Changes in O horizon mass,thickness and carbon content following fire in northern hardwood forests

This study examines temporal changes in the thickness, mass, and organic carbon content of the O horizon (forest floor) of eight forested plots in northern Michigan, USA. Each plot had experienced a recent burn (prescribed or accidental); burn dates ranged from 1798 to 1980. The climax forest in this region is mixed Pinus-Acer-Betula-Tsuga, whereas the fire successional species are predominantly Populus spp. and Betula papyrifera. O horizon data were fit to logarithmic functions (chronofunctions) that depicted rapid accumulations of mass and thickness in the first years after the fire, followed by decreasing rates of increase after 100 years. Extension of the chronofunctions to 5000 years allowed for a theoretical examination of forest floor conditions, e.g., steady state and time to steady state, after long periods without disturbance. The models predicted greater O horizon thicknesses and slightly lower mass for steady state conditions than have been reported for old-growth stands elsewhere. Steady state accumulations of litter in these mixed, temperate forests requires at least 200 and possibly > 1000 years, which is markedly longer than most other estimates. Although frequent disturbance by fire in these forests would likely preclude such values from being attained, these data provide theoretical maximum values for forest floor conditions in these ecosystems.     

Canopy cover and tree regeneration in old-growth cove forests of the Appalachian Mountains

Relationships between canopy cover and tree regeneration were determined for various species in cove forests of the Great Smoky Mountains. Old-growth stands were sampled with six plots covering a total area of 4.8 ha. Each plot was subdivided into contiguous 10×10 m quadrats. Canopy cover overlying each of the 480 quadrats was characterized with three different indices based on visual estimates of cover. Influences of: (1) overlying cover, (2) proximate openings, and (3) total area of proximate openings on quadrat regeneration densities were determined. Most species reproducing by seed and some species reproducing by vegetative means had higher densities in quadrats with openings, but only the intolerants were highly dependent on gaps. Tsuga canadensis, a very shade-tolerant species, was one of the few species with abundant regeneration beneath dense canopy cover. In general, understory areas near gaps had somewhat higher regeneration densities than other areas with overlying cover. Several shade-tolerant species showed a positive regeneration density response to canopy openings and an ability to regenerate in gaps 0.01–0.03 ha in area. These openings were too small for intolerant species. Many species exhibited a positive response to total size of the proximate opening(s). A sharp increase in regeneration density with area of the opening(s) was evident at approximately 0.04 ha for the shade-intolerant species.     

Fractal properties of forest spatial structure

The definition of fractal dimension of natural objects, which enables to deal with scale dependence of fractal dimension is discussed. Abrupt changes of fractal dimension of spatial structure of terrestrial ecosystems are considered in the context of hierarchical paradigm. On this ground the procedure is proposed for segmentation of a territory, which takes into account the scale dependence of spatial variability of ecological parameters. Using remotely sensed data — normalized difference vegetation index (NDVI) and thermal radiation in the infrared band — fractal dimensions and critical scales are evaluated for different forest types with the help of software, developed for this purpose. The results obtained corroborate the potentialities of fractal approach in ecology. These methods and results can be used for discrimination of remotely sensed data; but further investigations, including detailed comparison of fractal characteristics of remotely sensed forest images with results of on-site field studies are necessary to validate them.     

天然林内红松种群年龄更替数学模型及研究

本文给出天然林内红松种群年令更替数学模型（1）。通过对（1）进行定性分析,得到主要结论是：系统（1）在第一象限内存在唯一稳定周期解的充要条件是bk-bc-2d＞0其生态意义是天然林内红松幼树与母树随时间变化会产生一个有规律、互为消涨的变化特征。     

鼎湖山森林群落演替之研究

鼎湖山森林群落在自然状态下遵循一定的客观规律向更优化的气候顶极群落演变。本文分析其1955年至1989年(35年)来的演替结果,总结出鼎湖山森林群落演替的进程和模式,进一步应用植物群落演替系统的线性模型和非线性模型对演替进程进行定量研究,并做出相应的演替进程的数量预测。     

Scale dependence of vegetation-environment correlations: A case study of a North Carolina piedmont woodland

