Plant-topsoil relationships underlying subalpine grassland patchiness

Approximately half of the area in the Spanish Central Pyrenees is dedicated to pastures. A decrease in stocking rate coupled with changes in livestock management in recent decades have favoured the expansion of Nardus grasslands, which are considered undesirable for grazing use and for diversity conservation. The objective of this study was to analyse how topsoil properties are related to grassland plant composition occurring in erosion-disturbed (chalk grasslands) and undisturbed (Nardus mat-grasslands) soils in a subalpine area of the Spanish Central Pyrenees. We selected six paired sampling points for a side-by-side comparison of both communities. At each point, we 1) estimated the plant cover of each species through inventories and 2) analysed a set of physical–chemical topsoil properties (0–5 and 5–10 cm depth). Data were analysed through multivariate analysis. We found typical species of Nardus mat-grasslands in the undisturbed sites growing on non-eroded and well-structured soils that were low in calcium and acidic, with high contents of organic matter. In turn, we found earlier-successional grassland communities growing on slopes recently affected by soil erosion processes. The species composition was mainly species from stony slope grasslands and, to a lesser extent, from the long-term snow-covered environments of the high mountains. These soils were shallower and stonier and had a less-stable structure, higher pH, and lower organic matter and calcium content than undisturbed soils. Our results suggest that the differences between both communities emerge and are maintained by soil–plant feedback mechanisms mediated in Nardus mat-grasslands through soil stabilization and acidification and in chalk grasslands through soil erosion and basification. These findings suggest that the subalpine grassland mosaic results from a model of non-equilibrium plant coexistence due to soil disturbance and inexorable succession. Management should be focused on maintaining a disturbance regime, through grazing, sufficient to prevent the spreading of Nardus mat-grasslands

Immediate effects of prescribed burning on C-related topsoil properties in Central Pyrenees

Prescribed burning, i.e. the deliberate use of fire under specific conditions, is a management tool for recovering pasturelands affected by shrub encroachment. The objective of this work is to determine the immediate effects of prescribed burning on topsoil properties related to C cycle in soils covered with dense scrubs (Echinospartum horridum) in Tella (Huesca, Central Pyrenees, Spain). Soils were sampled in triplicate immediately before and after burning at 0-1 cm, 1-2 cm and 2-3 cm depths. We analysed the content of total oxidizable C (TOC); the content and mineralization rates of labile and recalcitrant C pools C, as inferred from incubation assays (141 days); microbial biomass C (MBC); and the ß-D-glucosidase (GL) activity. All studied soil properties were significantly affected by fire, varying in terms of intensity and affected depth. Fire produced a significant decrease in TOC (-41% on average), similarly affecting the upper 3 cm of soil. The content of labile C decreased considerably (-87% on average) at depths up to 3 cm, but its mineralization rate increased (+ 150% on average). The MBC was particularly affected at 0-1 cm (-53%), while GL activity showed significant decreases throughout the upper 3 cm (-49% on average). These results show a strong impact on the studied soil properties just after burning. Monitoring the evolution of these soils is necessary to assess their resilience in the short and medium terms, and check the sustainability of controlled burning for pasture management in the Pyrenees. Keywords. Pastureland – Controlled fire – Soil organic matter – Soil biological activity – Carbon mineralization. Effets immédiats du brûlage dirigé sur des propriétés du sol superficiel liées au C dans les Pyrénées Centrales Résumé. Le brûlage dirigé est un outil de gestion permettant le rétablissement des pâturages touchés par l'embroussaillement. L'objectif de ce travail est de déterminer les effets immédiats du brûlage dirigé sur les propriétés du sol superficiel liées au cycle du C dans des sols couverts par le genêt hérissé (Echinospartum horridum) à Tella (Huesca, Espagne). Les sols ont été échantillonnés en triple avant et après un brûlage sur 0-1 cm, 1-2 cm et 2-3 cm de profondeur. Nous avons analysé la teneuren C oxydable total sur sol (COT); la teneur etle taux de minéralisation du C labile et récalcitrant, déduit à partir de tests d'incubation (141 jours); le C issu de la biomasse microbienne (CBM); l'activité des ß-D-glucosidase (GL). Toutes les propriétés du sol étudiées ont été significativement affectées par le feu, variant en termes d'intensité et de profondeur affectée. Le feu a produit une diminution significative du COT (-41% en moyenne) et identique dans les premiers 3 cm de sol.Le contenu de C labile a considérablement diminué (-87% en moyenne) jusqu'à 3 cm, mais son taux de minéralisation a augmenté (+ 150% en moyenne). Le CBM a été particulièrement touché sur 0-1 cm (-53%), tandis que l'activité des GL a montré des diminutions significatives sur les premiers 3 cm de sol (-49% en moyenne). Ces résultats montrent un fort impact du brûlage sur les propriétés des sols étudiés. Le suivi de l'évolution de ces sols est nécessaire afin d'évaluer leur capacité de résilience dans les court et moyen termes et de vérifier la viabilité du brûlage dirigé pour la gestion des pâturages dans les Pyrénée

