黄土高原森林枯落物储量、厚度分布规律及其影响因素

森林枯落物的储量(LM)和厚度(LD)等物理属性,能够表征森林植被的物种多样性以及水源涵养、物质循环等生态功能,然而目前对枯落物储量和厚度分布规律与影响因素的深入探讨较少。以黄土高原为研究区,通过系统取样获得该区主要森林群落枯落物的储量与厚度数据,利用Kruskal-Wallis秩和检验、线性混合效应模型(LME)、普通最小二乘回归等统计方法,分别对不同林型枯落物储量和厚度的差异、储量和厚度的影响因素以及二者之间的关系进行分析。结果表明:1)针叶林与针阔混交林的枯落物储量和厚度差异不显著,但二者都显著大于阔叶林的储量和厚度。2)在纬度方向上,除南部个别点外,枯落物储量和厚度存在单峰格局,如储量在35°—36°N之间存在峰值,而厚度峰值则出现在36°—37°N之间。3)在海拔方向上,储量分布规律并不明显,厚度除了高海拔(3000 m以上)个别点外总体呈现递减格局;LME模型显示,枯落物储量与气温年较差、非生长季降水、总干面积和立木密度呈显著正相关,与乔木层丰富度呈显著负相关,而枯落物厚度与最冷月均温、生长季降水、总干面积和立木密度呈显著正相关,与乔木层丰富度、非生长季降水和坡度呈显著负相关;枯落物储量与厚度具有显著正相关关系,特别是在阔叶林和针叶林中,而对于针阔混交林来说二者并无显著相关性。研究结果可为黄土高原乃至中国北方地区生态系统碳循环评估和水土保持实践提供参考依据。

The effect of environmental factors on the distribution of litter mass and litter depth in forests of loess plateau region

The objectives of this study were to explore the features and distribution pattern of litter mass (LM) and litter depth (LD) in montane forests across the Loess Plateau region, Northern China, and to reveal the main potential environmental factors influencing LM and LD features through regression analysis. LM and LD data were obtained through systematic sampling. The differences in LM and LD with regard to forest types were analyzed using the Kruskal-Wallis rank sum test. The factors influencing LM and LD distributions were statistically examined by using a linear mixed-effects model. In addition, the correlation between LM and LD was analyzed using an ordinary least-squares regression model. The following results were obtained. 1) The LM and LD varied markedly among different forest types. The LM was significantly heavier and the LD significantly thicker in both conifer forest (CF) and conifer and broad-leaved mixed forest (CBMF) than in broad-leaved forest (BF). However, no significant difference in both LM and LD was detected between CF and CBMF. 2) Both LM and LD appeared in a unimodal pattern along the latitudinal gradient, peaking at 35°-36°N and 36°-37°N, respectively. 3) There was no significant pattern in LM distribution along an altitudinal gradient, whereas LM decreased with rising elevation; the exceptions being several sites over 3000 m a.s.l. 4) LM was positively and significantly correlated with the annual range of temperature, basal area, non-growing season precipitation, and stem density within stands, but negatively correlated with arborous layer species richness. Furthermore, LD was positively and significantly correlated with the mean temperature of the coldest month, aspect, growing season precipitation, basal area, and stem density within stands, but negatively correlated with slope, non-growing season precipitation, and arborous layer species richness. 5) There were positively significant correlations between LM and LD in both BF and CF, whereas no significant correlation was detected in CBMF.