贺兰山针叶林结构特征与种类组成的比较

贺兰山针叶林是我国西北地区珍贵的森林生态系统，本文通过研究其结构特征和植物种类组成，为森林保育提供建议。基于森林结构特征，贺兰山针叶林可分为4类，分别为乔木径级组成以小于lOcm为主，以10～20cm为主，径级组成较均衡和以大于30cm为主。分类的结果主要反映了砍伐后恢复时间的长短和海拔高度的影响。根据样方的物种组成分析，共得6个群丛，主要反映了海拔的影响。物种密度以云杉藓类林最低。云杉藓类林向上与高山灌丛草甸交错，物种密度增加。海拔降低，云杉林类型改变，物种密度增加。海拔最低的油松林，物种最为丰富。两种分类反映了贺兰山针叶林不同方面的特征，但也存在联系。海拔高度对于森林结构和物种组成的影响都是明显的，而当森林结构特征类似时，包含的群丛较多，但某一群丛则往往仅属于一种或两种结构类型。

Mangrove Flora of the World

The species composition and characteristics of mangrove flora in the world were reviewed and discussed. The results suggested that the world's mangrove plants have 84 species (including 12 varieties) in 24 genera and 16 families. Of which, true mangrove plants have 70 species (including 12 varieties) in 16 genera and 11 families, and semi-mangrove plants 14 species in eight genera and five families. The Eastern Group has 74 species (including 12 varieties) in 18 genera and 14 families, characterized by the genera Aegiceras, Osbornia, Aegialitis, Bruguiera, Ceriops, Kandelia, Scyphiphora and Nypa etc. The Western Group has only 10 species in six genera and five families, characterized by the endemic one-species family, Pelliceraceae, and the genus Laguncularia. The mangrove flora of China is composed of 26 species (including one variety) in 15 genera and 12 families, four of which are endemic. Hainan is most rich in mangrove species, making up about 96.2% of the Chinese total; Guangdong ranks second, making up about 42.3%. It has been demonstrated that Rhizophora stylosa was mistaken for R. mucronata in Taiwan by previous authors.

Effects of Corridor Networks on Plant Species Composition and Diversity in an Intensive Agriculture Landscape

The development of modern agriculture has resulted in much homogenization of the landscape consisting of large patches of farmland,so small remnant non-crop habitats especially linear corridors play an important role in the conservation of species and the maintenance of ecosystem functions.However,little attention has been paid to the effects of corridors structural characteristics on the plant species restricted to such habitats.In this study,we selected three types of corridors including ditch,hedgerow and road,and analyzed their structural characteristics.The plant species presented in these corridors were investigated,and the species diversity,abundance and frequency were estimated.Moreover,spatial arrangements of corridors were classified into different types to discuss whether there were significant effects of corridor network on plant distribution.The results show that three types of corridors have different effects on plant species composition and diversity.The one-one combined corridor networks and total network associated by three corridors have more complex structural features than each single type of corridor.However,there is no strong correlation between the corridor networks with their plant species.We suggest that carrying out a pointed vegetation survey at corridor intersections to further test the relationships between structural features of corridor and plants is necessary.

Natural vegetation recovery on waste dump in opencast coalmine area

The changes of vegetation compositions, plant species diversity, species important value and succession of plant community were studied on waste dumps in Haizhou opencast coalmine which is located in the west of Liaoning Province, China (41°41(-42°56( N, 121°1(-122°56(E). Four kinds of terraces with different ages (5, 10, 20 and 40 years) were selected for investigation of plants. Total of 63 species of natural colonized plants were recorded on the waste dump and they belong to 23 families. The main families were Compositae (15 species), Fabaceae (11 species) and Leguminosae (8 species), which accounted for 54.0% of total species and play an important role in natural vegetation recovery in waste dump area. The dominant species on 5-, 10-, 20-, 40-year-old terraces were Tribulus terrestris + Echinochloa hispidula + Salsola collina, Echinochloa hispidula + Artemisia sieversiana + Artemisia scoparia, Echinochloa hispidula + Clinelymus dahuricus + Artemisia scoparia + Artemisia sieversiana + Melilotus officinalis, Clinelymus dahuricus+Phragmites communis + Echinochloa hispidula+ Setaria viridis, respectively. According to the important value of species calculated. It is determined that Tribulus terrestris can act as pioneer species on waste dump and Clinelymus dahuricus, Phragmites communis and Echinochloah hispidula are important dominant species in vegetation restoration in Haizhou opencast coalmine. The study results can provide scientific basis for selecting and disposing appropriately plant species and rehabilitating vegetation on waste dumps of coalmine.

