Search Results (279)

Vegetation water use efficiency (WUE) is a crucial indicator for elucidating the interconnections between the carbon and water cycles of ecosystems and for discerning the response of vegetation ecosystems to climate change. Gansu Province in northwestern China is facing significant ecological water-related challenges. However, the response of vegetation WUE to climate environmental factors in this region remains unclear. In this study, the MODIS vegetation gross primary productivity (GPP) and evapotranspiration (ET) datasets were used to calculate the vegetation WUE in Gansu Province and, combined with meteorological data, Theil–Sen median trend analysis and partial correlation analysis were used to determine the spatial and temporal characteristics of vegetation WUE in this region and its response to climate environmental factors. Finally, the random forest model was used to rank the importance of climate environmental factors. The results indicate the following: (1) The average values of vegetation WUE, GPP, and ET in Gansu Province from 2000 to 2020 were 1.46 gC·mm⁻¹·m⁻², 510.22 gC·m⁻², and 343.68 mm, respectively, and their spatial distribution was high in the southeast and low in the northwest, which was closely related to the distribution of vegetation in the region. (2) Over the past 20 years, the vegetation WUE in this region showed a slowly decreasing trend in general, with a decrease rate of 16.57%. There were significant differences in the WUE of different vegetation types, among which forest WUE was the highest and grassland WUE the lowest. (3) The trend prediction of WUE in Gansu Province was performed by using the rescaled extreme difference method, and the Hurst index was 0.45, which means that the vegetation WUE in this region is expected to increase in the future. (4) In general, precipitation was the main factor influencing the change in vegetation WUE in Gansu Province, followed by vapor pressure deficit (VPD), temperature, and soil moisture. This study provides strategy support for the coupling process of vegetation ecosystems and the sustainable development of agriculture and animal husbandry in Gansu Province and has scientific reference value for promoting and planning the sustainable development of vegetation in arid and semi-arid areas. Full article

The ecosystems within the Qilian Mountain National Nature Reserve (QMNNR) and its surrounding areas have been significantly affected by changes in climate and land use, which have, in turn, constrained the region’s socio-economic development. This study investigates the regional characteristics and application requirements of the ecological environment in the arid and semi-arid zones of the reserve. In view of the saturated characteristics of NDVI in the reserve and the high-altitude saline-alkali environmental conditions, this study proposed a Modified Remote Sensing Ecology Index (MRSEI) by introducing the kernel NDVI and comprehensive salinity index (CSI). This approach enhances the applicability of the remote sensing ecological index. The temporal and spatial dynamics of ecological and environmental quality within the QMNNR from 2000 to 2022 were quantitatively assessed using the MRSEI. The effect of land use on ecological quality was quantified by analyzing the MRSEI contribution rate. The findings in this paper indicate that (1) in arid and semi-arid regions, the MRSEI provides a more precise representation of surface ecological environmental quality compared to the remote sensing ecological index (RSEI). The high correlation (R² = 0.908) and significant difference between MRSEI and RSEI demonstrate that MRSEI enhances the accuracy of evaluating ecological environmental quality. The impact of land use on ecological quality was quantitatively assessed by analyzing the contribution rate of the MRSEI. (2) The ecological quality of the QMNNR exhibited an upward trend from 2000 to 2022, with an increase rate of 1.3 × 10⁻³ y⁻¹. The area characterized by improved ecological and environmental quality constitutes approximately 53.68% of the total area. Conversely, the ecological quality of the degraded areas accounts for roughly 28.77%. (3) Among the various land use types, the improvement in ecological environmental quality within the reserve is primarily attributed to the expansion of forest and grassland areas, along with a reduction in unused land. Forest and grassland types account for over 90% of the total area classified with “good” and “excellent” ecological grades, whereas unused land types represent more than 44% of the total area classified with “poor” ecological grades. Overall, this study provides a valuable framework for analyzing ecological and environmental changes in arid and semi-arid regions. Full article

