Amount Of Bare Ground Research Articles

Invasive grass and litter accumulation constrain bee and plant diversity in altered grasslands

Ecologists consider biological invasions one of the primary drivers of global change. Many remaining grasslands in North America have extensive invasions of exotic grass species that have replaced native plant species. In the Northern Great Plains, exotic cool-season grasses Kentucky bluegrass (Poa pratensis) and smooth brome (Bromus inermis), paired with human alterations to the landscape and historical disturbance regimes, have resulted in functionally and structurally altered grassland plant communities. These changes may extend to impact species that rely on these plant communities, such as bees. Bees are ecologically diverse and serve important pollinator roles but are at risk from the loss and change of floral and nesting resources in plant communities. Our objectives were to determine whether Kentucky bluegrass and smooth brome alter the bee and forb species richness in invaded Northern Great Plains grasslands and how litter accumulation, grass cover, the amount of bare ground, and forb species richness interact with bee functional traits. To do this, we surveyed 67 grassland sites from 2017 to 2020 with two bee-sampling methods (268 netting and bee bowl surveys total) and vegetation cover surveys at each site. We collected 20,559 bees from 201 bee species and observed 249 forb and shrub species in vegetation surveys. Bee richness and Shannon diversity were associated with greater forb richness while forb richness was significantly lower with thicker litter depths and higher with a greater coverage of all grasses other than Kentucky bluegrass and smooth brome. Bee trait analyses showed varying relationships with plant community variables. Of these, litter depth and Kentucky bluegrass cover were associated with lower ground-nesting bee abundance while small-bodied bee abundance was positively associated with increasing bare ground. While our results support the close relationship between bee and plant diversity, we also found litter depth, in particular, contributed to the structure of these two communities. Specifically, Kentucky bluegrass and smooth brome are two exotic grass species associated with thatch-forming litter layers, especially under idle management that appear to simplify bee and forb communities. Our results make apparent the importance in maintaining structural and compositional diversity in invaded grasslands to support diverse bee communities.

Soil Properties Affected Vegetation Establishment and Persistence on Roadsides

Vegetation along roadsides reduces soil erosion, increases filtering of water runoff, and acts as a biodiversity corridor. The purpose of this study was to assess soil properties and evaluate their effect on vegetation establishment in roadsides. Furthermore, the effects of shoulder type (paved and unpaved) and time since seeding (0–1 year, 2–4 years, and ≥ 5 years) on soil properties were also evaluated. Roadside soil was sampled from 53 sites in three regions (Panhandle, Southcentral, and Southeastern) in Nebraska, USA. The soil was analyzed for pH, Na, Cl, electrical conductivity, exchangeable sodium percentage, and bulk density and heavy metals. At each site, vegetation was classified into one of four categories, (1) 50% plant canopy cover dominated by weedy annual grasses and forbs; and (4) > 50% plant canopy cover dominated by seeded perennial grasses. Sodium concentration exceeded the limits that can cause vegetation growth decline in all regions. Sodium and soil bulk density in all regions were clustered with the < 10% plant canopy cover category, meaning that these clustered soil properties have a significant influence on the amount of bare ground and establishment/persistence of vegetation. Heavy metal concentrations (lead, arsenic, zinc, cadmium, and nickel) were less than the thresholder in all regions. It was observed that 12–44% of roadside sites had less than 50% vegetation cover. Roadside soils of paved shoulders had lower Na and Cl concentrations than the roadside soils of unpaved shoulders. The 0–1 year since seeding had higher cadmium, arsenic, and nickel concentrations compared to ≥ 5 years since seeding. Soil degradation declined vegetation establishment along highways, and the degree of soil degradation of these roadsides varied depending on shoulder types and time since seeding.

Density and habitat selection of mice on cheatgrass-invaded sites in British Columbia, Canada

Globally, invasive species in grasslands and shrublands have substantially altered trophic interactions and ecosystem processes. In North America, cheatgrass (Bromus tectorum) has invaded much of the western sage-steppe, leading to substantial shifts in plant communities and fire regimes. The effects of this cheatgrass invasion on small mammals are inconsistent among species and regions, and the mechanisms behind these patterns may be trophic or non-trophic. Cheatgrass alters cover and the amount of bare ground, thus affecting movements and predation risk, but cheatgreass also provides food for some rodents. We examined the extent to which low-density cheatgrass invasion (<20% cover) affected population densities and habitat selection of mice in southern British Columbia, Canada. In this region, Great Basin pocket mice (Perognathus parvus) were far more common than western harvest mice (Reithrodontomys megalotis) and deermice (Peromyscus maniculatus). Density of Great Basin pocket mice increased with bare ground and annual grasses, but decreased with shrub cover; when pocket mice foraged, they selected habitats with cheatgrass and bare, open ground. Cheatgrass did not predict movements of deermice or harvest mice. These results indicate that low cheatgrass densities may not be negative for these three species of mice, at least in the northern distribution of sage-steppe.

