Silvicultural implications from analyzing light induced height growth development of eight North American juvenile tree species in mixed-conifer forests

Abstract

Modern silviculture is based on simulating natural disturbance regimes on the one side and reducing their impact on the other side. Disturbances modify light regimes of forests along complex spatial patterns, and species participating in the ecosystem tend to have unique adaptations to the multitude of light conditions found in forests. We studied the height growth reaction of saplings from eight native North American tree species to different light availabilities in a Sierra Nevada mixed conifer forest. Large height growth differences occurred between species. Height growth increased for most species with increasing light availability. However, black oak but also incense cedar and tanoak reached an optimal value or saturation point of light availability at intermediate light levels, above which their growth stayed the same or slightly declined on average. A variety of stand conditions, representing the range from early to late successional stages, are beneficial to maintain tree species diversity across stands. Such a gradient of conditions can be achieved by diversifying silvicultural regimes and using regeneration approaches that mimic a range of disturbance intensities. The results add to knowledge on the species' ecology by specifying their height growth in dependence of a quantified light environment. The quantification of the light environment can directly be linked to % canopy cover and a range of regeneration methods, respectively. With this, the results may help achieve a more precise and target-oriented management of Sierra Nevada mixed conifer forests.