Forest Analysis Techniques: Determining insect vulnerability

Introduction

What makes tree stands vulnerable, and how can we identify these stands?

Forests are affected by a host of natural disturbances, including windstorms, fires, diseases, and insects, on an ongoing basis. In fact, these disturbances contribute to the long-term ecological well-being of forests.

From a human perspective, though, these events seem destructive. After all, they destroy timber and nontimber commodities that we value highly. For this reason, society often protects its forests from these destructive events.

A good example is the long-standing battle against the spruce budworm (Choristoneura fumiferana). This insect has a long history of periodic outbreaks and defoliation of softwood-dominated forests in northeastern North America.

Outbreaks, of varying severity and length, have occurred on at least five occasions since the early 1700s. The most recent outbreak occurred in the late 1970s through the early 1980s and affected large areas of forest. It's just a matter of time before another outbreak occurs.

Typically, during outbreaks, efforts are made to target protection activities toward stands that are most vulnerable to tree mortality, and thus significant timber and nontimber losses.

Location

A small 1,400 ha woodlot in the Acadian-New England forest region of North America

Time to complete the lab

3 hours

Prerequisites

Students should have a basic working knowledge of GIS data, including the geodatabase, and ArcGIS in particular. Familiarity with forest inventory data is also helpful, but not essential.

Data used in this lab

Feature classes and rasters for a small woodlot (personal geodatabase)

Geographic coordinate system: NAD 1983 CSRS New Brunswick Stereographic

Datum: NAD83

Projection: New Brunswick Double Stereographic Grid (unless otherwise stated)