Nitrogen deposition, distribution and cycling in a subalpine spruce-fir forest in the Adirondacks, New York, USA

High-elevation red spruce (Picea rubens Sarg.) -Fraser fir (Abies fraseri (Pursh) Poir.) forests of the southern Appalachians exhibit considerable spatial heterogeneity in structure, and possibly in N uptake, because of a combination of natural disturbances and heavy fir mortality caused by infestations of the exotic balsam woolly adelgid (Adelges piceae Ratz). The objectives of this study are to determine spatial variability in tree N uptake in a small highelevation catchment in the Great Smoky Mountains National Park, compare outcomes among calculation methods, and assess the influence of stand and landscape properties on N uptake. Tree N uptake is estimated for fifty 20 × 20 m plots in the Noland Divide Watershed (NDW). Components considered in the calculations are stem growth, foliage increment, and mortality of spruce, fir, and yellow birch (Betula alleghaniensis Britt.) from 1993 and 1998 stand inventories; throughfall N flux measured in summers 1998 and 1999; litterfall N return for 1 year in a subset of 12 plots; tissue N analyses; and atmospheric N deposition and root turnover estimates from the literature. Overstory N uptake varies spatially within NDW, with a CV of 9-41% depending on the calculation method. Variability among methods is even higher, with an almost 15-fold difference between the smallest and largest average overstory uptake estimate (5 vs. 74 kg·ha -1 ·year -1 ). Only 5 and 3 kg·ha -1 ·year -1 of N is sequestered in wood and foliar increment, respectively, while 36 kg·ha -1 of N returns annually as aboveground litterfall. Uptake and its components are correlated with measures of stand structure but not with elevation or aspect.Résumé : Des forêts de haute altitude d'épinette rouge (Picea rubens Sarg.) et de sapin Fraser (Abies fraseri (Pursh) Poir.) du Sud des Appalaches montrent une hétérogénéité spatiale considérable dans leur structure et probablement dans leur prélèvement en azote du fait d'une combinaison de perturbations naturelles et d'une mortalité importante du sapin causée par des infestations du puceron lanigère du sapin (Adelges piceae Ratz.). Les objectifs de cette étude consistaient à déterminer la variabilité spatiale du prélèvement en azote des arbres dans un petit bassin de haute altitude localisé dans le parc national des Great Smoky Mountains, comparer les résultats entre les méthodes d'estimation et évaluer l'influence des propriétés du peuplement et du paysage sur le prélèvement en azote. Le prélèvement en azote des arbres a été estimé pour 50 placettes de 20 × 20 m dans le bassin du Noland Divide (BND). Les éléments considé-rés dans les calculs sont : la croissance de la tige, la croissance foliaire et la mortalité de l'épinette, du sapin et du bouleau jaune (Betula alleghaniensis Britt.) à partir des inventaires de peuplement de 1993 et 1998; le flux d'azote dans le pluviolessivage mesuré pendant les étés 1998 et 1999; le retour en azote par la litière pour une année dans un sous-ensemble de 12 placettes; les analyses d'azote dans les tissus; les dépôts ...

Section: Comparison Of Calculation Methodssupporting

confidence: 83%

Variation in overstory nitrogen uptake in a small, high-elevation southern Appalachian spruce-fir watershed

Barker¹,

Miegroet²,

Nicholas³

et al. 2002

“…Nitrogen deposited from the atmosphere between 1986 and 1995 exceeded N accumulated in biomass by sixfold, and midelevation forests on Whiteface Mountain monitored since 1986 leak mineral N at rates up to 6.2 kg·ha -1 ·year -1 (Friedland and Miller 1999). Estimates of N mineralization in Whiteface Mountain forests range from 40 to >100 kg·ha -1 ·year -1 (Sasser and Binkley 1989;Friedland et al 1991). Accordingly, we did not expect mineral N availability to limit ANPP.…”

