Vegetation Canopy Cover Research Articles

Radiometric Information from Airborne Laser Scanning for Archaeological Prospection

Airborne laser scanning (ALS) is widely used for the sampling of large landscapes for different application areas. Since several years ALS data is also often used in archaeological prospection, e.g. in order to detect archaeological features beneath the vegetation canopy cover. For most of the applications only the geometric information provided by ALS is utilized. However, next to geometric information ALS provides radiometric information for each acquired point. For its practical usability radiometric calibration is essential. This contribution presents, next to the basic theory, a radiometric calibration workflow for ALS data. As a result calibrated spectral information is added to the ALS point cloud. This information can be used to generate images displaying reflectance at the wavelength of the ALS sensor. The presented calibration workflow is furthermore applied to different ALS missions carried out in the study area Carnuntum, Austria. Due to the usage of ALS sensors with different laser wavelengths, next to single wavelength ALS data, multi-wavelength reflectance data is presented and compared. Additionally, the multi-temporal characteristics of reflectance data are discussed briefly. Finally, the paper is summarized and an outlook into future research work is presented.

Changes in Vegetation and Biological Soil Crust Communities on Sand Dunes Stabilizing after a Century of Grazing on San Miguel Island, Channel Islands National Park, California

San Miguel Island is the westernmost of the California Channel Islands and one of the windiest areas on the west coast of North America. The majority of the island is covered by coastal sand dunes, which were stripped of vegetation and subsequently mobilized due to droughts and sheep ranching during the late 19th century and early 20th century. Since the removal of grazing animals, vegetation and biological soil crusts have once again stabilized many of the island's dunes. In this study, historical aerial photographs and field surveys were used to develop a chronosequence of the pattern of change in vegetation communities and biological soil crust levels of development (LOD) along a gradient of dune stabilization. Historical aerial photographs from 1929, 1954, 1977, and 2009 were georeferenced and used to delineate changes in vegetation canopy cover and active (unvegetated) dune extent among 5 historical periods (pre-1929, 1929–1954, 1954–1977, 1977–2009, and 2009–2011). During fieldwork, vegetation and biological soil crust communities were mapped along transects distributed throughout San Miguel Island's central dune field on land forms that had stabilized during the 5 time periods of interest. Analyses in a geographic information system (GIS) quantified the pattern of changes that vegetation and biological soil crust communities have exhibited on the San Miguel Island dunes over the past 80 years. Results revealed that a continuing increase in total vegetation cover and a complex pattern of change in vegetation communities have taken place on the San Miguel Island dunes since the removal of grazing animals. The highly specialized native vascular vegetation (sea rocket, dunedelion, beach-bur, and locoweed) are the pioneer stabilizers of the dunes. This pioneer community is replaced in later stages by communities that are dominated by native shrubs (coastal goldenbush, silver lupine, coyote-brush, and giant coreopsis), with apparently overlapping or cyclical succession pathways. Many of the dunes that have been stabilized the longest (since before 1929) are dominated by exotic grasses. Stands of biological soil crusts (cyanobacteria) are found only on dunes where vascular vegetation is already present. Biological soil crusts are not found on dunes exhibiting a closed vascular plant canopy, which may indicate that the role of soil crusts in dune stabilization on the island is transitory. Particle-size analyses of soil samples from the study area reveal that higher biological soil crust LOD is positively correlated with increasing fine grain content. The findings indicate that changes in vegetation communities may be the most rapid at earlier and later stages of dune stabilization and that regular monitoring of dunes may help to identify the interactions between vegetation and soil crusts, as well as the potential transitions between native and exotic plant communities.

