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Forest canopies are the functional interface between ecosystem and the atmospheric nitrogen (N) deposition. However, the sources of spatio‐temporal variability and intra‐event variation of N deposition via throughfall (TF) remain ambiguous. Here, we analysed TF samples for concentrations and fluxes of ammonium (NH4+) and nitrate (NO3−) using an array of 20 fixed‐position collectors on an event and within event basis throughout the 2019 growing season in a Chinese pine plantation, Northern China. Results showed that the volume weighted mean concentrations of NH4+ and NO3− in TF were significantly higher than those in bulk precipitation (BP) during the study period. A canopy budget model indicated that canopy uptake was more dominant than dry deposition for NH4+, while the reverse was true for NO3−. This caused a comparable TF NH4+ flux but an enhanced TF NO3− fluxes compared to BP. The intra‐event trend and magnitude of TF NH4+ and NO3− concentrations were influenced by the antecedent dry period and rainfall intensity, and indicated that biological nitrification may occur in the canopies. In addition, due to the larger of canopy NH4+ uptake that counteracted the amplifying effect of dry deposition, the spatial variability of TF NH4+ concentration was significantly lower than that of TF NO3− concentration, and exhibited more temporal persistence. No relationship was found between the spatial distribution of TF NH4+ concentration and the TF amount, the distance to the nearest trunk, nor the canopy cover, whereas the TF NO3− concentration was significantly related to the TF amount and the canopy cover. These findings can enhance our understanding of N processes within canopies, and have important implications for evaluating the impacts of N deposition in forest ecosystems. [ABSTRACT FROM AUTHOR]

Recently, materials with controllable superwettability have attracted much attention. However, almost all studies focused on controlling wetting of water and oil; research on underwater gas bubble wetting control is still rare. Herein, we report a mesh film prepared by coating polypyrrole (PPy) film on Ti mesh. Briefly, the film mesh is underwater superaerophilic when PPy is doped with perfluorooctanesulfonate ions (PFOS−), and becomes underwater superaerophobic as the PFOS− are removed. The transition of the wettability can be triggered by electrical stimuli, which is attributed to the cooperative effect between the rough structure and chemical components variation. The controllable wettability allows adjustable bubble permeation. It can be envisioned that the film will provide potential applications in the future, such as underwater bubble capture/release and microfluidic devices. [ABSTRACT FROM AUTHOR]

An increasing number of studies have examined the effects of various biotic and abiotic factors on stemflow production. Of those that have ascribed the importance of canopy structure to stemflow production, there has been a bias towards field studies. Coupling Bayesian inference with the NIED (National Research Institute for Earth Science and Disaster Resilience, Tsukuba, Japan) large‐scale rainfall simulator, this study leveraged a unique opportunity to control rainfall amounts and intensities to pinpoint the canopy structural metrics that differentially influence stemflow funnelling ratios for three common tree species between leafed and leafless canopy states. For the first time, we examined whether canopy structure metrics exert a static control on stemflow funnelling ratios or whether different elements of canopy structure are more or less important under leafed or leafless states, thereby allowing us to determine if tacit assumptions about the static influence of canopy structure on stemflow production (and funnelling) are valid (or not). Rainfall simulations were conducted at 15, 20, 30, 40, 50, and 100 mm h−1 under both leafed and leafless tree conditions (12 simulations in total) to detect any differential effects on the presence or absence of foliage on stemflow funnelling ratios. For leafed conditions, the highest percentages of best‐fitting models (ΔDIC ≤2) indicated that stemflow funnelling ratios were mainly controlled by total dry aboveground biomass (Ball), diameter at breast height (DBH), total dry foliar biomass (Bf), tree height (H), and woody to foliar dry biomass ratio (BR). Whilst for the leafless state, the highest percentages of best‐fitting models (ΔDIC ≤2) indicated that total dry branch biomass (Bbr) was relatively dominant as was the interaction effects between crown projection area and species (CPA:species). These results compel us to reject any assumption of a static effect of different elements of canopy structure on stemflow funnelling. [ABSTRACT FROM AUTHOR]

The ambient dose rate (ADR) in a coniferous forest floor contaminated by Fukushima-derived 137Cs was calculated for small temporal scale as a function of depth. The calculated total ADR was statistically evaluated along the soil vertical strata and among the sampling time series. Moreover, the contribution of the forest floor components to the total radiation dose were examined. Accordingly, the litter and fragmented organic layers accounted for about 58 to 96% (mean 77 ± 14%) of the ambient dose, indicating the organic layer is a chief sources of external radiation exposure, and an important radiological soil section. [ABSTRACT FROM AUTHOR]

