Temperature sensitivity of soil respiration is dependent on readily decomposable C substrate concentration

International audienceTemperature acclimation of soil organic matter (SOM) decomposition is one of the major uncertainties in predicting soil CO2 efflux by the increase in global mean temperature. A reasonable explanation for an apparent acclimation proposed by Davidson and colleagues (2006) based on Michaelis-Menten kinetics suggests that temperature sensitivity decreases when both maximal activity of respiratory enzymes (Vmax) and half- saturation constant (Ks) cancel each other upon temperature increase. We tested the hypothesis of the canceling effect by the mathematical simulation of the data obtained in the incubation experiments with forest and arable soils. Our data confirm the hypothesis and suggest that concentration of readily decomposable C substrate as glucose equivalent is an important factor controlling temperature sensitivity. The highest temperature sensitivity was observed when C substrate concentration was much lower than Ks. Increase of substrate content to the half-saturation constant resulted in temperature acclimation associated with the canceling effect. Addition of the substrate to the level providing respiration at a maximal rate Vmax leads to the acclimation of the whole microbial community as such. However, growing microbial biomass was more sensitive to the temperature alterations. This study improves our understanding of the instability of temperature sensitivity of soil respiration under field conditions, explaining this phenomenon by changes in concentration of readily decomposable C substrate. It is worth noting that this pattern works regardless of the origin of C substrate: production by SOM decomposition, release into the soil by rhizodeposition, litter fall or drying-rewetting events

Эффективность быстродействующих бронхолитиков при бронхиальной астме у детей

A randomized open study was performed to compare bronchodilating activity of fomroterol (Foradyl) and salbutamol in 48 children aged 5 to 12 yrs with exacerbation of moderate bronchial asthma. The efficacy was evaluated within first 30 min and subsequent 8 to 10 hrs using FVC, FEV1, PEF values and bronchophonographic parameters. Formoterol was found to possess the bronchodilating effect rising equally but keeping longer than that of salbutamol. This fact allows to use formoterol as urgent therapy in mild and moderate bronchial obstruction.Проведено рандомизированное открытое исследование бронхолитической активности формотерола (форадил) в сравнении с сальбутамолом у 48 детей 5-12 лет со среднетяжелой бронхиальной астмой (обострение). Эффективность оценивалась в течение первых 30 мин и последующих 8-10 ч по данным ФЖЕЛ, ОФВ1 ПСВ и показателям бронхофонографии. Показано, что формотерол обладает сходным по быстроте появления бронхолитическим эффектом и более продолжительным, чем у сальбутамола, что позволяет использовать его для неотложной терапии при легких и среднетяжелых проявлениях бронхиальной обструкции

Temperature response of soil respiration is dependent on concentration of readily decomposable C

International audienceTemperature acclimation of soil organic matter (SOM) decomposition is one of the major uncertainties in predicting soil CO2 efflux associated with the increase in global mean temperature. A reasonable explanation for an apparent acclimation proposed by Davidson and colleagues (2006) based on Michaelis-Menten kinetics suggests that temperature sensitivity decreases when both maximal activity of respiratory enzymes (Vmax) and half-saturation constant (Ks) cancel each other upon temperature increase. We tested the hypothesis of the canceling effect by the mathematical simulation of data obtained in incubation experiments with forest and arable soils. Our data support the hypothesis and suggest that concentration of readily decomposable C substrate (as glucose equivalents) and temperature dependent substrate release are the important factors controlling temperature sensitivity of soil respiration. The highest temperature sensitivity of soil respiration was observed when substrate release was temperature dependent and C substrate concentration was much lower than Ks. Increase of substrate content to the half-saturation constant by glucose addition resulted in temperature acclimation associated with the canceling effect. Addition of the substrate to the level providing respiration at a maximal rate Vmax leads to the acclimation of the whole microbial community as such. However, growing microbial biomass was more sensitive to the temperature alterations. This study improves our understanding of the instability of temperature sensitivity of soil respiration under field conditions, attributing this phenomenon to changes in concentration of readily decomposable C substrate

MODELING THE DYNAMICS OF FOREST ECOSYSTEMS TAKING INTO ACCOUNT THEIR STRUCTURAL HETEROGENEITY AT DIFFERENT FUNCTIONAL AND SPATIAL LEVELS

In many problems of modern forest ecology, it is necessary to analyze the conjugated dynamics of processes occurring at different spatio-temporal scales of the functioning of plant communities and soils resulted from their interaction under the influence of all edaphic and anthropogenic factors. Mathematical models can be an efficient tool for such analysis. The aim of this study is to present the implementation of a new system of models that makes it possible to reproduce in simulation experiments the spatial structure of forest phytocenoses formed by tree and grass-shrub layers, as well as associated heterogeneity of soil conditions and the diversity of ecological niches at different hierarchical levels. To determine the required level of detail of the spatial heterogeneity of forest biogeocenoses related to the processes of their multi-scale functioning, experimental studies were carried out on permanent sampling plots in the Prioksko-Terrasny State Natural Biosphere Reserve and in the “Kaluzhskie Zaseki” State Nature Reserve. The spatial structure of communities and related heterogeneity of ecological conditions were studied using traditional soil and geobotanical, as well as modern instrumental methods. The obtained data were used to construct the algorithms and to estimate the parameters of different blocks of the new system of models. The implementation of a spatially-explicit process-based system of models has shown its ability to reproduce the dynamics of forest ecosystems, taking into account the species composition and spatial structure of different layers of vegetation and the associated patchiness of soil conditions. Because of a wide range of interrelated ecosystem characteristics implemented in the system of models it is possible to simulate productivity, biological turnover of C and N, and the dynamics of forest ecosystems, taking into account their characteristic spatial structure at different scales. This makes it possible to improve the understanding of ecosystem processes and their contribution to maintaining the sustainable functioning of forests, which can be used for predictive assessments of the efficiency of forest management techniques and in solving other forestry and environmental problems