Deriving RUSLE cover factor from time-series fractional vegetation cover for hillslope erosion modelling in New South Wales

Soil loss due to water erosion, in particular hillslope erosion, can be estimated using predictive models such as the Revised Universal Soil Loss Equation (RUSLE). One of the important and dynamic elements in the RUSLE model is the cover and management factor (C-factor), which represents effects of vegetation canopy and ground cover in reducing soil loss. This study explores the potential for using fractional vegetation cover, rather than traditional green vegetation indices (e.g. NDVI), to estimate C-factor and consequently hillslope erosion hazard across New South Wales (NSW), Australia. Values of the C-factor were estimated from the emerging time-series fractional cover products derived from Moderate Resolution Imaging Spectroradiometer (MODIS). Time-series C-factor and hillslope erosion maps were produced for NSW on monthly and annual bases for a 13-year period from 2000 to 2012 using automated scripts in a geographic information system. The estimated C-factor time-series values were compared with previous study and field measurements in NSW revealing good consistency in both spatial and temporal contexts. Using these time-series maps, the relationship was analysed between ground cover and hillslope erosion and their temporal variation across NSW. Outcomes from this time-series study are being used to assess hillslope erosion hazard, sediment and water quality (particularly after severe bushfires) across NSW at local, catchment and regional scales.

A Comparison of Three Dry Matter Forage Production Methods Used in South Africa

A common method for determining forage production of rangelands is by clipping and weighing forage from quadrats with predetermined areas. This technique is however time consuming. Other techniques which require less time and labour include amongst others using the disk pasture meter or phytomass derived from the vegetation classification program PHYTOTAB, in conjunction with the Plant Number Scale, which is used to determine vegetation canopy cover. The phytomass determined using PHYTOTAB/Plant Number Scale and the disk pasture meter was compared to the phytomass obtained from the actual clipping and weighing of forage. Tests showed that there were indeed statistically significant differences between the mean phytomass values of the three techniques. Considerable variation was shown in the results of the disk pasture meter readings compared to the other two techniques. The phytomass values obtained using the disk pasture meter were significantly higher than the phytomass determined using both the PHYTOTAB/Plant Number Scale and the clipping and weighing techniques. Results further indicated a significant similarity in the phytomass determined using the PHYTOTAB/Plant Number Scale and the clipping and weighing technique. The results of this pilot study need further investigation.

Spring Clipping, Fire, and Simulated Increased Atmospheric Nitrogen Deposition Effects on Tallgrass Prairie Vegetation

Defoliation aimed at introduced cool-season grasses, which uses similar resources of native grasses, could substantially reduce their competitiveness and improve the quality of the northern tallgrass prairie. The objective was to evaluate the use of early season clipping and fire in conjunction with simulated increased levels of atmospheric nitrogen deposition on foliar canopy cover of tallgrass prairie vegetation. This study was conducted from 2009 to 2012 at two locations in eastern South Dakota. Small plots arranged in a split-plot treatment design were randomized in four complete blocks on a warm-season grass interseeded and a native prairie site in east-central South Dakota. The whole plot consisted of seven treatments: annual clip, biennial clip, triennial clip, annual fire, biennial fire, triennial fire, and undefoliated control. The clip plots consisted of weekly clipping in May to simulate heavy grazing. Fire was applied in late April or early May. The subplot consisted of nitrogen applied at 0 or 15 kg N · ha−1 in early June. All treatments were initially applied in 2009. Biennial and triennial treatments were reapplied in 2011 and 2012, respectively. Canopy cover of species/major plant functional groups was estimated in late August/early September. Annual clipping was just as effective as annual fire in increasing native warm-season grass and decreasing introduced cool-season grass cover. Annual defoliation resulted in greater native warm-season grass cover, less introduced cool-season grass cover, and less native cool-season grass cover than biennial or triennial defoliation applications. Low levels of nitrogen did not affect native warm-season grass or introduced cool-season cover for any of the defoliation treatments, but it increased introduced cool-season grass cover in the undefoliated control at the native prairie site. This study supports the hypothesis that appropriately applied management results in consistent desired outcomes regardless of increased simulated atmospheric nitrogen depositions.

Can restoration of afforested peatland regulate pests and disease?

