Exploring the Water-Soil-Crop Dynamic Process and Water Use Efficiency of Typical Irrigation Units in the Agro-Pastoral Ecotone of Northern China.

Groundwater resources serve as the primary source of water in the agro-pastoral ecotone of northern China, where scarcity of water resources constrains the development of agriculture and animal husbandry. As a typical rainfed agricultural area, the agro-pastoral ecotone in Inner Mongolia is entirely dependent on groundwater for agricultural irrigation. Due to the substantial groundwater consumption of irrigated farmland, groundwater levels have been progressively declining. To obtain a sustainable irrigation pattern that significantly conserves water, this study faces the challenge of unclear water transport relationships among water, soil, and crops, undefined water cycle mechanism in typical irrigation units, and water use efficiency, which was not assessed. Therefore, this paper, based on in situ experimental observations and daily meteorological data in 2022-2023, utilized the DSSAT model to explore the growth processes of potato, oat, alfalfa, and sunflower, the soil water dynamics, the water balance, and water use efficiency, analyzed over a typical irrigation area. The results indicated that the simulation accuracy of the DSSAT model was ARE < 10%, nRMSE/% < 10%, and R2 ≥ 0.85. The consumption of the soil moisture during the rapid growth stage for the potatoes, oats, alfalfa, and sunflower was 7-13% more than that during the other periods, and the yield was 67,170, 3345, 6529, and 4020 kg/ha, respectively. The soil evaporation of oat, potato, alfalfa, and sunflower accounted for 18-22%, 78-82%; 57-68%, and 32-43%, and transpiration accounted for 40-44%, 56-60%, 45-47%, and 53-55% of ETa (333.8 mm-369.2 mm, 375.2 mm-414.2 mm, 415.7 mm-453.7 mm, and 355.0 mm-385.6 mm), respectively. It was advised that irrigation water could be appropriately reduced to decrease ineffective water consumption. The water use efficiency and irrigation water use efficiency for potatoes was at the maximum amount, ranging from 16.22 to 16.62 kg/m3 and 8.61 to 10.81 kg/m3, respectively, followed by alfalfa, sunflowers, and oats. For the perspective of water productivity, it was recommended that potatoes could be extensively cultivated, alfalfa planted appropriately, and oats and sunflowers planted less. The findings of this study provided a theoretical basis for efficient water resource use in the agro-pastoral ecotone of Northern China.

Study on Modeling and Evaluating Alfalfa Yield and Optimal Water Use Efficiency in the Agro-Pastoral Ecotone of Northern China.

The agro-pastoral ecotone in northern China is the main production area of agriculture and animal husbandry, in which agricultural development relies entirely on groundwater. Due to the increasing water consumption of groundwater year by year, groundwater resources are becoming increasingly scarce. The substantial water demand and low germination rate in the first year are the main characteristics of alfalfa (Medicago sativa L.) yield in the agro-pastoral ecotone in northern China. Due to unscientific irrigation, water resources are seriously wasted, which restricts the development of local agriculture and animal husbandry. The study constructed the Dssat-Forages-Alfalfa model and used soil water content, leaf area index, and yield data collected with in situ observation experiments in 2022 and 2023 to calibrate and validate the parameters. The study found ARE < 10%, ENRMS < 15%, and R2 ≥ 0.85. The model simulation accuracy was acceptable. The study revealed that the water consumption at the surface soil layer (0-20 cm) was more than 6~12% and 13~31% than that at the 20-40 cm and 40-60 cm soil layers, respectively. The study showed when the irrigation quota was 30 mm, the annual yield of alfalfa (Medicago sativa L.) (7435 kg/ha) was consistent with that of the irrigation quota of 33 mm, and increased by 3.99% to 5.34% and 6.86% to 10.67% compared with that of irrigation quotas of 27 mm and 24 mm, respectively. To ensure the germination rate of alfalfa (Medicago sativa L.), it is recommended to control the initial soil water content at 0.8 θfc~1.0 θfc, with an irrigation quota of 30 mm, which was the best scheme for water-use efficiency and economic yield. The study aimed to provide technological support for the rational utilization of groundwater and the scientific improvement of alfalfa yield in the agro-pastoral ecotone in northern China.

