Vikki L. Rodgers

Responses of insect pests, pathogens, and invasive plant species to climate change in the forests of northeastern North America: What can

Climate models project that by 2100, the northeastern US and eastern Canada will warm by approximately 3- 5 8C, with increased winter precipitation. These changes will affect trees directly and also indirectly through effects on nuisance species, such as insect pests, pathogens, and invasive plants. We review how basic ecological principles can be used to predict nuisance species responses to climate change and how this is likely to impact northeastern forests. We then examine in detail the potential responses of two pest species (hemlock woolly adelgid (Adelges tsugae Annand) and forest tent caterpillar (Malacosoma disstria Hubner)), two pathogens (armillaria root rot (Armillaria spp.) and beech bark disease (Cryptococcus fagisuga Lind. + Neonectria spp.)), and two invasive plant species (glossy buckthorn (Frangula alnus Mill.) and oriental bittersweet (Celastrus orbiculatus Thunb.)). Several of these species are likely to have stronger or more widespread effects on forest composition and structure under the projected climate. However, uncertainty pervades our predictions because we lack adequate data on the species and because some species depend on complex, incompletely understood, unstable relationships. While targeted research will increase our confidence in making predictions, some un-

Ready or Not, Garlic Mustard Is Moving In: Alliaria petiolata as a Member of Eastern North American Forests

ABSTRACT Garlic mustard (Alliaria petiolata) is a nonnative, shade-tolerant forb that was introduced into North America in the mid-1800s. Currently, garlic mustard is spreading across the landscape at a rate of 6400 square kilometers per year. In this article, we synthesize the current state of knowledge on the mechanisms underlying garlic mustards widespread success and the ecological impacts of its invasion. Although no single mechanism appears to explain the success of garlic mustard, a combination of plant traits—all slightly different from those of native plants—seems to confer garlic mustard with tremendous success in the new habitats it invades. The domination of this new species in eastern forests is clearly changing the ecology of these systems. The consequences of garlic mustard invasion include the loss of biological diversity, ripple effects through higher trophic levels, and changes in the function of soil microbial communities.

The invasive species Alliaria petiolata (garlic mustard) increases soil nutrient availability in northern hardwood-conifer forests

The invasion of non-native plants can alter the diversity and activity of soil microorganisms and nutrient cycling within forests. We used field studies to analyze the impact of a successful invasive groundcover, Alliaria petiolata, on fungal diversity, soil nutrient availability, and pH in five northeastern US forests. We also used laboratory and greenhouse experiments to test three mechanisms by which A. petiolata may alter soil processes: (1) the release of volatile, cyanogenic glucosides from plant tissue; (2) the exudation of plant secondary compounds from roots; and (3) the decomposition of litter. Fungal community composition was significantly different between invaded and uninvaded soils at one site. Compared to uninvaded plots, plots invaded by A. petiolata were consistently and significantly higher in N, P, Ca and Mg availability, and soil pH. In the laboratory, the release of volatile compounds from the leaves of A. petiolata did not significantly alter soil N availability. Similarly, in the greenhouse, the colonization of native soils by A. petiolata roots did not alter soil nutrient cycling, implying that the exudation of secondary compounds has little effect on soil processes. In a leaf litter decomposition experiment, however, green rosette leaves of A. petiolata significantly increased the rate of decomposition of native tree species. The accelerated decomposition of leaf litter from native trees in the presence of A. petiolata rosette leaves shows that the death of these high-nutrient-content leaves stimulates decomposition to a greater extent than any negative effect that secondary compounds may have on the activity of the microbes decomposing the native litter. The results presented here, integrated with recent related studies, suggest that this invasive plant may change soil nutrient availability in such a way as to create a positive feedback between site occupancy and continued proliferation.

Intact amino acid uptake by northern hardwood and conifer trees

Empirical and modeling studies of the N cycle in temperate forests of eastern North America have focused on the mechanisms regulating the production of inorganic N, and assumed that only inorganic forms of N are available for plant growth. Recent isotope studies in field conditions suggest that amino acid capture is a widespread ecological phenomenon, although northern temperate forests have yet to be studied. We quantified fine root biomass and applied tracer-level quantities of U–13C2–15N-glycine, 15NH4+ and 15NO3− in two stands, one dominated by sugar maple and white ash, the other dominated by red oak, beech, and hemlock, to assess the importance of amino acids to the N nutrition of northeastern US forests. Significant enrichment of 13C in fine roots 2 and 5xa0h following tracer application indicated intact glycine uptake in both stands. Glycine accounted for up to 77% of total N uptake in the oak–beech–hemlock stand, a stand that produces recalcitrant litter, cycles N slowly and has a thick, amino acid-rich organic horizon. By contrast, glycine accounted for only 20% of total N uptake in the sugar maple and white ash stand, a stand characterized by labile litter and rapid rates of amino acid production and turnover resulting in high rates of mineralization and nitrification. This study shows that amino acid uptake is an important process occurring in two widespread, northeastern US temperate forest types with widely differing rates of N cycling.

