长白山阔叶红松林不同强度择伐后关键树种的竞争关系

天然林择伐改变了林分的树种组成和结构,导致林木竞争关系发生变化,进而影响树木的生长和种群的动态.关键树种在维持群落结构和生态系统功能方面具有至关重要的作用.为了弄清长白山区阔叶红松林典型林型关键树种竞争关系的特点,本研究以红松、紫椴和水曲柳为研究对象,运用Hegyi竞争指数分析了受不同程度采伐干扰后形成的原始林(未受干扰)、轻度择伐林、中度择伐林和重度择伐林的林分结构和竞争关系.结果表明: 与原始林相比,轻度择伐林中关键树种的种群结构没有显著变化;中度择伐林和重度择伐林中3个关键树种大树(胸径DBH≥20 cm)的密度和平均胸径均显著减少,但幼树(2 cm≤DBH<10 cm)的数量增加.所有样地中关键树种的竞争指数均随径级的增加而减小,且二者服从幂函数分布,而林木胸径生长到20 cm后,竞争指数进入稳定状态.在原始林、轻度和中度择伐林中,3个树种的幼树的竞争指数受到非冠层树种的影响最大,而红松小树(10 cm≤DBH<20 cm)和大树主要受红松种内和非冠层树种的影响;水曲柳主要受红松和非冠层树种的影响,紫椴主要受种内和红松的影响.重度择伐林中,白桦是3个树种的主要竞争来源,贡献率均超过50%.根据以上关键树种竞争关系的特点,抚育非冠层树种有利于3个关键种幼树的更新和生长;对于小树来说,还需要根据树种类型来采取相应措施,而大树不需要采用抚育措施.本研究对关键树种培育和天然林择伐后快速恢复具有指导意义.     

Sleeping site preferences in tufted capuchin monkeys (Cebus apella nigritus)

The characteristics and availability of the sleeping sites used by a group of 27 tufted capuchin monkeys (Cebus apella nigritus) were studied during 17 months at the Iguazu National Park, Argentina. We tested different hypotheses regarding possible ultimate causes of sleeping-site selection. Most sleeping sites were located in areas of tall, mature forest. Of the 34 sleeping sites the monkeys used during 203 nights, five were more frequently used than the others (more than 20 times each, constituting 67% of the nights). Four species of tree (Peltophorum dubium, Parapiptadenia rigida, Copaifera langsdorfii and Cordia trichotoma) were the most frequently used. They constituted 82% of all the trees used, though they represent only 12% of the trees within the monkeys' home range which had a diameter at breast height (DBH) > 48.16 cm (1 SD below the mean DBH of sleeping trees). The sleeping trees share a set of characteristics not found in other trees: they are tall emergent (mean height +/- SD = 31.1+/-5.2 m) with large DBH (78.5+/-30.3 cm), they have large crown diameter (14+/-5.5 m), and they have many horizontal branches and forks. Adult females usually slept with their kin and infants, while peripheral adult males sometimes slept alone in nearby trees. We reject parasite avoidance as an adaptive explanation for the pattern of sleeping site use. Our results and those from other studies suggest that predation avoidance is a predominant factor driving sleeping site preferences. The patterns of aggregation at night and the preference for trees with low probability of shedding branches suggest that social preferences and safety from falling during windy nights may also affect sleeping tree selection. The importance of other factors, such as seeking comfort and maintaining group cohesion, was not supported by our results. Other capuchin populations show different sleeping habits which can be explained by differences in forest structure and by demographic differences.     

Forest Fragmentation Modifies Habitat Quality for Alouatta palliata

Fragmentation reduces habitat area, increases the number of habitat patches, decreases their size, and increases patch isolation. For arboreal mammals such as howlers (Alouatta palliata), canopy modifications from fragmentation processes could also negatively affect habitat quality. We analyzed changes in the composition and plant structure of 15 fragments (1–76 ha) and compared them with vegetation from a continuous tropical rain forest reserve (700 ha) in Los Tuxtlas, Mexico. At each site, we sampled 1000 m² of all trees, shrubs, and lianas with a diameter at breast height (DBH) ≥10 cm. We obtained estimates of species richness, density, and basal area for different ecological groups, DBH ranges, and top food resources for howlers. We used a stepwise multiple regression analysis to determine relationships between fragment characteristics (size, shape index, and isolation) and plant variables. Compared to continuous forest, fragments have altered composition and plant structure, with large trees absent from the canopy. The basal area of top food resources is higher in continuous forest. Fragment size is the best explanation for the differences in composition and plant structure. The largest fragments had greater basal area of top food resources and more large primary trees in the canopy. Overall, our results suggest that fragmentation altered the habitat quality for howlers.     

