0833-B3

Red Pine (Pinus resinosa Ait.) Ecology At Its North Eastern Limit In Newfoundland, Canada: A 25 Year Study Following Wildfire.

B.A. Roberts ¹, A. U. Mallik ² and K.W. Deering ³.

Abstract

Red pine, Pinus resinosa Ait., is the rarest coniferous tree (< 15,000 mature trees) in Newfoundland and is known from some 22+ locations occupying 3 major site types. The succession of red pine site types after cutting is from red pine to Kalmia - black spruce, Picea mariana (Mill) B.S.P., for RP1, to Cladonia- Kalmia - black spruce for types RP2 and RP3. Succession after fire is usually to the pre-fire type, but this depends on the severity of the fire. This study reports on a 25 year old wildfire in one of the largest natural stands. A high wildfire frequency (15-30 years) of both surface and crown fire regulates stand perimeters and is the main factor in regulating stand development. At the nucleus of current stands are a few grandparent trees greater than 200+ years old which have multiple fire scars (1904, 1946, 1979). Stem char heights confirmed the increased flammability and mortality for fires moving in the up slope position, as well as for mixed red pine - black spruce stands. Twenty five years after wildfire the understory is dominated by Ericaceous shrubs lichen patches and alder on slopes and under canopy conditions. Fire influences soil nutrient availability as pH increases in the RP1 type.

The pattern of regeneration is related to slope, density, age and species mixture of the stand as well as the thickness and composition of the duff layer. This study examines the role of Alders & Ericaceous shrubs in organic matter production and regeneration on dry forest soils.

INTRODUCTION

Natural Red Pine stands in Newfoundland are restricted to 22+ small, nutrient poor sites with an understory dominated by Kalmia angustifolia, other Ericaceous shrubs and Cladonia & Cladina Licnens. Red pine is found principally on coarse textured sands and gravels of glacial outwash or lake bottom material where it grows in excess of 18 metres in height in a 60 year rotation on the better sites, Roberts (1985), (1989), Roberts & Bajzak (1996). Figure 1. There are three major site types: 1. Red pine on medium-textured sands (RP1), 2. Red pine on coarse-textured glacio-fluvial deposits (RP2), 3. Red pine on Folisols over bedrock (RP3). The central Ecoregion, the largest forested ecoregion (Damman 1983), has had a long history of wildfire (Wilton & Evans 1974), harvesting (Roberts 1985, Roberts & Mallik 1994), ecological investigations, (Meades & Roberts 1992) and currently red pine is the rarest coniferous tree species in Newfoundland. In the continental part of its range (Horton & Bedell 1960) red pine is widely grown as an economic plantation species, (Hosie, 1969, Alban,1974, Beckwith et al. 1983, deNaurois & Buongiorno1986.

The succession of red pine site types after cutting is from red pine to Kalmia - black spruce, Picea mariana (Mill) B.S.P., for RP1, to Cladonia- Kalmia - black spruce for types (Damman1964, Roberts & Bajzak 1984) for RP2 and RP3. Succession to Larix laricina L. with an Ericaceous understory (Roberts & van Nostrand 1995) has also been observed in eastern and central Newfoundland. Succession after fire is usually to the pre-fire type, but this depends on the severity of the fire, (Roberts & Mallik 1994). Although occupying a relatively poor site red pine produces 3 times more volume in 60 years than black spruce, Roberts & Bajzak (1996) and there are severe alleopathic problems with this species Mallik (1987), Mallik & Roberts (1994), Mallik & Roberts (this volume).In natural red pine stands in Newfoundland merchantable volume of 140 - 280 m ha^-1 were recorded ie. CLI forest capability class 5 and class 4 ratings, (McCormack,1970), two capability classes higher than black spruce on the same site. Red pine root development (Fayle, 1975) is related to soil texture and the presence of hardpans (Roberts1983, Roberts & Mallik 1994). The best & poorest growing red pine are Nitrogen, (N) deficient and have foliar N concentrations below the 1.3% which is the critically low level (Madgwick 1964a, 1964b, Morrison,1974, Comerford,1981). Immediately after fire, foliar N reach this level and most other nutrients are low but are within the reported adequate levels for P,K,Ca and Mg, (Roberts & Mallik 1994, Roberts & Bajzak 1996).

