杜英等树种对盐雾胁迫的反应及其生理特性研究

以饱和NaCl溶液模拟盐雾胁迫,对杜英等11个树种在盆栽(其中的7个树种)和离体条件下的叶片和芽进行处理,通过对盐害症状及其时间极限的观察,结合叶片叶绿素含量、游离脯氨酸含量、超氧化物歧化酶(SOD)活性、丙二醛(MDA)含量等生理指标的测定,发现耐盐雾性的强弱依次为成熟叶组织＞嫩叶组织＞芽组织,盆栽条件下叶片耐盐雾性强于离体状况,阔叶树类耐盐雾性强于针叶树类,而7个参试树种耐盐雾性强弱的综合排序依次为杨梅＞木荷＞杜英＞二次结实板栗＞湿地松＞枫香＞马尾松.     

神木六道沟气候及地面组成物质特征对侵蚀产沙影响分析

在野外调查与试验研究的基础上,分析了六道沟及其相邻流域降雨、径流、气温、风力等气候因素及地面组成物质特征对侵蚀产沙的影响。认为暴雨强度大,疾风多、植被少,地面组成物质复杂松散,以及不良的土壤理化特性,是该区侵蚀产沙特别强烈的根本原因,该区的侵蚀具有复杂多样的特殊性,在时间与空间上差异较大,分布不均;地面物质粗、产沙量大、是粗沙的主要产区;掌握侵蚀特点,控制风沙直接入沟,入河及坡耕地的改造,防治沟头,沟壑崩塌,扩大草灌,发展多样性农业为治理重点。     

黄泛平原风沙区的水土流失及其治理开发探讨

由于人们对于平原风沙区的水土流失不如对山丘区的水土流失认识深刻,为了纠正这种偏见,本文以黄泛平原风沙区为例,从侵蚀方式、侵蚀程度及危害的严重性加以分析,以证明鲁西北黄泛平原已被联合国环境保护组织列为高度荒漠化危险区.同时对平原风沙区提出了治理开发对策以及选定的开发试区实施了多种治理措施,效益明显,使试区农民走上了脱贫致富的道路,已成为黄泛平原沙区治理开发的典范.     

Direct field measurement of wind drag on vegetation for application to windbreak design and modelling

A field instrument was designed and field tested for measuring the applied wind load on trees and surface-mounted obstacles in a natural boundary layer. Using this instrument, the effect of vegetation porosity on the drag coefficient of small conifer trees (h=1·4 m) was determined directly in the field. Drag coefficients for two simple solid geometric forms (cone and cylinder) having approximately the same size (height and diameter) as the conifer trees were also measured over a relatively wide range of Reynolds numbers and the results compared to published drag curves for these shapes. The field study found that the porous element had a higher drag coefficient than a solid element, both for the solid element tested and for the drag coefficient suggested for surface-mounted solid obstacles. The drag coefficient changed on a continuum with porosity, rising initially from the value measured for the element as a solid, reaching a peak at an intermediate value and eventually falling to zero when the element was removed. This peak in the drag coefficient versus porosity curve corresponds to reports that shelterbelt efficiency peaks at medium-porosities, and is an important relationship in terms of modelling momentum extraction of vegetation, one which has not been shown previously in the literature. Findings of this study have direct application to the modelling of shelterbelts and windbreaks and the assessment of the amount of vegetation cover required to suppress wind erosion in rangeland vegetation communities. © 1998 John Wiley & Sons, Ltd.     

保护性耕作农田风沙流空间分布规律研究

为了解保护性耕作农田风沙流的空间分布规律,对保护性耕作农田进行了野外风洞原位风蚀测试.结果表明:保护性耕作农田在不同风速下各高度的风沙流水平分布符合三次多项式规律,经过27行残茬、5.5 m的水平距离风沙流基本达到了平衡稳定状态;在垂直方向上风沙流分布符合高阶多项式规律,具有与砾石戈壁地表输沙量垂直分布极为相似的"象鼻"效应.试验还发现保护性耕作农田风沙流主要活动在近地表40 cm高度以下范围,占到风蚀物总质量的90%左右.     

