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Title:   Author  item
                                            Halvorson, Jonathanitem
                                            NICHOLS, KRISTINE - Rodale Instituteitem
                                            CRISAFULLI, CHARLES - Forest Service (FS)
  Submitted to: Book Chapter
                                    Publication Type: Book / Chapter
                                    Publication Acceptance Date: 5/4/2016
                                    Publication  Date: 1/30/2018
                                    Citation: Halvorson, J.J., Nichols, K.A., Crisafulli, C.M. 2018. Soil carbon, nitrogen, and evidence for formation of glomalin, a recalcitrant pool of soil organic matter, in developing Mount St. Helens pyroclastic substrates. Book Chapter. p:97-112. https://doi.org/10.1007/978-1-4939-7451-1_5.DOI: https://doi.org/10.1007/978-1-4939-7451-1_5                                                              
                                Interpretive Summary: Formation of stable soil organic matter is typically the result of a relatively slow series of processes that can be constrained by the availability of inputs from plants and animals or by environmental conditions that limit microbial activities. Alternatively, compounds such as glomalin, a glycoprotein of fungal origin, may form relatively early during soil development, and improve soil physical characteristics, water infiltration, and carbon and nitrogen storage. We measured soil carbon (C), nitrogen (N), and an indicator of glomalin, (BRSP), in soil collected at several depths from under different plant communities growing in a natural soil ecosystem at Mount St. Helens. After 31 years of development, significant amounts of soil C, N, and BRSP had accrued in patterns affected by both plant community type and soil depth. In general, greatest accumulations and highest variability among the plant communities were found near the soil surface. Soil from sites with shrubs contained much more organic matter than sites that were sparsely vegetated with grasses and herbs. The quantity of soil organic matter and differences among the plant communities decreased with soil depth. The amount of BRSP was related with soil C and N and was equivalent to about 6-8% of the total soil C and about 10% of the soil N. However, the proportion of BRSP-C increased with soil depth or, alternatively, as the amount of organic matter decreased. This study confirmed that significant amount of glomalin can accumulate early during soil development. Even small amounts of such microbially produced substances may have important effects on soil processes and plant development before accumulation of humified of soil organic matter.
                                Technical Abstract: Formation of stable soil organic matter is typically the result of a relatively slow series of decomposition processes that can be constrained, in early successional sites, by the availability of exogenous inputs or by environmental conditions that limit microbial activities. Alternatively, compounds such as glomalin, a glycoprotein of arbuscular mycorrhizal fungal origin, may form relatively early during soil development, and improve aggregate stabilization, water infiltration, and carbon and nitrogen storage. We measured total and soluble carbon (C) and nitrogen (N) and Bradford reactive soil protein (BRSP), an indicator of glomalin, in Mount St. Helens pyroclastic deposits soil collected in 2011 at three depth increments (0-5, 5-10, and 10-20 cm) from five different plant community types, representing a range of successional stages. Sites included low (LDH), intermediate (IDH), or high (HDH) densities of grasses and forbs with few shrubs, and dense shrub-dominated thickets of upland alder (Alnus) (SDU), and riparian willow (Salix) (SDR) with low herb cover. Concentrations of C, N, and BRSP varied as an interaction between plant community type and sample depth. In general, the highest values and greatest inter-site variability were observed at the 0-5 cm depth, lowest for LDH, intermediate for IDH, HDH and SDU, and highest for SDR. Both concentration and variability decreased with depth, and community types tended to be similar for all assays at the 10-20 cm depth. Thirty-one years post-eruption, estimated standing stocks of total C, N and BRSP in the top 20 cm, were arrayed similarly (SDR = SDU =HDH =IDH =LDH and ranged from about 400, 24 and 72 g m-2 in SDR to 121, 12, and 22 g m-2 in LDH. Our data demonstrate the presence of glomalin across all plant community types where even small amounts of such microbially-produced substances may have important effects on soil processes and vegetation development before accumulation of humified of soil organic matter.


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