Nutrient budget of a montane evergreen broad‐leaved forest at Ailao Mountain National Nature Reserve,Yunnan, southwest China

Hydrological fluxes and associated nutrient budget were studied during a 2 year period (1998–99) in a montane moist evergreen broad‐leaved forest at Ailao Mountain, Yunnan. Water samples of rainfall, throughfall, and stemflow, and of surface runoff, soil water, and stream flow were collected bimonthly to determine the concentration and fluxes of nutrients. Soil budgets were determined from the difference between precipitation input (including nutrient leaching from canopy) and output via runoff and drainage. The forest was characterized by low canopy interception and surface runoff, and high percolation and stream flow. Concentrations of nutrients were increased in throughfall and stemflow compared with precipitation. Surface runoff and drainage water had higher nutrient concentrations than precipitation and stream water. Total nitrogen and NH₄⁺‐N concentrations were higher in soil water than stream water, whereas K⁺, Ca²⁺, and Mg²⁺ concentrations were lower in the former than the latter. Annual nutrient fluxes decreased with soil depth following the pattern of water flux. Annual losses of most nutrient elements via stream flow were less than the corresponding inputs via throughfall and stemflow, except for calcium, for which solute loss was greater than the inputs via precipitation. Leaching losses of that element may be compensated by weathering. Losses of nitrogen, phosphorus, potassium, magnesium, sodium, and sulphur could be replaced through atmospheric inputs. Copyright © 2002 John Wiley & Sons, Ltd.     

Rainfall partitioning into throughfall,stemflow, and interception within a single beech (Fagus sylvatica L.) canopy: influence of foliation,rain event characteristics,and meteorology

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 (r_a² > 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.     

The effect of beech stemflow on spatial patterns of soil solution chemistry and seepage fluxes in a mixed beech/oak stand

Stemflow of beech (Fagus sylvatica L.) represents a significant input of water and elements to the soil and might influence the spatial patterns and the rate of seepage fluxes at the stand scale. We investigated the soil solution chemistry at different depths and distances from the stem and the element fluxes with stemflow, throughfall and seepage in proximal and distal stem areas of a 130‐year‐old beech/oak forest in Steigerwald (northern Bavaria, Germany). The proximal stem area (in total 286 m² ha⁻¹) was defined as a 1 m², 60 cm deep cylinder around the beech stem. Seepage fluxes were calculated by a soil hydrological model for 1996 using measured soil matrix potentials and tree xylem flow data for calibration. Stemflow represented 6·6% of the annual soil water input. With the exception of H⁺ fluxes, less than 10% of the total element fluxes with throughfall and stemflow reached the soil via stemflow. The volume‐weighted concentrations of H⁺, K⁺ and SO₄²⁻ in stemflow were higher than those in throughfall, while other elements had similar concentrations. Soil solution K⁺ concentrations decreased with stem distance, but the Na⁺, Mg²⁺, Cl⁻ and SO₄²⁻ concentrations increased. Gradients for other elements were not statistically significant. Stemflow had a strong influence on the spatial patterns of element fluxes with seepage. The water fluxes through the soil of the proximal stem areas at a depth of 60 cm contributed 13·5% to the total seepage at the stand scale. Proximal to the stems about 20% of total seepage for K⁺, Mn²⁺, Alⁿ⁺, dissolved organic N and dissolved organic C were concentrated, but only 8–10% for Na⁺, Mg²⁺ and Ca²⁺. The loss of acid‐neutralizing capacity calculated from the flux balance was about four times higher proximal to the stems compared with distal areas, indicating high rates of soil acidification proximal to the stems. Our results confirm the concept of a microsite around beech stems, characterized by high element and water fluxes in comparison with distal stem areas. Calculations of seepage fluxes and element budgets in beech stands have to consider the spatial heterogeneity of fluxes induced by stemflow. Copyright © 2000 John Wiley & Sons, Ltd.     

