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- Title
Influence of Forest Disturbance on Stable Nitrogen Isotope Ratios in Soil and Vegetation Profiles.
- Authors
Knoepp, Jennifer D.; Taylor, R. Scott; Boring, Lindsay R.; Miniat, Chelcy F.
- Abstract
Soil and plant stable N isotope ratios (δ15N) are influenced by atmospheric N2 inputs and processes that regulate organic matter (OM) transformation and N cycling. The resulting δ15N patterns may be useful for discerning ecosystem differences in N cycling. We studied two ecosystems, longleaf pine (Pinus palustris Mill.)-wiregrass (Aristida stricta Michx.) (LLP) and Appalachian hardwood (AHW) forests in the US Southeast under different management regimes. In LLP, burning removes OM. In AHW, clearcutting creates large OM pulses of logging residue. Although burning removes OM and clearcutting creates a pulse addition of OM, both management regimes increase soil N availability and N2-fixing plants. The LLP treatments included burning every 2 yr with N2 fixers and reference fire exclusion sites without N2 fixers. The AHW included 25-yr-old clearcut plots with and without N2 fixers, and uncut reference without N2 fixers. We hypothesized that: (i) compared with the reference, OM removal (LLP) would enrich δ15N values while OM addition (AHW) would deplete δ15N in soil and vegetation pools; and (ii) N2 fixers would mitigate δ15N enrichment in LLP response and exacerbate δ15N depletion in AHW. We examined total δ15N in soil profiles, tree increment cores, and foliage. The LLP soil and vegetation δ15N values showed no treatment effect. In AHW, δ15N values in clearcut subsurface soils (20-60 cm) were lower than the reference, but N2 fixers had no effect. Wood δ15N differed with treatment; N2 fixers had no effect. Our data suggest that AHW soil profile δ15N patterns may indicate past disturbance; however, wood and foliar δ15N response is species specific.
- Subjects
NITROGEN isotopes; SOIL profiles; ORGANIC compounds; HUMUS; SLASH (Logging)
- Publication
Soil Science Society of America Journal, 2015, Vol 79, Issue 5, p1470
- ISSN
0361-5995
- Publication type
Article
- DOI
10.2136/sssaj2015.03.0101