The Impact of Prescribed Burning on Native Bee Communities (Hymenoptera: Apoidea: Anthophila) in Longleaf Pine Savannas in the North Carolina Sandhills.

Prescribed burning is a common silvicultural practice used in the management of longleaf pine (Pinus palustris Mill., Pinales: Pinaceae) savannas to reduce hardwood encroachment and ground cover and to maintain biodiversity. We investigated the response of the native bee community (Hymenoptera: Apoidea: Anthophila) in the Sandhills of North Carolina to prescribed burning on a 3-yr rotation over two consecutive years (2012 and 2013). We deployed bee bowl traps in sites that had been burned the year of sampling, 1 yr before, 2 yr before, and in unburned controls. In total, 2,276 bees of 109 species were captured. Bee abundance declined with time since fire, with 2.3 times more bees captured in the most recently burned sites than in unburned controls. Bee diversity also declined with time since fire, with 2.1 times more species captured in the most recently burned sites than in controls. Bee community composition also responded to fire; we present evidence that this response was mediated in part by the effect of fire on the amount of bare ground and canopy cover. Bees nesting aboveground were unaffected by fire, contrary to our expectation that fire would destroy the wood and stems in which these species nest. Our results indicate that prescribed burning is a silvicultural practice consistent with pollinator conservation in longleaf pine ecosystems of the North Carolina sandhills.

Relationships Among Population Size, Environmental Factors, and Reproduction in Lupinus perennis (Fabaceae)

Wild Lupine (Lupinus perennis) is an indicator of Midwestern U.S.A. oak savannas and the main larval food for endangered Karner Blue butterflies. In the past 100 y, this perennial has declined in distribution and abundance. To determine if this decline was related to population size and/or environmental factors and to better understand patterns of reproduction, we compared frequencies of seed coat colors, seed production variables, and environmental factors among 16 populations ranging in size from 25 to 8300 plants. Seedlings were germinated in the greenhouse to measure early offspring vigor. A seed color/substrate field experiment examined differences in seed removal to look at predation risk. Higher seed production was associated with increased population size, while fewer seeds per fruit were associated with increased bare ground, and higher fruits per stem and seed mass were found as soil pH increased. Although seedling emergence declined with increased bare ground, seedling growth was most correlated with pH and light, but not population size. Small populations had reduced seed color variation. Seed removal rates averaged 65% across all treatments, but dark-colored seeds had higher predation than light-colored seeds, regardless of substrate. Seed removal increased over time and was influenced by vegetative cover and distance to roads and water. Our results suggest managers should minimize the amount of bare ground and strive to maintain population sizes over 500 in order to restore and conserve Lupine populations.

Long term effect of fire severity on carabid and lichen assemblages

Variation in fire severity strongly influences post-fire forest development. The resulting fine scale forest heterogeneity could impact biodiversity over long periods after fire events. In the James Bay area of northern Québec, differential seed mortality caused by high and low crown fire severity resulted in dramatic variation in regeneration density of both jack pine and black spruce. Sixty years after such fire event, we show that composition of lichen and carabid assemblages varied significantly between areas of high (c. 2600 stems/ha) and low (c. 560 stems/ha) stem density established by differential crown fire severity. The carabids, Notiophilus semistriatus and Miscodera arctica, were found in low stem density areas while Carabus taedatus and Pterostichus brevicornis were found in high stem density areas. Amount of bare ground was higher in low stem density area which may favor active visual diurnal hunters such as Notiophilus species. Cladonia rangiferina and C. stellaris were associated with high stem density area while C. uncialis and C. mitis were associated with low stem density area. This likely reflects the fact that photosynthetic rate of C. rangiferina is optimal under shady areas whereas C. uncialis is better adapted to hot, dry and sunny conditions. Thus, variation in fire behavior led to long-lasting variation in forest conditions that clearly affected both lichen and carabid assemblages even 60 years after fire.

