Distinct Rainfall Interception Profiles among Four Common Pacific Northwest Tree Species (original) (raw)
Related papers
Winter rainfall interception by two mature open‐grown trees in Davis, California
Hydrological Processes, 2000
A rainfall interception measuring system was developed and tested for open-grown trees. The system includes direct measurements of gross precipitation, throughfall and stem¯ow, 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-yearold broadleaf evergreen tree (cork oak, Quercus suber) representing trees having divergent canopy distributions of foliage and stems. Partitioning of gross precipitation into throughfall, stem¯ow 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 stem¯ow 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 signi®cant than rainfall rate and duration in determining interception losses. Both stem¯ow and throughfall varied with rainfall intensity and wind speed. Increasing precipitation rates and wind speed increased stem¯ow but reduced throughfall. Analysis of rainfall interception processes at dierent 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 re¯ected 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 speci®c to the Mediterranean climate region.
Agricultural and Forest Meteorology, 2005
The canopy water storage capacity (S), direct throughfall fraction ( p), the ratio of evaporation to rainfall intensity (Ē=R) and interception loss (I n ), of a Douglas-fir forest are influenced by short (seasonal) and long-term (decades to centuries) changes in the forest canopy. Gross precipitation (P G ) and net precipitation (P n ) were measured in a young (25-year-old) Douglas-fir forest and the results compared with measurements previously made in a nearby old-growth (>450-year-old) Douglas-fir forest . The dynamics of rainfall interception by a seasonal temperate rainforest. Agric. Forest Meteorol. 124,. Canopy rainfall variables were estimated using a regression-based method that estimates S, p andĒ=R for individual storms using the relationship between P G and P n . The individual storm estimates of S, p andĒ=R for the young forest were applied to a rainfall interception model Gash model [Gash, J.H.C., 1979. An analytical model of rainfall interception by forest. Q. J. R. Meteorol. Soc. 105, 43-55.]) to determine the effect of seasonal changes in canopy hydrologic variables have on estimates of I n (young forest only). The Gash model was previously applied to the old-growth forest [Link, T.E., Unsworth, M.H., Marks, D., 2004. The dynamics of rainfall interception by a seasonal temperate rainforest. Agric. Forest Meteorol. 124, 171-191.].
The dynamics of rainfall interception by a seasonal temperate rainforest
Agricultural and Forest Meteorology, 2004
Net canopy interception (I net ) during rainfall in an old-growth Douglas-fir-western hemlock ecosystem was 22.8 and 25.0% of the gross rainfall (P G ) for 1999 and 2000, respectively. The average direct throughfall proportion (p) and canopy storage capacity (S) derived from high-temporal resolution throughfall measurements were 0.36 and 3.3 mm, respectively. Derived values of S were very sensitive to the estimated evaporation during canopy wetting (I w ). Evaporation during wetting was typically small due to low vapor pressure deficits that usually occur at the start of an event, therefore I w is best estimated using the Penman method during canopy wetting, rather than assuming a constant evaporation rate over an entire event. S varied seasonally, from an average of 3.0 mm in the spring and fall, to 4.1 mm in the summer, coincident with canopy phenology changes. Interception losses during large storms that saturated the canopy accounted for 81% of I net . Canopy drying after events comprised 47% of I net , evaporation during rainfall comprised 33%, and evaporation during wetting accounted for 1%. Interception associated with small storms insufficient to saturate the canopy accounted for 19% of I net . The Gash analytical model accurately estimated both I net and the individual components of I net in this system when applied on an event basis, and when the Penman method was used to compute evaporation during rainfall. The Gash model performed poorly when applied on a daily basis, due to a rainfall regime characterized by long-duration events, which violated the assumption of one rain event per day.
Variation in rainfall interception along a forest succession gradient
Rainfall interception by forest canopies reduces the water influx to the forest floor. When forests are replaced by pasture, the process of canopy interception temporarily stops until a new forest develops on abandoned pasture land. Modern land-cover change typically involves regrowing forests but the relation between forest succession and canopy interception is hardly understood. This lack of knowledge is unfortunate because rainfall interception plays an important role in regional water cycles and needs to be quantified for modeling purposes. To help close the knowledge gap, we designed a chronosequence study of throughfall along a secondary succession gradient in a tropical forest region of Panama. The investigated gradient comprises 20 natural forest patches regrowing for 1 up to about 130 years. We sampled each patch with a minimum of 20 funnel-type throughfall collectors over a continuous two-month period that had nearly 900 mm of rain. At the same time and locations, we acqui...
