Interception Storage Capacity Research Articles

Assessing canopy rainfall partitioning by Mediterranean dryland shrubs under extreme rainfall

AbstractIntense rain events have become more frequent in some regions due to climate change, and this trend is particularly concerning in dryland regions where the ecological and geomorphological impacts of rainfall are intimately tied to its intensity. The interception of rainfall by vegetation is a critical process in the water balance of drylands; thus, this study estimated the canopy interception capacity and interception rates as well as stemflow of three typical Mediterranean shrub species (Rosmarinus officinalis, Thymus vulgaris, and Macrochloa tenacissima) of three size classes in Spain under a simulated extreme rainfall rate (~8 mm min−1, historical return period of >100 years). Given that these plants' canopy structures markedly differ from taller woody plants (i.e., trees), a novel method was developed to assess the stemflow fraction. Results showed significant differences in interception amount, rates, and storage capacity among the shrub species, with variations in plant morphology, such as shrub height and canopy diameter, being the key factors determining interception capacity. R. officinalis had the highest interception fraction per unit canopy area, or ‘specific interception,’ (18.4%). In contrast, the lowest specific interception fraction was measured for M. tenacissima (6.5%). Thymus vulgaris was characterized by the highest stemflow yields per unit canopy area (4.85 mm) and fraction (up to 29.6% of rainfall), which was the lowest for M. tenacissima (1.09 mm, ~1%–4%). Strong linear correlations were found between canopy interception and shrub canopy diameter (|r| > −0.51, max = −0.90), when observations were grouped for size class. These linear correlations between shrub morphology and partitioning enabled multiple‐regression linear models to be developed that predicted canopy interception and stemflow with good accuracy (r2 > 0.64, with a maximum of 0.82) from shrub height, canopy diameter, dry biomass, size class, and species. Despite these measurements being conducted under one extreme storm depth and intensity, the results provide: (i) values of rainfall partitioning for important shrub species in Mediterranean dryland environments; and (ii) a simple but reliable model that may be further developed (e.g., embedding variable rainfall values as weather input or incorporating other morphological parameters) and may be integrated into complex hydrological models.

Effects of leaf type, litter mass and rainfall characteristics on the interception storage capacity of leaf litter based on process simulation

Forest litter plays an important role in the hydrological process of an ecosystem, but the mechanism of interception is not well understood and has not been fully evaluated. We conducted a process-based experiment under five simulated rainfall intensities. We directly quantified the interception of leaf litter and determined the effects of litter mass (MA), rainfall characteristics (RI) and leaf type (SP) on the interception of six common subtropical tree species, including two coniferous (Cunninghamia lanceolata (Lamb.) Hook. and Pinus massoniana Lamb.) and four broadleaf deciduous (Phoebe bournei (Hemsl.) Yang, Schima superba Gardn. et Champ., Liquidambar formosana Hance and Cinnamomum camphora (L.) Presl) species. The results demonstrated the following. (1) The interception process of litter can be divided into three phases: the wetting phase, the saturation phase, and the postrainfall drainage phase. The first phase of which arrived approximately 95% of the maximum interception storage (Cmax) and the duration was longer in broadleaf species than in coniferous species. This phase was significantly different among the species and rainfall characteristics, but it was not affected by litter mass. (2) Cmax and the minimum interception storage capacity (Cmin) of litter were not significantly different between the two forest types, but among the six species, especially between P.bournei and each of the two coniferous species, these values showed the greatest differences. (3) Cmax and Cmin increased significantly with litter mass and rain intensity. (4) Based on commonality analysis, the interaction between MA and RI largely outweighed the other variables in terms of their contribution to Cmax; however, MA surpassed all the other variables in its contribution to Cmin. We also found that the effects of the individual variables on Cmax and Cmin as well as their interactions, were significantly different; the three most influential variables for Cmax ranked in the descending order of their contributions were the interaction between MA and RI (41.07%), RI alone (23.69%), and MA (20.81%), and those for Cmin were MA alone (52.59%), the interaction between MA and RI (25.81%) and leaf types (14.58%). The quantitative and mechanistic explanations regarding the effects of leaf types, rainfall characteristics, litter mass and their interactions on litter Cmax and Cmin presented in this study are expected to increase our understanding of the mechanism underlying litter interception.

