Tall Vegetation Research Articles

Variation in species-specific responses to habitat fragmentation and land cover structure in urban small mammal communities

Abstract Urbanization is a key driver of habitat loss and fragmentation worldwide, yet many urban ecosystems contain vegetated habitat patches that support diverse wildlife communities. Managing urban systems to support robust wildlife communities requires us to understand the mechanisms that drive the response of species to the urban environment. Small mammals are key components of terrestrial ecosystems (e.g., seed predators, prey) and likely also carry out these roles in urban ecosystems; however, the effects of urbanization on small mammal communities are understudied. To identify how species-specific responses to urban environments shape community composition, we quantified both overall community and species-specific changes in small mammal abundance across an urbanization gradient in a Midwestern US metropolitan area. We combined small mammal trapping and land cover data to generate a hierarchical community abundance model. Species diversity increased with increasing proportional cover of human-modified land cover (i.e., impervious surfaces and turfgrass). This finding is driven by high species diversity on sites bordering streams in mowed parks and low diversity on sites with high tree canopy closure. Additionally, modeling results indicated that species responded differently to landscape attributes, leading to variation in small mammal community composition across the urbanization gradient: prairie-associated species tended to be more abundant in tall vegetation bordering mowed parks while habitat generalists tended to be more abundant on sites with greater canopy closure and shrub cover. Our results suggest that studies that focus on community-level responses (e.g., species richness) to urbanization may miss important species-specific responses. It may be particularly important to assess both species-specific and community-level responses in cities at ecotones (e.g., between forest and grassland) where species with different habitat requirements may replace one another in different types of green spaces, thereby changing community composition without affecting species diversity or richness. Our findings also indicate that vegetated urban patches, especially patches with tall vegetation cover and low canopy cover, are important habitat for prairie-associated small mammal communities, providing conservation options in heavily altered landscapes.

Habitat quality in farmland influences the activity patterns of giant Galapagos tortoises

AbstractMany Galapagos giant tortoises make seasonal migrations from arid lowlands in the wet season, to humid highlands in the dry season. However, for critically endangered Western Santa Cruz giant tortoises (Chelonoidis porteri), at least 88% of the habitat in the highlands is now used for agriculture. To understand the impact of agricultural land use on tortoise behavior, we conducted 242 30-minute observations of tortoises on farms. We (1) recorded the time tortoises spent eating, walking, and resting in three different land-use types, (2) measured their temperature, and (3) quantified their selection of fine-scale vegetation characteristics. We found that tortoises rest for significantly longer periods when they are in abandoned land, compared to livestock, grazing, and touristic land. Generally, tortoises rested for longer when they were cooler. Time spent eating was increased by the density and proportion of ground vegetation, while time spent walking was reduced by tall vegetation. These findings suggest that the distribution of land-use types and the fine-scale composition of thermoregulatory and grazing resources within farmland have important implications for the behavior of tortoises while in human-modified land. Wildlife managers and landowners wishing to support tortoises on farms should focus on rehabilitating abandoned land and encouraging a heterogenous mix of sun and shade, and short ground vegetation across land-use types.

Assessing diurnal land surface temperature variations across landcover and local climate zones: Implications for urban planning and mitigation strategies on socio-economic factors

Rising temperatures and rapid urbanization globally reinforce the need to understand urban climates. We investigated the influence of land cover and local climate zones (LCZs) on diurnal land surface temperature (LST) in various seasons in greater Delhi region, India, and their implications on socio-economic factors. Day LST was the highest in the summer and night LST in the monsoon, which also had the lowest diurnal differences in LST. Higher height and density of built-up features contributed to greater heat at night. During the day, open built-up and vegetated areas experienced relatively less heat than their compact equivalents. The lowest diurnal difference was in medium height compact urban zones and tall vegetation. Social inequity in access to urban cooling was indicated by large low-income and heat-vulnerable populations inhabiting the hottest LCZs. This research highlighted that even in semi-arid and subtropical climates, spatial planning policy should consider both the seasonality and diurnal differences in temperature as much as appropriate morphologies for design of thermally comfortable and climate resilient urban spaces. These policies should address the evidenced social inequities in heat exposure to reduce the adverse health impacts on vulnerable groups and therefore contribute to wider societal and economic benefits of healthier populations.

