白龙江上游地区森林植物群落物种多样性的研究

 白龙江上游地区属长江防护林工程重点地区之一。根据36个样地的调查资料,分析了该地区森林植物群落物种多样性的特征：群落内各层物种丰富度指数的大小顺序为“灌木层>草本层>乔木层”;均匀度指数变化比较复杂,在杜鹃巴山冷杉（Rhododendron fastigiatum-Abies fargesii）林中为“草本层>灌木层>乔木层”,在苔藓巴山冷杉林中为“乔木层>灌木层>草本层”,其余群落中为“灌木层>草本层>乔木层”;多样性指数的大小顺序为“乔木层<灌木层和草本层”,而灌木层与草本层的多样性指数随林分郁闭度变化而变化,在郁闭度30%的杜鹃巴山冷杉林中,草本层大于灌木层,在郁闭度47%的箭竹巴山冷杉林中,草本层和灌木层相当,在郁闭度55%以上的各个群落内,灌木层大于草本层。同一海拔不同坡向群落的物种多样性表现为分布于阳坡的油松（Pinus tabulaeformis）林大于分布于阴坡的草类云杉（Picea asperata）林。物种多样性沿海拔梯度的变化表现为随海拔升高先降低后增加,从海拔2 400 m的栎类阔叶林,2 600 m的草类云杉林,2 800 m的箭竹(Sinarundinaria nitida)巴山冷杉林,到3 000 m的苔藓巴山冷杉林和3 200 m的杜鹃巴山冷杉林,物种多样性依次下降,到海拔3 400 m的高山杜鹃（Rhododendron fastigiatum）灌丛,物种多样性增加。物种多样性在紫果云杉(Picea purpurea)林的演替系列中表现为随群落演替发展而增加,后降低,在针阔混交林阶段达到最大。     

北京九龙山植物群落物种多样性特征对比分析

根据对北京九龙山植物群落的样地调查数据,采用Shannon-Wiener多样性指数、群落均匀度和生态优势度指标研究了九龙山封育植被乔灌草各层的物种多样性,并分别就阳坡和阴坡进行了乔木材、灌价群落的指标对比分析,结果表明,这3种指标能够有效地表征暖温带植物群落的组成结构特征,在九龙山封育植被中,阴阳坡的灌丛群落与乔木材相比,其灌木层的物种多样性Shannon-Wiener指数D高于乔木林中乔木层,而低于其灌木层;灌丛群落的草本层Shannon-Wiener指数小于乔木材中草本层;乔木材的草本层的物种多样性Shannon-Wiener指数大于灌木层,灌木层又大于乔木层,而生态优势度系数C在上述3种比较中与Shannon-Wiener指数表现相反,而群落均匀度指数J在比较中阴阳坡的表现不同,最后讨论了九龙坡地区植被演替序列及加速其进展演替的恢复措施。     

Herbivory on Temperate Rainforest Seedlings in Sun and Shade: Resistance,Tolerance and Habitat Distribution

Differential herbivory and/or differential plant resistance or tolerance in sun and shade environments may influence plant distribution along the light gradient. Embothrium coccineum is one of the few light-demanding tree species in the temperate rainforest of southern South America, and seedlings are frequently attacked by insects and snails. Herbivory may contribute to the exclusion of E. coccineum from the shade if 1) herbivory pressure is greater in the shade, which in turn can result from shade plants being less resistant or from habitat preferences of herbivores, and/or 2) consequences of damage are more detrimental in the shade, i.e., shade plants are less tolerant. We tested this in a field study with naturally established seedlings in treefall gaps (sun) and forest understory (shade) in a temperate rainforest of southern Chile. Seedlings growing in the sun sustained nearly 40% more herbivore damage and displayed half of the specific leaf area than those growing in the shade. A palatability test showed that a generalist snail consumed ten times more leaf area when fed on shade leaves compared to sun leaves, i.e., plant resistance was greater in sun-grown seedlings. Herbivore abundance (total biomass) was two-fold greater in treefall gaps compared to the forest understory. Undamaged seedlings survived better and showed a slightly higher growth rate in the sun. Whereas simulated herbivory in the shade decreased seedling survival and growth by 34% and 19%, respectively, damaged and undamaged seedlings showed similar survival and growth in the sun. Leaf tissue lost to herbivores in the shade appears to be too expensive to replace under the limiting light conditions of forest understory. Following evaluations of herbivore abundance and plant resistance and tolerance in contrasting light environments, we have shown how herbivory on a light-demanding tree species may contribute to its exclusion from shade sites. Thus, in the shaded forest understory, where the seedlings of some tree species are close to their physiological tolerance limit, herbivory could play an important role in plant establishment.     

