Impact of postfire logging on soil bacterial and fungal communities and soil biogeochemistry in a mixed-conifer forest in central Oregon

Postfire logging recoups the economic value of timber killed by wildfire, but whether such forest management activity supports or impedes forest recovery in stands differing in structure from historic conditions remains unclear. The aim of this study was to determine the impact of mechanical logging after wildfire on soil bacterial and fungal communities and other measures influencing soil productivity.KEYWORDS: T-RFLP, Wildfire, Community level physiological profiles, Soil bacterial and fungal communities, Postfire salvage logging, Soil chemical and physical propertiesThis is the publisher’s final pdf. The published article is copyrighted by Springer Science+Business Media and can be found at: http://www.springerlink.com/content/0032-079x/350/1-2

Effects of disturbance scale on soil microbial communities in the Western Cascades of Oregon

To gain a better understanding of how rapidly microbial communities respond to different magnitudes of perturbation that mimic minor or catastrophic disturbances. Two montane sites in the western Cascade Mountains of Oregon with adjacent areas of forest and meadow vegetation were studied. A reciprocal transplant experiment evaluated both minor (soil cores remaining in the same vegetation type) or more severe disturbance (soil cores transferred to a different vegetation type). The biomass and composition of the bacterial and fungal communities were measured for 2 years following the establishment of the experiment. Minor disturbance (coring) had little impact on microbial biomass but transferring between vegetation type showed greater fungal biomass in soil incubated in the forest environment. The composition of bacterial communities was not influenced by coring but responded strongly to transfers between vegetation sites, changing to reflect their new environment after 2 years. Fungal community composition responded somewhat to coring, probably from disrupting mycorrhizal fungal hyphae, but more strongly to being transferred to a new environment. The response of the microbial community to major disturbance was rapid, showing shifts reflective of their new environment within 2 years, suggesting that microbial communities have the capacity to quickly adjust to catastrophic disturbances.Keywords: Bacteria, Forest soil, Reciprocal transfer, FungiKeywords: Bacteria, Forest soil, Reciprocal transfer, Fung

Forest calcium depletion and biotic retention along a soil nitrogen gradient

High nitrogen (N) accumulation in terrestrial ecosystems can shift patterns of nutrient limitation and deficiency beyond N toward other nutrients, most notably phosphorus (P) and base cations (calcium [Ca], magnesium [Mg], and potassium [K]). We examined how naturally high N accumulation from a legacy of symbiotic N fixation shaped P and base cation cycling across a gradient of nine temperate conifer forests in the Oregon Coast Range. We were particularly interested in whether long-term legacies of symbiotic N fixation promoted coupled N and organic P accumulation in soils, and whether biotic demands by non-fixing vegetation could conserve ecosystem base cations as N accumulated. Total soil N (0–100 cm) pools increased nearly threefold across the N gradient, leading to increased nitrate leaching, declines in soil pH from 5.8 to 4.2, 10-fold declines in soil exchangeable Ca, Mg, and K, and increased mobilization of aluminum. These results suggest that long-term N enrichment had acidified soils and depleted much of the readily weatherable base cation pool. Soil organic P increased with both soil N and C across the gradient, but soil inorganic P, biomass P, and P leaching loss did not vary with N, implying that historic symbiotic N fixation promoted soil organic P accumulation and P sufficiency for non-fixers. Even though soil pools of Ca, Mg, and K all declined as soil N increased, only Ca declined in biomass pools, suggesting the emergence of Ca deficiency at high N. Biotic conservation and tight recycling of Ca increased in response to whole-ecosystem Ca depletion, as indicated by preferential accumulation of Ca in biomass and surface soil. Our findings support a hierarchical model of coupled N–Ca cycling under long-term soil N enrichment, whereby ecosystem-level N saturation and nitrate leaching deplete readily available soil Ca, stimulating biotic Ca conservation as overall supply diminishes. We conclude that a legacy of biological N fixation can increase N and P accumulation in soil organic matter to the point that neither nutrient is limiting to subsequent non-fixers, while also resulting in natural N saturation that intensifies base cation depletion and deficiency.Keywords: Potassium, Base cation depletion, Temperate forest, Calcium, Magnesium, Douglas-fir, Aluminum, Phosphorus, Nitrate leaching, Nitrogen saturatio

Mass, Nutrient Content, and Decay Rate of Dead Boles in Rain Forests of Olympic National Park

Analysis of the distribution of dead boles of Picea sitchensis and Tsuga heterophylla in open- and closed-canopy forests of the Olympic Peninsula, Washington, USA showed that T. heterophylla mortality in both forest types resulted mainly from windthrow, whereas P. sitchensis typically died upright. The open forest contained 120 t/ha and the closed forest 161 t/ha of dead bole wood. Boles of T. heterophylla decayed more rapidly than larger boles of P. sitchensis, though both showed considerable variation. Nutrient contents of dead boles in kg/ha for open- and closed-canopy (brackets) forests were: N 146 (223); Ca 147 (197); K 39 (61); Mg 18 (29) Na 6 (14); and P 17 (29). Except for N and Mg, nutrient concentration of the wood were not significantly different after 33-68 yr of decay. The N : P ratios increased with decay for both species. From authors\u27 summary

Appendix A. Soil bulk density for each sampling depth.

Soil bulk density for each sampling depth

Appendix C. Percentages of non-sea-salt fluxes in soil water at 20 cm and 100 cm for the nine study sites.

Percentages of non-sea-salt fluxes in soil water at 20 cm and 100 cm for the nine study sites