Extensive Forest Cover Research Articles

ANALISIS OF STREAM DISCHARGE OF MICRO WATERSHED AND ITS UTILIZATION POTENTIAL

Trough understanding of hydrology characteristic of watershed, water resource can be managed for wider goals such as economic, social, and sustainainable utilization. In fact, current watershed managements have more been focused on erosion, sedimentation, drought, and flood control and less attention paid on fulfilling the need of upper watershed inhabitat on water yield. The research of Micro Watershed was conducted in three Micro Watersheds as representation of priority watersheds in South Sulawesi namely Mamasa, Saddang, and Jeneberang. The aim was to find out stream discharge pattern of those three Micro Watershed related to precipitation, landuse and its utilization potential for local community. The results showed that the more extensive forest cover, the better water yield and the higher its utilization potential . Concerning to precipitation and water yield, the three micro watersheds have the potentially to be source of water for irigation and household consumption.

The use of quantitative models to assess long-term climate–vegetation dynamics – A case study from the northern Scandinavian Mountains

Quantitative vegetation models combined with fossil pollen records have large potentials for assessing long-term vegetation dynamics. In this study, vegetation cover as a function of July temperatures was modelled for the Dividalen valley area situated in the northern Scandinavian Mountains. Site-specific pollen deposition values of the two dominating tree species pine and birch were simulated and compared with empirical fossil pollen values. The applied vegetation model could not explain the forest dynamics prior to 7400 cal. BP, although after this date, the forest seemed to have received a modern structure, and summer temperatures could potentially explain the long-term variations in forest cover. The most extensive forest cover occurred c. 7400–3800 cal. BP, corresponding to July temperatures of 0.5–1°C above the present. The approach proved sensitive to both site location and data quality. Careful site-selection is of importance for the application, and pollen accumulation rates are to be preferred as pollen percentage values proved problematic.

Response of Mineral Soil Carbon to Clear-Cutting in a Northern Hardwood Forest

Northern New England is characterized by extensive forest cover (84%) and large reservoirs of soil carbon (C). There has been an increasing demand for forests to serve both as a C sink and a renewable energy source. Our understanding and management of the ecosystem C balance relies on accurate modeling of each compartment of the ecosystem. However, the dynamics of soil C storage with respect to forest use are poorly understood. For example, current regional models assume negligible mineral soil C loss after forest harvesting, while some studies on soil C demonstrate that belowground mineral soil C pools can be affected by disturbances at the soil surface. We investigated harvesting-related changes in mineral soil C to a depth of 60 cm in the Bartlett Experimental Forest in New Hampshire, USA. We found significantly lower concentrations of C in some recently harvested stands compared with >100-yr-old stands. Carbon concentrations among harvested stands varied significantly in all but the 0- to 10-cm depth increment. Mineral soil C pools were lower in some stands that had been harvested, with isolated significant differences occurring between the 120-yr-old stand and stands that were cut 5 or 55 yr before sampling. However, there were no trends in mineral soil C pools over time after harvest, and the isolated differences in C pools do not suggest widespread C loss with forest harvesting. When combined, stands that had been harvested within the last 100 yr had significantly lower C pools than the >100-yr-old stands. Further work is needed to elucidate the mechanisms underlying the observed loss of C after forest harvest. However, changes in C inputs and outputs to and from mineral soil in the decades following harvest could potentially lead to appreciable differences in C concentrations and pools across the landscape.

