生长季增温对黄土高原甘青针茅和铁杆蒿群落及其土壤养分的影响

Effects of growing season warming on Stipa przewalskyi and Artemisia sacrorum communities and soil nutrients on the Loess Plateau

为探究全球变暖背景下草原优势种变化规律及其土壤养分作用机制,本研究以黄土高原典型草原-宁夏云雾山国家级自然保护区优势种甘青针茅(Stipa przewalskyi)和铁杆蒿(Artemisia sacrorum)群落为研究对象,探究植物生长季增温条件下群落地上生物量及地下不同土层土壤有机碳、全氮、速效磷、微生物生物量碳、微生物生物量氮、硝态氮、铵态氮含量变化规律。结果表明:1)生长季增温分别使甘青针茅和铁杆蒿群落地上生物量提高了122.87%和36.65%,两者对增温响应的差异与其对磷等养分利用的差异有关。2)生长季增温使不同深度土壤平均温度升高2.03~2.93℃,表层(0-5 cm)土壤温度增幅高于深层;土壤温度的升高导致土壤水分含量降低。3)表层土壤养分对于增温的响应程度强于下层,增温使甘青针茅和铁杆蒿群落表层土壤有机碳含量分别显著降低了18.47%和2.35%(P <0.05)。此外,在甘青针茅群落中,增温极显著提高了表层土壤速效磷含量、降低了微生物生物量氮含量(P <0.01)。总之,生长季增温通过影响土壤温度、水分条件进而对甘青针茅、铁杆蒿群落的土壤养分状况及其地上生物量产生影响,甘青针茅群落对增温的响应更为敏感。本研究对了解全球增温黄土高原草地生态系统不同优势种的群落变化特征以及土壤养分变化及驱动机制具有重要意义。

To explore the change patterns of dominant species in grasslands and their supporting mechanisms of soil nutrients under global warming, we selected the dominant species Stipa przewalskyi and Artemisia sacrorum in a typical grassland in the Loess Plateau: Yunwu Mountain National Nature Reserve in Ningxia. We aimed to explore the changes in aboveground biomass of two dominant species as well as soil organic carbon(SOC), total nitrogen, available phosphorus(AP), microbial biomass carbon, microbial biomass nitrogen(MBN), nitrate nitrogen, and ammonium nitrogen content in different soil layers under growing season warming. We found that: 1) Growing season warming increased the aboveground biomass of the two communities by 122.87% and 36.65%, respectively. The differences in the responses to warming between the two communities may be related to the different utilization characteristics of phosphorus and other nutrients. 2) The average temperature in different soil layers increased by 2.03~2.93 ℃ under experimental warming, and the increment in the surface layer(0-5 cm) was higher than that in the deeper layers. Furthermore, we found that warming caused a decrease in soil moisture content. 3) Surface soil nutrients of the S. przewalskyi and A. sacrorum communities responded more strongly to warming than their deeper counterparts;in particular, the SOC content of the surface soil was significantly reduced by18.47% and 2.35%(P < 0.05), respectively. In addition, in the S. przewalskyi community, warming significantly increased the AP content in the surface soil and reduced the MBN content(P < 0.01). In short, growing season warming influences soil nutrient status and aboveground biomass of the S. przewalskyi and A. sacrorum communities by affecting soil temperature and water conditions, whereas S. przewalskyi community is more sensitive to these changes. The findings of the present study are of great significance for understanding the characteristics of community variation and soil nutrient cycles of different dominant species in grassland ecosystems on the Loess Plateau under global changes.