植物邻体干扰的研究范畴、热点及意义

系统介绍了确定邻体和度量邻体竞争指数的常用方法,以及邻体干扰研究的热点问题和研究意义。植物邻体干扰研究热点主要包括：(1)邻体干扰对植物个体存活率的影响;(2)邻体干扰对生物多样性的影响;(3)构件水平上的邻体干扰效应;(4)基株对邻体干扰的适应;(5)邻体干扰对植物个体生长速率的影响。     

邻体干扰指数通用模型及其应用

 本研究在前人工作的基础上提出邻体干扰指数的通用模型并讨论邻体干扰指数模型中生长速度、邻体及基株大小的度量方法的选择,进而提出通用模型在马尾松优势种群的经营管理中的具体应用。     

光皮桦群落邻体干扰指数的研究

影响植物个体生长的因素很多 ,这其中不仅有其自身的遗传特性在起作用 ,而且与其所处的生境立地质量以及它对环境资源的利用状况也有着密切地内在联系。生境在影响植物生长的同时 ,植物的生命活动及生长过程也在不断地影响和改变着环境条件 ,使其朝着有利于或不利于邻体生长的方向发展。生物与环境之间这种相互作用、相互影响 ,就是生态学领域里的邻体干扰。本文通过对福建卫闽光皮桦 (Ｂｅｔｕｌａｌｕｍｉｎｉｆｅｒａ)群落邻体干扰指数的研究 ,分析了邻体干扰指数与光皮桦生长速度间的相互联系 ,揭示了光皮桦个体大小与邻体干扰指数和生…     

黄山松种群邻体范围与邻体竞争强度的研究

当环境中可利用的资源低于种群最佳生长需要时,种群内个体之间就会产生竞争。竞争常发生在邻近植物之间,植物地上部分和地下部分的竞争范围是不同的。目前,有很多度量竞争强度和确定竞争范围的方法,能否对这些方法进行改进,提出更具有说服力的方法,是本研究的出发点。黄山松是常见的针叶树种,分布范围广,生存能力强,是亚热带中部中山地区代表群系的建群种,也是较高海拔地区重要的造林树种,具有较强的代表性。对黄山松的邻体竞争研究发现:(1)改进的竞争指数有更强的说服力;(2)逐步扩大范围的方法能很好地确定植株间的竞争范围;(3)邻体竞争强度随影响范围的增加而增加,在一定的范围内增加的较快,而超出该范围后增加的幅度变小,可以此为依据来确定邻体范围;(4)不同径级的基株,邻体范围有一定的差异;(5)邻体竞争强度和影响范围的关系服从对数函数关系(CI=AlnC+B)。结果表明,改进的竞争指数能很好地度量竞争强度,采用逐步扩大范围的方法能有效地确定邻体范围。     

不同邻体大头茶幼苗的适应特征

 在亚热带常绿阔叶林自然林窗下,以大头茶幼苗为基株,分别以马尾松、川灰木和大头茶幼苗为邻体。研究不同邻体如何改变可利用资源,影响大头茶幼苗基株生长动态和形态、树冠结构和生物量效应,并探讨影响基株生长的邻体的主导因素。结果表明,不同邻体的生长和截光效应差异明显;基株生长特征与邻体的树高、叶生物量、总生物量和树冠距地表10cm处截光量相关极小,却与邻体树冠距地表30cm处截光量相关极大,故影响基株生长的邻体主导因素是遮挡基株树冠的邻体的可利用光资源;基株生长动态,如树高、叶数、叶面积和叶大小,树冠结构和生物量显著受到不同邻体的影响,并且基株树高及增长量、叶面积、冠幅和生物量均为大头茶单株(GNO)>大头茶+川灰木(GNS)>大头茶+马尾松(GNP)>大头茶+大头茶(GNG)。大头茶幼苗种内竞争明显强于种间竞争。     

