Financial performance of diverse levels of early competition suppression and pre-commercial thinning on loblolly pine stand development

Abstract

Competition suppression within loblolly pine plantations (Pinus taeda L.) is typically carried out within the first 2 years of a plantation, but competition control for longer durations could improve productivity. As plantation growth improves with increasing vegetation suppression frequency, it may be necessary to pre-commercially thin stands to reduce intraspecific competition. The effect of these silvicultural activities for controlling inter- and intra-specific competition to optimize plantation financial performance is relatively unexplored. This study tests the financial performance of several operational mixtures of herbicides relative to sustained suppression of herbaceous, woody, and all non-crop vegetation based on 29-year yields and financial data; pre-commercial thinning was tested to understand whether reducing stand density affected responses to vegetation control. Intensive vegetation control increased financial returns compared to the control and sustained woody and herbaceous vegetation suppression, but it was similar to the operational-analogue treatments. Introducing pre-commercial thinning undermined financial performance of the intensive treatments, except for that of herbaceous control. While 5 years of vegetation suppression increased yields, in several cases the improved yields did not overcome intensive early-rotation costs; the rate of yield increase (plus any stumpage price increase) was less than the discount rate at 5%. On a 29-year rotation, increased discount rates increasingly favored treatments with fewer costs. Pre-commercial thinning increased the proportion of sawtimber, but it did not enhance financial performance of the vegetation suppression treatments.