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1.
D. L. Dunkerley 《水文研究》2008,22(12):1985-1995
Interception losses from the canopies of dryland plant taxa remain poorly understood, especially the relative contributions of intra‐storm and post‐storm evaporative losses. Employing a new measuring apparatus, this study uses low‐intensity simulated rain, matched to the properties of local rain, to explore interception processes in bluebush shrubs at an Australian dryland site. Five shrub specimens were exposed to simulated rain for 60–90 min. Experiments were repeated at three rainfall intensities (10, 15, and 20 mm h?1). Canopy evaporation was found from the difference between the flux of water delivered to the shrub and the flux of throughfall, once equilibrium had been established. The results show that evaporation from the wet foliage during rain proceeds at an average rate of 3·6 mm h?1. This figure is for relatively cool spring‐season conditions; evaporation rates in hot summer conditions would be larger. Intra‐storm evaporation is shown to exceed post‐rain evaporation from interception storage on the shrubs, and this differentiates dryland shrub interception processes from those of the better‐studied wet forest environment. Implications of the high dryland shrub canopy evaporation rates for aspects of dryland ecology are highlighted. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

2.
Heng Lu  Ming‐Zhe Liu  Xi Han 《水文研究》2017,31(8):1602-1612
Forest litter exerts an impact on the energy budget of snow surfaces, which lie beneath forest canopies. In this study, we measured shortwave and longwave radiation levels, as well as quantities of Asian spruce (Picea schrenkinan ) forest litter, over 3 snow study plots that representing an open environment, 20% forest canopy openness (20% FCO), and 80% forest canopy openness (80% FCO). The fractional litter coverage (lc ) was obtained through the binarization of digital photographs of forest litter. The effects of forest litter on snow surface albedo (α ), snow surface temperature (T s ), upward shortwave and longwave radiation (K ↑ and L ↑), and sensible heat flux (H ) were then analyzed. According to our results, the energy budget over snow surface influenced by forest litter principally due to forest litter forcing α decrease and T s increase. The effects of forest litter on the energy budget increased with time and lc . We found that forest litter exerted the most significant impact on K ↑ and L ↑ at daytime during the latter stages of the snowmelt period. The influence of forest litter on H was more apparent on windy days. The presence of forest litter increased gains in shortwave radiation and losses in longwave radiation and decreased gains in H . Compared to the simulated energy (K ↑ + L ↑ + H ) over a snow surface without litter, the calculated energy decreased by ?13.4 W/m2 and increased by 9.0 W/m2, respectively, at the 20% FCO and 80% FCO sites during the latter stages of the snowmelt period. Overall, forest litter facilitated snow surface energy gains at the 80% FCO site and impeded them at the 20% FCO site during the latter stages of the snowmelt period.  相似文献   

3.
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   

4.
Snow water equivalent was measured during three springs on north‐ and south‐exposed sites representing a range of stand structure and development stages of Quebec's balsam fir forest. Maximum snow water equivalent of the season, mean seasonal snowmelt rate, snowmelt season duration and total snowmelt season degree‐day factor were related to canopy height, canopy density, light interception fraction and basal area of the stands using random coefficient models. Seasonal mean snowmelt rate was better explained by stand characteristics (R2 from 0·41 to 0·61) than was maximum snow water equivalent (R2 from 0·08 to 0·23). The best relationship was found with light interception, which explained 61% of snowmelt rate variability between stands. These relationships were not significantly affected by stand aspect (Pr ≥ S = 0·14 or higher), as snow dynamics seemed less dependent on aspect than on stand characteristics. Snowmelt recovery rates could be used by forest planners to establish an acceptable time step for the harvesting of different parts of a watershed in order to prevent peak flow augmentations. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

