Native

Ferns in the Pennsylvania Pocono Mountains

Native biota pose risks to forest health. Methods developed to assist and inform management decisions for risk assessment at the landscape scale have been diverse, ranging from simple empirical correlations to complex systems models. Assessment methods, however, share a common theme: they aim to quantify expected levels of attack and loss. Both insects and plants can introduce risk, and often act in concert.  For example, increased overstory disturbance, whether from fire, insect defoliation, or other means of disturbance, selects for shade intolerant species with rapid rates of vegetative spread over slower growing, shade tolerant herbs and shrubs. The result is a low diversity but dense understory that can persist for long periods of time even if the canopy closes.

In this section, native biotic threats are examined through a review of bark beetle infestations and related assessment tools that have been developed as a result of these invasions.  Additionally, a useful worldwide review of the formation of dense understory layers in forests, and resulting consequences and implications for forest dynamics, biodiversity, and succession is provided.

To further review the impact of native invasive species, consider reading the following Environmental Threats Case Studies:

Evaluating the Impact of Invasive Species in Forest Landscapes: the Southern Pine Beetle and the Hemlock Woolly Adelgid

A Methodology for Assessing Annual Risk of Southern Pine Beetle Outbreaks across the Southern Region Using Pheromone Traps