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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]

Land use composition and patterns influence the hydrological response in mountainous and forest catchments. In plantation forest, management operations (FMO) modify the spatial and temporal dynamics of overland flow processes. However, we found a gap in the literature focussed on modelling hydrological connectivity (HC) in plantation forest under different FMO. In this study, we simulated HC in two steep paired forest subcatchments (K2 and K3, 33.2 ha), composed of Japanese cypress ( Chamaecyparis obtusa Endl.) and Japanese cedar ( Cryptomeria japonica D. Don) plantations (59% of the total area) against a tree thinning intensity of 50% at different time. Additionally, construction of new skidding trails and vegetation recovery was simulated on five thinning-based scenarios that covered a 40-month test period (July 2010 – October 2013). As a future scenario, six check-dams located in the main streams were proposed to reduce sediment and radionuclide delivery. An updated version of Borselli's index of runoff and sediment connectivity was run, using the D-infinity flow accumulation algorithm and exploiting three 0.5-m resolution digital elevation models. On the basis of the pre-FMO scenario, HC increased at catchment scale owing to tree thinning and the new skidding trails. This change was more noticeable within the area affected by the FMO, where HC increased by 11.4% and 10.5% in the cypress and cedar plantations in K2 respectively and by 8.8% in the cedar plantation in K3. At hillslope plot and stream scales, the evolution in the values of HC was less evident, except the increment (by 5.4%) observed in the streams at K2 after the FMO. Progressive vegetation recovery after the FMO triggered a slight reduction of connectivity in all compartments of both subcatchments. Forest roads and especially skidding trails presented the highest values of HC, appearing as the most efficient features connecting the different vegetation patches with the stream network. The spatial and temporal evolution of HC over the five past scenarios correlated well with the observed changes in runoff yield, as well as with the available values of rainfall interception and throughfall before, during, and after the FMO. The simulation of the proposed scenario recommends the construction of check-dams as effective landscape features to somewhat reduce HC and thus to decrease the sediment and radionuclide delivery rates from the two subcatchments. [ABSTRACT FROM AUTHOR]

Trunk xylem sap nitrogen (N) composition can provide key information for interpreting tree N transport strategies in a changing environment. However, there remains poorly explored to properly depict the spatial patterns and determinants of the xylem sap N composition in different tree species across climate zones. Here, we analyzed the trunk xylem sap N of dominant tree species from tropical to temperate forests in eastern China. The random forest (RF) approach was used to quantify the relative importance of biotic and abiotic variables in driving the spatial patterns of the trunk xylem sap N composition. The concentration ranges of total N (TN), ammonium (NH 4 +) and nitrate (NO 3 −) in the trunk xylem sap were 0.37–37.23, 0.01–2.60 and 0.01–0.49 mM, respectively. Dissolved organic nitrogen (DON) was the main component of TN in the xylem sap of forest trees, accounting for 83.4 ± 3.6%, followed by NH 4 + (11.8 ± 3.2%) and NO 3 − (4.8 ± 1.3%). In addition, the TN and NH 4 + concentrations increased from the tropical rainforest and then decreased to the northern temperate forest, with a peak in the subtropical deciduous forest in the middle-latitude climatic transition zone. The NO 3 − concentration in the temperate forest was higher than that in other forests, regardless of coniferous and broad-leaf forests. Tree species was the key factor affecting the spatial TN patterns, whereas soil pH primarily and conversely determined the spatial NH 4 + and NO 3 − patterns. Together, tree characteristics and soil properties were the most important factors affecting the spatial patterns of xylem sap N composition. These findings provide new insights into N cycling within forest trees and have implications for better understanding the adaptation to global changes in forest ecosystems. [Display omitted] • DON was the main N component of trunk xylem sap, followed by NH 4 + and NO 3 -. • Xylem sap TN and NH 4 + peaked in the middle-latitude climatic transition zone. • Xylem sap NO 3 − was higher in temperate forest than that in other forests. • Tree species was the key factor affecting the spatial TN patterns. • Soil pH primarily and conversely determined the spatial NH 4 + and NO 3 − patterns. [ABSTRACT FROM AUTHOR]

