Grassland Changes Research Articles

Aboveground net primary productivity and soil respiration display different responses to precipitation changes in desert grassland

AbstractPrecipitation (PPT) changes affect both aboveground vegetation dynamics and belowground carbon cycling processes, particularly in arid and semiarid regions. However, it remains unclear how extreme PPT variation can affect soil carbon sequestration potential. A 3-year PPT manipulation experiment with five levels (±40%, ±20% and ambient PPT) was conducted in a desert grassland of western Loess Plateau. Aboveground net primary productivity (ANPP) and soil respiration (Rs) were measured to examine whether the responses of ANPP and Rs to PPT changes displayed a double asymmetry model. The ANPP was more sensitive to extreme drought than extreme wet treatments in wet and dry years, which displayed a negative asymmetric model. The change in ANPP was mainly due to the direct effect of PPT change, and plant density variation also exerted some influence in the dry year. In contrast, Rs displayed a positive asymmetry response to PPT change in dry year. This may be ascribed to enhanced autotrophic respiration due to the enhanced positive responses of plant growth and ANPP to wet treatments as well as stronger birch effect of rainfall events on heterotrophic respiration. The saturating response of Rs to extreme drought (−40% PPT treatment) was also found in the dry year. Nevertheless, the response of Rs to PPT change displayed a negative asymmetry model in wet years. The contrasting models for ANPP and Rs in response to altered PPT regime suggest that extreme wet or dry treatments may increase soil C pools effluxes toward debt in this desert grassland.

Research Progress of Desertification and Its Prevention in Mongolia

Mongolia is a globally crucial region that has been suffering from land desertification. However, current understanding on Mongolia’s desertification is limited, constraining the desertification control and sustainable development in Mongolia and even other parts of the world. This paper studied spatiotemporal patterns, driving factors, mitigation strategies, and research methods of desertification in Mongolia through an extensive review of literature. Results showed that: (i) remote sensing monitoring of desertification in Mongolia has been subject to a relatively low spatial resolution and considerable time delay, and thus high-resolution and timely data are needed to perform a more precise and timely study; (ii) the contribution of desertification impacting factors has not been quantitatively assessed, and a decoupling analysis is desirable to quantify the contribution of factors in different regions of Mongolia; (iii) existing desertification prevention measures should be strengthened in the future. In particular, the relationship between grassland changes and husbandry development needs to be considered during the development of desertification prevention measures; (iv) the multi-method study (particularly interdisciplinary approaches) and desertification model development should be enhanced to facilitate an in-depth desertification research in Mongolia. This study provides a useful reference for desertification research and control in Mongolia and other regions of the world.

The contribution of forest and grassland change was greater than that of cropland in human-induced vegetation greening in China, especially in regions with high climate variability

Vegetation growth is strongly affected by both human activities and climate change. The contribution of land use change caused by human activities to vegetation growth may correlate with climate change, whereas climate variability has often been overlooked. To quantify vegetation growth during 1982–2017 in China, we used the Leaf Area Index (LAI). We also introduced climate variability to divide climate regimes using assignment entropy and built a relative greening performance indicator to identify the contribution of land use (forest, grassland, and cropland) changes to vegetation growth. The results showed that climate variability increased based on precipitation classification, and the regions with low and high climate variability accounted for 33.38%–34.41% and 12.18%–32.38% of China before and after 2000, respectively. Areas of vegetation growth affected by human activities accounted for 7.71%–19.31% and were located mainly in low variability regimes. The contribution of forest and grassland change was greater than that of cropland to vegetation greening in China, especially in high variability regimes. However, the contribution of cropland change was greater than that of forest and grassland in low variability regimes. These results imply the importance of forest and grassland change in human-induced vegetation greening, and this information can provide guidance for regional ecosystem management.

Interannual variation in riparian vegetation cover and its relationship with river flow under a high level of human intervention: an example from the Yongding River Basin.

