Streamflow responses to vegetation manipulations along a gradient of precipitation in the Colorado River Basin

The Colorado River Basin has been, and continues to be, the focus of a wide diversity of research efforts to learn more about the effects of natural and human-induced disturbances on the processes and functioning of the basin's upland watersheds. These watersheds are situated at the headwaters of streams and rivers that supply much of the water to downstream users in the western United States. Responses of streamflow to vegetation manipulations have been, and are, one of the research foci in this water-deficient part of the country. The watershed-scale research, led by the U.S. Forest Service and its cooperators, has spanned nearly a century and included an array of vegetation types along a wide range of precipitation gradients. Results from this research have shown that vegetation can be managed to enhance annual water yields while still providing the other natural resource benefits. Analyses of the research results suggest that the effect of vegetation manipulation on streamflow is associated with precipitation–elevational gradient and, therefore, vegetation type. An annual water yield increase between 25 and 100 mm could be achieved by implementing vegetation manipulations in the high elevation subalpine and mixed conifer forests, the ponderosa pine forests (in the Lower Basin), and portions of the low elevation chaparral shrublands. Negligible effects or small increases in water yield were observed for treating sagebrush, pinyon-juniper woodland and desert scrubs. Results from this research have improved our understanding of the basin's hydrology and provided much needed insights to manage forest to mitigate global climate change induced hydrologic impact and meet the increased needs of people living in the basin.     

Ericaceous shrubs affect black spruce physiology independently from inherent site fertility

Vegetative layering of black spruce (Picea mariana [Mill.] B.S.P.) is the principal mode of regeneration for over mature, uneven-aged stands subject to long fire cycles (>300 years) in northeastern Québec, Canada. However, growth response of black spruce layers following disturbance by fire or harvest can be slow, due to a lag of morphological acclimation and potential nutrient limitation. This phenomenon can be accentuated if black spruce is associated with ericaceous shrubs such as Kalmia angustifolia and Rhododendron groenlandicum, which are known to interfere with conifer growth through direct and indirect competition. Such interactions can result in productive stands being converted to unproductive heathlands. It is not known whether these effects of ericaceous shrubs on black spruce are accentuated on low fertility sites, or if the impacts are independent of inherent site fertility. The objectives of this study were to evaluate the effects of ericaceous shrubs on both resource availability and on functional traits of black spruce advance regeneration across a gradient of site fertility (as defined by a site classification system). We monitored black spruce advanced regeneration physiology and soil nutrient availability over two growing seasons on a gradient of ecological site types in northeastern Québec (Canada). The eradication of competing vegetation favored higher soil NH₄-N and K availability, with increases of 67% and 28% compared to control conditions, respectively. Black spruce photosynthesis rate (A) and foliar K content were higher in plots where vegetation was eradicated, compared to the control plots, but did not vary among ecological site types. Photosynthesis did not appear to be limited by nitrogen or water relations, but was possibly limited by a deficit of foliar K⁺, probably resulting from reduced availability following sequestration by the ericaceous root systems. The absence of interaction between inherent site fertility and the eradication of ericaceous shrubs suggests that vegetation management of ericaceous shrubs must be planned independently from the ecological site type.     

树轮生态学研究进展

树轮生态学是现代树轮年代学的重要分支, 在全球气候变化引起的资源、环境等压力日益增大的今天, 越来越显示出树轮生态学研究的理论和现实意义。文中简要概述了树轮分析在森林干扰、群落动态、森林结构、林分更新方式以及高山林线研究方面的进展。树轮生态学将对我国树木个体生长情况和群落动态的研究, 虫灾、火灾、风灾和森林动态的关系以及森林管理相关的研究发挥重要作用。     

福建武夷山自然保护区高山植物资源及应用初探

在对武夷山自然保护区高山植物资源调查的基础上,分析了保护区内高山植被的生活型、组成成分和植物形态特征,探讨了高山植物的应用价值、开发利用措施以及开发利用中出现的问题,并提出相应对策,以期为武夷山地区高山植物资源的开发利用提供参考。     

4种花灌木乔木化育苗技术研究

为了摸索如何把花灌木育成树状小乔木的育苗技术,选择了园林常见多花的扶桑、红花夹竹桃、黄花夹竹桃、紫薇等4个树种,采用保留单一中轴主枝,并按主枝全苗、主枝中截和主枝截顶三个处理方法,通过头年密植育干,第二年疏植养干,第三年储冠的育苗技术,育成了树状小乔木,改进了育苗期整形修剪技术.进一步提高了园林观赏效果.     

Ecological Wood Adaptation and Horizontal Variations of Vessel Element and Fibre Length of Calligonum mongolicum

INTRODUCTION The larger genus in Polygonaceae is Calligonum, which includes about 100 species of shrubs that grow in central Asia. It is well suited to arid climates with drought resistance, and grows more on clay, sandy and gravel grounds. These plants are often cultivated as ornamentals and a stabilizer of mobile sand dunes. There was published information on the wood anatomy of all the examined genera in Polygonaceae (Ma 1994), but the selected species have not yet been described. Ad…     

Utilisation of wood biomass residues from fruit tree branches,evergreen hardwood shrubs and Greek fir wood as raw materials for particleboard production. Part A. Mechanical properties

