The effect of disturbance by Phellinus weirii on decomposition and nutrient mineralization in a Tsuga mertensiana forest

Summary Microbial biomass in the upper 7 cm of soil and needle decomposition on the forest floor were measured seasonally for 10 months in a mountain hemlock (Tsuga mertensiana) old-growth forest and in a regrowth forest after Phellinus weirii, a root-rot pathogen infection, had caused disturbance. The microbial biomass was higher in the old-growth forest soil than in the regrowth forest soil. However, T. mertensiana needle decomposition rates were higher in the regrowth than in the old-growth forest. Total N, Ca, Fe, Cu, and Zn concentrations in needles increased during the 1st year of decomposition in both the old and the regrowth forests, but P, K, Mg, Mn, and B concentrations decreased. N, P, K, Mg, Cu, and Zn concentrations were lower in regrowth than in old-growth decomposing needles. During mineralization, needles in the regrowth forests released more N, P, and K as a result of higher needle decomposition rates. Our results suggest that higher needle decomposition rates increased the mineralization of N, P, and K, which may lead to increased soil fertility and faster tree growth rates in the regrowth forest.     

辽宁省东部山区5种森林植被类型水文生态效益综合评判

利用层次分析与Fuzzy数学相结合方法,对辽宁省东部山区5种森林植被类型水源涵养能力进行了多目标综合评判。首先利用层次分析法确定了评价因子林冠截留、林冠蒸散、枯落物蓄水、土壤容重、非毛管孔隙度、初渗速率、稳渗速率、土壤总蓄水和土壤有效水的权重集为C=(0.0245,0.0051,0.1993,0.0109,0.0762,0.0565,0.2827,0.0573,0.2866),然后利用最大模糊熵原则确定了评价因子的隶属函数,最后利用Fuzzy综合评判得出油松、落叶松、红松、柞木林、杂木林评价结果模糊子集为B=(0.4686,0.3784,0.4145,0.6128,0.4808),结果表明阔叶林水源涵养效益高于针叶林,其中柞木林效益最佳。     

Reciprocal transfer effects on denitrifying community composition and activity at forest and meadow sites in the Cascade Mountains of Oregon

In order to examine the effects of disturbance, vegetation type, and microclimate on denitrification and denitrifier community composition, experimental plots were established at the H. J. Andrews Experimental Forest in the Cascade Mountains of Oregon. Soil cores were reciprocally transplanted between meadow and forest and samples were collected after 1 and 2 years. Denitrifying enzyme activity (DEA) was measured using the acetylene block assay and terminal restriction length polymorphism profiles were generated with nosZ primers that target the gene coding for nitrous oxide reductase. Nitrate concentrations, C mineralization, and water content were measured to gain additional insights into soil properties controlling DEA. Meadow soils were significantly higher in DEA than forest soils, and the highest DEA levels were observed in cores transferred from the meadow into the forest. Nitrate concentrations were also different between forest and meadow soils, but did not correlate to DEA. DEA was higher in open versus closed cores, suggesting an association between denitrification and the rhizosphere. Denitrifier communities of undisturbed forest and meadow soils shifted through a 4-year period but remained distinct from each other. Similarly, denitrifier communities clustered by vegetation type of origin regardless of manipulation, suggesting that the overall denitrifier communities are well buffered against environmental changes.     

上海市区公园表层土壤铅含量及其污染评价

通过对上海市区44个公园土壤中Pb含量的调查,发现表层土壤中Pb的平均含量为55．06 mg/kg, 变幅为26．39-174．35 mg/kg,为上海市土壤环境背景值的1．04-6．85倍。运用地积累指数法对公园表层土壤Pb 污染进行评价,结果表明:超过半数的公园为轻度污染至中等污染,近1/3的公园无污染, 6个公园达到中等污染和中等污染至强污染水平。通过对土壤Pb含量的空间分布分析发现,上海市区公园土壤中Pb主要来源于交通和工业污染,土壤Pb含量与公园建成时间无显著性相关。     

Management strategies to increase stand structural diversity and enhance biodiversity in coastal rainforests of Alaska

Coastal rainforests of southeast Alaska have relatively simple species composition but complex structures with high diversity of tree ages, sizes and forest canopy layers, and an abundant understory plant community. Wildlife and fisheries resources also play an important role in the ecological functioning of forest and aquatic systems. Clearcutting has greatly altered these forest ecosystems with significant decreases in structural diversity of forest stands and greatly reduced wildlife habitat. This paper synthesizes information on management options in older forests that have never been actively managed, and in younger forests to increase diversity of stand structures and their associated effects on biodiversity. Light to moderate levels of partial cutting in old-growth forests can maintain the original diversity of overstory stand structures and understory plant communities. In younger forests that develop after clearcutting, mixed alder-conifer stands provide more heterogeneous structures and significantly higher understory biomass than in pure conifer forests. Research has shown that red alder increases diversity and abundance of understory plants, and provides forage for deer and small mammals. Results also show a clear linkage between alder and improved invertebrate diversity in aquatic systems. A combination of light partial cutting in older forests along with inclusion of red alder in conifer-dominated forests could provide the greatest amount of diversity and maintain the complex stand structures that are an important component of these forest ecosystems.     

