川西高山林线土壤活性碳、氮对短期增温的响应

随着温室效应的加剧,受低温限制的高山林线生态系统对全球气候变暖较为敏感,可能直接影响到植物的生长和土壤碳氮过程.本研究假设气候变暖会改变高山生态系统土壤活性碳氮含量,在四川省理县米亚罗高山生态系统定位站,采用开顶式模拟增温装置(OTC)模拟增温对土壤活性碳、氮的短期影响.分别于2017年4、7和10月,采集OTC以及对照样地(CK)内土壤有机层和矿质土壤层的原状土壤,测定土壤可溶性有机碳(DOC)、土壤微生物生物量碳(MBC)、土壤可溶性有机氮(DON)和土壤微生物生物量氮(MBN)含量.结果表明: 模拟增温使年均气温升高0.88 ℃,土壤有机层和矿质土壤层的年均温度分别提高0.48和0.23 ℃.模拟增温没有显著改变土壤有机质和含水量,但显著提高了矿质土壤层的pH值,同时显著降低了非生长季矿质土壤层的DOC、DON含量;季节变化对两个层次的DOC、DON和MBN含量有极显著影响,而MBC没有明显的季节动态;增温和季节交互作用对矿质土壤层的DOC和DON有显著影响.土壤有机层的MBC、MBN含量显著高于矿质土壤层.土壤活性碳、氮与土壤有机质和含水量呈极显著正相关,MBC、MBN与土壤pH呈极显著正相关,MBN与土壤温度呈显著负相关.

Responses of soil active carbon and nitrogen to short-term warming in alpine treeline of west Sichuan,China

Alpine treeline ecosystem is more sensitive to global warming under low temperature limitation with the aggravation of greenhouse effect, which may directly affect plant growth and soil carbon and nitrogen processes. We expected that climate warming would change soil active carbon and nitrogen content in alpine ecosystems. This experiment was conducted in long-term research station of alpine forest ecosystems, in Lixian County, Sichuan Province. The open top camber (OTC) was used to simulate warming, intact soil core (soil organic layer and mineral soil layer) of OTC and CK were collected in April, July and October 2017. Soil dissolved organic carbon (DOC), soil microbial biomass carbon (MBC), dissolved organic nitrogen (DON) and soil microbial biomass nitrogen (MBN) were measured. The results showed that average temperature increased by 0.88 ℃ for air, 0.48 ℃ for soil organic layer and 0.23 ℃ for mineral soil layer. The simulated warming did not significantly change soil organic matter and water content, but significantly increased pH of mine-ral soil layer, and significantly reduced DOC and DON contents of mineral soil layer in non-growing season. There was significant seasonal variation for the contents of DOC, DON and MBN in the two layers, but not for MBC. The MBC and MBN contents of soil organic layer were significantly higher than that of mineral soil layer. There was a significant positive correlation between active carbon and nitrogen with soil organic matter and water content. There was a significant positive correlation between MBC, MBN and soil pH, whereas MBN was negatively correlated with soil temperature.