Modulating local winds and turbulence around a single building obstacle with the obstruction of tall vegetation

Strategic vegetation placement can significantly alter airflow patterns and turbulence, fostering desired wind environments. By comparing scenarios where vegetation is placed upstream, downstream or absent (treeless) relative to a single building using large-eddy simulation, this study provides detailed insights into the sensitivity of flow dynamics to the positioning of the vegetation. Upstream vegetation more significantly disrupts the flow patterns around the building obstacle, altering vertical wind profiles and modifying wake circulations, compared to downstream vegetation. A small shear layer developed at the plant top for upstream vegetation markedly influences turbulent kinetic energy (TKE) on both the leeward and windward sides of the building, shifting the inflection point in vertical TKE profiles by up to 0.13H. By contrast, smaller tree-building separations lead to an effective merging of their aerodynamic profiles, whereas larger separations confine the streamwise breadth of turbulent fluxes, amplifying flux exchanges in the spanwise direction. Spectral analyses reveal that upstream vegetation consistently results in higher power spectral densities of the streamwise turbulence in the residential area than downstream vegetation. While small-scale spanwise velocity fluctuations are found to be comparably energetic at the building's windward side for upstream vegetation, the power becomes substantially concentrated on large-scale eddies in the building wake region, providing specific insights into modulating turbulent eddy motions within the residential zone.

The impact of green roofs’ composition on its overall life cycle

Green roof systems have been developed to improve the environmental, economic, and social aspects of sustainability. Selecting the appropriate version of the green roof composition plays an important role in the life cycle assessment of a green roof. In this study, 10 compositions of an intensive green roof for moderate zone and 4 green roof compositions for different climatic conditions were designed and comprehensively assessed in terms of their environmental and economic impacts within the “Cradle-to-Cradle” system boundary. The assessment was carried out over a 50-year period for a moderate climate zone. The results showed that asphalt strips and concrete slab produced the highest total emissions. It was found that most greenhouse gases emissions were released in the operational energy consumption phase and in the production phase. The energy consumption phase (48.78%) for automatic irrigation and maintenance caused the highest Global Warming Potential (GWP) value (758.39 kg CO2e) in the worst variant, which also caused the highest life cycle cost (878.47€). On the contrary, in the best variant, planting more vegetation and lower maintenance and irrigation requirements led to a reduction in GWP (445.0 kg CO2e), but in terms of cost (506.6€) this composition didn't represent the best variant. The Global Warming Potential Biogenic (GWP-bio) compared to the Global Warming Potential Total (GWP-total) represents a proportion ranging from 0.8% to 78% depending on the proposed vegetation. Overall higher biogenic carbon values (up to 1525 kg CO2e) were observed for the proposed tall vegetation of Magnolia, Red Mulberry, Hawthorne, Cherry, and Crab-apple Tree. Based on the results of the multicriteria analysis, which included core environmental & economic parameters, biogenic carbon emission levels, the outcome of this paper proposed optimal green roof composition. Optimal intensive green roof composition was subjected to a sensitivity analysis to determine the impact of changing climatic conditions on CO2 emissions and life cycle costs. The results of the sensitivity analysis show that the optimal variant of the green roof can be implemented in the cold and subtropical zone with regard to CO2 emissions, but not with regard to life cycle costs.

