Artykuły w czasopismach na temat „Dryland”
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Dannenberg, Matthew P., Mallory L. Barnes, William K. Smith, Miriam R. Johnston, Susan K. Meerdink, Xian Wang, Russell L. Scott i Joel A. Biederman. "Upscaling dryland carbon and water fluxes with artificial neural networks of optical, thermal, and microwave satellite remote sensing". Biogeosciences 20, nr 2 (25.01.2023): 383–404. http://dx.doi.org/10.5194/bg-20-383-2023.
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Abstract. Earth's drylands are home to more than two billion people, provide key ecosystem services, and exert a large influence on the trends and variability in Earth's carbon cycle. However, modeling dryland carbon and water fluxes with remote sensing suffers from unique challenges not typically encountered in mesic systems, particularly in capturing soil moisture stress. Here, we develop and evaluate an approach for the joint modeling of dryland gross primary production (GPP), net ecosystem exchange (NEE), and evapotranspiration (ET) in the western United States (US) using a suite of AmeriFlux eddy covariance sites spanning major functional types and aridity regimes. We use artificial neural networks (ANNs) to predict dryland ecosystem fluxes by fusing optical vegetation indices, multitemporal thermal observations, and microwave soil moisture and temperature retrievals from the Soil Moisture Active Passive (SMAP) sensor. Our new dryland ANN (DrylANNd) carbon and water flux model explains more than 70 % of monthly variance in GPP and ET, improving upon existing MODIS GPP and ET estimates at most dryland eddy covariance sites. DrylANNd predictions of NEE were considerably worse than its predictions of GPP and ET likely because soil and plant respiratory processes are largely invisible to satellite sensors. Optical vegetation indices, particularly the normalized difference vegetation index (NDVI) and near-infrared reflectance of vegetation (NIRv), were generally the most important variables contributing to model skill. However, daytime and nighttime land surface temperatures and SMAP soil moisture and soil temperature also contributed to model skill, with SMAP especially improving model predictions of shrubland, grassland, and savanna fluxes and land surface temperatures improving predictions in evergreen needleleaf forests. Our results show that a combination of optical vegetation indices and thermal infrared and microwave observations can substantially improve estimates of carbon and water fluxes in drylands, potentially providing the means to better monitor vegetation function and ecosystem services in these important regions that are undergoing rapid hydroclimatic change.
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Wang, L., P. D'Odorico, J. P. Evans, D. Eldridge, M. F. McCabe, K. K. Caylor i E. G. King. "Dryland ecohydrology and climate change: critical issues and technical advances". Hydrology and Earth System Sciences Discussions 9, nr 4 (16.04.2012): 4777–825. http://dx.doi.org/10.5194/hessd-9-4777-2012.
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Abstract. Drylands cover about 40% of the terrestrial land surface and account for approximately 40% of global net primary productivity. Water is fundamental to the biophysical processes that sustain ecosystem function and food production, particularly in drylands, where a tight coupling exists between water resource availability and ecosystem productivity, surface energy balance, and biogeochemical cycles. Currently, drylands support at least 2 billion people and comprise both natural and managed ecosystems. In this synthesis, we identify some current critical issues in the understanding of dryland systems and discuss how arid and semiarid environments are responding to the changes in climate and land use. Specifically, we focus on dryland agriculture and food security, dryland population growth, desertification, shrub encroachment and dryland development issues as factors of change requiring increased understanding and management. We also review recent technical advances in the quantitative assessment of human versus climate change related drivers of desertification, evapotranspiration partitioning using field deployable stable water isotope systems and the remote sensing of key ecohydrological processes. These technological advances provide new tools that assist in addressing major critical issues in dryland ecohydrology under climate change
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Metternicht, Graciela, i Mark Stafford Smith. "Commentary: on the under-valuing of Australia’s expertise in drylands research and practice globally". Rangeland Journal 42, nr 5 (2020): 253. http://dx.doi.org/10.1071/rj20055.
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Global drylands are a significant driver of earth system processes that affect the world’s common resources such as the climate. Their peoples are also among the first to be widely affected by global changes such as land degradation and climate change. Yet drylands are a source of many social and technical innovations, globally, as well as in Australia. As a major developed dryland nation, Australia has previously played a major role in extending these innovations to the rest of the world. The nation has reaped reputational and commercial benefits through major research and practice contributions to dryland agriculture, water management and governance, remote area services, indigenous partnerships, dryland monitoring systems, and ‘desert knowledge’ innovation. Australian researchers continue to contribute to various relevant international processes, yet recognition and support for this within Australia has dropped off markedly in recent years. We analyse the Australian government’s investment in research and in overseas aid for drylands over the last two decades, and explore trends in government’s active involvement in major international processes related to land. These trends are short-sighted, overlooking potential economic benefits for Australian enterprises, and undermining Australia’s stance and scientific leadership in dryland systems globally. In this commentary, we argue that it is time for the trends to be reversed, as this is an area of comparative advantage for Australian diplomacy with significant returns on investment for Australia, both direct and indirect, especially when most emerging economies contain substantial drylands. We identify four major pathways to obtaining benefits from science diplomacy, and four interrelated actions within Australia to enable these – to place a higher emphasis on science diplomacy, to re-forge a bipartisan recognition of Australian drylands expertise, to establish a dedicated Dryland Information Hub, and to create a network of relevant science and technology advisors.
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Young, Kristina E., Sasha C. Reed, Scott Ferrenberg, Akasha Faist, Daniel E. Winkler, Catherine Cort i Anthony Darrouzet-Nardi. "Incorporating Biogeochemistry into Dryland Restoration". BioScience 71, nr 9 (5.05.2021): 907–17. http://dx.doi.org/10.1093/biosci/biab043.
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Abstract Dryland degradation is a persistent and accelerating global problem. Although the mechanisms initiating and maintaining dryland degradation are largely understood, returning productivity and function through ecological restoration remains difficult. Water limitation commonly drives slow recovery rates within drylands; however, the altered biogeochemical cycles that accompany degradation also play key roles in limiting restoration outcomes. Addressing biogeochemical changes and resource limitations may help improve restoration efforts within this difficult-to-restore biome. In the present article, we present a synthesis of restoration literature that identifies multiple ways biogeochemical understandings might augment dryland restoration outcomes, including timing restoration around resource cycling and uptake, connecting heterogeneous landscapes, manipulating resource pools, and using organismal functional traits to a restoration advantage. We conclude by suggesting ways to incorporate biogeochemistry into existing restoration frameworks and discuss research directions that may help improve restoration outcomes in the world's highly altered dryland landscapes.
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Xie, Shuai, Guanyi Yin, Wei Wei, Qingzhi Sun i Zhan Zhang. "Spatial–Temporal Change in Paddy Field and Dryland in Different Topographic Gradients: A Case Study of China during 1990–2020". Land 11, nr 10 (20.10.2022): 1851. http://dx.doi.org/10.3390/land11101851.
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As a country with a vast area and complex terrain, the differentiation between paddy field and dryland under different topographic gradients in China is difficult. Based on a land-use grid data set with an accuracy of 1 km, this study applied the Topographic Potential Index and used land-use transition matrices and landscape analysis to compare the change in dryland and paddy field in China from 1990 to 2020 at different elevations, slopes, and slope aspects. The results indicate that paddy field and dryland were mostly distributed in areas with better photothermal conditions. However, in recent years, the paddy field and dryland on the “sunny” slope decreased. Specifically, the area of paddy field and dryland on the southeast, south, and southwest slopes decreased, while they increased on the northwest, north, and northeast slopes. From 1990 to 2020, land conversion among paddy field, dryland, and other land use was mostly concentrated in the third ladder (<500 m elevation) of China. However, the changes in paddy field and dryland have now become active on the second ladder of China. Moreover, the change from other land to dryland on the second ladder accounted for nearly 50% of the country’s change from other land to dryland. Paddy fields and drylands in areas with low elevation and low slopes were reduced, whereas those with higher elevation and higher slopes increased, indicating that the arable land in mountainous areas increased. This indicates that the topographic conditions of arable land that become worse may aggravate soil erosion in the planting process. The landscape fragmentation of paddy field and dryland increased. Compared with paddy field, the dryland was more aggregated, the shape was more complex, and the land plots were more fragmented. As a result, paddy field and dryland show significant differences in their spatial–temporal pattern, landscape characteristics, and land-use changes, and these results can provide an important reference for the sustainable utilization of arable land resources.
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Neswati, Risma, Sumbangan Baja, Samsu Arif i Hasni Hasni. "Dryland land-use conflicts in humid tropics: an analysis using geographic information systems and land capability evaluations". SAINS TANAH - Journal of Soil Science and Agroclimatology 17, nr 1 (29.06.2020): 57. http://dx.doi.org/10.20961/stjssa.v17i1.37824.
