Is the degree of clonality of forest herbs dependent on gap age? Using fingerprinting approaches to assess optimum successional stages for montane forest herbs

Using molecular fingerprinting (amplified fragment length polymorphism [AFLP] method), we explored the potential of small-scale population analysis for understanding colonization patterns of herb layer species in forests after canopy disturbance. We investigated three common forest understorey species with different life forms (Trientalis europaea, Calamagrostis villosa, and Vaccinium myrtillus) in the Harz Mountains in Germany in three different gap age classes and undisturbed forest. For two of them (T. europaea and C. villosa), we analyzed clone sizes and clonal structure. We hypothesized that clone sizes depend on age since gap formation and are affected by light availability. Mean patch sizes of V. myrtillus, T. europaea, and C. villosa formed were 3.7 m(2), 27.9 m(2), and 40.6 m(2), respectively. Trientalis europaea and C. villosa patches consisted mostly of more than one genet. Largest clone sizes of T. europaea were encountered in gaps of intermediate successional age (15-60 years, averaged minimum estimation of clone sizes: 6.56 m(2)) whereas clone size of C. villosa was found to be independent from gap age and had a mean minimum clone size of 0.49 m(2). In both species, clone size was positively related to light availability. Additionally, there was a positive relationship between clone size and ramet density for T. europaea and C. villosa. Genetic variation was higher within populations of T. europaea and C. villosa than among populations. Trientalis europaea was the only species with a clear genetic isolation by distance, pointing at an equilibrium between gene flow and genetic drift. In conclusion, we showed that forest canopy gap dynamics clearly affect the small-scale structure of populations of understorey plants. Species with high lateral growth rates, such as T. europaea offer the possibility to serve as "ecological clock" for dating ecological processes.     

中国西南六种广义拂子茅属( 禾本科) 植物的染色体数目

广义拂子茅属( Calamagrostis) 是一个世界温带广布的大属, 有些作者又分为拂子茅属和野青茅属, 但近期的研究表明处理为一个属较为合适。中国共有37 种广义拂子茅属植物, 但至今没有任何染色体的研究。本文报道了其中产于中国西南6 种野青茅的染色体数目, 其中Deyeuxia petelotii 4 个居群, D1 diffusa, D1 moupinensis, D1 nivicola 和D1f lavens 各一个居群都是四倍体( 2n= 4x= 28) , D1 neglecta 为六倍体( 2n= 6x= 42) 。根据广义拂子茅属植物染色体倍性特征, 该属植物中至今未发现二倍体, 四倍体是该属中倍性最低和最普遍的, 广义拂子茅属的演化很可能是在四倍体的水平上进行的。由于以上几个四倍体种均是狭域分布的类群, 所以可能是由四倍体的祖先隔离分化形成的。     

Plants inhabiting polygons for megapolis waste as promising species for phytoremediation

Screening of ruderal plant species inhabiting polygons for solid waste (SW) burying contaminated with heavy metals (HM). Among these plants, wood small-reedgrass (Calamagrostis epigeios L. Roth) was found; this plant is a perennial grass characterized by the highest level of HM, especially Ni, accumulation. The content of Ni was 703 mg/kg dry wt in wood small-reedgrass leaves and 346 mg/kg dry wt in its rhizomes. On the SW polygon closed 15 years ago, wood small-reedgrass produced a monoculture of high productivity (15 centner/ha), and this provided for extraction of HM moved from SW layers and maintenance of their concentrations in covering soil at the level not dangerous for plants (by 5–10 times below the threshold level). Under constant conditions, the tolerance of wood small-reedgrass seed germination to HM was established. Adult plants turned out to be tolerant to periodic mowing; they were capable of HM accumulation in above-ground organs; they also accumulated the osmorprotectant proline. It was concluded that wood small-reedgrass could be used for SW polygon recultivation and within the lawn grass mixtures for near-road lawns in cities.     

