土壤水含量变化对农田系统CO_2净排放影响的实验研究进展

面向"节水减排"的灌溉制度是应对气候变化的关键农业管理措施,土壤水含量变化对农田系统CO2净排放影响是其基础理论研究的热点。目前,国内外农田系统的土壤水含量变化对CO2排放、CO2吸收以及CO2净排放的影响实验研究成果主要集中于室内、田间和大区域三个尺度;大多数研究集中在对土壤呼吸的影响,而在农田系统CO2净排放方面的影响研究较少。作物整体呼吸作用对土壤含水量变化的响应、室内和大田尺度下实验条件的水分胁迫界限设定、不同灌溉方式及不同物候期下土壤含水量含量变化对农田系统CO2净排放量的影响研究将成为未来的研究热点。

Seasonal changes of soil respiration in Betula platyphylla forest in Changbai Mountain, China

A stdudy was conducted to determine the seasonal changes of soil respiration and the contribution of root respiration to soil respiration in Betula plaophylla forest in Changbai Mountain from May to September in 2004. Results indicated that the total soil respiration, root-severed soil respiration and the root respiration followed a similar seasonal trend, with a high rate in summer due to wet and high temperature and a low rate in spring and autumn due to lower temperature. The mean rates of total soil respiration, root-severed soil respiration and root respiration were 4.44, 2.30 and 2.14 μmol.m^-2.s^-1, respectively during the growing season, and they were all exponentially correlated with temperature. Soil respiration rate had a linear correlation with soil volumetric moisture. The Q10 values for total soil respiration, root-severed soil respiration and root respiration were 2,82, 2.59 and 3. 16, respectively. The contribution rate of root respiration to the total soil respiration was between 29.3% and 58.7% during the growing season, indicating that root is a major component of soil respiration. The annual mean rates of total soil respiration, root-severed soil respiration and root respiration were 1.96, 1.08, and 0.87 μmol.m^-2.s^-1, or 741.73 408.71, and 329.24 g.m^-2.a^-1, respectively. Root respiration contributed 44.4% to the annual total soil respiration. The relationship proposed for soil respiration with soil lemperature was useful for understanding and predicting potential changes in Changbai Mountain B. platyphylla forest ecosystem in response to forest management and climate change.

Study of elastic-plastic damage model of cement consolidated soil with high organic content

On the basis of elastic-plastic damage model of cement consolidated soil,the authors took organic contents into reasonable damage variable evolution equation in order to seek relation between the organic contents and parameters in the equation,and established the elastic-plastic damage model of cement consolidated soil considering organic contents.The results show that the parameters change correspondingly with difference of the organic contents.The higher the organic contents are,the less the valves of the parameters such as elastic modulus(E),material parameters(K,n) and damage evolution parameter(ε) become,but the larger strain damage threshold value(εd) of the sample is.Meanwhile,the calculation results obtained from established model are compared with the test data in the condition of common indoors test,which is testified with reliability.

Temporal Variations in Soil CO_2 Efflux Under Diferent Land Use Types in the Black Soil Zone of Northeast China

The quantification of soil CO2 effiux is crucial for better understanding the interactions between driving variables and C losses from black soils in Northeast China and for assessing the function of black soil as a net source or sink of atmospheric CO2 depending upon land use. This study investigated responses of soil CO2 effiux variability to soil temperature interactions with different soil moisture levels under various land use types including grassland, bare land, and arable （maize, soybean, and wheat） land in the black soil zone of Northeast China. The soil CO2 effiuxes with and without live roots, defined as the total CO2 efftux （FtS） and the root-free CO2 ei^lux （FrfS）, respectively, were measured from April 2009 to May 2010 using a static closed chamber technique with gas chromatography. The seasonal soil CO2 fluxes tended to increase from the beginning of the measurements until they peaked in summer and then declined afterwards. The mean seasonal FtS ranged from 20.3=h7.8 to 58.1~21.3 mg CO2-C m-2 h-1 for all land use types and decreased in the order of soybean land ~ grassland 〉 maize land ~ wheat land ） bare land, while the corresponding values of FrfS were relatively lower, ranging from 20.3~7.8 to 42.3~21.3 mg CO2-C m-2 h-1. The annual cumulative FtS was in the range of 107-315 g CO2-C m-2 across all land uses types. The seasonM CO2 effiuxes were significantly （P 〈： 0.001） sensitive to soil temperature at 10 cm depth and were responsible for up to 62% of the CO2 effiux variability. Correspondingly, the temperature coefficient Q10 values varied from 2.1 to 4.5 for the seasonal FtS and 2.2 to 3.9 for the FrfS during the growing season. Soil temperature interacting with soil moisture accounted for a significant fraction of the CO2 flux variability for FtS （up to 61%） and FrfS （up to 67%） via a well-defined multiple regression model, indicating that temperature sensitivity of C02 flux can be mediated by water availability, especially under water stress.