西双版纳片断化望天树林小气候边缘效应比较研究

对西双版纳片断望天树(Shorea chinensis)林林缘小气候的季节、水平变化进行了观测研究,对比分析了4个不同大小雨林斑块(30 hm2、25 hm2、20 hm2、3 hm2)的小气候边缘效应.结果表明:各雨林斑块林缘均存在明显的小气候边缘效应,其中在干季晴天最为明显,且在两个较小斑块林缘出现最高气温及气温日较差高于林外的现象;干季,部分林缘小气候要素(最高气温、总辐射、净辐射、最小相对湿度)林缘与林内的差值均是高于或大于雨季的相应值,而地表最高温林缘与林内的差值则是雨季强于干季;各斑块相比,小气候边缘效应波及林内的深度在最大斑块达到最浅(25 m),而在最小斑块达到最深(35 m),呈现出小气候边缘效应及其影响深度随片断雨林斑块面积减小而增强及向林内进一步延伸的趋势.     

缙云山片断常绿阔叶林小气候边缘效应的初步研究

对缙云山5个片断常绿阔叶林和1个连续常绿阔叶林林缘附近的小气候要素水平梯度分布进行测定.结果表明,各片断阔叶林斑块边缘均存在明显的小气候边缘效应.林缘与林内最高和最低气温、光合有效辐射、最小相对湿度均为干季高于或大于雨季,而地表最高温度则为雨季高于干季;各阔叶林斑块的小气候边缘效应以最大斑块波及林内的深度最浅、最小斑块波及林内的深度最深.     

缙云山生境片断化对常绿阔叶林生物多样性的影响

采用Simpson、Shannon-Wiener和Hill多样性指数以及逐步多元回归分析方法,在缙云山进行了植物群落调查、小气候观测和土壤肥力的测定以及各变量之间关系的分析。结果表明:片断常绿阔叶林物种多样性指数比连续常绿阔叶林低,不同生活型的表现不同;各片断阔叶林斑块边缘均存在明显的小气候边缘效应。随着斑块面积的减小,各斑块的ΔTa、林缘及林内ΔTs、林缘和林内ΔRH、林缘和林内Vmax、林缘和林内ΔPAR(正午)均呈增大的趋势。各斑块的小气候边缘效应,以最大斑块波及林内的深度最浅(约至林内15m)、最小斑块波及林内的深度最深(约至林内25m);常绿阔叶林物种多样性受林内外有效光合辐射(正午)差、气温日较差、土壤含水量、土壤有机质含量和土壤有效钾等因素的影响。     

西双版纳热带雨林片断小气候边缘效应的初步研究

本文以林缘为中心,研究了西双版纳地区３个热带干性季节性雨林片断和１个同样植被类型的连续森林林内至林外样带上小气候要素水平梯度分布。结果表明,热带雨林片断林缘对温度、相对湿度和光照的影响范围北向林缘伸至林内１５ｍ、南向林缘伸至林内２５ｍ。林外小气候水平梯度大于林内,这种梯度变异尤以林缘附近（－１０～１０ｍ范围）最大。热带雨林片断后,林内与林外之间的小气候环境差异和对林外气候变化的缓冲作用都明显减弱。本文还给出了温度和湿度随水平距离变化的线性关系,并探讨了小气候边缘效应对群落结构、物种分布的影响。     

