Weiguo Sang

Scale‐dependent relationships between tree species richness and ecosystem function in forests

1. The relationship between species richness and ecosystem function, as measured by productivity or biomass, is of long-standing theoretical and practical interest in ecology. This is especially true for forests, which represent a majority of global biomass, productivity and biodiversity.

Plant diversity patterns and their relationships with soil and climatic factors along an altitudinal gradient in the middle Tianshan Mountain area, Xinjiang, China.

Patterns of plant diversity along the altitudinal gradient of Tianshan in central Xinjiang, China were examined. Plant and environment characteristics were surveyed from higher, south of Bogeda peak, to lower, north of Guerbantonggute desert. There were a total of 341 vascular plant, 295 herbage, 41 shrub, and seven tree species in the sampled plots. The plant richness of vegetation types generally showed a unimodal pattern along altitude, with a bimodal change of plant species number at 100-m intervals of altitudinal samples. The two belts of higher plant richness were in transient areas between vegetation types, the first in areas from dry grass to forest, and the second from forest to sub-alpine grass and bush. The beta diversity varied with altitudinal changes, with herbaceous species accounting for most species, and thus had similar species turnover patterns to total species. Matching the change of richness of plant species to environmental factors along altitude and correlating these by redundancy analysis revealed that the environmental factors controlling species richness and its pattern were the combined effects of temperature, precipitation, soil water, and nutrition. Water was more important at low altitude, and temperature at high altitude, and soil chemical and physical characters at middle altitudes. This study provides insights into plant diversity conservation of Bogeda Natural Reserve Areas in Tianshan Mountain.

Effects of environmental factors on germination and emergence of Crofton weed (Eupatorium adenophorum)

Abstract Laboratory and greenhouse studies were conducted to determine the effect of several environmental factors on seed germination and seedling emergence of Crofton weed. Seeds germinated over a range of 10–30 C, with optimum germination at 25 C. High temperature markedly restricted germination, with no germination occurring at 35 C. Crofton weed was moderately photoblastic, with 17% germination occurring in the dark. Crofton weed germinated in a narrow range of pH (5–7). Maximum germination (94%) was observed in distilled water at pH 5.7. Germination was totally inhibited at osmotic stress higher than −0.7 MPa. Germination was greater than 65% at less than 100 mM NaCl, with no germination at 300 mM NaCl. Maximum emergence occurred when seeds were planted on the soil surface. No seedlings emerged when seeds were planted 1.5 cm deep. These results suggest that the future range of Crofton weed in China will be restricted largely to the Yunnan-Guizhou Plateau, which includes major parts of Yunnan and Guizhou provinces, the southwestern part of Sichuan province, and the western part of Guangxi province. Crofton weed also tends to be a sporadic problem in other regions, where the climatic and edaphic conditions are suitable for the seed germination. Nomenclature: Crofton weed (Eupatorium adenophorum ‘Spreng’).

Differential Responses of the Activities of Antioxidant Enzymes to Thermal Stresses between Two Invasive Eupatorium Species in China

The effect of thermal stress on the antioxidant system was investigated in two invasive plants, Eupatorium adenophorum Spreng. and E. odoratum L. The former is sensitive to high temperature, whereas the latter is sensitive to low temperature. Our aim was to explore the relationship between the response of antioxidant enzymes and temperature in the two invasive weeds with different distribution patterns in China. Plants were transferred from glasshouse to growth chambers at a constant 25 degrees C for 1 week to acclimatize to the environment. For the heat treatments, temperature was increased stepwise to 30, 35, 38 and finally to 42 degrees C. For the cold treatments, temperature was decreased stepwise to 20, 15, 10 and finally to 5 degrees C. Plants were kept in the growth chambers for 24 h at each temperature step. In E. adenophorum, the coordinated increase of the activities of antioxidant enzymes was effective in protecting the plant from the accumulation of active oxygen species (AOS) at low temperature, but the activities of catalase (CAT), guaiacol peroxidase (POD), ascorbate peroxidase (APX), glutathione reductase (GR), and monodehydroascorbate reductase (MDAR) were not accompanied by the increase of superoxide dismutase (SOD) during the heat treatments. As a result, the level of lipid peroxidation in E. adenophorum was higher under heat stress than under cold stress. In E. odoratum, however, the lesser degree of membrane damage, as indicated by low monodehydroascorbate content, and the coordinated increase of the oxygen. Detoxifying enzymes were observed in heat-treated plants, but the antioxidant enzymes were unable to operate in cold stress. This indicates that the plants have a higher capacity for scavenging oxygen radicals in heat stress than in cold stress. The different responses of antioxidant enzymes may be one of the possible mechanisms of the differences in temperature sensitivities of the two plant species.

