施氮对滇中高原云南松林凋落物木质素、纤维素分解的影响

Responses of Litter and Lignin,Cellulose Decomposition Characteristics in Pinus yunnanensis Forest to Nitrogen Addition in Central Yunnan Plateau,China

以位于云南省玉溪市新平彝族傣族自治县的磨盘山国家森林公园为研究地,在研究地内收集云南松(Pinus yunnanensis)林地表面未分解的云南松凋落叶、凋落枝,烘干后分别将其放入尼龙分解袋;在云南松林区内随机抽选3块样地(20 m×20 m),在每个样地中抽选4块3 m×3 m的小样方(间距不小于10 m),将凋落叶、凋落枝分解袋置于小样方内进行施氮处理。采用尿素溶液作为施氮氮源,按照设计的对照(不施氮)、低氮(10 g·m^(-2)·a^(-1))、中氮(20 g·m^(-2)·a^(-1))、高氮(25 g·m^(-2)·a^(-1))4个施氮处理,对各样方中凋落叶、凋落枝分解袋每月施氮1次,共施氮12次;施氮过程中,每月中旬收集1次样品,共采样12次,测定施氮后凋落叶、凋落枝的质量残留率、木质素残留率、纤维素残留率。采用重复测量方差法分析分解时间和氮处理及其交互作用对凋落叶、凋落枝质量残留率及其木质素和纤维素残留率的影响,采用独立样本t检验分析各施氮处理时凋落叶、凋落枝质量残留率及其木质素和纤维素残留率的差异,采用单因素方差法和最小显著差异法分析凋落叶、凋落枝质量残留率及其木质素和纤维素残留率在同一分解时间不同施氮处理时的差异,探索施氮对滇中高原云南松林凋落物木质素、纤维素分解的影响。结果表明:①各施氮处理,凋落叶、凋落枝质量残留率均随分解时间延长整体呈下降趋势;分解360 d时,高氮处理的凋落叶、凋落枝质量残留率显著高于对照(P<0.05)。②随分解时间延长,各施氮处理的凋落叶、凋落枝,木质素残留率呈先降低后升高趋势、纤维素残留率整体呈下降趋势。分解360 d时,低氮处理的凋落叶、凋落枝木质素残留率显著低于对照(P<0.05),而中氮和高氮处理的凋落叶、凋落枝木质素残留率显著高于对照(P<0.05);分解360 d时,低氮处理的凋落枝纤维素残留率显著低于对照(P<0.05),而高氮处理的凋落叶、凋落枝纤维素残留率显著高于对照(P<0.05)。③各施氮处理的凋落枝质量残留率、纤维素残留率,均显著高于凋落叶(P<0.05)。④相关分析结果表明,凋落叶、凋落枝质量残留率与其纤维素残留率呈极显著正相关(P<0.01)。综合研究结果表明,不同施氮处理,通过影响云南松凋落叶、凋落枝分解过程中木质素和纤维素的分解,进而影响云南松林凋落叶、凋落枝分解过程。

Taking Mopan Mountain National Forest Park,located in Xinping Yi and Dai Autonomous County,Yuxi City,Yunnan Province,as the research site,the leaf litter and twig litter of Pinus yunnanensis,which were not decomposed,were collected from the forest surface of P.yunnanensis in the study area,and then dried and put into nylon decomposition bags respectively.Three plots(20 m×20 m)were randomly selected in P.yunnanensis forest area,and 4 plots(spacing no less than 10 m)of 3 m×3 m squares were selected from each plot.Decomposition bags of leaf litter and twig litter were placed in the plots for nitrogen application.Urea solution was used as nitrogen source,according to the designed nitrogen application treatment of control(no nitrogen application),low nitrogen(10 g·m^(-2)·a^(-1)),medium nitrogen(20 g·m^(-2)·a^(-1))and high nitrogen(25 g·m^(-2)·a^(-1)),the leaf litter and twig litter bags were applied once a month,a total of 12 times.In the process of nitrogen application,samples were collected once in the middle of every month for 12 times in total.The mass remaining,lignin remaining and cellulose remaining of leaf litter and twig litter after nitrogen application were determined.Repeated measurement variance method was used to analyze the effects of decomposition time,nitrogen treatment and their interaction on the mass remaining,lignin remaining and cellulose remaining of leaf litter and twig litter.Independent sample t test was used to analyze the difference of mass remaining of leaf litter and twig litter as well as the lignin remaining and cellulose remaining under different nitrogen application treatments.The single factor variance method and the least significant difference method were used to analyze the difference of mass remaining of leaf litter and twig litter as well as lignin remaining and cellulose remaining at the same decomposition time under different nitrogen treatments.To explore the effects of nitrogen addition on the decomposition of lignin and cellulose in litters of P.yunnanensis forest in the middle Yunnan Plateau.The results showed that:(1)Under each nitrogen addition treatment,the mass remaining of leaf litter and twig litter decreased with the extension of decomposition time.After 360-d decomposition,the mass remaining of leaf litter and twig litter in high nitrogen treatment was significantly higher than that in the control(P<0.05).(2)With the extension of decomposition time,in the nitrogen addition treatment of leaf litter and twig litter,the lignin remaining decreased first and then increased,and the cellulose remaining showed a general downward trend.After 360 days of decomposition,the lignin remaining of leaf litter and twig litter in low nitrogen treatment was significantly lower in the control(P<0.05),while the lignin remaining of leaf litter and twig litter in medium nitrogen and high nitrogen treatment was significantly higher in the control(P<0.05).After 360 days of decomposition,the cellulose remaining of twig litter in low treatment was significantly lower in the control(P<0.05),while the cellulose remaining of leaf litter and twig litter in high nitrogen treatment was significantly higher in the control(P<0.05).(3)The mass remaining of twig litter and cellulose remaining were significantly higher than leaf litter in all nitrogen addition treatments(P<0.05).(4)The results of correlation analysis showed that there was a significant positive correlation between leaf litter and twig litter mass remaining and cellulose remaining(P<0.01).The combined results showed that different N addition treatments affected the decomposition of lignin and cellulose during the decomposition of leaf litter and twig litter in P.yunnanensis,and thus affected the decomposition process of leaf litter and twig litter.