Given global climate change and rapid land cover changes due to human activities, accurately identifying, extracting, and monitoring the long-term evolution of wetland resources is profoundly significant, particularly in areas with fragile ecological conditions. Gansu Province, located in northwest China, contains all wetland types except coastal wetlands. The complexity of its wetland types has resulted in a lack of accurate and comprehensive information on wetland changes. Using Gansu Province as a case study, we employed the GEE platform and Landsat time-series satellite data, combining high-quality sample datasets with feature-optimized multi-source feature sets. The random forest algorithm was utilized to create wetland classification maps for Gansu Province across eight periods from 1987 to 2020 at a 30 m resolution and to quantify changes in wetland area and type. The results showed that the wetland mapping method achieved robust classification results, with an average overall accuracy (OA) of 96.0% and a kappa coefficient of 0.954 across all years. The marsh type exhibited the highest average user accuracy (UA) and producer accuracy (PA), at 96.4% and 95.2%, respectively. Multi-source feature aggregation and feature optimization effectively improve classification accuracy. Topographic and seasonal features were identified as the most important for wetland extraction, while textural features were the least important. By 2020, the total wetland area in Gansu Province was 10,575.49 km², a decrease of 4536.86 km² compared to 1987. The area of marshes decreased the most, primarily converting into grasslands and forests. River, lake, and constructed wetland types generally exhibited an increasing trend with fluctuations. This study provides technical support for wetland ecological protection in Gansu Province and offers a reference for wetland mapping, monitoring, and sustainable development in arid and semi-arid regions. Full article

Evapotranspiration (ET) is a critical component of the hydrological cycle, and it has a decisive impact on the ecosystem balance in arid and semi-arid regions. The Yinchuan Plain, located in the Gobi of Northwest China, has a strong surface ET, which has a significant impact on the regional water resource cycle. However, there is a current lack of high-resolution evapotranspiration datasets and a substantial amount of time is required for long-time series remote sensing evapotranspiration estimation. In order to assess the ET pattern in this region, we obtained the actual ET (ET_a) of the Yinchuan Plain between 1987 and 2020 using the Google Earth Engine (GEE) platform. Specifically, we used Landsat TM+/OLI remote sensing imagery and the GEE Surface Energy Balance Model (geeSEBAL) to analyze the spatial distribution pattern of ET over different seasons. We then reproduced the interannual variation in ET from 1987 to 2020, and statistically analyzed the distribution patterns and contributions of ET with regard to different land use types. The results show that (1) the daily ET_a of the Yinchuan Plain is the highest in the central lake wetland area in spring, with a maximum value of 4.32 mm day⁻¹; in summer, it is concentrated around the croplands and water bodies, with a maximum value of 6.90 mm day⁻¹; in autumn and winter, it is mainly concentrated around the water bodies and impervious areas, with maximum values of 3.93 and 1.56 mm day⁻¹, respectively. (2) From 1987 to 2020, the ET of the Yinchuan Plain showed an obvious upward and downward trend in some areas with significant land use changes, but the overall ET of the region remained relatively stable without dramatic fluctuations. (3) The ET_a values for different land use types in the Yinchuan Plain region are ranked as follows: water body > cultivated land > impervious > grassland > bare land. Our results showed that geeSEBAL is highly applicable in the Yinchuan Plain area. It allows for the accurate and detailed inversion of ET and has great potential for evaluating long-term ET in data-scarce areas due to its low meteorological sensitivity, which facilitates the study of the regional hydrological cycle and water governance. Full article

Local microgeographic sites subdivided by sharp ecological and climatic contrasts are important platforms for measuring biodiversity patterns and inferring the possible effect of climatic and ecological variables on species distributions and habitat use. Here, we report results from 24 months (September 2019–August 2021) of continuous pitfall trapping collection in Lower Nahal Keziv, Western Upper Galilee, Israel (“Evolution Canyon” II (hereafter—EC II)). This site receives an average annual rainfall of 784 mm and contains two slopes that differ markedly by solar radiation and plant formation. The first is the south-facing slope (SFS), which is characterized as a semiarid garrigue and open grassland. The second is the contrasting north-facing slope (NFS), which is characterized by a more humid East Mediterranean forest. The slopes are separated by a narrow valley bottom (VB). Analysis of ca. 1750 arachnid specimens, collected from 70 pitfall traps along the slopes and valley, indicates significantly different arachnid assemblages between the NFS and SFS, likely due to the differences in solar radiation that affect plant-cover percentage, which in turn affects the arachnid assemblage composition. In addition to 98 arachnid taxa collected and identified to species and morphospecies level, this study resulted in the discovery of two species new to science, which are described as part of this publication (100 arachnid species and 11 additional taxa that were not identified to species, a total of 111 taxa). Our study, moreover, contributes new ecological data on the spatial and temporal distribution of arachnids, and therefore attests to the importance of year-round sampling in an understudied region. Overall, our study enables a better understanding of arachnid diversity and their distributions and serves as a reference for future research aimed at testing the effect of climate change and other environmental factors that influence arachnid assemblages in natural habitats. Full article

