毛竹高速生长期土壤碳氮动态及其微生物特性

研究了典型毛竹林毛竹高速生长期间土壤碳氮动态及其微生物生态特性。结果表明:毛竹高速生长期间,3个试验地土壤全氮、碱解氮、铵态氮、硝态氮及总有机碳和水溶性有机碳(DOC)的含量均有不同幅度的下降,其中25℃蒸馏水提取DOC(25℃DOC)降幅分别达到51%、22%和223%,且25℃DOC下降幅度明显大于80℃DOC的下降幅度。随毛竹生长,土壤全氮和有机碳含量变化较为明显,相关分析表明两者呈极显著的正相关(R2=0.89**)。同时,土壤微生物量碳含量大幅度降低,由原来的800 mg/kg降到了525 mg/kg。采用PLFA法对土壤微生物群落结构进行了分析,代表细菌的饱和脂肪酸(14:0,16:0,18:0,20:0,i15:0,i16:0,i17:0,i18:0,a15:0,a17:0)基本上都分布在载荷图的右侧;代表真菌的不饱和脂肪酸(18:2w6,9c/18:0ANTE)分布在主成分载荷图的左侧,表明随着毛竹生长,土壤中细菌含量减少,真菌含量增加。说明毛竹的高速生长消耗了土壤中的碳氮,同时对土壤微生物群落结构产生了明显的影响。

Soil carbon, nitrogen and microbiological characteristics during bamboo high-speed growth

The soil carbon,nitrogen dynamics and its microbiological ecological characteristic were investigated during bamboo high-speed growth in typical bamboo(Phyllostachys Pubescens) forests.The results showed that the content of total nitrogen(TN) reduced by 13%,22% and 6% respectively in the three testing spots.TN of soil showed a significant positive correlation with alkaline hydrolysis nitrogen,ammonium nitrogen and nitrate nitrogen(R2=0.48*,0.65**,0.70** respectively) during bamboo high-speed growth indicating that the soil nitrogen was absorbed in different forms by bamboo which caused soil total nitrogen reduction.Soil total organic carbon(TOC) and dissolve organic carbon(DOC) including extraction at 20℃(20℃ DOC) and at 80℃(80℃ DOC) were significantly decreased during bamboo growth.The results showed that TOC reduced by 26%,20% and 24% respectively in three testing spots.The content of the 20℃ DOC reduced by 51%,22% and 23% in three testing spot respectively,which was considerably greater(P<0.05) than the reduction of 80℃ DOC in the testing spots.The relationship between soil total nitrogen(TN) and total organic carbon(TOC) analysis showed that TN and TOC were strongly inter-correlated(R2=0.89**) indicating that the change of soil carbon was closely related with the content of soil nitrogen during bamboo high-speed growth.Soil microorganisms are important in the cycling of almost all the major plant nutrients including the turnover of organic matter.Environmental conditions and perturbation are likely to affect microbial population structures and their functions in soils which may result in a change of overall soil properties.During high-speed growth,bamboo consumed soil carbon and soil nitrogen which lead to soil nutrient deficiency,effected soil microbial biomass and excessive carbon reduction,it also changed the soil microbial community.The content of soil microbial biomass carbon decreased from 800 mg/kg at the first sampling day to 589 mg/kg at the last sampling day.Soil under different sampling date contained a variety of PLFAs composed of saturated,unsaturated,methyl-branched and cyclopropane fatty acids.Thirty-four PLFAs with chain lengths from C12 to C20 were identified.The PLFA concentration data were subjected to principal components analysis(PCA).The first two principal components(PC1 and PC2) accounted for 62.95% and 17.20% of the variation respectively,which showed soil microbial community was changed significantly during bamboo growth.Specific identified PLFAs including saturated fatty acids(14:0,16:0,18:0,20:0,i15:0,i16:0,i17:0,i18:0,a15:0,a17:0) which represented bacteria were found to be distributed on the right of the load diagram,while unsaturated fatty acids(18:2w6,9c/18:0ANTE) which represented fungi were found to be distributed on the left of the load diagram.Thus,these bacteria indicator PLFAs were more abundant in the later soil sampling,while the fungi indicator PLFAs were more abundant in the early soil sampling,indicating that with the soil nutrient consumption during bamboo high-speed growth,total PLFA and the PLFAs that represent bacteria decreased,While the PLFAs that represent fungi increased.Thus,the change of soil carbon and soil nitrogen can significantly affect soil microbial community structure in the bamboo forest soil.