IPCC第六次评估报告指出, 在未来20年内, 全球平均气温的上升幅度可能会超过1.5 ℃, 其中高海拔和高纬度地区受气候变化的影响尤为显著和迅速(Lee et al., 2021)。气候变化对森林生态系统构成了严重的威胁, 尤其是对山地森林生态系统。树线作为山体达到一定高度时森林分布的上限, 被视为高海拔生态系统中承受环境压力最大的地区之一(Hermes, 1955)。随着全球温度的持续升高, 树线位置可能会上移, 这一变化不仅改变了树线植物种群的分布格局, 也对整个山地生态系统的结构和功能造成影响(Körner & Paulsen, 2004; Adams et al., 2009)。高山树线交错带作为森林与高山草甸之间的生态过渡带, 由于其结构相对简单且对气候变化高度敏感, 正面临着日益加剧的气候变化威胁(Gauthier et al., 2015)。因此, 高山树线交错带的植物群落组成、结构以及动态变化逐渐成为研究者们关注的焦点(Barros et al., 2017)。
研究植物种群空间格局对揭示种群结构及其生态学过程至关重要(Getzin et al., 2008)。种群的空间分布格局通常可分为聚集、随机和均匀3种类型。其中聚集分布主要由基于生态位理论的生境异质性和基于中性理论的扩散限制所驱动(Condit et al., 2000; Wiegand & Moloney, 2014), 尤其是小尺度上的聚集多由扩散限制所致(Harms et al., 2001; 李立等, 2010)。相反, 均匀分布通常由自疏效应和种内竞争引起的密度制约所引发(Sterner et al., 1986; 安璐等, 2021)。空间关联性分析可以进一步探讨物种在空间上的相互作用, 包括正关联、负关联和不相关3种类型(张金屯, 1998)。正关联表明物种之间相互依赖或生态位重叠, 负关联则反映了物种间存在竞争或密度制约效应, 不相关则说明物种能够在资源充足的环境中共存, 彼此间无明显的相互影响(张金屯, 1998; 祝燕等, 2011)。点格局分析(spatial-point- pattern-analysis, SPPA)是研究种群空间格局的一种常用方法(Brown et al., 2011), 通过将每个个体的位置视为二维空间中的点, 允许在任意尺度上分析空间分布格局和关联性。与传统的样方法、距离法和角尺度法相比, 点格局分析能够更充分地利用空间信息, 为揭示种群空间分布特征与生态过程之间的联系提供了强有力的工具(Ripley, 1977; Wiegand & Moloney, 2004)。因此, 通过点格局分析, 能够更好地揭示种群的空间分布和维持机制(Nathan, 2006)。
环境因子特别是地形因子, 在塑造植物的空间格局方面起着决定性作用(Palmer, 1990)。地形因子通过改变土壤湿度、土壤养分和光照等综合环境条件, 从而影响物种分布(Balvanera et al., 2011)。例如, 沟谷生境因水分条件较好且资源可获得性高, 往往能够支撑更多的植物种类和数量。相反, 在资源相对匮乏的山脊生境, 仅能支撑有限的植物种群(Gibbons & Newbery, 2003)。研究显示, 由不同地形因子引起的生境异质性变化, 是塑造局域尺度上不同树种的空间分布格局的主要因素。例如, 梁爽等(2014)在对海南岛尖峰岭60 hm2热带山地雨林优势种空间分布的研究中发现, 坡度与不同生活史阶段的个体分布呈显著正相关关系, 海拔主要影响幼树的分布, 而凹凸度对幼树和中树的分布有显著影响。He等(2022)在研究秦岭皇冠25 hm2暖温性落叶阔叶林优势树种的空间分布格局时发现, 坡度和凹凸度主要与乔木层树种分布呈正相关关系, 而与亚乔木层和灌木层树种分布呈负相关关系。这说明不同地形因子在塑造种群空间分布格局中的相对重要性在不同森林类型间存在显著差异。
长苞冷杉(Abies georgei)是我国特有的松科冷杉属植物, 是组成寒温性针叶林的主要树种, 也是青藏高原东南缘主要的高山林线树种(刘庆等, 2001)。该树种种群的动态变化可能对当地的物种组成、群落结构以及区域生物多样性产生深远影响。目前对长苞冷杉林的研究主要集中在种子的特征与变异(王丹等, 2023)、幼苗的生长存活动态(刘庆, 2004)、树干的径向生长动态(张贇等, 2018; 张慧等, 2022), 以及小尺度上的分布格局(张桥英等, 2008; 顾荣等, 2021)等方面。然而, 在较大空间尺度上, 关于长苞冷杉群落优势树种的分布格局、种内和种间关联性及其影响因素的研究仍相对不足。
本研究基于长苞冷杉为优势种的云南香格里拉亚高山寒温性针叶林20 hm2动态监测样地的调查数据, 旨在探讨以下问题: (1)亚高山寒温性针叶林优势种的空间分布格局具有哪些特征? (2)长苞冷杉不同发育阶段的种内关联性如何? 长苞冷杉与其他优势种之间的种间关联性如何? (3)地形因子如何影响亚高山寒温性针叶林优势种的空间分布? 以期为揭示驱动亚高山寒温性针叶林物种多样性维持机制提供理论基础, 为普达措国家公园寒温性针叶林的经营规划提供科学依据。
1 材料和方法
1.1 研究区概况
普达措国家公园(99.90°-100.19° E, 27.73°- 28.08° N)位于云南省迪庆藏族自治州香格里拉县, 是青藏高原东南缘的一部分, 位于横断山脉高寒峡谷区北段(Chen et al., 2022), 海拔范围为3 200-4 159 m, 年平均气温为4.2 ℃, 4-10月降水量为817.3 mm (杨迎花等, 2021)。该地区主要受高原季风气候的影响, 形成具有明显季节性的雪被, 降雪期至融雪期长达4-6个月。独特的气候条件孕育了高山草甸、针叶林、阔叶林和湿地等多种植被类型(赵玉堂, 2023), 是亚热带常绿阔叶林向青藏高原高寒植被的重要过渡区域(张菊梅等, 2021)。位于低纬度高海拔的普达措国家公园保存着大片以长苞冷杉为优势种的寒温性针叶林。
1.2 样地调查
2022年, 按照全球森林观测网络(Forest Global Earth Observatory, Forest GEO)的技术规范(Condit, 1998), 在普达措国家公园内建立了一块20 hm2的寒温性针叶林生物多样性长期监测样地。样地东西宽500 m, 南北长400 m, 使用全站仪把样地分成500个20 m × 20 m的样方, 每个20 m × 20 m的样方又分成16个5 m × 5 m的小样方, 记录并鉴定所有胸径≥1 cm的木本植物个体。记录信息包括植物编号、物种名称、在样方内的位置(坐标x和y)、胸径、分枝情况以及生长状况(如枯立、倒伏和倾斜)等。样地共有39 106株活立木, 分属于10科15属28种。其中, 长苞冷杉为样地内优势度最高的物种, 有27 463株, 占总株数的70%。亚乔木层优势种为红棕杜鹃(Rhododendron rubiginosum), 有1 839株, 其次是西南花楸(Sorbus rehderiana), 有1 026株。灌木层优势种为唐古特忍冬(Lonicera tangutica), 有3 663株, 其次是云南双盾木(Dipelta yunnanensis), 有1 920株(顾荣等, 2025)。
1.3 地形因子测量
1.4 数据分析
1.4.1 发育阶段划分
1.4.2 种群空间分布格局及种内种间的空间关联性
