As the longest tributary on the right bank of upper Yangtze River, while also occupying the largest basin area in Guizhou Province, Wujiang River is of great importance to the economic and ecological environment in Yangtze Basin and Southwest China. However, the upper reaches of Wujiang River are suffering from long-term soil erosion and land degradation, which has threatened the local safety and development. This paper, based on the forest resource inventory data of Bijie prefecture in Guizhou Province in 2010, aims to estimate the water conservation of forest ecosystem in the upper reaches of Wujiang River and to analyze its spatial variation. The relationship between the unit water conversation of forest ecosystem, which is regarded as the Forest Water Conservation Capacity (FWCC) in this paper, and elevation, slope and land degradation types was deeply explored. The integrated storage capacity method and the linear regression was employed. The results show that: (1) In 2010, the water conservation of forest ecosystem in the study area was 563.05 million cubic meters in total, yielding a water conservation of 774.73 t/hm2 per unit area. FWCC presented a pattern of gradually decreasing from northeast to southwest in the east region, and an uneven pattern in the west region. (2) A significant negative correlation was found between FWCC and elevation, that FWCC decreased by 90.56 t/hm2 with every 1 km increase in elevation. (3) FWCC significantly decreased by 2.44 t/hm2 with every 1 degree increase in slope. (4) Land degradation showed a strong negative effect to FWCC, and the FWCC of degraded land dropped by 23.50% on average compared with the non-degraded land. A better understanding of the water conservation function and its spatial variation of forest ecosystem would be helpful to learn the status of local forest ecosystem, and to formulate and implement the sustainable utilization of water resources, as well as the restoration and construction of ecological environment, under the guidance of more targeted and efficient policies.
Wujiang River basin;
integrated storage capacity method;
Water conservation in total and the relevant values per unit area of different vegetation types and their comparison with the forest area
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Wilcox B., Thurow TL.Emerging issues in rangeland ecohydrology: vegetation change and the water cycle[J]. , 2006,59(2):220-224.
Rangelands have undergone—and continue to undergo—rapid change in response to changing land use and climate. A research priority in the emerging science of ecohydrology is an improved understanding of the implications of vegetation change for the water cycle. This paper describes some of the interactions between vegetation and water on rangelands and poses 3 questions that represent high-priority, emerging issues: 1) How do changes in woody plants affect water yield? 2) What are the ecohydrological consequences of invasion by exotic plants? 3) What ecohydrological feedbacks play a role in rangeland degradation processes? To effectively address these questions, we must expand our knowledge of hydrological connectivity and how it changes with scale, accurately identify “hydrologically sensitive” areas on the landscape, carry out detailed studies to learn where plants are accessing water, and investigate feedback loops between vegetation and the water cycle.
[ Yu X., Zhou., Lu X., et al.Evaluation of water conservation function in mountain forest areas of Beijing based on InVEST model[J]. , 2012,48(10):1-5. ]
Calder IR.Dependence of rainfall interception on drop size: development of the two-layer stochastic model[J]. , 1996,185(1):363-378.
The original stochastic interception model (Calder, 1986, J. Hydrol. , 89: 65鈥71) showed, through the use of Poisson probability statistics, that the rate at which vegetation canopies are wetted is dependent on the volume of the individual raindrops; for the same depth of rain applied, a greater depth of water will be retained on the canopy when raindrop volumes are small. This paper recognizes that vegetation canopies are wetted through both the primary impact of raindrops to the top layer of the canopy and secondary impacts, from drops falling from the vegetation, to lower layers of the canopy. It shows how drop volumes of primary raindrops can be calculated from the Marshall-Palmer distribution and drop volumes of secondary drops can be calculated from the `characteristic' volume appropriate to the particular vegetation species. A two-layer stochastic model is described which calculates the rate at which canopies are wetted in relation to both primary and secondary drops. The paper also shows that, in addition to the volume-dependent stochastic wetting effect, there is also another drop-size-dependent wetting effect, related to the kinetic energy of the raindrops, which influences the maximum storage that can be achieved on the canopy. The wetting functions predicted for canopies of different density are described and the application of the model for assessing interception loss from forests, in relation to vegetation, climate and possible climatic change, is discussed.
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Johnson RC.The interception, throughfall and stemflow in a forest Highland Scotland and the comparison with other upland forests in the U.K[J]. , 1990,118(1):281-287.
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This article presents an historical perspective of the controversy concerning the hydrological impact of forests, and shows how a mostly romantic and emotional confrontation finally evolved into a scientific debate. We first analyze the historical evolution of ideas, starting with the views of Pliny the Elder in the first century ad and ending with the debate on the ‘Eaux et Forêts’ in France in the 19th century. Then, we give an up-to-date overview of the paired-watershed experiments conducted throughout 20th century, and identify some research issues that should help forest hydrology science to move forward in the 21st century.