Spatial Patterns of Methylmercury Risks to Common Loons and Piscivorous Fish in Canada

Deposition of inorganic mercury (Hg) from the atmosphere remains the principle source of Hg contamination for most aquatic ecosystems. Inorganic Hg is readily converted to toxic methylmercury (MeHg) that bioaccumulates in aquatic food webs and may pose a risk to piscivorous fish and wildlife. We conducted a screening-level risk assessment to evaluate the extent of risk to top aquatic piscivores: the common loon (Gavia immer), walleye (Sander vitreus), and northern pike (Esox lucius). Risk quotients (RQs) were calculated on the basis of a dietary Hg exposure indicator (HgPREY) modeled from over 230,000 observations of fish Hg concentrations at over 1900 locations across Canada and dietary Hg exposure screening benchmarks derived specifically for this assessment. HgPREY exceeded benchmark thresholds related to impaired productivity and behavior in adult loons at 10% and 36% of sites, respectively, and exceeded benchmark thresholds for impaired reproduction and health in fishes at 82% and 73% of sites, respectively. The ecozones of southeastern Canada characterized by extensive forest cover, elevated Hg deposition, and poorly buffered soils had the greatest proportion of RQs > 1.0. Results of this assessment suggest that common loons and piscivorous fishes would likely benefit from reductions in Hg deposition, especially in southeastern Canada.

Multiscale Factors Influencing Distribution of the Eastern Hellbender Salamander (Cryptobranchus alleganiensis alleganiensis) in the Northern Segment of Its Range

Eastern Hellbender (Cryptobranchus alleganiensis alleganiensis) populations are experiencing drastic declines range-wide. Effective conservation strategies require understanding the environmental factors underlying population occurrence within the stream networks that Eastern Hellbenders inhabit. We contrasted habitat elements between historically occupied and apparently unoccupied sites throughout the Susquehanna River Basin in New York, an area that represents the northernmost segment of the species' range. Historically occupied sites contained larger rocks and less soft sediment than unoccupied sites. Regional-scale predictive models of Eastern Hellbender distribution in Pennsylvania indicated that specific geologic features—loamy till, clayey to loamy till, and mixed origin sand and gravel deposits—as well as extensive forest cover were the strongest predictors of Eastern Hellbender occurrence. We conclude that occurrence is dependent on isolated and uncommon geological features that cause the species' distribution to be highly patchy and that stream sedimentation is a major threat to this species in its northern range. Our research also indicates that predictive modeling can be useful in examining drivers of Eastern Hellbender distribution and targeting regions for population surveys and habitat conservation.

REMOVAL OF TREE OFFSETS FROM SRTM AND OTHER DIGITAL SURFACE MODELS

Abstract. The recently completed 1 second Digital Elevation Models (DEMs) for Australia are based on the 1 second Shuttle Radar Topographic Mission (SRTM) elevation data. The SRTM data was corrected by removing voids, striping, tree offsets and random noise and finally by integrating mapped drainage lines. This paper describes the removal of the tree offsets, which was a crucial step in the production of a credible bare-earth elevation model and was one of the most technically challenging aspects of the project, and the possible application of the methods to other digital surface model (DSM) sources. Methods for the removal of tree offsets rely on maps of tree presence/absence from sources such as remotely-sensed imagery, and the height offsets are computed from the DEM at the boundaries of tree patches. Tree offsets over most of Australia were successfully removed, but were underestimated in areas of extensive forest cover and poorly estimated where the mapping of tree patches did not match the patterns of offsets in the SRTM elevations. The tree offset removal methods could be applied to the near-global SRTM DSM to produce a near-global bare-earth product, provided that a suitable map of tree presence or density can be compiled from satellite remote sensing and other sources. The process could be improved by using supplementary tree-height information from ICESat or other sources. High resolution global DEMs other than SRTM are becoming available, notably ASTER GDEM and TANDEM-X. Both those products are subject to offsets due to vegetation in the same way as SRTM. The tree offset removal methods developed for SRTM could be adapted to the characteristics of these and other DSMs to provide a largely automated processing system to derive bareearth DEMs from new sources.

