Dynamics Of Nutrient Source-Sink Between Sublepine Bamboo Communities And Soil In Western Sichuan

Source-Sink theory, advanced by Masan and Maskell in 1928, plays an important role in the studies on plant physiology, crop breeding and planting. With the development of research, it has being become a key content for the studies of substance source and sink to understand the process and the harmonized mechanism of flow, accumulation and distribution between nutrient source and sink. Although there had more studies on the harmonized mechanisms between the photosynthesis source and production sink from the angle and level of physiology and ecology, which had layed a theory foundation for planting and management for crops to get high yield but no more to elucidate them between plant nutrient source and their soil nutrient sink from the angle and level of ecosystem. Otherwise, the studies on nutrient cycle of forest ecosystem, laying particular stress to clarify the nutrient flow processes among the components of vegetation and soil from the angle of ecosystem, can not notify the nutrient flow processes and harmonized mechanisms between the nutrient source of every species and its soil sink and their function, status, effects in whole nutrient cycling of forest ecosystem from the level of community (because it is very difficult for tall arbor species to sample). How to synthetize the studies on the mutual effect process and harmonized mechanisms between plant species nutrient source and their soil nutrient sink from the angle and level of individual, community and ecosystem, was a stress and difficulty to quantify the ecological process and management for forest ecosystem. Up to now, although the studies on the dynamic of nutrient source and sink for the dominant forest species have developedbroadly through controled experiments from the level of individual, but do not from the level of community which are helpful to notify completely the nutrient elements flow processes and harmonized mechanisms between vegetation nutrient source and soil nutrient sink, and to the management and continuable development for the forest species with special biological and ecological function.The subalpine coniferous forest in Western Sichan is an important green ecological barrier for the upper and middle reaches of the Changjiang river and for The Three Gorges Reservoir. However, it has become one of the ecological fragile regions in our country because of the human and nature distributions in recent decades. Bamboo (fargesia ) is giant panda's main feed, and is the most important population under the coniferous forest, playing an important role in ecological functions of subalpine coniferous forest. Nevertheless, because bamboo flowered and died widely in this region, it threatened the survival and propagation of panda heavily. Therefore, the mechanism why bamboo flowered is becoming an important research field of how to protect biology.Some researchers think bamboo flowers every sixty years because of its inherent biological traits. But, others think bamboo flowered because there have no enough nutrient to provide for their growth. In a word, these theories above mentioned all have no enough experimental evidences. In past time, Some studies on bamboo's biological traits such as propagation, growth, development, biological productivity and so on, can not provide valuable evidences to explain why bamboo flowered. Therefore, this project selected three bamboo communities with different densities (D1: 4.54x105tree.ha-1, D2: 6.32x105tree.ha-1, D3: 9.45 x105 tree .ha-1) and having similar forest crown density, slope, altitude, slope direction and agrotype under subalpine coniferous forest in WangLang Nature Reserve, dealt with the biomass and nutrient accumulation process, the nutrient return dynamic of litter and rainfall, the microbal quantity , enzymatic activity and nutrient property in rhizosphere and all root soil, the variation of nutrient element flux between the plant source and soil sink in three bamboo communities with different densities from the angle and level of community by the methods of combining field in...