夏季栾树群落冠层结构对其环境温湿度的调节作用

为探究栾树群落降温增湿作用与其冠层结构参数的相关性在一天中的变化趋势,于天气晴朗的夏季对北京奥林匹克森林公园栾树群落内部和对照点的温度、相对湿度、群落冠层结构参数进行了铡定.结果表明:栾树群落的郁闭度与叶面积指数、平均叶倾角呈显著相关,且叶面积指数与平均叶倾角呈显著相关;在夏季8:00-18:00,栾树群落可降低空气温度0.43～7.53℃,在12:00左右达到降温最大值,增加相对湿度1％ ～ 22％,且在10:00左右增湿作用最显著,而在18:00-次日8:00降温增湿效果不明显;9:00-12:00,郁闭度和叶面积指数显著影响栾树群落的降温增湿作用;12:00-14:00,仅郁闭度与降温增湿作用显著相关;直到18:00,郁闭度和叶面积指数共同决定了栾树群落的降温增湿作用.因此,影响栾树群落降温增湿作用的冠层结构参数在一天中随着时间的推移发生变化.     

北京市不同植物群落的降温增湿效应研究

在北京市植物园选取14个不同结构特征的植物群落作为研究对象,利用温湿度记录仪对其温湿度进行测定,分别研究郁闭度、平均冠幅、叶面积指数与降温增湿效应之间的相关性。结果表明,不同群落的降温增湿效果存在较大差异:碧桃(Prunus persica Batsch.var.duplex)、洋白蜡(Fraxinus pennsylvanica)、杂种鹅掌楸(Liriodendron chinense×tulipifera)、杜仲(Eucommia ulmoides)群落的降温增湿效果较好,而绦柳(Salix matsudana f.pendula)、楸树(Catalpa bungei)、毛泡桐(Paulownia tomentosa)群落的降温增湿效果相对较弱。对实验数据进行统计分析可知,郁闭度与群落降温效应呈极显著正相关,与增湿效应呈正相关但不显著;平均冠幅与群落的降温效应呈显著正相关,但与增湿效应的正相关并不显著;叶面积指数对群落的降温效应起到一定促进作用,但对增湿效应影响不大。除此之外,其他影响植物群落降温增湿效应的结构特征有待进一步探讨。     

城市绿地植物群落特征对亚微米颗粒物的影响

植物群落是构成城市绿地的基本单元之一,也是绿地发挥空气颗粒物调节功能的基础。亚微米级颗粒物,即PM1颗粒物对大气能见度、环境质量与人体健康等均存在严重的负面危害。为探究城市绿地植物群落对亚微米颗粒物水平的调节机制,本研究基于实地测量,针对不同类型植物群落内PM1颗粒物水平的差异,以及群落冠层结构对PM1浓度的影响开展定量研究。结果表明,植物群落对亚微米颗粒物具有一定的减滞效果。8种常见群落类型中,针阔-乔草型群落减滞PM1颗粒物的能力最优,阔叶-乔灌草群落次之,针叶-灌草型群落最弱,但不同类型植物群落内部的PM1浓度差异并不显著。植物群落的冠层结构同PM1颗粒物间存在明显的非线性响应关系,部分冠层指标存在关键的拐点阈值。当冠层郁闭度大于75%,疏透度小于55%左右时,植物群落减滞PM1颗粒物的效果最佳。     

成都市沙河主要绿化树种固碳释氧和降温增湿效益

以成都市沙河植物廊道广泛应用的8种绿化植物为材料,利用LI-6400XT便携式光合测定系统进行了光合生理生态指标的测定,并对其固碳释氧与降温增湿效应进行了量化研究.结果表明:整个生长季节同类植物各季节的单位叶面积固碳释氧和 降温增湿能力表现出夏季＞秋季＞春季.日固碳释氧能力由强到弱为桂花、垂柳、香樟、黄葛树、山杜英、银杏、天竺桂、水杉,年固碳释氧能力由强到弱为垂柳、香樟、黄葛树、银杏、桂花、天竺桂、水杉、山杜英,日降温增湿效果由强到弱为垂柳、山杜英、水杉、天竺桂、黄葛树、香樟、银杏、桂花.据估算,整个沙河植物群落中乔木树种年总固碳量约为5.87×104 t,总释氧量约为4.27×104 t.根据对主要树种固碳释氧和降温增湿能力的分析表明,在树种配置时,垂柳、桂花、山杜英、香樟为优选乔木树种,而银杏的固碳释氧和降温增湿能力较弱,可作为长寿树种和观赏树种适量引种,不宜大面积绿化.     