该研究以Ripley (1977)提出的Ripley’s K (K(r))函数为基础, 采用单变量成对相关函数(g(r)), 以样地中每个个体的空间坐标为基础, 分析长苞冷杉及其他4种优势种种群的空间格局。采用Monte-Carlo拟合检验, 计算上下包迹线, 即置信区间的范围, 拟合次数为999次, 得到99%的置信区间。若g(r)值高于上包迹线, 种群呈聚集分布; 若g(r)值低于下包迹线, 种群呈均匀分布; 若g(r)值在包迹线之间, 种群则呈随机分布。为检验生境异质性对空间分布格局形成的作用, 使用异质性泊松过程为零模型来分析长苞冷杉及其他4种优势种种群的空间格局, 本研究以地形因子作为模拟异质泊松点过程的协变量。
采用双变量成对相关函数(g12(r)), 分析长苞冷杉不同发育阶段个体间及其与优势种之间的关联性。同理, 采用Monte-Carlo拟合检验, 随机模拟999次, 得到99%的置信区间, 并生成上下两条包迹线。g12(r)值高于上包迹线, 则两者为正相关; g12(r)值在包迹线之间, 则两者无相关性; g12(r)值低于下包迹线, 则两者为负相关。此外, 使用拟合优度(Goodness of Fit, GoF)测试来评估实际点格局与零模型模拟的差异显著性(Loosmore & Ford, 2006)。
1.4.3 物种-地形生境的关联性
本研究采用Torus-translation方法检验亚高山寒温性针叶林优势种与4类地形因子之间的相关性(Harms et al., 2001)。该方法主要通过比较实际生境图和模拟生境图上物种在各类地形因子上的相对密度来确定其与地形因子的相关性。如果某个物种在某种地形因子上的实际相对密度落在最大的2.5%区间内, 则认为该物种与该地形因子呈正相关关系; 反之, 若实际相对密度落在最小的2.5%区间内, 则认为该物种与该地形因子呈负相关关系。本研究的所有数据分析和作图均在R 4.3.2软件中完成, 利用“spatstat”包分析种群的空间分布格局及其关联性, 利用“ggplot2”包作图。
2 结果和分析
2.1 寒温性针叶林优势种的空间分布格局
图1
图1
云南香格里拉亚高山寒温性针叶林20 hm2动态监测样地中长苞冷杉种群不同发育阶段的空间分布格局。A, 幼树。B, 中树。C, 成树。黑色实线表示单变量成对相关函数g(r)的函数值, 红色虚线表示单变量成对相关函数g(r)的期望值, 灰色阴影部分表示99%的置信区间。地图中绿色表示低海拔, 红色表示高海拔。p值为拟合优度检验结果。
Fig. 1
Spatial distribution pattern of Abies georgei at different developmental stages in the 20 hm2 dynamics plot of subalpine cold-temperate coniferous forest in Shangri-La, Yunnan. A, Saplings. B, Juvenile trees. C, Adult trees. Solid black lines represents the value of the univariate pair-correlation g(r) function, the dashed red line represents the expected value of the univariate pair-correlation g(r) function, and the gray shaded part represents the 99% confidence interval. Green on the map indicates low altitudes and red indicates high altitudes. The p-value is the goodness of fit test result.
图2
图2
云南香格里拉亚高山寒温性针叶林20 hm2动态监测样地中亚乔木层和灌木层优势种的空间分布格局。A, 红棕杜鹃。B, 西南花楸。C, 唐古特忍冬。D, 云南双盾木。黑色实线表示单变量成对相关函数g(r)的函数值, 红色虚线表示单变量成对相关函数g(r)的期望值, 灰色阴影部分表示99%的置信区间。地图中绿色表示低海拔, 红色表示高海拔。p值为拟合优度检验结果。
Fig. 2
Spatial distribution pattern of dominant species in the subtree layer and shrub layer in the 20 hm2 dynamics plot of subalpine cold-temperate coniferous forest in Shangri-La, Yunnan. A, Rhododendron rubiginosum. B, Sorbus rehderiana. C, Lonicera tangutica. D, Dipelta yunnanensis. Solid black lines represent the value of the univariate pair-correlation g(r) function, the dashed red lines represent the expected value of the univariate pair-correlation g(r) function, and the gray shaded parts represent the 99% confidence interval. Green on the map indicates low altitudes and red indicates high altitudes. The p-value is the goodness of fit test result.
2.2 寒温性针叶林优势种长苞冷杉种群不同发育阶段的种内关联性
图3
图3
云南香格里拉亚高山寒温性针叶林20 hm2动态监测样地中长苞冷杉种群不同发育阶段的种内关联性。A, 幼树和中树。B, 幼树和成树。C, 中树和成树。黑色曲线表示双变量成对相关函数g12(r)的函数值, 黑色直线表示双变量成对相关函数g12(r)的期望值, 灰色虚线表示99%的置信区间。p值为拟合优度检验结果。
Fig. 3
Intraspecific correlation of Abies georgei population at different developmental stages in the 20 hm2 dynamics plot of subalpine cold-temperate coniferous forest in Shangri-La, Yunnan. A, Sapling and juvenile trees. B, Sapling and adult trees. C, Juvenile and adult trees. The black curve represents the function value of the bivariate pair-correlation function g12(r), and the black straight line represents the expected value of the bivariate pair-correlation g12(r) function. The dashed gray line indicates a 99% confidence interval. The p-value is the goodness of fit test result.