Conversion of primary tropical rainforest into rubber plantation degrades the hydrological functions of forest litter: Insights from experimental study

Plant litter is an important component of forest ecosystems and has a key role in reducing soil and water loss. This study evaluated the effect of land use change on rainfall interception and other hydrological processes associated with the litter layer in the tropical region of Southwest China, where large areas of tropical rainforest (TR) have been converted into rubber monoculture (RM) in the past decades. Two litter types from the TR and RM were selected to determine the maximum water storage capacity (S), maximum and minimum interception storage capacities (i.e., Cmax and Cmin, respectively) and moisture dynamics under four litter masses and five simulated rainfall intensities. Results showed that the distribution of litter layer in the RM had a higher spatial variability than that in the TR. The average litter thickness in the TR and RM was 6.42 and 4.43 cm, respectively, and the S value of the litter layer in the TR and RM was 1.44 and 1.03 mm, respectively. Linear relationships among litter thickness, S, and litter mass were observed. The average Cmax and Cmin in the TR were respectively 1.25 and 1.30 times greater than that in the RM. Significant positive relationships among litter mass, rainfall intensity, and interception storage capacity were observed, indicating that litter mass and rainfall intensity played a critical role in determining rainfall interception of the litter layer. TR litter from mixed species had larger leaf surface area and higher water affinity, which resulted in 1.38 times greater litter interception (12.32%) than RM litter (8.96%). These results indicated that the conversion of TR into RM considerably weakened the hydrological functions of forest litter, such as water storage capacity and rainfall interception, and possibly subsequent erosion control. Introducing native rainforest species into rubber plantations can help improve the litter input and the hydrological attributes of forest litter.

Effect of leaf distribution pattern on the interception storage capacity of leaf litter under simulated rainfall conditions

AbstractRainwater interception by leaf litter is an important part of forest hydrological processes. The objective of this study was to investigate the interception storage capacity (ISC) of woodland leaf litter for three leaf distribution patterns, one flow path, two flow paths, and three flow paths, manually simulated via one‐by‐one leaf connection in the top leaf litter layer. A random pattern served as the control. Three different slopes (0°, 5° and 25°, representing flat, gentle and steep slopes, respectively) and two contrasting leaf litters (needle‐leaf litter, represented by P. massoniana leaves, and broad‐leaf litter, represented by C. camphora leaves) with a biomass of 0.5 kg/m2 per unit area were applied, at a rainfall intensity of 50 mm/h. Results suggested that leaf distribution pattern greatly impacts litter drainage and hence affects leaf litter ISC. The delaying capacity of litter drainage initiation and ISC of broad‐leaf litter were higher than those of needle‐leaf litter under the same slope conditions. The maximum ISC (Cmax) and minimum ISC (Cmin) of leaf litter at flat and gentle slopes were higher than those at steep slope. Cmin of the broad‐leaf litter was two times higher than that of needle‐leaf litter on average. When raindrops reached the litter layer, some were temporarily intercepted by the top litter layer while others infiltrated leaf litter sublayer along leaf edges, and in the process, some rainwater flowed through litter layer and contributed to lateral litter drainage along the potential flow path formed by leaves. The lateral litter drainage of broad‐leaf litter was higher than that of needle‐leaf litter, and the partitioning of rainwater into lateral litter drainage increased with increases in slope. The difference in leaf litter Cmax among different slopes and leaf shapes decreased with flow path increasing. Therefore, leaf distribution pattern notably impact leaf litter ISC, which is similar to leaf shape and slope impacts. On inclined slopes, avoiding leaf accumulation to form flow path is helpful for improving ISC.

