Search Results (76)

Rangelands form the ecological and economic backbone of Namibia, yet the woody plant dynamics that sustain these landscapes remain sporadically quantified across the semi-arid interior. We investigated the characteristics (stand structure, regeneration, richness, diversity, composition, ecological importance, and indicator species) of woody communities along a pronounced south-to-north rainfall gradient (85–346 mm yr⁻¹) at five representative sites: Warmbad, Gibeon, Otjimbingwe, Ovitoto, and Sesfontein. Field sampling combined point-centered quarter surveys (10 points site⁻¹) and belt transects (15 plots site⁻¹). The basal area increased almost ten-fold along the gradient (0.4–3.4 m² ha⁻¹). Principal Coordinates Analysis (PCoA) arranged plots in near-perfect rainfall order, and Permutational Multivariate Analysis of Variance (PERMANOVA) confirmed significant site differences (F_3,56 = 9.1, p < 0.001). Nanophanerophytes dominated hyper-arid zones, while microphanerophytes appeared progressively with increasing rainfall. Mean annual precipitation explained 45% of the variance in mean height and 34% of Shannon diversity but only 5% of stem density. Indicator value analysis highlighted Montinia caryophyllacea for Warmbad (IndVal = 100), Rhigozum trichotomum (75.8) for Gibeon, Senegalia senegal (72.6) for Otjimbingwe, and Senegalia mellifera (97.3) for Ovitoto. Rainfall significantly influences woody structure and diversity; however, other factors also modulate density and regeneration dynamics. This quantitative baseline can serve as a practical toolkit for designing site-specific management strategies across Namibia’s aridity gradient. Full article

Water scarcity is a growing global issue, especially in arid and semi-arid rangelands, primarily due to climate change and population growth. Groundwater is a crucial resource for vegetation in these ecosystems, yet its role in supporting plant life is often not fully understood. This review explores the interactions between groundwater and vegetation dynamics in various rangeland types. Groundwater serves as a critical water source that helps sustain plants, but changes in its availability, depth, and quality can significantly impact plant health, biodiversity, and ecosystem stability. Research indicates that groundwater depth affects vegetation types and their distribution, with specific plants thriving at certain groundwater levels. For instance, in grasslands, shallow groundwater can support diverse herbaceous species, while deeper conditions may favor drought-tolerant shrubs and trees. Similarly, in forest ecosystems, extensive root systems access both groundwater and soil moisture, playing a vital role in water regulation. Savanna environments showcase complex interactions, where trees and grasses compete for water, with groundwater potentially benefiting trees during dry seasons. Climate change poses additional challenges by altering rainfall patterns and temperatures, affecting groundwater recharge and availability. As a result, it is crucial to develop effective management strategies that integrate groundwater conservation with vegetation health. Innovative monitoring techniques, including remote sensing, can provide valuable information about groundwater levels and their impact on vegetation, enhancing water resource management. This review emphasizes the importance of understanding groundwater–vegetation interactions to guide sustainable land and water management practices. By enhancing our knowledge of these connections and utilizing advanced technologies, we can promote ecosystem resilience, secure water resources, and support biodiversity in rangeland systems. Collaborative efforts among local communities, scientists, and policymakers are essential to address the pressing issues of water scarcity and to ensure the sustainability of vital ecosystems for future generations. Full article

There are distinct management approaches for communal properties and commercial agricultural properties concerning bush encroachment. The utilisation of community-based knowledge possesses the capacity to enhance our comprehension of localised circumstances and provide valuable experience in endeavours targeted at supporting local communities. The perception of bush encroachment control as a sustained endeavour rather than a singular occurrence is of utmost importance. This may include considering other solutions that may not always be the most convenient or cost-effective. The objective of this study was to evaluate the predominant methods employed by rural communities in semi-arid savannah rangelands in Southern Africa to manage bush encroachment. Using the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines, a literature search was conducted in the field of communal strategies of bush encroachment management. The findings of this study indicate that the predominant and commonly utilised management strategy for mitigating bush encroachment includes the extraction of plants for medicinal applications, followed by firewood extraction. Indigenous and traditional knowledge systems have played a pivotal role in communal bush encroachment management. It is recommended that communal approaches to bush encroachment management in Southern Africa’s semi-arid savannah rangelands harness the power of indigenous knowledge while benefiting from modern scientific insights, ultimately leading to more effective and sustainable management practices. This can be accomplished by fostering community involvement and active participation, facilitating the exchange of knowledge, enhancing skills and expertise, preserving and safeguarding indigenous wisdom through documentation, and harmoniously blending traditional and scientific methodologies. Full article

