Effects Of Vegetation Cover Change Research Articles

Addendum: A dataset mapping the potential biophysical effects of vegetation cover change

Addendum: A dataset mapping the potential biophysical effects of vegetation cover change

Impacts on watershed-scale runoff and sediment yield resulting from synergetic changes in climate and vegetation

This study investigates the relations between climate change and both runoff and sediment yield in watersheds and provides a scientific basis for water resources planning and design as well as watershed-scale soil and water conservation. The impact of climate change on runoff and sediment yield in a watershed does not occur in isolation, but is a synergistic process in which climate and vegetation jointly influence runoff and sediment yield. Previous studies have seldom addressed this synergistic effect. For this study, a regression model between climate factors (temperature and precipitation) and the Normalized Difference Vegetation Index (NDVI) was established using data from the Zhenjiangguan Watershed in China. By combining data on climate-driven changes in vegetation cover, the Soil and Water Assessment Tool (SWAT) model was built to simulate runoff and sediment yield in the watershed under two scenarios: changes in climate, and synergistic changes in climate and vegetation cover. The simulation results show that precipitation is the most sensitive factor affecting runoff and sediment yield; 10% change in annual precipitation can cause 10%–14% change in annual runoff and 17%–24% change in annual sediment yield. Temperature is also an important factor affecting runoff and sediment yield in the watershed. Each temperature increase of 0.7 °C can result in a decrease of 1.4%–2% in annual runoff and 2%–3.7% in annual sediment yield. This research reveals that accounting for synergetic change in vegetation has an impact on runoff and sediment yield results, and that the magnitude and nature of this influence vary among different combinations of temperature and precipitation changes. When temperature was kept constant, the effect of vegetation cover change caused by precipitation change on runoff and sediment yield was relatively small (only 0.9%–1.5% of the total change), and vegetation cover change inhibited the effects of precipitation change on runoff and sediment yield. When precipitation was kept constant, the effects of vegetation cover change caused by temperature change on runoff and sediment yield were relatively large (20%–30% of the total change), and vegetation cover change enhanced the effects of temperature change on runoff and sediment yield. This investigation considers the synergistic effects of climate and vegetation cover change, and thus further clarifies the extent to which climate change impacts water and ecological resources.

Contrast Effects of Vegetation Cover Change on Evapotranspiration during a Revegetation Period in the Poyang Lake Basin, China

It is known that evapotranspiration (ET) differs before and after vegetation change in watersheds. However, impacts of vegetation change on ET remain incompletely understood. In this paper, we investigated the process-specific, nonclimatic contribution (mainly vegetation coverage changes) to ET at grid, sub-basin, and basin scales using observation and remote sensing data. The Poyang Lake Basin was selected as the study area, which experienced a fast vegetation restoration from 1983 to 2014. Our results showed that vegetation cover change produced contrasting effects on annual ET in magnitude and direction during shifts from a less covered to a more covered stage. At the early stage (1983–1990), with vegetation cover of 30%, vegetation cover change produced negative effects on ET over the basin. At the middle stage (1990–2000), the vegetation coverage increased at a fast pace and the negative effects gradually shifted to positive. At the late stage (2000–2014), the vegetation coverage remained high (over 60%) and maintained a positive relationship with ET. In summary, the vegetation effects are collaboratively influenced by both vegetation coverage and its change rate. Our findings should be helpful for a comprehensive understanding of complicated hydrological responses to anthropogenic revegetation.

A dataset mapping the potential biophysical effects of vegetation cover change

Changing the vegetation cover of the Earth has impacts on the biophysical properties of the surface and ultimately on the local climate. Depending on the specific type of vegetation change and on the background climate, the resulting competing biophysical processes can have a net warming or cooling effect, which can further vary both spatially and seasonally. Due to uncertain climate impacts and the lack of robust observations, biophysical effects are not yet considered in land-based climate policies. Here we present a dataset based on satellite remote sensing observations that provides the potential changes i) of the full surface energy balance, ii) at global scale, and iii) for multiple vegetation transitions, as would now be required for the comprehensive evaluation of land based mitigation plans. We anticipate that this dataset will provide valuable information to benchmark Earth system models, to assess future scenarios of land cover change and to develop the monitoring, reporting and verification guidelines required for the implementation of mitigation plans that account for biophysical land processes.

