共查询到20条相似文献，搜索用时 23 毫秒
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While the hydrological balance of forest ecosystems has often been studied at the annual level, quantitative studies on the factors determining rainfall partitioning of individual rain events are less frequently reported. Therefore, the effect of the seasonal variation in canopy cover on rainfall partitioning was studied for a mature deciduous beech (Fagus sylvatica L.) tree over a 2‐year period. At the annual level, throughfall amounted to 71% of precipitation, stemflow 8%, and interception 21%. Rainfall partitioning at the event level depended strongly on the amount of rainfall and differed significantly (p < 0·001) between the leafed and the leafless period of the year. Therefore, water fluxes of individual events were described using a multiple regression analysis (ra2 > 0·85, n = 205) with foliation, rainfall characteristics and meteorological variables as predictor variables. For a given amount of rainfall, foliation significantly increased interception and decreased throughfall and stemflow amounts. In addition, rainfall duration, maximum rainfall rate, vapour pressure deficit, and wind speed significantly affected rainfall partitioning at the event level. Increasing maximum hourly rainfall rate increased throughfall and decreased stemflow generation, while higher hourly vapour pressure deficit decreased event throughfall and stemflow amounts. Wind speed decreased throughfall in the growing period only. Since foliation and the event rainfall amount largely determined interception loss, the observed net water input under the deciduous canopy was sensitive to the temporal distribution of rainfall. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
3.
Crop canopies and residues have been shown to intercept a significant amount of rainfall. However, rainfall or irrigation interception by crops and residues has often been overlooked in hydrologic modelling. Crop canopy interception is controlled by canopy density and rainfall intensity and duration. Crop residue interception is a function of crop residue type, residue density and cover, and rainfall intensity and duration. We account for these controlling factors and present a model for both interception components based on Merriam's approach. The modified Merriam model and the current modelling approaches were examined and compared with two field studies and one laboratory study. The Merriam model is shown to agree well with measurements and was implemented within the Agricultural Research Service's Root Zone Water Quality Model (RZWQM). Using this enhanced version of RZWQM, three simulation studies were performed to examine the quantitative effects of rainfall interception by corn and wheat canopies and residues on soil hydrological components. Study I consisted of 10 separate hypothetical growing seasons (1991–2000) for canopy effects and 10 separate non‐growing seasons (1991–2000) for residue effects for eastern Colorado conditions. For actual management practices in a no‐till wheat–corn–fallow cropping sequence at Akron, Colorado (study II), a continuous 10‐year RZWQM simulation was performed to examine the cumulative changes on water balance components and crop growth caused by canopy and residue rainfall interception. Finally, to examine a higher precipitation environment, a hypothetical, no‐till wheat–corn–fallow rotation scenario at Corvallis, Oregon, was simulated (study III). For all studies, interception was shown to decrease infiltration, runoff, evapotranspiration from soil, deep seepage of water and chemical transport, macropore flow, leaf area index, and crop/grain yield. Because interception decreased both infiltration and soil evapotranspiration, no significant change in soil water storage was simulated. Nonetheless, these findings and the new interception models are significant new contributions for hydrologists. Published in 2006 John Wiley & Sons, Ltd. 相似文献
4.
Catriona M.O. Macinnis‐Ng Eric E. Flores Henry Müller Luitgard Schwendenmann 《水文研究》2014,28(4):2174-2184
Catchment hydrology is influenced by land‐use change through alteration of rainfall partitioning processes. We compared rainfall partitioning (throughfall, stemflow and interception) and soil water content in three land‐use types (primary forest, secondary forest and agriculture) in the Santa Fe region of Panama. Seasonal patterns were typified by larger volumes of throughfall and stemflow in the wet season, and the size of precipitation events was the main driver of variation in rainfall redistribution. Land‐use‐related differences in rainfall partitioning were difficult to identify due to the high variability of throughfall. However, annual throughfall in agricultural sites made up a larger proportion of gross precipitation than throughfall in forest sites (94 ± 1, 83 ± 6 and 81 ± 1% for agriculture, primary and secondary forests, respectively). Proportional throughfall (% of gross precipitation becoming throughfall) was consistent throughout the year for primary forest, but for secondary forest, it was larger in the dry season than the wet season. Furthermore, proportional stemflow in the dry season was larger in secondary forest than primary forest. Stemflow, measured only in primary and secondary forests, ranged between 0.9 and 3.2% of gross precipitation. Relative soil moisture content in agricultural plots was generally elevated during the first half of the dry season in comparison to primary and secondary forests. Because throughfall is elevated in agricultural plots, we suggest careful management of the spatial distribution and spread of this land‐use type to mitigate potential negative impacts in the form of floods and high erosion rates in the catchment. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
5.
