Friction velocity u* and roughness length z0 of atmospheric surface boundary layer in sparse-tree land

Sparse-tree land is one of the typical lands and can be considered as one typical rough surface in boundary layer meteorology. Many lands can be classified into the kind surface in the view of scale and distribution feature of the roughness elements such as agroforest, scatter planted or growing trees, savanna and so on. The structure of surface boundary layer in sparse-tree land is analyzed and the parameters, friction velocity u* and roughness length z0 are deduced based on energy balance law and other physical hypothesis. The models agree well with data of wind tunnel experiments and field measurements.     

Friction velocityu⋆ and roughness length zo of atmospheric surface boundary layer in sparse-tree land

Sparse-tree land is one of the typical lands and can be considered as one typical rough surface in boundary layer meteorology. Many lands can be classified into the kind surface in the view of scale and distribution feature of the roughness elements such as agroforest, scatter planted or growing trees, savanna and so on. The structure of surface boundary layer in sparse-tree land is analyzed and the parameters, friction velocityu⋆and roughness length z_o are deduced based on energy balance law and other physical hypothesis. The models agree well with data of wind tunnel experiments and field measurements. This project is supported by Chinese Academy of Science Responsible editor: Chai Ruihai     

甘肃民勤县荒漠化区未利用地的遥感分类研究

以荒漠化土地典型分布区甘肃省民勤县为研究对象,以30 m的Landsat TM5与TM7遥感影像为主要数据源,在分析不同典型地物光谱特征的基础上,建立基于专家知识的决策树分类模型,利用该模型对荒漠化区的戈壁、沙地、沙漠、风蚀劣地等未利用土地进行细分,总体分类精度达到87.06%。决策树分类法总体效果较好,为荒漠化区土地管理以及再利用提供了技术支撑。     

定西龙滩流域不同人工植被类型土壤水分动态研究

通过对定西市安定区龙滩流域7种人工植被类型（柠条林、油松林、侧柏林、山杏林、退耕紫花曹蓿地、退耕隔坡林地、农田）20个野外样点的土壤水分定位观测,研究了不同植被类型土壤水分动态变化规律。结果表明：1）不同植被类型间土壤水分具有显著性差异;2）坡位并非是影响该流域土壤水分变化的显著因子;3）坡度对土壤水分的影响以25°为具有显著性差异的分界点;4）土壤水分垂直层次可划分为土壤水分的弱利用层、主要利用层和调节层;5）剖面土壤水分的变异系数地表（0～20cm）最大,0～140cm土层呈递减趋势,140～200cm土层基本保持“恒定”,120～140cm土深为土壤水分速交层和稳定层的分界线。     

四川省退耕还林还草试点工作中有关问题的调查研究

对当前退耕还林还草试点工作普通存在的一些问题，如计划管理；退耕还林还草面积；退耕地界定和布局；退耕后还林的方向；种苗补助费；退还主体不一致；前期工作经费；林草管护形式与经费、退耕后不反弹以及承包耕地再分配和剩余劳动力转移等方面进行了分析探讨，并提出相应的解决对策和措施。     

山西省阳高县沙地的土壤风蚀规律

选择林地、未翻耕地、耕地、半流动沙地4种土地利用类型,通过定位实验观测与定量分析,研究阳高县沙地不同土地利用类型的风蚀规律。结果认为：1）不同类型近地层2 m内风速随高度近似地服从对数分布规律,林地的斜率最大为1.663 1,未翻耕地的斜率最小为0.895 4,说明林地上林分对风速梯度影响最大,风速降低比率最大,其他下垫面类型斜率大小次序是耕地〉半流动沙地〉未翻耕地。2）不同下垫面对应的粗糙度大小不同,林地粗糙度为3.267 9 cm,属于最大;其次为半流动沙地、耕地、未翻耕地。增大下垫面的粗糙度,可以控制风速和风沙流的产生及运动。3）林地、耕地、未翻耕地和半流动沙地土壤输沙量的大小依次为半流动沙地〉未翻耕地〉耕地〉林地。     

