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The quantification of changes in long-term trends in grassland net primary productivity (NPP) and its large-scale driving forces are important for understanding terrestrial ecosystem changes in arid and semi-arid regions. Based on the MODIS-NPP dataset, this study investigated patterns in the spatiotemporal variations in NPP and its possible influencing factors in Inner Mongolia during 2000–2014 using the linear trend analysis method, correlation analysis, and an F test. The results show that grassland NPP had an annual rate of increase of 4.53 g C/(m2·a) with a significant increasing trend (p < 0.01). Spatial analysis results indicate that the average grassland NPP presented a gradual increasing trend from southwest to northeast, with an area of longitudinal zonality being identified. Grassland NPP presented a significant increase (p < 0.05) in more than 31.93% of the region. Grassland NPP and growing season precipitation (GSP) had a significant negative correlation in 54.78% of the study area. Grassland NPP and the growing season average land surface temperature (GSALST) had a significant negative correlation for 65.93% of the study area; growing season average temperature (GSAT) had no significant effect on the grassland NPP. For different grassland types, GSP had the greatest impact on alpine meadows (r = 0.73), and GSALST had the greatest impact on alpine steppes and alpine meadows (r = −0.81). Related ecological restoration projects such as fenced rangeland and planted grass played a positive impact on annual NPP in the study area. Image 1 • Spatial-temporal changes of NPP were analyzed in Inner Mongolia from 2000 to 2014. • Linear trend analysis and partial correlation analyses were used to this study. • There was different correlation between NPP and GSAT/GSP/GSALST. • The correlations between NPP and GSAT/GSALST in different grassland types were similar. • Human activities played a decisive role for the yearly increases of grassland NPP. [ABSTRACT FROM AUTHOR]

In the Andes of southern South America, wet meadows are much more productive than nearby arid areas. Human activities, along with climate variations may reduce the productivity of these ecosystems. However, we do not know what the relative effect of climate and human activities on their degradation status is. Here, we first quantified the degradation extent through the temporal trend of normalized difference vegetation index (NDVI), a proxy of productivity, from 1999 to 2017. We did it in 736 wet meadow areas inserted in three nearby zones with contrasting land management. Second, we analyzed the relationship between NDVI and a large-scale mode of climate variability (El Niño Southern Oscillation, ENSO) and regional climate variables (precipitation and temperature) through a structured climate model. Finally, we evaluated human activities' effects through the temporal trends in the residuals of the climate model. Independently of land management, NDVI trends were mainly negative and affected 56% of the wet meadow areas. The climate model indicated that NDVI increased under La Niña, cool and wet years. Regarding land management, the degradation level was similar across the contrasted land management. Our results suggest that climate factors rather than human activities influenced the degradation process in these areas. • Productivity during 1999–2017 decreased in 56% of the wet meadow areas. • Productivity increased under La Niña, cool and wet years. • Productivity negative trends were mainly related to climate factors rather the human activities. [ABSTRACT FROM AUTHOR]

Wet meadows are seasonally saturated wetlands that can develop in arid and semi-arid areas. In the semi-arid region of North Patagonia, Argentina wet meadows are islands of high net primary productivity surrounded by low productivity steppe vegetation. Because of this, Patagonian wet meadows have been heavily grazed by livestock for more than a century. It has been shown that overgrazed wet meadows have lower soil carbon, however, little is known about how overgrazing impacts N dynamics. To this end, we measured ammonium (NH4+), nitrate (NO3-), and total nitrogen (Nt) in paired wet meadows that varied in long-term grazing intensity (heavy vs. light). Results indicate that heavily grazed sites had on average 43% less Nt and 57% less NH4+ than lightly grazed sites. Soil NH4+ concentrations were always significantly greater than NO3- concentrations, being the later often below detection levels. In addition, NH4+ concentrations were correlated with soil moisture in lightly grazed sites, but not in heavily grazed sites. These findings indicate that implementation of better management practices are currently needed to promote more sustainable grazing in semi-arid wet meadows of North Patagonia. [ABSTRACT FROM AUTHOR]