Gestión del conocimiento. Perspectiva multidisciplinaria. Volumen 17

El libro “Gestión del Conocimiento. Perspectiva Multidisciplinaria”, Volumen 17 de la Colección Unión Global, es resultado de investigaciones. Los capítulos del libro, son resultados de investigaciones desarrolladas por sus autores. El libro es una publicación internacional, seriada, continua, arbitrada, de acceso abierto a todas las áreas del conocimiento, orientada a contribuir con procesos de gestión del conocimiento científico, tecnológico y humanístico. Con esta colección, se aspira contribuir con el cultivo, la comprensión, la recopilación y la apropiación social del conocimiento en cuanto a patrimonio intangible de la humanidad, con el propósito de hacer aportes con la transformación de las relaciones socioculturales que sustentan la construcción social de los saberes y su reconocimiento como bien público

Factors affecting CO2 efflux rates and the stability of soil organic carbon storage in volcanic soils of the Canary Islands

Because volcanic soils store large amounts of soil organic carbon (SOC), they play a far more important role in the carbon (C) cycle than their limited global coverage suggests. We analysed the C released as CO2 from a range of volcanic soils under natural conditions and analysed the influence of environmental variables (moisture and temperature), substrate availability (as assessed from the contents of various SOC fractions and the inputs of plant residues from litterfall), respiratory agents (roots, microorganisms and decomposing enzymes) and other pedological features of the topsoils (0-30 cm depth) on the CO2 efflux rates over a 2-year experimental period. High CO2 efflux rates (419 g C-CO2 m(-2) y(-1) as the average for Andisols) were obtained that were related to significant decreases in the amount of SOC stored. CO2 release was strongly controlled by soil moisture, although it was inhibited in the Andisols with the highest moisture levels (above 50 kg m-2 in topsoil). It was not responsive to the availability of decomposing microorganisms or enzymes and appeared more related to the inputs of easily decomposable plant residues than to the amount of either labile or recalcitrant SOC. Among the SOC pools, only the water-soluble C in saturated paste extracts (WSCse) of air-dried soil samples was consistently correlated with the CO2 efflux rates. The desiccation of Andisols appeared to induce the release of previously stabilised SOC, which was readily mineralised when the moisture conditions became favourable. The results of this study indicate that SOC storage in Andisols is highly vulnerable to drying-wetting processes even in unmanaged natural ecosystems and that microclimate conditions can be critical for successful C sequestration in these soils

Composition and dynamics of cutin and suberin biomarkers in plants and soils under agricultural use

Composition and dynamics of cutin and suberin biomarkers in plants and soils under agricultural use. EGU 2017, European Geophysical Union General Assembly 201

Storage and depth distribution of organic carbon in volcanic soils as affected by environmental and pedological factors

International audienceIt has been recognised that volcanic soils, particularly Andosols, can store large amounts of soil organic carbon (SOC). This study investigates the factors controlling the regional and vertical distributions of SOC in soils of volcanic origin. To this aim, we investigated the vertical distribution of SOC in a total of 212 soil profiles representing all combinations of soil-forming factors in a volcanic area with a high diversity of ecosystems and soil types. We analysed the SOC contents in relation to intrinsic (soil type and relevant soil properties: texture and pH) and extrinsic factors (climate, parent material, relief), and we studied the patterns of SOC distribution with depth by fitting the SOC contents to different curve models. Furthermore, we selected ten soil profiles for a more detailed study to assess the effect of vegetation by examining the relationships of the SOC storage and depth distribution to the amount and allocation of plant roots and litterfall. SOC storage was controlled by the interaction of climatic (rainfall), time (substrate age), topographic (slope) and biotic (plant-mediated) factors. Our results indicate that under humid conditions, large organic inputs and the inhibition of microbial degradation due to low pH, AI-toxicity and persistent anaerobiosis within soil microaggregates largely contributed to SOC accumulation. Soil type was a poor predictor of SOC storage, most likely due to the co-occurrence of young and evolved Andosols and a certain andic character in many soils that did not qualify as Andosols. The distributions of root carbon and SOC appeared to be closely interrelated, suggesting a major role of roots in the supply of organic matter and the lack of significant bioturbation. The depth distribution of SOC was best fitted by the quadratic, cubic and power models, the latter being a feasible alternative that should be used to this aim in volcanic soils rather than the widely used exponential model