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<p>This study analyses land-use conflicts in specific dryland agricultural areas in relatively dry humid tropics based on the Regional Spatial Land Use Planning Regulations and land-capability evaluation. This research was conducted in the Regency of Jeneponto, South Sulawesi, Indonesia. The observation site was chosen based on several maps overlapping to produce 30 land units spread across 14 land systems in Jeneponto. This study integrates ground surveys and geographic information systems technology. The land capability analysis used a simple approach factor, according to United States Department of Agriculture definitions. The results indicate that land capability was dominated by Class IV, which covered 35,133 ha or 63.1%. Class VI covered 12,581 ha or 22.6%, Class III covered up to 4,378 ha or 7.9%, and Class VIII covered 3,130 ha or 5.6%. Class VII covered only 486 hectares, or 0.9%, the smallest area. These results indicate that the dryland area which had become a land-use conflict was delineated by Regional Spatial Land Use Planning Regulations. The drylands found in Jeneponto cover 22,214 ha or 39.9%, which has been divided into two: an area where non-dryland agriculture was converted into dryland farming (16,503 hectares, or 29.6%), and an area where dryland-farming was converted into non-agricultural dryland area (5,711 hectares, or 10.3%). Interviews with 50 farmers in the study location revealed factors that had changed agricultural dryland use into non-agricultural dryland use; lower incomes due to decreased soil fertility was a crucial factor.</p>
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Wang, L., P. D'Odorico, J. P. Evans, D. J. Eldridge, M. F. McCabe, K. K. Caylor i E. G. King. "Dryland ecohydrology and climate change: critical issues and technical advances". Hydrology and Earth System Sciences 16, nr 8 (9.08.2012): 2585–603. http://dx.doi.org/10.5194/hess-16-2585-2012.
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Abstract. Drylands cover about 40% of the terrestrial land surface and account for approximately 40% of global net primary productivity. Water is fundamental to the biophysical processes that sustain ecosystem function and food production, particularly in drylands where a tight coupling exists between ecosystem productivity, surface energy balance, biogeochemical cycles, and water resource availability. Currently, drylands support at least 2 billion people and comprise both natural and managed ecosystems. In this synthesis, we identify some current critical issues in the understanding of dryland systems and discuss how arid and semiarid environments are responding to the changes in climate and land use. The issues range from societal aspects such as rapid population growth, the resulting food and water security, and development issues, to natural aspects such as ecohydrological consequences of bush encroachment and the causes of desertification. To improve current understanding and inform upon the needed research efforts to address these critical issues, we identify some recent technical advances in terms of monitoring dryland water dynamics, water budget and vegetation water use, with a focus on the use of stable isotopes and remote sensing. These technological advances provide new tools that assist in addressing critical issues in dryland ecohydrology under climate change.
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Naorem, Anandkumar, Somasundaram Jayaraman, Ram C. Dalal, Ashok Patra, Cherukumalli Srinivasa Rao i Rattan Lal. "Soil Inorganic Carbon as a Potential Sink in Carbon Storage in Dryland Soils—A Review". Agriculture 12, nr 8 (18.08.2022): 1256. http://dx.doi.org/10.3390/agriculture12081256.
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Soil organic carbon (SOC) pool has been extensively studied in the carbon (C) cycling of terrestrial ecosystems. In dryland regions, however, soil inorganic carbon (SIC) has received increasing attention due to the high accumulation of SIC in arid soils contributed by its high temperature, low soil moisture, less vegetation, high salinity, and poor microbial activities. SIC storage in dryland soils is a complex process comprising multiple interactions of several factors such as climate, land use types, farm management practices, irrigation, inherent soil properties, soil biotic factors, etc. In addition, soil C studies in deeper layers of drylands have opened-up several study aspects on SIC storage. This review explains the mechanisms of SIC formation in dryland soils and critically discusses the SIC content in arid and semi-arid soils as compared to SOC. It also addresses the complex relationship between SIC and SOC in dryland soils. This review gives an overview of how climate change and anthropogenic management of soil might affect the SIC storage in dryland soils. Dryland soils could be an efficient sink in C sequestration through the formation of secondary carbonates. The review highlights the importance of an in-depth understanding of the C cycle in arid soils and emphasizes that SIC dynamics must be looked into broader perspective vis-à-vis C sequestration and climate change mitigation.
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Xu, Jinqin, Yan Zeng, Xinfa Qiu, Yongjian He, Guoping Shi i Xiaochen Zhu. "Aridity Changes and Related Climatic Drivers in the Drylands of China during 1960–2019". Journal of Applied Meteorology and Climatology 60, nr 4 (kwiecień 2021): 607–17. http://dx.doi.org/10.1175/jamc-d-20-0209.1.
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AbstractDrylands cover about one-half of the land surface in China and are highly sensitive to climate change. Understanding climate change and its impact drivers on dryland is essential for supporting dryland planning and sustainable development. Using meteorological observations for 1960–2019, the aridity changes in drylands of China were evaluated using aridity index (AI), and the impact of various climatic factors [i.e., precipitation P; sunshine duration (SSD); relative humidity (RH); maximum temperature (Tmax); minimum temperature (Tmin); wind speed (WS)] on the aridity changes was decomposed and quantified. Results of trend analysis based on Sen’s slope estimator and Mann–Kendall test indicated that the aridity trends were very weak when averaged over the whole drylands in China during 1960–2019 but exhibited a significant wetting trend in hyperarid and arid regions of drylands. The AI was most sensitive to changes in water factors (i.e., P and RH), followed by SSD, Tmax, and WS, but the sensitivity of AI to Tmin was very small and negligible. Interestingly, the dominant climatic driver to AI change varied in the four dryland subtypes. The significantly increased P dominated the increase in AI in the hyperarid and arid regions. The significantly reduced WS and the significantly increased Tmax contributed more to AI changes than the P in the semiarid and dry subhumid regions of drylands. Previous studies emphasized the impact of precipitation and temperature on the global or regional dry–wet changes; however, the findings of this study suggest that, beyond precipitation and temperature, the impact of wind speed on aridity changes of drylands in China should be given equal attention.
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Guirado, Emilio, Javier Blanco-Sacristán, Emilio Rodríguez-Caballero, Siham Tabik, Domingo Alcaraz-Segura, Jaime Martínez-Valderrama i Javier Cabello. "Mask R-CNN and OBIA Fusion Improves the Segmentation of Scattered Vegetation in Very High-Resolution Optical Sensors". Sensors 21, nr 1 (5.01.2021): 320. http://dx.doi.org/10.3390/s21010320.
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Vegetation generally appears scattered in drylands. Its structure, composition and spatial patterns are key controls of biotic interactions, water, and nutrient cycles. Applying segmentation methods to very high-resolution images for monitoring changes in vegetation cover can provide relevant information for dryland conservation ecology. For this reason, improving segmentation methods and understanding the effect of spatial resolution on segmentation results is key to improve dryland vegetation monitoring. We explored and analyzed the accuracy of Object-Based Image Analysis (OBIA) and Mask Region-based Convolutional Neural Networks (Mask R-CNN) and the fusion of both methods in the segmentation of scattered vegetation in a dryland ecosystem. As a case study, we mapped Ziziphus lotus, the dominant shrub of a habitat of conservation priority in one of the driest areas of Europe. Our results show for the first time that the fusion of the results from OBIA and Mask R-CNN increases the accuracy of the segmentation of scattered shrubs up to 25% compared to both methods separately. Hence, by fusing OBIA and Mask R-CNNs on very high-resolution images, the improved segmentation accuracy of vegetation mapping would lead to more precise and sensitive monitoring of changes in biodiversity and ecosystem services in drylands.
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Miguel, M. Florencia, H. Scott Butterfield i Christopher J. Lortie. "A meta-analysis contrasting active versus passive restoration practices in dryland agricultural ecosystems". PeerJ 8 (23.11.2020): e10428. http://dx.doi.org/10.7717/peerj.10428.
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Restoration of agricultural drylands globally, here farmlands and grazing lands, is a priority for ecosystem function and biodiversity preservation. Natural areas in drylands are recognized as biodiversity hotspots and face continued human impacts. Global water shortages are driving increased agricultural land retirement providing the opportunity to reclaim some of these lands for natural habitat. We used meta-analysis to contrast different classes of dryland restoration practices. All interventions were categorized as active and passive for the analyses of efficacy in dryland agricultural ecosystems. We evaluated the impact of 19 specific restoration practices from 42 studies on soil, plant, animal, and general habitat targets across 16 countries, for a total of 1,427 independent observations. Passive vegetation restoration and grazing exclusion led to net positive restoration outcomes. Passive restoration practices were more variable and less effective than active restoration practices. Furthermore, passive soil restoration led to net negative restoration outcomes. Active restoration practices consistently led to positive outcomes for soil, plant, and habitat targets. Water supplementation was the most effective restoration practice. These findings suggest that active interventions are necessary and critical in most instances for dryland agricultural ecosystems likely because of severe anthropogenic pressures and concurrent environmental stressors—both past and present.