冬春上海市郊外环林带防尘效应的初步研究

对上海市郊外环林带两侧总悬浮颗粒物浓度（简称TSP）和可吸入颗粒物浓度（简称PM10）同步测定表明：林带的防尘效应与风向有关,下风向处的TSP与PM10日均浓度均分别比上风向低19%-44%和39%-61%。林带边粒径分布测定结果表明：下风向处较大粒径颗粒物的相对含量比上风向处小一些;冬季的粒子谱分布呈现较大粒子和较小粒子重量累积百分比较高、中等粒子的重量累积百分比较低的态势;而春季则相反,中等粒子的重量累积百分比较高、较大粒子和较小粒子则比较低。说明冬春不同风向条件下上海市郊的大道旁林带区具有一定的防尘效应。     

林草间作地土壤低吸力段持水性能的初步研究

以庄浪县5种林草间作模式为对象,在田间采用张力计法测定各模式地的低吸力段土壤水分特征曲线,分析各模式地的土壤持水性能,比较不同模式地的比水容量,结果表明,各模式地土壤含水率随吸力变化较快;五种模式不同土层土壤持水力存在明显差异,表层土壤持水力较大,60cm土层土壤持水能力最差。仁用杏+红豆草模式地土壤持水能力和供水能力最强,是最为耐旱模式,油松+紫花苜蓿模式供水能力最差。     

鹤峰县天保工程建设成效定量分析

天保工程建设是生态环境建设的重要措施,是人与自然和谐发展的重要基础。我们对鹤峰实施天保工程以后,森林资源变化情况、水土流失变化情况等重要生态环境因子进行了详细调查,并与天保工程实施前比较,结果表明:5年来,鹤峰县天保工程建设取得了阶段性成效,生态、经济、社会三大效益显著,折算总效益784 959.90万元。     

基于WebGIS的森林旅游信息管理网站的构建

文章分析了旅游网站的现状、森林旅游的特点,介绍了基于WebGIS技术开发森林旅游信息管理网站的优势和系统设计方法。通过森林旅游网站的构建实现面向公众的森林旅游信息交流和面向管理部门的信息管理功能。     

Agroforestry techniques for the rehabilitation of degraded salt-affected lands in India

The development of appropriate technologies for the judicious use of India's 8.11 million ha of salt-affected lands would give increased food, fodder and fuelwood production. A sizeable portion of the salt-affected lands of the Indo-Gangetic plain have been reclaimed through chemical amendments and are being commercially used for arable farming. However, large areas of salt-affected common lands, village and government lands and waste lands near cities, along railway tracks and roads do not have any productive use. Owing to their sparse vegetative cover such lands are vulnerable to further degradation and can be a source of runoff causing floods, especially where cows congregate. Research at the Central Soil Salinity Research Institute, Karnal has generated agroforestry techniques which could enable the economic exploitation of such marginal lands. This paper deals with various aspects of these techniques, which have been applied to over 50 000 ha by 1994. Based on eight to ten years of growth and biomass figures, the most salt-tolerant woody species identified were: Prosopis juliflora, Acacia nilotica, Casuarina equisetifolia, Tamarix articulata, Leptochloa fusca (a palatable forage grass which was found to be a promising primary colonizer of salt lands). Agronomic practices for the successful establishment of trees such as planting methods, amendment use, irrigation, spacing and lopping schedules are discussed. A Prosopis juliflora-leptochloa fusca silvipastoral model was found to be excellent for fuelwood and forage production and for the amelioration of high pH soils. This system, when followed for little more than four years, reclaims alkali soils to such an extent that normal agriculture crops such as Trifolium alexandrinum and T. resupinatum can be grown successfully. A ridge-trench system of tree planting was found to be helpful in alkali soils, the in situ rainwater conservation it led to assisting biomass production. Eucalyptus tereticornis, Populus deltoides and Tectona grandis based agroforestry were promising for reclaimed salt-affected lands. The short- and long-term effects of various tree plantations on the physicochemical properties of the soil and on soil-water relations are also discussed. Agroforestry options for the development of salt-affected lands found in various agroclimatic zones of India are explored.