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Table of Content
    Volume 30 Issue 5
    30 September 2006
      
    Research Articles
    VEGETATION DYNAMICS IN THE DRY VALLEYS OF YUNNAN,CHINA, DURING THE LAST 150 YEARS: IMPLICATIONS FOR ECOLOGICAL RESTORATION
    MOSELEY Robert K, TANG Ya
    Chin J Plan Ecolo. 2006, 30 (5):  713-722.  doi:10.17521/cjpe.2006.0093
    Abstract ( 2182 )   PDF (442KB) ( 729 )   Save
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    In southwestern China, there are many opinions about past environmental conditions and the historical drivers of change, but little direct evidence. Such is the case in Dry Valley ecosystems, where current conservation programs appear to be based more on subjective perceptions than scientific understanding. Our research objective was to develop an historical profile— the description and explanation of environmental change —for the Dry Valleys to see if today’s perceptions about past change are supported by data. Our study area encompassed n orthwestern Yunnan and adjacent Sichuan and Tibet. Specifically, we assessed vegetation dynamics by comparing historical records from 1868-1949 to conditions in 2001-2005. We used two sources to establish baseline conditions from which to assess change: 28 historical publications and 56 old photographs for which we rephotographed the modern scene. Our major finding is that there has been no substantial change in the cover of Dry Valley vegetation during the last 150 years. We also found that the aerial coverage of crop fields has decreased and major land slide activity was caused by chronic geological instability and infrastructure development. Overall, we found that comparisons of written and photographic records between 1868 and 2005 do not support many common assumptions regarding environmental degradation in the Dry Valleys, upon which current ecological restoration programs are based.

    COMPARISON OF RAINFALL REDISTRIBUTION IN TWO ECOSYSTEMS IN MINJIANG UPPER CATCHMENTS, CHINA
    LI Zhen-Xin, OUYANG Zhi-Yun, ZHENG Hua, LIU Xing-Liang, SU Yi-Ming
    Chin J Plan Ecolo. 2006, 30 (5):  723-731.  doi:10.17521/cjpe.2006.0094
    Abstract ( 2068 )   PDF (321KB) ( 949 )   Save
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    Background and Aims Ecosystems in western Sichuan Province are diverse, and their hydrological functions are important to the ecological stability of the upper drainages of the Yangtse River. It is important to study rainfall redistribution by vegetation in this area to understand the hydrological functions of ecosystems. We studied Abies faxonianaconifer forest and Quercus aquifolioides shrubland in the Dengsheng subalpine dark coniferous forests positioning research station in the upper catchments of Minjiang River, Sichuan. Our objectives were to: 1) determine the magnitude of canopy layer interception, stem flow and water holding capability of ground litter and soil and 2) analyze factors that influence rainfall interception.
    Methods We studied rainfall redistribution in the ecosystems from July to September, 2001 and June to August, 2002. We measured total rainfall with one standard and two automatic rain gages, throughfall with eight randomly placed barrel gages (30 cm diameter and 40 cm height) in the forest ecosystem and four in the shrub ecosystem, stem flow of trees in the forest ecosystem but not in the shrub ecosystem, and microclimate in both ecosystems and on open ground outside of the forest. Pearson correlation and partial correlation methods were used to analyze five factors influencing rainfall interception: rainfall volume, rainfall intensi ty, duration of single rainfall events, time interval between consecutive rainfa ll events and average air temperature during individual rainfall events. 
    Key Results In the forest ecosystem, canopy rainfall interception accou nted for 33.33% of the total rainfall, stem flow 0.07% and throughfall 66.60%. For the shrubland ecosystem, rainfall interception accounted for 24.95% and throughfall 75.05%. Water holding capability was larger for conifer forest ground litter including lichens (1.746 mm) than for shrubland ground litter (0.941 mm). Bulk moist ure content was larger for conifer forest (39.66%) than shrubland (38.19%). The relationship between throughfall percentage and rainfall could be modeled with a logistic equation.
    Conclusions Interception in the conifer forest was mainly affected by rainfall volume, duration of rainfall and time interval time between consecutive rainfall events. For the shrubland, interception was mainly affected by rainfall volume, duration of rainfall and temperature. Differences between rainfall redistribution and factors affecting rainfall interception are analyzed and discussed in relation to local rainfall characteristics and microclimate differences between the two ecosystems.

    STUDY OF SOIL PREFERENTIAL FLOW IN THE DARK CONIFEROUS FOREST OF GONGGA MOUNTAIN, CHINA
    NIU Jian-Zhi, YU Xin-Xiao, ZHAO Yu-Tao, ZHANG Dong-Sheng, CHEN Li-Hua, ZHANG Zhi-Qiang
    Chin J Plan Ecolo. 2006, 30 (5):  732-742.  doi:10.17521/cjpe.2006.0095
    Abstract ( 2279 )   PDF (450KB) ( 969 )   Save
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    Background and Aims Preferential flow is the physical phenomenon of rapid transport of water and solutes in soil. It occurs in most soils and determines field_ scale transport of contaminants in soils, thereby contributing to groundwater pollution.
    Methods Research on preferential flow involves studying the mechanism of soil water movement and can answer key questions that could not be explained by Darcy’s law and Convective_Diffusive Equation in early hydrological research. Experimental or technological analyses are difficult because this movement is not detected easily. Preferential flow increases the difficulty and complexity of there search due to non_equilibrium, regional characteristics and the involvement of many influencing factors. To date, the mechanism of the movement of preferential flow has not been properly defined. This study involved
    detailed research on the influencing factors of preferential flow, using a soil column experiment in combination with dye_tracer analyzes in the root zone of the dark coniferous ecosystem in the upper drainage of the Yangtze River. Factors examined included rainfall processes, growth characteristics and water movement states of litter, moss, roots and soil. 
    Key Results The soil of the research area is porous with large pores, and rainfall is low in amount and intensity and long_lasting. The soil also has thick litter and moss and is rich in roots. Therefore, the Gongga Mountain ecosystem may have preferential flow. Water transport has opened up preferential flow pathways along soil pores and root channels, forming a water channel in litter, moss and soil. 
    Conclusions Soil will be transported continuously along these channels with longtime rainfall.