Although we know that rainfall interception (the rain caught, stored, and evaporated from aboveground vegetative surfaces and ground litter) is affected by rain and throughfall drop size, what was unknown until now is the relative proportion of each throughfall type (free throughfall, splash throughfall, canopy drip) beneath coniferous and broadleaved trees. Based on a multinational data set of >120 million throughfall drops, we found that the type, number, and volume of throughfall drops are different between coniferous and broadleaved tree species, leaf states, and timing within rain events. Compared with leafed broadleaved trees, conifers had a lower percentage of canopy drip (51% vs. 69% with respect to total throughfall volume) and slightly smaller diameter splash throughfall and canopy drip. Canopy drip from leafless broadleaved trees consisted of fewer and smaller diameter drops (D50_DR, 50th cumulative drop volume percentile for canopy drip, of 2.24 mm) than leafed broadleaved trees (D50_DR of 4.32 mm). Canopy drip was much larger in diameter under woody drip points (D50_DR of 5.92 mm) than leafed broadleaved trees. Based on throughfall volume, the percentage of canopy drip was significantly different between conifers, leafed broadleaved trees, leafless broadleaved trees, and woody surface drip points (p ranged from <0.001 to 0.005). These findings are partly attributable to differences in canopy structure and plant surface characteristics between plant functional types and canopy state (leaf, leafless), among other factors. Hence, our results demonstrating the importance of drop‐size‐dependent partitioning between coniferous and broadleaved tree species could be useful to those requiring more detailed information on throughfall fluxes to the forest floor. [ABSTRACT FROM AUTHOR]

Abstract: Spatial variability of throughfall (TF) isotopic composition, used as tracer input, influences isotope hydrological applications in forested watersheds. Notwithstanding, identification of the dominant canopy factors and processes that affect the patterns of TF isotopic variability remains ambiguous. Here, we examined the spatio‐temporal variability of TF isotopic composition in a Japanese cypress plantation, in which intensive strip thinning was performed and investigated whether canopy structure at a fine resolution of canopy effect analysis is related to TF isotopic composition and how this is affected by meteorological factors. Canopy openness, as an index of canopy structure, was calculated from hemispherical photographs at different zenith angles. TF samples were collected in a 10 × 10 m experimental plot in both pre‐thinning (from July to November 2010) and post‐thinning (from May 2012 to March 2013) periods. Our results show that thinning resulted in a smaller alteration of input δ18O of gross precipitation, whereas the changes in deuterium excess varied in both directions. Despite the temporal stability of spatial patterns in TF amount, the spatial variability of TF isotopic composition was not temporally stable in both pre‐ and post‐thinning periods. Additionally, after thinning, the isotopic composition of TF was best related to canopy openness calculated at the zenith angle of 7°, exhibiting three different relationships, that is, significantly negative, significantly positive, and nonsignificant. Changes in meteorological factors (wind speed, rainfall intensity, and temperature) were found to affect the relationships between TF δ18O and canopy openness. The observed shifts in the relationships reveal different dominant factors (partial evaporation and the selection), and canopy water flowpaths control such differences. This study provides useful insights into the spatial variability of TF isotopic composition and improves our understanding of the physical processes of interception through canopy passage. [ABSTRACT FROM AUTHOR]

Background and aims: Elevated ozone (O3) decreases nitrogen derived from rhizodeposition (NdfR). However, the changes in the partitioning of NdfR in soil N pools due to O3 remain unclear. The aims of this study were to investigate the contribution of NdfR to different soil N pools and its response to elevated O3 conditions.Methods: Spring wheat was labeled with 15N-urea using a split-root technique under ambient (~40 ppb) and elevated O3 treatments (60 ± 5 ppb and 110 ± 5 ppb) in open-top chambers. Mineral-N, microbial biomass (MB)-N and fixed ammonium (FA)-N in rhizospheric soils were analyzed.Results: N rhizodeposition contributed 12-33% of mineral N, 10-14% of FA-N and 6-16% of MB-N under ambient O3. Elevated O3 significantly decreased mineral-15NdfR and increased FA-15NdfR but had no significant influence on MB-15NdfR. The decrease in mineral-NdfR was likely due to the decrease in rhizodeposition inputs and the increase in FA-NdfR.Conclusions: Our results showed that elevated O3 altered the contribution of NdfR to soil N pools. The present study increases our understanding of the dynamics of NdfR and the changes in soil N cycling induced by projected future O3 levels. [ABSTRACT FROM AUTHOR]

Tipping-bucket rain gauges are used widely to measure the amount and intensity of gross rainfall and throughfall in forests, despite the fact that their systematic underestimations are well known. To the knowledge of the authors, no dynamic calibrations for the budget-conscious Davis gauge (Rain Collector II, Davis Instruments, California) have been published. Thus, five Davis gauges were dynamically calibrated under different constant intensities of inflow and a correction equation was derived. The derived correction equation for the Davis rain gauge is V=-0.2005Q2+0.702Q+1 (R2=0.95, p<0.001), where V is the actual volume of a single tip scaled by the static volume of single tip c (cm3 cm-3), and Q is actual inflow scaled by c (s-1). The Davis rain gauge was then compared to the Onset rain gauge and the Ota rain gauge, and the corrections were applied to field observation data of canopy interception loss from a temperate forest in Japan. It is necessary to apply corrections to gross rainfall and throughfall data by tipping-bucket gauges because the results reveal that such corrections change the actual interception loss computed by values from 220% to 40%, depending on the combination of gauges employed. This difference is not trivial. The systematic bias of the Davis gauge is larger than the Onset and Ota gauges. Thus, it is recommended that researchers using Davis rain gauges apply the dynamically calibrated correction equation presented here to ensure more reliable estimates of gross rainfall and canopy interception loss. [ABSTRACT FROM AUTHOR]