Summary Government policies are driving landscape‐scale changes in land use to provide ecosystem services; but there may be unconsidered cascading effects. A major land use change targeted for regulating climate and biodiversity is peatland restoration. This will cause changes in vegetation and, potentially, keystone species such as large herbivores, which are the main hosts to Ixodes ricinus (L.) ticks, the most important vector of disease‐causing pathogens in Europe. This study tested the impact of restoring peatlands from conifer forestry on Ixodes ricinus abundance and explored the likely mechanisms. Large‐scale surveys of Ixodes ricinus, vertebrate herbivores and vegetation were conducted in adjacent areas of forest, bog and areas felled 5–13 years previously. Questing tick abundance was greatest in forest and almost absent from blanket bog, with intermediate numbers in felled areas, where ticks were more abundant in young than in old felled areas. The likely mechanisms for these variations in tick abundance were deer habitat preferences (bog was the least preferred habitat) and ground vegetation height or canopy cover, which are generally associated with alternative tick hosts and micro‐climates that aid tick questing and survival. Synthesis and applications. Felling conifer forest to restore peatlands could produce a dramatic decline in tick abundance throughout the restoration process, with implications for disease risk. Therefore, a further ecosystem service of peatlands in addition to climate, biodiversity and water regulation is regulating pests and disease. Deer management and procedures that speed up the restoration process are likely to enhance the effect during the intermediate stages.

Assessment of ice mapping system and moderate resolution imaging spectroradiometer snow cover maps over Colorado Plateau

Satellite snow cover area (SCA) mapping using optical sensors has been known to suffer severe obstruction due to vegetation canopy and cloud cover. Several algorithms have been developed to reduce cloud cover contamination and enhance the SCA mapping. In this study we introduce the use of a daily SCA product from the Multisensor Snow and Ice Mapping System (IMS) at a nominal resolution of 4 km, assess its accuracy and error levels against in situ observations, and compare the IMS SCA product with the SCA products from moderate resolution imaging spectroradiometer (MODIS), a combination of daily Terra and Aqua satellites. The results show that the snow accuracies are higher during winter for both IMS and MODIS, and that there is not much difference between MODIS at 500 m and upscaled at 4 km. The IMS SCA mapping accuracies are significantly higher than MODIS accuracies for all sky conditions, while they are similar to or slightly lower than MODIS accuracies in clear sky conditions. The overestimate error of snow cover using IMS is higher (lower) than that of MODIS during ablation (accumulation) periods. Both MODIS and IMS show a similar pattern of underestimation errors of snow cover with the IMS being slightly higher than the MODIS. It is concluded that the IMS SCA product has potential as a good alternative for the MODIS daily SCA products or replacing those cloud pixels in the MODIS daily or multiday products.

Relationship between habitat characteristics and densities of southern Idaho ground squirrels

Many wildlife species living in sagebrush-steppe habitats of the Intermountain West of the United States have experienced population declines. Effective management of such species, especially restoration efforts, is contingent on understanding relationships between habitat characteristics and population densities of the target species. Unfortunately, even such basic information is often lacking. The goal of this 2-year study was to determine the relationship between southern Idaho ground squirrel (Urocitellus endemicus) population densities and habitat variables: soils (texture), topography (slope, aspect), and vegetation (canopy cover, species diversity). We measured population density indirectly through burrow entrance counts and categorized them into high-burrow and low-burrow densities. We used logistic regression and Akaike's Information Criterion to identify a best subset of models. We employed model averaging and calculated odds ratios for averaged parameter estimates found in the best models. A high density of burrows was associated with greater percentages of silt; east-facing aspects; greater plant species diversity; and greater cover of perennial grasses, perennial grasses and forbs, and native perennial forbs. Low burrow density was associated with greater percentages of sand; south-facing aspects; greater cover of exotic annuals; and lesser plant species diversity. Management of southern Idaho ground squirrel habitat should focus on protecting areas with existing native vegetation and restoring native, perennial vegetation in areas that are infested with exotic annuals, especially in areas possessing suitable soil types and topographic features. © 2013 The Wildlife Society.

Using LiDAR‐derived vegetation metrics for high‐resolution, species distribution models for conservation planning

