Soil Organic Matter Dynamics in Eurasian Steppes

包括哈萨克斯坦、乌克兰和匈牙利在内的欧亚草原土壤表层CO_2通量变化较大。在某些草原生态系统（哈萨克斯坦南部），这一比例高于大多数农田。然而，一个相当简单的关系，得到了在原位年土壤呼吸和生物环境因子（即“湿度和SOM积累”和“生物量积累”的因素）。与此同时，实验室方法来固定SOM的分解速率表现出整体相似的速率常数在每个各自的生态系统，如草原或森林。这可能是曾经建立的模拟模型明显成功的主要原因之一，在这些模型中，几个有机物质库主要是基于分解速率常数的顺序的差异来假定的。一个重要的 ...更多信息 天然草地开垦后的变化主要表现在土壤有机质中较不稳定组分的减少，如轻组分C或C_0。在区域尺度上，C_0值对CO_2排放的预测有一定的参考价值。相对而言，土壤化粪池土壤似乎是稳定的，对环境条件和/或土地利用的变化，而不是像森林生态系统，其中加速分解的有机质往往是观察后reclamation. Geostatistical分析表明，在北方哈萨克斯坦农业景观中的有机质的总体积累主要是由累积的初级生产力的土壤水分制度和土地利用/管理的结果。这种变化所造成的地形和水分状况也指出了乌克兰草原土壤。在所研究的草原生态系统中，初级生产的最重要决定因素是水的可用性，而分解的决定因素通常是温度。农业实践通常会改变土壤水分状况，以实现最大的作物产量，其次是去除初级生产作为收获，但它不会从根本上改变土壤有机质和/或养分的动态。如果农业措施对草原环境下有机质状况的不利影响实际上是有限的，从不同的方法，建议在现实中，一个合适的选择，协调可持续的农业生产与环境保护的有机质分解的空间格局的基础上，特定地点的农业管理将是一个合适的选择。少

The CO_2 flux from soil surfaces in Eurasian steppes, including Kazakhstan, Ukraine and Hungary, varied widely. It was higher in some grassland ecosystems (southern Kazakhstan) than in most of the cropland. Nonetheless a rather simple relationship was obtained between the in situ annual soil respiration and bio-environmental factors (namely "humidity and SOM accumulation" and "biomass accumulation" factors). At the same time, the laboratory approach to fix decomposition rates of SOM showed an overall similarity of the rate constants within each respective ecosystem such as steppe or forest. This might be one of main reasons for an apparent success of simulation models ever established, in which several pools of organic materials are supposed primarily based on the difference in the order of decomposition rate constants.Lowering soil respiration under cropped ecosystems tended to alleviate an active degradation of SOM-related properties of soils, which was initially observed. A signific … More ant change after reclamation of natural grassland mostly appeared in the decrease of more labile fractions of SOM, such as light fraction C or C_0. In the regional scale, the value of C_0 was useful for predicting CO_2 emission. Chemozem soils seemed to be, relatively speaking, stable against changes in environmental conditions and/or land use, not like as forest ecosystems, in which accelerated decomposition of SOM was often observed after reclamation.The geostatistical analysis suggested that the overall accumulation of SOM in agro-landscape in northern Kazakhstan was primarily affected by the cumulative primary production as a result of soil moisture regime and land use/management. Such a variation caused by topography and water regime was also pointed out for Ukrainian steppe soils. The most important determinant for primary production is water availability, whereas that of decomposition is usually temperature in the steppe ecosystems investigated. Agricultural practices usually modifies soil water regime for achieving maximum crop production, followed by removal of primary production as harvest, but it does not essentially change the dynamics of SOM and/or nutrients. If the adverse effects of agricultural practices on SOM regime under steppe environment are actually limited, as suggested from different approaches, a site-specific agricultural management based on the spatial patterns of organic matter dynamics would be a suitable option in reality for harmonizing sustainable agricultural production with environmental conservation by reducing organic matter decomposition. Less