RESUMO
Forest gap disturbance has important consequences on plant species assemblage, stand structure and ecosystem functions of forests via changing micro-scale heterogeneity and community succession. Here, we reviwed research progress in the effects of forest gap disturbance on forest ecosystem. The effects of forest gap disturbance on plant species assemblage was analyzed based on the intrinsic biological characteristics and external environmental factors. The effects of forest gap disturbance on stand structure was discussed from the perspectives of texture and architecture of plant community. Forest gap disturbance effect on forest ecosystem functions was reviewed. After analyzing the theoretical shortcomings and the key bottleneck of forest ecosystem management practices, the following research directions were proposed, including the methods of determining threshold of forest gap, the mechanism of canopy closure, the effect of forest gap disturbance on forest ecosystem processes, and the relationship between forest gap disturbance and forest productivity. The advantage of forest gap disturbance in accelerating plant species regeneration and structure complexities could provide scientific evidence for enhancing the quality of low yield and low function plantations in China.
Assuntos
Ecossistema , Florestas , China , ÁrvoresRESUMO
To analyze the genetic diversities and structures of Sassafras tsumu and to explore their changing patterns at five different altitudes, Bioptic Qsep 100 DNA fragment analyzer combined with 13 SSR primers was applied. The results showed that S. tsumu in Tianmushan Mountain had a relatively high genetic diversity, with the expected heterozygosity (He) and observed heterozygosity (Ho) being 0.84 and 0.61, respectively. According to Shannon index (I), the diversity of S. tsumu at middle altitude (500-800 m) was higher than that at low (200 m) and high altitudes (1100-1400 m). The coefficient of genetic differentiation and AMOVA results indicated that the genetic variation of S. tsumu was mainly distributed within populations. UPGMA cluster analysis and STRUCTURE analysis showed that S. tsumu populations at the middle and lower altitudes were similar, but different from that at higher altitude. The differences in genetic distance of S. tsumu populations at middle and low altitudes revealed that human disturbance posed a negative effect on the diversity, whereas, natural reserve played a significant positive role in protecting species diversity.
Assuntos
Altitude , Variação Genética , Genética Populacional , Sassafras/genética , ChinaRESUMO
The sap flow and environmental factors, including temperature, water content and water potential of soil, were continuously measured by using an auto-data collection system at the upper and lower slopes of Toona ciliata var. pubescens plantation in July to October, 2012 to investigate the relationships between the sap flow and environmental factors. The results showed that, the trunk sap flow velocity of the two positions both presented a typical single-peak curve, with high values in the daytime and low values in the nighttime. The average sap flow of the lower slope was significantly higher than that of the upper slope. Soil temperature of the upper slope was significantly higher than that of the lower slope, and soil water content and water potential were vice versa. Soil water content and water potential were the leading environmental factors affecting the trunk sap flow velocity at the lower slope, while soil temperature and water potential were the main environmental factors at the upper slope.