Rainfall partitioning and its effects on regional water balances: Evidence from the conversion of traditional cropland to apple orchards in a semi‐humid region

AbstractRainfall partitioning by vegetation cover plays an important role in local and regional water balances. Large areas of traditional cropland have been converted to apple orchards on the Loess Plateau, China, so the effect of the conversion of traditional cropland to these orchards on rainfall partitioning cannot be ignored. In this study, we measured precipitation, throughfall (TF), and stemflow (SF) and calculated canopy interception (I) and canopy storage capacity (S) in two neighbouring apple orchards (8 and 18 years old in 2013) on the plateau during the four growing seasons of 2013, 2014, 2015, and 2016. Besides, we also summarized the percentage of rainfall partitioning of various crops and tree species and assessed the effect of land use change on regional water balances. The results showed that the percentage of rainfall partitioning and S differed between the two orchards. Mean annual I, TF, and SF for the young and mature orchards during the 4 years accounted for 7.9, 89.8, and 2.6% and for 10.3, 87.5, and 2.3%, respectively, of the rainfall partitioning. The percentage accounted for by mean annual I and TF differed significantly between the two orchards, but the percentage of mean annual SF did not differ significantly between the two orchards. Mean annual S for 2013–2016 was significantly higher for the mature than the young orchard. Although the conversion of traditional cropland to apple orchards led to a more serious soil desiccation in this region, the I loss percentage was higher in maize (12.5%) than the apple orchards. Therefore, we inferred that the effect of the conversion of traditional cropland to apple orchards on regional water balances was likely not caused by differences in rainfall partitioning. Differences in tree morphology due to tree age accounted for the differences in rainfall partitioning and S between the two orchards. Thus, tree age should be taken into account when assessing the effect of apple orchards on rainfall partitioning in this or similar regions.

A proposed method for estimating interception from near-surface soil moisture response

Abstract. Interception is the storage and subsequent evaporation of rainfall by above-ground structures, including canopy and groundcover vegetation and surface litter. Accurately quantifying interception is critical for understanding how ecosystems partition incoming precipitation, but it is difficult and costly to measure, leading most studies to rely on modeled interception estimates. Moreover, forest interception estimates typically focus only on canopy storage, despite the potential for substantial interception by groundcover vegetation and surface litter. In this study, we developed an approach to quantify “total” interception (i.e., including forest canopy, understory, and surface litter layers) using measurements of shallow soil moisture dynamics during rainfall events. Across 34 pine and mixed forest stands in Florida (USA), we used soil moisture and precipitation (P) data to estimate interception storage capacity (βs), a parameter required to estimate total annual interception (Ia) relative to P. Estimated values for βs(mean βs=0.30 cm; 0.01≤βs≤0.62 cm) and Ia∕P (mean Ia/P=0.14; 0.06≤Ia/P≤0.21) were broadly consistent with reported literature values for these ecosystems and were significantly predicted by forest structural attributes (leaf area index and percent ground cover) as well as other site variables (e.g., water table depth). The best-fit model was dominated by LAI and explained nearly 80 % of observed βs variation. These results suggest that whole-forest interception can be estimated using near-surface soil moisture time series, though additional direct comparisons would further support this assertion. Additionally, variability in interception across a single forest type underscores the need for expanded empirical measurement. Potential cost savings and logistical advantages of this proposed method relative to conventional, labor-intensive interception measurements may improve empirical estimation of this critical water budget element.

Differences in submillimetre surface morphology and canopy interception storage capacities of Gleditsia triacanthos L. (honeylocust) in relation to canopy phenophase and position

AbstractThe purpose of this study is to examine submillimetre surface morphology and interception storage capacity of foliar surfaces for Gleditsia triacanthos L. (honeylocust) in relation to canopy phenophase (emergence, full leaf, and senescence) and bark surfaces with respect to canopy position through the integration of bioimaging microscopy techniques, three‐dimensional (3D) surface mapping, and laboratory‐based storage capacity analyses. The results demonstrate that there were some statistically significant differences in foliar microrelief and storage capacity across canopy phenophases. Mean foliar roughness and storage capacity peaked during the full leaf phenophase at 173 μm and 0.019 ml cm−2, respectively. Both foliar microrelief and storage capacity were least during emergence. The decreased surface roughness during senescence as compared with full leaf might be due to the tree's inability to repair environmentally induced degradation of the morphological microstructures and epicuticular wax during that phase. Bark microrelief and storage capacity both varied as a function of tree height, with the greatest mean roughness (859 μm) and storage capacity (0.094 ml cm−2) observed in the lower tree. The observed reduction in bark microrelief and storage capacity with height may be attributable to bark age and thickness. Further research that links the 3D submillimetre morphology of canopy surfaces by identifying specific physical mechanisms and processes that either promote or inhibit water storage on foliar and bark surfaces is needed.