5.
Litter layers develop across a diverse array of vegetated ecosystems and undergo significant temporal compositional changes due to canopy phenological phases and disturbances. Past research on temporal dynamics of litter interception has focused primarily on litter thickness and leaf fall, yet forest phenophases can change many more litter attributes (e.g., woody debris, bark shedding, and release of reproductive materials). In this study, weekly changes in litter composition over 1 year were used to estimate litter water storage dynamics and model event‐based litter interception. Litter interception substantially reduced throughfall (6–43%), and litter water storage capacity ranged from 1 to 3 mm, peaking when megastrobili release and liana leaf senescence occurred simultaneously during fall 2015. Tropical storm disturbances occurred during the sampling period, allowing evaluation of how meteorological disturbances altered litter interception. High wind speeds and intense rainfall from 2 tropical storms increased litter interception by introducing new woody debris, which, in this study, stored more water than the pre‐existing woody debris. After 2 extreme weather events, a third (Hurricane Hermine) did not increase woody debris (or litter interception), suggesting that the canopy pool of branches susceptible to breakage had been largely depleted. Needle and bark shedding had minor effects on litter interception. Results suggest that the release of reproductive materials and meteorological disturbances appear to be the major compositional drivers of litter interception beyond their obvious contribution to litter thickness.  相似文献   

6.
Winter‐forest processes affect global and local climates. The interception‐sublimation fraction (F) of snowfall in forests is a substantial part of the winter water budget (up to 40%). Climate, weather‐forecast and hydrological modellers incorporate increasingly realistic surface schemes into their models, and algorithms describing snow accumulation and snow‐interception sublimation are now finding their way into these schemes. Spatially variable data for calibration and verification of wintertime dynamics therefore are needed for such modelling schemes. The value of F was determined from snow courses in open and forested areas in Hokkaido, Japan. The value of F was related to species and canopy‐structure measures such as closure, sky‐view fraction (SVF) and leaf‐area index (LAI). Forest structure was deduced from fish‐eye photographs. The value of F showed a strong linear correlation to structure: F = 0·44 ? 0·6 × SVF for SVF < 0·72 and F = 0 for SVF > 0·72, and F = 0·11 LAI. These relationships seemed valid for evergreen conifers, larch trees, alder, birch and mixed deciduous stands. Forest snow accumulation (SF) could be estimated from snowfall in open fields (So) and to LAI according to SF = So (1 ? 0·11 LAI) as well as from SVF according to SF = So (0·56 + 0·6 SVF) for SVF < 0·72. The value of SF was equal to So for SVF values above 0·72. The value of sky‐view fraction was correlated to the normalized difference snow index (NDSI) using a Landsat‐TM image for observation plots exceeding 1 ha. Variables F and SF were related to NDSI for these plots according to: F = ?0·37NDSI + 0·29 and SF = So (0·81 + 0·37NDSI). These relationships are somewhat hypothetical because plot‐size limitation only allowed one sparse‐forest observation of NDSI to be used. There is, therefore, a need to confirm these relationships with further studies. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

7.
Evan Pugh  Eric Gordon 《水文研究》2013,27(14):2048-2060
In regions of western North America with snow‐dominated hydrology, the presence of forested watersheds can significantly influence streamflow compared to areas with other vegetation cover types. Widespread tree death in these watersheds can thus dramatically alter many ecohydrologic processes including transpiration, canopy solar transmission and snow interception, subcanopy wind regimes, soil infiltration, forest energy storage and snow surface albedo. One of the more important causes of conifer tree death is bark beetle infestation, which in some instances will kill nearly all of the canopy trees within forest stands. Since 1996, an ongoing outbreak of bark beetles (Coleoptera: Scolytidae) has caused widespread mortality across more than 600,000 km2 of coniferous forests in western North America, including numerous Rocky Mountain headwaters catchments with high rates of lodgepole pine (Pinus contorta) mortality from mountain pin beetle (Dendroctonous ponderosae) infestations. Few empirical studies have documented the effects of MPB infestations on hydrologic processes, and little is known about the direction and magnitude of changes in water yield and timing of runoff due to insect‐induced tree death. Here, we review and synthesize existing research and provide new results quantifying the effects of beetle infestations on canopy structure, snow interception and transmission to create a conceptual model of the hydrologic effects of MPB‐induced lodgepole pine death during different stages of mortality. We identify the primary hydrologic processes operating in living forest stands, stands in multiple stages of death and long‐dead stands undergoing regeneration and estimate the direction of change in new water yield. This conceptual model is intended to identify avenues for future research efforts. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

