Forest-canopy closure (FCC) reflects the coverage of the forest tree canopy, which is one of the most important indicators of forest structure and a core parameter in forest resources investigation. ...In recent years, the rapid development of UAV LiDAR and photogrammetry technology has provided effective support for FCC estimation. However, affected by factors such as different tree species and different stand densities, it is difficult to estimate FCC accurately based on the single-tree canopy-contour method in complex forest regions. Thus, this study proposes a method for estimating FCC accurately using algorithm integration with an optimal window size for treetop detection and an optimal algorithm for crown-boundary extraction using UAV LiDAR data in various scenes. The research results show that: (1) The FCC estimation accuracy was improved using the method proposed in this study. The accuracy of FCC in a camphor pine forest (Pinus sylvestris var. mongolica Litv.) was 89.11%, with an improvement of 6.77–11.25% compared to the results obtained from other combined conditions. The FCC accuracy for white birch (White birch platyphylla Suk) was about 87.53%, with an increase of 3.25–8.42%. (2) The size of the window used for treetop detection is closely related to tree species and stand density. With the same forest-stand density, the treetop-detection window size of camphor pine was larger than that of white birch. The optimal window size of camphor pine was between 5 × 5~11 × 11 (corresponding 2.5~5.5 m), while that of white birch was between 3 × 3~7 × 7 (corresponding 1.5~3.5 m). (3) There are significant differences in the optimal-canopy-outline extraction algorithms for different scenarios. With a medium forest-stand density, the marker-controlled watershed (MCW) algorithm has the best tree-crown extraction effect. The region-growing (RG) method has better extraction results in the sparse areas of camphor pine and the dense areas of white birch. The Voronoi tessellation (VT) algorithm is more suitable for the dense areas of camphor pine and the sparse regions of white birch. The method proposed in this study provides a reference for FCC estimation using high-resolution remote-sensing images in complex forest areas containing various scenes.
Due to the small size, variety, and high degree of mixing of herbaceous vegetation, remote sensing-based identification of grassland types primarily focuses on extracting major grassland categories, ...lacking detailed depiction. This limitation significantly hampers the development of effective evaluation and fine supervision for the rational utilization of grassland resources. To address this issue, this study concentrates on the representative grassland of Zhenglan Banner in Inner Mongolia as the study area. It integrates the strengths of Sentinel-1 and Sentinel-2 active-passive synergistic observations and introduces innovative object-oriented techniques for grassland type classification, thereby enhancing the accuracy and refinement of grassland classification. The results demonstrate the following: (1) To meet the supervision requirements of grassland resources, we propose a grassland type classification system based on remote sensing and the vegetation-habitat classification method, specifically applicable to natural grasslands in northern China. (2) By utilizing the high-spatial-resolution Normalized Difference Vegetation Index (NDVI) synthesized through the Spatial and Temporal Non-Local Filter-based Fusion Model (STNLFFM), we are able to capture the NDVI time profiles of grassland types, accurately extract vegetation phenological information within the year, and further enhance the temporal resolution. (3) The integration of multi-seasonal spectral, polarization, and phenological characteristics significantly improves the classification accuracy of grassland types. The overall accuracy reaches 82.61%, with a kappa coefficient of 0.79. Compared to using only multi-seasonal spectral features, the accuracy and kappa coefficient have improved by 15.94% and 0.19, respectively. Notably, the accuracy improvement of the gently sloping steppe is the highest, exceeding 38%. (4) Sandy grassland is the most widespread in the study area, and the growth season of grassland vegetation mainly occurs from May to September. The sandy meadow exhibits a longer growing season compared with typical grassland and meadow, and the distinct differences in phenological characteristics contribute to the accurate identification of various grassland types.