Landslide Hazard Prediction Based on Small Baseline Subset–Interferometric Synthetic-Aperture Radar Technology Combined with Land-Use Dynamic Change and Hydrological Conditions (Sichuan, China)

Le’an Town, located in the southwest of Qingchuan County, Guangyuan City, Sichuan Province, boasts a unique geographical position. The town’s terrain is complex, and its geological environment is fragile. Multiple phases of tectonic movements have resulted in numerous cracks and faults, making the area prone to landslides, debris flows, and other disasters. Additionally, heavy rainfall and fluctuating groundwater levels further exacerbate the instability of the mountains. Human activities, such as overdevelopment and deforestation, have significantly increased the risk of geological disasters. Currently, the methods for landslide prediction in Le’an Town are limited; traditional techniques cannot provide precise forecasts, and the study area is largely covered by tall vegetation. Therefore, this paper proposes a method that combines SBAS-InSAR technology with dynamic changes in land use and hydrological conditions. SBAS-InSAR technology is used to obtain surface deformation information, while land-use changes and hydrological condition data are incorporated to analyze the dynamic characteristics and potential influencing factors of landslide areas. The innovation of this method lies in its high-precision surface deformation monitoring capability and the integration of multi-source data, which can more comprehensively reveal the geological environmental characteristics of the study area, thereby achieving accurate predictions of landslide development. The study results indicate that the annual subsidence rate in most deformation areas of Le’an Town ranges from −10 to 0 mm, indicating slow subsidence. In some areas, the subsidence rate exceeds −50 mm per year, showing significant slope aspect differences, reflecting the combined effects of geological structures, climatic conditions, and human activities. It is evident that land-use changes and hydrological conditions have a significant impact on the occurrence and development of landslides. Therefore, by utilizing SBAS-InSAR technology and cross-verifying it with other techniques, the consistency of identified landslide deformation areas can be enhanced, thereby improving results. This method provides a scientific basis for the monitoring and early warning of landslide disasters and has important practical application value.

Long-term monitoring of desert restoration processes using historical stereoscopic imagery and laser scanning data: An example of the Błędów Desert (Poland)

This study aimed to present the spatiotemporal changes associated with the loss and subsequent regaining of the original character of the Błędów Desert (Poland) as a result of restoration efforts. The study area is one of the few places in Europe with a sandy desert character. The research period covered nearly 40 years, covering an area of approximately 1400 ha.The methodology is based on comparing the height structure parameters by analyzing point clouds created from contemporary and historical stereoscopic images. For this purpose, four sets of stereoscopic images were used, including two historical analog images from 1982 to 1996 and contemporary digital data from 2012 to 2018. Additional datasets such as airborne laser scanning data and cadastral databases were used as auxiliary data. The results showed an increase in the area covered by tall vegetation from 2% in 1982 to 18% and 41% in 1996 and 2012, respectively, which decreased to 30% after the completion of restoration activities in 2018. The restoration process has enabled the revival of the original desert character of the study area, although the total area covered by sand decreased compared to its state in the early 1980s. These results indicate the significant potential of the presented methodology in supporting ecosystem management systems, where changes in the height structure of vegetation play a crucial role. This applies to monitoring land abandonment, forest management, and large-scale reclamation work.

Habitat loss and degradation reduce the abundance of the glossy grass skink, Pseudemoia rawlinsoni

Context Habitat loss and degradation are major drivers of biodiversity loss worldwide. In particular, wetland environments are being removed and degraded faster than any other terrestrial habitat on earth. The loss and degradation of wetlands has been particularly pronounced in south-eastern Australia. Aims Here we investigated the impact of habitat loss and degradation on the Data Deficient glossy grass skink (Pseudemoia rawlinsoni), a species that predominantly favours wetland vegetation in south-eastern Australia. Methods We established artificial cover-object (roofing tiles) survey grids in paired remnant and disturbed sites at six locations across Victoria, Australia, and surveyed for skinks between November 2021 and April 2022. Key results Sites at which glossy grass skinks occur are characterised by tall dense vegetation, with a high cover of matted biomass. Thermal profiles within these complex vegetation structures remain much cooler during hot days, and warmer during cold nights, than external temperatures. Nearby disturbed sites (i.e. grazed or mowed areas within dispersal distance of remnant sites) are generally devoid of skinks, have very low and structurally simple (open) vegetation, and have thermal regimes that offer lizards no respite from high summer temperatures. We found that roofing tiles are an effective way to survey for glossy grass skinks; even on cool cloudy days, the temperature of tiles, and the lizards sheltering beneath them, are often much higher than ambient temperatures. Conclusions These findings implicate habitat loss and degradation as having a substantial negative impact on glossy grass skink presence and abundance; skinks largely avoid disturbed areas, even at sites immediately adjacent to remnant habitat. This may be driven not simply by the removal of tall and dense vegetation structures, but the consequent loss of the optimal thermal buffer afforded by such structures. Implications Our study emphasises the threat that habitat loss and degradation pose to wetland species in Australia, and throughout the world.