Rainfall partitioning through a mixed cedar swamp and associated C and N fluxes in Southern Ontario,Canada

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.     

The solute budget of a forest catchment and solute fluxes within a Pinus radiata and a secondary native forest site,southern Chile

Solute concentrations and fluxes in rainfall, throughfall and stemflow in two forest types, and stream flow in a 90 ha catchment in southern Chile (39°44′S, 73°10′W) were measured. Bulk precipitation pH was 6·1 and conductivity was low. Cation concentrations in rainfall were low (0·58 mg Ca²⁺ l^?1, 0·13 mg K⁺ l^?1, 0·11 mg Mg²⁺ l^?1 and <0·08 mg NH₄–N l^?1), except for sodium (1·10 mg l^?1). Unexpected high levels of nitrate deposition in rainfall (mean concentration 0·38 mg NO₃–N l^?1, total flux 6·3 kg NO₃–N ha^?1) were measured. Concentrations of soluble phosphorous in bulk precipitation and stream flow were below detection limits (<0·09 mg l^?1) for all events. Stream‐flow pH was 6·3 and conductivity was 28·3 μs. Stream‐water chemistry was also dominated by sodium (2·70 mg l^?1) followed by Ca, Mg and K (1·31, 0·70 and 0·36 mg l^?1). The solute budget indicated a net loss of 3·8 kg Na⁺ ha^?1 year^?1, 5·4 kg Mg²⁺ ha^?1 year^?1, 1·5 kg Ca²⁺ ha^?1 year^?1 and 0·9 kg K⁺ ha^?1 year^?1, while 4·9 kg NO₃–N ha^?1 year^?1 was retained by the ecosystem. Stream water is not suitable for domestic use owing to high manganese and, especially, iron concentrations. Throughfall and stemflow chemistry at a pine stand (Pinus radiata D. Don) and a native forest site (Siempreverde type), both located within the catchment, were compared. Nitrate fluxes within both forest sites were similar (1·3 kg NO₃–N ha^?1 year^?1 as throughfall). Cation fluxes in net rainfall (throughfall plus stemflow) at the pine stand generally were higher (34·8 kg Na⁺ ha^?1 year^?1, 21·5 kg K⁺ ha^?1 year^?1, 5·1 kg Mg²⁺ ha^?1 year^?1) compared with the secondary native forest site (24·7 kg Na⁺ ha^?1 year^?1, 18·9 kg K⁺ ha^?1 year^?1 and 4·4 kg Mg²⁺ ha^?1 year^?1). However, calcium deposition beneath the native forest stand was higher (15·9 kg Ca²⁺ ha^?1 year^?1) compared with the pine stand (12·6 kg Ca²⁺ ha^?1 year^?1). Copyright © 2002 John Wiley & Sons, Ltd.     

Importance of rainfall partitioning in a northern mixed forest canopy for soil water isotopic signatures in ecohydrological studies

The forest canopy can play a significant role in modifying the amount and isotopic composition of water during its passage throughout the near-surface critical zone. Here, partitioning of gross rainfall into interception, throughfall, and stemflow and its implications for the amount and isotopic composition of soil water was studied for red oak, eastern white pine, and eastern hemlock trees in a northern hardwood-conifer forest in south central Ontario, Canada. Stemflow production was greatest for red oak as a result of its upward-projecting branches and least for eastern white pine due to its horizontal branches and rougher bark. These stemflow contributions to the near-bole soil surface failed to produce consistently wetter soils relative to distal locations from the bole for all tree species. There was also no consistent evidence of isotopic enrichment of throughfall and stemflow relative to gross rainfall or of stemflow relative to throughfall for red oak or eastern hemlock. However, there was isotopic enrichment of both throughfall and stemflow for eastern white pine with increasing maximum atmospheric vapour pressure deficit, which may reflect the potential for evaporative fractionation as a result of retention and detention of water moving through the canopy by the rougher bark of this species. Dry soil conditions limited sampling of mobile soil water during the study, and there was no consistent evidence that either throughfall or stemflow fluxes controlled temporal changes in the isotopic signature of soil water beneath the tree. Thus, the potential for throughfall and stemflow fluxes in northern hardwood-conifer forests to modify the isotopic composition of water taken up by the tree via transpiration remains an open question.     

