关键词: 干旱指数, 人工林, 最大密度线, 落叶松, 分位数回归

Abstract: Based on data from 389 plots of Larix spp. plantations in Northeast China collected from the Seventh National Forest Inventory of China, we used the De Martonne aridity index (MAI) to quantify aridity conditions, and classified the aridity levels into five categories: Ⅰ ∈ (0, 40], Ⅱ ∈ (40, 50], Ⅲ ∈ (50, 60], Ⅳ ∈ (60, 70], and Ⅴ ∈ (70, ∞). We further employed quantile regression to develop the maximum stand density line models under different aridity levels, and simulated the effects of aridity level on the maximum stand density, stand volume, and carbon sequestration, which could provide a basis for precision management of Larix plantations in the region. The results showed that when aridity levels were not considered, the maximum stand density line slope for Larix spp. plantations in the region were -1.421, higher than Reineke's recommended value (-1.605). When aridity levels were considered, the slope generally increased with increasing MAI values, and there were significant differences in the response of maximum stand density to the aridity index across different growth stages of Larix spp. plantations. When the average stand diameter was less than 12 cm, the carrying capacity of the maximum stand density decreased with increasing MAI values. However, when the average diameter exceeded this threshold, the carrying capacity increased with increasing MAI values. At an average stand diameter of 40 cm, the maximum stand density under aridity level Ⅰ (144 trees·hm^-2) was significantly lower than the unclassified value, leading to a reduction in stand volume and carbon sequestration by 137.76 m³·hm^-2 and 55.68 t·hm^-2, respectively. In contrast, the maximum stand density under aridity levels Ⅱ to Ⅴ was significantly increased by approximately 80 to 211 trees·hm^-2, with corresponding increases in stand volume and carbon sequestration by 91.84 to 242.23 m³·hm^-2 and 37.12 to 97.91 t·hm^-2, respectively. Aridity conditions significantly affected the maximum density carrying capacity of Larix plantations. Therefore, reasonable stand density control tables should be developed based on the MAI values and growth stages to maximize stand volume and carbon sequestration benefits.

Key words: aridity index, plantation, maximum density line, Larix spp., quantile regression