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The Mission of the RWU SRS-4160 is to quantify above- and below-ground processes governing sustainability of forest function and productivity, predict forest functional dynamics, and model the interaction of soil processes, plant physiology, forest management, and the environment.

In-situ Root Decomposition & Methodology

FS-SRS- 4160-199 - Loblolly Pine Root Decomposition in-situ Under Two Levels of Fertilization.

Fine root decomposition will be affected by the substrate itself and the environmental conditions in which it decomposes. Tissue chemistry particularly N and C content), tissue physical condition (fresh or air-dried, as well as diameter), soil fertility and environmental condition (temperature and moisture conditions under which the tissue is produced and decomposed), will impact the rates of biomass and nutrient loss. Kim Ludovici and Lance Kress initiated this study in 1997.

Objectives

1. Quantify biomass and nutrient loss of roots of different qualities (N and C content, fresh vs. dried samples, different size classes)
2. Quantify biomass and nutrient loss of roots produced and decomposed under different environmental conditions (soil fertility and season)
3. Define the parameters that most affect fine root decomposition rate.

Methods

The study is located at SETRES, in Scotland County, North Carolina. The soil in the area is mapped as Psammentic Hapludult, and has an available water holding capacity of 8-10%. The site is conducive to long leaf pine production. A factorial combination of 2 nutrient and 2 water addition treatments were replicated in four complete blocks, and begun in an 8-year-old loblolly pine stand. Nutrient treatments are defined as optimum nutrition or no addition (a).

Root decomposition was measured under 2 fertility treatments and for two root size classes (0-2 and 2-5mm) and two initial conditions (fresh or dried). Decomposition studies were begun in each of four seasons (summer, fall, winter and spring), and were monitored six times during the first year and again at 18 months post commencement.

Roots were excavated from a block of soil (1m wide x 1m long x 25cm deep) within the treatment plot, but outside the measurement plot. Roots for decomposition were placed at the 5-10cm depth within stainless steel or plastic ingress corestm. Physical measurements included LOI, % moisture and mass. Chemical measurements of C, N, Ca, Mg, P K and carbohydrates were also made.

Products

Ludovici, K.H. and L.W. Kress. 2002. In-situ Decomposition of Fresh and Dried Loblolly Pine Roots under Two Fertilization Levels. (ready for SSSAJ)

Ludovici, K.H., and L.W. Kress. 2002. Seasonal Differences in Decomposition and Nutrient Release from Loblolly Pine Roots. (ready for SSSAJ)

(a) Albaugh, Allen, Dougherty, Kress and King. 1998. Leaf Area and Above- and Belowground Growth Responses of Loblolly Pine to Nutrient and Water additions. For. Sci. 44:317-328

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