Search Results (15)

Large herbivore communities are changing globally, with populations of wild herbivores generally declining while domestic herbivore populations are increasing, influencing ecosystem function along with the impacts of climate change. Manipulative experiments have rarely captured the interaction between patterns of large herbivore assemblage change and climatic conditions. This interaction may affect the functional traits and functional diversity of herbaceous communities; this requires investigation, as these metrics have been useful proxies for ecosystem function. We used a large herbivore exclosure experiment replicated along a topo-climatic gradient to explore the interaction between climate and herbivore assemblage on community-level functional traits and the functional diversity of herbaceous plant understories. Our findings demonstrate interacting effects between large herbivore assemblages and climate. We found a shift from drought-tolerant traits to drought-avoidant traits with increasing aridity, specifically with regard to plant leaf area and specific leaf area. We also determined that plant community responses to grazing changed from an herbivore avoidance strategy at drier sites to a more herbivore-tolerant strategy at wetter sites. We observed that the effects of herbivores on community-level traits can sometimes counteract those of climate. Finally, we found that cattle and large wild herbivores can differ in the magnitude and direction of effects on functional traits and diversity. Full article

Old growth forests are increasingly rare but important carbon sinks which harbour rich biodiversity. Chronic browsing by the white-tailed deer (Odocoileus virginianus) is a threat to the sustainability of the services provided by these forests, particularly in northern temperate forests where deer numbers have increased in recent decades (driven by stricter hunting rules and reduced predation) and necessitating local monitoring of vegetation responses. The objective of this study was to determine the effects of deer exclusion on tree regeneration dynamics and soil nutrients in an old growth Carolinian forest. This was performed using exclusion fencing and tip-up mounds at McMaster Forest Nature Preserve and the Sheelah Dunn Dooley Nature Sanctuary in Hamilton Ontario. Tree regeneration was surveyed from thirty 1 m × 1 m quadrats within exclusion plots and another thirty quadrats from deer-browsed areas adjacent to the exclusion plots. Soil samples were taken from each quadrat to analyze browsing impacts on nitrate, phosphate and soil organic matter. Red oak (Quercus rubra) was planted at the top and base of tip-up mounds of varying heights and widths and monitored for deer access and browsing activity. Results show a significantly higher density of woody plants within exclosures compared to non-exclosures (p = 0.0089) and twice more abundance of highly palatable species within the exclosures. However, species richness (p > 0.05) and diversity (p > 0.05) were minimally impacted by deer browsing, showing a resilient old growth forest. Soil nitrate was consistently higher in the non-exclosures, while phosphate was consistently higher within deer exclosures. Finally, more seedlings survived at the top of mounds than the bases, showing the potential of tip-up mounds to be a natural method of deer exclusion and a critical avenue for restoring over-browsed forests. Full article

We used a spatially explicit model to simulate the potential effects of exclosures and acaricides targeted at medium-sized mammalian hosts on the local distribution and abundance of lone star ticks (Amblyomma americanum) within forestlands of the southeastern United States. Both exclosures and acaricides were successful in markedly reducing the densities of all off-host tick life stages inside the treatment areas. Densities dropped to almost zero immediately inside the edges of the exclosures, with noticeably depressed densities extending outward 30 to 60 m from the exclosures, and the simulated exclosures maintained their effectiveness as their sizes were decreased from 4.5 to 2.25 to 0.8 ha. Densities exhibited a smooth gradient across the edges of the acaricide-treated areas, with depressed densities extending ≈100 m outward from the edges, but with perceptible densities extending ≈60 m inward from the edges; thus, the simulated acaricide areas lost their effectiveness as size was decreased to slightly less than one-half the diameter of the activity range of the targeted host. Our simulation results indicated that off-host nymph densities responded to reductions of medium-sized host densities. These results suggest that targeting acaricides at medium-sized hosts may be an effective, and currently under-utilized, method for tick suppression. Full article

