Spatial Variability Of Throughfall Research Articles

Spatial variability of throughfall in heavily fogged old-growth Fagus orientalis forests is controlled by fog precipitation and stand structural characteristics

Ecological impacts of the spatial heterogeneity of throughfall (TF) in forest ecosystems are recognized in ecohydrology. The objective of this study was to evaluate the spatial variability of TF and to quantify the effects of forest cover, fog, and gross rainfall (GR) characteristics on TF. Data were collected from May 2016 to November 2017 on an event basis in an intact, old-growth oriental beech (Fagus orientalis L.) stand in northern Iran. Over the measurement time period, 22 rainfall events were observed (total rain = 648 mm). Because the region experienced considerable fog, TF was greater than 100% of GR in 14 rainfall events with negative interception loss (total = -24.1 mm), causing low interception values, and 8 rainfall events were found with positive I (total = 25.5 mm). The low TF spatial variability and increasing TF depth observed in this study were related to increases in rainfall depth and intensity. TF was significantly and positively correlated with LAI and significantly and negatively correlated with canopy openness for rainfall events of more than 50 mm. The high amount of TF depth highlighted the role of LAI to enhance fog interception and the role of fog precipitation to increase TF in the study site. Spatial continuity at an effective range of 3-8 m was observed by variogram analyses. The increasing spatial continuity of TF with increasing GR observed in this study, along with the larger effective range for GR >50 mm and correspondingly similar LAI range, suggest an effect of LAI on the spatial patterning of TF for larger GR. Therefore, this heavily fogged ecosystem received considerable TF due to fog interception, and higher LAI increased TF for larger rainfall events. Our findings can optimize forest management practices by accounting for the effect of Fagus orientalis trees on the local hydrological processes of the Hyrcanian mountain forests.

Spatial Variability of Throughfall in a Larch (Larix gmelinii) Forest in Great Kingan Mountain, Northeastern China

Larix gmelinii forest is one of the dominant forest types in boreal forest and plays a unique eco-hydrological role in the terrestrial ecosystem. However, the throughfall variability in boreal forest ecosystems, which plays a crucial role in regulating hydrology, remains unclear. Here, we investigated the spatial variability and temporal stability of throughfall within a Larix gmelinii forest in the full leaf stage in Great Kingan Mountain, Northeast China, and the effects of rainfall properties and canopy structure on throughfall variability were systematically evaluated. The results indicate that throughfall represented 81.26% of the gross rainfall in the forest. The throughfall CV (coefficient of variation of throughfall) had a significant and negative correlation with the rainfall amount, rainfall intensity, rainfall duration, and distance from the nearest trunk, whereas it increased with increasing canopy thickness and LAI (leaf area index). The correlation analysis suggested that the throughfall variability was mainly affected by the rainfall amount (R2 = 0.7714) and canopy thickness (R2 = 0.7087). The temporal stability analysis indicated that the spatial distribution of the throughfall was temporally stable. Our findings will facilitate a better understanding of the spatiotemporal heterogeneity of throughfall and help the accurate assessment of throughfall and soil water within boreal forests.

Characteristics of throughfall kinetic energy under the banana (Musa nana Lour.) canopy: The role of leaf shapes

Banana (Musa nana Lour.) plants have a distinctive canopy pattern with their extremely long and wide leaves. However, the effects of such distinct leaf shapes on rainfall redistribution and splash erosion are still poorly understood. Here, we investigated the basic characteristics of throughfall (TF) distribution and throughfall kinetic energy (TKE) and clarified the effect of specific leaf shapes on TKE under the individual banana plant (IBP) and the whole banana plantation (WBP) canopies. We found that the TF under the IBP and WBP canopies was 80.2% and 84.7% of the incident rainfall, respectively. The spatial variability of TF was high, which was attributed to the prominent funnelling and shading effects of the banana canopy. The KE at canopy drip points was significantly higher than that at canopy non-drip points and in open fields under both the IBP and the WBP canopies, implying that the negative effect of banana canopy drip points was far greater than the protective effect of non-drip points on splash erosion. In addition, the leaves at canopy drip points were classified as valley (Va), overlap (Ov), leaf tip (Ti), breakage (Br) and complex shapes (Cs). Significant differences in TKE among these leaf shapes were found, and the significantly lower TKE in Ti and the greater TKE in Cs than those in Va, Ov and Br were observed. As a result, these leaf shapes potentially affected TF splash erosion under the banana canopy. Further ecohydrological studies are required to improve heavy TF splash erosion in banana plantation and to create environmental-friendly plantation.

