太白山森林群落和林下草本物种变化的环境解释

采用典范对应分析(CCA)、Pearson相关分析、冗余分析(RDA)分别研究了不同环境因子对太白山森林群落及林下草本物种组成、多样性、功能性状等方面的影响。结果表明:(1)9种环境因子对于群落及林下草本物种的组成变化的解释程度不高,分别为23.9%和21.1%,但与海拔和土壤含水量紧密相关的CCA 1轴能大致区分高、中、低海拔样方的群落所有物种和草本植物的组成差异。(2)沿海拔梯度,群落所有物种的α多样性先增加后降低,林下草本物种α多样性沿海拔梯度有下降趋势,但二者都与坡度(Slope)及木本层盖度(WCD)无关。(3)海拔是决定森林群落及林下草本层物种功能性状值变化的主要因子,与海拔密切相关的RDA1轴能解释森林群落和林下草本物种性状值变化的71.2%和54.7%,林下草本植物与群落的最大株高(Hmax)变化模式不一致。     

西双版纳勐腊南贡山季风常绿阔叶林蕨类植物初步研究

勐腊南贡山季风常绿阔叶林(山坡类型)1 hm2面积样地上有蕨类31种,在该森林群落草本层中占有 极其显著的地位。这些蕨类植物的地理成分分析表明它们属于亚洲热带的印度——马来西亚植物区系的一 部分,表现为东南亚热带北缘植物区系的性质,并有热带山地向亚热带山地过渡的特点。在生态表现上,它们 的生活型组成是高位芽蕨类(地生蕨种)占6．45％;地上芽蕨类12．90％;地面芽蕨类32．26％;地下芽蕨类 32．26％;附生蕨类16．13％。由于该地区的季节性干旱气候,高位芽蕨类较少和几种附生蕨类的附生高度也 相对较低,蕨类植物种群的数量与林下空气湿度及土壤表层的湿度一般成正相关。     

辽河源自然保护区不同年龄天然油松林林下草本层植物物种多样性及其环境解释

林下草本层植物在森林群落结构稳定性的调节和生态功能的发挥上具有非常重要的作用,是森林生态系统不可或缺的组成部分。本文从揭示天然林林下物种组成的主导因子出发,以不同年龄天然油松林林下草本层植物为研究对象,探讨了辽河源自然保护区林下草本层物种组成与环境因子间的相关关系。结果表明,林龄是影响林分土壤化学性质的空间变化的重要因子,但林龄与林下草本植物的物种丰富度和多样性指数间不存在线性关系。CCA排序及Monte Carlo检验结果表明,林龄、林分密度、平均胸径、郁闭度、坡度为显著影响天然油松林林下物种分布的因子,说明该地区林分的冠层结构特征主导了林下草本层植物群落的分布格局。     

白云山国家森林公园不同人为干扰强度的群落冠层结构和光照特征

为探究森林冠层结构与林下光照的变化规律及其相关性,在河南省白云山国家森林公园选取人工林、择伐林、皆伐林和老龄林建立四块面积为1 hm²（100 m×100 m）的固定监测样地,利用半球面影像技术获取冠层结构及林下光照数据。研究发现：1）随着人为干扰强度降低,冠层覆盖度与叶面积指数呈增加趋势,林下散射辐射与直接辐射呈减少趋势;2）择伐林冠层覆盖度与叶面积指数最大,平均叶倾角与透光比最小,林下光照（直接辐射、散射辐射）与冠层覆盖度和叶面积指数都呈显著负相关,林下散射辐射与冠层覆盖度和叶面积指数的负相关关系最强;3）处于不同干扰强度的群落由于冠层结构的差异,形成了不同群落内特定的光照环境。研究结果丰富了暖温带-亚热带生态过渡区森林冠层结构与林下光照动态变化研究资料,同时也为该区域森林的恢复与重建等提供科学的依据。     

