Low Vegetation Cover Research Articles

Effect of Check Dam on Sediment Load Under Vegetation Restoration in the Hekou-Longmen Region of the Yellow River

With years of vegetation restoration and check dam construction on the Loess Plateau, the sediment load of the middle reaches of the Yellow River have decreased sharply; however, the effects of check dam on this decrease of sediment load with such extensive vegetation restoration remains unclear. In order to further clarify the effects of check dam on sediment load reduction under vegetation restoration, we calculated vegetation coverage and check dam index based on multi-source remote sensing data, and calculated sediment reduction rate caused by human activities by Mann-Kendall statistical test and double cumulative curve, then established regression equations incorporating the check dam index and the sediment reduction rate using data from different geomorphic regions with different vegetation coverages. The results showed that sediment load in the Hekou-Longmen region and its 17 tributaries decreased significantly every year, and the change in sediment load could be divided into 3 typical periods: the base period (P1), the period mainly impacted by check dam construction (P2) and the period with comprehensive impact of check dam construction and vegetation restoration (P3). Compared with sediment load of the tributaries during P1, the sediment load decreased by 60.96% during P2 and by 91.76% during P3. Compared with the contribution of human activities to the reduction in sediment load in P2, the contribution of human activities in P3 increased significantly, while that of precipitation decreased slightly. The sediment reduction effect of check dams is greater in basins with low vegetation coverage than in basins with high vegetation coverage. There are differences in sediment reduction effect of vegetation restorations in different geomorphic regions, and the effect of vegetation restoration alone have certain upper limits. Such as, the upper limit of sediment reduction rate of vegetation restoration for rivers flowing through the sandstorm region is 47.86%. Hence, only combined the construction of check dam with vegetation restoration can it achieve more significant sediment reduction benefit and control soil erosion more effectively.

Changes in Reconstructed Soil Physicochemical Properties in an Opencast Mine Dump in the Loess Plateau Area of China.

Soil construction and revegetation are essential for ecological restoration in mining areas. The influence of vegetation on the horizontal and vertical distribution patterns of soil properties should be fully understood. However, most studies on reconstructed soils in mining areas only concentrate on the surface soil, without exploring the vertical variations in soil properties. Overall, this study aims to explore the potential mechanisms by which surface vegetation exerts some influence on the spatial distribution of soil physicochemical properties, and to provide some insight into revegetation and soil reclamation in mining areas. Descriptive statistics and one-way analysis of variance (one-way ANOVA) were employed to evaluate the differences in the soil physicochemical properties in horizontal and vertical directions under different land-use types in the south dump of Antaibao opencast mine in Pingshuo, Shanxi Province, China. The main results of this study are as follows: (1) In the horizontal direction, except for the strong variation (variation coefficient ≥ 100%) in soil organic matter (SOM) content at some depths, the degree of variation in other soil physicochemical properties at various depths was moderate or weak (variation coefficient < 100%). The soil physicochemical properties gradually remained constant after years of reclamation. In the vertical direction, the soil bulk density (SBD), soil porosity, SOM content, soil C/N ratio, soil total nitrogen (STN) content, soil available phosphorus (SAP) content, and soil available potassium (SAK) content showed significant variations (p < 0.05) between soil depths. In contrast, no significant difference was found for other physicochemical properties. (2) The SBD, STN, SAK, soil porosity, and soil clay content were significantly different (p < 0.05) under different vegetation cover types, but the influence of vegetation on other soil physicochemical properties seemed to be limited. The results reveal that trees have a stronger ability to reduce soil grain sizes and enhance SAP contents than shrubs or herbs; however, the beneficial effects of herbs on the physicochemical properties of shallow soil are more obvious than those of trees and shrubs. (3) This study indicates that more shrubs and trees should be planted in the areas with low vegetation coverage, and more measures should be taken to improve soil physicochemical properties in order to prevent the occurrence of large-scale degradation. The reconstruction of soil structure should be preferentially considered in the process of soil reconstruction and revegetation in areas under similar conditions. Herbs should first be planted in the early reclamation stage. At the same time, shrubs or trees can be adopted in the middle and late stages of vegetation reconstruction in order to achieve comprehensive revegetation.

Assessment of environmentally sensitive areas to desertification in the Blue Nile Basin driven by the MEDALUS-GEE framework

Assessing environmentally sensitive areas (ESA) to desertification and understanding their primary drivers are necessary for applying targeted management practices to combat land degradation at the basin scale. We have developed the MEditerranean Desertification And Land Use framework in the Google Earth Engine cloud platform (MEDALUS-GEE) to map and assess the ESA index at 300 m grids in the Blue Nile Basin (BNB). The ESA index was derived from elaborating 19 key indicators representing soil, climate, vegetation, and management through the geometric mean of their sensitivity scores. The results showed that 43.4%, 28.8%, and 70.4% of the entire BNB, Upper BNB, and Lower BNB, respectively, are highly susceptible to desertification, indicating appropriate land and water management measures should be urgently implemented. Our findings also showed that the main land degradation drivers are moderate to intensive cultivation across the BNB, high slope gradient and water erosion in the Upper BNB, and low soil organic matter and vegetation cover in the Lower BNB. The study presented an integrated monitoring and assessment framework for understanding desertification processes to help achieve land-related sustainable development goals.