    STUDY OF DOMINANT PLANT POPULATIONS AND THEIR SPATIAL PATTERNS IN EVERGREEN BROADLEAVED FOREST IN TIANMU MOUNTAIN, CHINA
    TANG Meng-Ping, ZHOU Guo-Mo, SHI Yong-Jun, CHEN Yong-Gang, WU Ya-Qi, ZHAO Min-Shui
    Chin J Plan Ecolo. 2006, 30 (5):  743-752.  doi:10.17521/cjpe.2006.0096
    Abstract ( 3060 )   PDF (469KB) ( 1529 )   Save
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    Background and Aims Evergreen broadleaved forest is an important vegetation type in Tianmu Mountain National Nature Reserve of Tianmu Mountain, Zhejiang Province. Study of dominant plant populations and their spatial patterns can reveal the roles of these populations and provide a theoretical basis for forest protection and restoration. 
    Methods A typical plot of 100 m×100 m was surveyed and dominance index analysis was applied to determine dominant plant populations. Ripley’s K(d) function was applied to diagnose spatial patterns and spatial associations between species pairs.
    Key Results The number of dominant tree species increases with size class, but the degree of aggregation decreases. The evergreen shrub Camellia fraterna dominates seedling and small tree size class. Cyclobalanopsis gracilis, Cyclobalanopsis glauca and Lithocarpus brevicaudatus dominate mid_ and large_tree classes and have structural characteristics of multi_dominant tree species. Camellia fraterna, Cyclobalanopsis gracilis and Cyclobalanopsis glauca have stable and significant aggregated spatial patterns. Spatial patterns of Litsea coreana var.sinensis and Lithocarpus brevicaudatus vary greatly. In general, the five dominant populations have aggregated distributions. Camellia fraterna and Cyclobalanopsis gracilis or Lithocarpus brevicaudatus or Litsea coreana var.sinensis, Cyclobalanopsis gracilis and Lithocarpus brevicaudatus, and Cyclobalan opsis glauca and Litsea coreana var. sinensis, are significantly spatially independent of each other. Cyclobalanopsis glauca and Lithocarpus brevicaudatus are negatively associated with each other, so are Cyclobalanopsis gracilis and Cyclobalanopsis glauca. The association between species pairs is transferable, in that the association of the third species pairs can be deduced from the known association of two species pairs in three species; the more significant the association of species pairs and the wider the distance scale, the more stable the transference is. 
    Conclusions The dominant evergreen broadleaved tree species in Tianmu Mountain National Nature Reserve are significantly aggregated, and most are strongly associated.

    STUDY ON COHORT STRUCTURE OF BETULA PLATYPHYLLA POPULATION IN VIRGIN FOREST, NORTHERN REGION OF DAXING’ANLING MOUNTAINS, CHINA
    QIU Yang, LI Zhan-Dong, ZHANG Yu-Jun, XU Hua-Cheng, YU Ru-Yuan, ZHANG Xi-Lai
    Chin J Plan Ecolo. 2006, 30 (5):  753-762.  doi:10.17521/cjpe.2006.0097
    Abstract ( 2247 )   PDF (345KB) ( 756 )   Save
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    Background and Aims Natural fire is a frequent driving force of communities and populations. However, the cohort structure of Betula platyphylla in the virgin forest of the northern region of Daxing’anling Mountains, China, has rarely been studied. The aim of this paper is to explore the abundance, type and spatial distribution of the cohort structure of B. platyphylla, based on the number of cohorts, the fire regime and their relationship to site factors. 
    Methods We used an integrative approach to statistically analyze natural fired isturbance and population structure of B. platyphylla. Data on fire disturbance and population structure were collected from 96 plots distributed throughout the landscape. Fire history at the landscape scale was reconstructed based on tree regeneration and fire scars. Population cohort structure was recognized based on the number and regeneration type of cohorts identified.
    Key Results Cohort structure based on the number of cohorts is diverse, consisting of one through five cohort groups with a patch_mosaic distribution in the landscape. The maintype, i.e., groups with one and two cohorts are aggregated in space, while the others have a heterogeneous distribution. The number of cohorts is influenced by fire frequency, fire severity and their interaction, but the effect of fire frequency is greatest. Fires of low frequency or high severity increase the number of population cohorts, while fires of high frequency or low severity decrease the number of cohorts. In addition, the number of cohorts
    differs by forest type, with the number of cohorts decreasing from the forest type near streams to the type with Alnus mandshurica to the type with Ledum palustre. Cohort structure based on regeneration type is also diverse, with three groups, five sub_groups and 11 types distributed in patch_mosaic. The main sub_types, i.e., post_fire cohort dominance and pre_fire cohort inferiority and regeneration cohort dominance and pre_fire cohort inferiority, are distributed aggregately, while the others are spatially heterogeneous.
    Cohort structure is strongly affected by fire frequency, fire severity and their interaction. With increa sing of frequency and decreasing of severity, the relative importance of both the regeneration cohort and the pre_fire cohort increases while that of the post_fire cohort decreases. The sub_group of post_fire cohort dominance and pre_fire cohort inferiority occurs on sites with mid_ and high_severity fires, while the sub_ group of regeneration cohort dominance and pre_fire cohort inferiority occurs on sites with low_severity fires. Both the group and the sub_group of cohort structure change with different types of sites. The cohort structure type is the same for sub_group of post_fire cohort dominance and pre_fire cohort inferiority on all sites, although there is significant
    difference in the relative importance of the dominance cohorts (i.e., post_fire and regeneration cohorts) among different types of sites. The sub_group of post_fire cohort dominance and pre_fire cohor t inferiority is found on sites toward the east, while the sub_group of regeneration cohort dominance and pre_fire cohort!inferiority is on sites toward the west and north. The group of post_fire cohort is located on forest compartment 224, while the group of regeneration cohort dominates on forest compartment 218.
    Conclusions This study suggests that the cohort structure ofB. platyphylla is highly diverse, with several dominant types of cohorts. B. platyphylla is weak in resistance to natural fires, but can maintain its role in the landscape after fire by strong resilience.

