Use of multi-temporal Landsat images for analyzing forest transition in relation to socioeconomic factors and the environment

Recently there have been reports of forest regrowth occurring in different regions across the world. There is also a growing recognition of the potential beneficial impact that secondary forests may have on the global environment: providing crucial ecosystem services such as soil conservation, stabilization of hydrological cycles, carbon sequestration, and support for forest dependent communities. Consequently, there is a growing awareness of the need to recognize that landscapes are complex shifting mosaics wherein forest clearing and reforestation take place. In this study, the rates of reforestation, deforestation, forest regrowth and degradation were measured using multi-temporal Landsat images of Danjiangkou, China. Landsat data from 1990, 1999 and 2007 were (1) classified as dense forest, open forest and non-forest areas and (2) compared between years to identify forest cutting, regeneration and degradation. The results showed that there was a net gain of 29,315 ha of forest area (including dense and open forest) from 1990 to 2007, showing a clear trend of reforestation in the study area. Forest modification (degradation and regrowth) and change categories (deforestation and reforestation) occurred simultaneously during the observation time period. Socioeconomic data from public statistics and environmental attributes allowed the assessment of the socioeconomic factors and the environmental conditions that caused these changes using non-metric multidimensional scaling (NMDS). The research showed that the socioeconomic factors due to different policies were major driving forces of forest transition, whereas environmental attributes of the underlying landscape constrained forest cover changes. These findings have led to a better understanding of forest transition at a local scale in our study region. Comprehensive knowledge of these relationships may be useful to reconstruct past forest transitions and predict future changes, and may help to enhance sustainable management practices aimed at preserving essential ecological functions.     

川西高原红原机场建设气象条件可行性分析

在为川西高原红原机场气候论证观测取得连续一年多资料的基础上,结合相邻的红原县、阿坝县气象站30年整编气候资料,利用山地气候推算分析方法,对机场场址的气候资料进行推算分析,根据推算的气候资料结合实际观测资料,对机场建设可能产生影响的气象要素进行分析评估,形成了可行性综合论证报告。本研究为红原机场工程建设提供了气象科学依据,取得了良好的社会效益和经济效益。     

四川东部和重庆西部一次ＭＣＣ致洪暴雨过程综合分析

吕梁山区出现局地大暴雨为小概率事件,在县局的订正预报中有很大的难度。2010年8月11日位于吕梁市东北端的岚县出现了106．2mm的大暴雨,而吕梁的其它县、市只出现中雨以下量级降水。本文分析了造成本次强降雨的高低空环流形势、主要影响系统、水汽条件、云图与雷达回波资料以及本县特殊的地形特征等结果表明：本次局地大暴雨天气是由高空短波槽、中层切变线、副热带高压边缘西南暖湿气流共同作用产生的;对流层低层强盛的偏南气流为大暴雨提供了源源不断的水汽;地面弱低压加强了辐合上升运动,特殊地形的抬升与阻挡作用,使强回波雨团长时间在迎风坡下的平坦地段停留,从而造成局地性的强降水。     

A study of partitioning Q vector on background conditions of a torrential rainfall over Shanghai, China on 25 August 2008

A rainfall that occurred during 0200–1400 Beijing Standard Time(BST)25 August 2008 shows the rapid development of a convective system,a short life span,and a record rate of 117.5 mm h-1for Xujiahui station since 1872.To study this torrential rainfall process,the partitioning method of Q vector is developed,in which a moist Q vector is first separated into a dry ageostrophic Q vector(DQ)and a diabatic-heating component.The dry ageostrophic Q vector is further partitioned along isothermal lines in the natural...     

2011年龙眼挂果率高的气象成因分析

通过对2010／2011年度玉林市龙眼秋梢抽生期一开花着果期的农业气象条件进行诊断分析,得出2011年挂果率高的主要原因是：2010年8-9月份的光温水条件配合较好对秋梢抽生相当有利,紧接着从10月份开始出现了秋、冬、春三季连旱,冬季和早春的气候也比较寒冷,在干旱和寒冷的双重作用下,非常有利于控制冬梢和促进花芽分化,也...     

