Response patterns of Vaccinium myrtillus and V. vitis-idaea along nutrient gradients in boreal forest

Abstract. The relationships between biomass of dwarf shrub species and nutrient gradients of forest soils was studied under field conditions in boreal forests. The biomass-response curves of Vaccinium myrtillus and V. vitis-idaea were fitted against soil nutrient gradients using Generalized Linear Models (GLM). Ecological niches of Vaccinium myrtillus and V. vitis-idaea were evaluated, and effects of nitrogen addition (manipulation of the nutrient gradient) on response function were tested. The Vaccinium species showed statistically significant Gaussian responses along soil nitrogen, phosphorus and calcium gradients, but not along other gradients (K and Mg). Furthermore, manipulation of the nitrogen gradient seemed to have a minor effect on response functions, i.e. addition of nitrogen did not change ecological niches of these species. Ecological optima of V. myrtillus and V. vitis-idaea on the nutrient gradients were about the same. This study suggests that differences in dominance between Vaccinium myrtillus and V. vitis-idaea in boreal forest is not determined by nutrient gradients, but may rather be explained by light conditions and/or moisture availability.     

哈尔滨市瞬时热力场空间格局分析

应用遥感(TM图象)及地理信息系统(ArcView)技术,对哈尔滨市瞬时热力场空间格局现状进行多角度分析,将TM成像时哈尔滨市不同地表辐射温度地块分为3个温度等级：相对低辐射温度(<10℃)、相对中等辐射温度(10～22℃)和相对高辐射温度(22～31℃)地块,其中相对高辐射温度的地块数量最多,占61％;相对低辐射温度地块最少,仅占17％;相对中等辐射温度地块居中,占22％,在相对高辐射温度地块(22～31℃)中。大于28℃的相对过热辐射温度的地块为7018块,总面积达12252hm^2,且大小不均。最大斑块面积是1489hm^2,最小斑块面积为0．72hm^2在这些斑块中面积小于1hm^2的占95．02％,1～5hm^2占3．46％,而大于5hm^2的占1．52％,它们以热团、热环及碎片的形式分布,形成分布格局,团状复合体内平均辐射温度为30．8℃,它们主要出现在哈尔滨市的道外区、道里区西南部,热环复合体的平均辐射温度为27℃,它们沿哈尔滨市现存的两条铁路环线构成过高热辐射环带,碎片复合体内的平均辐射温度为24．7℃,以小于1hm^2的过高热辐射地块构成碎片形状,分布在南岗区和动力区,还分析了覆盖率、绿地面积及建筑容积因素与城市热力场空间格局的关系,提出了改善哈尔滨城市热岛效应的一些思路。     

基于多源数据的三峡库区乐天溪流域林地植被覆盖动态监测

应用多时相、多来源遥感数据,采用图像融合和图像标准化等综合手段,分析了三峡库区乐天溪流域1978—2005年林地植被覆盖度的变化趋势.结果表明:27年来,该区域林地总面积从265.82km2增至346.45km2,植被覆盖度整体上也呈增加趋势,但增加率显现区域不均衡性,植被变化呈现轻度破坏、初步恢复和全面恢复3个发展阶段.林地重心发生了较大的改变.1987年以前,覆盖度<45%的林地重心向北迁移,1987年以后,其重心向南逐渐回归.覆盖度>45%的林地重心则持续从西北向东南逐渐移动.研究区植被覆盖度变化受人类活动干扰、区域经济发展和国家综合治理的影响明显.流域经过10余年的治理,林地植被受人类干扰逐渐减少,覆盖度>60%的林地面积达到217.88km2,占流域林地总面积的62.9%,生态环境逐步得到改善.     

贺兰山10种典型植物光合及水分利用效率特征研究

为了探究贺兰山不同乔灌草的光合生理特性及其对自然环境的适应特性和机制,该研究采用Li-6400XT便携式光合仪测定了贺兰山10种乔灌草气体交换参数及自然环境因子并分析其相关性.结果表明:(1)净光合速率(Pn)日均值从大到小为披针叶黄华>灰榆>山杨>栒子>冰草>油松>小叶忍冬>小檗>青海云杉>苔草,从不同生活型来看表现...     