辽东山区原始阔叶红松林主要树种空间结构特征

维持森林结构多样性通常被认为是确保森林生态系统稳定性和生物多样性的有效方式.本研究以辽东山区原始阔叶红松林为对象,运用相邻木空间关系构建林分空间结构参数,探究顶极群落内部主要优势乔木的空间结构特征,并以此顶极群落为借鉴,为低质量次生林改造和人工纯林结构优化经营提供参考.结果表明: 辽东山区原始阔叶红松林林分的径级分布呈倒“J”形,林下更新良好,同时保持一定比例的大径木存在;林分平均角尺度为0.507,整体呈随机分布状态,混交度平均值为0.82,混交度强;平均大小比数为0.506,反映出林分整体处于中庸状态.林分中不同优势度在极强混交维度下出现了一定程度的分化,反映出处于中下层绝对劣势的小径级被压木和主林层的绝对优势木在不同垂直空间上的优化分布与利用.林分中各优势树种的分布也随机镶嵌于总体的随机格局之中.     

Above-ground biomass estimation in closed canopy Neotropical forests using lidar remote sensing: factors affecting the generality of relationships

Aim Previous studies have developed strong, site‐specific relationships between canopy metrics from lidar (light detecting and ranging) remote sensing data and forest structural characteristics such as above‐ground biomass (AGBM), but the generality of these relationships is unknown. In this study, we examine the generality of relationships between lidar metrics and forest structural characteristics, including AGBM, from two study areas in Central America with different precipitation patterns. Location A series of tropical moist forest sites in Panama and a tropical wet forest in Costa Rica. Methods Canopy metrics (e.g. canopy height) were calculated from airborne lidar data. Basal area, mean stem diameter and AGBM were calculated from measurements taken as a part of ongoing forest dynamics studies in both areas. We examined the generality of relationship between lidar metrics and forest structure, and possible environmental effects (e.g. leaf phenology). Results We found that lidar metrics were strongly correlated (R²: 0.65–0.92) with mean stem diameter, basal area and AGBM in both regions. We also show that the relationships differed between these regions. Deciduousness of canopy trees in the tropical moist forest area accounted for the differences in predictive equations for stem diameter and basal area. The relationships between lidar metrics and AGBM, however, remained significantly different between the two study areas even after adjusting for leaf drop. We attribute this to significant differences in the underlying allometric relationships between stem diameter and AGBM in tropical wet and moist forests. Conclusions Important forest structural characteristics can be estimated reliably across a variety of conditions sampled in these closed‐canopy tropical forests. Environmental factors such as drought deciduousness have an important influence on these relationships. Future efforts should continue to examine climatic factors that may influence the generality of the relationships between lidar metrics and forest structural characteristics and assess more rigorously the generality of field‐derived allometric relationships.     

Structure of the Epiphyte Community in a Tropical Montane Forest in SW China

Vascular epiphytes are an understudied and particularly important component of tropical forest ecosystems. However, owing to the difficulties of access, little is known about the properties of epiphyte-host tree communities and the factors structuring them, especially in Asia. We investigated factors structuring the vascular epiphyte-host community and its network properties in a tropical montane forest in Xishuangbanna, SW China. Vascular epiphytes were surveyed in six plots located in mature forests. Six host and four micro-site environmental factors were investigated. Epiphyte diversity was strongly correlated with host size (DBH, diameter at breast height), while within hosts the highest epiphyte diversity was in the middle canopy and epiphyte diversity was significantly higher in sites with canopy soil or a moss mat than on bare bark. DBH, elevation and stem height explained 22% of the total variation in the epiphyte species assemblage among hosts, and DBH was the most important factor which alone explained 6% of the variation. Within hosts, 51% of the variation in epiphyte assemblage composition was explained by canopy position and substrate, and the most important single factor was substrate which accounted for 16% of the variation. Analysis of network properties indicated that the epiphyte host community was highly nested, with a low level of epiphyte specialization, and an almost even interaction strength between epiphytes and host trees. Together, these results indicate that large trees harbor a substantial proportion of the epiphyte community in this forest.     

