Low Vegetation Cover Research Articles

Quantitative Analysis of Tidal Creek Evolution and Vegetation Variation in Silting Muddy Flats on the Yellow Sea

Coastal wetland ecosystems around the world are facing serious challenges due to rapid economic development, climate change, and sea level rise. These factors have a great influence on the tidal creek network and vegetation ecosystem. Accordingly, based on long-term time-series remote sensing images, the evolution characteristics of tidal creeks and vegetation in silting muddy flats on the Yellow Sea were analyzed, and different quantitative methods were used to describe the relationship between tidal creeks and vegetation. The results showed that the total number of tidal creeks exhibited a downward trend, while the number of small creeks increased over time. The total length of the tidal creeks decreased at a rate of 16.1 km per year during the study period. The length of three-grade tidal creeks, the patch area ratio of Suaeda salsa, and a low vegetation coverage had a great influence on the average return flow length (LOP). LOP was negatively correlated with the patch area ratio of S. salsa, but positively correlated with the reclamation area, both significantly. With the increase in the patch area ratio of S. salsa, the total length of the tidal creeks increased by 12.95 km, and LOP decreased by 35.35 m.

Revealing the Environmental Characteristics of Towns in the Middle Himalayas Using a Geographic Information System and Self-Organizing Map

Through long-term interactions with the natural environment, the ethnic groups in the mid-Himalayas have formed unique urban environmental characteristics. Effectively identifying urban environmental characteristics is a prerequisite for implementing sustainable urban management strategies. This study took 194 towns in the mid-Himalayan as the research objects. GIS was used to statistically analyze the terrain, climate, soil, and other environmental characteristics of the towns. The SOM (Self-organizing map) method was used to classify the comprehensive environmental characteristics of the towns. The results show that the main urban environmental characteristics in this area are low-altitude towns account for a large proportion, gentle-slope towns account for a small proportion, rainfall is mainly 125–265 mm, vegetation cover is dominated by high-coverage towns, mainly distributed in central and southern parts, the soil is dominated by embryonic soil and alluvial soil. The SOM method overcomes the subjectivity and low degree of automation in traditional research on urban environmental characteristics using threshold indicator methods or feature interpretation methods. Based on environmental characteristics, the towns were divided into six categories, and the classification results showed a distinct north–south zonal distribution pattern. There were significant differences in the environmental characteristics of towns in different clusters, such as the towns in cluster 5 had high altitudes, low rainfall, and low vegetation coverage, while the towns in cluster 2 had low altitudes, high rainfall, and high vegetation coverage. Finally, based on the SOM clustering results, governance strategies were proposed for towns in different clusters to cope with climate and environmental changes and promote sustainable development in the mid-Himalayan.

Effect of time-variant NDVI on landside susceptibility: A case study in Quang Ngai province, Vietnam

Abstract Normalized difference vegetation index (NDVI) is a conditioning factor that significantly affects slope stabilization, as the low vegetation coverage can create conducive conditions for landslide occurrence. In previous studies, NDVI was often calculated from long-term average NDVI maps or specific yearly NDVI maps. However, this approach is unsuitable due to the time-varying nature of these data, influenced by numerous factors, including human activities. To solve this problem, this study uses NDVI as a time-varying factor. NDVI maps are generated from Sentinel 2 and Landsat_8 imagery at the onset of each rainy season between 2015 and 2020 in the mountainous region of Quang Ngai Province. Moreover, the landslide events that occurred within this 5-year period (2016–2020), along with a set of conditioning factors, are utilized to develop landslide susceptibility models based on three algorithms: logistic regression, support vector machine, and extreme gradient boosting (XGBoost). The obtained results demonstrate that using time-varying NDVI shows superior performance compared to using only NDVI from 2015. The outcomes also indicate that XGBoost is the most effective model. Selecting suitable NDVI maps can improve the predictive accuracy of landslide susceptibility mapping.

