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Abstract U.S. rice paddies, critical for food security, are increasingly contributing to non‐CO2 greenhouse gas (GHG) emissions like methane (CH4) and nitrous oxide (N2O). Yet, the full assessment of GHG balance, considering trade‐offs between soil organic carbon (SOC) change and non‐CO2 GHG emissions, is lacking. Integrating an improved agroecosystem model with a meta‐analysis of multiple field studies, we found that U.S. rice paddies were the rapidly growing net GHG emission sources, increased 138% from 3.7 ± 1.2 Tg CO2eq yr−1 in the 1960s to 8.9 ± 2.7 Tg CO2eq yr−1 in the 2010s. CH4, as the primary contributor, accounted for 10.1 ± 2.3 Tg CO2eq yr−1 in the 2010s, alongside a notable rise in N2O emissions by 0.21 ± 0.03 Tg CO2eq yr−1. SOC change could offset 14.0% (1.45 ± 0.46 Tg CO2eq yr−1) of the climate‐warming effects of soil non‐CO2 GHG emissions in the 2010s. This escalation in net GHG emissions is linked to intensified land use, increased atmospheric CO2, higher synthetic nitrogen fertilizer and manure application, and climate change. However, no/reduced tillage and non‐continuous irrigation could reduce net soil GHG emissions by approximately 10% and non‐CO2 GHG emissions by about 39%, respectively. Despite the rise in net GHG emissions, the cost of achieving higher rice yields has decreased over time, with an average of 0.84 ± 0.18 kg CO2eq ha−1 emitted per kilogram of rice produced in the 2010s. The study suggests the potential for significant GHG emission reductions to achieve climate‐friendly rice production in the U.S. through optimizing the ratio of synthetic N to manure fertilizer, reducing tillage, and implementing intermittent irrigation.

Amidst the acceleration of urbanization, a heightened focus on sustainable development is essential for maintaining urban ecological well-being. In China, the paradigm of urban construction is evolving from one of mainly expanding cities outward to one of advocating for essential and planned rebuilding through urban regeneration programs (URPs). This study aims to elucidate the interplay between URPs and wildlife, as well as to examine the implications of these programs for human well-being. To achieve these objectives, we used a superior urban regeneration approach that incorporates complex networks, topologies, and ecosystem services into the assessment framework. By adapting the spatial structure of older urban areas, we quantified consequential impacts on both wildlife and human well-being in a representative city located in southern China. Our results indicate that the habitat area for wildlife increased by 4.7% after the implementation of URPs. Moreover, the stability and connectivity of the ecological network significantly improved, as evidenced by changes in robustness curves and connectivity values. For example, the overall connectivity (IIC) of the study area increased by 1.1%, and the possible connectivity (PC) increased by 18.5%. Additionally, the URPs contributed to a partial restoration of ecosystem services in the study area, underscoring their potential to yield substantial improvements in the well-being of both humans and wildlife. Our study offers valuable insights for environmentalists and urban planners aiming to regenerate old human communities in cities while simultaneously bolstering urban ecological resilience.

The prolonged disregard for the Gross Ecosystem Product (GEP) has limited the effectiveness of regional ecological conservation. However, identifying and safeguarding areas with high GEP, and optimizing their distribution and spatial structure, are of great immense for preserving ecosystem services (ESs). Our goal is to refine the spatial configuration of ecological network (EN), and subsequently augment and sustain the stability of ESs. We have specifically chosen Hechi City, situated in the Karst region of southwest China, as our case study. Firstly, we devised a GEP evaluation system to pinpoint crucial areas as ecological sources. Subsequently, we utilized the circuit theory and minimum cumulative resistance model to construct the preliminary EN. Through the circuit theory model identified the key nodes in the EN and optimized the EN. Finally, by combining complex network analysis methods, we evaluated the robustness and topological characteristics of the EN. Our results showed that the area of ecological sources increased from 71 to 161 after optimization. The number of corridors increased from 161 to 423, resulting in an overall increment of 8.8% in the source area. The connectivity and stability of the optimized EN can be significantly enhanced. The addition of new nodes increases the overall importance of the network, making the importance of each node more balanced. Additionally, the complex network analysis method provided a detailed understanding about the spatial topology of the overall and local elements of the EN. The study results can provide a valuable reference for optimizing, restoring and evaluating ENs in karst areas.

