Decline of Red Spruce in the of Author(s): Thomas G. Siccama, Margaret Bliss and H. W. Vogelmann Source: Bulletin of the Torrey Botanical Club , Apr. - Jun., 1982, Vol. 109, No. 2 (Apr. - Jun., 1982), pp. 162-168 Published by: Torrey Botanical Society Stable URL: https://www.jstor.org/stable/2996256

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This content downloaded from 128.228.0.65 on Fri, 09 Apr 2021 01:23:36 UTC All use subject to https://about.jstor.org/terms B U L L E T I N O F T H E T O R R E Y B O T A N I C A L C L U B VOL. 109, No. 2, pp. 162-168 APRIL-JUNE, 1982

Decline of Red Spruce in the Green Mountains of Vermont

Thomas G. Siccama

Yale School of Forestry and Environmental Studies, New Haven, CT 06511

Margaret Bliss and H. W. Vogelmann

Department of Botany, University of Vermont, Burlington, VT 05405 SICCAMA, T. G. (Yale School For. Env. Stud., New Haven, CT 06511), M. Bliss and H. W. Vogelmann (Dept. Bot. Univ. Vermont, Burlington, VT 05405). Decline of red spruce in the Green Mountains of Vermont. Bull. Torrey Bot. Club 109: 162-168. 1982.-Red spruce (Picea rubens Sarg.), a potentially long lived (>300 yrs) shade tolerant major forest species of the re- gion, declined by about half in basal area and density in virgin mid to high elevation stands in the Green Mountains of Vermont between 1964 and 1979. The decrease is not logically related to forest successional development and no specific causes have been documented. Diminished growth rates and general low tree vigor in 1981 indicate that the decline is continuing. Keywords: Picea rubens; Vermont; population dynamics; dieback; montane boreal forest

Red spruce (Picea rubens Sarg.), a long- instability (Siccama 1974). Above 880 m lived (>300 years) shade-tolerant species, and extending to the alpine vegetation at Hart (1959), is a major component of forests 1230 m on the peaks, the boreal forest is of mid-upper slopes of the Green, White dominated by balsam fir and red spruce. and Adirondack Mountains (Siccama 1974; Red spruce is most abundant in the upper Bormann et al. 1970). During the past two transitional forest and lower boreal forest. decades the increasing rate of mortality of individuals of all size classes and lack of Methods. The forest on the west slope reproduction of red spruce has been ob- of Camels Hump (Huntington, VT) was served by us throughout the forests of cen- the primary study area with additional data from less intensive studies of the west tral and northern New England. In this slope of Mt. Abraham (22 km south of paper we report on quantitative changes of red spruce populations over a 15 year pe- Camels Hump), Bolton Mountain (14 km north of Camels Hump) and Jay Peak (70 riod (1964-1979) in the Green Mountains of Vermont. km north of Camels Hump). All these sites Forest vegetation on slopes of the are on the west side of the north-south trending axis of the Green Mountains that Green Mountains occurs in 3 fairly distinct elevational zones. Below 760 m sugar stretch from through Vermont to Massachusetts. maple (Acer saccharum Marsh.), beech (Fagus grandifolia Ehrh.) and yellow birch A study of the forests on Camels Hump, Jay Peak, Bolton Mt. and Mt. Ab- (Betula alleghaniensis Britt.) are dominant with red spruce as a minor, but common raham in 1964 was followed by an inten- associate. Between 760 and 880 m the forest sive study on Camels Hump in 1965 (Sic- is transitional to the higher boreal forest. cama 1974). The Camels Hump forests were restudied in 1979 as were forests above Sugar maple, beech, yellow birch, fir (Abies balsamea (L.) Mill.), red spruce and 760 m on the other 3 mountains. white birch (Betula papyrifera Marsh.) The specific location of the original dominate in a mosaic of age classes and stands studied on Camels Hump was well compositional patterns reflecting climatic established and the plots laid out in 1979 were within the same hectare area as were those in 1965. Although permanent plots Received for publication July 23, 1981. were not used, our thorough knowledge of