Advances in remotely sensed data for characterizing habitat have enabled development of spatially explicit predictive species distribution models (SDM) that can be essential tools for management. SDMs commonly use coarse‐grain metrics, such as forest patch size or patch connectivity, over broad spatial extents. However, species distributions are likely driven in part by local, fine‐grained habitat conditions. Conservation and management are often planned and applied locally, where coarse predictions may be uninformative or not sufficiently precise. We investigated the integration of high‐resolution LiDAR (Light Detection and Ranging) with avian point sampling data to develop a detection‐corrected occupancy model to quantify habitat‐occurrence relationships for two species with different habitats: the endangered golden‐cheeked warbler (Setophaga chrysoparia) and black‐capped vireo (Vireo atricapilla) on a military installation in central Texas. We compared occupancy models that used only the more conventional, coarse remotely sensed metrics to models that also incorporated high‐resolution LiDAR‐derived metrics for vegetation height and canopy cover, to assess their use for predicting distributions. Models including LiDAR‐derived vegetation height and canopy cover metrics were competitive for both species, and models without LiDAR‐derived vegetation height had substantially lower model weights and explanatory strength. Area under curve estimates for the highest ranked models were high for warblers (0.864) and moderate for vireos (0.746). Using the best supported models for each species, we predicted the occurrence distribution for both species. The resulting predictions provide a decision support tool that enables assessment of the status, impacts, and mitigation of impacts to endangered species habitat on the installation due to land management and military training activities that is more standardized and accurate than current assessment approaches based on visual gestalt of habitat and expert opinion. Additionally, although previous species distribution models have been created for our focal species, most fail to match the grain and extent of most management actions or include local, fine‐grained metrics that influence distributions. In contrast, we demonstrate that use of LiDAR with species occurrence data can provide precision and resolution at a scale that is relevant ecologically and to the operational scale of most conservation and management actions.

Plant and Small Vertebrate Composition and Diversity 36–39 Years After Root Plowing

Root plowing is a common management practice to reduce woody vegetation and increase herbaceous forage for livestock on rangelands. Our objective was to test the hypotheses that four decades after sites are root plowed they have 1) lower plant species diversity, less heterogeneity, greater percent canopy cover of exotic grasses; and 2) lower abundance and diversity of amphibians, reptiles, and small mammals, compared to sites that were not disturbed by root plowing. Pairs of 4-ha sites were selected for sampling: in each pair of sites, one was root plowed in 1965 and another was not disturbed by root plowing (untreated). We estimated canopy cover of woody and herbaceous vegetation during summer 2003 and canopy cover of herbaceous vegetation during spring 2004. We trapped small mammals and herpetofauna in pitfall traps during late spring and summer 2001–2004. Species diversity and richness of woody plants were less on root-plowed than on untreated sites; however, herbaceous plant and animal species did not differ greatly between treatments. Evenness of woody vegetation was less on root-plowed sites, in part because woody legumes were more abundant. Abundance of small mammals and herpetofauna varied with annual rainfall more than it varied with root plowing. Although structural differences existed between vegetation communities, secondary succession of vegetation reestablishing after root plowing appears to be leading to convergence in plant and small animal species composition with untreated sites.

Performance of exclosure in restoring soil fertility: A case of Gubalafto district in North Wello Zone, northern highlands of Ethiopia

Abstract Inappropriate agricultural practices and conversion of marginal land to cultivation and grazing have led to severe land degradation in the Ethiopian highlands. Consequently, the government has invested substantial resources in soil and water conservation (SWC). One of such interventions was exclosure, which was aimed restoring biodiversity, biomass and soil fertility. The aim of this study was to analyze the impact of exclosures on soil fertility restoration and examine its variability across age, agro-ecology and landscape position. The study was conducted in the Gubalafto district of North Wello Zone, northern Ethiopian highlands. Vegetation cover was estimated and soil samples were collected from three age categories (open sites, 10- and 27-year-old exclosures), two agro-ecological zones (mild and cool) and in three landscape positions (lower, mid and upper). The samples were analyzed for selected soil physico-chemical properties using standard laboratory procedures. The results were statistically tested using analysis of variance (ANOVA). Vegetation ground and canopy cover increased with exclosure age. The soils of the exclosures showed significantly higher organic carbon (9 g/kg) and total nitrogen content (1.2 g/kg p ≤ 0.06 at α = 0.05) than the open sites. However, no statistical significant difference was observed between the 10- and 27-year-old exclosures, indicating that the restoration rate decreased with increasing exclosure age. This could be related to the low quantity and quality of the biomass, which influenced organic matter input and mineralization. Exclosures in the mild zone showed significantly higher soil fertility restoration than those in the cool zone. The differences between the two zones could be attributed to the effect of micro-climate on biomass production, vegetation types and organic matter mineralization. The soil physico-chemical properties neither had significant differences nor followed a regular trend across the landscape positions. The non-significant soil fertility restoration variation across the landscape positions could be attributed to complementary effect of structural SWC measures. Therefore, exclosure implementation and utilization planning should consider soil fertility restoration variation with age, agro-ecology and management conditions of the respective exclosure.