Available Forage and the Conditions for Avoiding Predation of the Siberian Roe Deer (Capreolus pygargus) in the Lesser Xing’an Mountains

Our study focused on quantifying available forage and the conditions for avoiding predation provided within the home ranges of Siberian roe deer (Capreolus pygargus). We conducted transect surveys in both winter and summer–autumn home ranges of the Siberian roe deer in the Tieli Forestry Bureau of the Lesser Xing’an Mountains. Our results revealed significant differences: (1) In terms of the quantity and quality of available forage, the summer–autumn home range had substantially more available forage than the winter home range, with meadows and cornfields showing the highest edible biomass in each, respectively. In terms of forage quality, there were differences in hemicellulose, cellulose, and lignin content between the two ranges. (2) In terms of the conditions for avoiding predation, the winter home range had lower vegetation coverage and greater visibility, making escape strategies more viable. In contrast, the summer–autumn home range had denser vegetation and limited visibility, making hiding strategies more viable. Our study offers comprehensive insights into the available forage and the conditions for avoiding predation, which is crucial for wildlife conservation strategies and habitat management in the region, as it directly informs strategies that address the seasonal forage requirements and predation avoidance of these deer, ultimately enhancing their prospects for survival in the area.

Quantitative Analysis of Climate Variability and Human Activities on Vegetation Variations in the Qilian Mountain National Nature Reserve from 1986 to 2021

Rapid climate variability and intense human activities generate obvious impacts on the Qilian Mountains ecosystem. The time series of fractional vegetation coverage (FVC) from 1986 to 2021 were used to quantify the impact of climate variability and human activities on vegetation variations in the Qilian Mountain National Nature Reserve (QMNNR), using 3147 land satellite images based on the Google Earth Engine cloud platform. The contributions of climate variability and human activities to FVC were quantified using multiple regression residual analysis. Partial correlation and correlation methods were used to quantify the impact of temperature, precipitation, and human activity footprints on FVC. The results showed that from 1986 to 2021, the increase rate of FVC was 1.7 × 10−3 y−1, and the high vegetation coverage of the FVC was mainly distributed in the southeastern part of the reserve. In contrast, the low vegetation coverage was mainly distributed in the northwest part of the reserve. The Mann–Kendall mutation test found that the year of 2009 was the year of the mutation. The growth rate of FVC from 2010 to 2021 was greater than that from 1986 to 2009. In addition, climate variability and human activities exhibited a remarkable spatial heterogeneity in FVC changes. Climate variability and human activities contributed 49% and 51% to the increase in FVC in the reserve, respectively, and the contribution of human activities was greater than that of climate variability. The warming and humidification phenomena in the reserve were obvious. However, precipitation was the dominant factor affecting the dynamic changes in FVC. This study improves our understanding of the response of vegetation dynamics to the climate and human activities in the QMNNR.

Porous fiber materials can alleviate the risk of farmland drought and flooding disasters and prompt crop growth.

Floods and droughts on farmland seriously damage agricultural production. Porous fiber materials (PFM) made from mineral rocks have high porosity, permeability, and water retention and are utilized widely in green roofs and agricultural production. Therefore, studying the impact of PFM on the improvement of farmland is of great importance for soil and water conservation. We set 64 extreme rainfalls to analyze the impact of PFM on soil water content (SWC), runoff, nutrient loss, microorganism, and plant growth. The results showed that PFM can effectively reduce runoff and improve soil water distribution, and enhance the soil water holding capacity. Furthermore, PFM reduced the loss of nitrogen and phosphorus by 18.3% to 97% in the runoff, and the soil erosion of summer corn was more strongly influenced by lower vegetation cover, compared with winter wheat. Finally, when PFM was buried in the soil, the wheat yield increased by -6.7%-20.4%, but the corn yield in some PFM groups decreased by 5.1% to 42.5% under short-duration irrigation conditions. Our study emphasizes that the effectiveness of PFM depends mainly on the following: First, PFM with high porosity can increase soil water holding capacity and timely replenish the water lost from the surrounding soil. Second, PFM with high permeability can increase infiltration during rainfall and decrease runoff and nutrient loss, reducing the risk of farmland flooding and pollution. Finally, PFM consists of gold ions and alkali metal oxides, which can stabilize agglomerates and improve soil enzyme activity, thereby increasing the relative abundance of some microbial strains and promoting crop growth. However, when the rainfall amount was low or PFM volume was large, PFM could not store water sufficiently during rainfall, which seriously reduced the maximum saturated moisture content and water absorption performance. Meanwhile, the PFM could not release water in time and replenish the soil water deficit, which increased drought risk. In conclusion, the appropriate volume of PFM and irrigation system may enhance soil water storage capacity, minimize agricultural pollution, and promote crop production.

