The Experts below are selected from a list of 273 Experts worldwide ranked by ideXlab platform
Mariko Atarashi-andoh - One of the best experts on this subject based on the ideXlab platform.
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137Cs vertical migration in a Deciduous Forest soil following the Fukushima Dai-ichi Nuclear Power Plant accident
Journal of Environmental Radioactivity, 2014Co-Authors: Takahiro Nakanishi, Jun Koarashi, Takeshi Matsunaga, Mariko Atarashi-andohAbstract:The large amount of137Cs deposited on the Forest floor because of the Fukushima Dai-ichi Nuclear Power Plant accident represents a major potential long-term source for mobile137Cs. To investigate137Cs mobility in Forest soils, we investigated the vertical migration of137Cs through seepage water, using a lysimetric method. The study was conducted in a Deciduous Forest soil over a period spanning 2 month to 2y after the Fukushima nuclear accident. Our observations demonstrated that the major part of137Cs in the litter layer moved into the mineral soil within one year after the accident. On the other hand, the topsoil prevented migration of137Cs, and only 2% of137Cs in the leachate from litter and humus layer penetrated below a 10cm depth. The annual migration below a 10cm depth accounted for 0.1% of the total137Cs inventory. Therefore, the migration of137Cs by seepage water comprised only a very small part of the total137Cs inventory in the mineral soil, which was undetectable from the vertical distribution of137Cs in the soil profile. In the present and immediate future, most of the137Cs deposited on the Forest floor will probably remain in the topsoil successively, although a small but certain amount of bioavailable137Cs exists in Forest surface soil. © 2013 Elsevier Ltd.
P C Yang - One of the best experts on this subject based on the ideXlab platform.
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increased carbon sequestration by a boreal Deciduous Forest in years with a warm spring
Geophysical Research Letters, 2000Co-Authors: T A Black, Wenjun Chen, A G Barr, M A Arain, Z Chen, Zoran Nesic, E H Hogg, H H Neumann, P C YangAbstract:A boreal Deciduous Forest in Saskatchewan, Canada, sequestered 144±65, 80±60, 116±35 and 290±50 g C m−2 y−1 in 1994, 1996, 1997 and 1998, respectively. The increased carbon sequestration was the result of a warmer spring and earlier leaf emergence, which significantly increased ecosystem photosynthesis, but had little effect on respiration. The high carbon sequestration in 1998 was coincident with one of the strongest El Nino events of this century, and is considered a significant and unexpected benefit.
Olivia E Clifton - One of the best experts on this subject based on the ideXlab platform.
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interannual variability in ozone removal by a temperate Deciduous Forest
Geophysical Research Letters, 2017Co-Authors: Olivia E Clifton, Arlene M Fiore, J W Munger, S Malyshev, Larry W Horowitz, E Shevliakova, F PaulotAbstract:The ozone (O3) dry depositional sink and its contribution to observed variability in tropospheric O3 are both poorly understood. Distinguishing O3 uptake through plant stomata versus other pathways is relevant for quantifying the O3 influence on carbon and water cycles. We use a decade of O3, carbon, and energy eddy covariance (EC) fluxes at Harvard Forest to investigate interannual variability (IAV) in O3 deposition velocities ( vd,O3). In each month, monthly mean vd,O3 for the highest year is twice that for the lowest. Two independent stomatal conductance estimates, based on either water vapor EC or gross primary productivity, vary little from year to year relative to canopy conductance. We conclude that nonstomatal deposition controls the substantial observed IAV in summertime vd,O3 during the 1990s over this Deciduous Forest. The absence of obvious relationships between meteorology and vd,O3 implies a need for additional long-term, high-quality measurements and further investigation of nonstomatal mechanisms.
Christian Korner - One of the best experts on this subject based on the ideXlab platform.
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water savings in mature Deciduous Forest trees under elevated co2
Global Change Biology, 2007Co-Authors: Sebastian Leuzinger, Christian KornerAbstract:Stomatal conductance of plants exposed to elevated CO2 is often reduced. Whether this leads to water savings in tall Forest-trees under future CO2 concentrations is largely unknown but could have significant implications for climate and hydrology. We used three different sets of measurements (sap flow, soil moisture and canopy temperature) to quantify potential water savings under elevated CO2 in a ca. 35 m tall, ca. 100 years old mixed Deciduous Forest. Part of the Forest canopy was exposed to 540 ppm CO2 during daylight hours using free air CO2 enrichment (FACE) and the Swiss Canopy Crane (SCC). Across species and a wide range of weather conditions, sap flow was reduced by 14% in trees subjected to elevated CO2, yielding ca. 10% reduction in evapotranspiration. This signal is likely to diminish as atmospheric feedback through reduced moistening of the air comes into play at landscape scale. Vapour pressure deficit (VPD)-sap flow response curves show that the CO2 effect is greatest at low VPD, and that sap flow saturation tends to occur at lower VPD in CO2-treated trees. Matching stomatal response data, the CO2 effect was largely produced by Carpinus and Fagus, with Quercus contributing little. In line with these findings, soil moisture at 10 cm depth decreased at a slower rate under high-CO2 trees than under control trees during rainless periods, with a reversal of this trend during prolonged drought when CO2-treated trees take advantage from initial water savings. High-resolution thermal images taken at different heights above the Forest canopy did detect reduced water loss through altered energy balance only at > 5 m distance (0.44 K leaf warming of CO2-treated Fagus trees). Short discontinuations of CO2 supply during morning hours had no measurable canopy temperature effects, most likely because the stomatal effects were small compared with the aerodynamic constraints in these dense, broad-leaved canopies. Hence, on a seasonal basis, these data suggest a >10% reduction in water consumption in this type of Forest when the atmosphere reaches 540% ppm CO2.
