西双版纳片断化望天树林气候边缘效应比较研究

对西双版纳片断望天林树（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个个不小雨林斑块（30hm^2,25hm^2,20hm^2,3hm^2)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,且在上较小斑块林缘出现最高气温及气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至最浅（25m),而在最小斑块达到最深（35m)呈现出小气候边缘效应及其影响深度随片继雨林斑块面积减小而增强及向林内进一步延伸的趋势。     

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.     

Buffering of native forest edge microclimate by adjoining tree plantations

Abstract In the Waikato Region of New Zealand, Pinus radiata (D. Don) plantations are becoming increasingly common on land adjacent to native forest fragments. It is unclear whether this juxtaposition is beneficial or detrimental to native forest fragment quality and persistence. We hypothesized that adjacent dense plantations buffer native fragments from microclimatic exposure, reducing edge effects and expanding the area of interior‐like native forest. Microclimate parameters were measured in native forest fragments adjacent to grazed pasture (‘abrupt’ edges) and in fragments adjacent to mature P. radiata plantations (‘embedded’ edges) during late summer. Photosynthetically active radiation, air temperature and vapour pressure deficit (VPD) were measured along transects perpendicular to edges during the mid‐afternoon, when gradients were typically steady and maximal, to investigate spatial variation. At paired abrupt versus embedded edges these same variables were monitored for week‐long periods to determine temporal variation. In fragments adjacent to pasture, conditions were significantly lighter and warmer (but not drier) than the interior along transects at distances up to 20 m from the edge. In contrast, no variables differed significantly along transects adjacent to pine. The different microclimate variables measured at edges (except VPD) contributed to edge effects at different times through a daily cycle. Photosynthetically active radiation was significantly different between abrupt and embedded edges at all times of the day. Air temperature was significantly different during mid‐day and afternoon, but not during the morning nor at night. Vapour pressure deficit varied considerably over time and between sites, but was never consistently higher at one type of edge. We conclude that pine plantations in the Waikato Region provide valuable microclimate buffering during the day, principally due to their effect in reducing light and temperature to interior‐like conditions at native forest edges. Consequently, plantations are a compatible neighbouring land use to forest fragments. Such buffering could be extended through the pine harvesting‐replanting phase with appropriate management, such as leaving an undisturbed margin during harvest.     

片断化森林的边缘效应与自然保护区的设计管理

森林片断化引起了森林边缘物理环境与生物的变化。从森林边缘向林内,光辐射,温度、湿度、风等因素发生改变,这些反过 边缘上和边缘附近的生物产生极其重要的影响。有些研究表明,生物与非生物存在明显的边缘－核心的变化梯度,而有些则没有,除了影响边缘效应的客观因素（如边缘的取向、地势、年龄等）外,主观因素对这缘效应也有影响。边缘对生物与非生物的影响因片断化森林的面积、形状以及与其他森林片连接程度的不同而不同,     

Factors Limiting Tropical Rain Forest Regeneration in Abandoned Pasture: Seed Rain,Seed Germination,Microclimate, and Soil1

Vegetation, seed rain, seed germination, microclimate, and soil physical and chemical parameters were measured in a recently abandoned pasture and adjacent primary rain forest in southern Costa Rica. The goal of this study was to assess the importance of these factors in limiting forest regeneration in abandoned pastures. Seed rain of animal dispersed species decreased dramatically in the pasture >5 m from the forest/pasture edge; fewer wind dispersed seeds fell in the pasture than in the forest, but the difference was much less than for animal dispersed seeds. Percent seed germination of most species studied was similar in the forest and in pasture with grasses; seed germination was lower during the dry season in areas of pasture cleared of grasses. Air temperature, vapor pressure deficit (VPD), and photon flux density (PFD) were much higher in the pasture than in the forest at 1 m above the ground. VPD and PFD at ground level and soil temperature were similar in the pasture and the forest, indicating that pasture grasses strongly modify microclimatic conditions near the soil surface. The lowest gravimetric water content recorded in the pasture during the dry season was 0.5 and leaf relative water contents of the two species measured in the forest and pasture were identical, suggesting that plants in the pasture were not water stressed. Levels of most soil nutrients were lower in the pasture as compared to the forest; however, aboveground and root biomass for seedlings grown in pasture and forest soils did not differ significantly. Although a number of factors impede forest recovery in abandoned pastures, these results suggest that the most imporrant limitation is lack of seed dispersal.     