RETRACTED: Study on the throughfall, stemflow, and interception of two shrubs in the semiarid Loess region of China

Abstract The Loess Plateau, China, has been subject to 40 years of re-vegetation predominantly with the xerophytic shrubs Caragana korshinskii and Hippophae rhamnoides. Throughfall, stemflow, canopy interception, and water storage capacity experiments for the two shrubs were conducted from May to September during the period 2009–2013. The results showed that the throughfall percentages averaged 62.4% and 70.1% of gross rainfall for H. rhamnoides and C. korshinskii, respectively, while stemflow accounted for 2.4% and 6.7% of the gross rainfall for the two shrubs. The rainfall threshold for stemflow generation was 2.46 and 1.06 mm for H. rhamnoides and C. korshinskii, respectively. The wetting front depths for the two shrubs in the area around the stems were deeper than away from the shrubs. The averaged percentages of interception loss in H. rhamnoides and C. korshinskii were 35.2% and 23.2%. Additionally, H. rhamnoides had greater water storage capacity per leaf area for each simulated rainfall intensity (mean, 0.59 mm; range, 0.28–0.88 mm) than C. korshinskii (mean, 0.44 mm; range, 0.26–0.52 mm). Canopy water storage varied temporally with the eight simulated rainfall intensities. For all the tested rainfall intensities, H. rhamnoides could store more water per dry biomass (mean, 0.72 g−1; range, 0.39–1.06 g−1) than C. korshinskii (mean, 0.49 g−1; range, 0.31–0.69 g−1). The present study can inform re-vegetation projects, water budget analyses, and modeling efforts aimed at understanding rainfall water movement within shrub communities in the semiarid Chinese Loess Plateau, China.

Effects of forest litter cover on hydrological response of hillslopes in the Loess Plateau of China

Forest litter layer plays an important role in controlling water and soil loss; however, few studies have examined how litter cover affects hydrological processes. In this research, the effects of forest litter cover on interception, runoff, infiltration and soil erosion were investigated using rainfall simulation on a loess hillslope in China. Field experimental plots (10 m × 1.5 m, 5°) with two litter species (needle-leaf species and broad-leaf species) and three litter masses (300, 500 and 800 g m−2) were exposed to two rainfall intensities (30 and 60 mm h−1) for 40 min. A modified Merriam interception model as well as a WEPP (Water Erosion Prediction Project) Hillslope model were subsequently employed to analyze the experimental data of litter interception as well as runoff generation and soil erosion, respectively. Results showed that litter interception storage capacity ranged from 0.55 to 2.10 mm; thus, 1.8–9.2% of total rainfall was intercepted by the litter layer. Interception storage increased with increasing litter mass and rainfall intensity, and broad-leaf litter could intercept more rainwater than needle-leaf litter. Litter cover reduced runoff rates from plots covered with needle-leaf and broad-leaf litter by 18.6% and 25.9%, respectively, compared to the bare plot. Although runoff rates were slightly lower in litter-covered plots than in the bare plot, soil loss was effectively controlled when litter mass levels reached a threshold value of 500 g m−2. Compared to that from the bare plot, the mean soil loss rate for litter-covered plots was lowered by 58.5%, 74.5% and 78.3% for litter masses of 300, 500 and 800 g m−2, respectively. These results indicate that the litter layer was more conducive to controlling soil loss than runoff generation. Furthermore, the determination coefficient and Nash-Sutcliffe efficiency coefficient of the modified Merriam model ranged between 0.838–0.998 and 0.912–0.998, respectively, indicating that this model could successfully simulate the litter interception process. The WEPP model predictions also agreed well with the measured runoff and soil loss rates, but may have under-estimated the measured data in low rainfall intensity events and over-estimated the measured data in high rainfall intensity events. The performance of the WEPP model could be obviously improved by reducing the effective hydraulic conductivity and soil erodibility. Overall, this study will enable the development of more accurate modeling approaches and lead to a better understanding of hydrological processes under litter cover conditions.

