Changes in prairie vegetation under elevated carbon dioxide levels and two soil moisture regimes

Abstract. It is important to know how increasing levels of atmospheric CO₂ will affect native vegetation. The objective of this study was to determine the effect of elevated CO₂ concentrations on species composition in a tallgrass prairie kept at a high water level (730 mm of water in a 2000 mm soil profile) and a low water level (660 mm of water in 2000 mm). 16 cylindrical plastic chambers were placed on the prairie to maintain two levels of CO₂ (ambient or twice ambient) during two growing seasons in 1989 and 1990. Frequency of species was determined on 25 July 1989 and on 5 and 10 October 1990. At the beginning of the study, Poa pratensis (Kentucky bluegrass), the dominant C₃ species, had the highest frequency of 43.3%, but decreased with time. However, at the end of the experiment and under the high soil-water level, there were more P. pratensis plants in the elevated CO₂ treatment (frequency: 13.5%) than in the ambient CO₂ treatment (1.0%). Under the low soil water regime, the reverse occurred (frequencies: 3.6% and 11.0% for high and low CO₂, respectively). The frequency of major C₄ plants, Andropogon gerardii (big bluestem), A. scoparius (little bluestem) and Sorghastrum nutans (Indian grass) was not affected by CO₂. However, water did affect their frequency. Under low water, the frequency of A. gerardii decreased between 1989 and 1990. Under both soil moisture levels, the frequencies of S. nutans and A. scoparius increased. At the end of the study, Indian grass grown with high water had the highest frequency of all species on the prairie (frequency at the end of the study in October, 1990, of 44.4% and 47.4% for the high and low CO₂ levels, respectively). Unlike Indian grass, little bluestem grew better under low water conditions than under high water conditions. These results suggest that, if the climate becomes drier, A. scoparius will flourish more than S. nutans or A. gerardii, and P. pratensis may die out. Elevated CO₂ might not increase survival of C₃ plants under dry conditions, if temperatures are too high for them.     

东祁连山灌丛凋落叶水浸提液对垂穗披碱草种子萌发和幼苗生长的影响

为了解灌丛凋落叶在灌草群落结构维持中可能存在的潜在化感作用，以东祁连山3种优势灌木和灌下优势草种垂穗披碱草(Elymus nutans)为供试材料，分析了不同浓度(0.01 g/L、0.025 g/L、0.05 g/L、0.075 g/L、0.1 g/L)的金露梅(Potentilla fruticosa)、川滇柳(Salix rehderiana)、头花杜鹃(Rhododendron capitatum)及灌间草本的凋落叶水浸提液，对垂穗披碱草种子萌发、幼苗形态和生理指标的影响。结果表明：(1)垂穗披碱草种子发芽率与发芽势在金露梅与川滇柳凋落叶浸提液处理下呈“低促高抑”的浓度效应，在灌间草本凋落叶浸提液处理时表现为先升后降，而头花杜鹃凋落叶浸提液处理时均下降，并在浓度超过0.075 g/L时种子不发芽。(2)灌丛凋落叶浸提液对垂穗披碱草幼苗根长与干重均表现出抑制作用，且随浓度增大而增强；金露梅、川滇柳与灌间草本凋落叶浸提液对垂穗披碱草幼苗苗高表现出“低促高抑”的浓度效应；而头花杜鹃凋落叶浸提液处理对垂穗披碱草幼苗鲜重与苗高均呈抑制作用。(3)垂穗披碱草幼苗CAT、SOD活性随着浸提液...     

Warming leads to divergent responses but similarly improved performance of two invasive thistles

Plants’ responses to climate change are complex. Even the same net performance changes may involve different responses of multiple life history traits. Here we show that two congeneric thistles, Carduus nutans and Carduus acanthoides, both grew taller under increased temperature, albeit following divergent response patterns. For C. nutans, warming advanced bolting more than flowering, leading to a longer growing period before flowering and ultimately taller plant height at the end of the growing season. Carduus acanthoides maintained the same length of growing period because of equally shifted events in the phenological sequence, however, post-flowering growth rate was increased, which also led to enhanced final plant height. As seeds from taller plants disperse farther, their responses imply that future invasion spread rates of these two species will increase. Similar consequences due to divergent responses in life history traits, as demonstrated in this study, suggest that considering only ultimate performance outcomes, and not the underlying processes generating such outcomes, is not enough to understand the impacts of climate change.     

A taxonomic synopsis of the genus Campeiostachys Drobov

We have classified 11 species recently recognized as belonging to the genus Elymus into a resurrected and legitimate genus Campeiostachys Drobov according to the International Code of Botanical Nomenclature. Our action is based on the rationale of monophyly, discrimination, and practicality discussed in detail. Currently Elymus contains a vast number of species with different genomes which often, but not always, can be differentiated by cytological and molecular features, but are difficult to separate by tr...     

