黄土丘陵区植被与地形特征对土壤和土壤微生物生物量生态化学计量特征的影响

研究黄土丘陵区植被与地形特征对土壤和土壤微生物生物量生态化学计量特征影响有助于深入理解黄土丘陵区不同植被带下土壤和土壤微生物相互作用及养分循环规律.选择黄土丘陵区延河流域3个植被区(森林区、森林草原区、草原区)和5种地形部位(阴/阳沟坡、阴/阳梁峁坡、峁顶)的土壤作为研究对象,利用生态化学计量学理论研究植被和地形对土壤和土壤微生物生物量生态化学计量特征的影响.结果表明: 土壤及土壤微生物生物量碳、氮、磷含量在不同地形之间的差别主要表现在沟坡位置和阴坡高于其他坡位和阳坡.植被类型的变化对两个土层(0～10、10～20 cm)土壤和土壤微生物生物量碳、氮、磷的影响均达到显著水平,坡向对表层(0～10 cm)土壤和土壤微生物生物量碳、氮、磷的影响强于坡位,而在10～20 cm土层,坡位对土壤和土壤微生物生物量碳、氮、磷影响更显著.植被类型显著影响土壤C∶N、C∶P、N∶P和土壤微生物生物量C∶N、C∶P,坡向和坡位仅影响土壤C∶P和N∶P,植被类型的变化是影响土壤C∶N的主要因素.同时,植被类型对土壤养分和微生物生物量碳、氮、磷含量及其生态化学计量特征的影响大于地形因子.标准化主轴分析结果表明,黄土丘陵区不同植被带土壤微生物具有内稳性,特别在草原带,土壤微生物生物量生态化学计量学特征具有更加严格的约束比例.在黄土丘陵区,土壤微生物生物量N∶P或许可以作为判断养分限制的另一个有力工具,若将土壤微生物生物量N∶P与植物叶片N∶P配合使用可能有助于我们更加精确地判断黄土丘陵区的土壤养分限制情况.

Effects of vegetation and topography features on ecological stoichiometry of soil and soil microbial biomass in the hilly-gully region of the Loess Plateau,China.

The objectives of this study were to explore the effects of vegetation type, topographic features and their combined effects on soil microbial biomass stoichiometry, so as to better understand the interaction of soil, soil microbes and nutrient cycling under different vegetation types in the hilly-gully region of the Loess Plateau. Soils from three vegetation zones (forest zone, forest-steppe and steppe) and five slope positions (south/north backslope, south/north shoulder and summit) were chosen and the effects of vegetation types and topography features on soil and C:N:P ratios in soil microbial biomass were investigated in this study. The results showed that, among the five slope positions, the highest concentrations of soil and soil microbial biomass C, N, P were found at the backslope position and the north-facing slope. The effects of vegetation types on soil and soil microbial biomass C, N and P in the two soil layers were significantly different, whereas the effects of slope aspect and positions were only numerically different. As for different soil layers, the topsoil (0-10 cm) was more affected by slope aspect, while the subsoil (10-20 cm) was more influenced by slop position. While the effects of vegetation type on soil C:N, C:P and N:P and soil microbial biomass C:N, C:P were significant, slope aspect and slope position only influenced soil C:P and N:P. Consequently, on the Loess Plateau, the effects of vegetation type on soil and soil microbial biomass C, N, P were stronger than those of the topographic features. The standardized major axis tests showed that C:N:P stoichiometry in soil microbes was well-constrained, especially in the steppe zone. The soil microbial biomass N:P might be used as a useful tool to assess nutrient limitation of ecosystem processes in terrestrial ecosystems. If combined with plant leaf N:P, they could provide more accurate information to estimate the nutrient limitation of fragile ecosystem in hilly-gully region of the Loess Plateau.