Assessing the intraurban differences in vegetation coverage and surface climate in a heterogeneous area

Urban trees play a critical role in alleviating land surface temperatures in cities. In remote sensing studies, vegetation indices are widely used to examine the relationship between Land Surface Temperature (LST) and vegetation cover. The vegetation cover can be measured using the Normalised Difference Vegetation Index (NDVI). In this study, the LST-NDVI relationship was assessed in each of the seven city-regions (A-G) in Johannesburg using Moderate-Resolution Imaging Spectroradiometer (MODIS) datasets to provide a basis for urban ecological planning and environmental protection. This study's specific objective was to determine the intraurban differences in vegetation coverage and LST in the seven city-regions over 19 years. The relationship between LST and NDVI was also examined over the years of study. The results showed a significant intraurban difference in LST and NDVI values in the city-regions with a negative correlation between them, ranging from −0.03 to −0.76. The LST values increased in all the city-regions with the highest value of 20.1°C in city-region G, followed by 19.6°C in city-region E. The vegetation cover decreased over the years, with the lowest NDVI value in city-region G (0.39), followed by city-regions F (0.43) and D (0.48). The city-regions with high LST and low vegetation cover include the city-centre and highly populated suburbs. This indicates that areas with greater vegetation cover have low LSTs and vice versa. These findings provide useful information for municipal authorities and other stakeholders to undertake appropriate decisions to tackle Urban Heat Island (UHI) effects by adopting effective urban planning and management interventions.

引种降香黄檀和顶果木对石漠化山区土壤磷素转化及其有效性的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 引种降香黄檀和顶果木对石漠化山区土壤磷素转化及其有效性的影响 DOI: 10.5846/stxb202012223252 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目（31960240）；广西自然科学基金项目（2017GXNSFAA198207，2018GXNSFAA294139，2019GXNSFAA185023） Effects of introducing Dalbergia odorifera and Acricarpus fraxinifolius on soil phosphorus transformation and availability in rocky desertification mountainous regions Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:我国西南岩溶区石漠化严重，植被覆盖率低，土壤贫瘠。植被恢复作为一项重要的生态治理措施，在提高土壤养分有效性，增加生物多样性和改善生态环境等方面发挥着极其重要的作用。以广西马山县经过8年植被恢复的4种样地类型（降香黄檀纯林；顶果木纯林；降香黄檀/顶果木混交林；相邻的天然灌草丛作为对照组）为研究对象，探讨了引进固氮树种（降香黄檀和顶果木）及其种植模式对石漠化山区土壤磷素转化及其有效性的影响。研究结果表明：（1）降香黄檀/顶果木混交林土壤的有机质（SOM）、硝态氮（NO3--N）、有效磷（AP）、微生物生物量碳（MBC）、微生物生物量氮（MBN）和微生物生物量磷（MBP）含量均显著高于对照（P<0.05）；降香黄檀/顶果木混交林、顶果木纯林和降香黄檀纯林的全磷（TP）相比于对照组更易转化为AP，其中以降香黄檀/顶果木混交林的效果最佳。（2）相关分析结果表明，土壤NH4+-N、NO3--N和MBN与AP分别呈显著线性正相关（P<0.05），MBN与MBP呈极显著线性正相关（P<0.01）。（3）引种降香黄檀和顶果木后，各林分的土壤无机磷组分均发生变化，其中降香黄檀/顶果木混交林和顶果木纯林的各种无机磷含量显著增加（P<0.05）。（4）最后，冗余分析表明MBP、SOM和MBN可能是影响土壤无机磷组分变化的最主要因素（P<0.05）。研究表明降香黄檀和顶果木在一定程度上能改善石漠化山区土壤的养分状况和提高土壤磷的有效性，其中以二者混交种植模式的效果最显著，以期为珍贵固氮树种在石漠化生态恢复与重建中的推广应用提供理论依据和实践支持。 Abstract:Rocky desertification is serious in karst areas in southwest China, with low vegetation coverage and poor soil. As an important ecological management measure, vegetation restoration plays an extremely important role in improving the availability of soil nutrients, increasing biodiversity, and improving the ecological environment. In this study, four types of site (the pure plantation of Dalbergia odorifera; the pure plantation of Acricarpus fraxinifolius; the mixed plantation of D. odorifera and A. fraxinifolius; the adjacent natural weed field as the control) in Mashan, Guangxi were selected as the research objects after 8 years of vegetation restoration. The effects of introducing N2-fixing tree species (D. odorifera and A. fraxinifolius) and their planting patterns on the soil phosphorus transformation and availability in rocky desertification mountainous regions were discussed. The results showed that:(1) the contents of soil organic matter (SOM), nitrate nitrogen (NO3--N), available phosphorus (AP), soil microbial biomass carbon (MBC), soil microbial biomass nitrogen (MBN), and soil microbial biomass phosphorus (MBP) in the mixed plantation of D. odorifera and A. fraxinifolius were significantly higher than those of the control (P<0.05). The total phosphorus (TP) of the mixed plantation of D. odorifera and A. fraxinifolius, the pure plantation of A. fraxinifolius and the pure plantation of D. odorifera could be easily transformed into AP than control, among which the mixed plantation of D. odorifera and A. fraxinifolius had the best effect. (2) The results of correlation analysis showed that NH4+-N, NO3--N, and MBN had significant linear positive correlation with AP respectively (P<0.05), while MBN and MBP had extremely significant linear positive correlation (P<0.01). (3) After introducing D. odorifera and A. fraxinifolius, the soil inorganic phosphorus fractions in all sites changed, and the contents of various inorganic phosphorus in the mixed plantation of D. odorifera and A. fraxinifolius and the pure plantation of A. fraxinifolius increased significantly (P<0.05). (4) Finally, the redundancy analysis (RDA) indicated that MBP, SOM, and MBN would be the main factors affecting the changes of soil inorganic phosphorus fractions (P<0.05). Overall, D. odorifera and A. fraxinifolius could improve soil nutrient and phosphorus availability in rocky desertification mountain regions to a certain extent, among which the mixed planting pattern (the mixed plantation of D. odorifera and A. fraxinifolius) had the most significant effect. The purpose of the study could provide theoretical basis and practical support for the application of N2-fixing tree species in the ecological restoration and reconstruction of rocky desertification. 参考文献 相似文献 引证文献