Scientific understanding of the coupling relationship between grazing activities and grassland ecosystem is an important foundation for protecting and improving the ecological quality of grassland. This study took the Inner Mongolia Autonomous Region (Inner Mongolia) as the research area, systematically evaluated the grassland ecosystem and grazing intensity status in Inner Mongolia, and evaluated the ecological quality of Inner Mongolia county based on the four quadrant model. The results showed that: (1) The types of landscape patterns in Inner Mongolia were mainly grassland, forest, and desert. During the study period, the overall pattern of the landscape was stable, but problems such as urban expansion needed to be given more attention. (2) The areas with good grassland ecosystem carrying capacity were principally distributed in the eastern and southeastern Inner Mongolia, while the western Inner Mongolia and the northwest region of the Xilingol League were relatively low, and in the period 2000–2010 the ecological quality of the Inner Mongolia grassland in general belonged to the fair, middle level, but had been in a stable state and showed a good direction to improve the trend of ascension. (3) The grazing overload degree (GOD) in Inner Mongolia was significantly different in the region. GOD decreased from northeast to southwest in both periods. And most of the grassland stocking pressure was alleviated during 2000–2010. (4) The results of the four quadrant model analysis showed that there were obvious spatial differences in ecological quality in Inner Mongolia. And about 97% of the research area was located in the first, second, and fourth quadrants, with only 3% located in the third quadrant. From 2000 to 2010, the counties with nearly unchangeable and non-significantly worse accounted for 91.76% and 4.33%, respectively, indicating that the overall grassland ecosystem in Inner Mongolia remained stable and showed a slight improvement trend. This study can provide the necessary reference basis for the scientific formulation of grassland resources-related policies and plans and the promotion of grassland ecological protection in Inner Mongolia.

Research on synergies and trade-offs between ecosystem services (ES) contributes to a better understanding of the linkages between ecosystem functions. Relevant research mainly focuses on mountain areas, while research in arid areas is obviously insufficient. In this research, we use the northern sand-stabilization belt (NSB) as an example to explore how the synergies and trade-offs between different ES vary with the gradient of precipitation and fractional vegetation cover (FVC) over the period 2000-2020. Based on five simulated ecosystem services (habitat provision, sand-stabilization service, water conservation service, soil conservation service and carbon sequestration service), the Pearson correlation coefficient method was used to analyze the various characteristics of the trade-offs and synergies among the different ES pairs along the FVC and precipitation gradients. Results showed that: Synergies between most paired ES increased significantly with increasing precipitation and FVC. However, ES have different sensitivities to environmental change, FVC promotes bit more synergy of ES pairs than precipitation. The study also found that land use/land cover may be an important driving factor for trade-offs and synergies between paired ES. The findings demonstrate that increased precipitation and FVC promote synergy of ecosystem services in arid regions of China. In the future, it can be investigated whether anthropogenic increase in FVC in arid regions can significantly contribute to the synergy of ES. In the meantime, this study could improve our understanding of arid and semi-arid (or macro-regional) ecosystems and contribute to the development of ecosystem management and conservation measures in NSB.