Vertical differentiation and root cause of land use and ecosystem service intensity at dune-interdune in the agro-pastoral ecotone in northern China.

Desertification is showing a trend of overall reversal and partial expansion in the agro-pastoral ecotone in northern China (APENC). Dune-interdune is the typical micro-topography in APENC and is the expansion area of desertification. Research on anti-desertification strategy at dune-interdune is of great significance to further anti-desertification. This paper studies the vertical differentiation of land use and ecosystem service intensities at dune-interdune in APENC. The fundamental reason of the vertical differentiation of land use and ecosystem service intensities is explored with monitoring data of soil moisture at different locations of dune-interdune. Cultivated land is mainly distributed in areas with an elevation < 241 m. Grain provisioning ecosystem service intensity (GPESI) and maize leaf provisioning ecosystem service intensity (MLPESI) show a downward trend with the increase in elevation at dune-interdune. GPESI has a tipping point at the elevation of 241 m. Forage provisioning ecosystem service intensity and sand fixation regulating ecosystem service intensity are high in areas with low or high elevations while low in the central area. Groundwater depth is the root cause for vertical differentiation of land use and ecosystem service intensities at dune-interdune. According to vertical changes of land use and ecosystem service intensities, and groundwater level, cultivated land with an elevation greater than 241 m should be stopped for cultivation to anti-desertification. The area of dune-interdune within 6 m of groundwater depth can be used as cultivated land. The conclusion has an important reference for other similar regions in the world.

Designing a sustainable collection and transportation routes for domestic wastes in the agro-pastoral ecotone of the Tibetan Plateau.

The absence of an efficient and safe routes for the timely collection and transportation of domestic waste (DW) may have negative effects on the environment and public health. However, the existing collection and transportation routes (CTR) for domestic waste (DW) based on territorial management are not suitable for the special socio-ecological system of the agro-pastoral ecotone (APE). Therefore, it is crucial to develop a low-cost, high-efficiency, and risk-free CTR to mitigate the threat of DW to the environmental sustainability in the APE of the Tibetan Plateau. This study selected Haidong as a research case and constructed a sustainable CTR optimization framework based on an integrated perspective on temporal, spatial and eco-safety risk. We used the improved Ant Colony Optimization (ACO) to simulate optimal spatial-temporal routes, and the eco-safety risk level of the CTR was assessed by using the Minimum Cumulative Resistance model (MCR). Results demonstrated that: (1) After the sustainable model was optimized, the total transportation mileage and the frequency of collection and transportation were reduced by 45.88% and 38.07% respectively, the economic cost savings were decreased by 32.29%. Optimized routes were more effective and can better adapt to the dispersed pollution-producing characteristics in the APE. (2) The optimized routes reduced greenhouse gas (GHG) emissions by 41.09%, and reduced the eco-safety risk of the high and relative high-risk routes, which account for 29.05% of total routes, can protect important ecological functions and reduce the adverse impacts of DW transportation on soil, atmosphere, water, and the living environment. (3) The cores of adaptive management for sustainable CTR in APE were to change from the current single-county administrative organization to a cross-county administrative organization; adjust the transportation cycle based on pollution-producing characteristics; sort the DW locally; and cultivate environmental awareness among farmers and herdsmen. This study designed new sustainable collection and transportation routes for domestic waste to improve environmental sustainability in the agro-pastoral ecotone.

[Impacts of Land Use and Climate Change on Ecosystem Services in Agro-pastoral Ecotone].