Analysis of the Performance of two Rangeland Protocols, Monitoring and Assessment

&lt;p&gt;This study compared and contrasted data from the stick and modified Braun-Blanquet monitoring protocols in three areas with different land use histories: an unrestored barren area, a young and old restored areas. The study areas are part of extensive degraded of birch woodland and willow shrubland that have partly been re-vegetated.Vegetation and site characteristics were assessed in the three areas using the two protocols and soil sampling to characterize the ecological status of a land that has been re-vegetated. The analysis of the two protocols data indicates similar tendency which is the improvement of the ecological condition of the restored areas compared to the unrestored area. The soil carbon and nitrogen contents increased when the pH decreased with the restoration age. The improvement is better at the old restored area which has received more fertilization compared to the young restoration. Stick method estimated greater cover of vascular plants, litters, mosses and rocks, and lower amount of bare ground than modified Braun-Blanquet. The two protocols provided similar estimates cover of lichens and sedges. Stick method also provided three supplementary indicators which were not included in modified Braun-Blanquet: plants base, basal and canopy gaps. Another observation that could be proved by further studies, stick seemed to be more precise and economical than modified Braun-Blanquet. The indicators provided by the two protocols were related to the three attributes of ecosystems and the rangelands health indicators. This study is a preliminary that cannot be able to recommend one method, but it advocates stick method to assess and monitor vegetation dominated by herbaceous layer as grassland and modified Braun-Blanquet for the one dominated by woody layer.&lt;/p&gt;

Ecological indicators for assessing management effectiveness: A case study of horse riding in an Alpine National Park

SummaryRecreation activities and visitor use often have deleterious ecological impacts in protected areas. Management agencies then face the difficult task of providing recreation and tourism opportunities without compromising environmental values. This study assessed the success of efforts aimed at conserving alpine vegetation along the Mt Bogong Massif in Victoria, Australia, through controlling the use of horses. Vegetation condition was assessed in 2001 to coinciding with restrictions on the use of horse riding on trails and then resurveyed 10 years later. Sampling was undertaken in track plots that included the trail and surrounding vegetation, and control plots located away from the trail. There were significant differences in the amount of bare ground, the height of shrubs and ground layer vegetation, and shrub cover between track and control plots in 2001. Ten years later, track plots were recovering with reductions in bare ground and changes in vegetation, with improved ground layer vegetation height. Results show that vegetation condition has improved with restrictions of horse numbers. The indicators selected were sensitive to changes in vegetation condition and hence should be used for ongoing assessment of the effectiveness of this and similar management interventions.

Postharvest grazing of hogs in organic fruit orchards for weed, fruit, and insect pest management

In many perennial fruit systems, unharvested fruit left on the orchard floor can exacerbate insect pest problems by harboring insect pest larvae. Apple, cherry, and pear growers in the northeastern USA must control a number of challenging insect pests, including plum curculio Conotrachelus nenuphar (Herbst), codling moth (Cydia pomonella (L.)), and oriental fruit moth Grapholita molesta (Busck). Integrating livestock into tree fruit systems for the purpose of consuming leftover fruit may provide insect and weed pest management services. We rotationally grazed pigs after harvest in certified organic apple, cherry, and pear orchards to determine the amount of fruit the hogs would consume from the orchard floor, the impact hogs would have on orchard ground cover, and what pest insects the hogs could potentially suppress by consuming leftover fruit. The pigs consumed 100 % of leftover fruit in all three orchard types. Pigs significantly increased the amount of bare ground and decreased the amount of grass in all three orchard types. Both codling moth and oriental fruit moth larvae were found to be present in leftover apples and pears collected from the ground, whereas no pest insects were found in leftover cherries. Plum curculio fruit damage was significantly lower in grazed cherry plots, and codling moth/oriental fruit moth fruit damage was significantly lower in grazed pear plots following the first year of the study. Fruit damage data could not be collected following the second year of the study due to total crop loss.

