R. A. Black

Bio: R. A. Black is an academic researcher from University of Utah. The author has contributed to research in topics: Pennisetum & Pennisetum setaceum. The author has an hindex of 2, co-authored 2 publications receiving 183 citations.

Drought response of a native and introduced Hawaiian grass

Abstract: The alien grass, Pennisetum setaceum, dominates many of the lowland arid regions that once supported native Heteropogon contortus grassland on the island of Hawaii. Response to drought in a glasshouse was compared between these C4 grasses to test if success as an invader is related to drought tolerance or plasticity for traits that confer drought tolerance. Pennisetum produced 51% more total biomass, allocated 49% more biomass to leaves, and had higher net photosynthetic rates (P n) on a leaf area basis than Heteropogon. Plants of both species under drought produced less total biomass and increased their allocation to roots compared to well-watered plants, but there was no difference between the two species in the magnitude of these responses. The decline in P n with decreasing leaf water potential (ψ1) was greater for Pennisetum compared to Heteropogon. Plasticity in the response of P n to ψ1, osmotic potentials, and the water potentials at turgor loss in response to drought were not different between the two species. Stomata were more responsive to Δw in Heteropogon than in Pennisetum and for well-watered plants compared to droughted plants. Plasticity for the stomatal response to Δw, however, was not different between the species. There was no evidence that the alien, Pennisetum, had greater plasticity for traits related to drought tolerance compared to the native, Heteropogon. Higher P n and greater biomass allocation to leaves resulted in greater growth for Pennisetum compared to Heteropogon and may explain the success of Pennisetum as an invader of lowland arid zones on Hawaii.

Phenotypic variation in contrasting temperature environments : growth and photosynthesis in Pennisetum setaceum from different altitudes on Hawaii

Abstract: 1. Plasticity and genetic differentiation of growth, biomass allocation, and photosynthesis in response to temperature were investigated for populations of the introduced grass Pennisetum setaceum collected from different altitudes on the island of Hawaii. 2. The temperature optimum for photosynthesis was similar (35°C) for plants collected from different altitudes and grown in growth chambers with low (25/13°C) and high (33/25°C) temperature environments, indicating that P. setaceum has limited potential for photosynthetic temperature acclimation. Plants grown in the low-temperature environment, however, had 16% greater maximum photosynthetic rates on a leaf area basis than plants grown at the high temperature (25.4 and 21.4 μmol CO 2 m −2 s −1 , respectively)

PERFORMANCE COMPARISONS OF Co-OCCURRING NATIVE AND ALIEN INVASIVE PLANTS: Implications for Conservation and Restoration

Abstract: ▪ Abstract In the search to identify factors that make some plant species troublesome invaders, many studies have compared various measures of native and alien invasive plant performance. These comparative studies provide insights into the more general question “Do alien invasive plants usually outperform co-occurring native species, and to what degree does the answer depend on growing conditions?” Based on 79 independent native-invasive plant comparisons, the alien invaders were not statistically more likely to have higher growth rates, competitive ability, or fecundity. Rather, the relative performance of invaders and co-occurring natives often depended on growing conditions. In 94% of 55 comparisons involving more than one growing condition, the native's performance was equal or superior to that of the invader, at least for some key performance measures in some growing conditions. Most commonly, these conditions involved reduced resources (nutrients, light, water) and/or specific disturbance regimes. I...

Jack of all trades, master of some? On the role of phenotypic plasticity in plant invasions

Abstract: Invasion biologists often suggest that phenotypic plasticity plays an important role in successful plant invasions. Assuming that plasticity enhances ecological niche breadth and therefore confers a fitness advantage, recent studies have posed two main hypotheses: (1) invasive species are more plastic than non-invasive or native ones; (2) populations in the introduced range of an invasive species have evolved greater plasticity than populations in the native range. These two hypotheses largely reflect the disparate interests of ecologists and evolutionary biologists. Because these sciences are typically interested in different temporal and spatial scales, we describe what is required to assess phenotypic plasticity at different levels. We explore the inevitable tradeoffs of experiments conducted at the genotype vs. species level, outline components of experimental design required to identify plasticity at different levels, and review some examples from the recent literature. Moreover, we suggest that a successful invader may benefit from plasticity as either (1) a Jack-of-all-trades, better able to maintain fitness in unfavourable environments; (2) a Master-of-some, better able to increase fitness in favourable environments; or (3) a Jack-and-master that combines some level of both abilities. This new framework can be applied when testing both ecological or evolutionary oriented hypotheses, and therefore promises to bridge the gap between the two perspectives.