The complexity and fragility of the Yellow River Basin ecosystem limits its economic growth and sustainable social development as a strategic planning area for development in western China. The Chinese government has established the Loess Plateau Ecological Screen (LPES) in the region to eliminate or mitigate the negative ecological impacts of human activities represented by the expansion of impervious surfaces (IS) through active ecological conservation and restoration. However, there are few studies that quantify the effects of impervious surfaces on ecosystem services (ES). To fill this gap, this study takes the LPES in China as an example and explores the response of ES to IS changes and its scale effect from 2000 to 2020. Based on remote sensing, meteorological, soil, hydrological, social, and economic data using GIS spatial analysis techniques. The results show that: From 2000 to 2020, the urbanization of the LPES developed rapidly, and the IS increased rapidly. The increase in IS affected the supply of ES, which decreased with the increase in IS growth rate, and this phenomenon had a scale effect. Overall, except for soil conservation service (SCS) - IS, carbon storage service (C) - IS at the administrative scale, the negative correlation increased with increasing scale, while the opposite was true at the grid scale. There were thresholds for the response of ES to IS, and the thresholds were also influenced by the scale of study. The smaller the scale was, the lower the threshold was. However, there were differences in the ranking of each ES reaching the threshold with increasing IS at the grid-scale and administrative division scale. The ecosystem services composite index (ESCI) was found to be the best indicator for exploring the relationship between IS and ES compared to other single ecosystem services indices, with the largest negative correlation with IS and the least influenced by scale effects. Given the obvious scale effect of IS on ES, this study suggests that the development of ecological management programs at the national level should be macroscopically regulated at the provincial level, with specific measures at smaller grid scales (5 Km × 5 Km) to constrain IS expansion..

Urban expansion is leading to the loss and fragmentation of habitats, which poses a threat to wildlife. People are hopeful that, through scientific urban planning and the adoption of innovative models for human communities, such a situation can be improved. Thus, a case study was carried out in Nanning City, China, to extract habitats, build an ecological resistance surface, and construct a habitat connectivity network (HCN). To simulate changes to unused land in the future, we put forth the A (the parcel is divided into strips), B (the parcel is divided into two strips), C (the central area of the parcel is planned as a quadrangle), and D (opposite to Scenario C, the peripheral area is green space) scenarios of human communities that guarantee a 30% ratio of green space, and established the corresponding HCNs. The results indicate that: (1) Currently, the habitats cover approximately 153.24 km2 (34.08%) of the entire study area. The ecological corridors in this region amount to a total of 5337, and the topological indicators and robustness indicate a strong stability of the current HCN. (2) With urban expansion, once continuous habitats are being fragmented into smaller green spaces, it is estimated that the habitats will shrink by 64.60 km2. The topological indicators and robustness reveal that the stability of the HCNs becomes lower as well. Multiple scenario simulations demonstrated that Scenario D is better than Scenarios B and C, while Scenario A performed the worst. (3) Furthermore, we observed a stronger negative impact of urban expansion on local connectivity. This indicates that the influence of urban expansion on the local HCNs is often more pronounced and may even be destructive. Our findings can advise urban planners on decisions to minimize the impact of urban expansion on wildlife.

In recent years, rapid global changes have accelerated the loss of habitats and fragmentation of landscapes, emerging as primary drivers of the alarming decline in global biodiversity. Through the construction of ecological networks (ENs) that simulate the interactions between animal and plant species with their environment, it is possible to mitigate landscape fragmentation and the loss of biodiversity. In this study, we focused on the ecologically diverse southeastern region of the Qinghai–Tibetan Plateau (QTP) as our research area and developed a comprehensive Multi-Species Ecological Network (MEN) consisting of ten species. Through employing complex network analysis methods, we thoroughly examined the intra-species and inter-species interactions within the MEN, integrating the findings with the natural characteristics of the study area to yield valuable insights. The results of our study revealed considerable spatial variations in the MEN. Specifically, the western and eastern regions experienced significant ecological resistance, leading to fragmented ecological sources and a limited connectivity of ecological corridors. Furthermore, the application of complex network analysis revealed inadequate connectivity and stability in specific localized areas within the MEN. This emphasizes the pressing requirement for effective ecological preservation plans. Through this study, our aim is to advance research on multi-species ecological spatial networks and to offer novel perspectives and methodologies for biodiversity conservation and habitat maintenance in the Qinghai–Tibetan Plateau.