交通绿化带植物配置对空气颗粒物的净化效益

交通绿化带有显著的净化街道空气的环境效益。通过对上海浦东某交通干道旁侧绿化带不同季节大气中总悬浮颗粒物(TSP)的测定,定量研究了绿化带对TSP的净化效益;同时对研究区域内植物的配置情况用郁闭度和疏透度进行了表征,并研究了其与TSP的净化效益之间的相关性。研究结果表明:交通绿化带对由机动车引起的TSP污染有明显的净化作用,其中夏、秋季净化百分率较高,春、冬季较低;为达到较高的TSP净化效益,交通绿化带宽度应不小于5m,最佳为10m,采用先灌后乔的配置方式,并更多的选用常绿树种;绿地对TSP的净化百分率同植物群落的郁闭度成正相关,同疏透度成负相关关系;绿地内植物郁闭度的最佳范围为0.70～0.85,疏透度的最佳范围为0.25～0.33。研究结果可为评价现有交通绿化带植物配置情况和日后的城市绿地规划和建设提供技术依据。     

城市带状绿地结构类型与温湿效应的关系

利用小尺度定量测定的方法,选择北京典型的城市带状绿地--西四环旁侧4种不同内部结构以及5种不同郁闭度带状绿地(绿地宽度42 m)作为研究对象,研究带状绿地结构类型与温湿效应的关系.结果表明:与对照相比,草坪的降温增湿效应不显著,灌-草、乔-草和乔-灌-草绿地的降温增湿效果显著.当郁闭度为10%～31%时,绿地具有一定的降温增湿效应,但效应不显著;当郁闭度超过44%时,绿地降温增湿效应显著;当郁闭度超过67%时,绿地降温增湿效应显著且趋于稳定.     

南宁市植物群落结构特征与局地小气候效应关系分析

着重探讨植物群落结构特征与生态小气候因子间的相关性。结果表明:(1)在林荫处,植物群落总冠幅盖度、总密度、群落重要值均与温度成极显著的负相关;植物群落群落重要值还与相对湿度达到显著正相关。(2)在林隙处,植物群落总平均株高与光照强度成显著正相关,与风速成极显著负相关。(3)植物群落结构特征与其小气候生态效应间的相关性是:总平均株高与遮光效应值达到极显著的正相关,与挡风效应值亦达到显著的正相关。另外,总冠幅盖度与降温效应值成极显著的正相关。同时,总密度与降温效应值亦成极显著的正相关。特别是群落重要值与降温、增湿、挡风、遮光等生态效应值都成显著甚至极显著的正相关。通过分析与探讨南宁市植物群落结构和小气候因子间的相关性机理,可为科学地进行城市绿化、生态城市建设提供理论依据。     

上海环城林带景观美学评价及优化策略

选取上海环城林带7种植物群落,采用美景度评判法,从林内景观和林外景观2个空间层次和春、夏、秋、冬4个季节,应用数量化理论Ⅰ建立了美景度和各景观因子类目之间的景观评价与预测的多元回归模型,分析了群落的结构特征和季相特征对林内景观以及外貌特征对林外景观的影响,并提出相应的优化对策。结果表明:(1)群落结构特征对林内景观的影响主要因子为胸径(平均胸径和胸径变异系数)、郁闭度和疏透度。在春季,林内美景度随着树木胸径增大而增加;在夏季,郁闭度增大会提升林内美景度;在秋季,胸径变异小的群落具有更高的林内观赏性;在冬季,疏透度对林内景观美景度影响最大。(2)群落季相特征对林内景观的影响,在各季节表现亦不同。在春季,黄色、紫色等明度较高的色相和开花量适中的群落美景度最佳;在夏季,生长势好、林冠层变化小以及树干清晰度高的群落具较高的美景度,且观花可显著提高夏季林内美景度;在秋季,色彩越纯美景度越高;而在冬季,树皮颜色深的群落美景度高。(3)群落外貌特征对林外景观有显著影响,其中林冠线对林外景观美景度影响最大,其次为林缘线。具有起伏不大林冠线和自然流畅林缘线的植物群落美景度高。旨在通过对典型植被群落不同季相的美景度评价,对上海环城林带的群落景观进行定量的评价,进而为不同情景下的群落结构优化提出相应的对策,为城市森林的群落建构与管理提供科学依据。     

