Variability Of Throughfall Research Articles

Spatial variability of throughfall under single birch and pine tree canopies

The influence of tree characteristics and meteorological variables on spatial variability of throughfall under a single silver birch and black pine tree was evaluated. During the year 2016 throughfall was measured at 11 points under each tree canopy. For 30 analysed events total throughfall under the birch tree accounted for 73% and under the pine tree 56% of the rainfall in the open. The coefficient of variation of point throughfall was 30% and 40% for the birch and pine tree, respectively. In case of the birch tree both the distance from the stem and canopy coverage influenced throughfall spatial variability, which also showed different patterns during leafed and leafless periods. Additionally, the amount of rainfall and its microstructure influenced the spatial variability of throughfall under the birch tree. However, among the considered tree characteristics only canopy coverage was recognized as a parameter influencing spatial variability of throughfall under the pine. Furthermore, its spatial patterns were specified by meteorological variables, namely the amount of rainfall and its intensity.

Meteorological influences on process-based spatial-temporal pattern of throughfall of a xerophytic shrub in arid lands of northern China

Numerous field experiments had demonstrated great spatial variability and temporal stability of throughfall under tree canopies within forested ecosystems. Nonetheless, no known studies have investigated the intrastorm spatial-temporal variability of throughfall beneath xerophytic shrub canopies within arid desert ecosystems where water is typically the principal limiting factor determining the structure and dynamics of ecosystems. Here we investigated the spatial-temporal pattern of throughfall at intrastorm scale, and systematically examined the effects of meteorological variables on throughfall based on the principal components analysis (PCA) and a multiple regression model. Throughfall was monitored at 10-min intervals by placing tipping-bucket rain gauges at different radial directions beneath 3 shrubs of Caragana korshinskii during the growing season of 2016 within a water-limited arid desert ecosystem of northern China. We found the temporal heterogeneity of rainfall clearly affected the timing of throughfall beneath shrub canopies within discrete rainfall events. Throughfall also differed markedly among different radial directions beneath shrub canopies, which was found to be well associated with wind directions during rainfall events. PCA on meteorological variables indicated that three principal components accounted for 84.2% of the total variance, and we found that the second principal component (loaded strongly on rainfall amount and maximum 10-min rainfall intensity) was the dominant component controlling throughfall and its spatial variability after introducing three principal components into a multiple linear regression model. Our findings highlight the spatial-temporal variability of throughfall at the intrastorm scale, and are expected to be helpful for an improved process-based characterization and modelling of throughfall in vast arid desert ecosystems.

Throughfall and its spatial variability beneath xerophytic shrub canopies within water-limited arid desert ecosystems

Summary Throughfall is known to be a critical component of the hydrological and biogeochemical cycles of forested ecosystems with inherently temporal and spatial variability. Yet little is understood concerning the throughfall variability of shrubs and the associated controlling factors in arid desert ecosystems. Here we systematically investigated the variability of throughfall of two morphological distinct xerophytic shrubs (Caragana korshinskii and Artemisia ordosica) within a re-vegetated arid desert ecosystem, and evaluated the effects of shrub structure and rainfall characteristics on throughfall based on heavily gauged throughfall measurements at the event scale. We found that morphological differences were not sufficient to generate significant difference (P

Spatial variability of throughfall in a stand of Scots pine (Pinus sylvestris L.) with deciduous admixture as influenced by canopy cover and stem distance