Characteristics of canopy interception loss in Moso bamboo forests of Japan

In recent years, Moso bamboo (Phyllostachys pubescens) forests have rapidly expanded in Japan by replacing surrounding coniferous and/or broadleaved forests. To evaluate the change in water yield from forested areas because of this replacement, it is necessary to examine evapotranspiration for Moso bamboo forests. However, canopy interception loss, one of the major components of evapotranspiration in forested areas, has been observed in only two Moso bamboo forests in Japan with relatively high stem density (~7000 stems/ha). There are, in fact, many Moso bamboo forests with much lower stem density. Thus, we made precipitation (Pr), throughfall (Tf) and stemflow (Sf) observations for 1 year in a Moso bamboo forest with stem density of 3611 stems/ha and quantified canopy interception loss (Ic). Pr and Ic for the experimental period were 1636 and 166 mm, respectively, and Ic/Pr was 10%. The value was approximately the same as values for the other two Moso bamboo forests and lower than values for coniferous and broadleaved forests. On the other hand, Tf/Pr and Sf/Pr for our forest (86% and 4%, respectively) were approximately 10% of Pr larger and smaller than values for the other two Moso bamboo forests. These results suggest that the difference in stem density greatly affects precipitation partitioning (i.e. Tf/Pr and Sf/Pr) but does not greatly change Ic/Pr. Copyright © 2012 John Wiley & Sons, Ltd.     

Seasonal and annual throughfall and stemflow in Andean temperate rainforests

The partitioning of gross rainfall into throughfall, stemflow, and interception loss and their relationships with forest structure was studied for a period of four years (October 2002–September 2006) and two years (October 2005–September 2007) in seven experimental catchments of temperate rainforest ecosystems located in the Andes of south‐central Chile (39°37′S, 600–925 m a.s.l.). The amount of throughfall, stemflow, and interception loss was correlated with forest structure characteristics such as basal area, canopy cover, mean quadratic diameter (MQD), and tree species characteristics in evergreen and deciduous forests. Annual rainfall ranged from 4061 to 5308 mm at 815 m a.s.l. and from 3453 to 4660 mm at 714 m a.s.l. Throughfall ranged from 64 to 89% of gross rainfall. Stemflow contributed 0·3–3·4% of net precipitation. Interception losses ranged from 11 to 36% of gross rainfall and depended on the amount of rainfall and characteristics as well as on forest structure, particularly the MQD. For evergreen forests, strong correlations were found between stemflow per tree and tree characteristics such as diameter at breast height (R² = 0·92, P < 0·01) and crown projection area (R² = 0·65, P < 0·01). Stemflow per tree was also significantly correlated with epiphyte cover of trunks in the old‐growth evergreen forests (R² = 0·29, P < 0·05). The difference in the proportion of throughfall and interception loss among stands was significant only during winter. The reported relationships between rainfall partitioning and forest structure and composition provide valuable information for management practices, which aimed at producing other ecosystem services in addition to timber in native rainforests of southern Chile. Copyright © 2010 John Wiley & Sons, Ltd.     

Throughfall and stemflow vary seasonally in different land‐use types in a lower montane tropical region of Panama

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.     

Estimating fog deposition at a Puerto Rican elfin cloud forest site: comparison of the water budget and eddy covariance methods

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.     

