Increase In Vegetation Cover Research Articles

Linking Spatial–Temporal Changes of Vegetation Cover with Hydroclimatological Variables in Terrestrial Environments with a Focus on the Lake Urmia Basin

Investigation of vegetation cover is crucial to the study of terrestrial ecological environments as it has a close relationship with hydroclimatological variables and plays a dominant role in preserving the characteristics of a region. In Iran, the current study selected the watersheds of two rivers, Nazloo-Chay and Aji-Chay, to systematically investigate the implications and causes of vegetation cover variations under changing environments. These two rivers are among the essential inflows to Lake Urmia, the second largest saline lake on Earth, and are located on the west and east sides of the lake, respectively. There has been a debate between the people living in the rivers’ watersheds about who is responsible for the decline in the level of Lake Urmia—does responsibility fall with those on the east side or with those on the west side? In this study, the normalized difference vegetation index (NDVI) was used as a remotely sensed index to study spatial–temporal pattern changes in vegetation. Moreover, the temperature, precipitation, and streamflow time series were gathered using ground measurements to explore the causes and implications of changing vegetation cover. Discrete wavelet transform was applied to separate the different components of the time series. The Mann–Kendall (MK) test was applied to the time series on monthly, seasonal, and annual time scales. The connections and relationship between the NDVI time series and temperature, precipitation, and streamflow time series and any underlying causes were investigated using wavelet transform coherence (WTC). Land use maps were generated for different years using a support vector machine (SVM) in the final stage. The results indicated that the most dominant monthly, seasonal, and annual hydrological periodicities across the watersheds are 8 months, 6 months, and 2 years, respectively. The increasing vegetation cover during stable hydro-environmental periods revealed unusual conditions in the Aji-Chay watershed and reflected agricultural expansion. The WTC graphs indicated sudden changes in mutual periodicities and time-lags with different patterns between variables, which indicates the increasing anthropogenic activities in both watersheds. However, this was more dominant in the Aji-Chay watershed. The land use maps and investigation of the averaged NDVI maps also denoted that the areas of cultivated land have increased by 30% in the Aji-Chay watershed, and crop types have been changed to the crops with a higher demand for water in both watersheds.

Anthropogenic Factors Affecting the Vegetation Dynamics in the Arid Middle East

Abstract The spatiotemporal variability of vegetation in the Middle East was investigated for the period 2001–2019 using the Moderate Resolution Imaging Spectroradiometer (MODIS) 16-day/500 m composites of the Normalized Difference Vegetation Index (NDVI; MOD13A1). The results reveal a strong increase in NDVI coverage in the Middle East during the study period (R = 0.75, p-value = 0.05). In Egypt, the annual coverage exhibits the strongest positive trend (R = 0.99, p-value = 0.05). In Turkey, both the vegetation coverage and density increased from 2001 to 2019, which can be attributed to the construction of some of the biggest dams in the Middle East, such as the Atatürk and Ilisu dams. Significant increases in the annual coverage and maximum and average NDVI in Saudi Arabia are due to farming in the northern part of the country for which groundwater and desalinated seawater are used. The results of this study suggest that one of the main factors affecting vegetation coverage in the Middle East are governmental policies. These policies could lead to an increase in vegetation coverage in some countries such as Egypt, Saudi Arabia, Qatar, Kuwait, Iran, and Turkey.