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S. N, Nguluu, Karanja J., Kimatu J.N, Gicheru P.T, Musimba N., Njiru E., Kathuli P. i in. "Refining Dryland Farming Systems as a Means of Enhancing Agrodiversity and Food Security in Eastern Kenya: A review." JOURNAL OF ADVANCES IN AGRICULTURE 3, nr 1 (2.10.2014): 142–49. http://dx.doi.org/10.24297/jaa.v3i1.5410.
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Drylands which cover one third of the earth’s land surface and almost 80% of Kenya’s land surface are being used to grow dryland crops such as maize, beans, sorghum, millets and livestock. Studies show that refined farming systems can be used in enhancing ecosystem sustainability, through the promotion of species and crop diversity. For example, cropping patterns involving intercropping legumes and cereals have demonstrated varying success in maintenance of crop diversity in the Kenyan drylands showing land equivalent ratios (LER) > 1.0, although such benefits are often lost during low rainfall seasons. Research show that some genotypes can be used to reduce soil erosion, enhance nutrient availability, soil moisture retention, microbial earthworm activities and land use efficiency. Thus critical examination of farming systems for dryland areas suggests that long term multiple effects of the ecosystem, rather than the short term benefits not only increases yields but sustains the life of ecosystems. In this reveiw we submit that monocropping systems should be modified to include varieties that are suitable for different plots in the same site to enhance efficient utilization of underground diversity. In developing farming systems modelling approaches utilizing plant genotypic and epigenetic variations, ecological, edaphic and microbial cycles should be evaluated for dryland ecosystems.
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Yu, Zongxu, Tianye Wang, Ping Wang i Jingjie Yu. "The Spatiotemporal Response of Vegetation Changes to Precipitation and Soil Moisture in Drylands in the North Temperate Mid-Latitudes". Remote Sensing 14, nr 15 (22.07.2022): 3511. http://dx.doi.org/10.3390/rs14153511.
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Vegetation growth in drylands is highly constrained by water availability. How dryland vegetation responds to changes in precipitation and soil moisture in the context of a warming climate is not well understood. In this study, warm drylands in the temperate zone between 30 and 50° N, including North America (NA), the Mediterranean region (MD), Central Asia (CA), and East Asia (EA), were selected as the study area. After verifying the trends and anomalies of three kinds of leaf area index (LAI) datasets (GLASS LAI, GLEAM LAI, and GLOBAMAP LAI) in the study area, we mainly used the climate (GPCC precipitation and ERA5 temperature), GLEAM soil moisture, and GLASS LAI datasets from 1981 to 2018 to analyze the response of vegetation growth to changes in precipitation and soil moisture. The results of the three mutually validated LAI datasets show an overall greening of dryland vegetation with the same increasing trend of 0.002 per year in LAI over the past 38 years. LAI and precipitation exhibited a strong correlation in the eastern part of the NA drylands and the northeastern part of the EA drylands. LAI and soil moisture exhibited a strong correlation in the eastern part of the NA drylands, the eastern part of the MD drylands, the southern part of the CA drylands, and the northeastern part of the EA drylands. The results of this study will contribute to the understanding of vegetation dynamics and their response to changing water conditions in the Northern Hemisphere midlatitude drylands.
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Adhikari, Subodh, Arjun Adhikari, David Weaver, Anton Bekkerman i Fabian Menalled. "Impacts of Agricultural Management Systems on Biodiversity and Ecosystem Services in Highly Simplified Dryland Landscapes". Sustainability 11, nr 11 (11.06.2019): 3223. http://dx.doi.org/10.3390/su11113223.
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Covering about 40% of Earth’s land surface and sustaining at least 38% of global population, drylands are key crop and animal production regions with high economic and social values. However, land use changes associated with industrialized agricultural managements are threatening the sustainability of these systems. While previous studies assessing the impacts of agricultural management systems on biodiversity and their services focused on more diversified mesic landscapes, there is a dearth of such research in highly simplified dryland agroecosystems. In this paper, we 1) summarize previous research on the effects of farm management systems and agricultural expansion on biodiversity and biodiversity-based ecosystem services, 2) present four case studies assessing the impacts of management systems on biodiversity and ecosystem services across highly simplified dryland landscapes of the Northern Great Plains (NGP), USA, 3) discuss approaches to sustain biodiversity-based ecosystem services in drylands, and 4) present a conceptual framework for enhancing agricultural sustainability in the drylands through research, policy, economic valuation, and adaptive management. An analysis of the land use changes due to agricultural expansion within the Golden Triangle, a representative agricultural area in the NGP, indicated that the proportion of land conversion to agriculture area was 84%, 8%, and 7% from grassland, riparian, and shrubland habitats, respectively. Our results showed this simplification was associated with a potential reduction of pollination services. Also, our economic analysis projected that if 30% parasitism could be achieved through better management systems, the estimated potential economic returns to pest regulation services through parasitoids in Montana, USA alone could reach about $11.23 million. Overall, while dryland agroecosystems showed a significant loss of native biodiversity and its services, greater pest incidence, and a decrease in plant pollinator networks, these trends were moderately reversed in organically managed farming systems. In conclusion, although land use changes due to agricultural expansion and industrialized farming threaten the sustainability of dryland agroecosystems, this impact can be partially offset by coupling ecologically-based farming practices with adaptive management strategies.
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Sutton, Andres, Adrian Fisher i Graciela Metternicht. "Assessing the Accuracy of Landsat Vegetation Fractional Cover for Monitoring Australian Drylands". Remote Sensing 14, nr 24 (13.12.2022): 6322. http://dx.doi.org/10.3390/rs14246322.
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Satellite-derived vegetation fractional cover (VFC) has shown to be a promising tool for dryland ecosystem monitoring. This model, calibrated through biophysical field measurements, depicts the sub-pixel proportion of photosynthetic vegetation (PV), non-photosynthetic vegetation (NPV) and bare soil (BS). The distinction between NPV and BS makes it particularly important for drylands, as these fractions often dominate. Two Landsat VFC products are available for the Australian continent: the original Joint Remote Sensing Research Program (JRSRP) product, and a newer Digital Earth Australia (DEA) product. Although similar validation statistics have been presented for each, an evaluation of their differences has not been undertaken. Moreover, spatial variability of VFC accuracy within drylands has not been comprehensively assessed. Here, a large field dataset (4207 sites) was employed to compare Landsat VFC accuracy across the Australian continent, with detailed spatial and temporal analysis conducted on four regions of interest. Furthermore, spatiotemporal features of VFC unmixing error (UE) were explored to characterize model uncertainty in large areas yet to be field sampled. Our results showed that the JRSRP and DEA VFC were very similar (RMSE = 4.00–6.59) and can be employed interchangeably. Drylands did not show a substantial difference in accuracy compared to the continental assessment; however contrasting variations were observed in dryland subtypes (e.g., semi-arid and arid zones). Moreover, VFC effectively tracked total ground cover change over time. UE increased with tree cover and height, indicating that model uncertainty was low in typical dryland landscapes. Together, these results provide guiding points to understanding the Australian ecosystems where VFC can be used with confidence.
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Ganem, Khalil Ali, Yongkang Xue, Ariane de Almeida Rodrigues, Washington Franca-Rocha, Marceli Terra de Oliveira, Nathália Silva de Carvalho, Efrain Yury Turpo Cayo, Marcos Reis Rosa, Andeise Cerqueira Dutra i Yosio Edemir Shimabukuro. "Mapping South America’s Drylands through Remote Sensing—A Review of the Methodological Trends and Current Challenges". Remote Sensing 14, nr 3 (4.02.2022): 736. http://dx.doi.org/10.3390/rs14030736.
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The scientific grasp of the distribution and dynamics of land use and land cover (LULC) changes in South America is still limited. This is especially true for the continent’s hyperarid, arid, semiarid, and dry subhumid zones, collectively known as drylands, which are under-represented ecosystems that are highly threatened by climate change and human activity. Maps of LULC in drylands are, thus, essential in order to investigate their vulnerability to both natural and anthropogenic impacts. This paper comprehensively reviewed existing mapping initiatives of South America’s drylands to discuss the main knowledge gaps, as well as central methodological trends and challenges, for advancing our understanding of LULC dynamics in these fragile ecosystems. Our review centered on five essential aspects of remote-sensing-based LULC mapping: scale, datasets, classification techniques, number of classes (legends), and validation protocols. The results indicated that the Landsat sensor dataset was the most frequently used, followed by AVHRR and MODIS, and no studies used recently available high-resolution satellite sensors. Machine learning algorithms emerged as a broadly employed methodology for land cover classification in South America. Still, such advancement in classification methods did not yet reflect in the upsurge of detailed mapping of dryland vegetation types and functional groups. Among the 23 mapping initiatives, the number of LULC classes in their respective legends varied from 6 to 39, with 1 to 14 classes representing drylands. Validation protocols included fieldwork and automatic processes with sampling strategies ranging from solely random to stratified approaches. Finally, we discussed the opportunities and challenges for advancing research on desertification, climate change, fire mapping, and the resilience of dryland populations. By and large, multi-level studies for dryland vegetation mapping are still lacking.