Nataliia Kozii Hjalmar Laudon Mikaell Ottosson‐Löfvenius Niles J. Hasselquist 《水文研究》2017,31(20):3558-3567
Water losses from snow intercepted by forest canopy can significantly influence the hydrological cycle in seasonally snow‐covered regions, yet how snow interception losses (SIL) are influenced by a changing climate are poorly understood. In this study, we used a unique 30 year record (1986–2015) of snow accumulation and snow water equivalent measurements in a mature mixed coniferous (Picea abies and Pinus sylvestris ) forest stand and an adjacent open area to assess how changes in weather conditions influence SIL. Given little change in canopy cover during this study, the 20% increase in SIL was likely the result of changes in winter weather conditions. However, there was no significant change in average wintertime precipitation and temperature during the study period. Instead, mean monthly temperature values increased during the early winter months (i.e., November and December), whereas there was a significant decrease in precipitation in March. We also assessed how daily variation in meteorological variables influenced SIL and found that about 50% of the variation in SIL was correlated to the amount of precipitation that occurred when temperatures were lower than ?3 °C and to the proportion of days with mean daily temperatures higher than +0.4 °C. Taken together, this study highlights the importance of understanding the appropriate time scale and thresholds in which weather conditions influence SIL in order to better predict how projected climate change will influence snow accumulation and hydrology in boreal forests in the future. 相似文献
6.
Quantifying the spatial variability of species-specific tree transpiration across hillslopes is important for estimating watershed-scale evapotranspiration (ET) and predicting spatial drought effects on vegetation. The objectives of this study are to (1) assess sap flux density (Js) and tree-level transpiration (Ts) across three contrasting zones a (riparian buffer, mid-hillslope and upland-hillslope, (2) determine how species-specific Js responds to vapour pressure deficit (VPD) and (3) estimate watershed-level transpiration (Tw) using Ts derived from each zone. During 2015 and 2016, we measured Js in eight tree species in the three topographic zones in a small 12-ha forested watershed in the Piedmont region of central North Carolina. In the dry year of 2015, loblolly pine (Pinus taeda), Virginia pine (Pinus virginiana) and sweetgum (Liquidambar styraciflua) Js rates were significantly higher in the riparian buffer when compared to the other two zones. In contrast, Js rates in tulip poplar (Liriodendron tulipifera) and red maple (Acer rubrum) were significantly lower in the buffer than in the mid-hillslope. Daily Ts varied by zone and ranged from 10 to 93 L/day in the dry year and from 9 to 122 L/day in the wet year (2016). Js responded nonlinearly to VPD in all species and zones. Annual Tw was 447, 377 and 340 mm based on scaled-Js data for the buffer, mid-hillslope and upland-hillslope, respectively. We conclude that large spatial variability in Js and scaled Tw was driven by differences in soil moisture at each zone and forest composition. Consequently, spatial heterogeneity of vegetation and soil moisture must be considered when accurately quantifying watershed level ET. 相似文献
7.
