A Dynamic Stand Growth Model System for Loblolly Pine Responding to Mid-Rotation Treatments

Mauricio Zapata-Cuartas,Bronson P Bullock,Michael B Kane,Cristian R Montes

doi:10.3390/f12050556

Abstract

Intensive loblolly pine (Pinus taeda L.) plantation management in the southeastern United States includes mid-rotation silvicultural practices (MRSP) like thinning, fertilization, competitive vegetation control, and their combinations. Consistent and well-designed long-term studies considering interactions of MRSP are required to produce accurate projections and evaluate management decisions. Here we use longitudinal data from the regional Mid-Rotation Treatment study established by the Plantation Management Research Cooperative (PMRC) at the University of Georgia across the southeast U.S. to fit and validate a new dynamic model system rooted in theoretical and biological principles. A Weibull pdf was used as a modifier function coupled with the basal area growth model. The growth model system and error projection functions were estimated simultaneously. The new formulation results in a compatible and consistent growth and yield system and provides temporal responses to treatment. The results indicated that the model projections reproduce the observed behavior of stand characteristics. The model has high predictive accuracy (the cross-validation variance explained was 96.2%, 99.7%, and 98.6%; and the prediction root mean square distance was 0.704 m, 19.1 trees ha−1, and 1.03 m2ha−1 for dominant height (DH), trees per hectare (N), and basal area (BA), respectively), and can be used to project the current stand attributes following combinations of MRSP and with different thinning intensities. Simulations across southern physiographic regions allow us to conclude that the most overall ranking of MRSP after thinning is fertilization + competitive vegetation control (Fert + CVC) > fertilization only (Fert) > competitive vegetation control only (CVC), and Fert + CVC show less than additive effect. Because of the model structure, the response to treatment changes with location, age of application, and dominant height growth as indicators of site quality. Therefore, the proposed model adequately represents regional growth conditions.

Highlights

IntroductionThroughout the southeastern United States, pine plantations have made a significant expansion
Introduction published maps and institutional affilThroughout the southeastern United States, pine plantations have made a significant expansion
The Mid-Rotation Treatment Study (MRT) study design aggregates the UC and PI physiographic regions as one stratum, we modeled them as separate geographic regions

Summary

Introduction

Throughout the southeastern United States, pine plantations have made a significant expansion. Before 1952 the pine plantations in this region were marginal, but during. 1952–2010, the planted area accumulated 15.8 million hectares (19 percent of the total forest area in the Southeast) [1]. Forecasts reveal a positive rate of change of conversion from natural regenerated pine types to pine plantations. From 2010 to 2060, pine plantations are expected to represent between 24 and 36 percent of the Southeastern forest area [2]. That means a net increment between 3 and 11.4 million hectares, mainly with loblolly pine (Pinus taeda L.) plantations. Pine is the most planted species in the southeastern U.S

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Discussion

Conclusion