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1.
J Insect Sci ; 24(4)2024 Jul 01.
Artículo en Inglés | MEDLINE | ID: mdl-39126278

RESUMEN

World food supplies rely on pollination, making this plant-animal relationship a highly valued ecosystem service. Bees pollinate flowering plants in rangelands that constitute up to half of global terrestrial vegetation. Livestock grazing is the most widespread rangeland use and can affect insect pollinators through herbivory. We examined management effects on bee abundance and other insect pollinators on grazed and idle sagebrush rangelands in central Montana, USA. From 2016 to 2018, we sampled pollinators on lands enrolled in rest-rotation grazing, unenrolled grazing lands, and geographically separate idle lands without grazing for over a decade. Bare ground covered twice as much area (15% vs. 7) with half the litter (12% vs. 24) on grazed than idle regardless of enrollment. Bee pollinators were 2-3 times more prevalent in grazed than idle in 2016-2017. In 2018, bees were similar among grazed and idled during an unseasonably wet and cool summer that depressed pollinator catches; captures of secondary pollinators was similar among treatments 2 of 3 study years. Ground-nesting bees (94.6% of total bee abundance) were driven by periodic grazing that maintained bare ground and kept litter accumulations in check. In contrast, idle provided fewer nesting opportunities for bees that were mostly solitary, ground-nesting genera requiring unvegetated spaces for reproduction. Managed lands supported higher bee abundance that evolved with bison grazing on the eastern edge of the sagebrush ecosystem. Our findings suggest that periodic disturbance may enhance pollinator habitat, and that rangelands may benefit from periodic grazing by livestock.


Asunto(s)
Artemisia , Conservación de los Recursos Naturales , Ecosistema , Polinización , Animales , Abejas/fisiología , Artemisia/fisiología , Montana , Herbivoria , Ganado
2.
Ecol Appl ; 33(8): e2909, 2023 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-37602895

RESUMEN

Herbivore exclusion is implemented globally to recover ecosystems from grazing by introduced and native herbivores, but evidence for large-scale biodiversity benefits is inconsistent in arid ecosystems. We examined the effects of livestock exclusion on dryland plant richness and reproductive capacity. We collected data on plant species richness and seeding (reproductive capacity), rainfall, vegetation productivity and cover, soil strength and herbivore grazing intensity from 68 sites across 6500 km2 of arid Georgina gidgee (Acacia georginae) woodlands in central Australia between 2018 and 2020. Sites were on an actively grazed cattle station and two destocked conservation reserves. We used structural equation modeling to examine indirect (via soil or vegetation modification) versus direct (herbivory) effects of grazing intensity by two introduced herbivores (cattle, camels) and a native herbivore (red kangaroo), on seasonal plant species richness and seeding of all plants, and the richness and seeding of four plant groups (native grasses, forbs, annual chenopod shrubs, and palatable perennial shrubs). Non-native herbivores had a strong indirect effect on plant richness and seeding by reducing vegetative ground cover, resulting in decreased richness and seeding of native grasses and forbs. Herbivores also had small but negative direct impacts on plant richness and seeding. This direct effect was explained by reductions in annual chenopod and palatable perennial shrub richness under grazing activity. Responses to grazing were herbivore-dependent; introduced herbivore grazing reduced native plant richness and seeding, while native herbivore grazing had no significant effect on richness or seeding of different plant functional groups. Soil strength decreased under grazing by cattle but not camels or kangaroos. Cattle had direct effects on palatable perennial shrub richness and seeding, whereas camels had indirect effects, reducing richness and seeding by reducing the abundance of shrubs. We show that considering indirect pathways improves evaluations of the effects of disturbances on biodiversity, as focusing only on direct effects can mask critical mechanisms of change. Our results indicate substantial biodiversity benefits from excluding livestock and controlling camels in drylands. Reducing introduced herbivore impacts will improve soil and vegetation condition, ensure reproduction and seasonal persistence of species, and protect native plant diversity.


