Changes In Vegetation Dynamics Research Articles

An insight into effect of soil salinity on vegetation dynamics in the exposed seafloor of the Aral Sea

The desiccation of the Aral Sea has precipitated significant ecological degradation, resulting in the progressive development of vegetation on the exposed seafloor. Soil salinity emerges as a pivotal determinant in this ecological succession process. Employing a comprehensive methodology integrating multi-source datasets spanning from 1986 to 2023, this study elucidates the temporal changes in vegetation dynamics and soil salinity levels. Satellite imagery (Landsat-4/5/7/8), field soil samplings, hydrological and topographic data were analyzed to understand their interactions with regression analysis. The results reveal a consistent increasing trend in the Normalized Difference Vegetation Index (NDVI) across the exposed seabed since 1986. However, NDVI demonstrates a non-linear relationship with elevation in the North Aral Sea region. Interestingly, NDVI levels near an elevation of 42 m on the exposed seabed approximate those observed during the pre-recession period in the 1960s. Conversely, in the South Aral Sea region, NDVI demonstrates a linear upward trend with increasing elevation. Furthermore, the spatial distribution of soil salinity on the exposed seabed was delineated with linear regression analysis. It revealed water salinity levels at the time of sea recession can serve as a proxy for soil salinity in cases where direct soil data is unavailable. Through establishing a robust correlation between NDVI and soil salinity, the range of stable NDVI values on the exposed seabed was delineated. Lastly, three hypothetical scenarios of rising water levels were considered to evaluate changes in stable NDVI across different elevation gradients. If the water level returns to 45 m, the salt-desert area would decrease by 4.5 × 104 km2, accounting for 23 % of the total area in 1960. At this water level, it is anticipated that lake hydrological conditions and ecological environments may restore to those observed in 1981. This study provides a long-term perspective on environmental changes in the Aral Sea region by integrating multiple data sources and analytical methods. The predictive insights from the scenario analysis offer valuable guidance for future water management and ecological restoration efforts. Compared with previous studies, it presents a detailed and comprehensive picture of the interplay between vegetation dynamics and soil salinity, highlighting the critical impact of water level changes on the region's ecosystem.

Correction: A Fresh Take: Seasonal Changes in Terrestrial Freshwater Inputs Impact Salt Marsh Hydrology and Vegetation Dynamics

Correction: A Fresh Take: Seasonal Changes in Terrestrial Freshwater Inputs Impact Salt Marsh Hydrology and Vegetation Dynamics

Faster than expected: 5-year re-surveys reveal accelerating plant colonization in two proglacial forelands of the Gran Paradiso National Park (NW Italian Alps)

Abstract Proglacial vegetation communities are facing major challenges today due to fast glacier retreat and global warming, resulting in possible changes in plant colonization patterns. By re-surveying permanent plots along two alpine chronosequences (encompassing 5 to 165 years from deglaciation) with a 5-year time span, we aimed to (i) assess short-term vegetation changes and (ii) compare current vegetation trajectories with those predicted by the chronosequence approach. We analysed the number and cover of total, pioneer, and alpine grassland species and calculated the slopes of the trajectories of the chronosequence and observed on permanent plots. As expected, the number and cover of total, pioneer, and grassland species increased during the 5 years of the study. Moreover, we observed a significant acceleration in plant colonization (21 and 45 times faster increase in species richness and cover, respectively) compared to the chronosequence predictions. These dramatic changes in vegetation dynamics of proglacial plant communities were probably induced by the increased temperatures and longer growing seasons occurring in the Alps.

A Fresh Take: Seasonal Changes in Terrestrial Freshwater Inputs Impact Salt Marsh Hydrology and Vegetation Dynamics