杉木作为风电叶片复合材料增强相的性能评价

为开发风能作为全球的新能源,针对目前风电玻璃钢叶片存在问题,对分级杉木作风电叶片复合材料增强相的可行性进行了研究。结果表明:由一、二级分级杉木制成的风电叶片复合材料,其最大拉伸强度和最大压缩强度,均达到或超过目前国外使用的常规木材/环氧层积材风电叶片材料,完全能够替代玻璃钢叶片材料而大量使用。     

Integrating the risk of wind damage into forest planning

Wind is the major abiotic risk factor in Finnish forests. Therefore, tools that help managers to assess the risk of wind damage are required. This study developed simple regression models for predicting the critical wind speed needed to uproot Scots pine, Norway spruce and birch trees at the stand edges in Finnish conditions, using the characteristics of the retained forest both downwind and upwind stands as predictors. Using information on the prevailing wind conditions in the region, the critical wind speeds were converted into probabilities of wind damage, from which a mean risk index was calculated. The mean risk index was used as an objective variable in heuristic optimisation. The results of minimizing the mean risk index were compared to other objective variables such as minimal height differences between adjacent stands. The residuals of the regression models of critical wind speeds were small, especially in Scots pine and birch. Increasing tree height of the downwind stand or area of the upwind stand (gap size) decreased the critical wind speed regardless of tree species, whereas increases in the dbh/height ratio of the downwind stand increased the critical wind speed. The shelter effect of upwind stand height was stronger in Norway spruce than in other tree species, whereas the effect of tree height of the downwind stand was larger in Scots pine and birch. Minimization of the mean risk of wind damage within forest landscapes led to smooth and non-fragmented landscape structures in terms of tree height. Incorporating even-flow constraints into the planning model led to a slight increase in the mean risk of wind damage. Of the surrogate methods for risk assessment minimization of height differences between adjacent stands performed well but not equally well as minimization of the mean risk index.     

保护性耕作下农田土壤风蚀量及其影响因子的研究初报

本研究采用移动式风洞仪对北京市保护性耕作下农田土壤风蚀影响进行研究,并得出以下初步结论：（1）六种地块下土壤风蚀量以裸露翻旋地最高,种植越冬覆盖作物能显著降低土壤风蚀量;不同免耕播种机和秸秆处理方式下,风蚀量区别主要在于播种机,以迪尔风蚀量最低,农哈哈机型最高;四种耕作方式下土壤风蚀量以旋耕地最高,翻耕地比旋耕地降低80.81%,重耙和免耕地风蚀量分别比旋耕地降低95.35%和97.71%;冬小麦五种不同播期下土壤风蚀量随着播期的推后逐渐增大。（2）四种作物中小麦田的覆盖率最高,其次为紫花苜蓿和小黑麦,油菜覆盖率最低;四种耕作方式下耙耕小麦田覆盖率最高为84.00%,旋耕最低为55.33%;五个播期下9月27日播种的小麦田覆盖率显著高于其他播期,10月7日和10月12日最低。（3）将土壤风蚀量作为依变量,覆盖率、作物株高和土壤容重作为自变量进行多元回归分析,并建立多元回归方程：Y=173.186-0.449x1-0.485x2-72.699x3。     

海岸带沙质风口建立防护林关键技术与成本分析

通过对海岸风口沙地现状的观测和对该地段造林技术的综合分析表明:风口沙地营建防护林的关键是采用具有抗性强且又速生的木麻黄大苗,深穴整地,适时造林,放客土、施磷肥和建立有效的挡风屏障等综合配套技术,造林成活率可达到98.3%;保存率可达90.0%以上,无需补植。研究还表明,海岸带风口沙地造林,其造林成本较高,资金投入约为13 508.8元.hm-2;而以往常规造林方法,资金投入约4 535元.hm-2,但造林保存率一般仅有10%~15%,需多次重造或补植,因此还是应用本项总结的造林技术更节省经费,造林效果好、成林快,防护效能可提前发挥。     

Erosion and soil productivity in Australia and New Zealand

Soil erosion assumes a different form in Australia and New Zealand. Sheet, rill and gully erosion are common in eastern Australia and wind erosion in the dry cropland areas. In New Zealand, mass movement dominates the erosion landscape but other kinds, including wind erosion, do occur. It is unclear how much of the mass movement is a natural phenomenon and how much is human-induced. In either case, it causes long-term reductions in soil productivity. A landmark analysis of the soil productivity loss due to land degradation was conducted by the Australian state of New South Wales. Water erosion was a greater problem than wind erosion, but soil structure deterioration was more costly than either kind of erosion.