林分、土壤及空间因子对谷地云冷杉林叶面积指数空间异质性的影响

叶面积指数(LAI)的空间异质性对研究植物的生长状况、分布格局及其对气候变化的响应机制至关重要, 然而关于不同因素对解释LAI空间变异相对贡献率的报道尚少。该研究依托小兴安岭9.12 hm ² (380 m × 240 m)谷地云冷杉林固定样地, 采用LAI-2200植物冠层分析仪测定了228个小样方(20 m × 20 m)的LAI, 基于地统计学方法分析了LAI的空间异质性; 测定了每个小样方的28个林分因子和10个土壤因子, 利用主轴邻距法(PCNM)量化了空间因子, 并采用方差分解的方法解析了林分、土壤、空间因子及其相互作用对LAI空间变异的相对贡献率。结果表明: LAI在37 m尺度内具有强烈的空间自相关, 且在不同方向上LAI呈现相异的空间格局; 3种因子及其相互作用共同解释了LAI空间变异的50.4%, 其中空间因子的贡献率最大, 单独解释了LAI空间变异的25.5%; 中等树(5 cm <胸径≤ 10 cm)的密度和主要树种(冷杉(Abies nephrolepis)和云杉(Picea spp.))的胸高断面积均与LAI显著正相关, 质量含水率与LAI显著负相关。总体来看, 空间自相关对小兴安岭谷地云冷杉林LAI空间异质性的决定作用明显强于林分因子和土壤因子。

Influences of stand,soil and space factors on spatial heterogeneity of leaf area index in a spruce-fir valley forest in Xiao Hinggan Ling,China

AimsSpatial heterogeneity of leaf area index (LAI) is very important for exploring the growth and spatial distributions of plants, as well as response strategy of plants to climate changes. Many previous studies have shown that biotic and abiotic factors had significant influences on spatial heterogeneity of LAI. However, few studies have been conducted to show the relative contributions of different influencing factors to the total variations of LAI. Our aim was to quantify the relative contributions of stand, soil and space factors to the total spatial variations of LAI in a spruce-fir valley forest in northeast China.MethodsWe relied on a 9.12 hm ² (380 m × 240 m) spruce-fir valley forest plot in Xiao Hinggan Ling, China, which was divided into 228 subplots (20 m × 20 m). First, we measured LAI for each subplot by using the LAI-2200 plant canopy analyzer and then analyzed the spatial heterogeneity of LAI using geo-statistic methods (semivariogram and Kriging interpolation). Second, we measured 28 stand factors and 10 soil factors for each subplot, and quantified space factors using principal coordinates of neighbor matrices (PCNM). Finally, we quantified the relative contributions of stand, soil and space factors to the total spatial variations of LAI using the variance partitioning method.Important findings The results showed that strong spatial autocorrelations of LAI values within 37 m distances in the spruce-fir valley forest, and the LAI presented different spatial patterns along distinct directions. The stand, soil and space factors totally explained 50.4% of the total spatial variations of LAI in the forest plot. The space factors explained greater spatial variations of LAI in relative to stand and soil factors, and solely explained 25.5% of the total spatial variations. The density of middle tree group (5 cm < diameter at breast height ≤ 10 cm) and basal area of major tree groups (including Abies nephrolepis and Picea spp.) were both significantly and positively correlated with LAI; and soil mass moisture content was significantly and negatively correlated with LAI. These results generally suggest that the spatial autocorrelation is more important than stand factor and soil factor for determining spatial heterogeneity of LAI of the spruce-fir valley forest in Xiao Hinggan Ling, China.