Linking Tree Birth and Death: Relationships between Dead Wood and Tree Regeneration across the US
The attributes of dead wood (DW) are an important determinant of numerous forest ecosystem functions such as carbon cycling and tree regeneration, particularly following wildfires and other stand-replacing disturbances. In the context of tree regeneration, DW may not only provide a substrate for seedling establishment but also protection from browse and microclimate buffering to diurnal temperature/moisture stress. As there is an increasing focus on the quantity and dynamics associated with DW across US forests due to climate change and related carbon cycling concerns, establishing relationships between DW and tree regeneration using a nationwide forest inventory is paramount. This study aimed to use a DW and seedling inventory at national and regional scales (USDA Forest Service, Forest Inventory and Analysis Program) to jointly examine DW and tree regeneration dynamics. Results suggest that DW attributes and regeneration abundance may be temporally disassociated (i.e., temporal lags of several years between canopy disturbances and resulting seedling response) at the national scale and vary among species in relation to silvical characteristics at regional scales. For instance, increased hurricane blowdowns in the southeastern US and wildfires in the western US have generated large swaths of dead wood, with snags expected to subsequently become downed logs. A regional seedling demographic inventory suggests refinement of seedling “stocking” models to address emerging resource questions using data sources across spatial scales and platforms (e.g., strategic-scale inventories and terrestrial laser scanning). Findings support the refinement of silvicultural prescriptions for management of deadwood as a component of stand regeneration treatments, especially against a backdrop of global change (e.g., episodic precipitation, blowdowns, wildfires, and insects/disease induced tree mortality). Presented by Christopher Woodall from USDA Forest Service at the 2021 SAF National Virtual Convention.