RESUMEN
Understanding the determinants of post-fire regeneration is critical for determining an appropriate restoration program following fire disturbances. However, studies addressing the drivers of post-fire regeneration of forests in monsoon climate are rare. This study explored the temporal and spatial variations of post-fire forest regeneration in the Central Yunnan Plateau of Southwest China, and disentangled the direct and indirect effects of the environmental factors via structural equation models (SEMs). We found that the overall post-fire regeneration density was generally greater for the habitat with higher values of elevation, pre-fire abundance, and soil pH. Post-fire regeneration was mainly composed of resprouts; seedlings were less relevant and appeared later. The SEM approach showed more variation of recruitment in resprouting (R2 = 0.66) than seeding (R2 = 0.33), and revealed different direct and indirect pathways. Resprouts were widely distributed, and significantly influenced by pre-fire abundance, elevation, soil pH, and years since the last fire. In contrast, seedlings preferentially occurred in infertile habitats, and were mainly influenced by topographic position and soil nutrients, showing distinct distribution from that of resprouts. Overall, forests under the subtropical monsoon climate in the Central Yunnan Plateau were resilient to fire mainly due to rapid post-fire resprouting. These findings indicate the complementary roles of resprouting and seeding in post- fire regeneration, and help to understand the mechanisms that regulate post-fire plant regeneration in a spatially heterogeneous landscape. Our results should contribute to improving the post-fire management of forest ecosystems under the influence of a semi-humid monsoon climate.
Asunto(s)
Ecosistema , Incendios , China , Demografía , Bosques , ÁrbolesRESUMEN
Post-fire succession is an ideal case for studying effects of disturbance on community assembly, and the key is to disentangle the contributions of assembly processes to the variation of community composition, namely beta diversity, and the contingent scales. The central Yunnan Plateau of Southwest China is characterized by monsoon related seasonal drought, and frequent forest fires. We sampled five fire sites burned in different years and a middle aged forest, measured species composition dissimilarity and its species turnover and nestedness components, within each fire site and across all sites. Results indicated species turnover as the primary component of beta diversity within all communities. There was no trend of change with year-since-fire (YSF) in beta diversity among early post-fire communities, but beta diversity in the middle aged community was significantly higher. Species turnover patterns across fire sites revealed a weak dispersal limit effect, which was stronger at lower than upper slope position for woody plants, and reverse for herbs. At the site scale, the species dissimilarity and turnover both enlarged with increasing slope position difference, especially in the middle-aged community, but the species nestedness had no consistent trend among sites, except a decreasing trend in the middle-aged forest. (Partial) Mantel tests indicated habitat filtering [primarily indicating total nitrogen (TN) and slope position] played a much stronger role than dispersal limit and YSF (indicating competition intensity) for the post-fire forest assembly at the landscape scale, for both woody and herbaceous layers. However, at the site scale, Mantel tests indicated a diminishing effect of soil nutrient filtering with increasing YSF, while effects of topography and spatial distance in the middle aged community was stronger. This divergence suggests the primary assembly mechanism gradually shift away from the soil constraint. While the seasonal drought and the mountain topography dominate the environmental legacy, our results imply that fires may reinforce a priority effect in the forests assembly in this region, by creating a habitat filtering (e.g., moisture and nitrogen limitation) effect on species composition in post-fire communities.
RESUMEN
In this work, bi-functional SiO2-Pt@meso-SiO2 core-shell nanoparticles were designed to prepare a highly sensitive and selective electrochemical zinc(II) aptasensor. This core-shell structure boasts its SiO2 mesoporous shell and the inside Pt nanoparticles. SiO2 mesoporous shell can fix aptamer without affecting its configuration and can admit electrolyte through the shell. SiO2 core inside can be the substrate of larger amount of Pt nanoparticles that improve the conductivity of the modified electrode dramatically. Due to the application of such a special bi-functional structure and the aptamer's strong combination capacity with Zn(2+), Zn(2+) is pre-enriched onto the electrode effectively and specifically, so that it can be determined sensitively and selectively. Results have shown that the zinc(II) aptasensor can be utilized at a wide linear working range from 100 pM to 50 µM and a low detection limit of 65 pM, which makes it practical in both biological samples and environment monitoring. This method has been successfully applied in Zn(2+) monitoring in human blood and disrupted human cells (MCF-7).