Christian Gonzalo Domínguez Miguel Francisco García Vera Cédric Chaumont Julien Tournebize Marcos Villacís Noemi d'Ozouville Sophie Violette 《水文研究》2017,31(18):3191-3205
With changes in climate looming, quantifying often‐overlooked components of the canopy water budget, such as cloud water interception (CWI), is increasingly important. Commonly, CWI quantification requires detailed continuous measurements, which is extremely challenging, especially when throughfall is included. In this study, we propose a simplified approach to estimate CWI using the Rutter‐type interception model, where CWI inputs in the canopy vegetation are proportional to fog interception measured by an artificial fog gauge. The model requires the continuous acquisition of meteorological variables as input and calibration datasets. Throughfall measurements below the forest are used only for calibration and validation of the model; thus, CWI estimates can be provided even after the cessation of throughfall monitoring. This approach provides an indirect and undemanding way to quantify CWI by vegetation and allows the identification of its controlling factors, which could be useful to the comparison of CWI in contrasting land covers. The method is applied on a 2‐year dataset collected in an endemic highland forest of San Cristobal Island (Galapagos). Our results show that CWI reaches 21% ± 6% of the total water input during the first year, and 9% ± 2% during the second one. These values represent 32% ± 10% and 17% ± 5% of water inputs during the cool foggy season of the first and second year, respectively. The difference between seasons is attributed to a lower fog liquid water during the second season. 相似文献
8.
Allen G. Hunt; 《水文研究》2024,38(6):e15209
The essay describes how a combination of scaling theory from percolation, that relates pore scale flow and transport through catchment scales to global scales (bottom-up), as well as water fluxes to soil formation and vegetation growth, can be used to support an accurate ecological optimization that (top-down): solves the central problem of hydrology, that is., “the water balance,” and generates critically important derived quantities, namely streamflow response to climate change, net primary productivity, and plant species richness. Moreover, the essay describes how this particular theoretical approach came to be designed and how it, in retrospect, fits in with the vision of the Committee on Opportunities in the Hydrologic Sciences which met 34 years ago to formulate a research, teaching, and infrastructure guide for the community, and “rebrand our science as a geoscience.” Finally, it demonstrates how the research satisfies the present desires of the community to unite Darwinian and Newtonian scientific methods in the solution of this central problem and how it relates to present research directions in the fields of hydrologic sciences and ecology. 相似文献
9.
Three techniques for obtaining soil water solutions (gravitational and matrical waters extracted using both in situ tension lysimeters and in vitro pressure chambers) and their later chemical analysis were performed in order to know the evolution of the soil‐solution composition when water moves down through the soil, from the Ah soil horizon to the BwC‐ or C‐horizons of forest soils located in western Spain. Additionally, ion concentrations and water volumes of input waters to soil (canopy washout) and exported waters (drainage solutions from C‐horizons) were determined to establish the net balance of solutes in order to determine the rates of leaching or retention of ions. A generalized process of sorption or retention of most components (even Cl?) was observed, from the soil surface to the C‐horizon, in both gravitational and matrical waters, with H4SiO4, Mn2+, Na+, and SO42? being the net exported components from the soil through the groundwater. These results enhance the role of the recycling effect in these forest soils. The net percentages of elements retained in these forest soils, considering the inputs and the outputs balance, were 68% K+, 85% Ca2+, 58% Mg2+, 7% Al3+, 5% Fe3+, 34% Zn2+, 57% Cl?, and 20% NO3?, and about 75% of dissolved organic carbon was mineralized. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
10.
Chris Soulsby Hannah Braun Matthias Sprenger Markus Weiler Doerthe Tetzlaff 《水文研究》2017,31(24):4282-4296
Over a 4‐month summer period, we monitored how forest (Pinus sylvestris ) and heather moorland (Calluna spp. and Erica spp.) vegetation canopies altered the volume and isotopic composition of net precipitation (NP) in a southern boreal landscape in northern Scotland. During that summer period, interception losses were relatively high and higher under forests compared to moorland (46% of gross rainfall [GR] compared with 35%, respectively). Throughfall (TF) volumes exhibited marked spatial variability in forests, depending upon local canopy density, but were more evenly distributed under heather moorland. In the forest stands, stemflow was a relatively small canopy flow path accounting for only 0.9–1.6% of NP and only substantial in larger events. Overall, the isotopic composition of NP was not markedly affected by canopy interactions; temporal variation of stable water isotopes in TF closely corresponded to that of GR with differences of TF‐GR being ?0.52‰ for δ2H and ?0.14‰ for δ18O for forests and 0.29‰ for δ2H and ?0.04‰ for δ18O for heather moorland. These differences were close to, or within, analytical precision of isotope determination, though the greater differences under forest were statistically significant. Evidence for evaporative fractionation was generally restricted to low rainfall volumes in low intensity events, though at times, subtle effects of liquid–vapour moisture exchange and/or selective transmission though canopies were evident. Fractionation and other effects were more evident in stemflow but only marked in smaller events. The study confirmed earlier work that increased forest cover in the Scottish Highlands will likely cause an increase in interception and green water fluxes at the expenses of blue water fluxes to streams. However, the low‐energy, humid environment means that isotopic changes during such interactions will only have a minor overall effect on the isotopic composition of NP. 相似文献
11.