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Panigada, Cinzia, Giulia Tagliabue, Eli Zaady, Offer Rozenstein, Roberto Garzonio, Biagio Di Mauro, Mattia De Amicis i in. "A new approach for biocrust and vegetation monitoring in drylands using multi-temporal Sentinel-2 images". Progress in Physical Geography: Earth and Environment 43, nr 4 (14.04.2019): 496–520. http://dx.doi.org/10.1177/0309133319841903.
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Drylands, one of the planet’s largest terrestrial biomes, are suggested to be greatly threatened by climate change. Drylands are usually sparsely vegetated, and biological soil crusts (biocrusts) – that is, soil surface communities of cyanobacteria, mosses and/or lichens – can cover up to 70% of dryland cover. As they control key ecosystem processes, monitoring their spatial and temporal distribution can provide highly valuable information. In this study, we examine the potential of European Space Agency’s (ESA) Sentinel-2 (S2) data to characterize the spatial and temporal development of biocrust and vascular plant greening along a rainfall gradient of the Negev Desert (Israel). First, the chlorophyll a absorption feature in the red region (CRred) was identified as the index mostly sensitive to changes in biocrust greening but minimally affected by changes in soil moisture. This index was then computed on the S2 images and enabled monitoring the phenological dynamics of different dryland vegetation components from August 2015 to August 2017. The analysis of multi-temporal S2 images allowed us to successfully track the biocrust greening within 15 days from the first seasonal rain events in the north of Negev, and to identify the maximum development of annual vascular plants and greening of perennial ones. These results show potential for monitoring arid and semi-arid environments using the newly available S2 images, allowing new insights into dryland vegetation dynamics.
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Quichimbo, E. Andrés, Michael Bliss Singer, Katerina Michaelides, Daniel E. J. Hobley, Rafael Rosolem i Mark O. Cuthbert. "DRYP 1.0: a parsimonious hydrological model of DRYland Partitioning of the water balance". Geoscientific Model Development 14, nr 11 (15.11.2021): 6893–917. http://dx.doi.org/10.5194/gmd-14-6893-2021.
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Abstract. Dryland regions are characterised by water scarcity and are facing major challenges under climate change. One difficulty is anticipating how rainfall will be partitioned into evaporative losses, groundwater, soil moisture, and runoff (the water balance) in the future, which has important implications for water resources and dryland ecosystems. However, in order to effectively estimate the water balance, hydrological models in drylands need to capture the key processes at the appropriate spatio-temporal scales. These include spatially restricted and temporally brief rainfall, high evaporation rates, transmission losses, and focused groundwater recharge. Lack of available input and evaluation data and the high computational costs of explicit representation of ephemeral surface–groundwater interactions restrict the usefulness of most hydrological models in these environments. Therefore, here we have developed a parsimonious distributed hydrological model for DRYland Partitioning (DRYP). The DRYP model incorporates the key processes of water partitioning in dryland regions with limited data requirements, and we tested it in the data-rich Walnut Gulch Experimental Watershed against measurements of streamflow, soil moisture, and evapotranspiration. Overall, DRYP showed skill in quantifying the main components of the dryland water balance including monthly observations of streamflow (Nash–Sutcliffe efficiency, NSE, ∼ 0.7), evapotranspiration (NSE > 0.6), and soil moisture (NSE ∼ 0.7). The model showed that evapotranspiration consumes > 90 % of the total precipitation input to the catchment and that < 1 % leaves the catchment as streamflow. Greater than 90 % of the overland flow generated in the catchment is lost through ephemeral channels as transmission losses. However, only ∼ 35 % of the total transmission losses percolate to the groundwater aquifer as focused groundwater recharge, whereas the rest is lost to the atmosphere as riparian evapotranspiration. Overall, DRYP is a modular, versatile, and parsimonious Python-based model which can be used to anticipate and plan for climatic and anthropogenic changes to water fluxes and storage in dryland regions.
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Liu, Shanshan, Dabang Jiang i Xianmei Lang. "Mid-Holocene drylands: A multi-model analysis using Paleoclimate Modelling Intercomparison Project Phase III (PMIP3) simulations". Holocene 29, nr 9 (12.06.2019): 1425–38. http://dx.doi.org/10.1177/0959683619854512.
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This study examines changes in aridity levels during the mid-Holocene (approximately 6000 cal. yr ago) using multi-model simulations from the Paleoclimate Modelling Intercomparison Project Phase III. Overall, there is little difference in the total area of drylands from the preindustrial period; global drylands are 8% wetter than during the preindustrial period as measured by an aridity index; and 16% of preindustrial drylands convert to a wetter climate subtype, double the sum of zones that are replaced by a drier category. Considerable variations are present among regions with major contractions of each dryland subtype from northern Africa to South Asia and the main expansions of arid, semiarid, and dry subhumid climates in southern hemisphere continents. The difference in precipitation is the leading factor of the aforementioned changes. The second factor is the altered potential evapotranspiration as mainly induced by relative humidity, which contributes to additional aridity changes in a same direction as precipitation does. The collective effects of precipitation and relative humidity account for more than 80% of the dryland variations. In comparison, the simulated aridity change is in reasonable agreement with reconstructions, while there are model–data discrepancies for Australia and uncertainties across proxies for southern Africa.
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Sagi, Nevo, i Dror Hawlena. "Arthropods as the Engine of Nutrient Cycling in Arid Ecosystems". Insects 12, nr 8 (14.08.2021): 726. http://dx.doi.org/10.3390/insects12080726.
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Nutrient dynamics in most terrestrial ecosystems are regulated by moisture-dependent processes. In drylands, nutrient dynamics are often weakly associated with annual precipitation, suggesting that other factors are involved. In recent years, the majority of research on this topic focused on abiotic factors. We provide an arthropod-centric framework that aims to refocus research attention back on the fundamental role that macro-arthropods may play in regulating dryland nutrient dynamics. Macro-arthropods are prevalent in drylands and include many detritivores and burrowing taxa that remain active during long dry periods. Macro-arthropods consume and process large quantities of plant detritus and transport these nutrients to the decomposer haven within their climatically buffered and nutritionally enriched burrows. Consequently, arthropods may accelerate mineralization rates and generate a vertical nutrient recycling loop (VRL) that may assist in explaining the dryland decomposition conundrum, and how desert plants receive their nutrients when the shallow soil is dry. The burrowing activity of arthropods and the transportation of subterranean soil to the surface may alter the desert microtopography and promote desalinization, reducing resource leakage and enhancing productivity and species diversity. We conclude that these fundamental roles and the arthropods’ contribution to nutrient transportation and nitrogen fixation makes them key regulators of nutrient dynamics in drylands.
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Grainger, Alan, Andrew C. Millington i Ken Pye. "Dryland Change". Global Ecology and Biogeography Letters 5, nr 2 (marzec 1996): 104. http://dx.doi.org/10.2307/2997450.
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D'Odorico, Paolo. "Dryland climatology". Eos, Transactions American Geophysical Union 93, nr 39 (25.09.2012): 377–78. http://dx.doi.org/10.1029/2012eo390010.
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Young, Michael. "Dryland Ecohydrology". Vadose Zone Journal 5, nr 3 (sierpień 2006): 1065. http://dx.doi.org/10.2136/vzj2006.0053br.
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Williams, William D. "Dryland lakes1". Lakes and Reservoirs: Research and Management 5, nr 3 (15.09.2000): 207–12. http://dx.doi.org/10.1046/j.1440-1770.2000.00116.x.
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Solárová, Jarmila. "Dryland agriculture". Biologia Plantarum 27, nr 1 (styczeń 1985): 21. http://dx.doi.org/10.1007/bf02894627.
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Feldman, Andrew F., Daniel J. Short Gianotti, Alexandra G. Konings, Pierre Gentine i Dara Entekhabi. "Patterns of plant rehydration and growth following pulses of soil moisture availability". Biogeosciences 18, nr 3 (5.02.2021): 831–47. http://dx.doi.org/10.5194/bg-18-831-2021.
