Effect Of Forest Cover Research Articles

Some hydrological effects of changing forest cover from eucalypts to Pinus radiata

A study of the hydrological effects of clearing a catchment covered by native, dry sclerophyl eucalypt forest, and replanting it with a Pinus radiata plantation was undertaken. The purpose of this study was to examine the effects of vegetation species change and growth rates on streamflow. The water balance of the two forests was observed for a 27-year period; 11 years before and 16 years after the forest conversion. Data on precipitation, canopy interception, forest floor interception and water yield, combined with analysis of the rate of vegetative growth and development of the forest floor litter, enabled investigation of the effects of forest conversion on the water balance components for the whole period (1967–1993). The age of a P. radiata plantation during the first 16 years of its growth greatly affected the streamflow and other water balance components. For the first 4 years after forest conversion, the rates of evapotranspiration and streamflow changed completely. Transpiration and the evaporation of intercepted rainfall ceased after the forest was cleared. The changes in the first 4 years were followed by a further transformation of the whole evapotranspiration process as the pine plantation developed. A trend of increasing evapotranspiration and canopy and forest floor interception losses as the plantation grew, with decreases in runoff, was followed by an equilibrium situation in which streamflow, and the evapotranspiration from soil water storage were smaller than for the native forest.

Variations in snowmelt energy and energy balance characteristics with larch forest density on Mt Iwate, Japan: observations and energy balance analyses

The variation in snowmelt energy and energy components were evaluated with respect to forest density. Surface snowmelt rates, surface evaporation from snow cover and meteorological elements were measured in the open and under sparse (411 trees/ha) and dense (1433 trees/ha) larch canopies. The surface snowmelt rate decreased as the forest density increased. Based on the observations and energy balance analyses, we concluded the following. (1) Albedo decreased while the bulk coefficient for latent heat increased with forest density. (2) The duration of snowmelt increased with forest density because the energy for nocturnal cooling of the snow cover decreased. (3) When comparing the open and forested sites, the changes in snowmelt energy with forest density were caused by sensible heat flux. However, the contribution of net radiation was highest in the forested sites. Therefore, the effects of forest cover on the snowmelt energy were different when comparing both the open and forested sites and the sparse and densely forested sites. (4) The ratio of net radiation to snowmelt energy increased with forest density; although both snowmelt energy and net radiation decreased with increased forest density, the snowmelt energy decreased more rapidly. Sensible heat also decreased as forest density increased. Both albedo and downward long-wave radiation influenced net radiation. Copyright © 1999 John Wiley & Sons, Ltd.

Fragmentation Effects on Forest Birds: Relative Influence of Woodland Cover and Configuration on Landscape Occupancy

Abstract: Habitat fragmentation has been shown to influence the abundance, movements, and persistence of many species. We asked the following questions: (1) Do species respond mainly to habitat loss or to the changes in habitat configuration resulting from this loss? (2) Do species exhibit sharp thresholds in their response to forest cover or configuration? We compared the relative influence of forest cover and configuration on 15 bird species in 33 landscapes (6.25 km2) in eastern Ontario, Canada. Forest cover in these landscapes varied between 3.4% and 66.8%. The metrics we used to quantify forest configuration were correlated to forest cover, so we regressed these configuration metrics against cover and used the residuals in logistic regression models. Of the 15 forest bird species included in the analyses, the presence of only 3 (Downy Woodpecker [ Picoides pubescens], Brown Creeper [Certhia americana], and White‐breasted Nuthatch [ Sitta carolinensis]) was not significantly related to either cover or configuration of woodland. Forest cover and configuration each were significant predictors of the presence of 6 species in landscapes occupied in both years, and 3 species responded both to cover and configuration. Models based on single years showed variability in the landscape characteristics that were significant predictors of the presence of each species. These results indicate that (1) landscape structure was an important predictor of bird distribution, (2) both forest cover and configuration were important predictors of species presence, and (3) responses were species‐specific. Effects of forest cover and configuration on species presence generally were not characterized by sharp thresholds, preventing the application of simple management rules. Although forest cover is an important feature of landscape structure, our results indicate that woodland configuration is a far from negligible component that should also be incorporated in conservation strategies.