Rangelands play a crucial socioeconomic and environmental role worldwide. In South America, desertification and overgrazing has led to their deterioration and declining productivity. Breeding programs that use native forage species of economic and ecological importance, such as Festuca pallescens (St. Yves) Parodi, may provide locally adapted germplasm that enhances productivity without threatening local biodiversity. These programs may even promote the conservation of native species. To this end, we characterized the phenotypic variation of nondestructive variables (growth and reproductive traits) related to forage and seed production during spring and early summer (growth and reproductive periods). Plants from ten populations were grown under common garden conditions in two environmental settings (sites) over two years. By early summer of the second year, most populations maintained a consistent relative performance with higher values for basal diameter, height and synflorescence production at site 2. This suggests more favorable environmental conditions for the species and highlights their potential for enhancing both seed and forage production. The growth and reproductive traits were probably largely influenced by micro-environmental cues (i.e., soil type and moisture), showing predominantly plastic patterns. The populations displaying phenotypic plasticity and above-average values for both traits were selected for further evaluation in breeding programs. Full article

Prosopis glandulosa (Mesquite), an invasive alien tree species, poses major threats to soil health, native vegetation, and biodiversity in South African rangelands. The negative impacts of Prosopis on socio-economic, environmental, and ecological resources outweigh the benefits. Most South African researchers are afraid that if left uncontrolled or poorly managed, it can cause severe land degradation, reduced agricultural productivity, indigenous-species shift, and ultimately the loss of biodiversity. Consequently, this will undermine key sustainable development goals related to food security and environmental conservation. In this review we conducted a systematic review, identifying 309 peer-reviewed articles from Google Scholar and Web of Science, screening and analyzing 98 of these, and ultimately reviewing 34 publications in detail. Three key research gaps were identified: (1) insufficient research focused on Prosopis invasion in South Africa; (2) limited integration and collaboration between the agricultural sector, environmental conservation sector, and governmental bodies; and (3) challenges in policy implementation within invaded areas. The study seeks to address these gaps by highlighting the impact of this alien invasive Prosopis species on land, biodiversity, and overall ecosystem stability. It also investigates policy issues surrounding invasive species and their control. Effective management of Prosopis within the country will not only control the spread but also support the broader objectives of environmental conservation, agricultural sustainability, and socio-economic development. Full article

Communally owned rangelands serve as critical grazing areas for mixed livestock species such as cattle and goats, particularly in the arid and semi-arid regions of Southern Africa. This study aimed to evaluate the nutritional composition and woody species composition of communal rangelands where cattle and goat flocks graze together and to investigate the influence of grazing intensity on vegetation dynamics. Vegetation surveys were conducted across varying grazing intensities to assess species richness, biomass, and dietary preferences, while soil properties were analyzed to determine their interaction with vegetation attributes. Stepwise regression and path analyses were used to explore the relationships between soil characteristics, vegetation structure, and livestock dietary choices. The results revealed that high grazing pressure significantly reduced grass biomass (p = 0.003) and woody species density (p = 0.007) while increasing shrub cover (p = 0.018). Nutritional analysis indicated that goats preferred woody shrubs, which contributed 42.1% of their diet compared to 27.8% for cattle (p = 0.008). Regression analysis further showed that soil organic carbon (p = 0.002) and tree height (p = 0.041) were strong predictors of shrub cover. Seasonal variation significantly affected forage availability and nutritional content, with higher crude protein levels recorded during the wet season (p = 0.007). These findings suggest that grazing management strategies should be tailored to the distinct forage needs of cattle and goats to maintain the productivity and ecological stability of communal rangelands. A holistic approach that considers livestock dietary preferences, vegetation composition, and soil health is essential for sustainable rangeland management in mixed-species grazing systems. Full article