The ecosystem services (ES) can be influenced by various environmental factors. In order to efficiently allocate resources and manage ecosystems, it is important to understand the mechanisms by which these environmental effects impact the interactions and trade-offs among different ES. While previous studies have primarily examined the impact of individual environmental factors on ES, the intricate mechanisms underlying the effects of multiple environmental factors have been largely overlooked. In this study, we adopted a path analysis approach that considered interactions among explanatory variables. We analyzed multiple geospatial datasets from various sources, including remote sensing and climate data, to examine the main drivers—precipitation, temperature, FVC (fractional vegetation cover), NPP (net primary productivity), human activities, and altitude—affecting five ecosystem services: carbon sequestration service (C), habitat provision service (HP), soil conservation service (SCS), sand-stabilization service (SSS), and water conservation service (WCS) in arid and semi-arid mountainous regions. Our investigation found that all five ES have shown an upward trajectory over the past two decades. The most significant growth was observed in C, which increased by 39.4%. Among the environmental factors examined, precipitation has been identified as the predominant factor influencing the ES and the synergies and trade-offs among ES. The influence of precipitation on SCS reached a coefficient of 0.726. Human activity factors had the greatest influence on HP of the five ES with a path coefficient of 0.262. Conversely, temperature exhibited a suppressive influence on ES. The impact of factors such as NPP and altitude on ES was comparatively modest. Notably, human activities assumed a substantial contributory role in shaping the relationship encompassing WCS. It is worth noting that individual factors exerted differential effects on ES along distinct environmental gradients, including anthropogenic gradients. In this context, the combination of high altitude and substantial FVC demonstrated a notable contribution to WCS. Our study can provide valuable insights for the management of ES which can be utilized to optimize the regulation of the Loess Plateau Ecological Screen (LPES) ecological construction and promote regional sustainable development.

Identifying and protecting key sites of ecological assets and improving spatial connectivity and accessibility are important measures taken to protect ecological diversity. This study takes Guangxi as the research area. Based on the gross ecosystem product (GEP), the ecological source is identified, and the initial ecological network (EN) is constructed by identifying the ecological corridor with the minimum cumulative resistance model. The internal defects of the initial ecological network are extracted using the circuit theory, the priority areas for restoration and protection with clear spatial positions are determined according to the complex network analysis, and the network’s performance before and after optimization is comprehensively evaluated. The results show that 456 initial ecological sources and 1219 ecological corridors have been identified, forming the initial ecological network of Guangxi. Based on the circuit theory, 168 ecological barriers, 83 ecological pinch points, and 71 ecological stepping stones were extracted for network optimization. After optimizing the ecological network, there are 778 ecological sources with a total area of 73,950.56 km2 and 2078 ecological corridors with a total length of 23,922.07 km. The GEP of the optimized structure is 13.33% higher than that of the non-optimized structure. The priority areas for protection are distributed in a large area, and the attached GEP reaches USD 118 billion, accounting for 72% of the total GEP attached to the optimized ecological source area. The priority areas for restoration are scattered in small patches, with a GEP of USD 19.27 billion. The robustness and connectivity of the optimized ecological network have been improved obviously. This study attempts to identify key sites of ecological assets and the priority regions for restoration and conservation using genuine geographical location and reference materials for regional ecological network optimization and implementation.