Discontinuous DBH–height relationship of <Emphasis Type="Italic">Cryptomeria japonica</Emphasis> on Yakushima Island: effect of frequent typhoons on the maximum height

The mountain zone of Yakushima Island is covered with a mixed conifer-broadleaved forest dominated by old-growth Cryptomeria japonica (L.f.) D. Don trees. Even though Yakushima Island has been frequently struck by typhoons with wind velocities exceeding 55 m s⁻¹, the Cr. japonica trees in the mountain zone have survived for thousands of years without fatal damage. To evaluate the effect of storms on tree growth, the relationships between the stem diameter at breast height (DBH) and the heights of Cr. japonica and coexistent tree species were investigated. Two models based on an expanded allometric equation and a discontinuous piecewise allometric equation, respectively, to represent DBH–height relationships were evaluated. In all plots, the DBH–height relationship of Cr. japonica was discontinuous between small DBH and large DBH individuals. The tops of the large DBH individuals of Cr. japonica were lost to strong winds. However in each instance, they occupied the highest position in the canopy, even if they had lost their tops. In contrast, the DBH–height relationships of subcanopy broadleaved species were continuous in many plots and the equilibrium heights of the dominant broadleaved species were similar and almost in the same order regardless of the canopy heights of Cr. japonica. These results revealed a constant vertical structure in the Cr. japonica forest on Yakushima Island. Our results demonstrate a vertical niche segregation in the forest under high wind pressures and such vertical structure enables effective use of forest space and increases the basal area density.     

The effects of disturbance on the population structure and regeneration potential of five dominant woody species – in Hugumburda‐Gratkhassu National Forest Priority Area,North‐eastern Ethiopia

Vast areas of forests in North‐eastern Ethiopia have been replaced by cropland, shrub land or grazing areas. Thus, information about how vegetation composition and structure varies with disturbance is fundamental to conservation of such areas. This study aimed to investigate the effects of disturbance on the population structure and regeneration potential of five dominant woody species within forest where local communities harvest wood and graze livestock. Vegetation structure and environmental variables were assessed in 50 quadrats (20 m × 20 m). In most of both disturbed and undisturbed treatments, Juniperus procera was the highest contributor to the basal area of the forest, while that of Olinia rochetiana was the lowest. Analysis of population structure showed high density at lower Diameter at Breast Height (DBH) and low density at higher DBH classes. Undisturbed forest treatments had 84% canopy cover, 22 m mean vegetation height and a density of 1320 trees of dominant species and 1024 seedlings/saplings ha^?1. In disturbed habitats, canopy cover (73%), mean vegetation height (18 m) and density of dominant trees and saplings were significantly lower than in undisturbed habitats. Thus, to ensure species, survival and maintain species diversity managed use of the protected area is essential.     

Near‐ground solar radiation along the grassland–forest continuum: Tall‐tree canopy architecture imposes only muted trends and heterogeneity

Solar radiation directly and indirectly drives a variety of ecosystem processes. Our aim was to evaluate how tree canopy architecture affects near‐ground, incoming solar radiation along gradients of increasing tree cover, referred to as the grassland–forest continuum. We evaluated a common type of canopy architecture: tall trees that generally have their lowest level of foliage high above, rather than close to the ground as is often the case for shorter trees. We used hemispherical photographs to estimate near‐ground solar radiation using the metric of Direct Site Factor (DSF) on four sites in north Queensland, Australia that formed a grassland–forest continuum with tree canopy cover ranging from 0% to 71%. Three of the four sites had tall Eucalyptus trees with foliage several metres above the ground. We found that: (i) mean DSF exceeded >70% of the potential maximum for all sites, including the site with highest canopy cover; (ii) DSF variance was not highly sensitive to canopy coverage; and (iii) mean DSF for canopy locations beneath trees was not significantly lower than for adjacent intercanopy locations. Simulations that hypothetically placed Australian sites with tall tree canopies at other latitude–longitude locations demonstrated that differences in DSF were mostly due to canopy architecture, not specific site location effects. Our findings suggest that tall trees that have their lowest foliage many metres above the ground and have lower foliar density only weakly affect patterns of near‐ground solar radiation along the grassland–forest continuum. This markedly contrasts with the strong effect that shorter trees with foliage near the ground have on near‐ground solar radiation patterns along the continuum. This consequence of differential tree canopy architecture will fundamentally affect other ecosystem properties and may explain differential emphases that have been placed on canopy–intercanopy heterogeneity in diverse global ecosystem types that lie within the grassland–forest continuum.     