Responses of aquatic vegetation coverage to interannual variations of water level in different hydrologically connected sub-lakes of Poyang Lake, China

The variation of water level is the main environmental factor controlling the growth of aquatic vegetation. It is of significance to understand its influences on aquatic vegetation coverage in sub-lakes under different hydrolo-gical control modes. Taking the free connected sub-lake Bang Lake and locally controlled sub-lake Dahuchi Lake of Poyang Lake as a case and based on remote sensing cloud computing platform of the Google Earth Engine (GEE), we used the pixel binary model to estimate aquatic vegetation coverage from 2000 to 2019, and analyzed the temporal and spatial differentiation characteristics, and the variation trend was simulated by combining the method of Sen+M-K. We analyzed the water level change characteristics during the study period and the relationship between the hydrological parameters and the aquatic vegetation coverage area of sub-lakes with different hydrological connectivity was explored by setting up the water level fluctuation parameters. The results showed that the aquatic vegetation coverage of Bang Lake was more susceptible to water level changes, while Dahuchi Lake was more stable. The aquatic vegetation was patchily and sporadically distributed in the years with low vegetation coverage. In the years with high vegetation coverage, it was distributed in a ring-like pattern, spreading from the center of the lake to the shore. The aquatic vegetation coverage of Bang Lake was more likely influenced by water level fluctuation rate, while the aquatic vegetation coverage of Dahuchi Lake was more likely influenced by the flooding duration of 17 m characteristic water level. The flooding duration of 19 m characteristic water level had a strong negative correlation with the aquatic vegetation coverage of Bang Lake and Dahuchi Lake. The trend of aquatic vegetation in Bang Lake was dominated by stabilization and slight improvement, while that in Dahuchi Lake was dominated by stabilization and significant degradation. Our results could help to further understand the dynamics of water hydrological ecosystem with different hydrological connectivity and provide a reference for lake management and conservation.

Effects of nutrient transfer by great skuas (Stercorarius skua) and arctic skuas (Stercorarius parasiticus) on vegetation and soil at Breiðamerkurjökull, SE-Iceland

Seabirds can play a vital role in primary succession by transferring nutrients from sea to land. Here, we examine the effects of sparse seabird colonies on primary succession at the Breiðamerkurjökull glacial fore-field in SE-Iceland. The area is generally characterized by low vegetation cover, where mosses are dominant, with scattered, grassy vegetation “islands” (bird hummocks) formed through point-centered influence of seabirds. The aim of this study was to assess the influence of bird presence on vegetation and soil properties. This was done by examining how vegetation and soil properties changed with the distance from bird hummocks and the influence of time on that relationship. Total vegetation cover and grass and forb cover were found to be significantly affected by the birds’ presence, as well as the concentration of soil organic matter and pHH2O . These results demonstrate the importance of seabirds as natural fertilizers in primary succession and early soil formation processes.