Riparian vegetation cover is significantly affected by a river's hydrological conditions. Especially in arid and semiarid areas, low flow will degrade riparian vegetation, and recent, intensive human activities in the Yongding River Basin have caused a sharp decrease in river flow. We analyzed interannual change in riparian vegetation, river flow effects, and land use on vegetation coverage using the 40years (1977-2016) of remote sensing images and river flow, combined with 38years (1980-2018) of land use data. The normalized difference vegetation index (NDVI) was used to determine vegetation cover in five different categories: extremely low, low, medium, high, and extremely high based on the pixel dichotomy model. The weighted average was calculated to obtain vegetation cover trends. We show that riparian vegetation cover from four rivers increased. Compared with 1977, in 2016, combined high and extremely high vegetation covers at the Dongyang, Yang, Sanggan, and Yongding Rivers increased by 20.3%, 26.7%, 50.0%, and 39.2%, respectively. High (R = -0.976, P < 0.01) and extremely high (R = -0.762, P < 0.05) vegetation covers are negatively correlated with flow in the Yongding River. The high vegetation cover of the Sanggan River riparian zone is negatively correlated with river flow (R = -0.683, P < 0.05). In the Dongyang and Sanggan Rivers, land use analysis in the riparian zone showed that change in cultivated land, grassland, and forest were significantly correlated with high and extremely high vegetation cover. The abundant cultivated land and restoration activities are likely responsible for the increase of riparian vegetation cover as river flows decline.

The Spatiotemporal Changes and the Impacts of Climate Factors on Grassland in the Northern Songnen Plain (China)

Grassland is an important ecosystem; the spatiotemporal evolution trend of grassland and its impacts on climatic factors play an irreplaceable role in maintaining regional sustainable development and ecological balance. In this paper, based on the remote sensing images of 1990, 2000, 2010, 2020, and 3S technology, we use the methods of dynamic rate and transfer matrix to analyze the spatiotemporal evolution trend of the northern Songnen Plain (China). The method of grey correlation is used to analyze the impact of climate factors on it. The results showed that the grassland changed dramatically and unevenly across the three periods of 1990–2000, 2000–2010, and 2010–2020, with the biggest change in the last period. The internal conversion of grassland mainly occurred between H-grassland (high coverage grassland) and M-grassland (medium coverage grassland), while the transformation rarely occurred in L-grassland (low coverage grassland) due to its small area. There has been a transfer-in from cultivated land, woodland, and unused land to H-grassland and M-grassland. The grassland transfer-out was mainly from H-grassland and M-grassland to cultivated land and unused land. What’s more, the transformation mainly occurred in Daqing City, Suihua City, Qiqihar city, as well as occurring in the west of Harbin and the southwest of Heihe city. Climate change has exacerbated the reduction of grassland areas. In summary, the spatiotemporal change rates of grassland area in the north of Songnen Plain initially showed a mild decrease and were then followed by a rapid decrease. Climate factors were of great significance to the spatiotemporal changes of grassland, and precipitation had a greater impact on the reduction of grassland. The results can provide meaningful information for grassland change, grassland protection, and management in the northern Songnen Plain.

How Will Rwandan Land Use/Land Cover Change under High Population Pressure and Changing Climate?

In recent decades, population growth and economic development have greatly influenced the pattern of land use/land cover (LULC) in Rwanda. Nevertheless, LULC patterns and their underlying change mechanisms under future climate conditions are not well known. Therefore, it is particularly important to explore the direction of LULC transfer in the study area, identify the factors driving the transfer of different types of LULC and their changes, and simulate future LULC patterns under future climate conditions. Based on LULC analyses of Rwanda in 1990, 2000, 2010, and 2015, the LULC pattern of Rwanda in the next 30 years was simulated using an LULC transition matrix, random forest sampling, the Markov chain model, and the PLUS model. The results showed that LULC change in the study area primarily comprised a decrease in forest area and expansion of cropland area, accompanied by a small increase in grassland area and an annual increase in urban land area. Prior to 2000, the LULC in Rwanda was mainly converted from forest and grassland to cropland, with the ratio being 0.72:0.28. After 2010, the LULC was mainly converted from forest to grassland and cropland, with the ratio being 0.83:0.17. Changes in forests, grasslands, and cropland are driven by multiple factors, whereas changes in wetlands, water, urban land, and unused land are more likely to be driven by a single factor. The existing trend of LULC change will continue for the next 30 years, and the future LULC pattern will exhibit a trend in which cropland area will increase in the west and grassland area will decrease, whereas grassland area will increase in the east and cropland area will decrease.