Sensitivity of midnineteenth century tropospheric ozone to atmospheric chemistry‐vegetation interactions

AbstractWe use an Earth System model (HadGEM2‐ES) to investigate the sensitivity of midnineteenth century tropospheric ozone to vegetation distribution and atmospheric chemistry‐vegetation interaction processes. We conduct model experiments to isolate the response of midnineteenth century tropospheric ozone to vegetation cover changes between the 1860s and present day and to CO2‐induced changes in isoprene emissions and dry deposition over the same period. Changes in vegetation distribution and CO2 suppression of isoprene emissions between midnineteenth century and present day lead to decreases in global isoprene emissions of 19% and 21%, respectively. This results in increases in surface ozone over the continents of up to 2 ppbv and of 2–6 ppbv in the tropical upper troposphere. The effects of CO2 increases on suppression of isoprene emissions and suppression of dry deposition to vegetation are small compared with the effects of vegetation cover change. Accounting for present‐day climate in addition to present‐day vegetation cover and atmospheric CO2 concentrations leads to increases in surface ozone concentrations of up to 5 ppbv over the entire northern hemisphere (NH) and of up to 8 ppbv in the NH free troposphere, compared with a midnineteenth century control simulation. Ozone changes are dominated by the following: (1) the role of isoprene as an ozone sink in the low NOx midnineteenth century atmosphere and (2) the redistribution of NOx to remote regions and the free troposphere via PAN (peroxyacetyl nitrate) formed from isoprene oxidation. We estimate a tropospheric ozone radiative forcing of 0.264 W m−2 and a sensitivity in ozone radiative forcing to midnineteenth century to present‐day vegetation cover change of −0.012 W m−2.

Changes in streamflow regime following vegetation changes from paired catchments

AbstractVegetation changes can significantly affect catchment water balance. It is important to evaluate the effects of vegetation cover change on streamflow as changes in streamflow relate to water security. This study focuses on the use of statistical methods to determine responses in streamflow at seven paired catchments in Australia, New Zealand, and South Africa to vegetation change. The non‐parametric Mann–Kendall test and Pettitt's test were used to identify trends and change points in the annual streamflow records. Statistically significant trends in annual streamflow were detected for most of the treated catchments. It took between 3 and 10 years for a change in vegetation cover to result in significant change in annual streamflow. Presence of the change points in streamflow was associated with changes in the mean, variance, and distribution of annual streamflow. The streamflow in the deforestation catchments increased after the change points, whereas reduction in streamflow was observed in the afforestation catchments. The streamflow response is mainly affected by the climate and underlying vegetation change. Daily flow duration curves (FDCs) for the whole period and pre‐change and post‐change point periods also were analysed to investigate the changes in flow regime. Three types of vegetation change effects on the flow regime have been identified. The relative reductions in most percentile flows are constant in the afforestation catchments. The comparison of trend, change point, and FDC in the annual streamflow from the paired experiments reflects the important role of the vegetation change. Copyright © 2011 John Wiley & Sons, Ltd.

Effects of vegetation restoration on soil organic carbon sequestration at multiple scales in semi-arid Loess Plateau, China

Soil organic carbon (SOC) sequestration by vegetation restoration is the theme of much current research. Since 1999, the program of qGrain for Greenqhas been implemented in the semi-arid Loess Plateau, China. Its scope represents the largest vegetation restoration activity in China. However, it is still unclear for the SOC sequestration effects of vegetation cover change or natural succession promoted by the revegetation efforts at different scales under the semi-arid conditions. In this study, the changes in SOC stocks due to the vegetation restoration in the middle of Loess Plateau were estimated at patch, hill slope transect and small watershed scale from 1998 to 2006. Soil samples were taken from field for the determination of cesium-137 ((137)Cs) and SOC contents. Vegetation cover change from 1998 to 2006 at the small watershed scale was assessed using Geographic Information System. The results showed that cropland transforming to grassland or shrubland significantly increased SOC at patch scale. Immature woodland, however, has no significant effect. When vegetation cover has no transformation for mature woodland (25 years old), SOC has no significant increase implying that SOC has come to a stable level. At hill slope scale, three typical vegetation cover patterns showed different SOC sequestration effects of 8.6%, 24.6%, and 21.4% from 1998 to 2006, and these SOC increases mainly resulted from revegetation. At the small watershed scale, SOC stocks increased by 19% in the surface soil layer at 0-20 cm soil depth from 1998 to 2006, which was equivalent to an average SOC sequestration rate of 19.92 t Cy(-1) km(-2). Meanwhile. SOC contents showed a significant positive correlation (Pl0.001) with the (137)Cs inventory at every soil depth interval. This implied significant negative impacts of soil erosion on SOC sequestration. The results have demonstrated general positive effects of vegetation restoration on SOC sequestration at multiple scales. However, soil erosion under rugged topography modified the spatial distribution of the SOC sequestration effects. Therefore, vegetation restoration was proved to be a significant carbon sink, whereas, erosion could be a carbon source in high erosion sensitive regions. This research can contribute to the performance assessment of ecological rehabilitation projects such as qGrain to Greenq and the scientific understanding of the impacts of vegetation restoration and soil erosion on soil carbon dynamics in semi-arid environments. (C) 2010 Elsevier B.V. All rights reserved.