林窗对格氏栲天然林更新层物种多样性和稳定性的影响

采用物种多样性指数和改进的M.Godron稳定性法研究林窗干扰对格氏栲(Castanopsis kawakamii)自然保护区天然林更新层物种多样性和稳定性的影响.结果表明:林窗干扰改善了微环境,表现在林窗和林下乔灌层树种重要值和多样性存在差异.林窗乔木层中丰富度指数R、优势度指数D、Shannon-Wiener指数H、均优多指数Z均高于林下,均匀度指数Js和群落优势度指数C低于林下;灌木层中R、D、H、Js、Z指数均高于林下,群落优势度指数C低于林下,林窗物种多样性更为丰富,生态优势种不明显,群落向复杂化和均匀化方向发展.林窗与林下乔木层Jaccard相似性系数Cj、Sorenson相似性系数CS、Bray-Curtis指数CN相对较低,Morista-Horn指数CmH较高,林窗对树种更新具有促进作用;灌木层相似性系数Cj、Cs、CN、CmH均较高,物种组成基本一致.根据M.Godron稳定性原理拟合出稳定性模型,林窗和林下乔木层分别为对数模型与二次函数模型,林窗和林下灌木层最佳拟合模型均为对数模型.林窗乔木层植物处于稳定状态,林下乔木层植物不稳定;林窗和林下灌木层植物均处于稳定状态.林窗和林下乔木层树种中以桂北木姜子(Litsea subcoriacea)重要值最高,说明其在森林更新中占有重要地位,可能对格氏栲种群更新产生较大影响.林下乔木层中格氏栲重要值较低,格氏栲更新存在困难,而林窗干扰促进了格氏栲的向上生长和重要值的提升,可有效实现格氏栲种群的更新和恢复.     

湖南栎类天然次生林林分空间结构对灌木物种多样性的影响

林分空间结构会显著影响其林下植被多样性,为明确其影响灌木物种多样性的关键因子,以栎类天然次生林为研究对象,利用Pearson简单相关分析、多元线性逐步回归法与典型相关分析探索乔木层空间结构与林下灌木物种多样性的相关关系,为保护林下植被多样性提供生态经营建议。以混交度、聚集指数和开敞度表达林分空间结构,以Margalef指数、Pielou指数和AuclairGoff指数作为灌木物种多样性评价指标,利用3种统计分析方法分析两者之间的相关关系,研究结果表明:(1)Pearson相关分析结果显示混交度对灌木层Pielou指数和AuclairGoff指数影响显著(P0.05),其余指数均不显著;(2)多元线性逐步回归分析结果显示林下灌木物种多样性受到多个林分空间指标的综合影响,其中Pielou指数受到混交度、聚集指数和开敞度的显著影响,AuclairGoff指数受到混交度与开敞度的显著影响;(3)典型相关分析结果显示,第一对典型相关变量通过显著性检验,典型相关系数为0.5427,林分空间结构与灌木层多样性指标两组变量在整体上相关性较强,其中混交度是影响力最大的变量。因此,欲提高栎类天然次生林下灌木物种多样性,应选择以调整树种结构为主,综合考虑林木空间分布格局的调整方案。     