Impact of Habitat-Specific GPS Positional Error on Detection of Movement Scales by First-Passage Time Analysis

Advances in animal tracking technologies have reduced but not eliminated positional error. While aware of such inherent error, scientists often proceed with analyses that assume exact locations. The results of such analyses then represent one realization in a distribution of possible outcomes. Evaluating results within the context of that distribution can strengthen or weaken our confidence in conclusions drawn from the analysis in question. We evaluated the habitat-specific positional error of stationary GPS collars placed under a range of vegetation conditions that produced a gradient of canopy cover. We explored how variation of positional error in different vegetation cover types affects a researcher's ability to discern scales of movement in analyses of first-passage time for white-tailed deer (Odocoileus virginianus). We placed 11 GPS collars in 4 different vegetative canopy cover types classified as the proportion of cover above the collar (0–25%, 26–50%, 51–75%, and 76–100%). We simulated the effect of positional error on individual movement paths using cover-specific error distributions at each location. The different cover classes did not introduce any directional bias in positional observations (1 m≤mean≤6.51 m, 0.24≤p≤0.47), but the standard deviation of positional error of fixes increased significantly with increasing canopy cover class for the 0–25%, 26–50%, 51–75% classes (SD = 2.18 m, 3.07 m, and 4.61 m, respectively) and then leveled off in the 76–100% cover class (SD = 4.43 m). We then added cover-specific positional errors to individual deer movement paths and conducted first-passage time analyses on the noisy and original paths. First-passage time analyses were robust to habitat-specific error in a forest-agriculture landscape. For deer in a fragmented forest-agriculture environment, and species that move across similar geographic extents, we suggest that first-passage time analysis is robust with regard to positional errors.

Cold Season Respiration Across a Low Arctic Landscape: the Influence of Vegetation Type, Snow Depth, and Interannual Climatic Variation

Cold season respiration may significantly affect arctic terrestrial ecosystem annual net carbon balances. Here, the influences of vegetation type, experimentally deepened snow, and interannual climatic variation on total cold season CO2 efflux were investigated in a Canadian low arctic site containing dry heath, tall birch understory, birch hummock, and wet sedge ecosystems.Total efflux ranged from 34 to 126 g CO2-C m-2 among the vegetation types, with the tall birch understory respiring at least twice that of the birch hummock and four times that of either the dry heath or wet sedge. This variation did not correlate with soil temperature differences alone, but instead was attributed to ecosystem-specific interactions between snow depth, vegetation canopy cover, soil temperature, and moisture, as well as differences in plant biomass and litter production. Respiration from the birch hummock site was twice as high in 2006/2007 (the year of relatively warm fall and late winter soil temperature phases) as compared to 2004/2005, and was enhanced by the snow fence treatment only in the latter year. Together, these data demonstrate that cold season CO2 release differs substantially among tundra vegetation types, and strongly suggest that these effluxes can significantly offset growing season carbon gains, resulting in annual net carbon losses in some years.

Does Seeding a Locally Adapted Native Mixture Inhibit Ingress by Exotic Plants?

AbstractNon‐native plant species often colonize retired agricultural lands, creating monocultures with low species diversity that provide poor wildlife habitat. We assessed whether sowing a mix of 29 locally adapted native species reduced invasion of non‐native plant species compared to allowing vegetation to colonize naturally following tillage. There was a sampling date × treatment interaction for canopy cover of perennial exotic plant species. Plots that were not sown to natives had two to six times greater canopy cover of exotic species than did plots with both preparation (woody vegetation removed, plowed, and disked) and control (no preparation or sowing) plots. Canopy cover of exotic plants was similar in prepared‐only and control treatments from October 2008 to June 2010, ranging from 8 to 40%. Percent absolute canopy cover of native vegetation was 10–20 times greater on prepared and planted plots than on prepared‐only plots during March 2009 to June 2010. Sowing a mix of locally adapted native species may inhibit encroachment by non‐native species for up to two years after sowing on retired agricultural land in the Lower Rio Grande Valley of Texas.