Summary Vegetation cover affects the amount of precipitation, its chemical composition and its spatial distribution, and this may have implications for the distribution of water, nutrients and contaminants in the subsurface soil layer. The aim of this study was a detailed diagnosis of the spatio-temporal variability in the amount of throughfall (TF) and its chemical components in a 72-year-old pine stand with an admixture of oak and birch. The spatio-temporal variability in the amount of TF water and the concentrations and deposition of the TF components were studied. The components that are exchanged in canopy (H + , K, Mg, Mn, DOC, NH 4 + ) were more variable than the components whose TF deposition is the sum of wet and dry (including gas) deposition and which undergo little exchange in the canopy (Na, Cl, NO 3 − , SO 4 2− ). The spatial distribution was temporally stable, especially during the leafed period. This study also investigated the effect of the selected pine stand characteristics on the spatial distribution of throughfall and its chemical components; the characteristics included leaf area index (LAI), the proportion of the canopy covered by deciduous species and pine crowns, and the distance from the nearest tree trunk. The LAI measured during the leafed and leafless periods had the greatest effect on the spatial distribution of TF deposition. No relationship was found between the spatial distribution of the amount of TF water and (i) the LAI; (ii) the canopy cover of broadleaf species or pines; or (iii) the distance from the trunks.

Throughfall and its spatial variability in a temperate rainforest of simple structure

There are few throughfall data from southern hemisphere closed-forest, and none from Tasmanian callidendrous cool-temperate rainforest, which has a simpler structure than most primary rainforests. We determined throughfall, measured its local spatial variation, and tested its relationships with rainfall, rainfall intensity, wind speed, canopy dryness, canopy cover, and other structural variables in a cool-temperate callidendrous rainforest in Tasmania. Eighty-two percent of the precipitation was measured as throughfall, which occurred after 2.3 mm of rain fell on dry canopies. The cumulative rainfall in 25 randomly located funnel rain gauges on the forest floor varied from 160 to 567 mm. Canopy cover and other structural variables did not predict the spatial pattern of throughfall. While throughfall in rainfall events was related to rainfall amount and intensity, wind speed did not affect throughfall as a percentage of rainfall. Percentages of throughfall to rainfall over 100 for many low rainfall events may indicate a contribution of fog drip to precipitation on the forest floor. The high local spatial variability in throughfall indicates the mean moisture conditions on the forest floor may not be a good indicator of the potential for localised fire damage.