Effects of flupropanate application on bare ground and broadleaf weeds when used to control Chilean needle grass in introduced pastures

Chilean needle grass (Nassella neesiana [Trin. & Rupr.] Barkworth) (CNG) is a serious weed with low palatability in extensive grazing enterprises of south-eastern Australia. Flupropanate is a slow-acting soil uptake herbicide that is used to control CNG. Although flupropanate is registered as a selective chemical, the selectiveness has been questioned previously. This paper examines the effect of flupropanate under three grazing regimes (set, strategic and no grazing) on the amount of bare ground and the basal cover of broadleaf weeds, at several CNG-infected sites in south-eastern Australia for 5–6 years after application. Under grazing, when flupropanate was effective in reducing CNG basal cover, it was associated with large increases in bare ground and broadleaf weed basal cover. After its application, the annual average basal cover was often 15%–25% for bare ground and 10%–20% for broadleaf weeds. This makes the application of flupropanate to control CNG problematic within extensive grazing systems of south-eastern Australia.

Associations of wintering birds with habitat in semidesert and plains grasslands in Arizona

Abstract We studied associations with winter habitat for seven species of birds, one species-group (eastern and western meadowlarks combined), and total sparrows at seven sites in the semidesert and plains grasslands of southeastern Arizona from 1999–2001, sampling with mist-nets and survey-transects. We measured structure and composition of vegetation, assessing vegetative differences among sites, and modeled associations between indices of avian abundance and six vegetative variables using generalized linear models. For all vegetative variables, there were significant differences among sites. Numbers of northern harriers (Circus cyaneus) were positively associated with total number of sparrows. Indices of abundance for individual species of birds were statistically correlated with various measures of structure and composition of vegetation. In particular, grasshopper (Ammodramus savannarum) and vesper (Pooecetes gramineus) sparrows were negatively associated with amount of bare ground; horned larks (Ere...

Molehills as important larval habitats for the grizzled skipper, Pyrgus malvae (Lepidoptera: Hesperiidae), in calcareous grasslands

Small-scale soil disturbance, such as animal mounds created by subterraneous ecosystem engineers are important microhabitats for species of conservation concern. There are many studies on the effects of ecosystem engineers on plant species diversity and soil properties, but the influence of such organisms on other taxa, such as insects, are rarely analyzed. In this paper, we demonstrate for the first time the role of molehills produced by the European Mole (Talpa europaea) (Linnaeus, 1758) as a larval habitat for a threatened butterfly species within central European calcareous grasslands. We selected the grizzled skipper (Pyrgus malvae) (Linnaeus, 1758) as a study species as previous studies revealed that it prefers warm and open microhabitats for oviposition. Our study clearly showed that host plants occurring on or in the close vicinity of molehills were regularly occupied by immature stages of P. malvae. Occupied host plants at these disturbed sites were characterized by a more open vegetation structure with a higher proportion of bare ground or stones and a lower cover of the herb layer compared with available host plants (control samples). Among molehills those were preferred that had the highest cover of host plants, especially Agrimonia eupatoria. Molehills are important larval habitats for P. malvae in calcareous grasslands on deeper soils. At these sites succession occurs rapidly and the amount of bare ground is usually low, even when they are managed. In contrast to other known breeding sites in calcareous grasslands, molehills with a high cover of host plants provide ideal conditions for the successful larval development of P. malvae: (i) sufficient food during the larval period and (ii) warm microclimatic conditions.

Is biodiversity management effective? Cross-sectional relationships between management, bird response and vegetation attributes in an Australian agri-environment scheme

Do sites managed under an agri-environment scheme support significantly more biodiversity than sites managed in accordance with traditional agricultural practices? This is a key question underpinning agri-environment schemes worldwide, including one that we report on here that has been established in south-eastern Australia. To address this question, we established a large-scale, blocked and replicated cross-sectional study comprising 104 sites in four key “management” classes: (1) Agricultural production sites characterized by traditional set-stocking grazing. (2) Short-term conversion sites in which investments to improve conservation had recently (<2years ago) been made. (3) Long-term conversion sites where investments to improve conservation values were made >7years ago. And (4) Traveling stock reserves (TSRs) which have traditionally been subject to limited vegetation clearing and grazing pressure over the past 150years. Such TSRs are often considered ‘benchmarks’ of vegetation condition and biodiversity prior to European settlement.We identified significant (P<0.001) differences between management classes and bird species richness (including the richness of bird species of conservation concern), with a gradient of increasing richness from production sites, short-term conversion sites, long-term conversion sites to TSRs. We also found significant (P<0.001) differences in the composition of bird assemblages between management classes which followed a broadly similar gradient pattern to that identified for bird species richness. We also identified functional groups of birds associated with different management practices. In particular, small-bodied, non-seed eating and open-nesting bird species were significantly more likely to occur in TSRs than in production sites. We found that differences in bird species richness and assemblage composition could be explained by readily quantifiable relationships with vegetation structure and condition (i.e. native shrub cover, native ground ground cover, native plant species richness, percentage overstory regeneration, and the amount of bare ground).Our findings suggest that management intervention may shift some key characteristics of woodland vegetation typical of agricultural production sites toward those of “benchmark” TSRs and that these alterations in characteristics are, in turn, important for bird biota. Characteristics of particular importance include retention or improvement in the native shrub and sub-shrub layer and overstory regeneration.

