晋西黄土区不同密度刺槐人工林叶片-枯落物-土壤化学计量特征

Stoichiometric Characteristics of Leaves-litter-soil of Robinia pseudoacacia of Different Densities in the Loess Region of Western Shanxi Province

[目的]研究不同林分密度对刺槐人工林叶片、枯落物、土壤C、N、P化学计量特征的影响,为晋西黄土区刺槐人工林的经营管理提供科学参考。[方法]通过野外调查,选择晋西黄土区5种不同密度(500、1000、1500、2000、2500株·hm^(-2))刺槐人工林,测定和分析叶片、枯落物、土壤的养分。用单因素分析法分析密度对三者养分的影响,采用Pearson相关系数,分析刺槐人工林叶片、枯落物、土壤C、N、P及其化学计量比之间的相关性。[结果]随着密度增加,刺槐人工林叶片C、N、P含量先增加后减小,叶片C∶P、N∶P先降低后增加;枯落物的C、C∶N、C∶P、N∶P随着密度先减少后增大,N、P则先增大后减少;土壤C、P、N含量及C∶P、N∶P随密度的增大而降低;C∶N随密度呈先降低后增加的趋势。不同林分密度下,叶片N∶P均大于14,叶片-枯落物-土壤C、N、P及其化学计量比中除了叶片N、C∶N以外,均存在不同的显著差异性(p<0.05)。[结论]不同林分密度下,叶片N∶P均大于14,说明研究区刺槐人工林主要受到P限制;密度在一定程度上影响着刺槐人工林的养分循环及其分配和化学计量特征;在密度为1000~1500株·hm-2的刺槐人工林叶片、枯落物、土壤C、N、P含量最高,养分限制最弱,枯落物分解速率相对较快,为适宜经营密度。

[Objective]To study the effects of different stand densities on the stoichiometric characteristics of C,N and P in leaves,litter and soil of Robinia pseudoacacia plantation forests,and to provide scientific references for the management of plantation forests in the loess region of western Shanxi Province.[Methods]Based on five different densities(500,1000,1500,2000,2500 plants/hm^(2))of plantation forests in the loess region of western Shanxi Province,the nutrients of leaves,litter and soil were measured and analysed.The effects of density on the three nutrients were analysed by one-way analysis of variance(ANOVA),and the correlations between leaf,litter,soil C,N,P and their stoichiometric ratios in plantations were analyzed by Pearson's correlation coefficient.[Result]The C,N and P contents of leaves of plantation forest increased and then decreased with the increase of density,and the C∶P and N∶P of leaves decreased and then increased;the C,C∶N,C∶P and N∶P of litter decreased and then increased with the increase of density,and the N and P increased and then decreased;the C,P and N contents and C∶P and N∶P of soil decreased with the increase of density;and the C∶N showed a tendency of decreasing and then increasing with the increase of density.Leaf N∶P was greater than 14 in different stand densities,and there were different significant differences(p<0.05)in leaf-detritus-soil C,N,P and their stoichiometric ratios,except for leaf N,C∶N.[Conclusion]Leaf N∶P is greater than 14 in different stand densities,indicating that plantation forests in the study area are mainly P-limited;density affects nutrient cycling and its distribution and stoichiometric characteristics of plantation forests to a certain extent;Robinia pseudoacacia plantation forests with densities ranging from 1,000 to 1,500 plants/hm2 have the highest contents of leaf blade,litter,and soil C,N,and P,and the weakest nutrient limitation,and the decomposition rate of litter is relatively fast,which is suitable for the operation of the forests.