大兴安岭北部兴安落叶松(Larix gmelinii)林下穿透雨空间分布特征

PDF HTML阅读 XML下载 导出引用 引用提醒 大兴安岭北部兴安落叶松(Larix gmelinii)林下穿透雨空间分布特征 DOI: 10.5846/stxb201412152499 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 林业公益性行业科研专项（201404303）；中央高校科研专项（DL12BA10）；东北林业大学学术名师支持计划（PFT-1213-21） Characteristics of the spatial distribution of throughfall in a Larix gmelinii forest in the northern Greater Khingan Range, northeast China Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:森林冠层对降雨的水量和水质再分配是生态水文学研究的热点问题之一。为了研究兴安落叶松林下穿透雨的空间分布规律，探究森林冠层结构对穿透雨影响的生态机制，利用在兴安落叶松林下布设38个雨量筒，测定19场不同降雨事件的穿透雨数据（2013年7-8月），通过统计学方法分析冠层结构各因子与穿透雨的空间变异性规律，结果表明：观测期间，兴安落叶松林穿透雨量为148.3 mm，占同期大气降雨量的80.62%，穿透雨率随着降雨量的增加呈增加趋势；兴安落叶松林下穿透雨具有较大空间异质性，其变异程度随降雨量的增加而减小，以对数方程拟合较好（P<0.01）；冠层结构特征是影响穿透雨空间变异的重要因素，冠层复杂程度与穿透雨量呈负相关关系（P<0.01）；距树干距离、冠层厚度、叶面积指数等因素均可影响穿透雨的空间分布，以距树干距离影响最大，其与穿透雨率呈正相关关系（P<0.01），而冠层厚度、叶面积指数则均与穿透雨率呈负相关关系（P<0.01），但拟合效果不佳；从影响穿透雨的生态学机制来考虑，在冠层结构特征因子中，冠层厚度是决定穿透雨空间分布的最主要因素。 Abstract:In forested ecosystems, complex forest canopies may redistribute and chemically modify the composition of rain water; this field within the study of ecological hydrology has recently attracted a considerable amount of attention. Throughfall is a major part of the rainfall penetrating the forest canopy and redistributes rainfall, and throughfall patterns can affect the distribution of soil water as well as the cycling and use of nutrients. Furthermore, spatial variability in the amount of throughfall can affect the concentration and deposition of solutes and the spatial distribution of nutrients in a forested landscape. Therefore, changes in throughfall beneath the canopy have very important effects on water balance, hydrological processes, and nutrient cycling within forest ecosystems. Many studies have analyzed the effects of the forest canopy on the interception and redistribution of rainfall, and the regularity of throughfall in different forest types; these studies provide a clearer understanding of the hydrological processes involved in rainfall interception and redistribution. However, few studies have addressed the horizontal spatial distribution of throughfall under a forest canopy. An examination of the spatial distribution of throughfall would provide important data to aid comprehension of the eco-hydrological processes and nutrient cycling within a forest. The goal of the present study was to determine the spatial heterogeneity of throughfall under a forest canopy and to explore the ecological mechanisms of the effects of canopy structure in a Larix gmelinii forest on throughfall. Several factors, such as distance (of the sampling site to the trunk), canopy thickness, and leaf area index (LAI), can all influence the spatial distribution of throughfall. Throughfall was measured under a Larix gmelinii forest canopy at three locations-beneath the canopy itself, beneath the canopy edge, and in canopy gaps-during 19 rainfall events, using 38 rain gauges during the period of development of a stable canopy (Jul.-Aug. 2013). The spatial heterogeneity of both forest canopy structure (LAI and canopy thickness) and throughfall were analyzed using statistical methods. The spatial variability of throughfall in the Larix gmelinii forest analyzed here was estimated for different rainfall events. The results indicate that throughfall under a Larix gmelinii forest canopy was 148.33 mm during the observation period, and accounts for 80.62% of the rainfall in an open field. The throughfall ratio increased with increasing amounts of rainfall, and the relationship between these could be described with a power function (P<0.01). The coefficient of variance of throughfall decreased with increasing rainfall amounts, and the relationship between these could be described with a logarithmic function (P<0.01). Structural characteristics of the canopy were found to be the most important factors controlling the spatial variability of throughfall, and the throughfall amount was significantly negatively correlated with the degree of complexity within the canopy structure (P<0.01). The influence of distance was most important, and was significantly positively correlated with the throughfall ratio (r2=0.580, P<0.01). Canopy thickness and LAI were significantly negatively correlated with the throughfall ratio (P<0.01), but exhibited poor fitting results. When considering the ecological mechanism of throughfall, canopy thickness was the most important canopy structure/factor that affects the spatial redistribution of throughfall in a Larix gmelinii forest. 参考文献 相似文献 引证文献

Spatial variability of throughfall in a Pinus tabulaeformis plantation forest in Loess Plateau, China

ABSTRACTThroughfall varies in space, which complicates measurements and makes it difficult to achieve accurate spatial representation. In the present research, we measured gross rainfall and throughfall from May 2011 to September 2012, leaf area index, and locations of trees within a Pinus tabulaeformis plantation forest in the Loess Plateau of northwestern China. The spatial heterogeneity of throughfall and related factors, as well as the minimum number and locations of collectors needed to measure throughfall accurately, were analyzed by statistical techniques. The results indicated that the throughfall was concentrated at the canopy edge, indicating that the edge of the canopy of P. tabulaeformis had a convergence effect on throughfall. The analysis of semivariance of throughfall demonstrated that canopy structure was a key factor influencing spatial variation of throughfall in low rainfall events, but measurement errors and other nonspatial variables were the primary factors affecting the variation of throughfall in high rainfall events. Based on the mean throughfall at different proportions of canopy radius centered on the individual tree stem, the minimum number and locations of collectors needed to accurately measure throughfall was estimated. In this study, four rain collectors (diameter 20 cm) at the 3/5 canopy radius could reasonably represent the average throughfall under the individual P. tabulaeformis canopy.