Abstract: In extra-Andean Patagonia, wet meadows contrast with the prevailing arid steppes, and present a gradient of water availability from the periphery to the center. The objectives of this paper are to describe the spatial and temporal variation of aerial net primary production (ANPP) of Patagonian meadows, and to obtain a model for the relationship between the normalized difference vegetation index (NDVI) and ANPP. We determined ANPP in four regionally scattered meadows during 3–5 years and in three positions of the gradient of water availability. In one meadow, we correlated ANPP with NDVI during 2 years. Annual ANPP was 2–3 times larger in the center than in the periphery, and also varied 2–3 fold among the four meadows. The interannual variation of ANPP was high and similar across meadows and zones. ANPP was closely correlated with NDVI through a linear model. Within the growing season, the central zone had a more extended period of high NDVI into the summer than the peripheral and the intermediate zones. We conclude that (1) the local variation of ANPP across the gradient of water availability is strong and must be taken into account for management, and (2) the highly variable ANPP may be monitored by remote sensing. [Copyright &y& Elsevier]

Abstract: There is a growing requirement for techniques to assess land susceptibility to wind erosion, i.e. land erodibility, over large geographic areas (>104 km2). This requirement stems from a lack of wind erosion research between the field (101 km2) and regional scales, and a need to evaluate the performance of spatially explicit wind erosion models across these scales. This paper addresses this issue by presenting a methodology for monitoring land erodibility at the landscape scale (103 km2). First, we define criteria suitable for evaluating land erodibility based on empirical relationships between soil texture, vegetation cover, geomorphology, and wind erosion. The criteria were used to visually assess land erodibility over long distances (103 km) using vehicle-based transects run through the rangelands of western Queensland, Australia. Application of the data for testing the performance of a spatially explicit land erodibility model (AUSLEM) is then demonstrated by comparing the visual assessments of land erodibility with the model output. The model performed best in the west of the study area in the open rangelands. In regions with higher woody shrub and tree cover the model performance decreases. This highlights the need for research to better parameterise controls on erodibility in semi-arid landscapes consisting of forested and rangeland mosaics. [Copyright &y& Elsevier]

Abstract: Livestock grazing is the most common use of rangelands, and overgrazing by domestic livestock has stirred much debate concerning the continued use of public rangelands for livestock production. With the increase of wildlife-related enterprises on south Texas rangelands, there are little data available on the compatibility of livestock and wildlife management and in particular the effects of livestock grazing on plant communities in the semi-arid portions of the western South Texas Plains. The objective of this study was to compare forb diversity and density on rangelands subjected to various grazing under a high-intensity, low-frequency grazing system and nongrazed rangelands under controlled conditions. Four rangeland sites that were moderately grazed during the dormant season and 4 rangeland sites receiving long-term deferment from grazing were selected on the Chaparral Wildlife Management Area, Dimmit and La Salle Counties, Texas. Forb density was estimated with 20×50cm2 quadrats during early spring 2000 and 2001. Forb diversity was greatest on grazed sites. Important annuals such as hooker plantain (Plantago hookeriana) and Rough buttonweed (Diodia teres) were more prevalent on grazed sites. Lazy daisy (Aphanostephus spp.) was more frequently encountered on nongrazed sites. Golden dalea (Dalea aurea), a beneficial perennial, was more common on grazed sites. Long-term deferment from livestock grazing appears detrimental to forb communities. A high-intensity, low-frequency grazing system utilizing moderate stocking rates employed during the dormant season is recommended for enhancing forb diversity and abundance. [Copyright &y& Elsevier]