云南剑湖湿地省级自然保护区2003~2019年土地利用变化特征

以2003年和2019年剑湖保护区土地利用调查数据为基础数据,使用Excel软件进行了剑湖保护区2003年和2019年土地利用面积数据以及2003~2019年土地利用变化面积数据统计,并利用ArcGIS软件制作了2003年和2019年剑湖保护区土地利用分布图。结果表明:2003年13种土地利用类型面积从大到小的排序为乔木林地、旱地、湖泊水面、灌木林地、水田、其他林地、农村宅基地、水库水面、果园、坑塘水面、其他草地、沼泽地和采矿用地,2019年19种土地利用类型面积从大到小的排序为乔木林地、旱地、湖泊水面、灌木林地、水田、农村宅基地、水库水面、公路用地、沼泽地、其他草地、坑塘水面、果园、其他林地、河流水面、水浇地、机关团体用地、采矿用地、仓储用地和设施农用地。2006年和2019年,湖泊水面仅有分布于金华坝中的剑湖水域,沼泽地仅分布在剑湖湖滨带区域,水库水面仅有分布于山地区中的玉华水库水域,坑塘水面为仅分布于剑湖周边的鱼塘,水田、水浇地和河流水面全部分布于金华坝中剑湖的周边地区,旱地、农村宅基地和公路用地主要分布在金华坝中剑湖和山地区中玉华水库的周边区域,果园和其他林地主要分布在剑湖东面金华坝与周边山地区的过渡地段,乔木林地、灌木林地和其他草地主要分布在山地区,采矿用地仅分布在剑湖东北面靠近金华坝的山地区,机关团体用地仅有分布于剑湖环湖路外金龙河西侧的剑湖保护区管护局所在地,仓储用地仅有分布于剑湖西面环湖路外的堆矿场地,设施农用地呈现无规律分布特征。2003~2019年,呈减少的2种类型面积从大到小的排序为旱地和其他林地,呈增加的17种类型面积从大到小的排序为:灌木林地、乔木林地、公路用地、农村宅基地、沼泽地、其他草地、坑塘水面、水田、湖泊水面、河流水面、果园、水浇地、机关团体用地、采矿用地、仓储用地、水库水面和设施农用地。     

Implications of national land legislation and customary land and tree tenure on the adoption of alley farming

Increasing population in the forest zone of Cameroon has led to reduction of fallow periods and to diminution of per capita cropping land area. Alley farming is a promising technology for the zone; however, its large scale adoption depends on host of factors of which an important one is tree and land tenure. For this reason, a study was conducted in 1990 to determine implication of national land legislation and customary land and tree tenure on the adoption of alley farming in the forest zone of Cameroon.Despite national laws purposing to regulate land and tree use, ownership rights to land and trees are largely determined by customary tenure rules. According to the forest zone customs, land is passed on from father to son when the father dies. Owners of inherited lands have full rights on lands and these rights are rarely revoked. Women do not own lands but are allowed to crop any piece of their husband's land as long as they stay married. Despite the lack of land ownership, women might still readily adopt alley farming because they are primarily concerned about food crop production and the amount of land to be given to their sons in the future.Study funded by the International Livestock Center for Africa (ILCA), Addis-Abeba, Ethiopia, and technically supervised by the Land Tenure Center (LTC), University of Wisconsin, Wisconsin USA.     