    A MULTIVARIATE ANALYSIS OF NETPHYTOPLANKTON ASSEMBLAGES IN THE CHUKCHI SEA AND BERING SEA
    YANG Qing-Liang, LIN Geng-Ming
    Chin J Plan Ecolo. 2006, 30 (5):  763-770.  doi:10.17521/cjpe.2006.0098
    Abstract ( 2305 )   PDF (341KB) ( 1217 )   Save
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    Background and Aims The phytoplankton in the Arctic seas is rarely explored on a large geographic scale, particularly at the community level.The diversity, density and distribution variability of netphytoplankton assemblages were measured at 49 stations in the Chukchi Sea (66°0.3´-75°18.6´ N, 153°36.5´-174°59.5´ W) and Bering Sea (55°59.8´-66° 0.3´ N, 173°21.1´-175°53.9´ W) during the FCNARE (1999) cruise on the Xuelong Research Vessel of SOA, China.  Methods The diversity indices combining the data on the abundance within a species in a community into a single number were adopted to understand the state of the community. Principal component analysis (PCA) of data was applied for examing the distribution variability of netphytoplankton. Cluster analysis was used as indicative of the degree of similarity in species composition among stations to the selected species having a frequency of occurrence greater than 10% of the total samples.
    Key Results Both the mean index values of phytoplankton diversity and evenness were approximately equally low at the two study areas, ranging from 1.88 to 1 .90 and from 0.43 to 0.45, respectively. However,both the average cell density and total species numbers in the Chukchi Sea were far greater than these in the Bering Sea, reaching 9 122.56×104 cells•m-3 and 103 taxa in the Chukchi Sea but only 161.78×104 cells•m-3 and 71 taxa in the Bering Sea. The results of PCA indicated that the first two components (the most important species variables) explained 33.0% of the total variance in the netphytoplankton distribution in the study areas. The main populations belong to the arctic_boreal community (pan_arctic community) and boreal oceanic community, including some centric diatoms in the arctic_ boreal community, such as Chaetoceros curvisetus, C.debilis, C.socialis, C.furcellatus etc. belonging to the Chaetoceros_Oligochromatophorus group, and Lauderia glacialis, Leptocylindrus danicus, Thalassiosira nordenskioldii and Bacteriosira fragilis
    etc., as well as Corethron criophilum, Proboscia truncata, P. inermis, Dentecula seminaeandsomeand some species belonging to Chaetoceros_Phaeoceros_Polychromatophorus group such as Chaetoceros atla nticus etc. in the boreal oceanic community. Seven major netphytoplankton regions containing different phytoplankton communities in two study areas were distinguished by the cluster analysis. However, the extremely dynamic physical nature of the drifting packice (e.g. packing, breaking up and melting) introduce short_term variability into the water conditions that no doubt affect the species composition; hence, the groupings of the netphytoplankton in the different regions may reflect temporal conditions, particularly in the Chukchi Sea, that require repeated sampling in order to better classify the regions.
    Conclusions There were strong differences in the density and taxa of the netphytoplankton between the Chukchi Sea and Bering Sea. The density and composition were highly variable among sampling sites, particularly in Chukchi Sea.

    THE ESTIMATE OF FINE ROOT BIOMASS IN UPPER SOIL LAYER OF LARIX OLGENSIS PLANTATION BY GEOSTATISTICS METHOD
    SUN Zhi-Hu, MU Chang-Cheng, SUN Long
    Chin J Plan Ecolo. 2006, 30 (5):  771-779.  doi:10.17521/cjpe.2006.0099
    Abstract ( 2464 )   PDF (395KB) ( 1187 )   Save
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    Background and Aims Drilling soil core, simply averaging the surveying values and ignoring the information of sampling point locations are in common use in estimating the fine root biomass of forest. Owing to the significant heterogeneity of fine root distribution, using the method above may be not proper. The Larix olgensis stand was chosen for a case study. Answer to the following question was sought: is the fine root biomass estimated by combining the coordinates of sampling points.
    Methods Semivariance analysis of Geostatistics was used to quantify the spatial heterogeneity of fine root (<2 mm) biomass in upper layer of soil (0-10 cm) in Larix olgensis stand (14-40 year). Fine root biomass was estimated with kriging interpolation of Geostatistics and definite integral. 
    Key Results The semivariograms of fine roots in all six Larix olgensis stands were best described by spherical model. The spatial variability of fine root in all six Larix olgensis stands was mainly caused by structural factors with spatial structural ratio >25 %. The scales of spatial heterogeneity of fine roots (1. 76-5.58 m) showed a positive linear correlation (p=0.074 4) with stand age (14-40 year). The sign_test of nonparametric statistics of paired samples showed that the kriging interpolation, based on the results of semivariance analysis, could be used to estimate the fine root biomass in Larix olgensis stands. The relationship between the estimated fine root biomass and the values of its corresponding coordinates was best fitted by bivariate order 10 cosine series polynomial. Based on the result of definite integral to those polynomials (integral range was limited to plot size), total fine root biomass of the 14_year, 19_year, 22_year, 26_year, 32_year, 40_year_old stands was 1.097 3, 1.434 0, 1.185 4, 0.974 3 , 1. 682 6, 1.255 6 Mg•hm-2, respectively. No differences (α=0.037 3 ) were found in the fine root biomass in upper soil layer of Larix olgensis stands with difference stand ages. The estimated of fine root mass of individual stems increased exponentially with stand age (α=0.002).
    Conclusions Kriging interpolation method of Geostatistics, combined with multiple regression and definite integral, provide a new optimal alternative for the estimation of fine root biomass in Larix olgensis stands.

