Sherri J. Morris

Glomalin, an arbuscular-mycorrhizal fungal soil protein, responds to land-use change

Glomalin is a soil proteinaceous substance produced by arbuscular mycorrhizal fungi. Most of the information available concerning this protein has been collected in relation to its role in soil aggregation. In this study, we explored the distribution of glomalin across soil horizons, decomposition of glomalin, and relationship with soil C and N in an agricultural field, a native forest, and an afforested system. Glomalin was present in A, B, and C horizons in decreasing concentrations. Land-use type significantly affected glomalin concentrations (mg cm−3), with native forest soils having the highest concentrations of the three land-use types in both A and B horizons. In terms of glomalin stocks (Mg ha−1), calculated based on corrected horizon weights, the agricultural area was significantly lower than both afforested and native forest areas. As measured after a 413 day laboratory soil incubation, glomalin was least persistent in the A horizon of the afforested area.. In agricultural soils and native soils, ca. 50% of glomalin was still remaining after this incubation, indicating that some glomalin may be in the slow or recalcitrant soil C fraction. Comparison of glomalin decomposition with CO2-C respired during incubation indicates that glomalin makes a large contribution to active soil organic C pools. Soil C and N were highly correlated with glomalin across all soils and within each land-use type, indicating that glomalin may be under similar controls as soil C. Our results show that glomalin may be useful as an indicator of land-use change effects on deciduous forest soils.

Impacts of elevated CO2 concentration on the productivity and surface energy budget of the soybean and maize agroecosystem in the Midwest USA

The physiological response of vegetation to increasing atmospheric carbon dioxide concentration ([CO2 ]) modifies productivity and surface energy and water fluxes. Quantifying this response is required for assessments of future climate change. Many global climate models account for this response; however, significant uncertainty remains in model simulations of this vegetation response and its impacts. Data from in situ field experiments provide evidence that previous modeling studies may have overestimated the increase in productivity at elevated [CO2 ], and the impact on large-scale water cycling is largely unknown. We parameterized the Agro-IBIS dynamic global vegetation model with observations from the SoyFACE experiment to simulate the response of soybean and maize to an increase in [CO2 ] from 375 ppm to 550 ppm. The two key model parameters that were found to vary with [CO2 ] were the maximum carboxylation rate of photosynthesis and specific leaf area. Tests of the model that used SoyFACE parameter values showed a good fit to site-level data for all variables except latent heat flux over soybean and sensible heat flux over both crops. Simulations driven with historic climate data over the central USA showed that increased [CO2 ] resulted in decreased latent heat flux and increased sensible heat flux from both crops when averaged over 30 years. Thirty-year average soybean yield increased everywhere (ca. 10%); however, there was no increase in maize yield except during dry years. Without accounting for CO2 effects on the maximum carboxylation rate of photosynthesis and specific leaf area, soybean simulations at 550 ppm overestimated leaf area and yield. Our results highlight important model parameter values that, if not modified in other models, could result in biases when projecting future crop-climate-water relationships.

THE ECOLOGY OF SOIL ORGANISMS

Publisher Summary This chapter focuses on the processes that drive community structure (number and types of species) and the resultant impacts on ecosystem function (processes of energy transformations and nutrient turnover). A large part of ecology is the study of how organisms become distributed in the environment. There are numerous examples of studies for which predicting the population density of organisms is necessary (for example, for endangered species, commercial fish, and timber). In soil microbiology, it is desirable to be able to forecast the population dynamics of plant pathogens or inoculant species such as rhizobia, biocontrol agents, and genetically modified organisms. Population dynamics form the basis of community assembly, and interactions within the community have a profound influence on populations. Identifying populations and studying them in situ are difficult and provide limited understanding of the complexity of community assembly in soil systems. The concepts related to mechanisms that drive community structure are explained in the chapter along with ecosystem dynamics.

Microbe—Plant Interactions in Mediterranean-Type Habitats: Shifts in Fungal Symbiotic and Saprophytic Functioning in Response to Global Change

In any terrestrial ecosystem, the major allocation of carbon and the largest carbon sink is into components in soils responsible for the acquisition of nutrients and water. Although generally unappreciated, soil microbes are the dominant consumers of carbon. Mycorrhizal fungi are estimated to be the largest consumer group because of their large mass and direct access to the host carbon (Figure 14-1). Both these organisms and all others ultimately end up in decomposer mass, with most plant mass going directly to decomposers without passing through animals. Mediterranean-type habitats are semiarid regions that accumulate significant quantities of carbon below ground (e.g., Kummerow et al., 1978). Because of the arid conditions and the sclerophyllous nature of much of the plant tissue, decomposition tends to be very low. Therefore, the dynamics of microbes and their responses to change in the global environment are critical to predicting changes in ecosystem processes that will affect the regions of interest.

The Ecology of the Soil Biota and their Function

Microbial communities are fundamental cornerstones of terrestrial ecological systems. As such, microbial and soil ecologists are working to understand the mechanisms that determine species distribution and consequential impacts on the environment. In this chapter, we focus on the ecology of soil biota, particularly on the processes that drive community structure (number and types of species) examining specifically the environmental limitations to growth and the biotic interactions that influence species coexistence and ultimately determine diversity. We then discuss the impacts of community structure on their function in ecosystems. We explore how microbial community structure influences energy transformations and nutrient turnover and how these interactions result in ecosystems with unique emergent properties. The discussion of ecological principles is accompanied by examples from the literature on soil and microbial ecology. Ultimately, the chapter explains why the integrative approach provided by the field of ecology is necessary for understanding the complexity of soil systems.

Confident Voices: How Professional Development for Teachers by Teachers Using Video Promotes Inquiry-Based Practice

Abstract This study examined educators’ self-perception as practitioners of inquiry-based math and science instruction, their motivation to produce videos to share that practice, and the impact of video production on their use of inquiry and role in the professional development community. Semi-structured interviews were used to address the research questions. Participant responses indicated a high level of self-reflection and a keen understanding of the nature of inquiry-based math and science teaching. Participants were motivated to share their practice largely by their desire to help other educators develop as inquiry practitioners. Articulating how and why they used inquiry-based techniques for the videos deepened their already reflective teaching. The positive aspects of participation also increased their confidence in their ability to engage in professional development as teacher-leaders. Overall this study indicated that videos created for the purposes of professional development had a transforming effect on those who produced them in addition to their benefit for others.