North Central Research Station

Ecology and Silviculture of Northern Lake States Forests Research

Management approaches for sustaining ecological and production objectives

Riparian forest management Ecological forestry Forest productivity impacts Invasive shrubs

Restoring stand complexity in managed red pine (Pinus resinosa) ecosystems using overstory retention and understory control.

Principal Investigators:

Brian Palik, Christel Kern
North Central Research Station, Grand Rapids, MN

Cooperators:

Rebecca Montgomery, Peter Reich, Eric Zenner, University of Minnesota; Mike Ostry, North Central Research Station; Lisa Schulte (Iowa State University); Kelly Barrett (Chippewa National Forest); John Zasada (North Central Research Station, retired).

Background

In many parts of the Great Lakes region, commercially managed red pine forests differ greatly in structure and composition from historical conditions. Many stands were regenerated artificially in even-aged plantations. In other instances, red pine regenerated naturally, after initial logging, on sites it occupied historically. However, even in these cases, structure and composition are greatly simplified from the historical condition: for instance, single-cohort versus multi-cohort age structure and monospecific versus mixed-species composition. Still, these simplified stands are important biological templates that are closer to the historical condition of red pine growing on “red pine sites” than, for example, are white spruce (Picea glauca) plantations on northern hardwood sites. Where such stands exist, they provide opportunities to test silvicultural approaches for increasing structural and compositional complexity in managed forests.

For more formal background and introduction, please see Palik and Zasada 2002b.

Introduction

In this study, we are using overstory retention during regeneration harvests to add size, age, and compositional complexity to what are largely single-cohort, monotypic red pine stands, dominated by hazel (Corylus sp.) in the understory. We are managing these stands initially for two-cohort structure and, potentially, for multi-cohort structure by retaining the residual overstory through a second rotation, along with a new cohort of planted trees. We are adding compositional complexity by planting eastern white pine (Pinus strobes), red pine, and jack pine (Pinus banksiana). Overstory retention is combined with different levels of hazel control to provide better opportunities for tree recruitment and development of more species rich herbaceous and shrub layers.
In this project, we also are examining ways to manage trade-offs between restoration of ecological complexity and growth and yield of timber species. Our approach tests different spatial distributions of overstory retention for their effects on resource availability and growth and survival of planted and residual pine. In this research, overstory basal area is reduced to a similar low level in all treatments (e.g., ~30 m²/ha), but the spatial distribution of residual basal area differs from dispersed to small aggregate retention to large aggregate retention (Figure 1). We hypothesize, based on plant competition research in other pine systems (Palik et al. 1997, 2002a), that maximum resource availability and seedling growth of intolerant species at the whole stand-scale occurs with large aggregate retention, rather than dispersed or small aggregate retention, despite the fact that all three treatments have the same low residual basal area per unit area. Moreover, we hypothesize that residual cohort growth will be maximized with dispersed retention, because of greater light and soil resources aquistion with this spatial pattern.

Figure 1. Conceptual representation of spatially variable overstory retention ranging from uncut forest (top left), to dispersed retention (top right), to small aggregate retention (lower left) to large aggregate retention (lower right). The three harvest treatments have the same amount of residual basal area.

Moreover, we hypothesize that by experimentally altering the spatial pattern of the residual overstory, from dispersed to large aggregates, we will alter the resource environment in the understory so as to favor different species with different retention treatments. For instance, assuming appropriate seedbed and forest floor conditions, eastern white pine may grow best with dispersed or small aggregate retention, whereas red pine and jack pine should grow best with large aggregate retention. Ultimately, our interest is in evaluating approaches for establishing mixed-species forests using variable retention (sensu Franklin et al. 1997), by incorporating dispersed and aggregate retention within the same stand to favor different species in different locations.
The primary goals of this research focus on regeneration dynamics and productivity with different approaches for adding complexity to simplified stands. However, we expect that spatial distribution of overstory red pine will influence other ecosystem characteristics, goods, and services. For instance, the incidence of Sirococcus and Diplodia shoot blights in red pine seedlings, a concern when they are grown under a residual overstory, may vary with retention pattern. Similar to competitive inhibition of regeneration, we expect that the likelihood of Sirococcus and Diplodia infection will be minimized with large aggregate retention, because of greater spatial disassociation of overstory trees and seedlings. Abundance and production of competitive shrubs, as well as economically important non-timber plants, may also respond to retention pattern. For example, hazel and wild blueberries (Vaccinium sp.) would likely have higher production with dispersed and small aggregate retention, respectively, requiring more aggressive control for the former and providing more harvesting opportunities for the latter.

This study is a cooperative management experiment between the North Central Research Station and the Chippewa National Forest, with collaboration from the University of Minnesota. The experimental unit size and carefully controlled and replicated design of this study are unique for red pine research in the Lake States. Study duration is planned for 5+ years. Summary of the results and any publications will be posted as available on this website.