太白红杉种群邻体范围与邻体竞争强度的研究

采用逐步扩大范围的方法探讨了不同径级基株所受的邻体竞争强度 平均竞争强度和总竞争强度 与影响范围的关系 ,结果发现 : 1 邻体的平均竞争强度随影响范围的增加而降低 ,在一定的范围内下降较快 ,而超出该范围后下降的幅度变小 ,可以此为依据来确定邻体范围 ; 2 不同径级的基株 ,邻体范围有一定的差异 ; 3 邻体总的竞争强度和影响范围的关系服从对数函数关系 CI=Aln C+B .结果表明采用逐步扩大范围的方法能有效地确定邻体范围 ,提出了确定邻体范围的新方法     

邻体干扰模型的改进及其在营林中的应用

本文研究了植物群落中优势种个体间的相互干扰问题。在前人工作基础上提出了邻体干扰指数的改进模型及野外资料搜集方法。保证了数学模型的逻辑一致性,增加了生态学的解释意义。本文还讨论了邻体干扰效应模型的选择问题,进而得出了约束条件下的材积增长的数学优化模型。以四川省重庆市缙云山马尾松林为例,进行了实例研究。     

邻体干扰模型的改进及其在营林中的应用

 本文研究了植物群落中优势种个体间的相互干扰问题。在前人工作基础上提出了邻体干扰指数的改进模型及野外资料搜集方法。保证了数学模型的逻辑一致性,增加了生态学的解释意义。本文还讨论了邻体干扰效应模型的选择问题,进而提出了约束条件下的材积增长的数学优化模型。以四川省重庆市缙云山马尾松林为例,进行了实例研究。     

太白红杉种群邻体范围与邻体竞争强度的研究

采用逐步扩大范围的方法探讨了不同径级基株所受的邻体竞争强度(平均竞争强度和总竞争强度)与影响范围的关系,结果发现：(1)邻体的平均竞争强度随影响范围的增加而降低,在一定的范围内下降较快,而超出该范围后下降的幅度变小,可以此为依据来确定邻体范围;(2)不同径级的基株,邻体范围有一定的差异;(3)邻体总的竞争强度和影响范围的关系服从对数函数关系(CI=AinC B)。结果表明采用逐步扩大范围的方法能有效地确定邻体范围,提出了确定邻体范围的新方法。     

邻体竞争对植物个体生长速率和死亡概率的影响：基于日本落叶松种群试验的研究

选择 4种有代表性的植物邻体竞争指数 ,分析了竞争对日本落叶松 (L arix leptolepis)试验种群的个体生长速率和死亡概率的影响 ,发现在本试验条件下 ,引入竞争指数不能明显改善对生长速率的预测效果 ,但用竞争指数可以较好地预测个体于 1个月内在竞争压力下死亡的概率 ,从而为构造植物生长模型时处理个体死亡问题提供一个有益的定量化思路     

Factors determining plant–neighbour interactions on different spatial scales in young species-rich grassland communities

In naturally colonised species-rich grassland communities, we examined the properties of a plant’s aboveground neighbourhood that affect its performance (aboveground biomass). To this end a range of neighbourhood parameters were measured: number, biomass and species richness of the neighbours, number and biomass of the conspecific neighbours, and light availability at the base of the target plant. We also determined at which neighbourhood size the strongest target plant–neighbour interactions occurred, and whether conspecific neighbours affected competitively stronger or weaker target species differently. Target plant performance varied with target identity, and was significantly affected by light availability and the number of neighbouring plants (neighbourhood density). Depending on the target species, there was also an effect of total neighbour biomass on plant performance. The target plants were most strongly affected by their neighbours within a 3-cm distance, which could account for 78% of the variance in target biomass. Number or biomass of the conspecific neighbours did not contribute to the explanation of target performance in any of the target species. Whereas in an 8-cm neighbourhood the amount of light penetration was the strongest predictor of target performance, the number of neighbours was more important in a 3-cm neighbourhood. These experimental results might be useful to extend existing neighbourhood competition models for one or two species to multi-species competition models.     