    ECO_PROCESS OF LEAF LITTER DECOMPOSITION IN TROPICAL RAIN FOREST IN XISHUANGBANNA, CHINA. I. DECOMPOSITION DYNAMIC OF MIXED LEAF LITTERS
    ZHANG Rui-Qing, SUN Zhen-Jun, WANG Chong, GE Yuan, LI Yun-Le, QIAO Yu-Hui, PANG Jun-Zhu, ZHANG Lu-Da
    Chin J Plan Ecolo. 2006, 30 (5):  780-790.  doi:10.17521/cjpe.2006.0100
    Abstract ( 2680 )   PDF (505KB) ( 1161 )   Save
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    Background and Aims Decomposition of mixed leaf litters in Xishuang banna tropic rainforest was studied both in the field and laboratory. Negative exponential model xt=xoexp(-kt) and binomial exponential model xt=a×exp(-k1t)+b×exp(-k2t) were used to simulate the observed decomposition process with. Bio_models were introduced to analysis the contribution of biotic and abiotic factors to the decay rates of leaf litters.
    Methods Coarse (with mesh size of 1 mm) and fine (with mesh size of 100 μm) lit terbags were used in the field to examine the effects of different components of soil fauna on litter decomposition by restricting access by most soil macrofauna and mites, respectively, i.e. feasible for most mites to coarse mesh and nematodes to fine mesh. In the laboratory, sterilization and inoculation were adopted to investigate the effects of nematodes and microbiota on leaf litters.
    Key Results The decomposition process was a course fast incipiently then slowdown with stagnation periods.The decay rate of mixed leaf litters fluctuated over the decomposing period with the magnitude of fluctuation positively related to complexity of food_web. The binomial exponential model simulated the two different courses of leaf litter decomposition whereas the negative exponential model did not simulate the initial stage well and overestimated the long_term decay process. Soil fauna accounted for 78.1% of the decay rates while abiotic factors for 14.1% and microorganisms only for 7.8%. 
    Conclusions This study suggests that the decomposition of leaf litters was a cascade process and binomial exponential model can describe the process better than the negative exponential model. Soil fauna played a dominating role in litter decomposition in tropic rainforest.

    SOIL FAUNA AND LEAF LITTER DECOMPOSITION IN TROPICAL RAIN FOREST IN XISHUANGBANNA, SW CHINA: EFFECTS OF MESH SIZE OF LITTERBAGS
    YANG Xiao-Dong, ZOU Xiao-Ming
    Chin J Plan Ecolo. 2006, 30 (5):  791-801.  doi:10.17521/cjpe.2006.0101
    Abstract ( 2603 )   PDF (500KB) ( 1253 )   Save
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    Background and Aims The influence of soil fauna on litter decomposition is rarely explored in tropical rain forest. This study examined the effect of soil fauna on the decomposition of mixed substrate by litter bag technical at two tropical seasonal rain forest plots in Xishuangbanna, SW China in year of 2000. The following questions were considered in the present study: 1) What roles do soil fauna play in regulating litter mass loss and decomposition rate? 2) How do soil fauna influence litter nutrient release? Methods In order to examine the role of soil macro_mesofauna in mass loss and nutrient release of litter, litter bags with both fine mesh size (0.15 mm) that excludes the soil macro_mesofauna population from litter and coarse mesh size (2 mm) that allows soil fauna access to litter were used in this experiment. Mass loss and C, N, P, S, K, Ca, and Mg concentrations of leaf litter were determined from the litter in two different mesh size litterbags at monthly intervals. The soil fauna were extracted by hand and by heating the samples. 
    Key Results Higher relative density and taxonomic diversity of total soil fauna were found in the bags with 2 mm mesh size (22.3-21.77 individuals and 2.67- 2.83 orders per g of dry litter) compared to the bags with 0.15 mm mesh size ( 2.88-2.77 individuals and 0.27-0.28 orders per g of dry litter). Collembola and Acari were the most abundant group, and Hymenoptera(ant), Coleoptera, Hemiptera, Diptera, Diplopoda, Isopoda, Araneae, Pseudoscorpiones were common groups of soil fauna in litter bags with 2 mm mesh size. There were very few individuals of Collembola and Acari in the 0.15 mm litter bags. Our results suggested that soil macro_mesofauna contributed more to the decomposition of leaf litter in 2 mm litter bags than that in 0.15 mm litter bags. The higher mass loss rate (aroun d 71%), decomposition rate (k=1.88-2.44), and nutrient release in litter ba gs with 2 mm mesh size than in litter bags with 0.15 mm mesh size (34%-35%, k=0.48-0.58) indicated a significant influence of soil macro_mesofauna on mass loss and nutrient release in tropical seasonal rain forest. The release rates of N, S and Ca that could be attributable to the soil macro_mesofauna were higher than other elements whereas K release rate that could be attributable to the soil macro_mesofauna was the lowest. Soil macro_mesofauna caused greater decreases in C/N and C/P ratios in litter bags with 2 mm mesh size than litter bags with 0.1 5 mm mesh size. There were negative relationships of the percentage of litter mass remaining with order richness and individuals abundance of soil fauna. However, a positive relationship between Shannon_Wiener index of soil fauna and the decomposition rate was found. 
    Conclusions This study suggests that the presence of soil fauna accelerated plant litter decomposition in the tropical seasonal rain forest. The litter mass loss attributable to the soil macro_mesofauna was about 46%. The effects of soil macro_mesofauna on the nutrient release rates were different among elements. The diversity of soil fauna may have important ecosystem consequences, particularly in tropical rain forest.

