GREATER FUNDY ECOSYSTEM RESEARCH PROJECT

UNB Faculty of Forestry and Environmental Management

Forest Management Guidelines to Protect
Native Biodiversity in the Fundy Model Forest

Landscape Level Considerations

Incorporating Maturity into Forest Harvest Schedules

The above estimates represent the beginning of what we would consider maturity. How do we define the closure of a maturity window? New Brunswick's Ecological Land Classification of the enduring features (climate, geology, soils) of the province allows forest managers to identify the optimal tree species for particular growing conditions. The enduring features also provide an index to the proportion of forest communities found in each Ecodistrict. Some speci

es and communities have been altered by human activity, notably agricultural areas. But, at a broad scale, and with extrapolation from other sites, we can use the existing abundance of forest communities to determine the composition and amount that should be retained in a working landscape. Estimates tend to be general, particularly in historical-to-present estimates of the agriculturally dominated non-forested community. Large areas of the region were cleared for agriculture and, to varying degrees, have reverted back to natural communities, mostly early-successional assemblages.

Hemlock stand, Fundy National Park (Photo: G. Forbes)

The forest strata are still being developed and therefore may vary from those on this list. Work is still underway to estimate the historical abundance of these strata because large areas of the case study ecodistricts presently support proportions of forest types that are atypical for the ecodistrict. For example, the amount of Jack Pine and intolerant hardwood-White Spruce in some areas reflect human-caused disturbances instead of natural processes. These areas (and also regenerating stands) need to be re-allocated into typical forest types to estimate the amount of mature forest types. The historical abundance (i.e. near time of European arrival) is to be based on the enduring features (climate, geology, soils) for that ecodistrict. Where elevation influences community type, the managed strata can be re-allocated to natural strata based on the corresponding elevation range of the stand. The mature provisions will be estimated once these re-allocations are complete.

At present, the table consists of the dominant natural community types for the ecodistrict in the case study area, and the unallocated plantation and thinned stands in young-overmature age class ("PLAN"), regenerating ("REGEN"), and various community types that are in small quantity ("Other"). We have combined some strata to limit the total number because of the difficulties of spatially defining a large number of community types. The communities to be maintained in some proportion of a mature state are:


CONIFER (= RS, BS, RSBF, BSRS, BSJP, and other combinations)
CEDAR (= EC)
PINE (= JP, WPRP, and other Pine-dominated combinations)
MIXED (= RMMIX, POSP, RSSM, and other mix combinations)
TOLERANT HARDWOOD (= SMYB, SMBE)
INTOLERANT HARDWOOD (= RM, and other combinations of PO, WB)

Letters in brackets refer to strata that have been developed for the wood supply and management models in the FMF.

Twelve percent of each forest community type (except regenerating and non-forest communities) should be maintained in mature-overmature age class. The 12% value is a minimum value. The value is derived from the fact that under a sustainable stand-replacing disturbance regime of 100 years, roughly 37% of the forest would be composed of stands greater than 100 yrs. old.

While it would be ideal to replicate this 37% for forest management purposes, it was recognized by us that this figure was unattainable given wood supply considerations and the importance of the forestry industry to New Brunswick's economy. Furthermore, the entire forest is not necessary for biodiversity conservation needs. Therefore, we recommend 12% (a third of the 37% value) as a safe level to conserve biodiversity. Again, this figure is based on a consensus judgement of professionals.

Overmature Forest - Overmature age classes also are important habitats, particularly for species requiring large amounts of old and rotting forest. Fungi, lichens, beetles and woodpeckers require this "extra-old" forest. A curve showing the distribution of age classes in a fire-dominated region would indicate that about 10-12% of an area would be in an overmature age class.

Similar to the reasoning for the mature age class, we recommend that 4% or one-third of the forest community be in an overmature state.

Size of mature-overmature patches - On an ecodistrict level, the mature-overmature component should always exceed the minimum patch size of 375-500 ha. Thus, the mature values were calculated on the basis of minimum patch size - or 12% of the historical forest type area.

A range of sizes were chosen to reflect the variability of patch size in fire-affected Pine communities. Simulations of fire patch size in the area by Methven and Kendrick (1995) suggested fire-origin patches were 778 ha on average and, at times, as large as 111,000 ha. Fires vary in size and typically create many small patches and several large ones. Around 30% of patches are less than 50 ha and about 30% are greater than 1000 ha. It is not practical today to promote huge mature patches of Pine forest even if they are a natural phenomena. We suggest that mature, Pine-dominated stands exist in a range where 50% are 400 ha (modal value in typical fire distributions) and the remainder at a minimum of 20 ha.

Incorporating provisions for mature-overmature habitat into forest harvest schedules is easier for short-lived species like Balsam Fir, which die-off in even-aged stands. Incorporating long-lived communities such as Red Spruce forests is more difficult. Tree core samples taken of Red Spruce in FNP have indicated the presence of 300 year-old trees in the coastal ravines. Red Spruce can be considered 'mature' at an age when large-diameter rotting trees provide cavity conditions. Additional field surveys are needed to identify the age at which large and rotting Red Spruce generally occur within the GFE. At present, we recommend that the mature class window for Red Spruce communities be from 80-300 years. Twelve percent should be maintained within this age group, of which 20% of the trees are over 150 years old. In mixed hardwood-softwood stands, the mature age class would begin with the species first reaching its typical maturity age. For example, a mixed stand containing Balsam Fir would be classified as mature after trees reach 60 years of age.

For forests harvested by selection cuts, the old age category must be defined by age as well as crown closure. We recommend that old age forest types in the 12% category have a minimum crown closure of 60% and that 20% of old age forests have a minimum crown closure of 80%. This higher number is especially important in tolerant hardwood forests.

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Information provided by:
Dr. Graham Forbes
Faculty of Forestry and Environmental Management at UNB
Last Update: Dec 17, 1997
This document: http://www.unb.ca/web/forestry/centers/cwru/mature.htm