Rangeland Ecology & Management最新文献

Reduction of vegetation following wildfire in rangelands of the western United States can result in invasion of exotic annual grasses and elevated soil loss to wind erosion. In response to these threats, various mechanical seeding methods (such as drill seeding and mechanical mixing of broadcast seeds) are commonly employed by restoration practitioners. Despite their common use, little information exists about how additional disturbance from mechanical seeding (following wildfire disturbance) may further contribute to soil loss from wind erosion. Here, we compared the effects of mechanical seeding techniques on soil properties following two wildfires occurring in similar climates with contrasting soil textures (silty loam and gravelly loam soils). Using either a rangeland or minimum-till drill to create furrows or mix broadcasted seeds into soils, we quantified wind erosion risk for unburned sites, burned nonseeded sites, and seeded sites according to soil aggregate stability, horizontal sediment flux, surface microtopography, and soil compaction. Effects of mechanical seeding were small relative to those created by wildfire. For burned areas, differences in site stability were greatest between sites. Following wildfire, the largest decrease in site stability occurred in fine-textured soils, where horizontal sediment transport was increased by nearly five orders of magnitude relative to unburned areas. Despite these initial differences, site stability in fine-textured soils may have improved to a greater degree than stability at the coarse-textured site. Furthermore, we found minimal differences between drill types on site stability but, instead, observed that the largest differences in soil properties were created by furrow versus broadcast seeding. The different outcomes of rehabilitation on site stability found here, paired with the spatial extent to which wildfire affects landscapes, highlights the importance of postfire monitoring of site stability in more locations that vary by soil, plant, landscape, and climatic variables.

Habitat destruction is one of the biggest threats to wildlife populations. Climate change may exacerbate the impacts of habitat destruction and alter the distribution of species. We projected the impact of climate change on the distribution of mouflon (Ovis gmelini) in central Iran in 2055 and 2085, evaluated the efficiency of protected areas for protecting this species, and identified potential climatic refugia for this species. We analyzed presence data of mouflon according to climate and topographic factors and generated an ensemble model of habitat suitability based on nine species distribution models. In the modeling process, the most important uncorrelated variables were chosen. Using circuit theory, potential connectivity between habitat patches was estimated. To assess the impact of climate change on the study area in 2055 and 2085, two shared socioeconomic pathways (SSPs), SSP 2.6 and SSP 8.5, were used based on the global circulation models. Based on the climatic suitability model, approximately 34.11% of protected areas were recognized as suitable habitats for mouflon. In the forecasted climate conditions, approximately 3.30% of suitable habitats would become unsuitable and approximately 9.36% of the current protected areas will lose their efficiency in supporting this species. In addition, climate change may reduce habitat connectivity for mouflon in the future. We conclude that the development of the network of protected areas and attention to habitat connectivity are necessary for the future migration and survival of this species; therefore, conservation planning should consider the future potential of protected/unprotected areas in supporting mouflon populations.

Understanding the mechanistic link between plant functional traits and foraging patterns across seasons and grazing intensities is crucial for implementing sustainable grazing systems and predicting ecological successions. We assessed the interaction effects of grazing intensity, season, and leaf functional traits on herbivore grazing patterns in a native grassland composed of functionally diverse patches in four 10–14 ha paddocks managed under lenient or moderate grazing intensities. Seasonal botanical composition was estimated in permanent 20 × 20 cm patches. Defoliation events of species in patches were recorded every 7–10 d, four times during summer-autumn, and five times during winter and spring. Leaf dry matter content, specific area, tensile strength, and width of dominant grass species were measured seasonally, and species were allocated to functional groups. The proportion of total defoliation events occurring in each functional group and their selectivity index were estimated for each period and season. We tested the relationship between trait community weighted mean in the pasture and that grazed by cattle for each quadrant and period within seasons. Cows focused grazing on resource-acquisitive strategy species with wider and more tender leaves during summer-autumn under both grazing intensities. As herbage mass and accumulation decreased during winter, cows shifted their foraging strategy toward shorter patches and previously rejected, tougher-thinner leaves and resource-conservative strategy species stockpiled from summer-autumn, not overgrazing the resource-acquisitive species. However, this general pattern was modulated by grazing intensity; cows grazed taller patches and more tender and wider-leaved species under lenient than moderate grazing intensity. Thus, the spatiotemporal heterogeneity of desired and rejected stockpiled patches of different functional groups was managed by integrating seasonality, grazing intensity, and leaf functional traits. Therefore, the general principle of foraging selectivity toward desired species can be altered by management practices and inherent species attributes, maintaining communities of species of different ecosystem functions in equilibrium.

