Monitoreo de servicios ecosistémicos en un observatorio de cafetales agroforestales. Recomendaciones para el sector cafetalero

Ocho años de estudio de la ecofisiología del café, a través de experimentación y de modelación y el monitoreo de los servicios del ecosistema (SE) en una gran finca cafetalera en Costa Rica, revelaron varias recomendaciones prácticas para los agricultores y los formuladores de políticas. El sistema de cultivo estudiado dentro de nuestro observatorio colaborativo (Coffee-Flux), corresponde a un sistema agroforestal (SAF) a base de café bajo la sombra de grandes árboles de Erythrina poeppigiana (16% de la cubierta del dosel). Una gran cantidad de SE y limitantes dependen de las propiedades locales del suelo (en este caso Andisoles), especialmente de la erosión/infiltración, el agua/carbono y la capacidad de almacenamiento de nutrientes. Por lo tanto, para la evaluación de SE, el tipo de suelo es crucial. Una densidad adecuada de árboles de sombra (bastante baja aquí por la condición de libre crecimiento), redujo la severidad de las enfermedades de las hojas con la posibilidad de reducir el uso de plaguicidas y fungicidas. Un inventario simple del área basal en el collar de las plantas de café permitió estimar la biomasa subterránea y la edad promedio de la plantación, para juzgar su valor de mercado y decidir cuándo reemplazarla. Las fincas de café probablemente estén mucho más cerca de la neutralidad de C que lo indicado en el protocolo actual de C-neutralidad, que solo considera árboles de sombra, no los cafetos ni el suelo. Se proponen evaluaciones más completas, que ncluyen árboles, café, hojarasca, suelo y raíces en el balance C del SAF. Los árboles de sombra ofrecen muchos SE si se gestionan adecuadamente en el contexto local. En comparación con las condiciones a pleno sol, los árboles de sombra pueden (i) reducir la erosión laminar en un factor de 2; (ii) aumentar la fijación de N y el % de N reciclado en el sistema, reduciendo así los requisitos de fertilizantes; (iii) reducir la severidad de enfermedades de las hojas; (iv) aumentar el secuestro de C; (v) mejorar el microclima y (vi) reducir sustancialmente los efectos del cambio climático. En nuestro estudio de caso, no se encontró ningún efecto negativo sobre el rendimiento del café

Characterizing above- and belowground carbon partitioning in forest trees along an altitudinal gradient using area-based indicators

Characterizing the above- and belowground carbon stocks of ecosystems is vital for a better understanding of the role of vegetation in carbon cycling. Yet studies on forest ecosystems at high altitudes remain scarce. We examined above- and belowground carbon partitioning in trees growing in mixed montane/upper montane forest ecosystems in the French Alps. Field work was performed in three forests along a gradient of both altitude (1400 m, 1700 m, and 2000 m) and altitude-induced species composition (from lower altitude Abies alba and Fagus sylvatica to higher altitude Picea abies and Pinus uncinata). We performed forest inventories and root sampling along soil wall profiles, so that the stand basal area (SBA, in m2 ha-1) and root cross-sectional area (RCSA, in m2 ha-1) were estimated at each altitude. To characterize the carbon allocation trend between the above-and belowground compartments, the ratio of RCSA to SBA was then calculated. We found that both SBA and RCSA of coarse roots (diameter > 2 mm) were significantly different among the three altitudes. No significant difference in RCSA of fine roots (diameter ? 2 mm) was found among altitudes. The ratio of RCSA of fine roots to SBA augmented with increasing elevation, suggesting that forest ecosystems at higher altitudes allocate more carbon from above- to belowground organs. This increased allocation to fine roots would allow trees to scavenge nutrients more efficiently throughout the short growing season. Furthermore, this work highlighted the interest of using easy to measure area-based indicators as proxies of root and stem biomass when investigating carbon partitioning in highly heterogeneous montane/upper montane forests. (Résumé d'auteur

