云杉与阔叶树种新鲜凋落叶混合分解特征

Characteristics of the Mixed Decomposition of Fresh Litter of Picea asperata and Broadleaved Species

明确混合分解过程中凋落物的相互影响对于深入分析混合分解非加和效应的真实结果和产生机制,据此评价混合分解对生态系统物质循环的影响、指导混交造林和纯林混交改造具有重要意义。以云杉(Picea asperata)及拟与其混交的红桦(Betula albo-sinensis)、灰楸(Catalpa fargesii)、太白杨(Populus purdomii)、杜仲(Eucommia ulmoides)和秦岭槭(Acer tsinglingens)等6种树种为研究对象,采集其当年凋落物,采用分解袋法在室温(20-25℃)恒湿条件下进行为期180 d的室内模拟针阔混合分解试验。测定混合分解过程中针阔凋落物分解残留量的动态变化,以及与分解密切相关的土壤蔗糖酶、羧甲基纤维素酶和多酚氧化酶的活性动态,分析凋落物在混合分解过程中彼此影响的机理,并据此选择适宜的阔叶树种对云杉纯林进行混交改造。结果表明,(1)混合分解非加性效应及凋落物间的相互影响均随分解的进行趋于明显。至分解试验结束时,杉×桦混合促进彼此分解(分解率分别提高8.67%和8.11%);杉×楸混合显著促进云杉分解(分解率提高7.83%),同时显著抑制灰楸分解(分解率降低11.50%),但整体呈加性效应;杉×杨和杉×槭混合促进太白杨和秦岭槭分解(分解率分别提高3.11%和15.89%);杉×杜混合则抑制杜仲分解(分解率降低13.33%);上述结果与Olson模型拟合计算结果有所差异。(2)混合分解对土壤蔗糖酶、羧甲基纤维素酶和多酚氧化酶的非加和性影响与其对凋落物分解的影响一致。总之,某些情况下混合分解的总体非加和效应因凋落物间相互促进或抑制而无法被检测,但鉴于不同凋落物分解特征的差异,混合后其对彼此分解的影响仍可能干扰林地物质循环。仅从引入阔叶树种后应不妨碍林地凋落物分解的角度考虑,除杜仲外,其他4种阔叶树种均适宜于云杉纯林改造。

Investigating the interspecific effects of litter during decomposition lays a foundation for analyzing the actual results and mechanism of mixed-decomposition effects.Furthermore,this work is helpful for assessing the influence of mixed-decomposition on the material cycling in ecosystem and guiding the mixed afforestation and mixed transformation of pure forests.Therefore,in the present study,Betula albo-sinensis(Ba),Catalpa fargesii(Cf),Populus purdomii(Pp),Eucommia ulmoide(Eu)and Acer tsinglingense(At)litters were mixed with Picea asperata(Pas)litter respectively.Indoor simulated decomposition experiment was conducted by mixing fresh leaf litters of different species at room temperature(20-25℃)for 180 days with consistent soil moisture in litterbags.The dynamics of litter decomposition and sucrase,cellulase and polyphenol oxidase activities were determined,in order to analyze the mechanism of the interspecific effects among litters during mixed decomposition,and consequently choose suitable broadleaved species for mixed transformation of the pure forests of Picea asperata.The results indicated that:(1)Both of the non-additive effects of mixed decomposition and the interspecific effects of Pas and broadleaved litter became obvious over time.After 180 days decomposition,Pas×Ba litter mixture accelerated the mutual decomposition with 8.67%and 8.11%decomposition rates respectively;Pas×Cf litter mixture promoted the decomposition of Pas litter which was increased by 7.83%,whereas the decomposition rate of Cf litter was decreased by 11.50%,showing apparent additive mixed effect generally;Pas×Pp and Pas×At litter mixtures enhanced the decomposition rate of Pp litter by 3.11%and 15.89%for At litter;Pas×Eu litter mixture decreased the decomposition rate of Eu litter by 13.33%,which was slightly different from the result predicted by Olson model.(2)The effects of mixed decomposition on the activities of sucrase,cellulase and polyphenol oxidase were consistent with its effects on the decomposition of litter.In conclusion,sometimes the apparent non-additive effects of mixed decomposition could not be detected,because the decomposition of litter component was accelerated or inhibited by each other.However,as there were significant differences among the decomposition characteristics,the effects of litter component on the decomposition of each other might still affect the material cycling of forest.Only considering that the mixed planting should not hinder the decomposition of litter,all the broadleaved species could be used in the mixed transformation of the pure forests of P.asperata except for Eucommia ulmoide.