AbstractSalt marshes exist at the terrestrial-marine interface, providing important ecosystem services such as nutrient cycling and carbon sequestration. Tidal inputs play a dominant role in salt marsh porewater mixing, and terrestrially derived freshwater inputs are increasingly recognized as important sources of water and solutes to intertidal wetlands. However, there remains a critical gap in understanding the role of freshwater inputs on salt marsh hydrology, and how this may impact marsh subsurface salinity and plant productivity. Here, we address this knowledge gap by examining the hydrologic behavior, porewater salinity, and pickleweed (Sarcocornia pacifica also known as Salicornia pacifica) plant productivity along a salt marsh transect in an estuary along the central coast of California. Through the installation of a suite of hydrometric sensors and routine porewater sampling and vegetation surveys, we sought to understand how seasonal changes in terrestrial freshwater inputs impact salt marsh ecohydrologic processes. We found that salt marsh porewater salinity, shallow subsurface saturation, and pickleweed productivity are closely coupled with elevated upland water level during the winter and spring, and more influenced by tidal inputs during the summer and fall. This seasonal response indicates a switch in salt marsh hydrologic connectivity with the terrestrial upland that impacts ecosystem functioning. Through elucidating the interannual impacts of drought on salt marsh hydrology, we found that the severity of drought and historical precipitation can impact contemporary hydrologic behavior and the duration and timing of the upland-marsh hydrologic connectivity. This implies that the sensitivity of salt marshes to climate change involves a complex interaction between sea level rise and freshwater inputs that vary at seasonal to interannual timescales.

Study on the Application of Water Resource Management Based on GF-7 Stereo Mapping Satellite

Abstract. GF-7 satellite was successfully launched on 3 Nov 2019. The two-line stereo camera can effectively obtain 20 km-width panchromatic stereo images with resolution better than 0.8m and 3.2m-resolution multispectral images. Through the composite mapping mode of stereo camera and laser altimeter, the satellite realizes 1:10,000-scale stereo mapping. This article selected the Qiafuqihai Reservoir and its upstream of the Yili River Basin as the study area. Hydrological landforms and vegetation coverage were monitored and three-dimensional dynamic simulation software was developed to verify the potential application of GF-7 stereo mapping satellite data in supporting drainage basin water resource allocation and management in future scenarios. 3 meters DSM derived from GF-7 surveying and mapping satellite finely portrayed the characteristics of hydroponic landforms of small watersheds. The upstream of Qiafuqihai was divided into eleven small watersheds. The water density was 8.5 times more than which was produced from STRM 90m. The elevation of the water-level fluctuation zone of the Qiafuqihai Reservoir ranged from 970 to 998 meters with the water area changed from 28.3 to 57.6 square kilometres. The terrain in the northwest and northeast was flat, with the main vegetation types being natural grasslands (64.9%) and arid lands (5.03%). The three-dimensional dynamic visualization software was developed and demonstrated hydrology information, vegetation coverage information and dynamic changes in the landform of the basin in three-dimensional environment. GF-7, the stereo surveying and mapping satellite, could be perfectly able to support the application of water resources deployment and management in the future.

Impact of Ecological Water Transfer Project on Vegetation Recovery in Dried-Up Kongque River, Northwest China

The ecological water transfer project (EWTP) plays a pivotal role in reinstating the flow of dried-up rivers in arid regions, promoting river connectivity and vegetation resurgence. An essential facet in ensuring the efficacious execution of the EWTP lies in determining the optimal duration of irrigation to facilitate vegetation recovery. Nevertheless, comprehensive reports concerning the EWTP process in arid river ecosystems are scarce. Here, we leverage remote sensing imagery to assess changes in surface water and vegetation dynamics before and after the implementation of the EWTP in a dried-up river. The results show that before the EWTP (1987–2016), riparian vegetation’s mean normalized difference vegetation index (NDVI) decreased from 0.181 to 0.066. After EWTP (2017–2022), the river’s flow was restored for a distance of 347 km. This restoration resulted in the formation of 81.47 km2 of intermittent water bodies along the river. The mean NDVI increased from 0.065 to 0.093. As irrigation duration increased, the NDVI growth rate exhibited an initial rise followed by a subsequent decline, reaching its peak growth rate by irrigating for 18 days per year. The regions showing increased NDVI values exhibited a pronounced spatial correlation with the areas subjected to water transfer. These improvements in NDVI were predominantly concentrated on both sides of the river within a 550 m range. Interestingly, as moves farther away from the river, the growth rate of NDVI exhibited an initial increase followed by a subsequent decline. The pinnacle of NDVI growth rate materialized at a distance of 40–50 m from the river. These findings reveal the response characteristics of desert riparian vegetation to EWTP, providing valuable insights for selecting appropriate water transfer timing in future EWTP.

