Effects Of Vegetation Changes Research Articles

Spatiotemporal geographically weighted regression analysis for runoff variations in the Weihe River Basin

In order to investigate the effects of vegetation changes on runoff and to obtain recommendations for improving runoff in the Weihe River Basin (. In this study, a spatiotemporal geographic autocorrelation weighted regression analysis (SGAWRA) approach was newly developed based on previous studies. This approach investigates spatial non-stationarity of the dynamic response from vegetation variations to climatic change and human activity. Implications of spatial non-stationarity related to runoff variability were also discussed, which in turn yield the effect that vegetation changes have on runoff. The method systematically analysed the spatial non-stationarity of vegetation variations and its associated effects on runoff. Therefore, more closely related results with less error were produced at each step, and results with more accuracy were obtained. These results indicated that the average trend rates of NDVI in the annual average, each season, and the growing season (Growing season refers to April to September) exceeded 0. Areas where NDVI show a growing trend cover more than 50%, which is greater than the area with a decreasing trend. The GWR regression parameters of precipitation, average temperature, and NDVI are all greater than 0. The GWR regression parameters of human activities and NDVI also have more than 50% of the area greater than 0. Based on the visual analysis of the calculation results, it can be seen that there are obvious spatial trends in the data, and the spatial data are significantly different between different regions. Therefore, WRB can be regarded as spatio-temporally non-stationary. In the WRB, the underlying surface change with vegetation change as the prominent feature is the leading cause (about 60%) of the runoff attenuation. The results showed that WRB has spatial and temporal non-stationarity. The spatial non-stationarity of vegetation has a greater effect on runoff changes. The results of this study support recommendations for improving runoff in the WRB.

Climate and vegetation change impacts on future conterminous United States water yield

Future water availability is influenced by both climate and associated vegetation dynamics. This study coupled vegetation projections from a dynamic global vegetation model (MC2) with an ecohydrological model, Water Supply Stress Index (WaSSI), to predict water yield at the 8-digit Hydrologic Unit Code (HUC8) watershed level for the conterminous United States (CONUS) for the 21st century. We considered two contrasting warming scenarios (Representative Concentration Pathways 8.5 and 4.5) and accounted for simulation uncertainty by using a large ensemble of climate model outputs. The coupled model projects a decrease in water yield across much of CONUS, especially towards end-century (2080–2099) under RCP 8.5 (warmer scenario), reaching up to −30% at the regional level, relative to the 2008–2027 baseline period. Overall, the projected water yield reduction under RCP 8.5 is roughly twice as high as under RCP 4.5. Substantial changes in water yield for watersheds in the central and southeastern United States are expected by mid-century (2040–2059), reaching up to −40% (RCP 4.5) and −75% (RCP 8.5) at at the century’s end (2080–2099), relative to 2008–2027, respectively. Climate change, rather than vegetation change, strongly dominates the projected future changes in water yield, with contributions typically one order of magnitude higher. For a small number of watersheds, the effects of vegetation change can mitigate or exacerbate the effects of climate change on water yield. Our simulation results suggest a widespread increase in aridity and evaporative indices and a decrease in soil moisture, especially under RCP 8.5. Our integrated modeling results can inform policy makers and resource development planners quantitative information of future water availability.

Vegetation greening amplifies shallow soil temperature warming on the Tibetan Plateau

Vegetation changes are expected to alter soil thermal regimes, consequently modifying climate feedbacks related to frozen ground thawing and carbon cycling in cold regions. The Tibetan Plateau (TP) contains diverse alpine ecosystems and the largest area of frozen ground in low–mid latitude regions. Evidence suggests ongoing vegetation greening and permafrost degradation during the past several decades on the TP. However, the effect of vegetation changes on soil thermal regimes on the TP is not well understood. Here, we quantify the response of shallow soil temperature change to vegetation greening on the TP using remote–sensing data, in–situ observations, and physics–based modelling. Our results show that over the past 20 years, vegetation greening on the TP was accompanied a notable decrease in the area of bare land by approximately 0.7% (5000 km2). Annual mean soil temperature showed a significant warming trend of 0.57 °C decade–1 (p < 0.05) during the period 1983–2019, exceeding the warming rate of surface air temperature. Changes in vegetation resulted in a warming effect on annual shallow soil temperature of 0.15 ± 0.33 °C across the TP during the period 2000–2019. The warming effect varies with frozen soil types: 0.24 ± 0.48 °C in permafrost, 0.18 ± 0.36 °C in seasonally frozen ground, and 0.11 ± 0.32 °C in unfrozen ground. The net warming effect was caused by a decrease in albedo and increase in radiation penetrating the canopy, outweighing the cooling effect related to a limited increase in evapotranspiration.