The impact of sward height, forage quality and competitive conditions on foraging behaviour of free-ranging rabbits (Oryctolagus cuniculus L.)

The habitat choice of the small hindgut fermenter, the European rabbit (Oryctolagus cuniculus L.), was studied in relation to sward height, forage quality, population size fluctuations and spatial distribution of burrows in a temperate grassland. In a multi-phase differential clipping experiment with alternating short and tall vegetation strips, rabbits tended to graze near the closest burrows in situations of equal vegetation heights, while a clear preference for short swards was found during summer (July). In this period, general crude protein content was significantly lower than in spring (April) and autumn (September), apparently leading to a potential forage quality deficit. The summer behavioural pattern with short sward preference coincided with the relatively higher crude protein content of short swards as compared to tall swards in this period, and with higher intraspecific competition, due to significantly larger numbers of animals present in summer. In autumn, rabbit densities decreased, while crude protein content of both short and tall vegetation increased to a higher, though not significantly different level, comparable with spring crude protein content. In those conditions, significant preference for low vegetation height could no longer be detected. Data suggest that selection for nutritive quality appears when intraspecific competition is high and nutritive quality remains under a certain threshold value. When, in autumn, competition decreases and nutritive quality increases again, short sward preference disappears. We conclude that short sward preference is primarily caused by the better forage quality of re-growth in periods of forage quality limitation, while this preference disappears when forage quality limitation no longer occurs.

Application of lidar to assess the habitat selection of an endangered small mammal in an estuarine wetland environment.

Light detection and ranging (lidar) has emerged as a valuable tool for examining the fine-scale characteristics of vegetation. However, lidar is rarely used to examine coastal wetland vegetation or the habitat selection of small mammals. Extensive anthropogenic modification has threatened the endemic species in the estuarine wetlands of the California coast, such as the endangered salt marsh harvest mouse (Reithrodontomys raviventris; SMHM). A better understanding of SMHM habitat selection could help managers better protect this species. We assessed the ability of airborne topographic lidar imagery in measuring the vegetation structure of SMHM habitats in a coastal wetland with a narrow range of vegetation heights. We also aimed to better understand the role of vegetation structure in habitat selection at different spatial scales. Habitat selection was modeled from data compiled from 15 small mammal trapping grids collected in the highly urbanized San Francisco Estuary in California, USA. Analyses were conducted at three spatial scales: microhabitat (25 m2), mesohabitat (2025 m2), and macrohabitat (~10,000 m2). A suite of structural covariates was derived from raw lidar data to examine vegetation complexity. We found that adding structural covariates to conventional habitat selection variables significantly improved our models. At the microhabitat scale in managed wetlands, SMHM preferred areas with denser and shorter vegetation and selected for proximity to levees and taller vegetation in tidal wetlands. At the mesohabitat scale, SMHM were associated with a lower percentage of bare ground and with pickleweed (Salicornia pacifica) presence. All covariates were insignificant at the macrohabitat scale. Our results suggest that SMHM preferentially selected microhabitats with access to tidal refugia and mesohabitats with consistent food sources. Our findings showed that lidar can contribute to improving our understanding of habitat selection of wildlife in coastal wetlands and help to guide future conservation of an endangered species.