The effect of intercepted rainfall on the water balance of a hardwood forest
Water Resources Research, 1979
Evaporation from a large hardwood forest is estimated from measurements of the required meteorological variables and from measured stomatal resistances. A correction factor is derived to overcome the incorrect assumption that evaporative demand remains the same during wet and dry periods. The factor is based on the ratio of the isothermal resistances during the wet and subsequent dry periods. The stomatal measurements were converted to canopy resistances by dividing by the leaf area index and were used to obtain the water balance for the entire season. The results are analyzed to show that evaporation from a wet canopy is often 2-3 times greater than transpiration from the same surface. Rates of interceptionai loss, calculated from the wet and dry evaporation rates, were verified by direct measurements of throughfall and stemflow. Net interceptional loss, equal to the excess evaporation from a wet canopy over a dry one, depended on rainfall duration and character and was on the average about 60-80% of total interception, In the overall summer water balance of 442 mm of precipitation and 52-mm depletion of soil storage, transpiration via the trees accounted for 261 mm; evaporation from the wetted leaves and branches for 111 mm, and runoff for 131 mm, giving an error of closure in the water balance of only 9 mm. If transpiration only had been used instead of interception when the canopy was wet, the error in the water balance would have been 100 mm. INTRODUCTION At present there is much controversy regarding the effect of intercepted rainfall on the water balance of forested watersheds. The core of the argument is whether rain retained by vegetation represents a total loss or no loss of moisture beyond the normal evapotranspiration of the canopy. The dis-' agreement stems largely from the way in which intercepted rainfall is viewed. If it is considered as a reduction in rainfall reaching the ground, then it could indeed be a total loss. This early view was shared by hydrologists who looked at interception only in terms of the inputs of the hydrologic cycle. But if the water cycle of the entire soil-vegetation complex is considered, then intercepted rainfall is not a total loss, because when the foliage is wetted, transpirational withdrawal of soil moisture is reduced. The magnitude of transpirational saving during the evaporation of intercepted rainfall is therefore critical in determining how much of a moisture loss interception constitutes. If the rate of water loss is the same whether the vegetation is wet or dry, then it matters little whether evaporative demand is satisfied by intercepted water or soil moisture. Burgy and Pomeroy [1958] found that in vigorously growing laboratory grass plots the evaporation of a given amount of intercepted water (sprinkled on the plots) corresponded to an almost equal reduction in the amount of transpiration from the plants, in that total moisture loss was approximately the same for plots with wetted and dry leaf surfaces. Field studies by McMillan and Burgy [1960] on short, clipped grass in California gave similar results. The early ideas, based on these experiments, maintained that since a given supply of energy will evaporate only a given amount of water, then the evaporation of the moisture retained by the foliage must be compensated for by an equal reduction in transpiration. If, on the other hand, evaporation of intercepted rainfall is Copyright ¸ 1979 by the American Geophysical Union.
Modeling rainfall interception components of forests: Extending drip equations
Agricultural and Forest Meteorology, 2019
Assessment of forest interception, I, and its components; the average evaporation rate during the storm, Ē , and canopy storage, S, are essential for simulating the contribution of forests to the water cycle and the climate system. The objectives of this study were to: (i) propose a new model to predict I, Ē , and S, as well as rainfall duration, RD and rainfall intensity, R ; (ii) correlate Ē , RD, and R assessments; and (iii) quantify the role plant surfaces play on the generation of interception from four forests in Mexico. Based on extended drip equations, the model was calibrated using field measurements from forty-five forest interception case studies (N = case studies, n = number of rains) in tropical dry, TDF (N = 21, n = 347), arid/semi-arid, A&SF (N = 15, n = 659), temperate, TF (N = 4, n = 258), and tropical montane cloud, TMCF, forests (N = 6, n = 658) and validated using field measurements from sprinkling experiments in ne Mexico. The model performed very good in predicting both individual and cumulative I values, with average errors, ME%, as a function of precipitation, P, smaller than 4% and Nash-Sutcliffe, NSE, values > 0.33 for three out of four forests. Ē assessments accounted for between 65% and 93% of I in these forests. Higher Ē and I figures were found in individual trees (3.78 A mm h −1 , 27%) in contrast to forest plots (2.24 B mm h −1 , 14%). Ē assessments decreased as a function of RD but increased as a function of R for all forests (p ≤ 0.05). Leaf area index, LAI, significantly explained part of the I variance in complex non-linear fashions (p ≤ 0.05). The novel independent assessments of I, Ē , S, RD, and R , the significant relationships between I components, and the complex role plant surfaces play on the generation of I fill an important scientific gap in this area of forest hydrology.
