摘要
林火影响着林木的更新、生长发育以及林分演替,是森林生态系统的重要干扰因子。为了评估林火对不同龄级树木生长的影响,该文研究了西藏林芝市朗县2005年林火前后高山松(Pinus densata)的树轮变异特点。在林分内,选择62株过火林木,进行树芯样品采集,且依据胸径将样树分为幼树(胸径<10 cm)和成年树(胸径≥10 cm)。树木年轮学交叉定年结果显示样本最大年龄为102年,最小年龄为19年,平均年龄为48年。研究结果表明:过火前幼树径向生长与上一年11月平均最低气温显著负相关,成年树径向生长与当年9月平均最低气温和平均气温显著正相关;过火后幼树和成年树的径向生长均与当年1月平均气温和平均最高气温显著负相关。成年树对火干扰的抵抗力(过火年-过火前树轮宽度降低的百分比)和恢复力(过火后-过火前树轮宽度恢复的百分比)都显著高于幼树。过火后不同龄级的树木生长都加快。在地表火干扰中,成年树比幼树更能抵抗火干扰的影响。研究结果可为全球变化背景下森林恢复及林火应用提供科学依据。
Aims Forest fire plays a complex and important role in affecting forest regeneration, tree growth, and stand development. Despite the importance of forest fire in modulating forest dynamics, researches on the response patterns of trees of different age-classes to fire disturbances are scarce. This study was conducted to determine the growth patterns of surviving trees of different age-classes in an alpine pine（Pinus densata） forest in the southeastern Xizang Plateau, where a moderate surface fire occurred in 2005. Methods We collected tree-ring samples of P. densata in the Gong-Zi-Nong valley in Nang County, Xizang Autonomous Region, in western China. Based on the diameter at breast height（DBH）, the sampling trees were divided into saplings（DBH 10 cm） and mature trees（DBH ≥10 cm）. The tree-ring samples were subsequently polished, measured, cross-dated, and detrended to produce sequences of tree-ring width indices. The detrended tree-ring sequences were averaged using bi-weight robust method to develop chronologies for saplings and mature trees separately. Pearson correlation coefficients and response coefficients between the sequences of tree-ring width indices and climate factors（air temperature and precipitation） were calculated for examination of the responses of tree-ring sequences to monthly mean air temperature and monthly total precipitation both before and after the fire event. Indices of growth resistance and growth recovery were calculated based on the relative changes of trees＇ raw ring width before and after the fire event, for trees in different age-classes. These indices were then compared between the trees in different age classes to assess the impacts of fire on trees. Important findings Before the fire event, the radial growth of saplings showed a significantly negative response to the monthly mean minimum temperature of the preceding November, whereas the radial growth of mature treesshowed a significantly positive response to monthly mean minimum temperature and monthly mean temperature of current September; following the fire event, radial growth of both the saplings and the mature trees showed a significantly negative response to monthly mean temperature and monthly mean maximum temperature of January of the tree-ring formation year. Based on the ratios of mean tree-ring widths of 5 post-fire years to those of 5 pre-fire years, the mature trees were significantly more fire resistant than the saplings. Moreover, the mature trees also showed greater ability in post-fire recoveries than the burnt saplings. Our results demonstrated that moderate surface fire stimulated the radial growth of both saplings and mature trees, and that the mature trees better recovered from the fire event than the saplings. The changes in growth-climate relationships following the fire event may attribute to changes in understory vegetation and microenvironments.
出处
《植物生态学报》
CAS
CSCD
北大核心
2016年第5期436-446,共11页
Chinese Journal of Plant Ecology
基金
国家自然科学基金(31361130339
31330015和31300409)
中国科学院战略性先导科技专项(XDA05050404)
关键词
干扰
中度地表火
树木龄级
高山松
树木年轮
西藏
朗县
disturbance
moderate surface fire
age class
Pinus densata
tree-ring
Xizang
Nang County