Anthrax: Public health risk in india and socio-environmental determinants

Zoo authorities of Central Indian State of Chattisgarh reported a hyena suffering from the fatal anthrax disease in Nandanvan zoo in capital city Raipur. After laboratory confirmation of anthrax, the zoo was closed for 15 days as precautionary measure. According to the veterinarians of the zoo, all symptoms of anthrax were found in one of the hyenas. The Forest department officials decided to vaccinate animals within the 5 km radius of zoo to contain the disease. All employees of Nandanvan zoo had been put on prophylactic antibiotic medicine.(1) The report of death of a hyena due to anthrax in the state of Chattisgarh in India during June 2007 was very disturbing and was unusual occurrence by any standards. Chattisgarh state has never reported anthrax case either in animal or in humans. Anthrax is generally an epizootic disease which infects and kills herbivorous animals e.g. cattle, sheep, and goat.(2) Cattle get mostly infected by eating vegetations contaminated by spores. Elephants have been known to die of anthrax in north-east. They and other herbivores develop bacteriamic phase followed by death. So do poor humans. Occasionally dogs, horses, etc. are also found to be infected but are rarely fatal in them. Terminally ill animals tend to bleed from the nose, mouth, and bowel, thereby contaminating soil or water places with B. anthracis that can subsequently sporulate and persist in the environment. On further literature review, the Chattisgarh incident turns out to be the first case of death of non-herbivorous animal like hyena dying due to anthrax in India.(3) This event has a great epidemiological as well as public health significance. The reports of anthrax infection in hyena leading to death is a pointer towards the larger fact that the anthrax bacteria are in circulation in Chattisgarh, also it is a matter of concern from public health point of view, as once anthrax affected, the locale is always anthrax prone on account of longevity of viable spores lasting many decades. From public health point of view, it is very important that Chattisgarh should step up their mechanism for animal screening for anthrax. Since Chattisgarh never had history of anthrax, capacities and skills for the same need to be instituted. Once anthrax is fully established as enzootic disease in a region, it is only a matter of time before zoonotic transmission begin and human case of anthrax begin to appear posing as big public health problem. The case in point is Orissa, where anthrax is an endemic disease and already a major public health problem of Orissa; 14 out of 30 revenue districts in the state have witnessed outbreaks of anthrax as many as 61 times during the last 10 years affecting 750 people of which 418 had died.(4) The anthrax outbreaks are an annual phenomenon Orissa. With good forest cover, the soil being highly organic in with good moisture to support anthrax spores. Due to scanty agriculture, tribals mainly depend on forest for livelihood. Risk of infection increases due to anthrax spores in the wild. Outbreaks of anthrax in these indigenous populations very often occur as food poisoning following consumption of contaminated cattle meat. Tribals for that matter, any given community, in these states particularly if underprivileged, eat carcass of dead animals. Such people are vulnerable. Even if they do not eat, if they de-skin carcasses of infected animals, they are also vulnerable for anthrax infection. Anthrax is known to occur generally in underdeveloped regions.(5) Ecologically speaking, from vulnerability point of view, Chattisgarh shows striking parallels and Orissa, as far as potential proneness and risk of anthrax outbreaks in the human population in the coming years: Chattisgarh and Orissa rank almost similar on human development indices (HDIs); Like Orissa, Chattisgarh has very high concentration of tribal population (>35%); Both the states have extensive forest cover; The indigenous population of both these states depend less on agriculture and more on forest and animal produce for food; Overwhelming majority of people in both these states live below the poverty line. Both the states have poor public health infrastructure. This is the perfect amalgamation and interface of risk factors that are conducive for zoonotic transmission of anthrax to the human population. Hence the probability of occurrence of anthrax outbreak in the human population would increase on logarithmic scale, each time an episode of anthrax detected in animal population in a state like Chattisgarh. So, epizootology and epidemiology should be both applied not only for anthrax, but for every zoonotic disease, hence the importance of veterinary and doctors putting heads together.