Habitat preferences of the secretive forest buffalo (Syncerus caffer nanus) in Central Africa

The forest buffalo Syncerus caffer nanus is one of the three subspecies of African buffalo inhabiting the rainforests of Western and Central Africa. Because of its secretive behaviour and main habitat (dense rainforests), there is little quantitative information on the habitat preferences of this buffalo. We present here the first data on the frequencies of this species along a habitat gradient ranging from clearings and rivers to forests, as well as the characteristics of the buffalo's resting places. We recorded information from a buffalo herd during the period January 2002–January 2004 in the Bai-Hokou area (Dzanga-Ndoki National Park, Central African Republic). Resting places were firstly compared with available habitat (i.e. resting vs. random sites) and, successively, comparisons were made between diurnal versus nocturnal and wet versus dry season resting places. Forest buffalos were found to be highly dependent on clearings, as well as on the more open forest stands, characterized by large trees and open canopy. Such preferences could be due to the tendency of the buffalos to rest all together; open patches are likely to facilitate social interactions between the members of the herd.     

马占相思林冠层气孔导度对环境驱动因子的响应

利用Granier热消散探针在2003年10月测定了广东鹤山丘陵地马占相思林14株样树的树干液流,同时监测林冠上方的光合有效辐射、空气湿度和气温,结合树木的形态和林分的结构特征,计算马占相思的整树蒸腾(E)、林分总蒸腾(E_t)以及冠层平均气孔导度(g_c),分析树形特征与整树水分利用的关系、冠层气孔导度对光合有效辐射(PAR)和空气水汽压亏缺(D)的响应.结果表明,整树蒸腾与胸径(P＜0.0001)、边材面积(P＜0.0001)和冠幅(P=0.0007)以自然对数的形式、与树高(P=0.014)以幂函数的形式呈现显著正相关.冠层气孔导度最大值(g_cmax)随D的上升呈对数函数下降(P＜0.0001),对光合有效辐射的响应则呈双曲线函数增加(P＜0.0001).液流测定系统能提供连续和准确的整树和林分蒸腾速率值,经严格数学推导公式计算,最终可求出冠层气孔导度,是研究森林水分利用与环境因子相互关系的有效方法.     

Effects of size,neighbors, and site condition on tree growth in a subtropical evergreen and deciduous broad‐leaved mixed forest,China

Successful growth of a tree is the result of combined effects of biotic and abiotic factors. It is important to understand how biotic and abiotic factors affect changes in forest structure and dynamics under environmental fluctuations. In this study, we explored the effects of initial size [diameter at breast height (DBH)], neighborhood competition, and site condition on tree growth, based on a 3‐year monitoring of tree growth rate in a permanent plot (120 × 80 m) of montane Fagus engleriana–Cyclobalanopsis multiervis mixed forest on Mt. Shennongjia, China. We measured DBH increments every 6 months from October 2011 to October 2014 by field‐made dendrometers and calculated the mean annual growth rate over the 3 years for each individual tree. We also measured and calculated twelve soil properties and five topographic variables for 384 grids of 5 × 5 m. We defined two distance‐dependent neighborhood competition indices with and without considerations of phylogenetic relatedness between trees and tested for significant differences in growth rates among functional groups. On average, trees in this mixed montane forest grew 0.07 cm year^?1 in DBH. Deciduous, canopy, and early‐successional species grew faster than evergreen, small‐statured, and late‐successional species, respectively. Growth rates increased with initial DBH, but were not significantly related to neighborhood competition and site condition for overall trees. Phylogenetic relatedness between trees did not influence the neighborhood competition. Different factors were found to influence tree growth rates of different functional groups: Initial DBH was the dominant factor for all tree groups; neighborhood competition within 5 m radius decreased growth rates of evergreen trees; and site condition tended to be more related to growth rates of fast‐growing trees (deciduous, canopy, pioneer, and early‐successional species) than the slow‐growing trees (evergreen, understory, and late‐successional species).     