8.
Analyses of the response by a weighing lysimeter in Kioloa State Forest during and after rainfall provided values of interception loss rate. The derived rates for time scales between 0.1 and 1.0mm h?1 were generally similar throughout storm events to losses determined from throughfall and stemflow observations. During post-rainfall periods of canopy drying, enhanced rates of lysimeter evaporation were consistent with micrometeorological determinations of the partitioning of available radiant energy, based on atmospheric gradients of humidity and temperature. Interception losses from the eucalypt forest, deduced from the lysimeter response, varied between 10 and 15 per cent of gross rainfall in three consecutive 12 month periods whereas the corresponding rainfall ranged between 590 and 1530 mm yr?1. Daytime losses accounted for about two-thirds of total interception loss with a similar fraction occurring during rain periods. Storage capacity of the evergreen forest canopy was inferred to be 0.35 mm. Hourly loss rates during rainfall ranged up to 0.8 mm h?1 but with decreasing mean values and variability with increasing time scale resulting in a monthly mean value computed for the total number of hours of rain of approximately 0.1 mm h?1. A preliminary analysis of loss rate in terms of storm windspeed and rainfall intensity explained about half of its variation in statistically derived relationships. Improved time resolution of the order of seconds was considered a prerequisite to the physical understanding of turbulent transport from saturated canopies. The small value of interception storage capacity was considered in relation to that for pine forest as a basis for explaining observed differences in interception behaviour between eucalypt forest and coniferous plantations in the same area. Large differences in interception losses between the Kioloa site and evergreen forest in the South Island of New Zealand and also eucalypt forest in Western Australia were attributed to dissimilar meteorological conditions at the various sites.  相似文献   

9.
Rainfall interception loss plays an important role in ecohydrological processes in dryland shrub ecosystems, but its drivers still remain poorly understood. In this study, a statistical model was developed to simulate interception loss based on the mass balance measurements arising from the partitioning of rainfall in 2 dominant xerophytic shrub (Hippophae rhamnoides and Spiraea pubescens) communities in the Loess Plateau. We measured throughfall and stemflow in the field under natural rainfall, calculated the canopy storage capacity in the laboratory, and identified key factors controlling these components for the 2 shrubs. We quantified and scaled up the stemflow and the canopy storage capacity measurements from the branches and/or leaves to stand level. The average interception loss, throughfall, and stemflow fluxes account for 24.9%, 72.2%, and 2.9% of the gross rainfall for H. rhamnoides, and 19.2%, 70.7%, and 10.1% for S. pubescens, respectively. Throughfall increased with increasing rainfall for both shrubs; however, it was only correlated with the leaf area index for S. pubescens. For stemflow measured from individual branches, we found that the rainfall amount and basal diameter are the best predictors for H. rhamnoides, whereas rainfall amount and branch biomass appear to be the best predictors for S. pubescens. At the stand level, stemflow production is affected by the rainfall amount for H. rhamnoides, and it is affected by both the rainfall amount and the leaf area index for S. pubescens. The canopy storage capacity of H. rhamnoides (1.07–1.28 mm) was larger than S. pubescens (0.88–1.07 mm), and it is mainly determined by the branches and stems of H. rhamnoides and the leaves of S. pubescens. The differences in interception loss between the 2 shrub stands are mainly attributed to different canopy structures that induced differences in stemflow production and canopy storage. We evaluated the effects of canopy structure on rainfall interception loss, and our developed model provides a better understanding of the effects of the canopy structure on the water cycles in dryland shrub ecosystems.  相似文献   

