【作者】 缪宁；

【导师】 刘世荣； 史作民；

【作者基本信息】 中国林业科学研究院 ， 生态学， 2009， 博士

【摘要】 森林群落的空间格局是种群自身特性、种间关系及环境条件综合作用的结果。研究森林群落的种群空间格局可以预测森林群落演替变化趋势,为退化生态系统恢复和森林生态系统的可持续经营提供理论指导。川西亚高山地区的暗针叶林具有重要的生态、社会和经济价值,然而过度的森林采伐和不合理的土地利用导致了原始森林大面积减少,形成广泛分布、处于不同恢复阶段的天然次生林。由原始林破坏后发展起来的天然次生林已成为川西地区的主要森林景观。以往我们主要关注川西亚高山的原始林,而对这些人为干扰后的退化森林植被了解甚少。本研究在川西米亚罗地区海拔3300 m的阴坡,选择4 ha红桦-岷江冷杉天然次生林样地(N31°42′18.4″,E102°44′03.7″),进行了群落学调查和优势树种个体空间定位调查,主要采用了点格局分析法(包括Ripley’s L-函数和O-ring统计的O-函数),研究了:(1)群落结构和物种组成特征;(2)岷江冷杉种群的空间分布格局和种内关联;(3)岷江冷杉天然更新的影响因子;(4)优势树种的种间竞争;(5)采伐后的保留木效应。本研究的目的是探讨天然次生林自然恢复的驱动力机制,为川西亚高山暗针叶林的保育和恢复提供科学依据。主要研究结果如下:(1)红桦和岷江冷杉为红桦-岷江冷杉天然次生林群落的优势种,红桦的胸高断面积占49.0%,岷江冷杉占28.9%。红桦种群径级分布呈现单峰型,为演替的衰退种群。岷江冷杉种群径级分布呈倒“J”型,为演替的进展种群。点分布图表明优势种不同径级其空间分布也不同,但都表现出一定的聚集性和空间异质性。(2)岷江冷杉种群呈聚集分布,其各径级大多呈聚集分布。随着尺度增大聚集强度先增大后减小,趋于随机分布,存在过渡到随机分布的特定尺度:小树:63 m,中树在87 m。各径级间在小尺度范围内正关联较强,随尺度增大,空间关联趋于零,在所有尺度上都未出现负关联,说明岷江冷杉种内关系协调。各径级发生最大聚集强度的尺度依次为:幼苗:28 m;幼树:29 m;小树:15 m;中树:34 m;大树:49 m。大树与中树在所有尺度上均是显著的正关联;幼苗仅在7 m的尺度内和幼树显著的正关联。在所有尺度上幼苗和大树、中树和小树都显著的不关联。(3)红桦-岷江冷杉天然次生林中岷江冷杉幼苗和幼树数量丰富、年龄呈连续分布,说明岷江冷杉更新良好。样地内未发现树高2 m以下的红桦个体,说明红桦更新不良。对于岷江冷杉幼苗,1年生幼苗占幼苗总数的62.45%,2年以上生幼苗占幼苗和幼树总数的2.30%。分别有86.70%的1年生幼苗和81.08%的2年以上生幼苗生长在苔藓上。我们着重关注了小尺度范围内的空间关联特性,优势种不同径级树木与岷江冷杉幼苗、幼树空间关联性表现各异。岷江冷杉幼苗与小树、中树、大树分别在0～7 m、0～8 m和0～8 m尺度上表现为显著负关联。岷江冷杉幼树与小树、中树、大树间,分别在0～11 m、0～13 m、0～11 m尺度上为表现为显著正关联。在所有尺度内,岷江冷杉幼苗、幼树与红桦小树均趋于无关联。岷江冷杉幼苗、幼树与红桦中树分别在0～8 m、0～34 m尺度为表现为显著负关联。岷江冷杉幼苗、幼树与红桦大树在所有尺度上均表现为显著负关联。影响岷江冷杉天然更新的关键因子为苔藓层盖度、倒木蓄积量、母树(DBH≥16.5)密度、箭竹盖度和乔木郁闭度。苔藓层盖度、倒木蓄积量和母树密度对岷江冷杉天然更新起着促进作用,而箭竹盖度和乔木郁闭度对岷江冷杉天然更新起着阻碍作用。(4)空间格局分析结果揭示了红桦和岷江冷杉间的激烈竞争。原始林中优势种群之间在所有尺度上为表现为无关联,而天然次生林内红桦和岷江冷杉在所有尺度上表现为显著负关联。岷江冷杉与红桦大树在所有尺度上均为随机分布,其余径级在小尺度上为聚集分布,随尺度增大趋于随机分布和均匀分布,最大聚集强度随径级增大而减弱。岷江冷杉种内关联以小尺度正关联为主,红桦种内关联以小尺度负关联为主。对于两个种群的相同径级,小径级、中径级和大径级间,分别以空间无关联、负关联和无关联为主。两个种群间不同径级间以负关联为主,径级相差越大,其负关联越强。(5)大径级保留木对其他径级树木的空间分布具有显著的影响。红桦大径级保留木与其小树和中树分别在0～8 m和0～9 m尺度上表现为显著负关联。岷江冷杉大径级保留木与其幼苗在0～8 m尺度上为负关联。岷江冷杉大径级保留木与其幼树和小树分别在0～11 m和1～9 m尺度上为正关联。岷江冷杉大径级保留木与其中树在0～14 m尺度上则没有显著的空间关联关系。红桦大径级保留木与岷江冷杉幼苗、幼树、小树和中树在所有尺度上均为空间负关联。岷江冷杉大径级保留木与红桦小树在0～4 m尺度上为负关联。大径级保留木在促进演替后期优势树种岷江冷杉的更新和生长的同时,制约了先锋树种红桦的更新和生长。更多还原

【Abstract】 Spatial pattern is the results of integrated processs of population property, spatial association and environmental conditions. The study of spatial pattern of forest can infer the trend of forest community succession and provide theoretic support for the restoration of degraded ecosystems and sustainable management of forest ecosystem. The dark coniferous forest at sub-alpine area of western Sichuan, has important ecological, economic and social values. Due to extensive deforestation and long-term intensive agricultural land use, the area of primary forests has been reduced dramatically, and resulted in a wide distribution of natural secondary forests of different restoration stages. Therefore, the secondary forests that originated from those disturbed forests have become the main forest landscape in this region. However, the past ecological studies were mainly conducted in primary or old-growth forests, and we still know little about those degraded vegetation after anthropogenic disturbance. In this study, field investigations including individual spatial position of dominant tree species were conducted in a four ha sample plot in a natural secondary Betula-Abies forest. The plot locates in the north aspect at the altitude of 3300 m in Miyaluo, western Sichuan, China (N31°42′18.4″, E102°44′03.7″). Spatial point pattern analysis including Ripley’s L-function and O-ring statistic’s O-function were mainly adopted, we