Evidence of large rainfall partitioning patterns by banana and impact on surface runoff generation

In this article the effect of redistribution of rainfall by banana on local water fluxes and the possible impact of these fluxes on surface runoff has been studied. First the water redistribution by a banana canopy at three development stages (vegetative, flowering, and bunch stage) was measured. The results showed a considerable stemflow, proportional to the leaf area index (LAI), which represented 18 to 26% of the incident rainfall volume according to the age of the crop. Consequently, the rainfall rate was 28‐fold higher at the plant collar for a fully developed banana canopy. For the throughfall, on average, the higher the LAI, the lower the mean throughfall. In addition, the spatial distribution of the throughfall varied according to the distance from the pseudostem. Notably, for the earlier stages, the area between the pseudostem and 0·5 m from it received weak throughfall. Secondly, simulations were carried out with a simple two‐compartment model simulating the total surface runoff volume. The simulations showed stemflow combined with the agronomical practice of furrowing has an effect on runoff compared to bare soil. A relative increase in surface runoff volume of three‐fold was encountered on a plot with a fully developed banana and a infiltration rate of 60 mm h^?1. However, the absolute increase was only a few percentage of the incident rainfall volume, although it represented large water volumes given the tropical rains. These features must be taken into account for hydrological management of such systems. Copyright © 2007 John Wiley & Sons, Ltd.     

Partitioning of rainfall in a eucalypt forest and pine plantation in southeastern australia: IV the relationship of interception and canopy storage capacity,the interception of these forests,and the effect on interception of thinning the pine plantation

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.

     

Partitioning of rainfall in a eucalypt forest and pine plantation in southeastern australia: I throughfall measurement in a eucalypt forest: Effect of method and species composition

A seven year event-based study partitioning of rainfall into throughfall, stemflow, and interception was conducted in a dry sclerophyll eucalypt forest and a Pinus radiata plantation. Resulting information will be of use for process modelling. Stemflow was influenced by event type, rain angle having a major effect; and the yields of the different species are compared. Tree characteristics that influenced stemflow yields are outlined and discussed. The canopy storage capacity of the eucalypt forest was determined and the influence of species composition is shown. The likely influence of climate variations is discussed. The canopy storage capacity is compared to the interception values estimated for continuous events of various sizes. The interception of the eucalypt forest and the pine plantation are compared on event basis for event size classes and on an annual basis. The comparative interceptions for continuous events are also discussed, while the effect of thinning the pine plantation on throughfall, stemflow, and interception is shown. The hydrological consequences of this study are: more informed judgment can be made about techniques for measurement of throughfall, tree structural characteristics (species related) can more adequately be considered when selecting trees for measurement of stemflow, and the stemflow yields can in some cases be better understood from the information about effect of event type. This paper deals with the influence of measurement method, species composition, and tree characteristics on the estimation of throughfall in the eucalypt forest. The site is near Canberra, lat. 35°S, 145°E, with annual rainfall about 650 mm. Two methods of measuring throughfall are compared: randomly placed, 200 mm cylindrical gauges (standard) and 50 mm square opening wedge type gauges (plastic), and randomly placed 5 × 0–22 m troughs. Despite the high placement density (150 to 225 ha^?1), throughfall estimates from gauges has high variance and consistently underestimated those of the troughs, which had a total opening equivalent to 2325 raingauges (200 mm diameter) per hectare. Local concentration of stemflow into drip points provided by detaching bark pieces of one smooth barked species, Eucalyptus mannifera, is believed to be the principal cause of the lower collection and greater variance of the gauges. The low leaf area index (1–3) and large wood area of the forest together with a pendulous vertical habit of the leaves also contributed. The presence of E. mannifera is shown to substantially affect the relative values of throughfall as measured by troughs and gauges. The plastic receivers were found to underestimate rainfall or throughfall relative to the standard gauges, particularly for fine drop rainfall in multiperiod events.     

Hydrological characteristics of a moso-bamboo (Phyllostachys pubescens) forest in south china

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, f_c 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.     