Asunto(s)
Ecosistema , Ganado , Animales , Bovinos , Camelus , Plantas , Bosques , Biodiversidad , Poaceae , Suelo , Herbivoria/fisiología
3.
Environ Res ; 219: 114954, 2023 02 15.
Artículo en Inglés | MEDLINE | ID: mdl-36529322

RESUMEN

This study was carried out to evaluate the forage quantity and quality of several halophyte species grown in arid-saline environments. After identifying 44 halophytic species in the region and considering the potential of quantitative and qualitative forage production, 13 species from four families, i.e. Amaranthaceae, Asteraceae, Leguminosae and Convolvulaceae, and eight genera were selected for further evaluation. These species differed significantly in terms of both forage quantity, measured in terms of fresh (FW) and dry weight (DW), and forage quality assessed in terms of tissue water content (TWC), ash, nitrogen content (N), crude protein (CP), acid detergent fiber (ADF), neutral detergent fiber (NDF), dry matter digestibility and metabolizable energy (ME). The highest fresh and dry weights were obtained from Suaeda ferticosa (1006.3 g and 306.3 g, respectively) and Noaea mucronata (909.3 g and 309 g, respectively). However, based on forage quality characteristics, Alhagi maurorum, Bassia scoparia, Noaea mucronata, Halostachys belangriana and Cressa cretica showed the best forage potential. Values of ash, CP, ADF, NDF and ME measured in the halophytes species ranged between 7.9% and 33.2%, 6.2% and 15.8%, 30.0% and 50.3%, 33.2% and 56.4%, 5.6 and 8.7 MJ kg-1, respectively. The forage quality of the evaluated halophytic plants was influenced by unfavorable environmental conditions such as high soil salinity and low rainfall, however, these species can be considered as new sources of forage. Nevertheless, further studies are needed to improve the quality of such halophytic species by reducing the ash content and increasing the ME.


Asunto(s)
Fibras de la Dieta , Plantas Tolerantes a la Sal , Humanos , Plantas Tolerantes a la Sal/metabolismo , Fibras de la Dieta/metabolismo , Alimentación Animal/análisis , Digestión , Detergentes
4.
Environ Manage ; 72(4): 699-704, 2023 10.
Artículo en Inglés | MEDLINE | ID: mdl-37452138

RESUMEN

Grazing by domestic livestock is the most widespread use of public lands in the American West (USA) and their effects on climate change and ways to mitigate those effects are of interest to land managers, policy makers, and the broader public. Kauffman et al. (2022a) provided a meta-analysis of the ecosystem impacts, greenhouse gas (GHG) emissions, and social costs of carbon (SCC) associated with livestock grazing on public lands in the western USA. They determined that GHG emissions from cattle on public lands equaled 12.4 million t CO2e/year. At the scale of land use planning utilized by federal agencies, GHG emissions associated with allocated livestock numbers will typically exceed US Environmental Protection Agencies' reporting limits (25,000 t) for certain industrial greenhouse gas emitters. As such, these are essentially unreported sources of GHG emissions from public lands. Using the US government's most recent SCC estimate of $51/t, Kauffman et al. (2022a) determined the total SCC of cattle grazing on public lands to be approximately $264-630 million/year. However, recent advances in the determination of SCC reveal this is to be an underestimate. Using the latest science results in an estimated SCC of $1.1-2.4 billion/year for grazing on public lands. Furthermore, the SCC borne by the public exceeds the economic benefits to private livestock permittees by over $926 million/year. Cessation of public lands grazing is an environmentally and economically sound mitigation and adaptation approach to addressing the climate crisis; an approach that will also facilitate restoration of the myriad of ecosystem services provided by intact wildland ecosystems.


Asunto(s)
Ecosistema , Gases de Efecto Invernadero , Animales , Bovinos , Ganado , Cambio Climático , Carbono , Efecto Invernadero
5.
Glob Chang Biol ; 28(12): 3902-3919, 2022 06.
Artículo en Inglés | MEDLINE | ID: mdl-35320616