Assessment and Error Analysis of Satellite Soil Moisture Products Over the Third Pole

The Tibetan Plateau, known as the &#x201C;Third Pole&#x201D; of the world, is extremely sensitive to global climate change. Reliable soil moisture information is essential for understanding the impact of the Tibetan Plateau on the Asian monsoon. The study assessed a total of four satellite soil moisture products, namely the SMAP-SCA (V7), ESA CCI (V0.52), AMSR2 LPRM (V001), and FY-3C (V1) over the Tibetan Plateau using three densely-instrumented soil moisture networks (i.e., Maqu, Naqu, and Pali). Moreover, the possible error sources of these products were thoroughly investigated over the Tibetan Plateau, which had not yet been fully explored in previous studies. The results reveal the ESA CCI (V0.52) and SMAP-SCA (V7) generally perform better in the three networks with higher correlation coefficient (<inline-formula> <tex-math notation="LaTeX">$R$ </tex-math></inline-formula>) and lower standard deviation of the difference (STDD) compared to other products. The bias of ESA CCI (V0.52) is demonstrated to be dependent on the GLDAS Noah soil moisture, but it correlates much better with soil moisture measurements and also displays lower STDD value than the GLDAS Noah. SMAP brightness temperatures demonstrate much higher sensitivity to soil moisture than the AMSR<inline-formula> <tex-math notation="LaTeX">$2~C$ </tex-math></inline-formula>-band and FY-3C <inline-formula> <tex-math notation="LaTeX">$X$ </tex-math></inline-formula>-band measurements regardless of vegetation, surface roughness, and land cover heterogeneity. The auxiliary surface temperature used in SMAP-SCA (V7) also performs better than that used in AMSR2 LPRM (V001) and FY-3C (V1) though it is slightly colder than the ground measurements. These factors contribute to the better performance of SMAP-SCA (V7) soil moisture product compared to other satellite datasets. The AMSR2 LPRM (V001) product produces evidently larger absolute values than ground observations, but it can track the temporal trend of soil moisture in sparsely vegetated areas (Naqu and Pali). The FY-3C (V1) product exhibits some abnormal saturation values in Maqu with the highest vegetation biomass, while it performs better in Naqu and Pali with relatively lower vegetation coverage. The surface temperature derived from AMSR2 LPRM and FY-3C shows large uncertainties over the Tibetan Plateau which may be caused by the limited data used to calibrate the empirical surface temperature models.

Multi-taxon inventory and landscape characterization in an agrosystem of the Brazilian Midwest targeted for payment for environmental services

Abstract: The replacement of natural landscapes by anthropic environments has led to habitat loss and consequently, to the decline and extinction of many species populations. Several strategies, such as the creation of protected areas (PAs) and payment for ecosystem services have been adopted to mitigate the consequences of this biodiversity crisis. In Rio Verde, Goiás, Brazil, a Water Producer Program (WPP) was established, which provides payment for ecosystem services for the maintenance of riparian vegetation in the region of the Ribeirão Abóbora, a river which supplies the city and metropolitan area. In the absence of environmental diagnostic studies in the region, this present study contributes to reducing some knowledge gaps, through the: (i) characterization of the landscape in the WPP area, (ii) characterization of species of fauna (amphibians, birds, fish, and medium and large terrestrial mammals) and woody flora that occur in this area, and (iii) comparison of species diversity (fauna and flora) found in our study area with the diversity observed in the Cerrado protected area network. Our results reveal a low native vegetation cover (~21% of total area), but we recorded 300 total species: 20 species of anuran amphibians, 100 birds, 10 fish, 16 terrestrial mammals (medium and large), and 154 woody plants. Our sample comprises species considered endemic to the Cerrado (e.g., Anuran - Barycholos terntezi and Mammal - Callithrix penicillata), threatened species (e.g., Mammals - Herpailurus yagouaroundi, Myrmecophaga tridactyla and Tapirus terrestris), and exotic invasive species (Mammal - Sus scrofa). The results presented in this study are relevant and may help in the proposal of management actions within the scope of this important program of payment for environmental services.