百山祖自然保护区植物群落beta多样性

本文采用植物群落学的典型样方法,研究了百山祖自然保护区森林植物群落beta多样性格局及其维持机制。通过对45个20m?20m标准样地的调查数据进行分析,运用Chao’s群落距离指数衡量该植物群落beta多样性格局,并通过Mantel检验、基于距离矩阵的偏RDA分析和方差分解等方法初步检验和衡量了各环境因子差异（包括群落郁闭度、海拔、坡度、坡向和坡位）和群落空间距离对该区域beta多样性格局的影响。结果显示,该区域内植物群落beta多样性随着群落间综合环境差异或群落空间距离的增加而增大, 但环境差异和群落空间距离只能解释36%左右的beta多样性格局。检验的5个环境因子中,只有群落郁闭度和海拔对百山祖自然保护区植物群落beta多样性有显著影响,并且群落郁闭度对beta多样性的解释度（20.0%）略高于海拔对beta多样性的解释度（18.0%）。群落空间距离对百山祖自然保护区beta多样性的解释度最小（9.0%）。本文展现了百山祖自然保护区内植物群落beta多样性格局及其与群落环境和空间距离的关系,所获得的结果支持生境异质性和扩散限制联合对植物群落beta多样性起作用的假说。     

半湿润常绿阔叶林次生演替阶段植物多样性和群落结构特征

以飒马场不同次生演潜阶段的半湿润常绿阔叶林为对象,测定物种丰富度、群落数量特征指标,分析植物多样性与群落结构特征之间的关系.结果表明,随着植物群落演替,物种丰富度不断增加,物种丰富度最高演替阶段的乔木层物种达到24个;植物多样性与植物个体密度间呈正相关关系;乔木层植物个体平均高与植物多样性间呈负相关关系;群落郁闭度和胸高断面积与植物多样性之间则呈对数函数关系.植物多样性与优势种个体密度和群落地上部分现存量间未呈现一致性规律.植物种-个体数间呈幂函数关系.随着植物多样性增加,种间竞争加剧.每个植物种为了维持临界最低种群,可能采取最大种群策略,导致群落植物个体数增加,密度增大,从而改变了群落结构特征.     

黄土高原苹果园蒸腾导度大气驱动规律比较

植物蒸腾导度是表征土壤-植物-大气连续体（SPAC）中植物-大气间水汽传导过程、反映植物水分调控能力的一类重要变量，常见有冠层导度（G_c）、冠层气孔导度（G_s）与叶片气孔导度（g_s），明确三者在反映冠层蒸腾过程时的异同或关联性对于理解植物水分利用机制具有重要意义。本研究基于对黄土高原果园苹果树生长季内树干液流（J_s）及环境因子的连续观测，计算了G_c、G_s及脱耦联系数（Ω）等变量，并与短期连续观测的叶片气孔导度（g_s）比较，分析了G_c、G_s和g_s在反映冠层蒸腾特征方面的异同及其关系。结果表明，日变化过程中G_s、g_s呈"单峰"型曲线，而G_c则呈"先增后减，午后抬升"的"双峰"型曲线。g_s与G_s存在较紧密的线性关系（R²=0.80），但与G_c的线性关系较弱（R²=0.02）。G_c、G_s均随大气水汽压亏缺（VPD）的变化呈现确定的规律，其中，上边界函数呈递减的对数函数关系，平均值则符合先增后减的Log-Normal函数关系（R²>0.95），拐点对应的VPD值分别为1.33和1.16 kPa。在一日内，G_s对VPD变化的响应过程与g_s对VPDL （基于叶片温度计算的水汽压亏缺）变化的响应过程总体一致，其一致性高于G_c对VPD变化的响应。整个生长季（4-10月）中果树的Ω平均值为0.12，随着Ω递减，G_c与G_s的线性相关性愈趋紧密，其斜率呈递增趋势，G_c越来越趋近于G_s。研究结果表明，在北方地区，基于树干液流的监测能较准确的推导整株并估算林分的冠层蒸腾导度。与实测g_s的变化过程比较，G_s比G_c具有更高的一致性，G_s可以作为描述苹果树水分利用过程响应大气驱动的更为恰当的变量。     

Vertical stratification of feeding guilds and body size in beetle assemblages from an Australian tropical rainforest

