安徽省农民“退宅进城入镇”的实践与成效——以天长市铜城镇为例

天长市铜城镇根据当地工业基础较好、农村"空巢户"较多、农民进城入镇的愿望较强烈的现状,通过调查研究,在集中民意的基础上规范操作,开展试点,循序渐进,创造条件,引导农民"退宅进城入镇",并积极引导农村土地流转,解除"退宅进城入镇"农民的后顾之忧。通过开展"退宅进城入镇"工作,为开发土地资源,增加经济效益,促进农地规范流转及农业现代化发展,助推城镇化进程,提高居民的生活质量探索了新道路。     

贡嘎山海螺沟冰川退缩区土壤序列矿物组成变化

阐明土壤中矿物随时间变化的机制是理解矿物风化和土壤发育的基础。利用X射线衍射法对贡嘎山海螺沟冰川退缩区土壤矿物组成随成土作用时间变化进行了定量分析。结果表明,冰川退缩区成土母质的矿物组成同质性较高,以硅酸盐矿物为主(约90%),包括:斜长石(28.5%)、石英(24.5%)、黑云母、钾长石、普通辉石、角闪石、绿泥石、蛭石;并有少量碳酸盐矿物,如方解石(8%)、白云石(2.3%);以及磷酸盐矿物磷灰石(2.1%)。退缩区土壤的矿物组成总体呈新发育土壤特征,随着成土年龄的增加,方解石逐渐被风化成为草酸钙石,角闪石、黑云母、磷灰石和绿泥石含量逐渐降低,长英质矿物的相对含量有所增加。成土作用中矿物组成的变化受植被原生演替和土壤p H的影响,快速发育的植被导致土壤p H迅速降低,风化程度增强。     

Picking a tree: habitat use by the tree agama,Acanthocercus atricollis atricollis,in South Africa

We studied tree agama (Acanthocercus a. atricollis) habitat use in the Magaliesberg mountain range in northern South Africa using sightings of marked individuals, and in a few cases, radio-telemetry. Acanthocercus a. atricollis preferentially selected thorn trees (46%; Acacia karroo), followed by common sugarbush (10%; Protea caffra) and dead trees (9%). The type of tree selected was unrelated to lizard age class or sex. Multivariate analysis failed to show any age class or sex effects for specific tree physical characteristics, but did reveal a preference for trees with greater diameter, canopy cover and incidence of parasitic plants. We suggest that more ‘complex’ trees may enhance crypsis, facilitate escape from predation, or provide a foraging advantage. Acanthocercus a. atricollis selected night-time perches higher than those used during the day, possibly further offsetting predation risk.     

黄土坡面细沟沟头溯源侵蚀的量化研究

沟头溯源侵蚀占坡面细沟侵蚀量的60%以上。该文运用立体摄影测量技术和人工模拟径流冲刷的方法,研究不同流量和坡度下沟头溯源侵蚀过程及其产沙特征,探讨沟头下切造成的地表形态变化对坡面产沙的影响。结果表明:1)坡面产沙率和沟头溯源侵蚀速率随流量和坡度的增加而增大。流量每增加1 L/min,产沙率增加0.59~5.34倍;坡度从15°增加到20°,产沙率增加14.0%~89.7%。2)当流量小于或等于2 L/min时,产沙率在试验初期增加较快,而后缓慢上升;当流量大于2 L/min时,产沙率始终保持快速上升趋势,沟头溯源长度达到100 cm所需时间较流量为1 L/min时缩短12 min以上。3)坡度对沟头溯源侵蚀速率的影响随流量的增加逐渐减弱。4)细沟长度随时间的变化受流量和坡度的影响,其值可由线性增函数表达;产沙率受沟头溯源侵蚀速率、沟头跌坎高度和沟头下方沟槽内发育的二级沟头数影响,其值可由多元非线性回归方程表示。研究结果可为沟头溯源侵蚀预报模型建立和坡面水土保持措施布设提供理论依据。     