鼎湖山植物群落多样性的研究

根据鼎湖山自然保护区１６个植物群落的样地调查资料,从种丰富度和不同类型的物种多样性指数、均匀度与植被类型、人为干扰程度、演替阶段等方面的关系进行了分析。本区植被类型的多样性指数、均匀率指数变化反映了其结构复杂程度、生境的差异。物种丰富和多样性随着人为干扰程度的增强而降低。群落内各层的物种丰富度的大小的顺序为“灌木层＞草本层＞乔木层”,而群落多样性指数的大小顺序为“灌木层＞乔木层＞草本层”。群落多样     

我国南方4种常见人工林林下植物多样性特征及影响因素

为了解长期植被恢复的成熟人工林林下植物组成与多样性特征及其影响因素,基于广东鹤山生态系统国家野外科学观测研究站的南亚热带人工林生态系统,对环境相似(坡度、坡向、海拔)、30 a生4种类型人工林(桉树混交林、马占相思纯林、乡土混交林、针叶混交林)进行调查研究,分析林下植物组成和物种多样性(Shannon-Wiener指数、Simpson指数、Pielou指数)特征。结果表明,人工林林下植物类型丰富,均可形成乔-灌-草垂直结构;4种林型林下植物组成既有相似性,也有差异性,桉树混交林与针叶混交林、马占相思纯林与乡土混交林的灌木层组成相似;桉树混交林与马占相思纯林、乡土混交林与针叶混交林的草本层组成相似,而桉树混交林与针叶混交林的草本层组成极不相似。林分类型影响林下植物多样性,马占相思纯林林下灌草多样性显著低于其他3种混交林(P<0.05),灌木物种数、个体数最少;针叶混交林林下物种丰富度最高。林分郁闭度与林下植物多样性呈正相关(P<0.001),林下植物分布与土壤养分含量相关,桉树混交林、马占相思纯林林下植物多样性与不同形态氮含量相关,有效磷、全磷影响乡土混交林林下物种的分布,针叶混交林受土壤酸碱度、全钾的影响较为明显。在4种人工林林下植物群落中,乡土混交林多样性,均匀度最高,优势度最低,具有更佳的保育和维持林下生物多样性功能。因此,乡土树种混交林更适用于生态公益林构建或对一些针叶林及外来树种纯林进行林分改造。     

Stress from cold and drought as drivers of functional trait spectra in North American angiosperm tree assemblages

Understanding how environmental change alters the composition of plant assemblages, and how this in turn affects ecosystem functioning is a major challenge in the face of global climate change. Assuming that values of plant traits express species adaptations to the environment, the trait‐based approach is a promising way to achieve this goal. Nevertheless, how functional traits are related to species’ environmental tolerances and how trait spectra respond to broad‐scale environmental gradients remains largely unexplored. Here, we identify the main trait spectra for US angiosperm trees by testing hypotheses for the relationships between functional traits and species’ environmental tolerances to environmental stresses, as well as quantifying the environmental drivers of assemblage means and variances of these traits. We analyzed >74,000 community assemblages from the US Forest Inventory and Analysis using 12 functional traits, five traits expressing species’ environmental tolerances and 10 environmental variables. Results indicated that leaf traits, dispersal traits, and traits related to stem hydraulics were related to cold or drought tolerance, and their assemblage means were best explained by minimum temperatures. Assemblage means of traits related to shade tolerance (tree growth rate, leaf phosphorus content, and bark thickness) were best explained by aridity index. Surprisingly, aridity index, rather than minimum temperature, was the best predictors of assemblage variances of most traits, although these relationships were variable and weak overall. We conclude that temperature is likely to be the most important driver of functional community structure of North American angiosperm trees by selecting for optimum strategies along the cold and drought stress trade‐off. In turn, water availability primarily affects traits related to shade tolerance through its effect on forest canopy structure and vegetation openness.     