10.
Abstract

More than 40 years of re-vegetation using mainly xerophytic shrubs Artemisia ordosica Krasch. and Caragana korshinskii Kom. at Shapotou Desert Experimental Research Station near Lanzhou, China has resulted in established dwarf-shrub and herbaceous cover on sand dunes. Precipitation, as the sole source of water replenishment in the semiarid area, plays a pertinent role in sustaining the desert ecosystem. A field study was conducted to (a) measure interception loss on shrub canopies during individual rainfall events, (b) determine the canopy storage capacity of individual plants, and (c) explore the relationship between interception and rainfall parameters. The total rainfall and its respective partitions as throughfall were determined and the interception losses in the studied ecosystem were quantified. Interception loss was shown to differ among the xerophyte taxa studied. During the growing seasons, the average shrub community interception loss is 6.9% and 11.7% of the simultaneous overall precipitation, for A. ordosica and C. korshinskii, respectively. Taking into account the observed rainfall conditions and vegetation cover characteristics, it was concluded that the interception loss was 2.7% of the total annual precipitation verified in the period for the A. ordosica community with an average cover of 30%, canopy projection area of 0.8 m2 and canopy storage capacity of 0.75 mm. In contrast, interception loss for the C. korshinskii community was 3.8% with an average cover of 46%, canopy projection area of 3.8 m2 and canopy storage capacity of 0.71 mm. For individual plants of both shrubs, the proportion of interception loss to gross rainfall decreased notably as the rainfall intensity increased between 0 and 2 mm h?1, while it tended to remain constant at about 0.1–0.2 for A. ordosica and 0.1–0.3 for C. korshinskii when the rainfall intensity was >2 mm h?1.  相似文献   

11.
Leave Area Index (LAI) is one of the most basic parameters to describe the geometric structure of plant canopies. It is also important input data for climatic model and interaction model between Earth surface and atmosphere, and some other things. The spatial scaling of retrieved LAI has been widely studied in recent years. Based on the new canopy reflectance model, the mechanism of the scaling effect of continuous canopy Leaf Area Index is studied, and the scaling transform formula among different scales is found. Both the numerical simulation and the field validation show that the scale transform formula is reliable. Supported by National Basic Research Program of China (Grant No. 2007CB714402) and National Natural Science Foundation of China (Grant Nos. 40401036, 40734025 and 40401036)  相似文献   

12.
Rainfall interception in forests is influenced by properties of the canopy that tend to vary over small distances. Our objectives were: (i) to determine the variables needed to model the interception loss of the canopy of a lower montane forest in south Ecuador, i.e. the storage capacity of the leaves S and of the trunks and branches St, and the fractions of direct throughfall p and stemflow pt; (ii) to assess the influence of canopy density and epiphyte coverage of trees on the interception of rainfall and subsequent evaporation losses. The study site was located on the eastern slope of the eastern cordillera in the south Ecuadorian Andes at 1900–2000 m above sea level. We monitored incident rainfall, throughfall, and stemflow between April 1998 and April 2001. In 2001, the leaf area index (LAI), inferred from light transmission, and epiphyte coverage was determined. The mean annual incident rainfall at three gauging stations ranged between 2319 and 2561 mm. The mean annual interception loss at five study transects in the forest varied between 591 and 1321 mm, i.e. between 25 and 52% of the incident rainfall. Mean S was estimated at 1·91 mm for relatively dry weeks with a regression model and at 2·46 mm for all weeks with the analytical Gash model; the respective estimates of mean St were 0·04 mm and 0·09 mm, of mean p were 0·42 and 0·63, and of mean pt were 0·003 and 0·012. The LAI ranged from 5·19 to 9·32. Epiphytes, mostly bryophytes, covered up to 80% of the trunk and branch surfaces. The fraction of direct throughfall p and the LAI correlated significantly with interception loss (Pearson's correlation coefficient r = −0·77 and 0·35 respectively, n = 40). Bryophyte and lichen coverage tended to decrease St and vascular epiphytes tended to increase it, although there was no significant correlation between epiphyte coverage and interception loss. Our results demonstrate that canopy density influences interception loss but only explains part of the total variation in interception loss. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