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.     

Microclimatic Changes Induced by Ecological Restoration of Ponderosa Pine Forests in Northern Arizona

Restoration of ponderosa pine ecosystems results in altered stand structure, potentially affecting microclimatic conditions and habitat quality for forest organisms. This research focuses on microclimatic changes resulting from forest and landscape structural alterations caused by restoration treatments in southwestern ponderosa pine forests. Three microclimate variables—light intensity, air temperature, and vapor pressure deficit (VPD)—were monitored over two field seasons. Differences in microclimate between the treated forest and the surrounding untreated forest were measured, and microclimatic gradients across the structural edge between these two forest types were quantified. Restoration treatments increased sunlight penetration to the forest floor but did not significantly impact ambient air temperature or VPD. Mean values for air temperature and VPD did not differ significantly between treatments, although temperature and vapor pressure deficit did exhibit a trend in the morning; both variables were higher at the structural edge and in the treated forest during morning hours. Significant edge gradients were detected for air temperature and VPD in the morning and evening, increasing from the structural edge into the untreated forest. Our results show that microclimatic effects of these restoration treatments are generally modest, but the changes are more prominent at specific locations and during certain times of day. Because even modest changes in microclimate have the potential to impact a range of key ecological processes, microclimatic effects should be considered when forest restoration treatments at the landscape scale are being planned and implemented.     

Species richness and composition of Neuroptera in the forests fregments of the Taurus Mountains Range,Turkey

In this study, diversity, species richness and composition of Neuroptera has been studied in the forest edges and fragments in the Taurus Mountain Range, southern Turkey. Sampling for species collection was carried out from April 2017 to September 2018 at different distances from the forest center, i.e., (0–500 m), forest mid-interior (501–1000 m), and forest edge (1001–3000 m). A total of 975 adults were collected frequently belonging to the families Ascalaphidae, Coniopterygidae, and Hemerobiidae from the forest edges while Chrysopidae and Myrmeleontidae were most common along the mid-interior regions of the forest. Majority of adutls caught from the mid-interior region comprised of female adults while the males of most species were abundant along the forest edges. Although the forest center shows the largest value for the Dominance species-diversity index and the smallest value for the Shannon index, forest edge was found highest for the Simpson index. The abundance of Neuroptera decreased with wind speed but increased with the temperature in the edge regions. Principal Component Analysis (PCA) indicated that some environmental and habitat variables, e.g. wind speed, temperature, and distance to the forest center, mid-interior and edge, accounted for species distribution patterns in Neuroptera. In the forest center, a linear correlation between wind speed, temperature and specimen abundance was recorded, while these factors were found negatively correlated with specimens abundance in the mid-interior regions of the forest.     