Section: Site Descriptionmentioning

confidence: 84%

“…Atmospheric N deposition at Whiteface Mountain varies with elevation, ranging from 15 to 30 kg·ha -1 ·year -1 , depending largely on rainfall and cloudwater interception rates (Friedland et al 1991;Lovett 1992;Miller et al 1993). Nitrogen deposited from the atmosphere between 1986 and 1995 exceeded N accumulated in biomass by sixfold, and midelevation forests on Whiteface Mountain monitored since 1986 leak mineral N at rates up to 6.2 kg·ha -1 ·year -1 (Friedland and Miller 1999).…”

Section: Site Descriptionmentioning

confidence: 99%

Nitrogen availability and forest productivity along a climosequence on Whiteface Mountain, New York

Joshi¹,

Vann²,

Johnson³

et al. 2003

We studied broadleaf and needle-leaf forests along an elevation gradient (600-1200 m) at Whiteface Mountain, New York, to determine relationships among temperature, mineral N availability, and aboveground net primary productivity (ANPP) and controls on the latter two variables. We measured net N mineralization during the growing season, annual litterfall quantity and quality, aboveground woody biomass accumulation, and soil organic matter quality. Inorganic N deposition from cloudwater markedly increases mineral N availability above 1000 m in this region. Consequently, mineral N availability across the climosequence remains relatively constant because N mineralization decreases with increasing elevation. Across this climosequence, air temperature (as growing season degree-days) exerted the most control on ANPP. Nitrogen mineralization was most strongly related to soil growing season degree-days and less so to lignin to N ratios in litter. ANPP was correlated with N mineralization but not with mineral N availability. Combining our data with those from similar studies in other boreal and cool temperate forests shows that N mineralization and ANPP are correlated at local, regional, and interbiome scales. Regarding the persistent question concerning cause and effect in the N mineralization -forest productivity relationship, our data provide evidence that at least in this case, forest productivity is a control on N mineralization. We studied broadleaf and needle-leaf forests along an elevation gradient (600-1200 m) at Whiteface Mountain, New York, to determine relationships among temperature, mineral N availability, and aboveground net primary productivity (ANPP) and controls on the latter two variables. We measured net N mineralization during the growing season, annual litterfall quantity and quality, aboveground woody biomass accumulation, and soil organic matter quality. Inorganic N deposition from cloudwater markedly increases mineral N availability above 1000 m in this region. Consequently, mineral N availability across the climosequence remains relatively constant because N mineralization decreases with increasing elevation. Across this climosequence, air temperature (as growing season degree-days) exerted the most control on ANPP. Nitrogen mineralization was most strongly related to soil growing season degree-days and less so to lignin to N ratios in litter. ANPP was correlated with N mineralization but not with mineral N availability. Combining our data with those from similar studies in other boreal and cool temperate forests shows that N mineralization and ANPP are correlated at local, regional, and interbiome scales. Regarding the persistent question concerning cause and effect in the N mineralization -forest productivity relationship, our data provide evidence that at least in this case, forest productivity is a control on N mineralization. Résumé :Nous avons étudié des forêts de feuillus et de résineux le long d'un gradient altitudinal (600-1200 m) à Whiteface Mountain dans l'État de New York pou...

“…For canopy-sized trees (trees ≥9.5 cm DBH), we estimated parabolic volume as described above and then used volume as the independent variable to predict tree biomass from the allometric equations in Whittaker et al (1974) as updated by Siccama et al (1994b). This approach is the same as that applied by Friedland et al (1991) and Friedland and Miller (1999) for biogeochemical analyses at the Esther site. However, we used separate species-specific equations for trees smaller than 9.5 cm DBH to account for ontogenetic change in tree allometry.…”

Section: Discussionmentioning

confidence: 99%

Community and population dynamics of sprucefir forests on Whiteface Mountain, New York: recent trends, 19852000

Fahey¹,

Siccama²,

Johnson³

2003

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)(1986)(1987)(1988)(1989)(1990)(1991)(1992)(1993)(1994)(1995), and survivors grew more slowly than other species. The most obvious communitylevel trend at Esther (1985Esther ( -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. Abstract: 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)(1986)(1987)(1988)(1989)(1990)(1991)(1992)(1993)(1994)(1995), and survivors grew more slowly than other species. The most obvious community-level trend at Esther (1985Esther ( -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 prem...