短期氮磷添加对祁连山亚高山草地土壤呼吸组分的影响

Effects of Short-Term Nitrogen and Phosphorus Addition on Soil Respiration Components in a Subalpine Grassland of Qilian Mountains

为探究短期氮磷添加对祁连山亚高山草地土壤呼吸及其组分的影响,于2019年6~8月采用随机区组设计,设置氮添加[10g·(m^(2)·a)^(-1),N]、磷添加[5g·(m^(2)·a)^(-1),P]、氮磷混施[10g·(m^(2)·a)^(-1)N、 5g·(m^(2)·a)^(-1)P,NP]、对照(CK)和完全对照(CK′)这5个处理,测定了土壤总呼吸速率及其组分.结果表明,氮添加对土壤总呼吸和异养呼吸的降低速率均低于磷添加[-16.71%vs.(相对照,下同)^(-1)9.20%;-4.41%vs.-13.05%],但对自养呼吸的降低速率高于磷添加(-25.03%vs.-23.36%),而氮磷混施则对土壤总呼吸速率无显著影响.土壤总呼吸速率及其组分与土壤温度均呈显著的指数相关,其中氮添加降低了呼吸速率的温度敏感性(Q10:-5.64%~0.00%),而磷添加增加了Q10(3.38%~6.98%),氮磷混施降低了自养呼吸速率但增加了异养呼吸速率的Q10(16.86%),从而降低了土壤总呼吸速率的Q10(-2.63%~-2.02%).土壤pH、土壤全氮和根系磷含量与自养呼吸速率均具有显著相关性(P<0.05),而与异养呼吸速率无显著相关,且根系氮含量只与异养呼吸速率呈显著负相关(P<0.05).总体上,自养呼吸速率对氮添加更加敏感,而异养呼吸速率对磷添加更加敏感,氮或磷添加均显著降低了土壤总呼吸速率,而氮磷混施并未显著影响土壤总呼吸速率,此结果可为准确评估亚高山草地土壤碳排放提供科学依据.

In order to investigate the effects of short-term nitrogen and phosphorus addition on soil respiration and its components in a subalpine grassland located on the Qilian Mountains,a random block design of nitrogen[10 g·(m^(2)·a)^(-1),N],phosphorus[5 g·(m^(2)·a)^(-1),P],nitrogen and phosphorus addition[10 g·(m^(2)·a)^(-1)N and 5 g·(m^(2)·a)^(-1)P,NP],the control(CK),and complete control(CK')was conducted from June to August 2019,and total soil respiration and its component respiration rates were measured.The results showed that nitrogen addition reduced soil total respiration and heterotrophic respiration rates at a lower rate than P addition[-16.71%vs.-19.20%;-4.41%vs.-13.05%],but the rate of decrease in autotrophic respiration was higher than that of P addition(-25.03%vs.-23.36%);N and P mixed application had no significant effect on soil total respiration rate.The total soil respiration rate and its components were significantly exponentially correlated with soil temperature,and the temperature sensitivity of soil respiration rate was decreased by nitrogen addition(Q10:-5.64%-0.00%).P increased Q10(3.38%-6.98%),and N and P reduced autotrophic respiration rate but increased heterotrophic respiration rate Q10(16.86%)and decreased total soil respiration rate Q10(-2.63%--2.02%).Soil pH,soil total nitrogen,and root phosphorus content were significantly correlated with autotrophic respiration rate(P<0.05)but not with heterotrophic respiration rate,and root nitrogen content was significantly negatively correlated with heterotrophic respiration rate(P<0.05).In general,autotrophic respiration rate was more sensitive to N addition,whereas heterotrophic respiration rate was more sensitive to P addition.Both N and P addition significantly reduced soil total respiration rate,whereas N and P mixture did not significantly affect soil total respiration rate.These results can provide a scientific basis for the accurate assessment of soil carbon emission in subalpine grassland.