Showing papers on "Tree canopy published in 2004"

Response of the herbaceous layer to natural disturbance in North American forests

Abstract: Most work on the disturbance ecology of North American forests has focused on the tree canopy and woody understory, with little consideration of the herbaceous layer. Understanding how this species...

Canopy recovery after drought dieback in holm‐oak Mediterranean forests of Catalonia (NE Spain)

Abstract: Climate change is likely to produce more frequent and longer droughts in the Mediterranean region, like that of 1994, which produced important changes in the Quercus ilex forests, with up to 76% of the trees showing complete canopy dieback. At the landscape level, a mosaic of responses to the drought was observed, linked to the distribution of lithological substrates. Damage to the dominant tree species (Q. ilex) and the most common understorey shrub (Erica arborea) was more noticeable on the compact substrates (breccia) than on the fissured ones (schist). This result was consistent with observations documenting deeper root penetration in schist than in breccia materials, allowing the plants growing on fissured substrates to use water from deeper soil levels. Smaller plants were more vulnerable to drought than larger plants in the trees, but not in the shrubs. Overall, Q. ilex was more affected than E. arborea. The resilience of the system was evaluated from the canopy recovery 1 year after the episode. Stump and crown resprouting was fairly extensive, but the damage pattern in relation to substrate, plant size, and species remained similar. The effect of recurrent drought episodes was studied on vegetation patches of Q. ilex located on mountain slopes and surrounded by bare rock. We observed that plants that resprouted weakly after a previous drought in 1985 were more likely to die or to produce poor regeneration in 1995 than plants that had resprouted vigorously. Vegetation patches located on the lower part of the slope were also less damaged than patches situated uphill. The study provides evidence of relevant changes in forest canopy as a consequence of extreme climate events. The distribution of this effect across the landscape is mediated by lithological substrate, causing patchy patterns. The results also support the hypothesis that recurrent droughts can produce a progressive loss of resilience, by depleting the ability of surviving plants to regenerate.

Canopy damage and recovery after selective logging in amazonia: field and satellite studies

Abstract: We combined a detailed field study of canopy gap fraction with spectral mixture analyses of Landsat 7 ETM1 satellite imagery to assess landscape and regional dynamics of canopy damage following selective logging in an eastern Amazon forest. Our field studies encompassed measurements of ground damage and canopy gap fractions along multitemporal sequences of post-harvest regrowth of 0.5-3.5 yr. Areas used to stage har- vested logs prior to transport, called log decks, had the largest forest gap fractions, but their contribution to the landscape-level gap dynamics was minor. Tree falls were spatially the most extensive form of canopy damage following selective logging, but the canopy gap fractions resulting from them were small. Reduced-impact logging resulted in consistently less damage to the forest canopy than did conventional logging practices. This was true at the level of individual landscape strata such as roads, skids, and tree falls as well as at the area-integrated scale. A spectral mixture model was employed that utilizes bundles of field and image spectral reflectance measurements with Monte Carlo analysis to estimate high spatial resolution (subpixel) cover of forest canopies, exposed nonphotosynthetic vegetation, and soils in the Landsat imagery. The method proved highly useful for quantifying forest canopy cover fraction in log decks, roads, skids, tree fall, and intact forest areas, and it tracked canopy damage up to 3.5 yr post-harvest. Forest canopy cover fractions derived from the satellite observations were highly and inversely correlated with field-based canopy gap fraction. Subsequent regional-scale estimates of forest gap fraction were derived from the combi- nation of field- and satellite-based measurements. A 450-km 2 study of gap fraction showed that approximately one-half of the canopy opening caused by logging is closed within one year of regrowth following timber harvests. This is the first regional-scale study utilizing field measurements, satellite observations, and models to quantify forest canopy damage and recovery following selective logging in the Amazon.