Toward a better integration of biological data from precipitation manipulation experiments into Earth system models

The biological responses to precipitation within the terrestrial components of Earth system models, or land surface models (LSMs), are mechanistically simple and poorly constrained, leaving projections of terrestrial ecosystem functioning and feedbacks to climate change uncertain. A number of field experiments have been conducted or are underway to test how changing precipitation will affect terrestrial ecosystems. Results from these experiments have the potential to vastly improve modeled processes. However, the transformation of experimental results into model improvements still represents a grand challenge. Here we review the current state of precipitation manipulation experiments and the precipitation responses of biological processes in LSMs to explore how these experiments can help improve model realism. First, we discuss contemporary precipitation projections and then review the structure and function of current-generation LSMs. We then examine different experimental designs and discuss basic variables that, if measured, would increase a field experiments usefulness in a modeling context. Next, we compare biological processes commonly measured in the field with their model analogs and find that, in many cases, the way these processes are measured in the field is not compatible with the way they are represented in LSMs, an effect that hinders model development. We then discuss the challenge of scaling from the plot to the globe. Finally, we provide a series of recommendations aimed to improve the connectivity between experiments and LSMs and conclude that studies designed from the perspective of researchers in both communities will provide the greatest benefit to the broader global change community.

Leaf-Level Gas Exchange and Foliar Chemistry of Common Old-Field Species Responding to Warming and Precipitation Treatments.

We investigated the shifts in plant carbon (C) and water dynamics by measuring rates of photosynthesis, transpiration, and instantaneous water use efficiency (WUE) in three common species of “old-field” plants—two C3 forb species (Plantago lanceolata and Taraxacum officinale) and one C3 grass species (Elymus repens)—under 12 experimentally altered temperature and precipitation regimes at the Boston Area Climate Experiment (BACE) in Waltham, Massachusetts. We also measured shifts in foliar C and nitrogen (N) content to determine possible changes in plant C/nutrient balance. We hypothesized that the warming treatment would cause an increase in photosynthesis rates, unless water was limiting; therefore, we expected an interactive effect of warming and precipitation treatments. We found that warming and drought reduced leaf-level photosynthesis most dramatically when environmental or seasonal conditions produced soils that were already dry. In general, the plants transpired fastest when soils were wet and slowest when soils were dry. Drought treatments increased WUE relative to plants in the ambient and wet treatments but only during the driest and warmest background conditions. Leaf N concentration increased with warming, thereby indicating that future warming may cause some plants to take up more soil N and/or allocate more N to their leaves, possibly as consequences of increased nutrient availability. There were no significant interactive effects of the warming and precipitation treatments together across all seasons, indicating that responses were not synergistic or ameliorative.

Teaching a cross-disciplinary environmental science, policy, and culture course on Costa Rica’s ecotourism to business students

Within the business world, there is growing evidence and increasing acceptance that sustainability and environmental practices are the main drivers for current innovation and success. We developed an interdisciplinary, offshore course where undergraduate business students could truly investigate and experience the benefits of environmentally and socially responsible business through the lens of the ecotourism industry. Many in the environmental movement, as well as those who teach about it, see business and environmental issues as being in opposition to each other. We found that this is definitely not the case. By exploring the important ways in which ecology, law, policy, ethics, and culture need to inform business decisions, students were able to apply what they learned in the course to capstone projects in which they created business plans that took into account the ecology of the land, the laws they must adhere to, the culture of the Costa Rican people, and the financial opportunities for socially and environmentally responsible entrepreneurs.

Warming increases the sensitivity of seedling growth capacity to rainfall in six temperate deciduous tree species

Using a fully factorial precipitation by warming experiment in an old-field ecosystem in the northeastern USA we studied the climatic sensitivity of seedlings of six native tree species. Warm and dry conditions suppressed seedling growth, but affected species differently by increasing mortality, enhancing rates of herbivory or decreasing foliar carbon uptake. Our results indicate that, in the northeastern USA, dry years in a future warmer environment could have damaging effects on the growth capacity of early secondary successional forests, through species-specific effects on leaf production, herbivory and mortality.

Integrating Corporate Social Responsibility Awareness Into a Retail Management Course

Both students and industry are demanding that marketing instructors incorporate discussions of environmental and social responsibility into their courses. Marketing educators play a critical role in developing the knowledge and skills students need to effectively integrate corporate social responsibility (CSR) into their future business endeavors. Yet many educators struggle with developing meaningful and effective strategies to incorporate CSR authentically into their curricula. The project discussed in this article outlines a learning tool that encourages students to consider CSR in the context of their own purchase decisions while also considering CSR from a broader macro environmental perspective. The main goal is to build a CSR awareness that extends beyond a student’s initial purchase exchange. Using retail as the context, students are required to consider CSR challenges including labor laws, environmental regulations, sourcing issues, and so on from the retailer and supplier relationships as well as the retailer and consumer relationships. Based on preliminary results, students’ awareness of CSR challenges throughout the supply chain increased and the project proved to be an effective way to engage students in real learning about CSR.