基于地理探测器的喀斯特山区生态系统服务关系分异特征及驱动力解析——以贵州省为例

PDF HTML阅读 XML下载 导出引用 引用提醒 基于地理探测器的喀斯特山区生态系统服务关系分异特征及驱动力解析——以贵州省为例 DOI: 10.5846/stxb202109012470 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学青年基金项目（42001090）；重庆市教委科学技术研究项目（KJQN202000512） Differentiation characteristics and driving factors of ecosystem services relationships in karst mountainous area based on geographic detector modeling:A case study of Guizhou Province 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:生态系统服务关系的空间异质性及其驱动机制分析一直都是喀斯特生态系统服务研究的关键问题。以典型喀斯特山区--贵州省为例，选取植被净初级生产力(NPP)，土壤保持(SC)和产水(WY)3类生态系统服务，在对其进行准确估算的基础上，采用相关分析法、均方根误差法从多角度剖析生态系统服务关系变化及其空间分异规律，借助地理探测器对生态系统服务关系变化的驱动机理进行解析。结果表明：①2000-2015年贵州省NPP、土壤保持、产水服务均值均呈增长趋势，其中，NPP和土壤保持服务在研究区东北部及西北角增长最显著，产水服务在研究区东南部增加最明显。②研究时段内，区域生态系统服务关系以协同为主，只是协同关系在减弱并有向权衡发展的趋势。③不同背景条件下区域生态系统服务关系具有明显的分异特征。相较于白云岩，NPP与土壤保持的权衡度在石灰岩上更大；土壤保持与NPP的权衡度在地势平缓的岩溶盆地上较大，产水服务与NPP、土壤保持间的权衡度在陡峭的岩溶槽谷(峡谷)上更大；产水服务与土壤保持间的权衡度随着植被覆盖度的增加而逐渐增大。④地理探测器结果表明：造林总面积是影响NPP与土壤保持间权衡关系变化的主导因子，降水总量已成为制约NPP与产水服务间协同的最主要因子，高程和人均国内生产总值(GDP)是影响土壤保持与产水服务间关系的最主要因子；因子间的交互影响均高于单因子的影响。研究深化了喀斯特地区生态系统服务权衡/协同关系变化的机理解析研究，为喀斯特生态系统有效保护和管理提供了科学参考。 Abstract:The spatial heterogeneity of ecosystem services relationships and their driving mechanisms have always been the research focus regarding karst ecosystem services. Taking Guizhou Province, a typical karst mountainous area, as an example, this study selected three ecosystem services:net primary productivity (NPP), soil conservation (SC), and water yield (WY). Based on the accurate estimation of three ecosystem services through the Carnegie-Ames-Stanford approach (CASA) model, the Integrated Valuation of Ecosystem Services and Trade-offs (InVEST) model and the water balance formula, the spatio-temporal change and differentiation characteristics of ecosystem services relationships were analyzed using correlation analysis and root mean square error (RMSE). The driving mechanisms of changes in ecosystem services relationships were then analyzed using a geographic detector modeling. The results showed that:① from 2000 to 2015, the average values of NPP, SC, and WY in Guizhou Province showed an increasing trend. In terms of spatial distribution, NPP and SC presented an increasing trend in the northeast and northwest corner of the study area. The WY increased in the southeastern study area. ② During the study period, the relationships of regional ecosystem services were mainly synergistic, but the synergistic relationship was weakening, accompanied by a trade-off trend. So, due attention should be given to the coordination of ecosystem services relationships. ③ The relationship of regional ecosystem services under different conditions had obvious differentiation characteristics. Compared with dolomite, the trade-off intensity between NPP and SC was greater on limestone; the trade-off intensity between SC and NPP was greater on flat karst basins, and the trade-off intensity between WY and NPP, WY and SC was greater on steep karst slot valley (canyons). The trade-off intensity between WY and SC gradually increased with the increase in vegetation coverage. ④ The results of the geographic detector modeling showed that the total afforestation area was the leading factor affecting the trade-off change between NPP and SC. The total precipitation was the main factor restricting the collaboration between NPP and WY. The elevation and per capita gross domestic product (GDP) were the main factors affecting the relationship between SC and WY. Meantime, the explanatory power of the interaction of any two factors was higher than that of the single factor, indicating the influence intensity of the factor was obviously increased after the interaction. In the future, attention should be paid to multi-factors and their interactions. This study provided deeper insights into the mechanisms of the trade-off/synergy changes among ecosystem services in the karst area, and a scientific reference for the effective protection and management of the karst ecosystem. 参考文献 相似文献 引证文献