Effects of Landscape Structure on Nesting Songbird Distribution in a Harvested Boreal Forest

We studied the effects of forest cover and configuration on nesting songbird distribution in a harvested boreal forest. To emphasize landscape-level effects relative to stand effects, point count stations were established in mature stands only, but were surrounded by contrasting 100-ha landscapes. Seven of the 14 species studied responded significantly to landscape structure, but responses to specific landscape measures were found only in three species. Bay-breasted Warbler (Dendroica castanea) was absent from landscapes with <55% forest cover. Solitary Vireo (Vireo solitarius) also was associated with high forest cover per se. Conversely. American Robin (Turdus migratorius) was associated with poorly-forested landscapes. No species responded to mature forest configuration. Thus, clearcutting in boreal forests will reduce the use of remnant forest patches by certain species through a decrease of surrounding mature forest cover rather than changes in its spatial configuration.

INDEPENDENT EFFECTS OF FOREST COVER AND FRAGMENTATION ON THE DISTRIBUTION OF FOREST BREEDING BIRDS

The aims of this study were (1) to determine the relative importance of the independent effects of forest cover and fragmentation on the distribution of forest breeding birds, and (2) to test the hypothesis that the negative effect of forest fragmentation on species distribution increases with decreasing forest cover, i.e., the negative interaction effect of forest cover and fragmentation on distribution. The independent effects of forest cover and forest fragmentation on the distribution of forest breeding birds were studied in 94 landscapes, 10 × 10 km each, ranging in forest cover from 2.5% to 55.8%. For each landscape, percent forest cover was measured, and a fragmentation index (independent of forest cover) was generated using PCA from the measures of mean forest patch size, number of forest patches, and total forest edge. Presence of 31 forest breeding bird species in each landscape was determined using Breeding Bird Atlas data. The effects of forest cover and forest fragmentation on species presenc...

Independent Effects of Forest Cover and Fragmentation on the Distribution of Forest Breeding Birds

Independent Effects of Forest Cover and Fragmentation on the Distribution of Forest Breeding Birds

Air and soil microclimates of deciduous woodland compared to an open site

Forest microclimate has been monitored continuously for more than 3 yr at two sites in deciduous woodland at Wytham Woods, Oxford, UK. Automatic weather stations provided hourly data for wind speed, photosynthetically active radiation (PAR), vapor pressure deficit (VPD) and, in particular, temperature at different heights above the ground and at different depths in the soil. These data were compared with values from an open site at the same location. Air temperatures could be up to 3°C lower under the canopy than at the open site under sunny conditions in summer, but the differences averaged 0.6 and 0.9°C during the summer months and barely differed over winter. Effects of forest cover on soil temperatures were much greater and under the woodland they neither fell below 0°C nor rose above 20°C even at 5 mm depth, in contrast to temperatures under bare earth and grass. The temperature of a grass tussock at the soil surface under the canopy was intermediate between soil and air temperature; in comparison to grassland plants at an open site it experienced a much smaller range of temperatures. The differences between both soil and air temperature under the canopy and in the open were significantly correlated with solar radiation, presence or absence of canopy leaves and wind speed. Soil water content had no significant effect on soil temperature, partly because thermal diffusivity was relatively insensitive to it and partly because soil heat flux was small. Seasonal changes in canopy leaf cover caused a large peak of PAR under the canopy in spring prior to bud burst in trees and a much smaller one in the autumn after leaf fall. Wind speed under the canopy was also affected by the presence of leaves and was proportionally lower in summer and autumn than winter and spring.