Greening vegetation cools mean and extreme near-surface air temperature in China

Satellite observations have shown evident vegetation greening in China during the last two decades. The biophysical effects of vegetation changes on near-surface air temperature (SAT) remain elusive because prior studies focused on the effects on land surface temperature (LST). SAT is more relevant to climate mitigation and adaptation, as this temperature is experienced by humans. Here, we provide the first observational evidence of the greening effects on SAT and SAT extremes in China during 2001–2018 using the ‘space-for-time’ method. The results show a negative SAT sensitivity to greening (–0.35 °C m2 m–2) over China and a cooling effect of −0.08 °C on SAT driven by vegetation greening during the study period. Such a cooling effect is stronger on high SAT extremes, particularly over arid/semiarid areas, where greening could bring an additional cooling of −0.04 °C on the hottest days. An attribution analysis suggests that the main driving factor for the cooling effect of greening is the evapotranspiration change for arid/semiarid regions and the aerodynamic resistance change for humid regions. This study reveals a considerable climate benefit of greening on SAT, which is more concerned with natural and human system health than the greening effects on LST.

Critical influence of vegetation response to rising CO2 on runoff changes

Satellite observations show widespread greening over the global land, which potentially contributes to runoff (R) changes. However, there are discrepancies in the impacts of vegetation greening on R under elevated atmospheric CO2 concentration (eCO2). Here, we proposed an improved Budyko framework with full consideration of the vegetation structural (STR) effect and vegetation physiological (PHY) effect and evaluated runoff changes (ΔR) due to eCO2-induced vegetation variations. We found a better performance of the improved Budyko framework in simulating runoff changes from global climate models (the Nash-Sutcliffe efficiency coefficient (NSE) is 0.82). However, ΔR would be overestimated (underestimated) by 188 % (165 %) when considering the PHY (STR) effect only. Attribution analyses indicated that PHY and STR effects contribute to a ΔR of 12.8 % and − 62 %, respectively, suggesting that PHY and STR effects are indispensable variables in the projection of ΔR. The contribution of the STR effect to future ΔR is 4.8 times larger than the PHY effect, leading to a negative effect of vegetation changes on ΔR in response to eCO2. While the magnitude of PHY appears less than that of STR, the influence of PHY on ΔR follows a faster-increasing tendency in future R projections when compared to STR. Our findings emphasize the critical influence of vegetation response to eCO2 in future R projection.

Human activities further amplify the cooling effect of vegetation greening in Chinese drylands

Vegetation change can provide strong feedback to climate system, but there is a severe shortage of understanding regarding how biogeophysical (BGP) processes related to vegetation changes and their impact on local temperature in arid and semi-arid regions of China (ASAC), a unique region where large-scale ecological engineering projects have been implemented. To address this knowledge gap, this study is aims to investigate the BGP effects of vegetation changes (including growth change and type conversion) and elucidate the BGP mechanisms that link vegetation and surface temperature (Ts) through integrating the Intrinsic Biophysical Mechanism (IBM) method and pairwise comparison analysis. The findings reveal that vegetation change slows down climate warming rate of Ts in ASAC, with a cooling magnitude of -0.0096 K/year (Non-radiative forcing: -0.0114 K/year; Radiative forcing: 0.0018 K/year) from 2000 to 2018, embodied as cooling in summer-autumn and warming in winter-spring. Vegetation-induced BGP effects in ASAC are dominated by non-radiative mechanisms. During the study period, compared to the stable land use/land cover (LULC), cropland expansion and grassland restoration usually led to cooling exceeding -0.05 K and -0.01 K, respectively. However, afforestation and urbanization generally cause warming about 0.02 K and 0.04 K, respectively. From a BGP point of view, avoiding large-scale afforestation in extremely arid regions is an effective strategy. This study highlights the importance of land use/ land cover change (LULCC) in regulating regional climates, and emphasizes the necessity of fully considering the multiple effects of LULCC in the formulation or evaluation of climate change mitigation policies.