Species and structural diversity affect growth of oak,but not pine,in uneven-aged mature forests

The effects of mixing tree species on tree growth and stand production have been abundantly studied, mostly looking at tree species diversity effects while controlling for stand density and structure. Regarding the shift towards managing forests as complex adaptive systems, we also need insight into the effects of structural diversity. Strict forest reserves, left for spontaneous development, offer unique opportunities for studying the effects of diversity in tree species and stand structure. We used data from repeated inventories in ten forest reserves in the Netherlands and northern Belgium to study the growth of pine and oak. We investigated whether the diversity of a tree's local neighbourhood (i.e., species and structural diversity) is important in explaining its basal area growth. For the subcanopy oak trees, we found a negative effect of the tree species richness of the local neighbours, which – in the studied forests – was closely related to the share of shade-casting tree species in the neighbourhood. The growth of the taller oak trees was positively affected by the height diversity of the neighbour trees. Pine tree growth showed no relation with neighbourhood diversity. Tree growth decreased with neighbourhood density for both species (although no significant relationship was found for the small pines). We found no overall diversity-growth relationship in the studied uneven-aged mature forests; the relationship depended on tree species identity and the aspect of diversity considered (species vs. structural diversity).     

Density‐dependent pre‐dispersal seed predation and fruit set in a tropical tree

Negative density‐dependent demographic processes operating at post‐dispersal seed, seedling, and juvenile stages are the dominant explanation for the coexistence of high numbers of tree species in tropical forests. At adult stages, the effect of pollinators and pre‐dispersal fruit predators are often dependent on the density or abundance of flowers and fruit in the canopy, but each have opposite effects on individual realized reproduction. We studied the effect of density on total and mature fruit set and pre‐dispersal predation rates within individual tree canopies in a common canopy tree species, Jacaranda copaia in a 50‐ha forest census plot in central Panama. We sampled all reproductive sized trees in the plot (n = 188) across three years and estimated fruit set and predation rates. Population‐wide pre‐dispersal seed predation averaged between 6–37% across years. Using linear mixed effects models, we found that increased density and fecundity of conspecific neighbours increased focal tree fruit set, but also the rate of pre‐dispersal predation. An interaction between individual and neighbourhood fruit production predicted lower predation rates at high individual and neighbourhood fecundities, which suggests predator satiation at high fruit abundance levels. However, the rate at which fruit set increased with conspecific neighbour fruit production was greater than the rate at which fruit were lost to predation, resulting in an overall positive effect of neighbour density on mature fruit production in focal trees. Our results run counter to the expectation of a uniformly negative effect of density across all life stages in tropical trees and suggest further exploration of the role of spatial clumping, pollen dispersal limitation, and predation at pre‐dispersal adult stages in maintenance of species diversity in plant communities.     

Functional trait differences influence neighbourhood interactions in a hyperdiverse Amazonian forest

As distinct community assembly processes can produce similar community patterns, assessing the ecological mechanisms promoting coexistence in hyperdiverse rainforests remains a considerable challenge. We use spatially explicit neighbourhood models of tree growth to quantify how functional trait and phylogenetic similarities predict variation in growth and crowding effects for the 315 most abundant tree species in a 25‐ha lowland rainforest plot in Ecuador. We find that functional trait differences reflect variation in (1) species maximum potential growth, (2) the intensity of interspecific interactions for some species, and (3) species sensitivity to neighbours. We find that neighbours influenced tree growth in 28% of the 315 focal tree species. Neighbourhood effects are not detected in the remaining 72%, which may reflect the low statistical power to model rare taxa and/or species insensitivity to neighbours. Our results highlight the spectrum of ways in which functional trait differences can shape community dynamics in highly diverse rainforests.     

From competition to facilitation: how tree species respond to neighbourhood diversity

Studies on tree communities have demonstrated that species diversity can enhance forest productivity, but the driving mechanisms at the local neighbourhood level remain poorly understood. Here, we use data from a large‐scale biodiversity experiment with 24 subtropical tree species to show that neighbourhood tree species richness generally promotes individual tree productivity. We found that the underlying mechanisms depend on a focal tree's functional traits: For species with a conservative resource‐use strategy diversity effects were brought about by facilitation, and for species with acquisitive traits by competitive reduction. Moreover, positive diversity effects were strongest under low competition intensity (quantified as the total basal area of neighbours) for acquisitive species, and under high competition intensity for conservative species. Our findings demonstrate that net biodiversity effects in tree communities can vary over small spatial scales, emphasising the need to consider variation in local neighbourhood interactions to better understand effects at the community level.     