Red pine has been of considerable ecological interest on the extremes of its range (Roberts 1985, Bergeron & Gagnon 1987, Butson et al. 1987, Flannigan & Bergeron 1998, Sutton et al 2002) and its related fire ecology actively researched.

This paper reviews aspects of Red Pine fire ecology and natural regeneration over a 20 year period from pre fire observations and measurements in 1978 and 1979, immediately after the July 04, 1979 wildfire, yearly for five years and extended work at 10, 15 and 20 year intervals at the North eastern limit of its range.

Materials & Methods

Detail methods of site selection including pre-fire & post fire plots established before the July 04, 1979 wildfire, the over & understory plots, stand age, fire scar analysis, stand age, leaf & soil analysis, cone & seed dynamics Roberts 1989, Mosseler et al 1992) have already been reported in Roberts & Mallik 1994 , Mallik & Roberts 1994 and follow Wells & Roberts 1973 , Mueller-Dombois, D. and E. Ellenberg 1974. Measurements were repeated each 5 years in 1984,1989.1994 & 1999. Additional measurements were also made in 1986 and 2000- 2002. Lichen & plant nomenclature follow Fernald 1950, Hale & Culberson 1966, Hoise 1969, Brassard 1983. Soils and foliar analysis follow, CSSC 1978, Roberts 1980 and Zakrevsky 1984.

Results

The fire scar results and the fire intensity and effects on stand perimeters are given in figure 1 and figure 2 and confirm early observations. Table 1 shows the effects of wildfire on ground lichen species and confirms the succession outlined by Ahiti (1959) for black spruce lichen forests after wildfire. The changes in soil pH are given in Table 2 and remain elevated 20 years after fire. The change in understory characteristics show a 25% increase in the cover of Alnus crispa which are changing the quality & quantity of litter and foliar N figure 3. The effects of black spruce (bS) on stem char heights, fire intensity and lethal crown fire is given in Table 3. The nature of seedling establishment around the grandparent tree centre is shown from 1986 and 1999 in Table 4. Table 4 also shows the increase in alder clumps (22) and the number of bS (51) within a 3m radius of the grandparent tree.

Discussion

Wildfire has been influencing the vegetation of central Newfoundland for centuries see figure 1. A high wildfire frequency (15-30 years) of both surface and crown fire regulates stand perimeters and is the main factor in regulating stand development. At the nucleus of current stands are a few grandparent trees greater than 200 years old which usually have multiple fire scars, figures 1& 2. The ground shrub vegetation is usually totally consumed by fire and within 5 years is about the same as before fire except for the lichens which are usually lost in any fire, however, patches missed can be related to the fire interval. Cladonia and Cladina lichens follow the succession outline by Ahiti (1959), Table 1. All fire plots within the red pine (rP) stand at Grants Pit have gone through the first 3 phases ie they are now in the " Horn Lichen Phase 3", with the exception of the sites dominated by Alnus crispa which has increased from scattered stems before fire to 25 % of the current understory from roadsides adjacent to the Grants Pit stand. Alder was observed to alter ground fire direction on the edge of the 1979 fire and will continue to be important in future wildfires as well as in nutrient cycling (Figure3). This change to the understory includes increase shade and the quantity & quality of litter. Table 2, shows the effect fire temperature effects the soil and soil humus properties especially soil pH and confirms earlier data (Mallik & Roberts (1994) on lasting effects.

Stem char heights confirmed the increased flammability and mortality for fires moving in the upslope position, (Table 3) as well as for mixed rP - bS stands and natural regeneration is directly related to the intensity and frequency of wildfire, Roberts & Mallik (1994). In absence of fire, accumulation of a thick duff & litter layer inhibits natural regeneration first acting as a physical barrier to the root system and also the duff is known to have adverse allelopathic effects on seedling growth (Roberts & Mallik this volume, (especially root growth) through chemical inhibition. A moderately hot fire may remove the inhibitory substances and expose the more hospitable Ae horizon which facilitate seedling growth. Understory vegetation is also influenced by fire with vegetative re-growth from fire survived buds and seedling regeneration from soil seed reserve depending on fire severity.