Post‐fire regeneration in alpine heathland: Does fire severity matter?

AbstractFire severity is thought to be an important determinant of landscape patterns of post‐fire regeneration, yet there have been few studies of the effects of variation in fire severity at landscape scales on floristic diversity and composition, and none within alpine vegetation. Understanding how fire severity affects alpine vegetation is important because fire is relatively infrequent in alpine environments. Globally, alpine ecosystems are at risk from climate change, which, in addition to warming, is likely to increase the severity and frequency of fire in south‐eastern Australia. Here we examine the effects of variation in fire severity on plant diversity and vegetation composition, 5 years after the widespread fires of 2003. We used floristic data from two wide‐spread vegetation types on the Bogong High Plains: open heathland and closed heathland. Three alternative models were tested relating variation in plant community attributes (e.g. diversity, ground cover of dominant species, amount of bare ground) to variation in fire severity. The models were (i) ‘linear’, attributes vary linearly with fire severity; (ii) ‘intermediate disturbance’, attributes are highest at intermediate fire severity and lowest at both low‐ and high‐severity; and (iii) ‘null’, attributes are unaffected by fire severity. In both heathlands, there were few differences in floristic diversity, cover of dominant species and community composition, across the strong fire severity gradient. The null model was most supported in the vast majority of cases, with only limited support for either the linear and intermediate disturbance models. Our data indicate that in both heathlands, vegetation attributes in burnt vegetation were converging towards that of the unburnt state. We conclude that fire severity had little impact on post‐fire regeneration, and that both closed and open alpine heathlands are resilient to variation in fire severity during landscape scale fires.

Significantly Higher Carabid Beetle (Coleoptera: Carabidae) Catch in Conventionally than in Organically Managed Christmas Tree Plantations

Abstract Carabid beetles play an important role as consumers of pest organisms in forestry and agriculture. Application of pesticides may negatively affect abundance and activity of carabid beetles, thus reducing their potential beneficial effect. We investigated how abundance and diversity of pitfall trapped carabid beetles (Coleoptera, Carabidae) varied between conventionally and organically managed Caucasian Fir (Abies nordmanniana (Stev.)) plantations, in northern Zealand, Denmark. We recorded significantly higher numbers of carabid beetle specimens and species at conventionally than at organically managed sites. Carabid beetle abundance and richness did not decline more between two sampling periods at sites with pesticide application than at unamended sites. Apparently, the amount of bare ground, which dominated in the conventionally managed, herbicide treated sites, correlated closely with the number of recorded carabid beetle specimens. Thus we attribute the higher catch at the conventionally manag...

Effects of wildlife grazing on the production, ground cover and plant species composition of an established perennial pasture in the Midlands region, Tasmania