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0040-9618/82/02-0162-07$01.05/0 ? 1982 Torrey Botanical Club

This content downloaded from 128.228.0.65 on Fri, 09 Apr 2021 01:23:36 UTC All use subject to https://about.jstor.org/terms 1982] SICCAMA ET AL.: DECLINE OF RED SPRUCE 163 the location of the stands from previous in- in annual radial growth of large, living red tensive studies permitted the location of spruces on Camels Hump were studied by the 1979 plots such that they were super- comparison of tree cores obtained in 1964, imposed on the same area of forest studied 1971, and 1980 from the boreal zone on previously and most certainly overlapped Camels Hump. the areas measured in 1965. Sampling of forests on the slopes of the other moun- Results and discussion. Since 1964, all tains in 1979 was made along a transect in size classes of red spruce have declined in the general area of the forest stands sampled density in higher elevations zones (transi- in 1964 and thus does not represent such a tion 760-880 m and boreal >880 m) of all close resampling of the same stands as was mountains studied (Table 1). In the hard- the case on Camels Hump. wood forest on Camels Hump (550-760 m) Tree stems >2 cm dbh were tallied by spruce declined by 68 percent in the species on 3.0 X 30.5 m (10 X 100 ft.) plots. smaller size classes (2-9 cm). Although the Dead and living stems were recorded sep- number of stems >10 cm did not decline arately in 1979, but dead stems were not (remained constant), basal area of this size counted in 1964 and 1965. Stems <2 cm class declined 42 percent indicating that dbh were recorded on 6 1 X 1 m plots laid mortality of larger individuals in this size out within each larger plot. Smaller size class occurred. It should be noted that red stems (<2 cm) were studied in 1979 only on spruce makes up a very small proportion Camels Hump. A total of 85 large plots of total stems in the hardwood zone, thus and 510 m2 plots were used on Camels our sampling intensity for trees >2 cm Hump for each sample year; 115 plots were only weakly measured the changes in this examined on the other mountains. Changes species in this zone. The reduction of 81

Table 1. Comparison of density and basal area of red spruce (Picea rubens Sarg.) in forests of the Green Mountains of Vermont in 1965 and 1979.

DENSITY (Stems ha-') BASAL AREA (mi2 ha1') Size Class 1965' 1979 % Change Dead2 1965 1979 % Change Dead

(cm) Boreal Forest (>880 m) Camels Hump <2 4211 2866 -32 - - - - - 2-9 206 151 -27 39 0.52 0.30 -42 0.09 >10 125 60 -52 73 6.32 3.51 -44 7.00

Other mountains (pooled data)3 2-9 256 73 -71 73 0.48 0.15 -69 0.17 >10 145 76 -48 66 3.17 3.22 +2 1.98

Transition Forest (760-880 m) Camels Hump <2 8748 4333 -50 - - - - - 2-9 495 145 -70 102 0.89 0.14 -84 0.18 >10 91 54 -41 65 5.73 3.42 -40 8.55

Other mountains (pooled data) 2-9 352 45 -87 54 0.79 0.08 -90 0.11 >10 124 9 -93 9 2.03 0.26 -87 0.10 Northern Hardwood Forest (550-760 m)4 Camels Hump <2 216 42 -81 - - - - - 2-9 16 5 -68 0 0.02 0.004 -80 0 >10 13 13 0 8 1.49 0.86 -42 0.56

'Camels Hump studied in 1965, other mountains in 1964. 2 Dead stems measured in 1979 only. 3Jay Peak, Bolton Mt., and Mt. Abraham. Stems <2 cm dbh were not tallied. 4Stands below 760 m were not resampled on other mountains in 1979.

