Permafrost regime affects the nutritional status and productivity of larches in Central Siberia

Вечная мерзлота оказывает сильное влияние на развитие лесов благодаря доступности питательных веществ. Основные вопросы этого исследования касались влияния условий площадки на концентрацию макроэлементов в массе и стабильную изотопную (13C и 15N) динамику в течение вегетационного периода, а также стехиометрию питательных веществ и эффективность резорбции в листве двух общих видов лиственницы в Сибири. Концентрация личинок, выращенных на многолетнемерзлых почвах лиственных пород (N, P и K), была чрезвычайно высокой в юных иглах по сравнению с концентрациями в зоне без вечной мерзлоты, но была в 2 раза ниже с созреванием игл. В пределах вечной мерзлоты деревья с участков с более теплым и более глубоким почвенным активным слоем имели концентрацию питательных веществ на 15-60% и более высокую 15N в их иглах по сравнению с более слабыми, более холодными почвами. Лиственница без вечной мерзлоты демонстрировала обогащение листвой в 15N (от +1,4 до +2,4 ‰) по сравнению с вечной мерзлотой (от -2,0 до -6,9 ‰). Сезонная динамика листьев d13C, как правило, снижалась с июня по август на всех участках, положительно коррелируя с массовыми концентрациями N (r = 0,69, p <0,05) и отрицательно с отношением C: N (r = -0,79, p <0,05) , При старении концентрация питательных веществ в иглах лиственницы значительно уменьшилась на 60-90%. Эта сильная способность лиственницы сохранять питательные вещества посредством резорбции является важным механизмом, который поддерживает рост деревьев в начале вегетационного периода, когда почва остается замороженной. Высокая резорбтивная эффективность, обнаруженная для K и P для лиственниц, установленных на вечной мерзлоте, указывает на ограничение питательных веществ роста деревьев в Центрально-Сибирском плато не только по N, как сообщалось ранее, но и по P и K. Наряду с увеличением биомассы (до 50 раз ), более высокие концентрации питательных веществ и обогащение листьев 15N в более теплых местах указывают на сильную реакцию производительности лиственницы на углубление активного слоя почвы

Stable Cu Isotope Ratios Show Changes in Cu Uptake and Transport Mechanisms in Vitis vinifera Due to High Cu Exposure

International audienceEven though copper (Cu) is an essential plant nutrient, it can become toxic under certain conditions. Toxic effects do not only depend on soil Cu content, but also on environmental and physiological factors, that are not well understood. In this study, the mechanisms of Cu bioavailability and the homeostasis of Vitis vinifera L. cv. Tannat were investigated under controlled conditions, using stable Cu isotope analysis. We measured Cu concentrations and δ 65 Cu isotope ratios in soils, soil solutions, roots, and leaves of grapevine plants grown on six different vineyard soils, in a 16-week greenhouse experiment. The mobility of Cu in the soil solutions was controlled by the solubility of soil organic matter. No direct relationship between Cu contents in soils or soil solutions and Cu contents in roots could be established, indicating a partly homeostatic control of Cu uptake. Isotope fractionation between soil solutions and roots shifted from light to heavy with increasing Cu exposure, in line with a shift from active to passive uptake. Passive uptake appears to exceed active uptake for soil solution concentrations higher than 270 µg L −1. Isotope fractionation between roots and leaves was increasingly negative with increasing root Cu contents, even though the leaf Cu contents did not differ significantly. Our results suggest that Cu isotope analysis is a sensitive tool to monitor differences in Cu uptake and translocation pathways even before differences in tissue contents can be observed

Persisting impact of historical mining activity to metal (Pb, Zn, Cd, Tl, Hg) and metalloid (As, Sb) enrichment in sediments of the Gardon River, Southern France

In this study, we assessed past and present influence of ancient mining activity on metal(loid) enrichment in sediments of a former mining watershed (Gardon River, SE France), that is now industrialized and urbanized. A sedimentary archive and current sediments were characterized combining geochemical analyses, zinc isotopic analyses and sequential extractions. The archive was used to establish local geochemical background and recorded (i) increasing enrichment factors (EFs) for Pb, Zn, Cd, Tl, Hg, As and Sb throughout the industrial era, (ii) a contamination peak in 1976 attributed to a tailings dam failure, and (iii) current levels in 2002 and 2011 similar to those of 1969, except for Sb and Hg, reflecting a persisting contamination pattern. Inter-element relationships and spatial distribution of EF values of current sediments throughout the watershed suggested that both ancient and current contamination had a common origin for Pb, Zn, Cd, Tl and As related to the exploitation of Pb/Zn mineralization while old Sb mines and coal extraction area were the main sources for Sb and Hg respectively. This prevailing mining origin was reflected for Zn by a relatively uniform isotopic composition at δ66Zn = 0.23 ± 0.03‰, although slight decrease from 0.23‰ to 0.18‰ was recorded from upstream to downstream sites along the river course in relation with the contribution of the lighter δ66Zn signature (~ 0.08‰) of acid mine drainage impacted tributaries. Results from sequential extractions revealed that the potential mobility of the studied metal(loid)s varied in the order Sb < Tl ≈ As < Zn < Pb < Cd, with an increase of the mobile pool for Cd, Pb, Zn and to a lesser extent for As and Tl associated to increased enrichment. Altogether, these results tend to demonstrate that ancient mining activity still contributes to metal enrichment in the sediments of the Gardon River and that some of these metals may be mobilized toward the water compartment

Antimony isotopic composition in river waters affected by ancient mining activity

International audienc

Numerical investigation of evapotranspiration processes in a forested watershed of Central Siberia

International audienceEvapotranspiration has a major control on continental surfaces dynamics in forested boreal environments. For example, it has strong impacts on active layer thickness, mainly because of its effect on water content within the upper layers of the soil column. These are complex processes, depending not only on climate forcings (atmospheric water demand) but also on physical, geo-pedological and biological properties of the considered areas. Here we propose a numerical investigation of evapotranspiration processes in the active layer of slopes of a forested watershed in Central Siberia. The effect on actual evapotranspiration of the spatial contrasts in terms of exposure, root layer thickness and tree stand density within the watershed are simulated using a recently developed high performance computing cryohydrogeological model, permaFoam