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Abstract. Plant hydraulic and photosynthetic responses to individual rain pulses are not well understood because field experiments of pulse behavior are sparse. Understanding individual pulse responses would inform how rainfall intermittency impacts terrestrial biogeochemical cycles, especially in drylands, which play a large role in interannual global atmospheric carbon uptake variability. Using satellite-based estimates of predawn plant and soil water content from the Soil Moisture Active Passive (SMAP) satellite, we quantify the timescales of plant water content increases following rainfall pulses, which we expect bear the signature of whole-plant mechanisms. In wetter regions, we find that plant water content increases rapidly and dries along with soil moisture, which we attribute to predawn soil–plant water potential equilibrium. Global drylands, by contrast, show multi-day plant water content increases after rain pulses. Shorter increases are more common following dry initial soil conditions. These are attributed to slow plant rehydration due to high plant resistances using a plant hydraulic model. Longer multi-day dryland plant water content increases are attributed to pulse-driven growth, following larger rain pulses and wetter initial soil conditions. These dryland responses reflect widespread drought recovery rehydration responses and individual pulse-driven growth responses, as supported by previous isolated field experiments. The response dependence on moisture pulse characteristics, especially in drylands, also shows ecosystem sensitivity to intra-annual rainfall intensity and frequency, which are shifting with climate change.
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Huber-Sannwald, Elisabeth, Mónica Ribeiro Palacios, José Tulio Arredondo Moreno, Marco Braasch, Ruth Magnolia Martínez Peña, Javier García de Alba Verduzco i Karina Monzalvo Santos. "Navigating challenges and opportunities of land degradation and sustainable livelihood development in dryland social–ecological systems: a case study from Mexico". Philosophical Transactions of the Royal Society B: Biological Sciences 367, nr 1606 (19.11.2012): 3158–77. http://dx.doi.org/10.1098/rstb.2011.0349.
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Drylands are one of the most diverse yet highly vulnerable social–ecological systems on Earth. Water scarcity has contributed to high levels of heterogeneity, variability and unpredictability, which together have shaped the long coadaptative process of coupling humans and nature. Land degradation and desertification in drylands are some of the largest and most far-reaching global environmental and social change problems, and thus are a daunting challenge for science and society. In this study, we merged the Drylands Development Paradigm, Holling's adaptive cycle metaphor and resilience theory to assess the challenges and opportunities for livelihood development in the Amapola dryland social–ecological system (DSES), a small isolated village in the semi-arid region of Mexico. After 450 years of local social–ecological evolution, external drivers (neoliberal policies, change in land reform legislation) have become the most dominant force in livelihood development, at the cost of loss of natural and cultural capital and an increasingly dysfunctional landscape. Local DSESs have become increasingly coupled to dynamic larger-scale drivers. Hence, cross-scale connectedness feeds back on and transforms local self-sustaining subsistence farming conditions, causing loss of livelihood resilience and diversification in a globally changing world. Effective efforts to combat desertification and improve livelihood security in DSESs need to consider their cyclical rhythms. Hence, we advocate novel dryland stewardship strategies, which foster adaptive capacity, and continuous evaluation and social learning at all levels. Finally, we call for an effective, flexible and viable policy framework that enhances local biotic and cultural diversity of drylands to transform global drylands into a resilient biome in the context of global environmental and social change.
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Callow, J. Nikolaus, Matthew R. Hipsey i Ryan I. J. Vogwill. "Surface water as a cause of land degradation from dryland salinity". Hydrology and Earth System Sciences 24, nr 2 (17.02.2020): 717–34. http://dx.doi.org/10.5194/hess-24-717-2020.
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Abstract. Secondary dryland salinity is a global land degradation issue. Drylands are often less developed, less well instrumented and less well understood, requiring us to adapt and impose understanding from different hydro-geomorphological settings that are better instrumented and understood. Conceptual models of secondary dryland salinity, from wet and more hydrologically connected landscapes imposed with adjustments for rainfall and streamflow, have led to the pervasive understanding that land clearing alters water balance in favour of increased infiltration and rising groundwater that bring salts to the surface. This paper presents data from an intra-catchment surface flow gauging network run for 6 years and a surface-water–groundwater (SW–GW) interaction site to assess the adequacy of our conceptual understanding of secondary dryland salinity in environments with low gradients and runoff yield. The aim is to (re-)conceptualise pathways of water and salt redistribution in dryland landscapes and to investigate the role that surface water flows and connectivity plays in land degradation from salinity in low-gradient drylands. Based on the long-term end-of-catchment gauge, average annual runoff yield is only 0.14 % of rainfall. The internal gauging network that operated from 2007–2012 found pulses of internal water (also mobilising salt) in years when no flow was recorded at the catchment outlet. Data from a surface-water–groundwater interaction site show top-down recharge of surface water early in the water year that transitions to a bottom-up system of discharge later in the water year. This connection provides a mechanism for the vertical diffusion of salts to the surface waters, followed by evapo-concentration and downstream export when depression storage thresholds are exceeded. Intervention in this landscape by constructing a broad-based channel to address these processes resulted in a 25 % increase in flow volume and a 20 % reduction in salinity by allowing the lower catchment to more effectively support bypassing of the storages in the lower landscape that would otherwise retain water and allow salt to accumulate. Results from this study suggest catchment internal redistribution of relatively fresh runoff onto the valley floor is a major contributor to the development of secondary dryland salinity. Seasonally inundated areas are subject to significant transmission losses and drive processes of vertical salt mobility. These surface flow and connectivity processes are not only acting in isolation to cause secondary salinity but are also interacting with groundwater systems responding to land clearing and processes recognised in the more conventional understanding of hillslope recharge and groundwater discharge. The study landscape appears to have three functional hydrological components: upland, hillslope “flow” landscapes that generate fresh runoff; valley floor “fill” landscapes with high transmission losses and poor flow connectivity controlled by the micro-topography that promotes a surface–groundwater connection and salt movement; and the downstream “flood” landscapes, where flows are recorded only when internal storages (fill landscapes) are exceeded. This work highlights the role of surface water processes as a contributor to land degradation by dryland salinity in low-gradient landscapes.
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Hoover, David L., Brandon Bestelmeyer, Nancy B. Grimm, Travis E. Huxman, Sasha C. Reed, Osvaldo Sala, Timothy R. Seastedt, Hailey Wilmer i Scott Ferrenberg. "Traversing the Wasteland: A Framework for Assessing Ecological Threats to Drylands". BioScience 70, nr 1 (18.12.2019): 35–47. http://dx.doi.org/10.1093/biosci/biz126.
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Abstract Drylands cover 41% of the Earth's terrestrial surface, play a critical role in global ecosystem function, and are home to over two billion people. Like other biomes, drylands face increasing pressure from global change, but many of these ecosystems are close to tipping points, which, if crossed, can lead to abrupt transitions and persistent degraded states. Their limited but variable precipitation, low soil fertility, and low productivity have given rise to a perception that drylands are wastelands, needing societal intervention to bring value to them. Negative perceptions of drylands synergistically combine with conflicting sociocultural values regarding what constitutes a threat to these ecosystems. In the present article, we propose a framework for assessing threats to dryland ecosystems and suggest we must also combat the negative perceptions of drylands in order to preserve the ecosystem services that they offer.
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Dashti, Hamid, Andrew Poley, Nancy F. Glenn, Nayani Ilangakoon, Lucas Spaete, Dar Roberts, Josh Enterkine, Alejandro N. Flores, Susan L. Ustin i Jessica J. Mitchell. "Regional Scale Dryland Vegetation Classification with an Integrated Lidar-Hyperspectral Approach". Remote Sensing 11, nr 18 (14.09.2019): 2141. http://dx.doi.org/10.3390/rs11182141.
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The sparse canopy cover and large contribution of bright background soil, along with the heterogeneous vegetation types in close proximity, are common challenges for mapping dryland vegetation with remote sensing. Consequently, the results of a single classification algorithm or one type of sensor to characterize dryland vegetation typically show low accuracy and lack robustness. In our study, we improved classification accuracy in a semi-arid ecosystem based on the use of vegetation optical (hyperspectral) and structural (lidar) information combined with the environmental characteristics of the landscape. To accomplish this goal, we used both spectral angle mapper (SAM) and multiple endmember spectral mixture analysis (MESMA) for optical vegetation classification. Lidar-derived maximum vegetation height and delineated riparian zones were then used to modify the optical classification. Incorporating the lidar information into the classification scheme increased the overall accuracy from 60% to 89%. Canopy structure can have a strong influence on spectral variability and the lidar provided complementary information for SAM’s sensitivity to shape but not magnitude of the spectra. Similar approaches to map large regions of drylands with low uncertainty may be readily implemented with unmixing algorithms applied to upcoming space-based imaging spectroscopy and lidar. This study advances our understanding of the nuances associated with mapping xeric and mesic regions, and highlights the importance of incorporating complementary algorithms and sensors to accurately characterize the heterogeneity of dryland ecosystems.