Accurate evapotranspiration (ET) estimation is crucial for sustainable water management in the diverse and water-scarce Mediterranean region. This study compares three prominent models (Simulator of Terrestrial Ecohydrological Processes and Systems (STEPS), Soil-Canopy-Observation of Photosynthesis and Energy fluxes (SCOPE), and Two-Source Energy Balance (TSEB)) with established global datasets (Moderate Resolution Imaging Spectroradiometer 8-day global terrestrial product (MOD16A2), Global Land Evaporation Amsterdam Model (GLEAM), and TerraClimate) at multiple spatial and temporal scales and validates model outcomes with eddy covariance based ground measurements. Insufficient ground-based observations limit comprehensive model validation in the eastern Mediterranean part (Turkey and Balkans). The results reveal significant discrepancies among models and datasets, highlighting the challenges of capturing ET variability in this complex region. Differences are attributed to variations in ecosystem type, energy balance calculations, and water availability constraints. Ground validation shows that STEPS performs well in some French and Italian forests and crops sites but struggles with seasonal ET patterns in some locations. SCOPE mostly overestimates ET due to detailed radiation flux calculations and lacks accurate water limitation representation. TSEB faces challenges in capturing ET variations across different ecosystems at a coarser 10 km resolution. No single model and global dataset accurately represent ET across the entire region. Model performance varies by region and ecosystem. As GLEAM and TSEB excel in semi-arid Savannahs, STEPS and SCOPE are better in grasslands, croplands, and forests in few locations (5 out of 18 sites) which indicates these models need calibration for other locations and ecosystem types. Thus, a region-specific model calibration and validation, sensitive to extremely humid and arid conditions can improve ET estimation across the diverse Mediterranean region. Full article

Reforestation of native shrub on shifting sand dunes has been widely used for desertification control in semi-arid grassland in Northeast China. Previous studies have confirmed that plantation establishment facilitates fixing sand dunes, restoring vegetation, and improving soil properties, but very few have focused on the response of the soil fungal community. In this study, a chronosequence of Caragana microphylla (CM) shrub sand-fixation plantations (8-, 19-, and 33-year-old), non-vegetated shifting sand dunes (0 years), and adjacent natural CM forests (NCFs; 50-year-old) in the Horqin sandy land were selected as experimental sites. Soil properties including enzymatic activities were determined, and the composition and structure of the soil fungal community were investigated using the Illumina MiSeq sequencing technique based on the internal transcribed spacer (ITS) rDNA. This study aimed to (1) describe the response of the soil fungal community to revegetation onto a moving sand dune by planting a native shrub plantation; (2) determine the main soil factors driving the succession of the fungal community; and (3) discuss whether the soil fungal community can be restored to its original state by reforestation. The reforestation of CM significantly ameliorated soil properties, increased soil fungal diversity, and altered the composition and structure of the soil fungal community. Ascomycota, Basidiomycota, and Zoopagomycota were the dominant phyla in all sites. Ascomycota did not respond to plantation development, whereas the other two dominant phyla linearly increased or decreased with the plantation age. The relative abundance of dominant genera varied with sites and showed a waning and waxing characteristic. The composition and structure of the soil fungal community in the 33-year CM plantation were very close to that of the NCF, indicating the restorability of the soil fungal community. The succession of the soil fungal community was directly driven by soil properties, of which soil moisture, organic matter, total N, urease, and protease were the main affecting factors. Full article