The Effect of Returning Farmland to Grassland and Coniferous Forest on Watershed Runoff—A Case Study of the Naoli River Basin in Heilongjiang Province, China

In the 1950s and 1970s, China implemented large-scale wasteland reclamation in the Sanjiang Plain in eastern Heilongjiang Province, which expanded the area of cultivated land. Cultivated areas alter the quantity of water resources, provide the ecological requirements of river basins, and promote the ecological health of land use. In this study, the grid-based Sacramento (GSAC) model was adopted to simulate various changes in arable land, grassland, cultivated land, and deciduous coniferous forest. Quantitative analysis of the influence of cultivated land change on runoff and under dry season flow was conducted. The results showed that the GSAC model attains a high certainty coefficient in the process of simulating the daily basin discharge and reproduces the daily basin discharge process well for many years. The annual runoff increased between 5.07 and 64.05% due to the return of farmland to grassland and coniferous forest. The return of farmland to grassland greatly impacted runoff. The slope of the grassland and coniferous forest converted from farmland was negatively correlated with the discharge in the basin outlet section. The lower the gradient threshold in the scenario of returning arable land to forest or grassland, the more arable land will be replaced by grassland or deciduous coniferous forest, which could result in more water production in the watershed. Among the different change scenarios, the average flow rate of cultivated land with a slope larger than 15° was the closest to the ecological water demand of the studied watershed. The land use mode of converting cultivated land with a slope larger than 15° into grassland is expected to promote the ecological health of the watershed.

Climate Warming Consistently Reduces Grassland Ecosystem Productivity

AbstractFuture climate may profoundly impact the functioning of terrestrial ecosystems. However, we do not know well how the functioning of different types of grassland ecosystems is associated with variation in temperature and precipitation. Here, we used long‐term field measurements to examine how climatic changes between the 1980s and the 2010s (i.e., growing season temperature, precipitation, habitat moisture index, solar radiation, and sunshine duration) have affected aboveground net primary productivity (ANPP) for all major grassland types in northern China. We found that ANPP consistently declined over the 30‐year period across all types of grassland, on average by about 6.1%. Warming, associated with increased solar radiation and, hence, soil temperature, was the primary factor driving the decrease of ANPP. We further show that ANPP was more sensitive to climate change in alpine and lowland grasslands than in temperate grasslands. Together, our findings indicate that climate warming consistently reduces plant productivity of different types of grassland ecosystems, and emphasize the importance of soil temperature in driving the decline in grassland productivity under climate change.

Changes and controls of aboveground net primary production in response to grassland policy in Inner Mongolian grasslands of China

Over-reclamation of grassland resources has increasingly contributed to environmental degradation in China. With grassland degradation, actions have been taken to maintain or restore natural grasslands through efforts such as ecological engineering. Inner Mongolia is considered being one of the most severely degraded areas in China and consequently almost all of the national land restoration projects for environmental protection were implemented there, making it the province with the highest investment in environmental restoration programs in China. In this study, we use the estimation model relationship established between the vegetation index extracted from remote sensing images and the measured biomass in the field to inversely calculate the biomass in the study area. And then we focused on the changes in the aboveground net primary productivity (ANPP) of these grassland ecosystems, which is crucial for gaining a better understanding of grassland changes in the light of rapidly changing environmental policies and governance regimes in China. The interannual variation of ANPP fluctuated greatly (fluctuated from 87.81 g/m2 to 88.5234 g/m2 between 2000 and 2017). The grassland changes in the whole region are basically stable, but the changes in individual areas are more serious. The ANPP was negatively correlated with the mean annual temperature and positively correlated with the annual precipitation. The hydrothermal conditions directly affected the distribution and accumulation of ANPP along meadow, typical and desert grasslands. Different stages of grassland policy have different target orientations and have positive and negative impacts on ANPP.