F. Holwerda R. Burkard W. Eugster F. N. Scatena A. G. C. A. Meesters L. A. Bruijnzeel 《水文研究》2006,20(13):2669-2692
The deposition of fog to a wind‐exposed 3 m tall Puerto Rican cloud forest at 1010 m elevation was studied using the water budget and eddy covariance methods. Fog deposition was calculated from the water budget as throughfall plus stemflow plus interception loss minus rainfall corrected for wind‐induced loss and effect of slope. The eddy covariance method was used to calculate the turbulent liquid cloud water flux from instantaneous turbulent deviations of the surface‐normal wind component and cloud liquid water content as measured at 4 m above the forest canopy. Fog deposition rates according to the water budget under rain‐free conditions (0·11 ± 0·05 mm h?1) and rainy conditions (0·24 ± 0·13 mm h?1) were about three to six times the eddy‐covariance‐based estimate (0·04 ± 0·002 mm h?1). Under rain‐free conditions, water‐budget‐based fog deposition rates were positively correlated with horizontal fluxes of liquid cloud water (as calculated from wind speed and liquid water content data). Under rainy conditions, the correlation became very poor, presumably because of errors in the corrected rainfall amounts and very high spatial variability in throughfall. It was demonstrated that the turbulent liquid cloud water fluxes as measured at 4 m above the forest could be only ～40% of the fluxes at the canopy level itself due to condensation of moisture in air moving upslope. Other factors, which may have contributed to the discrepancy in results obtained with the two methods, were related to effects of footprint mismatch and methodological problems with rainfall measurements under the prevailing windy conditions. Best estimates of annual fog deposition amounted to ～770 mm year?1 for the summit cloud forest just below the ridge top (according to the water budget method) and ～785 mm year?1 for the cloud forest on the lower windward slope (using the eddy‐covariance‐based deposition rate corrected for estimated vertical flux divergence). Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
12.
Using a water balance modelling framework, this paper analyses the effects of urban design on the water balance, with a focus on evapotranspiration and storm water. First, two quite different urban water balance models are compared: Aquacycle which has been calibrated for a suburban catchment in Canberra, Australia, and the single‐source urban evapotranspiration‐interception scheme (SUES), an energy‐based approach with a biophysically advanced representation of interception and evapotranspiration. A fair agreement between the two modelled estimates of evapotranspiration was significantly improved by allowing the vegetation cover (leaf area index, LAI) to vary seasonally, demonstrating the potential of SUES to quantify the links between water sensitive urban design and microclimates and the advantage of comparing the two modelling approaches. The comparison also revealed where improvements to SUES are needed, chiefly through improved estimates of vegetation cover dynamics as input to SUES, and more rigorous parameterization of the surface resistance equations using local‐scale suburban flux measurements. Second, Aquacycle is used to identify the impact of an array of water sensitive urban design features on the water balance terms. This analysis confirms the potential to passively control urban microclimate by suburban design features that maximize evapotranspiration, such as vegetated roofs. The subsequent effects on daily maximum air temperatures are estimated using an atmospheric boundary layer budget. Potential energy savings of about 2% in summer cooling are estimated from this analysis. This is a clear ‘return on investment’ of using water to maintain urban greenspace, whether as parks distributed throughout an urban area or individual gardens or vegetated roofs. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
13.
