Effects Of Land Use Practices Research Articles

Anthropogenic land-use activities within watersheds reduce comammox activity and diversity in rivers

Nitrogen cycling plays a key role in maintaining river ecological functions which are threatened by anthropogenic activities. The newly discovered complete ammonia oxidation, comammox, provides novel insights into the ecological effects of nitrogen on that it oxidizes ammonia directly to nitrate without releasing nitrite as canonical ammonia oxidization conducted by AOA or AOB which is believed to play an important role in greenhouse gas generation. Theoretically, contribution of commamox, AOA and AOB to ammonia oxidization in rivers might be impacted by anthropogenic land-use activities through alterations in flow regime and nutrient input. While how land use pattern affects comammox and other canonical ammonia oxidizers remains elusive. In this study, we examined the ecological effects of land use practices on the activity and contribution of three distinctive groups of ammonia oxidizers (AOA, AOB, comammox) as well as the composition of comammox bacterial communities from 15 subbasins covering an area of 6166 km2 in North China. The results showed that comammox dominated nitrification (55.71%–81.21%) in less disturbed basins characterized by extensive forests and grassland, while AOB became the major player (53.83%–76.43%) in highly developed basins with drastic urban and agricultural development. In addition, increasing anthropogenic land use activities within the watershed lowered the alpha diversity of comammox communities and simplified the comammox network. Additionally, the alterations of NH4+-N, pH and C/N induced by land use change were found to be crucial drivers in determining the distribution and activity of AOB and comammox. Together, our findings cast a new light on aquatic-terrestrial linkages from the view of microorganism-mediated nitrogen cycling and can further be applied to target watershed land use management.

The effects of mowing and multi-level N fertilization on soil bacterial and fungal communities in a semiarid grassland are year-dependent

The diversity and structure of plant and soil microbial communities are influenced by temporal variability in environmental conditions (e.g., precipitation); however, it is unclear whether the responses of these biotic communities to land use practices (e.g., N fertilization and mowing) also vary over time. Here we investigated how harvesting hay by mowing and applications of N fertilization at different rates (0, 2.5, 5, 10, 20, and 40 g N m−2 yr−1) affected plant, bacterial, and fungal communities by exploring data collected from a field experiment in a semiarid grassland in northern China over two consecutive years of 2017 and 2018. The cumulative precipitation during the growing season differed between the two studied years. The sampling year had more effect on the structure of the plant and soil microbial community than N fertilization and mowing, suggesting that the effects of land use practices varied by year, and were difficult to predict over time. The diversity of bacteria and fungi showed a different response to N fertilization and mowing between the two years. For example, in the wet year, the fungal diversity was up to 11% lower in soil that had been treated using the highest N fertilizer application than in untreated soil, but showed little variation in the dry year. The bacterial diversity was higher for all N application rates in the mown than the unmown land during the wet year, but no difference was observed during the dry year. There were more opportunistic and sensitive taxa for the two years (over 36.9% of top 10% relative abundance of bacterial and fungal taxa) than for N fertilization and mowing (below 33.0% of top 10% relative abundance of bacterial and fungal taxa). The relationships between plant and soil microbial communities differed between the two years, and were much stronger in the dry year than the wet year. We conclude that N fertilization and mowing had varying effects on plant and soil microbial communities in the study area over the two-year period. Our results also suggest that precipitation is the main control on land use-related changes in plant and soil microbial communities in semiarid ecosystems.

Effects of Land-Use Practices on Woody Plant Cover Dynamics in Sahelian Agrosystems in Burkina Faso since the 1970s–1980s Droughts

The 1970s–1980s droughts in the Sahel caused a significant degradation of land and plant cover. To cope with this situation, populations have developed several biophysical and social adaptation practices. Many of these are agroforestry practices and contribute to the maintenance of agrosystems. Unfortunately, they remain insufficiently documented and their contributions to the resilience of agrosystems insufficiently evaluated. Many authors widely link the regreening in the Sahel after droughts to the resumption of rainfall. This study examines the contribution of agroforestry practices to the improvement of woody plant cover in the North of Burkina Faso after the 1970s–1980s droughts. The examination of practices is carried out by integrating the rainfall, soil, and geomorphology variables. Landsat images are used to detect changes in woody plant cover: increasing, decreasing, and no-change in the Enhanced Vegetation Index. In addition, 230 field observations, coupled with interviews conducted on the different categories of change, have allowed to characterize the biophysical environment and identify land-use practices. The results show a variability of vegetation index explained to 9% (R2 = 0.09) by rainfall. However, Chi-Squared independence tests show a strong dependence between changes in woody plant cover and geomorphology (p = 0.0018 *), land use, land cover (p = 0.0001 *), and land-use practices (p = 0.0001 *). Our results show that rainfall alone is not enough to explain the dynamics of agrosystems’ woody plant cover. Agricultural and social practices related to the dynamics of farmer perceptions play a key role.

