松嫩草甸不同退化程度生境土壤磷素动态研究

对松嫩草甸不同退化程度生境的几种代表植物群落土壤磷素状况的研究表明,各群落相同土层的全磷含量没有显著的差异,说明土壤磷库具有较强的弹性,土壤退化落后于地上植物群落的退化.各群落土壤全磷的季节变化相似,均经历迅速累积,达到峰值后下降,之后又有一个缓慢积累的过程.羊草、寸草苔和碱茅群落全磷含量随土层的加深而减少,虎尾草群落土壤全磷聚集于10~20cm土层.随退化程度的加重,土壤速效磷含量增加,虎尾草群落土壤速效磷占全磷的比重最高(2.8%),表明退化生境植物群落对速效磷素的利用并不充分.各群落土壤微生物量磷含量均高于速效磷含量,其季节动态均为单峰曲线,峰值出现在8月.虎尾草群落土壤微生物量磷在10~20cm的土层最多,其他群落土壤微生物量磷在0~10cm土层的含量最多.灰色分析的结果表明,土壤速效磷的形成主要受到土壤养分,尤其是碳、氮养分的影响;而土壤温度、水分状况、酸碱状况和盐化程度等因素对土壤微生物量磷的影响较强.图2表3参26

Dynamics of Soil Phosphorus in Differently Degraded Habitats of the Songnen Meadow

Seasonal variation of different phosphorus forms was investigated for two years from June 2002 to October 2003. Soil samples were randomly collected from each block at depth of 0~10 cm, 10~20cm and 20~30cm. Dynamics of soil total phosphorus (total-P) under four kinds of plant communities in the Songnen Meadow showed no significant difference at the same soil layer among Leymus chinensis community, Carex.duriuscula community, Puccinellia chinampoensis community and Chloris virgata community, indicating that soil total phosphorus had small change as plant communities were involved and reflecting that soil degradation got behind the succession of plant communities. There was a similar trend in the seasonal variation of total-P among the four kinds of communities. This process included the first phase during which total-P increased quickly, the second phase total-P declined after reaching peak value, and the third phase when total-P accumulated again. As to its vertical distribution in L. chinensis, C. duriuscula and P. chinampoensis communities, total-P content descended with the deepening of soil layer, while in C. virgata community its content in depth of 10~20 cm was higher than that in 0~10 cm and 20~30 cm. Compared with other communities, the proportion of soil available phosphorus (avail-P) to total-P in C. virgata community was the highest, which demonstrated that the plants growing on degraded habitats could not fully use soil avail-P. Soil microbial biomass phosphorus (MBP) was much more than avail-P in each community. The seasonal variation of MBP could be described as an unimodal curve, and in August the content of MBP reached its peak in the four communities. In C. virgata community MBP distributed mainly in 10~20 cm soil layer, while in other communities it accumulated mostly in 0~10 cm soil layer. Grey relational analysis showed that soil nutrients, especially C and N, could mainly affect avail-P. Soil factors, such as temperature, water content, pH and conductance, strongly influenced the MBP in each community. Fig 2, Tab 3, Ref 26