Although an important part of the ecosystem, large wild herbivores (LWH), especially red deer (Cervus elaphus L.), cause significant damage to economically valuable timber in forests of Central Europe. Recent work has demonstrated that less valuable softwood broadleaved trees can act as “biological control” that helps reduce bark browsing on more valuable trees in a mixed stand. To better understand the factors that influence how much bark area and mass are removed by LWH from these broadleaved trees, we took advantage of a novel “natural” experiment that occurred after a breach in a herbivory exclosure surrounding a 10-year old mixed broadleaved/conifer stand in the Western Carpathians in north-western Slovakia. We measured the area of old (up to 2 years previously) and new browsed patches on stems of common aspen (Populus tremula L.), common rowan (Sorbus aucuparia L.) and goat willow (Salix caprea L.), and their position along the vertical profile of the stem. The browsed bark area (cm²) was then converted to the bark mass (g) removed and the proportion of browsed bark to total bark (%) using conversion equations. Our models demonstrated that the amount of bark removed was influenced by tree species, stem diameter, age of browsing (old vs. new), and stem section along the vertical profile. LWH removed the most bark area from willow but the most bark mass from aspen because aspen had thicker bark than the other tree species. Bark browsing was greater on trees > 6 cm basal diameter. The distribution of bark browsing along the vertical profile was symmetrical (unimodal) with maximum intensity at 101–125 cm from the ground, which corresponds with the height most optimal for feeding by red deer. However, previous browsing in 2019 and 2020 caused new browsing on willow in 2021 to be focused in stem sections lower (51–75 cm) and higher (126–150 cm) than that optima. By quantifying browsing patterns and the amount of bark that is accessible to LWH for forage on the most attractive softwood broadleaved trees, our work will contribute to developing better methods for protecting commercially important species such as European beech (Fagus sylvatica L.) and Norway spruce (Picea abies L. Karst.) in areas of Central Europe that are greatly affected by increasing population density of LWH, especially red deer. Full article

Most grazing lands in Mediterranean ecosystems that support extensive sheep farming systems are characterized by unfavorable edapho-climatic conditions, especially in semi-arid areas. Often, though, their use is far from sustainable, causing erosion and ecosystem degradation impacts. In this paper, we explore the use, productivity, and flora diversity of typical Mediterranean grazing lands in four farms at the Agra locality in the western part of Lesvos Island, Greece. For a period of two consecutive growing seasons (September to June), we recorded herbage biomass on 16 plots of grazing lands with three measurements per season of land cover and plant productivity (biomass) inside small exclosures (cages) protected from grazing. We recorded the species richness of herbaceous plant communities within and outside the cages at the end of every growing season, the period of maximum growth of herbaceous species. We also chemically analyzed the biomass for crude protein at the end of each season. Results show sizable productivity differences among pasture plots as well as seasons and an overall medium to high degree of productivity and species richness considering the relatively intensive grazing, with little differences over the different cages and the degree of grazing intensity. These results suggest that the “history” of the fields is important, as grazing lands that had been used for arable crops in the past, as well as those leveled and in favorable locations, were the most productive and diverse ones, while shallower soils and inclined grazing lands showed signs of overuse and degradation. Overall, though, these ecosystems showed a high degree of resilience despite their intensive use. Full article

As a countermeasure to deforestation and forest degradation, there are many forests restoration practices with area exclosures. However, there has been limited scientific investigation of the biophysical status of the restoration practice to show whether it is successful or not for further interventions. Thus, this study aims to evaluate the impacts of forest restoration with area exclosures on vegetation and soil-property-changing aspects. The method followed the concept of forest restoration based on selected indicators and comparison against best practices. For this purpose, three districts in three agro-ecologies were selected. In each district, one exclosure, adjacent church forest, and adjacent grazing land were selected. Then, vegetation data and soil data were collected and analyzed using different diversity indices. Descriptive and inferential statistics were applied for data analysis with R.Vr.3.1. The result revealed that there was a significant difference (p < 0.03) in vegetation composition, biomass, and soil attributes across land use and agro-ecology. In terms of wood density, area exclosures were recorded with the highest (1963 trees ha⁻¹) wood density, followed by church forests (1079 trees ha⁻¹) and grazing lands (501 trees ha⁻¹). The highest species diversity was observed in church forests (1.53), followed by area exclosures (1.42) and grazing lands (0.64). Area exclosures show higher similarity (60%) with grazing lands than church forests (45%). Abundant woody species, herbs, and litter biomass were recorded in church forests (1320.8- and 1.8-ton ha⁻¹), followed by exclosures (613- and 1.69-ton ha⁻¹) and grazing lands (415- and 0.78-ton ha⁻¹), respectively. In terms of soil property, church forests recorded the best loam sand and better AvP, Organic Matter, and total nitrogen, followed by exclosures and grazing lands. All the above vegetation and soil parameters indicate that area exclosures show intermediate values between church forests and grazing lands. Therefore, forest restoration with area exclosures is the better tool for degraded forest restoration. Further research is required to understand the ecosystem services of area exclosures and the trajectory of successional changes in vegetation composition and soil parameters of the area exclosures. Full article