Land Use Practices in the Rural and Urban Sub Catchments of River Rwizi, Western-Uganda; Their Effect on Its Ecological Characteristics

The water quality of river Rwizi has increasingly become a concern at community, district and national levels, serving a wider catchment in the south western part of Uganda. With the increasing national human population, there has been an increase in land use activities posing a risk of degradation. This study assessed the land use practices around river Rwizi and the effects they have on the ecological situation of the river. Cross sectional and descriptive research designs were employed in studying the effects of land use practices on the ecological characteristics of the river. Both quantitative and qualitative data analysis techniques were used in analyzing the field data. The findings indicate that several land use practices are done around the river and adverse effects have also resulted from these activities. Existing policies and laws on the management of water resources need to be strengthened. Collaborative management should be emphasized to ensure effective management of this river.

Which Way Forward? Using simulation models and ethnography to understand changing livelihoods among Kenyan pastoralists in a “new commons”

Over the last several decades there has been a transformation of the Samburu pastoral commons to new forms of land tenure and use. Government led land adjudication in the 1970s and 1980s established new forms of land ownership including group ranches and, in some places, complete privatization of land into individual parcels. An important question is what forms of land use and social relations emerge in the wake of land adjudication, and with what consequences? Can a “new commons” arise following transformation of the traditional commons? We address these questions by examining the aftermath of privatization in a Samburu community. Through ethnographic observations and interviews, we gain insight into peoples’ understanding of land use and current norms and practices and propose two diverse visions of the future – the “pastoralist imperative” of continued extensive livestock production and “future farmers” seeking a more settled, crop and wage labour-based livelihood. Using computer simulation models of the environment and households we conduct scenario analyses tracing the effects of land use practices and choices resulting from these different perspectives on variables such as livestock wealth, household income and food requirements, and ecological resources including grasses and shrubs. Our analysis suggests that privatization has yielded a “new commons” combining elements of individual ownership with shared management. These institutional innovations enable a continuation of extensive livestock production with new livelihood strategies that include a degree of land enclosure such as cultivation and land leasing. The analysis indicates that seemingly contradictory norms and practices can co-exist on the same land allowing considerable flexibility in production of livestock and crops. However, the models also demonstrate the limits that may be reached, particularly if common access is heavily curtailed.

Environmental and anthropogenic factors structuring waterbird habitats of tropical coastal lagoons: Implications for management

Tropical coastal lagoons are among the most threatened ecosystems on Earth due to multiple factors. The loss and degradation of coastal lagoons can adversely affect waterbirds, which depend crucially on wetland habitats. This study investigates the effects of a number of environmental variables on waterbird habitat use. Specifically, we assessed the abundances of six waterbird guilds in relation to hydrochemical, structural, and anthropogenic factors in 351 survey blocks of 22 tropical coastal lagoons of southeastern Brazil. Patterns of habitat use were analyzed using generalized mixed models. We found that water depth was the most important variable influencing the waterbird assemblage. Increasing water depth reduced the abundance of small and large wading birds, dabbling ducks, and diving birds. Extreme values of salinity negatively affected diving birds and large wading birds. Vegetation height influenced shorebirds negatively, while it influenced vegetation gleaners positively. Anthropogenic factors played an important role in structuring the habitat of small wading birds, dabbling ducks, diving birds and fishing birds. Our study indicates that the various guilds showed specific responses to different habitat variables. We conclude that the maintenance of water depths in the range of 0–20cm, the preservation of a mosaic of vegetation heights, and the reduction of livestock grazing pressure are among the most important aspects for supporting high avian abundance and biodiversity in tropical coastal lagoons. Management strategies should therefore address a specific number of structural and hydrochemical attributes of coastal lagoons and should carefully consider the effects of land use practices.