The focus of our study was the changes in the composition of semi-natural dry grasslands in Hungary. Maintaining the favorable condition of grasslands is not only important from a theoretical nature conservation point of view, but it also has important economic implications. Since these valuable habitats were created with the help of humans, their preservation also requires active treatment. Our current experiment was aimed at investigating the suppression of tall grass, Calamagrostis epigejos L. Roth. In Hungary, in the Cserhát Mountains, eight permanent plots were mown twice a year. We surveyed the vegetation twice a year between 2001 and 2011. The effects of treatment were studied with repeated measures analysis of variance (ANOVA). After 10 years, the C. epigejos cover of the mown plots decreased significantly, from the initial average of 62.38 to 7.50%. Surprisingly, we noticed a decrease in the control plots as well. While percentage cover of C. epigejos decreased in all plots, the decrease was significantly stronger in the mown plots. Regular treatment caused an increase in the number of species and diversity. Species richness increased continuously in both treatment types, which indicates the combined effect of vegetation succession and treatment. The biomass growth of other Poaceae and Fabaceae species, which are important from a grassland management perspective, was also facilitated by mowing. Our results allow us to conclude that long-term regular mowing is recommended for preservation from the perspective of the richness and variety of grassland management functional groups and the functioning of the ecosystem in semi-arid regenerating grasslands. Full article

As a key soil carbon process, changes in plant root growth may have a dramatic impact on the global ecosystem’s carbon cycle. Fine root functional traits and fine root biomass can be used as important indexes of plant root growth. Compared with the much better understood relationships between aboveground plant functional traits and aboveground biomass, knowledge on the relationships between fine root functional traits and belowground biomass still remains limited. In this study, plant fine roots in 30 abandoned lands, 9 woodlands, 29 alfalfa grasslands, 30 Caragana shrublands and 29 croplands were sampled at 0–20 and 20–40 cm soil depths in Zhonglianchuan, Yuzhong County, Gansu Province, China (36°02′ N, 104°24′ E), to clarify the characteristics of the relationships between fine root functional traits (e.g., diameter, specific root area (SRA) and specific root length (SRL)) and fine root biomass at 0–20 and 20–40 cm soil depths. The results showed that the relationships between the fine root functional traits and fine root biomass in these ecosystems were robust, allowing for the use of an allometric growth model at both 0–20 and 20–40 cm soil depths (p < 0.05). Specifically, the relationship between root diameter and fine root biomass was consistent with highly significant positive power, while highly significant negative power relationships of SRA and SRL with fine root biomass were observed (p < 0.01, except the root diameter–biomass models in the woodlands in the 0–20 cm soil layer (p = 0.017) and 20–40 cm soil layer (p = 0.025)). The results can provide some parameters for these terrestrial ecosystem process models. From this perspective, our study is beneficial in the construction of suitable strategies to increase plant biomass, which will help with the restoration of the semi-arid region of the Loess Plateau of China. Full article

Soils and water are major resources that drive a country’s economy, and therefore should be conserved and utilized sustainably. However, in Kenya, these two resources are facing huge depletion and degradation due to anthropogenic factors and climate change. Bamboo species, especially on large plantations, can significantly alter ecological, hydrological, and biogeochemical processes in the long term. This study aimed to evaluate the effects of different species of bamboo and tree plantations on important soil–water processes like infiltration, bulk density, runoff, and soil loss in Kenya. The research was conducted at two sites (Gede in Arabuko Sokoke forest and at Baolala, in Kilifi County) managed by the Kenya Forestry Research Institute (KEFRI). The Arabuko Sokoke forest has a hot–humid coastal climate, while Baolala is a hot semi-arid area with little precipitation. The study involved measurement of soil–water infiltration rates using infiltrometers, installing runoff plots to quantify surface runoff and sediment loss, and analyzing soil properties like bulk density for growing periods for different bamboo and tree species. At the Gede forest site, the 30-year-old Thyrsostachys siamensis and Bambusa bambos plantations recorded the highest infiltration rates. Mature bamboo plantations of T. siamensis and B. bambos recorded higher infiltration rates compared to mature plantations of E. camaldulensis and G. arborea. It was observed that the bamboo plantations manifested lower soil bulk density compared to bare land, which recorded the highest bulk density. At Boalala, infiltration rates were significantly higher in the bamboo species compared to grassland and bare land. The painted bamboo (B. vulgaris vittata) had a slightly higher water infiltration rate compared to B. vulgaris. Runoff and erosion patterns reinforced the benefits of more mature bamboo plantations as well. There was a significant correlation between amount of runoff and collected soil loss through erosion. The data showed reductions in surface runoff volumes and sediment loss as the bamboo plantations aged compared to younger species. Therefore, by enhancing infiltration and reducing runoff and erosion, well-managed bamboo plantations can protect valuable soil resources, improve water recharge, and support sustainable land use over the long term. In conclusion, this study showed the strong potential of bamboo as a soil and water conservation tool in Kenya. Full article