Globally, there is a serious issue in carbon stock due to high deforestation and the loss of land, limited carbon storage pools in aboveground and underground forests in different regions, and increased carbon emissions to the atmosphere. This review paper highlights the impact of exclosures on above and below ground carbon stocks in biomass as a solution to globally curb carbon emissions. The data has been analyzed dependent on the Intergovernmental Panel on Climate Change (IPCC) guidelines, the Food and Agriculture Organization (FAO) Forest Resource Assessment report (FRA, 2020), and scientific journal publications mostly from the last decade, to show the research results of carbon stock and the impact of exclosures, particularly the challenges of deforestation and erosion of land and opportunities of area exclosures to provide a general outlook for policymakers. Overall, the world’s forest regions are declining, and although the forest loss rate has slowed, it has still not stopped sufficiently because the knowledge and practice of exclosures are limited. The global forest loss and carbon stock have decreased from 7.8 million ha/yr to 4.7 million ha/yr and from 668 gigatons to 662 gigatons respectively due to multiple factors that differ across the regions. However, a move toward natural rehabilitation and exclosures to reduce the emissions of Greenhouse Gas (GHGs) is needed. In the global production of carbon, the exclosure of forests plays an important role, in particular for permanent sinks of carbon. Full article

Gullies are sources and reservoirs of sediments and perform as efficient transfers of runoff and sediments. In recent years, several techniques and technologies emerged to facilitate monitoring of gully dynamics at unprecedented spatial and temporal resolutions. Here we present a detailed study of a valley-bottom gully in a Mediterranean rangeland with a savannah-like vegetation cover that was partially restored in 2017. Restoration activities included check dams (gabion weirs and fascines) and livestock exclosure by fencing. The specific objectives of this work were: (1) to analyze the effectiveness of the restoration activities, (2) to study erosion and deposition dynamics before and after the restoration activities using high-resolution digital elevation models (DEMs), (3) to examine the role of micro-morphology on the observed topographic changes, and (4) to compare the current and recent channel dynamics with previous studies conducted in the same study area through different methods and spatio-temporal scales, quantifying medium-term changes. Topographic changes were estimated using multi-temporal, high-resolution DEMs produced using structure-from-motion (SfM) photogrammetry and aerial images acquired by a fixed-wing unmanned aerial vehicle (UAV). The performance of the restoration activities was satisfactory to control gully erosion. Check dams were effective favoring sediment deposition and reducing lateral bank erosion. Livestock exclosure promoted the stabilization of bank headcuts. The implemented restoration measures increased notably sediment deposition. Full article

Rangeland management in former tropical rainforest areas may affect ecosystem services. We hypothesized that management practices like burning and overgrazing reduce supporting (soil quality) and consequently also provisioning (forage productivity and quality) and regulating (nutrient cycling) ecosystem services. We established 31 exclosures in two landscape categories (alluvial soils, low-hills), documented management practices, and assessed 18 soil quality indicators, litter decomposition as a proxy for nutrient cycling, and forage quantity and quality during one year in grasslands of the Lacandon region, southeast Mexico. Path analysis was used to explore direct and indirect effects of livestock management practices on soil-based ecosystem services. Landscape position had direct effects on management practices, and direct and indirect effects on soil properties. Altitude (a proxy for the soil catena, ranging from alluvial soils along the Lacantún river to Cambisols and Acrisols in the low-hills) was the variable showing most significant negative relations with soil quality and forage production. Decomposition rate was site-specific and had no relation with landscape position and management. Our study suggests that position on the landscape, which relates to nutrient and water availability, had stronger effects than management practices on forage productivity and quality and drives farmers management practices. Full article

