Slash Mulching and Incorporation as Mechanical Site Preparation for Pine Plantation Establishment and Subsequent Effects on Soil Moisture and Site Hydrology
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Abstract
Over one million hectares of pocosins and wet flats in the southeastern coastal plain are intensively managed for the production of loblolly pine (Pinus taeda) plantations. These management activities may have adverse effects on soil physical properties, site hydrology, and overall site productivity. Substantial quantities of wood residues are often left on these sites by timber harvesting operations, and it was hypothesized that the incorporation of this slash into the soil could improve the soil physical properties and site hydrology. One organic pocosin site and one mineral wet flat site were chosen post-harvest for treatment. The wet flat study was organized as an incomplete block design having four blocks and six treatments: (i) conventional bedding, (ii) strip surface mulching with bedding, (iii) strip surface mulching with tillage and bedding, (iv) broadcast mulch without bedding, (v) broadcast mulch with bedding, and (vi) flat planted control. The pocosin study was organized as a randomized complete block design with four blocks and four treatments. The treatments are identical to those of the wet flat site without the broadcast mulch treatments (iv and v). Soil physical property data was analyzed pre- and post-treatment, while post-treatment site hydrology and soil water chemistry data was analyzed periodically for one year. Seedling survival and height data were analyzed after one growing season.
The treatments had little effect on soil physical properties, site hydrology, soil water nutrients, or seedling survival on the wet flat study site. Bedding in general significantly increased tree height growth, but mulching had no significant effects. The treatments had little effect on soil physical properties on the pocosin study site except for soil macroporosity, which was significantly increased by bedding. Site hydrology and soil water nutrients were not significantly affected by the treatments, but seedling survival and height growth were significantly increased by bedding. Mulching had no significant effects on any of the parameters studied.