恒温和变温模式下不同施肥黄壤有机碳矿化特征及其影响因素

Characteristics and controlling factors of yellow soil organic carbon mineralization in different fertilization treatments under constant and variable temperature regimes

【目的】土壤有机碳(SOC)矿化是陆地生态系统碳循环的重要组成部分,温度变化显著影响SOC矿化特征。研究长期不同施肥管理下SOC矿化特征及其对温度模式(恒温vs.变温)的响应,可为优化农田碳管理,减缓农业生产对气候变化的影响提供理论依据。【方法】基于贵州省农业科学院内旱作黄壤长期定位试验,在不施肥(CK)、单施化肥(NPK)、单施有机肥(M)和有机无机肥配施(NPKM)4个处理小区采集耕层土壤样品用于室内培养实验。恒温处理为保持15℃;变温处理为10℃→15℃→20℃→15℃→10℃,每6 h匀速变化5℃,24 h为一个循环周期,两温度处理积温相同,共培养32天。采用碱液吸收法测定CO_(2)排放通量,并分析土壤物理化学及生物学性质,阐明不同温度模式下SOC矿化特征及其主要驱动因素。【结果】恒温培养条件下,CK、NPK、M和NPKM处理SOC累积矿化量分别为201、175、262和228 mg/kg,相对于CK,M和NPKM处理的SOC累积矿化分别显著增加了30.6%和13.3%,但NPK处理显著降低了12.7%。变温培养条件下,M处理SOC累积矿化量较CK显著增加了30.0%,NPK和NPKM处理间无显著差异。与恒温培养相比,变温培养下CK和NPK处理SOC累积矿化量分别增加了16.2%和25.6%,而M和NPKM处理无显著变化。恒温和变温培养条件下,CO_(2)累积排放量与土壤pH、SOC、全氮、微生物生物量碳氮等指标显著正相关;温度模式变化引起的CO_(2)排放强度变化与土壤微生物生物量碳氮、微生物呼吸熵和碳氮磷转化酶活性显著负相关。【结论】长期施用有机肥通过增加底物有效性、微生物生物量和酶活性显著促进了SOC矿化,通过改变土壤微生物呼吸熵和碳磷转化酶活性缓解了温度周期性变化对SOC矿化的促进作用。

【Objectives】Soil organic carbon(SOC)mineralization is an important process of carbon cycle in terrestrial ecosystems,and temperature changes significantly affect the characteristics of SOC mineralization.We investigated the SOC mineralization in response to constant and variable temperatures under different long-term fertilization management,so as to provide a theoretical basis for mitigating the impact of agricultural production on climate change through optimized farmland carbon management.【Methods】The soil samples were collected from the yellow soil long-term fertilization experiment at Guizhou Academy of Agricultural Sciences,with the following four treatments:no fertilizer(CK),chemical fertilizer(NPK),organic fertilizer(M),and combined organic and inorganic fertilizer(NPKM).The soil samples were incubated at constant temperature(15℃),and variable temperature(the incubation temperature changed from 10℃→15℃→20℃→15℃→10℃at interval of 6 hours,and the cycle repeated every 24 hours)for 32 days.The CO_(2)effluxes were determined by NaOH absorption method,and soil physicochemical and biological properties were analyzed,in order to elucidate the characteristics of SOC mineralization and its main driving factors under different temperature modes.【Results】Under constant temperature,compared with CK treatment(201 mg/kg),the cumulative CO_(2)emission significantly increased by 30.6%and 13.3%in M and NPKM treatments(262 and 228 mg/kg,respectively),and decreased by 12.7%in NPK treatment(175 mg/kg).Under variable temperature condition,cumulative CO_(2)emission significantly increased by 30%in the M treatment relative to the CK treatment,while there was no significant difference among the CK,NPK,and NPKM treatments.Compared to constant temperature condition,cumulative CO_(2)emission increased by 16.2%and 25.6%for the CK and NPK treatments,respectively,under variable temperature condition.However,there was little difference in cumulative CO_(2)emission under constant and variable temperature conditions for the M and NPKM treatments.The cumulative CO_(2)emissions were significantly and positively correlated with soil pH,SOC,total nitrogen,and microbial biomass carbon(MBC)and nitrogen(MBN)among fertilization treatments under both constant and variable temperature conditions.The changes in CO_(2)emission induced by temperature modes were negatively correlated with soil MBC,MBN,microbial respiratory quotient,and enzyme activities related to carbon,nitrogen and phosphorus cycling.【Conclusions】Long-term application of organic fertilizer could significantly increase SOC mineralization by increasing substrate availability and microbial biomass,and mitigate the positive effects of variable temperature on SOC mineralization via changing soil microbial respiratory quotient and enzyme activities related to carbon,nitrogen,and phosphorous cycling.