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1.
A rainfall interception measuring system was developed and tested for open‐grown trees. The system includes direct measurements of gross precipitation, throughfall and stemflow, as well as continuous collection of micrometeorological data. The data were sampled every second and collected at 30‐s time steps using pressure transducers monitoring water depth in collection containers coupled to Campbell CR10 dataloggers. The system was tested on a 9‐year‐old broadleaf deciduous tree (pear, Pyrus calleryana ‘Bradford’) and an 8‐year‐old broadleaf evergreen tree (cork oak, Quercus suber) representing trees having divergent canopy distributions of foliage and stems. Partitioning of gross precipitation into throughfall, stemflow and canopy interception is presented for these two mature open‐grown trees during the 1996–1998 rainy seasons. Interception losses accounted for about 15% of gross precipitation for the pear tree and 27% for the oak tree. The fraction of gross precipitation reaching the ground included 8% by stemflow and 77% by throughfall for the pear tree, as compared with 15% and 58%, respectively, for the oak tree. The analysis of temporal patterns in interception indicates that it was greatest at the beginning of each rainfall event. Rainfall frequency is more significant than rainfall rate and duration in determining interception losses. Both stemflow and throughfall varied with rainfall intensity and wind speed. Increasing precipitation rates and wind speed increased stemflow but reduced throughfall. Analysis of rainfall interception processes at different time‐scales indicates that canopy interception varied from 100% at the beginning of the rain event to about 3% at the maximum rain intensity for the oak tree. These values reflected the canopy surface water storage changes during the rain event. The winter domain precipitation at our study site in the Central Valley of California limited our opportunities to collect interception data during non‐winter seasons. This precipitation pattern makes the results more specific to the Mediterranean climate region. Copyright © 2000 John Wiley & Sons, Ltd.  相似文献   

2.
Di Wang  Li Wang 《水文研究》2019,33(3):372-382
Canopy interception is one of the most important processes in an ecosystem, but it is still neglected when assessing evapotranspiration (ET) partitioning in apple orchards on the Loess Plateau in China. To explore the importance of canopy interception, we monitored two neighbouring apple orchards on the Loess Plateau in China, one 8‐year‐old and the other 18‐years old at the start of the study, from May to September for four consecutive years (2013–2016). We measured parameters of canopy interception (I) including precipitation, throughfall, stemflow, leaf area index, transpiration (T), and soil evaporation (S) to quantify ET. The importance of canopy interception was then assessed by comparing the relationship between water supply (precipitation) and water demand (ET), calculated with and without considering canopy interception (T + S and T + S + I, respectively). Tree age clearly influenced canopy interception, as estimates of annual canopy interception during the study years in the younger and older orchards amounted to 22.2–29.4 mm and 26.8–39.9 mm, respectively. Daily incident rainfall and rainfall intensity in both orchards were significantly positively correlated with daily canopy interception in each year. The relationship between annual precipitation and annual ET (calculated with and without consideration of canopy interception) in the younger orchard differed during 2015 and 2016. Ignoring canopy interception would result in underestimation of annual ET in both apple orchards and hence incorrect evaluation of the relationship between water supply and water demand, particularly for the younger orchard during 2015 and 2016. Thus, for a complete understanding of water consumption in apple orchards in this and similar regions, canopy interception should not be ignored when assessing ET partitioning.  相似文献   

3.
Large‐scale exotic pine plantations have been developed for timber production in subtropical Australia. Few studies investigate the spatial variability of both throughfall and stemflow in such managed pine plantations despite their acknowledged effects on the heterogeneity of hydrological and biochemical processes of forested ecosystems. To examine the spatial variability of rainfall under a 12‐year‐old pine plantation in a subtropical coastal area of Australia, we observed gross rainfall, throughfall and stemflow over a 1‐year period. Our results show that the spatial variability of gross rainfall within a 50 m × 50 m plot is minimal. Throughfall is significantly different among three tree zones (midway between rows, west and east side of trunks), particularly for rainfall <50 mm, with the highest throughfall on the east side of the tree trunks (sum = 85% of gross rainfall) and the lowest in the midway between tree rows (sum = 68% of gross rainfall). These spatial patterns persist among 84% of recorded rainfall events. Spatial variability and time stability of throughfall are better explained by canopy interception of the inclined rainfall resulting from the prevailing easterly wind direction throughout the experiment. The annual stemflow is different among individual sample trees, which is mainly ascribed to the difference in tree size (e.g. projected canopy area and stem diameter). The outcomes of this study would help future investigators better design appropriate sampling strategies in these pine plantations under similar climate conditions. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

