施肥方式对紫色土土壤异养呼吸的影响

采用静态暗箱-气相色谱法于2010年12月至2011年10月对不同施肥方式下的紫色土土壤呼吸进行了研究,以揭示施肥方式对紫色土异养呼吸的影响。结果表明:施肥可对土壤异养呼吸产生激发效应。施肥后第5天出现峰值,猪厩肥处理的异养呼吸峰值为2356.8 mg CO2m-2h-1,显著高于秸秆配施氮磷钾(970.1 mgCO2m-2h-1)和常规氮磷钾处理(406.8 mgCO2m-2h-1)(P0.01);小麦季常规氮磷钾、猪厩肥和秸秆配施氮磷钾处理的平均土壤异养呼吸速率为212.9、285.8和305.8mgCO2m-2h-1,CO2排放量为255.1、342.3和369.5 gC/m2,玉米季为408.2、642.8和446.4 mgCO2m-2h-1,CO2排放量为344.7、542.8和376.9 gC/m2,玉米季土壤异养呼吸平均速率及CO2排放量均高于小麦季。全年平均土壤异养呼吸速率分别为310.6、446.3和377.4 mg CO2m-2h-1,CO2排放总量分别为599.8、885.1和746.4 gC/m2。猪厩肥对土壤异养呼吸速率和CO2排放量的影响最大,秸秆配施氮磷钾肥次之,氮磷钾肥最小,说明有机物料的投入是紫色土土壤异养呼吸速率的主要调控措施,低碳氮比的有机物料能促进土壤异养呼吸和CO2的排放。猪厩肥和秸秆配施氮磷钾肥处理相应地表和地下5 cm温度的Q10值分别为2.64、1.88和2.77、1.99,表明低碳氮比的有机物料还能增加土壤异养呼吸Q10值,使土壤异养呼吸速率对温度的敏感性加强。

Impacts of fertilization regimes on soil heterotrophic respiration of purple soil

Recent studies have shown that soil respiration is the critical importance in determining the carbon balance of terrestrial ecosystems. Respiration from soils is comprised of both the heterotrophic respiration of microorganisms (soil bacteria, fungi, and fauna) and autotrophic respiration from roots and mycorrhizae. Precise assessment of these components is important for calculating the carbon budgets of vegetation and the turnover rate of soil organic matter, as well as for understanding sources and sinks of carbon in terrestrial ecosystems in the face of global climate change. Although soil heterotrophic respirations have received considerable attention in recent decades, much less is known about the effects of various natural or artificial factors such as temperature, precipitation or fertilization etc. on it. The field study was conducted at a sloping cropland in Yanting Agro-ecological Station of Purple Soil, Chinese Academy of Science under Chinese Ecosystem Research Network (CERN), situated at N31°16°, E105°28', with the altitude of 400 to 600 meters in the middle of Sichuan Basin, where a set of long-term research plots is located. Three plots were randomly assigned to one of the following treatments: conventional chemical fertilizer (NPK), organic manure (pig slurry, OM) and crop residue with chemical fertilizer (RSDNPK). Total nitrogen for each fertilization treatment was applied at the same rate with 130 and 150 kgN/hm² for wheat and maize seasons, respectively. The results showed that soil heterotrophic respiration exhibited pronounced seasonal variations that clearly reflected those of soil temperature, with minimum values in winter and maximum values in summer. There was a pulse of soil heterotrophic respiration induced by fertilization at the 5th day after fertilization. The peak rate for OM treatment was 2356.8 mgCO₂m^-2h^-1 and it was significantly higher than that for both RSDNPK and NPK treatments (P < 0.01). Meanwhile, the respiration rate and the annual cumulative CO₂ emission in OM and RSDNPK treatments were higher than those in NPK treatment. During wheat growing season, average respiration rate for NPK, OM and RSDNPK treatments were 212.9, 285.8 and 305.8 mg CO₂m^-2h^-1, respectively, which were all lower than that in maize growing season. The cumulative soil CO₂ emissions from NPK, OM and RSDNPK were 255.1, 342.3 and 369.5 gC/m² for wheat season, and 344.7, 542.8 and 376.9 gC/m² for maize season, while 599.8, 885.1 and 746.4 gCm^-2 for the whole year, respectively. The results implied that lower C/N ratio organic material was the primary driving force for increasing soil heterotrophic rate and cumulative soil CO₂ emissions. The values of temperature sensitivity (Q₁₀) for soil heterotrophic respiration in wheat season and maize season were also measured. The results showed that Q₁₀ values in wheat season always higher than that in maize season at all plots. During the whole experiment time, the magnitudes of Q₁₀ both followed the order of OM > NPK > RSDNPK, which was clearly reflected that Q₁₀ was sensitive to lower C/N organic materials. Q₁₀ values obtained from soil temperature at soil surface (0 cm) and soil 5 cm depth in OM and RSDNPK were 2.64, 2.77 and 1.88, 1.99, respectively. It indicated that the Q₁₀ values for soil heterotrophic respiration rates were higher at lower temperatures and lower at higher temperature.