Characterization and Remediation Potential of Sorghum and Rice Straw-Derived Biochars on Incubated Spent-Oil Contaminated Soil

The volume and spread of spent lubricants that are indiscriminately let into the environment in developing countries are prohibitive for soil health and productivity, adversely altering soil structure, permeability and microbiota. These result to loss of arable lands and low vegetation cover, thereby contributing significantly to food insecurity and global warming. Biochars possess sustainable soil amendment potentials that depend on the choice of feedstocks. This study used suitable analytical techniques to characterize biochars derived from sorghum and rice straw after slow pyrolysis at 550°C for three hours and investigated their effects on the physicochemical properties of spent oil-contaminated soil in an incubation experiment. Both sorghum biochar (SB) and rice biochar (RB) have pH in the alkaline range (˃ 8.0), similar O/C ratio (0.24), and significant proportions of carbon (53.87–57.57%). Scanning electron microscopy of SB and RB surfaces revealed presence of porous structures. Fourier Transform Infrared Spectroscopy revealed presence of carboxyl, hydroxyl, halogens, and sulphur on the surfaces of SB and RB which are responsible for heavy metal adsorption. Compared with control, increasing biochar amendment at 1, 2 and 3% significantly increased the porosity, water holding capacity and pH of the soil. Besides, soil Fe increased while the extractable content of heavy metals decreased. From this study, the properties of SB and RB and corresponding application in spent oil-contaminated soil indicate their suitability for soil enrichment and amendment.

Extension of the revised wind erosion equation (RWEQ) to calculate grassland wind erosion rates based on the 137Cs tracing technique

The commonly used wind erosion models, including the Revised Wind Erosion Equation (RWEQ), are mainly based on data from loose soils, for which the erodibility factor (EF) reflects the abundance of erodible aggregates, and cannot be applied to simulate erosion of compacted soils such as some grassland soils. Taking the Inner Mongolia Autonomous Region in northern China as the study area, we used the 137Cs tracing technique to estimate the soil loss of grassland by wind erosion from 1963 to 2021, and used the results as criteria to verify the wind erosion rate (WER) predicted by RWEQ for the same period. We found that RWEQ accurately calculated the WER of cultivated farmland, but overestimated grassland WER. We believe that the main reason is that the equation did not consider the impact of soil compaction (SC) on EF, since the calculation methods for the weather factor, vegetation factor, surface roughness factor, and soil crust factor in RWEQ are applicable for grasslands. Therefore, we used the 137Cs tracing results to extrapolate the grassland EF while keeping the climate, soil crust, vegetation cover, and roughness factors constant, and combined SC and the proportion of aggregates smaller than 0.84 mm in diameter to develop an empirical equation for grassland EF. Compared with the original model, the extended model (RWEQext) that included the factor of SC more accurately estimated the WER of compacted grassland soil and could be applied to the whole study area. The RWEQext results showed that tolerable and slight levels of wind erosion dominated the grassland and gobi surfaces in the study area, whereas moderate wind erosion occurred in grasslands with sparse vegetation cover, and severe, very severe, and destructive wind erosion mainly occurred on loose surfaces such as sandy land with low vegetation cover.

Multi-scale analysis of surface thermal environment in relation to urban form: A case study of the Guangdong-Hong Kong-Macao Greater Bay Area

With the expansion of cities and urban agglomerations, the impact of urban form on the urban thermal environment exhibits notable scale variations. Moreover, the synergistic effect between land surface temperature (LST) and urban heat island intensity (UHII) in urban areas with strong spatial heterogeneity is unclear. Here we explored the spatiotemporal variations of LST and surface UHII (SUHII) over the Guangdong-Hong Kong-Macao Greater Bay Area (GBA) that includes cities of various urban form settings manifested by the local climate zone (LCZ) at multi-scale. The results confirm the LST and LCZ data obtained can effectively capture detailed thermal environment and urban form characteristics for large urban agglomeration (i.e., GBA). Our findings revealed the interactions of LST and SUHII have significant scale disparities. Regionally, the LST and SUHII exhibited strong spatial correlation in built-up area, but showed opposite variation trend in natural areas. At the city scale, the consistency of LST and SUHII is weak in cities with higher vegetation coverage, while strong in cities with lower vegetation coverage. Locally, LST and SUHII exhibited varied interactions in different LCZs. Finally, we proposed corresponding planning recommendations oriented by thermal environment optimization and sustainable development for GBA based on the conclusions.

