Soil organic carbon (SOC) represents a large component of the global carbon cycle, and the SOC pool varies in forest ecosystems depending on species composition, growth stage and management practice. In order to accurately evaluate SOC distribution and dynamics in forests in Hunan Province of China, we reviewed, assembled and analyzed a http: / / www.ecologica.cn comprehensive data package collected from (1) published estimates of SOC contents in various forested soil profiles (a total of 277 soil profiles in the province) in the past 15 years (from 2000 to 2014) , (2) four times of forest inventory data from 1983 to 2009 in Hunan忆s forests, (3) long鄄term field measurements in the Key National Observation Station of Central South University of Forestry and Technology in Huitong County, Hunan Province of China over the past 15 years (2000-2014) and (4) field surveys of 59 soil profiles taken from ten typical forest types in the province during the period of 2008 to 2014. All forests in the province were classified into four categories of timber鄄forests, economic鄄forests, bamboo鄄forests and shrub鄄forests. The timber鄄forests were further divided into eight major forest types based on the species composition of the forest stands. The results showed that the arithmetic average of SOC contents ranged from 9.53 to 22.86 g / kg in the four main forest categories, of which the shrub鄄forests had the highest SOC content. The differences of SOC mainly occurred in the 0-40 cm of soil layer among the studied forest groups. SOC density was in the range of 95.44-181.30 tC / hm 2 in the 0-80 cm soil layer, with an average of 137.15 tC / hm 2 in the examined forests. The differences of SOC density among the forest groups declined with the increase of soil depth, and the effect of forest types on variation of SOC density was gradually weakened with the increasing soil depth. From 1983 to 2009, SOC pool (0-80 cm soil depth) increases in Hunan忆 s timber鄄forests with a net increase of 414.86伊10 6 tC and the area weighted average of SOC density increased 10.98 tC / hm 2 in the studied timber鄄forested soils (0-80 cm soil depth) as well. The difference of SOC pool gradually increased with aged stands of timber鄄forests, mainly occurring in Chinese fir (Cunninghamia lanceolata) forests, Masson Pine (Pinus massoniana) forests and broad鄄leaved forests. Among the forest types, natural forest accounted for a large percentage (>50%) of the total SOC storage in Hunan忆 s forests. But the proportion of SOC in plantation forests increased as the plantation areas gradually increased in the studied province. Economic鄄forests, shrub鄄forests and bamboo鄄forests made different contributions to the total SOC pool (0-80 cm soil depth) in Hunan忆s forests, depending upon planting areas, cultivate systems and management practices. The changes in SOC pool in studied forests were closely associated with the alteration of forested area, convention of forest types and land use changes. These changes in terms of forested area and forest type were related to the fo...
In order to understand the influence of urbanization on distribution of heavy metals in soils, concentrations characteristics of 7 heavy metals (Zn, Cu, Ni, Pb, As, Cd, and Hg) in various forest types were investigated along an urban gradient in Changsha, a capital city of Hunan Province, China. The concentrations and potential ecological risk of heavy metals in the urban soils was assessed when compared to the background values of heavy metals in soils in both Changsha city and Hunan Province. A total nineteen major forest types were selected at three locations (namely urban district location, urban fringe location, and suburban location) along the urban gradient degree in urban forests soil in the Changsha city. Two forest plots (each with the size of 20m 伊 20m) were built in each forest types. Three subplots were (each with an area of 1 m 2) were set up in each of the plots. Five soil samples (from 0-20 cm depth) were randomly taken within each subplot and pooled to a soil sample for heavy metals chemical analysis, 0-20cm soil samples were collected from different urban gradient (urban district, urban fringe, suburban) forest to analyze the concentrations of Zn, Cu, Ni, Pb, As, Cd, and Hg, and the potential ecological hazard assessment indices by Hakanson was used to assess the
Cadmium (Cd) and its compounds are highly toxic to living organisms and are an environmental health hazard. Rice plants usually accumulate more Cd than other crops; therefore, serious concerns have been raised about human health risks resulting from food webs through Cd鄄contaminated rice paddy soils since rice is a staple food source for many Asian countries such as China and India. In hilly regions of southern China, rice plants are often cultivated near forests in a forest鄄 rice agroforestry system, where the forests often occupy the upper parts of the hilly areas and the rice paddy fields are often present in the lower parts and in natural depressions. Although forest鄄rice agroforestry systems have been a typical agricultural model in southern China for many years, the pattern of Cd distribution and cycling and mechanisms controlling its accumulation and transport are still poorly understood in these systems. In this present study, the distribution and dynamic characteristics of Cd were investigated in two types of forest鄄rice agroforestry systems and one rice paddy system (without forests, as a control) in Taoling Forest Farm, Human Province, China from late May to early September in 2012. The concentration and fluxes of Cd in rainfall water, runoff water, pond water, and rice paddy鄄field water were measured.
The Choerospondias axillaries broad鄄leaved community) 设立 1 hm 2 固定样地,对 其群落学特征进行调查,分析其植物多样性和更新动态。 结果表明:群落中胸径逸1cm 的乔木树种共有 25 科 42 属 59 种。 乔 木层中南酸枣(Choerospondias axillaries) 的重要值最大(23.57) ,是群落中的建群种;南酸枣胸径和树高结构均呈正态分布,南酸 枣幼苗(1.0cm臆DBH<1.5cm) 只有 6 株;群落中四川山矾(Symplocos setchuensis) 的重要值(10.46) 排第二,但胸径小于 1.5 cm 的 幼树数量较多(占种群数量的 22.0%) ,格药柃(Eurya muricata) 、千年桐(Aleurites montana) 和毛豹皮樟(Lindera coreana) 的重要 值分别为 7.98(幼树数占种群数量的 16.8%) ,5.39(幼树数占种群数量的 11.7%) ,4.17
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