Yoshinori Shinohara Tomo'omi Kumagai Kyoichi Otsuki Atsushi Kume Naoya Wada 《水文研究》2009,23(10):1418-1429
Hydrologic balance in high‐altitude, mid‐latitude mountain areas is important in terms of the water resources available to associated lowlands. This study examined how current and historical shifts in precipitation (P) patterns and concurrent increases in temperature (T) affected runoff (Q) and other hydrologic components in a mid‐latitude mountain catchment of central Japan, using a combination of long‐term data and a simplified hydrologic model, along with their stochastic treatment. The availability of intensive meteorological and hydrological data from the period 1997–2001 allowed the derivation of key relationships for the current climate that tie the forcing term to the parameters or state variables. By using the data recorded in the period 1965–2001, the force for driving the historical simulation was generated. Based on this model and historical shifts in P and T, the probability density functions of Q (pdf(Q)) was computed. A main novelty in this study is that such a stochastic representation, which is useful for considering the influence of projected shifts in environmental factors on the hydrologic budget, was provided. Despite the large increase in the rate of T in winter and spring, pdf(Q) in spring and summer varied appreciably during the time studied mainly because of an increase in snowmelt. An interannual change in whole‐year Q was robust to shifts in T because while Q in spring increased, in summer it decreased, implying a crucial effect of global warming on mountain hydrologic regimes is change in the timing of Q. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
14.
Evaporation of intercepted rain by a canopy is an important component of evapotranspiration, particularly in the humid boreal forest, which is subject to frequent precipitation and where conifers have a large surface water storage capacity. Unfortunately, our knowledge of interception processes for this type of environment is limited by the many challenges associated with experimental monitoring of the canopy water balance. The objective of this study is to observe and estimate canopy storage capacity and wet canopy evaporation at the sub-daily and seasonal time scales in a humid boreal forest. This study relies on field-based estimates of rainfall interception and evapotranspiration partitioning at the Montmorency Forest, Québec, Canada (mean annual precipitation: 1600 mm, mean annual evapotranspiration: 550 mm), in two balsam fir-white birch forest stands. Evapotranspiration was monitored using eddy covariance sensors and sap flow systems, whereas rainfall interception was measured using 12 sets of throughfall and six stemflow collectors randomly placed inside six 400-m2 plots. Changes in the amount of water stored on the canopy were also directly monitored using the stem compression method. The amount of water intercepted by the forest canopy was 11 ± 5% of the total rainfall during the snow-free (5 July–18 October) measurement periods of 2017 and 2018. The maximum canopy storage estimated from rainfall interception measurements was on average 1.6 ± 0.7 mm, though a higher value was found using the stem compression method (2.2 ± 1.6 mm). Taking the average of the two forest stands studied, evaporation of intercepted water represented 21 ± 8% of evapotranspiration, while the contribution of transpiration and understory evapotranspiration was 36 ± 9% and 18 ± 8%. The observations of each of the evapotranspiration terms underestimated the total evapotranspiration observed, so that 26 ± 12% of it was not attributed. These results highlight the importance to account for the evaporation of rain intercepted by humid boreal forests in hydrological models. 相似文献
15.
Wetlands in the coastal catchments adjacent to the Great Barrier Reef lagoon play an important role in local hydrological processes and provide important ecological habitats for terrestrial and aquatic species. Although many wetlands have been removed or degraded by agricultural expansion, there is now great interest in their protection and restoration as important aquatic ecosystems and potential filters of pollutant runoff. However, the filtering capacity of tropical wetlands is largely unknown, so the current study was established to quantify the water, sediment and nutrient balance of a natural riverine wetland in tropical north Queensland. Surface and groundwater fluxes of water, sediment and nutrients into and out of the wetland were monitored for a 3‐year period. This paper focuses on the water balance of this natural wetland and a companion paper presents its sediment and nutrient balance and estimates of water quality filtering. Wetland inflows and outflows were dominated by surface flows which varied by 3–4 orders of magnitude through the course of the year, with 90% of the annual flow occurring during the period January to March. Although groundwater inputs to the wetland were only 5% of the annual water balance, they are very important to sustaining the wetland during the dry season, when they can be the largest input of water (up to 90%). Water retention times in this type of wetland are very short, particularly when most of the flow and any associated materials are passing through it (i.e. 1–2 h), so there is little time to filter most of the annual flux of water through this wetland. Longer retention times occur at the end of the dry season (up to 8·5 days); but this is when the lowest fluxes of water pass through the wetland. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
16.
