bulk density and soil moisture were two
important factors. At the beginning of the succession, the soil was poor with high soil
bulk density and low soil organic matter content. Accordingly, the soil water holding
capacity was low, leading to greater soil erosion. The diagrams also showed soil
capillary moisture and soil saturated moisture were negatively related to soil bulk
density, indicating that meliorating soil structure was propitious to vegetation
restoration. At the same time, slope and aspect of a catchment could affect the
spatial-temporal distribution of water and heat. Generally, soil erosion was more
serious in steep lowland. The accumulation of soil organic matter and minerals was
relatively low in these areas. This effect was more pronounced in monsoon area. N
and soil organic matter were easy to decompose and relatively little was accumulated
in the soil because of the high temperature and intense dry-rewetting process.
However, at the latter stages, the microenvironment was improved; the accumulation
of soil organic matter and minerals increased. Therefore N and SOM became more
important in late succession.
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Discussion
Controlling factors of vegetation succession
The vegetation succession and ecological restoration represent processes in
community assembly that involves a series of filters and thresholds sifting species out
of the regional pool (Temperton et al., 2004; Whisenant, 1999; Díaz et al.1998). It
has been recognized that the importance and action of different filters will vary from
place to place and over time through restoration (Temperton et al., 2004; Woodward
and Diament, 1991). In extremely degraded sites, environmental stresses act as abiotic
filter and only some pioneer species may be able to tolerate the severe conditions.
South China is in the lower subtropical monsoon region. The annual precipitation is
about 1700mm and the rainfall is generally intense and easy to cause surface runoff,
which usually peels off the fertile topsoil, especially in hilly land. Consequently, the
soil becomes extremely lean, acidic and compact thus functions as an abiotic filter. In
these severely degraded areas, some pioneer gramineous species have extensive root
systems and can tolerate strong acidity and drought. As pioneer species, these species
can reduce surface runoff, accumulate soil organic matter, and improve soil structure,
thus act as nurse plants to facilitate the colonization of later species. They are also
keystone species in transition of threshold controlled by abiotic limitations. In the first
four stages, abiotic filters determined the fate of vegetation restoration and the species
composition was very simple, the vegetation cover was low, and thus the competition
was weak. However, as succession progressed, the substrate was improved, more
species emerged and plant cover increased, therefore, competition became stronger.
For example, in late succession, many species were shaded out and the total species
richness declined. In general, the importance of biotic filters increases along with
succession.
There are also five different kinds of plantations in the study site, which are of 23
years old. The understory vegetation was compared with 23 years natural restoration..
Most heliophytes such as Rhodomyrtus tomentosa, Baeckea frutescens were scanty
under all plantations. However, shade-tolerant species such as Psychotria rubra and
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Circaea mollis became most important components of understory community. This
indicated the importance of light in late succession. When forest canopy closed,
understory vegetation would shift from heliophilous to mesophytes and shade-tolerant
species. A common observation in both plantations and grassland was that few native
tree saplings were established.. The comparison of microclimate, soil mineral, and
soil structure with native forest showed that these environmental factors may be less
important because native saplings could survive in native forests with harsh
environments (Peng 2003). However, seed sources and seed dispersal may be the
most important biotic factors in late succession. Few seeds of native species were
found during our vegetation and seed bank survey. In general, the species have large
numbers of small seeds at the early stages and most of these seeds can be dispersed by
wind in great distances with little dispersal barrier. Nevertheless, most of the native
tree species such as Castanopsis chinensis, Cryptocarya chinensis, Aporosa
yunnanesis, and Castanopsis fissa had larger seeds and only appeared in late stages.
If the distance between the native forests and degraded land is far, seed dispersal of
heavy seeds is more difficult. Dispersal barrier may be the most important biotic filter
in the late succession stages.
It is always difficult to comprehensively analyze many environmental factors in a
single study. Here we identified and analyzed 13 environmental factors and concluded
that pH, SBD and soil moisture were the most important environmental factors in
vegetation restoration in the studies area. However, soil organic matter and nitrogen
were considered to be the dominant environment factors in many previous studies.