Intra-specific leaf trait responses to species richness at two different local scales

Plant functional traits, especially leaf traits, are accepted proxies for ecosystem properties. Typically, they are measured at the species level, neglecting within-species variation. While there is extensive knowledge about functional trait changes (both within and across species) along abiotic gradients, little is known about biotic influences, in particular at local scales. Here, we used a large biodiversity-ecosystem functioning experiment in subtropical China to investigate intra-specific trait changes of 16 tree species as a response to species richness of the local neighbourhood. We hypothesized that because of positive complementarity effects, species shift their leaf traits towards a more acquisitive growth strategy, when species richness of the local neighbourhood is higher. The trait shift should be most pronounced, when a focal tree's closest neighbour is from a different species, but should still be detectable as a response to species richness of the directly surrounding tree community. Consequently, we expected that trees with a con-specific closest neighbour have the strongest response to species richness of the surrounding tree community, i.e., the steepest increase of acquisitive traits. Our results indicate that species diversity promoted reduced competition and complementarity in resource use at both spatial scales considered. In addition, the closest neighbour had considerably stronger effects than the surrounding tree community. As expected, trees with a con-specific nearest neighbour showed the strongest trait shifts. However, the predicted positive effect of local hetero-specificity disappeared at the highest diversity levels of the surrounding tree community, potentially resulting from a higher probability to meet a strong competitor in a diverse environment. Our findings show that leaf traits within the same species vary not only in response to changing abiotic conditions, but also in response to local species richness. This highlights the benefit of including within-species trait variation when analysing relationships between plant functional traits and ecosystem functions.     

山西文峪河上游河岸林的土壤种子库与树种更新特征

以山西文峪河上游13种典型的河岸林为研究对象,通过土壤种子库和树种更新研究,分析群落种子库与林下更新随演替进展的变化趋势,以及该区河岸树种的繁殖对策。结果表明：13种群落的土壤种子库密度间于1290±103～3950±154粒/m2,63.5%的种子留存于0～5 cm的层次;种子库包含49种植物,以多年生草本为主,存在耐干扰种和湿地植物的种子;处于相同或相邻演替阶段的群落,种子库相似性较高;随演替进展,种子库密度、丰度、Shannon-Wiener指数及种子库与地上植被的相似性均呈降低趋势;处于演替后期的青杄Picea wilsonii林存在丰富的＂青杄幼苗库＂;先锋种白桦Betula platyphylla的种子存在于演替各阶段的群落中,储量丰富,其更新主要依赖于风媒种子,并存在少量萌蘖;青杄、白杄P.meyeri、华北落叶松Larix principis-rupprechtii、油松Pi-nus tabulaeformis和辽东栎Quercus liaotongensis的种子库损耗严重,没有或仅存少量种子,其中云杉和油松的更新幼苗幼树多,属持久幼苗库更新;华北落叶松幼苗幼树少,且仅出现于林缘或林窗等开阔地,属植被空隙中季节性更新;辽东栎主要依赖丰富的幼苗库进行更新,同时存在一定的萌蘖;青杨Populus cathayana以大量风媒种子更新结合营养扩展。     

Tree growth and competition in a Betula platyphylla-Larix cajanderi post-fire forest in central Kamchatka