Snow parameters derived from microwave measurements during the BOREAS winter field campaign

Passive microwave data have been used to infer the snow‐covered area and snow water equivalent (SWE) over forested areas, but the accuracy of these retrieved snow parameters cannot be easily validated for heterogeneous vegetated regions. The Boreal Ecosystem‐Atmosphere Study Winter Field Campaign provided the opportunity to study the effect of boreal forests on snow parameter retrieval in detail. Microwave radiometers (18, 37, and 92 GHz) were flown on board the Canadian National Aeronautical Establishment's Twin Otter. Flight lines covered both the southern study area near Prince Albert and the northern study area near Thompson, Canada. During the 1994 winter campaign, extensive ground‐based snow cover information, including depth, density, and grain size, was collected along most of the flight lines, jointly by U.S. and Canadian investigators. Satellite data collected by the special sensor microwave imager are also used for comparison. Preliminary results reconfirmed the relationship between microwave brightness temperature and SWE. However, the effect of forest cover observed by the aircraft sensors is different from that of the satellite observations. This is probably due to the difference in footprint averaging. There were also several flight lines flown over Candle Lake and Waskesiu Lake to assess lake ice signatures. Preliminary results show the thickness of the lake ice may be inferred from the airborne microwave observations. The microwave signature relationship between lake ice and snow matches the results from radiative transfer calculations.

Water temperature of Plynlimon streams

Abstract. Water temperature data were collected from five stations in the upper Severn system. Temperatures were compared between a stream with a 335 ha catchment after it had flowed for c. 1.5 km through clear felled land and a stream with a 347 ha catchment after it had flowed for c. 2.5 km through coniferous forest. The results suggest that the effect of forest cover was to lower the annual mean water temperature by c. 0.4°C, mainly in summer and through depression of both daily maxima and daily minima, though mainly the former. There was no clear evidence of temperature elevation in the afforested stream in winter. It is important to note that these conclusions depend on several assumptions that cannot be substantiated objectively. There is some evidence that water temperatures in some parts of the upper Severn system may be influenced by groundwater inputs.

Hydrological processes at two subtropical forest catchments: the Serra do Mar, São Paulo, Brazil

The Cunha Forest Hydrological Laboratory was established in the Serra do Mar, São Paulo, Brazil to achieve some understanding of the hydrological processes and the effects of forest cover on these processes in the headwater areas. Stream-gauging from two subtropical forest catchments (56.0 ha and 36.7 ha) covered with the Mata Atlântica commenced in 1982. Measurements of crown interception, surface runoff from a hillslope and estimation of soil water storage within the catchments quantified individual components of the hydrological processes. Ten years of field measurements and hydrograph analysis show that about 15% of annual rainfall is intercepted by the forest cover and returns directly to the atmosphere while 85% of the rainfall reaches the forest floor, where it infiltrates and remains in the soil to feed subsurface flow and baseflow or transpiration. Humid conditions obtain throughout the year and surface runoff is a rare occurrence on forested hillslopes. Stormflow is generated from wetland source areas adjacent to streams and from seepage from hillslopes. The total volume of stormflow is only 11% of annual rainfall. Fifty-nine % of annual rainfall is stored in the soil mantle and flows via subsurface routes to streams as baseflow throughout the year. This sustained flow of streams is one of the most important hydrological features and is controlled by such basin characteristics as the physical properties of the soil, the depth of the soil mantle and the vegetative cover. Soil evaporation and transpiration were estimated as 15% of annual rainfall by the water balance equation. Thus, the annual hydrological budget for the catchments is 70% streamflow and 30% evapotranspiration. Riparian areas are also places of stormflow production as well as of soil water and groundwater storage of water derived from hillslopes as interflow. An assessment of the area, depth of sediment and porosity of the riparian areas helps in understanding the runoff processes in low-order catchments in the Serra do Mar. ©1997 Elsevier Science B.V.