2.3 寒温性针叶林优势种的种间关联性
图4
图4
云南香格里拉亚高山寒温性针叶林20 hm2动态监测样地中长苞冷杉种群不同发育阶段与其他优势种的种间关联性。A, 长苞冷杉与亚乔木层优势种之间的关联性。B, 长苞冷杉与灌木层优势种之间的关联性。p值为拟合优度检验结果。
Fig. 4
Interspecific relationship between Abies georgei at different developmental stages and other dominant species in the 20 hm2 dynamics plot of subalpine cold-temperate coniferous forest in Shangri-La, Yunnan. A, Relationship between Rhododendron rubiginosum and dominant species in subtree layers. B, Relationship between Rhododendron rubiginosum and dominant species in shrub layers. DY, Dipelta yunnanensis; LT, Lonicera tangutica; RR, Rhododendron rubiginosum; SR, Sorbus rehderiana. The p-value is the goodness of fit test result.
图5
图5
云南香格里拉亚高山寒温性针叶林20 hm2动态监测样地中亚乔木层和灌木层优势种的种间关联性。p值为拟合优度检验结果。
Fig. 5
Interspecific relationship of dominant species in subtree layer and shrub layer in 20 hm2 dynamics plot of subalpine cold-temperate coniferous forest in Shangri-La, Yunnan. DY, Dipelta yunnanensis; LT, Lonicera tangutica; RR, Rhododendron rubiginosum; SR, Sorbus rehderiana. The p-value is the goodness of fit test result.
2.4 地形对寒温性针叶林优势种空间分布格局的影响
表1 云南香格里拉亚高山寒温性针叶林20 hm2动态监测样地长苞冷杉种群及其他优势种与地形因子的Torus-translation检验及物种密度与地形因子的Spearman相关系数
Table 1
| 发育阶段/物种 Development stage/species | 海拔 Altitude | 坡度 Slope | 凹凸度 Convex | 正弦坡向 Sin (aspect) | 余弦坡向 Cos (aspect) |
|---|---|---|---|---|---|
| 幼树 Sapling | 0.16 | -0.41* | 0.08 | -0.13 | -0.13 |
| 中树 Juvenile | 0.07 | -0.30* | -0.08 | 0.06 | 0.08 |
| 成树 Adult | 0.27* | 0.04 | 0.34* | 0.07 | 0.08 |
| 红棕杜鹃 Rhododendron rubiginosum | -0.17 | 0.39* | 0.28* | -0.07 | -0.07 |
| 西南花楸 Sorbus rehderiana | -0.26* | 0.15 | -0.08 | -0.07 | -0.10 |
| 唐古特忍冬 Lonicera tangutica | 0.50* | -0.04 | 0.17* | 0.35* | 0.38* |
| 云南双盾木Dipelta yunnanensis | 0.05 | 0.49* | 0.08 | 0.50* | 0.51* |
*, p < 0.05.
3 讨论
3.1 寒温性针叶林优势种的空间分布格局
本研究中, 云南香格里拉亚高山寒温性针叶林20 hm2动态监测样地内的长苞冷杉种群的幼树和中树主要呈聚集分布模式, 且聚集度随着尺度的增大而减小, 而成树的空间分布格局由均匀分布逐渐转变为随机分布(图1)。这一结果与国内外大多数关于自然森林优势种群空间格局的研究结果(兰国玉等, 2008; Liu et al., 2020; 顾荣等, 2021)一致。聚集分布是小径级个体最常见的分布类型, 主要受散布限制和环境过滤这两种生态过程驱动(Getzin et al., 2008)。长苞冷杉的种子以球果形式存在, 种子的散布主要靠重力的作用, 所以早期的聚集分布模式可能是受扩散限制的影响(朱文婷等, 2021)。此外, 本样地所在的海拔较高, 环境条件比较严酷, 例如11月至次年4月长时间的冬季积雪覆盖, 以及年平均气温低于4.2 ℃的低温环境(杨迎花等, 2021)。因此, 温度和湿度等环境因子引起的生境过滤也是长苞冷杉的幼树和中树呈现聚集分布的原因之一。种群通过聚集分布能够调节微气候和小生境, 增加种群优势, 增加个体存活的机会(韩路等, 2007)。随着个体径级的增大和对资源需求的增加, 种内竞争加剧, 竞争中处于劣势的个体逐渐死亡, 负密度制约引起的自疏作用最终导致长苞冷杉的成树个体从均匀分布最终转变为随机分布(Stoll & Bergius, 2005; Wang et al., 2010)。本研究的结果与青藏高原的岷江冷杉(Abies fargesii var. faxoniana)和色季拉山的急尖长苞冷杉(Abies georgei var. smithii)所呈现的随机分布格局, 以及米亚罗地区岷江冷杉的聚集分布结果有所差异(赵常明等, 2004; 赵广东等, 2022; 朱文婷等, 2022)。这一差异可能是由于不同研究样地的空间异质性及其面积大小的不同引起的, 较小的样地面积可能会掩盖环境过滤对物种分布的真实作用。此外, 本研究发现亚乔木层和灌木层的优势种的空间分布格局同样以聚集分布为主(图2), 这和以往的研究结果一致, 即群落内个体数量较少的物种往往聚集程度较高(Condit et al., 2000; Wang et al., 2010)。本研究样地内长苞冷杉个体数量占总株数的70%, 相比之下, 即使为各层优势种的红棕杜鹃、西南花楸、唐古特忍冬和云南双盾木在整个样地中的数量仍较少, 它们通过聚集分布来增加周围的同种个体的数量, 减少异种邻体, 减弱种间竞争, 从而实现与长苞冷杉在局域尺度上的稳定共存(Chacón- Labella et al., 2017; 毛子昆等, 2020)。剔除环境异质性的影响后, 西南花楸、唐古特忍冬和云南双盾木的空间分布格局显著地由聚集分布转变为随机分布(附录II), 这与大多数研究结果(Condit et al., 2000; Wang et al., 2010; 顾荣等, 2021; 邱婧等, 2022)一致。表明这3种物种的空间分布格局主要受环境异质性的调控。
3.2 寒温性针叶林优势种的种内、种间的关联性
空间关联描述了植物个体之间的关系, 可以反映种群的状态以及种内种间及其与环境的相互作用(Wang et al., 2010)。本研究发现长苞冷杉的幼树与中树整体呈正关联(图2), 说明两者对生境的选择具有一致性。小径级个体由于对资源的需求较少、种间竞争相对较弱, 倾向于通过集群作用来提高抵御外界环境胁迫的能力, 从而提高其生存能力(Cavieres et al., 2014; Liu et al., 2020)。然而, 幼树与成树间的负关联可能是受Janzen-Connell假说的距离制约效应影响, 主要受有害生物侵害和资源限制的影响, 靠近成树的幼树更易受专一性病原菌和植食性昆虫的攻击, 从而降低幼树存活率(Connell, 1971; Liu et al., 2012)。此外, 同种个体对资源的需求相似, 尤其在母树附近, 由于成树已经占据了大量资源, 幼树在资源竞争中处于劣势地位(祝燕等, 2009)。因此, 幼树在分布上倾向于远离母树, 寻找资源相对丰富、竞争压力较小的生境, 以提高自身的生存机会。中树与成树之间的负相关可能是大径级个体通过不对称竞争限制了中径级个体对空间、养分、光照等资源的获取(韩豪等, 2021), 尤其是长苞冷杉大径级个体树冠庞大, 占据较大的空间, 且对光照、水分和土壤养分具有更强的竞争能力, 限制了周围中径级个体的生长。