State and transition models (STMs) are widely used for organizing, understanding, and communicating complex information regarding ecological change. One foundational component of STMs is the representation of the current state of ecological sites (ecosites) delineated by topoedaphic features. Field inventory and assessment techniques used to characterize ecosites are labor-intensive and based on limited sampling in time and space. Remote sensing and Geographic Information System technologies increasingly offer opportunities to generate synoptic, high-resolution characterizations of ecosites in heterogeneous and remote rangelands. Here, we show how advanced remotely-sensed hyperspectral data acquired by the National Ecological Observatory Network can be combined with uncrewed aerial vehicle data within a GIS framework to quantify land cover at scales that inform STMs in Sonoran Desert landscapes in southern Arizona. Using 1 m airborne hyperspectral reflectance data, spectral vegetation and moisture indices (derived from hyperspectral bands and rendered together with the hyperspectral stack), and aerial imagery for ground-truthing, we were able to 1) produce a classification product quantifying some, but not all, plant and soil categories used in STMs and 2) delineate the spatial pattern and areal extent of ecological states on several ecological sites. Our remote sensing-based assessments were then compared to vegetation state maps based on traditional field surveys. We found that with the exception of native vs. nonnative grass ground cover, remote sensing picked up contributions of key ecostate classification variables. Remote sensing products thus have value for planning and prioritizing field surveys and pinpointing areas of concern or novelty. Furthermore, remote sensing approaches more thoroughly encompass greater spatial extents and are ostensibly more cost-effective than traditional field surveys when viewed through the lens of the time-series analyses needed to document whether the ecological states in STMs are stable or in the process or transitioning.

Land use and land cover (LULC) changes are known as the main factors causing soil degradation, which presents considerable obstacles to maintaining soil quality and the resilience of ecosystems. Human activities substantially impact LULC changes, particularly in areas experiencing rapid development. The objective of this study is to assess the changes in LULC, land surface temperature (LST), Normalized Differentiate Vegetation Index (NDVI), and Normalized Differentiate Built-up Index (NDBI) in Kasur District from 1991 to 2021. The study analyzed five major LULC classes: Water bodies, Urban areas, barren land, forest Cover, and vegetated areas. Our analysis revealed that the Urban area of Kasur expanded by around 16.27%. The vegetation cover experienced a slight decline of just 1%, while water bodies declined by 0.26%. Forest cover experienced a decrease of about 0.54%, and bare land decreased significantly by 14.4%. The imagery classification achieved an overall accuracy of 88% to 92%. The highest NDVI value was observed in 1991 (+0.89), while the lowest was in 2021 (+0.56). Similarly, the highest NDBI recorded was +0.83 in 2021, while the lowest was +0.65 in 1991. The linear regression analysis revealed a strong negative association between the NDVI and NDBI. LST results exhibited a 0.55°C increase between the years 1991 and 2021. The study's findings align with the Sustainable Development Goals (SDGs), particularly SDG-15, which aims to protect, restore, and promote sustainable use of terrestrial ecosystems, sustainably manage forests, combat desertification, and halt land degradation and biodiversity loss.

Huisache (Vachellia farnesiana (L.) Wight & Arn.) is a pest tree species on rangelands throughout South Texas and is expanding in range and density, due in part to prolific seed production. We aimed to determine the optimum diurnally-fluctuating temperature conditions for huisache seed germination by testing scarified and nonscarified seed in four temperature treatments: 35/25, 30/20, 25/15, and 20/10°C. We used alternating 12-hour light/dark photoperiods in a growth chamber, and seed germination was recorded daily. Germination of scarified and nonscarified seeds at each temperature treatment was analyzed via ANOVA for a completely randomized design (with appropriate posthoc tests). Although total cumulative germination percentages were similar among temperature treatments, seeds in the 20/10°C temperature treatment germinated more slowly. In addition, scarified seeds germinated more quickly, and with greater total percent germination. Results show that huisache seeds can be expected to germinate over a wide range of temperatures, with germination slowing when temperatures are low. Because we found huisache seeds germinated slowly in cooler temperatures, landscape managers may consider prioritizing control efforts of recently-germinated seedlings following warmer, wetter weather.