山西霍山森林群落林下物种多样性研究

在野外获得样方的基础上,采用多样性指数、丰富度指数、均匀度指数等对山西霍山森林群落林下灌木层和草本层的物种多样性进行了研究,结果表明,多数森林群落林下灌木层多样性指数和均匀度指数均高于草本层,而丰富度指数则相反。灌木层和草本层物种多样性指数的顺序为:针阔叶混交林>针叶林>落叶阔叶林,主要是由于针阔叶混交林兼有针叶林和落叶阔叶林的共同特征,因而具有较高的多样性。灌木层和草本层多样性指数、丰富度指数和均匀度指数在海拔梯度上呈单峰曲线变化趋势,即中海拔(1500 m)高度上物种多样性最大,这主要是由于在这一海拔范围内水热条件组合较好,人类活动干扰较少所致。     

Effects of Robinia pseudoacacia on the undergrowth of herbaceous plants and soil properties in the Loess Plateau of China

刺槐对黄土高原林下草本植物及土壤性质的影响 外来物种刺槐(Robinia pseudoacacia)的引入会对林下草本植物、土壤性质及二者之间的相互关系产 生一定影响,且这种影响可能与植被带有关。然而,在黄土高原较大面积范围内,关于刺槐对林下草本植物和土壤影响的研究依然很少。我们以黄土高原草原带、森林草原带和森林带作为研究区,选择了两种冠层植物类型：刺槐林分和相邻的原生植被。我们测定了5个叶片功能性状：叶片碳含量、叶片氮含量、叶片磷含量、比叶面积和叶组织密度,并计算了群落功能多样性、物种多样性和群落加权性状值。研究结果表明,(1)与原生植被相比,3个植被带内林下草本植物群落的叶氮、叶磷和比叶面积的群落加权性状值均显著提高,而叶碳和叶组织密度的群落加权性状值显著降低。(2)物种多样性、功能多样性和群落生物量在草原带内呈下降趋势,在森林带内呈上升趋势,在森林草原带内差异不显著。(3)与原生植被相比,土壤有机碳和土壤全氮仅在森林带内显著减少。(4)林下草本植物群落特性与土壤之间的关系是受刺槐和植被带所依赖的。总的来说,刺槐对林下草本植物和土壤性质的影响与植被带密切相关。该研究结果对黄土高原人工植被恢复与重建的规划具有重要指导意义。     

外来树种日本落叶松和日本花柏对鄂西北森林群落的影响

【目的】研究大面积栽植外来树种日本落叶松和日本花柏对鄂西北森林群落物种多样性的影响,为评价外来树种的入侵风险提供依据。【方法】采用样地调查法对比研究外来树种日本落叶松和日本花柏人工林与当地森林群落特征差异。【结果】日本落叶松人工林样地林下植物种类丰富,样地平均物种数与当地天然林样地物种数相比无显著差异;林下灌木层和草本层多样性指数较高,草本层多样性指数与当地天然林相比无显著差异;林下未发现日本落叶松的更新苗。日本花柏人工林样地平均物种数显著少于当地其他人工林样地;乔木层、灌木层和草本层的4个多样性指数值均小于当地其他人工林样地;在3个样地中出现日本花柏更新苗,更新苗数量达479株·hm~(-2)。【结论】引种栽培日本落叶松不会导致当地森林群落的物种多样性降低,不会引起生物入侵风险;但引种栽培日本花柏会明显降低当地森林群落的物种多样性,对当地森林生态系统的稳定构成一定威胁。     

粤北山地常绿阔叶林自然干扰后冠层结构与林下光照动态

以粤北车八岭2008年受冰灾破坏的山地常绿阔叶林为研究对象,设置2 hm2固定样地开展连续3a(2008—2010年)的群落调查,并采用半球面影像技术(Hemispherical photography)获取冠层结构和林下光照指标,分析灾后森林演替过程中冠层结构和林下光照的动态。研究发现:1)灾后森林恢复过程中,样地林下光照(直射光、散射光和总光照)均随林冠开度的减少、叶面积指数的增加而减少;2)从2008到2010年,各年度冠层结构和林下光照的差异均极显著(P<0.0001),但年间差异程度有逐年减少的趋势;3)灾后森林恢复前3a,林下直射光对林下总光照的贡献大于散射光,其时空波动性也大于散射光;4)林冠开度对冠层结构的反映程度比叶面积指数高,冠层结构对林下散射光的影响比对直射光大。灾后林木先是迅速生长然后生长速度缓慢下来并逐渐稳定,随森林逐渐郁闭林下光照也随之减少,其中林冠开度用于评价冠层结构动态的效果更佳,林下直射光比散射光的时空变化更复杂。     

