树轮分析用于森林干扰强度推测的实例研究

A case study on the verification of density of forest disturbance through tree-ring analysis

树木年轮生长释放一直广泛应用于重建森林干扰 ,但没有直接的研究证明利用树木年轮分析建立的干扰强度的可靠程度 ,本文试图通过一个取自青海省互助国家森林公园 (1987年经历过择伐 )的样方进行验证。在 40m×5 0m的青扦 (PiceawilsoniiMast.)林样方内取胸径≥ 5cm的树木 (12 4株 )树轮芯样并测定胸径、树高和择伐后山杨(PopulusdavilianaDode)树桩 (5 5个 )的基径以及树木与树桩的距离。分析结果表明 :1987和 1988年树木生长释放百分率为 38.7% ,与该林分的准确干扰强度 37.7% (树桩基部断面积与该断面积加树木胸高断面积之和的比值 )相接近。1980～ 1989年 10a间树木生长释放百分率为 6 2 .9% ,该 10a间的平均干扰强度为 37.0 % (生长释放百分率 6 2 .9% 生长释放平均次数 1.7) ,也接近于该林分的准确干扰强度 ,因而用树轮资料重建森林干扰强度是可行和可靠的。

Although growth release showed in tree\|ring series has been widely used for reconstructing past forest disturbance, no direct study provided that the disturbance intensity estimated from tree\|ring analysis reflected actual disturbance intensity in the past. A stand, where is in Huzhu National Forest Park, Qinghai Province, the selective cutting was carried out in 1987, provided a unique opportunity for this kind of case study. A 40m×50m sample plot in the stand was used to investigate the height and the DBH for all trees (DBH≥5 cm) of \%Picea wilsonii \%Mast., diameter at base for all stumps (55) of \%Populus daviliana \%Dode and distances among trees and stumps, as well as cores were collected for all trees of DBH≥5cm (124). The result showed that the percentage of growth release for1987and 1988 was 38.7%,\ which was nearly to 37.7%, actual disturbance intensity expressed by the percentage of section area at base of stumps (AB) in all section area at breast height of trees plus AB. The percentage of growth release in ten years (1980～1989) was 62.9%.\ The average disturbance intensity in ten years (1980～1989) was 37.0%,\ calculated by 62.9%/1.7 (the percentage of growth release/the average number of growth release for all trees), which was also nearly to the actual disturbance intensity, so it can be effective and reliable to reconstruct past disturbance intensity by using tree-ring data.