热带季节雨林林窗辐射特征研究

利用不同季节热带季节雨林林窗、林内及旷地不同波长太阳辐射的实测资料,探讨了热带季节雨林林窗不同波长辐射特征。结果表明,热带季节雨林林窗中央和北侧林冠下的不同波长太阳辐射存在“突跃现象”,中午前后各辐射量值迅速达到最大后又急速下降;林窗内不同波长太阳辐射日总量值均大于林内,却小于旷地;林窗中央和北侧林冠下比较可见,在干热季、雨季和雨季后期,林窗中央的各辐射要素总量值高于北侧林冠下,但雾凉季时受浓雾和太阳高度以及方位的影响,各辐射要素总量值较北侧林冠下低;林窗中央的总辐射日总量在雨季太阳高度角最大时最高,雨季后期和干热季其次,雾凉季时最小;林窗中央和北侧林冠下的红外辐射及可见光在总辐射中所占份额随季节的变化而不同,充分显示了林窗辐射环境的异质性;与旷地和林内相比,林窗内各测点的红外辐射在总辐射中所占份额介于旷地和林内之间．高于旷地却低于林内;而可见光占总辐射的比值情况正好相反．另外,林窗可见光分配率的季节变化都大于红外辐射;热带季节雨林林窗育增加红外辐射、减少可见光的特征．     

哀牢山和玉龙雪山不同海拔林内外温湿特征比较

以哀牢山和玉龙雪山不同海拔森林生态系统为研究对象,利用各海拔的林内、外气温、相对湿度观测数据,比较分析了两地不同海拔林内、外小气候特征及其变化规律。结果表明,哀牢山、玉龙雪山各海拔的林内、外气温年变化趋势均呈倒U型,雨季(5—10月)高于干季(11—4月),林外气温高于林内。哀牢山各海拔森林对气温影响(林内外气温差)强于玉龙雪山。林内外气温差绝对值一般随海拔增加而增大。年尺度上,哀牢山林内气温低于林外,玉龙雪山除3540 m也低于林外,显示出两种山地森林具有一定的降温调节作用。哀牢山年林内气温随海拔高度递减比率(0.52℃·100 m~(-1))略大于林外(0.50℃·100m~(-1)),均小于玉龙雪山(林内为0.55℃·100 m~(-1)、林外为0.56℃·100 m~(-1))。哀牢山、玉龙雪山各海拔林内、外相对湿度年变化趋势也呈倒U型,雨季大于干季,林外低于林内。年尺度上,高海拔的相对湿度较大。总体上,哀牢山、玉龙雪山森林兼有调节气温和相对湿度的作用,哀牢山森林对降低气温的调节能力更强,玉龙雪山森林增湿调节能力更强。     

川西周公山柳杉人工林群落的边缘效应

为研究人工林群落的边缘效应特征,本文以川西周公山森林公园的柳杉(Cryptomeria fortunei)人工林破碎化大斑块为对象,以植株平均胸径、平均高度、平均密度、丰富度指数(D)和Shannon-Wiener指数(H)来综合衡量边缘效应深度。在实地踏查的基础上,从林缘向林内(梯度1至梯度5)设置5条样带(宽度为10 m),在每条样带中设置4个10 m×10 m的小样方进行调查。结果表明:(1)从物种组成上看,在总面积为2,000 m~2的20个小样方中共记录到111个物种,隶属于54科96属,物种数从林缘至林内递减。(2)从群落结构上看,乔木层的平均胸径从林缘至林内呈减小趋势,平均密度则相反,平均高度无显著变化;灌木层的平均密度从林缘向林内减小,平均高度无显著变化;草本层的平均密度和平均高度均呈减小趋势。(3)从物种多样性上看,总体上各层次的丰富度指数和Shannon-Wiener指数均从林缘向林内呈减小趋势,其中灌木层和草本层的变化趋势最明显;同时,林内各梯度与梯度1(林缘)的共有种和相似性系数从林缘向林内递减。(4)分析各项群落特征发现,平均高度、平均密度和相似性系数的数值在梯度2向梯度3过渡时的起伏变化最明显,推断本研究中柳杉人工林斑块的边缘深度可达林内20 m。     

干季晴天橡胶林林窗温度剖线分布特征

以林窗北侧林缘为中心,研究了西双版纳地区橡胶林林窗及周国Ｎ－Ｓ样带上气温水平梯度分布。结果表明：干季落叶期林窗及周边主要热力作用面在地面,但林缘的增温效应也相当明显,各热力作用面热量收支是林窗小气候形成的物理基础;林缘冠层结构,林缘乔木高度与林窗直径之比,太阳高度角,方位角,天气状况将影响林窗辐射平衡各分量的变化,林缘乔木群落结构的不同是造成林窗小气候差异最直接的原因;     