This content downloaded from 128.228.0.65 on Fri, 09 Apr 2021 01:23:36 UTC All use subject to https://about.jstor.org/terms 164 BULLETIN OF THE TORREY BOTANICAL CLUB [VOL. 109 percent in stems <2 cm and 68 percent in trees (>2 cm dbh) declined from 45 to 25 stems 2-9 cm as well as the fact that while per ha. No spruce seedlings were found in only 13 stems per hectare (>10 cm) of this either sampling period. species occurred, 8 dead stems occurred or In addition to the decline in numbers 38 percent of larger spruce stems are dead and basal area of red spruce, the species in the hardwood zone. also shows a decline in the radial growth The boreal forest on the west slope of of surviving individuals in the lower bo- Camels Hump has never been cut over. In real zone of Camels Hump. By fortuitous 1964, numerous red spruces 200-300 years happenstance sets of tree cores taken from old existed in the boreal forest on Camels 10 to 20 of the larger living spruces in the Hump. In this zone, density of red spruce elevation range of 915-1036 m were ob- >10 cm dbh declined 52 percent and basal tained in 1964, 1971 and 1980. In this anal- area declined 44 percent between 1965 and ysis it is assumed that in each sampling 1979. Density and basal area of standing period, due to death of many of the trees, dead spruce in 1979 exceeded that of living trees were cored which would have been stems. passed over during the previous sampling Although this study documents decline in favor of the other still living individuals. of red spruce in the Green Mountains, the In Table 2 our interpretation of the re- phenomenon is of much wider occurrence. sults are that those spruces surviving the Air reconnaissance observations of the Adi- longest were those previously growing the rondack Mountains (July 1980) as well as most rapidly. Spruces surviving until 1980 on-ground inspection of these mature for- were growing much faster in 1964 than ests indicate that spruce mortality is occur- other spruces sampled in 1964 which have ring on about the same scale as in the since died. Such an interpretation is reason- Green Mountains. Numerous dead spruce able and consistent with anticipated pat- were seen throughout the area occupied by terns of tree mortality in a stressed condi- old-growth forests and a general yellowing tion in which the faster growing individuals of foliage and mortality of younger spruce are the most vigorous and will survive the was evident. longest. Radial growth rates of trees sur- Similar independent observations on viving until 1980 had declined to the same the apparent decline of spruce in the Adi- levels as rates measured in the population rondacks are reported by Raynal et al. sampled in 1964. The continued decline in (1980). growth implies a continuing overall de- Decline of spruce in the White Moun- crease in the vigor of spruce. tains of New Hampshire at the Hubbard It is not our purpose in this paper to Brook Experimental Forest has also been discuss the overall plant community dy- measured. At Hubbard Brook, in a com- namics of the forests under study. However parative study similar to the Vermont it is appropriate to put the role of spruce study, a forest sampled in 1965 was remeas- in perspective with respect to the rest of the ured in 1977 (unpublished data). Spruce forest community, especially in the transi- saplings declined from 117 in 1965 to 33 tion and boreal zones of Camels Hump- stems/ha in 1977 and numbers of larger our primary study area. Basal area and

Table 2. Average annual radial growth increment (mm yr-' ? S.E.) of red spruce in the boreal forest of Camels Hump based on increment cores obtained in 1964, 1971 and 1980.

Years cores obtained 5-year period 1980 1971 1964 ending N= (11) (21) (15)

1979 0.63 ? 0.07 1971 0.92 ? 0.07 0.72 ? 0.05 1964 1.33 ? 0.10 0.90 ? 0.05 0.64 ? 0.02

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Table 3. Basal area and density of the major tree species above 760 m (transition and boreal zones pooled) on Camels Hump, VT for stems >2 cm dbh).

