The spatial-temporal variations of vegetation cover in Qinba Mountains from 1982-2015 | Author : Li Tian | Abstract | Full Text | Abstract :Vegetation and its distribution are largely controlled by the regional landform (including soils) and the global climate changes. Qingling-Daba (Qinba) Mountains are located in the transitional zone between the subtropical and warm temperate climate in China, with its vegetation very sensitive to the changes in climate. In this study, we quantify the spatiotemporal changing trend of NDVI of the GIMMS-NDVI dataset during1982 and 2015 through linear regression analysis and the trend analysis, with Hurst index (H value) as a measure for the future trends of vegetation. We found that: (1) NDVI increased significantly, with a growth rate of 1.2%/10a. When examined at decadal scale (1980s, 1990s and after 2000), it appeared that changing rate was 3.6%/10a, 1.4%/10a, 1.1%/10a, respectively. For the most recent decade (2006-2015), however, the NDVI decreased at -0.3%/10a. (2) The seasonal variation of vegetation was dominated by an increasing spring NDVI (3%/10a). (3) The spatial variation of NDVI was low on the edge and high in the middle, low in the west and high in the east, low in the south and high in the north. (4) Around 63.48% of the vegetation had improved function, while 1.98% of the vegetation continue being degraded.
Key Words: spatiotemporal variation; vegetation coverage; GIMMS3g NDVI; Qingling-Daba (Qinba) Mountains |
| Structure characteristics and influencing factors of rodent community in Kangbo ranch | Author : Li Tian | Abstract | Full Text | Abstract :The purpose of this study was to understand the structure characteristics of rodent communities in different habitats of Kangbao ranch, and to analyze their influencing factors, so as to provide evidence for rodent control. Using rodent density was monitored by night trapping method from April to July of 2010 to 2013, rodent monitoring was conducted for five habitats including ridger, grass bank, farmland, woodland and wasteland. A total of 146 rodents were captured in this pastoral area, which were identified as belonging to 7 species of 5 genera and 3 families of 1 order, black line hamster and little hairy foot mouse were the dominant species in this area, and the number of rodents captured in the three main habitats of grassland, arable land and woodland accounted for 86.99% of the total rodents.The rodent density of five habitats is: Farmland > woodland > wasteland > ridge.In the grassland, the most diverse and complex community structure was found, and the farmland, woodland and ridge were reduced successively.The rodent community in wasteland has the lowest diversity and the simplest community structure. The result showed the density of rodents in Kangbao ranch was low, and the structure of rodents communities in different habitats was clear. We will continue to strengthen the monitoring of rat densities, classify and classify them, and prevent and control them scientifically, so as to reduce the occurrence and spread of rodent borne diseases.
Keywords: Kangbo ranch; Habitat; Rodent community; Population density; Structural features |
| Comparison of surface energy budgets and feedbacks to microclimate among different vegetation landscape on the Mongolian Plateau | Author : Li Tian | Abstract | Full Text | Abstract :The water and heat exchange between the atmosphere and the land surface plays a very important role. The Leaf area index (LAI), land surface albedo (LSA) and evapotranspiration (ET) which play a fundamental role in understanding many causes and consequences of land surface and climate interactions. However, relative contribution from altered albedo and ET to differences in energy budget in contrasting land use types is unclear in temperate climate zones. In this paper, to quantify the land surface water and heat fluxes arising from spatial patterns of land cover in the present climate, as well as enrich the land surface process field observations in the hinterland of Mongolian Plateau (MP) with rapid changes in vegetation growth by warming climate. Here, we focused on the LAI, albedo, ET and their relationships on the different roofing landscapes (the meadow steppe (MDW), the typical steppe (TPL), the desert steppe (DRT), the shrubland (SHB)). Based on the MODIS products 2000-2016, we found that there existed a significant linear negative correlation between LAI and albedo, but not found correlation between LAI and ET.
Among the four vegetation communities, the normalized annual mean Z-score of LAI and ET all showed increased trend, especially for the TPL (slope = 0.091, p=0.036 for LAI and slope =0.086, p=0.050 for ET). However, for the normalized annual mean
Z-score of albedo, other three landscapes all showed negative change trend, only for TPL, still showed pocitive change trend (slope =0.105, p=0.029). More importantly, the long-term changes in monthly albedo, ET and LAI values had different contributions to the annual values.
Keyword: Land surface albedo, evapotranspiration, leaf area index, land surface process |
| The Spatiotemporal Distribution of PM2.5 and its Relationship to Land-Use Patterns and Special to Land-Use and People in Hangzhou | Author : Li Tian | Abstract | Full Text | Abstract :Assessments have quantified the burden of air pollution at the national scale in China; air quality managers would benefit from assessments that disaggregate health impacts over regions and time. The air quality in Hangzhou City, which is one of the central cities of the Yangtze River Delta Urban Agglomeration, was not in great condition. We used the monitoring sites data and MODIS remote-sensing Aerosol optical thickness (AOT) for the inversion of the PM2.5 concentration map for all four seasons in 2015. Next, we combined the land use data, population density data, and school data (kindergarten, primary school, and middle school) to analyze their correlation; we found that the seasonal variation characteristics of PM2.5 concentration distribution was winter > spring > autumn > summer. For the different land use type in winter and spring, 59.86% and 56.62% land area showed the PM2.5 >50µg/m3, respectively. In autumn, 54.38% of the land area exposure was PM2.5 35~50µg/m3. In summer, the PM2.5 concentration was lowest, at 70.01%, and the land surface area showed PM2.5 <35µg/m3. Increasing the forest landscape performs the function of absorbing and filtering the particulate air pollution, resulting in high PM2.5 concentration at this landscape. It was also discovered that only 9.06% of the population lived in an environment that met the national air quality standards. Specifically, only 1.66% (14,055) of infants and juveniles were living in PM2.5 <35µg/m3. Considering the lag health effects of long-term PM2.5 exposure, it is necessary to track these infants’ and juveniles’ health conditions from now until they enter into adulthood. This should enable us to more effectively eliminate the PM2.5 that is harmful to our health. We firmly believe that not only in Hangzhou, but also spanning all of China, many infants and juveniles live in a severely polluted environment in which we need to pay close attention, as their future health is directly relative to the future prosperity of the country as a whole.
Keywords: PM2.5; spatial and temporal variations; Land surface landscape; infants and juveniles |
| Effects of landscape on the distributions of nutrients and polycyclic aromatic hydrocarbons in an urban river system | Author : Hai-Liang Zhu | Abstract | Full Text | Abstract :Urban river systems have large potentials for determining the fate, distribution, and transport of water contaminants. This study was conducted to investigate the distribution and identify the sources of 16 Environmental Protection Agency priority polycyclic aromatic hydrocarbons with respect to four different urban river landscapes (river channels managed with hard revetment, unmanaged, with wetland construction, and in city park). The significant differences of water nutrient physicochemical indices in the four landscapes were also compared with the general linear model, and their relationship with polycyclic aromatic hydrocarbons were analyzed using principal component analysis. The results showed that the city parks and wetlands may improve the water quality and accelerate degradation of contaminants. Furthermore, the river channels in the park and wetland had lowered proportions of low molecular weight (2, 3-rings) polycyclic aromatic hydrocarbons in the river sediment compared to urban river channels with other two landscapes.
Key words: Jialu River, Polycyclic aromatic hydrocarbons, Wetland, City park |
|
|