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Aerial photography provides a historical vehicle for determining long-term urban landscape change and, with concurrent daily streamflow and precipitation records, allows the historical relationship of anthropogenic impervious surfaces and streamflow to be explored. Anthropogenic impervious surface area in the upper Accotink Creek subwatershed (near Annandala, Virginia, USA) was mapped from six dates of rectified historical aerial photography ranging from 1949 to 1994. Results show that anthropogenic impervious surface area has grown from approximately 3% in 1949 to 33% in 1994. Coincident to this period, analysis of historical mean daily streamflow shows a statistically significant increase in the streamflow discharge response (per meter of precipitation) associated with normal and extreme daily precipitation levels. Significant changes were also observed in the frequency of daily streamflow discharge at given volumes above and below the historical daily mean. Simultaneously, the historical magnitude, frequency and pattern of precipitation values 0 mm, 6.0 mm and 35.0 mm show either no statistically significant change or influence on streamflow. Historical changes in streamflow in this basin appear to be related to increases in anthropogenic impervious surface cover. Historical aerial photography is a viable tool for revealing long-term landscape and ecosystem relationships, and allows landscape investigations to extend beyond the temporal and spatial constraints of historical satellite remote sensing data.This revised version was published online in May 2005 with corrections to the Cover Date. 相似文献
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In 2003, the Lost Creek fire burned 21,000 ha of nearly contiguous crown land forests in the headwater regions of the Oldman River Basin, Alberta. Seven small watersheds with various levels of land disturbance (burned, post-fire salvage logged, unburned) were instrumented and monitored for four years to measure stream discharge, sediment concentration, and sediment yields for a range of dominant flow periods characteristic of the region (baseflow, spring melt, and stormflow). Stream discharges reflected runoff regimes consistent with high regional precipitation and the high relief physiographic setting of the study area. Suspended sediment concentrations and yields were significantly higher in both burned and post-fire salvage logged watersheds than in unburned watersheds and were strongly influenced by topographic and hydro-climatic controls. Sediment availability was much higher in both the burned and post-fire salvage logged watersheds but it varied strongly with flow condition, particularly during the snowmelt freshet and high flow events. Because of increases in wildfire frequency and severity over recent decades, understanding the range of impacts from both wildfire and post-disturbance management strategies such as salvage logging is likely to become increasingly important for land managers. 相似文献
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Ferhat Gökbulak Yusuf Serengil Süleyman Özhan Necdet Özyuvacı A. Nihat Balcı 《European Journal of Forest Research》2008,127(3):203-212
The objectives of this study were to quantify the amount of the stream discharge, nutrient fluxes, suspended sediment loss,
and to define the relationship between streamflow and these parameters in a forest-covered watershed. The study was carried
out in an experimental watershed, which has been monitored since 1979 in the Belgrad forest in Istanbul. Significant linear
regressions were obtained between streamflow and discharge of selected water quality parameters. Mean monthly losses were
10.01 kg/ha for HCO3
−, 5.92 kg/ha for CI−, 0.07 kg/ha for total N, 1.29 kg/ha for Mg2+, 3.59 kg/ha for Ca2+, 2.59 kg/ha for Na+, 1.82 kg/ha for K+, 0.0113 kg/ha for P-PO4
3−, and 35.82 kg/ha for suspended sediments. Among the monitored water quality parameters, HCO3
−, CI−, and Ca2+ had greater losses than the rest of the chemical parameters studied in the watershed. Net gains (influx exceeded outflux)
calculated for total N, Mg2+, K+, and P-PO4
3− in the annual basis can be considered as an addition to the ecosystem’s organic nutrient pool. In contrast, net losses occurred
for HCO3
−, CI−, Ca2+, and Na+. 相似文献
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The current study investigates the spatial and temporal dynamics of post-fire vegetation and the subsequent influence on seasonal and annual hydrologic responses in chaparral-dominated watersheds. Post-fire climatology, burn severity, slope aspect, and vegetation behavior are evaluated for two basins burned during the 2003 Old Fire in the San Bernardino Mountains in Southern California. Climate and discharge data are used to evaluate seasonal and annual variability of post-fire hydrologic fluxes. Data obtained from the Moderate Resolution Imaging Spectroradiometer (MODIS) are used to estimate Enhanced Vegetation Index (EVI) and differenced Normalized Burn Ratio (dNBR). A Savitzky–Golay filtering technique and an integrated EVI annual fraction are utilized to assess vegetation recovery under a range of potential controls. Vegetation recovery is highly variable in both watersheds and is related to slope aspect (solar and water availability), initial biomass levels, and burn severity. South and west facing slopes show higher pre-fire EVI (biomass) and significant loss of vegetation cover after fire. Vegetation in both watersheds responds to an extreme wet season during the second post-fire year, however recovery rates are not sustained. North and east aspects show the quickest biomass gain relative to pre-fire conditions by the end of the study period (WY 2010), while the west and south slopes show lower biomass recovery. High burn severity areas show the slowest recovery across all slope aspects, with these regions just approaching 90% of pre-fire biomass by the end of the seven-year post-fire period. The variable rate of vegetation recovery across the watersheds results in significant changes in annual and seasonal discharge throughout the post-fire period. Runoff ratios remain elevated in both systems and there is increased dry season flow for much of the study period, indicating that plant water consumption and flowpaths are not back to pre-fire behavior by the end of WY 2010. 相似文献
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A. Lara C. Little R. Urrutia J. McPhee C. Álvarez-Garretón C. Oyarzún D. Soto P. Donoso L. Nahuelhual M. Pino I. Arismendi 《Forest Ecology and Management》2009
This paper quantifies two important native forest ecosystem services in southern Chile: water supply and recreational fishing opportunities. We analyzed streamflow in relation to forest cover in six watersheds located in the Valdivian Coastal Range (39°50′–40°05′S), the effect of forest management on streamflow in two watersheds in the Valdivian Andes (600–650 m of elevation; 39°37′S), and fish abundance as a function of forest cover in 17 watersheds located in the Coastal Range and the Central Depression (39°50′–42°30′S). We found that the annual direct runoff coefficient (quickflow/precipitation) and total streamflow/precipitation in the dry summer season were positively correlated with native forest cover in the watershed (R2 = 0.67 and 0.76; *P = 0.045 and 0.027, respectively) during four years of observations. Conversely, a negative correlation was found between summer runoff coefficients (total streamflow/precipitation) and cover of Eucalyptus spp. and Pinusradiata plantations (R2 = 0.84; *P = 0.010). We estimated a mean increase of 14.1% in total summer streamflow for every 10% increase in native forest cover in the watershed. The analysis of streamflow changes between two paired watersheds dominated by native secondary Nothofagus stands, one thinned with 35% of basal area removal and a control, showed that the former had a 40% increase during summer (four years of observations). The best correlation between fish abundance and forest cover was found between trout abundance (%) and secondary native forest area in 1000 m × 60 m stream buffers (R2 = 0.65, ***P < 0.0001). We estimated a 14.6% increase in trout abundance for every 10% increase of native forest cover in these buffers. Similar approaches to quantify forest ecosystem services could be used elsewhere and provide useful information for policy and decision-making regarding forest conservation and management. 相似文献
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