The survival of rP after fire also depends on the time of year, the topography, and % of bS in the stand which can intensify the impact of fire and cause lethal crown fires to develop from hot moving ground fires that normally stay close to the ground surface in pure rP stands (Table 3 and 4. In 1986 there were 100 red pine seedlings > 10cm in a 3m radius of the old grandparent tree this increased to 127 by 1999. At the same time however the number of bS went from no 10 cm seedlings in 1986 to 51 greater than 10 cm in 1999. By 1999 some 22 alder clumps had also established.

Red pine is known to produce numerous cones & viable seeds at both at its northeastern limit (Roberts 1989) and northwestern limit (Sutton et al 2002). Today, however there are problems with cone insects having spread from other conifers after a bumper cone crop in all species except red pine in 1988, (Mosseler et al 1992. Cone worms were not recorded in regular collections at the Grants Pit site from 1978-1987 and coincided with the 1 year lag bumper cone crop in red pine in 1989. The Grants Pit site (also the largest natural red pine stand) has had continuous fir cone worm attack for the past decade (Mosseler et al 1992) % and affecting up to 97 % of the cones in that period and reducing the number full seeds per cone by 93 percent.

In terms of Newfoundland red pine plantations and conservation activities, there are quite a number of young (<15yr) plantations on Crown limits and a comprehensive strategy for this species for the Province is currently being addressed by researchers from the Canadian Forest Service and Working Group Members from the Newfoundland Forest Service and other agencies.

Summary & Conclusions

1. Natural red pine stands and trees are in decline at the northeastern limit of its range with mesic substrate conditions a major reason why red pine is not regenerating at some stand locations.
2. The lack of high intensity ground fire and the presence of shade tolerant black spruce which leads to increase lethal crown fires causes a reduction in red pine stand size especially on irregular terrain.
3. The recent presence of the fir cone worm and the introduced red squirrel are likely to contribute to the lack of seed reaching safe sites near and adjacent to existing stands. Even with hot ground fire the best conditions for natural regeneration the lack of seed due to the fir cone worm and red squirrels will likely increase the percentage of black spruce and the likelihood of lethal crown fires to follow.

Caption Figure 1. Wildfires recorded by fire scars in each of the 3 geographic regions of Newfoundland (Figure 1) The * denotes the years that are matched with recorded wildfire published history of Wilton & Evans 1974.

I= 1891, 1916*,1947, 1950*, 1961, 1977

II= 1890*,1899,1904*, 1938*

III= 1904*, 1946*, 1979.

Table 1. The 5 phases of lichen succession after fire from the lichen woodland type (Ahti, 1959) in Newfoundland

Table 2. Changes in soil pH before wildfire, 3 months after, 2 years after, 10 years after & 20 years after wildfire at Grants Pit red pine PAI site, central Newfoundland.

Table 3. Effect of a spring (SL1 site) and summer (Grants pit site) wildfire on red pine stand structure.

Table 4. NATURE OF SEEDLING ESTABLISHMENT AROUND AN OLD GRANDPARENT RED PINE FOLLOWING CATASTROPHIC WILDFIRE AT GRANTS PIT IN 1979.

THE RE-GROWTH AND SPREAD OF ALNUS CLUMPS IS VERY IMPORTANT IN TERMS OF FOLIAR NUTRITION. THE HIGHEST FOLIAR NITROGEN VALUES WERE RECORDED IN RED PINE (TREE NO. 5, 1989) THAT HAVE A THICK UNDERSTORY OF ALNUS WHICH INCREASED DRAMATICALLY 10 YEARS AFTER THE 1979 WILDFIRE.

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¹ Canadian Forest Service, P.O. Box 960, Corner Brook, Newfoundland, Canada . A2H6J3. E-Mail: [email protected]
² Department of Biology, Lakehead University, Thunder Bay, Ontario,Canada, P7B 5E1. E-Mail [email protected]
³ Department of Forest Resources and Agrifoods, P. O. Box 159, Cartwright, Labrador, Canada. A0K 1V0. E- Mail [email protected]