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Pavey, Chris R., Elizabeth A. Jefferys i Catherine E. M. Nano. "Persistence of the plains mouse, Pseudomys australis, with cattle grazing is facilitated by a diet dominated by disturbance-tolerant plants". Journal of Mammalogy 97, nr 4 (11.04.2016): 1102–10. http://dx.doi.org/10.1093/jmammal/gyw059.
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Abstract A suite of dryland mammals rely on refuges for long-term persistence during alternating cycles of low and high resource availability. Refuges are small, discrete areas into which populations contract during the lengthy dry periods that characterize dryland environments. Little is known about the characteristics of a location that make it functional as a refuge. Similarly, no information exists on how grazing-facilitated landscape modification affects small mammal refuges. To examine these questions, we assessed diet at refuge sites across the low phase (“bust”) of the population cycle of the plains mouse (Pseudomys australis), a threatened, refuge-using rodent coexisting with extensive cattle production in Australia’s drylands. The species has a varied diet dominated by species of grasses and forbs (mostly seeds) with a small proportion of invertebrates. Most of the plants consumed are shallow-rooted and short-lived species that should germinate in response to small rainfall events. Coexistence with cattle production is likely to be possible because grazing-tolerant plants are a dominant component of the diet. Our findings provide a plausible explanation for the persistence of P. australis with cattle production in dryland Australia, which should be further investigated to develop management strategies that will enable continued coexistence. This investigation should be extended to consider other refuge-using species of small mammal in pastoral systems.
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D'Odorico, Paolo, i Abinash Bhattachan. "Hydrologic variability in dryland regions: impacts on ecosystem dynamics and food security". Philosophical Transactions of the Royal Society B: Biological Sciences 367, nr 1606 (19.11.2012): 3145–57. http://dx.doi.org/10.1098/rstb.2012.0016.
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Research on ecosystem and societal response to global environmental change typically considers the effects of shifts in mean climate conditions. There is, however, some evidence of ongoing changes also in the variance of hydrologic and climate fluctuations. A relatively high interannual variability is a distinctive feature of the hydrologic regime of dryland regions, particularly at the desert margins. Hydrologic variability has an important impact on ecosystem dynamics, food security and societal reliance on ecosystem services in water-limited environments. Here, we investigate some of the current patterns of hydrologic variability in drylands around the world and review the major effects of hydrologic fluctuations on ecosystem resilience, maintenance of biodiversity and food security. We show that random hydrologic fluctuations may enhance the resilience of dryland ecosystems by obliterating bistable deterministic behaviours and threshold-like responses to external drivers. Moreover, by increasing biodiversity and the associated ecosystem redundancy, hydrologic variability can indirectly enhance post-disturbance recovery, i.e. ecosystem resilience.
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Throop, Heather L., i Jayne Belnap. "Connectivity Dynamics in Dryland Litter Cycles: Moving Decomposition beyond Spatial Stasis". BioScience 69, nr 8 (10.07.2019): 602–14. http://dx.doi.org/10.1093/biosci/biz061.
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AbstractDrylands (arid and semiarid ecosystems) cover nearly half of Earth's terrestrial surface, but biogeochemical pools and processes in these systems remain poorly understood. Litter can account for a substantial portion of carbon and nutrient pools in these systems, with litter decomposition exerting important controls over biogeochemical cycling. Dryland decomposition is typically treated as a spatially static process in which litter is retained and decomposed where it is initially deposited. Although this assumption is reasonable for mesic systems with continuous plant canopy cover and a stable subcanopy litter layer, dryland pools generally reflect discontinuous inputs from heterogeneous canopy cover followed by substantial litter transport. In the present article, we review horizontal and vertical transport processes that move litter from the initial deposition point and retention elements that influence litter accumulation patterns. Appreciation of the spatially dynamic litter cycle, including quantitative assessment of transport patterns, will improve estimates of the fate and distribution of organic matter in current and future drylands.
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Meron, E. "Modeling Dryland Landscapes". Mathematical Modelling of Natural Phenomena 6, nr 1 (9.06.2010): 163–87. http://dx.doi.org/10.1051/mmnp/20116109.
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Pernetta, Angelo P. "Conserving dryland biodiversity". Biodiversity 15, nr 2-3 (3.07.2014): 237–38. http://dx.doi.org/10.1080/14888386.2014.942752.
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Portnov, B. A., i U. N. Safriel. "Combating desertification in the Negev: dryland agriculture vs. dryland urbanization". Journal of Arid Environments 56, nr 4 (marzec 2004): 659–80. http://dx.doi.org/10.1016/s0140-1963(03)00087-9.
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Gudka, Masumi, Jonathan Davies, Lene Poulsen, Björn Schulte-Herbrüggen, Kathy MacKinnon, Nigel Crawhall, William D. Henwood, Nigel Dudley i Jessica Smith. "Conserving dryland biodiversity: a future vision of sustainable dryland development". Biodiversity 15, nr 2-3 (3.07.2014): 143–47. http://dx.doi.org/10.1080/14888386.2014.930716.
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Shi, Xiaoliang, Xinyue Zhang, Shuaiyu Lu, Tielong Wang, Jiayi Zhang, Yuanpeng Liang i Jifeng Deng. "Dryland Ecological Restoration Research Dynamics: A Bibliometric Analysis Based on Web of Science Data". Sustainability 14, nr 16 (9.08.2022): 9843. http://dx.doi.org/10.3390/su14169843.
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Previous research on ecological restoration mainly includes three fields: water ecology, soil ecology, and atmospheric ecology, and the most abundant is in the field of soil ecology, among which the most abundant is in dryland ecological restoration. Research on dryland ecological restoration is very important in ensuring national food security, ecological security, and preventing a return to poverty. However, the previous research results do not clearly present the interconnection between the huge number of existing dryland ecological restoration studies and do not provide a three-dimensional understanding of the whole picture of dryland ecological restoration research from a broader perspective. Research on dryland ecological restoration has received wide attention from scholars at home and abroad, revealing the international research trends in the current field, which will provide a reference for the theory and practice of future dryland ecological restoration research. Using the SCI-E and SSCI databases of the “Web of Science Core Collection” as sample data sources and using CiteSpace optical measurement software, the 2254 literature in the field of international dryland ecological restoration research were systematically analyzed to track the situation and impact of research in this field by countries around the world, scientific research institutions and significant authors, and to analyze the interdisciplinary and research hotspots in this field, which is of great significance for the follow-up research of dryland ecological restoration. The research results show that: (1) The number of publications in international dryland ecological restoration has increased significantly with years and has strong development potential. (2) Journals representing the research frontier have an intense concentration with various journals. (3) The study of dryland ecological restoration belongs to a highly interdisciplinary discipline, while the two disciplines of ecology and environmental science are the pivot nodes of multidisciplinary disciplines. (4) China’s posts and total citations are among the best, but the average citation is low. (5) Dryland ecological restoration and protection is a hot research field at present, and special attention is paid to the dynamic changes and key driving factors of dryland ecological restoration and the full use of machine learning and extensive data mining to solve complex social-ecological problems. The study recommends that related disciplines must strengthen cooperation in the field of dryland ecological restoration, especially the two disciplines of ecology and environmental science, in order to promote the progress of dryland ecological restoration research theory and practice. China should continue to strengthen the investment of scientific research forces to improve the international influence of research in the field of dryland ecological restoration.
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Crain, Grace, Jennie McLaren, Benjamin Brunner i Anthony Darrouzet-Nardi. "Biologically Available Phosphorus in Biocrust-Dominated Soils of the Chihuahuan Desert". Soil Systems 2, nr 4 (10.10.2018): 56. http://dx.doi.org/10.3390/soilsystems2040056.
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In desert soils, phosphorus (P) cycling is controlled by both geochemical and biological factors and remains less studied than nitrogen and carbon. We examined these P cycling factors in the context of biological soil crusts (biocrusts), which are important drivers of nutrient cycling in drylands and have the potential to release bound labile P. We adopted the biologically-based P (BBP) method, which allows examination of biologically relevant P fractions. The BBP method incorporates four extractions: dilute calcium chloride (CaCl2), citric acid, phosphatase enzymes, and hydrochloric acid (HCl). We coupled the extractions with a 33P-labeled orthophosphate addition and incubation to assess the fate of freshly available phosphate (PO43−). Low P concentrations in the dilute CaCl2 extractions suggest that drylands lack accessible P in the soil solution, while higher amounts in the citric acid- and enzyme-extractable pools suggest that dryland microbes may acquire P through the release of organic acids and phosphatases. The addition of 33PO43− was, within 24 h, quickly adsorbed onto mineral surfaces or incorporated into hydrolysable organic compounds. Areas with biocrusts showed overall lower P concentrations across all four extractable pools. This suggests that biocrust organisms may prevent P adsorption onto mineral surfaces by incorporating P into their biomass. Overall, our results indicate that organisms may have to employ several viable strategies, including organic acid and enzyme production, to access P in dryland soils.