In 1903 the Swiss Federal Research Institute WSL started its first forest hydrology measurements with the aim to deliver a sound scientific basis for the implementation of new forest legislation introduced in Switzerland in 1876. This legislation was triggered by several large floods that occurred in Switzerland, for which a major cause was widely seen as the poor condition of forests at that time. Consequently, hydrologic research at WSL first focused on the influence of forests on floods. In the second half of the 20th century, other hydrological issues such as water quality, snow hydrology and sediment transport complemented the hydrologic research at WSL. Some recent results of this work are presented in three papers joining this introductory paper to mark the 100th anniversary of hydrologic research at WSL. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
17.
John T. Van Stan II 《水文科学杂志》2013,58(6):1061-1066
Abstract This technical note presents an instrumental method for the precise and timely installation of mechanical displacement sensors to investigate stem compression and relaxation associated with whole-tree rainwater loading and evaporation, respectively. We developed this procedure in response to the conclusions of Friesen et al. (2008), which called for the development of a precision mounting method for strain sensors on inherently-irregular trunk cross-sections so that rainfall interception, storage and evaporation may be distinguished from other strain-related phenomena. To supply precise sensor installation locations, high-resolution trunk profiles are generated using the LaserBarkTM automated tree measurement system. These scans are utilized to approximate the location of neutral bending axes. A routine then instructs a mobile rangefinder along the cross-section to optically indicate exact positioning for strain sensors over the bending axes. As imprecise sensor placement linearly increases error and diminishes signal-to-noise ratio, this automated installation routine is designed to remove significant distortions created by wind throw, off-centre loading within unevenly-distributed canopies, and human error that can lead to erroneous measurements of rainfall interception. Citation Van Stan, J. T. II, Jarvis, M. T., Levia, D. F. Jr & Friesen, J. (2011) Instrumental method for reducing error in compressionderived measurements of rainfall interception for individual trees. Hydrol. Sci. J. 56(6), 1061–1066. 相似文献
18.
Enrique Muñoz José Luis Arumí Thorsten Wagener Ricardo Oyarzún Victor Parra 《水文研究》2016,30(26):4934-4943
Groundwater storage, drainage, and interbasin water exchange are common hydrological processes but often difficult to quantify due to a lack of local observations. We present a study of three volcanic mountainous watersheds located in south‐central Chile (~36.9 ° S) in the Chillán volcanic complex (Chillán, Renegado, and Diguillín river basins). These are neighboring basins that are similar with respect to the metrics normally available for characterization everywhere (e.g., precipitation, temperature, and land cover). In a hydrological sense, similar (proportional) behavior would be expected if these catchments would be characterized with this general information. However, these watersheds show dissimilar behavior when analyzed in detail. The surface water balance does not fit for any of these watersheds individually; however, the water balance of the whole system can be explained by likely interbasin water exchanges. The Renegado river basin has an average annual runoff per unit of area on the order of 60–65% less than those of the Diguillín and Chillán rivers, which is contradictory to the hydrological similarity among the basins. To understand the main processes that control streamflow generation, two analyses were performed: (a) basin metrics (land cover, geologic, topographic, and climatological maps) and hydro‐meteorological data analyses and (b) a water balance model approach. The analyses contribute to a plausible explanation for the hydrogeological processes in the system. The soils, topography, and geology of the Chillán–Renegado–Diguillín system favor the infiltration and groundwater movements from the Renegado river basin, mainly to the neighboring Diguillín basin. The interbasin water exchanges affect hydrological similarity and explain the differences observed in the hydrological processes of these three apparently similar volcanic basins. The results highlight the complexity of hydrological processes in volcanic mountainous systems and suggest that a simple watershed classification approach based on widely available data is insufficient. Simple local analyses such as specific flow analysis with a review of the geology and morphology can contribute to a better understanding of the hydrology of volcanic mountainous areas. 相似文献
19.