Context Management of grazing wildlife on private land in Tasmania is a contentious issue for landowners, animal-welfare groups and the Tasmanian Government. Wildlife species known to graze pasture include Tasmanian pademelon (Thylogale billardierii), Bennett’s wallaby (Macropus rufogriseus rufogriseus), forester kangaroo (Macropus giganteus), brushtail possum (Trichosurus vulpecula) and fallow deer (Dama dama). Understanding the spatio-temporal patterns of wildlife grazing is important when considering wildlife-control options to mitigate pasture loss; however, limited research has been undertaken. Aims To quantify the impact of wildlife grazing on pasture production and to assess the spatial and temporal pasture biomass loss from an established pasture; to investigate the effect of protecting pastures from wildlife grazing on species composition of an existing perennial pasture; to determine whether wildlife grazing contributes to a decline in the composition of improved pasture species over time and an increase in-ground cover of less desirable grasses and broadleaf weeds; and to examine whether protecting pastures from wildlife grazing could increase ground cover. Methods Pasture biomass loss to wildlife grazing was determined by a paired exclusion-cage method over a 26-month period from February 2008 to April 2010. A quantitative pasture model was used to simulate pasture growth at the study site. Changes in the botanical composition of the sward in response to wildlife grazing were determined by hand-separation, drying and weighing of harvested material, and also by visual estimation of the ground cover of individual plant species. A wildlife faecal-pellet survey was used to develop an index of wildlife feeding activity. Key results Pasture loss to wildlife grazing varied spatially and temporally. Pasture loss decreased with increasing distance from the edge of cover vegetation. The proportion of pasture lost increased during periods of slow pasture growth. Visual estimates of ground cover showed that grazing by wildlife resulted in an increase in bare ground in unprotected swards, whereas protection from grazing resulted in an increase in production of perennial and annual species, as determined by hand-separation of harvested material, and a decrease in bare ground as determined by visual estimate. Faecal-pellet surveys were found to be strongly correlated with pasture biomass losses. Conclusions The proportion of pasture loss to wildlife grazing was found to be influenced by distance from native vegetation and also by pasture availability, which was seasonal. Wildlife can alter the composition of pastures by reducing the ground cover and yield of improved grasses. Continual grazing of pastures by wildlife in addition to rotational sheep grazing may increase the amount of bare ground. Implications Wildlife-control methods need to be carefully chosen if the intended benefits of alleviating pasture biomass losses are to be achieved. Quantifying the loss of pasture is important because it enables the extent and significance of losses to be determined and may inform decisions about the most appropriate wildlife control measures to adopt. Controlling wildlife during periods of slow pasture growth may be important in preventing damage and yield loss of plant species actively growing during these times. Failure to control wildlife may result in a decrease in the composition of desirable plant species.

Comparison of Unmanned Aerial Vehicle Platforms for Assessing Vegetation Cover in Sagebrush Steppe Ecosystems

In this study, the use of unmanned aerial vehicles (UAVs) as a quick and safe method for monitoring biotic resources was evaluated. Vegetation cover and the amount of bare ground are important factors in understanding the sustainability of many ecosystems. Methods that improve speed and cost efficiency could greatly improve how biotic resources are monitored on western lands. Sagebrush steppe ecosystems provide important habitat for a variety of species including sage grouse and pygmy rabbit. Improved methods of monitoring these habitats are needed because not enough resource specialists or funds are available for comprehensive on-the-ground evaluations. In this project, two UAV platforms, fixed-wing and helicopter, were used to collect still-frame imagery to assess vegetation cover in sagebrush steppe ecosystems. This paper discusses the process for collecting and analyzing imagery from the UAVs to 1) estimate percentage of cover for six different vegetation types (shrub, dead shrub, grass, forb, litter, and bare ground) and 2) locate sage grouse using representative decoys. The field plots were located on the Idaho National Laboratory site west of Idaho Falls, Idaho, in areas with varying amounts and types of vegetation cover. A software program called SamplePoint was used along with visual inspection to evaluate percentage of cover for the six cover types. Results were compared against standard field measurements to assess accuracy. The comparison of fixed-wing and helicopter UAV technology against field estimates shows good agreement for the measurement of bare ground. This study shows that if a high degree of detail and data accuracy is desired, then a helicopter UAV may be a good platform to use. If the data collection objective is to assess broad-scale landscape level changes, then the collection of imagery with a fixed-wing system is probably more appropriate. En este estudio se evaluó el uso de vehículos aéreos no tripulados (VANT) como un método rápido y seguro para monitorear recursos bióticos. La cubierta vegetal y la cantidad de suelo desnudo son factores importantes para entender la sustentabilidad de varios ecosistemas. Métodos que mejoren la rapidez y el costo podrían mejorar la manera en que los recursos bióticos de las tierras del oeste son monitoreados. El ecosistema de estepa de artemisa provee hábitat para varias especies que incluyen al ganso sage y conejo pigmeo. Es necesario mejorar los métodos de monitoreo de estos hábitat porque no hay suficientes especialistas en recursos o fondos disponibles para evaluaciones completas en el terreno. En este proyecto, se utilizaron dos plataformas de VANT, alas fijas y helicóptero para recolectar imágenes fotográficas para evaluar la cubierta vegetal en un ecosistema de estepa de artemisa. En este artículo se discute el proceso de recolección y análisis de imágenes de un VANT para 1) estimar el porcentaje de cubierta de seis diferentes tipos de vegetación (matorral, matorral seco, zacate, hierbas, mantillo y suelo desnudo) y 2) ubicar gansos sage usando señuelos. Las parcelas experimentales se ubicaron en el Laboratorio Nacional de Idaho sitio localizado en Idaho Falls, Idaho en áreas con diferentes cantidades y tipos de cubierta vegetal. Se uso el programa de software SamplePoint junto con inspecciones oculares para evaluar el porcentaje de cubierta de seis tipos de cubiertas. Los resultados se compararon contra medidas de campo estándar para evaluar su precisión. La comparación de la tecnología de helicóptero VANT y alas fijas contra estimaciones de campo muestra buena relación para las medidas de suelo desnudo. El estudio muestra que sí se requiere alto grado de detalle y precisión en los datos el helicóptero VANT podría ser una buena plataforma para usarse. Pero sí el objetivo de recopilación de datos, es evaluar a gran escala los niveles de cambio en el paisaje entonces, la recopilación de imágenes con el sistema de alas fijas es probablemente más apropiado.

