How to apply NPC silvicultural strategies in forest management

This guide steps through the process of using Native Plant Community (NPC) data and silvicultural strategies to support forest stand prescriptions.

Note that "Managing for an NPC", is not an appropriate or desired end goal. NPC data and silviculture strategies are tools used for helping create ecologically defensible silvicultural prescriptions that meet forest plan goals.

  1. Determine the NPC of the stand. Check the Geospatial Commons for DNR Native Plant Communities data to see if your land has been mapped and which NPC the stand is in (this will require GIS software such as ArcMap). If NPC map data is unavailable, the NPC can be determined by completing an ECS Site Classification Worksheet and making a determination using the field guides.
  2. Determine the desired future condition (DFC) for the stand. DFCs include a narrative description of the species composition and structure within the overstory, subcanopy, understory, and ground layers. DFCs emphasize desired vegetation conditions when regeneration is established, usually 3-10 years after timber harvest, and at the next planned entry such as a first thinning. Additional factors to consider include:
    1. Stand composition – whether there is a need to increase or decrease the presence of certain overstory or understory species in a cover type. The silvicultural strategy and tree suitability table for the NPC will indicate how feasible changes are given current conditions on the site.
    2. Age class distribution – whether there is a need to increase or decrease certain age classes on the site.
  3. Consider rare species that may receive special consideration in the stand prescription.
  4. Look up the silviculture strategy for the NPC of interest. Reading the entire webpage will give the user a good understanding of the NPC, but if time is a constraint, take special note of the following elements in bold in the table below.

Brief description of NPC information and silviculture strategies

There are 52 forested native plant communities in Minnesota. Each one has NPC information and 2-page silvicultural strategies and includes the following elements shown in the table. The bolded elements are the most useful sections to review when writing a silvicultural prescription.

ElementDescriptionHow to Use

Photo of the Community

What to expect the forest to look like at a particular growth stage.

Helps verify if you have determined the correct NPC

Forest Description

A brief description of the type of forest found in that NPC.

Helps verify if you have determined the correct NPC

Community Description

A description of the NPC community and where it occurs.

Helps verify if you have determined the correct NPC

Distribution in Minnesota

A distribution map of the particular NPC, showing documented plot locations and estimated extent of NPC on the landscape

Provide a spatial overview of what NPCs are present in the state.

Vegetation Structure and Composition

A summary of the plants most commonly found in the NPC.

Indicates what plants may need protection for wildlife or ecological benefits, or may require control for successful reforestation.

Landscape Setting and Soils

A description of the landforms, topography and soils typically associated with the NPC

Provides context for equipment operability – if rutting may be an issue or frozen ground operations required.

Tree Suitability

A description of how to use the tree suitability table.

Indicates which tree species are expected to be most successful in the NPC, and also guides which tree species to favor, maintain or introduce for future crop trees and non-timber objectives. The DFC should anticipate site competition if species ranked more suitable that the chosen crop tree species are present.

Tree Response to Climate Change

A description of the factors and assumptions used to create the tree habitat responses

Indicates which tree species may benefit or suffer for long term growth and survival if local environmental conditions become warmer or wetter

Tree Establishment and Recruitment

A description of the ability of tree species to naturally regenerate, recruit and become a large tree.

Indicates which trees species may naturally regenerate and recruit to the overstory and which species may need additional silvicultural assistance such as site preparation, artificial regeneration, release, or stand improvement.

Natural Disturbance Rotations

A calculation of the natural frequency of disturbance by fire or wind.

Guides design of silvicultural treatments that emulate natural processes.  The disturbance regime is a major component in deciding which silvicultural strategies are appropriate for each NPC as described in the 2 page handouts.  Higher historical frequency of "maintenance" disturbances can be emulated by gap/partial canopy removal harvests

Stand Dynamics & Growth Stages

A description of the compositional succession and structural change found in a natural NPC system.

Helps to identify current growth stage and expected tree species composition at each growth stage. Supports prescription alignment to a desired future condition by growth stage and successional pathway.

Silviculture Strategies

A summarization of the above elements into a field ("tatum") guide for prescription writing. Provides links to related case studies and scientific literature.