4.
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   

5.
Tim P. Duval 《水文研究》2019,33(11):1510-1524
Partitioning of rainfall through a forest canopy into throughfall, stemflow, and canopy interception is a critical process in the water cycle, and the contact of precipitation with vegetated surfaces leads to increased delivery of solutes to the forest floor. This study investigates the rainfall partitioning over a growing season through a temperate, riparian, mixed coniferous‐deciduous cedar swamp, an ecosystem not well studied with respect to this process. Seasonal throughfall, stemflow, and interception were 69.2%, 1.5%, and 29.3% of recorded above‐canopy precipitation, respectively. Event throughfall ranged from a low of 31.5 ± 6.8% for a small 0.8‐mm event to a high of 82.9 ± 2.4% for a large 42.7‐mm event. Rain fluxes of at least 8 mm were needed to generate stemflow from all instrumented trees. Most trees had funnelling ratios <1.0, with an exponential decrease in funnelling ratio with increasing tree size. Despite this, stand‐scale funnelling ratios averaged 2.81 ± 1.73, indicating equivalent depth of water delivered across the swamp floor by stemflow was greater than incident precipitation. Throughfall dissolved organic carbon (DOC) and total dissolved nitrogen (TDN) averaged 26.60 ± 2.96 and 2.02 ± 0.16 mg L?1, respectively, which were ~11 and three times above‐canopy rain levels. Stemflow DOC averaged 73.33 ± 7.43 mg L?1, 35 times higher than precipitation, and TDN was 4.45 ± 0.56 mg L?1, 7.5 times higher than rain. Stemflow DOC concentration was highest from Populus balsamifera and TDN greatest from Thuja occidentalis trees. Although total below‐canopy flux of TDN increased with increasing event size, DOC flux was greatest for events 20–30 mm, suggesting a canopy storage threshold of DOC was readily diluted. In addition to documenting rainfall partitioning in a novel ecosystem, this study demonstrates the excess carbon and nitrogen delivered to riparian swamps, suggesting the assimilative capacity of these zones may be underestimated.  相似文献   

6.
A study of partitioning of rainfall into throughfall, stemflow, and interception was conducted in a dry sclerophyll eucalypt forest and an adjacent pine plantation over a period of seven years, on a rainfall event basis. The following three issues are discussed: (1) the relationship between canopy storage capacity and interception of continuous events, (2) interception, throughfall, and stemflow, and (3) the effect on interception of thinning the pine plantation.
  • 1 The canopy storage capacity/interception interaction for the eucalypt forest was assessed by comparing a gravimetric estimate of canopy storage capacity with interception. The maximum possible value for canopy storage capacity was found to be a small proportion of interception for events of all sizes. This suggests that evaporation of intercepted water during the continuous events was responsible for most of the interception. This ‘within event’ evaporation appears to be responsible also for the net rainfall/gross rainfall estimate of canopy storage capacity being four times the gravimetric value. For the pines the regression estimate was more closely related to interception.
  • 2 Interception, throughfall, and stemflow of these forests were measured for four years. Data are presented for each year with overall average interception being 11-4 per cent of precipitation for the eucalypt forest and 18-3 per cent for the pine plantation. Topography and rainfall event type are considered in the comparison.
Species composition and tree type are considered when comparing these results with published studies from similar forest types in southeastern Australia. The periodic (annual) variations of interception in this and the other studies makes comparison difficult.
  • 3 The effect of thinning on the throughfall, stemflow, and interception in a Pinus radiata plantation is examined. Throughfall increased, interception decreased but not in proportion to the removed biomass; stemflow decreased on an area basis, but increased on a per tree basis. A positive relationshiip is established between interception and stemflow on the thinned plantation but not in the unthinned. Reasons for this are suggested. The results are compared to those reported from similar experiments in other forests.
  • 4 The periodic variations in interception and errors inherent in its estimation suggest that caution should be exercised when using average interception figures in water balance studies.
  相似文献   