佛坪国家级自然保护区植物群落物种多样性特征

用物种多样性指数（Simpson指数和Shannon指数）、均匀度指数（Pielou均匀度）和物种丰富度,对佛坪国家级自然保护区主要高等植物群落物种多样性进行了测度。结果表明：森林群落的多样性程度高于灌丛和草甸,落叶阔叶林高于针叶林,栎林高于杨桦林。群落物种多样性有随海拔高度的升高而降低的趋势。物种多样性在森林群落垂直结构上的分布特点,表现为一般乔木层与灌木层接近但低于草本层。     

三江平原沼泽湿地岛状林植物多样性

 基于Quick Bird影像选择样地区域,采用样方法进行群落学调查。选取丰富度指数（R）、Simpson指数（D）、Shannon-Wiener指数（H′）、Pielou均匀度指数（J_sw）测度多样性水平。结果表明：19个岛状林共记录到维管植物140种,隶属于44科,102属,与相邻的洪河自然保护区内的同类型群落相比较有些物种已经消失。山杨林(Ass. Populus davidiana)、白桦林(Ass. Betula platyphylla)和杨桦林(Ass. P. davidiana+B. platyphylla)3种群落类型多样性指数在灌木层之间差异显著（p<0.05）。岛状林总体3个层次之间的R、D、H′大小顺序均为草本层>灌木层>乔木层,3者之间差异极显著（p<0.01）。岛状林斑块的物种丰富度与斑块面积（r=0.591, p<0.01）、周长（r=0.674 , p<0.01）和形状指数（r=0.584,p<0.01）极显著相关,而D、H′、J_sw与周长、面积和形状指数相关均不显著。受到一定人为干扰的岛状林群落仍具有较高的植物多样性,其中草本层植物多样性占有重要地位。林窗干扰是导致林下植物多样性较高的重要原因。边缘效应可能是引起群落斑块物种丰富度随着斑块面积、周长和形状指数的增大而增加的重要原因。岛状林群落斑块对于维持该地区的植物多样性具有重要意义。     

Direct topsoil transfer to already planted reforestation sites increases native plant understory and not ruderals

Forests restored passively or by tree planting can take many decades to be recolonized by native forest understory plant species, if at all. Our study tested (1) the ability of forest topsoil transfer to accelerate the recovery of native forest plant communities in post-agricultural reforestation sites after tree-planting and without previous topsoil removal and (2) the effect of adding combinations of woody debris (WD), shrub plantings, and shade shelters (SS) on top of the transferred topsoil. Five 12.5 × 10 m treatment blocks were established in each of three recipient sites, which included two post-agricultural reforestation sites, and one abandoned gravel pit site. Each treatment blocks received forest topsoil and a combination of additional treatments. Treatment and control plots were sampled for all vascular species in spring and summer. Native forest plant species richness in topsoil recipient plots was similar (p > 0.05) to that of mature donor forest sites, and significantly higher (p < 0.05) than that of passive control plots in the recipient sites. The plant community composition of all topsoil recipient plots had also become more like the donor forests and less like recipient site controls. Only the unplanted gravel pit-site increased in non-native ruderal plant species after topsoil transfer. The addition of WD, shrub plantings, or SS had no significant effect after two growing seasons. We recommend that topsoil should when possible be added where trees have already been planted, allowing for shorter time to canopy closure and thereby higher survival of shade-adapted understory species.     

辽东山区林权制度改革中林下种植模式对林下植物物种多样性的影响

以样方调查数据为基础,采用物种丰富度指数、均匀度指数和多样性指数,对辽宁省东部山区森林生态系统中种植林下参和大叶芹这两种作物对林下植物物种多样性的影响进行了研究,并分析了不同作物种植样地和未种植样地以及不同种植作物样地之间的各种指数的差异程度。结果表明:(1)种植两种作物均对灌木层物种产生了显著的影响,降低了物种多样性。(2)种植林下参使得草本层的物种丰富度显著降低,均匀度显著增加,而多样性指数差异不显著。(3)种植大叶芹使得草本层的物种丰富度、均匀度和多样性指数均显著降低。(4)林下参种植样地和大叶芹种植样地之间草本层的物种丰富度指数、均匀度指数和多样性指数之间存在显著差异。     