宁南山区华北落叶松林下草本层群落特征及其影响因素

林下草本植物是森林生态系统的基本组成要素,对森林的更新、生态系统结构、功能的维持和提升具有重要作用,理解林下草本层群落特征及其影响因素,有助于构建理想的林-草结合模式。本研究以宁南山区泾源县无人为干扰的华北落叶松林人工林、间伐处理的华北落叶松林人工林和华北落叶松与白桦自然混交林为研究对象,探究林下草本层群落特征(物种多样性和地上生物量)及其与土壤理化特性(土壤容重、含水量、全碳含量、全氮含量及全磷含量)和林分结构(密度和郁闭度)的关系。结果表明：(1)与人工林相比,自然混交林林下草本植物组成最丰富(34种),且物种多样性和地上生物量也最高;(2)自然混交林林下土壤特性均优于人工林,但间伐处理的人工林林下土壤特性较无人为干扰的人工林土壤特性有显著提高;(3)冗余分析表明,林下草本层物种多样性主要与土壤含水量、土壤全碳、全氮和全磷含量呈正相关,与土壤容重、林分密度和郁闭度呈负相关,且林分密度、0～20 cm土层含水量对林下草本物种多样性有显著影响(P<0.05);(4)回归分析结果表明,0～20 cm土层的土壤特性、物种丰富度和优势度、林分密度及郁闭度显著影响林下草本地上生物量的积累...     

川中丘陵区人工柏木林林下群落谱系结构

探索人工林不同生长发育阶段林下群落的谱系结构,可以为森林群落构建机制的解释和生态修复等提供理论依据。本研究选择川中丘陵区不同林龄(15～24年、25～34年、35年以上)的人工柏木(Cupressus funebris)纯林为对象,基于被子植物分类系统Ⅲ谱系框架,选择净亲缘指数(NRI)和最近类群指数(NTI),研究不同生长发育阶段林下灌草层的谱系结构及其变化规律。结果表明：15～24年人工柏木林的林下灌草层物种的组成均表现出了谱系发散(NRI<0,NTI<0),即共存物种亲缘关系疏远;25～34年林下灌草层的谱系结构趋于谱系随机;35年以上的林下灌草层的谱系结构表现为聚集(NRI>0,NTI>0)。不同生长发育阶段林下灌草的谱系多样性指数均表现出显著正相关;不同生长发育阶段林下灌木层之间的NRI指数均呈显著差异,草本层之间NTI的指数也表现出同样的结果;处在25～34年和35年以上林下草本层之间的NRI以及灌木层之间的NTI均无差异,而与15～24年的相应指数呈显著差异。从同一林龄不同林下层之间的比较看,灌木层的谱系结构指数显著不同于草本层;不同生长发育阶段人...     

The contribution of understory light availability and biotic neighborhood to seedling survival in secondary versus old-growth temperate forest

Seedling survival plays an important role in the maintenance of species diversity and forest dynamics. Although substantial gains have been made in understanding the factors driving patterns of seedling survival in forests, few studies have considered the simultaneous contribution of understory light availability and the local biotic neighborhood to seedling survival in temperate forests at different successional stages. Here, we used generalized linear mixed models to assess the relative importance of understory light availability and biotic neighborhood variables on seedling survival in secondary and old-growth temperate forest in north eastern China at two levels (community and guild). At the community level, biotic neighborhood effects on seedling survival were more important than understory light availability in both forests. In both the old-growth and secondary forests, conspecific basal area had a negative effect on seedling survival, consistent with negative conspecific density dependence. At guild levels, the relative importance of light and biotic neighborhood on seedling survival showed considerable variation among guilds in both forests. Available understory light tended to have positive effects on seedling survival for shrub and light-demanding species in the old-growth forest, but negative effects on survival of shade-tolerant seedlings in the secondary forest. For tree species and shade-tolerant species, the best fit models included neighborhood variables, but that was not the case for shrubs, light-demanding, or mid shade-tolerant species. Overall, our results demonstrate that the relative importance of understory light availability and biotic factors on seedling survival vary with species life-history strategy and forest successional stage.     