Key message: Thinning resulted in evapotranspiration decrease and caused the relative contributions of each component to evapotranspiration to become very close. Abstract: To increase the understanding of forest management to control water cycles, we examined the effect of 50% strip thinning on evapotranspiration (ET) and its partitioning into canopy interception ( E ), tree transpiration ( E ), and forest floor evaporation ( E ) in a Japanese cypress ( Chamaecyparis obtusa Endl.) plantation. Intensive measurements were employed to monitor each component of ET during the pre- and post-thinning periods. The results showed the annual E was the dominant component of ET followed by E , whereas E was the smallest component in both periods. Thinning has significant impact on the process of ET partitioning. In such that it decreased from 42.3 to 33.7% in E /ET and from 45.0 to 34.9% in E /ET, and increased from 12.7 to 31.4% in E /ET on an annual scale. The relative contributions of each ET component to the whole ET became more or less the same after thinning. Additionally, the monthly E / P had relative stable values in both pre- and post-thinning periods, contributing significantly to the ET/ P during heavy rainfall conditions. After thinning, ET decreased by 21.4% from 629.3 to 494.8 mm during the growing season and by 20.4% from 979.8 to 780.1 mm at the annual scale, demonstrating that thinning results in an increase in water availability in the forested watershed. This study can improve the understanding of forest water budget in response to thinning and aid in development of appropriate forest management practices accordingly. [ABSTRACT FROM AUTHOR]

We 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 postthinning 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 >25mm 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. [ABSTRACT FROM AUTHOR]

ABSTRACT We investigated the contribution of three evapotranspiration (ET) components including canopy interception ( Ei), tree transpiration ( Et) and forest floor evaporation ( Ef) and identified the sources depth of evaporated water in a Japanese cypress stand. Monitoring primarily focused on the growing season of July-October 2011. In a 12 × 13 m plot with 28 trees with a DBH of 19.1 ± 3.9 cm, Ei was calculated as the difference between precipitation on an open field and precipitation under a canopy as the sum of throughfall and stemflow, and Et was measured using the Granier method. Ef was measured by weighing lysimeters. Total ET during the monitoring period was 446.3 mm, accounting for 47.5% of the total precipitation of 938.8 mm. Ei was the dominant evaporation flux and accounted for 53.6% of ET or 25.5% of rainfall, followed by Et with 33.7% of ET or 16.0% of rainfall. The average Et was 1.5 ± 0.6 mm d−1. It was well correlated with soil moisture at a depth of 5-15 cm, which reflected the forest properties, i.e. tree roots were exposed on the forest floor. Ef accounted for 12.7% of ET or 6.0% of rainfall with a daily mean of 0.55 ± 0.26 mm d−1, and was best correlated with soil moisture in the upper 5 cm of soil. These results can improve the understanding of water budget in forested watershed and also be used to build and validate hydrologic models for water resource managements. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Interception loss ( E) in forests has been studied widely. However, E parameters and modeling as well as spatial patterns of throughfall ( TF) in abandoned Japanese cypress ( Chamaecyparis obtusa) plantations remain poorly documented. In this study, gross precipitation ( P), stemflow ( SF), and TF were monitored in an unmanaged 32-year-old Japanese cypress stand throughout the 2011 rainy season. Results indicate that P partitioning into TF, SF, and E were, respectively, 64.2 ± 3.6, 10.6 ± 0.6, and 25.2 ± 1.1 % of the 880.8 mm cumulative P from 29 rainfall events. Direct throughfall proportion ( p) and drainage from the canopy contributed about 14 ± 7 and 50 ± 21 % of the total TF for the events, respectively. The mean canopy storage capacity ( S) was 2.4 ± 0.7 mm. The coefficient of variability (CV) of TF rate decreased asymptotically with increasing P amount, ranging from 16 to 56 % with median 26 %. The CV of TF rate was not significantly correlated with canopy cover ( r = 0.152, P = 0.521, n = 20) and distance from the nearest trunk ( r = 0.196, P = 0.408, n = 20). Based on the revised Gash analytical model, the total simulated E was close to the observed, with a general underestimation magnitude of 5.7 %. The E components were quantified, and most of the interception loss (62.9 %) evaporated during rainfall, while 26.8 % evaporated after rainfall ceased. Climatic and forest structural parameters required by the model were identified and analyzed by sensitivity analysis, implying that the revised Gash analytical model is robust and reliable enough for abandoned Japanese cypress plantations in a maritime climate. [ABSTRACT FROM AUTHOR]