Invasiveness, invasibility and the role of environmental stress in the spread of non-native plants

Abstract: Invasion ecology, the study of how organisms spread in habitats to which they are not native, asks both about the invasiveness of species and the invasibility of habitats: Which species are most likely to become invasive? Which habitats are most susceptible to invasion? To set the stage for considering these questions with regard to plants, we offer a two-way classification of nativeness and invasiveness that distinguishes natives, non-invasive non-natives and invasive non-natives. We then consider the current state of knowledge about invasiveness and invasibility. Despite much investigation, it has proven difficult to identify traits that consistently predict invasiveness. This may be largely because different traits favour invasiveness in different habitats. It has proven easier to identify types of habitats that are relatively invasible, such as islands and riverbanks. Factors thought to render habitats invasible include low intensities of competition, altered disturbance regimes and low levels of environmental stress, especially high resource availability. These factors probably often interact; the combination of altered disturbance with high resource availability may particularly promote invasibility. When biotic factors control invasibility, non-natives that are unlike native species may prove more invasive; the converse may also be true. We end with a simple conceptual model for cases in which high levels of environmental stress should and should not reduce invasibility. In some cases, it may be possible to manipulate stress to control biological invasions by plants.

Parameterization and Sensitivity Analysis of the BIOME–BGC Terrestrial Ecosystem Model: Net Primary Production Controls

Abstract: Ecosystem simulation models use descriptive input parameters to establish the physiology, biochemistry, structure, and allocation patterns of vegetation functional types, or biomes. For single-stand simulations it is possible to measure required data, but as spatial resolution increases, so too does data unavailability. Generalized biome parameterizations are then required. Undocumented parameter selection and unknown model sensitivity to parameter variation for larger-resolution simulations are currently the major limitations to global and regional modeling. The authors present documented input parameters for a process-based ecosystem simulation model, BIOME–BGC, for major natural temperate biomes. Parameter groups include the following: turnover and mortality; allocation; carbon to nitrogen ratios (C:N); the percent of plant material in labile, cellulose, and lignin pools; leaf morphology; leaf conductance rates and limitations; canopy water interception and light extinction; and the percent of...

Plant carbon metabolism and climate change: elevated CO2 and temperature impacts on photosynthesis, photorespiration and respiration.

Abstract: Contents Summary 32 I. The importance of plant carbon metabolism for climate change 32 II. Rising atmospheric CO2 and carbon metabolism 33 III. Rising temperatures and carbon metabolism 37 IV. Thermal acclimation responses of carbon metabolic processes can be best understood when studied together 38 V. Will elevated CO2 offset warming-induced changes in carbon metabolism? 40 VI. No plant is an island: water and nutrient limitations define plant responses to climate drivers 41 VII. Conclusions 42 Acknowledgements 42 References 42 Appendix A1 48 SUMMARY: Plant carbon metabolism is impacted by rising CO2 concentrations and temperatures, but also feeds back onto the climate system to help determine the trajectory of future climate change. Here we review how photosynthesis, photorespiration and respiration are affected by increasing atmospheric CO2 concentrations and climate warming, both separately and in combination. We also compile data from the literature on plants grown at multiple temperatures, focusing on net CO2 assimilation rates and leaf dark respiration rates measured at the growth temperature (Agrowth and Rgrowth , respectively). Our analyses show that the ratio of Agrowth to Rgrowth is generally homeostatic across a wide range of species and growth temperatures, and that species that have reduced Agrowth at higher growth temperatures also tend to have reduced Rgrowth , while species that show stimulations in Agrowth under warming tend to have higher Rgrowth in the hotter environment. These results highlight the need to study these physiological processes together to better predict how vegetation carbon metabolism will respond to climate change.