Shade trees and tree pruning alter throughfall and microclimate in cocoa (Theobroma cacao L.) production systems

Shade trees in agroforestry systems protect the understory cocoa from climate extremes. Shade tree pruning manages microclimatic conditions in favor of cocoa production while tree diversity is maintained. Adaptation of pruning has to consider seasonal changes in temperature and precipitation to protect the understory cocoa. Structural characteristics of tree stands such as species diversity, tree density, and stratification can affect throughfall and microclimate. Pruning changes the canopy and may therefore modulate internal conditions. The aim of this study is to assess the environmental growing conditions of cocoa trees. We monitored canopy openness and the impact of stand structure on throughfall and microclimate in three cocoa production systems (monoculture, agroforestry, and successional agroforestry) and a natural regrowth in a long-term trial in Bolivia from 2013 to 2015. We further focused on the effect of annual shade tree and cocoa pruning on these variables to evaluate the potential impact of this activity. Agroforestry systems buffered extreme climate events like temperature fluctuations compared to monocultures but reduced light and throughfall drastically. Spatial variability of throughfall and transmitted light were low under a high and closed shade tree canopy. Shade tree pruning resulted in higher canopy openness, light transmittance, and throughfall, while the buffer function of the agroforestry systems concerning temperature and humidity fluctuations was reduced. Differences between cocoa production systems regarding throughfall and microclimate were overlain by pruning activities. Cocoa agroforestry systems are temporal dynamic systems. Pruning timing and intensity is pivotal for balancing light and water availability under seasonally varying environmental conditions to conserve micro-environments for cocoa production with less exposure to unfavorable climate.

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.

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.

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.

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 <50 mm, with the highest throughfall on the east side of the tree trunks (sum = 85% of gross rainfall) and the lowest in the midway between tree rows (sum = 68% of gross rainfall). These spatial patterns persist among 84% of recorded rainfall events. Spatial variability and time stability of throughfall are better explained by canopy interception of the inclined rainfall resulting from the prevailing easterly wind direction throughout the experiment. The annual stemflow is different among individual sample trees, which is mainly ascribed to the difference in tree size (e.g. projected canopy area and stem diameter). The outcomes of this study would help future investigators better design appropriate sampling strategies in these pine plantations under similar climate conditions. Copyright © 2014 John Wiley & Sons, Ltd.

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.

Rainfall partitioning along a tree diversity gradient in a deciduous old‐growth forest in Central Germany

AbstractThis study investigated whether rainfall partitioning into throughfall, stemflow, and interception changes along a tree species diversity gradient. The 12 study plots in old‐growth forest stands in the Hainich National Park, Germany, were composed of up to 11 tree species. Fagus sylvatica (beech) formed the monospecific plots. Mixed forest plots consisted of a variable admixture of other broad‐leaved deciduous species such as Tilia spec., Fraxinus excelsior, Carpinus betulus, and Acer pseudoplatanus. Rainfall partitioning was influenced by several stand characteristics. Tree species diversity expressed as Shannon index was the variable that explained throughfall for different seasons most frequently. For example, in high‐rainfall summer 2007, median throughfall per stand was between 66 and 77% of gross precipitation, whereas stemflow played a minor role (2–6% per stand). Throughfall correlated positively with Shannon index (rs = 0·74, p = 0·008), stemflow negatively (rs = − 0·87, p < 0·001), and interception showed no correlation along this beech to mixed forest gradient. These relationships were similar in summer 2005 and autumn 2006, but no or weak changes of throughfall with tree diversity were observed during other study periods. Multiple linear regressions supported the assumption that combinations of several characteristics are important. Shannon index in combination with mean dbh explained much of the variability observed in throughfall among stands in two seasons (up to R2adj = 0·63, p < 0·01). Influential stand characteristics varied between seasons and years due to different rainfall conditions. Spatial variability of throughfall within a stand did not change consistently with any stand characteristic. Copyright © 2009 John Wiley & Sons, Ltd.