RESUMEN

Although the role of livestock in future food systems is debated, animal proteins are unlikely to completely disappear from our diet. Grasslands are a key source of primary productivity for livestock, and feed-food competition is often limited on such land. Previous research on the potential for sustainable grazing has focused on restricted geographical areas or does not consider inter-annual changes in grazing opportunities. Here, we developed a robust method to estimate trends and interannual variability (IV) in global livestock carrying capacity (number of grazing animals a piece of land can support) over 2001-2015, as well as relative stocking density (the reported livestock distribution relative to the estimated carrying capacity [CC]) in 2010. We first estimated the aboveground biomass that is available for grazers on global grasslands based on the MODIS Net Primary Production product. This was then used to calculate livestock carrying capacities using slopes, forest cover, and animal forage requirements as restrictions. We found that globally, CC decreased on 27% of total grasslands area, mostly in Europe and southeastern Brazil, while it increased on 15% of grasslands, particularly in Sudano-Sahel and some parts of South America. In 2010, livestock forage requirements exceeded forage availability in northwestern Europe, and southern and eastern Asia. Although our findings imply some opportunities to increase grazing pressures in cold regions, Central Africa, and Australia, the high IV or low biomass supply might prevent considerable increases in stocking densities. The approach and derived open access data sets can feed into global food system modelling, support conservation efforts to reduce land degradation associated with overgrazing, and help identify undergrazed areas for targeted sustainable intensification efforts or rewilding purposes.


Asunto(s)
Conservación de los Recursos Naturales , Ganado , Animales , Biomasa , Brasil , Pradera
6.
J Environ Manage ; 322: 116092, 2022 Nov 15.
Artículo en Inglés | MEDLINE | ID: mdl-36055100

RESUMEN

Wildfire activity has recently increased in California, impacting ecosystems and human well-being. California's rangelands are complex social-ecological systems composed of multiple ecosystems and the people who live and work in them. Livestock grazing has been proposed as a tool for reducing wildfire activity. Here, we explore how grazing affects wildfire at large spatial scales, assessing burn probability on rangelands with different grazing levels. We collected grazing data by surveying 140 large private landowners in three social-ecological regions: California's North Bay, Central Coast, and Central Valley and Foothills. Using pre-regression matching and mixed effects regression, we calculate the burn probability from 2001 to 2017 in points sampled from grazed and ungrazed properties in each region in grasslands, shrub/scrublands, and forests. We find that in the Central Coast and North Bay, annual burn probability decreases as stocking levels increase across all vegetation types, with reductions of 0.008-0.036. In the Central Valley and Foothills, the relationship is complex, with burn probability increasing over some grazing levels and variations in the effect of higher stocking densities. Our results indicate that livestock grazing may reduce annual burn probability in some regions and ecosystems in California, providing the first large-scale assessment of this relationship.


Asunto(s)
Ganado , Incendios Forestales , Animales , Ecosistema , Bosques , Probabilidad
7.
J Environ Manage ; 301: 113766, 2022 Jan 01.
Artículo en Inglés | MEDLINE | ID: mdl-34731965

RESUMEN

Stocking rate and rangeland area are key variables to provide the livelihood of herders in different climatic zones. To evaluate the economic and ecological management of pastoral units, this study aims to determine the optimal economic size of pastoral units for livestock grazing use considering the ecological capacity of semi-arid rangelands in different climatic scenarios. Therefore, 12 pastoral units (an area of 47,355 ha) were selected in two climatic zones (summer and winter rangelands) in the Kalat region of Razavi Khorasan Province, Iran. By measuring forage production, carrying capacity was calculated. Based on the results, the costs of traditional livestock management in winter rangelands are higher than those of summer rangelands. Moreover, the current size of the assigned rangeland, especially the summer rangeland, is lower than that of the economic justification. The results emphasize that rangeland-based livestock husbandry cannot create a good livelihood for herders in the region, and it is necessary to pay special attention to other services and aspects, despite the existing ecological and socio-economic complexities. In this regard, providing multi-purpose rangeland use and useable technologies to better manage these areas is necessary to increase per capita household income and reduce the stocking rate in the region's rangelands. Ultimately, both increasing the level of available rangelands and reducing costs by applying new technology are required, as is the economic consideration of pastoral units by using rangelands for multiple purposes.