A portable LIDAR system for rapid determination of forest canopy structure

Abstract: Summary 1. The functional characteristics of forests are related to the organization of their canopies. However, understanding the relationship between canopy structure and function has been limited by a paucity of methods for determining structure at scales consistent with those of function measurements. 2. We describe here a portable system, assembled from commercially available components, for acquiring measurements of distances to overhead plant surfaces. These measurements can be aggregated to assess canopy structure rapidly at scales of ecological interest. Deployed from the forest floor, the system includes a narrow-beam rapidly pulsed first-return laser rangefinder coupled with a data recording system. 3. Tests in an age sequence of broad-leaved closed-canopy forests showed that the system provides results significantly more rapidly than previous methods, at spatial scales as small as 1 m in all dimensions. The estimated mean vertical canopy structure is consistent with that found from more laborious, manual approaches, such as the foliage height profile method. The system has some biases due to beam width and range averaging but, from a variety of tests, we found these have relatively little effect on the structure estimates. 4. Various field sampling schemes and methods of aggregating the measurements yield a variety of representations of structure, including mean profiles, tomographic sections, three-dimensional distributions of canopy surface density and maximum height surfaces. Derivable summary measures include canopy cover and area index, porosity, the size distribution of overhead openings and indices of structural complexity. Moreover, the approach can provide estimates of spatial variability and covariance not previously obtainable. 5. Synthesis and applications. Portable light detection and ranging (LIDAR) systems, such as the one we describe here, provide a new tool for rapid measurement of small-scale forest structure. These can contribute efficiently and relatively inexpensively to canopy research and forestry programmes, covering a range of ecological and production needs.

Coordinated changes in photosynthesis, water relations and leaf nutritional traits of canopy trees along a precipitation gradient in lowland tropical forest

Abstract: We investigated leaf physiological traits of dominant canopy trees in four lowland Panamanian forests with contrasting mean annual precipitation (1,800, 2,300, 3,100 and 3,500 mm). There was near complete turn-over of dominant canopy tree species among sites, resulting in greater dominance of evergreen species with long-lived leaves as precipitation increased. Mean structural and physiological traits changed along this gradient as predicted by cost-benefit theories of leaf life span. Nitrogen content per unit mass (Nmass) and light- and CO2-saturated photosynthetic rates per unit mass (Pmass) of upper canopy leaves decreased with annual precipita- tion, and these changes were partially explained by increasing leaf thickness and decreasing specific leaf area (SLA). Comparison of 1,800 mm and 3,100 mm sites, where canopy access was available through the use of construction cranes, revealed an association among extended leaf longevity, greater structural defense, higher midday leaf water potential, and lower Pmass ,N mass, and SLA at wetter sites. Shorter leaf life spans and more enriched foliar δ 15 N values in drier sites suggest greater resorption and re-metabolism of leaf N in drier forest. Greater dominance of short-lived leaves with relatively high Pmass in drier sites reflects a strategy to maximize photosynthesis when water is available and to minimize water loss and respiration costs during rainless periods. Overall, our study links coordinated change in leaf functional traits that affect productivity and nutrient cycling to seasonality in lowland tropical forests.

A Sensitivity Study of Daytime Net Radiation during Snowmelt to Forest Canopy and Atmospheric Conditions

Abstract: This study investigates the dependence of net radiation at snow surfaces under forest canopies on the overlying canopy density. The daily sum of positive values of net radiation is used as an index of the snowmelt rate. Canopy cover is represented in terms of shortwave transmissivity and sky-view factor. The cases studied are a spruce forest in the Wolf Creek basin, Yukon Territory, Canada, and a pine forest near Fraser, Colorado. Of particular interest are the atmospheric conditions that favor an offset between shortwave energy attenuation and longwave irradiance enhancement by the canopy, such that net radiation does not decrease with increasing forest density. Such an offset is favored in dry climates and at high altitudes, where atmospheric emissivities are low, and in early spring when snow albedos are high and solar elevations are low. For low snow albedos, a steady decrease in snowmelt energy with increasing canopy cover is found, up to a forest density close to the actual densities of mature spruce forests. Snowmelt rates for high albedos are either insensitive or increase with increasing canopy cover. At both sites, foliage area indices close to 2 are associated with a minimum in net radiation, independent of snow albedo or cloud cover. However, these results are more uncertain for open forests because solar heating of trees may invalidate the longwave assumptions, increasing the longwave irradiance.

NOTES AND CORRESPONDENCE An Empirical Relation Describing Leaf-Area Density inside the Forest for Environmental Modeling

Abstract: The spatial distribution of the leaf-area density is a key parameter in describing the forest canopy characteristics, which has a strong impact on its radiation balance and the mass and energy exchange with the atmosphere as well. The objective of this short study is to define an empirical relation describing the vertical distribution of leaf-area density that can be used for an improved estimation of the turbulent transfer coefficient inside the forest as well as above it. To check the validity of the method proposed, the calculated values are compared with the observations using datasets from eight observational sites located in four different types of forest, covering a broad range of mean values of leaf-area indices between 2 and 18.

