施肥方式对紫色土土壤异养呼吸的影响

Abstract

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 oneof 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 and150 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-1and it was significantly higher than that for both RSDNPK and NPK treatments( P0. 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 mgCO2m-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. 3and 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. 4gCm-2for 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 were2. 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.