Grassland vegetation height affects bird responses to forest edges in Mediterranean open farmland

Afforestation affects Mediterranean farmland biodiversity due to loss and fragmentation of grassland habitats. While the influence of landscape context and plantation edges on farmland bird responses to afforestation is well-documented, less is known about the influence of grassland vegetation height and how it interacts with afforestation to influence bird communities. Here, we examined how changes in grassland vegetation height affect bird responses to afforestation in a farmland region in southern Portugal, and how these are affected by plantation type and edge. This region has experienced afforestation with eucalyptus, pine and oak stands, agricultural intensification, and frequent dry periods. To capture local and landscape-level changes, we collected data in two periods (2005 and 2014–15). Grassland vegetation height varied between sampling periods, emerging as a key factor affecting changes observed. Ground-nesting and cereal-associated species increased in abundance with taller vegetation in 2014–15, while in 2005, with drier weather and shorter vegetation, the species associated with ploughed fields were more abundant. Vegetation height effects on bird assemblages depended on plantation type and distance to plantation edges. Farmland bird abundance, including ground-nesting and cereal crops-associated species, increased with taller vegetation, particularly near oak and pine plantations. Conversely, species associated with ploughed fields declined with taller vegetation, especially near eucalyptus plantations. Results highlight complex interactions between vegetation height, plantation type, and edge proximity shaping avian assemblages. This study supports the importance of field and landscape-level management with special focus on grassland vegetation height and landscape heterogeneity for preserving open-farmland birds in fast-changing Mediterranean farmland landscapes.

Heavy Ungulate Pressure behind the Disappearance of Regeneration in Hungarian Forests

Ungulate populations have surged to unsustainable levels in multiple areas in recent decades due to human intervention, making forestry and conservation practices arduous. The population of ungulates is also currently displaying a rising trend in Hungary, prompting decision-makers to commence substantial reduction efforts. Our study examined the ungulate impact in three forested regions of Hungary, employing field survey sampling plots on almost 50,000 hectares. Our findings revealed that regeneration browsing and soil disturbance were evenly high in these areas, while the cover of the regeneration layer was extremely low. Ungulate pressure was suspected as the cause of the lack of regeneration. Based on habitat and vegetation conditions, we divided our sample as favourable and unfavourable for regeneration. The cover of the regeneration categories was not significantly different between the two sets. The evidence of the direct indicators, including browsing and soil disturbance, coupled with the lack of regeneration, leads us to infer indirect signs of ungulate pressure. The absence of older and taller vegetation in the area also suggests long-standing ungulate pressure. Our investigation suggests that the high ungulate population can cause low abundance, even the lack of regeneration, not only locally but also at a regional scale.

Land use types at the boundaries between settlements and open landscape in suburbanised settlements on the example of the Czech Republic from the perspective of the potential for planting tall vegetation

Background and aimsSettlement boundaries in suburbanised areas represent a specific environment connecting the settlements with the surrounding open landscape. Traditionally, tall vegetation (such as orchards planted in the backyards) used to form this boundary, providing a gradual transition as well as a wide range of ecosystem services. With suburbanisation, however, there appears to be a trend towards sharper boundaries between the open landscape and the settlement. The degree of the effect of suburbanisation on the boundary has, however, not been thoroughly explored yet. In this paper, the current character of such boundaries is evaluated from the perspective of land use and potential for tall vegetation. In addition, possible impacts of such changes are discussed, and measures for preventing these impacts are proposed. MethodsOn 50 suburbanised settlements in the Czech Republic, the land use types, water permeability, and suitability for the growth of tall vegetation within an 80 m belt enveloping the boundary between the settlement and open landscape were analysed using ArcGIS tools and artificial intelligence algorithms. ResultsThe dominant land use types were Residential on the inner side of the margins and Farmland on the outside of the margins, with a few meters of the transitional zone. These homogeneous land use types represented approx. 70 % of land use types at a distance of 10 m or more from the boundary. The representation of water-absorbing areas on the residential side of the boundary declined from 80 % at the settlement boundary to approx. 55 % at 40 m inside the settlement; this drop was even more pronounced for areas suitable for tall vegetation (from 90 % at 20 m outside of the boundary to 70 % at the boundary and 35 % at 40 m within the settlement). However, the potential for planting tall vegetation at the outer margins is underutilised. ConclusionsThe dominance of farmland in the immediate vicinity of the boundary between suburbanised settlements and open landscape and the underutilisation of the potential for planting tall vegetation on the outer margins deprive the settlements of ecosystem services of such ecotone and lead to the loss of habitats for wild animal and plant species.