Canopy precipitation interception in urban forests in relation to stand structure
Urban Ecosystems, 2017
Urban forests provide important ecosystem services. In terms of hydrological benefits, forest ecosystems in urban environments represent qualitative and quantitative filter for rainwater. We quantified the canopy interception in relation to urban forest stand structure and rainfall intensity in an urban transect of the mixed (upland) forest in the city centre, towards a riparian pine forest and a floodplain hardwood forest in the City of Ljubljana, Slovenia. Bulk precipitation in open areas and throughfall were measured with fixed rainfall collectors in each forest. Stemflow was estimated from a review of relevant literature. We found that canopy interception in selected urban forests was mainly affected by tree species composition and other stand structure variables, such as canopy cover and tree dimensions. Average annual canopy interception was highest in the mixed forest (18.0% of bulk precipitation), while the riparian pine forest had the lowest level (3.9% of bulk precipitation) and the floodplain hardwood forest had the intermediate level for interception (7.1% of bulk precipitation). The mixed forest exhibited the stand structure factors that contributed to the highest canopy interception among the studied forests: high assemblage of dominant coniferous trees, denser canopy cover and the highest growing stock. Furthermore, rainfall intensity has proven to be an important factor for the seasonal partitioning (comparing the leafed and leafless period) of canopy interception. A better understanding of precipitation interception processes in urban forests is needed to assist urban forest managing and planning, aiming at maximizing canopy interception for the mitigation of stormwater runoff and flooding in urbanized watershed.
Rainfall interception by Sacramento's urban forest
1998
A one-dimensional mass and energy balance model was developed to simulate rainfall interception in Sacramento County, California. The model describes tree interception processes: gross precipitation, leaf drip, stem flow, and evaporation. Kriging was used to extend existing meteorological point data over the region. Regional land use/ land cover and tree canopy cover were parameterized with data obtained by remote sensing and ground sampling. Annual interception was 1.1% for the entire county and 11.1% of precipitation falling on the urban forest canopy. Summer interception at the urban forest canopy level was 36% for an urban forest stand dominated by large, broadleaf evergreens and conifers (leaf area index = 6.1) and 18% for a stand dominated by medium-sized conifers and broadleaf deciduous trees (leaf area index = 3.7). For 5 precipitation events with return frequencies ranging from 2 to 200 years, interception was greatest for small storms and least for large storms. Because small storms are responsible for most pollutant washout, urban forests are likely to produce greater benefits through water quality protection than through flood control.
A New Approach in Measuring Rainfall Interception by Urban Trees in Coastal British Columbia
Water Quality Research Journal, 2009
Interception loss plays an important role in controlling the water balance of a watershed, especially where urban development has taken place. The aim of this study was to illustrate the importance of urban trees as a form of ‘green infrastructure’ where they reduce stormwater runoff and rainwater intensity. In addition, trees cause a delay in precipitation reaching the ground. Interception loss was studied in the North Shore of British Columbia. We applied a unique methodology for measuring throughfall under six different urban trees using a system of long polyvinyl chloride pipes hung beneath the canopy capturing the throughfall and draining it to a rain gauge attached to a data logger. Different tree species (Douglas-fir [Pseudotsuga menziesii] and western red cedar [Thuja plicata]) in variable landscape sites (streets, parks, and natural forested areas) and elevations were selected to ensure that the system adequately captured the throughfall variability. Interception and throug...