哀牢山中山湿性常绿阔叶林木质藤本对边缘效应的响应

全球范围内森林片断化现象日益严重。与其他木本植物(乔木和灌木)相比,木质藤本更趋向于分布在片断化森林的边缘,因而了解木质藤本对边缘效应的响应对于进一步了解其对森林动态的影响极其必要。本文对哀牢山中山湿性常绿阔叶林林缘到林内环境梯度上木质藤本的变化进行了调查。在形成年龄分别为13年、35年和53年的3种类型的林缘,设置从林缘向林内连续延伸的长方形样地(20 m×50 m)各10个(总面积3 ha),每个样地再划分为5个20 m×10 m的样方。在每个样方内对胸径≥0.2 cm且长度≥2.0 m的木质藤本进行了每木调查。在3 ha的林缘样地中共记录到木质藤本植物2,426株,隶属于14科19属31种。木质藤本的物种丰富度和多度均随距林缘距离的增加而降低,边缘效应深度在35年林缘的边缘为30 m,13和53年林缘的边缘则为20 m;它们的胸高断面积在53年林缘的边缘效应深度为20 m,但在13和35年林缘的不同距离上差异不显著。木质藤本对边缘效应的响应在物种水平上存在显著差异,主要呈现正向和中性的响应格局,包括只分布于林缘的物种,和从林缘到林内环境梯度上密度逐渐降低的物种;也有对边缘效应不敏感的物种。典范对应分析(CCA)表明,林冠开度、边缘形成年龄和土壤水分是决定木质藤本在片断化森林边缘分布的重要影响因子。     

边缘效应对原始花旗松林冬季温度的影响

由林缘到林内,夏季温度有明显的梯度变化,但还未有人对其它季节的温度变化,进行研究,自1991年10至1992年5月,对林缘至原始花旗松林林内的温度,进行了连续的实地测量,并与相应的夏季温度变化加以比较,主要研究目的,是测定沿林缘两侧,是否存在有一最小的温度阈值,当温度低于这个阈值时,林缘及林内的温度差异会消失。研究中,由林缘到240m的林风,设立了一条样带0,30,60,120,180,和240m,6处装设气象站,每30min连续记录气温、土壤温度和其他微气象指标。通过计算每点的相对温度并同实际温度加以对比,夏季和冬季的林缘效应显著性指数（Significance of edge influences,SEI)进行了分析。此外,计算了不同气象条件下的林缘效应深度（EDI）。结果表明,非夏季最小的气温阈值在0℃左右。土温的变化则因土壤很少结冻,而存在明显不同的最小的温度阈值格局。林缘效应对土壤温度的影响,比对气温的影响更显著,但冬季和夏季之间没有太大的差异,但以DEI而论,林缘效应对气温的影响比较大,对非生长季节气候库子沿林缘梯度的分析,有助于进一步了解几个相关的生物和非生物过程。     

西双版纳望天树林林窗小气候特征研究

 对西双版纳望天树林林窗小气候要素的季节变化、水平差异进行了观测研究,并对比分析了两个大小不同林窗内温度垂直分布状况、相对湿度差别。结果表明：大林窗内温度、湿度、光照的日变化均比林内大;大林窗中央光照强度为林内的10倍以上,太阳总辐射量、净辐射量为林内的5倍以上,大林窗中央的蒸发耗热量大于林内,且均占各自净辐射的较大比例(70％～80％),干季大林窗内温度、湿度日变化比雨季剧烈,大林窗内具有两个加热层(幼苗冠层、地表),小林窗仅有一个加热层(幼树冠层),且前者的加热强度大于后者,相对湿度日变化则是大林窗内较剧烈。     