Large-Scale Analysis of the Spatiotemporal Changes of Net Ecosystem Production in Hindu Kush Himalayan Region

The Hindu Kush Himalayan (HKH) region is one of the most ecologically vulnerable regions in the world. Several studies have been conducted on the dynamic changes of grassland in the HKH region, but few have considered grassland net ecosystem productivity (NEP). In this study, we quantitatively analyzed the temporal and spatial changes of NEP magnitude and the influence of climate factors on the HKH region from 2001 to 2018. The NEP magnitude was obtained by calculating the difference between the net primary production (NPP) estimated by the Carnegie–Ames Stanford Approach (CASA) model and the heterotrophic respiration (Rh) estimated by the geostatistical model. The results showed that the grassland ecosystem in the HKH region exhibited weak net carbon uptake with NEP values of 42.03 gC∙m−2∙yr−1, and the total net carbon sequestration was 0.077 Pg C. The distribution of NEP gradually increased from west to east, and in the Qinghai–Tibet Plateau, it gradually increased from northwest to southeast. The grassland carbon sources and sinks differed at different altitudes. The grassland was a carbon sink at 3000–5000 m, while grasslands below 3000 m and above 5000 m were carbon sources. Grassland NEP exhibited the strongest correlation with precipitation, and it had a lagging effect on precipitation. The correlation between NEP and the precipitation of the previous year was stronger than that of the current year. NEP was negatively correlated with temperature but not with solar radiation. The study of the temporal and spatial dynamics of NEP in the HKH region can provide a theoretical basis to help herders balance grazing and forage.

Interaction of climate change, potentially toxic elements (PTEs), and topography on plant diversity and ecosystem functions in a high-altitude mountainous region of the Tibetan Plateau

Potentially toxic elements (PTEs) generated from mining activities have affected ecological diversity and ecosystem functions around the world. Accurately assessing the long-term effects of PTEs is critical to classifying recoverable areas and proposing management strategies. Mining activities that shape geographical patterns of biodiversity in individual regions are increasingly understood, but the complex interactions on broad scales and in changing environments are still unclear. In this study, we developed a series of empirical models that simulate the changes in biodiversity and ecosystem functions in mine-affected regions along elevation gradients (1500–3600 m a.s.l) in the metal-rich Qilian Mountains (∼800 km) on the northeastern Tibetan Plateau (China). Our results confirmed the crucial role of PTEs dispersal, topography, and climatic heterogeneity in the diversification of plant community composition. On average, 54% of the changes in ecosystem functions were explained by the interactions among topography, climate, and PTEs. However, merely 30% of the changes were correlated with a single driver. The changes in species composition (explained variables = 94.8%) in the PTE-polluted habitats located in the warm and humid low-elevation deserts and grasslands were greater than those occurring in the dry alpine deserts and grasslands. The ecosystem functions (soil characteristics, nutrient migration, and plant biomass) experienced greater changes in the humid low-elevation grasslands and alpine deserts. Our results suggest that the processes driven by climate or other factors can result in high-altitude PTE-affected habitat facing greater threats.

Grass functional trait responses to experimental warming and fire in Afromontane grasslands

Climate change is one of the main challenges facing humanity in the coming century. To understand the impact of climate change on biodiversity and ecosystem functioning, we urgently require a better understanding of plant responses to climate change. To address this knowledge gap we established a full-factorial warming experiment using open-top chambers (OTCs) inside a long-term fire-manipulation experiment in Afromontane fire-climax grasslands. Fire is an essential ecosystem driver in these grasslands, but has rarely been included in experimental climate change research. To assess growth responses to elevated temperatures and fire frequency, we measured four functional traits: vegetative height, leaf area (LA), specific leaf area (SLA), and leaf dry matter content (LDMC). Grasses responded to fire exclusion with increased height, and lower LA, SLA, and LDMC. Grasses responded to warming with lower height and LA, and higher LDMC, suggesting that plant growth was negatively affected by warming. This response was mostly attributed to intra-specific trait variability, highlighting an important role for trait plasticity in community-level processes to mediate the response of montane grassland communities to elevated temperatures and associated drought effects. These results are a first step towards establishing a more mechanistic basis for understanding future climatic changes in Afromontane grasslands.

