青藏高原东缘红桦-岷江冷杉次生林中大径级保留木对其他林木的影响

为了研究森林采伐后保留木在次生群落恢复过程中对其他林木的影响, 采用Hegyi单木竞争指数(CI)和标记相关点格局k_d(r)函数对4 hm ²红桦-岷江冷杉(Betula albosinensis-Abies faxoniana)次生林样地中大径级保留木与其他林木的空间关系进行了分析。结果表明: 1)优势树种红桦(Betula albosinensis)与岷江冷杉(Abies faxoniana)的种间、种内竞争中, 种间Hegyi单木竞争指数(CI) (2.484) >红桦种内CI (1.711) >岷江冷杉种内CI (1.548); 2)大径级保留木与其他径级林木间的竞争指数中, 红桦大径级保留木与红桦小树的竞争指数最大, 红桦大径级保留木与岷江冷杉小树、岷江冷杉大径级保留木与红桦小树和岷江冷杉小树这三组的竞争指数之间无显著差异, 且三者的值最小; 3)在14.5-15.5 m尺度上, 红桦大径级保留木与岷江冷杉幼树呈显著的空间正关联; 在6.5-7.5 m的尺度上, 岷江冷杉大径级保留木与岷江冷杉幼树呈显著的空间负关联; 0-100 m尺度上, 岷江冷杉幼苗(树龄≥4年)与两种大径级保留木均呈相互独立的空间关系。

Effects of remnant old-growth trees on other tree stems in a secondary Betula albosinensis-Abies faxoniana forest on the eastern edge of Qinghai-Xizang Plateau,China

Aims As one of the biological legacies in degraded forest ecosystems after severe disturbance, remnant trees have many ecological effects in biodiversity maintenance and recovery of ecosystem structure and functioning. This study aims to understand the effects of remnant old-growth trees on other tree stems in a secondary Betula albosinensis-Abies faxoniana forest on the eastern edge of Qinghai-Xizang Plateau, China. Methods We established a 4 hm² forest plot in a sub-alpine Betula albosinensis-Abies faxoniana stand in Miyaluo in western Sichuan, China. The species names, tree heights, diameters at breast height (DBH) (>1.3 m in height), and basal diameters (≥4 years, and ≤1.3 m in height) of all woody stems were recorded and the specific locations of all trees were mapped. Hegyi’s competition index model was used to calculate the competition intensity between remnant old-growth trees and other dominant trees of different size-classes as well as the intra- and inter-specific competition intensity of the two dominant tree species, Abies faxoniana and Betula albosinensis. We used mark correlation functions k_d(r) to explore the associations of the remnant old-growth trees with seedlings and saplings of A. faxoniana. Important findings The value of the inter-specific competition index (Hegyi’s competition index (CI) = 2.484) between B. albosinensis and A. faxoniana was significantly greater (p < 0.05) than the values of the intra-specific competition indices of B. albosinensis (CI = 1.711) and A. faxoniana (CI = 1.548). The value of the competition index between remnant old-growth trees and the small trees of B. albosinensis was largest among the competition indices between the remnant old-growth trees and tree stems of different size-classes. The competition indices between remnant old-growth trees of B. albosinensis and small trees of A. faxoniana, between remnant old-growth trees and small trees of A. faxoniana and between remnant old-growth trees of A. faxoniana and small trees ofB. albosinensis did not differ significantly, and were smallest among the competition indices between trees of different size-classes. Saplings of A. faxoniana showed a significantly positive association with remnant old-growth trees of B. albosinensis at scale 14.5–15.5 m, and a significantly negative association with remnant old-growth trees of A. faxoniana at scale 6.5–7.5 m. The seedlings of A. faxoniana showed a spatial independence to remnant old-growth trees of both B. albosinensis and A. faxoniana at all spatial scales (0–100 m).