Stability of landscape trees in engineered and conventional urban soil mixes

Urban trees are frequently exposed to unsuitable soil conditions that can hamper root system development, potentially affecting both tree health and stability. Engineered soil designs have been developed to increase soil volume for trees planted in confined spaces, and past research has shown that these designs improve growing conditions. However, tree stability in these engineered soils has received limited attention from researchers. In this study, we evaluated the stability of two tree species of contrasting soil quality tolerance (Prunus serrulata and Ulmus parvifolia) after 3 years growth in two skeletal soil mixes, in a suspended pavement design (uncompacted soil), and in a conventionally prepared soil pit. Tree stability was evaluated by measuring trunk resistance to a lateral deflecting force applied with a rope winch system under both ambient and near-saturated soil conditions. Although heavily irrigating the experimental soils had no effect on tree stability, species-specific responses to soil mixes were observed. P. serrulata grown in the gravel-based skeletal soil showed greater trunk deflection resistance than trees grown in the other soil treatments, yet the stability of U. parvifolia was unaffected by soil type. These species-specific responses were consistent with earlier observations of root development in which P. serrulata grew up to 60 times greater root length in gravel-based skeletal soil whereas U. parvifolia root growth was similar in all soil treatments. This research provides evidence that certain tree species planted in conventional tree pits may be more prone to uprooting due to poor root development and that root anchorage might be improved for these species by utilizing a skeletal soil mix.     

青岛市园林绿化树种的调查研究

本项研究通过生态调查法调查了青岛市内356条道路的行道树;公园、山头、小区、学校等28个地块92个样方的乔木和灌木。通过调查发现法桐、黑松、刺槐、雪松、樱花、小龙柏、金叶女贞、大叶黄杨、红叶小蘖等使用率较高,数量较多;白皮松、侧柏、糯米条、溲疏等生长较好,但是应用比较少。对青岛市园林绿化树种的总体应用状况作出了一个较为客观公正的评价。     

基于特征筛选算法的数字土壤制图研究

平缓地带数字土壤制图中，环境协变量的选择是提高制图精度的关键。已有研究证明遥感影像可作为推理制图的辅助因子，而如何确定环境因子推理制图时各自的权重已成为现阶段研究的重点。选取湖北省麻城市乘马岗镇为研究区，采用3种特征筛选方法进行有效环境变量筛选，探索参与平原-丘陵混合区域制图的因子并确定其重要性，依据选择的相对稳定的指标，进一步探索提高土壤类型制图准确性的途径。根据141个野外独立样点的检验结果表明：在推理制图中，遥感因子在平原区域的重要性程度高于丘陵区域，且遥感因子中归一化植被指数(NDVI)和均值(Mean)较为稳定；基于递归特征算法的按地形推理制图精度最高为75.89%，分别高于ReliefF算法和基于Tree的特征筛选算法13.48%和4.97%；此外3种特征筛选算法制图结果中，按地形因子分区制图的精度均高于整体区域制图。因此，遥感因子作为辅助手段参与推理过程可有效提高制图精度。本研究采用的特征挖掘与机器学习算法对提升土壤制图精度具有一定的理论意义。     

The effect ofDendrolimus superans breakout on growth of trees

The effect ofDendrolimus superans on growth of trees was investigated after the breakout in Shibazhan forest area in 1990. Stem analysis was conducted for determining the tree increment loss. The result showed that the current annual increment for extreme heavily damaged, heavily damaged, moderately damaged and lightly damaged stands is 14%, 39.8%, 64% and 82% of that of the control forest respectively. (Responsible Editor: Chai Ruihai)     

Water Use of Tree Lines: Importance of Leaf Area and Micrometeorology in Sub-Humid Kenya

In this research the relative importance of leaf area and microclimatic factors in determining water use of tree lines was examined in sub-humid Western Kenya. Measurements of tree water-use by a heat-balance technique, leaf area, bulk air saturation deficit, daily radiation, and soil water content were done in an experiment with tree lines within crop fields. The tree species were Eucalyptus grandis W. Hill ex Maiden, Grevillea robusta A. Cunn. and Cedrella serrata Royle, grown to produce poles on a phosphorus-fixing Oxisol/Ferralsol with (+P) or without (−P) phosphorus application. Doubling the leaf area of Cedrella and Grevillea doubled water use in a leaf area (LA) range of 1–11 m² per tree. The response of Eucalyptus water use (W) to increases in leaf area was slightly less marked, with W = LAⁿ, n<1. Transpiration rate per unit leaf area (Tr) was the other important determinant of water use, being affected by both tree species and phosphorus fertilization. A doubling of the saturation deficit (SD) halved the water use of all trees except for Cedrella +P, in which water use increased. A direct effect of soil water content on water use was only found in Grevillea -P, with a small increase (60%) as available water increased from 1.4 to 8.9% above wilting point (32%). This low direct response to soil water content is probably due to the extensive tree-root systems and the deep clayey soils supplying sufficient water to meet the evaporative demand. Indirect responses to soil water content via decreases in leaf area occurred in the dry season. The results showed that water use of tree lines was more determined by leaf area and transpiration rate per unit leaf area than by micro meteorological factors. The linear response of tree water use to leaf area, over a wide range leaf areas, is a specific characteristic of tree line configurations and distinguished them from forest stands. In tree lines light interception and canopy conductance increase with leaf area much more than a similar leaf area increase would have caused in a closed forest canopy.     