Canopy closure (CC) is an important parameter in many fields. It can be obtained from digital hemispherical photographs (DHPs) by converting the pixels to black or white according to their nature: canopy or not. DHP exposure is a key factor that controls accuracy in CC determination. Many accurate pre- and post-treatments exist for enhancing the exposure, but these methods often require specific knowledge. To be more “user-friendly” compared to the raw equations provided in the literature, we have proposed a new software, DHPT 1.0, that calculates CC from DHPs using hue-enhancing methods before an automatic thresholding calculation. DHPT 1.0 does not require manual settings, thus avoiding errors caused by operator misjudgement. The first step of this study was to calibrate the enhancement methods to make DHPT 1.0 able to accurately calculate CC regardless of the photograph exposure. We have therefore used 210 digital photographs that regroup seven locations along a visual gradient of CC and of exposures. After calibration, the accuracy of DHPT 1.0 was compared with the accuracy of three software packages that are widely used by experts: Canopon2, GLA 2.0, and WINPHOT 5.0. A batch of two sets of 10 DHPs divided into one set of over-exposed DHPs and one set of under-exposed DHPs from 10 locations along a gradient of CC was used for the comparison. DHPT 1.0 provides the most accurate results, with an average error of 8% between the same under-saturated or over-saturated DHP. [ABSTRACT FROM AUTHOR]

Thinning results in more open-stand canopies and then immediately modifies the environmental factors that influence forest floor evaporation ( E f ). Thus, the changes in E f induced by thinning would play an important role in the forest water cycle, whereas few studies have reported this topic. This study analyzes the effect of strip thinning on E f , its spatial variation and identifies the factors influencing it in a Japanese cypress ( Chamaecyparis obtusa Endl.) plantation in Tochigi Prefecture, Japan. Strip thinning, which removed 50% of the stems, was conducted in a headwater basin during the period of October 11–November 5, 2011. The E f was monitored by weighing lysimeters before and after thinning. The daily E f was strongly correlated with the daily solar radiation ( R 2 = 0.62) followed by vapor pressure deficit ( R 2 = 0.41) below the canopy, whereas the soil water content had a poor effect on it in post-thinning. After thinning, the daily E f among the measuring points had no significant difference, indicating that the daily E f had a small spatial variation. This responded to the small spatial variability in the daily solar radiation under the canopy. Additionally, on an annual scale, thinning resulted in the daily mean E f increasing from 0.34 ± 0.23 to 0.68 ± 0.47 mm d −1 . The total E f increased by 97.6% from 124.0 to 245.0 mm. These findings indicate that E f composes a significant part of the forest water budget after thinning and emphasize the importance of E f measurements for management practices. This study also provides useful information for modeling the changes in hydrological processes at the forest floor and for evaluating the E f response to different management practices. [ABSTRACT FROM AUTHOR]

Summary We examined the effect of strip thinning on rainfall interception ( E i ) in a 32-year-old Japanese cypress plantation in central Japan. Strip thinning was conducted in the catchment in October 2011; that removed 50% of the stems. The gross precipitation ( P g ), throughfall ( TF ) and stemflow ( SF ) were monitored in a 12-m × 13-m plot before and after thinning. E i was calculated as the difference between P g and the sum of TF and SF . The interception processes were illustrated using the revised Gash model with quantifying interception parameters. The results showed that the Gash model successfully predicted E i on a rainy-season basis in both pre- and post-thinning periods. Thinning altered the interception components whereas the largest part during and after rainfall accounted for similar proportion in both periods. Additionally, after thinning, the annual TF rate was increased from 61.4% to 73.0%, whereas the annual SF rate was decreased from 9.8% to 6.1%, and the annual E i rate was decreased from 28.7% to 20.8%. The summarized findings of previous studies indicate that the degree of decline in the E i caused by thinning is related to P g and the thinning ratio. These results provide useful information for understanding the changes in interception processes induced by thinning, and for acquiring a more accurate forecast of the effects of forest management practices on water resources in the watershed. The response in rainfall partitioning to strip thinning can also help us to acquire an integrated understanding of the changes in canopy water balance under different forest practices. [ABSTRACT FROM AUTHOR]