Mapping Total Vegetation Cover Across Western Rangelands With Moderate-Resolution Imaging Spectroradiometer Data

Remotely sensed observations of rangelands provide a synoptic view of vegetation condition unavailable from other means. Multiple satellite platforms in operation today (e.g. Landsat , moderate-resolution imaging spectroradiometer [MODIS]) offer opportunities for regional monitoring of rangelands. However, the spatial and temporal variability of rangelands pose challenges to consistent and accurate mapping of vegetation condition. For instance, soil properties can have a large impact on the reflectance registered at the satellite sensor. Additionally, senescent vegetation, which is often abundant on rangeland, is dynamic and its physical and photochemical properties can change rapidly along with moisture availability. Remote sensing has been successfully used to map local rangeland conditions. However, regional and frequently updated maps of vegetation cover in rangelands are not currently available. In this research, we compare ground measurements of total vegetation cover, including both green and senescent cover, to reflectance observed by the satellite and develop a robust method for estimating total vegetation canopy cover over diverse regions of the western United States. We test the effects of scaling from ground observations up to the Landsat 30-m scale, then to the MODIS 500-m scale, and quantify sources of noise. The soil-adjusted total vegetation index (SATVI) captures 55% of the variability in ground measured total vegetation cover from diverse sites in New Mexico, Arizona, Wyoming, and Nevada. Scaling from the Landsat to MODIS scale introduces noise and loss of spatial detail, but offers inexpensive and frequent observations and the ability to track trends in cover over large regions. Observaciones de pastizales con sensores remotos proporcionan una vista sinóptica de la condición de la vegetación que no está disponible usando otros medios. Múltiples plataformas satelitales en operación hoy en día (e.g. Landsat, MODIS) proporcionan oportunidades para un monitoreo regional de los pastizales. Sin embargo, la variabilidad espacial y temporal de los pastizales posee retos relacionados con el mapeo de la condición de la vegetación. Por ejemplo, las propiedades del suelo pueden tener gran impacto en la reflectancia registrada por el sensor del satélite. Adicionalmente, la vegetación senescente, la cual es a menudo abundante en los pastizales, es dinámica y sus propiedades físicas y fotoquímicas pueden cambiar rápidamente debido al contenido de humedad disponible. Los sensores remotos han sido utilizados con éxito para mapear las condiciones locales de los pastizales. Sin embargo, mapas regionales y frecuentemente actualizados de la cobertura de la vegetación en pastizales no están disponibles en la actualidad. En esta investigación, se compararon medidas del suelo del total de la cobertura, incluyendo ambas coberturas la verde y la senescente, contra la observada por el satélite para desarrollar un método robusto con la finalidad de estimar el total de la cobertura de la copa de la vegetación sobre la diversa región del Oeste de estado Unidos. Se evaluaron los efectos de escala desde observaciones al ras de suelo hasta aquellas usando Landsat a una escala de 30 m, entonces a la escala de 500 m en MODIS y se cuantificaron las fuentes de variación. El índice ajustado total de vegetación (SATV) captura 55% de la variabilidad en la estimación del total de la cobertura vegetal de diversos sitios en Nuevo México, Arizona, Wyoming, y Nevada. La conversión de escala de Landsat a MODIS introduce cierto margen de error y pérdida de detalle espacial, pero ofrece observaciones baratas y frecuentes así como la capacidad de rastrear las tendencias en cobertura sobre extensas regiones.

