Local climate influences on precipitation, cloud water, and dry depositionto an Adirondack subalpine forest: Insights from observations 1986-1996

Few studies of total atmospheric deposition (dry deposition, cloud droplet capture, rainfall, and snowfall) of major elements (S, N, Ca, Mg, and K) ha ve been conducted in high-elevation forests, This paper presents the result s of the first long-term observations (1986-1996) of total atmospheric depo sition (wet + dry + cloud water) to a subalpine forest in the northeastern USA. Total atmospheric deposition of N to a forest at 1050 m elevation on W hiteface Mountain, NY, averaged 17.2 kg ha(=1) yr(-1), with 6.5 kg ha(=1) y r(-1) deposited as NH4 and 10.8 kg ha(-1) yr(-1) as NO3. Total S deposition averaged 18.3 kg ha(-1) yr(-1). Orographic effects both enhanced rainfall and increased interannual variance of ion concentrations and met deposition compared to nearby low-elevation monitoring stations. Cloud droplet captur e by the forest canopy varied substantially from year-to-year in response t o changing meteorological conditions, contributing between 6 and 31% of tot al annual water inputs, which averaged 156.1 cm yr(-1). Cloud water deposit ion was responsible for approximately 50%, and dry deposition approximately 10% of total annual N and S deposition. The signal from known decadal tren ds in atmospheric concentrations and fluxes of S in the northeastern USA wa s partially masked by high-frequency (intra- and inter-annual) variance ass ociated with local climatic effects on precipitation and cloud water fluxes at this high-elevation site. These observations suggest that atmospheric d eposition rates to high-elevation forests may be more responsive to climati c fluctuations and less responsive to recent and expected changes in atmosp heric chemical burdens than in surrounding low-elevation ecosystems.