乌兰布和沙漠绿洲4种灌木片林防风效果研究

选取了乌兰布和沙漠绿洲边缘4种灌木防风阻沙林地为研究对象,对4种林地的地表粗糙度、防风效能及其风速变化规律进行了观测和研究。结果表明：4种灌木均能够有效地减小风速,并随着高度的增加风速均呈增加的趋势。与林前相比,林内5H处的风速明显降低。4种灌木林的粗糙度均显著高于迎风面旷野处;2 m高度处,在林内距迎风侧1H~5H范围内,其防风效能花棒最大为24.79%;在20 cm高度处4种灌木的防风效能比较,花棒〉沙棘〉柠条〉柽柳,其防风效能分别为73.78%、57.64%、27.68%和21.78%,花棒的防风效果好于其他3种灌木。     

Voluntary agreements in protecting privately owned forests in Finland — To buy or to lease?

A voluntary conservation approach may reveal environmentally minded landowners who are willing to protect their lands with a compensation that is lower than the market price based compensation. Consequently, voluntary conservation programs may induce lower costs than traditional obligatory programs, such as a land taking. We compared the costs accrued from land purchasing with those from temporal land leasing. The costs included both direct costs, such as fees of land acquisition and compensation payments in land leasing, and transaction costs. We used a data set from a Finnish pilot program called Trading in Natural Values (TNV). In this new practice landowners and the authority that represents the Finnish government sign a fixed-term contract. According to these contracts the forest owners produce biodiversity services on their lands and receive a compensation payment. We developed a framework where land purchasing and leasing can be treated equivalently in terms of duration of time, so that their costs can be compared consistently. Land purchasing and leasing yielded quite similar cost levels. This indicates that the competitive bidding process in TNV has not worked properly.     

合肥环城公园廊道景观及生态环境作用分析

从景观生态学角度分析合肥市环城公园,具有鲜明的廊道结构特征,对城市空间格局,城市景观及生态环境起着重要的作用,合肥市绿地系统的建设目标,应以市域范围内生态廊道为依托,真正形成环状与放射状结合,楔形绿地切入的框架结构。       

樟树林地土壤多环芳烃的含量及其分布特征

研究樟树林地和无林地土壤中PAHs的含量和分布特征,并对两种土地类型土壤中的PAHs含量水平进行评价.结果表明:两种土地类型土壤中PAHs主要积累在0～30 cm的表土层,并随土层加深而明显减少,各土层中以高环的PAHs组分为主,PAHs主要源于燃烧源;樟树林地土壤中PAHs含量明显低于无林地,无林地表土层中PAHs含量是樟树林地表土层的1.1倍;对两种土壤中的PAHs含量水平进行评价,得知樟树林地土壤PAHs超标5种,无林地土壤不仅超标8种,且超标倍数明显大于樟树林地,樟树林地土壤的PAHs污染程度小于无林地.     

水蚀风蚀交错区典型人工林土壤水分亏缺特征

为充分了解水蚀风蚀交错区典型林地土壤水分差异性及其生态水文效应,选择陕西省延安市吴起县水蚀风蚀交错区长城镇退耕还林后形成的典型人工林(小叶杨、山杏、山桃、柠条、河北杨和沙棘林)为研究对象,采用烘干法测定土壤含水量,分析0~300 cm土层土壤水分季节变化特征、贮水量特征和土壤贮水亏缺程度。结果表明:在0~300 cm土层,6种林地土壤水分具有明显的垂直变异特征,即随着土层深度的增加,土壤含水量先升高后降低;6种林地各土层的土壤含水量均具有明显的季节变化特征,且变异系数在表土层较大,随着深度的增加而减小;6种林地土壤水分活跃层存在一定的差异性;其中,沙棘林土壤水分活跃层最深(0~80 cm),其它林地相对较浅(20~40 cm);在0~100 cm土层,各林地土壤贮水量垂直变化趋势差异较大,且小叶杨、河北杨与沙棘林差异显著(P<0.05),沙棘各季节土壤贮水量随着土层深度的增加呈现先增大后减小的趋势。不同植被类型土壤贮水亏缺度存在差异,土壤水分亏缺度在季节上表现为秋季>春季>夏季。     