Differences in interception storage capacities of undecomposed broad-leaf and needle-leaf litter under simulated rainfall conditions

Leaf litter is an important component of agroforestry ecosystems that plays a key role in soil and water conservation. This study assessed the effect of leaf shape on water interception under controlled laboratory conditions. Two contrasting leaf shapes (needle-leaf, represented by Pinus massoniana; and broad-leaf, represented by Magnolia grandiflora) were placed in a steel box (2 m long and 1 m wide) for separate experiments with different leaf masses per ground area (0.5, 1.0 and 1.5 kg/m2); the steel box was positioned on two different slopes (5° and 20°) corresponding to gentle and steep slopes; the rainfall intensity was 90 mm/h. The results indicated that leaf shapes had specific effects on the interception storage capacity of the leaf litter on a slope. The needle-leaf litter intercepted 2.08 times more rainwater than the broad-leaf litter on average. As the leaf mass increased, the interception storage capacity of the leaf litter successively increased for the needle-leaf litter, while there were no obvious patterns for the broad-leaf litter. This difference occurred because the initially erect broad leaves were easily flattened by raindrop impacts due to their large surface areas and hence formed a horizontal leaf cover (or leaf overlap). This leaf accumulation structure restricted the infiltration of rainwater into the lower leaf litter while providing a short path for rainwater to leave the leaf litter, hence promoting litter flow and leading to less rainwater intercepted by the broad-leaf litter than the needle-leaf litter. Our results provide a better understanding of the effects of leaf shape on leaf litter interception on inclined slopes, which is lacking in the current literature.

Ex-situ estimation of interception storage capacity of small urban plant species

An important knowledge gap in current urban hydrological models are reliable, generic data about interception storage capacities of small urban plant species. These data are crucial to calculate interception losses and learning their effect on the urban hydrological cycle. This study addresses this knowledge gap through simulating rainfall events in an ex-situ, controlled environment on several urban plant species. Four plant species, Lonicera nitida, Lavandula angustifolia, Pennisetum alopecuroides and a grass mix were selected based on their abundance in urban environments and their morphological differences. Several vegetation characteristics such as height and diameter were altered to create as much variation as possible in the dataset to determine the underlying characteristics influencing the interception storage capacity. Estimating the interception storage capacity of each plant (SP) using multiple linear regression models, biomass (BP) was found to be the most important predictor variable for all species. Therefore predictive models to estimate the biomass of an individual plant were developed, using some easy to measure vegetation characteristics. When using the results of these biomass models as input in the storage capacity models, reasonable estimations of interception storage capacity were achieved with mean absolute errors between 17.7 and 40.8%, depending on the model. Extrapolating SP to a reference area of one m2 showed that L. angustifolia had the highest interception storage capacity due to its high biomass density, followed by P. alopecuroides, L. nitida and finally the grass mix. As a proof of concept, a mixed modelling approach was proposed to include species not covered in this research in the analysis. The findings in this research can be used to create a firm basis for calculations of intra- and interspecies interception storage capacities, essential for improving current urban hydrological models.

Oxygen and hydrogen isotopic characterization of rainfall and throughfall in four South Korean cool temperate forests

ABSTRACTUnderstanding the isotopic composition of precipitation in a forested catchment is critical for ecohydrological studies. Changes in the water isotopes of rainfall were assessed during its passage through the canopy in throughfall, and the effect of different forest stands on the isotope composition of throughfall. In a cool temperate forest in Korea, rainfall and throughfall samples collected under Pinus densiflora (red pine), Castanea crenata (chestnut), Robinia pseudoacacia (black locust) and mixed stands (mix of these three species) were analysed for oxygen and hydrogen isotopes. Throughfall δ18O and δD were enriched compared to rainfall. A difference of δ18O and δD among throughfall may be related to the difference in interception–storage capacity of different species due to dissimilar canopy characteristics. Since isotopic composition of throughfall and rainfall are different due to canopy isotopic effects, use of rainfall isotopic signatures for ecohydrological studies in forested ecosystem can lead to biases.

Estimating linkages between forest structural variables and rainfall interception parameters in semi-arid deciduous oak forest stands

An understanding of the relationship between canopy structure and the water balance is needed for predicting how forest structure changes affect rainfall partitioning and, consequently, water resources. The objective of this study was to predict rainfall interception (I) and canopy storage capacity (S) using canopy structure variables and to investigate how seasonal changes influence their relationship. The study was conducted in twelve 50m×50m plots in the Zagros forest in the western Iranian state of Ilam, protected forests of Dalab region. Average cumulative I was 84.2mm, accounting for 10.2% of cumulative gross precipitation (GP) over a 1-year period. Using a regression based method, S averaged ~1mm and 0.1mm in the leafed and leafless periods, respectively. There were no relationships between tree density and I:GP or S, but I:GP and S increased with leaf area index, canopy cover fraction, basal area, tree height, and diameter at breast height in the leafed period. In addition, wood area index and canopy cover fraction were related to I:GP or S in the leafless period.

