Community and population dynamics of spruce-fir forests on Whiteface Mountain, New York: recent trends, 1985-2000

We remeasured two sets of permanent plots in old-growth, spruce–fir forests on Whiteface Mountain to quantify ongoing vegetation dynamics at sites impacted by spruce decline. One set of plots was a stratified random sample of the vegetation in a subalpine watershed (Baldwin site). The other was selected to represent forest conditions in a high-elevation subset of the spruce–fir forest (Esther site). Between 1987 and 1997, there was a significant increase in aboveground tree biomass at Baldwin with the majority of the increment due to the growth of canopy-sized trees. This growth occurred with little change in either species composition or size structure. The annual mortality rate of 1.2%·year–1 for canopy-sized red spruce (Picea rubens Sarg.) in Baldwin almost matched the recruitment rate of 1.4 stems/ha per year. In addition, the relative growth rate of spruce was significantly faster than associated species. In contrast, spruce trees in Esther died at a rate of the 3.6%·year–1 (1985–1995), and survivors grew more slowly than other species. The most obvious communitylevel trend at Esther (1985–2000) was an increase in overall tree density with most of this increase due to ingrowth of small trees. The demography of the spruce population at Baldwin suggests that the decline is over for at least this population. Comments Copyright NRC Research Press. Published in Canadian Journal of Forest Research, Volume 33, Number 1, January 2003, pages 54-63. Publisher URL: http://pubs.nrc-cnrc.gc.ca This journal article is available at ScholarlyCommons: http://repository.upenn.edu/ees_papers/11 Community and population dynamics of spruce–fir forests on Whiteface Mountain, New York: recent trends, 1985–2000 John J. Battles, Timothy J. Fahey, Thomas G. Siccama, and Arthur H. Johnson Abstract: We remeasured two sets of permanent plots in old-growth, spruce–fir forests on Whiteface Mountain to We remeasured two sets of permanent plots in old-growth, spruce–fir forests on Whiteface Mountain to quantify ongoing vegetation dynamics at sites impacted by spruce decline. One set of plots was a stratified random sample of the vegetation in a subalpine watershed (Baldwin site). The other was selected to represent forest conditions in a high-elevation subset of the spruce–fir forest (Esther site). Between 1987 and 1997, there was a significant increase in aboveground tree biomass at Baldwin with the majority of the increment due to the growth of canopy-sized trees. This growth occurred with little change in either species composition or size structure. The annual mortality rate of 1.2%·year–1 for canopy-sized red spruce (Picea rubens Sarg.) in Baldwin almost matched the recruitment rate of 1.4 stems/ha per year. In addition, the relative growth rate of spruce was significantly faster than associated species. In contrast, spruce trees in Esther died at a rate of the 3.6%·year–1 (1985–1995), and survivors grew more slowly than other species. The most obvious community-level trend at Esther (1985–2000) was an increase in overall tree density with most of this increase due to ingrowth of small trees. The demography of the spruce population at Baldwin suggests that the decline is over for at least this population. Résumé : Nous avons remesuré deux groupes de parcelles permanentes dans de vieilles forêts de sapin et épinette du mont Whiteface pour quantifier la dynamique actuelle de la végétation dans des stations affectées par le dépérissement de l’épinette. Un premier groupe de parcelles constituait un échantillonnage aléatoire stratifié de la végétation dans un bassin versant subalpin (la station Baldwin). L’autre groupe de parcelles avait été choisi de manière à représenter les conditions de la forêt dans un sous-ensemble à haute altitude de la forêt de sapin et épinette (la station Esther). Entre 1987 et 1997, il y a eu une augmentation significative de la biomasse épigée des arbres dans la station Baldwin où la majeure partie de l’accroissement est due à la croissance des arbres formant le couvert. Cette croissance s’est produite avec peu de changements dans la composition en espèces, ni dans la structure dimensionnelle. Le taux annuel de mortalité de 1,2 %·an–1 pour l’épinette rouge (Picea rubens Sarg.) présente dans le couvert de la station Baldwin correspond à peu de chose près au taux de recrutement de 1,4 tiges/ha par an. De plus, le taux relatif de croissance de l’épinette est significativement plus élevé que celui des autres essences auxquelles cette essence est associée. Par contre, le taux de mortalité des épinettes de la station Esther est de 3,6 %·an–1 (1985–1995) et les tiges qui ont survécu ont crû plus lentement que les autres espèces. La tendance la plus évidente observée à l’échelle de la communauté dans la station Esther (1985–2000) est une augmentation générale de la densité des arbres où la majeure partie de l’augmentation est due au recrutement de petits arbres. La démographie de la population d’épinette à la station Baldwin porte à croire que le dépérissement est terminé, au moins dans cette population. [Traduit par la Rédaction] Battles et al. 63