Shade tolerance and herbivory are associated with RGR of tree species via different functional traits

• Relative growth rate (RGR) plays an important role in plant adaptation to the light environment through the growth potential/survival trade‐off. RGR is a complex trait with physiological and biomass allocation components. It has been argued that herbivory may influence the evolution of plant strategies to cope with the light environment, but little is known about the relation between susceptibility to herbivores and growth‐related functional traits.
• Here, we examined in 11 evergreen tree species from a temperate rainforest the association between growth‐related functional traits and (i) species’ shade‐tolerance, and (ii) herbivory rate in the field. We aimed at elucidating the differential linkage of shade and herbivory with RGR via growth‐related functional traits.
• We found that RGR was associated negatively with shade‐tolerance and positively with herbivory rate. However, herbivory rate and shade‐tolerance were not significantly related. RGR was determined mainly by photosynthetic rate (A_max) and specific leaf area (SLA). Results suggest that shade tolerance and herbivore resistance do not covary with the same functional traits. Whereas shade‐tolerance was strongly related to A_max and to a lesser extent to leaf mass ratio (LMR) and dark respiration (R_d), herbivory rate was closely related to allocation traits (SLA and LMR) and slightly associated with protein content.
• The effects of low light on RGR would be mediated by A_max, while the effects of herbivory on RGR would be mediated by SLA. Our findings suggest that shade and herbivores may differentially contribute to shape RGR of tree species through their effects on different resource‐uptake functional traits.

     

Changes in woody vegetation abundance and diversity after natural disturbances causing different levels of mortality

Questions: How does woody vegetation abundance and diversity differ after natural disturbances causing different levels of mortality? Location: Abies balsamea–Betula papyrifera boreal mixed‐wood stands of southeast Quebec, Canada. Methods: Woody vegetation abundance and diversity were quantified and compared among three disturbance‐caused mortality classes, canopy gap, moderate‐severity disturbances, and catastrophic fire, using redundancy analysis, a constrained linear ordination technique, and diversity indices. Results: Substantial changes in canopy tree species abundance and diversity only occurred after catastrophic fire. Shade‐tolerant, late‐successional conifer species remained dominant after canopy gap and moderate‐severity disturbances, whereas shade‐intolerant, early‐successional colonizers dominated canopy tree regeneration after catastrophic fire. Density and diversity of mid‐tolerant and shade‐intolerant understory tree and shrub species increased as the impact of disturbance increased. Highest species richness estimates were observed after catastrophic fire, with several species establishing exclusively under these conditions. Relative abundance of canopy tree regeneration was most similar after canopy gap and moderate‐severity disturbances. For the sub‐canopy tree and shrub community, relative species abundances were most similar after moderate‐severity disturbances and catastrophic fire. Vegetation responses to moderate‐severity disturbances thus had commonalities with both extremes of the disturbance‐caused mortality gradient, but for different regeneration layers. Conclusions: Current spatio‐temporal parameters of natural disturbances causing varying degrees of mortality promote the development of a complex, multi‐cohort forest condition throughout the landscape. The projected increase in time intervals between catastrophic fires may lead to reduced diversity within the system.     

Effects of introduced ungulates on forest understory communities in northern Patagonia are modified by timing and severity of stand mortality