Influence of the UAN Fertilizer Application on Quantitative and Qualitative Changes in Semi-Natural Grassland in Western Carpathians

Semi-natural grasslands are particularly important in mountainous areas of Romania, being the only source of forage for many farmers. The aim of this study was to investigate the changes in forage quantity and quality as a result of Urea Ammonium nitrate (UAN) liquid fertilization. The experiment was carried out in the eastern part of Apuseni Mountains, Romania on a Festuca rubra L.-Agrostis capillaris L. grassland located at 1240 m altitude. Studies were made over three years of experimental trial (2014–2016) and covered four experimental plots in three replicates, as follows: V1–control plot, unfertilized; V2–plot fertilized with 50 kg UAN ha−1 year−1; V3–plot fertilized with 75 kg UAN ha−1 year−1, and V4–plot fertilized with 100 kg UAN ha−1 year−1. The experimental plots were harvested once per year and the botanical composition, dry matter yield and forage quality were assessed. Our results showed important changes in forage quantity, quality and diversity as a result of UAN fertilization. Starting from the second experimental year the dominance/co-dominance ratio changed favoring the species from Poaceae family. Dry matter increased as a result of UAN fertilization but forage quality was negatively affected by the higher percentage of participation of species from other botanical families which have higher crude fiber content and lower crude protein. Based on our results we recommend moderate fertilization with UAN up to 50 kg UAN ha−1 year−1 for semi-natural grasslands located in soil-climatic conditions similar to those in our experiment.

Grazing and the vanishing complexity of plant association networks in grasslands

Interactions are key drivers of the functioning and fate of plant communities. A traditional way to measure them is to use pairwise experiments, but such experiments do not scale up to species‐rich communities. For those, using association networks based on spatial patterns may provide a more realistic approach. While this method has been successful in abiotically‐stressed environments (alpine and arid ecosystems), it is unclear how well it generalizes to other types of environments.We help fill this knowledge gap by documenting how the structure of plant communities changes in a Mediterranean dry grassland grazed by sheep using plant spatial association networks. We investigated how the structure of these networks changed with grazing intensity to show the effect of biotic disturbance on community structure.We found that these grazed grassland communities were mostly dominated by negative associations, suggesting a dominance of interference over facilitation regardless of the disturbance level. The topology of the networks revealed that the number of associations were not evenly‐distributed across species, but rather that a small subset of species established most negative associations under low grazing conditions. All these aspects of spatial organization vanished under high level of grazing as association networks became more similar to null expectations.Our study shows that grazed herbaceous plant communities display a highly non‐random organization that responds strongly to disturbance and can be measured through association networks. This approach thus appears insightful to test general hypotheses about plant communities, and in particular understand how anthropogenic perturbations affect the organization of ecological communities.

Specialist Birds Replace Generalists in Grassland Remnants as Land Use Change Intensifies

The ideal free distribution theory predicts that mobile species distribute themselves among habitat patches so as to optimize their fitness. Changes in land use alter the quality of habitat patches and thereby affect the distribution of species. Following the loss of native habitat, habitat specialists are expected to move to patches where native habitat still remains in order to survive. Competition for resources in habitat remnants should consequently increase. As generalists are able to use other habitats, generalists are expected to gradually disappear in remnants in order to avoid increasing competition with specialists. Here, we test these predictions by studying the response of habitat specialist and generalist birds to land-use change in Brazil's southern grasslands. Using a space-for-time substitution approach, we surveyed bird communities in native grassland sites (~4 ha) in 31 regions (10 × 10 km) with differing levels of conversion to agriculture (1–94%). We found a higher abundance of specialists in native grassland patches with increasing agricultural cover in the region, while the total number of individuals in remnants remained constant. At the same time, the share of generalists in total abundance and total species richness decreased. To gain insights into whether these patterns could be driven by shifts in competition, we tested whether generalists that continued to co-occur with specialists in remnants, had less dietary overlap with specialists. As a consequence of community composition in remnants, a higher proportion of generalists were omnivorous and the average generalist species fed less on seeds, whereas the average specialist species fed more on seeds when agricultural cover was high in the region. Our results, therefore, support predictions of the ideal free distribution theory. Specialists that are assumed to have a low survivorship outside of their specialized habitat, distribute to remnants of this habitat when it is converted elsewhere, while generalists, being able to survive in other habitats, disappear gradually in remnants. Such a process could partly explain the segregation of habitat specialist and generalist birds observed in many agricultural landscapes. Finally, our results suggest that native habitat remnants can be important temporary refugia for specialists.