Extensive dune grasslands largely lacking human disturbance are an important refuge for a vole-dependent raptor

Agricultural intensification and abandonment have led to a dramatic decrease of semi-natural grasslands such as low-intensity pastures and hay meadows. The Short-eared owl (Asio flammeus) is a ground-nesting raptor of open grasslands that has severely suffered from these changes. We studied the habitat preferences of this umbrella species of open grasslands in its last permanent breeding area in Germany (East Frisian Islands, southern North Sea). We analysed the breeding-territory preferences based on 576 territories on six of the islands. Moreover, we assessed nest-site preferences of 13 breeding pairs on the German abundance hot spot, the island of Spiekeroog. Our investigation revealed that the Short-eared owl strongly preferred open dunes for breeding, especially dune grasslands. By contrast, built-up areas and small stands of trees were avoided. For nest-building, microhabitats with a high cover of the herb layer and litter resulting in tall vegetation were favoured. By contrast, the vegetation in the wider surrounding of the nest was characterised by more bare ground and shorter vegetation but still a high cover of the herb layer and litter. In conclusion, our study highlights the prime importance of extensive open grasslands with a pronounced litter layer and largely lacking human disturbance as breeding habitats for the Short-eared owl. At the nesting site, we suggest that tall and dense vegetation with a high cover of litter (i) might enhance concealment and (ii) causes a favourable microclimate by protecting fledglings against adverse weather conditions. In the wider surrounding of the nest, shorter vegetation with a pronounced litter layer (i) improves fledgling mobility, (ii) fosters vole abundance and (iii) increases prey accessibility.

Deer survey from drone thermal imagery using enhanced faster R-CNN based on ResNets and FPN

Deer surveys play an important role in the estimation of local ecological balance. In the Chitwan National Park of Nepal, the dense tree canopies and tall vegetation often obscure the presence of wild deer, which has a negative effect on the accurate population surveys of wild deer. UAVs equipped with infrared sensors have been increasingly used to monitor wild deer by capturing a lot of images. How to automatically recognize and obtain the number of deer objects from thermal images is becoming an important research topic. Due to the difference between thermal images and true-color images, as well as the variations in deer object sizes in these two types of images, current ready-to-use object detection models, designed for true-color imagery, are ill-suited for the task of detecting small deer objects within thermal imagery. In this paper, an enhanced Faster R-CNN was constructed to detect small deer objects from thermal images, in which a Feature Pyramid Network (FPN) based on a residual network is used to improve feature extraction for small deer objects and multi-scale feature map constrution for the subsequent region proposals searching, bounding box regression, and regions of interest (RoIs) classification. In addition, small-scaled anchor boxes and a multi-scale feature map selection criterion are devised to improve the detection accuracy of small objects. Finally, based on Faster R-CNN, FPN, and different residual networks including ResNet18, ResNet34, ResNet50, ResNet101, and ResNet152, we constructed five object detection models, and evaluated their detection performance by using COCO evaluation matrix. Under the condition of IoU≥0.5, the integration of Faster R-CNN, FPN, and ResNet18 demonstrated to perform better than others. Specifically, The COCO evaluation results revealed an Average Precision (AP) score of 91.6% for all deer objects. Small deer objects (area ≤ 200 pixels) achieved an AP score of 73.6%, medium deer objects (200 < area ≤ 400 pixels) demonstrated an AP score of 93.4%, and large deer objects (area > 400 pixels) achieved the highest AP score of 94.3%. Our research is helpful for effective wild deer monitoring and conservation and can be a valuable reference for the exploration of small object detection from low-resolution thermal images.