analyzed: (1) community structure and species composition; (2) spatial distribution pattern and intra-specific association of A. faxoniana population; (3) influencing factors on natural regeneration of A. faxoniana; (4) inter-specific competition of dominant tree species; (5) effects of remnant trees. Driving factors of natural restoration in natural secondary forest were discussed to provide the scientific basis for conservation and restoration of dark coniferous forest at sub-alpine area of western Sichuan. The main results are as follows:(1)B. albo-sinensis and A. faxoniana are the two dominant tree species in the natural secondary Betula-Abies forest. B. albo-sinensis took up 49.0% of total basal area and A. faxoniana took up 28.9%, respectively. DBH frequency distribution of B. albo-sinensis had a unimodal distribution, indicating a declining population with succession. In contrast, A. faxoniana had a reverse J-shaped pattern, showed an increasing population with succession. Point distribution map indicated that spatial distributions varied with size class, but all showed an aggregate and heterogeneous pattern.(2)A. faxoniana distributed as a clumped population, all size-classes exhibited clumped distributions at most spatial scales. Intensity of the assemblage increased firstly, and then decreased with increasing scale and then turned to random distribution. There existed a critical scale in which distribution pattern transfered from clumped to random, for example, small trees: 63 m and medium trees 87 m. All size-classes showed a positive association at small scales. Spatial association turned from strongly positive association to zero with the increasing of scale. However, there were no negative spatial associations in size-classes at all scales. It indicated that the population had a harmonious relationship internally. We found that different size class exhibited maximal intensity of assemblage at a critical scale: seedlings (28 m), saplings (29 m), small trees (15 m), medium trees (34 m), big trees (49 m). Big trees and medium trees had significantly positive association at all scales. Seedlings had significantly positive association with saplings only within the scale of 7 m, but they had no significant spatial associations with big, medium and small trees.(3)The seedlings and saplings of A. faxoniana were very abundant with continuous age distribution in Betula-Abies forest, suggesting its successful regeneration. We did not found alive B. albo-sinensis individuals lower than two m in the plot, suggesting its poor regeneration. As to A. faxoniana, one-year old seedlings accounted for 62.45% of total number of seedlings and saplings, and seedlings more than two-years old accounted for 2.30%. 86.70% of one-year old seedlings and 81.08% of seedlings more than two-years old habitated on moss. Particularly, we focused on spatial association at small scale. Spatial association of different size class of dominant tree species varied with seedlings and saplings. Spatial association of A. faxoniana’s seedlings along with its small trees, medium trees and large trees showed significantly negative at the scales of 0~7 m, 0~8 m and 0~8 m, respectively. Spatial association of A. faxoniana’s saplings with its small trees, medium trees and large trees showed significantly negative at the scales of 0~11 m, 0~13 m and 0~11 m, respectively. No significant spatial association was detected between A. faxoniana’s seedlings and B. albo-sinensis’s small trees and