Forest decline in the boreal montane ecosystems of the southern Appalachian Mountains

Research was initiated in 1984 in an attempt to quantify and test possible hypotheses for the systematic decline and mortality of red spruce (Picea rubens Sarg.) observed in the southern Appalachian Mountains. Field surveys have documented increases in decline symptoms. By 1986, 7% of all tagged red spruce trees in permanent plots were dead. This number, partially due to the effects of severe weather, increased to 41% in 1987. An insect and disease survey initiated in 1985 on 100 permanent plots has yielded little significant pathology or insect infestation. With the exception of the balsam wooly adelgid (Adelges picea (Ratz)), few signs or symptoms of disease or insect attack were noted on either Fraser fir (Abies fraseri) (Pursh Poir) or red spruce populations. Cultures from destructively-sampled root systems yielded few significant pathogens that could contribute to decline symptoms. Measurements of throughfall in 1986 yielded estimates of total wet deposition for NO₃ ^? and SO₄ ^2? of 25 and 75 kg ha^?1 yr^?1 respectively. Using net throughfall quantities, we estimate that between 40 and 60% of this input was due to cloud impact. Mean-volume-weighted pH per cloud event was 3.5. Over 75% of the cloud events sampled had a pH < 4.0. Cloud and rain water was dominated by H⁺, NH₄ ⁺, NO₃ ^?,, and SO₄ ^2? ions. Interaction with the forest canopy resulted in an enrichment of throughfall with base cations (K⁺, Ca²⁺, and Mg²⁺) and a loss of H⁺ and NH₄ ⁺. Mean-volume-weighted pH for throughfall was 3.9. The effects of simulated acidic cloud water on the epicuticular waxes of red spruce needles were studied during the summer of 1987. The cuticle proper of both 1986 and 1987 needles did not appear to be damaged by the treatments. The wax crystals which constitute the stomatal wax plugs, however, exhibited substantial degradation by simulated treatments at or below pH 3.5.     

Effects of immunocontraception on a suburban population of white-tailed deer Odocoileus virginianus

Abundant populations of white-tailed deer (Odocoileus virginianus) in North America have altered the structure of some forest communities and caused serious conflicts with farmers, gardeners, and motorists, encouraging the search for novel techniques to control populations of deer and other wildlife. We administered the porcine zona pellucida (PZP) immunocontraceptive vaccine to female white-tailed deer living on the 233-ha campus of the National Institute of Standards and Technology (NIST) in Gaithersburg, Maryland, USA. Although some tested PZP preparations proved more effective than others, the number of fawns produced per female was significantly lower in treated than untreated females. Following the onset of contraceptive treatments, the population declined by an average of 7.9% per year, and population declines were larger following years when a higher proportion of females was treated. High mortality due largely to deer-vehicle collisions and low population fertility associated with high deer densities facilitated the observed population decline.     

Effects of Climate, Land Management, and Sulfur Deposition on Soil Base Cation Supply in National Forests of the Southern Appalachian Mountains

Forest soils having low exchangeable calcium (Ca) and other nutrient base cation (BC) reserves may induce nutrient deficiencies in acid-sensitive plants and impact commercially important tree species. Past and future depletion of soil BC in response to acidic sulfur (S) deposition, forest management, and climate change alter the health and productivity of forest trees. This study used a process model (Model of Acidification of Groundwater in Catchments [MAGIC]) to address a number of questions related to soil BC status for a group of 65 streams and their watersheds in the southern Blue Ridge physiographic province of the southern Appalachian Mountains. Future S deposition to the study watersheds used for the Base Scenario was specified according to proposed reductions in S emissions at the time of this study, representing a reduction of 42 % of ambient S deposition by 2020. Twenty additional simulations were considered, reflecting four alternate S deposition scenarios (6 %, 58 %, 65 %, and 78 % reduction), and various changes in timber harvest, temperature, and precipitation. Base Scenario soil exchangeable Ca and % base saturation showed decreasing trends from 1860 to 2100. Changes in tree harvesting had the largest effect on stream sum of base cations (SBC) and soil BC supply. Each of the scenario projections indicated that median year 2100 soil exchangeable Ca will be at least 20 % lower than pre-industrial values. The simulations suggested that substantial mass loss of soil BC has already occurred since pre-industrial times. Nearly the same magnitude of BC loss is expected to occur over the next 145 years, even under relatively large additional future reductions in S deposition.     