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Wang, Qinggang, Shengdan Wu, Xiangyan Su, Linjing Zhang, Xiaoting Xu, Lisha Lyu, Hongyu Cai i in. "Niche conservatism and elevated diversification shape species diversity in drylands: evidence from Zygophyllaceae". Proceedings of the Royal Society B: Biological Sciences 285, nr 1890 (31.10.2018): 20181742. http://dx.doi.org/10.1098/rspb.2018.1742.
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The integrated contributions of climate and macroevolutionary processes to global patterns of species diversity are still controversial in spite of a long history of studies. The niche conservatism hypothesis and the net diversification rate hypothesis have gained wide attention in recent literature. Many studies have tested these two hypotheses for woody species in humid forests; however, the determinants of species diversity patterns for arid-adapted plants remain largely ignored. Here, using a molecular phylogeny and the global distributions of Zygophyllaceae, a typical arid-adapted plant family, we assessed the effects of contemporary climate and net diversification rates on species diversity patterns in drylands. We found the variables representing water availability to be the best predictors for Zygophyllaceae diversity. Specifically, Zygophyllaceae species diversity significantly decreased with the increase in water availability, probably owing to phylogenetic conservatism of water-related niches. The net diversification rates of Zygophyllaceae accelerated sharply in the recent 10 Myr, coinciding roughly with the period of global aridification. The species diversity of Zygophyllaceae significantly increased with the increase in mean net diversification rates per geographical unit, especially in the Old World, supporting the net diversification rate hypothesis. Our study provides a case exploring climatic and evolutionary mechanisms of dryland species diversity patterns, and suggests that the conservatism in water-related niches and elevated net diversification rates in drylands may have jointly determined the global patterns of dryland species diversity.
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Wang, Di, Chang-An Liu, Yan Zeng, Tian Tian i Zheng Sun. "Dryland Crop Classification Combining Multitype Features and Multitemporal Quad-Polarimetric RADARSAT-2 Imagery in Hebei Plain, China". Sensors 21, nr 2 (6.01.2021): 332. http://dx.doi.org/10.3390/s21020332.
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The accuracy of dryland crop classification using satellite-based synthetic aperture radar (SAR) data is often unsatisfactory owing to the similar dielectric properties that exist between the crops and their surroundings. The main objective of this study was to improve the accuracy of dryland crop (maize and cotton) classification by combining multitype features and multitemporal polarimetric SAR (PolSAR) images in Hebei plain, China. Three quad-polarimetric RADARSAT-2 scenes were acquired between July and September 2018, from which 117 features were extracted using the Cloude–Pottier, Freeman–Durden, Yamaguchi, and multiple-component polarization decomposition methods, together with two polarization matrices (i.e., the coherency matrix and the covariance matrix). Random forest (RF) and support vector machine (SVM) algorithms were used for classification of dryland crops and other land-cover types in this study. The accuracy of dryland crop classification using various single features and their combinations was compared for different imagery acquisition dates, and the performance of the two algorithms was evaluated quantitatively. The importance of all investigated features was assessed using the RF algorithm to optimize the features used and the imagery acquisition date for dryland crop classification. Results showed that the accuracy of dryland crop classification increases with evolution of the phenological period. In comparison with SVM, the RF algorithm showed better performance for dryland crop classification when using full polarimetric RADARSAT-2 data. Dryland crop classification accuracy was not improved substantially when using only backscattering intensity features or polarization decomposition parameters extracted from a single-date image. Satisfactory classification accuracy was achieved using 11 optimized features (derived from the Cloude–Pottier decomposition and the coherency matrix) from 2 RADARSAT-2 images (acquisition dates corresponding to the middle and late stages of dryland crop growth). This study provides an important reference for timely and accurate classification of dryland crop in Hebei plain, China.
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Nugraha, Dika Aditya, Eko Rini Indrayatie i Suyanto Suyanto. "ANALISIS PERUBAHAN TUTUPAN LAHAN DAS ASAM–ASAM KECAMATAN JORONG KABUPATEN TANAH LAUT PERIODE 2000 SAMPAI 2017". Jurnal Sylva Scienteae 3, nr 3 (19.07.2020): 466. http://dx.doi.org/10.20527/jss.v3i3.2180.
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This study aims to analyze the shape and rate of land cover change for the period 2000 to 2017, the method used in this study is image interpretation and data analysis. There are 15 classifications namely water body, shrub, swamp shrub, secondary mangrove forest, primary dryland forest, secondary dryland forest, plantations, mixed dryland agriculture, plantations, settlements, dry land agriculture, swamps, open land, open land, mining and pond. There is an increase in the type of land cover in 2017. The most dominant land cover in 2000 in the Asam-Asam watershed was 39399 ha of forest with a percentage of 78.66% while based on land cover data of Landsat 7 in 2017 the forest area was reduced to 16755, 6 Ha with a percentage of 33.45%. The function of forest area in the APL area is the biggest change, namely secondary dryland forest to dryland agriculture with an area of 2118.8 Ha, for the function of forest area in the HL region the largest is secondary dryland forest into shrubs with an area of 507.4 Ha, at HP area has the biggest change, namely plantation forest to plantation with an area of 5036.2 Ha, the function of HPK area is the biggest change in secondary dryland forest into shrubs with an area of 238.2 Ha, the next area Riam Kanan is primary dryland forest into secondary dryland forest with an area of 3545.7 ha and in the area of the Pelaihari TWA forest function the largest is secondary swamp forest into swampland with an area of 217.9 ha.
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Meloni, Fernando, Berta F. Civieta, Juan A. Zaragoza, María Lourdes Moraza i Susana Bautista. "Vegetation Pattern Modulates Ground Arthropod Diversity in Semi-Arid Mediterranean Steppes". Insects 11, nr 1 (18.01.2020): 59. http://dx.doi.org/10.3390/insects11010059.
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The ecological functioning of dryland ecosystems is closely related to the spatial pattern of the vegetation, which is typically structured in patches. Ground arthropods mediate key soil functions and ecological processes, yet little is known about the influence of dryland vegetation pattern on their abundance and diversity. Here, we investigate how patch size and cover, and distance between patches relate to the abundance and diversity of meso-and microarthropods in semi-arid steppes. We found that species richness and abundance of ground arthropods exponentially increase with vegetation cover, patch size, and patch closeness. The communities under vegetation patches mainly respond to patch size, while the communities in the bare-soil interpatches are mostly controlled by the average distance between patches, independently of the concurrent changes in vegetation cover. Large patches seem to play a critical role as reserve and source of ground arthropod diversity. Our results suggest that decreasing vegetation cover and/or changes in vegetation pattern towards small and over-dispersed vegetation patches can fast lead to a significant loss of ground arthropods diversity in drylands.
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Verbruggen, Wim. "Dryland Ecosystems of the Sudano-Sahel: A Vegetation Model Perspective". Afrika Focus 35, nr 1 (30.06.2022): 199–212. http://dx.doi.org/10.1163/2031356x-35010012.
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Abstract Dryland ecosystems are globally widespread and have a large impact on the global land carbon sink. Yet a detailed optimisation of dynamic vegetation models for these ecosystems is lacking. This works contributes to resolving this problem. Based on data from our own field work, we parameterised two dynamic vegetation models to dryland conditions, specifically the Sudano-Sahel region. The optimised parameterisation enables the models to realistically simulate carbon and water fluxes measured at several fluxtower sites across the region, as well as several satellite data products. Using these models, we then studied how climatic factors and soil texture may influence the functioning of dryland ecosystems. By using and tuning dynamic vegetation models for simulating dryland vegetation, this work provides a unique insight into dryland ecosystem functioning.
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Verbruggen, Wim, Guy Schurgers, Stéphanie Horion, Jonas Ardö, Paulo N. Bernardino, Bernard Cappelaere, Jérôme Demarty i in. "Contrasting responses of woody and herbaceous vegetation to altered rainfall characteristics in the Sahel". Biogeosciences 18, nr 1 (7.01.2021): 77–93. http://dx.doi.org/10.5194/bg-18-77-2021.