This paper investigates the potential of utilising wood biomass from fruit tree branches and evergreen hardwood shrubs as raw materials in the production of particleboards when mixed with Greek fir wood particles. The main mechanical properties of the boards made therefrom were determined and compared with those made of typical industrial wood (IW) particles. The highest modulus of rupture and elasticity (30.0 N/mm² and 4330 N/mm², respectively) in bending and screw withdrawal (SW) resistance (127.8 N/mm) were reported for boards made of Greek fir and were downgraded when the fruit tree branches or evergreen hardwood shrub particles also participated. The participation of fruit tree branch particles in proportions higher than 50% improved the internal bond (IB) of fir produced boards, while the highest IB strength (0.95 N/mm²) was reported for boards made of fruit tree branches. Particleboards made of evergreen hardwood shrubs showed inferior mechanical properties compared with those made of IW particles. The latter also showed superior bending strength but inferior SW resistance compared with boards made of fruit tree branches. Hygroscopic and other properties are under determination and will be presented and discussed in the second part of the work.     

基于随机森林的高寒湿地地区土地覆盖遥感分类方法

高寒湿地是青藏高原典型独特的生态系统,是全球气候变化的敏感地带和预警区。利用遥感技术快速、准确地分类提取高寒湿地的土地覆盖信息,对当地生态安全监测和保护具有重要意义。本文以若尔盖湿地国家级自然保护区为研究区,首先,以高分一号(GF-1)遥感影像为数据源,融合光谱特征、水体指数、地形特征、植被指数和纹理信息等26个变量进行随机森林(Random forest,RF)分类实验;然后,根据袋外数据(Out of bag,OOB)的特征变量重要性得分和精度评价结果,选出高寒湿地地区土地覆盖类型的最优分类方案和特征;最后,对特征变量进行降维,并基于相同的变量,采用极大似然法(Maximum likelihood classification,MLC)、支持向量机(Support vector machine,SVM)、人工神经网络(Artificial neural network,ANN)和RF等方法进行分类,比较不同方法的优适性。结果表明:结合GF-1影像光谱、水体、植被、纹理特征和地形信息,使用26个变量的RF模型的分类精度最高,总体精度(Overall accuracy,OA)为90.07%,Kappa系数为0.86;通过RF模型的变量重要性分析可以有效选出重要的特征信息,在降低特征变量维度的同时,还能保证较高的分类精度; 4种分类方法中,RF算法是高寒湿地地区较合适的分类方法,OA比MLC基准方法高17.63个百分点,比SVM和ANN等机器学习算法分别高6.98、6.56个百分点。     

Soil bacterial community responses to cadmium and lead stabilization during ecological restoration of an abandoned mine

Ecological restoration refers to the gradual recovery of damaged ecosystems by utilizing their self-recovery capacity and artificial measures. It is considered as an effective technique to alleviate heavy metal pollution in open-pit mining soils. However, little is known about the stability of heavy metals and soil bacterial responses in artificially restored soil-plant systems. In this study, different vegetation restoration strategies were established in the Dabaoshan mining area, China, and the accumulation and transfer of Cd/Pb in the soil-plant system and the responses of the soil bacterial community were investigated. Results showed that ecological restoration with a combination of trees, shrubs and grasses/herbs could increase soil cation-exchange capacity and organic matter content, but not soil pH. The mixture of trees, shrubs and grasses/herbs was most effective for reducing the available Pb content to 33.7% of the content in the control, and the mixture of trees and grasses/herbs was beneficial in reducing Cd to 60.4% of the content in the control. Data showed that ecological restoration could change the quantity, composition and community structure of soil microorganisms. The soils in which a mixture of trees, shrubs and grasses/herbs were grown had the greatest abundance and diversity of bacteria; the abundances of Proteobacteria increased by 12% and Actinobacteria by 5% from those of the control. Plant coverage, soil available Cd content, and organic matter emerged as major determinants of bacterial community composition. This study demonstrates a promising remediation strategy for limiting Cd/Pb mobility in mining areas.     

高寒城市郊区外来园林树种适应性评价

为了确定外来园林树种在高寒城市郊区的适应性,以典型区域——青海西宁市火烧沟外来园林树种为对象,基于野外定株监测及室内统计分析,对其抗寒性、性状稳定性及生长发育能力等进行了研究,并综合评价了不同树种的适应能力。结果表明：（1）乔木树种紫叶稠李主干基部在晚冬期出现轻微冻裂,其他3种乔木在早春期发生了严重的抽条及轻度的冻害,4者叶色或叶形均明显改变,适应能力依次为：紫叶稠李>金叶复叶槭>金枝国槐>金叶榆。（2）小乔木类树种均发生了较严重的抽条,芽、叶、花出现了明显的冻斑,花朵变色或畸形率低于10%,适应性强弱依次为：西府海棠>独干红叶榆叶梅=绚丽海棠>红叶碧桃。（3）几种丁香属植物抵御冻害能力较强,仅部分物种一年生枝发生了轻微的抽条,但一些物种后期生长发育能力较差,例如黄丁香不发育花器官,综合适应能力大小为：紫罗兰丁香=波峰丁香=红叶丁香>辽东丁香>其他5者。（4）小灌木类树种胶东卫矛和小叶黄杨冬季地上部全部冻干,其他小灌木也发生了不同程度的冻害和抽条,球冠类适应能力为：榆叶梅=珍珠绣线菊>金叶榆>圆柏,绿篱类为：水蜡=紫叶矮樱>金...