Abstract The vertical stratification of insect species assemblages inhabiting tropical rainforests is well established but few have examined whether these patterns are reflected in vertical stratification of body size or feeding guilds. We used Malaise and Flight Interception Traps to sample beetle assemblages from five locations, at both canopy and ground zones of a tropical lowland rainforest site near Cape Tribulation, Australia. Beetles from 4 years of sampling were sorted to Family and morphospecies, and allocated to one of five feeding guilds. Within feeding guilds the number of species and individuals, from canopy‐ and ground‐caught traps were compared. The body lengths of species were measure and compared within feeding guilds and families. Herbivores was the dominant guild but was not the majority of all species or individuals. Most beetle species (69%) were less than 5 mm in length and the mean size of canopy‐caught species was greater than that for ground‐caught species. This was probably due to slightly more species of plant feeders (herbivores and xylophages) present in the canopy, which were significantly larger than saprophages, fungivores and predators. Among feeding guilds, there were few overall canopy–ground differences. These results contrast with species composition results presented elsewhere where strong differences between the canopy and the ground were evident. We suggest that our guild groupings may have been too coarse to detect fine‐scale differences and that resource partitioning may have also masked faunal stratification. We propose that fine‐scale differences in resources between the canopy and the ground, together with strong microclimate gradients, are likely to be important in structuring the vertical stratification of insect assemblages at the level of species, but not with respect to functional groups.     

Three-dimensional soil heterogeneity modulates responses of grassland mesocosms to an experimentally imposed drought extreme

Heterogeneity is an intrinsic characteristic of soils, which regulates plant diversity and ecosystem functioning. However, whether soil heterogeneity also modulates responses of plant communities to climate change, including climate extremes, remains largely an open question. Here, we explore responses of plant communities to drought extremes across four levels of spatial soil heterogeneity, with cell sizes varying from very small to very large, i.e. 0, 12, 24 and 48 cm. These were created in mesocosms by alternating nutrient-rich and nutrient-poor substrate in three dimensions. A seed mixture of 24 grassland species was evenly sown on each mesocosm in spring. In late summer, a three-week drought was imposed with a rainout shelter. During the drought, soil water content at the mesocosm scale decreased more at intermediate (12 and 24 cm) than at small or large (0 and 48 cm) cell sizes, which was reflected in increased senescence and drought-induced heat stress. These responses could be traced to greater plant biomass coupled with higher water demand at those intermediate cell sizes, likely related to between-cell access to nutrients and effects of diversity and community composition. Our results indicate that soil heterogeneity can modulate the impact of drought extremes on plant communities, though more research is needed on the transition between intermediate and extreme cell sizes, where heterogeneity effects seem to change most. We propose that soil heterogeneity be considered more explicitly in studies of changing precipitation regimes.     

大明山常绿阔叶林冠层垂直结构与林下植物更新

2009—2011年,在广西大明山常绿阔叶林一个典型坡面的上坡、中坡和下坡分别建立24个20 m×20 m的固定样地,测定不同林冠层次(上层、中层和下层冠高分别为:>8、4～8和0～4 m)的覆盖度并监测林下植物的更新,研究林冠垂直结构的动态变化及其对林下植物更新的影响.结果表明: 随着2008年特大冰冻灾害后森林的恢复,林冠总覆盖度显著增加,从2009年的54.0%提高到2011年的67.4%,不同冠层覆盖度和恢复增长存在显著差异,上层林冠覆盖度显著高于中、下层,而中、下层林冠的恢复增长显著优于上层林冠.林下更新的木本植物共55种,优势科和优势种与现有群落的基本一致.同一年份不同坡位林下更新植物的物种多样性指数差异不显著,但同一坡位不同年份间存在显著差异.不同冠层的覆盖度与更新植物的物种丰富度和多度相关性不显著;中层、下层和林冠总覆盖度与林下更新植物的Shannon指数、Simpson指数和Pielou均匀度指数呈显著负相关,表明冠层覆盖度显著影响着林下更新,中、下层林冠对林下更新植物多样性的作用更明显.     

Microclimate and fluxes of water vapour, sensible heat and carbon dioxide in structurally differing subalpine plant communities in the Central Caucasus

Effects of canopy structure on microclimate, energy budget and CO₂ exchange were analysed in a pasture, two hay meadows, a tall herb community and a dwarf shrub community in the subalpine belt of the Central Caucasus. The results show that canopy structure exerts a marked influence on the distribution of photon flux density, temperature and canopy photosynthesis A_c. Three canopy types were distinguished. Type 1 (pasture) has a small LAI (leaf area index) and more than two-thirds of the phytomass is concentrated in the lowest few cm of the canopy, mainly as planophile leaves. This results in (1) a low degree of utilization of photosynthetic photon flux density (PPFD) by assimilatory plant components, (2) high leaf temperatures and a high soil heat flux during the phase of incoming radiation, and (3) a relatively low A_c/ LAI ratio. Type 2 (meadows), in spite of its erect leaves, which at high solar elevations permit light to penetrate to the lower canopy layers, is characterized by (1) marked effects of mutual shading in the lower canopy layers for most of the day, and thus (2) only slight variations in air and leaf temperatures and (3) a comparatively low A_c/LAI ratio. In canopies of type 3 (tall herb and dwarf shrub communities), there is a concentration of flat leaves in the upper layers. This results in (1) very good utilization of PPFD; (2) no strong fluctuations in canopy temperature as the flat leaves act as a buffer, reducing the amounts of incoming and outgoing radiation in lower canopy layers, and (3) high values of the A_c/LAI ratio. The energy budgets of the canopies investigated are governed not so much by their spatial structure, but rather indirectly by LAI and the degree of coupling of the canopy with the atmosphere.     