Small-scale topographic variability influences tree species distribution and canopy throughfall partitioning in a temperate deciduous forest

At very large spatial scales, the impacts of topography, elevation, and aspect on throughfall variability are apparent. However, within relatively small catchments (<50ha), differences in species composition induced by slight changes in elevation coupled with slope orientation, could result in sufficient canopy variability whereby throughfall hydrology would be definitively different across small gradients. This study aims to (1) quantify the differences in throughfall hydrology across small topographic gradients, (2) determine the variability of throughfall across such gradients, and (3) determine the seasonal effects on throughfall hydrology resulting from differences in species composition and growing niches.Throughfall partitioning was measured during 15 sampling periods at 4 landscape positions including 3 hillslopes with aspects facing north (NF), west (WF), and south (SF) in addition to a flat area (F) situated in the center of a 12ha deciduous catchment. Throughfall partitioning was significantly lower on the steepest SF plot (TF=75.0%) than on the moderately sloping NF (TF=83.9%, p=0.001) and F (TF=81.7%, p=0.037) plots. SF also had the largest degree of throughfall variability (CV=20.1), resulting from overlapping canopies, which led to higher rates of canopy interception. NF and WF plots exhibited the largest inter-seasonal differences with decreases in throughfall partitioning of 13.2% (p=0.013) and 12.1% (p=0.052), respectively, and corresponded to the largest differences in plant canopy indices (PAI) between seasons. Although slope and aspect were found to be distinguishing variables in our study, it was the influence of these variables on species composition that led to differences in throughfall quantity. Our study illustrates the systematic distribution of water resources across topographic positions within a relatively small forested catchment and highlights the need for additional consideration of topography-induced controls on microclimate and growing space, which ultimately influence water quality and quantity for effective management strategies.

Immediate change in throughfall spatial distribution and canopy water balance after heavy thinning in a dense mature Japanese cypress plantation

AbstractThis study revealed the influence of change in forest canopy structure by forest management practice for throughfall generation and canopy water interception process. Throughfall and stemflow were observed in a mature Japanese cypress (Chamaecyparis obtusa) plantation before and after thinning. Decreased stem density (from 2400 to 1300 trees ha−1) and basal area (from 107.6 to 60.4 m2 ha−1) resulted in an increase in the throughfall fraction (from 58% to 79%) and decreases in the stemflow fraction (from 14% to 8.6%) and the canopy interception loss fraction (from 27% to 12%). Thinning also decreased spatial variability in throughfall and smoothed temporal persistence of throughfall among sampling points or rainfall events. These results were supported by the change in the throughfall balance between direct throughfall and released throughfall. The proportion of direct throughfall of incident rainfall changed from 0.16 to 0.42 owing to an increase in canopy gap. The distribution ratio of released throughfall from intercepted rainwater by canopy changed from 50% to 64% because of a decrease in foliage; this led to lower water storage in the canopy (from 1.83 to 0.82 mm), and thus less precipitation was needed to saturate the canopy. Consequently, the amount of throughfall increased and less precipitation was needed to stabilize the water flow path during the post‐thinning period. This study contributes to knowledge of differential canopy wetting processes and spatiotemporal heterogeneity of throughfall distribution in response to specific silvicultural prescription. Copyright © 2015 John Wiley &amp; Sons, Ltd.

The effect of strip thinning on spatial and temporal variability of throughfall in a Japanese cypress plantation

