Nematomorph parasites manipulate crickets to enter streams where the reproduce. These manipulated become a substantial food subsidy for stream fishes. We used field experiment investigate how this affects community and ecosystem function. When were available, predatory fish ate fewer benthic invertebrates. The resulting release of invertebrate from predation indirectly decreased biomass algae slightly increased leaf break-down rate. This is first experimental demonstration that host...

Abstract An accurate estimate of total forest carbon (C) stock and C uptake is crucial for predicting global warming scenarios planning CO 2 emission reductions. Forest inventory, based on field measurements individual tree sizes, considered the most estimation method stock. Japan’s national inventory (NFI) provides stand-scale stem volume entire forested area (1) direct (m-NFI) (2) prediction using yield tables (p-NFI). Here, we show that Japanese local forestry agencies some research...

Abstract Inter‐catchment groundwater flow (IGF) plays an essential role in streamflow generation and water quality forested headwaters. Multiple factors are thought to contribute IGF, including climate, topographical, geological factors. However, studies have not clarified the relationships between IGF catchment properties headwater catchments due lack of observational data at scales smaller than 100 ha. This study examined possible influencing using random forest analysis based on annual...

Abstract Direct‐seeded rice ( Oryza sativa ) cultivation (DSR) is gradually replacing transplanted (TPR) across tropical Asia owing to labor shortages. However, the yields in DSR are lower than those TPR under current farmer practices (FPs). It would be useful introduce best management (BMPs), holistic technology packages prepared by researchers and extension staff, improve yield. We aimed at quantifying effect of BMPs application on on‐farm yield, input factors (labor requirements...

Abstract In this paper, we examined the role of bedrock groundwater discharge and recharge on water balance runoff characteristics in forested headwater catchments. Using rigorous observations catchment precipitation, streamwater chemistry, quantified net flow rates contributions to three catchments (second‐order third‐order catchments) underlain by uniform Japan. We found that annual rainfall 2010 was 3130 mm. same period, varied from 1800 3900 mm/year. Annual estimated chloride mass method...

Abstract Understanding changes in evapotranspiration during forest regrowth is essential to predict of stream runoff and recovery after cutting. Canopy interception ( Ic ) an important component evapotranspiration, however the impact on cutting remains unclear due limited observations. The objective this study was examine effects long‐term a Japanese cedar cypress following clear‐cutting. This conducted two 1‐ha paired headwater catchments at Fukuroyamasawa Experimental Watershed Japan. were...

Abstract There has been a great deal of research interest regarding changes in flow path/runoff source with increases catchment area. However, there have very few quantitative studies taking subscale variability and convergence into account, especially relation to headwater catchments. This study was performed elucidate how the contributions discharge rates subsurface water (water soil layer) groundwater fractured bedrock) aggregate change area increase, whether spatial rate determines...

Abstract Understanding how spatial variability in stream discharge and water chemistry decrease with increasing catchment area is required to improve our ability predict hydrological biogeochemical processes ungauged basins. We investigated differences this of among catchments specific ( Q s ) parameters. defined the slope as rate standard deviation coefficient variation (δ SD δ CV , respectively), both which are −0.5 for simple mixing random variables (random mixing). All values were less...

We investigated bed load yields from a headwater catchment (7.0 ha) in the eastern Tanzawa Mountains Kanagawa Prefecture, Japan 2009–2014 using measurements weir pond catchment. Precipitation and stream discharge were continuously monitored at 10-min intervals. The mean (± standard deviation) volume of transported was 0.019 ± 0.040 m3/ha/day (0.023 0.049 t/ha/day by yield) zero events observed during monitoring period. particle size sediment tended to be small compared that bed. Bed...

This study investigated whether the representative elementary area (REA) concept can be adopted in catchments with multiple geologies. We observed stream discharge at 65 points and water chemistry 157 a 55 km2 catchment that included At observation uniform geology, became constant beyond about 1 granodiorite volcanic rocks. geologies, spatial variability remained large few square kilometers. SiO2 Mg2+ concentrations above 10 km2, but Ca2+ electrical conductivity did not become until km2. Our...

Carbon sequestration via afforestation and forest growth is effective for mitigating global warming. Accurate robust information on characteristics by tree species, region, large-scale land-use change vital future prediction of carbon stocks based this great significance. We presented the age–carbon density functions four major plantation species in Japan: Cryptomeria japonica, Chamaecyparis obtusa, Pinus spp., Larix kaempferi. then investigated differences potential forests,...

Abstract The quantitative evaluation of the effects bedrock groundwater discharge on spatial variability stream dissolved organic carbon (DOC), inorganic nitrogen (DIN) and phosphorous (DIP) concentrations has still been insufficient. We examined relationships between DOC, DIN DIP contribution to water in forest headwater catchments warm‐humid climate zones. sampled springs at multiple points September December 2013 a 5 km 2 catchment Japan soil layer small hillslopes. assumed that consisted...

Abstract Predicting inter‐catchment groundwater flow (IGF) is essential because IGF greatly affects stream water discharge and chemistry. However, methods for estimating sub‐annual clarifying its mechanisms using minimal data are limited. Thus, we quantified the elucidated driving factors short‐term balance method (STWB) three forest headwater catchments in Japan (named here catchment A, B As). Our previous study chloride mass indicated that annual of A (49.0 ha) can be negligible....

A hydrological process model that takes into account the effects of forest status on water yield is a powerful tool for effective management and resources. Evapotranspiration (ET), is, interception (IC) plus transpiration (TR), uses from resources, thus ET changes resulting practices, mainly thinning, should form submodel use with models. In this study, first we derived monthly TR in coniferous plantation watershed using short-term budget (STWB) method an eight-year record. Next, determined...

Abstract An understanding of nitrogen processes in a paddy field, characterised by large water flux for irrigation and outflows under continuous irrigation, is required to manage adequate inputs outputs. This study identifies the effect flux, especially high infiltration rate, on field irrigation. The developed process model this was applied two fields having different rates (216 106 mm day − 1 average), simulated physicochemical biological ponded water, soil soil, including whole flows as...

Domestic wood production in Japan is low, and more than 60% of the consumed imported. This surprising because two-thirds Japan’s land area covered by forests. The dominant explanations for this low self-sufficiency rate are lack forest road infrastructure small-scale ownership structure. Austria a country that similar topography structure but has high rate. Therefore, previous research compared to Austria. However, these studies did not address basic properties much detail. study uses...

水文・水資源学会創立30周年を記念し，本学会に所属する12人の若手研究者が取り組む水文・水資源学の研究分野の歴史と展望を取りまとめた．本総説では， 現在の若手研究者の研究内容を示すことで水文・水資源学分野の現在のトレンドを理解し，次世代が参照できる形で現在の若手研究者の考える今後の展望と若手研究者としての今後の決意表明を各著者の専門分野に分けて述べる．対象分野は大気・水象から，データ解析，降雨流出，環境水文，農業水利まで多岐にわたり，各研究分野の最新の知見および今後の展望を解説する．最後に，これら複数の研究内容を俯瞰することで得られた応用研究の学術的価値，現地観測と数値解析の関係，人工知能技術の台頭による制御問題の拡大，学際性，研究内容による評価の違い，データ共有の重要性に関する視点をまとめる．