The identification and restoration of damaged ecosystems are key to achieving ecological conservation and sustainable. Hainan Island is experiencing a serious crisis of biodiversity and habitat ...degradation. Therefore, its ecological conservation has become a priority and challenge for China. This study aimed to construct a multi-level ecological security pattern (ESP) based on the synergy of multiple ecosystem service functions and identify important ecological elements and ecological restoration areas. Based on the InVEST model, the circuit theory model, and a series of GIS spatial analysis methods, the importance of ecosystem functions (biodiversity maintenance, water conservation, carbon sequestration, and soil conservation) was evaluated, and ecological sources, ecological corridors, ecological pinch points, and ecological barrier points were identified. The results are as follows: 1) The best habitats in Hainan Island were distributed in the central mountainous area with diverse ecosystems, with an area of 10982.5 km 2 , accounting for 34.25% of the total suitable habitats. Low-level habitats are mainly distributed on tableland and coastal zones. Human disturbance is the direct cause of landscape patch fragmentation in low-level habitat areas. 2) A total of 65 large ecological sources with a total area of 8238.23 km 2 were identified, which were concentrated in the biodiversity and water conservation areas in the central part of the island. 3) Crucial areas in Hainan Island mainly comprised forests and water bodies. Ecological corridors radiated across the entire area in the form of a spider web and connected all important ecological patches, including 138 ecological corridors (73 primary ecological corridors and 65 secondary ecological corridors), 222 ecological pinch points, and 198 ecological barrier points. In addition, the identified areas for restoration are primary areas in urgent need of protection and restoration. In general, the ecological pinch points are natural conservation areas supplemented by anthropogenic restoration, and the ecological barrier points demand equal attention for anthropogenic restoration and nature conservation. The ecosystem protection plan developed in this study will enrich the theoretical achievements of territorial spatial ecological planning in Hainan Island, and provides clear guidance for alleviating the contradiction between land use and economic development in Hainan Island.
•A useful method for vegetation degradation monitoring and assessment was introduced.•The improved NPP estimation method was suitable for sparse vegetation areas.•Driving forces were distinguished in ...a quantitative manner at the pixel scale.•Specific driving forces of human activities were analyzed.•The series of ecological engineering implemented have achieved remarkable effects.
Vegetation degradation is a direct distinguishing feature of land degradation in drylands and seriously affects the ecological balance and sustainable development of drylands. Existing assessment methods of vegetation degradation at the regional scale based on long-time-series data have many shortcomings, including coarse resolution and a diversity of vegetation indicators that are typically complex. In the present study, net primary productivity (NPP) was selected as a primary vegetation indicator. Taking Zhenglanqi in the Inner Mongolia Autonomous Region as the study area, a technical process for the assessment of vegetation degradation/regeneration and analysis of the associated driving forces was proposed at a medium–high resolution scale. First, integrating the high spatial resolution advantage of Landsat data and the high temporal resolution advantage of moderate resolution imaging spectroradiometer (MODIS) data, a time series annual NPP dataset from 2001 to 2016 at 30 m resolution was constructed by applying the spatial and temporal adaptive reflectance fusion model (STARFM) and improved Carnegie–Ames–Stanford Approach (CASA) model. Then, the areas of vegetation degradation and regeneration from 2001 to 2016 were identified and determined by annual NPP trend analysis using the Sen + Mann-Kendall method. Overall, vegetation in Zhenglanqi was generally characterized by regeneration, with the degraded and recovered areas being 0.8% and 11.4%, respectively. Nearly 20% of the areas covered by sandy land showed a significant trend of vegetation regeneration, which indicated that the sand-drifting control measures introduced in the Otindag sandy land and its surroundings had achieved significant results. Next, the driving forces of vegetation degradation and regeneration in Zhenglanqi were distinguished over the past 16 years through proposed multiple and partial regression methods. Human activities were the main driver of vegetation degradation and regeneration (68.6% for degradation, 59.9% for regeneration), and the combination of human activities and climate variation also played an important role in vegetation degradation and regeneration (29.3% for degradation, 39.4% for regeneration), which indicated that the significant improvement of vegetation was related to the implemented eco-restoration projects, and visually proved by comparison of high resolution satellite images taking in different years. This research is expected to provide technical support and scientific reference data for ecological protection and land management in the study area, as well as the development of ecological engineering strategies in the drylands of northern China.
