Model-Based Growth Comparisons between Loblolly and Slash Pine and between Silvicultural Intensities in East Texas

Yuhui Weng,Xiongwei Lou,Jing Tao,Bilawal Cheema,Harold Burkhart,Jason Grogan

doi:10.3390/f12121611

Abstract

Growth differences between key commercial species and between silvicultural intensities (phases) within a species in a region are of great interest to foresters. This study used modeling methods to investigate these differences in east Texas. Datasets collected from loblolly and slash pine plots installed in extensively managed plantations (Phase I) and loblolly pine plots installed in intensively managed plantations (Phase II) were used. Species and silvicultural phase growth differences were determined by comparing their height–age, diameter–age, and height–diameter relationships. Slash and loblolly pine had significantly different parameter estimates for the Chapman and Richards function-based height– and diameter–age models. Slash pine grew faster than loblolly pine, with the superiority in height increasing while that of diameter growth decreased slightly with age. Slash and loblolly pine differed also in all parameter estimates of the exponential function-based height-diameter model. Loblolly pine was taller than the slash for small size (DBH ≤ 18 cm) trees, but thereafter, slash pine outperformed loblolly. While these results may encourage planting slash pine in the region, more studies are needed before definitive conclusions can be made. The differences in the height–age models for loblolly pine Phase I and II plots suggest that intensive management significantly enhanced tree height growth. However, this enhancement did not substantially change the maximum height; instead, trees reached the maximum height younger, thus effectively shortening the rotation age.

Highlights

Are there differences in growth between loblolly (P. taeda L.) and slash (P. elliottii Engelm.) pine when they are planted in east Texas? To date, few studies have sought to answer this question
Reference [8] argued that southern pine in United States (US) provides the best example in improving forest productivity via silviculture including genetics, which, based on an estimation by Fox et al [7], has enhanced pine plantation productivity greatly with average volumes per acre, increasing from 3000 ft3/acre for plantations established in the 1970s to 5000 ft3/acre for those established in the 1990s
Model predictions in average tree H showed that slash pine was consistently taller than loblolly pine at a given age, with this advantage increasing with age (Figure 2a)

Summary

Introduction

Are there differences in growth between loblolly (P. taeda L.) and slash (P. elliottii Engelm.) pine when they are planted in east Texas? To date, few studies have sought to answer this question. Are there differences in growth between loblolly (P. taeda L.) and slash (P. elliottii Engelm.) pine when they are planted in east Texas? Reference [1] compared young pine plantations in east Texas and found that slash pine outperformed loblolly pine in general. The planting of the first-generation genetically improved seed sources became prevalent These plantations are conventionally referred to as extensively managed plantations, hereafter. Around the 1990s, the application of chemical site preparation, fertilization, midrotation thinning, and planting more advanced genetically improved seedlings became common. These plantations are referred to as intensively managed plantations. Reference [8] argued that southern pine in US provides the best example in improving forest productivity via silviculture including genetics, which, based on an estimation by Fox et al [7], has enhanced pine plantation productivity greatly with average volumes per acre, increasing from 3000 ft3/acre for plantations established in the 1970s to 5000 ft3/acre for those established in the 1990s

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