Transcription analysis of peloric mutants of Phalaenopsis orchids derived from tissue culture

Tissue culture has been widely used for mass propagation of Phalaenopsis. However, somaclonal variation occurred during micropropagation process posed a severe problem by affecting product quality. In this study, wild type and peloric flower buds of Phalaenopsis hybrids derived from flower stalk nodal culture were used for cDNA-RAPD and cDNA suppression subtractive hybridization analyses in order to study their genetic difference in terms of expressed sequence tags. A total of 209 ESTs from normal flower buds and 230 from mutants were sequenced. These ESTs sequences can be grouped into several functional categories involved in different cellular processes including metabolism, signal transduction, transcription, cell growth and division, protein synthesis, and protein localization, and into a subcat- egory of proteins with unknown function. Cymbidium mosaic virus transcript was surprisingly found expressed fre- quently in the peloric mutant of P. Little Mary. Real-time RT-PCR analysis on selected ESTs showed that in mutant flower buds, a bZIP transcription factor (TGA1a-like protein) was down-regulated, while up-regulated genes include auxin-regulated protein kinase, cyclophilin, and TCP-like genes. A retroelement clone was also preferentially expressed in the peloric mutant flowers. On the other hand, ESTs involved in DNA methylation, chromatin remodeling and post- transcriptional regulation, such as DNA methyltransferase, histone acetyltransferase, ERECTA, and DEAD/DEAH RNA helicase, were enriched in normal flower buds than the mutants. The enriched transcripts in the wild type indicate the down regulation of these transcripts in the mutants, and vice versa. The potential roles of the analyzed transcripts in the development of Phalaenopsis flowers are discussed.

Phytoplankton community composition in the surrounding waters of Changli, Hebei, China

The seasonal and spatial variations of phytoplankton abundance weresupported with microscopic analyses in the surrounding waters of Changli in the spring(May) and summer (August) of 2015. Nineteen sampling stations were selected in thisstudied area (39°26′30"-39°39′ N, 119°17′30"-119°34′03"). During the survey period, atotal of 27 species of phytoplankton have been documented in spring and 63 species insummer. In terms of the community composition at the seasonal level and the spatialdistribution, Dinoflagellates was absolutely dominant in spring and Bacillariophyta wasdominant in summer. The average phytoplankton cell density of phytoplankton speciesshowed substantial seasonal differences. In addition, the dominant species in differentseasons were different. The average values of Shannon-Wiener diversity index (H')were 0.99 in spring and 3.25 in summer, which implied that species diversity in summeris higher than that in spring. Redundancy analysis (RDA) revealed that ammonium(NH4+-N) and nitrites nitrate nitrogens (NO3--N) were the important environmentalfactors influencing the phytoplankton distribution. N is the main environmental drivingfactor result from environmental indicators and RDA analysis.

Effects of Topography and Land use on Woody Plant Species Composition and Beta Diversity in an Arid Trans-Himalayan Landscape, Nepal

Distribution patterns of plant species are believed to be impacted by small-scale habitat heterogeneity. However, there have been few comparative studies examining how woody vegetation composition and diversity varies with aspects of different orientations in the Trans-Himalayan region at a local scale. Here, we examined the effects of incoming solar radiation on variation in woody species composition and compared the diversity between the northeast- and southwest-facing slopes in a Trans-Himalayan valley of Nepal. We also examined the implicit interactions between slope orientation and land use in determining the compositional variations between the slopes. We selected two pairs of northeast- and southwest-facing slopes where the first pair has a similar land use and differs in exposure only(Pisang site) while the other pair has clear differences in land use in addition to slope exposure(Braka site). In each site, we sampled 72 plots(36 on each slope) in which the presence and absence of woody species, environmental variables, and disturbance were recorded. Correspondence Analysis(CA) results suggested that the woody species composition significantly varied between northeast- and southwest-facing slopes at both sites, and was significantly correlated with measured environmental variables such as radiation index, altitude, and canopy openness. In the Braka site,mean alpha diversity was significantly higher on southwest-facing slopes. In contrast, beta diversity and gamma diversity were greater on northeast-facing slopes at both sites. Our results suggest that topographic variables(e.g., radiation index) affect species composition between the slopes, likely due to their influence on small scale abiotic environmental variables. However, the effects of land use, such as livestock browsing/grazing may interact with the effects of slope exposure, effectively reducing differences in species composition within slopes but enhancing the differences in beta diversity between contrasting slopes in the Braka. We conclude that slope orientation and land use are important factors in structuring the woody species composition and diversity in the arid Trans-Himalayan region. We suggest that both environmental and land use variables should be taken into consideration in future studies on plant community structure along the cultural landscapes.

Influences of sea ice on eastern Bering Sea phytoplankton

The influence of sea ice on the species composition and cell density of phytoplankton was investigated in the eastern Bering Sea in spring 2008. Diatoms, particularly pennate diatoms, dominated the phytoplankton community. The dominant species were Grammonema islandica （Grunow in Van Heurck） Hasle, Fragilariopsis cylindrus （Grunow） Krieger, F. oceanica （Cleve） Hasle, Navicula vanhoeffenii Gran, Thalassiosira antarctica Comber, T. gravida Cleve, T. nordenskioeldii Cleve, and T. rotula Meunier. Phytoplankton cell densities varied from 0.08× 10^4 to 428.8× 10^4 cells/L, with an average of 30.3× 10^4 cells/L. Using cluster analysis, phytoplankton were grouped into three assemblages defined by ice-forming conditions： open wate.r, ice edge, and sea ice assemblages. In spring, when the sea ice melts, the phytoplankton dispersed from the sea ice to the ice edge and even into open waters. Thus, these phytoplankton in the sea ice may serve as a “seed bank” for phytoplankton population succession in the subarctic ecosystem. Moreover, historical studies combined with these results suggest that the sizes of diatom species have become smaller, shifting from microplankton to nannoplankton-dominated communities.