Effects of land use practices on soil organic carbon, nitrogen and phosphorus in river Nzoia drainage basin, Kenya

Land use activities along River Nzoia Drainage Basin, Kenya, include cultivation along the river banks, over grazing, deforestation, draining of wetlands for horticulture, harvesting of sand and brick-making. These activities have brought about changes in soil properties in the drainage basin adversely affecting farming output and the ecosystem in general. Consequently, it is important to understand how the different land use activities influence the soil properties in order to design and implement effective soil management strategies. This study examined the effects of land use practices on selected soil nutrients in Nzoia River Drainage Basin in Bungoma County. Cultivation and grazing were identified as important land use practices, while undisturbed sites were treated as controls. Land use practices along the river were identified by actual surveying of the study area. Secondary data on land use practices were obtained from technical reports, from local authorities and government offices. Soil samples were collected from different land use areas using randomly placed 5mx5m quadrats. Solis were collected at depths of 15cm in zigzag grid layout in each sample quadrat using soil auger. A total of 72 soil samples were collected in the study sites and analyzed for total nitrogen (N), available phosphorus (P) and organic carbon (C). Analysis of variance and correlation were performed to determine the significant land use practices affecting soil N, C and P. Cultivation had a significant effect on soil organic C mean value of 1.91 but negatively correlated with total Nitrogen and soil C while undisturbed sites exhibited positive correlation with C (P≤ 0.05). On the basis of our findings, it is recommended that conservation agriculture be practiced in the River Nzoia and its drainage system.

Preface "Hillslope hydrological modelling for landslides prediction"

Looking at natural hazards and risks, such as landslides, debris flow and floods, we see a broad range of science fields involved: from earth science to engineering science, to management, policy and social science. Although research on natural hazards and risks contains mono-disciplinary aspects, it is best characterized by its multi-disciplinary nature. Moreover, the link to society has always been a very important driver in natural hazards research, pushed by the need for reliable prediction models to be implemented into early warning systems as well as by the required complete understanding of the physical mechanisms for the design of mitigation works. If we focus on landslide and debris flows as in this special issue of HESS, we will see impressive progress in the geotechnical and slope stability modelling needed for hazard analysis. Similarly, the risk management aspects, such as hazard mapping and risk assessment, have received much attention. Hydrology is an important aspect of landslide and debris flow assessment. Precipitation and snowmelt water infiltration, leading to local pore water pressure increase and/or matric suction decrease, is amongst the most common triggers of landslides. Fundamental knowledge about underlying processes affecting this infiltration process, such as macropore and fissure flow, water repellency, soil structure, soil–plant–atmosphere interactions as well as the effects of land use practices (e.g. deforestation, terracing, grazing), has strongly improved in the last decade or so, with a clear focus on more detailed knowledge of hydrological process dynamics. The hydrological process understanding progressed rapidly under pressure of societal needs such as prediction of discharge generation and contaminant transport, to name a few. Although hydrology research is very strongly linked to natural hazards, such as landslides and debris flows, this improved hydrological knowledge has found its way into the landslide community rather modestly. In particular, the incorporation of hydrological processes into large-scale models is still incomplete and their application to landslide prediction limited. Landslide research tends to be more focused on novel methods to include spatial data and on the practical applicability of, e.g. landslide triggering modelling and statistical analyses for regional hazard and risk assessment. However, without stating that these fields have been fully exploited, we see that in our quantitative landslide and debris flow modelling the inclusion of increased process knowledge seems to lag behind. This in depth process understanding needs to be incorporated in our technical predictions in order to improve the reliability of early warning systems, mitigation works and landslide zonation. This special issue aims to present innovative hydrological research applied to landslide studies to improve the understanding of the spatio-temporal patterns of slope movement mechanisms induced by precipitation. The initiative struck a sympathetic note, as many colleagues were facing these challenges. The topic of hydrology and landslides is finding more and more space in hydrological research, as witnessed by the number of relevant papers published, in special issues, e.g. on hydrology of unstable clay shales (Bogaard et al., 2012) and through the organization of workshops and special conference sessions, such as six EGU sessions on hydrology and landslides, three editions of the Italian Workshop on Landslides mainly dedicated to landslide hydrology (www.iwl.unina2.it), and special sessions at IAEG2014. Therefore, this Special Issue discusses the representation of

The influence of land use practices on earthworm communities in saline agriculture soils of the west coast region of China's Bohai Bay