El Niño–Southern Oscillation (ENSO)-driven hypersedimentation in the Poechos Reservoir, northern Peru

Abstract. Although extreme El Niño events (EENEs) have always impacted hydrological anomalies and sediment transport in South America, their intensification by global warming and their association with changes in human activities and land cover after humid periods may lead to the acceleration of sediment transfers in river systems and dam reservoirs. This situation may threaten soil and water resources in arid and semiarid regions highly dependent on water originating from large dams. In this study, we investigated the sediment sequence accumulated in the Poechos Reservoir (northern Peru) and provided a retrospective reconstruction of the interactions of El Niño–Southern Oscillation (ENSO), agricultural practices and vegetation cover changes with sediment dynamics (1978–2019). To this end, a sediment core was dated and characterized by physical and chemical analyses (e.g., scanner tomography, X-ray fluorescence, particle size analysis) to estimate the evolution of sedimentation rates and changes in sediment sources during the last 5 decades. Sediment tracing results indicated the occurrence of changes in sediment sources associated with positive and negative phases of the Eastern Pacific index with a greater contribution of the lowland dry-forest area in comparison to that of the Andean area to sediment during the El Niño events (mean contribution of 76 %; up to 90 % during the coastal El Niño events (CENEs) of 2016–2017). This source contribution was mostly controlled by the stationary rainfall occurring during the EENEs in the lowland dry-forest area characterized by a low vegetation cover. Overall, after an extreme phase of ENSO, like after the EENE 1982–1983, the normal discharges and persistent sediment supplies from the middle- and upper-catchment parts led to river aggradation and the storage of substantial amounts of sediment in alluvial plains. In the absence of a significant EENE between 1983 and 1997, the large volume of sediment stored in the alluvial plains was exported by the EENE 1997–1998 resulting in an increase in sedimentation rate of 140 % after 1997 with a significant aggradation of the deltaic zone of the reservoir. In addition to the impact of extreme climate events on sediment dynamics, the development of agriculture along the riverine system after an extreme phase of ENSO increased the availability of sediments in the main channel of the rivers, easily transported by the next EENE. This study suggests that intensification of human activities associated with a higher frequency of extreme rainfall events amplified the quantity of sediment transported by the river system, which will significantly decrease the lifespan of the reservoir, which is essential to meeting the freshwater demands of the farmers and the populations living in this arid and semiarid region.

Dynamic monitoring of vegetation coverage in weibei dry plateau based on remote sensing

Taking Fu County, a typical area of Weibei dry plateau, as the research object, the normalized difference vegetation index ( NDVI ) was calculated by using Landsat 8 OLI remote sensing image. On this basis, the vegetation coverage in the study area was estimated and graded according to the binary pixel model, and the dynamic changes of vegetation coverage in the study area from 2013 to 2017 were quantitatively analyzed. Results showed that the overall NDVI value in the study area increased from 2013 to 2017. The vegetation cover in the study area is dominated by extremely high vegetation cover. The coverage area of low, medium and high vegetation cover decreases, and the coverage area of extremely high and extremely low vegetation cover increases. The coverage area of high vegetation and extremely high vegetation cover accounts for more than 75% of the study area. The study area showed a transfer trend of extremely low vegetation→low vegetation→medium vegetation→high vegetation coverage. The vegetation coverage generally developed to a good trend, but there was also a transfer of high vegetation coverage to medium vegetation coverage. The areas with the greatest changes in the study area are mainly concentrated in the northwest and near the southern Damagou, and the high NDVI area of Ziwuling National Nature Reserve has moved eastward and narrowed. Accuracy assessment indicates that the dynamic monitoring using the fused image time series produces results with relatively high accuracy. Bangladesh J. Bot. 52(2): 479-486, 2023 (June) Special

Dynamic monitoring of vegetation coverage in weibei dry plateau based on remote sensing

