Responses of Japanese tree species to excessive nitrogen load

国立環境研究所東京農工大学Proceeding : International Symposium of Kanazawa University 21st-Century COE Program Vol.2(2004),Schedule: February 29(SUN)-March 3(WED), Venue: 29 FEB, Ishikawa Life-Long Learning Center(Former Prefectural Government Building) / 1-3 MAR Kanazawa Art Hall, Organized by: Kanazawa University 21st-Century COE Program / Ishikawa International Cooperation Research Centre / United Nations University-Institute of Advanced Studies, Supported by: Ishikawa Prefectural Government / City of Kanazawa, Eds : Hayakawa, Kazuichi / Kizu, Ryoichi / Kamata, Naok

Limitation in the Photosynthetic Acclimation to High Temperature in Canopy Leaves of Quercus serrata

As temperature dependence in many biological processes is generally a bell-shaped curve, warming may be benefitial at cooler climate but deterimental at warmer climate. Although warming responses are expected to vary between different temperature regimes even in the same species, such variations are poorly understood. We established open-top canopy chambers, in which average daytime leaf temperature was increased by ca. 1.0°C, at the canopy top of Quercus serrata in a deciduous forest in high (HL) and low (LL) latitude sites and studied temperature dependence of photosynthesis in the leaves across seasons. In control leaves, photosynthetic rates were higher in LL than in HL. Reponse to warming was different between HL and LL; an increase in growth temperature increased photosynthetic rates at higher leaf temperatures in HL but decreased in LL. Lower photosynthetic rate in the warming treatment in LL was partly explained by lower leaf mass per area and leaf nitrogen content per unit leaf area. Optimal temperature that maximizes photosynthetic rate (Topt) linearly increased with increasing growth temperature (GT) in HL, whereas it was saturating against GT in LL, suggesting that Topt in Q. serrata has an upper limit. The variation in Topt was explained by the activation energy of the maximum carboxylation rate (EaV). Our results suggest an upper limit in temperature acclimation of photosynthesis, which may be one of the determinants of southern limitation of the distribution

Interpreting canopy development and physiology using the EUROPhen camera network at flux sites

Peer reviewe

Assessment of canopy photosynthetic capacity and estimation of GPP by using spectral vegetation indices and the light–response function in a larch forest

Integration of CO2 flux observations with remote sensing technique and ecosystem modeling is expected to be useful for estimation of gross primary production (GPP). We focused on the changes in the two main parameters for the canopy-scale light-response curve-Pmax (maximum GPP at light saturation) and φ (initial slope)-as indicators to represent canopy photosynthetic capacity. We hypothesized that Pmax and φ could be evaluated by using spectral reflectance related to the changes in the levels of canopy nitrogen and chlorophyll. We analyzed the relationships between Pmax and φ, derived from tower-based CO2 flux observations, and ground-based spectral vegetation indices (VIs) in a temperate deciduous coniferous forest. The canopy-scale Pmax and φ showed clear seasonal changes accompanying phenological stages. Both the variations in Pmax and φ were strongly correlated with VIs, especially with the ratio vegetation index (RVI) and enhanced vegetation index (EVI), independent of the growth stages. Moreover, day-to-day short-term variations of Pmax and φ were affected by meteorological conditions such as vapor pressure deficit (VPD) and relative solar radiation which was calculated as the ratio of monitored radiation per theoretical maximum radiation. Thus, seasonal changes of Pmax and φ were effectively assessed by RVI or EVI, and their short-term variations were evaluated by the empirical relationships with VPD and relative solar radiation. We propose a new simple method for estimating GPP with good precision; by fitting the light-response function with the evaluated parameters, the estimated GPP reflects 3 types of temporal variation: diurnal, day-to-day, and seasonal

Impact of elevated CO2 on root traits of a sapling community of three birches and an oak : a free-air-CO2 enrichment (FACE) in northern Japan

We evaluated the root response to elevated CO2 fumigation of 3 birches (Betula sp.) and 1 deciduous oak (Quercus sp.) grown in immature volcanic ash soil (VA) or brown forest soil (BF). VA is a nutrient-poor, phosphorus-impoverished soil, broadly distributed in northern Japan. Each species had been exposed to either ambient (375-395 mu mol mol(-1)) (aCO(2)) or elevated (500 mu mol mol(-1)) (eCO(2)) CO2 during the daytime (more than 70 mu mol m(-2) s(-1)) over 4 growing seasons. The results suggest that eCO(2) did not cause an increase in total root production when the community had grown in fertile BF soil, however, it did cause a large increase when the community was grown in infertile VA soil. Yet, carbon allocation to plant roots was not affected by eCO(2) in either the BF or VA soils. Rhizo-morphogenesis appeared to occur to a greater extent under eCO(2). It seems that the saplings developed a massive amount of fine roots under the VA and eCO(2) conditions. Unexpectedly, eCO(2) resulted in a larger total root mass when the community was grown in VA soil than when grown in BF soil (eCO(2) x VA vs. eCO(2) x BF). These results may hint to a site-specific potential of communities to sequester future atmospheric carbon. The growing substance of plants is an important factor which root response to eCO(2) depends on, however, further studies are needed for a better understanding