Small-tree development affects future stand dynamics and dictates many ecological processes within a site. Accurately representing this critical component of stand development is important for evaluating treatment alternatives from fuel hazard reduction to harvest scheduling. As with all forest growth, competition with other vegetation is known to regulate small-tree growth dynamics. This study uses three Nelder plots with 45 years of ponderosa pine growth to understand competition effects on seedling growth and evaluate the Forest Vegetation Simulator (FVS) Central Rockies (CR) variant’s ability to represent these dynamics. Removal of herbaceous competition before planting increased tree diameters by 50–135% and height by 35–75% across a planting density gradient at age 12. However, by age 45, the effect of herbaceous competition on tree size was no longer evident. Instead, trees at the lowest planting density had diameters 2.5–3 times larger than the most densely grown trees. Forest Vegetation Simulator (FVS) simulations underpredicted diameter at breast height (dbh) by 35–50% and 0–35% for 12 and 45-year-old trees, respectively. There was an underprediction bias of 15–20% for heights at age 12 and overpredictions of 5–10% at age 45. Continuous underprediction of dbh will affect the reliability of modeled fuel treatment longevity and sustainable harvest scheduling.

中文翻译：

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使用 Nelder 图和美国南达科他州布莱克山的森林植被模拟器 (FVS) 评估不同密度的长期幼苗生长

小树的发展会影响未来的林分动态，并决定场地内的许多生态过程。准确代表林分发展的这一关键组成部分对于评估从减少燃料危害到收获计划的处理替代方案非常重要。与所有森林生长一样，众所周知，与其他植被的竞争可以调节小树的生长动态。本研究使用三个具有 45 年黄松生长历史的 Nelder 图来了解竞争对幼苗生长的影响，并评估森林植被模拟器 (FVS) 中央落基山脉 (CR) 变体代表这些动态的能力。在种植前去除草本竞争使树木在 12 岁时的种植密度梯度上增加了 50-135% 的直径和 35-75% 的高度。然而，到 45 岁时，草本竞争对树木大小的影响不再明显。相反，种植密度最低的树木的直径是种植密度最高的树木的 2.5-3 倍。森林植被模拟器 (FVS) 模拟分别低估了 12 和 45 年树龄树木的胸高 (dbh) 直径 35-50% 和 0-35%。12 岁时的身高存在 15-20% 的低估偏差，45 岁时的高估偏差为 5-10%。持续低估 dbh 将影响模拟燃料处理寿命和可持续收获计划的可靠性。分别。12 岁时的身高存在 15-20% 的低估偏差，45 岁时的高估偏差为 5-10%。持续低估 dbh 将影响模拟燃料处理寿命和可持续收获计划的可靠性。分别。12 岁时的身高存在 15-20% 的低估偏差，45 岁时的高估偏差为 5-10%。持续低估 dbh 将影响模拟燃料处理寿命和可持续收获计划的可靠性。