    SOIL ENZYME ACTIVITIES IN DIFFERENT PLANTATIONS IN LOWLANDS OF THE YELLOW RIVER DELTA, CHINA
    LI Chuan-Rong, XU Jing-Wei, SONG Hai-Yan, LI Chun-Yan, ZHENG Li, WANG Wei-Dong, WANG Yue-Hai
    Chin J Plan Ecolo. 2006, 30 (5):  802-809.  doi:10.17521/cjpe.2006.0102
    Abstract ( 2230 )   PDF (299KB) ( 1370 )   Save
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    Background and Aims More attention is being paid to utilization of the ecological resources in the lowlands of the Yellow River Delta. However, most proposed measures emphasize breeding, irrigation and cultivation. Soil enzymes play an important role in soil biochemical processes, such as litter decomposition, nutrient fixation and nutrient release. Insufficient attention has been paid to the relatio nships among soil enzymes, soil microbes and soil physical_chemical quality, yet such study can indicate the dynamic process of soil nutrients and soil health. Our objectives were to determine: 1) the distribution of soil enzymes of different plantations at different soil depths, 2) the correlations among microbes, soil nutrients and soil physical and chemical characteristics and 3) soil enzymes that are key factors in maintaining soil fertility.
    Methods We analyzed soil enzymes, soil chemical characteristics and soil microbes for six kinds of plantations (Tamarix chinensis, Salix matsudana, Robinia pseudoacacia, Fraxinus chinensis, Ziziphus jujube and Morus alba) in Kenli County, Dongying, Shandong Province. Soil samples were collected at 0-20 cm and 20-50 cm depths. Established methods were used to analyze soil enzymes and soil physical and chemical characteristics. Analysis was done using an integrative method combining correlation and component analyses in SPSS. 
    Key Results Soil urease and soil peroxidase decrease with increasing soil depth.There are positive relationships between soil peroxidase and soil urease, and soil peroxidase and soil polyphenol oxidase, while there is negative correlation between soil urease and soil polyphenol oxidase. The kind of plant ation clearly affects soil urease and soil polyphenol oxidase, but not soil catalase and soil peroxidase. Soil urease activity of different plantations is higher than that of the Tamarix chinensis forest; the soil polyphenol oxidase activity is lower than that of the Tamarix chinensis forest, except for the Robinia pseudoacacia forest. There are close correlations among soil enzymes and soil nutrients, and few correlations with pH values and soil microbes. Among them, soil urease shows positive relationships with total N, organic C and available C. Soil polyphenol oxidase shows a positive relationship with available K and negativer elationships with soil catalase, total N, available P, organic C, peroxidase and soil urease. 
    Conclusions This study suggests that plantation type affects soil enzyme activities. The activities of soil urease and soil polyphenol oxidase can be regarded as indexes to assess soil quality in the lowlands.

    A STUDY ON VEGETATIVE COMPENSATORY GROWTH OF SHRUB, CARAGANA KORSHINSKII, UNDER DIFFERENT CLIPPING TREATMENTS IN DISTURBANCE ENVIRONMENT
    FANG Xiang-Wen, WANG Wan-Peng, HE Xiao-Qin, WANG Gang
    Chin J Plan Ecolo. 2006, 30 (5):  810-816.  doi:10.17521/cjpe.2006.0103
    Abstract ( 2493 )   PDF (324KB) ( 1036 )   Save
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    Background and Aims After browsing or clipping, Caragana korshinskii can compensate for loss of biomass, which is the foundation for repeated use of resources of this species. However, the pattern of vegetative compensatory growth under different clipping treatments is still poorly understood. 
    Methods In order to test the effects of removal of partial shoot length (RSL) and partial shoot number (RSN) on vegetative growth, we removed 30% (30%RSL), 60% (60%RSL) of main shoot length, and 25% (25%RSN), 50% (50%RSN), and 100% (100%RSN) of main shoot number.
    Key Results Clipped shrubs overcompensated for tissue loss, and current years hoot number per shoot, current year shoot length, current year shoot biomass per shoot and current year shoot biomass per shrub were higher than those of the control. The control, 30%RSL and 60% RSL shrubs did not resprout after clipping, while 25%RSN, 60%RSN and 100%RSN treatments did resprout and the biomass per shrub increased when more shoot biomass were removed. Differences in resprout number per removal shoot, resprout length, individual resprout biomass were not significant between 25%RSN and 50%RSN treatment, but resprout number per removal shoot, resprout length, individual resprout biomass of both were less than those of 100%RSN treatment. Fruit production in clipping treatments was higher or equal to that of the control with the exception of 100%RSN, which grew no fruit. There was a negative relationship between annual shoot biomass and fruit production with the exception of the control, which had less fruit production and the annual shoots almost did not grow. During growth season, biomass of current year vegetative growth increased quickly from current year’s shoot growth to fruit ripeness. In the following three months, from fruit ripeness to leaf abscission, however, it increased slowly. 
    Conclusions 100%RSN treatment may be a reasonable mode to prompt shrubs to recover quickly from damage. Plants’ responses associated with compensation may include: increased branching or tillering after alteration of the apical dominance, increased availability of water and/or nutrients after the change in the ratio of shoot to root, and remobilization of resources reserved in roots to aboveground organs. Decreased allocation of resources to  reproductive growth may be another important mechanism for 100%RSN shrubs to compensate for the loss of organs.