Community structures of Mesostigmata, Prostigmata and Oribatida in broad-leaved regeneration forests and conifer plantations of various ages

The community structures of Mesostigmata, Prostigmata, and Oribatida in the soil of broad-leaved regeneration forests and conifer plantations of various ages were assessed alongside soil and plant environmental variables using three response metrics (density, species richness, and species–abundance distribution). The density and species richness of mites recovered swiftly after clear-cutting or replanting. Oribatid mites dominated the soil mite communities in terms of densities and species richness for both forest types. Soil mite communities in broad-leaved forests was related to forest age, the crown tree communities index, and forest-floor litter weight. In contrast, soil mite communities in the conifer plantation sites were related to various indices of understory plants. The development of the understory plants was synchronized with the silvicultural schedules, including a closed canopy and thinning. Such a conifer plantation management may affect indirectly the community of mites.     

Forest plant community as a driver of soil biodiversity: experimental evidence from collembolan assemblages through large‐scale and long‐term removal of oak canopy trees Quercus petraea

Plant–soil interactions are increasingly recognized to play a major role in terrestrial ecosystems functioning. However, few studies to date have focused on slow dynamic ecosystems such as forests. As they are vertically stratified by multiple vegetation strata, canopy tree removal by thinning operations could alter forest plant community through tree canopy opening. Very little is known about cascading effects on soil biodiversity. We conducted a large‐scale, multi‐site assessment of collembolan assemblage response to long‐term canopy tree removal in sessile oak Quercus petraea temperate forests. A total of 33 experimental plots were studied covering a large gradient of canopy tree basal area, stand age and local abiotic contexts. Collembolan abundance strongly declined with canopy tree removal in early forest successional stage and this was mediated by negative effect of understory plant community composition changes, i.e. shift from moss and forb to tree seedling, fern, shrub and grass species. Negative effect of this composition shift on collembolan species richness was largely offset by positive effect of the increase in understory plant species richness. This gives support to both the plant mass‐ratio and functional diversity hypotheses. Collembolan functional groups had contrasting response patterns, which were mediated by different ecological factors. Epedaphic (r‐strategist) abundance and species richness increased with canopy tree removal in relation with the increase in understory plant species richness. In contrast, euedaphic (K‐strategist) abundance and species richness declined with canopy tree removal in early forest successional stage in relation with changes in understory plant community composition and species richness, as well as microclimatic conditions. Overall, our study provides experimental evidence that forest plant community can be a strong driver of collembolan assemblages. It also emphasizes the role of trees as foundation species of forest ecosystems that can shape soil biodiversity through their regulation of understory plant community and ecosystem abiotic conditions.     

Slow understory redevelopment after clearcutting in high mountain forests

Besides natural tree regeneration itself, the development of the forest understory community is highly indicative of the ecological recovery of forest stands post-harvesting, and therefore of the sustainability of forest management. High mountain forests might show particularly slow recovery of the understory plant community because of harsh environmental conditions. We compared understory community richness and composition among three age classes of forest stands in the subalpine Engelmann Spruce–Subalpine Fir zone in the interior of British Columbia, Canada. Species composition was found to differ significantly between mature stands (>110 years old and never harvested) and both recent clearcuts (5–8 years old) and the oldest clearcuts present in the study area (second growth: 24–28 years old). A non-metric multidimensional scaling (NMDS) ordination revealed no unidirectional return of species composition in harvested stands towards that of mature forest; indeed, plots in recent clearcuts and second growth stands were similar to one another and clearly separated from the mature stands. Indicator Species Analysis revealed that moss species were particularly indicative of mature forest, with four moss species being common in mature stands but absent from both younger stages. Compared to what has been reported for lower elevation coniferous forests, e.g. in the U.S. Pacific Northwest, redevelopment of the understory appears to be slow after harvesting in these high elevation mountain forests. Rotation intervals that consider the natural temporal pattern of species turnover and the occurrence interval of major natural disturbances (here: fire) should provide effective approaches to sustainable forest management of these forests.     