13.
Analyses were made of the concurrent canopy precipitation balances of a seed orchard pine and a mature forest eucalypt during protracted rainfalls selected for their representativeness of the range of variation encountered in the two canopy types at Tallanganda State Forest (ca. 990 m a.s.l.) in the Upper Shoalhaven Valley of southeastern New South Wales. Although their canopy storage capacities were widely different there was consistent interception behaviour in the pine and the eucalypt in all events. Detailed weather data and the time courses of interception loss provided circumstantial evidence for a varying and, at times, substantial influence of cloud or mist deposition on the canopy precipitation balances during rainfall that made a significant contribution to the variation in rainfall interception data. Mean evaporation rates from the saturated canopies during rainfall varied from ?0·02 mm hr?1 up to 0·68 mm hr?1 in the pine; and from ?0·04 mm hr?1 up to 0·13 mm hr?1 in the eucalypt. The implications of cloud-capture during rainfall for studies of rainfall interception in forests of southeastern Australia are discussed.  相似文献   

14.
The Canadian Land Surface Scheme (CLASS) was modified to correct an underestimation of the winter albedo in evergreen needleleaf forests. Default values for the visible and near‐infrared albedo of a canopy with intercepted snow, αVIS,cs and αNIR,cs, respectively, were too small, and the fraction of the canopy covered with snow, fsnow, increased too slowly with interception, producing a damped albedo response. A new model for fsnow is based on zI*, the effective depth of newly intercepted snow required to increase the canopy albedo to its maximum, which corresponds in the model with fsnow = 1. Snow unloading rates were extracted from visual assessments of photographs and modelled based on relationships with meteorological variables, replacing the time‐based method employed in CLASS. These parameterizations were tested in CLASS version 3.6 at boreal black spruce and jack pine forests in Saskatchewan, Canada, a subalpine Norway spruce and silver fir forest at Alptal, Switzerland, and a boreal maritime forest at Hitsujigaoka, Japan. Model configurations were assessed based on the index of agreement, d, relating simulated and observed daily albedo. The new model employs αVIS,cs = 0.27, αNIR,cs = 0.38 and zI* = 3 cm. The best single‐variable snow unloading algorithm, determined by the average cross‐site d, was based on wind speed. Two model configurations employing ensemble averages of the unloading rate as a function of total incoming radiation and wind speed, and air temperature and wind speed, respectively, produced larger minimum cross‐site d values but a smaller average. The default configuration of CLASS 3.6 produced a cross‐site average d from October to April of 0.58. The best model employing a single parameter (wind speed at the canopy top) for modelling the unloading rate produced an average d of 0.86, while the two‐parameter ensemble‐average unloading models produced a minimum d of 0.81 and an average d of 0.84. © 2015 Her Majesty the Queen in Right of Canada. Hydrological Processes published by John Wiley & Sons, Ltd.  相似文献   

15.
A. Iroum  A. Huber 《水文研究》2002,16(12):2347-2361
For a 26 month period, between 1 February 1998 and 31 March 2000, total precipitation, throughfall, stemflow and interception losses were measured for two different forest covers, one a managed broadleaved native forest and the other a Pseudotsuga menziesii (Mirb.) Franco (Douglas fir) plantation. Regressions between throughfall and stemflow and total precipitation (P) for individual storms and forest covers were computed and also for values of interception losses (expressed as a percentage of P) and P for each forest cover and period of development of the forest vegetation. Results obtained demonstrate the importance of forest canopies in rainfall distribution processes and for the availability of water resources. Also, that these forests generate particular interception patterns not strongly associated with the variation in crown cover throughout the year. These patterns are more closely related to the characteristics of rainfall and meteorological conditions during the growing and dormant periods. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

