Hana Skálová

Small‐scale variability as a mechanism for large‐scale stability in mountain grasslands

. Data from a 7-yr permanent plot study of grassland dynamics were used to address the relationship between processes at two levels of resolution (3.3 cm x 3.3 cm, 50 cm x 50 cm). Grasslands mown and manured in the traditional way in the Krkonose Mts. (Riesengebirge) were used as a model system. Spatial dynamics at the finest scale were very high, as demonstrated by turnover of individual species in 3.3 cm x 3.3 cm subplots and year-to-year transition matrices of the same subplots. The direction of these dynamics was not correlated with grassland treatment, although there was some correlation within years. An extrapolation of such year-to-year dynamics to larger time scales would result in big large-scale changes on the community level, and large shifts in species composition of the whole sward. However, dynamics at larger spatial or temporal scales were generally small. Some directional change occurred in manured plots, whereas little change occurred in unmanured plots. Large-scale dynamics were not correlated with small-scale dynamics in plots without manuring, but some correlation was detectable in manured plots. There are probably several processes that drive small-scale dynamics, such as non-linear interactions and environmental fluctuations. We argue that within certain limits these forces act on species composition so as to make small-scale dynamics non-directional. This results in both large-scale species diversity and apparent large-scale stability of these grasslands. However, if these forces are beyond these limits, the small-scale dynamics may become directional, resulting in rapid changes at larger spatial scales.

Within population genetic differentiation in traits affecting clonal growth: Festuca rubra in a mountain grassland

Festuca rubra , a clonal grass of mountain grasslands, possesses a considerable variability in traits related to spatial spreading (rhizome production, length and branching; tussock architecture). Since these traits highly influence the success of the species in a spatially heterogeneous system of grasslands, a combined field and growth chamber approach was adopted to determine the within‐population variation in these parameters. Clones were sampled in a mountain grassland (The Krkonoše Mts., Czech Republic); the environment (mean neighbour density) of individual clones varied highly. Before the clones were collected, shoot demography and tussock architecture within these clones were recorded in the field for four seasons. Their clone identity was determined using DNA RAPD. Vegetatively propagated plants from these clones were cultivated in a common garden experiment to demonstrate variation in tussock growth and architecture. Their response to change in red/far red light ratio was determined in the growth chamber.

Seedling traits, plasticity and local differentiation as strategies of invasive species of Impatiens in central Europe

Background and Aims Invasiveness of some alien plants is associated with their traits, plastic responses to environmental conditions and interpopulation differentiation. To obtain insights into the role of these processes in contributing to variation in performance, we compared congeneric species of Impatiens (Balsaminaceae) with different origin and invasion status that occur in central Europe. Methods Native I. noli-tangere and three alien species (highly invasive I. glandulifera, less invasive I. parviflora and potentially invasive I. capensis) were studied and their responses to simulated canopy shading and different nutrient and moisture levels were determined in terms of survival and seedling traits. Key Results and Conclusions Impatiens glandulifera produced high biomass in all the treatments and the control, exhibiting the ‘Jack-and-master’ strategy that makes it a strong competitor from germination onwards. The results suggest that plasticity and differentiation occurred in all the species tested and that along the continuum from plasticity to differentiation, the species at the plasticity end is the better invader. The most invasive species I. glandulifera appears to be highly plastic, whereas the other two less invasive species, I. parviflora and I. capensis, exhibited lower plasticity but rather strong population differentiation. The invasive Impatiens species were taller and exhibited higher plasticity and differentiation than native I. noli-tangere. This suggests that even within one genus, the relative importance of the phenomena contributing to invasiveness appears to be speciesspecific.

