降水量对荒漠草原凋落物-土壤碳氮磷生态化学计量学特征的影响

Effects of Precipitation on Ecological Stoichiometric Characteristics of Litter and Soil Carbon,Nitrogen and Phosphorus in Desert Steppe

以2014年在宁夏荒漠草原设置的野外降水量控制试验(减少50%、减少30%、自然、增加30%、增加50%)为研究平台,采用为期480d的原位分解袋法,研究不同降水量处理下凋落物分解特征(碳、氮、磷释放及其生态化学计量学特征)、土壤碳氮磷生态化学计量学特征以及二者的关系。结果表明:480d的分解过程中,各处理下凋落物碳释放速率较为平缓,氮和磷先快速释放后缓慢释放(前60d释放最快),因而碳氮比和碳磷比先快速降低后趋于稳定。土壤碳氮磷生态化学计量学特征未呈现出明显的时间变化规律;与自然降水量相比,减少和增加30%降水量对凋落物分解和土壤碳氮磷生态化学计量学特征影响较小,但增加50%降水量显著降低了凋落物全氮和全磷浓度,提高了凋落物碳氮比和碳磷比,增加了土壤有机碳、全氮含量和碳磷比(P<0.05);土壤有机碳含量与凋落物氮释放量呈显著正相关,土壤全磷含量和碳氮比与凋落物氮、磷释放量呈显著正相关(P<0.05),土壤氮磷比与凋落物氮、磷释放量呈显著负相关(P<0.05)。结果表明,小幅度的降水量变化对凋落物元素释放过程影响较小,降水量的大幅度增加会促进凋落物氮和磷释放,从而有助于提高土壤有机碳积累和磷供给,缓解土壤磷限制。

Based on a field experiment of changing precipitation regimes(50%reduction,30%reduction,control,30%increase,and 50%increase)set up in desert steppe in Ningxia(2014),the litter decomposition characteristics,soil ecological stoichiometric characteristics,and their interactions were studied using an in-situ decomposition bag method for 480 d.The results showed that carbon(C)of litter was released steadily during 480 d of decomposition,whereas nitrogen(N)and phosphorus(P)were released rapidly in the first 60 d and then steadily after that.So litter C∶N and C∶P quickly decreased and then became steadily.However,soil C∶N∶P ecological stoichiometric characteristics did not show evident temporal dynamics.Compared with natural precipitation,30%precipitation reduction or increase had less influence on litter decomposition and soil C∶N∶P ecological stoichiometric characteristics,whereas 50%precipitation increase significantly decreased litter total N and P concentrations,increased litter C∶N and C∶P,and soil organic C content,total N content,and C∶P(P<0.05).Soil organic C content positively correlated with litter N release amount(P<0.05).Soil total P content and C∶N positively correlated with litter N and P release amounts(P<0.05).Furthermore,soil N∶P negatively correlated with litter N and P release amounts(P<0.05).In conclusion,the slight changes in precipitation had minimal effects on the release of elements from litter.In contrast,the significant increase in precipitation promoted the release of N and P from litter,thereby improving soil organic C accumulation and P supply and alleviating soil P limitation.