This could be mainly due to the mineralization of nitrogen, and the decomposition of
organic matter was comparatively faster at our study sites. In addition, some essential
minerals were swept away by surface runoff due to heavy rainfall in the region.
Consequently, the nitrogen and organic matter content were similar in the first 4
stages and could not be the limiting factors. However, the soils of our study sites are
acidic and the availability of P, K, Ca, and Mg were closely correlated with pH.
Therefore, soil acidity could be a determinant of vegetation succession. Although the
laterite soil has strong capillary attraction and is difficult for rain water to infiltrate,
10
the evaporation is high and precipitation varies greatly in different seasons. Thus, soil
moisture is also an important factor affecting vegetation succession. It is noteworthy
to point out, however, that these observations may only be the case in early succession
stages and the situation may be different in later succession stages.
The community assembly models
There are three models of community assembly, i.e., deterministic, stochastic,
and alternative stable states (ASS). Most ecologists tend to agree that the ASS model
of species assembly is likely to be the one that better reflects reality in nature
(Temperton et al., 2004). ASS asserts that communities are structured and restricted to
a certain extent but can be developed into numerous states because an element of
randomness can be inherent in all ecosystems (Sutherland, 1974; Gleick, 1987). In our
study, the vegetation succession did not follow one fixed pathway; instead, it was
diverted into two parallel directions during early stages and then incorporated in the
late stages. This conclusion is different from early studies of spontaneous succession
(Bornkamm 2006; Karlo 2006; Calvo 2005; Scholes 1997) but seems to support the
ASS theory.
Many factors can result in the formation of different communities and the
succession pathways. Soil seed banks vary greatly across space partly due to their
different distances to seed sources; therefore, seed dispersers can affect the
colonization of certain species. Consequently, the sequences of species settlement can
be quite different. For example, early settled species always affect the colonization of
latter species. In addition, different environmental conditions gave rise to different
communities in sites with identical species pools, as clearly illustrated at stage IV
(Figures 4-7). At this stage, some plots with better soil structure and high N content
were mainly occupied by Dicranopteris linearis. The coverage was relatively high.
However, in some plots with relative poorer soil structure and nutrient condition,
some pioneer species such as Miscanthus sinensis were abundant.
Conclusions
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Our results clearly show that, in order to accelerate the restoration process, some
immediate new strategies need to be planned and adopted.. On the one hand, a more
flexible restoration plan should be in place. The climax communities may be different
because vegetation succession and ecological restoration are determined by somewhat
different and uncertain factors. Moreover, because of the effect of microtopography,
microclimate, and substrates, vegetation succession may be diverted into different
trajectories and various patterns can be observed in the same succession stage.
Therefore, to establish various self-sustaining ecosystem with abundant species and
integrated function should be our goal of restoration. On the other hand, different
steps should be taken to accelerate the transition of threshold at different restoration
stages. The first step is to reduce water loss and soil erosion as soil erosion is one of
the most serious problems in South China. We will then need to enhance soil pH and
improve soil structure. In late stages of restoration, increasing seed supply may be
helpful to facilitate seed dispersal and sapling establishment (Guo, 2007).
Methods
Study Site
The study was conducted at Heshan Hilly Land Interdisciplinary Experimental
Station (112 °54' E, 22 °41' N) located in Heshan County, Guangdong, China. The
station was established in 1984 and it is located in a degraded costal ecosystem in the
central Guangdong with a typical climate of subtropical monsoon. Its elevation varies
from 0 to 90 m. The soil is laterite, a type of heavy acid soil with little soil organic
matter (about 18.03 g/kg), N (total N is about 0.86g/kg) and available P (1.33mg/kg).
The mean annual temperature is 21.7 ℃, the mean rainfall is 1,700 mm, and the
mean evaporation is 1,600 mm. The region is a hilly agricultural zone with 78.6% of
hilly land, 17.1% of farming land, and 4.3% of water body. The vegetation is
evergreen broad-leaved forest of typical subtropics. The representative species of
climax community are Cryptocarya concinna and Cryptocarya chinensis. Due to
human disturbances, much of the current vegetation is degraded into hilly land
grassland.