Stratospheric ozone reduction and ecosystem processes: enhanced UV-B radiation affects chemical quality and decomposition of leaves of the dune grassland species Calamagrostis epigeios

This study reports changes in the plant's chemical composition and the decomposition of this plant material under enhanced solar UV-B radiation. Calamagrostis epigeios, a dominant grass species in the dune grassland in The Netherlands, was grown outdoor on an experimental field under ambient and enhanced solar UV-B (5 and 7.5 kJ m^-2 day^-1 UV-B_BE, respectively), corresponding to about 15% stratospheric ozone depletion. After one growing season aerial plant parts were harvested. The decomposition of this harvested leaf material was studied in a dune grassland and on the above mentioned experimental field under ambient (5 kJ m^-2 day^-1 UV-B_BE) and enhanced (7.5 kJ m^-2 day^-1 UV-B_BE) radiation, using litter bags. The chemical quality of the leaves grown under enhanced solar UV-B changed. There was an increase in the leaf content of lignin, while no significant changes occurred for the content of -cellulose, hemicellulose and tannins under enhanced UV-B. In the field, the rate of decomposition of leaf material grown under enhanced UV-B (with an increased content of lignin) was reduced. The content of lignin of the decomposing leaf material increased, but less under exposure to enhanced UV-B. The latter may be explained by photodegradation of the lignin. The consequences of enhanced UV-B radiation for carbon fluxes in the dune grassland ecosystem are discussed.     

Reproductive challenges of a rare grass,Calamagrostis porteri subsp. insperata (Swallen) C. Greene: implications for habitat restoration

Background: Habitat management for reproductively challenged rare species is a problem when there is insufficient knowledge of their autecology. This study investigated reproductive failure in the rare grass Calamagrostis porteri ssp. insperata (Swallen) C. Greene (Reed bentgrass). Does the management recommendation of high light stimulate clonal growth, flowering, and seed production? Location: Shawnee National Forest, IL, USA, and in a greenhouse and an experimental garden at Southern Illinois University, Carbondale, IL, USA. Methods: Clones obtained from the three known Illinois populations were grown in a glasshouse under experimental light and soil moisture treatments. After 3 years, plants from the high light treatment were planted outside in an experimental garden where the light treatments were maintained for two more years. In the field, vegetative and flowering tiller density, canopy cover, and associated biotic and abiotic variables including abundance of co‐occurring plant species were monitored for 5 years. The overhead tree canopy was cleared over a portion of one population. Results: In the glasshouse, plants increased in size under high light and moist soil, and there were size differences among populations. Sixty‐six per cent (20 of 30) of the genets flowered when planted outdoors under full sunlight but did not produce seed. In the field, flowering only occurred in Calamagrostis growing in the cleared area, but no seed were produced. The plants in the flowering population were smaller than plants in the other two populations. The herbaceous community associated with Calamagrostis in the open diverged from the communities remaining under the shade. Conclusions: This study highlights the difficulty of managing reproductively challenged rare species. Calamagrostis populations can be managed to enhance clonal growth, but establishment of new populations would require translocation of vegetative material as it is highly unlikely that seed can be obtained.     

Grass allometry and estimation of above‐ground biomass in tropical alpine tussock grasslands

The puna/páramo grasslands span across the highest altitudes of the tropical Andes, and their ecosystem dynamics are still poorly understood. In this study we examined the above‐ground biomass and developed species specific and multispecies power‐law allometric equations for four tussock grass species in Peruvian high altitude grasslands, considering maximum height (h_max), elliptical crown area and elliptical basal area. Although these predictors are commonly used among allometric literature, they have not previously been used for estimating puna grassland biomass. Total above‐ground biomass was estimated to be of 6.7 ± 0.2 Mg ha^?1 (3.35 ± 0.1 Mg C ha^?1). All allometric relationships fitted to similar power‐law models, with basal area and crown area as the most influential predictors, although the fit improved when tussock maximum height was included in the model. Multispecies allometries gave better fits than the other species‐specific equations, but the best equation should be used depending on the species composition of the target grassland. These allometric equations provide an useful approach for measuring above‐ground biomass and productivity in high‐altitude Andean grasslands, where destructive sampling can be challenging and difficult because of the remoteness of the area. These equations can be also applicable for establishing above‐ground reference levels before the adoption of carbon compensation mechanisms or grassland management policies, as well as for measuring the impact of land use changes in Andean ecosystems.     