An Empirical Relation Describing Leaf-Area Density inside the Forest for Environmental Modeling

Abstract: The spatial distribution of the leaf-area density is a key parameter in describing the forest canopy characteristics, which has a strong impact on its radiation balance and the mass and energy exchange with the atmosphere as well. The objective of this short study is to define an empirical relation describing the vertical distribution of leaf-area density that can be used for an improved estimation of the turbulent transfer coefficient inside the forest as well as above it. To check the validity of the method proposed, the calculated values are compared with the observations using datasets from eight observational sites located in four different types of forest, covering a broad range of mean values of leaf-area indices between 2 and 18.

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

Abstract: 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 reducedimpact 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 (o2%). 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 (m 2 ) per tree felled. In recently logged forest (0.5 years postharvest), gap fractions were highest in log decks (mean RIL 5 0.83, CL 5 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 areaintegrated forest gap fraction minor. In contrast, tree falls accounted for more than twothirds 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.

Light interception in apple trees influenced by canopy architecture manipulation

Abstract: Improvement of light penetration within tree canopies has been a constant objective of fruit tree architecture manipulation through the setting up of training systems. Recently, centrifugal training, i.e. the removal of fruiting shoots in the tree centre and on the underside of branches, has been proposed to improve fruit size and colour as well as return-bloom as compared to conventional solaxe-trained trees with equivalent crop loads. The present study was conducted to quantify the benefits of centrifugal training on light interception by the fruiting shoots via computer-assisted three-dimensional representations of foliage geometry. Data were collected on six 5-year-old apple trees cv.Galaxy, trained either with solaxe or centrifugal training systems, using an electromagnetic 3D digitiser. The 3D distribution of the foliage in the tree canopy was recreated by combining both the spatial locations of shoots (as measured from 3D digitising) and foliage reconstruction. Light interception efficiency properties of the trees were characterised by silhouette to total area ratio (STAR) values computed from images of the 3D mock-ups. Compared to the solaxe system, centrifugal training significantly improved the STAR of the whole tree by 20%. It also increased both leaf area and STAR of the fruiting shoots by approximately 15%, regardless of their position in the canopy. In this paper, we discuss the role of this enhanced light interception by the canopy in increasing the autonomy of the fruiting shoot, i.e. improved fruit size and colour, and return-bloom.

A tree-scattering model for improved propagation prediction in urban microcells

Abstract: This paper presents a model for the scattering of radiowaves from the canopy of a single tree. The canopy is modeled as a cylindrical volume containing randomly distributed and oriented cylinders, representing the branches, and thin disks, representing the leaves. A simple expression for the incoherent scattered field outside the canopy is obtained using Twersky's multiple scattering theory. This expression is shown to agree well with results of scattering measurements on a live tree typical of those found in urban environments. The scattering model can be readily incorporated in ray-based propagation prediction tools that assist the planning of microcellular radio networks. This involves the use of so-called tree-scattered rays, which interact at the tree centers. Path loss predictions generated with the aid of the new model are shown and compared with measured data to illustrate the considerable improvement in prediction accuracy that can be achieved in realistic urban microcellular scenarios by taking into account the scatter from trees.

Neighborhood analyses of small‐mammal dynamics: impacts on seed predation and seedling establishment

Abstract: The spatial distribution of canopy trees in the temperate deciduous forests of the northeastern United States creates "neighborhoods" that vary in species composition as well as understory features. These neighborhoods may affect the distribution and abun- dance of generalist small-mammal seed predators by creating spatial variation in the avail- ability of food resources, protective cover, and interactions with competitors. Small-mammal distribution and abundance may then influence tree population dynamics through variation in seed predation and seedling establishment. To determine if small-mammal activity pat- terns, seed survival, and seedling recruitment varied with neighborhood structure, we de- signed a study conducted at two habitat levels: canopy-tree neighborhoods, which reflected variation in seed production, and understory neighborhoods, which reflected differences in protective cover and interactions among animals. We live-trapped small mammals during the summer and fall of 1995 and 1996, experimentally measured seed survival in the falls of 1995 and 1996, and quantified total tree seedling recruitment in the spring of 1997. We developed a new method for nonlinear Poisson regression to relate canopy and understory neighborhood composition to small-mammal distribution and activity, seed survival, and seedling establishment. Small-mammal activity patterns changed between 1995 and 1996 in response to seed production. Canopy tree neighborhoods were a good predictor of overall small-mammal activity, and neighborhoods with high small-mammal activity had low seed survival. The canopy-tree neighborhoods with sufficient seed rain and high seed survival displayed increased seedling recruitment. Understory structure was a poor predictor of seed survival and seedling recruitment but appeared to be the primary axis along which habitat partitioning among mammal species took place when population densities were low. This study demonstrates that small-mammal seed predators influence tree recruitment patterns through their actions as seed predators in temperate deciduous forests, and that local effects of small mammals on seedling recruitment can be predicted from the species composition of tree neighborhoods.