The 2-page tatum guide provides the components to write a stand prescription including trees species and conditions necessary to remove or favor, gap size concepts, operability concerns, site prep options, regeneration species and future actions. It provides successional pathway options to achieve the desired outcomes for each main natural disturbance agent and favored tree species for future stand composition. Select a strategy that best emulates the desired disturbance regime and achieves management objectives at the lowest cost.

Glossary of Terms

Desired Future Condition (DFC)

A broad vision of site vegetation conditions in the distant future. DFCs include a narrative description of the species composition and structure within the overstory, subcanopy, understory, and ground layers. DFCs emphasize desired vegetation conditions when regeneration is established, usually 3-10 years after timber harvest, and at the next planned entry such as a first thinning. Due to the dynamic nature of forest ecosystems, designing a long-term vision for the stand structure over the life of the stand must account for stand in-growth and ecological changes due to natural disturbance events.

Forest covertype

The main tree species composition defined across an area and mapped into relatively distinct units for the purposes of forest inventory, planning and management.

Growth stage

An interpretation of periods of stability and change throughout the course of natural succession. Each growth stage is characterized by differences in composition and structure that result from ecological processes that change after stand regenerating disturbances and biological characteristics of the trees cause them to react differently to these changes. There are typically four stages within forested native plant communities of Minnesota: Young, Transition, Mature, and Old. A basic understanding of growth stage stand dynamics is important for predicting the type and quality of vegetation response following a disturbance event thereby maintaining stands indefinitely by mimicking maintenance disturbance regimes, or to direct succession during transitional episodes of mortality and replacement by other species. A growth stage is not a desired end goal or required condition for management. It is an ecological construct for understanding changes in stand structure and the processes that help shape and define them.

Native Plant Community (NPC)

A group of native plants that interact with each other and with their environment. NPCs are classified and described by hydrology, landforms, soils, and natural disturbance regime (e.g., wildfire, wind storm, insect and disease outbreak).

Natural Disturbance

Changes to the forest structure from natural forces such as fire, insect and disease or wind. Calculation of the frequency of natural disturbances for each NPC is based on Public Land Survey record notes on the condition of the trees at survey corners.

Silvicultural Strategies

Sequences of treatment outcomes designed to emulate natural stand dynamics and promote natural regeneration. They are not silvicultural systems in the traditional sense because they do not cover a full rotation or have attached the implied goal of maintaining a particular species or cover-type indefinitely. Most involve 1-2 stand entries over a short period of time that will move a stand towards a forest plan objective—with enough inertia that little silvicultural intervention will be needed to meet long-term goals.

Silvicultural System

A planned system of treatments over the entire life of the stand which include regeneration, tending, intermediate treatments, harvest, and protection measures to meet management objectives.

Site Prescription

A site prescription is a planned series of treatments designed to move a site from its current state to a Desired Future Condition (DFC) while allowing for natural succession over time. A prescription should include all treatments and activities, including harvest system, regeneration and tending. The prescription should also include the sequence and timing of treatments. It can also indicate which stands will be altered, deferred or where no management action is required. Documented prescriptions are very intentional in describing the DFC, the treatments necessary to achieve it, and a timeline to reach a free-to-grow condition.

Stand Dynamics

The study of change in forest stand structure and composition over time, especially related to stand behavior after disturbance.

Successional Pathway

The temporal pattern of vegetation change. A successional pathway can show the change in species composition over time with management, or by natural succession, and is closely related to growth stage and a chosen silvicultural system. We recognize four successional pathways options:

  1. Regenerate (or re-initiate): very large scale canopy disturbance that result in harvesting most of the trees and moving mature forests to a younger growth stage, often with less than 10 percent overstory cover.
  2. Transition: partial to large scale disturbance that result in "transitioning" young forests to mature forest growth stage, often with greater than 30 percent overstory cover.
  3. Accelerate:management action moving a stand into a later growth stage by promoting tree species that are more common in a mature forest.
  4. Maintain:small scale or no disturbance that result in "maintaining" mature or old forests, often with greater than 50 percent overstory cover.
  5. Defer:management and schedule a future treatment or assessment.
Synecological scores

The numerical value of a plant's habitat suitability across moisture, nutrient, heat, and light gradients. Synecology is the study of whole plant communities.

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