Growth of plants and formation of net primary productivity (NPP) of salinized meadows in hyperarid regions in the north of the Tarim Basin, Xinjiang, China, mainly depends on the undergroundwater which provides the transpiration requirement of plants and supports the evaporation of water from the soil. Based on the understanding that the more the underground-water evaporates, the greater the soil water regime keeps, and the more the NPP of salinized meadows form, we developed a model for estimating the NPP of salinized meadows in hyperarid regions in the north of the Tarim Basin. Responses of NPP of salinized meadows to global change were predicted with the model. The results showed that the NPP of salinized meadows is a function of the undergroundwater table (UWT) and the air temperature. The NPP of salinized meadows varied with the difference in UWT, and declined logarithmically with decrease of UWT. The NPP of salinized meadows with shallower UWT is greater than that with deeper UWT in similar climate and soil conditions in hyperarid regions in the north of the Tarim Basin. Responses of the NPP with deeper UWT to variation of UWT and air temperature resulting from global change are more sensitive than that with shallower UWT. Impacts of global change on NPP of salinized meadows in hyperarid regions, therefore, depend largely on the salinized meadows with various UWT. [Copyright &y& Elsevier]

Predicting the impact of overgrazing on soil properties, and thus on plant succession, in the Qinghai-Tibet Plateau (QTP) is one of the primary technical bottlenecks in alpine meadow conservation. Four degradation intensities, namely D1: light degradation, D2: moderate degradation, D3: high degradation, and a non-degraded site as the control (CK), were identified. The soil properties and plant community data were analyzed. With the increase in degradation intensity, the soil pH, conductivity (EC), and bulk density (BD) values significantly increased, while the soil water content, total carbon, total nitrogen, and C/N ratio significantly decreased (p < 0.05). Plant aboveground biomass and Shannon diversity significantly decreased with the increase in degradation intensity (p < 0.05). The dominant species changed from Poa pratensis (CK) to Potentilla multifida (D1), to Iris lactea (D2), and finally to Achnatherum splendens (D3). Overgrazing can lead to changes in soil properties, and changes in soil pH and BD are the primary factors that control the changes in plant community structure and composition with grassland degradation. Soil degradation is conducive to the growth of individual species such as A. splendens , which are associated with a reduction in plant diversity in an alpine meadow of the northeastern QTP. Future research should pay more attention to the key species and soil properties in degraded grasslands. • Overgrazing is one of the primary contributors to degraded land in Tibetan alpine meadow • Plant aboveground biomass and Shannon diversity decreased in degraded alpine meadow • The dominant vegetation changed from Poa pratensis to Achnatherum splendens • Soil degradation caused by overgrazing controls plant succession from grasses to forbs [ABSTRACT FROM AUTHOR]

This study examined whether soil microbial composition would respond differently between alpine meadow and desert grasslands located in the Qilian mountain range in the semi-arid region of northwestern China. The measurements were carried out along a soil profile up to 40 cm. The total nitrogen (TN), total carbon (TC), soil organic carbon (SOC) and soil water content (SWC) were significantly higher (P-value < 0.05) in alpine meadow than in desert. In alpine meadows, all these properties decreased with increasing soil depth, and in desert grassland these properties – except SWC and TN - remained the same at all soil depths. The bacterial phyla Actinobacteria dominated both grasslands, significantly more so in desert grassland (P-value< 0.05). In alpine meadows Proteobacteria, Acidobacteria, Gemmatimonadetes, Planctomycetes and Rokubacteria abundance was significantly higher (P-value < 0.05). The distribution pattern of bacterial phyla along soil depth was different between the two grasslands. The abundance of Ascomycota and Basidiomycota was unaffected by grassland type or soil depth. Alpha and beta diversity analysis revealed two grasslands harbored distinct bacterial and fungal communities. We identified soil carbon, nitrogen and water as important factors that shaped the bacterial and fungal community in these semi-arid grasslands. • Alpine meadow and desert grasslands harbor distinct bacterial and fungal communities. • The bacterial phyla Actinobacteria dominated both grasslands, with significantly more so in the desert. • The fungal phyla Ascomycota and Basidiomycota dominated both grasslands, but were unaffected by grassland type and soil depth. • Carbon, nitrogen and water changes along the soil depth shaped microbial diversity. [ABSTRACT FROM AUTHOR]