Securing a Future for China's Wild Plant Resources

China harbors one of the most species-rich floras in the world. This plant diversity is currently severely threatened by high levels of habitat degradation and unsustainable resource extraction, the countrys exceptionally fast economic growth, an uncontrolled increase in tourism, invasive species, and climate change. Furthermore, Chinas current system of protected areas is ineffective at conserving the countrys plant resources, with low levels of enforcement and only a few small reserves located in both the most phytodiverse regions and in areas facing the highest anthropogenic pressure. Seven strategic steps are required in order to secure a future for Chinas wild plants, including surveys to establish current species distributions and threat levels, the creation of an effective protected-area system focused on quality rather than quantity, resettlement of parts of the scattered rural population, control of the illegal export trade and invasive species, and a streamlining of administrative responsibilities and capacity building in conservation.

Irradiance acclimation, capture ability, and efficiency in invasive and non-invasive alien plant species

We tested the hypothesis that invasive (IN) species could capture resources more rapidly and efficiently than noninvasive (NIN) species. Two IN alien species, Ageratina adenophora and Chromolaena odorata, and one NIN alien species, Gynura sp. were compared at five irradiances. Photon-saturated photosynthetic rate (Pmax), leaf mass (LMA) and nitrogen content (NA) per unit area, and photosynthetic nitrogen utilization efficiency (PNUE) increased significantly with irradiance. LMA, NA, and PNUE all contributed to the increased Pmax, indicating that both morphological and physiological acclimation were important for the three alien species. Under stronger irradiance, PNUE was improved through changes in N allocation. With the increase of irradiance, the amount of N converted into carboxylation and bioenergetics increased, whereas that allocated to light-harvesting components decreased. The three alien species could adequately acclimate to high irradiance by increasing the ability to utilize and dissipate photon energy and decreasing the efficiency of photon capture. The two IN species survived at 4.5 % irradiance while the NIN species Gynura died, representing their different invasiveness. Ageratina generally exhibited higher respiration rate (RD) and NA. However, distinctly higher Pmax, PNUE, Pmax/RD, or Pmax/LMA were not detected in the two invasive species, nor was lower LMA. Hence the abilities to capture and utilize resources were not always associated with invasiveness of the alien species.

Relationships between plant diversity and the abundance and α-diversity of predatory ground beetles (Coleoptera: Carabidae) in a mature Asian temperate forest ecosystem.

A positive relationship between plant diversity and both abundance and diversity of predatory arthropods is postulated by the Enemies Hypothesis, a central ecological top-down control hypothesis. It has been supported by experimental studies and investigations of agricultural and grassland ecosystems, while evidence from more complex mature forest ecosystems is limited. Our study was conducted on Changbai Mountain in one of the last remaining large pristine temperate forest environments in China. We used predatory ground beetles (Coleoptera: Carabidae) as target taxon to establish the relationship between phytodiversity and their activity abundance and diversity. Results showed that elevation was the only variable included in both models predicting carabid activity abundance and α-diversity. Shrub diversity was negatively and herb diversity positively correlated with beetle abundance, while shrub diversity was positively correlated with beetle α-diversity. Within the different forest types, a negative relationship between plant diversity and carabid activity abundance was observed, which stands in direct contrast to the Enemies Hypothesis. Furthermore, plant species density did not predict carabid α-diversity. In addition, the density of herbs, which is commonly believed to influence carabid movement, had little impact on the beetle activity abundance recorded on Changbai Mountain. Our study indicates that in a relatively large and heterogeneous mature forest area, relationships between plant and carabid diversity are driven by variations in environmental factors linked with altitudinal change. In addition, traditional top-down control theories that are suitable in explaining diversity patterns in ecosystems of low diversity appear to play a much less pronounced role in highly complex forest ecosystems.

