Evaluating long-term seedling growth across densities using Nelder plots and FVS in the Black Hills

Abstract

Management and modeling of small-tree growth can affect decision-making for a range of treatment plans. Accurately representing this critical component of stand development is important for evaluating treatment alternatives from fuel hazard reduction to harvest scheduling. In the Black Hills of South Dakota and Wyoming, USA, favorable growing conditions and prolific seed crops often coincide, resulting in abundant natural ponderosa pine (Pinus ponderosa var. scopulorum Dougl. Ex Laws.) seedling establishment. This study seeks to quantify the influence of planting density and site preparation on small-tree development through 45 years of ponderosa pine growth in the Black Hills Experimental Forest. Using three Nelder plots (fig. 1) with 16 densities from 296 to 11,132 trees ha-1 and two site-preparation strategies, the analysis characterizes the effects of density and site preparation on average tree size at 12 and 45 years following planting. Additionally, simulations from the Forest Vegetation Simulator Central Rockies variant (FVS-CR) initiated from bare ground are used to evaluate the model’s ability to represent early stand development until age 45. Our results demonstrate that both herbaceous vegetation and tree density affect tree size, but their influences varied with the tree development stage (fig. 2). Through the first 12 years of field observations, site preparation had the strongest effect on diameter and height growth, with a weaker effect from planting density. By age 45, the effect of planting density strengthened (fig. 2), with the lowest planting density trees approximately 2.5-3 times larger in QMD than the densely grown trees. Additionally, at age 45, site preparation no longer influences QMD or height. The FVS-CR predictions of age 45 height were within 10 percent of the field observed values (fig. 3). However, age 45 predictions of QMD varied from ±5 percent at the greatest planting densities to 35 percent underprediction for the most open-grown condition.

Parent Publication

• Sixth Forest Vegetation Simulator Conference; 2023 March 7-9; Fort Collins, CO

Citation

Tinkham, Wade T.; Battaglia, Mike A.; Hoffman, Chad M. 2024. Evaluating long-term seedling growth across densities using Nelder plots and FVS in the Black Hills. In: Shaw, John D; Battaglia, Mike A.; Castle, Mark, [comps.]. Sixth Forest Vegetation Simulator Conference; 2023 March 7-9; Fort Collins, CO. Proceedings RMRS-P-81. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station. p. 3-6.