The effects of land use practices on soil fauna, especially earthworms, are poorly known in coastal saline agricultural soils. Here we compare earthworm communities in six types of land use practice in the coastal region of China’s Bohai Bay, namely uncultivated saline soil, two orchard (pear and winter jujube) lands, man-made forests (chinese ash), vegetable land and cropped land (maize). In addition, we recorded selected physicochemical properties of the soil. Soil organic matter content and total N were significantly higher under pear orchard and vegetable land than under the other land use practices, and their lowest values were observed from uncultivated saline soil. Vegetable land and pear orchard land showed a significantly higher abundance of earthworms than the other land use practices, whereas no earthworm was found in uncultivated saline soil. The sites under individual practices supported one to three earthworm species. Aporrectodea trapezoides species was present under four types of land use practice, and the biomass of this species accounted for more than 60% of the community. Vegetable land and pear orchard land supported richer earthworm community than the other land use practices, dominated by Aporrectodea trapezoides and Drawida japonica. These preliminary results indicated that land use practices have substantial effects on the abundance and composition of earthworm communities in saline soils.

Addressing Land Degradation in Tanzania: Contemporary Issues Related to Policies and Strategies

Several attempts have been made since the early years of independence of Tanzania to address land degradation. Policies and strategies were formulated that emphasized on the importance of land conservation in achieving economic growth. However, the context in which the earlier strategies were designed and implemented led to further land degradation. Failure of these interventions was partly because policies which backed them remained sectoral and most of them adopted the top-down approach with very little involvement of communities. The United Nations Conference on Environment and Development (UNCED) of 1992 in Rio de Janeiro created a new chapter in the country by insisting on the importance of sustainable development. The new policies and strategies were formulated with intentions to correct the past mistakes. This paper has assessed the extent to which Tanzania’s post-UNCED policies and strategies address the recent challenges of climate change on land degradation as reported by the IPCC in 2007. It involved review of selected policies, strategies and related literature on land degradation and climate change. The National Strategy for Growth and Reduction of Poverty (NSGRP) and two other sectoral strategies were reviewed in addition to the environmental, agricultural and water policies. The study finds that significant short and long-term measures to combat the negative effects of land use practices on the land resource are addressed. However, constant review of the policies and strategies is required to ensure that emerging challenges are addressed as part of the overall efforts to combat impacts of global climate change.

A Reconnaissance of Small Mammal Communities in Garland and Government Prairies, Arizona

Small mammals play key ecological roles in grassland ecosystems, yet little is known regarding small mammal communities in large (>50 km2), high-elevation prairies embedded in ponderosa pine (Pinus ponderosa) forests in north central Arizona. To provide information on community composition and habitat relationships, we live-trapped small mammals on 6 transects in 2 prairies in 2008. We captured 78 individuals in 5501 trap occasions. Capture rates were low and varied widely among transects. Community composition was simple, with only 3 species of small mammals captured. In order of relative abundance, these species were deer mouse (Peromyscus maniculatus, n = 44 individuals), Mogollon vole (Microtus mogollonensis, n = 22), and spotted ground squirrel (Spermophilus spilosoma, n = 12). Deer mice were captured on all transects and voles on all but one transect. In contrast, spotted ground squirrels were captured on only 2 transects and were relatively common on only one transect. There were no previous records of spotted ground squirrels in these prairies. Deer mice were positively associated with rock cover and vegetation height. Voles were positively associated with shrub cover and combined cover of live and dead vegetation and were negatively associated with bare ground. Spotted ground squirrels were positively associated with forb cover. This study provides baseline data on small mammal communities in these prairies and documents the presence of a previously unknown species. Further studies would be desirable to better understand spatial and temporal variation in these communities, habitat relationships, and effects of land-use practices on small mammals and their habitats.

Land-use changes alter CO2 flux patterns of a tall-grass Andropogon field and a savanna-woodland continuum in the Orinoco lowlands