Reactive response to predation risk affects foraging time of hares, yet not their phosphorus intake

Antipredator responses could affect nutrient intake, which could lead to nutritional deficits. However, little is known about the antipredator response of small herbivores because most are nocturnal or crepuscular and therefore very difficult to study in the field. Therefore, we experimentally assessed the effect of a reactive response to predation risk on the nutrient (i.e., phosphorous) intake of the European hare (Lepus europaeus) using three different playback sounds. Additionally, we studied the time spent being costly vigilant, the time spent foraging, and the vegetation height in which the hares were present using accelerometers and GPS. Our results showed that elevated predation risk from our playback experiment did not affect the (1) phosphorus intake, (2) time spent being costly vigilant, and (3) time spent in tall vegetation. However, elevated predation risk did increase the time spent foraging. Possibly hares spent more time foraging with an increased predation risk because hares cannot seek refuge from predators. Additionally, the effect on phosphorus intake could be weak because phosphorous intake does not benefit a flight escape, while the reactive response acts late in the predation sequence limiting the effect on hare ecology. Prey anti-predator responses seem strongly related to the escape tactics of prey species that can differ between different habitats and the time of the day. More detailed field studies are necessary to get a better insight into species’ anti-predator-food tactics.

Insect-friendly harvest in hay meadows – Uncut refuges are of vital importance for conservation management

With ongoing industrialisation of farming practise, the area of species-rich temperate grasslands has strongly declined. Today, the remnants of these grasslands often suffer from habitat degradation due to unsuitable management. Here, we investigated the effects of the complete harvest process over the course of two harvest periods (mid-June and mid-August) on Orthoptera (hereinafter referred to as ‘grasshoppers’) in species-rich lowland hay meadows in southwestern Bavaria (Germany). We set up a randomised split-plot design including mown meadows (tractor-operated rotary-disc vs. double-bladed bar mower) and uncut refuges within grassland patches. Our study revealed that mower types did not differ in their effects on grasshopper mortality and that direct mortality through cutting was very low. By contrast, after mowing, on average 85–91 % of the individuals or biomass was lost by the end of the harvest process. However, in uncut refuges, grasshopper densities and biomass increased on average by 234–328 %. From the first to the second harvest period, an alignment in grasshopper densities and biomass between meadows and uncut refuges occurred. We explain the lack of direct cutting effects by the tall and dense vegetation of the hay meadows and, hence, the location of the grasshoppers far above the sphere of the mowers. Moreover, we assume that in particular emigration from the short and homogeneous meadows to uncut refuges or patch edges but also increased vertebrate predation were responsible for the severe grasshopper losses. Moreover, we hypothesise that grasshopper recolonization from the refuges to the meadows strongly contributed to the alignment in grasshopper densities from mid-June to mid-August. Hence, to protect abundant grasshopper populations in meadows in the long run, uncut refuges are of prime importance. Firstly, such refuges guarantee a continuity in (i) food resources, (ii) a balanced microclimate and (iii) shelter against predators and extreme weather events for the resident individuals. Consequently, they are not affected by any of the harvest-related losses. Secondly, they serve as an important refuge for the emigrants from the mown parts of the meadow.

Vegetation patch dynamics in rangelands: How feedbacks between large herbivores, vegetation and soil fauna alter patches over space and through time