柴达木盆地蒸散发遥感估算与耗水有效性评价

PDF HTML阅读 XML下载 导出引用 引用提醒 柴达木盆地蒸散发遥感估算与耗水有效性评价 DOI: 10.5846/stxb202105211328 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 青海省重大科技专项(2019-SF-A4);青海省基础研究计划项目(2020-ZJ-715);国家自然科学基金(42071032) Remote sensing estimation of evapotranspiration and efficiency evaluation of water consumption in Qaidam Basin Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:陆面蒸散发(ET)是自然生态系统水分耗散的主要方式,准确把握其时空变化特征,对于区域水资源合理利用与生态环境保护具有重要意义。针对我国西北干旱内陆区实测资料匮乏的现状,基于MODIS产品,构建了具有时空二维属性的地表温度-植被指数特征空间,实现了柴达木盆地陆面蒸散发的时空连续估算;在此基础上,进一步分离土壤蒸发与植被蒸腾,开展研究区自然生态系统耗水有效性评价。结果表明:(1)柴达木盆地近九年多年平均ET为188.75 mm,受降水空间分布格局影响,ET具有明显的从东南向西北减少趋势;(2)土壤蒸发与植被蒸腾多年平均值为171.06 mm和14.26 mm,后者年内峰值出现时间总体比前者晚1个月,具有滞后效应;(3)盆地陆地生态系统多年平均耗水总量为430.94亿m3,其中高效、中效和低效耗水的占比分别为6.55%、52.57%和40.88%。在区域尺度以时空连续的方式揭示了ET水分消耗的有效性,可为基于ET水资源管理目标的实现提供重要科学支撑。 Abstract:Terrestrial evapotranspiration (ET), composed of soil evaporation and plant transpiration, is the main mode of water dissipation in the natural ecosystems. In general, ET returns about two thirds of the annually terrestrial precipitation to the atmosphere on the global scale, and the ratio can reach as high as 80% in arid areas. As a result, accurate knowledge of ET is crucial to understand the water budget as well as its effect on ecosystems. This is particularly important for water resources management and eco-environmental protection in arid regions. Compared with ground-based ET measurements recorded by sparse flux towers, satellite remote sensing (RS) is a suitable tool to map regional ET patterns in a temporally and spatially consistent manner, yielding a series of RS-based ET models with varying mechanisms and degrees of complexity. Considering the sparse distribution of meteorological observations in the Northwest of China, we adopted the surface temperature-vegetation index (TVX) method in this study to estimate daily ET in Qaidam Basin from 2011 to 2019. Uniquely, the theoretical boundaries of the TVX feature space were determined pixel by pixel based on the surface energy balance principle, so ET could be mapped for regions with complex topography in a spatially consistent manner. Then a simple dual-source ET framework was used to partition evapotranspiration into soil evaporation (E) and plant transpiration (T), and finally the water consumption efficiency of natural ecosystems was evaluated by further partitioning E into soil evaporation over bare land and soil evaporation beneath the canopy. All the above schemes were demonstrated with Terra Moderate Resolution Imaging Spectroradiometer (MODIS) products. Results show that the annual ET of Qaidam Basin from 2011 to 2019 decreased at first and then increased, with an average value of 188.75 mm. As for seasonal variations, ET from April to September accounted for 80% of the annual ET with the peak value arising in June or July. Influenced by the spatial patterns of precipitation, the ET presents an obviously decreasing trend from southeast to northwest and from the surrounding mountains to the interior of the basin. Local high ET values in the interior of the basin are mainly distributed around the rivers, lakes, and springs. The annual average E and T in the recent nine years is 171.06 mm and 14.26 mm, respectively. Although the seasonal variations of both E and T follow a trend similar to sinusoidal curves with the peak values observed in summer, the peak of the latter appears one month later than that of the former. In terms of spatial distribution, soil evaporation shares patterns consistent with total ET, but plant transpiration is mainly observed in the southeast of the basin, showing a semi-ring structure. The annually total water consumption of terrestrial ecosystems in the basin is 43.094 billion m3 on average. The corresponding proportion of high-efficiency, medium-efficiency and low-efficiency water consumption is 6.55%, 52.57% and 40.88%, respectively. Due to the extremely low fractional vegetation cover of Qaidam Basin, the amount of water consumption with high-efficiency is much lower than the other two. However, when considered water consumed by bare land and dense canopy, the water consumed by dense canopy per unit area is 297.83 mm, which is much higher than that consumed by bare land. In conclusion, this study reveals the water consumption efficiency of ET in the whole Qaidam Basin in a temporally and spatially consistent manner, which provides important scientific support for ET-based water resources management. 参考文献 相似文献 引证文献

EFFECT OF HUMAN DISTURBANCES ON ANT COMMUNITY AND AMAZONIAN LANDSCAPE

The present work aimed to evaluate the effect of anthropogenic disturbances on the ant community and on the Amazonian landscape in areas of tropical rain forest. The study was conducted in two areas: Cabo Rosa Forest and Tauari Forest with different levels of human disturbances in the municipality of Marabá, Pará, Brazil. A characterization of the descriptors of anthropogenic activities was carried out for each study area in order to generate an index of anthropogenic disturbance. The vegetation structure was classified into: exposed soil, low, medium and high vegetation cover through NDVI. Ant sampling was carried out using pitfall traps. The vegetation structure, diversity and abundance parameters were related to the areas. Similarities between the species composition of the ant communities were verified by a similarity analysis. We found that human disturbances are modifying the vegetation structure by reducing the forest cover of the tree stratum and leaving the landscape with a higher occurrence of open areas. Regarding the ant community, we corroborate the hypothesis that anthropic disturbances are reducing the local biodiversity. Thus, this study shows that anthropogenic disturbances have negative effects on the Amazonian landscape and on the ant community through the reduction of forest cover and decrease in ant biodiversity. These changes can cause the conversion of climax communities in early successional stages and reduce the ecological services provided by ants (e.g. seed dispersal).

