Effect of desert soil algae on the stabilization of fine sands

Four filamentous cyanobacteria, Microcoleus vaginatus, Phormidium tenue, Scytonema javanicum (Kutz.) and Nostoc sp., and a single-celled green alga, Desmococcus olivaceus, all isolated from Shapotou (Ningxia Hui Autonomous Region of China), were batch cultured and inoculated onto unconsolidated sand in greenhouse and field experiments. Their ability to reduce wind erosion in sands was quantified by using a wind tunnel laboratory. The major factors related to cohesion of algal crusts, such as biomass, species, species combinations, bioactivity, niche, growth phase of algae, moisture, thickness of the crusts, dust accretion (including dust content and manner of dust added) and other cryptogams (lichens, fungi and mosses) were studied. The best of the five species were M. vaginatus and P. tenue, while the best mix was a blend of 80% M. vaginatus and 5% each of P. tenue, S. javanicum, Nostoc sp. and D. olivaceus. The threshold friction velocity was significantly increased by the presence of all of the cyanobacterial species, while the threshold impact velocity was notably increased only by the filamentous species. Thick crusts were less easily eroded than thin crusts, while biomass was more effective than thickness. Dust was incorporated best into Microcoleus crust when added in small amounts over time, and appeared to increase growth of the cyanobacterium as well as strengthen the cohesion of the crust. Microbial crust cohesion was mainly attributed to algal aggregation, while lichens, fungi and mosses affected more the soil structure and physico-chemical properties.

城市森林滞尘能力及其应用模式研究

本文以沈阳市城市森林为研究对象，定量研究不同树种、不同结构城市森林的滞尘能力及城市森林滞尘效益，并设计最佳的城市森林滞尘模式，为城市森林树种选择及配置模式提供科学依据。1．通过对沈阳市51种主要绿化树种滞尘能力的研究，表明不同树木滞尘力不同，决定植物滞尘能力的主要因素有，叶表面结构、叶表面积的大小，口一卜片生物量，及树木的叶面积绿量。其中计卜表面结构决定单位叶面积滞尘能力。2．单位生物量滞尘能力较强的落叶乔木有：大叶朴、紫锻、元宝械，黄金树、山里红、暴马丁香、假色械、小叶朴，糠锻，国槐；灌木或藤本类有：地锦、锦带花、重瓣黄刺玫、欧洲英迷、水蜡、金银忍冬、珍珠梅、金银花、大花水娅木。3，单位面积滞尘量最大的乔木有：辽东栎、元宝械，稠李、大叶朴、暴马丁香、山里红、枫杨、小叶朴、糠锻、紫锻。灌木有：紫丁香、水蜡、重瓣黄刺玫、东北连翘、金银忍冬、锦带花。4，通过对不同树木的单株滞尘量的测定，得出树木单株滞尘能力强的乔木有：糠锻、辽东栎、枫杨、国槐、小叶朴、元宝械、加拿大杨、大叶朴、旱柳、紫锻、蒙古栋、榆、刺槐、稠李。滞尘能力强的灌木有：紫丁香、水蜡、金银忍冬、榆计卜梅、大花水娅木、东北连翘、锦带花、红瑞木、山梅花、风箱果、重瓣黄刺玫、金银花。5．不同树种的滞尘能力与其叶表面形状和结构密切相关，通过对75种树木叶表面超微结构的观察及其与滞尘能力的对比，得出滞尘能力强的叶片表面呈凹形的并且质地较硬、较厚；叶表面有毛；叶表面细胞与细胞之间有沟谷：叶表面有凹槽；叶表面细胞上有脊状突起。滞尘能力较差的树种阶卜片表面较光滑，叶表面细胞平滑，细胞与细胞间排列整齐。6．根据树木单株滞尘量计算沈阳市城市森林总滞尘量，沈阳市城市森林主要树种的滞尘量429701.67t／年，沈阳市城市森林的滞尘量为605554.75t／年，绿化滞尘效益为4886万元／年。7．通过对滞尘后树木生理抗性的研究，结果表明不同树木滞尘后生理抗性不同，其中对粉尘污染抗性较强的树种有：榆树、榆叶梅、丁香和东北红豆杉。8，根据不同城市森林群落组成的滞尘能力及城市森林主要树种的滞尘能力研究，设计出沈阳市不同功能类型的城市森林滞尘模式。

从沙尘暴看黄土的沉积及黄土高原的形成

以近年来我国西北地区多发的沙尘暴现象为缘起 ,对沙尘暴的特征、发生机制等进行了讨论 ;论述了沙尘暴引起的降尘与黄土的堆积和沉积的过程 ;黄土堆积沉积的年龄、颗粒成分等 ;以及沙尘暴与黄土高原的形成之间的关系 ,同时论述了黄土高原的环境变迁 .认为高空均质粉尘的降落是不均匀的 ;高空降尘是突发的 ,而风及流水对堆积粉尘的改造是长期和连续的

Using the RBFN model and GIS technique to assess wind erosion hazard of inner Mongolia, China

Soil wind erosion is the primary process and the main driving force for land desertification and sand-dust storms in and and semi-arid areas of Northern China. While many researchers have studied this issue, this study quantified the various indicators of soil wind erosion, using the GIS technology to extract the spatial data and to construct a RBFN (Radial Basis Function Network) model for Inner Mongolia. By calibrating sample data of the different levels of wind erosion hazard, the model parameters were established, and then the assessment of wind erosion hazard. Results show that in the southern parts of Inner Mongolia wind erosion hazards are very severe, counties in the middle regions of Inner Mongolia vary from moderate to severe, and in eastern are slight. Comparison of the results with other research shows conformity with actual conditions, proving the reasonability and applicability of the RBFN model. Copyright (C) 2007 John Wiley & Sons, Ltd.

NDVI spatial pattern and its differentiation on the Mongolian Plateau

GIMMS NDVI database and geo-statistics were used to depict the spatial distribution and temporal stability of NDVI on the Mongolian Plateau. The results demonstrated that: (1) Regions of interest with high NDVI indices were distributed primarily in forested mountainous regions of the east and the north, areas with low NDVI indices were primarily distributed in the Gobi desert regions of the west and the southwest, and areas with moderate NDVI values were mainly distributed in a middle steppe strap from northwest to southeast. (2) The maximum NDVI values maintained for the past 22 years showed little variation. The average NDVI variance coefficient for the 22-year period was 15.2%. (3) NDVI distribution and vegetation cover showed spatial autocorrelations on a global scale. NDVI patterns from the vegetation cover also demonstrated anisotropy; a higher positive spatial correlation was indicated in a NW-SE direction, which suggested that vegetation cover in a NW-SE direction maintained increased integrity, and vegetation assemblage was mainly distributed in the same specific direction. (4) The NDVI spatial distribution was mainly controlled by structural factors, 88.7% of the total spatial variation was influenced by structural and 11.3% by random factors. And the global autocorrelation distance was 1178 km, and the average vegetation patch length (NW-SE) to width (NE-SW) ratio was approximately 2.4:1.0.