between A. faxoniana’s saplings and B. albo-sinensis’s small trees at all scales. There were significantly negative spatial associations between A. faxoniana’s seedlings and B. albo-sinensis’s medium trees and between A. faxoniana’s saplings and B. albo-sinensis’s medium trees at the scales of 0~18 m, 0~34 m, respectively. There were significantly negative spatial associations between A. faxoniana’s seedlings and B. albo-sinensis’s big trees and between A. faxoniana’s saplings and B. albo-sinensis’s big trees at all scales. Coverage of moss, stock of logs, density of mother trees of A. faxoniana, coverage of bamboo and coverage of trees were the key factors influencing natural regeneration of A. faxoniana. Coverage of moss, stock of logs and density of mother tree (DBH≥16.5) were favorable to natural regeneration of A. faxoniana, while coverage of bamboo and coverage of trees were obstructive to the natural regeneration of A. faxoniana.(4)The results of spatial pattern analysis revealed severe competition between B. albo-sinensis and A. faxoniana. No association was detected among dominant tree species of the primary forest, while the spatial association between B. albo-sinensis and A. faxoniana exhibited significantly negative at all scales. All big trees of B. albo-sinensis and A. faxoniana were spatially clumped at all scales that were examined. Other size-classes were spatially clumped at small scales, while they tended to be randomly or regularly spatially distributed with increasing spatial scale. Their maximum aggregation degree decreased with increasing size class. Intra- and interspecies spatial associations occurred generally at small scales. A. faxoniana generally showed a positive inner-specific association, while B. albo-sinensis generally showed a negative inner-specific association. For the same size-classes of the two populations, no significant spatial association were found for big trees and small trees, but the negative spatial associations were for medium trees. The negative spatial associations of the two populations at the different size-classes were commonly found, the larger difference size-classes, the stronger negative spatial associations.(5)Large size class of remnant trees had strong inpacts on other size class trees. There were significantly negative spatial associations between B. albo-sinensis’s large size class of remnant trees and its small and medium trees at the scale of 0~8 m, 0~9 m, respectively. There were significantly negative spatial associations between A. faxoniana’s large size class of remnant trees and its seedlings at the scale of 0~8 m. There were significantly positive spatial associations between A. faxoniana’s large size class of remnant trees and its saplings and small trees at the scale of 0~11 m, 0~9 m. No association was detected between A. faxoniana’s large size class of remnant trees and its medium trees at 0~14 m scales. Spatial association of B. albo-sinensis’s large size class of remnant trees with A. faxoniana’s seedlings, saplings, small trees and medium trees showed significantly negative at all scale. There were significantly negative spatial associations between A. faxoniana’s large size class of remnant trees and B. albo-sinensis’s small trees at the scale of 0~4 m. Large size class of remnant trees facilitated the regeneration and growth of A. faxoniana as late successional and dominant tree species, while impeding the regeneration and growth of B. albo-sinensis as a pioneer tree species.更多还原