Study On The Soil Organic Matter Decomposition、Accumulation And Storage Prediction Of Subalpine Abies Faxoniana Forest In Western Sichuan

Soil organic matter (SOM), a significant part in soil, is one critical index on soil fertility and soil quality evaluation, plays an important role in mitigating the global climate change. The equilibrium and stable increase of forest SOM is an important way to consolidate and improve the capability of carbon storage in forest soil ecosystem, and also take a significant part on global carbon cycle. The area of western Sichuan is a sensitive zone with the temperature changes, the forest soil organic matter storage in total of this area decreases or increases when the global climate changes is still uncertainly, it is the right factor that the status of SOM storage over the time can explain the uncertain. Therefore, to carry out the research on the forest SOM decomposition、accumulation and storage prediction in subalpine western Sichuan can help us predict the effect of forest on global carbon balance scientifically, and is also of great significance to looking for ways to mitigate climate change in the future.The experiment was carried out for the first time on June2011, the Abies faxoniana forest and its soil in MuGecuo scenic area of state GanZi in SiChuan province were chosed as the research object, the litter production, SOM oxidation/decomposition rate and litter humification coefficient were researched based on the period of the whole year positioning observation and research, and then built the SOM storage mathematical models over the time, meanwhile these models was uesd to predict SOM storage of the study area. The results are showed as follows:(1) The annual litter production of positioning area was2.82×103kg, which converted to soil organic matter up to2.54×103kg in total every year; the components of annual litter production was leaf(2.13×103kg)>branches(0.656×103kg)>fruits(0.33×103kg). There were two peak in the whole year as a result of the differences and properties of the species composition, which were spring(0.62×103kg) and(1.263×103kg) autumn respectively.(2) Soil temperature and water content were two of critical significance to the decomposition and accumulation of soil organic compound. Suffered from the influence of the soil temperature、water content and organic compound concentration, the processes of SOM decomposition and the dynamic of litter humiliation into soil were all appeared the principle of fast at the beginning and slow at the last time. Because the temperature reduced in soil layer A2was slower than layer A1which caused the temperature layer A2higher than A1in winter, so the SOM decomposition and humification in layer A2was faster than A1result from the microbial thermotaxis. (3) The soil organic storage layer A1and layer A2now were77.14×103kg and84.89×103kg, respectively(the soil deep is about10cm layer A1and half than that of layer A2), the SOM oxidation coefficient in layer A1was0.0439and larger than layer A2(0.0339), the turnaround period were22.8and29.5a, respectively. The annual amount of oxidation of SOM layer A, was3.39×103kg and layer A2was2.88×103kg. We could calculate and drew the conclusion that the amount of organic matter return to soil by litter production(2.54×103kg) was still less than the amount of oxidation every year, even though the proportion of litter production convert to SOM was100%. As the soil fertility of study area was declining, so we should continually increase the forest litter production every year in order to improve the soil fertility and make sure the soil can be managed sustainability in future.(4) The litter humification coefficient in layer A1and A2were relatively greater than research result ever before which were0.597and0.493, this result was related to the high ratio of C/N(145.00±9.92)、high content of lignin(44%) and low temperature decomposition environment all over the whole year. These study results also concluded that litter was very important to maintain soil fertility in our positioning research area, the organic matter amount dedication litter to the soil every year was layer A11.52×103kg and layer A20.75×103kg, which was of great significance to the accumulation of SOM in study area, especially in layer A1which has great soil carbon sequestration potential.(5) There was great forest SOM storage potential, the surface soil organic matter was relatively high and up to162.03×103kg in total, but it was absolutely not stable and could reduce with the time easily suffered from global warming. The SOM storage would reduced down to34.62×103kg layer A, and22.12×103kg layer A2and56.74×103kg the surface soil in total when the time was very long(t�'∞). With the decay and decomposition of original forest, the forest and its SOM storage would present a decline trend. We should add more Abies faxoniana(3.16～3.27×103kg) and R.concinuum Hemsl(3.36～3.42×103kg)litter to the soil from the perspective of keeping the balance of SOM in study area. Take artificial measures in time、update the original forest and raise the species density to increase litter production with the destination to maintain the quality of soil fertility and improve the carbon sequestration in forest ecosystems would be the focus of further research in future.