7.
Forest canopies present irregular surfaces that alter both the quantity and spatiotemporal variability of precipitation inputs. The drop size distribution (DSD) of rainfall varies with rainfall event characteristics and is altered substantially by the forest stand properties. Yet, the influence of two major European tree species, European beech (Fagus sylvatica L.) and Norway spruce (Picea abies (L.) H. Karst), on throughfall DSD is largely unknown. In order to assess the impact of these two species with differing canopy structures on throughfall DSD, two optical disdrometers, one above and one below the canopy of each European beech and Norway spruce, measured DSD of both incident rainfall and throughfall over 2 months at a 10‐s resolution. Fractions of different throughfall categories were analysed for single‐precipitation events of different intensities. While penetrating the canopies, clear shifts in drop size and temporal distributions of incoming rainfall were observed. Beech and spruce, however, had different DSD, behaved differently in their effect on diameter volume percentiles as well as width of drop spectrum. The maximum drop sizes under beech were higher than under spruce. The mean ± standard deviation of the median volume drops size (D50) over all rain events was 2.7 ± 0.28 mm for beech and 0.80 ± 0.04 mm for spruce, respectively. In general, there was a high‐DSD variability within events indicating varying amounts of the different throughfall fractions. These findings help to better understand the effects of different tree species on rainfall partitioning processes and small‐scale variations in subcanopy rainfall inputs, thereby demonstrating the need for further research in high‐resolution spatial and temporal properties of rainfall and throughfall.  相似文献   

8.
We investigated the spatial and seasonal variations in throughfall (Tf) in relation to spatial and seasonal variations in canopy structure and gross rainfall (Rf) and assessed the impacts of the variations in Tf on stand‐scale Tf estimates. We observed the canopy structure expressed as the leaf area index (LAI) once a month and Tf once a week in 25 grids placed in a Moso bamboo (Phyllostachys pubescens) forest for 1 year. The mean LAI and spatial variation in LAI did have some seasonal variations. The spatial variations in Tf reduced with increasing Rf, and the relationship between the spatial variation and the Rf held throughout the year. These results indicate that the seasonal change in LAI had little impact on spatial variations in Tf, and that Rf is a critical factor determining the spatial variations in Tf at the study site. We evaluated potential errors in stand‐scale Tf estimates on the basis of measured Tf data using Monte Carlo sampling. The results showed that the error decreases greatly with increasing sample size when the sample size was less than ～8, whereas it was near stable when the sample size was 8 or more, regardless of Rf. A sample size of eight results in less than 10% error for Tf estimates based on Student's t‐value analysis and would be satisfactory for interception loss estimates when considering errors included in Rf data. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

9.
This article presents a comprehensive study of canopy interception in six rainforests in Australia's Wet Tropics for periods ranging between 2 and 3·5 years. Measurements of rainfall, throughfall, stemflow and cloud interception were made at sites characterized by different forest types, canopy structure, altitude, rainfall and exposure to prevailing winds. Throughfall at these sites ranged between 64 and 83% of total precipitation inputs, while stemflow ranged between 2 and 11%. At sites higher than 1000 m, cloud interception was found to contribute up to 66% of the monthly water input to the forest, more than twice the rainfall at these times. Over the entire study period, cloud interception accounted for between 4 and 30% of total precipitation inputs, and was related more to the exposure of sites to prevailing winds than to altitudinal differences alone. Over the duration of the study period, interception losses ranged between 22 and 29% of total water input (rainfall and cloud interception) at all sites except the highest altitude site on Bellenden Ker, where interception was 6% of total water input. This smaller interception loss was the result of extremely high rainfall, prolonged immersion in cloud and a sparser canopy. On a monthly basis, interception losses from the six sites varied between 10 and 88% of rainfall. All sites had much higher interception losses during the dry season than in the wet season because of the differences in storm size and rainfall intensity. The link between rainfall conditions and interception losses has important implications for how evaporative losses from forests may respond to altered rainfall regimes under climate change and/or large‐scale atmospheric circulation variations such as El Niño. Copyright © 2007 John Wiley & Sons, Ltd.  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.
Methods for measuring throughfall, stemflow and, hence, interception in the tropical rainforests of the Wet Tropics region of North Queensland, Australia, were tested at three sites for between 581 and 787 days. The throughfall system design was based on long troughs mounted beneath the canopy and worked successfully under a range of rainfall conditions. Comparison of replicated systems demonstrated that the methodology is capable of capturing the variability in throughfall exhibited beneath our tropical rainforest canopies. Similarly, the stemflow system design which used spiral collars attached to sample trees worked well under a range of rainfall conditions and also produced similar estimates of stemflow in replicated systems. Higher altitude rainforests (>1000 m) in North Queensland can receive significant extra inputs of water as the canopy intercepts passing cloud droplets. This additional source of water is referred to as ‘cloud interception’ and an instrument for detecting this is described. The results obtained from this gauge are compared with cloud interception estimates made using a canopy water balance method. This method is based on stemflow and throughfall measurements and provides an alternative means to fog or cloud interception gauge calibration techniques used in the literature. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

