Effects of leaf litter extraction fluid from dominant forest tree species on functional characteristics of soil microbial communities

The effects of extraction fluids from the leaf litter from different dominant tree species on the functional characteristics of the soil microbial community were studied to understand how changes in soil quality and synergism between plants and soil contribute to the process of forest succession. Leaf litter from dominant tree species at different stages of succession were collected and extracted with sterile deionized water. After treating the soil of abandoned land with the different extraction fluids, we analyzed changes in carbon utilization of the soil microbial community in Biolog EcoPlates, then considered these results with those of our previous study on forest vegetation succession in the Malan forest. The leaf litter enhanced the metabolic capacity and functional diversity of the soil microbes, especially in the following combinations： the leaf litter of Quercus liaotungensis-Pinus tabulae- formis, P. tabulaeformis-Betula platyphylla, Q. liaotun- gensis and P. tabulaeformiss. Second, when litter from onespecies evaluated, the species enhanced metabolism and diversity in the order of their successional relationship： B. Platyphylla 〈 P. tabulaeformis 〈 Q. liaotungensis. After soils were treated with different leaf litters at 25 ℃ for 7 days, the sorting pattern of the PCA values, based on the similarity of carbon source utilization by the soil microbes, corresponded to the successional pattern on the basis of the similarity of community composition of forest plants. Thus, changes in soil properties caused by leaf litter from different dominant trees probably play a unique role in the successional pattern of a forest community. We thus pro- pose a successional mechanism that underlies the natural succession process within the Malan forest region. When the dominant forest species of the climax successional stage develops during the early successional stages, its forest litter probably alters soil properties such that the soil becomes unsuitable for the gradual growth and regenera- tion of the original dominant tree species but promotes the growth and establishment of later-invasive plants. In this way, the originally dominant species is replaced by the newly dominant tree species during forest succession.

Response of Polygonum viviparum Species and Community Level to Long-term Livestock Grazing in Alpine Shrub Meadow in Qinghai-Tibet Plateau

Grazing by domestic herbivores is generally recognized as a major ecological factor and an important evolutionary force in grasslands, Grazing has both extensive and profound effects on individual plants and communities, We investigated the response patterns of Polygonum viviparum species and the species diversity of an alpine shrub meadow in response to long-term livestock grazing by a field manipulative experiment controlling livestock numbers on the Qinghai-Tibet Plateau in China, Here, we hypothesize that within a range of grazing pressure, grazing can alter relative allocation to different plant parts without changing total biomass for some plant species if there is life history trade-offs between plant traits, The same type of communities exposed to different grazing pressures may only alter relative species＇ abundances or species composition and not vary species diversity because plant species differ in resistant capability to herbivory, The results show that plant height and biomass of different organs differed among grazing treatments but total biomass remained constant, Biomass allocation and absolute investments to both reproduction and growth decreased and to belowground storage increased with increased grazing pressure, indicating the increasing in storage function was attained at a cost of reducing reproduction of bulbils and represented an optimal allocation and an adaptive response of the species to long- term aboveground damage, Moreover, our results showed multiform response types for either species groups or single species along the gradient of grazing intensity, Heavy grazing caused a 13,2% increase in species richness, There was difference in species composition of about 18%-20% among grazing treatment, Shannon-Wiener （H′） diversity index and species evenness （E） index did not differ among grazing treatments, These results support our hypothesis,

A small scale expression screen identifies tissue specific markers in the Dugesia japonica strain Pek-1

Freshwater planaria has tremendous capacity to reform the missing part of the body and therefore is considered as one of the most important model organism for regeneration study. At present, Schmidtea mediterranea and Dugesia japonica are the two major species utilized for laboratory manipulations. Dugesia japonica flatworms are widely distributed in the Far East including Cherry Valley region in the north-west area of Beijing, China. We reported here the establishment of an asexual Dugesiajaponica strain Pek-1, as a suitable system for regeneration study. Using morphological, karyotypical as well as phylogenetic analyses, we confirmed that these flatworms indeed belonged to Dugesia japonica. We went on to show that the commonly used in situ probes and immunohistochemistry reagents and protocols were applicable to the Pek-1 strain. Using this strain, we carried out small scale analysis on EST, RNAi and gene expression. We identified 193 unique EST sequences and 65 of them had not been reported in planarian. By RNAi analysis, we showed that 48 genes, when down-regulated individually, had no effect on regeneration. Furthermore, we identified 3 groups of tissue specific expressing genes that were useful for cell lineage analysis. We concluded that the Dugesiajaponica Pek-1 strain could be another suitable animal model to regeneration research.