Tree and forest characteristics influence sleeping site choice by golden lion tamarins

Lion tamarin monkeys are among a small number of primates that repeatedly use a few tree holes for the majority of their sleeping sites. To better understand why lion tamarins rely on tree holes as sleeping sites, we compared the physical characteristics of frequently used sleeping sites, infrequently used sleeping sites, and randomly selected forest locations at multiple spatial scales. From 1990 to 2004, we recorded 5,235 occurrences of sleeping site use by 10 groups of golden lion tamarins (Leontopithecus rosalia) in Poço das Antas Reserve, Rio de Janeiro State, Brazil. Of those, 63.6% were tree holes. Bamboo accounted for an additional 17.5% of observations. Frequently used tree holes were more likely to be found in living trees and their entrances were at lower canopy heights than infrequently used tree holes. We also found that frequently used sleeping sites, in comparison to random sites, were more likely to be found on hillsides, be close to other large trees, have a lower percent of canopy cover, and have larger diameter at breast height. Topography and small‐scale variables were more accurate than were habitat‐level classifications in predicting frequently used sleeping sites. There are ample tree holes available to these lion tamarins but few preferred sites to which they return repeatedly. The lion tamarins find these preferred sites wherever they occur including in mature forest and in relics of older forest embedded in a matrix of secondary forest. Am. J. Primatol. 69:976–988, 2007. © 2007 Wiley‐Liss, Inc.     

Linking dominant Hawaiian tree species to understory development in recovering pastures via impacts on soils and litter

Large areas of tropical forest have been cleared and planted with exotic grass species for use as cattle pasture. These often remain persistent grasslands after grazer removal, which is problematic for restoring native forest communities. It is often hoped that remnant and/or planted trees can jump‐start forest succession; however, there is little mechanistic information on how different canopy species affect community trajectories. To investigate this, I surveyed understory communities, exotic grass biomass, standing litter pools, and soil properties under two dominant canopy trees—Metrosideros polymorpha (‘ōhi‘a) and Acacia koa (koa)—in recovering Hawaiian forests. I then used structural equation models (SEMs) to elucidate direct and indirect effects of trees on native understory. Native understory communities developed under ‘ōhi‘a, which had larger standing litter pools, lower soil nitrogen, and lower exotic grass biomass than koa. This pattern was variable, potentially due to historical site differences and/or distance to intact forest. Koa, in contrast, showed little understory development. Instead, data suggest that increased soil nitrogen under koa leads to high grass biomass that stalls native recruitment. SEMs suggested that indirect effects of trees via litter and soils were as or more important than direct effects for determining native cover. It is suggested that diverse plantings which incorporate species that have high carbon to nitrogen ratios may help ameliorate the negative indirect effects of koa on natural understory regeneration.     

Spatial and temporal dynamics of forest canopy gaps following selective logging in the eastern Amazon

Selective logging is a dominant form of land use in the Amazon basin and throughout the humid tropics, yet little is known about the spatial variability of forest canopy gap formation and closure following timber harvests. We established chronosequences of large‐area (14–158 ha) selective logging sites spanning a 3.5‐year period of forest regeneration and two distinct harvest methods: conventional logging (CL) and reduced‐impact logging (RIL). Our goals were to: (1) determine the spatial characteristics of canopy gap fraction immediately following selective logging in the eastern Amazon; (2) determine the degree and rate of canopy closure in early years following harvest among the major landscape features associated with logging – tree falls, roads, skid trails and log decks; and (3) quantify spatial and temporal differences in canopy opening and closure in high‐ and low‐damage harvests (CL vs. RIL). Across a wide range of harvest intensities (2.6–6.4 felled trees ha^?1), the majority of ground damage occurred as skid trails (4–12%), whereas log decks and roads were only a small contributor to the total ground damage (<2%). Despite similar timber harvest intensities, CL resulted in more ground damage than RIL. Neither the number of log decks nor their individual or total area was correlated with the number of trees removed or intensity of tree harvesting (trees ha^?1). The area of skids was well correlated with the ground area damaged (m²) per tree felled. In recently logged forest (0.5 years postharvest), gap fractions were highest in log decks (mean RIL=0.83, CL=0.99) and lowest in tree‐fall areas (RIL: 0.26, CL: 0.41). However, the small surface area of log decks made their contribution to the total area‐integrated forest gap fraction minor. In contrast, tree falls accounted for more than two‐thirds of the area disturbed, but the canopy gaps associated with felled trees were much smaller than for log decks, roads and skids. Canopy openings decreased in size with distance from each felled tree crown. At 0.5 years postharvest, the area initially affected by the felling of each tree was approximately 100 m in radius for CL and 50 m for RIL. Initial decreases in gap fraction during the first 1.5 years of regrowth diminished in subsequent years. Throughout the 3.5‐year period of forest recovery, tree‐fall gap fractions remained higher in CL than in RIL treatments, but canopy gap closure rates were higher in CL than in RIL areas. During the observed recovery period, the canopy gap area affected by harvesting decreased in radius around each felled tree from 100 to 40 m in CL, and from 50 to 10 m in RIL. The results suggest that the full spatial and temporal dynamics of canopy gap fraction must be understood and monitored to predict the effects of selective logging on regional energy balance and climate regimes, biogeochemical processes including carbon cycling, and plant and faunal population dynamics. This paper also shows that remote sensing of log decks alone will not provide an accurate assessment of total forest area impacted by selective logging, nor will it be closely correlated to damage levels and canopy gap closure rates.     