    FERTILIZATION EFFECTS ON SPECIES REPRODUCTIVE ALLOCATION IN AN ALPINE MEADOW PLANT COMMUNITY
    NIU Ke-Chang, ZHAO Zhi-Gang, LUO Yan-Jiang, DU Guo-Zhen
    Chin J Plan Ecolo. 2006, 30 (5):  817-826.  doi:10.17521/cjpe.2006.0104
    Abstract ( 2300 )   PDF (394KB) ( 1231 )   Save
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    Background and Aims Plant resource allocation strategies are important in determining community structure in variable environments. However, observations of changes in species reproductive allocation under disturbance at the community level are rare. This study addresses the following questions: 1) does fertilization alter patterns of species reproductive allocation in natural plant communities, 2) are there interspecific differences for a fertilization effect, and 3) what is the effect of fertilization on assemblage_level reproductive allocation?
    Methods The study was conducted at the Alpine Meadow Ecosystem Field Station of Lanzhou University, Maqu (101°53′E, 35°58′N). The experimental plant communities are typical of alpine meadow of the eastern QingHai_Tibetan Plateau. In mid May of 2002 and 2003, we established a soil nutrient gradient of diammonium phosphate (DAP) in the natural plant communities using a completely randomized design (3 levels of fertilization treatments and 3 repetitions of each level). From June to September, we sampled above_ground parts of 24 plant species at their fruiting stage, randomly selecting 20 individuals at every treatment level. The samples were dried to constant weight for 10 h at 80 ℃, and each individual was dissected into fruits, stems and leaves, which were weighed by Sartorius balances (to the nearest 10-4 g). Reproductive, stem, and leaf allocations were calculated as the proportion of total biomass. ANOVA was used to test the effect of fertilization on patterns of species reproductive allocation.
    Key Results Fertilization significantly affected both the biomass and the biomass allocation of most species. Total biomass, leaf biomass, and stem biomass of most species increased with soil nutrient level, but reproductive biomass remained constant or decreased. Reproductive allocation decreased, stem allocation increased, and leaf allocation was constant in most species. The degree and directi on of responses differed among species, indicating the differences of life history. Reproductive allocation at the assemblage_level decreased with fertilization.
    Conclusions The study suggests that plant individuals tend to become larger, reproductive allocation decreases, and stem allocation and leaf allocation increase as fertility increases. The effect of fertilization on resource allocation strategies is different among species within the same plant community.

    EFFECTS OF SEAWATER ON PHOTOSYNTHESIS AND CHLOROPHYLL FLUORESCENCE IN HELIANTHUS TUBEROSUS SEEDLINGS IN DIFFERENT REGIONS
    LONG Xiao-Hua, LIU Zhao-Pu, JIANG Yun-Fang, CHEN Ming-Da, WANG Lin
    Chin J Plan Ecolo. 2006, 30 (5):  827-834.  doi:10.17521/cjpe.2006.0105
    Abstract ( 2544 )   PDF (465KB) ( 1128 )   Save
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    Background and Aims Growing plants that are tolerant to saltwater is an option for use of coastal mudflats and application of seawater. 
    Methods Pot experiments were carried out to study the effects of the seawater on photosynthesis and chlorophyll Ⅱ fluorescence of Helianthus tuberosus seedlings from three different regions, Yancheng (YC), Wuwei (WW), and Yantai (YT). Three different concentrations of seawater were applied: 0 (CK), 15%, and 30% seawater. 
    Key Results Fresh and dry weights of roots and shoots of seedlings decreased with increasing seawater concentrations for all regions, but less at YC. Net photosynthetic rate (Pn), transpiration rate (Tr), water use efficiency (WUE), stomatal conductance (Gs), and stomatal limitation (Ls) decreased with increasing seawater concentration for all regions; however, intracellular CO2 (Ci) increased with increasing seawater concentration. The Pn and  Tr were the highest for YC, whereas WUE and Ci were lower and Gs and Ls were higher than those for WW and YT with the 15% seawater treatment. Minimal fluorescence (Fo), maximum fluorescence (Fm), variable fluorescence (Fv), stable fluorescence (Fs), difference between Fs and Fo (ΔFo), PSⅡ potential fluorescence efficiency (Fv/Fo), and PSⅡ maximum fluorescence efficiency (Fv/Fm) all decreased with increasing seawater concentration. Values of Fm, Fv, Fs, andFv/Fo were the highest for YC. Electronic transfer rate ( ETR), photochemical quench (qP), and photochemistry rate of YC leaves changed slightly. Compared to the controls, values for WW and YT all decreased markedly with 30% seawater and were lower than for YC. The PSⅡ actual fluorescence efficiency (ΦPSⅡ) changed differently with different treatments. TheΦPSⅡfor YC and WW was the highes with 15% seawater than other seawater concentration, andΦPSⅡfor YT was highest with CK. The Chlacontents all decreased and Chlb contents changed slightly with increasing seawater concentration. The ratio of Chla and Chlb for WW and YC deceased with increasing seawater concentration, and the ratio for YT changed slightly with the 0 and 15% seawater treatments. 
    Conclusions Seawater suppressed the growth, photosynthesis, and chlorophyllⅡfluorescence of H. tuberosus seedlings, and effects increased with increasing seawater concentration. Seedlings grown in the YC region were less affected by seawater than those in the WW and YT regions.

    COVER SHIFT AND MORPHOLOGICAL PLASTICITY OF INVASIVE ALTERNANTHERA PHILOXEROIDES ALONG A RIPARIAN ZONE IN SOUTH CHINA
    PAN Xiao-Yun, GENG Yu-Peng, ZHANG Wen-Ju, Li Bo, CHEN Jia-Kuan
    Chin J Plan Ecolo. 2006, 30 (5):  835-843.  doi:10.17521/cjpe.2006.0106
    Abstract ( 2097 )   PDF (411KB) ( 1430 )   Save
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    Background and Aims Biological invasions by non_native species have become a major environmental problem and a focus of ecological research. Relatively few studies have focused on invasibility and invasivness among microhabitats within communities. We compared the abundance and performance of non_native Alternanthera philoxeroides (alligator weed) and its co_occurring native congener, Alternanthera sessilis (sessile joyweed), in a wetland community along a riparian zone in southeast China to test the hypotheses that: 1) the degree of invasion differs between different types of microhabitats within the community; 2) microhabitat types that differ in invasion also differ in soil resource availability or in sediment characteristics likely to affect resource availability; and 3) phenotypic plasticity must have played a key role in adaptation to diverse habitats for A. philoxeroides because of its extremely low genetic diversity throughout China. 
    Methods Field surveys of natural distribution and performance of the two varieties on adjacent and contrasting microhabitat types (abandoned field, swamp, marsh dunes and gravel dunes) along a riparian zone were conducted in the autumn of 2003. 
    Key Results Soil organic matter, total N, available P and K were significantly higher and pH was lower in dryland and swamp than in dunes. Total vegetation coverage was significantly higher in dryland and swamp than in dunes. The relative coverage of A. philoxeroides was much higher than that of A. sessilis in more p roductive habitats (i.e. dry land and swamps), but this pattern reversed in less productive habitats (i.e. marsh and gravel dunes). A. philoxeroides showed greater morphological plasticity in response to habitat variation. Especially, the CV(coefficient of variation) of leaf area and branch angle in A.
    philoxeroides was 70 and 83 times greater than those in A. sessilis, respectively. Several morp hological traits related to light foraging increased significantly from marsh and gravel dunes to more productive habitats (dry land and swamps). These traits included stem length, internode length, the number of nodes, and leaf length and width. Moreover, the leaf_bearing stems grew more vertically in dry land and swamps. Meanwhile, these traits in  A. sessilis had no obvious variations among microhabitats. 
    Conclusions These results suggest that high plasticity in vertical growth and occupancy of soil microhabitat of rich nutrient resources may facilitate the invasions of A. philoxeroides.