江西安福不同类型毛竹林地土壤微生物量碳特征研究

为了掌握毛竹林地土壤微生物量碳的动态变化特征,以江西省安福林区的毛竹纯林、竹阔混交林、竹杉混交林这3种不同类型毛竹林地作为研究对象,同时以中亚热带阔叶林和杉木纯林林地为对照,对其土壤微生物量碳(SMBC)含量的季节变化情况及其在各土层的剖面分布情况进行了研究。结果表明:不同类型毛竹林地的SMBC含量间差异较大,不同类型林地0~60 cm土层的SMBC含量平均值的大小顺序为竹阔混交林(157.62 mg·kg~(-1))毛竹纯林(143.17 mg·kg~(-1))竹杉混交林(110.19 mg·kg~(-1))阔叶林(101.07 mg·kg~(-1))杉木林(86.56 mg·kg~(-1));各林分类型的SMBC含量均表现出明显的季节差异,春季的SMBC含量均极显著高于其他季节;各林分类型其SMBC含量的平均值均随土层的加深而降低,其分布在各土层的含量间的差异均达到显著水平,说明土壤表层的积聚作用明显;毛竹林地的SMBC占土壤总有机碳(TOC)的比率为1.01%~1.11%,高于阔叶林地的0.67%和杉木林的0.79%;毛竹纯林、竹阔混交林和竹杉混交林的SMBC与TOC的相关系数分别为0.71、0.55和0.47。     

林地使用权的相关问题探讨

林地使用权仅限于从林地所有权人处获得初始使用权,以及通过转让方式从原林地使用权人处获得的权利。林地使用权出租形成林地租赁权,不应纳入林地使用权的范畴。林地承包经营权则属于林地使用权中的一个类别。林地使用权的性质为用益物权,内容包括种植林木,利用林下资源从事采集、种植或养殖,以及森林景观开发等权利。     

Urban land-use impacts on composition and spatiotemporal variations in abundance and biomass of earthworm community

Soil fauna can sensitively respond to alterations in soil environment induced by land-use changes.However,little is known about the impact of urban land-use changes on earthworm communities.In this study,three land-use types(i.e.,forest,nursery and abandoned lands)were chosen to identify differences in diversity,abundance and biomass of earthworm community in Kunming City.Urban land-use had a pronounced difference in species composition,evenness and diversity of earthworm communities.Forest land had the highest density,biomass and diversity of the earthworm communities.Total abundance was dominated by endogeic species in nursery land(70%)and abandoned land(80%),whereas in the forest land,the earthworm community comprised epigeic,endogeic and anecic species.Temporal changes in earthworm density and biomass were also significantly affected by land-use change.Total density and biomass of earthworms in the forest and nursery lands were highest in September,but highest in the abandoned land in October.The influence of soil physicochemical properties on the earthworm density and biomass also varied with land-use types.Soil temperature significantly affected earthworm density and biomass in the three land-use types.Soil pH was positively correlated with earthworm biomass in the forest land,but negatively associated with earthworm density in the abandoned land.Soil organic matter was positively correlated only with density and biomass of earthworms in the nursery and abandoned lands.Our results suggest that the species composition,abundance and biomass of earthworm communities can be determined by the modification of soil properties associated with urban land-use type.     

城市绿地自动分类管理信息系统研究——以乌鲁木齐新市区为研究对象

绿地作为城市景观的重要组成部分,是城市中最能体现生态性的生态空间(Eco-logical Space)。在我国大部分城市绿地的破碎化程度非常高,采用人工的手段提取绿地信息工作难度较大,而随着地理信息系统相关技术的发展,已经可以实现采用3S技术获取城市绿地的基本信息,本研究正是基于此现状,以乌鲁木齐新市区作为研究对象,结合提供制图与空间分析功能的ActiveX控件MapObjects,以及VB的程序设计环境,针对城市绿地特有属性开发出一套用于城市绿地分类及信息管理的软件系统。     

