Mike Wagner, Professor of Pest Management

Bob Mathiasen, Assistant Professor of Forest Pathology

Introduction

A major research gap currently exists in our understanding of how landscape-level operational silviculture affects forest ecosystem health in northern Arizona. We are filling that gap with a multi-year, multiple-investigator research project in the ponderosa pine forests of the Coconino and Mogollon Plateaus. More than 70% of our landscape is in relatively young, even-aged stands resulting from a management history of grazing, fire exclusion, atypical climatic events, and overstory yellow pine removal. The project focuses on four broad categories of forest condition (treatments): stands that have been thinned to improve forest ecosystem health, stands that were thinned and treated with prescribed burning, untreated stands, and untreated stands that were consumed by stand-removing wildfire. These four broad treatments are defined below in detail.

STIFH augments ponderosa pine restoration ecology research with a more operational silviculture approach. Restoration ecology is dependent on certain stand structural elements being present (i.e., older, larger trees) which are not present in sufficient density in many northern Arizona stands. Also, restoration treatments are often complicated and costly, and presettlement stand conditions will likely not be the objective of many landowners and managers. In contrast, stand treatments to improve forest health (and fire safety and aesthetics) will be a likely objective for much of the landscape, even though forest health issues have been typically viewed as a limitation to forest management. Such stand treatments will be spawned from traditional silvicultural practices, as well as new ecosystem-based management ideas and practices (including aspects of restoration ecology). These initial four STIFH treatments represent our best first guess at two reasonable silvicultural options and their logical comparisons.

Objectives

The objectives of this project are to: 1) characterize and compare thinned, thinned and broadcast burned, wildire, and no treatment stands in terms of overstory and understory vegetation richness, diversity (among and within species), composition, and physical arrangement;

2) characterize and compare the four treatments in terms of community organization and structure of four insect guilds: ants, butterflies, bark beetles, and ground beetles -- and how these relate to vegetation patterns;

3) evaluate current insect resistance as measured by resin flow and foliar toughness, and project insect resistance into the near future based on stand projections;

4) characterize and compare the four treatments in terms of dwarf mistletoe infection rates and spread, mycorrhizal fungal populations and species richness, and other measures of forest health as part of the Forest Health Initiative;

5) solicit cooperative research in areas of tree physiology, small mammal and bird communities, aesthetics and human perception, recreation potential, nutrient cycling, forage quality, and botanical invasions;

6) develop insect and fungal ecological indicators of the above stands conditions and test robustness of these indicators and;

7) use experimental treatments to asses ecosystem functioning (based on ecological indicators) under various management strategies.

Methods

Stand Selection: We identified stands of 50-200 acres on the Coconino or Mogollon Plateau (within two hours of Flagstaff) in each of the following four treatments:

	1) Thinned stands (TH) - stands of mature, even-aged blackjack ponderosa pine that have had >30% of their basal area removed between 1987 and 1993, at least 50% of which came from diameter classes <12" (30cm - "pulpwood" size). The density of large, yellow pine (>25" or 64cm DBH) in these stands does not exceed approximately 10 trees/ha;
	2) Thinned and prescribed burned stands (TB) - stands like the above, which also received a broadcast burn treatment within 3-4 years of thinning (1988 to 1996). Overstory survival to date following the broadcast burn is >90%;
	3) Unmanaged (UN) - blackjack dominated stands like the above but having not received a density altering treatment within the last 30 years, such that the stands have >90% crown closure and relative density >70% (and thus are actively self-thinning). The density of large, yellow pine (>25" or 64cm DBH) in these stands does not exceed approximately 10 trees/ha;
	4) Wildfire areas (WF) - stands like the above (but with perhaps as great as 20 trees/ha of large yellow pines) in which >90% of the basal area was killed and/or consumed by wildfire since 1994.

Several dozen such stands were identified in 1997. Preliminary sampling and specific stand selection took place in 1998, and plot installation began in 1999. Below is a table that summarizes stand parameters (live trees only) for data collected during the 1999 field season:

Field Data Collection: In each stand > 10, randomly-located (systematic following a random start), 20m by20m square plots (~1/10 acre) are established and measured using standard forestry and botanical techniques. The intent is to 1. augment existing data available for each stand from the land management agencies; 2. establish permanent plot locations that can be re-measured over time and; 3. to provide identifiable locations for sampling of other taxa (plant, animal, and fungi) which may be related to forest ecosystem health. Permanent plot centers and corners are marked with iron pins inside a labeled PVC sleeve. Neighboring trees were tagged with similar labels.

Standardized archiving procedures were established for understory plants, insects, fungi, and other taxa of interest to ensure that taxonomic status can be examined in the future. Taxonomy of insect and fungal specimens is confirmed using noted taxonomic authorities and conventional procedures.

Statistics: Systematic random sampling within stands (along a grid with a random start) allows the calculation of stand means and variances for comparisons among stands. It also allows the exploration of correlation among different taxa within stands.

Comparisons among treatments are based on the 10, randomly selected stands within each treatment; variances may differ markedly among treatments dictating weighed comparisons or non-parametric procedures (e.g., ranked sums comparisons).

Preliminary Findings

• Overstory Vegetation Structural Responses
  
  

• Ground Beetle Community Structure as a Bioindicator of Forest Health
  
  

• Bark Beetles and Associated Insects
  
  

• Understory Diversity
  
  

• Sporocarp production of ectotrophic ectomycorrhizae (coming soon)
  
  

• Surface Fuels (coming soon)
  
  

New Research

• Changing patterns in Gambel oak growth and age structure
  
  

• Other Potential Studies