Site Index Prediction for Willow and Cherrybark Oaks in East Texas Bottomland Forests

Weng Y,Kronrad Gd,Oswald Bp

doi:10.4172/2168-9776.1000210

Abstract

Estimating site quality for a specific tree species is an important tool in forest management. While intensively managed pine species are often the focus of site quality studies using site index, hardwood species found in bottomland hardwood sites are often lacking in quality growth prediction equations. Two valuable hardwood species, willow oak (Quercus phellos) and cherrybark oak (Q. pagoda), are of interest for forest managers of east Texas bottomland sites. The objective of this study was to develop site index prediction equations and curves for these two species. Using height and age data from 267 cherrybark oaks and 460 willow oaks collected from sites across east Texas, remarkably similar equations were developed, with coefficient of determination (R2) of 0.63 for cherrybark oak and 0.52 for willow oak.

Highlights

Of the 72.8 million ha of commercial forest land in the southernUnited States, approximately 4.8 million ha may be found in east Texas, approximately 728,000 ha of that have been classified as bottomland types [1]
While potentially very productive for a variety of hardwood species, species composition is greatly influenced by levels of drainage, soil texture, soil moisture, soil structure and soil pH, with elevational changes of 1 m leading to dramatic changes in productivity [3]
Site index curves for both species were developed from the above height-age regression equations, following [8] for guide curve development with steps of transformation, definition and arrangement (Table 2)

Summary

Introduction

Of the 72.8 million ha of commercial forest land in the southernUnited States, approximately 4.8 million ha may be found in east Texas, approximately 728,000 ha of that have been classified as bottomland types [1]. Bottomland types refer to low lying flood plains along river systems characterized by typical relief features such as bars, fronts, sloughs, ridges, flats and swamps with slight changes in elevation [2]. Willow oak can reach 36 m in height and up to 101 cm in diameter, but its growth rate is moderate compared to its associates on higher productive sites; they develop best on clay loam ridges [5]. These oaks grow on a variety of alluvial soils occurring on ridges and high flats on first bottoms of major streams; in minor stream bottoms, they are found on ridges, flats, and sloughs

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