Increased impact of the El Niño–Southern Oscillation on global vegetation under future warming environment

There are broad effects of vegetation changes on regional climate, carbon budget, the water cycle, and ecosystems’ productivity. Therefore, further knowledge of the drivers of future vegetation changes is critical to mitigate the influences of global warming. The El Niño–Southern Oscillation (ENSO) is a major mode of interannual climate variability and is likely to affect vegetation on the global scale. Nonetheless, little is known about the causal impacts of ENSO on future vegetation cover with changes in land use and a warming environment. Here, we examined the connections between ENSO and vegetation using leaf area index (LAI) data over the period 2015–2100 from Coupled Modeling Intercomparison Project Phase 6. Our findings indicate that, compared with the historical period 1915–2000, the vegetated areas influenced by ENSO are projected to rise by approximately 55.2% and 20.7% during the twenty-first century of the scenarios SSP2-4.5 and SSP5-8.5, respectively. Though uncertainty for the causal link between ENSO and vegetation changes remains in several regions (i.e., parts of North America, southern Australia, and western Asia), ENSO signature on LAI variations is robust over northern Australia, Amazonia, and parts of Southeast Asia. These results indicate that the influences of ENSO on global vegetation may strengthen in the future.

Review of vegetation phenology trends in China in a changing climate

Vegetation phenology is sensitive to climate change and has been defined as the footprint of ongoing climate change. Previous studies have shown that the spatial difference in China’s vegetation phenology varies substantially in both spring and autumn. Here, we reviewed phenological dynamics at the national and the regional scale of China over the period 1982−2020 using a remote sensing-based dataset and meta-analysis from phenological studies in China. We also explored the underlying mechanisms of both spring and autumn phenology and discussed potential phenological studies under future climate conditions. We found that, over the past four decades, the spring phenology advanced at a rate of 0.23 ± 0.47 days/year, while the autumn phenology was delayed at a rate of 0.17 ± 0.46 days/year. This led to an extended vegetation growth season of approximately 5 days per decade. The trends in the spring and autumn phenology were spatially specific in the Northern region, Northwest region, Qinghai–Tibet region, and Southern region: the change in spring phenology was −0.16, −0.46, −0.18, and −0.13 days/year, respectively, while the change in autumn phenology was 0.02, 0.32, 0.09, and 0.28 days/year, respectively. We also explored the dominant climatic drivers of regional phenological changes. We found that temperature was the dominant factor for spring phenology in cold regions, while precipitation, radiation, and temperature co-determined spring phenology in warm regions. The autumn phenology was affected by all three environmental cues but the effect of temperature was larger than that of radiation and precipitation across all regions. In future climate warming conditions, we recommend that studies focus on the phenological feedback mechanisms, such as the climatic and hydrological effects of vegetation changes, and agricultural phenology to investigate its fundamental role in crop productivity, especially under extreme climate events, to ensure national food security and ecological security.

Quantitatively Computing the Influence of Vegetation Changes on Surface Discharge in the Middle-Upper Reaches of the Huaihe River, China

Changes in meteorology, hydrology, and vegetation will have significant impacts on the ecological environment of a basin, and the middle-upper reach of Huaihe River (MUHR) is one of the key regions for vegetation restoration in China. However, less studies have quantitatively accounted for the contribution of vegetation changes to land surface discharge in the MUHR. To quantitatively evaluate the influence of vegetation changes on land surface discharge in the MUHR, the Bernaola–Galavan (B–G) segmentation algorithm was utilized to recognize the mutation year of the Normalized Difference Vegetation Index (NDVI) time sequence data. Next, the functional relationship between the underlying surface parameter and the NDVI was quantitatively analyzed, and an adjusted Budyko formula was constructed. Finally, the effects of vegetation changes, climate factors, and mankind activities on the surface discharge in the MUHR were computed using the adjusted Budyko formula and elastic coefficient method. The results showed the following: (1) the surface runoff and precipitation from 1982 to 2015 in the MUHR presented a falling trend, yet the NDVI and potential evaporation presented an upward trend; (2) 2004 was the mutation year of the NDVI time series data, and the underlying surface parameter showed a significant linear regression relationship with the NDVI (p &lt; 0.05); (3) the vegetation variation played a major role in the runoff variation during the changing period (2005–2015) in the MUHR. Precipitation, potential evaporation, and human activities accounted for −0.32%, −15.11%, and 18.24% of the surface runoff variation, respectively.