植被覆盖度对夏季降温效应的影响——以内蒙古为例

PDF HTML阅读 XML下载 导出引用 引用提醒 植被覆盖度对夏季降温效应的影响——以内蒙古为例 DOI: 10.5846/stxb202107091846 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 中央级公益性科研院所基本科研业务费专项资金项目（CAFYBB2020SY032） The influence of vegetation coverage on cooling effect in summer: A case study of the Inner Mongolia 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:随着全球变暖的加剧，区域热环境问题日益凸显，植被的降温作用逐渐得到广泛关注。目前已有的研究多从样地尺度分析不同类型植被的降温效应。而区域尺度的研究多从定性的角度揭示地表温度与植被覆盖的关系，对评估植被的实际降温效应具有一定的局限性。以内蒙古为研究区，以MODIS地表温度数据为基础，采用近邻分析法，将森林、灌丛和草地的MODIS地表温度与相邻5km范围内的低覆盖地表作为对照，分析植被的降温效应以及植被覆盖度对降温效应的影响。从2015年7月地表温度平均值的结果来看，降温度数在蒙东、蒙中和蒙甘区均呈现森林>灌丛>草地。森林的降温范围在0.67-1.03℃，灌丛为0.60-0.95℃，草地为0.47-0.86℃。植被降温度数与植被覆盖度的回归拟合为对数分布，均呈显著正相关（P<0.01）。且在不同的植被覆盖度范围内植被降温效应具有显著差异，植被覆盖度水平较低时（<40%），植被覆盖度的增加能更显著地降低地表温度。从整体来看，植被覆盖度每增加10%，森林降温0.12-0.39℃；灌丛降温0.1-0.2℃；草地降温0.049-0.075℃。综上，内蒙古作为全球气候变化最为敏感的区域之一，研究植被的夏季降温效应能够为内蒙古的气候调节服务评估提供重要的理论支撑及案例参考。 Abstract:As global warming intensifies, regional thermal environment problems are becoming increasingly prominent. Therefore, the cooling effect of vegetation has gradually gained widely attention. Existing studies mostly analyzed the cooling effect of different types of vegetation from plot-scale. However, studies on region scale mostly focused on the qualitative analysis of relationship between vegetation parameters and surface temperature. Due to lack of comparative analysis between test plot and control plot, there have certain limitations for evaluate actual cooling effect and calculate corresponding cooling value. Using the nearest neighbor analysis in this article, the MODIS surface temperature of forest, shrub and grassland were compared with the surface temperature of low coverage to analyze the cooling effect of vegetation. The range of the control area was selected as 5km because adequate control plots were found within this distance. The regression fitting was used to analyze the influence of vegetation coverage on cooling effect. According to the results, cooling effect in Eastern Inner Mongolia, Central Inner Mongolia, and Inner Mongolia-Gansu subregions all showed forest > shrub > grassland. The range of temperature reduction in forest was 0.67-1.03℃, that in shrub was 0.60-0.95℃, and that in grassland was 0.47-0.86℃. The regression fitting of vegetation cooling degree and vegetation coverage was logarithmic distribution, and which showed significantly positive correlation (P < 0.01). When the vegetation coverage level is lower (< 40%), the increase of vegetation coverage can significantly reduce the surface temperature. For example, every 10% increase in low coverage forests (< 40%), the range of temperature reduction was 0.20-0.27℃, that in medium coverage forests (40%-60%) was 0.12-0.16℃, and that in high coverage forests (>60%) was 0.07-0.10℃. Differences in the cooling effect of different vegetation coverage may be affected by multiple factors such as vegetation transpiration, surface reflection, shading, roughness, and so on. The results showed that trees can effectively block direct sunlight, and the cooling effect is significantly higher than that of shrubs and herbs. For instance, every 10% increase in vegetation coverage would result in forest cooling of 0.12-0.39℃, shrub cooling of 0.1-0.2℃ and grassland cooling of 0.049-0.075℃. In conclusion, Inner Mongolia is one of the most sensitive regions to global climate change. To study the cooling effect of vegetation can provide importantly theoretical support and case reference for the assessment of climate regulation services in the Inner Mongolia. 参考文献 相似文献 引证文献

Tundra vegetation change and impacts on permafrost

Tundra vegetation productivity and composition are responding rapidly to climatic changes in the Arctic. These changes can, in turn, mitigate or amplify permafrost thaw. In this Review, we synthesize remotely sensed and field-observed vegetation change across the tundra biome, and outline how these shifts could influence permafrost thaw. Permafrost ice content appears to be an important control on local vegetation changes; woody vegetation generally increases in ice-poor uplands, whereas replacement of woody vegetation by (aquatic) graminoids following abrupt permafrost thaw is more frequent in ice-rich Arctic lowlands. These locally observed vegetation changes contribute to regional satellite-observed greening trends, although the interpretation of greening and browning is complicated. Increases in vegetation cover and height generally mitigate permafrost thaw in summer, yet, increase annual soil temperatures through snow-related winter soil warming effects. Strong vegetation–soil feedbacks currently alleviate the consequences of thaw-related disturbances. However, if the increasing scale and frequency of disturbances in a warming Arctic exceeds the capacity for vegetation and permafrost recovery, changes to Arctic ecosystems could be irreversible. To better disentangle vegetation–soil–permafrost interactions, ecological field studies remain crucial, but require better integration with geophysical assessments. Greening and vegetation community shifts have been observed across Arctic environments. This Review examines these changes and their impact on underlying permafrost.