Land use changes in the savannas of the Orinoco lowlands have resulted in a mosaic of vegetation. To elucidate how these changes have affected carbon exchanges with the atmosphere, we measured CO2 fluxes by eddy covariance and soil CO2 efflux systems along a disturbance gradient beginning with a cultivated tall-grass Andropogon field (S1) and extending over three savanna sites with increasing woody cover growing above native herbaceous vegetation. The savanna sites included a herbaceous savanna (S2), a tree savanna (S3) and a woodland savanna (S4). During the wet season, maximum diurnal net ecosystem exchange (NEE) over the S1-S4 sites was 6.6-9.3, 6.6-7.9, 10.6-11.3 and 9.3-10.6 micromol m(-2) s(-1), respectively. The rate of CO2 uptake over S1 was lower than that for C4 grasses elsewhere because of pasture degradation. Soil respiration and temperature were exponentially related when soil water content (theta) was above 0.083 m(3) m(-3); however, soil respiration declined markedly as theta decreased from 0.083-0.090 to 0.033-0.056 m(3) m(-3). There were bursts of CO2 emission when dry soils were rewetted by rainfall. During the wet season, all sites constituted carbon sinks with maximum net daily ecosystem production (NEP) of 2.1, 1.7, 2.1 and 2.1 g C m(-2) day(-1), respectively. During the dry season, the savanna sites (S2-S4) became carbon sources with maximum emission fluxes of -0.5, -1.4 and -1.6 g C m(-2) day(-1), respectively, whereas the tall-grass field (S1) remained a carbon sink with a maximum NEP of 0.3 g C m(-2) day(-1) at the end of the season. For all measurement periods, annual NEP of sites S1-S4 was 366, 6, 116 and 139 g C m(-2), respectively. Comparisons of carbon source/sink dynamics across a wide range of savannas indicate that savanna carbon budgets can change in sign and magnitude. On an annual basis, gross primary production over the S1-S4 stands was 797, 803, 136 and 1230 g C m(-2), respectively. Net primary productivity (NPP) of the S1-S4 stands, calculated from eddy covariance measurements as the daily sum of NEE and day and night heterotrophic respiration was 498, 169, 181 and 402 g C m-2 year-1, respectively. These values were slightly higher than NPP based on harvest measurements (432, 162, 176 and 386 g C m(-2) year(-1), respectively), presumably because fine roots were incompletely harvested. Soil water content limited carbon uptake at all sites, and water-use efficiency (WUE) was related to rainfall dynamics. During the dry season, all sites except the cultivated tall-grass Andropogon field (S1) had a negative WUE. Although our results are specific to the Orinoco vegetational mosaic, the effects of land-use practices on the controls and physiological functions of the studied ecosystems may be generalized to other savannas.

Sampling on private property to evaluate population status and effects of land use practices on the gopher tortoise, Gopherus polyphemus

Although private properties are predicted to play an increasingly significant role in conservation, surveys of species of special concern are rare on these lands. We created a template for a multi-county survey of randomly selected sites and sampled for burrows of the gopher tortoise ( Gopherus polyphemus) in south-central Georgia, USA. Current land use was strongly correlated with tortoise population condition. The highest densities of tortoise burrows were found on lands with open-canopied pine stands that were managed with prescribed fire, a practice associated with types of selection forestry and/or wildlife management. Agricultural sites and unburned areas provided poor habitat and pine plantations were only slightly better. Our estimates of tortoise population densities indicated that the current landscape supports less than 20% of the animals present before implementation of modern land use practices. In addition, our estimate for density of active burrows was approximately one third of that projected for the entire state range 20 years ago by Auffenberg and Franz [Auffenberg, W., Franz, R., 1982. The status and distribution of the gopher tortoise ( Gopherus polyphemus). In: Bury, R.B. (Ed.), North American Tortoises: Conservation and Ecology (US Fish and Wildlife Service Wildlife Research Report 12). pp. 95–126]. However, some good sites for gopher tortoises remain in south Georgia and our data also suggested that extraordinary conservation actions may not be required if ways can be developed to retain traditional land management practices on private property.

Evidence that local land use practices influence regional climate, vegetation, and stream flow patterns in adjacent natural areas

AbstractWe present evidence that land use practices in the plains of Colorado influence regional climate and vegetation in adjacent natural areas in the Rocky Mountains in predictable ways. Mesoscale climate model simulations using the Colorado State University Regional Atmospheric Modelling System (RAMS) projected that modifications to natural vegetation in the plains, primarily due to agriculture and urbanization, could produce lower summer temperatures in the mountains. We corroborate the RAMS simulations with three independent sets of data: (i) climate records from 16 weather stations, which showed significant trends of decreasing July temperatures in recent decades; (ii) the distribution of seedlings of five dominant conifer species in Rocky Mountain National Park, Colorado, which suggested that cooler, wetter conditions occurred over roughly the same time period; and (iii) increased stream flow, normalized for changes in precipitation, during the summer months in four river basins, which also indicates cooler summer temperatures and lower transpiration at landscape scales. Combined, the mesoscale atmospheric/land‐surface model, short‐term trends in regional temperatures, forest distribution changes, and hydrology data indicate that the effects of land use practices on regional climate may overshadow larger‐scale temperature changes commonly associated with observed increases in CO2 and other greenhouse gases.