Drylands, as highly vulnerable ecosystems, support environmental functions and human well-being. Nevertheless, widespread land degradation and desertification present significant global and regional ...environmental challenges, with limited consensus on their area and degree. This study used time-series vegetation productivity and meteorological data from 2000 to 2020 to quantify global land degradation trends and driving factors in drylands. The results show a notable restoration of land degradation in drylands worldwide, with the area of improved land exceeding the degraded area by 1.4 times, although the threat of degradation persists. India and China emerge as pioneers in effective land improvement strategies, offering valuable experiences for other regions. Combined effects, as quantitatively distinguished by our established model, dominate the degradation and improvement processes. Notably, human activities play a decisive role in influencing land degradation trends, with the potential for either exacerbation or reversal. This study provides new perspectives on environmental health and human activities from global and regional observations. Finally, our research provides scientific support for desertification control and contributes to the overall advancement of the SDGs globally.
•A climate change-considered land degradation assessment method was developed.•Global drylands show significant improvement trend in land degradation over 20 years.•Climate change and human actions jointly drive land degradation shifts.•Potential degradation challenges persist behind the positive improvement trend.•Ecological restoration and agrarian reform can reverse the land degradation trend.
•An improved NPP conversion method was applied for grass yield estimation.•Phenological information of grassland vegetation growth was finely captured.•Optimum temperature of the temperature stress ...was redefined in the CASA model.•Improvements in the lagged effect of vegetation growth to temperature were noted.
Grass yield (GY) is a critical component of the comprehensive analysis of the grass–livestock balance in grassland. Net primary productivity (NPP) conversion methods, such as the Carnegie–Ames–Stanford approach (CASA) model, are an important tool for remote-sensing-based estimations of GY. However, the application of such approaches is limited by the simplification of key vegetation growth processes. In this study, we integrated high spatial and temporal resolution normalized difference vegetation index (NDVI) data collected from Gaofen-6 (GF-6) and the Moderate Resolution Imaging Spectroradiometer (MODIS), respectively, in 2020 with the climatic characteristics of grassland vegetation to derive a reasonable expression of the optimum temperature. We then improved the CASA model for the accurate estimation of GY for six different grassland types in Zhenglan Banner (sandy sparse forest grassland, sandy shrub grassland, sandy meadow, low hill steppe, gently sloping steppe, and lowland meadow) at high spatial and temporal resolution. The model estimations were evaluated using field data. The results reveal that adopting the optimum temperature to incorporate vegetation growth characteristics achieves a better theoretical basis and minimizes the influence of anomalous NDVI maxima compared with the original CASA model. This largely avoids the influence of the lagged response of grassland vegetation growth to temperature. The developed GY model has strong applicability, and the correlation between the measured and estimated GY before and after optimization reached 0.75. Moreover, the overall estimation accuracy was improved by nearly 15%. The spatial distribution of GY in Zhenglan Banner was found to be similar to the spatial distribution of grassland types with obvious seasonal differences, and summer was the critical period for GY, accounting for more than 80% of growth. The proposed model aims to provide scientific and technical guidance for the regulation of grassland resources and reasonable grazing utilization in Northern China.
Overgrazing directly leads to grassland degradation, which is a serious constraint to the sustainable development of animal husbandry. In drylands, grassland biomass is highly heterogeneous in space ...and time. It is difficult to achieve sustainable utilization of grassland resources by focusing only on the average annual carrying capacity assessment obtained from grass yield. Here, we proposed a novel approach for assessing grassland carrying capacity, taking Zhenglan Banner (County) in Inner Mongolia as the study area. First, monthly grass yield at 30 m spatial resolution was estimated, derived from Carnegie–Ames–Stanford Approach (CASA) model and spatial and temporal adaptive reflectance fusion model (STARFM). Then, based on the degree of sand mobility and degradation condition of typical steppe, the utilization patterns for sandy land and typical steppe in different grazing seasons were developed separately to obtain available grass yield. Finally, the carrying capacity at the Gacha (Village)-scale was estimated and the current livestock carrying status was evaluated to facilitate the grassland refined management. In Zhenglan Banner, the carrying capacity was 237.46 thousand cattle-units in summer. The grassland resources are being overgrazed, with an overload rate of 19.32%. At Gacha-scale, the maximum reasonable stock density was ranged from 0.06 cattle-unit/ha to 0.42 cattle-unit/ha. Fifty-one Gachas exhibited livestock overload. This study is expected to provide technical support and scientific reference data for ecological conservation and grassland management in the study area, as well as in dryland pastoral areas of northern China.