Aboveground Biomass Estimation and Time Series Analyses in Mongolian Grasslands Utilizing PlanetScope Imagery

Mongolia, situated in central Asia and bordered by Russia to the north and China to the south, experiences a semi-arid climate across most of its territory. Grasslands are pivotal in Mongolia’s agricultural sustainability and food security, facing rapid changes in the last two decades that underscore the ongoing need for innovative approaches to assess vegetation conditions. This study aims to evaluate grassland biomass measurement and prediction through the analysis of high-resolution satellite data. By conducting a time series assessment of grazing-induced changes in vegetation dynamics at the long-term monitoring sites of the Botanic Garden and Research Institute, Mongolian Academy of Sciences, we seek to refine our understanding. The investigation covers biomass estimation across various Mongolian grassland landscapes, encompassing desert, steppe, and mountain regions. Spanning the grassland growing season from May 2020 to October 2023, the research leveraged diverse ground data types, including surface reflectance measurements, geographic coordinates for satellite data correction, and aboveground dry biomass. These components were instrumental in developing a biomass estimation model reliant on establishing correlations between the satellite-derived Normalized Difference Vegetation Index and biomass. The predicted biomass facilitated the time series map analysis and dynamic analysis. The PlanetScope surface reflectance correlates strongly at 0.97 with field measurements, indicating robust relations. Biomass and the Normalized Difference Vegetation Index show correlations of 0.82 for dry grassland, 0.80 for mountain grassland, and 0.65 for desert grassland, with a combined correlation coefficient of 0.62, revealing distinct characteristics across these grasslands. Time series dynamic analysis reveals rising biomass differences between grazed and ungrazed areas, suggesting potential grassland degradation. Variations in the slope coefficient of biomass differences among grassland types indicate differing degradation patterns, emphasizing the need for effective grazing management practices to sustain and conserve Mongolian grasslands. This highlights the potential of remote sensing in monitoring and managing grassland ecosystems.

Assessment of observed changes in drought characteristics and recent vegetation dynamics over arid and semiarid areas in Sudan

Assessment of observed changes in drought characteristics and recent vegetation dynamics over arid and semiarid areas in Sudan

中亚地区2001–2020年250m及2020年30m分辨率植被生长季NDVI数据集

Central Asia is the largest arid and semi-arid region in the Northern Hemisphere, and its ecological environment is extremely fragile and susceptible to the effects of global climate change. Maintaining the stability of the region's ecosystem is crucial to global economic and social development due to its unique geographic location. Vegetation serves as a significant indicator of the ecological environment, and the spatial and temporal distribution pattern, as well as the change trend of vegetation, are important indicators in evaluating the ecological status of the region. The Normalized Difference Vegetation Index (NDVI) is a commonly used remote sensing index to study vegetation, which characterizes the spatio-temporal changes of vegetation. This dataset utilized MODIS13Q1 to generate long-term time series growing season mean NDVI data with a spatial resolution of 250m in Central Asia from 2001 to 2020. To obtain the 2020 growing season mean NDVI data with a higher spatial resolution of 30m, the Cubist algorithm based on rule segmentation regression was utilized to fuse the Landsat data and MODIS data. Meanwhile, this dataset carried out quality control of data products from three aspects: data source quality control, model training optimization, and model independent verification to ensure the accuracy and reliability of data. The generation of this dataset provides powerful data support for the analysis of vegetation dynamic change and spatial pattern in Central Asia.

Editorial: Carbon sequestration and climate change in crops, natural vegetation, and wetland dynamics in the high Andes

Editorial: Carbon sequestration and climate change in crops, natural vegetation, and wetland dynamics in the high Andes

Climatic and Anthropogenic Contributions to Vegetation Changes in Guangdong Province of South China

How to distinguish the relative role of climate change and human activities in vegetation dynamics has attracted increasing attention. However, most of the current studies concentrate on arid and semiarid regions, while the relative contributions of climate change and human activities to vegetation changes remain unclear in warm-humid regions. Based on the normalized difference vegetation index (NDVI) and climatic variables (temperature, precipitation, radiation) during 2001–2020, this study used the Theil–Sen median trend analysis, partial correlation analysis, and residual trend analysis to analyze the spatiotemporal pattern of vegetation trends, the response of vegetation to climate variations, and the climatic and anthropogenic contributions to vegetation dynamics in the warm and humid Guangdong Province of south China. Results showed that the NDVI in most areas exhibited an increasing trend. Changes in climatic variables displayed different spatial variations which, however, were not significant in most areas. Vegetation responded diversely to climate change with temperature as the most important climatic factor for vegetation improvement in most areas, while precipitation was the dominant climatic factor in the southern edge region and radiation was the dominant climatic factor in the central and western regions. Vegetation in most areas was influenced by both climate change and human activities, but the contribution rate of human activities was commonly much higher than climate change. The findings of this study are expected to enhance our understanding of the relative climatic and anthropogenic contributions to vegetation changes in warm-humid regions and provide a scientific basis for future ecological policies and ecosystem management in highly urbanized regions.