本研究还发现, 长苞冷杉的幼树与亚乔木层优势种红棕杜鹃、西南花楸呈正关联(图3), 一方面可能与长苞冷杉是耐荫树种的生物学特性有关, 亚乔木层树种的树冠为其提供适度的遮阴环境有利于幼树的生长(Wang et al., 2010; Liu et al., 2020)。另一方面, 亚乔木层的树冠能够分散并承载部分积雪, 为林下长苞冷杉幼树的生长提供了更好的生存条件。相反, 长苞冷杉的幼树与灌木层、中树与亚乔木层和灌木层的优势树种呈负关联(图3), 这说明长苞冷杉中小径级个体与灌木层树种存在激烈的种间竞争, 可能原因是两者具有相似的生态需求和资源利用策略, 导致林下更新和生长能力较强的灌木能够与长苞冷杉的幼树和中树争夺光照、水分和养分等限制性资源, 并抢占长苞冷杉小径级个体的生态位空间(Yang et al., 2018; 董雪等, 2020)。长苞冷杉的成树与各层优势种之间普遍呈正关联(图3), 这表明长苞冷杉的成树可能通过改善微环境, 减少竞争压力, 从而为其他树种提供了有利条件。乔木层和灌木层优势种之间也普遍表现出正关联, 这可能是因为这些优势种通过其生态位特化来促进资源的互补利用。因此, 在亚高山寒温性针叶林中, 不同优势种之间的相互作用构成了一个错综复杂的动态平衡系统。随着森林群落的演替, 本样地最终形成以长苞冷杉为代表的相对稳定的顶极群落。在这一过程中, 长苞冷杉种群与其他优势种通过各自的生态策略形成互利共生或互补的种间关系, 有效利用和补充资源, 最终实现长期稳定共存(叶权平等, 2018)。
3.3 地形对寒温性针叶林优势种空间分布格局的影响
在较小尺度上, 种群分布格局主要受周围同种和异种邻体相互作用的影响, 而在较大空间尺度上, 生境过滤作用更加显著(HilleRisLambers et al., 2012; Shen et al., 2013)。地形在塑造植物局域尺度物种分布中起着重要作用(Webb & Peart, 2000; Chuyong et al., 2011)。通过Torus-translation检验发现, 本样地的优势树种的密度至少与一种地形因子显著关联性(表1)。高海拔地区具有低温、低氧和紫外线辐射强等恶劣条件, 这对许多物种的生存构成了巨大的挑战(Sun et al., 2018)。本样地的优势种大多与海拔呈正相关关系, 其经过长期的自然选择和进化过程, 已经形成了适应高海拔环境的能力和生存策略。然而, 西南花楸与海拔呈负相关关系, 说明随着海拔的升高, 其植株数量逐渐减少, 可能原因是作为落叶型植物的西南花楸对环境变化较为敏感, 其更倾向于利用环境变化相对缓慢的低海拔区域(Xing et al., 2023; 邢红爽等, 2024)。长苞冷杉的幼树和中树与坡度呈显著负相关关系, 说明这些中小径级个体更偏好较缓的坡度。其中幼树的这种偏好可能与其繁殖策略有关, 因为陡峭坡面不利于长苞冷杉种子的萌发和幼苗的定植, 相反, 在相对平缓的地形中, 脱落的球果更易于在土壤中停留, 增加了定植的机会。中树阶段的长苞冷杉, 随着其根系和树冠的扩展, 对养分和水分等资源的需求量增加, 坡度较大的区域可能会因为土壤浅薄和养分供应不足而不利于中树生长。红棕杜鹃和云南双盾木偏好坡度较陡的生境, 与长苞冷杉发生坡度生态位的分化, 从而减少了种间竞争, 促进了这些物种的稳定共存(朱文婷等, 2021)。长苞冷杉成树、红棕杜鹃和唐古特忍冬的密度与凹凸度的正相关可能反映了较凹区域积雪较厚且覆盖时间较长, 土壤温度过低而不利于树种的更新。此外, 本研究还发现灌木层的优势种唐古特忍冬和云南双盾木对坡向的偏好, 暗示坡向引起的光照和水分等生态位分化对亚高山针叶林物种共存的重要性(Punchi-Manage et al., 2013)。总之, 地形通过影响生境异质性, 对植物空间分布格局产生作用, 为不同生活史策略和生态需求的物种提供了相应的定居机会, 从而有利于生物多样性的维持(Palmer, 1990)。
4 结论
云南香格里拉亚高山寒温性针叶林20 hm2动态监测样地内的优势种整体表现出强烈的聚集分布, 聚集程度随着尺度的增加而逐渐降低。而不同优势种的聚集模式受不同的生态学过程所驱动。但随着径级的增大, 自疏作用的增强, 导致长苞冷杉的成树最终趋于随机分布。本研究的种内和种间关联性表现出了正关联、负关联和不关联3种关系, 其中以正、负关联为主, 表明物种间的相互作用(如竞争和互惠等)在群落构建中共同发挥作用。此外, 优势种的空间分布主要受地形因子(海拔、坡度和凹凸度)的显著影响, 说明地形异质性是引起长苞冷杉林优势种间分布格局差异的主要原因。研究表明幼苗空间格局是影响森林群落组成的重要因素。因此, 需要进行长期的动态监测, 进一步探讨幼苗的空间格局, 以揭示更新阶段的潜在生态学机制。
致谢
感谢中国科学院西双版纳热带植物园的马朗、马玖、成发玉、李亚雄、姚志良、邵晓娜、马小花、李亚雄、张兰、李树琼、杨欣、潘霞、施国杉、苏维翰、王金蒙、张悦、孙健博等参加样地建设工作; 感谢香格里拉普达措国家公园管理局为样地建设提供大力支持和后勤保障, 感谢香格里拉高山植物园在样地建设过程中给予的帮助。
附录
附录I 云南香格里拉亚高山寒温性针叶林20 hm2动态监测样地中长苞冷杉种群不同发育阶段在异质泊松零模型(HP)下的空间分布
Supplement I Spatial distribution pattern of Abies georgei at different developmental stages under the null model of heterogeneous Poisson (HP) in the 20 hm2 dynamics plot of subalpine cold-temperateconiferous forest in Shangri-La, Yunnan
附录II 云南香格里拉亚高山寒温性针叶林20 hm2动态监测样地中亚乔木层和灌木层优势种在异质泊松零模型(HP)下的空间分布
Supplement II Spatial distribution pattern of dominant species in subtree and shrub layer under the null model of heterogeneous Poisson (HP) in the 20 hm2 dynamics plot of subalpine cold-temperateconiferous forest in Shangri-La, Yunnan
附录III 云南香格里拉亚高山寒温性针叶林20 hm2动态监测样地中长苞冷杉种群不同发育阶段与其他优势种的种间关联分布
Supplement III Interspecific relationship distribution between Abies georgei at different developmental stages and other dominant species in the 20 hm2 dynamics plot of subalpine cold-temperateconiferous forest in Shangri-La, Yunnan
附录IV 云南香格里拉亚高山寒温性针叶林20 hm2动态监测样地中亚乔木层和灌木层优势种的种间关联分布
Supplement IV Interspecific relationship distribution of dominant species in subtree layer and shrub layer in the 20 hm2 dynamics plot of subalpine cold-temperateconiferous forest in Shangri-La, Yunnan
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DOI:10.3773/j.issn.1005-264x.2010.03.001
[本文引用: 1]
基于24 hm2古田山中亚热带常绿阔叶林长期监测样地调查资料, 采用Ripley的K函数点格局分析等方法, 具体分析了古田山常绿阔叶林优势树种甜槠(Castanopsis eyrei)与木荷(Schima superba)不同年龄阶段的空间分布格局以及它们之间的空间关联性。结果表明: 两种优势物种在总体上及不同年龄阶段主要呈聚集分布, 且随年龄阶段的增加, 聚集程度有降低的趋势。两物种在大尺度直观上有明显的生境偏好。两种优势物种的幼树、小树与大树和老树主要呈空间负相关或无空间关联性, 与中树呈空间正相关。甜槠中树与大树、大树与老树主要呈空间正相关, 而甜槠的中树与老树呈空间负相关。木荷中树与大树和老树、大树与老树均呈现空间负相关或无关联。我们发现古田山优势物种通过密度制约和Janzen-Connell效应释放空间, 为其他物种共存提供了条件, 密度制约和Janzen-Connell效应可能是古田山样地甜槠和木荷空间格局形成的重要原因。
Spatial distribution pattern of the dominant species Gironniera subaequalis in tropical montane rainforest of Jianfengling, Hainan Island, China
