冻融交替对高寒土壤轻组分有机质矿化影响的试验研究

Effects of Simulated Freezing and Thawing on Mineralization of Light-fraction Organic Matter of Subalpine Forest Soil

为研究冻融交替对轻组分有机质(LFOM)动态的影响,设置不冻处理T(4℃恒温培养),长冻处理F(-10℃持续冻结)和冻融交替FT(-10℃和4℃各12h交替)3个模式,对轻组分有机质(LFOM)进行为期147d的试验培养,定期采样分析LFOM中物质累积释放总量、C、N、P、K、Ca、Mg元素的动态情况。结果表明:(1)与处理F和T相比,处理FT显著提高了LFOM中物质累积释放总量和C、N、P、Ca、Mg的累积矿化,处理FT和处理F的K累积矿化相近且高于处理T。(2)处理F与处理T比较,OM、P、Ca、Mg矿化量相近,但总量及N矿化量处理F高于处理T。(3)利用单室模型对不同处理分解动态的回归进行分析,表明不同处理分解动态间均达到显著水平,证实了有机质进行密度分组的合理性及LFOM内不同组分的共性,冻融交替下LFOM中C、N和P的平均存留时间(MRT)分别为700,875,133d,冻融交替次数减少(长冻、不冻)均延长了这些元素的MRT。因此,在全球变暖背景下,只有在高寒土壤冻融交替次数增加的情形下才加剧土壤LFOM中有机碳、氮和磷的矿化,如果仅是引起土壤解冻时间延长,并不会增加亚高山森林季节性冻土中LFOM的矿化。

In order to understand the impact of patterns of freeze-thaw on materials mineralization in LFOM,a 147 dincubation experiment of soil LFOM with three treatments,freeze-thaw cycles（incubated alternating at-10 ℃ 12 hand 4 ℃ 12 h,F-T）,persistent freeze（incubated at-10 ℃ persistently,F）,and frost-free（incubated at 4 ℃ persistently,T）was carried out.The results showed that：（1）Gross weight loss of LFOM and mineralization of C,N,P,Ca,Mg in LFOM were enhanced significantly in F-T compared to F and T,while a similar K release occurred in both F-T and F and higher than that in T.（2）Gross weight loss and N mineralization in F were higher than T,and a similar OM and P mineralization occurred in both F and T.（3）The trajectories mineralization ratio in LFOM were regressed by simple exponential model significantly,which indicated that LFOM was composed of almost pure nature of organic and mineral materials.Mean residence time（MRT）of incubated LFOM were also evaluated,and MRT values of C,N and P in F-T were700,875,133 drespectively,while they were doubled at least in F or T.The results suggested that carbon and nitrogen mineralization and nutrients release of LFOM in subalpine forest soil would be promoted only in the context of freeze-thaw cycles increasing,whilst there was few effects on mineralization ratio of LFOM just frost-free period extension compared with persistent freeze when global warming.