1988-2013年布加岗日地区冰川变化及其对气候变化的响应

基于Landsat TM/ETM+/OLI遥感影像,采用比值阈值和目视解译相结合的方法提取分析了唐古拉山东段布加岗日地区近25 a来冰川现状及其变化,对比研究了四个时段的冰川变化特征及其对气候变化的响应。结果表明:1988—2013年研究区冰川退缩比较严重,面积退缩34.25 km²,占1988年冰川面积的18.67%,且不同时段冰川退缩速率不同,1988—1994—1999—2006—2013年冰川退缩表现为:慢—最快—中等—快的特点,冰储量预测减少15.38%。夏季气温升高很可能是造成冰川加速退缩的主因,冰川变化对气候变化的响应更好地体现在长时段的气候变化上,而短时段气候变化对冰川总体变化趋势有一定的作用,这是造成各个时段冰川变化差异性的原因。研究区北坡冰川退缩明显快于南坡,这种变化的差异性一方面可能是由研究区季风气候特征和水汽来源对不同朝向冰川的影响造成的,另一方面也受冰川发育规模、分布海拔的影响。     

Medium-term gully headcut retreat rates in Southeast Spain determined from aerial photographs and ground measurements

This paper deals with gully retreat rates at different time scales, whereby the short-term time scale may span a time interval of 1–5 years, the medium-term time scale a time interval of 5–50 years, and the long-term time scale a time interval of more than 50 years. An analysis of high-altitude aerial photographs in combination with ground measurements allowed us to quantify volumetric gully-head retreat rates for 12 permanent gullies in Southeast Spain (Guadalentin and Guadix study areas) over a 40–43 year time interval (medium-term time scale). This resulted in an average retreat rate (V_e) of 17.4 m³ year⁻¹. A power relationship between drainage-basin area (A) and medium-term volumetric gully-head retreat rate, V_e=0.069A^0.380 (R²=0.51, n=21), was found by combining the gully-head retreat rates obtained in this study with those obtained by a dendrochronological method. The exponent (b) and the coefficient of determination (R²) of the power relationships V_e=aA^b increases from the short-term to the long-term time scale, expressing the increasing importance of drainage-basin area in gully development with time. Considerable differences between gully-head retreat rates measured at the short and medium-term time scales at individual gullies showed the importance of land-use changes and unsuccessful management practices on gully-head retreat, and the episodic nature of gully-head retreat when piping and tension cracking are involved. Higher gully-head retreat rates are obtained at the medium-term time scale compared to the short-term time scale but the differences are not significantly different at α=10%. The medium-term methods tend to measure proportionally more high gully retreat rates, but less extreme values compared to the short-term method. This is explained by a more equal distribution of extreme rainfall events both in space and time at a longer-term time scale, and hence a higher probability of measuring the average effect of both small and extreme rainfall events at each gully.     

Effect of topography on the changes of Urumqi Glacier No. 1 in the Chinese Tianshan Mountains

Topography plays an important role in determining the glacier changes. However, topography has often been oversimplified in the studies of the glacier changes. No systematic studies have been conducted to evaluate the relationship between the glacier changes and topographic features. The present study provided a detailed insight into the changes in the two branches (east branch and west branch) of Urumqi Glacier No. 1 in the Chinese Tianshan Mountains since 1993 and systematically discussed the effect of topography on the glacier parameters. This study analyzed comprehensive recently observed data (from 1992/1993 to 2018/2019), including mass balance, ice thickness, surface elevation, ice velocity, terminus, and area, and then determined the differences in the changes of the two branches and explored the effect of topography on the glacier changes. We also applied a topographic solar radiation model to analyze the influence of topography on the incoming shortwave radiation (SW_in) across the entire glacier, focusing on the difference in the SW_in between the two branches. The glacier mass balance of the east branch was more negative than that of the west branch from 1992/1993 to 2018/2019, and this was mainly attributed to the lower average altitude of the east branch. Compared with the west branch, the decrease rate of the ice velocity was lower in the east branch owing to its relatively increased slope. The narrow shape of the west branch and its southeast aspect in the earlier period resulted in a larger glacier terminus retreat of the west branch. The spatial variability of the SW_in across the glacier surface became much larger as altitude increased. The SW_in received by the east branch was slightly larger than that received by the west branch, and the northern aspect could receive more SW_in, leading to glacier melting. In the future, the difference of the glacier changes between the two branches will continue to exist due to their topographic differences. This work is fundamental to understanding how topographic features affect the glacier changes, and provides information for building different types of relationship between the glacier area and ice volume to promote further studies on the basin-scale glacier classification.     