Hot, wet and rare: modelling the occupancy dynamics of the narrowly distributed Dixie Valley toad

Context Small population sizes and no possibility of metapopulation rescue put narrowly distributed endemic species under elevated risk of extinction from anthropogenic change. Desert spring wetlands host many endemic species that require aquatic habitat and are isolated by the surrounding xeric terrestrial habitat. Aims We sought to model the occupancy dynamics of the Dixie Valley toad (Anaxyrus williamsi), a recently described species endemic to a small desert spring wetland complex in Nevada, USA. Methods We divided the species’ range into 20 m × 20 m cells and surveyed for Dixie Valley toads at 60 cells during six primary periods from 2018 to 2021, following an occupancy study design. We analysed our survey data by using a multi-state dynamic occupancy model to estimate the probability of adult occurrence, colonisation, site survival, and larval occurrence and the relationship of each to environmental covariates. Key results The detection probabilities of adult and larval toads were affected by survey length and time of day. Adult Dixie Valley toads were widely distributed, with detections in 75% of surveyed cells at some point during the 3-year study, whereas larvae were observed only in 20% of cells during the study. Dixie Valley toad larvae were more likely to occur in cells far from spring heads with a high coverage of surface water, low emergent vegetation cover, and water temperatures between 20°C and 28°C. Adult toads were more likely to occur in cells with a greater coverage of surface water and water depth &gt;10 cm. Cells with more emergent vegetation cover and surface water were more likely to be colonised by adult toads. Conclusions Our results showed that Dixie Valley toads are highly dependent on surface water in both spring and autumn. Adults and larvae require different environmental conditions, with larvae occurring farther from spring heads and in fewer cells. Implications Disturbances to the hydrology of the desert spring wetlands in Dixie Valley could threaten the persistence of this narrowly distributed toad.

Study on the Characteristics and Driving Factors of Vegetation Cover in Shiyang River Basin from 1990 to 2015

The earth is the home of human survival, and vegetation, as an important natural resource on the land surface, has the functions of sand sealing and soil consolidation, water conservation and so on. Change of vegetation can reflect the change of ecological environment. It is also an important role in the energy cycle and water cycle of the earth's surface and atmosphere. By studying the change of vegetation coverage, we can get the information of ecology and water source. Then, we need to take effective measures to improve our ecological environment. It is also of great significance for us to understand the ecological environment. In this paper, the clear images of 1990, 1998, 2015and 2018in June and July are downloaded from Landsat 8 satellite image data. The vegetation index NDVI of each year is calculated by ArcMap software, and the vegetation coverage is calculated by NDVI. The changes of NDVI and vegetation coverage are analysed. The influencing factors of vegetation coverage and the objective control methods are put forward. Based on the change of vegetation coverage from 1990to 2018, it is concluded that the area of vegetation restoration in the upper reaches of Shiyang River Basin is larger than that of degradation, that in the middle reaches of the basin is larger than that of degradation that in the lower reaches of the basin is larger than that of vegetation restoration, and that in Minqin Basin is larger than that of vegetation restoration Product. Generally speaking, the area of vegetation restoration in Shiyang River Basin is slightly larger than that of vegetation degradation. Based on the statistical analysis of the vegetation coverage in the basin, we should focus on the control of the vegetation in the extremely low vegetation coverage area and the medium vegetation coverage area.