Land use and climate change are the most important factors driving the change in ecosystem services (ESs). It is critical to understand the mechanisms behind such changes for improving ESs. However, there is still a lack of accurate understanding of change and dominant influencing factors of ESs in the agro-pastoral ecotone. This study took Naiman Banner, a typical farming pastoral ecotone in China, as the case study area. Based on the InVEST model, the revised wind erosion equation (RWEQ) and the revised universal soil loss equation (RUSLE) were used to calculate water yield, soil retention, and windbreak and sand-fixing in Naiman Banner in 2005 and 2015. Finally, the impacts of land use and climate change on these three ecosystem services were analyzed by using contribution rate formula, Pearson correlation coefficient, and geodetector methods. The results indicate that:① from 2005 to 2015, water yield and soil retention in Naiman Banner showed an overall upward trend, increasing by 22.41% and 6.74%, respectively, and windbreak and sand-fixing decreased by 66.24%. ② The change in water yield and windbreak and sand-fixing was mainly affected by climate change, and the change in soil retention was mainly affected by land use change. ③ Actual evapotranspiration change and land use change were the main factors affecting the spatial differentiation of water yield, with the explanatory powers of 94.50% and 50.05%, respectively. The main factors influencing the spatial differentiation of windbreak and sand-fixing were actual evapotranspiration change and land desertification degree, with the explanatory power of 19.84% and 16.15%, respectively. ④ The correlation of ESs in Naiman Banner was weak, and only windbreak and sand-fixing and water yield showed a weak significant synergy. Based on the results, we recommend that managers increase the proportion of grassland in sandy areas, implement closed management in pastoral areas, and introduce drip irrigation and other water-saving technologies in farmland, and ecological protection should continue to be given priority in city.

Mitogenome analysis reveals predominantly ancient Yellow River origin of population inhabiting Datong agro-pastoral ecotone along Great Wall.

The Datong Basin was an important arena for population movement and admixture between the Yellow River Valley and Eastern Steppe. In historical materials, the region was often the setting for a tug-of-war between Han farmers and non-Han nomads. The genetic makeup and population history of this Datong population has, however, remained uncertain. In this study, we analysed 289 mitogenomes from Datong individuals. Our primary findings were: (1) population summary statistics analysis revealed a high level of genetic diversity and strong signals of population expansion in the Datong population; (2) inter-population comparisons (PCA and Fst heatmap) exhibited a close clustering between the Datong population and Northern Han, especially northern frontier groups, such as the Inner Mongolia Han, Heilongjiang Han, Liaoning Han and Tianjin Han; (3) phylogeographic analysis of complete mitogenomes revealed the presence of different components in the maternal gene pools of Datong population-the northern East Asian component was dominant (66.44%), whereas the southern East Asians were the second largest component with 31.49%. We also observed a much reduced west Eurasian (2.07%) component; (4) direct comparisons with ancient groups showed closer relationship between Datong and Yellow River farmers than Eastern Steppe nomads. Despite, therefore, centuries of Eastern Steppe nomadic control over the Datong area, Yellow River farmers had a much more significant impact on the Datong population.

[Effects of Long-term Fertilization on Soil Microbial Diversity and Community Structure in the Agro-pastoral Ecotone].

To explore the effects of different long-term fertilization treatments on soil microbial diversity and community structure in the drylands of an agro-pastoral ecotone, a long-term fertilization experiment at the Inner Mongolia cultivated land conservation science observation and experiment station, Ministry of Agriculture, and rural areas was taken as the research object. Four treatments, including no fertilizer (CK), single nitrogen fertilizer (NF), single chemical fertilizer (CF), and the combined application of organic manure and chemical fertilizer (CFM), were selected for the collection of 0-10 cm and 10-20 cm soil at potato maturity 16 years after the experiment (2019). High-throughput sequencing technology was used to assess the soil bacterial and fungal communities to explore the effects of different fertilization measures on soil quality from the perspective of microorganisms, and the partial least squares path model (PLS-PM) was used to reveal the key environmental driving factors of soil microbial community alternation and crop yield improvement in dryland during fertilization mode transformation. The results showed that:① the CF and CFM treatments significantly improved soil fertility, but the effect of the latter was significantly better than that of the former. Soil available nitrogen, available phosphorus, and available potassium in the CFM treatment increased by 131.9%-174.7%, 216.9%-283.3%, and 103.3%-109.3%, respectively, and organic matter and total nitrogen content also increased significantly. The CF treatment still maintained a high soil pH, whereas the NF treatment significantly decreased soil pH and had little effect in improving soil fertility. ② Compared with that under CK, the NF treatment significantly reduced the soil bacterial Chao1 and Shannon index, and the CFM treatment significantly increased the soil bacterial species richness, Chao1 index, and soil fungal Shannon index, whereas soil bacterial and fungal diversity in the CF treatment did not reach a significant difference level with CK. ③ The soil microbial community composition at 0-10 cm and 10-20 cm was similar. The CFM treatment increased the relative abundance of soil beneficial bacteria and decreased the relative abundance of pathogenic bacteria. The relative abundance of dominant bacteria such as Proteobacteria, Bacteroidetes, and Gemmatimonadetes increased. The relative abundances of Actinobacteria, Ascomycota, and Basidiomycota were decreased, whereas the NF and CF treatments showed the opposite trend. ④ PLS-PM analysis showed that with the gradual change in fertilization mode from CK→NF→CF→CFM, the driving factors affecting microbial community succession and yield increase were also changed from soil pH→soil NPK content→soil pH, SOM, and NPK content. In general, long-term fertilization had significant effects on soil chemical properties and microbial communities in drylands in the agro-pastoral ecotone. As the optimal fertilization choice, CFM was significantly better than NF and CF in improving soil fertility and inhibiting the growth of pathogenic microorganisms. The number of pathogens in long-term non-fertilization and unbalanced fertilization soil was significantly increased, and the risk of crop infection to indigenous diseases was increased. The research results can provide scientific reference for farmland nutrient balance management and soil microenvironment improvement of the agricultural ecosystem in the agro-pastoral ecotone in North China.