12.
Curtis D. Holder 《水文研究》2003,17(10):2001-2010
Fog precipitation occurs when fog droplets are filtered by the forest canopy and coalesce on the vegetative surfaces to form larger water droplets that drip to the forest floor. This study examines the quantity of throughfall compared with incident precipitation produced by the canopy of a lower montane rain forest (2100 m) and an upper montane cloud forest (2550 m) in the Sierra de las Minas Biosphere Reserve, Guatemala. Fog precipitation was measured with throughfall and precipitation gauges from 23 July 1995 to 7 June 1996. Fog precipitation occurred during sampling periods when throughfall exceeded incident precipitation. Fog precipitation contributed <1% of total water inputs in the cloud forest at 2100 m during the 44‐week period, whereas fog precipitation contributed 7·4% at 2550 m during the same period. The depth equivalent of fog precipitation was greater at 2550 m (203·4 mm) than at 2100 m (23·4 mm). The calculation of fog precipitation in this study is underestimated. The degree of underestimation may be evident in the difference in apparent rainfall interception between 2100 m (35%) and 2550 m (4%). Because the apparent interception rate at 2550 m is significantly lower than 2100 m, the canopy probably is saturated for longer periods as a result of cloud water contributions. Data show a seasonal pattern of fog precipitation most evident at the 2550 m site. Fog precipitation represented a larger proportion of total water inputs during the dry season (November to May). Because cloud forests generate greater than 1 mm day?1 of fog precipitation in higher elevations of the Sierra de las Minas, the conservation of the cloud forest may be important to meet the water demands of a growing population in the surrounding arid lowlands. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

13.
Stable isotopes of water can give clues to the physical processes of forest canopy interception. We examined whether fine‐scale canopy structure is related to throughfall amount and isotopic variation by intensively quantifying both throughfall and canopy structure in a broadleaf, deciduous forest in Louisiana, USA. Local throughfall amount was correlated with canopy structure quantified as distance to the nearest tree, local crown coverage, and local crown length; isotopic composition was also correlated with the same variables but weakly. Spatial patterns of throughfall amount showed some consistency across storms, but spatial patterns of stable isotopes were much weaker and inconsistent. Spatial autocorrelation was consistent in throughfall amount across events, which suggests fixed controls over patterning of throughfall to the forest floor by the canopy. In contrast, lower spatial and temporal autocorrelation in isotopic composition suggested temporally varying controls over patterning, and that routing through the canopy, intra‐storm isotopic variation of rainfall, isotopic exchange, and evaporation interacted to affect the stable isotopic composition. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

14.
Depending on season, rainfall characteristics and tree species, interception amounts to 15–50% of total precipitation in a forest under temperate climates. Many studies have investigated the importance of interception of different tree species in all kinds of different climates. Often authors merely determine interception storage capacity of that specific species and the considered event, and only sometimes a distinction is made between foliated and non‐foliated trees. However, interception is highly variable in time and space. First, since potential evaporation is higher in summer, but secondly because the storage capacity has a seasonal pattern. Besides weather characteristics, such as wind and rain intensity, snow causes large variations in the maximum storage capacity. In an experimental beech plot in Luxembourg, we found storage capacity of canopy interception to show a clear seasonal pattern varying from 0·1 mm in winter to 1·2 mm in summer. The capacity of the forest floor appears to be rather constant over time at 1·8 mm. Both have a standard deviation as high as ± 100%. However, the process is not sensitive to this variability resulting only in 11% variation of evaporation estimates. Hence, the number of raindays and the potential evaporation are stronger driving factors on interception. Furthermore, the spatial correlation of the throughfall and infiltration has been investigated with semi‐variograms and time stability plots. Within 6–7 m distance, throughfall and infiltration are correlated and the general persistence is rather weak. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

