东北地区大秃顶子山土壤-微生物-胞外酶C:N:P化学计量特征沿海拔梯度的变化

Changes in soil-microbe-exoenzyme C:N:P stoichiometry along an altitudinal gradient in Mt.Datudingzi,Northeast China

海拔变化导致温度、水分、植被等条件的改变会显著影响土壤碳(Csoil)、氮(Nsoil)、磷(Psoil)含量及其化学计量特征,土壤微生物如何通过调整自身生物量和胞外酶化学计量特征进行适应仍不明确。为了研究海拔梯度变化对土壤微生物生物量和胞外酶活性的影响,探索土壤-微生物-胞外酶C:N:P化学计量特征间的协变性,该文以黑龙江省雪乡大秃顶子山800、1100、1600和1700 m分布的典型生态系统(针阔混交林、针叶林、岳桦林和草地)为研究对象,测定其Csoil、Nsoil、Psoil含量,微生物生物量C(Cmic)、N(Nmic)、P(Pmic)含量,以及微生物获取C(β-1,4-葡萄糖苷酶,BG),N(几丁质酶,NAG),P(酸性磷酸酶,AP)资源的相关胞外酶活性。结果表明:(1)海拔梯度变化对Csoil和Cmic含量没有显著影响;不同海拔间土壤和微生物生物量N、P含量存在显著差异。(2)BG和NAG活性随着海拔的升高呈现显著降低趋势,表明海拔升高导致的温度降低抑制了微生物的活性。(3)海拔对土壤C:N、微生物C:N:P以及胞外酶C:N:P均具有显著影响。胞外酶C:N:P随着微生物与土壤间C:N:P化学计量不平衡性(土壤C:N:P与微生物C:N:P的比值)的增加而逐渐降低。微生物可以通过调整自身生物量以及胞外酶C:N:P适应土壤化学计量特征的变异,该结果支持了微生物的资源分配理论。

Aims Altitude-induced changes in temperature, moisture, vegetation types and other conditions would significantly affect soil carbon(Csoil), nitrogen(Nsoil), phosphorus(Psoil) concentrations and their stoichiometry. How soil microorganisms adapt to the variability of soil resource stoichiometry by regulating their biomass and extracellular enzymatic stoichiometry remains uncertain. The objective of this study was to quantify the altitudinal trends of soil-microbe-exoenzyme C:N:P stoichiometry and to explore the correlations among soil-microbeexoenzyme stoichiometry. Methods In the present study, we investigated the Csoil, Nsoil, Psoil concentrations, microbial biomass C(Cmic), N(Nmic), P(Pmic) concentrations, and the activities of C(β-1,4-glucosidase, BG), N(N-acetyl-β-glucosaminidase, NAG), and P(acid phosphatase) acquiring extracellular enzymes for microorganisms in four ecosystems along an altitudinal gradient on Mt. Datudingzi, Northeast China. These four ecosystems are a mixed broadleaf-coniferous forest at 800 m, a coniferous forest at 1 100 m, a Betula ermanii forest at 1 600 m and a grassland at 1 700 m. Important findings The results showed that:(1) altitude had no significant effect on Csoil and Cmic concentrations but had significant effects on soil and microbial biomass N and P concentrations.(2) The activities of BG and NAG decreased significantly with increasing altitude, likely due to the high elevation induced low temperature that inhibits microbial activities.(3) Altitude had significant effects on soil C:N, microbe C:N:P, and exoenzyme C:N:P;exoenzyme C:N:P decreased with the increasing stoichiometric imbalances between microorganisms and soils(ratios of soil C:N:P to microbe C:N:P, respectively). Overall, these results suggested that microorganisms can adapt to the variability of soil C:N:P by regulating their biomass C:N:P and exoenzyme C:N:P, and supported the microbial resource allocation theory.