Year Year 1965 1979 net dead

A. Basal area (m2 ha-') species Red spruce 6.7 3.7 -3.0 (7.8) Balsam fir 11.9 11.6 -0.3 (8.5) White birch 4.6 5.2 0.6 (0.4) Other 6.4 6.0 -0.4 (1.1) total 29.6 26.5 -3.1 (17.8) B. Density (stems ha-') species 1965 1979 net dead Red spruce 445 206 -239 (136) Balsam fir 1527 1564 37 (500) White birch 304 241 -63 (24) Other* 1144 489 -655 (180) total 3420 2500 -920 (840)

* Note: The major change in the "other" category is due to a sampling problem of determining dbh of stems in shrubby clumps of mt. maple and striped maple in which many stems were not vertical.

density for stems >2 cm dbh for the pooled base. A whole network of railroads and data of the stands above 760 m (transi- mills in the White Mountains was estab- tion and boreal) are summarized in Table lished for the harvesting of red spruce 3. Spruce is a relatively small proportion timber from the late 1800's to the 1920's. A of the total population (10-20%) with fir mill for the production of spruce wood being the leading species and white birch products, especially butter boxes, existed in of about the same abundance as spruce. the valley adjacent to our study area on With our sampling intensity on Camels Camels Hump. Based on an analysis of the Hump the net decline in basal area of 10%, original land survey records for lands although not statistically significant, may above 700 m in the vicinity of Camels reflect a net degradation of this virgin Hump, approximately 50% of the witness forest ecosystem. Balsam fir, the dominant trees (in the virgin forest-1763-1790) were species has not vigorously responded to the recorded as spruce (Siccama 1971). The de- spruce decline to take up the "growing cline of this long lived shade tolerant co- space" released by the death of spruce. Fir nifer over a major part of its regional in general "appears" to be vigorously range (slopes of the New England moun- growing in that individuals do not show tains) is not the anticipated pattern based the symptoms of stress and necrosis shown on its known ecological strategies and pre- by the co-occurring spruce. However, fir sumed former abundance. growth as measured by the ring width Most of the larger red spruce in current sampling scheme discussed for spruce, second growth forests of the lower and mid shows a decrease similar to that of spruce. slope areas are survivors of the original Relatively large numbers of dead fir are (virgin) forest which were too small to cut present. White birch has very low mortality. 100 years ago at the time of the first log- The broad scale decline of red spruce is ging at these elevations. The largest trees especially significant in terms of its present at both Hubbard Brook and Camels Hump, population trends relative to its presumed (lower slope hardwood zone) show release importance in the presettlement virgin patterns in their annual growth in response forests of the region. Historically the vir- to the early logging of their competitors. gin forests of the lower and mid slopes of The cause of the decline of red spruce is the mountains of New England had suffi- not known. A variety of conflicting hypo- cient red spruce to support a major forestry theses and observations tend to confuse in-