Comparative landscape dynamics of two anuran species: climate‐driven interaction of local and regional processes

The dynamics of ecological communities emerge from the interplay of local and regional processes, but there are few long‐term data on multiple interacting species across multiple sites to evaluate these processes. We report the population dynamics of two species of treefrogs, the spring peeper (Pseudacris crucifer) and the chorus frog (P. triseriata), in 37 ponds over 11 years. We examined the relation between larval traits of these species and responses to environmental change (a severe drought) at the local (pond) level, and the consequences to regional dynamics of the species. Consistent with experimental evidence, predators limited abundances of both species, competitive effects were undetectable, and pond hydroperiod and forest canopy cover affected species' presences and population sizes. The drought caused strong reductions in pond hydroperiods and predator densities, which led to increases in colonization probability and decreases in extinction probability for the chorus frog. These habitat dynamics resulted in the colonization of 15 new ponds and exponential growth in regional population size of the chorus frog. Colonization probability was positively related to pond connectivity. Pond occupancy rates for the spring peeper were relatively constant, but important source ponds on the landscape changed with the drought. Ponds with extensive forest canopy cover were sink habitats for both species, and high pond connectivity appeared to be necessary to maintain species' presences in these habitats. Landscape dynamics were responsible for changes in the fundamental spatial structure of species' populations, e.g., the chorus frog transitioned between approximations of a classic metapopulation and a patchy population over the course of the study. Many of these results were driven by the interplay of climate variation and spatial food web structure, indicating the importance of incorporating this interaction into metacommunity theory. Our results further indicate the crucial role of habitat (pond) heterogeneity to species persistence, i.e., moderating the potential Moran effects of spatially correlated weather conditions. Overall this study illustrates: (1) how natural systems constantly transition between metapopulation/metacommunity states typically treated as static in the literature, (2) the extensive interconnection of phenomena at different scales in ecology, and (3) the importance of habitat heterogeneity and landscape context for amphibian conservation strategies.

Fluvial development and the sediment regime of the lower Calder, Ribble catchment, northwest England

In the lower reaches of the Calder (Lancashire) tributary of the Ribble catchment (northwest England), five river terraces set into the surrounding glacial terrain have been mapped and their underlying sediments radiocarbon dated. The earliest terrace (T1) reflects sandur-style deposition during deglaciation and it aggraded in a reach cut into glacial diamict and glaciolacustrine muds. Incision below T1 spanned the start of the Holocene, driven by a combination of reduced sediment supply under a stabilising landscape and lower base-levels. T2 had aggraded and was being abandoned by 4000 BC; its formation latterly involving a period of comparative stability in terms of channel migration, perhaps a function of extensive forest cover and sea levels reaching above present day levels. The last 3000 years were marked by substantial changes in the sedimentary regime, with increased and varying sediment supply driving cycles of cut-and-fill and greater lateral channel migration. These changes coincided with the first widespread and substantial reductions in forest cover and a progression towards an agricultural landscape. Between the aggradation of terraces T3 and T4 there was a substantial increase in sediment supply, which is broadly in keeping with the erosion history in the surrounding uplands. This sediment slug appears to have induced a switch from highly sinuous meandering to lower sinuosity channels characterised by lateral scroll-style migration. Late Holocene vegetation changes, particularly woodland removal, driven by anthropogenic land-pressure appear to have rendered the floodplain prone to channel migration and the landscape more susceptible to erosion.

Relief influence on the spatial distribution of the Atlantic Forest cover on the Ibiúna Plateau, SP

Several studies suggest that, on a large scale, relief conditions influence the Atlantic Forest cover. The aim of this work was to explore these relationships on a local scale, in Caucaia do Alto, on the Ibiúna Plateau. Within an area of about 78 km(2), the distribution of forest cover, divided into two successional stages, was associated with relief attribute data (slope, slope orientation and altitude). The mapping of the vegetation was based on the interpretation of stereoscopic pairs of aerial photographs, from April 2000, on a scale of 1:10,000, while the relief attributes were obtained by geoprocessing from digitalized topographic maps on a scale of 1:10,000. Statistical analyses, based on qui-square tests, revealed that there was a more extensive forest cover, irrespective of the successional stage, in steeper areas (>10 degrees) located at higher altitudes (>923 m), but no influence of the slope orientation. There was no sign of direct influence of relief on the forest cover through environmental gradients that might have contributed to the forest regeneration. Likewise, there was no evidence that these results could have been influenced by the distance from roads or urban areas or with respect to permanent preservation areas. Relief seems to influence the forest cover indirectly, since agricultural land use is preferably made in flatter and lower areas. These results suggest a general distribution pattern of the forest remnants, independent of the scale of study, on which relief indirectly has a strong influence, since it determines human occupation.

