Growth of two loblolly pine clones planted in agroforestry and plantation settings: nine-year results

Selecting suitable tree species, cultivars or clones in agroforestry is essential for maximizing volume growth and reducing mortality. While most studies have investigated the performance of understory crops, more information is needed about the performance of trees in agroforestry systems. In the last decades, the forest industry in the Southeast has produced high-yielding loblolly pine varieties that can be propagated by cloning. We evaluated the performance of two forest industry-rated loblolly pine clones (Pinus taeda L.) that we planted in an agroforestry and a plantation setting at a northern Alabama site. Specifically, we assessed and compared the survival and growth of two genetically improved pine clones: clone 1 (CF Q3802-43) and clone 2 (CF L3519-41). Clone 1 had a significantly higher overall survival rate than clone 2 (86% vs. 83%). However, clone 2 demonstrated a superior performance growth compared to clone 1. Tree basal area, live crown ratio, height and total tree volume inside-bark of clone 2 averaged 0.027 m², 70%, 10.7 m and 0.11 m³, respectively, and all were significantly higher than those of clone 1 (0.024 m², 63%, 9.8 m, and 0.09 m³). Therefore, clone 1 is preferred over clone 2 for our region and in similar site conditions if survival is considered a selection criterion and clone 2 is preferred from the wood production viewpoint. However, it will be more advantageous to use clone 2 overall since its higher average tree volume (0.11 m³ vs. 0.09 m³ of clone 1) can easily offset the lower survival rate.