Experimental and Modelling Studies of Competition for Light in Roadside Grasses

Equiproportional mixtures and monocultures of two roadside grass species (Elymus repens (L.) Gould and Puccinellia distans (L.) Pari.) were grown in experimental field plots under non-limiting water and nutrient conditions. During the course of the season, E. repens increasingly overgrew and shaded plants of P. distans which eventually died. A multispecies canopy photosynthesis model was parameterized using measurements of structural and physiological characteristics from three different stages of canopy development. Results of simulations clearly revealed that canopy photosynthesis of P. distans was highly dependent on the degree of light competition caused by E. repens. Since P. distans has recently invaded stands of roadside vegetation throughout Central Europe where it has replaced the native and highly competitive E. repens, it is hypothesized that this success is due to disturbance factors that keep E. repens from growing tall and shading P. distans.     

Arthropod Abundance,Canopy Structure,and Microclimate in a Bornean Lowland Tropical Rain Forest1

This study applies a novel, vertically stratified fogging protocol to document arthropod abundance, density, and biomass across a vertical gradient in a primary, lowland dipterocarp forest canopy in Borneo. We fogged arthropods at 5 m vertical intervals and 20 m horizontal intervals along six full‐canopy transects and measured leaf surface areas along the same transects. The results show that arthropod biomass in the aboveground regions was 23.6 kg/ha, the abundance was 23.9 million individuals/ha, and the density on leaf surfaces was 280 individuals/m² leaf area. All three numbers are five to ten times higher than estimated by previous surveys of tropical lowland rain forest canopies using mass‐collection techniques. Arthropod abundance and biomass were analyzed in relation to canopy structure, composition, vapor pressure deficit (VPD), photosynthetic photon flux density (PPFD), and height. Using stepwise regression we found that 13 of 14 arthropod groups had significant positive relationships with one‐sided leaf area, 11 had significant negative relationships with VPD, 3 had significant relationships with height, and none showed positive relationships with light. Classifying the 14 taxa based on their responses to leaf area and VPD created three groups that corresponded roughly to the biology of these taxa. This study suggests that the biomass and abundance, and perhaps therefore—by extrapolation—the biodiversity, of tropical canopy arthropods may be very much higher than previously estimated.     

亚高山云冷杉混交林树木生长释放与干扰分析

对云南碧塔海亚高山云冷杉林内４个样地冠层树木的生长压制和释放的历史,用树木年轮分析方法进行了重建,然后根据生长释放频率推测林冠干扰强度（每１０年冠层树木的死亡百分率）。４个林分（１个中龄林,３个成过熟林）生长释放的平均百分率为４８％～９２％。中龄林内,平均生长释放频率为７１％／１０ａ,成过熟林则为７４％～９５％／１０ａ,在油麦吊云杉〔Ｐｉｃｅａｂｒａｃｈｙｔｙｌａｖａｒ．ｃｏｍｐｌａｎａｔａ（Ｍａｓｔ．）ＣｈｅｎｇｅｘＲｅｈｄ．〕占优势的林分和大果红杉（Ｌａｒｉｘｐｏｔａｎｉｎｉｖａｒ．ｍａｃｒｏｃａｒｐａＬａｗ）油麦吊云杉混交林分内,估测的林冠干扰强度分别为４８％／１０ａ和５９％／１０ａ。     

森林冠层昆虫多样性研究方法

森林冠层是森林昆虫栖息、取食、避敌的重要生境,其中生活着十分丰富的昆虫物种。但由于乔木树体高大,冠层难于接近,在很大程度上限制了冠层昆虫多样性的研究。冠层昆虫类群结构的划分和冠层昆虫取样技术也是冠层昆虫多样性研究的重要基础。文章综述当前冠层接近和冠层昆虫抽样技术的最新进展,并评述冠层昆虫类群结构划分的方法。