林窗对格氏栲天然林更新层物种生态位的影响

采用改进更新生态位宽度和更新生态位重叠模型分析林窗干扰对福建三明市格氏栲天然林更新层物种生态位的影响。结果表明:林窗中格氏栲更新生态宽度值大于林下,林窗在促进格氏栲更新过程中具有重要作用。林窗和林下更新生态位宽度最大的为桂北木姜子,其与格氏栲更新生态位重叠值也较大。林窗中的格氏栲与其它物种更新生态位重叠值低于0.6,林窗微生境的异质性导致格氏栲与其它树种间对资源的利用存在明显的共享趋势,促进了物种间共存。林下的格氏栲与木荷、木荚红豆和短尾越桔的更新生态位重叠值均高于0.6,格氏栲与这些物种相互争夺资源与空间,种间竞争较强。格氏栲天然林未来树种组成中,主要由桂北木姜子、木荷、矩圆叶鼠刺与格氏栲等组成的混交群落,整个群落正向物种组成多样化的方向演变。     

Evidence that fungal pathogens inhibit recruitment of a shade-intolerant tree,white birch (<Emphasis Type="Italic">Betula papyrifera</Emphasis>), in understory habitats

Evidence from tropical forests suggests understory habitats are associated with a high risk of disease, which may prevent the establishment of vulnerable tree species; in contrast, canopy gaps can act as refuges from these pathogens. However, few studies have investigated the impacts of pathogens on regeneration in temperate forests. To determine whether losses to fungi of seeds of Betula papyrifera, a light-loving species, varied between habitats that differed in their degree of openness, we applied fungicide to seeds buried in old fields, treefall gaps, and forest understory sites. We found that the application of fungicide significantly reduced losses in all habitats, relative to control values. This effect was habitat-dependent: the benefit of fungicide was greater in forest understory than in openings. This suggests that B. papyrifera is prevented from establishing in understory environments in part by its susceptibility to pathogen attack, and not solely because of a high light requirement.     

Importance of the understory stratum to entomofaunal diversity in a temperate deciduous forest

The vertical stratification of lepidopteran and coleopteran communities in a cool-temperate deciduous forest in Japan was examined to evaluate the hypothesis of an expected uniform distribution of mobile flying insects between the canopy and understory of temperate forests. Lepidopteran and coleopteran insects were trapped using light traps at three sites in each of the canopy and understory for three consecutive nights each month from April to October 2001. For Lepidoptera, species richness, abundance, and family richness were significantly higher in the understory than in the canopy. For Coleoptera, only abundance was larger in the canopy relative to the understory; species and family richness did not differ between the strata. The beta diversity of the lepidopteran community was larger between the strata than among sites, but the coleopteran community showed an inverse pattern. These results imply the presence of vertical stratification within the lepidopteran community, but not within the coleopteran community, in the temperate forest. The understory contributes more than the canopy to lepidopteran diversity in the temperate forest, although this stratification may be relatively weak because, in contrast to the situation in tropical forests, the canopy and understory assemblages share many species.     

Phylogenetic Structure of Tree Species across Different Life Stages from Seedlings to Canopy Trees in a Subtropical Evergreen Broad-Leaved Forest