The impact of climate change on aeolian desertification: A case of the agro-pastoral ecotone in northern China.

Land desertification, one of the gravest eco-environmental problems in the world, has been proven to be critically influenced by climate change. However, the information on the future spatial-temporal patterns of land desertification under climate change has been rarely explored, which restricts the proposal of reasonable desertification control countermeasures to adapt to climate change. The agro-pastoral ecotone in northern China (APENC) is the most critical eco-environmental barrier in China and is also a climate change-sensitive area prone to aeolian desertification. We quantitatively assessed the risk of aeolian desertification in the APENC to climate change and social-economic development in the near-term (2010-2039), mid-term (2040-2069) and long-term (2070-2099) by integrating the representative concentration pathway (RCP) scenarios and the shared socioeconomic pathway (SSP) scenarios using a data-mining approach. The C5.0 decision tree algorithm demonstrated acceptable reliability in aeolian desertification classification. Aeolian desertification in the APENC shows a significant persistent decreasing trend in 2010-2099 under RCP2.6-SSP1 and RCP8.5-SSP3 scenarios, whereas first increased in mid-term then decreased under RCP6.0-SSP2 scenarios. Aeolian desertification risk is lowest under the RCP2.6-SSP1 scenarios, while it is highest under the RCP6.0-SSP2 scenarios. With climate change and socioeconomic development, the risk of aeolian desertification in APENC was generally dominated by a slight grade, i.e., >70 %. While the moderate and severe grades still occupy vast areas, approximately 20 %, and 10 %, respectively, which mainly distributed in and around the Hulunbuir Sandy Land and the Horqin Sandy Land, showing the hot spots of desertification in the APENC. The reversal trend of aeolian desertification risk in the APENC might be initiated by the significant decrease of wind speed. This work highlights the great potential of data-mining approaches on climate change and social-economic development-related land desertification assessment.

Canopy structure: An intermediate factor regulating grassland diversity-function relationships under human disturbances.

Grasslands are one of the largest coupled human-nature terrestrial ecosystems on Earth, and severe anthropogenic-induced grassland ecosystem function declines have been reported recently. Understanding factors influencing grassland ecosystem functions is critical for making sustainable management policies. Canopy structure is an important factor influencing plant growth through mediating within-canopy microclimate (e.g., light, water, and wind), and it is found coordinating tightly with plant species diversity to influence forest ecosystem functions. However, the role of canopy structure in regulating grassland ecosystem functions along with plant species diversity has been rarely investigated. Here, we investigated this problem by collecting field data from 170 field plots distributed along an over 2000 km transect across the northern agro-pastoral ecotone of China. Aboveground net primary productivity (ANPP) and resilience, two indicators of grassland ecosystem functions, were measured from field data and satellite remote sensing data. Terrestrial laser scanning data were collected to measure canopy structure (represented by mean height and canopy cover). Our results showed that plant species diversity was positively correlated to canopy structural traits, and negatively correlated to human activity intensity. Canopy structure was a significant indicator for ANPP and resilience, but their correlations were inconsistent under different human activity intensity levels. Compared to plant species diversity, canopy structural traits were better indicators for grassland ecosystem functions, especially for ANPP. Through structure equation modeling analyses, we found that plant species diversity did not have a direct influence on ANPP under human disturbances. Instead, it had a strong indirect effect on ANPP by altering canopy structural traits. As to resilience, plant species diversity had both a direct positive contribution and an indirect contribution through mediating canopy cover. This study highlights that canopy structure is an important intermediate factor regulating grassland diversity-function relationships under human disturbances, which should be included in future grassland monitoring and management.