Canopy structure in savannas along a moisture gradient on Kalahari sands

Abstract: Measurements of tree canopy architecture were made at six savanna sites on deep, sandy soils, along a gradient of increasing aridity. There was substantial variation in the leaf area estimated within each site, using the same sample frame, but different measurement techniques. The trends in canopy properties in relation to the aridity gradient were consistent, regardless of the technique used for estimating the properties. The effective plant area index for the tree canopy (the sum of the stem area index and the leaf area index (LAI)) declined from around 2 to around 0.8 m 2 m � 2 over a gradient of mean annual rainfall from 1000 to 350 mm. Stems contributed 2–5% of the tree canopy plant area index. Since the tree canopy cover decreased from 50% to 20% over this aridity range, the leaf area index within the area covered by tree canopies remained fairly constant at 3–4 m 2 m � 2 . Tree leaves tended from a horizontal orientation to a more random orientation as the aridity increased. On the same gradient, the leaf minor axis dimension decreased from around 30 mm to around 3 mm, and the mean specific leaf area decreased from 14 to 5 m 2 kg ha � 1 . There was good agreement between LAI observed in the field using a line ceptometer and the LAI inferred by the MODIS sensor on the Terra satellite platform, 2 months later in the same season.

Effects of foliage density and ground speed on ultrasonic measurement of citrus tree volume

Abstract: Ultrasonic sensors can be used to quantify and map tree canopy volume, which is useful for planning site-specific management practices within a grove and estimating crop yield. An experiment was conducted to examine the effects of the canopy foliage density and ground speed on the performance of the Durand-Wayland ultrasonic system in tree volume measurement. Fifteen densely foliated (dense) and 15 partially defoliated (light) citrus trees were scanned from both sides at three ground speeds in three replications. The measurements were compared to those calculated from manual measurements of the tree dimensions. The difference between ultrasonic and manual volumes was used to evaluate the performance of the ultrasonic system. The difference between ultrasonic and manual volumes ranged from –17.3% to 28.71% at the 95% confidence level. Ninety five percent of the ultrasonic measurements were repeatable within –12.7% to 30.9% of the manual volume. Canopy foliage density had significant effect on ultrasonic measurements of canopy volume. The volume difference was higher in light than dense trees. There was no significant effect of ground speed (1.6 to 4.7 km/h) on ultrasonic volume measurements. Variability of the measurements in partially defoliated canopies increased as ground speed increased. There was a significant difference between the volumes of two sides of the trees.

Effects of understory foliage on patterns of light attenuation near the forest floor

Abstract: Understory light availability is an important component of the environment for canopy tree seedlings. Understanding what generates variation in understory light availability represents one step in understanding processes regulating seedling banks, the beginning capital of regeneration in tropical forests. Near the forest floor, variation in light availability may be strongly influenced by the structure and composition of the understory. I examined abundance of understory foliage and patterns of light attenuation in five Neotropical forests (La Selva Biological Station, Costa Rica = LS; Barro Colorado Nature Monument, Panama = BCI; Cocha Cashu Biological Station, Manu National Park, Peru = CC; Kilometer 41, Manaus, Brazil = KM41; and Nouragues, French Guiana = NG). I used hemispherical canopy photos to estimate light availability at two heights (0.65 and 1.7 m) above the forest floor and counted foliage between these heights. Light availability differed significantly among sites, and site rankings depended on measurement height. At 0.65 m, NG had significantly lower mean light availability than CC, with KM41, LS, and BCI equivalent and intermediate. At 1.7 m, light availability was still lowest at NG, and highest at CC, but LS had levels similar to CC while KM41 and BCI remained intermediate. Across sites, light attenuation was positively related to foliage density. LS had the most understory foliage and the highest light attenuation between 0.65 and 1.7 m. KM41, NG and CC had intermediate amounts of foliage and intermediate light attenuation. BCI had the lowest density of understory foliage and no difference between light at the two measurement heights. My results show significant effects of understory foliage on understory light and indicate that the selective environment of canopy tree seedlings differs among sites.