An Improved Annual Temperature Cycle Model With the Consideration of Vegetation Change

Land surface temperature (LST) is an important parameter in land surface processes with strong relationship between surface energy and water exchange. To effectively capture the surface thermal dynamics, the annual temperature cycle model is a good option by depicting the annual variation as a constant term plus a sine function. However, this type model suffers from the assumption of constant surface thermal property which is hardly satisfied due to the changes in vegetation cover. To well address this issue, the normalized difference vegetation index (NDVI) is introduced as an indicator to characterize the variation in surface thermal property and added to the original form to propose an improved version. Through comparison between the fitting effects of the proposed model with the original one, the improvement shows good performance in suppressing the annual maximum temperature and elevating the annual minimum temperature with the increase in vegetation cover. The difference in the annual maximum and minimum temperature between the estimates from the proposed model and the original model shows good linear regression with NDVI difference when compared with the annual mean value, with the speed of −3.22 and 4.84, respectively. In addition, the fitting accuracy is also improved with a slight increase in the coefficient of determination (0.002) and a decrease in the root mean squared error (0.018 K). The application of the proposed model also provides reasonable distribution of the annual temperature parameters in the southwest of Europe and part of North Africa, confirming its potential effect in thermal dynamic monitoring.

Flash flood simulation in the urbanised catchment: a case study of Bratislava-Karlova Ves

Flash floods are a dangerous phenomenon that generally affects small drainage basins. They are primarily initiated in the upper parts of the slopes, but their damaging effects are manifested mostly in residential areas, where naturally flowing streams were removed from the surface to the underground artificial channels. Therefore, there are no precise data about stream water levels available and only using surface runoff modelling is possible to simulate what happened during flash floods. Karlova Ves (Bratislava City District), formerly a small viniculture village, was threatened by floods (most probably including pluvial type) in history. In this paper, we used GRASS GIS tool r.sim.water to simulate the surface runoff of a flash flood that occurred in summer 2014 in the catchment of Čierny potok. The flood on 23 August 2014 was reported to have the highest rainfall per hour ~40 mm during the time of local meteorological measurements. The current orthophotomap was used to classify the land cover classes, which were assigned the value of the Manning’s roughness coefficient and infiltration rate. The topography was expressed by DTM from high-resolution LiDAR data. Our preliminary results indicate that land cover and land use are the essential factors that influence the initiation of flash floods, although the main driver of lower infiltration and change in flow direction is caused by urbanisation and a high proportion of impervious areas. Simulation showed that during 60 minutes of extreme rainfall (40 mm/hr) a surface runoff can reach a depth of water up to two meters in terrain depressions by a maximum discharge of 25 cubic meters. The revitalisation of natural urban areas by increasing vegetation cover in areas prone to flash floods and accumulation of water during higher rainfalls helps to prevent the damage caused by floods. URL: https://www.gcass.science.upjs.sk/

Tibetan Dust Accumulation Linked to Ecological and Landscape Response to Global Climate Change

AbstractThe Tibetan Plateau (TP) is a hotspot of earth system research, and understanding its landscape and ecosystem evolution has been hampered by the lack of time‐constrained geological records. Geochronological data from 14 loess sites covering a large region in the Tibetan interior show that the TP loess, rather than accumulating during glacial periods, began aggrading at either 13.4 ± 0.4 or 9.9 ± 0.2 ka. An ecological threshold was crossed, when warmer and wetter conditions resulted in increased vegetation cover enabling dust trapping. This dust accumulation model is out of phase with that of the Chinese Loess Plateau (CLP) where high sedimentation rates occurred during the cold/dry glacial stages. The TP loess accumulation is in response to global climate change, at both orbital (glacial/interglacial) and millennial (e.g., Younger Dryas event) time scales, despite more complexity via ecological and landscape processes than the CLP loess.