AbstractWe examined the effect of strip thinning on the spatio‐temporal variability of throughfall (TF) in a mature Japanese cypress (Chamaecyparis obtusa) stand. Strip thinning, which removed 50% of stems, was performed in a catchment in October 2011. TF was examined by setting up 20 tipping‐bucket rain gauges in an experimental plot. Canopy interception parameters were derived from high‐temporal‐resolution TF data. Observations were obtained during the growing season in the pre‐thinning and post‐thinning periods. The results demonstrated that after thinning, the TF rate increased from 64.3 to 76.2%, and the mean coefficient of variation of the TF rate significantly decreased from 27.3 ± 9.7 to 22.5 ± 6.8%. The spatial TF patterns were largely related to the rainfall class. There was no significant difference in the TF rate for the rainfall amount &gt;25 mm between the periods. The temporal persistence of the normalized TF was slightly stable in the post‐thinning period and was not significantly related to canopy cover or the distance to the nearest trunk of each rain gauge in either period. Additionally, thinning resulted in an increase in the proportion of direct TF (from 0.14 ± 0.07 to 0.33 ± 0.11) and a decrease in canopy water storage (from 2.4 ± 0.7 to 1.5 ± 0.5 mm). The quantification of the canopy interception parameters can aid in modelling the changes in interception loss and its processes induced by thinning. These findings also help recognize the changes in spatial TF patterns under different forest management practices. Copyright © 2015 John Wiley &amp; Sons, Ltd.

Detection, quantification and modelling of small-scale lateral translocation of throughfall in tree crowns of European beech (Fagus sylvatica L.) and Norway spruce (Picea abies (L.) Karst.)

Summary The redistribution of precipitation in forests depends on the amount of above-canopy precipitation and is characterised by high small-scale variability. Although higher and lower values of net forest precipitation at small scales are typically averaged at larger spatial scales, the small-scale variability of throughfall needs to be understood because subordinate ecological processes in the forest ecosystem, e.g., regeneration of tree species, often take place at the same small scale. High stemflow amounts and canopy driplines at the crown edge of particular tree species can only be explained by lateral flow processes within tree crowns. This study tests the hypothesis that lateral water translocation within the crown can be determined from simultaneous records of precipitation at defined measurement points below and above the canopy by taking single-tree characteristics such as species and crown width into account. Spatially explicit simultaneous measurements of gross precipitation (above-canopy reference) and throughfall were conducted repeatedly at 175 measurements points in a mixed European beech-Norway spruce stand for a total of 26 individual rain events. Subsequent analysis with a new regression approach resulted in an estimated average canopy storage capacity of 3.5 mm and 5.8 mm for beech (leaf-bearing period) and spruce stands, respectively. Values of calculated lateral flow showed considerable variability between individual measurement points. The highest discharge amounts were observed at positions below the inner beech crowns during the leaf-bearing period. For an exemplary rainfall event with a gross precipitation of 25 mm, the predicted discharge ranged from 5 mm underneath the inner beech crown to about zero near the crown edge. A comparison with the measured values indicated that the predicted amount of lateral flow, which could be translated into stemflow for single beech trees, was realistic. However, for the same rainfall event, lateral flow in spruce crowns was mainly identified in the outer crown. The derived functions for calculating lateral water translocation may be incorporated into single-tree models.

Rainfall interception and spatial variability of throughfall in spruce stand

Abstract The interception was recognized as an important part of the catchment water balance in temperate climate. The mountainous forest ecosystem at experimental headwater catchment Liz has been subject of long-term monitoring. Unique dataset in terms of time resolution serves to determine canopy storage capacity and free throughfall. Spatial variability of throughfall was studied using one weighing and five tipping bucket rain gauges. The basic characteristics of forest affecting interception process were determined for the Norway spruce stand at the experimental area - the leaf area index was 5.66 - 6.00 m2 m-2, the basal area was 55.7 m2 ha-1, and the crown closure above individual rain gauges was between 19 and 95%. The total interception loss in both growing seasons analyzed was 34.5%. The mean value of the interception capacity determined was about 2 mm. Throughfall exhibited high variability from place to place and it was strongly affected by character of rainfall. On the other hand, spatial pattern of throughfall in average showed low variability.