Reconsidering the importance of harvested forests for the conservation of tree-dwelling bats

Intensively managed forests are often seen as of low priority to preserve forest bats. The main conservation strategy recommended, i.e. saving unmanaged “habitat islands” from logging to preserve some suitable habitat, detracts conservationists’ attention from ameliorating conditions for bats in harvested sites. We studied the threatened bat Barbastella barbastellus, mostly roosting in snags, in two beech forests: an unmanaged forest—the main maternity site—and a nearby, periodically logged area. We compared roost availability, roost use, capture rates, food availability and movement between these areas. The managed forest had a greater canopy closure, fewer dead trees, a smaller tree diameter and trees bearing fewer cavities than the unmanaged one. These differences helped explain the larger number of bats recorded in the unmanaged forest, where the sex ratio was skewed towards females. Prey availability was similar in both areas. We radiotracked bats to 49 day roosts. Five individuals caught in the managed area roosted in the unmanaged one at 6.7–8.2 km from the capture site. Few bats roosted in the managed forest, but those doing so proved flexible, using live trees and even rock crevices. Therefore, bats utilise areas in the matrix surrounding optimal roosting sites and sometimes roost there, highlighting the conservation potential of harvested forests. Besides leaving unmanaged patches, at least small numbers of dead trees should be retained in logged areas to favour population expansion and landscape connectivity. Our findings also question the validity of adopting presence records as indicators of forest quality on a site scale.     

Hiding Without Cover? Defining Elk Security in a Beetle-Killed Forest

Recent mountain pine beetle (Dendroctonus ponderosae; pine beetle) outbreaks in the western United States have affected nearly 18 million ha of pine (Pinus spp.) forest and are unprecedented in spatial extent, severity, and duration, yet little is known about wildlife responses to large-scale insect outbreaks. Elk (Cervus canadensis) are important wildlife whose dominant management paradigm on public lands has focused on providing security habitat to increase survival during hunting seasons and to maintain elk presence on public lands to promote hunter opportunity. To assess the effect of pine beetles and associated changes in forest structure on elk security, we used a time series to characterize canopy cover pre- and post-pine beetle outbreak, characterized relative canopy cover among the dominant forest types in the study area post-pine beetle outbreak, and used global positioning system location data from male and female elk to define habitat relationships and security during the archery and rifle hunting seasons. Our study area was within the Elkhorn Mountains of southwest Montana, USA, 2015–2017, which experienced 80% mortality of lodgepole pine (Pinus contorta) forests during a pine beetle outbreak that peaked in 2008. We observed an 8.5% reduction in canopy cover within pine beetle-infested lodgepole pine forests, yet canopy cover remained relatively high among other forest types post-outbreak. The top-ranked habitat security models contained positive relationships with canopy cover, distance to motorized routes, terrain ruggedness, and slope with few notable differences among sexes and seasons. Across sexes and seasons, 75% and 50% of elk use was within areas with average canopy cover values ≥31 ± 6.65 (SD)% and ≥53 ± 5.7% that were an average of ≥2,072 ± 187.93 m and ≥3,496 ± 157.32 m from a motorized route, respectively. Therefore, we recommend fall elk security be defined as areas that meet these criteria for minimum canopy cover and distance from motorized routes in the Elkhorn Mountains and in other landscapes with similar forest characteristics and hunting pressures. Although we observed expected reductions in canopy cover within pine beetle-infested forests, defoliation alone did not appear to negatively affect elk security or reduce canopy cover below our management recommendations. Nonetheless, because of the prevalence of standing dead trees in our study area, we recommend future work that investigates the relationships with pine beetle-infested areas post-blowdown because changes in ground structure and costs of locomotion may affect elk habitat and security. © 2019 The Authors. Journal of Wildlife Management published by Wiley Periodicals, Inc. on behalf of The Wildlife Society.     