Arabidopsis thaliana High-Affinity Phosphate Transporters Exhibit Multiple Levels of Posttranslational Regulation[C][W]

In Arabidopsis, the PHOSPHATE TRANSPORTER1 (PHT1) family encodes the high affinity phosphate transporters. This analysis revealed multiple steps of regulation in various cell compartments modulating the level of PHT1 proteins present in the plasma membrane in response to the level of inorganic phosphate

Mechanical traits of fine roots as a function of topology and anatomy

Background and Aims Root mechanical traits, including tensile strength (T-r), tensile strain (epsilon(r)) and modulus of elasticity (E-r), are key functional traits that help characterize plant anchorage and the physical contribution of vegetation to landslides and erosion. The variability in these traits is high among tree fine roots and is poorly understood. Here, we explore the variation in root mechanical traits as well as their underlying links with morphological (diameter), architectural (topological order) and anatomical (stele and cortex sizes) traits.Methods We investigated the four tropical tree species Pometia tomentosa, Barringtonia fusicarpa, Baccaurea ramiflora and Pittosporopsis kerrii in Xishuangbanna, Yunnan, China. For each species, we excavated intact, fresh, fine roots and measured mechanical and anatomical traits for each branching order.Key Results Mechanical traits varied enormously among the four species within a narrow range of diameters (<2 mm): <0.1-65 MPa for T-r, 4-1135 MPa for E-r and 0.4-37 % for epsilon(r). Across species, T-r and E-r were strongly correlated with stele area ratio, which was also better correlated with topological order than with root diameter, especially at interspecific levels.Conclusions Root topological order plays an important role in explaining variability in fine-root mechanical traits due to its reflection of root tissue development. Accounting for topological order when measuring fine-root traits therefore leads to greater empirical understanding of plant functions (e.g. anchorage) within and across species

Sensitivity of the landslide model LAPSUS_LS to vegetation and soil parameters

The influence of vegetation on slope stability is well understood at the slope level but scaling up to the catchment level is still a challenge, partially because of a lack of suitable data to validate models. We tested the physical landslide model, LAPSUS_LS, which models slope stability at the catchment scale. LAPSUS_LS combines a hydrological model with a Limit Equilibrium Method model, and calculates the factor of safety of individual cells based on their hydrological and geomorphological characteristics. We tested two types of vegetation on slope stability: (i) coffee monoculture (Coffea arabica) and (ii) a mixed plantation of coffee and deep rooting Erythrina (Erythrina poeppigiana), trees. Using detailed data from Costa Rica, we performed simulations to test the response of LAPSUS_LS to root reinforcement, soil bulk density, transmissivity and depth of shear plane. Furthermore, we modified the model to include biomass surcharge effect in the calculations. Results show that LAPSUS_LS was most sensitive to changes in additional cohesion from roots. When the depth of the shear plane was fixed at 1.0 m, slopeswere not unstable. However, when the shear plane was fixed to 1.5m, the mixed crop of coffee and trees stabilized slopes, but the coffee monoculture was highly unstable, because root reinforcement was low at a depth of 1.5 m. Soil transmissivity had a limited impact on the results compared to bulk density. Biomass surcharge did not have any significant effect on the simulations. In conclusion, LAPSUS_LS responded well to the soil and vegetation input data, and is a suitable candidate for modeling the stability of vegetated slopes at the catchment leve