PENDEKATAN EKO-SOSIO SISTEM DALAM PENGELOLAAN POTENSI BANJIR KOTA SEMARANG

The diversity and density of vegetation is key in managing flood throughout the watershed, especially in the central and downstream regions. Measures of vegetation diversity and density that can be used are the Normalized Difference Vegetation Index (NDVI) which is a measure of vegetation greenness (chlorophyll levels), Normalized Difference Water Index (NDVI) to measure vegetation wetness levels, and soil adjusted vegetation index (SAVI) for low canopy vegetation cover. For watersheds that stretch long to downstream or coastal areas, the measure of land diversity needs to be supplemented by using the Normalized Difference Built-Up Index (NDBI) indicator that is useful for land use planning. Information on this vegetation index can be obtained by processing a satellite imagery map. The benefits of processing vegetation indexes in watershed management are becoming increasingly important in the era of climate change, especially with regard to efforts to harmonization of relationships between environmental elements that include the diversity of the interests of the resident population. That's why this research was done in order to find the link between natural factors including the impacts of climate change and humans. The test began by looking for changes in the ND VI, ND WI, SA VI, and NDBI indexes from the last 5 years with the Global Indicator Spatial Association (GISA) analysis using Moran's I Global Index followed by looking for the association with the pattern of population change and the percentage of the area of the settlement. The results showed a link between Moran's I Global Index change pattern of population change and the spread of residential developments. The tendency of the distribution of this settlement area is an important point in analyzing the influence of its dispersal patterns in a watershed so that the continued impact of potential erosion, sedimentation, and flooding triggered that will be the main consideration in watershed management.

Quantifying the variability in water use efficiency from the canopy to ecosystem scale across main croplands

Current, how to use limited water resources efficiently and improve agricultural water use efficiency, has become one of the greatest challenges for global food security. In this study, multiple site-years of carbon and water flux data across the major crops including maize, winter wheat and soybean, were used to quantify the variability in canopy-scale transpiration (T), ecosystem-scale evapotranspiration (ET) as well as the associated water use efficiencies (WUET and WUEET). On the basis of ET partitioning, the results indicated that the transpiration ratio–T/ET as well as T and ET exhibited an obvious single-peak seasonal pattern across the typical croplands. However, at the early and late growing stages, there existed large discrepancies in T and ET owing to low vegetation coverage, while T and ET were very close during the peak period. Among them, maize exhibited the largest T/ET by 0.50 ± 0.12, followed by soybean of 0.43 ± 0.08 and winter wheat of 0.38 ± 0.09, respectively. Furthermore, the coupling relationships between gross primary productivity (GPP) and water fluxes including T and ET changed from linear to nonlinear. The study also found that the variability in WUET and WUEET were not consistent. Specifically, WUEET showed distinct seasonal characteristic whereas WUET kept constant as a plateau almost throughout the growth period, which reflected the inherent physiological property controlled by plant stomata at the canopy scale. Among these crops, maize exhibited the largest WUET and WUEET (5.30 ± 0.89 and 2.48 ± 1.14 g C kg−1 H2O), followed by winter wheat (4.97 ± 1.52 and 2.35 ± 0.64 g C kg−1 H2O) and soybean (4.88 ± 1.59 and 1.89 ± 0.99 g C kg−1 H2O), respectively.

Monitoring post-fire neighborhood competition effects on pine saplings under different environmental conditions by means of UAV multispectral data and structure-from-motion photogrammetry

In burned landscapes, the recruitment success of the tree dominant species mainly depends on plant competition mechanisms operating at fine spatial scale, that may hinder resource availability during the former years after the disturbance. Data acquisition at very high spatial resolution from unmanned aerial vehicles (UAV) have promoted new opportunities for understanding context-dependent competition processes in post-fire environments. Here, we explored the potentiality of UAV-borne data for assessing inter-specific competition effects of understory woody vegetation on pine saplings, as well as intra-specific interactions of neighboring saplings, across three burned landscapes located along a climatic/productivity gradient in the Iberian Peninsula. Geographic object-based image analysis (GEOBIA), including multiresolution segmentation and support vector machine (SVM) classification, was used to map pine saplings and understory shrubs at species level. Input data were, on the one hand, multispectral (11.31 cm·pixel−1) and Structure-from-Motion (SfM) canopy height model (CHM) data fusion, hereafter MS-CHM, and, on the other, RGB (3.29 cm·pixel−1) and CHM data fusion, hereafter RGB-CHM. A Random Forest (RF) regression algorithm was used to evaluate the effects of neighborhood competition on the relative growth in height of 50 pine saplings randomly sampled across the MS-CHM classified map. Circular plots of 3 m radius were set from the centroid of each target pine sapling to measure percentage cover, mean height of all individuals in the plot and mean height of individuals contacting the target sapling. Competing shrub species were differentiated according to their fire-adaptive traits (i.e. seeders vs resprouters). Object-based image classification applied on MS-CHM yielded higher overall accuracy for the three sites (83.67% ± 3.06%) than RGB-CHM (74.33% ± 3.21%). Intra-specific competitive effects were not detected, whereas increasing cover and height of shrub neighbors had a significant non-linear impact on the growth on pine saplings across the study sites. The strongest competitive effects of seeder shrubs occurred in open areas with low vegetation cover and fuel continuity, following a gap-dependent model. The non-linear relationships evidenced in this study between the structure of neighboring shrubs and the growth of pine seedlings/saplings have profound implications for considering possible competing thresholds in post-fire decision-making processes. These results endorse the use of UAV multispectral and SfM photogrammetry as a valuable post-fire management tool for measuring accurately the effect of competition in heterogeneous burned landscapes.