Riparian vegetation removal alters consumer - resource stoichiometry in an Australian lowland stream

Anthropogenic impacts on stream ecosystems generate changes in nutrient and carbon availability which act as stoichiometric challenges to consumers. We tested the hypothesis that removal of Eucalyptus riparian vegetation alters in-stream resource stoichiometry with flow-on effects for a benthic consumer (the freshwater crayfish, Cherax destructor). Sites with high and low riparian canopy cover were selected on a lowland stream in south-eastern Australia. A reduction in riparian vegetation canopy cover was associated with decreased terrestrial detritus (low nutritional quality; high carbon to nitrogen (C : N) ratio) and increased cover of macrophytes and filamentous algae (high quality; low C : N ratio). This resource-quality shift was associated with a small but significant decrease in C. destructor C : N ratio (molar ratio of muscle tissue). This suggests that the animals are deviating from homeostasis and may be in better condition in the stream pools dominated by in-stream productivity. A significant negative relationship between C. destructor length and C : N ratio was observed, suggesting that resource-quality impacts may differ with age. The present study has shown that riparian loss alters stoichiometric interactions in stream benthic ecosystems, with potential consequences for stream processes such as nutrient cycling. Ecological stoichiometric theory should therefore be further utilised to make predictions of ecological impacts in freshwater systems.

EXCLOSURE LAND MANAGEMENT FOR RESTORATION OF THE SOILS IN DEGRADED COMMUNAL GRAZING LANDS IN NORTHERN ETHIOPIA

ABSTRACTIn the northern highlands of Ethiopia, establishment of exclosures to restore degraded communal grazing lands has been practiced for the past three decades. However, empirical data on the effectiveness of exclosures in restoring degraded soils are lacking. We investigated the influence of exclosure age on degree of restoration of degraded soil and identified easily measurable biophysical and management‐related factors that can be used to predict soil nutrient restoration. We selected replicated (n = 3) 5‐, 10‐, 15‐, and 20‐year‐old exclosures and paired each exclosure with samples from adjacent communal grazing lands. All exclosures showed higher total soil nitrogen (N), available phosphorus (P), and cation exchange capacity than the communal grazing lands. The differences varied between 2·4 (±0·61) and 6·9 (±1·85) Mg ha−1 for the total N stock and from 17 (±3) to 39 (±7) kg ha−1 for the available P stock. The differences in N and P increased with exclosure age. In exclosures, much of the variability in soil N (R2 = 0·64) and P (R2 = 0·71) stocks were explained by a combination of annual average precipitation, woody biomass, and exclosure age. Precipitation and vegetation canopy cover also explained much of the variability in soil N (R2 = 0·74) and P (R2 = 0·52) stocks in communal grazing lands. Converting degraded communal grazing lands into exclosures is a viable option to restore degraded soils. Our results also confirm that the possibility to predict the changes in soil nutrient content after exclosure establishment using regression models is based on field measurements. Copyright © 2011 John Wiley & Sons, Ltd.

Environmental quality of Lower Little Bow River and riparian zone along an unfenced reach with off-stream watering

► We evaluated off-stream watering on riparian zone and river. ► Off-stream watering reduced cattle on the river bank and in river. ► The BMP improved riparian health and prevented river pollution by cattle. ► Certain vegetative properties were improved at the cattle access site. ► Rainfall simulation quality at cattle access site was not affected. The goal of beneficial management practices (BMPs) such as off-stream watering without fencing is to direct cattle away from rivers, improve the environmental quality of the riparian zone, and prevent or reduce river pollution. We conducted a four year (2005–2008) study on an unfenced 1.3 km reach of the Lower Little Bow (LLB) River in southern Alberta, Canada where three off-stream watering systems were installed 290 to ≥730 m from the river in August, 2005. Our hypothesis was that off-stream watering would reduce cattle activity at the river, improve riparian health, prevent river pollution by cattle, and improve the soil, vegetative, and rainfall simulation runoff variables at a cattle access site near the river. Off-stream watering did not significantly ( p > 0.10) reduce the median number of cattle on the river bank, in the river, or drinking from the river one year later. However, there was a reduction of 20% ( p = 0.15) for median number of cattle on the river bank and a 72% reduction ( p = 0.20) for cattle in the river. The BMP moderately improved the riparian health score from 60% (2005) to 65% (2007). Our spatial analysis (upstream–downstream) of base-flow during the post-BMP period (2006–2008) suggested that off-stream watering prevented river pollution by cattle for the majority of water quality variables measured. Canopy cover at the cattle access site near the river was significantly ( p ≤ 0.10) increased by 26–53% one and two years after the BMP. Two years after the BMP was implemented, total basal area, biomass, and mulch were significantly increased by 37–106%, while bare soil and NO 3 -N in surface soil were decreased by 38–89%, respectively. In contrast, other vegetative and soil properties were not significantly improved. Concentrations of the majority of N and P fractions in rainfall simulation runoff were not significantly reduced, and may be related to the high precipitation in the pre-BMP year of 2005. We accept the hypothesis that off-stream watering improved riparian health, prevented river pollution by cattle, and improved certain vegetative (canopy cover, total basal area, mulch, bare soil) and soil properties (soil NO 3 -N) near the river. However, we reject the hypothesis that off-stream watering improved other vegetation (live basal area) and soil properties (bulk density, NH 4 -N, total N and C), or improved rainfall simulation runoff quality near the river. Although we cannot statistically prove that the positive benefits of off-stream watering on certain environmental variables was due to reduced cattle activity, the non-significant reductions in cattle activity suggested this may be a possibility.