Flash Drought and Its Characteristics in Northeastern South America during 2004–2022 Using Satellite-Based Products

The term flash drought describes a special category of drought with rapid onset and strong intensity over the course of days or weeks. To characterize the impact of flash droughts on vegetation coverage, this study assessed the influence of soil water deficits on vegetation dynamics in the northeastern South America region by combining time series of vegetation index, rainfall, and soil moisture based on satellite products at a daily time scale. An 18-year analysis, from 2004 to 2022, of the Normalized Difference Vegetation Index (NDVI), Standard Precipitation Index (SPI), and surface soil moisture (SSM) was performed based on three different satellite remote sensing estimates: the spinning enhanced visible and infrared imager (SEVIRI) and the integrated multi-satellite retrievals algorithm (IMERG), and the soil moisture and ocean salinity (SMOS). The results revealed that flash drought events exerted dramatic impacts on terrestrial ecosystems in the study region during the first two decades of the 2000s, with changes in seasonal and regional vegetation dynamics. Further, the fixed-threshold values to characterize flash drought events were suggested as the timing when the water deficit was less than −1.0 units and vegetation index reached the value equal to +0.3 during five consecutive weeks or more, coupled with soil moisture rates below 40% percentile, leading to a strong region-wide drought throughout the entire region. Additionally, the results of linear least squares trend analyses revealed a negative trend in the pentad-SEVIRI radiance for the solar channel 1 within the semiarid ecosystems of the study region (i.e., the Caatinga biome) that was suggested as a reduction in clouds in the 18 years of the study. Developing combined threshold measures of flash drought based on satellite remote sensing may lead to an accurate assessment of flash drought mitigation.

Attribution of vegetation fluorescence changes in China based on a decision tree stratification strategy

Vegetation photosynthesis plays a key role in maintaining carbon balance in terrestrial ecosystems. Solar-Induced chlorophyll Fluorescence (SIF) was utilized as a proxy for vegetation photosynthesis in this study, and the Theil-Sen and Mann-Kendall methods were used to examine trends of vegetation change in China. The impacts of climate conditions on vegetation photosynthesis were examined with the correlation analysis and recursive feature elimination (RFE) method. To distinguish the contributions of climate change and human activities on vegetation photosynthesis, land use data and SIF change trends were employed as inputs to a decision tree model. The results revealed that 81.5% of the areas in China exhibited an improving trend of vegetation photosynthesis. Vegetation degradation areas were mainly located in Northern arid and semi-arid region (NASR), Qinghai Tibet Plateau (QTP) and Huang-Huai-Hai Plain (HHHP). Precipitation dominated the effect of vegetation photosynthesis in these regions. The increase of vegetation photosynthesis in the southern regions was positively impacted by solar radiation. The growth of agricultural technology obviously benefited the improvement of vegetation photosynthesis in the Middle-lower Yangtze Plain (MLYP) and Northeast China Plain (NCP). Furthermore, the establishment of ecological conservation programs has helped to restore vegetation in arid and semi-arid areas. The detrimental effects of human activities included overgrazing disturbance and coal mining activities, which resulted in vegetation deterioration in areas of QTP and HHHP. The methodologies and findings of this study can help to comprehend changes in vegetation dynamics and give a theoretical foundation for evaluating regional ecological conservation initiatives.