Assessing effects of the Returning Farmland to Forest Program on vegetation cover changes at multiple spatial scales: The case of northwest Yunnan, China

Chinese state authorities have successfully accelerated afforestation over large areas through the Returning Farmland to Forest Program (RFFP). However, variation in the implementation of the RFFP among villages may lead to uncertainty in forest transitions at multiple spatial levels. Here, we combined remote sensing analysis with field quadrats and questionnaire surveys to assess the RFFP's effectiveness in increasing vegetation cover at the Lancang watershed, township and natural village levels in Weixi County, a biodiversity hotspot in northwest Yunnan. From 2000 to 2010 and 2010 to 2014, forest coverage increased, and areas of shrubland and agricultural land decreased at both watershed and township levels, which reflected a positive impact of the RFFP. However, the new forests established under the RFFP in the study area mostly consisted of monocultures of walnut and pine trees, a situation that could threaten local biodiversity. Changes in forest and shrub coverage varied among natural villages—gain and loss trends both occurred, indicating a limited impact of the RFFP. Nonparticipating RFFP households also abandoned cropland, and agricultural land area in these villages declined over the study period. At the watershed and township levels, RFFP greatly promoted increases in forest coverage. Elevation, the behavior of village officials and household livelihoods were often the most relevant factors at the natural village level. Interactions among these multiple drivers resulted in cross-scale heterogeneity of vegetation cover changes in northwest Yunnan. Future forest policies need to be tailored to specific regions and be based on assessments of local natural and socioeconomic conditions.

Restoration of Degraded Grassland Significantly Improves Water Storage in Alpine Grasslands in the Qinghai-Tibet Plateau.

Alpine grassland has very important water conservation function. Grassland degradation seriously affects the water conservation function; moreover, there is little understanding of the change of water state during grassland restoration. Our study aims to bridge this gap and improve our understanding of changes in soil moisture during the restoration process. In this study, the water storage, vegetation, and meteorology of a non-degradation grassland (grazing intensity of 7.5 sheep/ha) and a severely degraded grassland (grazing intensity of 12–18 sheep/ha) were monitored in the Qinghai-Tibet Plateau for seven consecutive years. We used correlation, stepwise regression, and the boosted regression trees (BRT) model analyses, five environmental factors were considered to be the most important factors affecting water storage. The severely degraded grassland recovered by light grazing treatment for 7 years, with increases in biomass, litter, and vegetation cover, and a soil-water storage capacity 41.9% higher in 2018 compared to that in 2012. This increase in soil-water storage was primarily due to the increase in surface soil moisture content. The key factors that influenced water storage were listed in a decreasing order: air temperature, litter, soil heat flux, precipitation, and wind speed. Their percentage contributions to soil-water storage were 50.52, 24.02, 10.86, 7.82, and 6.77%, respectively. Current and future climate change threatens soil-water conservation in alpine grasslands; however, grassland restoration is an effective solution to improve the soil-water retention capacity in degraded grassland soils.

Impacts of anthropogenic activities on vegetation cover changes in the Circum-Bohai-Sea region, China

Besides climate change, intensive anthropogenic activities affect vegetation cover variations, particularly in highly populated regions. Herein, we investigated the impacts of anthropogenic activities in the Circum-Bohai-Sea (CBS) region in China using correlation analysis between the normalized difference vegetation index (NDVI) and indicators related to urban development, agricultural practices, and afforestation efforts; multivariate linear regression and residual analyses were used to quantify how anthropogenic activities contribute to NDVI change. We found that the vegetation cover in most of the study area significantly increased from 1982 to 2015. In major cities, the decrease in vegetation cover was not as expected because of the opposing effects of rapid urbanization and greening. Afforestation and improved agricultural practices dominated the increase in vegetation cover in different regions. Anthropogenic activities accounted for 42% of the increase in vegetation cover in the CBS region. Therefore, to achieve regional sustainable development, the effects of human activities in highly populated area must be heeded.

Permafrost thaw driven changes in hydrology and vegetation cover increase trace gas emissions and climate forcing in Stordalen Mire from 1970 to 2014.