Forest vegetation management can improve planted seedling survival and growth and is thus widely used in plantation silviculture. In some jurisdictions, mechanical release using brushsaws has replaced the traditional use of chemical herbicides for forest vegetation management purposes. However, its associated costs and the increasing difficulty of finding qualified labor represent a challenge. The browsing of competition by large herbivores may represent an alternative to mechanical release when planted seedlings are resistant to browsing. Here, we compare the efficacy of moose browsing relative to mechanical release in controlling competing vegetation and in promoting white spruce growth in plantations. In a high moose density region, we used an experimental design consisting of four pairs of moose exclosures and unfenced plots; fifty percent of both the access-restricted and unrestricted study areas received a mechanical release treatment. Moose browsing was more efficient than mechanical release in diminishing the sapling density and basal area of competing species. Mechanical release only reduced the sapling density of taller competitors (height > 201 cm), whereas browsing reduced the sapling densities of competitors across a greater size range (height > 130 cm). These effects of moose browsing on competition translated into a greater positive effect of moose browsing on the basal area of planted spruces. We attribute the higher effectiveness of moose browsing relative to mechanical release to its chronic nature. Moose browsed continuously throughout the year and for multiple years, whereas mechanical release was applied only one time between the second and fourth years after planting. Our results suggest that pairing wildlife management and silviculture decisions could be in the best interest of both the hunting and forestry industries in regions where plantations are frequent and use browse-resistant crop trees. Favouring browsers in controlling the density of competing species could increase the hunting experience and income, while providing an effective, cost-free, and socially acceptable forest vegetation management service. Full article

Horse grazing may benefit biodiversity, but the impact of year-round grazing on nutrient dynamics has not been evaluated previously. This study compared pasture quality in a forest-grassland landscape grazed year-round by horses with that in exclosed mown areas. Twelve Gotlandsruss stallions were kept without supplementary feeding in three enclosures (~0.35 horse/ha) outside Uppsala, Sweden, from May 2014 to September 2016. Each enclosure contained three mown exclosures, where grass sward samples were collected monthly and analyzed for chemical composition and vegetation density. Fecal grab samples were collected and analyzed for crude protein (CP) and organic matter (OM) content. There were no differences in exclosure pasture energy or CP content between enclosures (p > 0.05). In grazed areas, there were differences in grass energy and CP content (p > 0.05) between enclosures. During the three summers studied, energy and CP content increased in the enclosures, but decreased in the exclosures. By the end, biomass content/ha was greater in the enclosures than in the exclosures. Fecal OM and CP content showed moderate to strong correlations with pasture nutrient content (r = 0.3–0.8, p < 0.05). Thus, in contrast to monthly mowing, horse grazing diversified pasture chemical composition and increased its nutritive value. Full article

Changes in the extent of woody vegetation represent a major conservation question in many savannah systems around the globe. To address the problem of the current lack of broad-scale cost-effective tools for land cover monitoring in complex savannah environments, we use a multi-scale approach to quantifying vegetation change in Kruger National Park (KNP), South Africa. We test whether medium spatial resolution satellite data (Landsat, existing back to the 1970s), which have pixel sizes larger than typical vegetation patches, can nevertheless capture the thematic detail required to detect woody encroachment in savannahs. We quantify vegetation change over a 13-year period in KNP, examine the changes that have occurred, assess the drivers of these changes, and compare appropriate remote sensing data sources for monitoring change. We generate land cover maps for three areas of southern KNP using very high resolution (VHR) and medium resolution satellite sensor imagery from February 2001 to 2014. Considerable land cover change has occurred, with large increases in shrubs replacing both trees and grassland. Examination of exclosure areas and potential environmental driver data suggests two mechanisms: elephant herbivory removing trees and at least one separate mechanism responsible for conversion of grassland to shrubs, theorised to be increasing atmospheric CO₂. Thus, the combination of these mechanisms causes the novel two-directional shrub encroachment that we observe (tree loss and grassland conversion). Multi-scale comparison of classifications indicates that although spatial detail is lost when using medium resolution rather than VHR imagery for land cover classification (e.g., Landsat imagery cannot readily distinguish between tree and shrub classes, while VHR imagery can), the thematic detail contained within both VHR and medium resolution classifications is remarkably congruent. This suggests that medium resolution imagery contains sufficient thematic information for most broad-scale land cover monitoring requirements in heterogeneous savannahs, while having the benefits of being cost-free and providing a longer historical archive of data than VHR sources. We conclude that monitoring of broad-scale land cover change using remote sensing has considerable potential as a cost-effective tool for both better informing land management practitioners, and for monitoring the future landscape-scale impacts of management policies in savannahs. Full article