Agro-biodiversity and Traditional Knowledge on Tunisian Coastal Oases

The Tunisian coastal oases constitute a model of very rich plant biodiversity, organized in different floors of cultivation. The date palm is the highest, the second is the diversified fruit trees and the smallest is composed by various other productions. The present paper is the results of a RAA diagnosis and bibliographic analysis of nearly thirty years of work on oases. The aim of this study is to focus on the plant diversity and the traditions in using different products. The survey revealed the existence of nearly 45 local date palm varieties, about 26 fruit trees, 65 vegetables and divers other species. It also raises nearly 30 uses of dates and date palm by-products. This survey shows also that oases inhabitants keep in possessing, for a long time, a knowledge to make ingenious concerning use and conservation of the products and by products of the date palm. This survey has all as much demonstrated the risks from weakening this balance which has long been maintained. Some recommendations to maintain and conserve this system are also presented in this paper.

Plant Response and Grape Composition of Vitis vinifera L, cv Tannat in Different Climatic Regions

In wine production, the typical characteristics of variety, defined by its place of their origin, contribute to the development of distinctive and unique wines. In the current study, we analyzed the effect of the environment using vine response and grape composition as indicators. Four cv. Tannat vineyards in three different climatic regions of Uruguay with similar soil conditions were studied in 2008 and 2009. Vines grafted onto SO4 （Vitis berlandieri × Vitis riparia） rootstock and were trained on a trellis system. Weather information was obtained from weather stations （MMO standards）. At each vineyard, we recorded： yield per plant, pruning weight, leaf area and pre-dawn leaf water potential. We analyzed sugars, total acidity and pH, polyphenolic potential, organic acids and berry weight. Analysis of variance, Pearson correlations and discriminant analysis were carried out. The climate factors with the highest discriminant weight were water balance, degree days （〉 10 ℃） of maturation and rainfall during the vegetative growth period. Plant response allowed us to discriminate between vineyards regardless of the year and was consistent with climate. Exposed leaf area and length of maturation period were the indexes with the highest values, followed by leaf water potential and grape yield. The total anthocyanin content, sugar contents and their daily accumulation, and acid composition statistically separate regions regardless of the year. We concluded that plant response and grape composition were strongly influenced by water supply and thermal conditions during ripening.

The Distribution Patterns of Timberline and Its Response to Climate Change in the Himalayas

Himalayan region represents the highest and most diverse treeline over the world.As one of the most conspicuous boundaries between montane forests and alpine vegetation,the alpine timberline attracted the interest of researchers for many decades.However,timberline in the Himalayas is understudied compared with European counterparts due to remoteness.Here we review the distribution pattern of timberline and its climatic condition,the carbon and nutrient supply mechanism for treeline formation,and treeline shift and treeline tree recruitment under climate change scenarios.Growth limitation,rather than carbon source limitation is the physiological cause of timberline under the low temperature condition.Nutrient limitation and water stress are not the direct cause of timberline formation.However,more clear local limitation factors are need to integrate in order to enable us to predict the potential impacts and changes caused by human activity and related global change in this sensitive region.

Changes in vegetation and soil properties following 6 years of enclosure in riparian corridors

Aims Riparian corridors play vital roles in the maintenance of biodiversity.Nonetheless,plant species diversity and vegetation coverage in riparian corridors are seriously threatened by increasing pressure owing to livestock consumption and anthropogenic disturbance;even the stability of river courses has been threatened.The establishment of enclosures is a widely used strategy to restore degraded grassland ecosystems,but its impact on degraded herbaceous riparian vegetation and soil properties remains unclear.The aim of this study was to evaluate whether species composition,richness,diversity,and soil properties can be recovered by the enclosure.Methods Twenty long-term monitoring sample plots were set in the Liaohe main stream river,Liaohe main stream river was enclosed for grazing and farmland exclusion in 2012.The height,coverage and individual numbers of plant were recorded for species richness and diversity evaluation from 2012 to 2017;soil nutrients were measured for comparative analysis in 2012 and 2017.We examined the effects of the establishment of enclosures on plant species diversity and soil properties from 2012 to 2017 in the riparian corridors of the Liaohe River system in China.Important Findings Plant species richness and diversity significantly increased from 2012 to 2017.The dominance of Asteraceae plants increased,while the abundance of Gramineae plants decreased over time.The difference in abundance increased each year since enclosure was implemented in 2012.The concentrations of phosphorus and potassium in the soil significantly decreased as a result of the combined effects of vegetation restoration and prohibition of farming practices following the establishment of enclosures.There was also a lag time related to the response of soil organic matter to the establishment of enclosures.In conclusion,our study provides new evidence regarding the response of species diversity,species composition and soil properties following riparian vegetation restoration efforts through enclosure development.