Understanding vegetation seasonality and its driving mechanisms improves decision-making in the management of ecological systems in a warming global climate. Using multiple statistical methods (i.e., trend analysis, abrupt changes, and partial correlation analysis), this study analyzed the spatiotemporal variations in the Normalized Difference Vegetation Index (NDVI) in the Equatorial Africa (EQA) region and their responses to climate factors from 1982 to 2021. The NDVI values declined at a rate of 0.00023 year⁻¹, while the precipitation (P) and mean temperature (TMEAN) values increased at rates of 0.22 mm year⁻¹ and 0.22 °C year⁻¹, respectively. The mean minimum temperature (TMIN) had a higher rate of 0.2 °C year⁻¹ than the mean maximum temperature (TMAX) at 0.02 °C year⁻¹. An abrupt change analysis showed that the TMAX, P, and NDVI breakpoints occurred in 2000, 2002, and 2009, respectively; TMEAN and TMIN breakpoints occurred in 2001. The NDVI trends declined in forest and cropland areas but increased in shrubland and grassland areas. The summer NDVI trends declined for all vegetation types and were reversed in the winter season. The NDVI positively correlated with the P (r = 0.50) and TMEAN (r = 0.60). All seasonal analyses varied across four seasons. A temporal analysis was conducted using partial correlation analysis (PCR), and the results revealed that TMIN had a greater impact on the NDVI (PCR = −0.45), followed by the TMAX (PCR = 0.31) and then the P (PCR = −0.19). The annual trend showed that areas with significant greening were consistent with stronger wetter and weaker warming trends. Both precipitation and temperature showed a positive relationship with vegetation in semi-arid and arid regions but a negative relationship with humid regions. Our findings improve our insight into scientific knowledge on ecological conservation. Full article

Salicornia europaea L. is a well-known model plant for studying the mechanism of salt tolerance. A substantial decline in the S. europaea population has been observed in the semi-arid steppe of the Mongolian Plateau. The relationship between environmental factors and its population dynamics in the grassland ecosystem remains inadequately investigated. Rhizosphere microbial communities, representing the most direct and influential biological factors affecting plant populations, have received limited research attention in the context of halophytes. Four density treatments of S. europaea (bare land—SEB, low density—SEL, medium density—SEM, and high density—SEH) in a single-factor randomized-block design with five replications were established to evaluate the relationship between rhizosphere soil bacterial communities and environmental factors. The results showed that as the density of S. europaea increased, the soil pH decreased, while available phosphorus increased. Rhizosphere soil bacterial communities associated with S. europaea populations in the saline-alkali wetland were dominated by Proteobacteria, Bacteroidota, Actinobacteria, Gemmatimonadota, and Halobacterota. Notably, the genera Antarcticibacterium, Wenzhouxiangella, BD2-11_terrestrial_groupBD2-11, Halomonas, and Natronorubrum were found to be particularly abundant. The Simpson index of the rhizosphere soil bacterial community in the S. europaea treatments was significantly higher than that in bare land. Soil pH and nitrate nitrogen were the primary environmental drivers of the rhizosphere bacterial community. Overall, the rhizosphere soil’s bacterial diversity in saline wetlands under a high-salt environment was not affected by the decrease in the S. europaea population. S. europaea plays an important role in shaping soil bacterial community structure through its influence on the surrounding soil environment. The cultivation of S. europaea is a phytoremediation strategy to improve soil salinization. Full article