Effects of Vegetation Change on Soil Erosion by Water in Major Basins, Central Asia

The uncertainties in soil erosion (SE) are further intensified by various factors, such as global warming, regional warming and humidification, and vegetation cover changes. Moreover, quantitative evaluations of SE in major basins of Central Asia (CA) under changing environments have rarely been conducted. This study conducted quantitative evaluation of SE in four major basins (Syr Darya Basin (SDB), Amu Darya Basin (ADB), Ili River Basin (IRB) and Tarim River Basin (TRB) using the Revised Universal Soil Loss Equation (RUSLE) and analyzed the main driving factors. SE quantities in the basins presented relatively consistent upward fluctuating trends from 1982 to 2017. Vegetation cover variation fluctuated significantly from 1982 to 2017. Specifically, vegetation cover decreased continuously in SDB, ADB, and IRB, but increased gradually in TRB. Pixels with positive spatial variation of vegetation mainly occurred around lakes and oases near rivers. The Normalized Difference Vegetation Index (NDVI) showed higher correlation with precipitation (80.5%) than with temperature (48.3%). During the study period, the area of arable land (AL) exhibited the largest change among all land use types in CA. Under long-term human activities, the proportion of NDVI of other land types converting to AL was the highest. In the structural equation model (SEM), precipitation, temperature, Shannon Diversity Index (SHDI), and NDVI strongly influenced SE. Overall, the major basins in CA were jointly affected by climate, human activities, and vegetation. Specifically, climatic factors exerted the strongest influence, followed by SHDI (human activities). SE was found to be relatively serious in ADB, SDB, and IRB, with SE in SDB even approaching that in the Loess Plateau. Under the background of global changes, appropriate water and land resource management and optimization configurations should be implemented in CA with reference to TRB in order to relieve local SE problems.

Effects of Vegetation Changes and Multiple Environmental Factors on Evapotranspiration Across China Over the Past 34 Years

AbstractDocumenting the spatiotemporal changes in vegetation cover and hydrological cycle of the Earth system and understanding how they interact are important especially under climate warming. In this research, we quantified the changes in vegetation and evapotranspiration (E) across China during 1982–2015 and then revealed the complex relationships in climate–vegetation–evapotranspiration system. Results show that the upward trend in vegetation leaf area index (LAI) during 2000–2015 (an increase of 0.95% per year) was almost 8 times the trend during 1982–1999. The zones of the Loess Plateau and the Three‐North Shelter Forest Program are the most notable areas for LAI increases between these two periods, with increases of 11.65% and 2.87%, respectively. Increased LAI, along with the warming climate, has accelerated E across China in the past several decades, and the annual increase in the E rate was 0.34% (1.34 mm year−1) during 1982–1999 and 0.40% (1.62 mm year−1) during 2000–2015. The zones of the Loess Plateau and the karst landform are the most notable areas for transpiration increases, with individual increases of 10% and 5%, respectively. In general, the dominant causes for evaporation changes across all of China are temperature and precipitation, while the main reasons for transpiration changes include temperature, LAI, and sunshine duration. This study improves our understanding of the relationships within the climate–vegetation–evapotranspiration system and provides important support for future ecological policies across China.