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Field and Laboratory Methodology
To study the composition and structure of various plant communities, quadrat
samples were set up at different succession stages. Quadrats of 20×20, 5×5, and 1×
1 m were used for investigating the vegetation of arbor, shrub and grass species,
respectively. Three small quadrats for grassland or shrub land were nested in the large
ones for shrub land and tree land. In each quadrat, the height, density and basal
diameter of various arbor and shrub species, as well as the height and coverage of
different grass species were recorded. In order to get accurate coverage of grasses, 1
×1m frame with small pane (5×5 cm) was used. The cover of grasses was
determined by counting the number of pane covered by grasses. A total of 41 plots at
different succession stages were established and investigated.
Soil samples were randomly collected from 5 points in each quadrat using a 5 cm
diameter soil corer to a depth of 20 cm after removing surface litter. A composite soil
sample of about 1 kg from each point was collected, air-dried and sieved for analysis
of soil chemical characteristics (Institute of soil science, CAS 1978; Liu 1996). To
measure the soil physical characteristics, 9 intact soil cores were taken randomly in
each quadrat using ring knifes after removing the litter and humus layer, and 3 of
them were used to determine the soil bulk density, soil saturate moisture, and soil
capillary moisture, respectively.
Data analysis
A total of 60 species were recorded in the 41 plots (Table 1). The species
importance values (IV) in each sample were calculated using the following formula:
IV tree and shrub= (Relative density + Relative frequency + Relative dominance)/3
IV herb= (Relative coverage + Relative height)/2
Frequency refers to the percentage of the quadrat containing a tree species over the
total quadrat number at the same succession stage and stands. Dominance value refers
to the sum of the basal areas of a tree or shrub species within a quadrat. We developed
13
a matrix of IVs of 60 species × 41 Plots and used it as the basis of the succession
analysis. First, we used Two-way Indicator-Species Analysis (TWINSPAN; Hill 1979)
to classify the succession stages of the communities. Second, we analyzed the
relationships between the succession stages by De-trended Correspondence Analysis
(DCA; Hill & Gauch 1980). Finally, the relationships between vegetation and
environmental factors were analyzed using Canonical Correspondence Analysis (CCA;
Braak 1986).
Acknowledgements
This research was funded by National Natural Science Foundation of China (No.
30200035) and Field Station Project of the Chinese Academy of Sciences (CAS) to
Heshan Interdisciplinary Field Station, CAS. The authors are indebted to Dr Zhian Li,
Jingping Zhang and Zuoyun Yin for helpful suggestions. The authors thank Bi Zou for
soil analysis, Fuwu Xing for plant species identification, and Yongbiao Lin for field
assistance.
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Figure legends
Figure1. The restoration model of plant communities in degraded lowland in South
China
Figure2. DCA ordination of the 60 species at six successional stages. The S + Arabic
numbers and P + Arabic numbers represent species and quadrats, respectively.
Figure3. DCA ordination of the 41 quadrats in 6 succession stages based on species
composition
Figure 4. DCA ordination of the 41 quadrats in 6 successional stages based on their
environment conditions
Figure 5. Changes of species number in different life forms during the six
successional stages
Figure 6. Changes of species composition during the six successional stages
Figure 7. Changes of dominant environmental factors along the six successional
