How is Shrub Cover Related to Soil Moisture and Patch Geometry in the Fragmented Landscape of the Northern Negev desert?

Among the major challenges of landscape ecologists is to develop relatively simple models to quantify ecological processes over large areas. Application of such models can be well demonstrated in fragmented semi-arid ecosystems where competition over resources is intense due to habitat loss, however, only a few studies have done so. Our aim was to model and study the integrated effect of spatial variation in potential soil moisture and patch size and shape on shrub–grass ratio (SGR) in a semi-arid fragmented environment. We specifically ask: (i) what factors most strongly relate to SGR in large remnant patches (> 1.6 ha), and (ii) do different factors more strongly relate to SGR in small patches (< 1.6 ha)? The study was carried out using 60 patches within a semi-arid fragmented environment in the Northern Negev of Israel. Aerial photographs and digital elevation models were used to map six environmental variables: wetness index, aspect, rock cover, rock pattern, patch area, and patch shape. The variables were designed in GIS and were modeled using fuzzy logic procedures to predict SGR, and these predictions were compared to shrub cover maps extracted using maximum likelihood classification of aerial photographs taken in September 2003. We found that in the study area, factors indicating potential soil moisture are most strongly related to SGR in large patches, whereas patch geometric attributes are more strongly relate to SGR in small patches.     

汉中市低山丘陵区飞播造林树种选择试验研究

通过汉中市低山丘陵区飞播造林成苗调查分析,对筛选适宜低山丘陵区飞播造林树种,具有一定的指导意义。     

陕西飞机播种造林技术浅析

本文总结、分析和调查研究陕西飞播造林,为今后飞播造林设计、施工、成苗成效调查和科学经营管护提供科学依据。     

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.     

合肥市绿化现状的遥感调查

本研究采用航空遥感技术,调查研究了合肥市老城区绿化现状。查明合肥市老城区绿化覆盖率为３３．５１％,绿化覆盖面积为２,１５０,０１８ｍ２,其中公共绿地６６．３５％,专用绿地占２２．６０％,道路绿化覆盖面积占１１．０５％。本文还对老城区绿化指标、布局、效应进行了分析评价并提出了合理的建议。     

低空无人机航空摄影测量技术在土地整治项目规划设计阶段的运用

低空无人机航空摄影测量技术是现代新型应用测绘技术,该技术的运用将有助于提高土地整治项目规划设计工作的开展.该研究主要阐述了低空无人机航空摄影测量系统的组成及特点,介绍了低空无人机航空摄影测量作业流程及测绘成果在土地整治项目规划设计阶段的运用,比较了相对于传统野外实测地形图,低空无人机航空摄影测量技术运用的优势.     

航空象片成数样点判读取得马尾松面积

本文利用航空象片成数点判读与地面样点(或二类调查固定样地资料)检查纠正判读中错误的方法获得总体内马尾松面积,并结合必要的地面马尾松根根量的调查,取得总体内马尾松根资源的数据,为建立马尾松松根综合利用企业的规模提供必要的依据。     

毛乌素沙地飞播后植被演替规律研究——以内蒙古乌审旗为例

通过对乌审旗境内飞播后的毛乌素沙地植被进行调查研究,初步得出以下结论:毛乌素沙地的演替规律是,第一阶段为先锋阶段,植被表现为籽蒿+羊柴群落;第二阶段为过渡阶段,植被表现为羊柴+油蒿群落;第三阶段植被表现为羊柴群落。人为干扰在一定程度上决定着羊柴群落的演替,合理放牧和经营管理可使羊柴群落处于相对稳定的阶段。     

Historical landscape photographs for calibration of Landsat land use/cover in the northern Ethiopian highlands

The combined effects of erosive rains, steep slopes and human land use have caused severe land degradation in the Ethiopian Highlands for several thousand years, but since the 1970s, however, land rehabilitation programmes have been established to try to reverse deterioration. In order to characterize and quantify the transformations in the north Ethiopian Highlands, a study was carried out over 8884 km² of the Tigray Highlands of northern Ethiopia. Using Landsat Multispectral Scanner and later Thematic Mapper imagery (1972, 1984/1986 and 2000), historical terrestrial photographs (1974–1975) and fieldwork (2008), we prepared land use and cover maps. For assessing the use of the historical terrestrial photographs, Landsat images from 1972 were classified using two different methods, namely conventional change detection (image differencing) and ground truthing (using the historical photographs of 1974–1975). Results show that the use of terrestrial photographs is promising, as the classification accuracy based on this method (Kappa coefficient 0·54) is better than the classification accuracy of the method based on image differencing (Kappa coefficient 0·46). Major land use and cover changes indicate the following: (1) a gradual but significant decline in bare ground (32 per cent in 1972 to 8 per cent in 2000); (2) a significant increase of bushland (25 to 43 per cent) and total forest area (including eucalypt plantations, 2·6 to 6·3 per cent); and (3) creation of numerous lakes and ponds. The dominant change trajectory (27 per cent of the study area) indicates a gradual or recent vegetation increase. These changes can be linked to the population growth and the introduction of land rehabilitation initiatives, complemented by growing awareness of land holders. Copyright © 2012 John Wiley & Sons, Ltd.     

DASM系统在云南新松叶峰虫灾航空调查中的应用

介绍了美国林务局广泛使用的航空快速勾绘系统DASM,阐述了其采集模板的数据库结构、工作底图制作与导入、采集界面设置以及数据后处理问题.并以“小松鼠”直升机为搭载平台,在云南省大理巍山县林区进行了不同悬停高度(100,200,400 m)下的祥云新松叶峰虫灾面积勾绘作业,验证了系统主要关键技术在我国西南林区的适应情况,探讨了提高系统精度的几种可能途径.结果表明,该系统可以满足林业病虫害的发生位置、致病面积快速调查的需要;同时,直升机悬停高度控制在200 m以下更易于实现勾绘的精确性.