尖峰岭热带山地雨林优势树种白颜树空间分布格局
Separating the effects of environment and space on tree species distribution: from population to community
Competition and facilitation co-regulate the spatial patterns of boreal tree species in Kanas of Xinjiang, northwest China
The effects of gap size and within gap position on the survival and growth of naturally regenerated Abies georgei seedlings
林窗对长苞冷杉自然更新幼苗存活和生长的影响
DOI:10.17521/cjpe.2004.0030
[本文引用: 1]
长苞冷杉(Abies georgei)林是我国西南亚高山针叶林的重要类型之一，分布于海拔3 200～4 200 m。目前对于该森林林窗对树苗更新的调节还很少了解。通过1997～2000年对20个林窗的连续观测调查，研究了滇西北白马雪山自然保护区西坡亚高山长苞冷杉林林窗大小和林窗位置对自然更新幼苗存活和生长的影响。长苞冷杉针叶林林窗大小分布为，面积大于100 m2的大林窗占20%左右，中等林窗面积为50～100 m2，占35%左右，小林窗面积小于50 m2，占45%左右。4个生长季节的连续观测结果表明：林窗与林下非林窗内的幼苗大小和幼苗存活数量差异明显。林窗由小到大，单位面积内的自然更新苗木数量逐渐增加，大林窗中更新苗为小林窗的1.5倍左右，而林下的更新苗很少，0.5 ind.·10 m-2。中等林窗和小林窗内的幼苗数量在从南到中心到北的位置上几乎没有明显的差异；大林窗中存在由南到北的位置差异，更新幼苗数量逐渐增加。从更新幼苗的生长来看，中等林窗内的幼苗，高度最大、生长最快，定居阶段的平均年高生长为(7.8±0.5) cm·a-1，小林窗次之，大林窗和林下幼苗个体最小，生长最慢。更新幼苗的基径随林窗大小的变化与高度变化相似。进一步从林窗位置来看，中、小林窗幼苗大小和年平均高生长量几乎无位置差异，大林窗则由南到北，幼苗由大变小，年高生长量逐渐减低。从幼苗存活数量、生长大小来看，中等林窗大小是长苞冷杉幼苗更新的适宜面积，这为该类型退化亚高山针叶林恢复提供了一定的参考。
Ecological problems of subalpine coniferous forest in the southwest of China
中国西南亚高山针叶林的生态学问题
Experimental evidence for a phylogenetic Janzen- Connell effect in a subtropical forest
Statistical inference using the G or K point pattern spatial statistics
Spatial point pattern analysis provides a statistical method to compare an observed spatial pattern against a hypothesized spatial process model. The G statistic, which considers the distribution of nearest neighbor distances, and the K statistic, which evaluates the distribution of all neighbor distances, are commonly used in such analyses. One method of employing these statistics involves building a simulation envelope from the result of many simulated patterns of the hypothesized model. Specifically, a simulation envelope is created by calculating, at every distance, the minimum and maximum results computed across the simulated patterns. A statistical test is performed by evaluating where the results from an observed pattern fall with respect to the simulation envelope. However, this method, which differs from P. Diggle's suggested approach, is invalid for inference because it violates the assumptions of Monte Carlo methods and results in incorrect type I error rate performance. Similarly, using the simulation envelope to estimate the range of distances over which an observed pattern deviates from the hypothesized model is also suspect. The technical details of why the simulation envelope provides incorrect type I error rate performance are described. A valid test is then proposed, and details about how the number of simulated patterns impacts the statistical significance are explained. Finally, an example of using the proposed test within an exploratory data analysis framework is provided.
Abundance-asymmetry in conspecific aggregation and interspecific interaction
物种聚集分布与种间关系的多度不对称性
Long-distance dispersal of plants
DOI:10.1126/science.1124975
PMID:16902126
[本文引用: 1]
Long-distance dispersal (LDD) of plants poses challenges to research because it involves rare events driven by complex and highly stochastic processes. The current surge of renewed interest in LDD, motivated by growing recognition of its critical importance for natural populations and communities and for humanity, promises an improved, quantitatively derived understanding of LDD. To gain deep insights into the patterns, mechanisms, causes, and consequences of LDD, we must look beyond the standard dispersal vectors and the mean trend of the distribution of dispersal distances. "Nonstandard" mechanisms such as extreme climatic events and generalized LDD vectors seem to hold the greatest explanatory power for the drastic deviations from the mean trend, deviations that make the nearly impossible LDD a reality.
