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The effect of organic matter manipulations on site productivity, soil nutrients, and soil carbon on a southern loblolly pine plantation

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Title The effect of organic matter manipulations on site productivity, soil nutrients, and soil carbon on a southern loblolly pine plantation
Names Mack, Jason (creator)
Hatten, Jeff (creator)
Sucre, Eric (creator)
Roberts, Scott (creator)
Leggett, Zakiya (creator)
Dewey, Janet (creator)
Date Issued 2014-08-15 (iso8601)
Note This is an author's peer-reviewed final manuscript, as accepted by the publisher. The published article is copyrighted by Elsevier and can be found at: http://www.journals.elsevier.com/forest-ecology-and-management.
Abstract Forest harvesting intrinsically removes organic matter and associated nutrients; these
exports may impact soil productivity and soil carbon stores of managed forests. This study
examined the effect of manipulating forest floor and harvest residue inputs on nutrient
availability and carbon content in the context of intensive forest management. Treatments were
applied 15 years prior to this study and included removal and addition of forest floor and harvest
residues, and a reference. We examined stand volume, litterfall, root biomass and foliar N and P
at year 14 or 15. Soil moisture and temperature (0-10 cm) and available N and P in the O and 0-20 cm depths were measured once per month during year 15. Soil carbon and nitrogen were
measured on whole soils as well as two density fractions in the O-horizon, 0-20, 20-40, and 40-60 cm soil depths at year 15. In general, many of the initial responses found by an earlier study
(age 10) have dissipated. Standing volume in the added treatment was 31% higher than the
removed, but no significant difference was found between the removed and reference treatments.
The added treatment resulted in higher concentrations of N in the light and heavy density
fractions of the 0-20 cm depth, which led to higher mass of N in both of these fractions. The
added treatment had the greatest whole soil heavy fraction N mass. There were no differences in
available N in the O-horizon or 0-20 cm depth as tested using ion exchange membranes; however
available P was significantly lower in the O-horizon of the removed treatment (37% lower than
the reference). Bole volume was correlated with some measures of total and available N and P in
the O and 0-20 cm soil horizons, suggesting that increases in growth found in the added treatment
were a result of additional nutrients. There were no significant differences between C
concentration or mass of the 0-20 cm or 20-40 cm soil depths between the treatments; however the
added treatment had significantly more (51% more than the reference) carbon at the 40-60 cm
soil depth. The added treatment had a significantly higher C:N relative to the reference in the 20-40 cm (21.0 and 14.5, respectively) and 40-60 cm (18.0 and 11.4, respectively) depths, suggesting
that relatively fresh, undegraded organic matter had enriched this depth. This additional carbon
sequestered at depth could contribute to a long-term soil carbon pool. The results of this study
suggest that higher intensity use, such as forest floor removal and whole tree harvest, of these
forests may not impact long term productivity at this site with typical soil nutrient status;
however, more research is necessary to determine the mechanism(s) of this resilience.
Genre Article
Identifier Mack, J., Hatten, J., Sucre, E., Roberts, S., Leggett, Z., & Dewey, J. (2014). The effect of organic matter manipulations on site productivity, soil nutrients, and soil carbon on a southern loblolly pine plantation. Forest Ecology and Management, 326, 25-35. doi:10.1016/j.foreco.2014.04.008

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