Permafrost thaw increases active layer thickness, changes landscape hydrology and influences vegetation species composition. These changes alter belowground microbial and geochemical processes, affecting production, consumption and net emission rates of climate forcing trace gases. Net carbon dioxide (CO2) and methane (CH4) fluxes determine the radiative forcing contribution from these climate-sensitive ecosystems. Permafrost peatlands may be a mosaic of dry frozen hummocks, semi-thawed or perched sphagnum dominated areas, wet permafrost-free sedge dominated sites and open water ponds. We revisited estimates of climate forcing made for 1970 and 2000 for Stordalen Mire in northern Sweden and found the trend of increasing forcing continued into 2014. The Mire continued to transition from dry permafrost to sedge and open water areas, increasing by 100% and 35%, respectively, over the 45-year period, causing the net radiative forcing of Stordalen Mire to shift from negative to positive. This trend is driven by transitioning vegetation community composition, improved estimates of annual CO2 and CH4 exchange and a 22% increase in the IPCC's 100-year global warming potential (GWP_100) value for CH4. These results indicate that discontinuous permafrost ecosystems, while still remaining a net overall sink of C, can become a positive feedback to climate change on decadal timescales.This article is part of a discussion meeting issue ‘Rising methane: is warming feeding warming? (part 2)’.

Unravelling the role of vegetation on the different trends between climatic and hydrologic drought in headwater catchments of Spain

The availability of water resources is a major challenge of the Mediterranean region. Intense land use transformation has impacted the headwaters of river basins that generate most of the water resources, reducing streamflow This study analyses the evolution of hydrological and climatic drought in headwater catchments of Spain and it explores the extent to which vegetation can reinforce trends in hydrological drought severity in comparison to the evolution of cFlimatic drought severity. We have used the Standardized Precipitation Evapotranspiration Index and Standardized Streamflow Index to examine hydrological and climatic drought, respectively, and examined the changes in the frequency, magnitude, and duration of climatic and hydrologic droughts over non-perturbed headwater catchments of Spain from 1961 to 2013. We quantified vegetation changes over time in the analysed catchments and we compared the changes in the climatic and hydrological droughts with changes in vegetation coverage using Pearson’s r correlations and linear regression model. The results show that the trends toward higher frequency, duration and severity of hydrological droughts are more marked than the observed trends in climatic droughts, which can be associated to the dominant increase in vegetation coverage and activity in the study domain. Finally, it is concluded that the spatial differences observed between the trends of climatic and hydrological droughts show some relationship with the patterns of forest succession observed in recent decades. Our results stress the relevance of land transformation processes on trends in water resources availability, particularly during periods of climatic droughts in which competence between vegetation water consumption and streamflow production is much more relevant.

Analysing the day/night seasonal and annual changes and trends in land surface temperature and surface urban heat island intensity (SUHII) for Indian cities

• Day/night seasonal and annual changes and trends (2001- 2018) in land surface temperature and surface urban heat island intensity (SUHII) for Indian cities (Lucknow, Kolkata and Pune). • Nighttime LST is a better indicator to study the urban heating effect due to its sensitivity towards urbanization. • Positive trends in mean annual daytime (0.003 to 0.059 °C/year) and nighttime (0.030 to 0.078 °C/year) LST are observed in all cities, except in Pune where urban cooling occurs during daytime. • Nighttime SUHII is positive for all cities with mean annual SUHII ranging from 1.34 to 2.07 °C. Understanding the patterns and possible causes of urban heat islands (UHI) effect due to urbanisation-induced anthropogenic activities is an important area in urban climatic research. Few studies on long-term thermal behaviour of Indian cities are available in the literature. Towards this, the present study investigates the day/night seasonal and annual changes and trends in land surface temperature (LST) and surface urban heat island intensity (SUHII) during the last two decades for three Indian cities (Lucknow, Kolkata and Pune) with distinct urban, physiographic and climatic setting. Moderate Resolution Imaging Spectroradiometer (MODIS) LST data products acquired during daytime and nighttime from 2001 to 2018 are processed and analysed for this purpose. MODIS-based aerosol optical depth (AOD) and normalised difference vegetation index (NDVI) products are used to understand the plausible reasons of change in LST and SUHII patterns. The urban (contiguous built-up) and non-urban (surrounding rural) areas are delineated by applying city clustering algorithm on MODIS Land Cover datasets of 500 m spatial resolution. Mann-Kendall and Seasonal-Kendall tests along with Theil-Sen estimator are used for trend analysis. The findings show that the diurnal temperature range (DTR) has decreased from 2001 to 2018 due to higher increase in nighttime LST as compared to daytime. Nighttime LST is a better indicator to study the urban heating effect due to its sensitivity towards urbanisation. Positive trends in mean annual daytime (0.003 to 0.059 °C/year) and nighttime (0.030 to 0.078 °C/year) LST are observed in all cities, except in Pune where urban cooling occurs during daytime. Increase in aerosol loading (with consequent decrease in air temperature and surface insolation) and vegetative cover over time are attributed as the primary reasons of urban cooling effect in Pune during daytime. Seasonal analysis indicate high warming rates during monsoon and summer seasons, particularly during nighttime (0.062 to 0.1 °C/year). Nighttime SUHII is positive for all cities with mean annual SUHII ranging from 1.34 to 2.07 °C. Statistically significant ( p <0.01) increasing trends are observed in mean annual SUHII (0.009 °C/year to 0.022 °C/year) for Kolkata and Pune. Decreasing trend in SUHII is observed over Lucknow due to higher rate of increase in LST in non-urban area as compared to urban area. The study highlights that geographical, physiographic and climatic setting along with anthropogenic processes in urban and its surrounding non-urban areas are critical towards understanding the causative factors in exacerbating the phenomenon of urban heating.