Evidence of lay and professional forest-based development discourses in three contrasting regions of Finland

The paper examines the perceived importance of forests and forestry for rural development in three contrasting districts in Finland: an area of intensive farming and moderate forest cover, and two dairying farming regions with extensive forest cover, one of which has long suffered from socio-economic marginalisation. Forest-related rural discourses that have been elicited in other European countries are identified in Finland: namely, a private-use, production-oriented discourse, a collective-use non-timber benefits discourse and an environmental benefits discourse. Farmers in the intensive farming district do not identify strongly with any of the forest discourses. Conversely, farmers in the poorer farming regions with extensive forests identify with each of the discourses. Advisors in each district identify mostly with the production-oriented discourse. A strong dichotomy therefore exists between lay farmers (who own the land) and professional advisors (who often administer policy) with respect to forest-related discourses. The dichotomy can have considerable repercussions on how forest policy instruments and rural policy programmes are promoted, as advisors do not seem to recognise that non-timber resources are a basis for rural enterprise.

The relative importance of climatic effects, wildfires and management for future forest landscape dynamics in the Swiss Alps

AbstractForest landscape dynamics result from the complex interaction of driving forces and ecological processes operating on various scales. Projected climate change for the 21st century will alter climate‐sensitive processes, causing shifts in species composition and also bringing about changes in disturbance regimes, particularly regarding wildfires. Previous studies of the impact of climate change on forests have focused mainly on the direct effects of climate. In the present study, we assessed the interactions among forest dynamics, climate change and large‐scale disturbances such as fire, wind and forest management. We used the LandClim model to investigate the influence, interactions and the relative importance of these different drivers of landscape dynamics in two case study areas of the European Alps. The simulations revealed that projected future climate change would cause extensive forest cover changes, beginning in the coming decades. Fire is likely to become almost as important for shaping the landscape as the direct effects of climate change, even in areas where major wildfires do not occur under current climatic conditions. The effects of variable wind disturbances and harvesting regimes, however, are less likely to have a considerable impact on forest development compared with the direct effects of climate change coupled with the indirect effects of increased fire activity. We conclude that the joint direct and indirect effects of climate change are likely to have major consequences for mountain forests in the European Alps, including their ability to provide protection against natural hazards.

Natural History of Terrapene carolina (Box Turtles) in an Urbanized Landscape

Urbanization and other anthropogenic factors are often implicated in turtle population declines, yet limited research on the natural history of turtles in urban areas has been conducted. To assess the effects of urbanization and to help develop proper conservation strategies for Terrapene c. carolina (Eastern Box Turtles), we conducted a mark-recapture study in the vicinity of Davidson, NC, from 1999 to 2004. We made 354 turtle captures, 42 of which were recapture events. We evaluated meristic characters, body condition, activity patterns, population structure, and growth rates, and then examined relationships among these variables and the amount of anthropogenically-modified habitat within 100 m of each turtle's collection location. Males and females had different patterns of seasonal activity and body condition indices. Growth rates decreased with turtle age and varied between developed and forested habitats. More turtles over the age of 20 were found in areas with extensive forest cover than in areas that were developed. Although box turtles may persist in urbanized landscapes and may grow more quickly there, they suffer higher mortality in these habitats compared to forested landscapes.