Exploring subjective well-being and ecosystem services perception in the agro-pastoral ecotone of northern China.

Understanding stakeholders' perceptions about human well-being and ecosystem services is essential for designing efficient public policies and sustainable environmental management that help to improve people's quality of life. Despite the fragile ecosystem and poverty concentration in the agro-pastoral ecotone, research in this field remains scarce. We selected a typical agro-pastoral ecotone, Duolun County, Inner Mongolia, China, to explore how socioeconomic and demographic factors affect subjective well-being and perceptions of ecosystem services through structural equation modelling (SEM) and canonical correspondence analysis (CCA). Our results showed that health had the highest correlation with subjective well-being among the five dimensions, but respondents were least satisfied with it. Formal education had the greatest effect on subjective well-being, followed by age, income, and livelihood. Gender had no effect on subjective well-being. Older respondents with lower formal education who had a lower level of subjective well-being considered supporting and provisioning services more important for well-being. In contrast, younger respondents with higher education levels (mostly jobs not associated with working the land) mainly valued cultural services. Finally, we discussed the factors that influence subjective well-being and perceptions of ecosystem services and their implications for local management decision-making.

[Village-level landscape succession and its driving mechanism in the agro-pastoral ecotone of Ningxia, China]. / 宁夏农牧交错带村域景观演替及驱动机制.

The relationship between human activities and landscape patterns and its regulation are one of the core fields in landscape ecology. The ecological conditions and local cultures of agro-pastoral ecotone are gradually wea-kening due to environmental fluctuations, land-use characteristics (suitable for both farming and grazing), and unstable policy. Therefore, protecting and restoring this semi-natural landscape and the resulting biological, ecolo-gical and cultural functions are becoming increasingly urgent. Here, by combing remote sensing data with interview survey and geographic investigation, we characterized the landscape changes (1964 to 2019) of Wanjigou Village in Yanchi County of Ningxia Hui Autonomous Region, which lay within the agro-pastoral ecotone. We further explored the rules of landscape succession and the underlying natural and social mechanism, as well as the interactions between landscape types. Results showed that Wanjigou Village had been subjected to a succession from the landscape characterized by grassland, arable land and sandy land to that characterized by grassland, shrub land, sandy land and arable land. The change from the competition of landscape function separation to the preliminary integration had formed a definite succession path for grassland-arable land-sandy land-shrub land. The main driving factors were a synthesis of policy, human needs, and environment. Policy often promoted landscape change through large-scale and intensified human activities, while environment promoted landscape succession through internal driving force of ecosystem toward a mutual adaption between landscape and the innate conditions. The driving factors of landscape succession were soil moisture variations caused by the change of soil physical structure, and vegetation change in adapting to new environment. In agro-pastoral ecotone with low resource density, the separation of landscape functions was one of the main reasons for land desertification. The integration and coordination of landscape functions greatly alleviated the situation of ecological deterioration. The critical path to maintain sustainable development of agro-pastoral ecotone was to achieve complementation among landscape types and even integrating with external resources by transforming landscape separation competition into landscape symbiosis.

Short-term effects of grazing intensity on soil stoichiometric characteristics of typical grassland in the agro-pastoral ecotone of northern China.