寿山石的成矿地质条件和矿物组成

长期研究表明,寿山石的成矿地质条件主要受地层、构造、火山机构和火山成矿等综合作用控制。寿山石的矿物成分主要为地开石、高岭石和叶蜡石。因寿山石的成矿地质条件、矿物组成和产出部位的不同,形成色彩绚丽、命名异样、品种繁多、分类殊异。但通常以其成因、产状和历史传统分为田坑石、山坑石和水坑石三类。为便于识别、研究和讨论,将寿山石的主要品种及其特征一并简介。     

Zooplankton succession during extraordinary drought–flood cycles: A case study in a South American floodplain lake

We examined the zooplankton abundance and composition of Laguna Grande, a floodplain wetland of the Lower Paraná Basin (Argentina), during an extraordinary drought–flood cycle that affected both the environment and the biological conditions of the lake. Low waters were characterised by remarkably high conductivities and pH values, and high phytoplankton and bacterioplankton abundances with cyanobacterial blooms, while high waters showed opposite features. In relation to zooplankton, the mean abundances of all the taxonomic groups (rotifers, cladocerans, copepods, ciliates, and heterotrophic nanoflagellates) were slightly higher at low waters. Major changes were observed in the specific composition of metazooplankton: the euryhaline species assemblage that dominated in the dry warm period was replaced by several oligohaline littoral and planktonic species characteristic of the Paraná River Basin, when the water level rose. Mean species richness values at high waters doubled those of low waters and were directly correlated to water depth. Most of the rotifers of the genus Brachionus and the cladoceran Moina micrura switched from parthenogenetic to sexual reproduction during low waters, as a response to a harsh environment and crowding. We suggest that the main changes in the environmental conditions in this eutrophic floodplain lake are driven by the hydrology, which regulates the zooplankton succession. The herein described shifts in the zooplankton structure and dynamics of Laguna Grande over an extraordinary drought–flood cycle contribute to the understanding of the processes that might occur under the scenarios predicted by climate change models.     

Distribution of n-alkanes in lacustrine sediments from subtropical lake in Brazil

The geochemical composition of lake bed sediments of a tropical reservoir in Brazil have been investigated. The C, N, P composition showed almost no variation between the different sampling points. All samples contained inorganic phosphorus (IP) ranging from 52 to 70%. The Redfield ratios show that the lake is without significant anthropogenic inputs. Most of the organic matter is composed by higher plants decomposition revealed in the total organic carbon (TOC):nitrogen (N) ratio ranging from 15.4 to 57.2. Also, TOC:organic phosphorus (OP) ranged from 265.3 to 933.6, suggesting that most of the organic matter has terrestrial origin from wood plants. The ratios suggest that most organic matter is influenced by the terrestrial characteristics of the watershed. Furthermore, the relative abundance of n-alkane homologues in the sediments was investigated. All samples have been analyzed for the n-alkanes C₈ to C₄₀. The sediments were dominated by n-alkanes C₂₅–C₃₈. It is concluded that n-alkane in sediments mainly come from terrestrial plants, however there is a contribution of submerged aquatic plants, especially in those sites in deeper areas of the lake. On the basis of P_aq index the n-alkanes in sediments comes from terrestrial plants, however there is a contribution from emerged/floating plants.The investigated lake seems to be considered as meso to eutrophic. Because of the relatively high primary productivity in the lakes, there is a substantial organic-matter flux to the sediments, which rapidly becomes anoxic. According to the pristine/phytane ratio the sediments represent an anoxic environment with values found between 0.38 and 1.72.     

塔南凹陷岩性油藏成藏条件与4种成藏模式

本文分析了塔南凹陷岩性油藏的成藏条件,结果表明,开阔的复式箕状断陷结构使塔南凹陷形成了多凸多凹、凹隆相间的构造格局,为岩性油藏的形成创造了有利的空间;南屯组多沉积中心发育的优质烃源岩为岩性油藏发育提供了物质基础;同沉积断裂及其配置关系决定了塔南凹陷具有沟谷控源、转换带控扇、断坡控砂的成盆特点,水下扇中扇,三角洲前缘和远...     

四川九龙县溪谷输变电工程场地稳定性的岩体力学分析

溪谷输变电站工程场地具有较复杂的双层地质结构.岩土体拉分变形明显.场地后缘及底部岩土体的主应力和剪应力集中明显,堆积体内部岩体处于拉分松弛状态.岩土体的潜在变形模式以蠕滑-拉裂为主.在水库蓄水与地震共同作用的极限工况下.场地处于潜在不稳定状态.