Search

Raphanus sativus L. is a potential source of raw material for biodiesel fuel due to the high oil content in its grains. In Brazil, this species is cultivated in the low rainfall off-season, which limits the productivity of the crop. The present study investigated the effects of water restriction on the physiological and biochemical responses, production components, and oil quality of R. sativus at different development stages. The treatments consisted of 100% water replacement (control), 66%, and 33% of field capacity during the phenological stages of vegetative growth, flowering, and grain filling. We evaluated characteristics of water relations, gas exchange, chlorophyll a fluorescence, chloroplast pigment, proline, and sugar content. The production components and chemical properties of the oil were also determined at the end of the harvest cycle. Drought tolerance of R. sativus was found to be mediated primarily during the vegetative growth stage by changes in photosynthetic metabolism, stability of photochemical efficiency, increased proline concentrations, and maintenance of tissue hydration. Grain filling was most sensitive to water limitation and showed a reduction in yield and oil content. However, the chemical composition of the oil was not altered by the water deficit. Our data suggest that R. sativus is a drought-tolerant species. [ABSTRACT FROM AUTHOR]

Questions: Carbon dynamics in tropical forests is influenced by a variety of biotic and abiotic factors that act over temporal and spatial scales. At the local scale, carbon stock and dynamics can be determined by the environment and ecosystem diversity. Also, during forest regeneration, which is a temporal process, it is expected that those factors that influence carbon also change over time. Here we examine how carbon stock and dynamics are influenced by forest age, environment and functional diversity during forest regeneration. Using the relative effects of the different drivers of carbon dynamics, we attempt to discern the mechanisms (mass effect or niche complementarity) that explain those processes. Location: We carried out this study in Atlantic Forest of different ages during natural regeneration in southern Brazil. Methods: We measured environmental characteristics (soil physical and chemical attributes and canopy openness), estimated functional diversity and above‐ground carbon and its dynamics over time. We examined univariate and multivariate predictors of carbon stock and dynamics using structural equation models. Results: We found that age had the strongest influence on carbon stock, while environmental characteristics, functional and taxonomic diversities were much less important or unimportant. Our results suggest that the influence of time on tropical forest carbon dynamics overlaps and outweighs the effects due to environmental limits and mechanisms mediated by diversity (mass effects, niche complementarity). Conclusions: Natural regeneration can be an effective strategy for restoring carbon sequestration and methods that use manipulation of regenerating forests with the hope of improving the process are unlikely to bring additional advantage in terms of carbon sequestration. [ABSTRACT FROM AUTHOR]

Natural regeneration has been considered an important strategy for improving large-scale forest restoration to revert the losses resulting from the fragmentation of tropical landscapes in recent years. However, local, regional, and spatial factors can influence the dynamics of regeneration, thereby affecting its efficiency. We investigated how time after disturbance, landscape characteristics, and climate gradients affect the efficiency of natural regeneration in the Brazilian Atlantic Forest. We searched for studies that addressed the post-logging regenerating of forests throughout the biome. For each included study, we extracted the forest age, species richness, and basal area (used as an estimate of carbon). Additionally, for each studied site (total 100 sites) we used land use maps to extract the landscape metrics and obtained bioclimatic variables from the global dataset. Further, we used forest age, landscape metrics, and bioclimatic variables to build models and predict forest species richness and carbon stock. Our results showed that species richness was positively affected by habitat amount (evaluated through patch area and perimeter-area ratio), isothermality, and forest age. Carbon stock was positively affected only by the forest age. These findings show that natural regeneration will yield the best results in terms of conserving the biodiversity among landscapes with a large number of habitats. Conversely, a landscape with a predominance of mature forest will be more efficient as carbon stock. We conclude that, when planning the restoration of large-scale landscapes, natural regeneration must be considered along with other strategies to ensure that multiple objectives are achieved. • Greater amount of habitat positively affects the species richness. • Isothermally is an important variable for species richness. • The forest age affects the carbon stock. • Natural regeneration is efficient to recover the diversity and carbon stock. [ABSTRACT FROM AUTHOR]