Spatial scale and patterns of species- environment relationships in hardwood forest of the North Carolina piedmont
Effects of topography on structuring local species assemblages in a Sri Lankan mixed dipterocarp forest
Spatial distribution pattern and intraspecific association of dominant species Quercus aliena var. acutiserrata in Qinling Mountains, China
秦岭优势乔木锐齿槲栎的空间分布格局及种内关联
DOI:10.13287/j.1001-9332.202208.002
[本文引用: 1]
为探究锐齿槲栎种群的空间分布特征及关联性,本研究以秦岭皇冠暖温性落叶阔叶林25 hm<sup>2</sup>森林样地内优势树种锐齿槲栎为对象,采用成对相关函数g(r)对其空间格局及其种内关联性进行了研究。结果表明: 锐齿槲栎径级结构呈“双峰”型,幼树(1 cm≤胸径DBH＜5 cm)个体数较多,种群呈增长型结构,更新良好;中树(15 cm≤DBH＜25 cm)比大树(25 cm≤DBH＜35 cm)、老树(DBH≥35 cm)的个体数略多,但远少于幼树和小树(5 cm≤DBH＜15 cm)。锐齿槲栎空间分布具有明显的海拔依赖性,主要分布在中高海拔地区。完全空间随机零模型分析表明,各径级个体在＜60 m的大尺度范围聚集分布。使用异质泊松模型剔除生境异质性分析表明,各径级的个体转变为大尺度的随机分布,表明树种的分布明显受到生境变化的影响。在＜40 m的小尺度范围内,径级差距小的个体间的空间关联性为正关联,径级差距大的个体间的空间关联性转变为负关联和无关联;在＞40 m的大尺度范围内,大径级个体间的空间关联性为正关联,而幼树和其他径级个体间的空间关联性为负关联或无关联。锐齿槲栎自身生物学特性和环境异质性是种群空间格局形成的重要原因。
Modelling spatial patterns
Quantifying effects of habitat heterogeneity and other clustering processes on spatial distributions of tree species
Spatially explicit consideration of species distribution can significantly add to our understanding of species coexistence. In this paper, we evaluated the relative importance of habitat heterogeneity and other clustering processes (e.g., dispersal limitation, collectively called the non-habitat clustering process) in explaining the spatial distribution patterns of 341 tree species in three stem-mapped 25-50 ha plots of tropical, subtropical, and temperate forests. Their relative importance was estimated by a method that can take one mechanism into account when estimating the effects of the other mechanism and vice versa. Our results demonstrated that habitat heterogeneity was less important in explaining the observed species patterns than other clustering processes in plots with flat topography but was more important in one of the three plots that had a complex topography. Meanwhile, both types of clustering mechanisms (habitat or non-habitat) were pervasive among species at the 50-ha scale across the studied plots. Our analyses also revealed considerable variation among species in the relative importance of the two types of mechanism within each plot and showed that this species-level variation can be partially explained by differences in dispersal mode and growth form of species in a highly heterogeneous environment. Our findings provide new perspectives on the formation of species clustering. One important finding is that a significant species-habitat association does not necessarily mean that the habitat heterogeneity has a decisive influence on species distribution. The second insight is that the large species-level variation in the relative importance of the two types of clustering mechanisms should not be ignored. Non-habitat clustering processes can play an important role on species distribution.
Testing for life historical changes in spatial patterns of four tropical tree species
Pattern and process: competition causes regular spacing of individuals within plant populations
Species groups distributed across elevational gradients reveal convergent and continuous genetic adaptation to high elevations
Fruiting and seed characteristics of Abies in northwest Yunnan
滇西北冷杉属植物结实特性及种子特征研究
DOI:10.7525/j.issn.1673-5102.2023.05.002
[本文引用: 1]
探究滇西北冷杉属（Abies）植物的结实特性和种子特征及其变异模式，为促进冷杉林的更新及恢复提供材料支持和理论依据。收集滇西北分布7种冷杉的标本及球果，分析种子形态特征、种子生活力和结实特性，探究其种间及地区间差异。结果发现：滇西北7种冷杉种子的长、宽、厚分别是6.04~10.22、2.03~3.32、1.26~2.24 mm，千粒质量是4.26~30.50 g，千粒质量与种子长度、宽度、厚度均显著相关（r>0.8，P<0.01）。滇西北7种冷杉的种子饱满率、虫蚀粒率和空秕粒率的平均值分别为27.51%、4.92%和67.58%，种子饱满率不高、空秕粒和虫蚀粒严重。野外调查发现大多数云南黄果冷杉（Abies ernestii var. salouenensis）均未结球果，且仅收集得到一棵树的球果，因此在本文中未进行比较分析。滇西北其余6种冷杉的虫蚀粒率在不同种之间（P=0.750）和不同地区之间（P=0.204）均没有显著差异，饱满率（P=0.005）和空秕粒率（P=0.007）均存在种间差异，而种子生活力存在种间（P=0.008）及地区间（P=0.036）差异，因此冷杉种子生活力同时受物种特性及环境因素的影响。
Spatial distributions of species in an old-growth temperate forest, northeastern China
Habitat associations of trees and seedlings in a Bornean rain forest
Rings, circles, and null- models for point pattern analysis in ecology
Response of leaf traits to altitude in Quercus aquifolioides and Sorbus rehderiana on the eastern edge of the Qinghai-Tibet Plateau, China
青藏高原东缘川滇高山栎和西南花楸叶片性状对海拔的响应
DOI:10.13287/j.1001-9332.202403.003
[本文引用: 1]