The determination of catalytically active sites is crucial for the design of efficient and stable catalysts toward desired reactions. However, the complexity of supported noble metal catalysts has ...led to controversy over the locations of catalytically active sites (e.g., metal, support, and metal/support interface). Here we develop a structurally controllable catalyst system (Pd/SBA-15) to reveal the catalytic active sites for the selective hydrogenation of ketones to alcohol using acetophenone hydrogenation as model reaction. Systematic investigations demonstrated that unsupported Pd nanocrystals have no catalytic activity for acetophenone hydrogenation. However, oxidized Pd species were catalytically highly active for acetophenone hydrogenation. The catalytic activity decreased with the decreased oxidation state of Pd. This work provides insights into the hydrogenation mechanism of ketones but also other unsaturated compounds containing polar bonds, e.g., nitrobenzene, N-benzylidene-benzylamine, and carbon dioxide.
Field ridges are commonly viewed as the stable semi-natural habitats for maintaining plant diversity in the agricultural landscape. The high plant diversity could further support higher animal ...diversity. But following the adoption of well-facilitated farmland construction measures in China, many field ridges have been disproportionately neglected or destroyed. Empirical studies delineating the relationships between plant and animal diversity in these field ridges in the paddy landscape remain scant, especially in China, which has the most rice production. A two-year field ridge evaluation was conducted in the Chengdu Plain area, covering 30 paddy landscapes. This investigation scrutinizes the shape attributes of field ridges, their plant diversity, and the associated animal α-diversity and community compositions, including spiders, carabids, birds, frogs, and rice planthoppers. In the results of Pearson’s correlation analysis, a significant inconsistent correlation was observed between plant diversity and animal diversity. The analysis of community structure heterogeneity also revealed no correspondence for species composition between plant and animal communities (i.e., spiders, carabids, and birds), while the non-metric multidimensional scale analysis indicated a substantial difference in the species composition of spiders or plants even within the same field ridge between 2020 and 2021. We argue that the implementation of intensive management practices in paddy landscapes, such as machine ploughing and harvesting and herbicide spraying with drones, leads to a scarcity of stable animal and plant communities in field ridges. Therefore, besides retaining these field ridges in paddy landscapes, maintaining the long-term stable ridges by refraining from herbicide spraying or artificial weeding, as well as avoiding winter wheat cultivating in field ridges, will contribute to protecting biodiversity of field ridges as semi-natural habitats.
Liver iron overload can induce hepatic expression of bone morphogenic protein (BMP) 6 and activate the BMP/SMAD pathway. However, serum iron overload can also activate SMAD but does not induce BMP6 ...expression. Therefore, the mechanisms through which serum iron overload activates the BMP/SMAD pathway remain unclear. This study aimed to clarify the role of SMURF1 in serum iron overload and the BMP/SMAD pathway.
A cell model of serum iron overload was established by treating hepatocytes with 2 mg/mL of holo-transferrin (Holo-Tf). A serum iron overload mouse model and a liver iron overload mouse model were established by intraperitoneally injecting 10 mg of Holo-Tf into C57BL/6 mice and administering a high-iron diet for 1 week followed by a low-iron diet for 2 days. Western blotting and real-time PCR were performed to evaluate the activation of the BMP/SMAD pathway and the expression of hepcidin.
Holo-Tf augmented the sensitivity and responsiveness of hepatocytes to BMP6. The E3 ubiquitin-protein ligase SMURF1 mediated Holo-Tf-induced SMAD1/5 activation and hepcidin expression; specifically, SMURF1 expression dramatically decreased when the serum iron concentration was increased. Additionally, the expression of SMURF1 substrates, which are important molecules involved in the transduction of BMP/SMAD signaling, was significantly upregulated. Furthermore,
analyses confirmed that SMURF1 specifically regulated the BMP/SMAD pathway during serum iron overload.
SMURF1 can specifically regulate the BMP/SMAD pathway by augmenting the responsiveness of hepatocytes to BMPs during serum iron overload.
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