Attribution of climate change and human activities to vegetation NDVI in Jilin Province, China during 1998–2020

Vegetation is among the key elements of ecosystems, and the normalized difference vegetation index (NDVI) is among the most frequently used tools for studying changes in regional vegetation dynamics. Studying these changes and their drivers is essential for understanding the interactions between vegetation and ecosystems; therefore, here, we analyzed the spatial and temporal patterns of NDVI in Jilin Province and their influencing factors. The correlation between NDVI and climatic factors was analyzed using Pearson’s correlation analysis. Additionally, we explored the correlation between NDVI and human activity using geographically weighted regression analysis. The results were as follows: (1) From 1998 to 2020, although the temporal trends of NDVI for different vegetation types in Jilin Province showed some differences in general, they all showed an increasing trend. (2) The spatial trends of NDVI in Jilin Province ranged from − 0.031 to 0.046. The NDVI values exhibited a trend toward growth in most regions. (3) Climate change factors are more important than human activity factors for improving vegetation. (4) Among the climatic factors, the negative correlation between temperature and NDVI was stronger than the positive correlation, while the positive and negative correlations between precipitation and NDVI were equally strong. (5) Human activity factors such as GDP and population have mostly negative effects on regional NDVI, whereas land-use type shifts have mostly positive effects. The results of this study contribute to a deeper understanding of the drivers of vegetation change. Additionally, some discussions can provide theoretical references for ecological management and sustainable development in Jilin Province.

Relict soil features in cave sediments record periods of wet climate and dense vegetation over the last 100 kyr in a present-day semiarid region of northeast Brazil

The present-day semiarid region of NE Brazil experienced multiple periods of increased precipitation during the Quaternary. They were likely linked to global-scale events (e.g., Heinrich Events) and drove changes in vegetation dynamics, leading to the expansion of rainforest vegetation. Here, we hypothesize that soil features preserved in cave sediments records paleoenvironmental changes induced by global-scale events that affected NE Brazil during the Late Pleistocene - Early Holocene. To test this hypothesis, we analyzed the elemental and isotopic geochemistry composition, bulk sediment mineralogy, soil micromorphological features, and fauna fossil type and content of a well-preserved 6 m cave sediment profile spanning 103 kyr – 8 kyr in Toca de Cima do Pilão at the Serra da Capivara National Park. Our approach provides new information on the history of soil formation, vegetation, and climate of NE Brazil during the Late Pleistocene - Early Holocene. The results demonstrated that severe weathering and dense vegetation was the dominant paleoenvironmental conditions during wet periods, when latosolization was the main soil forming process. The evidence for wet and intense weathering periods was the co-existence of speleothems layers with Ferralsol features, such as runiquartz, granular microstructure, Fe nodules and gibbsite formation. Some of these features were found in layers deposited in synchrony with Heinrich Stadial and Younger Dryas periods, suggesting that past soil processes in NE Brazil were affected by those global-scale events. We propose five phases of latosolization in our study area during the last 100 kyr. The first was identified around 80 kyr, the second occurred around 29 kyr. The third coincided with Heinrich Stadial 1 (16 kyr) and the fourth likely occur during the Younger Dryas, and the fifth phase occurred during the middle Holocene.

Impact of climatic and vegetation dynamic change on runoff over the Three Rivers Source Region based on the Community Land Model

Impact of climatic and vegetation dynamic change on runoff over the Three Rivers Source Region based on the Community Land Model

Response of vegetation dynamic change to multi-scale drought stress in the high-latitude Nenjiang River basin in China

Vegetation is an integral part of terrestrial ecosystem and plays an important role in responding to climate change, with its dynamic characteristics reflecting the ecological environmental quality. Recently, the continually increasing frequency and intensity of droughts has greatly changed how vegetation growth and development respond to drought. In this study, using normalized difference vegetation index and standardized precipitation evapotranspiration index (SPEI), we studied the response characteristics of vegetation dynamics to multi-scale drought stress (SPEI-1, SPEI-3, and SPEI-12) in the Nenjiang River basin (NRB) via Pearson correlation analysis, along with further exploration of the vegetation stability under drought. The results showed that the same period effect of drought on vegetation growth in NRB mainly occurs during the early and middle stages of vegetation growth. Furthermore, the proportion of significant positive correlation between them is 15.3%–43.3%, mainly in the central and southern parts of the basin. The lagged period effect of drought on vegetation growth mainly occurred during autumn in the southeast and middle of the basin, with a significant positive correlation of 20.8%. Under drought stress, the forest vegetation stability in NRB was the highest, with the resilience of wetland and grassland vegetation being the best and worst, respectively. Our study results will not only deepen our understanding of the dynamic vegetation changes in the high-latitude semi-arid basin under global climate change, but also provide a scientific basis for the management and water resources allocation of “agriculture-wetland-forest” complex ecosystem in the future.

