Effects of salvage options for beetle-killed pine stands on ECA: December 2008 update. A synthesis of currently available data and uncertainties

This project synthesizes currently available local data related to the effects of salvaging or not salvaging stands killed by mountain pine beetle on equivalent clearcut area (ECA) value of a stand. The current report examines four main aspects needed to predict the immediate and longer-term ECA effects of stand management options:

1) Relationships between the height and canopy cover of regenerating conifers and ECA,

2) Contributions from dead pines over time, including their fall rates and decreasing canopy cover,

3) Stand components expected to be unaffected by MPB – understory and non-pine overstory,

4) Expected growth and mortality of surviving non-pine canopy trees, saplings and seedlings, or planted seedlings, and natural ingress.

The contributions to reducing ECA from non-pine overstory, dead pine, saplings, seedlings and natural or planted regeneration are then combined to predict the ECA value of stands that are clearcut-salvaged and planted, partially salvaged and unsalvaged. ECA is calculated immediately after disturbance and through time subsequently, for three example stand types. Uncertainties associated with each parameter are estimated and followed through the analysis to determine the uncertainty associated with the ECA predictions.

As expected, unsalvaged stands have a lower ECA value than clearcut-salvaged stands initially, due mainly to non-pine canopy trees and the contributions of dead pine snags. However, the planted salvaged stands are expected to recover more quickly. Which option produces the least total ECA effect over time depends on many factors, but the amount of nonpine species in the canopy and growth rates had large effects in our analysis. ‘Partial salvage’ produces less ECA effect than clearcut salvage if planted trees grow as well, but somewhat greater total ECA if retention lowers growth rates considerably. The project will also look at how the stand-level comparisons roll-up into a watershed-level ECA value over time.

This project makes a number of assumptions and simplifications, and is intended to provide some quickly-available guidance for professional hydrologists and other decisionmakers. Ongoing research and detailed stand and watershed modeling will provide better guidance when these are completed.