Effect of Intra- and Interspecific Competition on the Performance of Native and Invasive Species of Impatiens under Varying Levels of Shade and Moisture

Many alien plants are thought to be invasive because of unique traits and greater phenotypic plasticity relative to resident species. However, many studies of invasive species are unable to quantify the importance of particular traits and phenotypic plasticity in conferring invasive behavior because traits used in comparative studies are often measured in a single environment and by using plants from a single population. To obtain a deeper insight into the role of environmental factors, local differences and competition in plant invasions, we compared species of Impatiens (Balsaminaceae) of different origin and invasion status that occur in central Europe: native I. noli-tangere and three alien species (highly invasive I. glandulifera, less invasive I. parviflora and potentially invasive I. capensis). In two experiments we harvested late-stage reproductive plants to estimate performance. The first experiment quantified how populations differed in performance under varying light and moisture levels in the absence of competition. The second experiment quantified performance across these environments in the presence of intra- and inter-specific competition. The highly invasive I. glandulifera was the strongest competitor, was the tallest and produced the greatest biomass. Small size and high plasticity were characteristic for I. parviflora. This species appeared to be the second strongest competitor, especially under low soil moisture. The performance of I. capensis was within the range of the other Impatiens species studied, but sometimes limited by alien competitors. Our results suggest that invasion success within the genus Impatiens depends on the ability to grow large under a range of environmental conditions, including competition. The invasive species also exhibited greater phenotypic plasticity across environmental conditions than the native species. Finally, the decreased performance of the native I. noli-tangere in competition with other species studied indicates that this species may be possibly excluded from its sites by invading congeners.

Growth response of threeFestuca rubra clones to light quality and arbuscular mycorrhiza

The influence of the arbuscular mycorrhizal fungus—Glomus etunicatum and changes in light quality (decrease of red/far-red ratio) on the growth of threeFestuca rubra clones, ecotypes originating from a mountain grassland region, was studied in a growth chamber experiment. Inoculation with the arbuscular mycorrhizal fungus and low red/far-red ratio decreased both the number of tillers and the biomass of treated plants. Significant interactions between the treatments were found and most of the growth characteristics were reduced further when both treatments were applied simultaneously. Inoculation with the arbuscular mycorrhizal fungus also resulted in reduced maximum height of tillers, whereas low red/far-red ratio caused the maximum height of tillers to increase. Differences in plasticity were found for the threeFestuca rubra clones. Response to one treatment was strongly modified by the other treatment. This indicates that the arbuscular mycorrhizal fungus and red/far-red ratio can differentially influence the growth ofFestuca rubra clones and thus modify their relative competitive abilities which can consequently have implications for the coexistence mechanisms within plant population, thereby potentially influencing plant canopy and community structure.

Competition among native and invasive Impatiens species: the roles of environmental factors, population density, and life stage

We examined competition effects in an experiment with three Impatiens species (Balsaminaceae) sharing similar life-history characteristics and habitats: the native I. noli-tangere, and two invasive species, I. parviflora and I. glandulifera. The results suggest that the effect of competition on the performance of invasive Impatiens species exceeds that of environmental factors, i.e. light and soil moisture. Competitive interactions with co-occurring congeners may thus be a more important predictor of the invasion success of an invasive species and its population dynamics than its response to abiotic factors, and should be taken into account when evaluating their invasion potential.

Global networks for invasion science: benefits, challenges and guidelines

Much has been done to address the challenges of biological invasions, but fundamental questions (e.g., which species invade? Which habitats are invaded? How can invasions be effectively managed?) still need to be answered before the spread and impact of alien taxa can be effectively managed. Questions on the role of biogeography (e.g., how does biogeography influence ecosystem susceptibility, resistance and resilience against invasion?) have the greatest potential to address this goal by increasing our capacity to understand and accurately predict invasions at local, continental and global scales. This paper proposes a framework for the development of ‘Global Networks for Invasion Science’ to help generate approaches to address these critical and fundamentally biogeographic questions. We define global networks on the basis of their focus on research questions at the global scale, collection of primary data, use of standardized protocols and metrics, and commitment to long-term global data. Global networks are critical for the future of invasion science because of their potential to extend beyond the capacity of individual partners to identify global priorities for research agendas and coordinate data collection over space and time, assess risks and emerging trends, understand the complex influences of biogeography on mechanisms of invasion, predict the future of invasion dynamics, and use these new insights to improve the efficiency and effectiveness of evidence-based management techniques. While the pace and scale of global change continues to escalate, strategic and collaborative global networks offer a powerful approach to inform responses to the threats posed by biological invasions.