Asunto(s)
Conservación de los Recursos Naturales , Ganado , Animales , Irán , Estaciones del Año
8.
Ecol Appl ; 31(6): e02368, 2021 09.
Artículo en Inglés | MEDLINE | ID: mdl-33938594

RESUMEN

Pastoral systems are the dominant livestock production system in arid and semiarid regions of sub-Saharan Africa (SSA). They are often the only form of agriculture that can be practiced due to unfavorable climate and soil fertility levels that prevent crop cultivation. Pastoralism can have negative impacts on the environment, including land degradation, greenhouse gas emissions and other gases to the atmosphere, soil erosion, water pollution and biodiversity loss. Here, we review the current knowledge on nitrogen (N) cycling, storage, and loss pathways, with an emphasis on identification of N emission hotspots. Our review reports a large uncertainty in the amount of N lost as ammonia from excreta and manure storage, as well as N losses via nitrate and DON leaching. We also found that another major N loss pathway (18%), soil N2 emissions, has not yet been measured. In order to summarize the available information, we use a virtual pastoral farm, with characteristics and management practices obtained from a real farm, Kapiti Research Station in Kenya. For outlining N flows at this virtual farm, we used published data, data from global studies, satellite imagery and geographic information system (GIS) tools. Our results show that N inputs in pastoral systems are dominated by atmospheric N deposition (˜80%), while inputs due to biological nitrogen fixation seems to play a smaller role. A major N loss pathway is nitrogen leaching (nitrate > DON) from pastures (33%). Cattle enclosures (bomas), where animals are kept during night, represent N emissions hotspots, representing 16% of the total N losses from the system. N losses via ammonia volatilization and N2 O were four and three orders of magnitude higher from bomas than from the pasture, respectively. Based on our results, we further identify future research requirements and highlight the urgent need for experimental data collection to quantify nitrogen losses from manure in animal congregation areas. Such information is needed to improve our understanding on N cycling in pastoral systems in semiarid regions and to provide practical recommendations for managers that can help with decision-making on management strategies in pastoral systems in semiarid savannas.


Asunto(s)
Fertilizantes , Ganado , Agricultura , Animales , Bovinos , Fertilizantes/análisis , Kenia , Estiércol , Nitrógeno/análisis , Suelo
9.
Environ Manage ; 67(6): 1075-1087, 2021 06.
Artículo en Inglés | MEDLINE | ID: mdl-33730191

RESUMEN

Woody plant encroachments are major concerns across the grasslands biome, while the patterns of individual species existence at a landscape level can be limited locally and regionally. The paper assesses the species composition, community structure, and density of individual and combined encroacher woody species in terms of tree equivalent per hectare (TE ha-1) within five different height classes at four elevation levels in Borana arid thorn bush savanna grasslands in Southern Ethiopia. At each elevation class, a grid of 20 × 20 m main plot was placed, and samples were collected randomly from three 100 m2 sub-plot within the main plot. Using a single-factor analysis of variance, the effects of four elevation classes were considered on encroacher woody plant species composition, total, and individual density (TE ha-1) within height classes. A total of 22 encroacher woody plant species composition were identified. The identified woody plants are seemingly a threat to the Borana rangelands of Southern Ethiopia with various patterns of distribution and density (TE ha-1) among the different elevation levels. Of the identified species, Acacia reficiens had the highest density (1052.22 ± 265.34 TE ha-1) at elevation level II. The most important encroaching species in each elevation level was varied considerably, while the combined woody plants density (TE ha-1) within height classes across elevation levels showed minimal variations. This suggests that the management of a specific ecological site might require greater focus in terms of the functional traits of individual woody species composition, density coverage within height classes, and community structure. Hence, identifying the patterns, distribution, and density of encroaching woody species is crucial for the control of key encroacher woody species at a landscape level.


Asunto(s)
Ecosistema , Árboles , Etiopía , Plantas
10.
Environ Monit Assess ; 193(12): 815, 2021 Nov 17.
Artículo en Inglés | MEDLINE | ID: mdl-34787728