Transverse fault zones of subtle geomorphic signature in northern Evia island (central Greece extensional province): An introduction to the Quaternary Nileas graben

Reconnaissance level geomorphological observations in the northern part of Evia (Euboea) Island, suggest that a major topographic feature, the 17 km long and 15 km wide Nileas depression (NDpr), corresponds to a previously undetected graben structure, bounded by fault zones of ENE–WSW to NE–SW general strike. These fault zones have been active in the Quaternary, since they affect the Neogene deposits of the Limni–Histiaia basin. They strike transverse to the NW–SE active fault zones that bound northern Evia in the specific area and are characterised along most of their length by subtle geomorphic signatures in areas of extensive forest cover and poor exposure. The NDpr was formed during the Early–Middle Quaternary, after the deposition of the Neogene basin fill. During the Middle–Late Quaternary, the NW–SE fault zones that bound northern Evia have been the main active structures, truncating and uplifting the NDpr to a perched position in relation to the northern Gulf of Evia graben and the submarine basin on the Aegean side of the island. The present-day morphology of the NDpr, with an interior (floor) comprised of Middle Pleistocene erosional surfaces extensively dissected by drainages, was shaped by erosion during this uplift. Judging from their geomorphic signatures, the fault zones that bound the NDpr must have been characterised by low or very low rates of activity during the Late Quaternary. Yet, that they may still be accommodating strain today is suggested by moderate earthquakes that have been recorded within the NDpr. The fault zone at the SE flank of the NDpr (Prokopi–Pelion fault zone) may be very important in terms of earthquake segmentation of the active NW–SE Dirfys fault zone that controls the Aegean coast of northern Evia, given that the intersection between the two presents striking morpho-structural similarities with the intersection of two fault zones with the same directions on the mainland (the Atalanti and Hyampolis fault zones), which is known to have acted as a barrier to the propagation of the Atalanti earthquake ruptures in 1894.

A remote sensing methodology to assess the costs of preparing abandoned farmland for energy crop cultivation in northern Sweden

Abstract In regions of extensive forest cover relative to agricultural open ground, as in northern Scandinavia, farmland abandonment greatly changes the landscape pattern. Cultivation of herbaceous energy crops would help to keep an open landscape as a positive side effect of bioenergy production and the lowland rental costs of abandoned farmland would positively improve the economy of energy grass cultivation. For this study, in the municipality of Bjurholm in the northeast of Sweden, a method was developed to separate abandoned fields into two classes, A and B, with low and high preparation costs, respectively, by using digital orthophoto interpretation. From field studies of a chosen sample, the mean preparation cost per hectare was determined to be 173 and 3990 SEK, respectively, for fields in class A and B. Peat and fine sediment soils had higher preparation costs than coarse sediment soils.

Influence of vegetation change on watershed hydrology: implications for paleoclimatic interpretation of lacustrine δ18O records

Stratigraphic shifts in the oxygen isotopic (δ18O) and trace element (Mg and Sr) composition of biogenic carbonate from tropical lake sediment cores are often interpreted as a proxy record of the changing relation between evaporation and precipitation (E/P). Holocene δ18O and Mg and Sr records from Lakes Salpetén and Petén Itzá, Guatemala were apparently affected by drainage basin vegetation changes that influenced watershed hydrology, thereby confounding paleoclimatic interpretations. Oxygen isotope values and trace element concentrations in the two lowland lakes were greatest between ~ 9000 and 6800 14C-yr BP, suggesting relatively high E/P, but pollen data indicate moist conditions and extensive forest cover in the early Holocene. The discrepancy between pollen- and geochemically-inferred climate conditions may be reconciled if the high early Holocene δ18O and trace element values were controlled principally by low surface runoff and groundwater flow to the lake, rather than high E/P. Dense forest cover in the early Holocene would have increased evapotranspiration and soil moisture storage, thereby reducing delivery of meteoric water to the lakes. Carbonate δ18O and Mg and Sr decreased between 7200 and 3500 14C-yr BP in Lake Salpetén and between 6800 and 5000 14C-yr BP in Lake Petén Itzá. This decline coincided with palynologically documented forest loss that may have led to increased surface and groundwater flow to the lakes. In Lake Salpetén, minimum δ18O values (i.e., high lake levels) occurred between 3500 and 1800 14C-yr BP. Relatively high lake levels were confirmed by 14C-dated aquatic gastropods from subaerial soil profiles ~ 1.0–7.5 m above present lake stage. High lake levels were a consequence of lower E/P and/or greater surface runoff and groundwater inflow caused by human-induced deforestation.