Multivariate control of plant species richness and community biomass in blackland prairie

Abstract: Recent studies have shown that patterns of plant species richness and community biomass are best understood in a multivariate context. The objective of this study was to develop and evaluate a multivariate hypothesis about how herbaceous biomass and richness relate to gradients in soil conditions and woody plant cover in blackland prairies. Structural equation modeling was used to investigate how soil characteristics and shade by scattered Juniperus virginiana trees relate to standing biomass and species richness in 99 0.25 m2 quadrats collected in eastern Mississippi, USA. Analysis proceeded in two stages. In the first stage, we evaluated the hypothesis that correlations among soil parameters could be represented by two underlying (latent) soil factors, mineral content and organic content. In the second stage, we evaluated the hypothesis that richness and biomass were related to (1) soil properties, (2) tree canopy extent, and (3) each other (i.e. reciprocal effects between richness and biomass). With some modification to the details of the original model, it was found that soil properties could be represented as two latent variables. In the overall model, 51% and 53% of the observed variation in richness and biomass were explained. The order of importance for variables explaining variations in richness was (1) soil organic content, (2) soil mineral content, (3) community biomass, and (4) tree canopy extent. The order of importance for variables explaining biomass was (1) tree canopy and (2) soil organic content, with neither soil mineral content nor species richness explaining significant variation in biomass. Based on these findings, we conclude that variations in richness are uniquely related to both variations in soil conditions and variations in herbaceous biomass. We further conclude that there is no evidence in these data for effects of species richness on biomass.

Development of a laser scanner for measuring tree canopy characteristics: Phase 1. Prototype development

Abstract: Automatically measuring canopy characteristics is an essential step for tree-specific management of a grove. Alaser scanning system and corresponding algorithms were developed for potential use in measurement of tree canopy height,width, and volume. Tests with fixed-length PVC pipes demonstrated that the system had accuracies of 97% for length measurementsin three perpendicular directions with coefficients of variation (CV) less than 4%. Volume measurement of a rectangularbox gave a CV of 5.4% and a relative error of 4.4%. Spatial resolution of the system was estimated to be smaller than6.0 cm (horizontal) × 1.9 cm (vertical) for potential field applications.

Drought acclimation of two deciduous tree species of different layers in a temperate forest canopy

Abstract: Water-use strategies of Populus tremula and Tilia cordata, and the role of abscisic acid in these strategies, were analysed. P. tremula dominated in the overstorey and T. cordata in the lower layer of the tree canopy of the temperate deciduous forest canopy. Shoot water potential (Ψ), bulk-leaf abscisic acid concentration ([ABA]leaf), abscisic acid concentration in xylem sap ([ABA]xyl), and rate of stomatal closure following the supply of exogenous ABA (v) decreased acropetally through the whole tree canopy, and foliar water content per area (w), concentration of the leaf osmoticum (c), maximum leaf-specific hydraulic conductance of shoot (L), stomatal conductance (g s), and the threshold dose per leaf area of the exogenous ABA (d a) required to reduce stomatal conductance increased acropetally through the tree canopy (from the base of the foliage of T. cordata to the top of the foliage of P. tremula) in non-stressed trees. The threshold dose per leaf dry mass of the exogenous ABA (d w) required to reduce stomatal conductance, was similar through the tree canopy. After a drought period (3 weeks), the Ψ, w, L, g s, d a and d w had decreased, and c and v had increased in both species. Yet, the effect of the drought period was more pronounced on L, g s, d a, d w and v in T. cordata, and on Ψ, w and c in P. tremula. It was concluded that the water use of the species of the lower canopy layer—T. cordata, is more conservative than that of the species of the overstorey, P. tremula. [ABA]leaf had not been significantly changed in these trees, and [ABA]xyl had increased during the drought period only in P. tremula. The relations between [ABA]leaf, [ABA]xyl and the stomatal conductance, the osmotic adjustment and the shoot hydraulic conductance are also discussed.