Edge Effects of Linear Canopy Openings on Tropical Rain Forest Understory Microclimate

We investigated microclimatic edge gradients associated with grassy powerlines, paved highways and perennial creeks in wet tropical forest in northeastern Australia during wet and dry seasons. Photosynthetically active radiation, air temperature and vapor pressure deficit, soil temperature, canopy temperature, soil moisture, and air speed in the rain forest understory were measured during traverses perpendicular to the forest edge. Light intensity was elevated near the edges of powerlines, highways, and creeks, but this effect was strongest for creek edges. Air temperature and vapor pressure deficit were elevated near powerline edges in the dry season and highway edges in both wet and dry seasons but were not elevated near creek edges in either season. In contrast, soil moisture was lowered near creek edges but not near either powerline or highway edges. No edge gradients were detected for air speed. Canopy temperature was elevated near highway edges and lowered near powerline edges in the wet season but no edge gradients in canopy temperature were detected near creek edges in either the wet or the dry season. We suggest that these different edge gradients may be largely the result of differences in the fluxes of latent and sensible heat within each type of linear canopy opening, with periodic flood disturbance assisting by maintaining a more open canopy near creek edges. Our data indicate that the nature of the linear canopy opening is at least as important as the width in determining the nature and severity of microclimatic edge effects, analogous to the "matrix effect" of traditional fragmentation studies.     

Detection of seasonal variability in microclimatic borders and ecotones between forest and savanna

Along eight forest-savanna transects, the borders, the width of associated ecotones, and the depth-of-edge influence (DEI) towards the forest interior were determined on the basis of microclimatic parameters. The analysis focused on the seasonal variability of microclimate at the forest-savanna ecotone that has so far rarely been investigated. The study was located in an intact mosaic of semi-deciduous forests and savanna in the Comoé National Park (north-eastern Ivory Coast). The microclimatic parameters air temperature, air humidity, and vapor pressure deficit were measured from the dry season (February) until the rainy season (September) during five measurement periods (MP). Borders and ecotones including their confidence intervals were determined by a border-and-ecotone detection analysis, which is based on non-linear regression analysis. The ecotone limits were interpreted as DEI towards the two habitats. During the dry season, the microclimatic border between forest and savanna was located further towards the forest interior than during the rainy season. This may be caused by different foliation patterns of tree species at the forest interior and the forest boundary, with the latter being completely defoliated during the dry season. In addition, the variability of microclimatic parameters was higher and differences between forest and savanna were less pronounced during the dry season. The minimum DEI towards the forest interior was 27.4±15.5 m for air humidity in the rainy season (MP-5). The maximum DEI of 137.3 ±138.3 m occurred for air temperature in the dry season (MP-1). The average DEI for all microclimate parameters and MPs was 50.5 m. These DEI values are similar to observations from temperate and tropical forest boundaries in the literature. As microclimate borders proved to shift over the seasons, detailed knowledge of species’ responses to this variability appears to be essential for predicting concomitant dynamics of forest core areas.     

热带山地雨林尖峰栲边材液流及其与环境因子的关系

应用热扩散法,采用ICT-2000TE环境与蒸腾系统同步监测了热带山地雨林尖峰栲边材液流速率和环境因子的变化.结果表明：尖峰栲边材液流速率的变化规律是晴天为单峰曲线、阴雨天气为双峰或多峰曲线.边材液流速率与太阳辐射、空气温度、蒸汽压亏缺、林内风速呈极显著正相关,与空气相对湿度呈极显著负相关.在旱季监测期间,其与土壤温度呈极显著正相关、与土壤湿度相关不显著;而在雨季,其与土壤湿度呈极显著正相关,与土壤温度相关不显著,说明降雨过程对边材液流影响较大.建立了旱季和雨季监测期间的边材液流与环境因子多元线性回归模型,经过F值检验,达极显著水平.旱季、雨季监测期间尖峰栲单株平均蒸腾量分别为103.5和41.3 kg·d^-1,单位林地面积蒸腾量分别为1.94和0.77 mm·d^-1.     

