采伐残余物不同处理方式对杉木幼林土壤有机碳组分和相关酶活性的影响

Effects of Logging Residue on Composition of Soil Carbon and Activity of Related Enzymes in Soil of a Young Chinese Fir Plantation as Affected by Residue Handling Mode

对福建三明格氏栲自然保护区40多年生杉木成熟林的采伐残余物进行保留(Residue retained,RR)、清除(Residue removed,R)、火烧(Residue burnt,RB)处理,种植杉木三年后不同土层(0~10 cm和10~20 cm)土壤有机碳组分及相关酶活性进行研究。结果表明,(1)RR处理显著提高土壤有机碳及各组分的含量,在0~10 cm土层RR处理土壤有机碳含量(24.74 g·kg^-1)显著高于R(13.43 g·kg^-1)和RB处理(20.14 g·kg^-1);R处理土壤有机碳的活性指数(土壤有机碳活性组分占土壤总有机碳的比例)(43.5%)显著高于RR(32.6%)和RB(36.1%)处理(P<0.05),RR和RB处理土壤有机碳的难降解指数(67.4%和64%)分别为R处理(56.52%)的1.2倍和1.1倍,但RR和RB处理间土壤有机碳难降解指数差异不显著(P>0.05)。(2)在10~20 cm土层,RR和RB处理土壤有机碳含量(20.54 g·kg^-1和16.84 g·kg^-1)差异不显著(P>0.05),但明显高于R处理(10.8 g·kg^-1)。RR处理的土壤有机碳活性指数最低,难降解指数最高。同一处理不同土层土壤有机碳的活性指数大小均表现为10~20 cm高于0~10 cm,而10~20 cm土壤有机碳的难降解指数却低于0~10 cm。(3)RR处理土壤中β-葡糖苷酶(βG)、纤维素水解酶(CBH)、过氧化物酶(PER)活性高于RB和R处理。RR处理0~10 cm土层土壤的β-葡糖苷酶和纤维素水解酶活性显著高于10~20 cm土层(P<0.05)。RB处理0~10 cm土层仅有纤维素水解酶活性明显高于10~20 cm土层,R处理两土层间3种酶活性差异均不显著(P>0.05)。(4)相关性分析表明,β-葡糖苷酶、纤维素水解酶活性分别与土壤活性组分Ⅰ(LP Ⅰ)、活性组分Ⅱ(LP Ⅱ)呈显著正相关,而过氧化物酶活性与难降解组分(RP)显著相关。可见RR处理对提高土壤有机碳的含量和稳定性具有积极影响,同时有利于提高土壤养分有效性和土壤质量。

【Objective】In this study,analysis was done of effects of logging residue on soil carbon composition and activity of related soil enzymes in different soil layers as affected by residue handling mode in the soil of a young Chinese fir plantation in the Castanopsis kawakamii Nature Reserve located in Sanming,Fujian,China【.Method】Logging residue was handled in the following ways,i.e.,residue retained(RR),residue removed(R)and residue burnt(RB).Soil organic carbon was divided into 3 fractions:labile CⅠ(LPⅠ-C),labile CⅡ(LPⅡ-C)and recalcitrant C(RP-C).Acidolytic organic carbon and residue of acidolysis was separated using two-step sulfuric acid hydrolysis.Activities ofβ-1,4-glucosidase(βG)and cellobiohydrolase(CBH)were measured using a spectrophotometer at 410 nm with methylumbelliferone(MUB)as substrate,whereas activity of peroxidase(PER)was at 460 nm with L-dihydroxyphenylalanine(L-DOPA)as substrate.【Result】Results show:(1)RR significantly increased the content of soil organic carbon and those of its fractions.Treatment RR(24.74 g·kg^-1)was significantly higher than Treatment R(13.43 g·kg^-1)and Treatment RB(20.14 g·kg^-1)in soil organic carbon content in the 0~10 cm soil layer.Treatment R(43.5%)was significantly higher than Treatment RR(32.6%)and Treatment RB(36.1%)in labile index of the soil organic carbon(ratio of the fraction of labile organic C to total organic C)(P<0.05).Treatment RR and Treatment RB(67.4%and 64%)was 1.2 and 1.1 times higher than Treatment R(56.52%),respectively,in soil organic carbon recalcitrance index.Obviously,Treatment RR and Treatment RB were quite similar in this aspect(P>0.05);(2)Treatment RR and Treatment RB did not differ much in soil organic carbon content in the 10~20 cm soil layer(P>0.05),but significantly higher than R(10.8 g·kg^-1).Treatment RR was the lowest in labile index and the highest in recalcitrance index.Labile index was higher in the 10~20 cm soil layer than in the 0~10 cm soil layer,while recalcitrant index was just contrary;(3)Treatment RR was higher than Treatment RB and R in activities ofβG,CBH and PER.In Treatment RR,βG and CBH activities were significantly higher in the 0~10 cm soil layer than in the 10~20 cm soil layer,while in Treatment RB CBH activity was significantly higher in the 0~10 cm soil layer than in the 10~20 cm layer(P<0.05).In contrast,no significant differences were found in activity of the three enzymes between the two soil layers in Treatment R(P>0.05).(4)Correlation analysis shows thatβG and CBH activities were significantly and positively related to contents of LPⅠ-C and LPⅡ-C,while PER activity was significantly related to content of RP-C.【Conclusion】Organic carbon content in the surface soil was significantly higher in Treatment RR than in Treatments R and RB.Contribution of RP-C to soil organic carbon was higher in Treatment RR than in Treatments R and RB,and soil enzyme activity was higher in Treatment RR than in the others.Therefore,it can be concluded that Treatment RR has some positive effects on soil organic carbon in content and stability,and hence improve soil nutrient availability and soil quality as well.