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sights as to possible cause and effect rela- species distribution along the altitudinal tionships. Current ideas on causes include complex gradient, since red spruce reaches 1) climatic change, 2) air pollution-acid its climatic range limit on the upper rain, heavy metals especially lead, gaseous slopes. Precipitation increases with eleva- pollutants, etc.-direct and indirect effects tion and temperature decreases so that of these and 3) insects and diseases and changes in these parameters should favor combinations of these factors as primary the growth at some elevation and reduce and secondary causes. The center of our growth at others. Since the decline occurs discussion should focus on the transition throughout the elevational gradient and and boreal zones on the Green Mountains, across all age and size classes a climatic but is also inclusive of these same zones in change hypothesis is not a strong one in the Adirondacks and White Mountains and explaining the decline. the lower slope hardwood zone in which Two other aspects of soil moisture are spruce is (or was) the major conifer. worth mentioning. First is that an exten- The characteristic pattern of death of sive sampling of the forest floor moisture red spruce is a general browning and loss on Camels Hump in the summers of 1965, of needles from the crown apex downward 1966 and 1967 (Siccama 1974) showed that and from the terminals of lateral branches ambient soil moisture stayed above the field inwards over several to many years. This capacity of the humus material of the forest pattern seems to hold for large old trees floor and the upper mineral soil horizons, 30 m tall as well as saplings 2 m tall in the thus further substantiating that soil mois- shrub stratum. These symptoms are typical ture is not limiting during the summer. of death due to drought stress and the lack Secondly, in a study of the relationship of vigor and mortality of red spruce on Mt. of tree rings with precipitation and stream Monadnock in New Hampshire was at- water runoff (an index of soil moisture) at tributed to drought stress based on similar Hubbard Brook (unpublished data), spruce symptoms (Baldwin 1977). However Kin- as well as all the other major species over a caid and Lyons (1981) measured moisture variety of sub-sites in the same altitudinal stress on spruce twigs on Mt. Monadnock range as Camels Hump (hardwood and to test Baldwins's hypothesis and found transition zones) were negatively correlated no indication of water stress in winter with June runoff and August precipita- conditions, the hypothesized time of year tion. This implies that the growth of most when "winter kill" of alpine plants occurs species on these rocky acidic till soils is due to dessication of leaves when water is better in dry years than wet years. A late not available from the roots due to sup- spring, as evidenced by the effects of June posed frozen soil. The lack of success of red runoff, slows the start of growth and wet spruce on the essentially bare rock summit Augusts seem to truncate late summer of Mt. Monadnock is significant of spruce growth. Spruce was the species most pre- decline in the region but not comparable dictively responsive to these variables thus in equal terms to the slope forests of the indicating that in these soils, dry condi- Green Mountains where the trees are rooted tions favor growth rather than retard it. in adequately deep glacial till soils or in a The symptoms of drought stress in spruce deep forest floor humus layer over mineral may not be related to the amount of water soil, bare rock ledges (not that commonly), available in the soil, but rather to the trees or paleofelsenmeer (thick forest floor mat ability to take up that water. over a mass of loose boulders). The affect of air pollution, especially It is not reasonable to invoke a climatic acid rain, is currently in vogue as a cause change as the cause of spruce decline on of spruce decline. Two possible modes of the mountain slopes. Climatic change in impact of increasing concentration of H+ the form of cooling, warming, wetter, drier in the precipitation are the potential effect or some combination of these should logi- on needles by leaching and/or other physi- cally cause a shift in the relative growth cal or chemical disturbances of needle rate of the species at some locus on the tissues and the potential effects on the

This content downloaded from 128.228.0.65 on Fri, 09 Apr 2021 01:23:36 UTC All use subject to https://about.jstor.org/terms 1982] SICCAMA ET AL.: DECLINE OF RED SPRUCE 167 chemistry of mineral soil or forest floor spruce stand at Hubbard Brook. The iden- humus, in which much spruce is rooted at tification and ecology of these insects mid and high elevations. awaits further study. Raynal et al. 1980 and Hanson (1980) During the autumn of 1981 we visited have shown strong evidence of measurable and inspected spruce in a number of stands leaching losses of plant nutrient cations in the Green Mountain National Forest in from the forest floor due to acid rain. Han- southern Vermont. The spruce roots and son found exceptionally low pH of forest root crowns in these stands were heavily floor humus in the subalpine fir forests of infected by the shoestring fungus (Armilla- Vermont (both north and south of Camels ria mellea Vahl). Quel. (per. comm. Dr. Hump) and has shown that acid rain is Philip Wargo, NEFES). leaching Mn, Ca, Mg, K, and Zn. Although In these stands, the pattern of crown this may be occurring at the higher eleva- mortality was not typical of that occurring tions in very acid humus, it is not reasona- in our major study areas or observed in the ble that a similar process is going on Adirondack and White Mountains. The where spruce, rooted in "rich" mineral crowns of trees infected with the fungus soil, is also dying at lower elevations. tended to be dying from the bottom up Heavy metals, especially lead, are ac- rather than the top down. We have not had cumulating in the forest floor throughout an opportunity to look at the degree to the northeast (Johnson et al. 1981-in which the root crowns of trees in our major press; Hanson 1980, Reiners et al. 1975). study may be infected by the Armillaria. While at higher elevations, where spruce The general pattern of death, symp- roots are predominantly in the forest floor, toms of water stress, may be due not to lack the metal accumulation may be affecting of soil moisture, but to some sort of root them, certainly the same mechanism is not damage. We have pulled up numerous operating where the dying spruce are specimens of red spruce, fir, and white rooted in relatively high pH nutrient rich birch where these species co-occur and the mineral soils at lower elevations. roots of the red spruce look "unhealthy" in The acidity of the cloud moisture, comparison to the apparently more vigor- which is a major source of precipitation ous roots of the fir and white birch. above 800 m via the mechanism of "fog Acknowledgments. This is contribution 482 from drip" (Vogelmann et al. 1968), is about 0.5 the Vermont Agricultural Experiment Station sup- to 1.0 pH unit lower than the rain (Tom- ported by Hatch 319 and grants from the Northeast linson et al. 1980). At the higher elevations Forest Experiment Station and American Electric where "fog drip" occurs this higher acidity Power Service Corporation. We especially thank Anne may be a factor in its effects on the needles. Winchester for her indispensible help in collecting field data. This mechanism is not operating at lower elevations. Literature Cited