Assessing the Spatiotemporal Evolution of Anthropogenic Impacts on Remotely Sensed Vegetation Dynamics in Xinjiang, China

The dynamics of the ecosystem represented by vegetation under the influence of human activities have become an important issue in the study of the regional ecological environment. Xinjiang is one of the most ecologically fragile areas in the world, and vegetation changes have received extensive attention. Xinjiang is one of the most ecologically fragile areas in the world, and vegetation changes have received extensive attention. However, the spatiotemporal patterns and evolutionary trends of anthropogenic impacts on vegetation dynamics in Xinjiang are still unclear. In this study, the anthropogenic impacts on vegetation dynamics were quantitatively assessed by combining the improved normalized difference vegetation index (NDVI) prediction model and the residual analysis method in Xinjiang, China. The human driving factors were analyzed with the support of a stepwise multiple regression model for vegetation changes at the county scale. Based on trend analysis and the Hurst exponent, the spatiotemporal characteristics and evolutionary trends of the impact of human activities on vegetation change were discussed. The results show that (1) the NDVI values in Xinjiang showed a gradually increasing trend at a rate of 0.005/10 years from 1982 to 2018, and the vegetation dynamics mainly showed significant improvements (57.09% of the vegetated areas), especially for crops. (2) The anthropogenic effects of vegetation changes in Xinjiang mainly included positive impact increases (43.22% of the vegetated areas) from 2000 to 2018. Human activities promoted the increase in the NDVI of various vegetation types. Both the positive and negative impacts of human activities increased over the study period, and the growth rate of the positive influence (0.08%/10 years) was higher than that of the negative influence (0.04%/10 years). (3) The cultivated area, GDP of primary industry, and population are the main anthropogenic factors causing the increase in NDVI, which dominate the vegetation greening in 30.34%, 29.22%, and 28.09% of the counties in Xinjiang, respectively. The animal husbandry population, agricultural population, and livestock number are the main anthropogenic factors causing the decrease in NDVI, which dominate the vegetation degradation in 23.60%, 21.35%, and 17.98% of the counties in Xinjiang, respectively. (4) The evolutionary trend of the anthropogenic impact on vegetation dynamics in Xinjiang will be dominated by anti-persistence (53.84% of the vegetated areas), thereby mainly showing that the positive impacts continued to increase (22.56% of the vegetated areas), especially for crops, shrubs, grasslands, and alpine vegetation. Our results are helpful in understanding the characteristics and evolutionary trends of vegetation changes in arid areas caused by human activities and are of significance as a reference for policymakers to appropriately adjust policy guidance in a timely manner to promote the protection and sustainable development of fragile ecosystems.

Long‐term precipitation and stream discharge records at seven forested experimental watersheds along a latitudinal transect in Japan: Jozankei, Kamabuchi, Takaragawa, Tsukuba, Tatsunokuchi‐yama, Kahoku and Sarukawa

AbstractThis data note introduces a database of long‐term daily total precipitation and stream discharge data for seven forested watersheds in Japan that have been continuously monitored by the Forestry and Forest Products Research Institute. Three of the watersheds started data collection in the 1930s. Forest cover across the sites ranges from cool to warm temperate regions with the latitude spanning from 31 to 44° N and annual precipitation ranging from 1200 to 3000 mm yr−1. The effects of vegetation change via clearcutting, thinning and forest fire (among other stressors) on stream discharge can be analysed from the long‐term observation sites. Moreover, this multi‐site dataset allows for inter‐ and intra‐site comparisons of annual water loss (difference of annual precipitation and stream discharge). These long‐term datasets can provide comprehensive insights into the effects of climate change and other stressors on forested ecosystems, not only in Japan but across a spectrum of forest types, if combined with other long‐term records from other forested watersheds across the world.

Site Characteristics More Than Vegetation Type Influence Food Web Structure of Intertidal Salt Marshes

Salt marshes are under increasing anthropogenic pressures that have been reported to affect the diet of fish (e.g., change in prey composition and availability), eventually resulting in alterations in their nursery function. Most studies in Europe are based on fish gut content analysis, which only reflect a small proportion of pressures to salt marshes, and do not necessarily reflect long-term disturbances. In this study, we investigated the impact of salt-marsh vegetation type on trophic network structures (i.e., fish diet and trophic position). Primary producers (particulate organic matter, microphytobenthos, and dominant terrestrial plants), potential aquatic and terrestrial prey, and fish of two dominant species (sea bass and thinlip mullet) were sampled during the summer of 2010 in four creeks from two sites from Western France (the Mont-Saint-Michel Bay and the Seine Estuary). Analysis was undertaken using C and N stable-isotope compositions. Tested response variables (diet and trophic position) suggested a dominant site effect and a weaker effect of surrounding vegetation type. Site effect was attributed to differences in anthropogenic nitrogen inputs (with a steep increase in the Mont-Saint-Michel Bay) and tidal regime between the two bays, with more marine signatures associated with a higher frequency and duration of tidal flooding events in the Seine Estuary. A second hypothesis is that invasiveElytrigia acuta, which has recently replaced typical salt-marsh vegetation in Mont-Saint-Michel Bay, negatively impacted the native salt-marshes nursery function by modifying the access to terrestrial prey on this site. The trophic position of the sea bass and the thinlip mullet was unchanged by local salt-marsh vegetation, and considered consistent with their diet. This study highlights the relevance of stable-isotopes analyses for assessing long-term and integrative effects of changes in vegetation resulting from human disturbances in salt marshes.