stages pH,(×10); SOM, soil organic matter (×10g/kg); SBD, soil bulk density
(g/cm3); SSM, soil saturation moisture (×100%); SCM, soil capillary moisture(×
100%); N, hydrolyzed nitrogen (×103mg/kg); P, available phosphorus (mg/kg); K,
exchanged kalium (×102mg/kg)
Figure 8. The CCA ordination diagram of the 60 species and 13 environmental factors
from 41 quadrats
18
Table 1.The species and codes recorded in sampling quadrats
Code
S1
S2
S3
S4
S5
S6
S7
S8
S9
S10
S11
S12
S13
S14
S15
S16
S17
S18
S19
S20
S21
S22
S23
S24
S25
S26
S27
S28
S29
S30
Name
Dicranopteris linearis
Cynodon dactylon
Imperata cylindrica
Circaea mollis
Polygonum chiensis
Melastoma dodecandrum
Miscanthus.sinensis
Blechnum orientale
Rubus alceaefolius
Paederia scandens
Mussaenda pubescens
Ischaemum indicum
Lycopodium cernuum
Schizoloma heterophyllum
Adiantum capillus-veneris
Adiantum flabellulatum
Lophatherum gracile
Dianella ensifolia
Dianella ensifolia
Neyraudia neyraudiana
Fimbristylis dichotoma
Abrus precatorius
Desmodium triflorum
Eupatorium catarium
Panicum repens
Urena lobata
Murdannia triquetra
Desmodium heterocarpon
Hedyotis diffusa
Cassytha filiformis
Code
S31
S32
S33
S34
S35
S36
S37
S38
S39
S40
S41
S42
S43
S44
S45
S46
S47
S48
S49
S50
S51
S52
S53
S54
S55
S56
S57
S58
S59
S60
19
Name
Smilax china
Embelia laeta
Microlepia hancei
Lygodium japonicum
Clerodendron fortunatum
Psychotria rubra
Eurya chinensis
Melastoma candidum
Wikstroemia indica
Rhaphiolepis indica
Ficus hirta
Glochidion eriocarpum
Panax stipuleanatus
Mallotus apelta
Litsea cubeba
Litsea rotundifolia
Gardenia sootepensis
Rhodomyrtus tomentosa
Baeckea frutescens
Evodia lepta
Litsea gluinosa
Trema cannabina
Schefflera octophylla
Ilex asprella
Pinus massoniana
Breynia fruticosa
Mimosa sepiaria
Setaria viridis
Pseudosasa hindsii
Ficus variolosa
II-I
III-I
IV-I
Stage
V
Stage I
Stage II
Stage III
Stage IV
IV-II
II-II
Stage VI
III-II
Figure1. The restoration model of plant communities in degraded lowland in South
China
Figure2. DCA ordination of the 60 species at six successional stages. The S + Arabic
numbers and P + Arabic numbers represent species and quadrats, respectively.
20
Figure3. DCA ordination of the 41 quadrats in 6 succession stages based on species
composition
21
Figure 4. DCA ordination of the 41 quadrats in 6 successional stages based on their
environment conditions
herbs
shrubs
trees
lianes
total number of species
25
15
10
5
succession stages
22
VI
V
IV
-I
I
IV
-I
II
III
II
II
II
-I
I
II
-I
0
I
number of species
20
Figure 5. Changes of species number in different life forms during the six
successional stages
drought-resisted species
heliophytes
leanness-resisted species
110
100
90
%
80
70
60
50
40
30
I
II-I
II-II
III-I
III-II
IV-I
IV-II
V
VI
succession stages
Figure 6. Changes of species composition during the six successional stages
2.5
pH
SOM
SBD
SSM
SCM
N
P
K
2
1.5
1
0.5
VI
V
IV
-I
IV
-I
I
II
II
II
III
II
-I
II
-I
I
I
0
succession stages
Figure 7. Changes of dominant environmental factors along the six successional
stages pH,(×10); SOM, soil organic matter (×10g/kg); SBD, soil bulk density
(g/cm3); SSM, soil saturation moisture (×100%); SCM, soil capillary moisture(×
100%); N, hydrolyzed nitrogen (×103mg/kg); P, available phosphorus (mg/kg); K,
exchanged kalium (×102mg/kg)
23
Axis 2
2.0
s36
s14
s57
s40
s4
s50
s25
s29
s60
s17
s46
s43
s59
s28
1.0
s16
s27
s37
s56
s47
s13
s3
Na
SLO
s2
s23
KASP
s60
s10
N
SSM
s12
s26
P
s24
-2.0
s15
Mg
Axis 1
s35
Ca
-3.0
SCM
s1
ORG
0.0
s48
s20
-1.0
0.0
s38
s11
s39
s42
1.0
s58
s18s5
s6
SBD
s34
PH
s9
s8
s21
s41
s32
s54
s49
s45
s7
-1.0
s33
s44
s55
s51 s31s61
s30
s19
s22
-2.0
Figure 8. The CCA ordination diagram of the 60 species and 13 environmental
factors from 41 quadrats
24