Grazing is the dominant land use way for natural grasslands. Different grazing intensities could affect soil stoichiometry in grasslands by influencing the selective feeding by livestock, litter input, and microbial community structure. In this study, a grazing experiment was carried out in a grassland of agro-pastoral ecotone in Northern China for three years (2017-2019). The concentrations of total carbon (TC), total nitrogen (TN), dissolved organic carbon (DOC), dissolved nitrogen (DN), microbial biomass carbon (MBC), and microbial biomass nitrogen (MBN) in soils were measured. We analyzed the stoichiometric characteristics of those parameters. The results showed that different grazing intensities (1, 2, 4 sheep·0.2 hm-2) had no significant effect on soil TC after three years. The moderate grazing intensity significantly reduced soil TN in 10-20 cm layer in 2019. The light, moderate, and heavy grazing intensities significantly increased soil C/N at 10-20 cm layer, while grazing intensities did not affect soil DOC, DN and DOC/DN. The soil DOC and DN content showed a decreasing trend with the increase of grazing intensity in 2019. It indicated that continuous high intensity grazing might reduce soil dissolved nutrients. The light grazing inten-sity increased soil MBC, while heavy grazing intensity reduced soil MBC significantly, with the increase of grazing year. Different grazing intensities did not affect soil MBN and MBC/MBN.

Revegetation projects significantly improved ecosystem service values in the agro-pastoral ecotone of northern China in recent 20 years.

Revegetation is a conventional approach used for ecological protection and restoration projects, especially in the agro-pastoral ecotone of northern China (AENC). However, for this ecologically vulnerable area, the changes in land use and ecosystem service values (ESV) resulting from revegetation projects have received little attention and have not been fully elucidated. In this study, based on a rapid valuation tool-the benefit transfer method modified by the biomass factor (net primary productivity, NPP)-we assessed the ESV of the AENC at multiple-time scales by designing land scenarios related to local revegetation projects. The results showed that forestland expansion (+697 thousand ha) and grassland shrinkage (-650 thousand ha) dominated the land use change in the AENC in 2000-2018 and indirectly resulted in a net increase of US$8.18 billion in total ESV, in which revegetation projects generated nearly 1.5 million ha of new vegetated land and a corresponding US$6.86 billion in ESV (83.83% of the total increase). For future revegetation, the returning-farmland-to-forestland scenario exhibited a greater potential with increases of 5.66 million ha of forestland and US$65.20 billion in ESV to be provided. Overall, revegetation projects improved the ESV of the AENC in the last two decades because of the pronounced expansion in forestland of high ESV at the expense of the reductions in farmland and grassland, and this trend will be led continually by the Grain for Green Project in the future through the rapid assessment based on the modified benefit transfer method. Specifically, more investments and attention must be directed to the protection and restoration of grassland and wetland ecosystems.

Quantifying the Impact of the Grain-for-Green Program on Ecosystem Health in the Typical Agro-Pastoral Ecotone: A Case Study in the Xilin Gol League, Inner Mongolia.

The Green-for-Grain program (GGP) is the largest environmental restoration program in China. It is effective in controlling land desertification but at the same time is highly affected by regional differences. Ecosystem health, as an important indicator of ecosystem sustainability, can effectively assess the ecological impact of the GGP and provide a basis for follow-up actions. As a typical agro-pastoral ecotone along the Great Wall, the Xilin Gol League has seen increasing land-use intensity, thus, it is crucial to understand the ecological conditions of the region in order to deploy a policy of the GGP in accordance with local conditions. In this study, using remote sensing images and social statistics data from 1990-2015, land-use transformation and the turning point of vegetation coverage was determined. Based on the pressure-state-response (PSR) model, an ecological health evaluation system was constructed to quantify the temporal and spatial variation of ecosystem health. Then, the spatial correlation between the changes in forest and grass coverage, as well as the changes in the ecosystem health index (EHI), was evaluated using GeoDa software. The results showed that (1) grassland was the primary land-use/land-cover (LULC) in the Xilin Gol League. Since 2000, land-use transfer types changed significantly and grassland degradation weakened; landscape connectivity increased, and vegetation coverage increased. (2) Over the past 25 years, the ecosystem in the study area was at a subhealthy level and showed a trend toward a healthy level. (3) The spatial correlation between △Area% (change in forest and grass coverage) and △EHI (change in ecosystem health index) was positive between 2000 and 2015 and the correlation gradually increased, indicating that the GGP did enhance the health of the ecosystem of Xilin Gol. This study provided a specific reference for the evaluation of ecosystem health in the agro-pastoral ecotone of China and a theoretical basis for the implementation of sustainable management policies in the study area.

Assessing the Effects of Desertification Control Projects from the Farmers' Perspective: A Case Study of Yanchi County, Northern China.