Abstract. Vegetation and its correlation with environment has been traditionally studied at a single scale of observation. If different ecological processes are dominant at different spatial and temporal scales, the results obtained from such observations will be specific to the single scale of observation employed and will lack generality. Consequently, it is important to assess whether the processes that determine community structure and function are similar at different scales, or whether, how rapidly, and under what circumstances the dominant processes change with scale of observation. Indeed, early work by Greig-Smith and associates (Greig-Smith 1952; Austin & Greig-Smith 1968; see Greig-Smith 1979; Kershaw & Looney 1985; Austin & Nicholls 1988) suggested that plant-plant interactions are typically important at small scales, but that the physical environment dominates at large scales. Using a gridded and mapped 6.6 ha portion of the Duke Forest on the North Carolina piedmont for a case study, we examined the importance of scale in vegetation studies by testing four hypotheses. First, we hypothesized that the correlation between vegetation composition and environment should increase with increasing grain (quadrat) size. Our results support this hypothesis. Second, we hypothesized that the environmental factors most highly correlated with species composition should be similar at all grain sizes within the 6.6-ha study area, and should be among the environmental factors strongly correlated with species composition over the much larger extent of the ca. 3500 ha Duke Forest. Our data are not consistent with either portion of this hypothesis. Third, we hypothesized that at the smaller grain sizes employed in this study (< 256 m²), the composition of the tree canopy should contribute significantly to the vegetation pattern in the under-story. Our results do not support this hypothesis. Finally, we predicted that with increased extent of sampling, the correlation between environment and vegetation should increase. Our data suggest the opposite may be true. This study confirms that results of vegetation analyses can depend greatly on the grain and extent of the samples employed. Whenever possible, sampling should include a variety of grain sizes and a carefully selected sample extent so as to ensure that the results obtained are robust. Application of the methods used here to a variety of vegetation types could lead to a better understanding of whether different ecological processes typically dominate at different spatial scales.     

Frog call transmission in forestry monocultures: Are there drawbacks?

Anuran males emit advertisement calls for the purpose of attracting females and repelling conspecific males. Call transmission is influenced by the acoustics of the propagation environment, including vegetation. Thus, forestry monocultures of non-native trees represent artificial environments that could modify call transmission. These monocultures have substituted large areas of Atlantic Forest in southern Brazil, representing a conservation challenge. Considering this context, we hypothesized that anurans have calls that are less attenuated in their native environment than in forest plantations. To test it, we performed sound transmission experiments using calls of three anuran species native to southern Brazil: Boana bischoffi, B. leptolineata, and Hylodes meridionalis. We compared sound attenuation between the native forest and forestry monocultures (Eucalyptus sp. and Pinus sp. forests), and included distance from the sound source, air temperature, humidity, and vegetation density as cofactors in linear mixed models. Our results show that the advertisement calls of the two tree frogs (Boana) attenuate less in tree plantations than in native forests, while the third species shows either no differences or less attenuation in native forests. Our results can be understood according to differences in natural history and microhabitat use among the studied species. The two tree frog species vocalize perched from vegetation so their calls become better transmitted in forestry monocultures, which have fewer trees than the native forest. On the other hand, H. meridionalis calls from rocks on streams and the propagation is finely tuned to this peculiar microhabitat. We discuss the conservation implications of our findings for anurans and for the Atlantic Forest. Abstract in Portuguese and Spanish are available with online material.     

The effects of grazing on the pollen production of grasses

Samples from moss polsters taken over three consecutive years during a controlled grazing experiment in a nature reserve in the Netherlands were analysed for their pollen content, particularly grass pollen. Samples were also taken in the year following the experiment, with grazing pressure strongly diminished. This yielded data regarding the effect of grazing on the pollen production of grasses in open habitats, plantations, and unproductive and productive woods under different grazing pressures.     

海南潜在世界自然遗产地的突出普遍价值初探

世界自然遗产地是全球最具有保护价值的自然保护地,强调全球突出普遍价值的完整性和在全球的唯一性。世界自然遗产有助于更好地保护生态系统的完整性和原真性,促进人类与自然的可持续发展。该研究在大量文献资料的基础上,以海南潜在世界自然遗产地(海南热带雨林国家公园)原生动植物及植被群落(亚洲北缘热带雨林)为研究对象,从植被类型、物种多样性、区系组成、特有种等生物生态过程方面,评估海南潜在世界自然遗产地的全球突出普遍价值。结果表明:(1)海南潜在世界自然遗产地分布有3 653种野生维管植物,资源植物种类丰富。陆栖脊椎动物有540种,各类野生动物占全国的比例高达10%～30%,生物多样性极高。(2)植物区系独特,海南岛的热带雨林植被区划属于印度-马来雨林群系,属马来区的部分呈现出热带性和与中国华南大陆的共源性显示出明显的热带边缘性质,为中国华南植物区系与亚洲热带雨林的过渡类型。(3)植物区系中的植物物种特有性较低,特有属仅有7个,特有种仅约占岛内植物的1/10,较低的特有性表明了其大陆起源特征,是生物多样性不可替代的元素,具有鲜明的环境指示特色。该研究明确了海南潜在世界自然遗产地在全球背景下的突出普遍价值,为海南未来申遗提供科学依据和技术支撑。     

广椭牛齿兰，中国兰科一新记录种

报道了在海南热带雨林国家公园内发现的兰科牛齿兰属中国一新记录种：广椭牛齿兰[Appendicula ovalis(Schltr.) J.J.Sm. ex Mansf.]。该种原分布于马来半岛、苏门答腊岛、爪哇岛、婆罗洲、苏拉威西岛,在形态上与国内记录的4种牛齿兰属植物均有较大差别,如茎中部具分枝、叶广椭圆形、单个花序仅着生1朵花、且唇瓣扭转具粉紫色斑块等特征。对产自海南的该种形态和生境进行了详细描述,并提供高清解剖照片。凭证标本保存于海南大学林学院教学标本馆(HUFB)。