15.
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   

16.
Although we know that rainfall interception (the rain caught, stored, and evaporated from aboveground vegetative surfaces and ground litter) is affected by rain and throughfall drop size, what was unknown until now is the relative proportion of each throughfall type (free throughfall, splash throughfall, canopy drip) beneath coniferous and broadleaved trees. Based on a multinational data set of >120 million throughfall drops, we found that the type, number, and volume of throughfall drops are different between coniferous and broadleaved tree species, leaf states, and timing within rain events. Compared with leafed broadleaved trees, conifers had a lower percentage of canopy drip (51% vs. 69% with respect to total throughfall volume) and slightly smaller diameter splash throughfall and canopy drip. Canopy drip from leafless broadleaved trees consisted of fewer and smaller diameter drops (D50_DR, 50th cumulative drop volume percentile for canopy drip, of 2.24 mm) than leafed broadleaved trees (D50_DR of 4.32 mm). Canopy drip was much larger in diameter under woody drip points (D50_DR of 5.92 mm) than leafed broadleaved trees. Based on throughfall volume, the percentage of canopy drip was significantly different between conifers, leafed broadleaved trees, leafless broadleaved trees, and woody surface drip points (p ranged from <0.001 to 0.005). These findings are partly attributable to differences in canopy structure and plant surface characteristics between plant functional types and canopy state (leaf, leafless), among other factors. Hence, our results demonstrating the importance of drop‐size‐dependent partitioning between coniferous and broadleaved tree species could be useful to those requiring more detailed information on throughfall fluxes to the forest floor.  相似文献   

17.
Measurements are reported of rainfall, throughfall, stemflow, and derived interception losses made on a daily basis during two consecutive rainy seasons in a 4–5 year old and rapidly growing plantation forest of Acacia auriculiformis in a humid tropical environment. During the first observation period throughfall, stemflow, and interception loss amounted to respectively 81, 8, and 11 per cent of gross precipitation, whilst corresponding values for the second observation period were 75, 7, and 18 per cent. All three components correlated strongly with amounts of daily rainfall, but slopes of linear regression equations differed significantly between seasons for each component. Such differences are thought to reflect a 20 per cent increase in foliar mass as well as a certain instrumental bias introduced by the use of a fixed grid of throughfall troughs that differed between seasons. Tests did not reveal any effects of differences in rainfall characteristics although the two observation periods differed markedly in this respect. Although the present results fell within the (lower part of the) range reported for other sites in Southeast Asia application of Gash's analytical model suggested the results obtained during the second observation period to be anomalous. The model was tested with data from the second halves of the two observation periods, using parameters derived from the corresponding first halves. Discrepancies between estimated and observed losses were +9·4 and ?14·3 per cent for the two periods respectively. The bulk of the interception loss consisted of evaporation from a saturated canopy (69–80 per cent) and of evaporation after rainfall had ceased (25 and 15 per cent for the two periods respectively). Although the results were encouraging it would seem that a major difficulty in applying the analytical model to the humid tropics lies in obtaining a reliable estimate of the evaporation rate from a saturated canopy.  相似文献   

18.
《Journal of Hydrology》1999,214(1-4):103-110
During the growing season of 1995, canopy water fluxes were measured within a northern hardwood stand in southern Ontario, Canada. Observed canopy interception loss, throughfall, and stemflow fluxes from the stand were 19.3±3.5%, 76.4±2.9%, and 4.3±2.0% of incident precipitation, respectively. Both the original and revised Gash analytical rainfall interception loss models simulated these fluxes within the standard error of the observed estimates, suggesting that the analytical model may be appropriate for further applications within this forest type. The revised Gash model is recommended for further applications as it is better physically based. Both the original and revised models suggest that ∼60% of interception loss during the study period was evaporation from the canopy once rainfall has ceased while evaporation from the saturated canopy during rainfall accounted for ∼27%–33% of interception loss. Additional components of interception (e.g., evaporation from trunks) were computed to be minor contributors to total canopy interception loss.  相似文献   

19.
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   

20.
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   

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