Objectives

1. Creating two-cohort, mixed-species stands through retention of residual mature red pine and planting of pine species mixtures, including jack, red, and eastern white pine.

2. Comparing different spatial patterns of overstory retention for effects on regeneration, understory plant communities, aboveground productivity, and resource availability.

3. Assessing survival and growth of regeneration under different spatial patterns of overstory retention combined with different levels of understory competition control.

4. Assessing approaches for balancing regeneration, growth, and productivity of timber species with creation of compositionally and structurally complex forest stands.

Hypotheses

1) Maximum stand-level resource availability in the understory occurs with aggregate overstory retention rather than dispersed retention, despite constant residual basal area.

2) Pine species respond differentially to the retention gradient, with greatest growth of white pine occurring with dispersed retention, greatest growth of red pine occurring with small aggregate retention, and highest growth of jack pine occurring with large aggregate retention.

3) Above-ground productivity of the residual overstory will be greatest with dispersed retention, while new tree cohort and understory production will be greatest with large aggregate retention.

4) At the stand-scale, total ABNPP will be highest with large aggregate retention.

5) Native understory plant species richness and diversity will be highest with large aggregate retention and lowest with dispersed retention.

6) Resource preemption by pre-established understory shrubs decouples pine seedling growth and understory plant community responses from overstory retention patterns.

Approach

The study is a split-plot, complete block design replicated four times (blocks). Four overstory retention treatments are split with two understory competition treatments. Each block is ~64 ha and consists of four ~16 ha stands.

Understory competition treatment:

Overstory retention treatments
(Thinning spatial pattern from above):

Data collected

	Tree/Sapling heights and diameters			Shrub counts by diameter class
	Herbaceous vegetation cover			Destructive biomass collection
	Tree stem mapping			Forest floor coding
	Seedling counts			Soil moisture
	Canopy cover			N availability
	Pathogen monitoring

Current Status

Logging, understory release, and planting completed in spring 2003. Understory release repeated in 2004 and planned for 2005. Animal protection applied in 2003 and 2004; planned for 2005.
Pre-harvest, 1 & 2 year Post-harvest aboveground productivity, abundance, diversity & composition data on overstory, midstory, and understory vegetation was collected
Armallaria pockets mapped (Mike Ostry, NCRS –St. Paul)
Stem mapped 1 hectare area in each overstory treatment (Eric Zenner, U.Minn.)
Gap Dynamics sub-study on-going (Eric Zenner, U.Minn.)
Shrub Competition for Resources sub-study on-going (Rebecca Montgomery, U.Minn.)
Avian Community Response sub-study on-going (Lisa Schulte, ISU)

Literature Cited

Franklin, J. F., D. R. Berg, D. A. Thornburgh, and J. C. Tappeiner. 1997. Alternative silvicultural approaches to timber harvesting: variable retention harvest systems, In: Kohm, K. A., Franklin, J. F. (Eds.), Creating a forestry for the 21st century. Island Press, pp. 111-140.

Palik, B., R. J. Mitchell, S. Pecot, M. Battaglia, and P. Mou. 2002a. Spatial Distribution of Overstory Retention Influences Resource Availability and Seedling Growth: a Silvicultural Experiment using Longleaf Pine. Unpublished manuscript.

Palik, B.J. and J.C. Zasada. 2002b. An Ecological Context for Regenerating Multi-cohort, Mixed-species Red Pine Forests. In Proceedings of the Red Pine SAF Region V Technical Conference, eds., D.W. Gilmore and L.S. Yount, 54-64. Staff Paper no. 157. St. Paul, MN: University of Minnesota, College of Natural Resources, Department of Forest Resources.

Palik, B. J., R. J. Mitchell, G. Houseal, and N. Pederson. 1997. Effects of canopy structure on resource availability and seedling responses in a longleaf pine ecosystem. Can. J. For. Res., 27, 1458-1464.

Links

Background Information:

• Natural History
  • http://www.fs.fed.us/ne/delaware/atlas/lh125.htm
• Silvics Manual
  • http://www.na.fs.fed.us/spfo/pubs/silvics_manual/Volume_1/pinus/resinosa.htm
• Taxonomy:
  • http://www.treeguide.com/Species.asp?SpeciesID=730
  • http://www.nearctica.com/trees/conifer/pinus/Presin.htm
  • http://www.borealforest.org/trees/tree9.htm
  • http://www.rook.org/earl/bwca/nature/trees/pinusres.html

Other Reports:

• Red Pine Type: Silviculture and Forest Aesthetics Handbook by the Wisconsin DNR
• Managing Red Pine for Timber Productivity and Sustainability: Lessons Learned Over the Past Century by A. Lundgren and R. Buckman
• Applying Ecological Principles to the Management of U.S. National Forests by J. Aber et al.
• Effects of Partial Cutting on Eastern White and Red Pine by the Canadian Forest Service