The effects of insects and diseases on BALDWIN, H. I. 1977. The induced timberline of the decline of spruce has not been deter- Mount Monadnock, N.H. Bull. Torrey Bot. mined. Spruce budworm, a major pest of Club 104: 324-333. BORMANN, F. H., T. G. SICCAMA, G. E. LIKENS and fir and spruce in Maine, is not evident in R. H. WHITTAKER. 1970. The Hubbard Brook the study areas on the Green Mountains. Ecosystem Study: Composition and dynamics However, during the late summer of 1981, of the tree stratum. Ecol. Monogr. 40: 373-388. while collecting samples of the forest floor HANSON, D. W. 1980. Acidic precipitation-induced chemical changes in subalpine fir forest or- humus on Camels Hump in the boreal ganic soil layers. Master of Science Thesis, zone, we found several specimens of what The Graduate School, Univ. of Maine at have been determined to be Lepidopteran Orono. larvae (2-3 cm long) in the humus with fir HART, A. C. 1959. Silvical characteristics of red and spruce roots. We later found more of spruce (Picea rubens). U.S.D.A. Forest Service. Northeastern Forest Expt. Station Paper No. these at a lower elevation on Camels 124. Hump and also found one directly in the JOHNSON, A. H., T. G. SICCAMA and A. J. FRIEDLAND. root crown of a young red spruce in a pure 1981. The Forest Floor in the Northeast United

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States: An Important Sink for Lead. Jour. vegetation in northern Vermont with special Env. Qual. In press. reference to Chittenden County. Amer. Midl. KINCAID, D. T. and E. E. LYONS. 1981. Winter water Nat. 85: 153-172. relations of red spruce on Mount Monadnock, . 1974. Vegetation, soil, and climate on New Hampshire. Ecology 62: 1155-1162. the Green Mountains of Vermont. Ecol. Mo- RAYNAL, D. J., A. L. LEAF, P. D. MANION and C. J. nogr. 44: 325-349. K. WANG. 1980. Actual and potential effects of TOMLINSON, G. H., R. J. P. BROUZES, R. A. N. acid precipitation on a forest ecosystem in the McLEAN and J. KADLECEK. 1980. The role of Adirondack Mountains. New York State En- cloud water in atmospheric transport. In: Eco- ergy Research and Development Authority. logical impact of acid precipitation. Proceed- ERDA 80-28. Forestry Dept., Syracuse Univ., ings of an international conference, Sandef- Syracuse, New York. jord, Norway. March 11-14, 1980. REINERS, W. A., R. H. MARKS and P. M. VITOUSEK. VOGELMANN, H. W., T. G. SICCAMA, D. LEEDY and 1975. Heavy metals in subalpine and alpine D. OVITT. 1968. Precipitation from fog mois- soils of New Hampshire. Oikos 26: 264-275. ture in the Green Mountains of Vermont. SICCAMA, T. G. 1971. Presettlement and present forest Ecology 49: 1205-1207.

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