西双版纳热带次生林林窗小气候要素的时空分布特征

利用西双版纳雾凉季和干热季热带次生林林窗的小气候垂直观测资料,探讨了昼间林窗区域树表温、气温、水汽压及相对湿度的时空分布和变化规律,指出在林窗区域,林窗边缘不仅具有显著的热力效应,同样具有明显的水汽效应。并由此构成了林窗区域立体空间的环境异质性,其结果对深入探讨林窗区域的热量、水汽传输,小气候的形成机制,生物多样性和更新等问题均具有重要意义。利用西双版纳雾凉季和干热季热带次生林林窗的小气候垂直观测资料,探讨了昼间林窗区域树表温、气温、水汽压及相对湿度的时空分布和变化规律,指出在林窗区域,林窗边缘不仅具有显著的热力效应,同样具有明显的水汽效应。并由此构成了林窗区域立体空间的环境异质性,其结果对深入探讨林窗区域的热量、水汽传输,小气候的形成机制,生物多样性和更新等问题均具有重要意义。     

Edge effects and extinction proneness in a herpetofauna from Madagascar

Edge effects are thought to play a key role in fragmented habitats. It is often assumed that edge-avoiding species are more prone to local extinction than non-edge-avoiding species, but there are few data to support this assumption. Also, few data are available on the effects of edges on some groups, and there is little understanding of seasonal changes in edge effect intensity. To better understand the role that edge effects play in fragmented tropical forests, we assessed the distribution of reptiles and amphibians in six littoral rainforest fragments in southeastern Madagascar in 1999 (dry season) and 2000 (wet season). Using randomization tests, we found all three types of edge responses: edge-avoiders, interior-avoiders, and omnipresent species. However, edge responses varied considerably among seasons. For example, some species (e.g., Mantidactylus bicalcaratus, Phelsuma quadriocellata) were strong edge-avoiders in the dry season, but showed no preference for edge or interior habitats during the wet season. Also, edge-avoiding species tended to be more extinction-prone than non-edge-avoiding species. Abiotic data documented significantly higher temperatures and dew point temperatures near edges. Wind speed also tended to be higher and relative humidity tended to be lower near edges. Our results indicate that many amphibians and reptiles respond to altered microclimates near edges and these responses have a strong seasonal component. For many species, edge sensitivity does seem to be correlated with extinction vulnerability and therefore should be of primary consideration in plans to conserve biodiversity in fragmented tropical forests.     

Edge Structure Determines the Magnitude of Changes in Microclimate and Vegetation Structure in Tropical Forest Fragments1

Edge structure is one of the principal determinants of the extent and magnitude of edge effects in forest fragments. In central Amazonia, natural succession at forest edges typically produces a dense wall of vegetation dominated by Cecropia spp. that buffers the forest interior. Fire encroachment into forest edges, however, eliminates the soil seed bank, enhances plant mortality, and promotes succession to an open, Vismia–dominated edge that does not buffer the forest interior. Contrasting open, fire–encroached forest edges and closed, non–fire–encroached edges were examined in central Amazonia to assess the effects of edge structure on microclimate and vegetation structure in tropical forest fragments. Edge penetration distances for most microclimate and vegetation structure variables were as much as two to five times greater at open edges than at closed edges. The magnitude of these differences suggests that edge structure is one of the main determinants of microclimate and vegetation structure within tropical forest fragments. Edge effects also varied systematically with fragment area. For a given edge type, 100–ha fragments had consistently lower canopy height, higher foliage density, higher temperature, a higher rate of evaporative drying, lower leaf litter moisture content, and lower litter depth than continuous forest, at all distances from the forest edge. These differences, however, were relatively minor compared to the striking differences in edge penetration between open and closed forest edges. For organisms in small fragments, the difference between open and closed edges may be the difference between total edge encroachment on one hand and an effective nature reserve on the other, relatively independent of absolute fragment area.     