Investigating patterns of phylogenetic structure across different life stages of tree species in forests is crucial to understanding forest community assembly, and investigating forest gap influence on the phylogenetic structure of forest regeneration is necessary for understanding forest community assembly. Here, we examine the phylogenetic structure of tree species across life stages from seedlings to canopy trees, as well as forest gap influence on the phylogenetic structure of forest regeneration in a forest of the subtropical region in China. We investigate changes in phylogenetic relatedness (measured as NRI) of tree species from seedlings, saplings, treelets to canopy trees; we compare the phylogenetic turnover (measured as β_NRI) between canopy trees and seedlings in forest understory with that between canopy trees and seedlings in forest gaps. We found that phylogenetic relatedness generally increases from seedlings through saplings and treelets up to canopy trees, and that phylogenetic relatedness does not differ between seedlings in forest understory and those in forest gaps, but phylogenetic turnover between canopy trees and seedlings in forest understory is lower than that between canopy trees and seedlings in forest gaps. We conclude that tree species tend to be more closely related from seedling to canopy layers, and that forest gaps alter the seedling phylogenetic turnover of the studied forest. It is likely that the increasing trend of phylogenetic clustering as tree stem size increases observed in this subtropical forest is primarily driven by abiotic filtering processes, which select a set of closely related evergreen broad-leaved tree species whose regeneration has adapted to the closed canopy environments of the subtropical forest developed under the regional monsoon climate.     

Vertical stratification of ichneumonid wasp communities: the effects of forest structure and life‐history traits

Parasitoid wasp communities of the canopy of temperate forests are still largely unexplored. Very little is known about the community composition of parasitoids between canopy and understory and how much of this difference is related to forest structure or parasitoid biological strategies. In this study we investigated upon the difference in the community composition of the parasitic wasps Ichneumonidae between canopy and understory in a lowland temperate forest in northern Italy. We used general linear models to test whether parasitic strategy modifies species vertical stratification and the effect of forest structure. We also tested differences in β‐diversity between canopy and understory traps and over time within single forest layers. We found that stand basal area was positively related to species richness, suggesting that the presence of mature trees can influence local wasp diversity, providing a higher number of microhabitats and hosts. The ichneumonid community of the canopy was different from that of the understory, and the β‐diversity analysis showed higher values for the canopy, due to a higher degree of species turnover between traps. In our analyses, the vertical stratification was different between groups of ichneumonids sharing different parasitic strategies. Idiobiont parasitoids of weakly or deeply concealed hosts were more diverse in the understory than in the canopy while parasitoids of spiders were equally distributed between the two layers. Even though the ichneumonid community was not particularly species‐rich in the canopy of the temperate forests, the extension of sampling to that habitat significantly increased the number of species recorded.     

Understory Plant Community Composition Is Associated with Fine-Scale Above- and Below-Ground Resource Heterogeneity in Mature Lodgepole Pine (Pinus contorta) Forests

Understory plant communities play critical ecological roles in forest ecosystems. Both above- and below-ground ecosystem properties and processes influence these communities but relatively little is known about such effects at fine (i.e., one to several meters within-stand) scales, particularly for forests in which the canopy is dominated by a single species. An improved understanding of these effects is critical for understanding how understory biodiversity is regulated in such forests and for anticipating impacts of changing disturbance regimes. Our primary objective was to examine the patterns of fine-scale variation in understory plant communities and their relationships to above- and below-ground resource and environmental heterogeneity within mature lodgepole pine forests. We assessed composition and diversity of understory vegetation in relation to heterogeneity of both the above-ground (canopy tree density, canopy and tall shrub basal area and cover, downed wood biomass, litter cover) and below-ground (soil nutrient availability, decomposition, forest floor thickness, pH, and phospholipid fatty acids (PLFAs) and multiple carbon-source substrate-induced respiration (MSIR) of the forest floor microbial community) environment. There was notable variation in fine-scale plant community composition; cluster and indicator species analyses of the 24 most commonly occurring understory species distinguished four assemblages, one for which a pioneer forb species had the highest cover levels, and three others that were characterized by different bryophyte species having the highest cover. Constrained ordination (distance-based redundancy analysis) showed that two above-ground (mean tree diameter, litter cover) and eight below-ground (forest floor pH, plant available boron, microbial community composition and function as indicated by MSIR and PLFAs) properties were associated with variation in understory plant community composition. These results provide novel insights into the important ecological associations between understory plant community composition and heterogeneity in ecosystem properties and processes within forests dominated by a single canopy species.