A preliminary evaluation of throughfall sampling techniques in a mature coniferous forest

Rainfall, throughfall and stemflow were measured and canopy interception loss was derived for 14 rainfall events from June 22 to August 30, 2008 within a mature declining hybrid white spruce (Picea glauca (Moench) Voss × P. engelmannii Parry ex Engelm.)-subalpine fir (Abies lasiocarpa (Hook.) Nutt.)-lodgepole pine (Pinus contorta var. latifolia Dougl. ex Loud.) stand in south-central British Columbia, Canada. Stemflow was negligible during the study period, while, respectively, throughfall and canopy interception loss accounted for approximately 59.4% and 40.6% of the 50.1 mm of cumulative rainfall. Throughfall variability was assessed with three approaches involving roving and stationary wedge-type gauges, and stationary trough gauges. Throughfall exhibited large spatial variability with the coefficient of variability of study period throughfall sampled using 16 stationary trough gauges being 30.3%, while it was 38.0% and 28.7% for 32 stationary and 32 roving wedge gauges, respectively. Our analysis suggests that a roving gauge method is better than a stationary approach since the errors associated with event mean throughfalls are summed quadratically and a greater portion of the canopy area is sampled. Trough gauges were more efficient than wedge gauges; however, this efficiency was less than expected given their much larger sampling areas, suggesting that spatial autocorrelation lengths of throughfall may be longer than the trough systems. The spatial distribution of throughfall showed a high degree of temporal persistence throughout the study suggesting the existence of stable “wet” and “dry” inputs to the floors of these coniferous forests.

Spatial variability of throughfall and stemflow in an exotic pine plantation of subtropical coastal Australia

AbstractLarge‐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 &lt;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 &amp; Sons, Ltd.

Effect of canopy interception on spatial variability and isotopic composition of throughfall in Japanese cypress plantations

Summary We conducted a field monitoring experiment examining throughfall in Japanese cypress plantations located in Tochigi Prefecture, eastern Japan. A set of 20 tipping-bucket rain gauges and throughfall collectors were placed in a lattice-like distribution throughout a 10 × 10-m experimental plot to investigate the effect of the forest canopy on the spatial variability of throughfall. The isotopic composition of throughfall and open rainfall were analyzed and compared for each rainfall event. A clear relationship between throughfall rate and the radial distance to the nearest tree trunk was observed when the influence of wind was negligible; however, such a systematic pattern of throughfall was not observed during rainfall events that occurred during windy conditions. The δ 18 O and δD values in throughfall varied considerably, reflecting different rainwater flow paths in the saturated canopy. The analysis of stable isotope ratios in the throughfall and its comparison with isotopic composition of rainwater hitting the canopy can help elucidate the interception processes in the forest canopy.

Shrub Hydropedology: Preferential Water Availability to Deep Soil Layer

The complex interactions between shrub traits, soil structure, and soil water dynamics are not well understood yet. This study investigated rainfall partition byC. microphyllaL., spatial soil water pattern, soil hydraulic conductivity, and soil macropores to ascertain preferential water flow to deep soil layer by shrub. Results indicated that high variability in throughfall existed within individual shrub stand: average coefficient of variation was 0.36 ± 0.13 for shrub and 0.15 ± 0.13 for interspace grass. Throughfall was less at the center of the shrub patch (30–60% of rainfall) than the outward positions at the edges of the canopy (70–90% of rainfall). Soil water responded differently to rainfall, soil depth, and vegetation type and showed high variability within shrub patches and on the slope. Greater and deeper infiltration was observed beneathC. microphyllaL. canopy than interspaces grass after rainfall with large amount and high intensity, suggesting that macropore flow dominated in shrub patches. X‐ray CT showed that macroporosity was over six times greater in soil underC. microphyllaL. than interspace grass. Soil hydraulic conductivity for shrub at saturation and the pressure heads of −30, −60, and −150 mm were 3, 2, 2.5, and 2 times than those of grass, respectively. Shrub patches had a significant lower bulk density and higher porosity than grass patches at the top 0‐ to 30‐cm depth. Soil hydraulic conductivity was significantly correlated to organic matter content, total N, bulk density, and porosity. This study suggests that rainfall partition by shrub's canopy and subsurface soil macropores induced by root architecture results in preferential water flow into deep soil layer, which might favor competitive advantages for water by shrubs under arid conditions.