Heavy metal contamination of urban topsoil in a petrochemical industrial city in Xinjiang,China

Heavy metal pollution is a widespread phenomenon in many countries of the world.In this study,we conducted a field investigation to assess the status of heavy metal pollution in urban soils of Dushanzi,a district of Karamay city in Xinjiang,China.A total of 56 soil samples in the topsoil layer of 0–15 cm were collected within the urban area and seven elements(Cu,Zn,Cd,Pb,Cr,As and Ni) were analyzed.The mean concentrations of these metals were all higher than their corresponding background values of soils in Xinjiang.We used the pollution index and ecological risk index to assess the degree of heavy metal pollution and the potential ecological risk of urban soils.The pollution index values of Cu,Zn,Cd,Pb,Cr,As and Ni were 1.81,1.35,4.64,1.27,1.80,1.39 and 1.22,respectively;and the potential ecological risk index values for them were 12.03,1.79,185.05,8.39,4.78,18.44 and 1.79,respectively.These results indicated that urban soils in Dushanzi were polluted by heavy metals to some extent and demonstrated a high ecological risk,as influenced by industrial activities.Cd was the key element for the metal pollution of urban soils in the study area.Correlation analyses,principal component analysis coupled with the spatial distribution maps of element concentrations further revealed that heavy metal pollution of urban soils can be mainly attributed to petrochemical industry,coal chemical industry,traffic and commercial activities.     

沦落 退却与回归——女性主义视野下的《黑暗前的夏天》

《黑暗前的夏天》是多丽丝.莱辛对于女性命运的又一次关注。小说以主人公凯特四个多月的夏日旅程为主线展开,这次旅程既是一次实际的旅程,也是一次心理的旅程。本文从女性主义的视角阐释凯特在这一心理旅程中的沦落、退却以及最后的回归。这一艰难的旅程正是试图寻找自我的女性的必经之旅。     

Changes in soil properties and erodibility of gully heads induced by vegetation restoration on the Loess Plateau,China

Soil erosion on the Loess Plateau of China is effectively controlled due to the implementation of several ecological restoration projects that improve soil properties and reduce soil erodibility. However, few studies have examined the effects of vegetation restoration on soil properties and erodibility of gully head in the gully regions of the Loess Plateau. The objectives of this study were to quantify the effects of vegetation restoration on soil properties and erodibility in this region. Specifically, a control site in a slope cropland and 9 sites in 3 restored land-use types(5 sites in grassland, 3 in woodland and 1 in shrubland) in the Nanxiaohegou watershed of a typical gully region on the Loess Plateau were selected, and soil and root samples were collected to assess soil properties and root characteristics. Soil erodibility factor was calculated by the Erosion Productivity Impact Calculator method. Our results revealed that vegetation restoration increased soil sand content, soil saturated hydraulic conductivity, organic matter content and mean weight diameter of water-stable aggregate but decreased soil silt and clay contents and soil disintegration rate. A significant difference in soil erodibility was observed among different vegetation restoration patterns or land-use types. Compared with cropland, soil erodibility decreased in the restored lands by 3.99% to 21.43%. The restoration patterns of Cleistogenes caespitosa K. and Artemisia sacrorum L. in the grassland showed the lowest soil erodibility and can be considered as the optimal vegetation restoration pattern for improving soil anti-erodibility of the gully heads. Additionally, the negative linear change in soil erodibility for grassland with restoration time was faster than those of woodland and shrubland. Soil erodibility was significantly correlated with soil particle size distribution, soil disintegration rate, soil saturated hydraulic conductivity, water-stable aggregate stability, organic matter content and root characteristics(including root average diameter, root length density, root surface density and root biomass density), but it showed no association with soil bulk density and soil total porosity. These findings indicate that although vegetation destruction is a short-term process, returning the soil erodibility of cropland to the level of grassland, woodland and shrubland is a long-term process(8–50 years).