Long-term protection effects of national reserve to forest vegetation in 4 decades: biodiversity change analysis of major forest types in Changbai Mountain Nature Reserve, China

The Changbai Mountain Nature Reserve (CNR) was established in 1960 to protect the virgin Korean pine mixed hardwood forest, a typical temperate forest of northeast China. We conducted systematic studies of vascular diversity patterns on the north slope of the CNR mountainside forests (800–1700 m a.s.l.) in 1963 and 2006 respectively. The aim of this comparison is to assess the long-term effects of the protection on plant biodiversity of CNR during the interval 43 years. The research was carried out in three types of forests: mixed coniferous and broad-leaved forest (MCBF), mixed coniferous forest (MCF), and sub-alpine coniferous forest (SCF), characterized by different dominant species. The alpha diversity indicted by species richness and the Shannon-Wiener index were found different in the same elevations and forest types during the 43-year interval. The floral composition and the diversity of vascular species were generally similar along altitudinal gradients before and after the 43-year interval, but some substantial changes were evident with the altitude gradient. In the tree layers, the dominant species in 2006 were similar to those of 1963, though diversity declined with altitude. The indices in the three forest types did not differ significantly between 1963 and 2006, and these values even increased in the MCBF and MCF from 1963 to 2006. However, originally dominant species, P. koraiensis for example, tended to decline, while the proportion of broad-leaved trees increased, and the species turnover in the succession layers trended to shift to higher altitudes. The diversity pattern of the under canopy fluctuated along the altitudinal gradient due to micro-environmental variations. Comparison of the alpha diversity in the three forests shows that the diversity of the shrub and herb layer decreased with time. During the process of survey, we also found some rare and medicinal species disappeared. Analysis indicates that the changes of the diversity pattern in this region are caused by both nature and human factors. Meteorological records revealed that climate has changed significantly in the past 43 years. We also found the most severe human disturbance to the CNR forests in the process of another field survey that is the exploitation of herb medicines and Korean pine nuts. We hope this research would give some guidance to the future reserve management in Changbai Mountain area.

Assembly of forest communities across East Asia - insights from phylogenetic community structure and species pool scaling

Local communities are assembled from larger-scale species pools via dispersal, environmental filtering, biotic interactions, and local stochastic demographic processes. The relative importance, scaling and interplay of these assembly processes can be elucidated by comparing local communities to variously circumscribed species pools. Here we present the first study applying this approach to forest tree communities across East Asia, focusing on community phylogenetic structure and using data from a global network of tropical, subtropical and temperate forest plots. We found that Net Relatedness Index (NRI) and Nearest Taxon Index (NTI) values were generally lower with geographically broad species pools (global and Asian species pools) than with an East Asian species pool, except that global species pool produced higher NTI than the East Asian species pool. The lower NRI for the global relative to the East Asian species pool may indicate an important role of intercontinental migration during the Neogene and Quaternary and climatic conservatism in shaping the deeper phylogenetic structure of tree communities in East Asia. In contrast, higher NTI for the global relative to the East Asian species pool is consistent with recent localized diversification determining the shallow phylogenetic structure.

Altitudinal diversity patterns of ground beetles (Coleoptera: Carabidae) in the forests of Changbai Mountain, Northeast China

Little is currently known about the biodiversity harboured by Chinas last remaining pristine temperate forests. Especially, studies into the diversity patterns of highly diverse insect taxa are very rare, while such studies are highly valuable, for example, as baseline to evaluate the effectiveness of Chinas ongoing large‐scale reforestation efforts in restoring forest biodiversity. We sampled ground beetles (Coleoptera: Carabidae) on 33 plots distributed across five distinct mature forest ecosystems occurring at altitudes between 700 and 2000 m on Changbai Mountain to address these prevailing knowledge gaps. Pitfall trapping yielded a total of 4834 ground beetles representing 47 species. Carabid abundance increased while α‐diversity decreased with increasing elevation. No significant correlation was observed between the abundance of common species and their elevational distribution. Beetle assemblages originating from the high‐elevation forest types formed a partly overlapping cluster, while beetle assemblages at lower elevations were more strongly differentiated according to forest type. Our results support the assumption that carabids are highly sensitive to climate change. The Korean pine‐dominated forest, which has not previously been distinguished as a discrete forest type, showed a distinct carabid beetle composition, indicating its requirement of specific conservation attention. The carabid diversity in high‐elevation birch forest and low‐elevation mixed broad‐leaved and conifer forests is particularly threatened by climate change, and long‐term future monitoring of ground beetle diversity on Changbai Mountain is expected to provide extremely valuable insights into climate change‐effects on insect communities in Chinas pristine temperate forests.