莫斯科州针阔混交林带森林群落的灌木层结构分析

本文通过分析莫斯科州针阔混交林带１０种类型的森林群落的灌木层结构,指出森林群落中灌木层的结构（垂直结构和水平结构）特点首先取决于组成该层次的灌木种的生物学特性,此外,在不同的群落中乔木层的郁闭度、群落内生境的不一致性（如土壤的水分和肥力状况的差异）以及幼木层的盖度等在不同的程度上影响着灌木的成层和结构。分析表明,灌木在不同的针阔混交林群落中的垂直分布可归纳为三种几何类型：金字塔式、菱形式和倒三角形式。灌木的水平配置多为集团分布或随机分布,趋于集团分布。     

Effects of Prescribed Burning on Herbaceous and Woody Vegetation in Northern Lowland Meadows

Abstract Spring burning of sedge‐grass meadows in the Slave River Lowlands (SRL), Northwest Territories, Canada was applied between 1992 and 1998 to reduce shrub encroachment and enhance Bison bison (bison) habitat, although the impact of fire on preferred bison forage was unknown before management. In the summer of 1998 we conducted a study in the Hook Lake area of the SRL to test the effect of burn frequency (unburned, burned once, or burned three times since 1992) on herbaceous plant community composition and Salix spp. L. (willow) shrub vigor. Plant species abundance, litter biomass, soil pH, and depth of the organic soil horizon were measured in 300 1‐m² quadrats nested within 30 1,000‐m² plots in both burned and unburned dry meadows. To test the relationship between frequency and willow vigor, all willow shrubs within the plots were assigned a vigor score from I (dead) to IV (flourishing). The spring burns appear to have reduced willow vigor; however, shrub survival remained high (76%) on the most frequently burned meadows. Ordination plots resulting from canonical correspondence analysis suggest that multiple spring burns influenced plant community composition in dry meadow areas and that less palatable bison forage species (e.g., Carex aenea Fern. and Juncus balticus L.) were correlated with a regime of three spring burns. Our results suggest that frequent spring fires in the Hook Lake area have only a small negative effect on willow cover but may reduce the abundance of primary bison forage plants compared with less frequently burned meadows.     

Post‐Establishment Seedling Success in the Brazilian Cerrado: A Comparison of Savanna and Forest Species1

Due to frequent fire, low nutrient availability, and prolonged drought, tropical savanna is a stressful environment for the survival and growth of woody plant seedlings. To understand why forest species do not succeed in this environment while savanna species are able to persist, the effects of fire and woody cover on seedlings of these two functional groups were investigated in the Brazilian Cerrado. Seedlings were established in experimental plots under three densities of woody cover, in sites protected from fire and sites to be subjected to fire. There was a clear difference in the ability of savanna and forest species to survive fire. None of the three forest species were able to survive fire during the first two years of life, whereas eight of the nine savanna species were able to resprout following fire. The small seed size of the ninth savanna species, Miconia albicans, predisposed its seedlings to be sensitive to fire, because there was a strong positive correlation between seed size and survivorship. Savanna species were less dependent on woody cover than were forest species, which exhibited higher growth and survival under tree canopies than in open grassland. The low rates of establishment and survival of forest trees in savanna, combined with high sensitivity to fire, appear sufficient to prevent the expansion of forest into savanna under current fire regimes in the Cerrado.     

河北卢龙饮马河流域全新世冲积物孢粉分析及对全新世植被时空变化的初步探讨

 依据河北省卢龙县闫深港4.6m厚的冲积物剖面，揭示了较高时间分辨率的孢粉分析，参照现代冲积物孢粉与植被的对应关系，探讨了距今11000年以来饮马河流域植被的时空变化。11000～9000aBP的森林覆盖率约10％，9000～7000aBP约30％～40％，7000～4000aBP约20％～40％，3000～2500aBP约10％～20％。在9000aBP左右出现了云杉、冷杉花粉的高峰值，表明饮马河流域曾出现垂直植被带的变化。