新疆温性草原土壤pH特征及影响因素

Patterns and drivers of soil pH on the Xinjiang temperate steppe

土壤pH是影响草地生态系统植物生长和土壤养分有效性的主要因素之一,现有研究发现其受到海拔、气候和土壤理化性质的影响。之前研究多集中在这些因子对表层土壤pH变化的影响,而不同土层pH对这些因子的响应是否一致仍缺乏探讨。基于此,本研究以新疆温性草原为研究对象,于2011-2013年对86个样地的不同土层(0-5、5-10、10-20、20-30、30-50、50-70和70-100 cm)土壤pH和相关理化性质(土壤有机质、土壤全氮含量、容重和土石比)进行测定,并重点分析了地表微环境(凋落物、立枯、覆沙、砾石、风蚀和水蚀程度)对不同土层pH的影响,以及海拔、气候(年均温度和年均降水量)和相关理化性质与土壤pH之间的关系。研究发现:1)随土层增加,土壤pH呈逐渐增大的变化特征,而土壤有机质和全氮含量则呈降低的趋势。2)凋落物、砾石和风蚀对各土层pH均无显著影响(P>0.05),立枯显著降低了0-50 cm各土层中pH(P<0.05),水蚀仅增加了0-20 cm各土层pH,覆沙则降低了70-100 cm土层中pH。3)各土层pH与海拔以及0-10 cm土层pH与年平均温度之间呈显著正相关关系(P<0.05),年平均降水量与0-30 cm土层pH呈显著负相关关系(P<0.05)。各土层pH与土壤有机质和全氮含量之间多表现为显著负相关关系(P<0.05),而与容重和土石比仅在个别土层有内在联系。主成分分析进一步表明,土壤有机质、全氮含量、土石比和年平均温度对pH的影响强度高于其他因素。结果表明,新疆温性草原土壤pH的变化均受到地表微环境、海拔、气候和土壤理化性质的影响,但影响强度在不同因子和不同土层间存在差异。

Soil pH is one of the most important factors in regulating plant growth and soil nutrient availability in grasslands.A large number of studies have revealed that soil pH is determined by elevation,climate,and soil physicochemical properties.However,previous studies have focused on the effects of these variables on surface soil pH,while our knowledge about their effects on pH among different soil layers is still limited.To address this knowledge gap,we collected soil pH and related soil physicochemical properties[soil organic matter(SOM),soil total nitrogen(STN)content,soil bulk density(SBD),and volume ratio of rock to soil(RRS)]of the different soil layers at 0-5,5-10,10-20,20-30,30-50,50-70,and 70-100 cm among 86 sites on the Xinjiang temperate steppe during 2011-2013.We also surveyed the surface microenvironment(standing litter,litter,sand covering,and gravel,wind,and water erosion),elevation,and climate[mean annual temperature(MAT)and mean annual precipitation(MAP)]for each site.Finally,we explored the effects of surface microenvironment on soil pH as well as the relationships between soil pH and elevation,climate,and soil physicochemical properties.Our results showed that on the Xinjiang temperate steppe,soil pH gradually increases,while SOM and STN content gradually decrease with increasing soil depth.Litter,gravel,and wind erosion had no significant effects on pH(P>0.05).However,standing litter decreased pH at the 0-50 cm layer,while water erosion only increased pH at the 0-20 cm layer and sand covering decreased pH at the 70-100 cm layer.Besides,pH in all soil layers was positively associated with elevation.Soil pH at the 0-10 cm layer also gradually increased with increasing MAT.With increasing MAP,pH at the 0-30 cm layer gradually decreased.In addition,pH at most soil layers was negatively correlated with SOM and STN content,while pH was tightly associated with SBD and RRS in only a few soil layers.Taking all these factors together,we found that on the Xinjiang temperate steppe,SOM,STN content,RRS and MAT play a more important role in regulating pH variation than other factors.These results showed that the changes of soil pH on the Xinjiang temperate steppe were simultaneously affected by surface microenvironment,elevation,climate,and soil physicochemical properties,but their relative importance differed among different factors and soil layers.