Evaluating spatio-temporal soil erosion dynamics in the Winam Gulf catchment, Kenya for enhanced decision making in the land-lake interface

Soil erosion accelerated by poor agricultural practices, land degradation, deprived infrastructure development and other anthropogenic activities has important implications for nutrient cycling, land and lake productivity, loss of livelihoods and ecosystem services, as well as socioeconomic disruption. Enhanced knowledge of dynamic factors influencing soil erosion is critical for policymakers engaged in land use decision-making. This study presents the first spatio-temporal assessment of soil erosion risk modelling in the Winam Gulf, Kenya using the Revised Universal Soil Loss Equation (RUSLE) within a geospatial framework at a monthly resolution between January 2017 and June 2020. Dynamic rainfall erosivity and land cover management factors were derived from existing datasets to determine their effect on average monthly soil loss by water erosion. By assessing soil erosion rates with enhanced temporal resolution, it is possible to provide greater knowledge regarding months that are particularly susceptible to soil erosion and can better inform future strategies for targeted mitigation measures. Whilst the pseudo monthly average soil loss was calculated (0.80 t ha−1 month−1), the application of this value would lead to misrepresentation of monthly soil loss throughout the year. Our results indicate that the highest erosion rates occur between February and April (average 0.95 t ha−1 month−1). In contrast, between May and August, there is a significantly reduced risk (average 0.72 t ha−1 month−1) due to the low rainfall erosivity and increased vegetation cover as a result of the long rainy season. The mean annual gross soil loss by water erosion in the Winam Gulf catchment amounts to 10.71 Mt year−1, with a mean soil loss rate of 9.63 t ha−1 year−1. These findings highlight the need to consider dynamic factors within the RUSLE model and can prove vital for identifying areas of high erosion risk for future targeted investigation and conservation action.

Responses of Xilingol Fractional Vegetation Cover to Climate Change and Human Activities

Based on the MODIS NDVI product data source of Xilingol from 2010 to 2019, we use the pixel dichotomous model to retrieve the vegetation coverage in our study. The spatiotemporal changes of the vegetation cover were analyzed in the model by using the meteorological data from researched sites or the vicinal meteorological stations for evaluating the meteorological influence on the vegetation cover changes. Based on this, an evaluation method was established to estimate the relative influences of the climate changes and anthropogenic activities. The main conclusions are as follows: (1) Fractional vegetation cover in Xilingol was decreased from the northeast to the southwest. (2) The overall trend in Xilingol fractional vegetation cover in the 10-year period shows a fluctuating increasing trend. (3) An opposite distribution pattern was detected between mean precipitation and mean temperature in the study site. (4) Compared with temperature, annual precipitation has a higher correlation with fractional vegetation cover in the study site and is the main climatic factor that affects vegetation growth in the study site. (5) During the 10-year period in the study site, anthropogenic human activities have slightly greater inhibitory effects on vegetation growth than promoting effects. (6) Climate change is a major factor to accelerate grassland degradation from 2010 to 2019 in vegetation degradation regions. The promotion effect of precipitation on vegetation coverage is obviously higher than the limitation of human activities, which leads to the increase of vegetation coverage in 2010–2019.