RESUMEN

Assessing the role of machine learning (ML) models concerning environmental predictors on spatial variation of soil organic carbon stocks (SOCS) in arid rangelands is very necessary. This study was conducted to explore the variability of surface SOCS in rangeland in the west of Iran using ML approaches. A number of 33 environmental predictors derived from Sentinel-2B and DEM were used. The optimal soil sampling (n = 80) position was determined by Latin hypercube sampling (cLHS) method. Robust and popular random Forest (RF), cubist (CB) along with random forest-ordinary kriging (RF-OK), and cubist-ordinary kriging (CB-OK) hybrid ML models were applied to the prediction of SOCS. Ten-fold CV was implemented for modeling performance and uncertainty map. According to data analysis, the maximum, minimum, and average values of SOCS are 44.50, 10.50, and 20.50 (ton. ha-1) at the surface depth (0-30 cm), respectively. In general, normalized and standardized height covariates had a higher effect related to other predictors. On the other hand, two remote sensing (RS) indices, including salinity ratio (salinity) and GNDVI index, had a better impact on SOCS variability. The external validation of model performance indicated that RF-OK with (R2 = 0.75, RMSE = 6.33 ton. ha-1) with the high and low uncertainty range (3.33-9.50 ton. ha-1) was the outperformed ML model in compare with other models as RF (R2 = 0.65, RMSE = 7.38 ton. ha-1), CB-OK (R2 = 0.56, RMSE = 9.22 ton. ha-1), and CB (R2 = 0.33, RMSE = 10.42 ton. ha-1). In general, the hybrid models improved the accuracy of RF and CB with increased 0.11 until 0.23 of R2, and 1.05 to 1.2 (ton. ha-1) decreased RMSE of model's prediction. Hence, we conclude that the topographic attributes (especially normalized and standardized height) were the most critical factors in controlling surface SOCS in arid rangelands when combining with robust RF ML model, and optimized soil sampling methods like RF-cLHS can prepare acceptable soil properties maps.


Asunto(s)
Carbono , Suelo , Algoritmos , Carbono/análisis , Monitoreo del Ambiente , Aprendizaje Automático
11.
Ecol Appl ; 30(3): e02053, 2020 04.
Artículo en Inglés | MEDLINE | ID: mdl-31829472

RESUMEN

Rangeland ecosystems worldwide are characterized by a high degree of uncertainty in precipitation, both within and across years. Such uncertainty creates challenges for livestock managers seeking to match herbivore numbers with forage availability to prevent vegetation degradation and optimize livestock production. Here, we assess variation in annual large herbivore production (LHP, kg/ha) across multiple herbivore densities over a 78-yr period (1940-2018) in a semiarid rangeland ecosystem (shortgrass steppe of eastern Colorado, USA) that has experienced several phase changes in global-level sea surface temperature (SST) anomalies, as measured by the Pacific Decadal Oscillation (PDO) and the El Niño-Southern Oscillation (ENSO). We examined the influence of prevailing PDO phase, magnitude of late winter (February-April) ENSO, prior growing-season precipitation (prior April to prior September) and precipitation during the six months (prior October to current April) preceding the growing season on LHP. All of these are known prior to the start of the growing season in the shortgrass steppe and could potentially be used by livestock managers to adjust herbivore densities. Annual LHP was greater during warm PDO irrespective of herbivore density, while variance in LHP increased by 69% (moderate density) and 91% (high density) under cold-phase compared to warm-phase PDO. No differences in LHP attributed to PDO phase were observed with low herbivore density. ENSO effects on LHP, specifically La Niña, were more pronounced during cold-phase PDO years. High herbivore density increased LHP at a greater rate than at moderate and low densities with increasing fall and winter precipitation. Differential gain, a weighted measure of LHP under higher relative to lower herbivore densities, was sensitive to prevailing PDO phase, ENSO magnitude, and precipitation amounts from the prior growing season and current fall-winter season. Temporal hierarchical approaches using PDO, ENSO, and local-scale precipitation can enhance decision-making for flexible herbivore densities. Herbivore densities could be increased above recommended levels with lowered risk of negative returns for managers during warm-phase PDO to result in greater LHP and less variability. Conversely, during cold-phase PDO, managers should be cognizant of the additional influences of ENSO and prior fall-winter precipitation, which can help predict when to reduce herbivore densities and minimize risk of forage shortages.