叶片作为响应环境变化最为敏感的植物器官,是反映植物生存策略的重要指示者。为明晰高山植物响应海拔变化的生态适应策略,本研究于青藏高原东缘选取不同海拔(2600、2800、3000、3200和3400 m)下常绿阔叶树种川滇高山栎和落叶阔叶树种西南花楸为对象,测量叶片形态、解剖性状、气体交换参数、叶绿素荧光参数等指标,研究二者响应海拔变化的异同及生态适应策略。结果表明: 随着海拔的升高,川滇高山栎的叶片干物质含量显著降低,西南花楸显著增加,两者叶片均逐渐变小;川滇高山栎的栅栏系数呈下降趋势,西南花楸的栅栏系数呈上升趋势,二者的叶片、栅栏组织、海绵组织、上表皮和下表皮的厚度均显著增加,与海拔2600 m相比,海拔3400 m处分别增加22.4%、4.9%、45.1%、23.3%、19.6%和28.2%、46.9%、8.9%、25.9%、20.8%。西南花楸叶片气体交换参数和叶绿素荧光参数随着海拔升高显著增大,而川滇高山栎与之相反。两者叶片解剖性状、气体交换和叶绿素荧光参数均具有较强的可塑性,绝大多数叶片性状间以及叶片性状与海拔之间存在显著相关关系。川滇高山栎应对海拔变化的生存策略较为保守,西南花楸的生存策略则较为积极,两者均通过调节自身性状以适应不同海拔。
Leaf traits divergence and correlations of woody plants among the three plant functional types on the eastern Qinghai-Tibetan Plateau, China
Spatial distribution patterns of Symplocos congeners in a subtropical evergreen broad-leaf forest of Southern China
Characteristics and trend of climate change in Pudacuo National Park in recent years
普达措国家公园近几年气候变化特征及趋势分析
Interspecific association of the main tree populations of the Quercus acutissima community in the Qiaoshan forest area
桥山林区麻栎群落主要乔木种群的种间联结性
Intra-annual radial growth of Abies georgei and Larix potaninii and its responses to environmental factors in the Baima Snow Mountain, Northwest Yunnan, China
滇西北白马雪山长苞冷杉和大果红杉年内径向生长动态及其对环境因子的响应
DOI:10.13287/j.1001-9332.202211.004
[本文引用: 1]
以滇西北白马雪山亚高山寒温性针叶林的常绿树种长苞冷杉和落叶树种大果红杉为对象,采用高精度生长仪监测了2个树种的年内径向生长动态,分析其径向生长的季节动态特征及其对环境因子的响应。结果表明: 大果红杉和长苞冷杉的径向生长主要发生在4—8月,6月是生长最快的时期。与长苞冷杉相比,大果红杉径向生长的开始时间较早,停止生长时间稍晚,其生长季持续时间明显长于长苞冷杉。大果红杉最大生长速率和年生长量均略高于长苞冷杉。长苞冷杉日生长量与降水量呈显著正相关,与饱和水汽压亏缺、空气温度呈显著负相关;而大果红杉的日径向生长量与降水量呈显著正相关,与土壤体积含水量和饱和水汽压亏缺呈显著负相关。长苞冷杉和大果红杉的径向生长均受到水分的限制,大果红杉对水分条件更敏感。在全球变暖的背景下,植物蒸腾作用和土壤蒸发散的增加,可能进一步加剧土壤水分丧失和植物可利用水分下降,进而导致长苞冷杉和大果红杉更易受到干旱胁迫。
Radial growth responses of four coniferous species to climate change in the Potatso National Park, China
普达措国家公园四种针叶树径向生长对气候因子的响应
DOI:10.13287/j.1001-9332.202110.033
[本文引用: 1]
运用树木年代学的原理和方法,对普达措国家公园大果红杉、长苞冷杉、高山松和麦吊云杉4个优势针叶树种的年轮宽度进行测量,建立年轮宽度差值年表。分析年表与香格里拉气象站的日、月气候数据的相关性,研究4个优势针叶树种的径向生长对气候因子的响应。结果表明: 大果红杉的年生长速率最高,长苞冷杉的年生长速率最低;4种针叶树径向生长对气候因子的响应存在物种特异性,大果红杉与气候因子的相关性最强,麦吊云杉的径向生长对气候因子的响应不敏感;长苞冷杉树轮宽度年表与上年冬季(11、12月)和当年夏季(7月)的平均温度呈显著正相关;大果红杉树轮宽度年表与生长季早期(6月)温度呈显著正相关,与同期降水量和相对湿度呈显著负相关;而高山松树轮宽度年表与生长季早期(5月)的降水量和相对湿度呈显著正相关,与同期最高温度呈显著负相关,表明高山松的径向生长主要受生长季早期水分可利用性的影响。
Analysis of spatial point pattern for plant species
植物种群空间分布的点格局分析
植物种群在群落中的分布格局与空间尺度有着密切关系，传统的样方取样及其格局分析方法，只能分析一种尺度下的格局。本文引入一种新的格局分析方法——点格局分析，其是以种群空间分布的坐标点图为基础，通过本文对美国密西根州克林顿县栎林3个优势种格局分析，它有3个明显的优点：1）能够分析各种尺度下的种群格局和种间关系，结果清楚，直观；2）所描述的结果更符合实际，尤其是对群落结构的描述；3）它有利于定点观察，研究时间与种群格局的关系，本文分析的3个种集群特征明显，但随尺度的变化有不同的分布趋势，3个种间的关系也是如此。
Ecological characteristics of Abies georgei population at timberline on the north-facing slope of Baima Snow Mountain, Southwest China
白马雪山阴坡林线长苞冷杉(Abies georgei)种群结构特征
Response of radial growth of two conifers to temperature and precipitation in Potatso National Park, Southwest China
普达措国家公园2个针叶树种径向生长对温度和降水的响应
Structure and spatial pattern of a natural Abies faxoniana population on the eastern edge of Qinghai-Tibetan Plateau
青藏高原东缘岷江冷杉天然群落的种群结构和空间分布格局
DOI:10.17521/cjpe.2004.0050
[本文引用: 1]
岷江冷杉(Abies faxoniana)是青藏高原东缘亚高山顶极森林植被的优势种之一，主要分布于岷江、大渡河和白龙江的上游地区。该文研究了岷江冷杉天然原始群落的种群结构和空间分布格局。样方大小为100 m ×60 m。测定了所有个体的坐标及其胸径、高度和冠幅。将岷江冷杉按大小级分为5级，即幼苗：H（高度）
Spatial patterns and associations of main dominant species Abies fargesii var. faxoniana and Betula utilis in Miyaluo subalpine dark coniferous forest of western Sichuan, China
川西米亚罗亚高山暗针叶林岷江冷杉和糙皮桦空间格局及其关联性分析
Evaluation and analysis of forest ecosystem services value in Pudacuo National Park
普达措国家公园森林生态系统服务价值评估与分析
Spatial point pattern analysis and spatio-temporal dynamics of Abies georgei var. smithii forests in southeast Tibet
藏东南急尖长苞冷杉群落空间点格局分析及其时空动态
Species-habitat association of a deciduous broadleaved forest in the subtropical and temperate transition zone
亚热带-温带气候过渡区落叶阔叶林物种-生境关联分析
DOI:10.13287/j.1001-9332.202108.009
[本文引用: 2]
物种-生境关联分析有利于更好地理解物种共存理论和群落构建机制。根据秦岭落叶阔叶林25 hm<sup>2</sup>固定监测样地的调查数据,将树种分为幼苗、幼树和成树3个生活阶段,利用Torus-translation检验方法分析物种与不同生境类型之间的关联性。结果表明: 生境对各物种的影响不同。与高坡显著关联的物种数最多,其中95.7%为负关联;与低坡呈负相关的物种占89.5%;与山脊呈显著负关联的物种占90.9%;物种与高谷生境多存在显著正关联,呈负相关的只有1种,占0.03%。物种在幼苗、幼树和成树阶段与生境分别存在80、44和23个关联,表明幼苗阶段对生境的依赖程度更大。幼苗阶段的物种中有38个(占总物种数的90.5%)至少与一类生境存在显著的关联性;幼树阶段有25个(占总物种数的58.1%)至少与一类生境存在显著关联;成树阶段只有17个(占总物种数的39.5%)至少与一类生境存在显著关联。同一生境对不同生活史阶段物种的影响存在差异,到生活史阶段后期,生境的影响逐渐减弱。由于特定的环境需求,多数物种在不同生活史阶段表现出不同的生境偏好。
Population distribution patterns and interspecific spatial associations in warm temperate secondary forests, Beijing
DOI:10.3724/SP.J.1003.2011.08024
[本文引用: 1]