Oxidized nitrogen and ozone interaction with forests. I: Experimental observations and analysis of exchange with Douglas fir

Abstract: Measurements of NOx and O3 exchange to and from a forest canopy are described with reference to canopy and ecosystem processes leading to emission of NO2. The soil below the forested measurement location is shown to be a net source of reactive oxidized nitrogen (as NO). It is shown that a large fraction (around 58% on average) of the emitted NO escapes out of the trunk space to react within and above the canopy. Fluxes of NO2 above the canopy are bi-directional, with large fluxes and most emission events taking place during the day. Deposition is shown to take place without significant changes in the vertical flux; however there appears to be rapid chemical reaction leading to significant flux divergence taking place during emission events. Above the top of the canopy (22 m), changes of 200% in the NO2 flux between 25 and 35 m are not uncommon. Ozone deposition to the forest system has been investigated. The flux is often related to stomatal deposition, but there are periods when large non-stomatal fluxes are observed. At night there is a large vertical divergence in the ozone flux above the canopy, probably related to reaction with NO from the forest soil. The reaction of O3 with volatile organic compounds is found, in general, to be negligible with respect to ozone concentrations and fluxes. Ozone is found to deposit mainly to leaf stomata during the day, with a small but not insignificant contribution from NO reaction. However, the nocturnal ozone budget for the forest changes significantly, with most of the measured deposition accounted for by soil uptake and reaction with NO. The resultant problems related to inadequate treatment of air chemistry when interpreting O3 fluxes in high NO emission environments are identified. Copyright © 2004 Royal Meteorological Society.

Arboreal Ant Species Richness in Primary Forest, Secondary Forest, and Pasture Habitats of a Tropical Montane Landscape

Abstract: Canopy invertebrates may reflect changes in tree structure and microhabitat that are brought about by human activities. We used the canopy fogging method to collect ants from tree crowns in primary forest, secondary forest, and pasture in a Neotropical cloud forest landscape. The total number of species collected was similar in primary forest (21) and pasture (20) habitats, but lower in secondary forest (9). Lower diversity in secondary forest was caused by lower species density (no. of species per sample). Rarefaction curves based on number of species occurrences suggest similar community species richness among the three habitats. This study has implications for conservation of tropical montane habitats in two ways. First, arboreal ant species density is reduced if secondary forest replaces primary forest, which increases the chance of extinction among rare species. Second, pasture trees may serve as repositories of primary forest ant communities due to similar tree structure.

Effects of selective logging on the arboreal ants of a Bornean rainforest

Abstract: We examined the effect of selective logging and corresponding forest canopy loss on arboreal ant diversity in a tropical rainforest. Arboreal ants were collected from an unlogged forest plot and from forest plots selectively logged 14 years and 24 years earlier in Danum Valley, Sabah, Malaysia, using a canopy fogging method. Selective logging was associated with a significant decrease in canopy cover and an increase in understory vegetation density relative to unlogged forest. Our study showed that selective logging in primary forest might not dramatically decrease total species number and overall abundance of arboreal ants; however, it may influence the species composition and dominance structure of the ant community, accompanied by an increase in abundance of Shrub-layer species and trophobiotic species. In view of the results of this study, management techniques that minimize logging impact on understory vegetation structure are likely to help maintain the conservation value of logged forests for arboreal ants. Our results also suggest that accurate assessment of the impacts on biodiversity should not be based only on measurement of species number and overall abundance, but also on analysis of species composition and community structure.

Severe drought, leafing phenology, leaf damage and lepidopteran abundance in the canopy of a Bornean aseasonal tropical rain forest

Abstract: Rainfall fluctuation influences the physiology and leaf production of the trees in tropical rain forests (Burslem et al. 1996, Condit et al. 1995, Reekie & Wayne 1992, Reich 1995), and consequently it may have an impact on the community of herbivores that depend on forest trees for their food resources (Aide 1988, 1992; Basset 1991, Coley 1998, Lowman 1985, van Schaik et al. 1993).

Light availability and understory vegetation four years after thinning in a Larix leptolepis plantation of central Korea

Abstract: We measured photosynthetically active radiation (PAR) beneath the forest canopy, understory species’ richness and diversity, and biomass in a Larix leptolepis plantation in central Korea 4 years after thinning. Four different thinning intensities (control, 10%, 20%, and 40% stocking reduction) were applied in 1997. Mean annual intercepted PAR at 30 cm and 1 m above ground level was significantly different among the thinning intensities and strongly correlated with the number of stems remaining after thinning. Understory species richness and diversity were lowest in the unthinned stands and increased with thinning intensity, and there were significant correlations between the total number of understory species or diversity index (Shannon’s diversity index, H″) and the number of stems per hectare after thinning. Also understory above-ground biomass was significantly increased with thinning intensity in both sampling months (June and August 2001). Thinning increased light inputs to the ground and resulted in higher species richness and diversity and above-ground biomass. These results suggested that light availability and understory responses to thinning at a comparable intensity are likely to last well beyond the 4 years of this study.