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Abstract. Dryland ecosystems are a major source of land cover, account for about 40% of Earth's terrestrial surface and net primary productivity, and house more than 30 % of the human population. These ecosystems are subject to climate extremes (e.g. large-scale droughts and extreme floods) that are projected to increase in frequency and severity under most future climate scenarios. In this modelling study we assessed the impact of single years of extreme (high or low) rainfall on dryland vegetation in the Sahel. The magnitude and legacy of these impacts were quantified on both the plant functional type and the ecosystem levels. In order to understand the impact of differences in the rainfall distribution over the year, these rainfall anomalies were driven by changing either rainfall intensity, event frequency or rainy-season length. The Lund–Potsdam–Jena General Ecosystem Simulator (LPJ-GUESS) dynamic vegetation model was parameterized to represent dryland plant functional types (PFTs) and was validated against flux tower measurements across the Sahel. Different scenarios of extreme rainfall were derived from existing Sahel rainfall products and applied during a single year of the model simulation timeline. Herbaceous vegetation responded immediately to the different scenarios, while woody vegetation had a weaker and slower response, integrating precipitation changes over a longer timeframe. An increased season length had a larger impact than increased intensity or frequency, while impacts of decreased rainfall scenarios were strong and independent of the season characteristics. Soil control on surface water balance explains these contrasts between the scenarios. None of the applied disturbances caused a permanent vegetation shift in the simulations. Dryland ecosystems are known to play a dominant role in the trend and variability of the global terrestrial CO2 sink. We showed that single extremely dry and wet years can have a strong impact on the productivity of drylands ecosystems, which typically lasts an order of magnitude longer than the duration of the disturbance. Therefore, this study sheds new light on potential drivers and mechanisms behind this variability.
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Mirgol, Behnam, i Meisam Nazari. "Possible Scenarios of Winter Wheat Yield Reduction of Dryland Qazvin Province, Iran, Based on Prediction of Temperature and Precipitation Till the End of the Century". Climate 6, nr 4 (23.09.2018): 78. http://dx.doi.org/10.3390/cli6040078.
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The climate of the Earth is changing. The Earth’s temperature is projected to maintain its upward trend in the next few decades. Temperature and precipitation are two very important factors affecting crop yields, especially in arid and semi-arid regions. There is a need for future climate predictions to protect vulnerable sectors like agriculture in drylands. In this study, the downscaling of two important climatic variables—temperature and precipitation—was done by the CanESM2 and HadCM3 models under five different scenarios for the semi-arid province of Qazvin, located in Iran. The most efficient scenario was selected to predict the dryland winter wheat yield of the province for the three periods: 2010–2039, 2040–2069, and 2070–2099. The results showed that the models are able to satisfactorily predict the daily mean temperature and annual precipitation for the three mentioned periods. Generally, the daily mean temperature and annual precipitation tended to decrease in these periods when compared to the current reference values. However, the scenarios rcp2.6 and B2, respectively, predicted that the precipitation will fall less or even increase in the period 2070–2099. The scenario rcp2.6 seemed to be the most efficient to predict the dryland winter wheat yield of the province for the next few decades. The grain yield is projected to drop considerably over the three periods, especially in the last period, mainly due to the reduction in precipitation in March. This leads us to devise some adaptive strategies to prevent the detrimental impacts of climate change on the dryland winter wheat yield of the province.
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Yao, Shuran, Muhammad Adnan Akram, Weigang Hu, Yuan Sun, Ying Sun, Yan Deng, Jinzhi Ran i Jianming Deng. "Effects of Water and Energy on Plant Diversity along the Aridity Gradient across Dryland in China". Plants 10, nr 4 (27.03.2021): 636. http://dx.doi.org/10.3390/plants10040636.
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Plants need water and energy for their growth and reproduction. However, how water and energy availability influence dryland plant diversity along the aridity gradient in water-limited regions is still lacking. Hence, quantitative analyses were conducted to evaluate the relative importance of water and energy to dryland plant diversity based on 1039 quadrats across 184 sites in China’s dryland. The results indicated that water availability and the water–energy interaction were pivotal to plant diversity in the entire dryland and consistent with the predictions of the water–energy dynamic hypothesis. The predominance of water limitation on dryland plant diversity showed a weak trend with decreasing aridity, while the effects of energy on plants were found to be significant in mesic regions. Moreover, the responses of different plant lifeforms to water and energy were found to vary along the aridity gradient. In conclusion, the study will enrich the limited knowledge about the effects of water and energy on plant diversity (overall plants and different lifeforms) in the dryland of China along the aridity gradient.
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Maestre, Fernando T., Yoann Le Bagousse-Pinguet, Manuel Delgado-Baquerizo, David J. Eldridge, Hugo Saiz, Miguel Berdugo, Beatriz Gozalo i in. "Grazing and ecosystem service delivery in global drylands". Science 378, nr 6622 (25.11.2022): 915–20. http://dx.doi.org/10.1126/science.abq4062.
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Grazing represents the most extensive use of land worldwide. Yet its impacts on ecosystem services remain uncertain because pervasive interactions between grazing pressure, climate, soil properties, and biodiversity may occur but have never been addressed simultaneously. Using a standardized survey at 98 sites across six continents, we show that interactions between grazing pressure, climate, soil, and biodiversity are critical to explain the delivery of fundamental ecosystem services across drylands worldwide. Increasing grazing pressure reduced ecosystem service delivery in warmer and species-poor drylands, whereas positive effects of grazing were observed in colder and species-rich areas. Considering interactions between grazing and local abiotic and biotic factors is key for understanding the fate of dryland ecosystems under climate change and increasing human pressure.
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Suhartono, Eva Fauziyah i Ary Widiyanto. "The efficiency of dryland farming in Panggang Forest KPH Yogyakarta". E3S Web of Conferences 306 (2021): 02019. http://dx.doi.org/10.1051/e3sconf/202130602019.
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Dryland farming is still to be a main activity of the community around the part of Forest Area (Bagian Daerah Hutan/BDH), Panggang, Kesatuan Pengelolaan Hutan (KPH) Yogyakarta. This study aimed to determine the efficiency of dryland farming and the factors that influencefarming income. The survey method was used to carry out farming data and information by interview the farmer. The R/C analysis, labor productivity analysis, and capital productivity analysis were used to determine the efficiency of dryland farming. Furthermore, to determine the effect of production input factors on farming efficiency, a multiple linear regression analysis was carried out. The results showed that dryland farming by the community around BDH Panggang forest was not efficient because the value of R/C<1 (0,44), labor productivity Rp 29.522,69/working people’s day is lower than a local standard wage Rp 50.000/ working people’s day, and the productivities of land and capital are negative value. The factors production, land area, seed cost, fertilizer cost, pesticide cost, and labor have simultaneously impacted the farmers’ income for dryland farming. The factors of seed cost have been a significant effect on the farmers’ income in dryland farming.
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Ghimire, Rajan, i Babu Ram Khanal. "Soil organic matter dynamics in semiarid agroecosystems transitioning to dryland". PeerJ 8 (20.10.2020): e10199. http://dx.doi.org/10.7717/peerj.10199.
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Recent interest in improving soil health and agricultural sustainability recognizes the value of soil organic carbon (SOC) sequestration and nutrient cycling. The main goal of this study was to evaluate the response of various SOC and nitrogen (N) components in semiarid cropping systems transitioning from limited-irrigation to dryland and a restored grassland in the Southern High Plains of USA. Cropping systems evaluated include dryland winter wheat (Triticum aestivum L.)–sorghum (Sorghum bicolor L.)–fallow with conventional tillage (DLCTF) and no-tillage (DLNTF), limited-irrigation winter wheat–sorghum–fallow with no-tillage and cover cropping (LINTC) and no-tillage fallow (LINTF), and an undisturbed grassland (NG). Soil samples were collected from 0–15 cm and 15–30 cm depths and analyzed for SOC, total N, inorganic N, and soil microbial biomass carbon (SMBC) contents. The CO2 and N2O release during a eight-weeks long laboratory incubation were also analyzed. Results show 14% and 13% reduction in SOC and total N from 0–30 cm depth with the transition from limited-irrigation to dryland cropping systems while 51% more SOC and 41% more total N with the transition to grassland. The SMBC was 42% less in dryland cropping systems and 100% more in NG than the limited-irrigation cropping systems. However, the grassland was N limited, with 93% less inorganic N in NG compared to only 11% less in dryland cropping systems than in limited-irrigation cropping systems. The microbial respiration measured as CO2-C was highest in NG, followed by limited-irrigation and dryland cropping systems. The N2O-N release showed the lowest rate of N loss from dryland cropping systems, followed by NG and limited-irrigation cropping systems. This study demonstrated loss of SOC and N in agroecosystems transitioned to dryland crop-fallow systems, with greater magnitude of change observed in the biologically active fraction of soil organic matter. Grassland restoration could be an important strategy to increase SOC and nutrients in hot, dry, semiarid agroecosystems transitioning to dryland.