Taking Fu County, a typical area of Weibei dry plateau, as the research object, the normalized difference vegetation index ( NDVI ) was calculated by using Landsat 8 OLI remote sensing image. On this basis, the vegetation coverage in the study area was estimated and graded according to the binary pixel model, and the dynamic changes of vegetation coverage in the study area from 2013 to 2017 were quantitatively analyzed. Results showed that the overall NDVI value in the study area increased from 2013 to 2017. The vegetation cover in the study area is dominated by extremely high vegetation cover. The coverage area of low, medium and high vegetation cover decreases, and the coverage area of extremely high and extremely low vegetation cover increases. The coverage area of high vegetation and extremely high vegetation cover accounts for more than 75% of the study area. The study area showed a transfer trend of extremely low vegetation→low vegetation→medium vegetation→high vegetation coverage. The vegetation coverage generally developed to a good trend, but there was also a transfer of high vegetation coverage to medium vegetation coverage. The areas with the greatest changes in the study area are mainly concentrated in the northwest and near the southern Damagou, and the high NDVI area of Ziwuling National Nature Reserve has moved eastward and narrowed. Accuracy assessment indicates that the dynamic monitoring using the fused image time series produces results with relatively high accuracy. Bangladesh J. Bot. 52(2): 479-486, 2023 (June) Special

Macroinvertebrate traits in Arctic streams reveal latitudinal patterns in physiology and habits that are strongly linked to climate

IntroductionArctic freshwater ecosystems are undergoing rapid environmental transformation because of climate change, which is predicted to produce fundamental alterations in river community structure and function.MethodsWe explored how climate change affects benthic invertebrate communities of Arctic streams by examining patterns of their biological traits along latitudinal and climatic gradients in eastern North America (Canada) and northwestern Europe (Sweden, Norway).ResultsDespite differences in taxonomic composition between continents, we identified similarities in the functional trait niche (FTN) of predominant macroinvertebrate taxonomic groups. Trait composition differed by latitude in eastern Canada, with a predominance of cold-tolerant taxa, tubular body shape, and cased and attached habits at the highest latitudes. Differences in trait composition were evident among ecoregions in Europe, with trait dominance at the highest latitudes that was comparable to North America. There was a similar increase in the relative abundance of cold tolerance and tubular body shape and a decrease in obligate shredders and trait richness with decreasing temperatures across both continents.DiscussionThese patterns are indicative of FTNs that include physiological traits and habits that are advantageous for the low temperatures, short ice-free period, and low riparian vegetation cover at the highest latitudes. We predict that climate change will lead to an increase in functional diversity at high latitudes, as organisms with trait modalities that are currently only found at lower latitudes move northward. However, this change in trait composition will be mediated by the effect of spatial connectivity on dispersal ability, with slower change occurring on Arctic islands. These findings can support modelling of future change in Arctic freshwater assemblages in response to ongoing climate change.

Assessing the Relationship between Ecological Water Demand of Haloxlon ammodendron and Its Wind Erosion Prevention Effect

Desert vegetation in the outer transition zone of an arid oasis serves as a protective barrier against wind and sand, safeguarding the oasis ecosystem. However, intensive agricultural water usage within the oasis has led to water depletion, posing a threat to the survival and growth of desert vegetation, as well as the associated increase in wind and sand phenomena. To ensure the sustainable distribution of water resources and maintain the stability of the oasis peripheral ecosystem, this study aimed to investigate the relationship between the ecological water demand of desert vegetation and its effectiveness in preventing wind erosion. Through a combination of field sample tests, field pit tests, and data analysis, this research focused on Haloxlon ammodendron, the most prevalent species on the oasis periphery, to explore the intricate relationship between its ecological water demand and resistance to wind erosion. The results showed that medium-vegetation-coverage soils exhibited a higher soil moisture content (7.02%) compared to high-vegetation-coverage soils (1.57%) and low-vegetation-coverage soils (3.41%). As the soil water content decreased, the growth rate of H. ammodendron’s plant height, new branches, and crown width decelerated. The ecological water requirement of H. ammodendron during its growth period was 70.95 mm under medium-vegetation-coverage conditions, exhibiting a significant increase of 14.6% and 12.3% compared to high- and low-vegetation-coverage conditions, respectively. Meanwhile, H. ammodendron exhibits remarkable wind erosion prevention effects in moderate coverage conditions, resulting in a significant reduction in surface sand collection and sand transport by 53.15% and 51.29%, respectively, compared to low vegetation coverage; however, no significant difference was observed when compared to high vegetation coverage. The SEM model results revealed that soil water content had an indirect effect on sand transport (R2 = 0.90) and sand collection (R2 = 0.96) through three pathways of action, namely: volatile water content–crown growth rate–wind speed–sediment discharge; volatile water content–plant height growth rate–vegetation coverage–wind speed–sediment discharge; and volatile water content–plant height growth rate–vegetation coverage–sediment accumulation. This study provides valuable insights for the scientific formulation and implementation of strategies aimed at protecting desert vegetation.