北京市平谷区生态系统服务价值动态

以北京市平谷区1995年和2004年土地利用/覆被数据为基础,利用中国不同陆地生态系统单位面积生态服务价值表对平谷区生态系统服务价值进行了动态分析.结果表明：平谷区生态系统服务价值由1995年的3.291×10⁹元减少到2004年的3.044×10⁹元,变化幅度为-7.50%;耕地和水域面积的减少是该区生态系统服务功能丧失的最主要原因;研究区水域生态系统单位面积生态服务价值量最大,森林生态系统对平谷区生态系统服务价值的贡献最大;该区生态系统服务价值动态变化凸显出研究区土地利用结构的不合理性,应加大研究区森林、农田和水域面积的比重,严格控制耕地向建设用地的转化.作为北京市的应急水源地和生态涵养区,今后须加强对平谷区生态和环境保护力度,促进其经济社会可持续发展,以保障首都水资源和生态的安全.     

Calamagrostis hakonensis (Poaceae): Distribution and differentiation of cytotypes

Chromosome counts were made for a total of 540 collections ofCalamagrostis hakonensis from 66 localities ranging from Kyushu to Hokkaido. Distribution and habitat preferences of the cytotypes involved are described. Sympatric occurrence of tetraploids (=semidiploids, 2n=28) and higher polyploids, as well as that of septaploids and plants at hexaploid and/or octoploid levels, was confirmed in several localities, and mixtures of hexaploids and octoploids within a population were frequently observed. Plants at hexaploid and octoploid levels were the most abundant and widespread. An examination of pollen of the voucher specimens showed that tetraploids (amphimictic) had good pollen, while higher polyploids (apomictic) were generally devoid of pollen and very rarely produced moderately good pollen, the grains of higher polyploids being larger than those of tetraploids. Distributions of tetraploids and higher polyploids were more precisely delineated through an examination of pollen of many herbarium specimens. In relation to the processes by which the complicated internal structure ofC. hakonensis has been established, the following subjects are discussed: infraspecific hybridization between ecotypically differentiated populations, enrichment of variability through occasional sexual reproduction expected in plants with more than 2n=42, persistence of the variants by apomictic reproduction, and probable roles of some extinct taxa.     

Biogeochemical cycle of Sulfer in the Calamagrostis angustifolia wetland ecosystem in the Sanjiang Plain, China

To better understand the Sulfur (S) cycle in the wetland ecosystem, the S cycle and its compartmental distribution within an atmosphere-plant-soil system were studied using a compartment model in the Calamagrostis angustifolia wetland in the Sanjiang Plain, Northeast China. The results showed that the soil was the main S storage and flux hinge in which 97.78% S was accumulated. In the plant subsystem, the root was the main S storage, and it remained at 79.60% of the total S contents, which in the Calamagrostis angustifolia wetland ecosystem showed that the parts above the ground took up 0.75 g S/m², the S re-transferring biomass to the root was 0.24 g S/m², and to the litter was 0.51 g S/m²; the root took up 3.76 g S/m² and the S transferring biomass to the soil took up 3.07 g S/m²; the litter S biomass was 0.75 g S/(m²·a) and the S transferring biomass to the soil was more than 0.52 g S/(m²·a). The emission amount of H2S from the Calamagrostis angustifolia wetland ecosystem to the atmosphere was 1.42 mg S/m², whereas carbonyl sulfide (COS) was absorbed by the Calamagrostis angustifolia wetland from the atmosphere and the absorption amount was 1.83 mg S/m². The S input biomass from the rain to the ecosystem was 4.85mg S/m² during the growing season. The difference between input and output amounts was 5.26 mg S/m², which indicated that S was accumulated in the ecosystem and would lead to wetland acidification in the future.