Nutrient conditions mediate mycorrhizal effects on biomass production and cell wall chemistry in poplar.

Large-scale biofuel production from lignocellulosic feedstock is limited by the financial and environmental costs associated with growing and processing lignocellulosic material and the resilience of these plants to environmental stress. Symbiotic associations with arbuscular (AM) and ectomycorrhizal (EM) fungi represent a potential strategy for expanding feedstock production while reducing nutrient inputs. Comparing AM and EM effects on wood production and chemical composition is a necessary step in developing biofuel feedstocks.

Feast or famine: How is global change affecting forage supply for Yellowstone's ungulate herds?

The ecological integrity of US national parks and other protected areas are under threat in the Anthropocene. For Yellowstone National Park (YNP), the impacts that global change has already had on the park's capacity to sustain its large migratory herds of wild ungulates is incompletely understood. Here we examine how two understudied components of global change, the historical increase in atmospheric CO and the spread of nonnative, invasive plant species, may have altered the capacity of YNP to provide forage for ungulates over the last 200-plus years.

CO studies remain key to understanding a future world.

Contents 34 I. 34 II. 36 III.

Examining Plant Physiological Responses to Climate Change through an Evolutionary Lens.

Integrating knowledge from physiological ecology, evolutionary biology, phylogenetics, and paleobiology provides novel insights into factors driving plant physiological responses to both past and future climate change.

Host Plant Physiology and Mycorrhizal Functioning Shift across a Glacial through Future [CO2] Gradient.

Rising atmospheric carbon dioxide concentration ([CO]) may modulate the functioning of mycorrhizal associations by altering the relative degree of nutrient and carbohydrate limitations in plants. To test this, we grew Taraxacum ceratophorum and Taraxacum officinale (native and exotic dandelions) with and without mycorrhizal fungi across a broad [CO] gradient (180-1,000 µL L). Differential plant growth rates and vegetative plasticity were hypothesized to drive species-specific responses to [CO] and arbuscular mycorrhizal fungi.

A dynamic leaf gas-exchange strategy is conserved in woody plants under changing ambient CO2 : evidence from carbon isotope discrimination in paleo and CO2 enrichment studies.

Rising atmospheric [CO2 ], ca , is expected to affect stomatal regulation of leaf gas-exchange of woody plants, thus influencing energy fluxes as well as carbon (C), water, and nutrient cycling of forests. Researchers have proposed various strategies for stomatal regulation of leaf gas-exchange that include maintaining a constant leaf internal [CO2 ], ci , a constant drawdown in CO2 (ca  - ci ), and a constant ci /ca . These strategies can result in drastically different consequences for leaf gas-exchange.

Evolutionary history underlies plant physiological responses to global change since the last glacial maximum.

Assessing family- and species-level variation in physiological responses to global change across geologic time is critical for understanding factors that underlie changes in species distributions and community composition. Here, we used stable carbon isotopes, leaf nitrogen content and stomatal measurements to assess changes in leaf-level physiology in a mixed conifer community that underwent significant changes in composition since the last glacial maximum (LGM) (21 kyr BP). Our results indicate that most plant taxa decreased stomatal conductance and/or maximum photosynthetic capacity in response to changing conditions since the LGM.

Host identity impacts rhizosphere fungal communities associated with three alpine plant species.

Fungal diversity and composition are still relatively unknown in many ecosystems; however, host identity and environmental conditions are hypothesized to influence fungal community assembly. To test these hypotheses, we characterized the richness, diversity, and composition of rhizosphere fungi colonizing three alpine plant species, Taraxacum ceratophorum, Taraxacum officinale, and Polemonium viscosum. Roots were collected from open meadow and willow understory habitats at treeline on Pennsylvania Mountain, Colorado, USA.

Soil fungal effects on floral signals, rewards, and aboveground interactions in an alpine pollination web.

Premise Of The Study: Plants interact with above- and belowground organisms; the combined effects of these interactions determine plant fitness and trait evolution. To better understand the ecological and evolutionary implications of multispecies interactions, we explored linkages between soil fungi, pollinators, and floral larcenists in Polemonium viscosum (Polemoniaceae).

Methods: Using a fungicide, we experimentally reduced fungal colonization of krummholz and tundra P.