Throughfall partitioning by trees

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 (D_{50_DR}, 50th cumulative drop volume percentile for canopy drip, of 2.24 mm) than leafed broadleaved trees (D_{50_DR} of 4.32 mm). Canopy drip was much larger in diameter under woody drip points (D_{50_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.     

Characteristics of stemflow for tall stewartia (Stewartia monadelpha) growing on a hillslope

The characteristics of stemflow were observed in a tall stewartia (Stewartia monadelpha) deciduous forest on a hillslope in central Japan, revealing new findings for a previously unreported type of deciduous forest. Using 2-year observations of 250 rainfall events, we analyzed seasonal and spatial variations in stemflow for several trees, and applied additional data sets of throughfall and plant area index (PAI) to produce a rough estimate of seasonal variations in rainfall redistribution processes and canopy architecture for a single tree. Compared to previous findings for other deciduous tree species, the ratios of throughfall, stemflow, and interception to open-area rainfall obviously varied with PAI changes for tall stewartia. Meteorological conditions of rainfall amount, rainfall intensity, wind speed, and wind direction had little effect on stemflow generation, which was mainly affected by variation in canopy architecture. Three novel characteristics of stemflow were identified for several tall stewartia trees. First, the yearly stemflow ratio at the forest-stand level for tall stewartia (12%) was high compared to previous findings on beech and oak stands, indicating tall stewartia has considerably high potential to generate a great amount of stemflow. Second, stemflow tended to be 1.3–2.0 times greater in the leafed period than in the leafless period. Third, the amount of stemflow was 12–132 times greater on the downslope side of the stem than on the upslope side. It likely caused by the uneven area between the upslope and downslope sides of the canopy and by asymmetrical stemflow pathways between the upslope and downslope sides of the trunk due to downslope tilting of the tree trunk.     

Winter rainfall interception by two mature open‐grown trees in Davis,California

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.     

Water and nutrient fluxes in a cool temperate rainforest at the Cordillera de la Costa in southern Chile

Water and nutrient fluxes were studied during a 12-month period in an alerce (Fitzroya cupressoides) forest, located in a remote site at the Cordillera de la Costa (40°05′S) in southern Chile. Measurements of precipitation, throughfall, stemflow, effective precipitation, soil infiltration and stream flow were carried out in an experimental, small watershed. Simultaneously, monthly water samples were collected to determine the concentrations and transport of organic-N, NO₃-N, total-P, K⁺, Ca²⁺, Na⁺ and Mg²⁺ in all levels of forest. Concentration of organic-N, NO₃-N, total-P and K⁺ showed a clear pattern of enrichment in the throughfall, stemflow, effective precipitation and soil infiltration. For Ca²⁺ and Mg²⁺, enrichment was observed in the effective precipitation, soil infiltration and stream flow. Annual transport of K⁺, Na⁺, Ca²⁺ and Mg²⁺ showed that the amounts exported from the forest via stream flow (K⁺=0·95, Na⁺=32·44, Ca²⁺=8·76 and Mg²⁺=7·16 kg ha⁻¹ yr⁻¹) are less than the inputs via precipitation (K⁺=6·39, Na⁺=40·99, Ca²⁺=15·13 and Mg²⁺=7·61 kg ha⁻¹ yr⁻¹). The amounts of organic-N and NO₃-N exported via stream flow (organic-N=1·04 and No₃-N=3·06 kg ha⁻¹ yr⁻¹) were relatively small; however, they represented greater amounts than the inputs via precipitation (organic-N=0·74 and NO₃-N=0·97 kg ha⁻¹ yr⁻¹), because of the great contribution of this element in the superficial soil horizon, where the processes of decomposition of organic material, mineralization and immobilization of the nutrients occurs. © 1998 John Wiley & Sons, Ltd.     

Modeling rainfall interception loss by two xerophytic shrubs in the Loess Plateau

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.     

An evaluation of the Gash interception model in a northern hardwood stand

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.