Spatial variability of throughfall in a Chinese pine (Pinus tabulaeformis) plantation in northern China

The interception of rainfall by vegetation and the subsequent evaporation of intercepted water from the canopy surface play an important role in hydrological processes, and the water and energy balance of forest ecosystems. Spatial variability of interception has different effects on water yield from watersheds located in different climatic and biome regions. In order to explain the spatial patterns of interception, we adopted grid-sampling method to install rain-gauges to measure throughfall. Results show that the coefficient of variation (Cv) of throughfall tends to decline as rain intensity increases. After the canopy is saturated, Cv of throughfall remained at a constant value, which is close to the Cv of the canopy leaf area index (LAI) value 0.18. Thus, the Cv of LAI is regarded as the extremum of that of throughfall. Because of the special characteristic of Chinese pine (Pinus tabulaeformis), and the lower droopy branches, negative values for interception account for only 13% of the total samples. Furthermore, the max is above 70% of gross rainfall.

Spatial variability and temporal stability of throughfall deposition under beech ( Fagus sylvatica L.) in relationship to canopy structure

Although the spatial variability of throughfall (TF) in forest ecosystems can have important ecological implications, little is known about the driving factors of within-stand TF variability, particularly in deciduous forests. While the spatial variability of TF water amount and H + deposition under a dominant beech ( Fagus sylvatica L.) tree was significantly higher in the leafed period than in the leafless period, the spatial TF deposition patterns of most major ions were similar in both periods. The semiannual TF depositions of all ions other than H + were significantly positively correlated ( r = 0.68–0.90, p < 0.05) with canopy structure above sample locations throughout the entire year. The amounts of TF water and H + deposition during the leafed period were negatively correlated with branch cover. We conclude that the spatial heterogeneity of ion deposition under beech was significantly affected by leaves in the growing period and by branches in non-foliated conditions.

The interception, throughfall and stemflow in a forest in Highland Scotland and the comparison with other upland forests in the U.K.

Interception loss from a 50-year-old Sitka spruce forest at Balquhidder in Highland Scotland has been determined by measuring precipitation, throughfall and stemflow. Annual mean precipitation at the site was 2130mm and for the period October 1983 to June 1986, the average interception was 28% with throughfall and stemflow comprising 69 and 3%, respectively of the precipitation. This interception loss is similar to results from other upland forests in the U.K. While large variations were found throughout the year, interception was greatest in the summer months, reaching 79% in May 1985, and least in the winter, 0% in January 1985. Snow interception can be large, 37% in January 1984 when storage on the canopy was estimated to have reached 22mm water equivalent. The spatial variability of throughfall was dependent on distance away from the tree stem and on the density of the canopy cover. Tree age does not appear to determine interception values but comparison of the relative amounts of throughfall and stemflow with those from other sites shows that there is an increase in throughfall with the age of the tree. This has important consequences for water quality in young forests.

Spatial variability of throughfall and stemflow measurements in Amazonian rainforest

The spatial variability of throughfall and stemflow in Amazonian tropical rainforest is analysed. Statistical tests are used to assess the minimum sampling size and number of gauges required. Random relocation of throughfall gauges is shown to be better than fixed position gauges and random relocation of gauges on a transect line is better than over an area. During the study period, throughfall and stemflow, calculated as percentages of gross rainfall, were 91(± 2) and 1.8(± 1)%, respectively. No attempt was made in this study to investigate storm size dependency of these figures.