Assessment of the desertification sensitivity of Northwestern El Minya Governorate, Egypt using MEDALUS model

Desertification leads to a decline in land production, resulting from biophysical interaction and human factors with temporal and spatial changes. This paper aims to evaluate the desertification sensitivity using Mediterranean Desertification and Land Use (MEDALUS) approach in the Northwestern El Minya Governorate in Egypt. The study area is one of the promising and important areas for land reclamation and developmental projects. Four indicators; climate, vegetation, management, and soil, were used in this study. Landsat 8 (OLI) satellite image 2021 was processed to calculate NDVI index to assess vegetation quality index. Then, it was classified into land cover classes to calculate the management quality index. ASTERDEM satellite data and the climate data were used in the climate quality index. Seventy soil samples were collected and analyzed for chemical and physical properties to be used for the retrieval of soil quality index. These indicators were integrated and used as input criteria in the model of desertification sensitivity. The physiographic unit extraction indicated that significant landforms were included in the study area namely; Old wadi Sediments, Peniplain, old river terraces, Shoulders, Sand sheets, Rock outcrops, and Sand dunes, Erosional Plains, Hill and Plain out wash. The obtained results showed that the severely sensitive area to desertification was represented by 86.7 % of the study area. The main factors affecting the sensitivity were climate conditions (arid, semi-arid), low soil quality and management in addition to the low vegetation cover. Furthermore, about 3% of the study area was located in the moderate sensitive class while the low sensitive area exhibits 1.06 %. Present study supports decision makers to reduce the constraining environmental conditions.

Fire influences ant diversity by modifying vegetation structure in an Australian tropical savanna.

Fire is a dominant ecological force shaping many faunal communities globally. Fire affects fauna either directly, such as by killing individuals, or indirectly, such as by modifying vegetation structure. Vegetation structure itself also modulates fire frequency and intensity. As such, faunal responses to fire need to be seen through the lens of variable fire activity and vegetation structure. Here, we incorporate information on fire activity and vegetation structure to enhance an understanding of the response of ants to long-term (17-year) experimental fire treatments in an extremely fire-prone tropical savanna in northern Australia. A previous analysis revealed limited divergence in ant communities after five years of experimental fire treatment. Hence, we first investigated the extent to which ant communities diverged over a subsequent 12 years of treatment. We then assessed the relative contribution of fire treatment, cumulative fire intensity (fire activity) and woody cover to responses of ant species frequency of occurrence, richness and composition. We found that, even after 17 years, fire treatments explained little variation in any ant response variable. In contrast, woody cover was a strong predictor for all of them, while fire activity was a moderate predictor for abundance and richness. Ant species occurrence and richness increased in open habitats receiving higher levels of fire activity, compared with plots with higher vegetation cover experiencing low (or no) fire activity. Moreover, species composition differed between plots with high and low vegetation cover. Our findings provide experimental support to the principle that the effects of fire on fauna are primarily indirect, via its effect on vegetation structure. Furthermore, our results show that a 'uniform' fire regime does not have uniform impacts on the ant fauna, because of variability imposed by interactions between vegetation structure and fire activity. This helps explain why there is often a weak relationship between pyrodiversity and biodiversity, and it lessens the need for active management of pyrodiversity to maintain biodiversity. This article is protected by copyright. All rights reserved.

Spatiotemporal Dynamics of Land Use and Land Cover through Physical–Hydraulic Indices: Insights in the São Francisco River Transboundary Region, Brazilian Semiarid Area

This article presents a study on the spatiotemporal dynamics of land cover and use, vegetation indices, and water content in the semiarid region of Pernambuco, Brazil. This study is based on an analysis of satellite images from the years 2016, 2018, and 2019 using the MapBiomas platform. The results show changes in the predominant land cover classes over time, with an increase in the caatinga area and a decrease in the pasture area. An analysis of the vegetation indices (NDVI and LAI) indicated low vegetation cover and biomass in the study area, with a slight increase in the NDVI in 2018. An analysis of the Modified Normalized Difference Water Index (MNDWI) showed that the water content in the study area was generally low, with no significant variations over time. An increase in the water bodies, mainly due to the construction of a reservoir, was noted. The results of this study have provided important information for natural resource management in the region, including the development of strategies for the sustainable use and management of natural resources, particularly water resources, vegetation cover, and soil conservation.