EFFECTS OF FOREST ON THE SNOW PARAMETERS DERIVED FROM MICROWAVE MEASUREMENTS DURING THE BOREAS WINTER FIELD CAMPAIGN

Passive microwave data have been used to infer the areal snow water equivalent (SWE) with some success. However, the accuracy of these retrieved SWE values have not been well determined for heterogeneous vegetated regions. The Boreal Ecosystem-Atmosphere Study (BOREAS) Winter Field Campaign (WFC), which took place in February 1994, provided the opportunity to study in detail the effects of boreal forests on snow parameter retrievals. Preliminary results reconfirmed the relationship between microwave brightness temperature and snow water equivalent. The pronounced effect of forest cover on SWE retrieval was studied. A modified vegetation mixing algorithm is proposed to account for the forest cover. The relationship between the microwave signature and observed snowpack parameters matches results from this model.

Influences of habitat fragmentation on bird species distributions and regional population sizes

A simple modelling approach was used to investigate the influence of habitat fragmentation on the distributions and regional population sizes of passerines breeding in 145 small woods in an arable landscape. Observed distributions in three consecutive years were compared with those predicted by random selection of woods by pairs (based on a Poisson distribution), and by a simulation model based on the area of habitat available and estimates of individual species minimum area requirements and territory sizes. None of the species studied were distributed randomly; some were distributed according to the area of woodland available, whereas others preferred either small or large woods. However, species distributions were influenced by their regional population sizes. When species population sizes were small, observed distributions could be predicted using algorithms based on area alone, but as numbers increased, algorithms using territory parameters were required. An absence of detectable territorial interaction suggested that space for more pairs of the species concerned had been available in our woods. Of the 14 species investigated, the models for only two consistently required the use of territory parameters, indicating that the available habitat could probably have accommodated more pairs of most of the species. Thus habitat fragmentation may reduce regional population sizes more than expected from the loss of habitat alone, to the extent that patches of suitable habitat may be unused, or occupied at low density.

Effects of forest cover, terrain, and scale on timber volume estimation with Thematic Mapper data in a rocky mountain site

The biophysical basis of the utility of Landsat Thematic Mapper (TM) data to estimate coniferous timber volume was assessed for a mountainous, mixed-conifer species site in southeast British Columbia. Classification of forest inventory polygons with TM data was found to be 78% accurate to within 25% of the inventory volume for stand volumes between 150 m 3 ha −1 and 300 m 3 ha −1, compared to an accuracy of 44% for polygons with stand volumes less than 150 m 3 ha −1. In polygons with timber volumes less than 150 m 3 ha −1, variations in stand density and background reflectance, identified from MEIS-3 meter imagery, impeded volume classification from TM data. Forest ground call samples and corresponding terrain data, derived from a digital terrain model, were classified according to spatially homogeneous TM data, and the resulting classes were used to analyze the sensitivity of TM data to stand characteristics. From correlation and analysis of variance of classes, TM Bands 4 and 5 were found to be strongly inversely related to stand timber volume ( P = 0. 01) with TM Band 5 having the greatest dynamic range. Timber volume was strongly related to the bulk reflectance characteristics of the stand including stand height, age, species composition, slope, and aspect, and could thus be estimated from the remote sensing data. A geometric-optical reflectance simulation was used to estimate the relative contributions of forest cover and terrain to stand reflectance. The effects of terrain on the relationship between TM data and volume were small relative to the effects of forest cover. The radiometric basis of these relationships was discussed in relation to simulations of stand reflectance. For stand volumes of less than 400 m 3 ha −1, simulated stand reflectance in both TM Bands 4 and 5 was sensitive to the proportions of shadow and exposed background in the stand, but had little sensitivity at volumes greater than 400 m 3 ha −1. TM data may be used to estimate timber volume in other sites that possess similar characteristics to the site assessed here.