Asunto(s)
Ecosistema , Herbivoria , Colorado , El Niño Oscilación del Sur , Estaciones del Año
12.
Disasters ; 44(3): 435-454, 2020 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-31294854

RESUMEN

Rangeland Fire Protection Associations (RFPAs) are volunteer-based groups of trained private landowners who are authorised to respond to events in partnership with governmental agencies. This study analysed the functioning and structure of RFPAs in Idaho and Oregon in the western United States to characterise this under-researched model of disaster response. RFPAs represent an expanding type of disaster response organisation that interfaces with established fire suppression entities, yet 'emergent behaviour' manifested in some RFPA response actions. This appeared to lessen and mediate with time, as well as due to recognition of the issues, increased experience of fires, and training that fostered new mutual understandings. There is a need for continued examination of the effect of repeat experience in developing the characteristics of disaster response organisations. In addition, it is crucial to know how the interface between established and other types of organisations may be enhanced to make cooperative disaster response more effective.


Asunto(s)
Desastres/prevención & control , Incendios/prevención & control , Sistemas de Socorro/organización & administración , Voluntarios/psicología , Humanos , Idaho , Modelos Organizacionales , Oregon
13.
J Environ Manage ; 255: 109889, 2020 Feb 01.
Artículo en Inglés | MEDLINE | ID: mdl-32063324

RESUMEN

Rangeland-based livestock production (RBLP) primarily occurs in drylands where interannual variation in rainfall directly and indirectly affects economies, plant primary productivity (forage production), and livestock reproduction and mortality. Tight ecological and economic links to climate variation constrain production in dryland systems, but producers have a breadth of strategies to reduce climate-related risks and maintain RBLP. Research on these strategies has focused on context-specific tactics linked to specific systems and/or geographies. Inspired by studies that look for broader patterns to offer frameworks for discourse and to advance collective knowledge, we review global literature to identify risk management strategies related to climate variability that are in widespread use across dryland rangeland systems and geographies. We organize strategies within three key decision areas for producers engaged in RBLP: profit and return options, land use, and herd management. Across the decision areas, four strategies emerge as playing a strong role in risk management across the globe, with refinements based on local conditions. These shared and prevalent producer driven strategies are dynamic management of forage supply (in the decision area of land use), dynamic management of animal demand (in the area of herd management), and diversification and use of social networks (both of which apply across all three decision areas). Within each of the decision areas, we found diversification reduces climate related risks but has circumstances under which it is less effective; for example, large landholders already buffered to risk via landscape diversity benefit less from livelihood diversification. In practice, implementation of the four strategies often results in livestock producers who do not maximize short-term profits but instead prioritize land resilience, large herd sizes, lifestyle goals, and longer-term economic sustainability. In this synthesis, we considered existing producer strategies for reducing risk related to climate related variability -- an intrinsic and defining characteristic of dryland rangelands -- in order to highlight valuable areas in which research can support problem solving across diverse RBLP geographies and economies, especially in a changing climate.


Asunto(s)
Conservación de los Recursos Naturales , Ganado , Animales , Clima , Geografía , Gestión de Riesgos
14.
Environ Monit Assess ; 192(5): 269, 2020 Apr 06.
Artículo en Inglés | MEDLINE | ID: mdl-32253518

RESUMEN

The recent availability of small and low-cost sensor carrying unmanned aerial systems (UAS, commonly known as drones) coupled with advances in image processing software (i.e., structure from motion photogrammetry) has made drone-collected imagery a potentially valuable tool for rangeland inventory and monitoring. Drone-imagery methods can observe larger extents to estimate indicators at landscape scales with higher confidence than traditional field sampling. They also have the potential to replace field methods in some instances and enable the development of indicators not measurable from the ground. Much research has already demonstrated that several quantitative rangeland indicators can be estimated from high-resolution imagery. Developing a suite of monitoring methods that are useful for supporting management decisions (e.g., repeatable, cost-effective, and validated against field methods) will require additional exploration to develop best practices for image acquisition and analytical workflows that can efficiently estimate multiple indicators. We embedded with a Bureau of Land Management (BLM) field monitoring crew in Northern California, USA to compare field-measured and imagery-derived indicator values and to evaluate the logistics of using small UAS within the framework of an existing monitoring program. The unified workflow we developed to measure fractional cover, canopy gaps, and vegetation height was specific for the sagebrush steppe, an ecosystem that is common in other BLM managed lands. The correspondence between imagery and field methods yielded encouraging agreement while revealing systematic differences between the methods. Workflow best practices for producing repeatable rangeland indicators is likely to vary by vegetation composition and phenology. An online space dedicated to sharing imagery-based workflows could spur collaboration among researchers and quicken the pace of integrating drone-imagery data within adaptive management of rangelands. Though drone-imagery methods are not likely to replace most field methods in large monitoring programs, they could be a valuable enhancement for pressing local management needs.