    A MODEL TO SIMULATE NET PRIMARY PRODUCTION OF DEYEUXIA ANGUSTIFOLIAIN WETLANDS IN SANJIANG PLAIN, CHINA
    ZHANG Wen-Ju, TONG Cheng-Li, LIU Shou-Long, SONG Chang-Chun, WU Jin-Shui
    Chin J Plan Ecolo. 2006, 30 (5):  844-851.  doi:10.17521/cjpe.2006.0107
    Abstract ( 2337 )   PDF (393KB) ( 914 )   Save
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    Background and Aims Carbon sequestration in ecosystems is determined largely by primary production of ecosystems. The application of long_term observation of vegetation biomass limits ecological and global change research. Therefore, it is necessary to apply simulation models to estimate an ecosystem’s input of or ganic carbon and forecast the impact of climate change. 
    Methods Based on the principles of plant physiology, a simulation model was developed to simulate primary production of Deyeuxia angustifolia in wetland ecosystems. It is driven by conventional parameters observed from meteorological stations. This model consists of three main function modules: photosynthesis_respiration, accumulation of assimilated matter and distribution of assimilated matter. The effects of temperature, waterlogging and increased  concentration of atmosphere CO2 on the growth of D.angustifoliawere taken into account in this model. The model was validated by comparing observed and simulated data of aboveground living and litter biomass of D. angustifolia. 
    Key Results The dynamics of aboveground living biomass, total litter, stem litter and leaf litter of D. angustifolia were simulated correctly. The liner correlation between simulated and observed values was highly significant. 
    Conclusions Validation results from an adjacent area and a field experiment station also showed that the simulated values were significantly correlated with observed values in seasonally and permanently waterlogged D. angustifolia ecosystems. Daily changes of primary production, biomass and liter of D. a ngustifoliain wetland ecosystems could be effectively simulated by this model .

    THREE TEMPERTURE (3T) MODEL—A METHOD TO ESTIMATE EVAPO_TRANSPIRATION AND EVALUATE ENVIRONMENTAL QUALITYY BASED ON SURFACE TEMPERATURE. IV. PLANT TRANSPI_RATION TRANSFER COEFFICIENT
    QIU Guo-Yu, WU Xiao, WANG Shuai, SONG Xian-Fang
    Chin J Plan Ecolo. 2006, 30 (5):  852-860.  doi:10.17521/cjpe.2006.0108
    Abstract ( 2194 )   PDF (506KB) ( 823 )   Save
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    Background and Aims Vegetation transpiration rate sensitively responses to environmental stress introduced by air pollution, environmental degradation (soil and water), and global change. Based on energy balance analysis, by introducing the temperature of a canopy without transpiration, the objectives of this study are to propose a remotely measurable plant transpiration transfer coefficient (hat) and to verify its characteristics under various environmental conditions. 
    Methods The hat is defined as (Tc-Ta)/(Tp-Ta), where Tc, Tp, and Ta are temperatures of vegetation canopy, a non_transpiring canopy, and air, respectively. Five experiments were carried out to verify the proposed coefficient. 
    Key Results Theoretical analysis and experimental results show hat≤1. If Tc=Tp, hat has its maximum value (hat = 1) and transpiration rate has its minimum value (zero). This boundary is determined by lack of water for transpiration. On the other hand, when hat has a minimum value, transpiration can reach its maximum value (potential transpiration rate). This boundary is determined by the avail ability of energy for transpiration. 
    Conclusions Therefore, hat can determine transpiration rate from its minimum value to its maximum value. A lower value of hat corresponds to a higher transpiration rate.

    SIMULATION OF GREENHOUSE CUCUMBER LEAF AREA BASED ON RADIATION AND THERMAL EFFECTIVENESS
    LI Yong-Xiu, LUO Wei-Hong, NI Ji-Heng, CHEN Yong-Shan, XU Guo -Bin, JIN Liang, DAI Jian-Feng, CHEN Chun-Hong, BU Chong-Xing
    Chin J Plan Ecolo. 2006, 30 (5):  861-867.  doi:10.17521/cjpe.2006.0109
    Abstract ( 2554 )   PDF (305KB) ( 1196 )   Save
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    Background and Aims Leaf area index (LAI) is one of the most import ant crop parameters in photosynthesis driven crop growth simulation models. Temperature and radiation are important climate factors affecting crop leaf growth. The aim of this study is to quantitatively investigate the effects of both temperature and photosynthetically active radiation (PAR) on the leaf growth of greenhouse cucumber (Cucumis sativus).
    Methods Experiments with different cultivars and sowing dates were conducted in greenhouses of Shanghai Academy of Agricultural Sciences during August, 2003 and July, 2004. We used the following quantitative relationships based on experi mental data to model the relationship between the product of thermal effectiveness and PAR(TEP): accumulated TEP to the number of unfolding leaves per plant and the number of old leaves removed per plant, leaf position relative to the rate of increase in leaf length and the maximum leaf length; and the ratio of leaf area to leaf length. Based on these quantitative relationships, a leaf area simulation model for greenhouse cucumber was developed. Independent experimental data were used to validate the model. The simulated results of the model developed in this study were compared with those of the traditional GDD based model (which predict leaf area based on
    growing degree days) and SLA based model (which predict leaf area based on the specific leaf area and leaf dry weight).
    Key Results The coefficient of determination (R2) and the root mean squared error (RMSE) between the simulated and the measured leaf area index (LAI) based on the 1∶1 line are 0.879 2 and 0.398 0, respectively. The prediction accuracy of this model is 37% and 74% higher, respectively, than that of the traditional GDD and SLA based models. 
    Conclusions The model developed in this study can predict LAI satisfactorily using air temperature, radiation, date of the first leaf unfolding and planting density. The simple model input makes the model user friendly and more applicable in greenhouse crop and climate management practices.