Spatio-Temporal Grassland Development in Inner Mongolia after Implementation of the First Comprehensive Nation-Wide Grassland Conservation Program

Protection of the grassland’s ecological environment and improvement of people’s livelihoods are major tasks for the management of pastoral areas in Inner Mongolia. The comprehensive program for grassland conservation in China, the Subsidy and Incentive System for Grassland Conservation (SISGC), was launched in 2011. To comprehend the effects of this major step towards sustainable grassland development, this study focuses on the spatio-temporal development of grasslands in Inner Mongolia since 2011. Through the combination of MODIS (Moderate-resolution Imaging Spectroradiometer) satellite data with up to date meteorological data, we used the indicators of Fractional Vegetation Cover (FVC) and Net Primary Productivity (NPP) to analyze qualitative and quantitative grassland changes. A classification system on the pixel level, reflecting change trends and fluctuations of both FVC and NPP, was applied to monitor and analyze the grassland development from 2011 to 2019. In particular, the spatial transfer matrix of the recent two years (2018 to 2019) was analyzed to reveal the latest potential issues and random impact factors. The results show a positive overall but spatially unbalanced effect of SISGC, with a prominent positive impact in the semi-desert grassland area. The potential threats from both social and natural aspects as well as the importance of a forecast system for local stakeholders in the pastoral area are discussed.

基于多源数据的三江源区生态工程建设前后草地动态变化及驱动因素研究

基于2000-2015年的NDVI、NPP和GPP多源数据，并结合人类干扰强度等级的构建，采用线性回归分析和地理加权回归分析方法，对比分析了在不同干扰等级下三江源区生态工程实施前5年和后10年草地的动态变化及其驱动因素。结果表明：（1）人类干扰强度和NDVI、NPP、GPP在空间上具有显著的区域差异，均表现为从西北向东南增加的趋势，且2006-2010年和2011-2015年草地NDVI、NPP和GPP值明显高于2000-2004年；（2）与2000-2004年相比，2006-2010年草地NDVI、NPP和GPP值的草地退化面积均减少，而2011-2015年退化面积又均增加，表明生态工程建设后的5年较前5年草地退化状况得到改善，然而在下一个5年草地又出现退化趋势；（3）在各人类干扰等级下生态工程实施后的5年内70%以上的草地处于改善状态，均出现退化面积比例显著减少，改善面积比例显著增加的趋势，而在2011-2015后5年草地退化面积比例增加，表明生态工程的实施促进了草地生态系统的改善，尤其在重度人类干扰区，草地由2000-2004年的52.71%退化区域到2006-2010年84.95%的改善区域。（4）影响草地动态变化的主要因素为距离道路的距离、距离居民点的距离、人口密度、干旱、温度和坡度等，各影响因素分布具有明显的空间异质性。研究结果将有助于为三江源区草地生态系统恢复、管理和战略制定提供科学指导和决策依据。;Using Normalized Difference Vegetation Index (NDVI), Net Primary Productivity (NPP) and Gross Primary Productivity (GPP) data from 2000 to 2015 and combining with of human interference level, linear regression analysis and geographically weighted regression (GWR) analysis were used to compare and analyze the grassland dynamics and their driving factors in the Three-River headwaters region before and after the implementation of ecological construction projects. Results showed that:(1) spatially, human interference and NDVI, NPP and GPP had significantly regional differences, which all showed increasing trends from northwest to southeast, and the grassland NDVI, NPP and GPP values during 2006-2010 and 2011-2015 were significantly larger than that during 2000-2004. (2) Compared with 2000-2004, the NDVI, NPP and GPP values of grassland have been improved during 2006-2010 after ecological construction project, while NDVI, NPP and GPP values showed degrading tendencies again during 2011-2015. (3) In all human interference levels, 70% of the grassland was improved within 5 years after the implementation of ecological projects, and the area ratio of degraded grassland significantly decreased and that of the improved grassland showed significant increasing trend, indicating that the implementation of ecological projects has contributed to the improvement of grassland ecosystems. Especially in areas of severe human disturbance, grassland changed from 52.71% degraded areas in 2000-2004 to 84.95% improved areas in 2006-2010. (4) The main driving factors affecting the dynamic changes of grassland were distance to roads, distance to settlements, population density, drought, temperature and topographic slope, and the distribution of each influencing factor had obvious spatial heterogeneity. The study will help to provide scientific guidance and decision-making basis for grassland ecosystem restoration, management and strategy formulation in the Three River Source Region.