Asunto(s)
Conservación de los Recursos Naturales , Monitoreo del Ambiente/métodos , Tecnología de Sensores Remotos , Aeronaves , California , Ecosistema , Procesamiento de Imagen Asistido por Computador
15.
Trop Anim Health Prod ; 52(1): 321-330, 2020 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-31342453

RESUMEN

The objective of the study was to examine strategies employed by farmers to mitigate the effects of drought on cattle production in communal rangelands of Zimbabwe. Data were collected from a total of 316 communal cattle farming households selected from semi-arid and sub-humid environments (158 each) using structured questionnaires. Farmers in sub-humid environments mostly resorted to controlled migration in search of pastures during drought whilst those in semi-arid environments mainly supplemented their cattle (P < 0.05). Travelling long distances to centralized water tanks was ranked first as a strategy to counter water shortage in sub-humid environments whilst in semi-arid environments farmers mostly resorted to use of boreholes (P < 0.05). Farmers in sub-humid environments were more than twice more likely to supplement their cattle than those in semi-arid environments (P < 0.05). Crop residues were the main type of feed used to supplement cattle during drought periods (P > 0.05). Mashona cattle were the most preferred breed (P > 0.05). Conformation traits were less preferred in both environments (P < 0.05). It was concluded that communal cattle producers in both environments use dietary supplementation with crop residues and controlled migration in search of pastures and water to mitigate drought effects. Given the shortcomings associated with drought mitigation strategies being used by communal cattle farmers, current findings suggest the need to design and implement sustainable strategies such as breeding cattle for drought resilience and selective supplementary feeding.


Asunto(s)
Crianza de Animales Domésticos/métodos , Bovinos , Sequías , Adulto , Agricultura , Animales , Suplementos Dietéticos , Composición Familiar , Agricultores , Femenino , Respuesta al Choque Térmico , Humanos , Masculino , Encuestas y Cuestionarios , Agua , Zimbabwe
16.
Ecol Lett ; 22(10): 1658-1667, 2019 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-31298471

RESUMEN

Environmental variability can structure species coexistence by enhancing niche partitioning. Modern coexistence theory highlights two fluctuation-dependent temporal coexistence mechanisms -the storage effect and relative nonlinearity - but empirical tests are rare. Here, we experimentally test if environmental fluctuations enhance coexistence in a California annual grassland. We manipulate rainfall timing and relative densities of the grass Avena barbata and forb Erodium botrys, parameterise a demographic model, and partition coexistence mechanisms. Rainfall variability was integral to grass-forb coexistence. Variability enhanced growth rates of both species, and early-season drought was essential for Erodium persistence. While theoretical developments have focused on the storage effect, it was not critical for coexistence. In comparison, relative nonlinearity strongly stabilised coexistence, where Erodium experienced disproportionately high growth under early-season drought due to competitive release from Avena. Our results underscore the importance of environmental variability and suggest that relative nonlinearity is a critical if underappreciated coexistence mechanism.


Asunto(s)
Pradera , Poaceae/clasificación , Poaceae/crecimiento & desarrollo , Lluvia , California , Sequías
18.
Ecol Appl ; 29(3): e01862, 2019 04.
Artículo en Inglés | MEDLINE | ID: mdl-30706573

RESUMEN

Rangelands cover 40-50% of the Earth's terrestrial surface. While often characterized by limited, yet variable resource availability, rangelands are vital for humans, providing numerous ecosystem goods and services. In the conterminous United States (CONUS), the dominant component of rangeland conservation is a network of public rangelands, concentrated in the west. Public rangelands are interspersed with private and tribal rangelands resulting in a complex mosaic of land tenure and management priorities. We quantify ownership patterns of rangeland production at multiple scales across CONUS and find that both total production and average productivity of private rangelands is more than twice that of public and tribal rangelands. At finer scales, private rangelands are consistently more productive than their public counterparts. We also demonstrate an inverse relationship between public rangeland acreage and productivity. While conserving acreage is crucial to rangeland conservation, just as critical are broad-scale ecological patterns and processes that sustain ecosystem services. Across CONUS, ownership regimes capture distinct elements of these patterns and services, demonstrated through disparate production dynamics. As ownership determines the range of feasible conservation actions, and the technical and financial resources available to implement them, understanding ownership-production dynamics is critical for effective and sustained conservation of rangeland ecosystem services.


