What is Old Growth?

‘Workin on it (Dec 30, 2018 – )


The question of What is Old Growth was posed directly by SM On Stop Spraying & Clear-Cutting In Nova Scotia as follows:

Can someone please explain the process for selecting old growth forest? In layman’s terms. As owners of our land, we should be able to understand this process. If not, than maybe it needs to be looked at and changed.

So this is a good place to start.

Nova Scotia is one of the few places for which there is an operational definition of Old Growth forest, meaning that there are standard, measurable criteria, and if a stand meets those criteria, it is accepted by NSDNR/L&F as “Old Growth”. View Nova Scotia’s Old Forest Policy  (NSDNR, Aug 2012); also other documents listed on NSFN>Natural History>Conservation>NSDNR Old Forest Policy

It’s fairly technical process to do the appropriate measurements, described in a paper by Stewart et al. 2003, and it requires use of some specialized equipment, notably a wedge prism and an increment borer (used to determine age of a tree) and some experience/training in using them and in following the overall procedure.

So in response to the question above let’s look at some other approaches. I will often use forest in the area of Sandy Lake at Bedford, Nova Scotia for examples or illustrations, as I have investigated that area for presence of Old Growth; also some stands in the Five Bridge Lakes Wilderness Area on the Chebucto Peninsula.

– Use the interactive map tools to determine if,  a particular site is located in a stand which according to NS’s mapping (recognizing it is not all ground-truthed), is currently set-aside as Old Growth or to allowed to grow old enough to be Ol Growth
(i) Look at the Old Forest Layer in the Nova Scotia Provincial Landscape ViewerFrom the Help Page:
Once in the Viewer, Select the layer at Forestry>Forestry>Old Forest Policy.

The old forest layer maps the locations of stands that were selected under the Interim Old Forest Policy of 1999 (novascotia.ca/natr/library/forestry/reports/Old-Forest-Policy-2012.pdf). The forests identified in the layer consist of old growth stands, as well as mature stands set aside to restore old growth. According to the policy these stands will be maintained and left to mature naturally with no management intervention. Most of the forests in this layer are not old growth. The majority are mature climax stands that provide good opportunities for long-term old growth restoration. They were selected following the Procedures in the Interim Old Forest Policy. True old growth forests are uncommon, and make up only a small proportion of the stands in this layer. The location of all old growth in the Province is unknown, however DNR maintains a registry of old stands that have been evaluated using DNR’s Old Forest Scoring system (novascotia.ca/natr/forestry/programs/ecosystems/scoresht.asp). The 2008 report “Implementation of Nova Scotia Interim Old Forest Policy for Crown Land – A Status Report” provides a summary of the forest stands contained within the old forest layer. (novascotia.ca/natr/library/forestry/reports/state-of-forest-old-growth.pdf).

So if a site of interest lies in one of the red patches on this map, that means as I understand it, it is Crown land on which harvesting is not permitted because it is protected as Old Growth or future Old Growth.

View also maps at https://data.novascotia.ca/Lands-Forests-and-Wildlife/Old-Forest-2006/wanf-acts & http://nsforestnotes.ca/keeping-track/compiled-maps/

(ii) Look at the Development Class Layer in the Nova Scotia Provincial Landscape Viewer. From the Help Page:

This layer describes the structure of forests as they age and grow (e.g. forest establishment, young forest, mature forest).Four development classes describe the structure of forests as they age and grow. Assignments are based on stand height:

· Establishment (Height 0-6m): Influx of new growth following a stand initiating disturbance, and characterized by a high diversity of forbs, shrubs, and tree regeneration.
· Young Stem Exclusion (Height 7-11 m): Young developing tree canopies characterized by vigorous self thinning, crown differentiation, and competitive exclusion of many individuals.
· Mature (Height > 11 m): Stands dominated by upper canopy trees with full differentiation into dominance classes. Canopy gaps are soon closed by neighbouring tree growth.
· Multi-age and Old Growth (Age 999 and Old Forest Policy): Overstory exhibiting a variety of crown sizes and canopy densities. Canopy gaps are persistent promoting multi-layered understory development and recruitment to the overstory.

…More to be written on this page (admin, Jan 3, 2019); ‘may take a while

Also see: Compiled Maps

A disclaimer: as an Academic, albeit retired, I could be expected to approach such a question very rigorously with peer review etc. and I fully acknowledge that limitation to whatever I might write (the same goes for everything I write on NS Forest Notes). I write such materials because there is a dearth of information of this sort for NS in a form that most Nova Scotians can read and make use of and I am concerned about that because of the pressures on our forests, so I will make a stab at it. One hope is that it will prompt academics with much more formal knowledge of NS forests than I to become more involved in the public domain and write appropriate materials.

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