Soil Bio- and Eco-Engineering : The Use of Vegetation to Improve Slope Stability

The influence of vegetation on slope stability is well understood at the slope level but scaling up to the catchment level is still a challenge, partially because of a lack of suitable data to validate models. We tested the physical landslide model, LAPSUS_LS, which models slope stability at the catchment scale. LAPSUS_LS combines a hydrological model with a Limit Equilibrium Method model, and calculates the factor of safety of individual cells based on their hydrological and geomorphological characteristics. We tested two types of vegetation on slope stability: (i) coffee monoculture (Coffea arabica) and (ii) a mixed plantation of coffee and deep rooting Erythrina (Erythrina poeppigiana) trees. Using soil and root data from Costa Rica, we performed simulations to test the response of LAPSUS_ LS to root reinforcement, soil bulk density, transmissivity, internal friction angle and depth of shear plane. Furthermore, we modified the model to include biomass surcharge effect in the calculations. Results show that LAPSUS_ LS was most sensitive to changes in additional cohesion from roots. When the depth of the shear plane was fixed at 1.0 m, slopes were not unstable. However, when the shear plane was fixed to 1.5 m, the mixed plantation of coffee and trees stabilized slopes, but the coffee monoculture was highly unstable, because root reinforcement was low at a depth of 1.5 m. Soil transmissivity had a limited impact on the results compared to bulk density and internal friction angle. Biomass surcharge did not have any significant effect on the simulations. In conclusion, LAPSUS_ LS responded well to the soil and vegetation input data, and is a suitable candidate for modeling the stability of vegetated slopes at the catchment level

Revealing human impact on natural ecosystems through soil bacterial DNA sampled from an archaeological site

Data supporting the findings of this study are available in the paper and its Supporting Information files. The raw sequencing data are available at GenBank BioProject PRJNA1037340: https://www.ncbi.nlm.nih.gov/bioproject/PRJNA1037340.International audienceHuman activities have affected the surrounding natural ecosystems, including belowground microorganisms, for millennia. Their short‐ and medium‐term effects on the diversity and the composition of soil microbial communities are well‐documented, but their lasting effects remain unknown. When unoccupied for centuries, archaeological sites are appropriate for studying the long‐term effects of past human occupancy on natural ecosystems, including the soil compartment. In this work, the soil chemical and bacterial compositions were compared between the Roman fort of Hegra (Saudi Arabia) abandoned for 1500 years, and a preserved area located at 120 m of the southern wall of the Roman fort where no human occupancy was detected. We show that the four centuries of human occupancy have deeply and lastingly modified both the soil chemical and bacterial compositions inside the Roman fort. We also highlight different bacterial putative functions between the two areas, notably associated with human occupancy. Finally, this work shows that the use of soils from archaeological sites causes little disruption and can bring relevant information, at a large scale, during the initial surveys of archaeological sites

Intra‐ and inter‐specific variation in root mechanical traits for twelve herbaceous plants and their link with the root economics space

International audiencePlant root traits are diverse and variable, and the way in which they interact has consequences for fundamental functions such as anchorage, or services such as soil fixation. Here, we characterize mechanical traits related to anchorage (tensile strength, strain, stiffness and toughness) at both intra- and inter-specific levels and examine how they covary with other traits related to the root economics space. We grew twelve herbaceous species from contrasting taxonomical families in a common garden experiment. For each species, we excavated root systems and measured mechanical, morphological and chemical traits at two locations (proximal versus distal) for two root types (absorptive versus transport roots). At the intraspecific level, transport roots tended to be stronger and tougher than absorptive roots and could extend further before failure, but were as stiff as absorptive roots. Where the root was sampled (proximalversus distal) had a limited effect on any root mechanical trait. The five monocots (Poaceae) had stronger and tougher root material than the seven dicots (Fabaceae, Plantaginaceae and Rosaceae), but there were no differences in stiffness. At the interspecific level, mechanical traits covaried positively and were strongly and positively correlated with specific root length (a trait related to the ‘do-it-yourself ’ soil exploration strategy), and negatively with root diameter (a trait related to the ‘outsourcing’ soil exploration strategy) and root tissue density (a trait related to root lifespan). We demonstrate the important role of species’ taxonomical subgroup (monocot versus dicot) and root type in governing mechanical trait variation at both intra- and inter-specific levels. Our results can be regarded as the first evidence of a link between root mechanical robustness and the root economics space, through a strong association with the ‘do-it-yourself ’ soil exploration strategy