Desertification has inflicted severe damage on the natural environment and social economy for decades, particularly in the arid and semi-arid regions of northern China. In Yanchi County, a series of projects were implemented to combat desertification after 2000. To assess the effects of these Desertification Control Projects from the farmers' perspective, we divided Yanchi County into two regions (the northern and southern regions) according to their different environmental conditions. We collected data including basic family information, farmers' perceptions and attitudes, and farmers' suggestions, in a questionnaire investigation following the Participatory Rural Appraisal approach. Data analysis using the Mann-Whitney U test and Fisher's exact test revealed that the Desertification Control Projects were generally successful, as the local environment and farmers' incomes were both improved. Farmers were all satisfied with the effects of the projects, but the farmers in the southern region had a higher acceptance of the projects than those in the northern region. In addition, three problems with the Desertification Control Projects were noted: the farmers had a low degree of participation in the projects, the farmer's low incomes affected the sustainability of the projects, and the implementation of the complete grazing ban had several adverse effects. We provided suggestions for solving these problems. Our findings have important implications for assessing the effects of environmental conservation projects, especially from a participant's perspective.

In situ measurements and meta-analysis reveal that land-use changes combined with low nitrogen application promote methane uptake by temperate grasslands in China.

Methane (CH4) oxidation in well-aerated grassland soils is an important sink for atmospheric CH4, which can be largely modified by land-use changes. However, the impacts of land-use changes (i.e., from native grasslands to artificial grasslands (AG) and croplands (CL)) on soil CH4 uptake in China remain uncertain. Therefore, the 2-year CH4 flux was measured from 3 land-use types, including heavily grazed steppe (HG, control), AG, and CL, in the agro-pastoral ecotone of Northern China to elucidate this impact. Moreover, a meta-analysis was conducted to elucidate this effect across Chinese grasslands. The results showed that the land-use types could not change the seasonal patterns but significantly (p < 0.05) influenced the strength of soil CH4 uptake. The mean annual CH4 uptake followed the decreasing order of 14.7 ± 0.48 (mean ± 1 standard error) (CL), 3.28 ± 0.09 (AG), and 1.24 ± 0.07 kg CH4-C ha-1 yr-1 (HG) in 2012-2014. This spatial variation pattern was linear and negatively (n = 6, radj.2= 0.73, p < 0.05) associated with the annual mean soil water-filled pore space. Non-growing season CH4 uptake contributed 22-46% to the annual CH4 uptake across land-use types. The meta-analysis also confirmed that the land-use changes significantly (p < 0.05) promoted the annual soil CH4 uptake in temperate grasslands in China. This increased uptake is primarily related to the significant (p < 0.05) decrease in the soil water contents and the increase in the sand contents due to the land-use changes. Furthermore, nitrogen application not exceeding 100 kg N ha-1 yr-1 in these N-limited ecosystems significantly (p < 0.05) promoted soil CH4 uptake. Collectively, our study demonstrated that land-use changes combined with low N application promoted soil CH4 uptake in the temperate grasslands of China.

Spatiotemporal Variation Characteristics of Ecosystem Service Losses in the Agro-Pastoral Ecotone of Northern China.

Being subject to climate change and human intervention, the land-use pattern in the agro-pastoral ecotone of Northern China has undergone complex changes over the past few decades, which may jeopardize the provision of ecosystem services. Thus, for sustainable land management, ecosystem services should be evaluated and monitored. In this study, based on Landsat TM/ETM data, we quantitatively evaluated the losses of ecosystem service values (ESV) in three sections of the agro-pastoral ecotone from 1980-2015. The results were as follows: (1) the main characteristic of the land conversions was that a large area of grassland was converted into cultivated land in the agro-pastoral ecotone; (2) on the spatial scale, the ESV losses of the agro-pastoral ecotone can be called an "inclined surface" in the direction of the northeast to southwest, and the northeastern section of the agro-pastoral ecotone lost more ESV than the middle and northwest sections (p < 0.05), on the temporal scale, the order of losses was 1990-2000 > 1980-1990 > 2000-2015; (3) the agro-pastoral ecotone lost more ESV, which was mainly due to four kinds of land conversion, which were grassland that was transformed into cultivated land, grassland transformed into unused land, grassland transformed into built-up areas, and cultivated land transformed into built-up areas; (4) although these land conversions were curbed after the implementation of protection policies at the end of the 1990s, due to reduced precipitation and increasing temperatures, the agro-pastoral ecotone will face a more severe situation in the future; and, (5) during the period of 1990-2015, the overall dynamic processes of increasing population gradually expanded to the sparsely populated pastoral area. Therefore, we believe that human interventions are the main cause of ecological deterioration in the agro-pastoral ecotone. This study provides references for fully understanding the regional differences in the ecological and environmental effects of land use change and it helps to objectively evaluate ecological civilization construction in the agro-pastoral ecotone of Northern China.