Observations and Numerical Simulations of Winds within a Broad Forested Valley

Abstract The Tennessee River Valley in the eastern part of Tennessee is a broad valley with a moist climate and extensive forest cover. A series of 50–100-m-high parallel ridges forms corrugations along the floor of the valley. Tower measurements and numerical simulations are used in this paper to study the channeling of the winds in this valley over the diurnal cycle. At night, pressure-driven channeling caused by geostrophic imbalances is often present, but this channeling tends to be concentrated on the leeward side of the valley (relative to the winds aloft). The channeling is significantly weaker during the afternoon, so the winds on top of the corrugations are more closely aligned with those aloft. In the bottomlands between the corrugations, however, the daytime winds are more effectively channeled parallel to the valley axis. Although thermally driven winds are not dominant in the Tennessee Valley, a discernible pattern of upvalley daytime winds and downvalley nighttime winds is observed in the to...

Regional Forest Fragmentation and the Nesting Success of Migratory Birds

Forest fragmentation, the disruption in the continuity of forest habitat, is hypothesized to be a major cause of population decline for some species of forest birds because fragmentation reduces nesting (reproductive) success. Nest predation and parasitism by cowbirds increased with forest fragmentation in nine midwestern (United States) landscapes that varied from 6 to 95 percent forest cover within a 10-kilometer radius of the study areas. Observed reproductive rates were low enough for some species in the most fragmented landscapes to suggest that their populations are sinks that depend for perpetuation on immigration from reproductive source populations in landscapes with more extensive forest cover. Conservation strategies should consider preservation and restoration of large, unfragmented "core" areas in each region.

A future for Palawan's forests?

Palawan is one of the last relatively undeveloped islands in the Philippines. It still has extensive forest cover, and is of considerable conservation importance. However, the remaining forests are disappearing fast in the face of rapid population growth and uncontrolled logging. The authors visited the island to carry out ecological fieldwork in 1984. Here they report on threats to the forests, and discuss the prospects for sustainable development on Palawan.

Periglacial wedges and the late Pleistocene environment of Wyoming's intermontane basins

Nonsorted polygons in the uppermost 2 to 3 m beneath Pleistocene surfaces indicate permafrost at 1340 m and higher elevations in the intermontane and piedmont plains of Wyoming during the Wisconsin, and perhaps earlier, glacial maxima. The polygons, as much as 10 m in diameter, are delineated by wedges that vary in depths, range from narrow to moderately flared forms, and deform host materials. The wedges have silty fine-to-medium sand matrices (largely eolian) with pebbles or clasts from hosts of gravel or bedrock. Some wedges may reflect seasonal cracking in a periglacial active zone, but most are either permafrost sand-wedge relics or, less commonly, ice-wedge casts. Alternative explanations are rejected largely because similar features are apparently lacking in the lower and warmer plains from eastern Colorado southward. The wedges suggest an arid, windy, periglacial environment whose mean-annual temperatures are conservatively estimated as some 10° to 13°C colder than those at present. Although late Wisconsin-early Holocene floral and faunal evidence indicates lowered montane biotic zones, the eolian and periglacial features indicate a lack of extensive forest cover on the basin floors. In conjunction with vertebrate-fossil associations of grazing and tundra animals, the wedges may provide a parallel line of evidence for a former periglacial steppe, or “steppe-tundra”, in the Wyoming basins.