SandströmK.Can forests provide water: widespread myth or scientific reality?[J]. , 1998,27(2):132-138.
The article presents two contrasting views of deforestation and groundwater recharge/dry season flow. Seven variables causing the dichotomy are identified and analyzed. These include the comparative importance of various hydrological processes, research methodological aspects, people's perception of change, and unclear definitions. A simple model indicating the most likely catchment response to deforestation is presented. Recharge through macropores is argued to be the key mechanism for conveying rainwater to groundwater in the dry tropics. Management aspects of forests and water are discussed.
Vertessy R., Zhang., Dawes WR.Plantations, river flows and river salinity[J]. , 2003,66(1):55-61.
Large-scale plantation development will exert additional pressure on a water resource system that is already under considerable stress. Tree planting will reduce river flows and recharge to groundwater and, in certain circumstances, may lead to short-term worsening of river salinity prior to any improvement. Reductions in flow will be particularly problematic during dry spells, when water resources are sorely stretched. Most of the likely hydrologic impacts of afforestation can be predicted using current catchment models, but new field data are needed to test and improve their accuracy. Reductions in river flow induced by afforestation can be minimised with careful planning, and various strategies to minimise impact are recommended. It is argued that a regulatory framework needs to be erected to control the development of new plantations in order to complement other policies to preserve water resources, such as the cap on diversions in the Murray-Darling Basin and recently introduced legislation on farm dams. Given the future need to allocate additional river flows to the environment, new allocations of water to plantations should be offset by up-front transfers of water from other uses. We argue that water use by plantations should be factored into the water economy of catchments. Keywords: forest plantations; water yield; stream flow; salinity; saline water; water allocation; water management; runoff; land use
Bonell., Purandara B., Venkatesh., et al.The impact of forest use and reforestation on soil hydraulic conductivity in the Western Ghats of India: Implications for surface and sub-surface hydrology[J]. , 2010,391(1):47-62.
Jobbagy E., Jackson RB.Groundwater use and salinization with grassland afforestation[J]. , 2004,10(8):1299-1312.
Abstract Vegetation changes, particularly transitions between tree- and grass-dominated states, can alter ecosystem water balances and soluble salt fluxes. Here we outline a general predictive framework for understanding salinization of afforested grasslands based on biophysical, hydrologic, and edaphic factors. We tested this framework in 20 paired grassland and adjacent afforested plots across ten sites in the Argentine Pampas. Rapid salinization of groundwater and soils in afforested plots was associated with increased evapotranspiration and groundwater consumption by trees, with maximum salinization occurring on intermediately textured soils. Afforested plots (10–10065ha in size) showed 4–19-fold increases in groundwater salinity on silty upland soils but
Nosetto M., Jobbagy E., Paruelo JM.Land-use change and water losses: the case of grassland afforestation across a soil textural gradient in central Argentina[J]. , 2005,11(7):1101-1117.
Abstract Vegetation changes, particularly those involving transitions between tree- and grass-dominated covers, often modify evaporative water losses as a result of plant-mediated shifts in moisture access and demand. Massive afforestation of native grasslands, particularly important in the Southern Hemisphere, may have strong yet poorly quantified effects on the hydrological cycle. We explored water use patterns in plantations and the native humid grasslands that they replace in Central Argentina. In order to uncover the interactive effects that land cover type, soil texture and climate variability may have on evaporative water losses and water use efficiency, we estimated daily evapotranspiration (ET) in 117 tree plantations and grasslands plots across a soil textural gradient (clay-textured Vertisols to sandy-textured Entisols) using radiometric information from seven Landsat scenes, existing timber productions records, and C measurements in tree stems. Tree plantations had cooler surface temperatures (615°C on average) and evaporated more water (+80% on average) than grasslands at all times and across all sites. Absolute ET differences between grasslands and plantations ranged from 650.6 to 265mm65dayand annual up-scaling suggested values of 65630 and 65115065mm65yrfor each vegetation type, respectively. The temporal variability of ET was significantly lower in plantations compared with grasslands (coefficient of variation 36% vs. 49%). Daily ET increased as the water balance became more positive (accumulated balance for previous 18 days) with a saturation response in grassland vs. a continuous linear increase in plantations, suggesting lower ecophysiological limits to water loss in tree canopies compared with the native vegetation. Plantation ET was more strongly affected by soil texture than grassland ET and peaked in coarse textured sites followed by medium and fine textured sites. Timber productivity as well as C concentration in stems peaked in medium textured sites, indicating lower water use efficiency on extreme textures and suggesting that water limitation was not responsible for productivity declines towards finer and coarser soils. Our study highlighted the key role that vegetation type plays on evapotranspiration and, therefore, in the hydrological cycle. Considering that tree plantations may continue their expansion over grasslands, problematic changes in water management and, perhaps, in local climate can develop from the higher evaporative water losses of tree plantations.