• Spring wheat was 15N-labeled via a split-root technique. • The NdfR was estimated by the isotope ratio and isotope mass balance approaches. • The isotope ratio approach underestimated NdfR before plant maturity. • The two approaches had no difference for estimation of NdfR after plant maturity. • Selecting appropriate calculation approach to quantify NdfR should be considered. Accurate quantification of nitrogen (N) derived from rhizodeposition (NdfR) is crucial to assess N stored in plants and the total N balance in plant-soil systems. However, there remains uncertainty in the estimates of NdfR for 15N-labeled plants with the split-root technique using the isotope ratio approach and the isotope mass balance approach. Here, we examined the two calculation approaches that estimate NdfR from 15N-urea (99 atom%) labeling of spring wheat (Triticum aestivum L.) using the split-root technique in a pot experiment over plant growth, and assessed the causative factors of their potential bias. The results showed that independent of the approach, the total amount of NdfR was 5.3–9.8 mg plant−1 and contributed up to 19.9–26.3% of total plant N throughout the growth period. At the heading and filling stages after labeling, the amounts of NdfR using the isotope ratio approach (5.3 and 6.6 mg plant−1, respectively) were significantly lower than those (7.1 and 7.8 mg plant−1, respectively) using the isotope mass balance approach, due to soil N losses and an uneven distribution of 15N. At the ripening stage after labeling, however, the differences in the amount of NdfR between the two approaches disappeared (9.8 and 9.6 mg plant−1, respectively). This indicated that the isotope ratio approach underestimates the amount of NdfR during the plant developmental period, while both approaches can be used to quantify the amount of NdfR at plant maturity. [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]

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]

Knowledge of the characteristics of chemical components transported in the xylem sap of trunks remains deficient and limited because no appropriate method exists to extract the xylem sap from this part of the tree. We thus explored the differences in xylem sap components extracted by means of centrifugation and water displacement methods and depicted the level and behavior of chemical components in the xylem sap of trunks and branches of different aged trees from a pine forest in northern China. There were no significant differences between the two methods with respect to nitrogen (N) compounds and inorganic ions in the xylem sap. Potassium concentrations obtained by the methods were similar and consistent with the values obtained from earlier publications on woody species. This suggests that contamination of the xylem sap by the centrifugation method is negligible, and this method would be a reliable and robust tool for collection of the trunk xylem sap. Dissolved organic N was the dominant component of total N followed by nitrate (NO 3 −) and ammonium (NH 4 +). Potassium and chloride were the predominant cation and anion, respectively, of the xylem sap. The NO 3 − concentration basically did not change, whereas the NH 4 + concentration was larger transported from the trunk to branches for the large tree class during foliage senescence. More inorganic N components (mainly NO 3 −) were found in young trees than in old trees. Our study contributes to improve the diagnostic assessments of tree physiological processes and growth in mature forest trees under environmental changes. • A centrifugation method was proposed to collect the trunk xylem sap of forest trees. • DON was the dominant component of TN in trunk xylem sap followed by NO 3 − and NH 4 +. • K+ and Cl− were the predominant cation and anion, respectively, of trunk xylem sap. • NO 3 − and NH 4 + had different behaviors when transported from the trunk to branches. • More inorganic N components (mainly NO 3 −) were found in young trees. [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]