Land use model research in agro-pastoral ecotone in northern China: A case study of Horqin Left Back Banner.

The agro-pastoral ecotone in northern China is an ecological fragile region, where desertification is a prominent problem and mainly induced by extensive cultivation. The typical topography of the area is dune-interdune. The irrational land use model of dune-interdune should be investigated to benefit crop production and anti-desertification. This study investigated vegetation growth status by calculating land surface temperature and soil moisture differentiation along dune-interdune. Dry land maize growth status worsened, and grass growth status showed a trend of worsening first and then improving with increasing elevation of the dune-interdune topography; meanwhile, soil moisture decreased. A land use model was designed according to soil moisture differentiation and vegetation growth condition to obtain crop production and anti-desertification. In the top region of the dune-interdune, water tolerance grass should be maintained for anti-desertification. In the middle region, cultivated land infrastructures should be established to obtain sustainable cultivated land use and avoid frequent change in land use. In the bottom region, rice can be planted, and drainage facilities should be constructed if maize is planted. Crop production and anti-desertification can be completed simultaneously in the land use model of dune-interdune.

Impact of grassland degradation on the distribution and bioavailability of soil silicon: Implications for the Si cycle in grasslands.

Grassland ecosystems play an important role in the global terrestrial silicon (Si) cycle, and Si is a beneficial element and structural constituent for the growth of grasses. In previous decades, grasslands have been degraded to different degrees because of the drying climate and intense human disturbance. However, the impact of grassland degradation on the distribution and bioavailability of soil Si is largely unknown. Here, we investigated vegetation and soil conditions of 30 sites to characterize different degrees of degradation for grasslands in the agro-pastoral ecotone of northern China. We then explored the impact of grassland degradation on the distribution and bioavailability of soil Si, including total Si and four forms of noncrystalline Si in three horizons (0-10, 10-20 and 20-40 cm) of different soil profiles. The concentrations of noncrystalline Si in soil profiles significantly decreased with increasing degrees of degradation, being 7.35 ±â€¯0.88 mg g-1, 5.36 ±â€¯0.39 mg g-1, 3.81 ±â€¯0.37 mg g-1 and 3.60 ±â€¯0.26 mg g-1 in non-degraded, lightly degraded, moderately degraded and seriously degraded grasslands, respectively. Moreover, the storage of noncrystalline Si decreased from higher than 40 t ha-1 to lower than 23 t ha-1. The corresponding bioavailability of soil Si also generally decreased with grassland degradation. These processes may not only affect the Si pools and fluxes in soils but also influence the Si uptake in plants. We suggest that grassland degradation can significantly affect the global grassland Si cycle. Grassland management methods such as fertilizing and avoiding overgrazing can potentially double the content and storage of noncrystalline Si in soils, thereby enhancing the soil Si bioavailability by >17%.

Land use and land cover change in agro-pastoral ecotone in Northern China: A review.

Land use/cover change (LUCC) is the most direct manifestation of the interaction between human activities and natural ecosystems. In recent years, due to the increasing human activities, regional environment has been dramatically changed. As one of heavily influenced and fragile and vulnerable ecosystems, the agro-pastoral ecotone in Northern China is a "hot spot" for land use/cover change research. Based on a literature review of LUCC in the agro-pastoral ecotone in Northern China, we first systematically summarized the progress of the boundary definitions of the agro-pastoral ecotone, and then synthesized the current findings, methods, procedures, topics, environmental impacts and adaption of LUCC in the region. Finally, we proposed that few comprehensive, process-based ecosystem simulations and eco-environmental impact studies had been reported in the current LUCC research and called for more multi-disciplinary, multi-methods, and multi-scale researches in the future LULC research in this area.