Patterns of Ovenbird (Seiurus aurocapillus) Pairing Success in Missouri Forest Tracts

Minimum-area-requirement estimates for area-sensitive birds may underestimate the actual area needed to provide long-term breeding habitat because they do not consider the pairing and mating success of territorial males. Patterns of pairing success were studied in Ovenbirds (Seiurus aurocapillus) in north-central Missouri in forest tracts below, approaching, and exceeding minimum-area-requirement estimates for this species. The possible roles of habitat area, isolation, and edge effect in causing reduced pairing success were examined. Male Ovenbird territories were spot mapped within seven forest tracts. Each male was observed to determine if he had acquired a mate. The percentage of paired male Ovenbirds was directly related to forest-tract area and total estimated male Ovenbird population. A higher percentage of males with territories more than 300 m from the forest edge were paired than males with territories less than or equal to 300 m from the forest edge. The combined effect of total forest area, edge-to-interior ratio, and percent forest cover within a 5-km radius of the tracts was highly correlated with pairing success. Edge effects are an important consideration that should be a contributing factor when developing minimum-area-requirement estimates.

Mountain Climatology and Past and Potential Future Climatic Changes in Mountain Regions: A Review

Climatic knowledge of mountain regions is limited by paucity of observations and insufficient theoretical attention to processes within these regions. This review article discusses the basic controls of mountain climate and the scales of climatic features, and illustrates data availability in several mountainous regions. Areas where our understanding is incomplete include orographic precipitation, especially extreme events, pollutant transport and deposition, and effects of forest cover on evapotranspiration and runoff. Sources of evidence for past climatic conditions in mountain areas are surveyed and particular aspects of mountain-lowland climate differences during the last glacial maximum, the Little Ice Age, and the 100-year observational record are noted. Finally, analogue and modeling approaches to assessing potential future climatic states are discussed in the context of mountain areas. The significance of such states in terms of snow cover and snowmelt runoff is described. The survey concludes with a series of recommendations for necessary actions.

The Influence of Island and Mainland Lakeshore Landscapes on Boreal Forest Fire Regimes

In order to characterize the fire regime of the southern boreal forest and to understand the way in which landscape and fire regime interact, a detailed study of fire history was undertaken in two adjacent contrasting landscapes in northwestern Quebec. The fire history for the islands of Lake Duparquet was reconstructed and compared to that of the surrounding lakeshore. Fire occurrence was determined by archival search and by collection of information from the fire scars. Dendroecological techniques were used to determine years of stand initiation on the lakeshore and for a subsample of the islands. Stand initiation data were used to estimate fire frequency, fire cycle, and fire intensity (lethal and non—lethal fires). Tree composition and surficial deposits were sampled in order to assess the possible effect of topography and forest cover on fire frequency. Dated fire scars (n = 273) revealed 82 fire years, with the earliest dated to 1593. Islands experienced more fire years (56) than the lakeshore (37), and fire years were uncorrelated. Most 72%) of the lakeshore stands were initiated by a few large fires (eight), whereas the fire size on islands was variable, ranging from &lt;10% to 100% of the total surface of the island. Despite these differences in fire regime, fire occurrence and fire frequency decreased concurrently on the islands and the lakeshore starting °120 yr ago. The lakeshore fire cycle was 63 yr before 1870 and 99 yr since 1870, whereas the fire cycle on the islands was slightly longer (74 yr and 112 yr) during the same intervals. The long—term decrease in fire frequency of both the lakeshore and the islands was possibly driven by climatic change. Fire frequency was generally similar for all surficial deposits and fuel types on the lakeshore, whereas fires were more abundant in pine woodland growing on bedrock on the islands. Lakeshore fires were generally of lethal intensity, whereas both a long cycle of lethal fires and a shorter cycle of non—lethal fires were observed on 50% of the islands. The morphology and location of islands with both types of fires suggest that a higher frequency of lightning strikes resulted in a regime characterized by more frequent fires and fires of variable intensity. The specific fire regime observed in the island landscape may be the cause of the abundance of pines, whose presence may contribute, in turn, to the continuation of this regime of less intense and more frequent fires. We suggest that fire regime in the boreal forest is controlled by long—term climate change at the regional scale, and by a strong interaction with landscape at the local scale, both components having a great impact on the distribution and the dynamics of boreal vegetation.