Interdecadal climate variability identified in aeolian deposits in southern Santa Catarina, Brazil

Changes have occurred to the patterns of surface morphology in coastal aeolian deposits in a chrono-correlated way in different geographical areas at different time scales. These changes can be recognized and associated with meso and large-scale climatic events, thus establishing a teleconnection. In the present study, surface and subsurface data, combined with Optically Stimulated Luminescence (OSL) dating, allowed us to establish the evolutionary chronology and the environmental context of aeolian features that cover a stretch of the Holocene coastal barrier in the southern coast of Santa Catarina, Brazil. According to geophysical and geochronological data and geomorphological indicators, the section shows regressive coastal line behavior (progradational pattern). The sedimentary cover of this Holocene coastal barrier, so far dominated by active dunes, began to change after the 1930s. The subsequent decades were marked by a significant increase in vegetation, fixing the precipitation crests of the transgressive sand sheets (TSS). This increase in vegetation cover over the last century results from climatic variability associated with the Pacific Decadal Oscillation.

Effect of Climate Change on Spring Massive Sand/Dust Storms in Iraq

Sand and Dust storms are considered a major natural disaster that cause many damages to society and environment in Iraq and surrounded deserted regions. Two spring sand/dust storms on May in two different years were synoptically analyzed. These sand/dust storms were compared in terms of dust surface concentration from NMMB/BSC-Dust model, sea level pressure, surface wind vector, satellite vegetation index and stations rainfall. The findings of this sand/dust storms comparison indicate that Iraq in spring may be affected by two types of wind one dust storm initiated by Shamal which have long occurred in this region and caused frequent dust storms in spring and second by Al-Khamsian. Dust storm in 2012 is massive than sand/dust storm in 2018 where the highest dust surface concentration is reached to (7700 μg/m3) in 22 May 2012 and about (3100 μg/m3) in 11 May 2018. Increase in vegetation cover over Iraq in 2018 was about 23% more than in 2012. Rainfall level in season (2017-2018) was higher than in rainfall season (2011-2012) in Iraqi dust sources regions. Low pressure gradient, less strong wind, rise in rainfall level and enhancement in vegetation cover are contributed to decrease the storm concentration of 2018 roughly by half.

Vegetation Cover Effects on Outdoor Thermal Comfort Around High-rise Developments; A Case Study of Havelock City, Colombo, Sri Lanka

Colombo, with its rapid development, is experiencing an influx of high-rise developments. These developments create a significant influence on the microclimate of the area around them, and therefore impact outdoor thermal comfort. With the intension of mitigating outdoor thermal comfort concerns, the enhancement of the vegetation cover is an often-proposed strategy. This is a research initiative to ascertain the optimum vegetation cover percentage to achieve outdoor thermal comfort around high-rise developments, utilising Havelock City, Colombo, Sri Lanka as a case study. A computer simulation process is adopted, using the software ENVI-met, to explore the optimum form and coverage of vegetation for outdoor thermal comfort. Results show, overall thermal comfort levels diminish, with the increased infusion of vegetation. Vegetation cover had a little or no impact in the daytime, while the strategy had distinct negative impacts in the night-time. The nature of the built morphology of the development together with the vegetation cover increase is shown to have significant impact on wind movement and nocturnal heat loss, therefore outdoor thermal comfort levels. Conclusions highlight the need for the extensive exploration of morphological studies, while encompassing key amelioration strategies, particularly for the high-rise development typology.

Effects of restoration and management of Mediterranean traditional water systems on Odonata alpha diversity: a long-term monitoring survey

The progressive abandonment and disappearance of traditional water uses and management of wetlands during the twentieth century has led not only to a loss of identity, heritage, and landscape values, but also to significant declines in the diversity and abundance of many organisms. Here, we take advantage of an existing project for the restoration and management of traditional irrigation infrastructures in the wetland of El Prado (Pinoso, south-eastern Spain) to evaluate the spatio-temporal effect of this action on the alpha diversity and abundance of Odonata. The wetland was organized in different sectors according to the coverage of riparian and aquatic vegetation, width and depth of watercourses, ditches and ponds, water flow, and restoration and management. Odonates were sampled every month for ten years. We used alpha diversity to measure biodiversity using Hill’s number diversity. To analyse how alpha diversity measures varied across all sectors sampled over the years, we determined diversity-time relationships. To assess the effects of the different variables on odonate biodiversity we used partial least squares regressions. Our results showed that restoration of traditional water infrastructures, encouraging the increase of aquatic vegetation cover, an adequate and regular management of riparian vegetation naturalizing the margins, as well as reducing speed of water flow have a positive effect on odonate diversity and abundance. Our study provides useful information for conservation and management of semi-arid wetlands and its associated water infrastructures by showing which actions are most successful to enhance biodiversity in one of the priority habitats for conservation in Europe.