Monitoring litter interception of rainfall using leaf wetness sensor under controlled and field conditions

AbstractLeaf litter interception of water is an integral component of the water budget for some vegetated ecosystems. However, loss of rainfall to litter receives considerably less attention than canopy interception due to lack of suitable sensors to measure changes in litter water content. In this study, a commercially available leaf wetness sensor was calibrated to the gravimetric water content of eastern redcedar (Juniperus virginiana) litter and used to estimate litter interception in a subhumid eastern redcedar woodland in north‐central Oklahoma. Under controlled laboratory conditions, a strong positive correlation between the leaf wetness sensor output voltage (mV) and measured gravimetric litter water content (ϴg) was determined: ϴg = (.0009 × mV2) − (0.14 × mV) − 11.41 (R2 = .94, p < .0001). This relationship was validated with field sampling and the output voltage (mV) accounted for 48% of the observed variance in the measured water content. The maximum and minimum interception storage capacity ranged between 1.16 and 12.04 and 1.12 and 9.62 mm, respectively. The maximum and minimum amount of intercepted rain was positively correlated to rainfall amount and intensity. The continuous field measurements demonstrated that eastern redcedar litter intercepted approximately 8% of the gross rainfall that fell between December 16, 2014 and May 31, 2015. Therefore, rainfall loss to litter can constitute a substantial component of the annual water budget. Long‐term in situ measurement of litter interception loss is necessary to gain a better estimate of water availability for streamflow and recharge. This is critical to manage water resources in the south‐central Great Plains, USA where grasslands are rapidly being transformed to woodland or woody dominated savanna.

Sediment and nutrient removal by integrated tree-grass riparian buffers in Taihu Lake watershed, eastern China

Loss of nitrogen (N) and phosphorus (P) from agricultural runoff is a leading cause of eutrophication in Taihu Lake, China. Riparian buffer strips can effectively remove sediment and nutrients from surface runoff. A field-scale study was conducted to assess the effectiveness of the integrated poplar (<i>Populus</i>)-grass buffer strips with different tree planting density in reducing sediment, N, and P from agricultural runoff during natural rainfall events in Taihu Lake watershed, eastern China. The experimental site consisted of four treatments, including a control plot with no buffer strip (T₀) and three poplar-grass buffer strips with different planting densities of 1,346 trees ha⁻¹ (T₁), 769 trees ha⁻¹ (T₂), and 577 trees ha⁻¹ (T₃) with planting spacing of 2 × 5 m (6.5 × 16.4 ft), 4 × 5 m (13.1 × 16.4 ft), and 6 × 5 m (19.7 × 16.4 ft), respectively. The integrated poplar-grass buffer strips significantly reduced runoff volume, sediment, total N, and total P masses by 49.3% to 61.6%, 78.7% to 90.2%, 57.2% to 71.5%, and 65.4% to 81.4%, respectively. With increasing poplar planting density in buffer strips, the canopy interception and maximum water storage capacity of litter layer increased, while the loss of sediments and nutrients from runoff decreased. There was significantly higher removal efficiency in buffer T₁ than that in buffers T₂ and T₃ for sediment, particle-bound N (PN), and particle-bound P (PP). There was no significant difference in removal efficiency for ammonium as N (NH₄-N), nitrate as N (NO₃-N), and phosphate P (PO₄-P) between buffers T₁ and T₂. According to different rainfall regimes, we found that the reduction in runoff volume, sediment, and nutrients load for buffers were higher under mild-long duration events (rainfall intensity class 2 to 4 mm h⁻¹ [0.078 to 0.15 in hr⁻¹]) and lower under intense-short duration events (rainfall intensity class 6 to 8 mm h⁻¹ [0.23 to 0.31 in hr⁻¹]). The removal efficiency of the buffers was negatively correlated with both precipitation and rainfall intensity, and the rainfall intensity had more effect on the removal efficiency than the precipitation. The results indicated that the impact of tree planting density on the effectiveness of buffer strips depended on the measured parameter. That is, the impact on sediment, PN, and PP was greater than that on the soluble N and P. The effect of tree planting density on the performance of buffer strips is mainly due to the interception of canopy and litter layer.