Background: In the Sahel, one of the largest semi-arid areas in the world, pastoral livestock is the main source of protein for the local population. The quantification of herbaceous biomass in the Sahelian rangelands is of major importance since it provides food for the livestock. The main method used to monitor the biomass consists of cutting, drying, and weighting it. However, indirect methods are available and allow a reliable biomass estimation. Methods: In this study, we developed a non-destructive method for estimating herbaceous biomass for the Sahelian rangelands based on measurements of its height and coverage. Results: Results show that the fit is better in the fenced area. The volume index (height × coverage) provides a better biomass prediction with relative differences between measured and predicted biomass of 11% in 2017 and 8% in 2019. Conclusions: Monitoring herbaceous biomass without destroying it is possible by measuring only its height and coverage. Full article

In agrarian systems where animal mobility is crucial for feed management, nutrient cycles and household economy, there is a notable lack of precise data on livestock mobility and herding practices. We introduce a methodology leveraging GPS-based behavioural models to analyse and document pastoral mobility in the Sahel. Over 2.5 years, we conducted a continuous collection of GPS data from transhumant and resident cattle herds in the Senegalese agropastoral semiarid rangelands. We developed a Hidden Markov Model robustly fitted to these data to classify recordings into three states of activity: resting (47% overall), foraging (37%) and travelling (16%). We detail our process for selecting the states and testing data subsets to guide future similar endeavours. The model describes state changes and how temperature affects them. By combining the resulting dataset with satellite-based land-use data, we show the distribution of activities across landscapes and seasons and within a day. We accurately reproduced key aspects of cattle mobility and characterised rarely documented features of Sahel agropastoral practices, such as transhumance phases, nocturnal grazing and in-field rainy season paddocking. These results suggest that our methodology, which we make available, could be valuable in addressing issues related to the future of Sahelian pastoralism. Full article

The dynamic of rangelands results from complex interactions between vegetation, soil, climate, and human activity. This scenario makes rangeland’s condition challenging to monitor, and degradation assessment should be carefully considered when studying grazing pressures. In the present work, we study the interaction of vegetation and soil moisture in semiarid rangelands using vegetation and soil moisture indices. We aim to study the feasibility of using soil moisture negative anomalies as a warning index for vegetation or agricultural drought. Two semiarid agricultural regions were selected in Spain for this study: Los Vélez (Almería) and Bajo Aragón (Teruel). MODIS images, with 250 m and 500 m spatial resolution, from 2002 to 2019, were acquired to calculate the Vegetation Condition Index (VCI) and the Water Condition Index (WCI) based on the Normalised Difference Vegetation Index (NDVI) and soil moisture component (W), respectively. The Optical Trapezoid Model (OPTRAM) estimated this latter W index. From them, the anomaly (Z-score) for each index was calculated, being $Z_{VCI}$ and $Z_{WCI}$, respectively. The probability of coincidence of their negative anomalies was calculated every 10 days (10-day periods). The results show that for specific months, the $Z_{WCI}$ had a strong probability of informing in advance, where the negative $Z_{VCI}$ will decrease. Soil moisture content and vegetation indices show more similar dynamics in the months with lower temperatures (from autumn to spring). In these months, given the low temperatures, precipitation leads to vegetation growth. In the following months, water availability depends on evapotranspiration and vegetation type as the temperature rises and the precipitation falls. The stronger relationship between vegetation and precipitation from autumn to the beginning of spring is reflected in the feasibility of $Z_{WCI}$ to aid the prediction of $Z_{VCI}$. During these months, using $Z_{WCI}$ as a warning index is possible for both areas studied. Notably, November to the beginning of February showed an average increase of 20–30% in the predictability of vegetation anomalies, knowing moisture soil anomalies four lags in advance. We found other periods of relevant increment in the predictability, such as March and April for Los Vélez, and from July to September for Bajo Aragón. Full article