Simulation of the effects of forest cover, and its removal, on subsurface water

A distributed, physically based mathematical model was developed to simulate the effects of forestry operations on both soil water and streamflow. It combines Galerkin's finite‐element method with an implicit backward finite‐difference scheme to solve the Darcy‐Richards equation of porous media flow, and uses sink concepts to simulate water use by trees. The validity of the model was checked by simulation of one‐dimensional vertical infiltration into a soil column. Five forest configurations, imposed on a hillslope, were simulated: fully treed, upper slope clear‐cut, lower slope clear‐cut, patch‐cut, and entire slope clear‐cut. The results, displayed as total potential and soil water fields, were qualitatively compatible with accepted hydrological concepts. A field study was simulated and the results compared with field measurements. Explanations are offered for discrepancies between the simulation results and the field measurements. The model's primary usefulness rests in its capability to simulate soil water movement and redistribution, on a distributed basis, in response to the processes of infiltration, evaporation, and transpiration.

Effects of Nontropical Forest Cover on Climate

The albedo of a forest with snow on the ground is much less than that of snow-covered low vegetation such as tundra. As a result, simulation of the Northern Hemisphere climate, when fully forested south of a suitably chosen taiga/tundra boundary (ecocline), produces a hemispheric surface air temperature 1.9 K higher than that of an earth devoid of trees. Using variations of the solar constant to force climate changes in the GLAS Multi-Layer Energy Balance Model, the role of snow-albedo feedback in increasing the climate sensitivity to external perturbations is reexamined. The effect of snow-albedo feedback is found to be significantly reduced when a low albedo is used for snow over taiga, south of the fixed latitude of the ecocline. If the ecocline shifts to maintain equilibrium with the new climate - which is presumed to occur in a prolonged perturbation when time is sufficient for trees to grow or die and fall - the feedback is stronger than for a fixed ecocline, especially at high latitudes. However, this snow/vegetation-albedo feedback is still essentially weaker than the snow-albedo feedback in the forest-free case. The loss of forest to agriculture and other land-use would put the present climate further away from that associated with the fully forested earth south of the ecocline and closer to the forest-free case. Thus, the decrease in nontropical forest cover since prehistoric times has probably affected the climate by reducing the temperatures and by increasing the sensitivity to perturbations, with both effects more pronounced at high latitudes.

Effect of forest cover on rainfall distribution at Andaman and Car Nicobar islands

Effect of forest cover on rainfall distribution at Andaman and Car Nicobar islands

The Fundamental Studies on the Opimal Development and Allocation of Forests

Forest lands are utilized and managed for a multiplicity of purposes, with usually one use, frequently timber production, dominant on a particular area. Forest lands can often be utilized and managed for several uses, sometimes on the same area and sometimes with different dominant uses assigned to separate areas. Utilization and management of the whole are directed to obtain the total net benefit of forest lands. Forest lands managed primarily for timber production can be frequently, and with comparatively small adjustment, served watershed, wildlife, or recreational purposes. A major use, well managed, often ensures others. In some conditions, the usage of forest lands are incompatible, one with another, and priority decision must be made.Japan, compared with western countries, even with asiatic countries having relatively high percentage of forest land, is one of the most forested countries in the world. However, there was no precise knowledge of the effect of forest cover upon environmental supplies. Much has been explained about sustained yield as a major objective of timber management, and it has been regarded as something of a general cureall.Environmental stress of forest lands refers to a discordance between man's economic activities and his natural surroundings. The result of the discordance is a deterioration in the quality of the natural surroundings that leads to a reduction in social welfare. The phyical environment and its characteristics have an important influence on the economic and ecological structure of a region. I took a statistical approach, (principal component analysis) to the collection and presentation of envionmental data of forest lands, and indicated the results of valuation and classification of forest lands in Yamagata Prefecture on the use of a map and graphs, to summarize information visually, for easy comparisons among forest lands.If the above-mentioned standards of classification of forest lands are supplied by public organizations, they may be possible to indicate the appropriate environmental measures such as the choice species and regeneration procedures.