Evidence that local land use practices influence regional climate, vegetation, and stream flow patterns in adjacent natural areas

We present evidence that land use practices in the plains of Colorado influence regional climate and vegetation in adjacent natural areas in the Rocky Mountains in predictable ways. Mesoscale climate model simulations using the Colorado State University Regional Atmospheric Modelling System (RAMS) projected that modifications to natural vegetation in the plains, primarily due to agriculture and urbanization, could produce lower summer temperatures in the mountains. We corroborate the RAMS simulations with three independent sets of data: (i) climate records from 16 weather stations, which showed significant trends of decreasing July temperatures in recent decades; (ii) the distribution of seedlings of five dominant conifer species in Rocky Mountain National Park, Colorado, which suggested that cooler, wetter conditions occurred over roughly the same time period; and (iii) increased stream flow, normalized for changes in precipitation, during the summer months in four river basins, which also indicates cooler summer temperatures and lower transpiration at landscape scales. Combined, the mesoscale atmospheric/land-surface model, short-term trends in regional temperatures, forest distribution changes, and hydrology data indicate that the effects of land use practices on regional climate may overshadow larger-scale temperature changes commonly associated with observed increases in CO2 and other greenhouse gases.

Observations on the Effects of Land-use Practices on Water Resources in Upper Benue Basin of Nigeria

Observations on the Effects of Land-use Practices on Water Resources in Upper Benue Basin of Nigeria

Grizzly Bear: Habitat Relationships in the Yellowstone Area

Habitat use by grizzly bears (Ursus arctos) was studied from 1977 through 1979 in a 20,000-km2 area with Yellow? stone National Park in the center. Of 1826 aerial radio locations of 46 instrumented grizzlies, 90% were in timber. Threefourths of the locations were 100 m or less from an edge between timber and an opening. Timber over 3 m tail with a canopy cover of 26-75% accounted for 50% of all activity sites from March through November. The Abies lasiocarpalVaccinium scoparium community alone contained 23% of the total activity sites and 35% of the forested activity sites. Of 507 observations of feeding activity, 45% were recorded in timber over 3 m tail with a canopy cover of 26-100%, 34% in timber with a 0.1-25% canopy cover, 20% in open habitats, and 3% in timber less than 3 m tail. Ninety-nine percent of examined day beds were in for? ested communities. Int. Conf. Bear Res. and Manage. 5:118-123 In 1975 the grizzly bear south of Canada was listed as a threatened species. To comply with the Endangered Species Act of 1973, Federal agencies must, therefore, avoid destruction or adverse modification of grizzly bear habitat. However, a lack of data has limited the ability of management agencies to define critical habitat and evaluate the effects of land use practices upon the grizzly. Research to determine the rela? tionships between grizzly bears and habitat has been continuing and data are accumulating. The use of timber as shelter by grizzlies has been documented (Jonkel and Cowan 1971; Craighead and Craighead 1972; J.Sumner and J.J. Craighead, unpubl. rep., Mont. Coop. Wild? life Res. Unit, Missoula, 1973; R. Knight et al., unpubl. annu. reps., Interagency Study Team, U.S. Dep. Inter., Park Ser., Bozeman, Mont., 1977, 1978; Roth and Osti 1979). Research has also determined that meadows are important for? aging habitats for grizzlies (Graham 1978, Mealy et al. 1977). The extent to which grizzly bears used timbered areas for foraging was unknown and has been an important management-related question; therefore, since 1977 the Interagency Grizzly Bear Study (IGBS) has addressed this problem. This paper reports the findings of the IGBS on grizzly bear-habitat relationships. Funding for this study was provided by the Na? tional Park Service and the U.S. Fish and Wildlife Service. The field work was facilitated by the cooperation of personnel from Yellowstone Nation? al Park, district U.S. Forest Service offices within the study area, and the wildlife departments of Wyoming, Idaho, and Montana. Special thanks are extended to the numerous IGBS seasonal em? ployees for gathering the data, to Dave and Roger Stradley for magnificent piloting throughout the years of the study, and to R. Knight and T. Weaver for critically reviewing the manuscript.