AbstractAimLarge herbivore grazing is a popular conservation management tool to promote vegetation structural diversity of rangelands. However, vegetation patch dynamics, that is, how patches of grazing‐defended tall vegetation and grazer‐preferred short lawns shift over space and time, is poorly understood. Here, we describe a new conceptual framework for patch dynamics within rangelands, combining theories of classical cyclical succession, self‐organization and multitrophic feedbacks between grazers, vegetation and bioturbating soil fauna.LocationWe use the cattle‐grazed salt marsh of the island Schiermonnikoog, The Netherlands, as a model system. The grazed salt marsh is characterized by distinct tall vegetation patches dominated by the grazing‐defended rush Juncus maritimus and grazing‐intolerant grass Elytrigia atherica, surrounded by a matrix of grazing lawn (dominated by Festuca rubra).The FrameworkBased on previous observational and experimental studies, we propose a cyclical patch dynamic where plant species composition and structure transitions through four phases: patch initiation (a) occurs when the grazing‐defended rush J. maritimus establishes in the grazed lawn. Patch establishment (b) follows when the grazing‐intolerant grass E. atherica establishes in the patch due to associational defence by J. maritimus and produces a large amount of litter that attracts the key bioturbating amphipod Orchestia gammarellus. Patch expansion (c) occurs when O. gammarellus activities improve soil properties of the patch, which favours E. atherica growth, leading to E. atherica competitively displacing J. maritimus in the centre of the patch. Patch degeneration (d) follows when cattle enter the enlarged patch to consume E. atherica in the centre, trample the soil, displace O. gammarellus and decrease vegetation cover, opening space for grazing‐lawn species to invade. The cycle restarts when remnants of the rush J. maritimus in the degenerated patches (or individuals recently established from seed dispersal) initiate new patches in the grazing lawn.SynthesisOur proposed patch‐dynamic model provides a means to describe the mechanisms driving vegetation patch dynamics and serves as a foundation for further experimental and observational exploration, not only for this specific system, but more generally for grazed systems worldwide that show patches of typical grazing‐defended and grazer‐preferred vegetation.

Estimating Permafrost Distribution Using Co‐Located Temperature and Electrical Resistivity Measurements

AbstractAssessing the lateral and vertical extent of permafrost is critical to understanding the fate of Arctic ecosystems under climate change. Yet, direct measurements of permafrost distribution and temperature are often limited to a small number of borehole locations. Here, we assess the use of co‐located shallow temperature and electrical resistivity tomography (ERT) measurements to estimate at high‐resolution the distribution of permafrost in three watersheds underlain by discontinuous permafrost. Synthetic modeling shows that co‐located temperature and ERT measurements allow for supervised classification schemes that provide 60% higher accuracy compared to unsupervised methods. Linking resistivity and size of the identified permafrost bodies to surface observations, we show that tall vegetation (&gt;0.5 m) and gentle slopes (&lt;15°) are related to warmer and smaller permafrost bodies, and a more frequent occurrence of taliks.

Wind regimes above and below a dense oil palm canopy: Detection of decoupling and its implications on CO2 flux estimates

In tall vegetation canopies, calm weather conditions may result in the formation of an isolated below-canopy air layer. Especially during night, below-canopy carbon dioxide (CO2) fluxes may be concealed from above-canopy eddy covariance (EC) measurements, masking the magnitude of CO2 net ecosystem exchange (NEE). Particular attention to this “nighttime problem” needs to be paid in oil palm (Elaeis guineensis Jacq.) plantations, which can form a dense top canopy and which are grown in tropical regions where wind speeds are often low. Here, we investigated EC-based NEE measurements, wind and micrometeorological patterns, and LiDAR-derived terrain and canopy structure in a mature commercial oil palm plantation in the tropical lowlands of Jambi province, Sumatra, Indonesia. Over 3 years, we assessed the strength of turbulent and thermal mixing and tested five different methods to determine decoupling: (i) single-level (above-canopy) and (ii) two-level (above- and below-canopy) friction velocity (u*), (iii) above- and below-canopy standard deviation of the vertical wind (σw), (iv) bulk Richardson number (Rib), and (v) vertical turbulence intensity (ITurb). Our results show that decoupling is a common phenomenon in this plantation, with the two-level filters of σw and u* being most sensitive in its determination, showing ∼93% nocturnal decoupling. Decoupling is driven by the oil palm canopy structure, which develops a marked blocking layer at ∼10 m above the ground, high frequency of calm weather conditions, inverse temperature gradients and a terrain slope of 3° which was enough to create a thermally-induced drainage flow. Filtering NEE data, especially the two-level filters of σw and u*, challenged estimations of the plantation's CO2 balance due to high uncertainties in nocturnal respiration rates which could not be reduced by adding storage components to the measured fluxes highlighting the importance of additional below-canopy CO2 flux measurements, especially in such a weak-wind and dense-canopy tropical environment.