    NEUTRAL THEORY IN COMMUNITY ECOLOGY
    ZHOU Shu-Rong, ZHANG Da-Yong
    Chin J Plan Ecolo. 2006, 30 (5):  868-877.  doi:10.17521/cjpe.2006.0110
    Abstract ( 3918 )   PDF (378KB) ( 1972 )   Save
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    A central goal of community ecology is to understand the forces that maintain species diversity within communities. The traditional niche_assembly theory asserts that species co_occur in a community only when they differ from one another in resource use. But this theory has some difficulties to explaining the diversity often observed in species_rich communities such as tropical forests. As an alternative to niche theory, Hubbell and other ecologists introduced a neutral model. Hubbell argues that the number of species in a community is controlled by species extinction and immigration and speciation of new species. Assuming that all individuals of all species in a trophically similar community are ecologically equivalent, Hubbell’s neutral theory predicts two important statistical distributions. One is the asymptotic log_series distribution for the metacommunity under point mutation speciation, and the other is the zero_sum multinomial distribution for both local community under dispersal limitation and metacommunity under random fission speciation. Unlike the niche_assembly theory, the neutral theory takes similarity in species and individuals as a departure for investigating species diversity. Based on the fundamental processes of birth, death, dispersal and speciation, the neutral theory first presented a mechanism that generates species abundance distributions remarkably similar to those observed in nature. Since the publication of the neutral theory, there has been much discussion of it, pro and con. In this paper, we summarize new progresses in research on assumption, prediction and speciation mode of neutral theory, including progress in the theory itself and tests about the theory’s assumption, prediction and speciation mode at metacommunity level. We also suggest that the most important task in the future is to bridge the niche_assembly theory and the neutral theory, and to add niche_differences in neutral theory and more stochasticity into niche theory.

    AN EFFECTIVE WAY TO IMPROVE SOIL FERTILITY IN TRADITIONAL AGROFORESTRY: PLANTING ALNUS NEPALENSIS
    LI Su-Mei, LONG Chun-Lin, DAO Zhi-Ling
    Chin J Plan Ecolo. 2006, 30 (5):  878-886.  doi:10.17521/cjpe.2006.0111
    Abstract ( 2375 )   PDF (330KB) ( 1229 )   Save
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    Alder (Alnus nepalensis), an important non_legume nitrogen_fixing plant, occurs widely in the eastern Himalayas. In traditional agroecosystems of Asia, alder is commonly used as a fallow tree or is intercropped. There has been growing concern about ecological and economical values of alder, and this has resulted in greater interest in the utilization of this species. Soil_improvement functions of alder in traditional agroecosystems were reviewed based on research results for the last 30 years, in order to bring attention to alder’s role in traditional agroecosystems, promote the development of agriculture in mountain areas and protect the environment. Soil improvement functions of alder in traditional agroecosystems were as follow s: 1) Seasonal nitrogen accretion in alder stands was high during the growing season between June and November (95%–98% of total annual accretion) and very low from December to April (2%– 5%). Annual accretion of nitrogen was the highest (117 kg•hm-2) in a 7_year stand. Annual symbiotic nitrogen fixation in alder_cardamom (Elettaria cardamomum) plantations was the highest (155 kg•hm-2) in a 15_year stand and decreased with increasing plantation age. 2) Alder performed well with intercropping or as a fallow tree. When intercropped, it could improve the agronomic yield of crops. The agronomic yield of cardamom was 2.2 times greater under the canopy of alder than under natural forest. As a fallow tree after a 6_year fallow period, the above_ground biomass in alder fallows was 4 times greater than in grass fallows, N accumulation was 3 times greater than in grass fallows and P and K were both about double the level found in grass fallows. 3) Alder seemed to have the most desirable rooting characteristics for agroforestry systems. Most fine roots were concentrated in the upper 10 cm of the soil, but coarse roots were concentrated at 10-20 cm depth. The fine root biomass (FRB) in intercropping was 5% greater than when grown as a fallow tree. Sixty percent of the fine roots were distributed 0.5 m from the tree trunk. Most of the woody roots (>5 mm diameter) were present within 0-10 cm depth near the tree trunk in both intercropping and fallow_tree situations. Total root length of woody roots was <1 m. 4) Nutrient cycling rates were higher in alder plantations than under other plantations. Rates of litter production and decomposition were 1.59 and 1.79 times higher, respectively, in alder_cardamom stands than in forest_cardamom stands. The litter from N2_fixing species may accelerate the decomposition of other types of litter. When mingling with alder litter, other types of litter decomposed as rapidly as the alder litter. 5) In the traditional swidden agricultural system, fertility of t he soil under alder fallow could be rejuvenated in 3-6 years, which reduced the fallow period remarkably, and physical and chemical properties of the soil could be improved greatly. Although the functions of the alder for improving soil have been researched much , the problem of how to simultaneously achieve the best economical and ecological values of co_planting crops and the alder in mountain areas needs further study.


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