鲁东沿海丘陵茶园防护林的小气候特征

近年来山东乳山茶业逐渐兴起, 但由于北方冬春季温度低和倒春寒频繁发生, 茶叶种植面积逐年减小。如何在低成本管理的基础上提高茶叶产量和品质, 成为乳山茶园管理的一大难题。以2007年春季采用水平梯田整地种植的茶园为试验区, 以梯田周围营造的4种网格(8 m × 80 m, 12 m × 80 m, 20 m × 80 m, 40 m × 80 m)茶园防护林为研究对象, 分别在2013年4月、8月和12月, 测定风速、空气温度、土壤温度、空气相对湿度及土壤相对湿度, 以纯茶园作为对照, 进行了小气候因子测定和分析。结果表明: (1) 4种防护林均能有效地降低茶园内风速, 调节气温、土壤温度和土壤相对湿度, 增加空气相对湿度, 为茶树生长提供适宜的生态环境; (2)由于区域水分通量和太阳辐射的季节变化, 4种防护林的小气候调节效应也表现出一定的季节性差异; (3)主成分分析结果表明, 4种茶园防护林中, 影响小气候因子的主要因素是气温和土壤温度, 其因子负荷量分别为-0.978和0.986, 但风速与气温呈极显著相关关系, 与土壤温度之间无显著线性关系, 因此, 风速也能间接地影响林内小气候; (4) 8 m × 80 m的防护林对小气候的总体调节效应优于其他3种防护林。     

Feeding by the pine weevil Hylobius abietis in relation to sun exposure and distance to forest edges

Abstract 1 The intensity of feeding by adult pine weevils Hylobius abietis (L.) on the stem bark of Norway spruce Picea abies (L.) Karst. seedlings planted in rows with a north–south orientation across a clear‐cutting, was measured throughout a growth season. The feeding was then correlated to light interception, soil temperature and distance to the nearest forest edge. 2 Feeding was at least twice as intense on seedlings in the central part of the clear‐cutting compared to those at the edges. The decline began approximatety 15 m from the edge and was of similar proportions on both the sun‐exposed and shaded sides. 3 Measures of global radiation and soil temperature correlated well with consumption on the shaded side. However, on the sun‐exposed side, there were no apparent correlations with global radiation or soil temperature that could explain the decline in consumed bark area. 4 We conclude that the decline in feeding towards the forest edges was mainly due to factors other than the microclimate variables we monitored. We suggest that the presence of roots of living trees along the forest edge may reduce damage to seedlings, since they provide an alternative source of food for the weevils. This alternative‐food hypothesis may also explain why seedlings in shelterwoods usually suffer less damage from pine weevils than seedlings in clear‐cuttings.     

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。     

黄土高原半干旱区柠条(Caragana korshinskii)树干液流动态及其影响因子

应用热脉冲技术在黄土高原神木县六道沟小流域于2006年6月13至25日测定了两种不同密度柠条(Caragana korshinskii)群落的树干液流动态.同时测量了土壤水分、太阳辐射、大气温度、相对湿度、风速、水汽压亏缺和作物参考蒸散等环境因子,并根据植物蒸腾的P-M公式,反推计算冠层导度.结果表明,除风速外,柠条树木液流与太阳辐射、大气温度、相对湿度、水汽压亏缺、作物参考蒸散均显著相关,且可用太阳辐射的线性表达式来估测.不同密度群落的日蒸腾量随叶面积指数增大而增加,叶面积指数为2.3的群落平均日蒸腾为3.83mm d-1m-2,而叶面积指数为1.1的林分平均日蒸腾1.64mm d-1m-2.冠层导度与气象因子关系复杂,当土壤水分不存在亏缺时,冠层导度与太阳辐射、大气温度、作物参考蒸散因子显著相关,与水汽亏缺和相对湿度因子无相关性;当土壤水分存在亏缺时,冠层导度与太阳辐射、大气温度、作物参考蒸散因子无相关关系,而与水汽亏缺和相对湿度因子显著相关.     

黄土高原半干旱区侧柏(Platycladus orientalis)树干液流动态

应用热扩散式树干茎流计(TDP)于2008年4～10月对黄土高原安塞县侧柏人工林树干液流速率进行了连续测定,并对周围气象、土壤水分等多个环境因子进行了同步测定.结果表明:侧柏在不同月份晴天树干液流速率变化具有明显的昼夜节律性,呈单峰曲线;且各月液流速率日均值受土壤供水水平限制总体上呈下降趋势,即4月份最大,为0.00135 cm · s-1;10月份最小为0.00011cm · s-1;树干液流速率与光合有效辐射、大气温度、水汽压差呈极显著正相关,与相对湿度呈负相关,其相关程度:光合有效辐射＞水汽压差＞大气温度＞相对湿度,并可用线性表达式来估算;侧柏边材面积和地径呈幂指数关系,并以此结合密度估算出样地侧柏人工林的边材面积为4.65m2,最终估算出侧柏人工林生长季总耗水量为1159.6 t · hm-2.     