Natural disturbances such as fires, windstorms, floods, and herbivory often act on plant communities, affecting their structure and the abundance and composition of their species. Most research has focused on the effects of single disturbances on plant communities whereas the synergistic effects of several disturbances have received less attention. In this study, we evaluated how timing and severity of tree mortality modified plant use by introduced deer and early post-mortality successional trajectories in northern Patagonian conifer forests. We sampled understory composition and deer use in Austrocedrus chilensis (ciprés de la cordillera) forest stands undergoing varying timing and severity of forest mortality as reconstructed using dendroecological techniques. In addition, we evaluated the effect of fallen logs on plant composition and deer use of plants by monitoring areas of massive dieback where fallen logs had been removed for fire hazard reduction, and nearby control areas not subjected to such removal. Stepwise regression analyses showed that history and severity of tree mortality strongly influence plant composition and deer use of plants. For deer use (with pellet counts and browsing index as response variables), results showed a positive relationship with degree of stand mortality and a negative relationship with cover of fallen logs. Similarly, cover of unpalatable shrub species was explained by canopy mortality history, whereas cover of palatable shrub species was positively associated with severity of canopy mortality. In areas where fallen logs had been removed, pellet counts were six times higher than those in control areas. Though total shrub species cover was similar between log removal and control areas, proportion of unpalatable shrubs increased in areas where fallen logs had been removed. In conclusion, deer use of plants was strongly limited by tall fallen logs, allowing palatable species to establish and grow. Fallen log removal accelerated deer entrance and changed understory composition toward more browse-resistant and unpalatable species. These results underscore the importance of considering the dynamics (timing, severity, and extent) of fallen woody debris influencing understory herbivory and post-disturbance succession. In addition, experimental results underpin the importance of maintaining snags and large woody debris in disturbed landscapes where salvage logging is a routine procedure.     

林分密度对云顶山柏木人工林林下物种多样性和土壤理化性质的影响

以成都云顶山柏木(Cupressus funebris)人工林为对象,采用典型样地法研究不同林分密度(1100、950、800、650、500株/hm~2)对林下物种多样性和土壤理化性质及林下物种多样性与土壤理化性质相关性的影响。结果表明:共发现维管植物168种,隶属75科140属。随林分密度的降低,灌木层多样性指数呈先增后减的单峰变化,在密度650株/hm~2出现峰值,草本层多样性指数呈先增后减再增再减的双峰变化,在密度950株/hm~2和650株/hm~2出现峰值。同时发现光照为影响林下植物多样性的重要因素。林分密度对土壤全氮、全钾、速效钾、有机质影响显著,有机质、全氮、全钾、速效钾随林分密度降低呈先增后减的变化趋势。钾、氮、有机质与林下植被物种多样性关系最密切。结论:林分密度650株/hm~2为云顶山柏木人工林最适密度,该密度能较好的提高林下物种多样性和土壤肥力。     

Shade Tree Diversity,Cocoa Pest Damage,Yield Compensating Inputs and Farmers' Net Returns in West Africa

Cocoa agroforests can significantly support biodiversity, yet intensification of farming practices is degrading agroforestry habitats and compromising ecosystem services such as biological pest control. Effective conservation strategies depend on the type of relationship between agricultural matrix, biodiversity and ecosystem services, but to date the shape of this relationship is unknown. We linked shade index calculated from eight vegetation variables, with insect pests and beneficial insects (ants, wasps and spiders) in 20 cocoa agroforests differing in woody and herbaceous vegetation diversity. We measured herbivory and predatory rates, and quantified resulting increases in cocoa yield and net returns. We found that number of spider webs and wasp nests significantly decreased with increasing density of exotic shade tree species. Greater species richness of native shade tree species was associated with a higher number of wasp nests and spider webs while species richness of understory plants did not have a strong impact on these beneficial species. Species richness of ants, wasp nests and spider webs peaked at higher levels of plant species richness. The number of herbivore species (mirid bugs and cocoa pod borers) and the rate of herbivory on cocoa pods decreased with increasing shade index. Shade index was negatively related to yield, with yield significantly higher at shade and herb covers<50%. However, higher inputs in the cocoa farms do not necessarily result in a higher net return. In conclusion, our study shows the importance of a diverse shade canopy in reducing damage caused by cocoa pests. It also highlights the importance of conservation initiatives in tropical agroforestry landscapes.     