The Tibetan Plateau (TP) serves as a crucial ecological barrier in Asia, with vegetation playing a pivotal role in the terrestrial ecosystem by facilitating energy exchange between the land and atmosphere, regulating climate, and participating in the carbon cycle. In this study, we analyze the characteristics of surface vegetation on the TP in the growing season during 1982–2018 using satellite remote sensing data obtained from the National Oceanic and Atmospheric Administration (NOAA) and China Meteorological Forcing Dataset (CMFD). We investigate how these characteristics respond to climate change under different warming and humidification conditions across the TP. The main conclusions are as follows. (1) The normalized difference vegetation index (NDVI) values on the TP exhibit a gradual decrease from southeast to northwest during the growing season. There is a significant overall increasing trend at a climate tendency rate of 0.01·decade⁻¹ (p < 0.01) from 1982 to 2018, characterized by a notable mutation of around 1998. Over the past 37 years, a polarized trend of vegetation was observed on the TP, with notable improvement in its central and eastern regions. However, there has been noticeable degradation in northwestern TP, specifically within the Kunlun Mountains and Qaidam Basin. (2) The climate of the TP demonstrates distinct regional disparities in terms of warming and humidification characteristics before and after 1998. During the period of 1982–1998 (1998–2018), the temperature increase is primarily concentrated in the northern (southern) TP, while precipitation increase is mainly observed in the southern and northwestern (northeastern and western) regions of the TP. (3) The responses of surface vegetation to climate factors exhibit significant variations across diverse climatic backgrounds. It is noteworthy that moisture conditions have a substantial impact on the response of vegetation to air temperature on the TP. During the period of 1982–1998, under relatively insufficient moisture conditions, a positive correlation was observed between air temperature and surface vegetation in the humid and semi-humid regions of the southeastern TP, while a negative correlation was found in the semi-arid regions of northeastern TP. During 1998–2018, as moisture conditions became relatively sufficient, surface vegetation in the semi-arid regions showed positive correlations with both temperature and precipitation. However, surface vegetation in the humid and semi-humid regions exhibited a significant negative correlation with precipitation. During this period, the synergistic effects between warm and humid climates in the semi-arid regions of northeastern TP and warm and dry climates in humid and semi-humid regions of southeastern TP substantially enhanced surface vegetation on the TP. Furthermore, our results indicate that thermal factors (air temperature) primarily influence variations in surface vegetation within the high-altitude arid region of the TP. During 1998–2018, a significant cooling trend was observed in the northwestern TP, which could potentially account for the degradation of surface vegetation in the Kunlun Mountains. The findings of this study establish a scientific basis for the sustainable development of grassland ecosystems on the TP. Full article

The research on the significant toxic weed Oxytropis glabra, which adversely affects the grazing industry and the ecological integrity of natural grasslands in the arid and semi-arid regions of northern China, aims to delineate its potential distribution amidst changing climate conditions. This analysis involves both current conditions (1970–2000) and future projections (2050s and 2070s) under four climate scenarios using an R-optimized MaxEnt model. The results indicate that the distribution of O. glabra was primarily influenced by the temperature of the coldest quarter (bio11, ranging from −12.04 to −0.07 °C), precipitation of the coldest quarter (bio19, 0 to 15.17 mm), and precipitation of the warmest quarter (bio18, 0 to 269.50 mm). Currently, the weed predominantly occupies parts of Xinjiang, Inner Mongolia, Gansu, Qinghai, Ningxia, and Tibet. Projections indicate that, across four future climate scenarios, the area of suitable habitats for O. glabra is expected to expand and shift toward higher latitudes and elevations. The research provides valuable information and a theoretical foundation for the management of O. glabra, alongside advancing grassland ecological research and grazing practices. Full article

The accurate assessment of the rise in nitrous oxide (N₂O) under global changes in grasslands has been hindered because of inadequate annual observations. To measure the seasonal response of N₂O emissions to increased water and nitrogen (N) deposition, one year round N₂O emissions were investigated by chamber weekly in the growing season and every two weeks in the non-growing season in semi-arid temperate grasslands northern China. The results showed the temperate semi-arid grassland to be a source of N₂O with greater variability and contribution during the non-growing season. The individual effects of water or N addition increased N₂O emissions during the growing season, while the effects of water or N addition depended on the N application rates during the non-growing season. Soil properties, particularly soil temperature and water-filled pore space (WFPS), played key roles in regulating N₂O emissions. Structural equation modeling revealed that these factors explained 71% and 35% of the variation in N₂O fluxes during the growing and non-growing season, respectively. This study suggested that without observations during the non-growing season it is possible to misestimate the annual N₂O emissions and the risk of N₂O emissions increasing under global change. This would provide insights for future management strategies for mitigating greenhouse gas emissions. Full article