Evaluation of a Global Positioning System backpack transmitter for wild turkey research

AbstractRadiotelemetry is the standard method for monitoring wild turkey (Meleagris gallapavo) movements and habitat use. Spatial data collected using telemetry‐based monitoring are frequently inaccurate due to triangulation error. However, new technology, such as Global Positioning Systems (GPS) has increased ecologists' ability to accurately evaluate animal movements and habitat selection. We evaluated the efficacy of micro‐GPS backpack units for use on wild turkeys. We tested a micro‐GPS developed specifically for avian species that incorporated a GPS antenna with a lightweight rechargeable battery and a very high frequency (VHF) transmitter. We conducted a series of static tests to evaluate performance in varying types of vegetative canopy cover and terrain. After static testing, we deployed micro‐GPS on 8 adult male Rio Grande wild turkeys (M. g. intermedia) trapped in south Texas and 2 adult females trapped in the Texas panhandle. Micro‐GPS units collected 26,439 locations out of 26,506 scheduled attempts (99.7% fix rate) during static testing. Mean distance error across all static tests was 15.5 m (SE = 0.1). In summer 2009, we recovered micro‐GPS from 4 tagged males and both females to evaluate data collection. Units on males acquired approximately 2,500 locations over a 65‐day test period (94.5% fix rate). We recovered units from the 2 females after 19 days and 53 days; those units acquired 301 and 837 locations, respectively, for a 96% fix rate. Cost analysis indicated that VHF will be cost effective when 1 location per day is required up to 181 days, but micro‐GPS becomes less expensive as frequency of daily locations increases. Our results indicate that micro‐GPS have the potential to provide increased reliable data on turkey movement ecology and habitat selection at a higher resolution than conventional VHF telemetric methods. © 2011 The Wildlife Society.

Restoration of Ecosystem Carbon Stocks Following Exclosure Establishment in Communal Grazing Lands in Tigray, Ethiopia

Degraded lands are common in human‐influenced tropical semiarid areas, and the potential for C sequestration through rehabilitation of these areas is substantial. In this study, we investigated changes in ecosystem C stocks (ECS) after establishing exclosures on degraded communal grazing lands, and identified easily measurable biophysical and management‐related factors that can be used to predict ECS restoration in the highlands of Tigray, Ethiopia. We selected replicated (n = 3) 5‐, 10‐, 15‐, and 20‐yr‐old exclosures and paired each exclosure with an adjacent communal grazing land. All exclosures displayed higher ECS than the communal grazing lands. Differences in ECS between exclosures and grazing lands varied between 29 (±4.9) and 61 (±6.7) Mg C ha−1 and increased with exclosure duration. In exclosures, much of the variability in ECS was explained by a combination of the following variables: precipitation, clay content, vegetation canopy cover, woody biomass, and exclosure duration (R2 = 0.77–0.90). Precipitation and vegetation canopy cover also explained much of the variability of ECS in communal grazing lands (R2 = 0.48–0.55). Our results help to establish baseline information for C sequestration projects and to predict the expected ecosystem C sequestration under exclosures. Expansion of exclosures would increase grazing pressure on the remaining communal grazing area. Therefore, the decision to establish additional exclosures should also include an economic analysis and an evaluation of the social consequences.