Cosmopolitan Species As Models for Ecophysiological Responses to Global Change: The Common Reed Phragmites australis

Phragmites australis is a cosmopolitan grass and often the dominant species in the ecosystems it inhabits. Due to high intraspecific diversity and phenotypic plasticity, P. australis has an extensive ecological amplitude and a great capacity to acclimate to adverse environmental conditions; it can therefore offer valuable insights into plant responses to global change. Here we review the ecology and ecophysiology of prominent P. australis lineages and their responses to multiple forms of global change. Key findings of our review are that: (1) P. australis lineages are well-adapted to regions of their phylogeographic origin and therefore respond differently to changes in climatic conditions such as temperature or atmospheric CO2; (2) each lineage consists of populations that may occur in geographically different habitats and contain multiple genotypes; (3) the phenotypic plasticity of functional and fitness-related traits of a genotype determine the responses to global change factors; (4) genotypes with high plasticity to environmental drivers may acclimate or even vastly expand their ranges, genotypes of medium plasticity must acclimate or experience range-shifts, and those with low plasticity may face local extinction; (5) responses to ancillary types of global change, like shifting levels of soil salinity, flooding, and drought, are not consistent within lineages and depend on adaptation of individual genotypes. These patterns suggest that the diverse lineages of P. australis will undergo intense selective pressure in the face of global change such that the distributions and interactions of co-occurring lineages, as well as those of genotypes within-lineages, are very likely to be altered. We propose that the strong latitudinal clines within and between P. australis lineages can be a useful tool for predicting plant responses to climate change in general and present a conceptual framework for using P. australis lineages to predict plant responses to global change and its consequences.

Genetic differentiation and plasticity interact along temperature and precipitation gradients to determine plant performance under climate change

Summary Understanding species’ abilities to cope with changing climate is a key prerequisite for predicting the future fates of species and ecosystems. Despite considerable research on species responses to changing climate, we still lack understanding of the role of specific climatic factors, and their interactions, for species responses. We also lack understanding of the relative importance of plasticity vs. adaptation in determining the observed responses. As a model, we use a dominant clonal grass, Festuca rubra, originating from a natural climatic grid of 12 localities in western Norway that allows factorial combinations of temperature (mean growing season temperatures ranging from 6.5°C to 10.5°C) and precipitation (annual precipitation ranging from 600 mm to 2700 mm). We grew clones from all populations in four growth chambers representing the four climatic extremes in the climate grid (warm/cold × wet/dry). Genetic differentiation and direction and magnitude of plastic responses vary systematically among populations throughout the climatic grid. Growth-related plant traits are highly plastic and their degree of plasticity depends on their origin. In contrast, the traits reflecting species’ foraging strategy are not plastic but vary with the climate of origin. Levels of plasticity of growth-related traits and genetically differentiated foraging traits thus might constrain local populations’ ability to cope with novel climates. Synthesis: Shifts in temperature and precipitation, at the scale and direction expected for the region in the next century, are likely to dramatically affect plant performance. This study illustrates how the interplay between genetic differentiation and plasticity in response to both temperature and precipitation will affect the specific responses of species to climate change. Such complex responses will affect how climate-change impacts scale up to the community and ecosystem levels. Future studies thus need to specifically consider regionally relevant climate-change projections, and also explore the role of genetic differentiation and plasticity and how this varies within local floras. Our study also demonstrates that even widespread species with seemingly broad climatic niches may strongly differ in their population performance and plasticity. Climate-change studies should therefore not be limited to rare and restricted species. This article is protected by copyright. All rights reserved.

Effect of temperature and nutrients on the growth and development of seedlings of an invasive plant

Little is known about how alien plants that arrive in central Europe from climatically warmer regions cope with the temperature conditions at the early stage of population development. Using Ambrosia artemisiifolia (common ragweed), an invasive annual plant as a model, we found that the rate of seedling development decreased with decrease in temperature and nutrient supply. Our results thus highlight temperature as the main determinant of common ragweeds distribution and identify nutrient availability as a factor that results in the realized niche being smaller than the fundamental niche.