中国东部森林样带典型森林水源涵养功能

通过对我国东部森林样带四个森林生态系统定位研究站（长白山站、北京站、会同站和鼎湖山站）的九种森林类型水源涵养监测数据的分析,研究了水热梯度下不同森林生态系统水源涵养功能。结果表明：在生长季的5-10月份,各森林类型的水源涵养特性表现出较大差异。林冠截留率的大小依次为：阔叶红松林＞杉木林＞常绿阔叶林＞针阔混交林＞季风常绿阔叶林＞落叶阔叶混交林＞马尾松林＞落叶松林＞油松林,最高的长白山站阔叶红松林的截留率是最低的北京站油松林的2.2倍。森林降雨截留量与林外降雨量呈显著的正相关,林冠截留率与降雨量呈显著负相关。枯落物最大持水深（5-10月份）以北京站落叶阔叶林最大,为6.0mm;鼎湖山站的季风常绿阔叶林最小,为1.0mm。0-60cm土层蓄水量最大的是会同站的人工杉木林,为247mm;最小的是北京站的落叶松林,仅为45.5mm;林分总持水量依次为：杉木林＞阔叶红松林＞常绿阔叶林＞针阔混交林＞季风常绿阔叶林＞落叶阔叶混交林＞马尾松林＞落叶松林＞油松林。各林分总持水量主要集中在土壤层,占总比例的90%以上。     

Tree mortality due to an El Niño flood along the lower Tana River, Kenya

This study investigated forest tree mortality as a result of the extremely strong 1997–1998 El Niño flood in Tana River, Kenya, directly tested how mortality varied in relation to tree species and diameter at breast height (DBH), and indirectly tested how mortality varied in relation to floodwater depth. The study forest was under 2 m of water for approximately 71 days, from December 1997 until February 1998. Twenty-five liana, subcanopy tree, and canopy tree species were selected based on their importance in the diet of the Tana River mangabey ( Cercocebus galeritus Peters), a critically endangered primate endemic to the Tana River. Reproductive-sized individuals of these species were enumerated in 16.25 ha. I also enumerated trees killed by the El Niño flood, recorded their location in the forest, and measured their DBH. Ninety-two trees in fifteen species were killed by the flood. There were significant differences in mortality by species and by 0.25 ha quadrat. There were negative correlations between number of dead and DBH, number of dead and distance from the river, and per cent of quadrat killed and distance from the river. There appear to have been few long-term consequences of the El Niño flood in the forest or for the mangabeys.     

Insect diversity: facts,fiction and speculation*

Biologists are still trying to grasp the global dimensions of the phylum Arthropoda and its major class the Insecta, in spite of the fact that over a million species of arthropods have been described. The canopy of rain forest trees is believed by many to hold the key to the immense diversity of insects. In recent years the use of knock-down insecticides to sample insects from rain forest canopy has revealed information on the canopy's arthropod inhabitants and community structure. The sampling techniques involved are outlined and data reviewed on taxonomic and guild structure, species abundance, body size and biomass of insects, and the faunal similarity of trees. Calculations by Erwin (1982), based on knock-down insecticide studies of the beetle fauna of one species of Central American tree, suggest there may be 30 million species of tropical forest arthropods. Reanalysis of these calculations, using additional data, produces a range of possible estimates from about 10 to 80 million. The unknown range of plant host-specificities of tropical insects is the main weakness of this method of calculation. Assessment of the faunal importance of the canopy in relation to that of other rain forest biotopes requires comparative quantitative studies. The preliminary results of one such simple study suggest that over 42 million arthropods may be found in a hectare of Seram rain forest (at the time of study), and that 70% occur in the soil and leaf litter and 14% in the canopy. They also suggest that Collembola and Acarina are the dominant groups in this hectare, and that there are as many ants as all the other insects (excluding Collembola).