The effect of spatial throughfall patterns on soil moisture patterns at the hillslope scale

Abstract. Improving the understanding of the controls on subsurface stormflow generation has been the goal of numerous experimental and modeling studies. However, the effect of the spatial variability of throughfall on soil moisture patterns and subsurface stormflow (SSF) generation has not yet been studied in detail. The objectives of this study are three-fold: (1) to investigate the influence of a spatially variable throughfall pattern on soil moisture; (2) to investigate if soil moisture patterns reflect a balance between a throughfall and bedrock topography patterns; and (3) to investigate how this balance changes when soil depth, storm size and slope angle are varied. Virtual experiments are used to address these questions. A virtual experiment is a numerical experiment driven by collective field intelligence. It provides a learning tool to investigate the effect of individual processes in a complex system. In our virtual experiment we combined spatial throughfall data from the Huewelerbach catchment in Luxembourg with the topography of a well-studied hillslope within the Panola Mountain Research Watershed, Georgia, USA. We used HYDRUS-3D as a modeling platform. The virtual experiment shows that throughfall patterns influence soil moisture patterns, but only during and shortly after a storm. With a semi-variogram analysis we showed how the effective range of the soil moisture pattern (i.e., the main descriptor of a spatial pattern in case of a small nugget to sill ratio), is similar to the effective range of the throughfall pattern during the storm and gradually returns to the effective range of the bedrock topography after throughfall has ceased. The same analysis was carried out to investigate how this balance changes due to changes in storm size, soil depth, and slope. The analysis showed that the throughfall pattern is more important during large storms on gentle slopes. For steeper slopes the bedrock topography becomes more important.

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

AbstractCatchment 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 &amp; Sons, Ltd.

Spatial Variation of Throughfall in Two Tree Plantations in Abeokuta, South-Western Nigeria

This paper determined the variability of throughfall in two tree plantations on the campus of University of Agriculture, Abeokuta, South Western Nigeria. It involved the use of experimental plots consisting of Tectona Grandis and Gmeliba Arborea. Gross precipitation and thoughfall were measured and determined for a month. The data obtained was analysed using simple descriptive statistics such as means, percentages and frequency counts. Correlation analysis was used to determine the relationship between gross precipitation and throughfall under each tree plantation. Results show that Tectona plantation had more throughfall throughout the period of study than that of Grnelna plantation. Also there is a strong relationship between gross precipitation and throughtfall in the two plantation. The implication of the results for the management and use of water resources in the study area were discussed and recommendations made as to how water trapped through interception can be better managed.

Rainfall partitioning into throughfall and stemflow and associated nutrient fluxes: land use impacts in a lower montane tropical region of Panama

Land-use change alters catchment hydrology by influencing the quality and quantity of partitioned rainfall. We compared rainfall partitioning (throughfall, stemflow and interception) and nutrient concentrations in rainfall, throughfall and stemflow in three land-use types [primary forest (PF), secondary forest (SF) and agriculture (A)] in Panama. Measurements of throughfall were highly variable which may have masked seasonal and land use differences but it was clear that throughfall at agricultural sites made up a larger proportion of gross precipitation than at forest sites. Of incident precipitation, 94% became throughfall in agriculture sites while 83 and 81% of gross precipitation became throughfall in PF and SF, respectively. The size of the precipitation event was the main driver of variation in throughfall and stemflow. Consistent patterns in nutrient cycling were also difficult to identify. Vegetation has a vital role in delivering nutrients as throughfall deposition of K was often larger than precipitation deposition. A canopy budget model indicated that canopy exchange was often more dominant than dry deposition. Throughfall was generally enriched with nutrients, especially K and Mg, with enrichment factors of up to 17 and 5 for K and Mg, respectively, in PF. In contrast, Ca was sometimes taken up by the canopy. Values of nutrient deposition were high (with up to 15, 3, 30 and 15 kg ha−1 month−1 in stand deposition of Ca, Mg, K and Na, respectively in PF), possibly due to the slash-and-burn agricultural practices in the area or marine inputs. Throughfall and stemflow are vital sources of nutrients in these ecosystems.