In the United States, rangelands comprise 30% of the total land cover and serve as a valuable resource for livestock, wildlife, water, and recreation. Rangelands vary in climate and are often subject to disturbances like drought and wildfire. Historic wildfire trends have indicated an increase in wildfire size and frequency, raising societal and ecological concerns about the management of these lands, both pre- and post-wildfire. While there has been investigation into the effects of grazing prior to a wildfire on fire severity and plant mortality, there is limited research related to grazing post-wildfire even though current management paradigms suggest deferring grazing rangeland for two years after a wildfire to avoid additional stress on native plant species. Based on the diversity found across rangeland ecotypes and history with wildfire, the two-year deferment recommendation may need to be reconsidered for some ecosystems. Species found in perennial bunchgrass rangelands like Pseudoroegneria spicata (bluebunch wheatgrass) and Festuca idahoensis (Idaho fescue) may be less susceptible to post-fire grazing than initially thought, necessitating the need for research into different rangeland ecosystems. Full article

The sagebrush steppe ecosystem plays a critical role in water cycling in arid and semiarid landscapes of the western United States; yet, there is limited information regarding individual sagebrush plant water uptake. We used the stem heat balance (SHB) method to measure transpiration in mountain big sagebrush (Artemisia tridentata subsp. vaseyana) plants in a semiarid rangeland ecosystem in central Oregon, Pacific Northwest Region, USA. We evaluated the relationship between sagebrush transpiration and environmental factors from July 2022 to May 2023 for two individual plants representative of the average sagebrush stand height and crown width at the study site; transpiration rates varied by plant and by season. This study encompassed one below-average (2022; 278 mm) and one above-average (2023; 414 mm) precipitation years. Study results showed that the average water use during the entire period of study was 2.1 L d⁻¹ for Plant 1 and 5.0 L d⁻¹ for Plant 2. During the dry year, maximum transpiration was observed during the summer (Plant 1 = 4.8 L d⁻¹; Plant 2 = 11.1 L d⁻¹). For the wet year, both plants showed maximum transpiration levels at the end of the recording period in mid-May (Plant 1 = 9.6 L d⁻¹; Plant 2 = 8.6 L d⁻¹). The highest seasonal transpiration of both plants occurred in summer (2.87 L d⁻¹), whereas the lowest transpiration was obtained in winter (0.21 L d⁻¹). For all seasons but winter, soil moisture (SM), soil temperature (ST), and vapor pressure deficit (VPD) variables generally showed positive correlations with transpiration. Transpiration rates decreased in the summer of 2022 as the surface soil gradually dried. The two plants’ most significant water uptake differences were obtained during the dry year. It is possible that the larger stem diameter of plant 2 may have contributed to its higher transpiration rates during times of limited water availability. The study results add to the understanding of water use by sagebrush and its potential impact on the water balance of cool-climate rangeland ecosystems. The findings also highlight the sensitivity of sagebrush to variations in seasonal soil moisture availability, soil temperature, and vapor pressure deficit. Future research should involve studying the combined effects of water use by various dominant vegetation species and its effects on the water budget at the watershed scale. Full article

Unmanned aerial systems offer a cost-effective and reproducible method for monitoring natural resources in expansive areas. But the transferability of developed models, which are often based on single snapshots, is rarely tested. This is particularly relevant in rangelands where forage resources are inherently patchy in space and time, which may limit model transfer. Here, we investigated the accuracy of drone-based models in estimating key proxies of forage provision across two land tenure systems and between two periods of the growing season in semi-arid rangelands. We tested case-specific models and a landscape model, with the expectation that the landscape model performs better than the case-specific models as it captures the highest variability expected in the rangeland system. The landscape model did achieve the lowest error when predicting herbaceous biomass and predicted land cover with better or similar accuracy to the case-specific models. This reinforces the importance of incorporating the widest variation of conditions in predictive models. This study contributes to understanding model transferability in drier rangeland systems characterized by spatial and temporal heterogeneity. By advancing the integration of drone technology for accurate monitoring of such dynamic ecosystems, this research contributes to sustainable rangeland management practices. Full article

Soil degradation due to loss of soil organic carbon is a serious concern in semiarid agroecosystems. Biochar and other organic char products have long been known to increase soil organic carbon. In this study, three-year field observations were carried out on use of coal char (CC) and biochar (BC) as soil amendments in unirrigated semiarid rangeland soil. Coal was pyrolyzed at three different temperatures of 650, 750, and 800 °C to form CC650, CC750, and CC800, respectively, and BC was obtained from a local commercial producer. Manure, CC, and BC were incorporated in soil at 10% (v/v). Analyses of plant growth (aboveground biomass) and soil properties were performed and compared with the control treatment without char. In all three years, CC applied with manure (CC650M) produced significantly greater grass biomass, by 95, 42, 101%, and BC applied with manure (BCM) increased grass biomass by 89, 39, 52% in 2018, 2019, and 2020, than the controls in the respective years. Soil tests a year after application of char indicated significantly increased soil organic matter (OM) with CC and BC treatments (1.60–2.93%) compared with the control (1.37%). However, further detailed studies are required to investigate CC and BC interactions with soil in unirrigated semiarid rangelands. Full article

