Incorporating Intermediate-Severity Disturbances in Oak Stand Development

Abstract

Abstract:We propose a conceptual framework for the development of closed canopy oak (Quercus) stands that incorporates the influence of intermediate-severity canopy disturbance events, provides for the possibility of multiple developmental pathways, and does not narrowly define an endpoint given the stochastic nature of natural disturbances. The proposed model differs from the current oak stand development model in three primary ways. First, our proposed model acknowledges more than one mixed stage of development after an intermediate-severity disturbance based on the pre-disturbance condition and disturbance agent. Second, we suggest that these discrete mixed stages may progress in their development along different pathways and stands may be structurally dissimilar when they reach the complex stage. Third, we contend that the complex stage of development in oak stands is not usually achieved in the absence of the mixed stage because the return interval of these events is shorter than the period required for oak stands to reach the complex developmental stage via gap-phase processes alone. Our proposed framework for oak stand development should aid decision making in oak-dominated systems.

What Are Intermediate-Severity Forest Disturbances and Why Are They Important?

“…Therefore, we suggest that most stands will experience an intermediate-severity event between stand initiation and a stand replacing disturbance. We speculate that intermediate-severity disturbances are more common and more important drivers of forest ecosystem change than is typically recognized and we call for more research into intermediate-severity disturbance, especially with regard to the impacts of these events on successional and developmental pathways [92]. Intermediate-severity disturbance patterns may be incorporated into silvicultural systems, and this may become more important as management goals increasingly include promotion of intra-stand heterogeneity [111,129].…”

“…Spatial patterns of mortality and residual trees of intermediate-severity disturbances can typically be classified as uniform, patch, or linear [6,92] (Figure 2). Derechos and ice storms may remove the largest and most dominant canopy trees throughout a stand resulting in a uniform pattern [83,93].…”

“…Thus, multiple interacting disturbances may impact forest succession and development in ways that are distinct from isolated disturbance events, and it is important to consider the impacts of intermediate-severity disturbances in the context of other disturbances. Spatial patterns of mortality and residual trees of intermediate-severity disturbances can typically be classified as uniform, patch, or linear [6,92] (Figure 2). Derechos and ice storms may remove the largest and most dominant canopy trees throughout a stand resulting in a uniform pattern [83,93].…”

“…These events may result in complete mortality of overstory individuals so that they are catastrophic at local scales, but intermediate in severity at the stand scale. The spatial patterns of residual trees may influence the developmental and successional pathways following intermediate-severity disturbance [92]. In the uniform pattern, canopy trees were removed relatively evenly throughout.…”

“…In the silvicultural system, time between entries may be based on the return interval of intermediate-severity disturbances in that forest type and region. Intermediate-severity disturbances result in a wide range of stand structures and alter developmental pathways [15,92,120,121], and thus, provide wide flexibility to forest managers for incorporation into management plans.…”