A wide area of paddy fields was contaminated by radiocesium derived from the Fukushima nuclear accident. Implement of agricultural countermeasures is one of the principle methods to reduce the contamination of rice plants. In this study, the effect of topsoil removal measure and fertilizer application on radiocesium uptake by rice plants was investigated over a four-year period. Some other available countermeasures carried out after the Fukushima nuclear accident were also summarized. The results indicate that the effect of topsoil removal measure on the accumulation of radiocesium in rice plants was effective, but the concentration ratio of radiocesium activity concentration between rice plant and soil increased. This may be correlated with the radiocesium imported from irrigation water and relatively high exchangeable radiocesium proportion of plowing soil in the topsoil removal paddy. We summarized four year's data to further confirm that potassium and nitrogen fertilizers had an opposite effect on the accumulation of radiocesium in rice plants. Increasing potassium and reducing nitrogen fertilizer conditions tended to inhibit the radiocesium uptake by rice plants. Moreover, of all the available countermeasures applied in the paddy fields, the most effective countermeasure was the application of phlogopite. However, further analyses are required to confirm the effectiveness of application of phlogopite considering the limited available information. [ABSTRACT FROM AUTHOR]

• TF , SF and Ei had no significant differences between UP and LP. • TF NO 3 −-N and SO 4 2−-S fluxes were slightly/significantly lower in UP compared to LP. • SF NO 3 −-N and SO 4 2−-S fluxes were quite similar between the two slope plots. • NTF NO 3 −-N and SO 4 2−-S fluxes were negative at both UP and LP. • Canopy exchange may be dominant factor on these hydrochemical fluxes in watershed. Forest canopies create a high spatial variability of both canopy interception (Ei) and acid deposition. However, spatial characteristics of these hydrochemical fluxes along a slope gradient in forest watersheds remain unclear. Here we monitored bulk precipitation (BP), throughfall (TF), stemflow (SF), and associated nitrate (NO 3 −) and sulfate (SO 4 2−) in an upper slope plot (UP) and a lower slope plot (LP) in a subtropical broadleaved forest, Southeast China. Results showed that annual rates of TF , SF and Ei to BP in UP were 85.2%, 2.6%, and 12.2%, respectively. Corresponding values in LP were 88.6%, 2.2%, and 9.2%. There were no significant differences among these rainfall partitioning components between UP and LP. Additionally, annual volume weighted mean concentrations of NO 3 −-N in TF and SF were significantly lower than in BP , whereas no significant differences were found for SO 4 2−-S among BP , TF and SF. Unlike annual TF NO 3 −-N fluxes were similar in UP and LP, annual TF SO 4 2−-S fluxes significantly increased along the UP to LP. Net TF + SF (NTF) fluxes were negative for NO 3 −-N and SO 4 2−-S at the two slope plots, illustrating retained/uptake in the canopy. Dormant season NTF S fluxes were close to zero, indicating that dry deposition does not appear to play a major role, whereas exchange with foliage surfaces should be the dominant factor controlling the spatial patterns of TF N and S fluxes in the watershed. This study can contribute to the evaluation of watershed-scale water and acidifying input into the soil during canopy passage, and further consequent effects on forest ecosystems. [ABSTRACT FROM AUTHOR]

Since excessive nitrite is a serious carcinogen to human beings, it is necessary to generate a convenient and sensitive means for its detection. Owing to this point, thus, UiO-66-NH 2 had been successfully employed as a fluorescence turn-off probe for the detection of NO 2 − through diazotization and reduction. It could detect nitrite sensitively and selectively under acidic conditions (pH ​= ​1.0) at room temperature. The linear range of nitrite was 0–10 ​mM, the detection limit was 77 ​ μ M, and a short response time (120 ​s) had been displayed by UiO-66-NH 2. Whilst, it could specifically recognize nitrite and would hardly be affected by other possibly coexistent interfering substances. Furthermore, quantitative analysis of three real samples also confirmed the reliability and sensitivity of this probe. All these results had shown that the detecting method of UiO-66-NH 2 to nitrite was simple in operation, and mild in reaction condition. Image 1 • It is the first time for UiO-66-NH 2 as a "turn off" fluorescent probe to detect nitrite. • UiO-66-NH 2 detected nitrite for the first time which was based on diazotization and reduction reaction. • The UiO-66-NH 2 exhibited significant selectivity and sensitivity to nitrite. [ABSTRACT FROM AUTHOR]