This study describes spatial and temporal patterns in fire across the US Western Great Plains over the last 40 years. Although pyrogeographic studies have explored the nexus of fire patterns in relation to the bio-physical environment and socio-ecological trends, most of this research has focused on forested ecosystems and regions long known for conflict between wildfires and human development, especially at the wildland–urban interface. But evidence suggests large wildfire activity is increasing in the US Great Plains, and the Western Great Plains—a Land Resource Region comprised of four ecoregions, Northwestern Plains, High Plains, Nebraska Sandhills, and Southwestern Tablelands—not only contains some of the largest areas of rangeland in the US but also the highest concentration of public land in the Great Plains. As such, the Western Great Plains provides an opportunity to explore fire activity in primarily rural landscapes with a combination of public and private ownership, all dominated by rangeland vegetation. We combined several publicly-available datasets containing fire records between 1992 and 2020 to create two databases, one with georeferenced point data on 60,575 wildfire events in the region, and another with georeferenced perimeter data for 2665 fires. Ignition by humans was the dominant cause of fires. No ecoregion showed a statistically significant trend towards either increasing or decreasing the annual burned area. The Northwestern Plains had the most burned area and the greatest number of incidents—consistently around or above 1000 incidents per year since 1992—with the majority in July. The High Plains showed the greatest increase in annual fire incidence, never reaching more than 200–300 per year 1992–2009, and averaging above 1000 incidents per year since 2010. Few long-term trends in human population, weather, or fuel metrics appear strongly associated with fire patterns in any ecoregion, although the years 2006, 2012, and 2017 stood out for their levels of fire activity, and these years often frequently logged extreme values in wildland fuel metrics. These relationships merit much closer examination in the Western Great Plains, because like other rangeland-dominated landscapes, the fine fuels that comprise these wildland fuelbeds are much more responsive to fine-scale changes in moisture conditions. Rural Western Great Plains landscapes are a mosaic of public and private land ownership, and an increasing impact of wildfires on public grazing lands—which are often situated within other jurisdictions or ownership—will likely have an impact on rural livelihoods. Full article

There is scarce information regarding the interactions between young tree water uptake and the environment in water-limited ecosystems. This study was conducted in a semiarid rangeland ecosystem in central Oregon, Pacific Northwest Region, USA. We measured the tree transpiration of western juniper (Juniperus occidentalis) saplings using the stem heat balance (SHB) method. We analyzed the correlation between transpiration and environmental factors affecting the saplings’ water use from May to October for 2017, 2018, 2019, 2021, and 2022. The study results showed that total annual precipitation for all but one year was below the long-term (2005 to 2022) mean precipitation value of 307 mm for the study site. Significantly higher transpiration rates were observed in the wet vs. dry years. The highest monthly averaged transpiration rates (2.95 L d⁻¹) were obtained in August during the above-average precipitation year (2017). Peak transpiration rates for the below-average precipitation years were generally reached in June or July, ranging from 0.91 to 1.65 L d⁻¹. The seasonal response of transpiration to different environmental factors varied. For all years, vapor pressure deficit (VPD), solar radiation (SR), and air temperature (AT) showed a positive correlation with transpiration, whereas precipitation (Pr) and relative humidity (RH) indicated a negative correlation with transpiration. Soil moisture (SM) and soil temperature (ST) positively correlated with transpiration for most years. A strong association between VPD and transpiration was observed during the wettest (2017; 327 mm) and driest (2021; 198 mm) years. Results from this study add to the limited literature on sapling transpiration and can contribute to the improved management of cool-climate rangeland ecosystems through an enhanced understanding of water use by young-stage trees and its potential impacts on the water balance of restored juniper landscapes. Full article