Plant community functional shifts in response to livestock grazing in intermountain depressional wetlands in British Columbia, Canada

Wetlands are ecologically and economically important ecosystems with high conservation value. Although wetland vegetation is strongly determined by abiotic factors, grazing disturbance may also be an important influence on this community. We evaluated the effects of livestock grazing on wetland vegetation in marsh and wet meadow zones in intermountain depressional wetlands in the southern interior of British Columbia, Canada. We sampled marshes and wet meadows in 36 wetlands along a grazing intensity gradient ranging from fully fenced and ungrazed wetlands to unfenced wetlands heavily grazed by livestock. The amount of bare ground was used as a surrogate measure of the intensity of livestock grazing. Vegetation community structure and composition was strongly associated with grazing intensity. Increased livestock grazing favored shorter-lived and smaller plants; conversely, the frequency of tall and rhizomatous species, which constitute the dominant plant species in these systems, declined with higher livestock use. The effects of grazing were more pronounced in the marsh than in the wet meadow. Associations between species richness and grazing differed between zones: native and exotic species richness showed a unimodal response in the marsh while in the wet meadow exotic richness increased and native richness showed no response. The relationship between exotic frequency and grazing was also inconsistent between zones, with a negative association in the marsh and a positive but weak association in the wet meadow. Grazing-related changes in vegetation along the grazing intensity gradient were substantial and may affect the habitat value of these wetlands for dependent wildlife such as breeding waterfowl.

Effects of excluding sheep from an alpine dwarf-herb community

Background: The Festuca ovina–Alchemilla alpina–Silene acaulis dwarf-herb community is a rare component of the few and scattered calcareous grasslands found at high altitude in the Scottish Highlands. It contains nationally scarce and rare arctic-alpine species. The community is often heavily grazed and it has been suggested that it is a plagioclimax maintained by herbivores, principally sheep. Aim: Determine the role of sheep grazing in conserving the dwarf-herb community on Ben Lawers, Perthshire, Scotland. Methods: Sheep-proof cages were erected each spring from 1987 to 1996 and dismantled again each autumn. Species cover, the height of the vegetation, the amount of litter and the extent of bare ground were estimated every summer. Data were analysed by repeated measures analysis of variance. Results: Excluding sheep caused major shifts in the balance amongst species. Initially, graminoids and some forbs increased in cover, the vegetation increased in height and the amount of bare ground decreased. However this was followed by a decline in the cover of graminoids as bryophytes proliferated and litter accumulated. Conclusion: Sheep grazing is essential to the maintenance of the dwarf-herb community. Permanent removal of sheep might lead to the development of bryophyte-rich, tall-herb and/or scrub vegetation.

Invasion level of alien plants in semi-natural agricultural habitats in boreal region

We quantified the level of invasion (i.e. number or proportion of aliens of all species) of archaeophytes (introduced before 17th century) and neophytes (introduced after 17th century) in five semi-natural agricultural habitats and identified the factors affecting the occurrence of alien species in boreal region. The differences in native and alien plant species richness were analysed with generalized linear mixed models. One-third of the recorded plant species were aliens. The highest levels of invasion were detected from frequently disturbed field and road margins, whereas the lowest levels were in grasslands and forest margins. All species groups had temperature-related decreasing trend northward, and increasing trend towards east. Archaeophytes responded like neophytes to geographical location and the amount of bare ground. Factors related to disturbance (the amount of bare ground, mowing) may increase the level of invasion. To prevent the establishment and spread of invasive alien species, management practices, which increase the disturbance, should be limited.