Asunto(s)
Ecosistema , Propiedad , Conservación de los Recursos Naturales , Ecología , Humanos , Programas Informáticos
19.
Environ Manage ; 64(1): 40-51, 2019 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-31161233

RESUMEN

Integrating traditional ecological knowledge (TEK) with remote sensing capabilities to monitor rangeland dynamics could lead to more acceptable, efficient, and beneficial rangeland management schemes for stakeholders of grazing systems. We contrasted pastoralists' perception of summer pasture quality in the Altai Mountains of Central Asia with normalized difference vegetation index (NDVI) metrics obtained from Terra Moderate Resolution Imaging Spectroradiometer (MODIS) satellite sensor. The spatial relationship between satellite-based assessment of the grassland quality and on-the-ground evaluation by local herders was first assessed for a single year using 49, 1 × 1 km grassland blocks sampled in July 2013. Herder-derived forage value was positively and strongly (63% of variance explained) related to satellite-derived NDVI values (MODIS 1 km monthly data, MOD13A3) as well as field estimates of % vegetation cover (62% explained) and to a lesser degree to vegetation height (28% explained). Herders' multi-year perception (i.e., recall ability) was also contrasted with satellite observations of their herding areas over the period of 2006-2016 during which NDVI temporal anomaly explained >11% of variance in estimates of pasture quality recalled. Few herders in Kazakhstan could recall pasture conditions, most herders in Russia and China could but inconsistently (4 and 7% variation explained, respectively), whereas most herders in Mongolia could recall pasture conditions in strong agreement with NDVI anomaly (30% variation explained), patterns reflecting herders' regional dependence on herding as a livelihood. Corroboration of herder-derived estimates and satellite-derived vegetation indices creates opportunity for re-expression of satellite data in map form as TEK-derived indices more compatible with herder perceptions.


Asunto(s)
Ecología , Tecnología de Sensores Remotos , China , Monitoreo del Ambiente , Mongolia , Imágenes Satelitales
20.
Environ Monit Assess ; 191(10): 635, 2019 Sep 15.
Artículo en Inglés | MEDLINE | ID: mdl-31522254

RESUMEN

This study aimed to analyze the spatial and temporal variation of the vegetation in the northern Argentine Puna, utilizing both field sampling and remote-sensing tools. The study was performed within the Pozuelos Biosphere Reserve (Jujuy province, Argentina), which aims to generate socio-economic development compatible with biodiversity conservation. Our study was designed to analyze the dynamics of the Puna vegetation at local scale and assess and monitor the seasonal (dry and wet seasons), interannual, and spatial variation of the vegetation cover, biomass, dominant species, and vegetation indices. Ten vegetation units (with differences in composition, cover, and high and low stratum biomass) were identified at our study site. The diversity of these vegetation units correlated with geomorphology and soil type. In the dry season, the vegetation unit with greatest vegetation cover and biomass was the Festuca chrysophylla grassland, whereas in the wet season, the units with greatest cover and biomass were vegas (peatlands) and short grasslands. The Festuca chrysophylla grasslands and short grasslands were located in areas with clay soils, except peatlands, associated with valleys and coarse-texture soils. The vegetation indices used (NDVI, SAVI, and MSAVI2) were able to differentiate functional types of vegetation and showed a good statistical fit with cover values. Our results suggest that the integrated utilization of remote-sensing tools and field surveys improves the assessment of the Puna vegetation and would allow a periodic monitoring at production unit scale taking into account its spatial and temporal variation.


Asunto(s)
Monitoreo del Ambiente/métodos , Pradera , Plantas/clasificación , Argentina , Biodiversidad , Biomasa , Parques Recreativos , Tecnología de Sensores Remotos , Estaciones del Año , Suelo/química
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