Sahin., Hall MJ.The effects of afforestation and deforestation on water yields[J]. , 1996,178(1):293-309.
The exploitation of land and water resources to sustain an ever-increasing population inevitably involves the utilisation for both urban and agricultural development of rural areas and the natural landscape. This process can result in profound changes to the flow regime of river basins that are so affected, the scope and magnitude of which have been investigated by means of experimental catchment studies. The extensive data base that has resulted from such activities has provided a basis for developing a series of generalised relationships which can be used by water resources planners to anticipate the changes in water yield that can result from alterations to the predominant vegetative cover of a catchment. The application of fuzzy linear regression analysis to data from 145 experiments has shown that, for a 10% reduction in cover, the yield from conifer-type forest increased by some 20鈥25 mm, whereas that for eucalyptus-type forest increased by only 6 mm. Both values were somewhat lower than those previously published, as was the 5 mm decrease in yield associated with a 10% afforestation of scrub. A 10% reduction in the cover of deciduous hardwood gave a 17鈥19 mm increase in yield, broadly in line with earlier estimates.
Brauman K., Freyberg D., Daily GC.Forest structure influences on rainfall partitioning and cloud interception: a comparison of native forest sites in Kona, Hawai'i[J]. , 2010,150(2):265-275.
Vegetation can play a major role in the hydrologic ecosystem service tradeoffs resulting from land use change: by affecting the volume of rain that reaches the ground surface, vegetation affects supply. But because canopy interception of rainfall is affected in complex and competing ways by forest structure and ambient weather conditions, both of which vary at small and large scales, predicting the impacts of vegetation change is challenging. We explore rainfall and cloud interception in two native forests sites on leeward Hawai'i Island and find that although our study forests are superficially similar, with identical dominant species and no history of logging, throughfall in one forest is nearly double that in the other. Using micrometeorological and vegetation data collected over 20 months, we examine the dominance of different hydrologic processes at each site. Direct fog input accounted for at least 12% of total input in the North forest site, an average of about 0.1mm/day, and 27% of total input in the South forest, an average of 0.3mm/day. In the North forest, canopy interception of rainfall dominates, and annual throughfall amounts to only 64% of rainfall. A large canopy surface area and low rainfall rates cause the high rate of interception. Direct interception of clouds by the canopy dominates in the South forest, where throughfall is 113% of rainfall. Increased throughfall at this site is not attributable to increased fogginess. Instead, taller trees and a denser mid-canopy increase canopy surface area, causing increased cloud interception. The denser forest structure is likely a result of exclusion and limited grazing in this forest. This study illustrates the effects of subtle differences in vegetation structure on hydrologic fluxes and, by extension, the hydrologic effects of land use change. It also underscores the importance of replicate sites in ecohydrologic investigations.
Cornish P., Vertessy RA.Forest age-induced changes in evapotranspiration and water yield in a eucalypt forest[J]. , 2001,242(1):43-63.
Water yields in a regrowth eucalypt forest were found to increase initially and then to decline below pre-treatment levels during the 16-year period which followed the logging of a moist old-growth eucalypt forest in Eastern Australia. Both regrowth and old-growth stands were dominated by Sydney Blue Gum ( Eucalyptus saligna Smith) and Silvertop Stringybark ( Eucalyptus laevopinea R. Baker). Using a paired-catchment approach we observed significant reductions in five of six gauged catchments, and were able to associate their magnitude with forest growth rate, canopy cover and soil depth. Regular yield declines were interrupted for a period in some catchments, possibly due to foliar insect attack. Yield reductions of up to a maximum 600mm per year in logged and regenerated areas were in accord with water yield reductions observed in Mountain Ash ( Eucalyptus regnans F.J. Muell.) regeneration in Victoria. This study therefore represents the first confirmation of these Maroondah Mountain Ash results in another forest type that has also undergone eucalypt-to-eucalypt succession. Baseflow analysis indicated that baseflow and stormflow both increased after logging, with stormflow increases dominant in catchments with shallower soils. The lower runoff observed when the regenerating forest was aged 13鈥16years was principally a consequence of lower baseflow.
Vitousek P., Mooney H., Lubchenco., et al.Human domination of Earth's ecosystems[J]. , 1997,277(5325):494-499.
Crawford R M.. Eco-hydrology: plants and water in terrestrial and aquatic environments.[J]. , 2000,88(6):1095-1096.
This book provides an overview of the relationship between plants and water in a range of terrestrial and aquatic environments. It comprises 10 chapters discussing the water relations of plants, scales of interactions in eco-hydrological relations, plants and water in drylands, water and plants in fresh wetlands, forests, woodlands, streams, rivers, water adjacent to lakes, examines deficiencie...