Numerical classification of the coastal vegetation of Attu Island,Aleutian Islands,Alaska

Abstract. This phytosociological study of the beaches, dunes, and associated lower mountain slopes of Attu Island is the first effort to identify the major coastal vegetation types of the Aleutian Islands using numerical methods. It is the first attempt to use the relevé method in southern coastal Alaska and provides a basis for future comparison with other areas. 76 relevés represent the range of structural and compositional variation in the matrix of vegetation and landform zonation at 16 locations. Data are analyzed by multivariate methods using the MULVA-4 computer package and ordered with Wildi's numerical procedure to produce results similar to traditional phytosociological tabular classification. Nine major community types are distinguished in four physiognomic groups: 1. Dwarf-shrub mire: Vaccinium uliginosum-Empetrum nigrum; 2. Meadow: Athyrium filix-femina-Streptopus amplexifolius, Artemisia tilesii-Veratrum album, Elymus mollis-Montia (Claytonia) sibirica, Ligusticum scoticum-Elymus mollis; 3. Beach meadow: Elymus mollis-Senecio pseudo-arnica, Lathyrus maritimus-Elymus mollis; and 4. Beach: Mertensia maritima and Arenaria (Honckenya) peploides. These community types are described and interpreted in response to a complex, topographic gradient. Phytogeographic comparison of Attu Island with neighboring areas suggests close relationship to the beach and beach-meadow types of eastern Kamchatka and to the mesic meadows of the Alaskan Semidi Islands; there is a slightly lower relationship to the mesic meadows of nearby Buldir Island.     

Population structure affected by excess gene flow in self-pollinating Elymus nutans and E. burchan-buddae (Triticeae: Poaceae)

Seed-mediated gene flow can considerably affect population genetic structure of strictly self-pollinating species, but little is known on the extent and nature of such gene flow among pastoral plant populations. Molecular fingerprints provide a powerful tool to address the relevant issues. Genetic structure of 22 populations of two self-pollinating pasture species, Elymus nutans and E. burchan-buddae, collected from various altitudes of the Qinghai–Tibetan Plateau was studied using fluorescence-based amplified fragment length polymorphism technique. Analysis of molecular variance revealed 42.97% and 37.63% among-population variation for the two Elymus species, respectively, indicating that the majority of the total variation presented within populations. This result contradicts the common genetic variation pattern for a selfing plant species: lower genetic variation within populations. Further analysis suggested higher level of gene flow among populations within the same region than among different regions across the sampled area for the two Elymus species. STRUCTURE analyses of the Elymus populations indicated an evident admixture genetic structure, particularly among neighboring populations from the same region, supporting the hypothesis of considerable seed dispersal among populations. The excess within-region gene flow of E. nutans and E. burchan-buddae might be caused by grazing animals that promote seed dispersal when moved around the pastoral lands during foraging. The among-population gene flow promulgated by grazing animals may promote the maintenance of genetic diversity in the pasture species, particularly in small and fragmented populations within a given region.     

Local Adaptation and Effects of Grazing among Seedlings of Two Native California Bunchgrass Species: Implications for Restoration

Adaptation to environmental factors may influence the germination and establishment of focal species in ecological restoration. Reciprocal transplants remain one of the best methods to detect local adaptation, but long‐term studies are often not feasible. We conducted reciprocal transplants of the native California bunchgrasses Elymus glaucus and Bromus carinatus between two central California locations to seek evidence of adaptation to local environmental conditions in a single growing season. Experimental plots at one location included grazed and ungrazed sites. The combination of locations and grazing treatments allowed us to determine whether the ability to detect evidence for adaptation depended on grazing regime. In addition, we measured the direct effects of grazing on seedling growth and survival concurrent with our investigation of local adaptation. We detected a homesite advantage for seedling growth or survival in both species, but the factors contributing to adaptive differentiation were species specific. Evidence of local adaptation was detected for seedling biomass in Bromus and for survivorship in Elymus. The homesite advantage observed in both species was greatly reduced under grazed conditions and in Elymus was significant only in the ungrazed plots. Climate and soil analyses detected significant differences between locations in five soil attributes and two climate variables. In particular, differences in exchangeable magnesium indicated that one of the two transplant locations consisted of serpentine soil, which is widely known to drive adaptation in plant populations. Together, these results suggest that it is possible to investigate the scale and factors involved in local adaptation with short‐term transplant studies.     

Management of three endangered plant species in dynamic Baltic seashore meadows

Question: Arctophila fulva var. pendulina, Primula nutans var. jokelae and Puccinellia phryganodes are threatened early successional species growing in the seashore meadows of the northern Baltic Sea. Patches formed by these species are destined to be replaced by other species during primary succession and in order to persist in the area they have to continuously colonize new areas. We studied whether the displacement of the species could be slowed down and their sexual and/or vegetative reproduction enhanced by management targeted to surrounding vegetation. Location: Bothnian Bay, Baltic Sea, W Finland. Methods: Vegetation surrounding patches of all study species was mown in four successional growing seasons. Moreover, the impact of additional soil turning on creating new favourable growing sites was tested for A. fulva. Results: Deterioration of suitable habitats of A. fulva and P. nutans was markedly slowed down by management and the vegetative and/or sexual reproduction of these species was enhanced. In the case of P. phryganodes, however, no positive response to management was obtained. Conclusions: In order to improve the long‐term persistence of these three species successional vegetation changes should be slowed down and their dispersal and colonization success improved by continuous management of the populations. We further suggest that the colonization of new areas should be aided by transplantations to the non‐vegetated islets, which have recently risen from the sea and cannot be reached by means of dispersal.