Spatial Evaluation of Greenhouse Gas Fluxes in a Sasa (Dwarf Bamboo) Invaded Wetland Ecosystem in Central Hokkaido, Japan

To evaluate the effect of vegetation change on greenhouse gas (GHG) budget from a wetland ecosystem, the CO2, CH4 and N2O budgets from whole area (21.5 ha) of the Bibai Wetland, where dwarf bamboo (Sasa) or Ilex has invaded into original Sphagnum dominated vegetation, located in Hokkaido, Japan were estimated. The original Sphagnum-dominated vegetation was changed from a sink to a source of CO2 by invasion of short-Sasa (50 cm &gt; height), while the invasion of tall-Sasa (50 cm &lt; height &lt; 150 cm) or Ilex increased CO2 uptake. Annual CH4 emission was decreased by the invasion of Sasa or Ilex. The annual N2O emission was slightly increased by invasion of Ilex only. These GHG budgets were correlated with the environmental factors related to the water table depth. The distribution of vegetation and environmental factors was estimated from satellite image bands, and the GHG budget of the entire wetland was estimated. The whole wetland area was considered to be a sink for GHG (−113 Mg CO2-eq y−1) and CO2 uptake by tall-Sasa occupied 71% of the GHG budget. The vegetation change due to the lowering of the water table depth currently increases the rate of carbon accumulation in the ecosystem by about 5 times.

Legacy of forest composition and changes over the long-term on tree radial growth

The forests of North America have undergone important changes since European settlement, particularly in terms of stand composition and associated changes in soil properties. While soil nutrients availability is known to influence forest productivity, the causes and consequences of its variation through time remain poorly understood. This study investigates the effects of long-term changes in forest composition and soil properties on the radial growth of sugar maple (Acer saccharum Marsh.) and balsam fir (Abies balsamea (L.) Mill.), two important species of northeastern North America’s forests. Using data from 130 plots measured in 1930 and in 2012–2014 and a mixed-effects modelling approach, we studied the links between radial growth, soil nutrients availability, current stand composition, and shifts in vegetation. The radial growth of balsam fir was found to vary with soil available nitrogen and present-day relative basal area of yellow birch in the stand, while that of sugar maple was found to be invariant to soil characteristics, but proportional to present-day spruce (Picea spp.) relative basal area. However, no direct effects of vegetation change on radial growth were detected. Our results suggest that prior stand composition had no influence on radial growth of both studied species, yet vegetation change could indirectly influence balsam fir growth through an improvement of litter quality with an increase in the abundance of yellow birch (Betula alleghaniensis Britton). Moreover, despite clear differences between the studied species, we conclude that maintaining a certain proportion of compositional diversity may enhance radial growth of both balsam fir and sugar maple.

Sensitivity and attribution analysis of vegetation changes on evapotranspiration with the Budyko framework in the Baiyangdian catchment, China