16.
Studies of evapotranspiration (ET) processes in forests often only measure one component of total ET, most commonly interception. This study examined all three components of annual ET (interception, evaporation from the forest floor and transpiration) and the correlations between them at 18 plantation forest sites in two species. All plantations had closed canopies, and sparse or no understorey. Single‐sided leaf area index averaged 3.5 (standard deviation ±0.5) in Eucalyptus globulus Labill. and 6.1 (±0.8) in Pinus radiata D.Don. Measurements included annual totals of rainfall in the open and under the canopy, stem flow (four sites only), evaporation from the forest floor and transpiration by the overstorey. Interception (I) averaged 19% (±4.9) of annual rainfall in E. globulus compared with 31% (±11.1) in P. radiata. However, higher annual interception in P. radiata did not result in higher total ET because annual evaporation from the forest floor (E) averaged 29% (±4.9) of rainfall in E. globulus but only 15% (±3.5) in P. radiata. Hence, the relative contribution of annual I plus E to ET did not differ significantly between the two species, averaging 48% (±7.3) of annual rainfall in E. globulus compared with 46% (±11.8) in P. radiata. As reported previously, transpiration did not differ significantly between the two species either, but was strongly related to depth‐to‐groundwater. In closed canopy plantations, mean annual ET did not differ between the two species. We conclude that when grown in plantations under similar soil and climatic conditions, conifer and broad‐leaved tree species can have similar annual ET, once the canopy of the plantation has closed. Lower average annual interception in broad‐leaved trees was offset by higher soil evaporation. These results highlight the importance of measuring all components of ET in studies of vegetation water use. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

17.
ABSTRACT

We present a new model extension for the Water balance Simulation Model, WaSiM, which features (i) snow interception and (ii) modified meteorological conditions under coniferous forest canopies, complementing recently developed model extensions for particular mountain hydrological processes. Two study areas in Austria and Germany are considered in this study. To supplement and constrain the modelling experiments with on-site observations, a network of terrestrial time-lapse cameras was set up in one of these catchments. The spatiotemporal patterns of snow depth inside the forest and at the adjacent open field sites were recorded along with snow interception dynamics. Comparison of observed and modelled snow cover and canopy interception indicates that the new version of WaSiM reliably reconstructs the variability of snow accumulation for both the forest and the open field. The Nash-Sutcliffe efficiency computed for selected runoff events in spring increases from ?0.68 to 0.71 and 0.21 to 0.87, respectively.  相似文献   

18.
José Návar 《水文研究》2013,27(11):1626-1633
The quantitative importance of rainfall interception loss and the performance of the reformulated Gash model were evaluated as a function of basal area in Mexico's northeastern temperate forest communities. A sensitivity analysis as well as an iterative search of parameters matched interception loss measurements and assessments and isolated coefficient values that drive the model performance. Set hypothesis was tested with a total of 73 rainfalls recorded on four forest stands with different canopy cover for model fitting (39) and validation (34). The reformulated Gash model predicted well rainfall interception loss because mean deviations between recorded and modelled interception loss as a function of gross rainfall, MD, were <2.6% and 5.3% for fitting and validating parameter data sets, respectively. Basal area was negatively related to the model performance, but maximum projected MD range values can be found in most interception loss studies, for example, <7% when basal area is <5 m2 ha?1. The wet canopy evaporation rate and the canopy storage coefficient drive interception loss and the iterative parameter search showed that high wet canopy evaporation rates were expected in these forests. These parameters must be further studied to physically explain drivers of high wet canopy evaporation rates. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

19.
The storage capacity of a temperate mixed oak–beech stand was investigated as a function of stand density and species composition. Measurements were performed in selected zones delimited by three neighbouring trees. Three independent approaches were compared: (i) a spraying laboratory experiment to estimate the water storage on foliage before and after dripping; (ii) a mechanistic model describing rainfall partitioning within the forest canopy and providing estimates of foliage storage capacities; and (iii) linear regression analyses to evaluate the canopy (foliage + branches) storage capacity using the relationship between throughfall and rainfall. Good agreement was generally observed between the laboratory experiment and the mechanistic model estimates, while estimations from the regression method tended to exceed those from the other approaches. Storage capacity estimates ranged from 0·22 mm to 0·80 mm for pure oak zones, from 0·24 mm to 1·12 mm for mixed zones and from 0·53 mm to 1·17 mm for pure beech zones. The increase of storage capacity with increasing proportion of beech in the canopy resulted from higher beech LAI compared with oak. Similarly, for mixed and pure beech canopies, storage capacity was higher for high density zones than for low density zones as a result of the increase in LAI with increasing local basal area; in contrast, for pure oak, the storage capacity was not related to basal area because of the lower shade‐tolerance of this species compared with beech. Copyright © 2008 John Wiley & Sons, Ltd.  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   

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