Chlorophyll-a(chl-a) has been used as an important indicator of water quality. Great efforts have been invested to develop remote-sensing-based chl-a retrieval models. However, due to the spatial difference in chl-a concentration, a single model usually cannot accurately predict the whole range of chl-a concentration. To test the performance of precedent chl-a models, we carried out an experiment along the upper and middle reaches of the Kaidu River and around some small ponds in the Bayanbulak Wetland. We measured water surface reflectance in the field and analyzed the chl-a concentration in the laboratory. Initially, we performed a sensitivity analysis of the spectrum band to chl-a concentration with the aim of identifying the most suitable bands for various chl-a models. We found that the water samples could be divided into two groups with a threshold of 4.50 mg/m3. Then, we tested the performance of 11 precedent chl-a retrieval models and 7 spectral index-based regression models from this study for all the sample datasets and the two separate datasets with relatively high and low chl-a concentrations. Through a complete comparison of the performance of these models, we selected the D3B model for water bodies with high chl-a concentration and OC2 model (ocean color 2) for low chl-a concentration waters, resulting in the hierarchical and piecewise retrieval algorithm OC2-D3B. The chl-a concentration of 4.50 mg/m3 corresponded to the D3B value of −0.051; therefore, we used −0.051 as the threshold value of the OC2-D3B model. The result of the OC2-D3B model showed a better performance than the other algorithms. Finally, we mapped the spatial distribution and seasonal pattern of chl-a concentration in Bayanbulak Wetland using Sentinel-2 images from 2016 to 2019. The results indicated that the chl-a concentration in the riparian ponds was generally in the range of 8–10 mg/m3, which was higher than that in rivers with a range of 2–4 mg/m3. The highest chl-a concentration usually appears in summer, followed by spring and autumn, and the lowest in winter. The correlation between meteorological data and chl-a concentration showed that temperature is the dominant factor for chl-a concentration changes. Our analytical framework could provide a better way to accurately map the spatial distribution of chl-a concentration in complex river systems.

The ability of process-based biogeochemical models in estimating the gross primary productivity (GPP) of alpine vegetation is largely hampered by the poor representation of phenology and insufficient calibration of model parameters. The development of remote sensing technology and the eddy covariance (EC) technique has made it possible to overcome this dilemma. In this study, we have incorporated remotely sensed phenology into the Biome-BGC model and calibrated its parameters to improve the modeling of GPP of alpine grasslands on the Tibetan Plateau (TP). Specifically, we first used the remotely sensed phenology to modify the original meteorological-based phenology module in the Biome-BGC to better prescribe the phenological states within the model. Then, based on the GPP derived from EC measurements, we combined the global sensitivity analysis method and the simulated annealing optimization algorithm to effectively calibrate the ecophysiological parameters of the Biome-BGC model. Finally, we simulated the GPP of alpine grasslands on the TP from 1982 to 2015 based on the Biome-BGC model after a phenology module modification and parameter calibration. The results indicate that the improved Biome-BGC model effectively overcomes the limitations of the original Biome-BGC model and is able to reproduce the seasonal dynamics and magnitude of GPP in alpine grasslands. Meanwhile, the simulated results also reveal that the GPP of alpine grasslands on the TP has increased significantly from 1982 to 2015 and shows a large spatial heterogeneity, with a mean of 289.8 gC/m2/yr or 305.8 TgC/yr. Our study demonstrates that the incorporation of remotely sensed phenology into the Biome-BGC model and the use of EC measurements to calibrate model parameters can effectively overcome the limitations of its application in alpine grassland ecosystems, which is important for detecting trends in vegetation productivity. This approach could also be upscaled to regional and global scales.

Automatic detection of buildings from very high resolution (VHR) satellite images is a current research hotspot in remote sensing and computer vision. However, many irrelevant objects with similar spectral characteristics to buildings will cause a large amount of interference to the detection of buildings, thus making the accurate detection of buildings still a challenging task, especially for images captured in complex environments. Therefore, it is crucial to develop a method that can effectively eliminate these interferences and accurately detect buildings from complex image scenes. To this end, a new building detection method based on the morphological building index (MBI) is proposed in this study. First, the local feature points are detected from the VHR remote sensing imagery and they are optimized by the saliency index proposed in this study. Second, a voting matrix is calculated based on these optimized local feature points to extract built-up areas. Finally, buildings are detected from the extracted built-up areas using the MBI algorithm. Experiments confirm that our proposed method can effectively and accurately detect buildings in VHR remote sensing images captured in complex environments.