Pedoecological effects of a sand-fixing poplar (Populus simonii Carr.) forest in a desertified sandy land of Inner Mongolia, China

To assess the pedoecological effects of a 23-year old poplar ( Populus simonii Carr.) forest on soil amelioration and vegetation restoration via soil erosion reduction and atmospheric dust retention in a desertified sandy land ecosystem, daily dynamics of wind speed, sand transport and dust deposition rates were monitored over an erosive period from April through June in 2001, using fixed observation sites located at different positions within and around the forest. Soil and vegetation characteristics at these sites were also measured. The observation sites were placed at distances of 15H (as control), 6H and 3H (H is mean tree height) from the forest edge of the windward side (abbreviated CK, 6H-W and 3H-W respectively), forest center (FC), and at distances of 0H, 6H and 8H from the forest edge of the leeward side (FE-L, 6H-L and 8H-L respectively). Daily mean wind speed was significantly lower in different observation sites than CK, with FC having the greatest reduction of wind speed and 6H-W the least reduction. Daily transport rate of sand by wind was also significantly lower in different observation sites than CK, with FE-L having the greatest reduction of wind erosion and 6H-W the least reduction. The fact that the poplar forest will lose its functions against wind at a distance of about 12-fold tree height from the forest edge of the leeward side suggests that the effective wind-preventing range of the poplar forest is about 150 m. There was marked spatial and seasonal distribution of dust-fall rate. Over space, the rate of dust-fall was much greater within the forest than outside the forest. Over time, the daily dust deposition rate was greatest in April, followed in decreasing order by May, June, July, September and August, closely linked to the seasonal distribution pattern of dust storm. Significant positive changes in soil and vegetation parameters of the different observation sites during the 23 years that the poplar forest was established suggest the perceptible pedoecological effects of the poplar forest on soil development and restorative succession of plant community within its immediate vicinity through windbreak, soil erosion reduction and atmospheric dust retention. Understanding these pedoecological effects may aid in the design of protective forest systems in arid and semi-arid areas.     

Effects of Severe Tropical Cyclone Larry on rainforest vegetation and understorey microclimate near a road,powerline and stream

Abstract Severe Tropical Cyclone Larry damaged a large swathe of rainforest to the west of Innisfail in north‐eastern Queensland on 20 March 2006. Within the path of the most destructive core of the cyclone were sites previously established along human‐made (powerlines and highways) and natural (streams) linear canopy openings for a study of edge effects on adjacent rainforest plant communities and associated microclimates. Vegetation damage and understorey microclimate parameters were measured 6 months after the passage of Cyclone Larry and compared with results before the cyclone. We examined the spatial patterns of vegetation damage in relation to natural and artificial linear clearing edges and the vegetation structural factors influencing these patterns as well as resulting alterations to microclimate regimes experienced in the rainforest understorey. Vegetation damage was spatially patchy and not elevated near linear clearing edges relative to the forest interior and did not differ between edge types. Vegetation damage was influenced, albeit relatively weakly, by structural traits of individual trees and saplings, especially size (diameter at breast height, d.b.h.) and successional status: tree damage was greater in pioneer species and in larger trees, while sapling damage was greater in canopy tree species than in understorey tree or shrub species. Changes in the understorey microclimate mirrored the degree of damage to vegetation. Where vegetation damage appeared greater, the understorey microclimate was brighter, warmer, drier and windier than below less‐damaged areas of the forest canopy. Overall, understorey light availability, wind speed and the diurnal ranges of air temperature and vapour pressure deficit increased dramatically after Cyclone Larry, while pre‐cyclone edge gradients in light availability were lost and temperature and vapour pressure deficit gradients were reversed.     