基于三维显微系统的木材切削表面粗糙度分析

以榆木、杨木和松木为试验材料,采用不同的测试模式、木材切面、放大倍数和切削加工方式对切削表面粗糙度进行测定评价,比较分析上述因素的影响。结果表明:测定模式对于粗糙度值有一定影响;同一树种、同一切面时,磨削表面粗糙度明显低于锯切和旋切,表面粗糙度值为锯切>旋切>磨削;榆木磨削加工中,显微构造明显部位的三切面粗糙度值为径切面>弦切面>横切面;放大倍数与木材显微构造有关,对表面粗糙度值有影响。基于试验结果提出,木材切削表面粗糙度测定评价宜采用先选定被测试件的评价部位,再确定满足精度等级的测试模式的两步法进行。     

Numerical Simulation of the Interaction between Forest Ecological System and Atmospheric Boundary Layer

Based on the basic principles of the micrometeorology of atmospheric boundary layers and vegetation canopy, a numerical model of the interaction between forest ecosystems and atmospheric boundary layers was developed. The model is used to simulate the diurnal variations of heat balance in forest ecosystems, canopy temperatures, ground surface temperatures, as well as the profiles of temporal and spatial distributions of potential temperatures, wind speeds, specific humidity, and turbulence exchange coefficients. Our study indicates that the model can be applied to study the interaction between land surface processes and atmospheric boundary layers over various underlying surfaces and their regional climate effects. This paper will establish a solid foundation to investigations on the coupling of climate models and the biosphere. Translated from Chinese Journal of Applied Ecology, 2004, 15(11) (in Chinese)     

Agroforestry in the management of sloping lands in Asia and the Pacific

Steeply sloping lands are widespread in the tropics. An estimated 500 million people practice subsistence agriculture in these marginal areas. Continued population growth has led to the intensified cultivation of large areas of the sloping lands, exacerbating the problem of soil erosion. Although research shows that alley cropping and other contour agroforestry systems can stabilize the sloping lands, these systems have not been widely adopted by farmers. The Framework for Evaluating Sustainable Land Management (FESLM) has been tested in sloping land areas in the Philippines. Sustainable land management must be productive, stable, viable, and acceptable to farmers, while protecting soil and water resources. Farms on which contour hedgerow intercropping has been adopted meet the multifaceted requirements of FESLM, whereas the farmers' current practice does not. Appropriate land management measures for particular locations depend on a complex suite of social, economic, and biophysical factors, and need to be developed in participation with farmers. The role of agroforestry in sustainable management of sloping lands is the subject of networks coordinated by the International Board for Soil Research and Management (IBSRAM) in seven countries in Asia (ASIALAND) and four countries in the Pacific (PACIFICLAND). We review selected outcomes from a wealth of network data. From these results the following conclusions about the sustainability of various agroforestry systems for sloping lands can be drawn: • In the Pacific, soil loss from sloping lands due to water erosion under farmers' current practices is episodic, unpredictable, and possibly not severe; • Agroforestry systems that utilize legume shrubs, fruit trees, coffee (Coffea spp.) or rubber (Hevea brasiliensis) provide useful economic returns, but are not an essential component in terms of soil protection because grass or pineapple (Ananas comosus) planted on the contour are equally effective in reducing erosion; • Agricultural intensification will lead to nutrient mining, reduction of aboveground biomass, declining yields, and less soil protection unless external sources of nutrients are used; • nitrogen can be effectively supplied using legumes; • Cash derived from hedgerow trees and/or shrubs may providean incentive for their adoption by farmers, as well as funds to purchase external inputs such as fertilizers; • Labor may be a major constraint to the adoption of complex agroforestry systems. We also discuss the information management systems required to effectively manage and utilize the extensive sets of experimental and indigenous data being accumulated. We believe such information systems can facilitate technology transfer across and between regions, and improve the efficiency of research into agroforestry and other land-management approaches. This revised version was published online in June 2006 with corrections to the Cover Date.