Do edge effects increase the susceptibility of rainforest fragments to structural damage resulting from a severe tropical cyclone?

Abstract If changes in the structural characteristics of rainforest at edges are caused by wind, then physical damage from a tropical cyclone might be greatest at edges or in small fragments that have a high proportion of edge. We tested whether this was true of a fragmented rainforest landscape impacted by a category 4 severe tropical cyclone in March 2006. Six structural variables (canopy cover, canopy height, cover of ground vegetation, leaf litter, stem density and counts of woody debris) were surveyed at 18 rainforest sites (six small linear remnants, and both edges and interiors of six large remnants) on the Atherton Tableland in north‐eastern Queensland, Australia. Data collected 7 and 12 months after the passage of Cyclone Larry were compared with an identical survey conducted 4 years prior to the cyclone. The cyclone had large effects across many components of forest structure. However, sites within 30 m of forest edges in small and large remnants were not impacted more than the interiors of large remnants. It is likely that the high wind intensity from severe tropical cyclones overrides the modest wind protection provided by surrounding forest. The cyclone's effects were highly patchy at local scales (0.5–1.0 km), leading to an increase in among‐site variation in forest structure and the disappearance of significant spatial autocorrelation among large remnant edge‐interior site pairs which had existed prior to the cyclone. The main effect of Cyclone Larry at these study sites was to increase the spatial heterogeneity of forest structure at local scales.     

西双版纳热带季节雨林优势植物热值

为探讨西双版纳热带季节雨林植物热值的变化规律,用SDACM-Ⅲa型量热值仪测定了该群落不同层次37种优势植物不同器官干湿季节的热值。结果表明:西双版纳热带季节雨林各层优势种的平均干质量热值在17.05～20.23kJ.g-1,乔木、层间藤本、灌木、草本干质量热值分别为18.86～20.23、17.97～19.76、17.71～18.83和17.05～17.45kJ.g-1。各层优势种平均干质量热值在干湿季节均表现为:乔木层>层间藤本>灌木层>草本层。所有层次相同各器官平均干质量热值在器官间存在差异,但只有叶与根、枝之间差异显著(P<0.05);不同层次中的同种植物干质量热值在干湿季节差异均不显著(P>0.05);各层优势植物的干质量热值在干湿季节之间差异不显著(P>0.05)。     

Vegetation and microclimatic edge effects in two mixed-mesophytic forest fragments

Forest edges are known to consist of microenvironments that may provide habitat for a different suite of species than forest interiors. Several abiotic attributes of the microenvironment may contribute to this change across the edge to center gradient (e.g., light, air temperature, soil moisture, humidity). Biotic components, such as seed dispersal, may also give rise to changes in species composition from forest edge to interior. We predicted that abiotic and biotic measures would correlate with distance from forest edge and would differ among aspects. To test these predictions, we measured abiotic and biotic variables on twelve 175 m transects in each of two 24 ha forest fragments in east-central Illinois that have remained in continuous isolation for upwards of 100 years. Both univariate and multivariate techniques were used to best describe the complex relationships among abiotic factors and between abiotic and biotic factors. Results indicate that microclimatic variables differ in the degree to and distance over which they show an edge effect. Relative humidity shows the widest edge, while light and soil moisture have the steepest gradients. Aspect influences are evidenced by the existence of more pronounced edge effects on south and west edges, except when these edges are protected by adjacent habitat. Edges bordered by agricultural fields have more extreme changes in microclimate than those bordered by trees. According to PCA results, species richness correlates well with microclimatic variation, especially light and soil moisture; however, in many cases species richness had a different depth of edge influence than either of these variables. The herbaceous plant community is heavily dominated by three species. Distributions of individual species as well as changes in plant community composition, estimated with a similarity index, indicate that competition may be influencing the response of the vegetation to the edge to interior gradient. This study indicates that edge effects must be considered when the size and potential buffering habitat of forest preserves are planned.