Changbai Vertical Transect Carbon Mineralization And Its Temperature Sensitivity Of Forest Soils

As we know, it is common for us that the earth has been subjected to a clear change trends, such as atmospheric temperature, N deposition and land use change; and the unbalance of carbon cycle plays an important role in the increasing atmospheric temperature. Carbon (C) storage in soil are main component of the C pool in terrestrial ecosystems, and understanding the effect of soil C sequestration and its stability in the different regions is therefore essential to scientifically evaluate the feedback of terrestrial ecosystems to future climate change. The altitudinal patterns of soil organic matter (SOM) decomposition and temperature sensitivity can represent to some extent the latitude patterns of terrestrial ecosystems. Therefore, we selected five different location along along an altitudinal transect (500-2100m) on the northern slope of Changbai Mountain, which involved Mixed coniferous broadleaved forest (MCB), Dark-coniferous sprucefir forest (DCF), Ermans birch forest (EB), Alpine tundra (AT). The main objectives here were to investigate soil C mineralization rate and its temperature sensitivity in different ecosystem types, and explore indirectly the response of SOM decomposition and soil C storages in different terrestrial ecosystems under future global climate change. The main conclusions were as following:Ⅰ. Soil carbon mineralization is an important way of CO2exchange between soil and atmosphere, and it has been much attention in recent years. The aim of this research was to better understand the effect of temperature and moisture on soil carbon mineralization in the forest soil across elevation gradients in Changbai Mountain while controlling the effects of soil characteristics. The soil C mineralization were measured during laboratory incubations of samples from five sites under different temperature (5、10、15、20、25and30℃) and moisture contents (30%,60%,90%SSM, saturated soil moisture), The result show that:Temperature (F=1425.10, P＜0.001), moisture (F=1327.65, P＜0.001) and elevation gradient (F=1937.54, P＜0.001) have a significant influence on soil C mineralization rate, and there is a significant interaction effect among three factors (P＜0.001). The higher the temperature, the greater the soil C mineralization rate; the moisture content and soil C mineralization had an exponential positively regression; Soil moisture and temperature,as a confounded factor, can affect80%—93%of soil C mineralization; The elevation has a significant impact on soil C mineralization, but soil C mineralization trend with elevation gradient is not well. but the soil microbial and C mineralization are positive proportion (P ＜0.0084); Q10is greatly affect by the moisture content and elevation gradient, Q10has no obvious trend. According to our study, we found that the moisture can significant influence the Q10. The moisture is a major factor on Qio, so we should pay more attention to the effect of soil moisture on soil carbon pool and carbon cycle with global warming.Ⅱ. The protection mechanism of soil aggregates is an important mechanism to maintain soil structure, and the responses of different aggregates to temperature change should be different. So understanding the decomposition process of different soil aggregates and their temperature sensitivity is very important. We tested this hypothesis by a incubation experiments with bulk soil, macroaggregates (250-2000μm, Ma), microaggregates (53-200μm, Mi), and mineral fractions (＜53μm, Mf), which collected from Changbai mountain altitude transect. The results showed that temperature, elevation and aggregate size significantly influenced soil C mineralization (all p＜0.0001), with notable interactive effects (P＜0.0001). Decomposition rates of soil and mineral fractions increased with incubation temperature, and macroaggregates and microaggregates were more complex. the particle size of soil aggregates is not directly proportional to C mineralization rate, the highest of C:nitrogen (N) ratio don’t indicate the highest C mineralization rate. In addition, the elevation has a significantly on the temperature sensitivity of soil C mineralization, the Q10of micro aggregate and bulk soil have similar trend along elevation gradient, the bulk soil and aggregate has a significant different in five location. Our findings demonstrated that the feedbacks of SOM decomposition to temperature were driven unequally by different soil aggregates, and highlight the complex response of ecosystem C budgets to future warming scenarios.