Tanzanian Forest Edge Microclimatic Gradients: Dynamic Patterns1

Air temperature, vapor pressure deficit, and light intensity microclimatic gradients were examined along four forest edge and four paired forest interior transects in the East and West Usambara Mountains, Tanzania. Between 14 August 1995 and 11 August 1998, 287, 282, and 196 air temperature, vapor pressure deficit, and light intensity gradients, respectively, were measured along the four forest edge and four interior transects. The relationship between microclimate and distance from the forest edge was examined using piecewise linear regression. All microclimatic gradients were classified into one of nine shapes based on the sign and the size of the two estimated slopes. The relative frequency in the shapes of 65 percent of air temperature gradients, 52 percent of vapor pressure deficit gradients, and 62 percent of light intensity gradients along forest edge transects exceeded the relative frequency of these same shapes along forest interior transects, indicating that a majority of the forest edge microclimatic gradients measured were influenced by edge effects. Yet this result also indicated that approximately one‐third of all air temperature and light intensity gradients and nearly one‐half of all vapor pressure deficit gradients recorded during this study were affected by factors independent of edge effects per se, and that forest edge microclimatic gradients were temporally nonconstant. For air temperature and vapor pressure deficit gradients, low spatial but high temporal variation existed in estimated edge width and the relative change in microclimate between the forest edge and interior. For light intensity gradients, both high spatial and temporal variability characterized estimated edge width and relative change in microclimate between the forest edge and interior. The pooled mean edge width and relative change in microclimate between die forest edge and interior across the four forest edge transects for air temperature, vapor pressure deficit, and light intensity gradients were 94.1 m and 2.00°C, 82.6 m and 0.29 kPa, and 60.5 m and 10.6 joules/sec/m², respectively. These results suggest that forest edge microclimatic gradients in general may be inherently dynamic and nonconstant.     

祁连山青海云杉低液流特征及其影响因素

植被蒸腾作为林区生态水文的重要组成部分,是分析林区水分循环及其植被健康生长的基础,对林区保护和科学管理至关重要。本研究于2017—2018年运用热扩散探针对祁连山青海云杉树干液流进行连续监测,探究祁连山青海云杉蒸腾耗水特征,并分析影响云杉生长和蒸腾过程的主控因素。结果表明: 青海云杉树干液流的瞬时变化在晴天呈单峰曲线,在阴天呈多峰或双峰型曲线,在雨天基本无明显规律。青海云杉液流密度与太阳辐射变化趋势一致,晴天液流启动较早,结束较晚,液流历时12～14 h。因该地区海拔较高(2700 m),空气温度较低,饱和水汽压差(VPD)较低,导致液流密度整体偏低,平均为(0.86±0.49) kg·d^-1。在小时尺度上,液流瞬时速率受太阳辐射和VPD的显著影响,而在日尺度下,0～40 cm土层土壤温度和土壤水分含量与液流密度显著相关。云杉液流密度随着太阳辐射、空气温度和VPD的降低而降低,在祁连山高海拔林区,较低的土壤和空气温度以及较低的VPD和太阳辐射是导致该地区青海云杉液流偏低的主要原因。     

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。     

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.     

中国热带静风区林缘水平热力特征的初步分析

利用我国热静风区－西双版纳橡胶林西南向边缘１月的温度观测资料,探讨了昼间林缘区域热力特征及时空变化规律,结果表明,在林缘存在着明显的热力效应;对地面温度的影响深度可至林内约１３ｍ处,地面温度在林处４．５ｍ处达最高,气温则在林缘（０ｍ）出现最大;林缘附近热量的输送在数值和方向上存在较大差异,即林外热量从地面向空中输送;林内在午后与林外相反,热量由上（林冠）向下（地面）输送;林缘附近则在不同地点、不同