Quantifying Grass Coverage Trends to Identify the Hot Plots of Grassland Degradation in the Tibetan Plateau during 2000-2019.

Grassland covers 54% of the Tibetan Plateau (TP) and suffered overgrazing and degradation problems during past decades. To alleviate these problems, a series of policy measures have been implemented during recent two decades and inevitably caused changes of the grassland. To this end, this study quantitatively analyzed the grassland changes and the effects of reduced grazing intensity, and identified the hot plots of grassland degradation in the TP during 2000–2019. The grassland status was indicated by the Fractional Vegetation Cover in the green grass period (GP), i.e., FVCGP, and its changes and spatial variations were detected by analyzing the FVCGP trends and their distribution, using the Mann–Kendal, Sen’s Slope, and ArcGIS buffering methods, and data of the MOD13Q1 Collection 6 products and other sources. The results showed that 62.12% of the grasslands were significantly increased in the FVCGP, and 28.34% had no apparent changes. The remaining 9.54% of the grassland significantly decreased in the FVCGP, mainly occurring in the areas nearby roads, rivers, and lakes, and distributed mostly in a point pattern. Of the total FVCGP decreased grassland area, 27.03% was clustered and identified as the hot plots of grassland degradation in six main regions. Decreased grazing intensity and increased precipitation contributed to the increase of grassland FVC in the TP, while local overgrazing could be the main cause of the FVC decrease. To strength the grassland restoration in the TP, the government supports and supervision should be enhanced to further mitigate the grassland pressure of animal grazing, particularly in the hot plot areas of degradation.

Three decades of vegetation changes in a submontane grassland after the cessation of intensive fertilization

Three decades of vegetation changes in a submontane grassland after the cessation of intensive fertilization

Geoparcel-Based Spatial Prediction Method for Grassland Fractional Vegetation Cover Mapping

Grassland resources guarantee the balance of ecosystems and the sustainable development of animal husbandry. Spatial information is essential for grass resource management in pastoral areas, which can be extracted quickly on a large-scale by using remote sensing data. However, most conventional methods are based on the grid pixels of remote sensing images. The spatial information based on these regular units inevitably has the phenomenon of mixed pixels, which leads to the unreliability of grassland resource information with irregular spatial heterogeneity. To resolve this problem, this article takes the spatial mapping of fractional vegetation cover (FVC) as a typical target task of information extraction of grassland resources and proposes a geoparcel-based spatial prediction method in which irregular geographic objects from high spatial resolution remote sensing images, i.e., grassland geoparcels, are used as basic mapping units instead of traditional regular units. This change can make the spatial expression of mapping closer to the reality of grassland due to the fine spatial structure. Moreover, multisource spatial data can be integrated together in the regression-based procedure of prediction through the geoparcel as a unified spatial benchmark. A case experiment of Abag Banner, Inner Mongolia, China, shows that the proposed method can achieve good FVC mapping results. The spatial prediction of FVC based on grassland geoparcels is verified to be effective when a random forest regression is used in the modeling. In comparison with traditional regular grid-based methods, the proposed method achieves higher accuracy with 11.89% in relative root mean squared error (%RMSE), and 0.86 in determination coefficient of regression ( R 2). It has advantages in sensing the tiny spatial heterogeneity of FVC at the boundary of grassland change. The formalized procedure potentially promotes the development of spatial mapping technology for grassland resources.