Effects of rodent-induced land degradation on ecosystem carbon fluxes in an alpine meadow in the Qinghai–Tibet Plateau, China

摘要

The widespread land degradation in an alpine meadow ecosystem would affectecosystem carbon (C) balance. Biomass, soil chemical properties and carbondioxide (CO₂) of six levels of degraded lands (D1–D6, according to thenumber of rodent holes and coverage) were investigated to examine the effectsof rodent-induced land degradation on an alpine meadow ecosystem. Soilorganic carbon (SOC), labile soil carbon (LC), total nitrogen (TN) andinorganic nitrogen (N) were obtained by chemical analysis. Soil respiration(R_s), net ecosystem exchange (NEE) and ecosystem respiration (ER)were measured by a Li-Cor 6400XT. Gross ecosystem production (GEP) was thesum of NEE and ER. Aboveground biomass (AGB) was based on a linear regressionwith coverage and plant height as independent variables. Root biomass (RB)was obtained by using a core method. Soil respiration, ER, GEP and AGB weresignificantly higher in slightly degraded (D3 and D6, group I) than inseverely degraded land (D1, D2, D4 and D5, group II). Positive values of NEEaverage indicate that the alpine meadow ecosystem is a weak C sink during thegrowing season. The only significant difference was in ER among differentdegradation levels. R_s, ER and GEP were 38.2, 44.3 and 46.5%higher in group I than in group II, respectively. Similar difference of ERand GEP between the two groups resulted in an insignificant difference ofNEE. Positive correlations of AGB with ER, NEE and GEP, and relatively smallAGB and lower CO₂ fluxes in group II, suggest the control of AGB onecosystem CO₂ fluxes. Correlations of RB with SOC, LC, TN and inorganicN indicate the regulation of RB on soil C and N with increasing number ofrodent holes in an alpine meadow ecosystem in the permafrost region of theQinghai–Tibet Plateau (QTP).