Needle-leaved trees impacts on rainfall interception and canopy storage capacity in an arid environment

In semiarid and arid areas, it is important to understand the amount of rainfall reaching the ground in order to develop effective water plan strategies for the selection of the tree species for afforestation goals. We measured the rainfall interception and canopy storage capacity of individual trees of Pinus eldarica and Cupressus arizonica growing in an afforested Park located in an arid region of Iran. Correlations between percent relative interception and gross rainfall, mean daily wind speed, mean daily air temperature, and mean daily relative humidity were examined both for the wet and dry seasons. Canopy storage capacity was estimated by indirect methods: the Pereira, mean, minimum, and Gash and Morton. The cumulative mean values of percent relative interception and gross rainfall for P. eldarica and C. arizonica trees averaged 66 and 53 %, respectively. Combining meteorological parameters with rainfall depth only slightly improved the correlation with the percent of gross rainfall lost to interception loss in the dry season for P. eldarica (from 0.87 to 0.90) and C. arizonica (from 0.90 to 0.92). For P. eldarica, the mean estimate of canopy storage capacity was 1.31 versus 1.00 mm in C. arizonica trees. Because the storms in this region are small, the large canopy water storage of P. eldarica will result in greater interception losses relative to C. arizonica. Therefore, afforestation efforts would be better served planting C. arizonica over P. eldarica, if maximizing water inputs is a main management goal.

Is canopy interception increased in semiarid tree plantations? Evidence from a field investigation in Tehran, Iran

From 30 January 2011 to 30 January 2012, we measured the rainfall interception (I) and canopy storage capacity (S) of individual trees of Pinus eldarica and Cupressus arizonica planted in the Chitgar Forest Park near Tehran, Iran. Gross rainfall (GR) in this semiarid region was measured using the mean of 6 plastic rain gauges placed in an open area adjacent to the trees. To measure throughfall (TF), 20 plastic rain gauges were installed beneath the crowns of 5 individual trees of each species. I was calculated as GR minus TF. S was estimated using indirect methods: the minimum, Gash and Morton, mean, and Pereira methods. The cumulative mean values of relative percentage of I (I:GR) for P. eldarica and C. arizonica trees averaged 44.2% and 34.4%, respectively. Significant negative relationships were observed between the percent of I:GR and GR for P. eldarica (R^2 = 0.63) and C. arizonica (R^2 = 0.67) trees. For P. eldarica, S was estimated to be 1.10 mm, 1.00 mm, 1.09 mm, and 1.05 mm using the minimum, Gash and Morton, mean, and Pereira methods, respectively. For C. arizonica, the corresponding values are 0.58 mm, 0.52 mm, 0.56 mm, and 0.55 mm. This study proposes that in this climate dominated by small storms, planting C. arizonica is preferable to planting P. eldarica. However, the differences in the transpiration of these species should be quantified. Our results also indicated that the I value in this semiarid climate was higher than that of a humid climate.

Study on Hydrological Functions of Litter Layers in North China

Canopy interception, throughfall, stemflow, and runoff have received considerable attention during the study of water balance and hydrological processes in forested ecosystems. Past research has either neglected or underestimated the role of hydrological functions of litter layers, although some studies have considered the impact of various characteristics of rainfall and litter on litter interception. Based on both simulated rainfall and litter conditions in North China, the effect of litter mass, rainfall intensity and litter type on the maximum water storage capacity of litter (S) and litter interception storage capacity (C) were investigated under five simulated rainfall intensities and four litter masses for two litter types. The results indicated: 1) the S values increased linearly with litter mass, and the S values of broadleaf litter were on average 2.65 times larger than the S values of needle leaf litter; 2) rainfall intensity rather than litter mass determined the maximum interception storage capacity (Cmax); Cmax increased linearly with increasing rainfall intensity; by contrast, the minimum interception storage capacity (Cmin) showed a linear relationship with litter mass, but a poor correlation with rainfall intensity; 3) litter type impacted Cmax and Cmin; the values of Cmax and Cmin for broadleaf litter were larger than those of needle leaf litter, which indicated that broadleaf litter could intercepte and store more water than needle leaf litter; 4) a gap existed between Cmax and Cmin, indicating that litter played a significant role by allowing rainwater to infiltrate or to produce runoff rather than intercepting it and allowing it to evaporate after the rainfall event; 5) Cmin was always less than S at the same litter mass, which should be considered in future interception predictions. Vegetation and precipitation characteristics played important roles in hydrological characteristics.