Sustainable forest management requires a continuous assessment of the forest conditions covering the species distribution, standing tree volume as well as volume increment rates. Forest inventories are designed to record this information. They, in combination with ecosystem models, are the conceptual framework for sustainable forest management. While such management systems are common in many countries, no forest inventory system and/or modeling tools for deriving forest growth information are available in Ethiopia. This study assesses, for the first time, timber volume, carbon, and Net Primary Production (NPP) of forested areas in the Amhara region of northwestern Ethiopia by combining (i) terrestrial inventory data, and (ii) land cover classification information. The inventory data were collected from five sites across the Amhara region (Ambober, Gelawdiwos, Katassi, Mahiberesilasse and Taragedam) covering three forest types: (i) forests, (ii) shrublands (exclosures) and (ii) woodlands. The data were recorded on 198 sample plots and cover diameter at breast height, tree height, and increment information. In order to extrapolate the local terrestrial inventory data to the whole Amhara region, a digital land cover map from the Amhara’s Bureau of Agriculture was simplified into (i) forest, (ii) shrubland, and (iii) woodland. In addition, the forest area is further stratified in five elevation classes. Our results suggest that the forest area in the Amhara region covers 2% of the total land area with an average volume stock of 65.7 m³·ha⁻¹; the shrubland covers 27% and a volume stock of 3.7 m³·ha⁻¹; and the woodland covers 6% and an average volume stock of 27.6 m³·ha⁻¹. The corresponding annual volume increment rates are 3.0 m³·ha⁻¹, for the forest area; 1.0 m³·ha⁻¹, for the shrubland; and 1.2 m³·ha⁻¹, for the woodland. The estimated current total volume stock in the Amhara region is 59 million m³. Full article

In Ethiopia, deforestation rates remain high and the gap between demand and domestic supply of forest products is expanding, even though government-initiated re-greening efforts began over a century ago. Today, over 3 million hectares (ha) of degraded forest land are under area exclosure; smallholder plantations cover 0.8 million ha; and state-owned industrial plantations stagnate at under 0.25 million ha. This review captures experiences related to re-greening practices in Ethiopia, specifically with regards to area exclosure and afforestation and reforestation, and distills lessons regarding processes, achievements and challenges. The findings show that farmers and non-governmental organizations (NGOs) are the main players, and that the private sector has so far played only a small role. The role of the government was mixed: supportive in some cases and hindering in others. The challenges of state- and NGO-led re-greening practices are: inadequate involvement of communities; poorly defined rehabilitation objectives; lack of management plans; unclear responsibilities and benefit-sharing arrangements; and poor silvicultural practices. The lessons include: a more active role for non-state actors in re-greening initiatives; more attention to market signals; devolution of management responsibility; clear definition of responsibilities and benefit-sharing arrangements; and better tenure security, which are all major factors to success. Full article

Minirhizotrons were used to study root growth characteristics in recently established fields dominated by perennial C4-grasses that were managed either for cattle grazing or biomass production for bioenergy in Virginia, USA. Measurements over a 13-month period showed that grazing resulted in smaller total root volumes and root diameters. Under biomass management, root volume was 40% higher (49 vs. 35 mm³) and diameters were 20% larger (0.29 vs. 0.24 mm) compared to grazing. While total root length did not differ between grazed and biomass treatments, root distribution was shallower under grazed areas, with 50% of total root length in the top 7 cm of soil, compared to 41% in ungrazed exclosures. These changes (i.e., longer roots and greater root volume in the top 10 cm of soil under grazing but the reverse at 17–28 cm soil depths) were likely caused by a shift in plant species composition as grazing reduced C4 grass biomass and allowed invasion of annual unsown species. The data suggest that management of perennial C4 grasslands for either grazing or biomass production can affect root growth in different ways and this, in turn, may have implications for the subsequent carbon sequestration potential of these grasslands. Full article