Belowground competition among invading detritivores

Author Posting. © Ecological Society of America, 2016. This article is posted here by permission of Ecological Society of America for personal use, not for redistribution. The definitive version was published in Ecology 97 (2016): 160–170, doi:10.1890/15-0551.1.The factors regulating soil animal communities are poorly understood. Current theory favors niche complementarity and facilitation over competition as the primary forms of non-trophic interspecific interaction in soil fauna; however, competition has frequently been suggested as an important community-structuring factor in earthworms, ecosystem engineers that influence belowground processes. To date, direct evidence of competition in earthworms is lacking due to the difficulty inherent in identifying a limiting resource for saprophagous animals. In the present study, we offer the first direct evidence of interspecific competition for food in this dominant soil detritivore group by combining field observations with laboratory mesocosm experiments using 13C and 15N double-enriched leaf litter to track consumption patterns. In our experiments, the Asian invasive species Amynthas hilgendorfi was a dominant competitor for leaf litter against two European species currently invading the temperate deciduous forests in North America. This competitive advantage may account for recent invasion success of A. hilgendorfi in forests with established populations of European species, and we hypothesize that specific phenological differences play an important role in determining the outcome of the belowground competition. In contrast, Eisenoides lonnbergi, a common native species in the Eastern United States, occupied a unique trophic position with limited interactions with other species, which may contribute to its persistence in habitats dominated by invasive species. Furthermore, our results supported neither the hypothesis that facilitation occurs between species of different functional groups nor the hypothesis that species in the same group exhibit functional equivalency in C and N translocation in the soil. We propose that species identity is a more powerful approach to understand earthworm invasion and its impacts on belowground processes.EPS Field Funds; National Science Foundation Grant Numbers: EEC-0540832, ACI 1244820, EAR-0748574; Microsoft Researc

Understanding and Enhancing Soil Biological Health: The Solution for Reversing Soil Degradation

Our objective is to provide an optimistic strategy for reversing soil degradation by increasing public and private research efforts to understand the role of soil biology, particularly microbiology, on the health of our world’s soils. We begin by defining soil quality/soil health (which we consider to be interchangeable terms), characterizing healthy soil resources, and relating the significance of soil health to agroecosystems and their functions. We examine how soil biology influences soil health and how biological properties and processes contribute to sustainability of agriculture and ecosystem services. We continue by examining what can be done to manipulate soil biology to: (i) increase nutrient availability for production of high yielding, high quality crops; (ii) protect crops from pests, pathogens, weeds; and (iii) manage other factors limiting production, provision of ecosystem services, and resilience to stresses like droughts. Next we look to the future by asking what needs to be known about soil biology that is not currently recognized or fully understood and how these needs could be addressed using emerging research tools. We conclude, based on our perceptions of how new knowledge regarding soil biology will help make agriculture more sustainable and productive, by recommending research emphases that should receive first priority through enhanced public and private research in order to reverse the trajectory toward global soil degradation

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Not AvailableArbuscular mycorrhizal fungi (AMF) are well-known plant symbionts which provide enhanced phosphorus uptake as well as other benefits to their host plants. Quantification of mycorrhizal density and root colonization has traditionally been performed by root staining and microscopic examination methods, which are time-consuming, laborious, and difficult to reproduce between laboratories. A number of biochemical markers for estimating mycorrhizal hyphae and spores have been published. In this study we grew maize plants in three different soils in a replicated greenhouse experiment and compared the results from two microscopic methods, spore density and root colonization, to the results from three lipid biomarker methods: neutral lipid fatty acid, phospholipid fatty acid, and ester-linked fatty acid analysis. Ester-linked fatty acid analysis gave consistent results for both spore density and root colonization, but neutral lipid fatty acid analysis had the highest correlation to AMF spore counts. Phospholipid fatty acid analysis was not correlated to spore density and did not reproducibly correlate to root colonization.Department of Biotechnology for funding overseas post doc fellowship and DARE/ICAR for granting deputation abroa

Monoclonal Antibodies to Ferric Pseudobactin, the Siderophore of Plant Growth-Promoting Pseudomonas putida B10

Monoclonal antibodies to ferric pseudobactin, the siderophore (microbial iron transport agent) of plant growth-promoting Pseudomonas putida B10, have been developed. Three immunoglobulin G subclass 1-type monoclonal antibodies have been characterized. Each antibody appears to be unique on the basis of their reactions with ferric pseudobactin and with culture supernatants from other pseudomonads. None of the three cross-reacts with ferric pseudobactin-type siderophores produced by seven other pseudomonads. However, P. aeruginosa ATCC 15692 and P. fluorescens ATCC 17400 produced relatively high-molecular-mass compounds (mass greater than approximately 30,000 daltons) that did react with the antibodies. The compound from P. aeruginosa was not iron regulated, while the compound from P. fluorescens was produced only under iron-limiting conditions. A competitive assay using these antibodies has a detection limit of 5 × 10(−12) mol of ferric pseudobactin. This is, to our knowledge, the first report of monoclonal antibodies reactive with siderophores

Recovery of soil microbial community structure after fire in a sagebrush-grassland ecosystem

Recovery of the soil microbial community after fire in a sagebrush-grassland ecosystem was examined using a chronosequence of four sites ranging in time since fire from 3-39 years. The successional stage communities examined included Recent Burn (3 years since fire, ysf), Establishment (7 ysf), Expansion (21 ysf), and Mature (39 ysf). Aboveground standing plant biomass increased with time since disturbance to the Mature stage where sagebrush became dominant over herbaceous species. Phospholipid fatty acid (PLFA) analysis was used to characterize the microbial community structure. Soil microbial community productivity generally appeared to be similar to the Mature site soil (39 ysf) within 7 years of fire. Diversity of PLFAs detected in soils, at both depths, increased from a low value of 29 at the Recent site to a high of 37 at the Establishment site and then decreased again to 31 at the Mature stage site. Canonical variates analysis indicated important disparities in microbial community structure at the four sites. Greatest disparities were observed in microbial community structure between the Recent and Establishment stages but greater similarity between the Recent stage and the sagebrush dominated Mature stage. This study emphasizes both short-term and long-term changes in the belowground community and suggests that soil microbial communities are highly resilient to disturbances after prescribed fire

Understanding and Enhancing Soil Biological Health: The Solution for Reversing Soil Degradation

Our objective is to provide an optimistic strategy for reversing soil degradation by increasing public and private research efforts to understand the role of soil biology, particularly microbiology, on the health of our world’s soils. We begin by defining soil quality/soil health (which we consider to be interchangeable terms), characterizing healthy soil resources, and relating the significance of soil health to agroecosystems and their functions. We examine how soil biology influences soil health and how biological properties and processes contribute to sustainability of agriculture and ecosystem services. We continue by examining what can be done to manipulate soil biology to: (i) increase nutrient availability for production of high yielding, high quality crops; (ii) protect crops from pests, pathogens, weeds; and (iii) manage other factors limiting production, provision of ecosystem services, and resilience to stresses like droughts. Next we look to the future by asking what needs to be known about soil biology that is not currently recognized or fully understood and how these needs could be addressed using emerging research tools. We conclude, based on our perceptions of how new knowledge regarding soil biology will help make agriculture more sustainable and productive, by recommending research emphases that should receive first priority through enhanced public and private research in order to reverse the trajectory toward global soil degradation