BACKGROUND AND AIMS: Fire is the dominant disturbance in central Kamchatka boreal forests, yet patterns and mechanisms of stand recovery have not been investigated. METHODS: Measurements were made of 1433 stems > or =1.3 m height and annual radial increments of 225 randomly selected trees in a 0.4-ha plot of a 53-year-old fire-origin mixed-species stand to examine the spatio-temporal variation in establishment, growth, size inequality and the mode of competition among individual trees. Growth variations were related to tree size, age and local interference with neighbours. KEY RESULTS: Betula platyphylla formed the main canopy following a fire in 1947, with Larix cajanderi and Pinus pumila progressively reinvading the lower tree and shrub stratum. Most B. platyphylla originated from sprouts in small patches (polycormons) during the first 15 post-fire years. Betula platyphylla had normal distributions of diameter and age classes, but negatively skewed height distribution, as expected from shade-intolerant, pioneer species. Larix cajanderi had fewer tall and many short individuals. The smaller and younger B. platyphylla grew disproportionately more in diameter than larger trees from 1950 to 1975, and hence stem size inequalities decreased. The reverse trend was observed from 1995 to 2000: larger trees grew more, indicating an increasing asymmetry of competition for light. Betula platyphylla had steady diameter growth in the first 25 post-fire years, after which the growth declined in smaller trees. Neighbourhood analysis showed that the decline resulted from increased competition from taller neighbours. CONCLUSIONS: The observed growth patterns suggest that mode of interactions altered during stand development from early stages of weak competition for soil resources released by fire to later stages of asymmetric competition for light. Asymmetric crown competition started later than reported in other studies, which can be attributed to the lower stem density leaving much space for individual growth, greater relative importance of below-ground competition in this site of nutrient-poor volcanic soil, and the vegetative origin of B. platyphylla. Larix cajanderi growing under B. platyphylla had steady diameter growth during the first 20 years, after which growth declined. It is suggested that early succession fits the tolerance model of succession, while inhibition dominates in later stages.     

Responses of crown architecture in Betula pendula to competition are dependent on the species of neighbouring trees

We measured the growth responses of individual shoots and branches of Betula pendula when growing next to trees of the same species or Pinus sylvestris, Larix sibirica or Alnus glutinosa. We used the three-dimensionally digitized response variables and the size and distance of trees growing within a 5-m radius of the study trees to establish a relationship between tree performance and the effect of competing neighbouring tree species on crown architecture. B. pendula was able to modify its crown architecture and thus alter its strategy to compete with different neighbours. Trees of B. pendula growing beside species counterparts had the highest growth of new long shoots in relation to the already existing branch length [growth vigour (GV)], while GV was the lowest next to L. sibirica. With B. pendula or P. sylvestris as its main neighbour, B. pendula invested in short shoots by growing them rather densely in short branches with limited numbers, whereas with L. sibirica the number, length and angle of the branches were high. The competitive response was also strongly dependent on tree ontogeny and the shoot and branch characteristics were significantly affected by their location inside the crown. B. pendula was able to respond to the challenges posed by its neighbours, which was also reflected in the GV. The ability to maintain steady growth with alternative crown designs in different neighbourhoods reflects plasticity in the crown responses.     

Spatial pattern,regeneration and growth rates of Brachystegia spiciformis and Julbernardia globiflora

Past work on tree-to-tree interactions in semi-arid savannas, through the use of nearest neighbour analysis, has shown both a regular dispersion pattern and a positive correlation between the size of a tree and the distance to its nearest neighbour. From these results, the importance of competition has been inferred. In the present study, tree-to-tree interactions in a mesic savanna woodland at Marondera, Zimbabwe, dominated by relatively small-sized individuals of Brachystegia spiciformis and Julbernardia globiflora, were examined. Results show that the regular dispersion pattern is uncommon; that there are few significant positive correlations between size of individual and distance to nearest neighbour; and that growth rate is not consistently correlated with size and distance of nearest neighbour. Results of a study of regeneration relative to canopy cover suggest a possible mechanism for these findings: unlike semi-arid savannas, young plants often grow in under-canopy environments so that early spacing of young trees does not occur. Significant positive correlations between the size of a tree and the distance to its nearest neighbour were found in a stand of larger, presumably older, trees, suggesting that such a relationship only develops in mesic miombo woodland through a thinning process as the trees mature. Familial clumping, which is common in the study area, may mask spatial patterns.Abbreviations RBAI Relative basal area increment