海南尖峰岭热带山地雨林土壤有机碳密度空间分布特征

森林土壤有机碳是陆地碳库的重要组成部分,在碳循环中有着重要的作用。研究热带雨林土壤性质的空间异质性对于深入分析热带雨林植被分布格局与土壤的关系,促进热带雨林的保护等具有重要指导意义。在海南岛尖峰岭热带山地雨林60 hm2大样地内采用野外布点采样、实验室测定和地统计学分析相结合的方法,定量研究了土壤有机碳密度在局域范围内的空间异质性及分布特征。研究结果表明:(1)A(0—10 cm)、B(10—30 cm)、C(30—60 cm)3层土壤有机碳平均密度分别为2.699、2.782、2.434 kg/m2,A、B两层差异性不显著,与C层差异性显著(P0.05);(2)不同层次土壤有机碳密度模型交叉验证结果表明:A层拟合的半方差函数最适模型为指数模型,B、C两层为球状模型;3层土壤有机碳密度的变程分别为:54.2、70.9、97.2 m;块金值与基台值比值分别为:0.512、0.708、0.882,表明A、B两层属中等程度变异,C层具有较大的块金值,属于弱变异,说明在小尺度范围具有更明显的空间异质性,也说明不同层次土壤有机碳密度具有不同程度的空间自相关性;Person相关性分析表明不同层次土壤有机碳密度之间具有不同的相关性:A层与B层及C层之间的相关性要小于B层和C层之间的相关性,说明热带雨林中土壤有机碳密度表层与下层受到不同生态过程的控制。(3)普通克里格插值及绘制的空间分布轮廓图表明:在研究尺度上A、B两层不同深度的土壤有机碳密度的空间分布具有一定的一致性,空间异质性明显,呈斑块状分布;C层空间异质性较弱,具有一定的连续性,呈条带状分布;(4)地形引起的水热分配是影响不同层次土壤有机碳密度空间分布格局的一个重要因素。

Spatial distribution characteristics of soil organic carbon density in a tropical mountain rainforest of Jianfengling, Hainan Island, China

Forest soil organic carbon (SOC) is the main component of the terrestrial carbon reservoir, and plays a crucial role in the Earth''s carbon cycle. This study aimed to quantify the spatial heterogeneity and distribution patterns of SOC density. The study was conducted in a 60 hm² forest plot in a tropical mountain rainforest of Jianfengling, Hainan Island, China, using field investigation, laboratory analysis, and geostatistical methods. The results showed that the mean SOC density at different soil profile depths (A 0-10 cm], B 10-30 cm], and C 30-60 cm]) was 2.699, 2.782, 2.434 kg/m², respectively. The differences for A versus C and, B versus C layers were statistically significant (P < 0.05), but there was no significant difference between A and B layers (P > 0.05). Cross-validation results showed that the most fitted models for SOC density at different layers was exponential for A and spherical for B and C. The ranges of SOC density were 54.2 m, 70.9 m, and 97.2 m for A, B, and C, respectively, while the Nugget:Sill ratios were 0.512, 0.708, and 0.882, respectively. This result implies that SOC density is moderately variable for A and B, but weakly variable for C. Thus, SOC had more significant spatial variability at the small scale.Pearson correlation analysis showed that the correlation coefficients for A versus C and B versus C were less than that between B and C, indicating that different ecological processes may regulate SOC density across surface and subsurface soil layers. Ordinary Kriging interpolation showed that A and B soil layers had moderate spatial autocorrelation, whereas the C layer had weak spatial autocorrelation. Meanwhile, the contour maps produced scattered spatial distributions for the A and B layers, but a banded distribution for the C layer. Topography-induced water and heat distribution may represent an important factor affecting the spatial distribution patterns of SOC density in different soil layers.