Comparison of methods for revegetation of vehicle tracks in High Arctic tundra on Svalbard

Natural regeneration after anthropogenic disturbance is slow in the tundra biome, but assisted regeneration can help speed up this process. A tracked off-road vehicle damaged a High Arctic dwarf shrub heath in Svalbard in May 2009, drastically reducing the vegetation cover, soil seed banks, and incoming seed rain. We assisted regeneration the following year using six different revegetation treatments and monitored their effects one month, and one and eight years after their application. By 2018, all treatments still had lower vegetation cover and limited species composition than the undamaged reference vegetation. The fertiliser treatment was the most effective in restoring vegetation cover (71% vegetation cover, of which 62% were bryophytes and 38% were vascular plant species). Compared to the reference plots (98% vegetation cover, of which 32% were bryophytes and 66% were vascular plant species), the composition of the disturbed vegetation was still far from regenerated to its original state nine years after the tracks were made. The slow regrowth demonstrated in this study underlines the importance of avoiding the disturbance of fragile tundra and implementing and upholding regulations that restrict or ban such disturbances.

Cartografía de Unidades Ambientales Homogéneas (UAH): Un insumo para el ordenamiento del bosque chaqueño en Salta

The north of the Bermejo River, territory of Salta province, was zoned as categories I and II, according to the Law 7543 of Native Forest Territorial Planning. The Category II allows forest use or raising cattle under forests. The technologies involved in implanting pastures under silvopastoral systems meet the requirements of the Law and are being successfully implemented in sites with high forest and developed soils, but not in shrubland with low vegetation cover, where they quickly disappear. The aim of this work is to elaborate cartography of the Homogeneous Environmental Units (HEU) covering Semiarid Chaco Pilot Site (SPChSA) of the National Observatory of Land Degradation and Desertification (ONDTyD), grouped by criteria of vegetation and soils, as input for land use planning. A supervised classification of the study area was carried out using geographic information system (GIS) and sampling soil and vegetation. Six EHU were identified. Thematic mapping of the pilot site was prepared, and the area occupied by each unit was calculated as a contribution to current environmental legislation. It is reported that 30% of Category II is covered with shrublands that do not have the ability to maintain sustainable SSP in the long term, but are valuable for the functioning of the ecosystem. This is a warning of the need to properly map the areas that should be protected in the current zoning to avoid further degradation processes in the territory.

Evaluating the Dominant Controls of Water Erosion in Three Dry Valley Types Using the RUSLE and Geodetector Method

The dry valley is a unique geographic phenomenon in Southwest China with severe water erosion. However, little is known regarding its dominant controls and the discrepancies between dry valley subtypes, leading to the poor management of water erosion. To solve these problems, the revised universal soil loss equation (RUSLE) and Geodetector method were used in a dry temperate (DT), dry warm (DW), and dry hot (DH) valley. Results indicated that dry valleys suffer severe water erosion with a value of 64.78, 43.85, and 33.81 t·ha−1·yr−1. The Geodetector method is proven to be an efficient tool to quantify the dominant factor of water erosion. It was established that land use types (LUT) have the closest relationship with water erosion. The controls for water erosion could be better explained by multi-factor interactions analysis, particularly for the combination of slope and LUT in DW (q = 0.71) and DH (q = 0.66). Additionally, regions at high risk of water erosion were characterized by steep slope (&gt;30°) and low vegetation coverage (&lt;50%) in DT, while the opposite is shown in DH. These findings could provide insight for guiding soil erosion management and ecological restoration strategies that balance economic and environmental sustainability.

Combined impacts of the abnormal and urban heat island effect in Guiyang, a typical Karst Mountain City in China

The abnormal heat island (AHI) effect has recently been reported in several karst cities. However, the combined effect of the abnormal and urban heat island (UHI) effect is still a gap. This study analyzed the combined effect the AHI and UHI in Guiyang, a typical rapidly urbanizing karst mountain city, to provide insights into the variation and formation of AHIs and UHIs using Landsat imagery. Although the AHI effect remained the major component of the thermal environment, the impact of UHI intensified with rapid urbanization. Moreover, in addition to suitable topographic conditions such as shallow slopes and high elevations in sunny aspects, the low and low-medium vegetation coverage lands were highly related to the formation of the AHI, and the AHI intensity increased in almost all directions with urban expansion. In addition, the formation conditions and mechanism of the AHI can be attributed to the unique thermal properties of karst carbonate. The above results suggest that karst rock desertification is the key point for the improvement of the regional thermal environment, so comprehensive prevention of rock desertification and rational planning of construction projects should be involved in environmental protection in karst mountain cities.