Due to its role in intercepting and evaporating water, vegetation has a great influence on the catchment hydrological process, and an increased quantitative understanding of how vegetation changes affect the terrestrial water cycle is of considerable interest for a range of spatial scales. In this study, we determine the effects of vegetation changes on evapotranspiration within the Budyko framework by adapting an analytical expression between vegetation and the Budyko parameter at a steady state. We then analyzed the attributions for evapotranspiration change in the Baiyangdian catchment and quantified the effects of vegetation change. The evapotranspiration changes during 1998–2017 in the Baiyangdian catchment were mainly caused by climate change, which accounted for 58.56%, and the contribution of the Budyko parameter (n) change to evapotranspiration was 40.04%. Among the impact factors, the effect of vegetation change on evapotranspiration was not the largest, with vegetation changes in the Baiyangdian catchment resulting in a decrease in evapotranspiration of 22.9715 mm, but only accounting for 10.23%. And we also discuss the spatial pattern of the sensitivities of evapotranspiration to vegetation based on the 66 catchments in the Hai River basin, and the results indicate that an increase in the normalized difference vegetation index (NDVI) would cause a decrease in evapotranspiration in dry regions (W < 1) and cause an increase in evapotranspiration in wet regions (W > 1). Evapotranspiration was more sensitive to NDVI changes in regions of W closer to 1.

Quantitative assessment on the effects of vegetation changes on runoff based on Budyko theory in the Kuyehe River Basin of northern China

Quantitative assessment on the effects of vegetation changes on runoff based on Budyko theory in the Kuyehe River Basin of northern China

Using integrated modelling to understand seasonal vegetation dynamics and its relationship to runoff generation

AbstractVegetation dynamics and hydrological processes are major components of terrestrial ecosystems, and they interact strongly with each other. Studies of hydrological responses to vegetation dynamics are usually conducted on a long‐term scale, whereas the hydrological responses within a single year have rarely been studied. In the present study, Poyang Lake runoff (PYL‐R) model, a new hydrological model coupled with leaf area index (LAI) remote sensing products, was established and applied to simulate the runoff process in the Poyang Lake Watershed. The simulation results obtained in three sub‐watersheds of the Poyang Lake Watershed (Ganjiang Watershed, Xinjiang Watershed, and Fuhe Watershed) agreed well with the observations (Nash efficiency coefficient values and R values exceeded 0.6 and 0.9, respectively). The PYL‐R experiment (PYL‐R‐E) model was designed as a contrast model without considering the impact of LAI. The simulated monthly runoff results obtained using the PYL‐R and PYL‐R‐E models were compared, and the within‐year changes in the differences between the two results were analysed to evaluate and quantify the impact of vegetation dynamic on runoff. From January to July, when LAI values increased by around 2.6 m2 m−2, monthly runoff depth differences between PYL‐R and PYL‐R‐E results increased by 35.25, 27.98, and 29.14 mm in the Ganjiang, Xinjiang, and Fuhe watersheds, respectively. Dense vegetation caused high interception and evapotranspiration during summer, which largely reduced runoff. By contrast, during winter, the effect of vegetation was weaker on runoff process whereas the impacts of other factors (e.g., precipitation) were higher. The sensitivity of monthly runoff to vegetation dynamics varied greatly throughout the whole year. In particular, during August and September, the LAI‐caused runoff changes were very high, accounting for 28–42% of monthly runoff in the sub‐watersheds. Our findings clarify the effects of changes in vegetation on hydrological processes over short time scales, thereby providing insights into the effects of scale on eco‐hydrological processes.

The rebound effects of recent vegetation restoration projects in Mu Us Sandy land of China

The sustainability of vegetation restoration projects implemented in China and their effect on water storage in arid and semi-arid regions has been a contentious topic of discussion in China. In this study, the combination of land use-land cover changes (LULCC) and the normalized difference vegetation index (NDVI) was used to understand the processes responsible for changing vegetation patterns over time, particularly in the Mu Us Sandy Land. The effect of vegetation change on the region’s water storage was further analyzed using the Global Land Data Assimilation System (GLDAS) and the Gravity Recovery and Climate Experiment (GRACE) remote-sensing products. The results showed remarkable restoration of the Mu Us Sandy Land from 2000 to 2018, with regions in which the NDVI showed a significant increase (P < 0.05) and decrease accounting for 67.73% and 0.23% of the study area, respectively. Most increases in NDVI were evident in areas with no transformation between land categories. The effects of vegetation restoration on surface and ground water remain contentious. While a high density of plants is recognized to retain surface soil moisture, there are also indications that it leads to reduced groundwater storage in the Mu Us Sandy Land. Considering the outcomes of this study, we recommend that the water balance should be considered in future ecological restoration projects in China and globally to ensure environmental sustainability.