Referencing of Continental‐Scale InSAR‐Derived Velocity Fields: Case Study of the Eastern Tibetan Plateau

AbstractThe wealth of Sentinel‐1 data in eastern Tibet allows to discuss whether InSAR‐derived velocity maps measure ground motion in the ITRF reference frame with sufficient accuracy for large‐scale tectonic applications. High elevation, moderate relief and low vegetation cover in eastern Tibet ensure reliable multi‐temporal InSAR results. We automatically process seven 1,200 km long ascending and descending orbits, divided into 2 or 3 overlapping segments along‐track. Linear phase ramps in range and azimuth are removed from interferograms. The ramps and the flattened interferograms are separately inverted into time series and analyzed. The ramps are modeled by their Solid Earth Tides (SET) contribution, seasonal variations, and a trend in time. SET oscillations are clearly visible in the ramp time series. Seasonal tidal amplifications of probable atmospheric origin are also evidenced. Ramp rates are shown to precisely quantify the plate motion of each segment in the ITRF reference frame. They are thus added back to the velocity maps before along‐track merging. Then, a simple referencing procedure implying only a constant and a tilt in azimuth adjusted for each track is constrained by horizontal GNSS data. It allows straightforward vertical and horizontal decomposition. The quality of the merged and referenced data sets can then be quantitatively assessed at 1 mm/yr by the differences between InSAR and GNSS velocities and by the InSAR residuals on track overlaps. The vertical velocity field is dominated at first order by the effect of permafrost degradation, while the horizontal velocity highlights strain accumulation across major strike‐slip faults in eastern Tibet.

Mapping the sensitivity of land degradation in the Ouergha catchment (Morocco) using the MEDALUS approach

Soil degradation is a global phenomenon affecting the productivity of agricultural land. Due to the low vegetation cover and the aggressive climate, Morocco presents a significant case of soil degradation through erosion and desertification. The Ouergha catchment is highly vulnerable to this scourge. The objective of this study was to assess the sensitivity of land to degradation in the Ouergha catchment area. The MEDALUS approach, widely used in the Mediterranean region, was used to assess the sensitivity of soils to degradation/desertification. This approach integrates four indicators that strongly influence this phenomenon (climate, soil, vegetation and human pressure). The results show that more than half of the study area has a medium sensitivity of land to degradation. The critical areas represent 16.2% and correspond to bare land characterized by steep slopes and absence of vegetation. Low sensitivity areas occupy a limited proportion of 21.9% and correspond to wet summits and conserved forest areas. Climate change could lead to a further increase in areas susceptible to degradation.

A Rapid and Easy Way for National Forest Heights Retrieval in China Using ICESat-2/ATL08 in 2019

Continuous and extensive monitoring of forest height is essential for estimating forest above-ground biomass and predicting the ability of forests to absorb CO2. In particular, forest height at the national scale is an important indicator reflecting the national forestry economic construction, environmental governance, and ecological balance. However, the lack of inventory data restricts large-scale monitoring of forest height to some extent. Conducting manual surveys of forest height for large-scale areas would be labor-intensive and time-consuming. The successful launch of the new generation of spaceborne light detection and ranging (LiDAR) (The Ice, Cloud, and Land Elevation Satellite-2/the Advanced Topographic Laser Altimeter System, ICESat-2/ATLAS) has brought new opportunities for national-scale forestry resource surveys. This paper explores a method to survey national forest canopy height from the new generation of ICESat-2/ATLAS data. In view of the sparse sampling and little overlap between repeated spaceborne LiDAR data, a strategy for assessing the overall change of canopy height for large scales is provided. Some spatially continuous ancillary data were used to assist ICESat-2/ATLAS data to generate a wall-to-wall (spatially continuous) forest canopy height map in China by using the machine learning approach and then quantifying the analysis of forest canopy height in various provinces. The results show that there is a good correlation between the model forest height and the verification data, with a root mean squared error (RMSE) of 3.30 m and a coefficient of determination (R2) of 0.87. This indicates that the method for retrieving national forest canopy height is reliable. There are some limitations in areas with lower vegetation coverage or complex topography which need additional filtering or terrain correction to achieve higher accuracy in measuring forest canopy height. Our analysis suggests that ICESat-2/ATLAS data can achieve the retrieval of national forest height at an overall level, and it would be feasible to use ICESAT-2/ATLAS products to estimate forest canopy height change for large-scale areas.