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canopy co2 enrichment permits tracing the fate of recently assimilated carbon in a mature Deciduous Forest
New Phytologist, 2006Co-Authors: Sonja G Keel, Rolf T W Siegwolf, Christian KornerAbstract:Summary • How rapidly newly assimilated carbon (C) is invested into recalcitrant structures of Forests, and how closely C pools and fluxes are tied to photosynthesis, is largely unknown. • A crane and a purpose-built free-air CO2 enrichment (FACE) system permitted us to label the canopy of a mature Deciduous Forest with 13C-depleted CO2 for 4 yr and continuously trace the flow of recent C through the Forest without disturbance. Potted C4 grasses in the canopy (‘isometers’) served as a reference for the C-isotope input signal. • After four growing seasons, leaves were completely labelled, while newly formed wood (tree rings) still contained 9% old C. Distinct labels were found in fine roots (38%) and sporocarps of mycorrhizal fungi (62%). Soil particles attached to fine roots contained 9% new C, whereas no measurable signal was detected in bulk soil. Soil-air CO2 consisted of 35% new C, indicating that considerable amounts of assimilates were rapidly returned back to the atmosphere. • These data illustrate a relatively slow dilution of old mobile C pools in trees, but a pronounced allocation of very recent assimilates to C pools of short residence times.
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responses of Deciduous Forest trees to severe drought in central europe
Tree Physiology, 2005Co-Authors: Sebastian Leuzinger, Gerhard Zotz, Roman Asshoff, Christian KornerAbstract:In 2003, Central Europe experienced the warmest summer on record combined with unusually low precipitation. We studied plant water relations and phenology in a 100-year-old mixed Deciduous Forest on a slope (no ground water table) near Basel using the Swiss Canopy Crane (SCC). The drought lasted from early June to mid September. We studied five Deciduous tree species; half of the individuals were exposed to elevated CO2 concentration ([CO2]) (530 ppm) using a free-air, atmospheric CO2-enrichment system. In late July, after the first eight weeks of drought, mean predawn leaf water potential about 30 m above ground was -0.9 MPa across all trees, dropping to a mean of -1.5 MPa in mid-August when the top 1 m of the soil profile had no plant accessible moisture. Mean stomatal conductance and rates of maximum net photosynthesis decreased considerably in mid-August across all species. However, daily peak values of sap flow remained surprisingly constant over the whole period in Quercus petraea (Matt.) Liebl., and decreased to only about half of the early summer maxima in Fagus sylvatica L. and Carpinus betulus L. (stomatal down-regulation of flux). Although we detected no differences in most parameters between CO2-treated and control trees, predawn leaf water potential tended to be less negative in trees exposed to elevated [CO2]. Leaf longevity was greater in 2003 compared with the previous years, but the seasonal increase in stem basal area reached only about 75 data suggest that the investigated tree species, particularly Q. petraea, did not experience severe water stress. However, an increased frequency of such exceptionally dry summers may have a more serious impact than a single event and would give Q. petraea a competitive advantage in the long run.
Adriana Florentino - One of the best experts on this subject based on the ideXlab platform.
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Water flux through a semi-Deciduous Forest grove of the Orinoco savannas
Oecologia, 1995Co-Authors: José J. San José, Ruben A. Montes, Adriana FlorentinoAbstract:Water relations were analysed in a semi-Deciduous Forest grove occurring in the oxisols of the Orinoco savannas. This grove has a shallow unconsolidated ironstone cuirass, which is overlaid by a sandy loam layer (0.0–0.5 m) that contains more than 90% of the grove Forest root phytomass. Evapotranspiration and through drainage were calculated by using data from the soil profile as related to physical characteristics of the site root zone, hydraulic conductivity, volumetric water content and potential hydraulic gradient. Mean annual evapotranspiration was 783 mm year^−1 and annual through drainage below the root zone was 14% (162 mm year^−1) of the gross rainfall. This drainage recharged the 42% of the annual saturation deficit of the water table. Similar mean annual evapotranspiration (770 mm year^−1) was also calculated by using the water balance components. The mean daily coupling omega factor (Ω) between the grove canopy and the surrounding atmosphere indicated that a high degree of coupling (Ω=0.14±0.16) occurs in the grove and evapotranspiration was mainly controlled by surface conductance. As the dry season proceeded, the soil saturation deficit (δθ) increased rapidly resulting in a threshold surface conductance (0.030–0.005 m s^−1) for δθ ranging from 0.05 to 0.10. Hypotheses to explain the omnipresence of perennial species in the wide range of physical conditions in neotropical savannas are discussed.