Influence of ecohydrologic feedbacks from simulated crop growth on integrated regional hydrologic simulations under climate scenarios

Abstract. Hydrologic climate change modelling is hampered by climate-dependent model parameterizations. To reduce this dependency, we extended the regional hydrologic modelling framework SIMGRO to host a two-way coupling between the soil moisture model MetaSWAP and the crop growth simulation model WOFOST, accounting for ecohydrologic feedbacks in terms of radiation fraction that reaches the soil, crop coefficient, interception fraction of rainfall, interception storage capacity, and root zone depth. Except for the last, these feedbacks are dependent on the leaf area index (LAI). The influence of regional groundwater on crop growth is included via a coupling to MODFLOW. Two versions of the MetaSWAP-WOFOST coupling were set up: one with exogenous vegetation parameters, the "static" model, and one with endogenous crop growth simulation, the "dynamic" model. Parameterization of the static and dynamic models ensured that for the current climate the simulated long-term averages of actual evapotranspiration are the same for both models. Simulations were made for two climate scenarios and two crops: grass and potato. In the dynamic model, higher temperatures in a warm year under the current climate resulted in accelerated crop development, and in the case of potato a shorter growing season, thus partly avoiding the late summer heat. The static model has a higher potential transpiration; depending on the available soil moisture, this translates to a higher actual transpiration. This difference between static and dynamic models is enlarged by climate change in combination with higher CO2 concentrations. Including the dynamic crop simulation gives for potato (and other annual arable land crops) systematically higher effects on the predicted recharge change due to climate change. Crop yields from soils with poor water retention capacities strongly depend on capillary rise if moisture supply from other sources is limited. Thus, including a crop simulation model in an integrated hydrologic simulation provides a valuable addition for hydrologic modelling as well as for crop modelling.

Fog interception by Ball moss (&amp;lt;i&amp;gt;Tillandsia recurvata&amp;lt;/i&amp;gt;)

Abstract. Interception losses are a major influence in the water yield of vegetated areas. For most storms, rain interception results in less water reaching the ground. However, fog interception can increase the overall water storage capacity of the vegetation and once the storage is exceeded, fog drip is a common hydrological input. Fog interception is disregarded in water budgets of semiarid regions, but for some plant communities, it could be a mechanism offsetting evaporation losses. Tillandsia recurvata is a cosmopolitan epiphyte adapted to arid habitats where fog may be an important water source. Therefore, the interception storage capacity by T. recurvata was measured in controlled conditions and applying simulated rain or fog. Juvenile, vegetative specimens were used to determine the potential upperbound storage capacities. The storage capacity was proportional to dry weight mass. Interception storage capacity (Cmin) was 0.19 and 0.56 mm for rainfall and fog respectively. The coefficients obtained in the laboratory were used together with biomass measurements for T. recurvata in a xeric scrub to calculate the depth of water intercepted by rain. T. recurvata contributed 20 % to the rain interception capacity of their shrub hosts: Acacia farnesiana and Prosopis laevigata and; also potentially intercepted 4.8 % of the annual rainfall. Nocturnal stomatic opening in T. recurvata is not only relevant for CO2 but for water vapor, as suggested by the higher weight change of specimens wetted with fog for 1 h at dark in comparison to those wetted during daylight (543 ± 77 vs. 325 ± 56 mg, p = 0.048). The storage capacity of T. recurvata leaf surfaces could increase the amount of water available for evaporation, but as this species colonise montane forests, the effect could be negative on water recharge, because potential storage capacity is very high, in the laboratory experiments it took up to 12 h at a rate of 0.26 l h−1 to reach saturation conditions when fog was applied.