牦牛粪沉积对青藏高原高寒草甸土壤酶活性的影响

牦牛粪归还是维持青藏高原草地生态系统功能的主要途径之一.以往的研究主要关注牦牛粪沉积对土壤理化性质的影响,但是对土壤微生物群落及其功能的研究较少.本研究分析了牦牛粪沉积对青藏高原高寒草甸土壤酶活性及其潜在调控因子的影响,结果表明:牦牛粪添加显著增加了土壤微生物生物量碳(MBC)(P<0.001)和土壤微生物生物量氮(MBN)(P<0.001)含量,分别增加了14.24％和20.29％.牦牛粪添加显著增加了土壤β-1,4-葡萄糖苷酶(BG)(P<0.001)、β-1,4-木糖苷酶(BX)(P<0.001)和脲酶(URE)(P<0.001)活性,分别增加了8.4％、8.2％和6.6％.牦牛粪添加显著增加了土壤水分含量(SMC)(P<0.01)、可溶性有机碳(DOC)(P<0.001)和可溶性有机氮(DON)(P<0.001)含量,但降低了土壤pH(P<0.001).冗余分析表明,土壤酶活性与DOC(P<0.001)、DON(P<0.001)、MBC(P<0.001)和MBN(P<0.001)呈显著正相关关系,而与土壤pH(P<0.05)呈显著负相关关系.此外,可利用性基质(DOC和DON)对土壤酶活性的调控比微生物生物量(MBC和MBN)更重要.本研究结果表明,牦牛粪沉积通过为土壤微生物提供易于利用的碳源和养分,促进了土壤微生物活动,在调节青藏高原放牧生态系统土壤碳和养分循环中起着重要作用.

Effects of yak dung deposition on soil enzyme activities in an alpine meadow in the Tibetan Plateau

Yak dung deposition is one of the important ways to maintain the function of grassland ecosystems in the Tibetan Plateau. The effects of yak dung deposition on soil physicochemical properties are well established; however, little is known regarding the effects of yak dung deposition on soil enzyme activities. the present study investigated the effects of yak dung deposition on soil enzyme activities and its potential regulatory factors in a Tibetan alpine meadow. Dung deposition significantly increased soil microbial biomass carbon (MBC) (P < 0.001) and nitrogen (MBN) (P < 0.001) content by 14.24% and 20.29%, respectively. Dung depositionn significantly increased the enzyme activity of β-1, 4-glucosidase (BG) (P < 0.001), β-1, 4-xylosidase (BX) (P < 0.001) and urease (URE) (P < 0.001) by 8.4%, 8.2% , and 6.6%, respectively. Further, dung deposition significantly increased soil moisture content (SMC) (P < 0.01) dissolved organic carbon (DOC) (P < 0.001), and dissolved organic nitrogen (DON) (P < 0.001), but decreased soil pH (P < 0.001). Redundancy analysis revealed that soil enzyme activities were significantly and positively associated with DOC (P < 0.001), DON (P < 0.001), MBC (P < 0.001) and MBN (P < 0.001) but significantly and negatively associated with soil pH (P < 0.05). Moreover, dung-induced variations in available substrates (DOC and DON) were more important in regulating soil enzyme activities than those in microbial biomass (MBC and MBN). These results indicate that yak dung deposition can improve soil microbial activity through providing liable carbon and available nutrients, and it can be play an important role in regulating soil carbon and nutrient cycling in a grazed alpine grassland ecosystem in The Tibetan Plateau.