Jessica D. Lundquist Susan Dickerson-Lange Ethan Gutmann Tobias Jonas Cassie Lumbrazo Dylan Reynolds 《水文研究》2021,35(7):e14274
When formulating a hydrologic model, scientists rely on parameterizations of multiple processes based on field data, but literature review suggests that more frequently people select parameterizations that were included in pre-existing models rather than re-evaluating the underlying field experiments. Problems arise when limited field data exist, when “trusted” approaches do not get reevaluated, and when sensitivities fundamentally change in different environments. The physics and dynamics of snow interception by conifers is just such a case, and it is critical to simulation of the water budget and surface albedo. The most commonly used interception parameterization is based on data from four trees from one site, but results from this field study are not directly transferable to locations with relatively warmer winters, where the dominant processes differ dramatically. Here, we combine a literature review with model experiments to demonstrate needed improvements. Our results show that the choice of model form and parameters can vary the fraction of snow lost through interception by as much as 30%. In most simulations, the warming of mean winter temperatures from −7 to 0°C reduces the modelled fraction of snow under the canopy compared to the open, but the magnitude of simulated decrease varies from about 10% to 40%. The range of results is even larger when considering models that neglect the melting of in-canopy snow in higher-humidity environments where canopy sublimation plays less of a role. Thus, we recommend that all models represent canopy snowmelt and include representation of increased loading due to increased adhesion and cohesion when temperatures rise from −3 to 0°C. In addition to model improvements, field experiments across climates and forest types are needed to investigate how to best model the combination of dynamically changing forest cover and snow cover to better understand and predict changes to albedo and water supplies. 相似文献
20.
Since 1986 the multiple benefits of moso-bamboo forest, a special forest type found mainly in south China, have been investigated in a small 11.7 ha watershed in Fenyi County, Jiangxi Province. The mean annual precipitation in the study area is 1593.3 mm. For the 0–60 cm soil layer the average soil bulk density is 1.00 g/cm3, and the mean values for other soil properties are: total porosity 71.74%; non-capillary porosity 5.81%; and water retention capacity 430 mm. The maximum effective water retention capacity of 313 mm is 28% higher than that for Chinese fir (Cunninghamia lanceolata) plantations and natural broadleaved forest in the neighbouring area. The parameters f0, fc and k, in Horton's infiltration equation, measured using the double-ring method under drought conditions, are 29.10 mm/min, 8.28 mm/min and 0.2391, respectively. These infiltration properties are more favourable than those under nearby Chinese fir plantations. Compared with a Chinese fir plantation, the canopy interception ratio of moso-bamboo is lower, but the stemflow ratio is higher. The annual canopy interception ratio is 11.1%. Because of snowfall, the interception ratios in January, February and March are higher, with values of 12.1–17.2%, whereas during the period of leaf fall in April, May and June the interception ratios are lower with values of 9.2–9.5%. During the other months they are relatively constant. The annual stemflow ratio is 4.4%. Again, because of snowfall, the stemflow ratios in January, February and March are lower with values of 2.8–2.9%, whereas during the remaining months they are fairly constant. Runoff analysis shows that the annual runoff ratio in this research watershed is 54.8%, but the ratio for quick runoff, composed of direct runoff and surface runoff, is only 0.8%. The upper interflow ratio is 15% and the ratio for the slow runoff composed of deeper interflow and underflow is 39%. The moso-bamboo forest is very effective in reducing peak runoff and increasing low flows. The annual nutrient element inputs (kg/ha) to the moso-bamboo forest ecosystem associated with throughfall and stemflow are N 17.7, P 0.38, K 56.5, Ca 31.,4, Mg 4.8 and SiO2 26.2, respectively. All the measured element inputs, with the exception of P, are higher than those associated with precipitation in the open, where typical values are N 10.1, P 0.89, K 18.8, Ca 25.8, Mg 3.1 and SiO2 10.1. The annual outputs in streamflow are N 3.0, P 0.28, K 16.6, Ca 38.9, Mg 8.3 and SiO2 125.7, indicating that for N, P and K the moso-bamboo forest ecosystem is an accumulating system, whereas for Ca, Mg and SiO2 the reverse applies. All the pH values associated with precipitation in the open, throughfall, stemflow, surface runoff from runoff plots and streamflow in the research watershed vary between 6.45 and 7.60 and are close to neutral. 相似文献
