Climatic deterioration and the end of the Gortian Interglacial in sediments from Derrynadivva and Burren Townland,near Castlebar,County Mayo,Ireland

Pollen and macrofossil analyses of two sequences of organic sediment in western Ireland have allowed the recognition of the latter parts of the Gortian Interglacial, a Middle Pleistocene temperate stage. The palaeobotanical information from the two sites identifies the preservation of partial sequences from the Gortian Interglacial (believed to be the equivalent of the Hoxnian Stage of Britain and the Holsteinian of Europe). The pollen and macrofossil data from one of the sites, Derrynadivva, span the middle and latter parts of the temperate stage. The results show that fire influenced the vegetation throughout the middle part of the temperate stage, and the termination of the organic depositional sequence appears to have been due to environmental deterioration. The former is identified through the abundant occurrence of charcoal in the sediments, whereas the latter is apparent in the sediment sequence and in the reworking of thermophilous pollen types into the upper part of the deposit. The second site, Burren Townland, records only part of the later zones of the interglacial, but the ericaceous assemblages of the latter part of the Gortian Interglacial are well developed and well preserved. Macrofossil analyses and scanning electron microscopy work on the pollen at the latter site has allowed the recognition of Rhododendron ponticum, adding to previous records of this species, which now has a very disjunct European distribution.     

Evergreen Understory Dynamics in Coweeta Forest,North Carolina

A number of studies have elucidated the distributional patterns of various components of Southern Appalachian forests. The evergreen understory here is composed largely of a dominant ericaceous shrub, Rhododendron maximum L., which is believed to be expanding and inhibiting the development of other species with consequent impacts on overall forest structure and composition. We use a GIS and logistic regression to examine this less-studied forest element in the Coweeta Hydrological Laboratory, North Carolina, over a 17-year period to determine whether expansion is occurring and, if so, whether it can be predicted based on terrain characteristics. We examine two adjacent, physically similar basins with differing degrees of experimental manipulation in the 20th century in an attempt to examine the role of environmental and historical factors in determining spatial patterns of persistence, expansion, and decline of the evergreen understory. Results indicate that significant expansion of the evergreen understory occurred in both basins during the period 1976-1993, and that stream proximity, topographic setting, and elevation are related to patterns of evergreen-understory dynamics. Patterns differ between the two basins, suggesting that disturbance and differing land-use histories are also influential. Predictive power of models based on terrain factors alone ranges from <10% to >50%.     

高山杜鹃植物挥发油的化学成分

用毛细管气相色谱保留指数定性、标准样品叠加和色谱-质谱-计算机联用技术,对紫丁杜鹃、毛蕊杜鹃、草原杜鹃和雪层杜鹃挥发油的化学成分进行了分离和鉴定,共定出单萜烃18个,倍半萜烃31个,并测得了各化合物的相对含量。它们的主要成分基本相似,即:檀香醇、醋酸冰片酯、β-石竹烯、β-蒎烯、α-蒎烯、莰烯和异醋酸冰片酯等。     

甲基卡稀有金属矿区北方雪层杜鹃植物地球化学特征及对隐伏锂矿的指示

北方雪层杜鹃（Rhododendron nivale Hook. f. subsp. boreale Philipson et M. N. Philipson）是川西高原甲基卡稀有金属矿区的优势植物种属。为了研究利用植物地球化学寻找隐伏锂矿体的有效性, 文章以甲基卡矿区内有代表性的804号、烧炭沟（ST）隐伏锂矿体上方生长的北方雪层杜鹃为研究对象,研究其植物地球化学异常特征及对矿体的指示性。研究表明：甲基卡矿区北方雪层杜鹃中Li、Be、Rb、Nb、Ta等成矿元素能形成明显的异常;在隐伏锂矿体上方的植物地球化学异常位置与矿体的位置对应性较好,能有效反映不同埋深隐伏矿体的存在,探测深度可达100 m,结果为甲基卡稀有金属矿区寻找隐伏矿体提供新的找矿方法。     

云南上新世杜鹃属和松属化石木研究及其古气候意义

研究了云南西部龙陵县上新世的化石木。鉴定出两种木材类型。杜鹃花科杜鹃属的似腋花杜鹃Rhododendron cf. racemosum Franchet，其主要木材特征有散孔材，生长轮略明显，导管具多角形轮廓，螺纹加厚出现在整个导管壁上，梯状穿孔板，射线异形II型。松科华山松Pinus armandii Franchet的主要特征有交叉场纹孔窗格状，具正常轴向和纵向树脂道，且泌脂细胞壁薄，射线管胞内壁平滑或具稀疏的微锯齿。两种类型的化石木在我国均属首次报道。根据化石木结构和现代相应树种和植被的生境范围，当时植物生长于亚热带温凉湿润的山地环境，其海拔大约在1800米左右。     

Ecological consequences of land use change: Forest structure and regeneration across the forest-grassland ecotone in mountain pastures in Nepal

The ecotone, the spatial transition zone between two vegetation communities, is claimed to have more species than the adjoining communities. However, empirical studies do not always confirm higher richness at the ecotone. The ecotone position and structure are dynamic over time and space and it is driven by the changes in climate, land use or their interaction. In this context, we assessed the forest- grassland ecotone of temperate mountains in central Nepal by i） comparing species composition and richness across the ecotone, ii） analyzing if the forestgrassland ecotone is shifting towards the grassland center by colonizing them with trees, and iii） discussing the consequence of changed disturbance regime in the dynamics of this ecotone and the surrounding grasslands. We analyzed vegetation data sampled from belt transects laid across the forest- grassland ecotone in semi-natural grassland patches. Vegetation data consisting of species richness and composition, and size structure and regeneration of the two most dominant tree species, namely Rhododendron arboreum and Abies spectabilis, from the transects, were used to analyze the trend of the forest-grassland ecotone. Forest and grasslands were different in terms of floristic composition and diversity. Vascular plant speciesrichness linearly increased while moving from forest interior to grassland center. Spatial pattern of tree size structure and regeneration infers that forest boundary is advancing towards the grasslands at the expense of the grassland area, and tree establishment in the grasslands is part of a suceessional process. Temporally, tree establishment in grasslands started following the gradual decline in disturbance. We argue that local processes in terms of changed land use may best explain the phenomenon of ecotone shift and consequent forest expansion in these grasslands. We underpin the need for further research on the mechanism, rate and spatial extent of ecotone shift by using advaneed tools to understand the process indepth.