<p>Exploring tree population distribution patterns and interspecific spatial associations are helpful in elucidating the mechanisms underlying species coexistence in forest communities. We analyzed population distribution patterns and interspecific adult–adult spatial associations of common tree species at scales of 0–50 m in five 1-ha warm temperate secondary forest plots near Beijing, China. We found that: (1) all species showed aggregated spatial patterns at some scales; aggregation occurred mainly at neighborhood scales of < 15 m, tended to peak within a 1-m radius around focal conspecific trees, and the percentage of species exhibiting a random or regular pattern increased with scale, mainly occurring at scales of > 15 m; (2) the proportion of species pairs showing non-significant associations was high (~50%), and even in those species pairs that showed significant associations, segregation and partial overlap were dominant association types. Few species pairs (~4%) showed mixing. We feel that population spatial distribution of trees, particularly the observed prevalence of conspecific aggregation, in these plots was regulated by seed dispersal limitation and environmental heterogeneity. Moreover, aggregated distributions also promoted interspecific segregation and partial overlap. It is possible that distribution patterns were associated with habitats. Few species pairs showed interspecific mixing, in this case, interspecific competition exclusion difficultly occured, but in the interior of conspecific aggregation, density dependence should be a dominant mechanism regulating population distributions. Our findings contribute to a clearer understanding of the mechanisms influencing the structure of these forests.</p>
北京暖温带次生林种群分布格局与种间空间关联性
DOI:10.3724/SP.J.1003.2011.08024
[本文引用: 1]
种群分布格局和种间空间关联性研究有助于深入理解物种共存机制。本研究在北京地区5个1 ha典型暖温带森林样地, 在0–50 m尺度范围内综合分析了常见种的种群分布格局及成年树种间的空间关联性。研究发现: (1)所有检验的物种都表现了聚集格局, 主要发生在较小(0–15 m)的尺度范围内, 并且同种聚集强度峰值普遍出现在目标个体周围1 m的距离内; 在>15 m的较大尺度上, 随着尺度增加, 随机和规则格局成为物种分布的主要形式; (2)种间不相关联的比例高(～50%), 即使种间存在显著的关联性, 也是以隔离和部分重叠为主要的关联形式; 很少的物种对(～4%)呈混合分布。种子扩散限制和生境异质性在某种程度上解释了种群普遍聚集的格局, 种群聚集分布又促使种间分布不相关联, 或者种间呈现隔离和部分重叠格局, 反映了物种分布与生境存在紧密的关联性。另外, 种间隔离的格局会阻止种间个体相互竞争。然而, 由于同种个体聚集分布, 密度制约成为调节种群分布的主要形式。本结果将有助于揭示森林群落物种共存的潜在维持机制。
A mechanism of plant species coexistence: the negative density-dependent hypothesis
DOI:10.3724/SP.J.1003.2009.09183
[本文引用: 1]
The negative density-dependent hypothesis focuses mainly on conspecific interactions to explain the coexistence of diverse species in natural communities. The hypothesis describes the impairment of per-formance among conspecific individuals due to resource competition, predation of pests (e.g., pathogen, her-bivore) and so on. Impairment of conspecific individuals decreases growth and increases mortality, thereby freeing space for other species, and thus promotes coexistence of diverse species. There are three main kinds of density dependent effects including distance-dependence of mortality and abundance of offspring near parents (Janzen-Connell hypothesis), density dependent thinning (random-mortality hypothesis), and com-munity compensatory trends (CCT). Research has shown that density dependence among phylogenetically closely-related species results partially from competition for similar resources. This fact led to the proposal of species herd protection and phylodiversity dependence models. Density dependence has long history of study and the recent establishment of a global network of large-scale forest dynamic plots facilitates the detection of density dependence in natural communities. However, there are many challenges when testing for density dependence. For example, some previous studies can not disentangle density dependence from other con-founding effects, and most studies focus exclusively on the tropical zone, seldom considering other zones. Therefore, though strong evidence to contrary does not exist, debate continues on the importance of density dependence in maintaining diverse-species coexistence.
植物群落物种共存机制: 负密度制约假说
DOI:10.3724/SP.J.1003.2009.09183
[本文引用: 1]
负密度制约假说主要描述由于资源竞争、有害生物侵害(比如病原微生物、食草动物捕食)等, 同种个体之间发生的相互损害行为; 它主要强调同种个体之间的相互作用, 解释自然群落物种共存的机理; 负密度制约机制主要在小尺度上降低群落内同种个体生长率, 同时提高个体死亡率, 从而为其他物种的生存提供空间和资源, 促进物种共存。目前负密度制约假说的检验研究主要侧重密度制约、距离制约、群落补偿效应等三个方面。最近, 研究者又探讨了近缘物种之间由于对相似资源的竞争所产生的负效应, 扩展了负密度制约假说, 进而提出异群保护假说和谱系多样性制约假说。负密度制约假说引起生态学家长久的探讨和关注, 世界范围内大尺度森林动态样地的建立, 又为探索不同尺度上密度制约效应的研究提供了条件。然而目前的研究仍然存在不足, 比如负密度制约假说的检验受到其他因素的干扰、区域研究不平衡等。因此, 生态学家们仍然怀疑负密度制约效应调节群落物种共存的重要性, 但是目前的研究还没有发现否定负密度制约假说的充分证据。