Soil characteristics and response thresholds of salt meadow on lake beaches of the Ordos platform

Salt meadow on lake beaches is the most dynamic plant community. Studying its soil characteristics and response threshold allows us to understand the external driving forces of vegetation stable-state maintenance and dynamic changes, and provide a theoretical basis for the utilization and ecological restoration of lake beach wetland resources. In this study, the community diversity, physical and chemical properties of soil, and ecological response thresholds of key soil indexes of four groups of meadows are discussed: (I) succulent salt-tolerant plant meadow, (II) Carex meadow, (III) grass meadow, and (IV) weed grass meadow. The major findings are as follows. First, Group I is easy to form a single-optimal community in the inland salt marsh beach, with patchy distribution. Group II has a lot of associated species, and most of them grew in clusters. Group III often has obvious dominant species, and the populations and individuals are evenly distributed in the community. The dominant species of Group IV are diverse, and the distribution is the most uniform. Second, there are significant differences in water content, salinity, nutrient and particle size composition of the four types of salt meadows. For Groups I-IV, the soil water content (WC) follows I > II > IV > III; the total salt content (TS) of soil follows I > III > II > IV; the pH value follows III > II > IV > I. Third, the diversity of salt meadow plants in lake beaches is closely related to the contents of WC, TS, Na+, HCO3−, particle size, available potassium (AK), alkali hydrolyzable nitrogen (AN) and available phosphorus (AP) in soil. The vegetation of the four formation groups shows different ecological response threshold intervals. Fourth, the response thresholds of salt meadow vegetation to water content, salt content and sand content of soil are inherently related (but the response threshold to nutrients in soil is unclear).

Vegetation dynamics of Sangkub watershed in North Sulawesi Province indicated by NDVI of Landsat data

<p>Vegetation can be an important indicator of ecosystem change, the influence of anthropogenic and non-anthropogenic factors. Therefore, it is important to study the dynamics of vegetation changes. One technique that can be used for vegetation analysis is the Normalized Difference Vegetation Index (NDVI). NDVI is an indicator of the active biomass that helps distinguish vegetation from other land cover and can provide information about changes in Spatio-temporal vegetation dynamics, thus allowing for assessment of the ecological conditions. This study aimed to investigate the dynamic of vegetation in the Sangkub watershed area located in North Sulawesi Province. This analysis used geospatial technology with the NDVI method, utilizing Landsat 5 and Landsat 8 satellite imagery data in three periods the year 2000, 2015, and 2020. The results showed that vegetation cover of the Sangkub watershed decreased substantially, whereas the non-vegetated area increased gradually over time.</p>

Global spatial distribution of vegetation and 20-years dynamic changes

Global spatial distribution of vegetation is determined jointly by climate, monsoon, ocean current and human activities. In recent decades, surface vegetation changes caused by global warming, extreme climate events and intensified human activities need a further understood. In this paper, we adopted available MODIS land cover dataset (MCD12Q1) to investigate the spatial distribution feature of global vegetation sand dynamics during the past 20 years. Results show that: (1) the spatial distribution pattern of global vegetation formed by the long-term ecosystem evolution exhibits stable with less variation in both latitude and vertical dimensions. Generally, the percent of forest, shrubland, grass and cropland respectively are 15.27%, 9.39%, 39.46% and 8.91% of surface covers, with a distinct land cover transition trend from rainforest at equator region to moss and lichen at the north and south pole. (2) In the past 20 years, the global forest land decreased by 3.0×105 km2, with an average annual decrease of 1.255%, open shrubs experienced slight fluctuations in 2001-2017 and increased sharply by 1.6×105 km2 in 2017-2018. And the grassland, croplands and cropland/natural vegetation mosaics had different degrees of growth rate, with an average annual dynamic increase of 0.021%, 0.019% and 0.502%, respectively. (3) There are about 4.2×106 km2 of forest changed into grassland in West Siberia and the Amazon, and 2.5×106 km2 of grassland into shrubs, as well as 1.9×106 km2 of grassland vegetation into farmland, and 9.4×104 km2 of forest into shrubs.