不同密度巨桉人工林林下植物多样性及根际土壤化感物质

为探究巨桉人工林林下植物多样性的影响因素,选择四川省丹棱县4和8年生不同密度(1200、1600和2000株·hm^-2)巨桉人工林为对象,研究林下植物多样性和根际土壤酚类化感物质。结果表明: 共发现植物45种,隶属于33科44属;随林龄增加和林分密度降低,巨桉人工林林下植物种类增加且重要值分布更为均匀;各林分植物生活型以高位芽植物为主。4年生林地灌木Shannon指数和Margalef指数在1600株·hm^-2下显著升高,4年生林地除Margalef指数外其余草本多样性指数及8年生林地草本Pielou指数随林分密度降低均显著升高;灌木Shannon指数及Margalef指数在1200株·hm^-2下8年生林地显著高于4年生林地。根际土壤中鉴定出5种酚类化感物质,4年生林地根际土壤中水杨酸浓度在1600株·hm^-2下显著降低,5,7-二羟基黄酮浓度随林分密度降低而显著降低;水杨酸浓度在8年生林地根际土壤中随林分密度降低显著升高;水杨酸浓度在2000株·hm^-2下4年生林地显著高于8年生林地,在1600株·hm^-2下相反;5,7-二羟基黄酮浓度在1200株·hm^-2下8年生林地显著高于4年生林地。冗余分析(RDA)结果表明,土壤pH、容重、有机质、全磷、全氮及化感物质是林下植物多样性的主要环境影响因子。适度延长轮伐期、调节林分密度以改善林内微环境、缓冲巨桉的化感作用,可促进林下植被发育。     

Leaf diffusion resistance pattern in an oak-hornbeam forest

Four tree, five shrub, and ten herbaceous species growing naturally in an oak-hornbeam forest were used for simultaneous study of the leaf diffusive resistances in the course of several summer days. Absolute minima of the stomatal resistance in the sun tree, the shrub, and the herbaceous species leaves were 1.7 to 6.2 s cm^-1, 6.1 to 10.8 s cm^-1, and 4.8 to 9.7 (17.3 inConvallaria majalis leaves) s cm^-1, respectively. Minimum daily leaf resistances in the course of a day were noted earlier in the morning in sun leaves of large trees than in shade leaves of other species. Stomata were fully opened later in the morning and they began to close sooner in the afternoon in usual shade leaves of the plants in the interior of the forest canopy than those in sun leaves in active surfaces of the canopy (tops of tree crowns). The relatively large differences in leaf resistances found among investigated species may be explained by differences in leaf anatomy (stomata frequency and size) and in ambient leaf or plant environment caused by leaf (plant) position in different vertical layers.     

间伐对日本落叶松人工林林下更新木本植物组成和生长影响的时间效应

明确间伐对针叶人工林林下更新阔叶木本植物组成和生长影响的时间效应,可为促进人工纯林向针阔混交林转化、进而解决纯林生产与生态功能无法兼顾的问题提供参考。本研究以我国北方重要针叶人工林——日本落叶松人工林为例,比较间伐后短期(1～3年)、中期(4～9年)和长期(>9年)人工林林下更新木本植物组成的差异;并选择具有较高重要值且与落叶松互惠共生的3种更新树种蒙古栎、色木槭、糠椴,分析不同间伐时期人工林内光照(郁闭度)与更新木本植物生长的关系。结果表明: 在间伐样地内更新的阔叶木本植物达46种,不同间伐时期样地内共有且占据优势的乔木树种为色木槭,灌木树种为忍冬和卫矛。随间伐后时间的推移,更新物种数逐渐减少,但乔灌比呈增大的趋势;中性树种占据优势地位。间伐对更新树种生长影响的时间效应受树种耐荫性的影响,糠椴的基径和树高均高于蒙古栎和色木槭。随间伐后时间的延长,糠椴的基径、色木槭的树高对光照响应较敏感,分别倾向于采用“耐荫策略”和“避荫策略”以适应间伐后变化的环境。间伐对日本落叶松人工林林下更新阔叶木本植物组成和生长的影响具有明显的时间效应;在制定以促进人工林林下树种更新为目标的间伐措施时,应该考虑适当延长间伐间隔,从而保证糠椴和色木槭等阔叶树幼苗的生长,使其进入林冠层,促进形成针阔混交林,实现人工林的可持续发展。