青檀耐荫性的初步研究

在连续３年测定比较几个不同树种的生理特性和树冠结构的基础上，本文对青檀的耐荫性进行了初步分析，结果表明，青檀的耐荫性随年龄的增大而降低，１２年生以前，青檀是耐荫的；１３至２５年生之间，青檀是喜光树种；２６年生以后青檀则逐渐变为阳性树种。比较的结果还表明，青檀的耐荫性较马尾松强，较杉木弱，从总体看属中偏阳树种。     

Evaluation and selection of multipurpose tree for improving soil hydro-physical behaviour under hilly eco-system of north east India

Soil hydro-physical behaviour was studied under a 20-year old agroforestry plantation consisting of five multipurpose tree species (Pinus kesiya Royle ex-Gordon, Alnus nepalensis D.Don, Parkia roxburghii G.Don, Michelia oblonga Wall. and Gmelina arboria Roxb.) maintained under normal recommended practices at Indian Council of Agricultural Research (ICAR) Complex, Umiam, Meghalaya, India. The aim was to select tree species, which could act as better bio-ameliorant as well as provides higher economic return in highly degraded soil of northeastern hill region of India. A site without vegetation (no tree) nearby the plantation was also selected as control for comparison. Soil samples for various hydro-physical analysis, were taken from 0–15 and 15–30 cm soil depth at a distance of 1 m from respective tree species during wet and dry season of 2003–2004. No appreciable differences in relative contents of textural separates of sand, silt and clay were observed among various tree covers. Surface cover with constant leaf litter fall and extensive root system increased soil organic carbon, helped in better soil aggregation, improved water transmissivity and infiltrability and in turn, reduced soil erosion in the present study. However, due to variation in quantity of leaf litter fall and root biomass, these parameters differed among tree species. Of the tree species, P. kesiya, M. oblonga and A. nepalensis were found to be rated best for bio-amelioration of soils as these tree covers had more root and shoot biomass and more litter fall compared to other species. However, considering both timber production and improvement in hydro-physical behaviour, M. oblonga was found best among the tested tree species. The study, thus, suggested that inclusion of tree species M. oblonga in agroforestry system is a viable option for natural resource management and could sustain long-term soil productivity in a highly degraded soil of this region as well as for food security of the resource poor people of North East India.     

Planting free trees on private property: understanding urban residents’ motivations and hesitations

In order to meet comprehensive planting goals, tree-planting campaigns must plant on private properties, in residential front and backyards. Successful engagement in these kinds of neighborhood plantings requires an understanding of residents' decision making. Through surveys with past recipients of free 1″-caliper trees, past neighborhood leaders of tree-planting recruiting, and door-to-door canvassing in a pilot neighborhood, this study shows the top factors for accepting free trees and main reasons for declining. Surveys asked past tree recipients their main motivations for accepting a free tree, and three reasons rose to the top: trees provide beauty, trees help the environment, and trees keep people healthy. Top barriers for declining a free tree included not desiring more trees than they had, concerns about maintenance, and a language barrier. These results can inform tree-planting campaigns and tree-focused organizations in order to improve messaging and neighborhood engagement – all to ensure that more trees are planted and canopy is increased.     

Determination of Mean Tree Height of Forest Stands by Digital Photogrammetry

The mean tree height of 73 forest stands in a 1000 ha forest area was determined from canopy heights generated by automatic image matching using a digital photogrammetric workstation and digitized panchromatic aerial photographs with a scale of 1:15 000. First, the mean height of each stand was computed as the arithmetic mean of the quantile corresponding to the 75th percentile of the distribution of the canopy heights from the image matching within square grid cells with cell sizes of 236-400 m². The mean heights from the image matching underestimated the true heights by 5.42 m. Secondly, field-measured mean tree heights of 165 georeferenced sample plots distributed systematically throughout the 1000 ha forest area were regressed against the mean heights derived from the image matching. The regression equations were used to predict the mean heights of the 73 stands. In very young forest stands, the predicted mean heights overestimated the true heights by 0.4 m and the precision was 0.9-1.0 m. In young and mature stands, the average difference between predicted height and ground-truth ranged between -1.6 and 0.5 m, and the precision ranged from 1.1 to 2.1 m.     

宁化国有林场树种结构调整方案探讨

以现有人工纯林地力普遍衰退,林分总体质量下降为背景,从分析宁化国有林场森林资源现状入手,分析总结较优的混交造林模式和选择适宜造林树种,以优化造林模式,增加阔叶树造林面积,利用阔叶树在林地养护、地力保持、维持生态系统平衡等诸多方面的作用,从而达到调整和优化宁化国有林场树种结构的目的。