Long-term response of spring flora to chronic herbivory and deer exclusion in Great Smoky Mountains National Park, USA

Chronic herbivory by white-tailed deer (Odocoileus virginianus Zimmerman) can have profound impacts on the function and structure of forest ecosystems. We examined the combined influence of intense herbivory associated with a deer population eruption and chronic herbivory by the post eruption population on the spring flora of Cades Cove, Great Smoky Mountains National Park. During the 1970s the deer population reached a peak of 43 deer per km², from which it has slowly declined in recent decades. To examine the influence of intense herbivory, we compared the abundance and flowering rates of early flowering plants in Cades Cove to a nearby reference site with similar bedrock geology, vegetation, and disturbance history but contrasting history of deer abundance. Our results suggest that significant changes (p ? 0.05) in the diversity, evenness, and species richness of the spring flora occurred during the eruptive phase. Trillium spp. and other liliaceous species appeared to be disproportionately impacted. Comparisons between control and exclosure plots established after the deer population eruption indicate that recovery has been largely restricted to species that were able to persist under intense herbivory. These species have increased in number in exclosures, suggesting continued impacts by deer on the plant community outside the exclosures. Little to no recolonization by browse sensitive species was observed. Consequently, to restore the natural diversity of early flowering plants once present in Cades Cove, active restoration may be necessary in addition to maintaining deer densities below current levels.     

Analysis of airborne particles sampled in the southern Appalachian mountains

Over 3 yr of particulate measurements were made at two high elevation sites in the southern Appalachian Mountains of Tennessee and Virginia. Both dichotomous samplers and filter packs were used to obtain day and night, week-long samples for subsequent elemental and ionic analysis. Total No _inf3 ^sup? (HNO₃ + No _in3 ^sup? ) and SO _inf4 ^sup2? averaged, respectively, 1.1 and 5.0 µg m^?3 at Look Rock, Tennessee and 2.0 and 6.4 µg m^?3 at Whitetop Mountain, Virginia. At Whitetop Mountain, the spring and summer seasons had the highest average SO _inf4 ^sup2? concentrations. Seasonally, total N03 varied little. The diurnal variation of elements and SO _inf4 ^sup2? was small. Only total NO _inf3 ^sup? varied substantially with highest values during the day. The fine fraction (particle diameter < 2.5 µm) accounted for about 67% of the total mass. Fine mass and elemental concentrations were generally higher at Look Rock. The elements comprising the principal mass fraction of the coarse samples (2.5 gm < particle diameter < 10 to 15 µm) were of crustal origin (e.g., Al, Si, Ca, Fe) while the element comprising the principal mass fraction of the fine samples (i.e., S) was of manmade origin. Cluster analysis identified two groups of elements at Whitetop Mountain. These groups, in both the coarse and fine fraction, were associate with a soil and an automobile emission component. At Look Rock, only a soil component was obvious.     

Landscape-level processes and wetland conservation in the Southern Appalachian Mountains

The function of wetland ecosystems is not independent of the landscapes in which they are embedded. They have strong physical and biotic linkages to the surrounding landscape. Therefore, incorporating a broad-scale perspective in our study of wetland ecology will promote our understanding of these habitats in the Southern Appalachians. Changes in the surrounding landscape will likely affect wetlands. Broad-scale changes that are likely to affect wetlands include: 1) climate change, 2) land use and land cover change, 3) water and air-borne pollution, 4) a shift in disturbance/recovery regimes, and 5) habitat loss and fragmentation. Changes in climate and land cover can affect the hydrology of the landscape and, therefore, the water balance of wetlands. Excessive nutrients and toxin transported by air and water to wetlands can disrupt natural patterns of nutrient cycling. Periodic disturbances, like flooding in riparian zones, is required to maintain some wetlands. A change in disturbance regimes, such as an increase in fire frequency, could alter species composition and nutrient cycles in certain wetlands. Many plant and animal species that found in small, isolated wetlands have populations that are dependent on complementary habitats found in the surrounding landscape. Loss or fragmentation of these complementary habitats could result in the collapse of wetland populations.     

美国北阿巴拉契亚地区耕作措施和土地利用管理对土壤团聚体和有机碳的影响

Promoting soil carbon sequestration in agricultural land is one of the viable strategies to decelerate the observed climate changes.However,soil physical disturbances have aggravated the soil degradation process by accelerating erosion.Thus,reducing the magnitude and intensity of soil physical disturbance through appropriate farming/agricultural systems is essential to management of soil carbon sink capacity of agricultural lands.Four sites of different land use types/tillage practices,i) no-till (NT) corn (Zea mays L.) (NTC),ii) conventional till (CT) corn (CTC),iii) pastureland (PL),and iv) native forest (NF),were selected at the North Appalachian Experimental Watershed Station,Ohio,USA to assess the impact of NT farming on soil aggregate indices including water-stable aggregation,mean weight diameter (MWD) and geometric mean diameter (GMD),and soil organic carbon and total nitrogen contents.The NTC plots received cow manure additions (about 15 t ha-1) every other year.The CTC plots involved disking and chisel ploughing and liquid fertilizer application (110 L ha-1).The results showed that both water-stable aggregation and MWD were greater in soil for NTC than for CTC.In the 0-10 cm soil layer,the ＞ 4.75-mm size fraction dominated NTC and was 46％ more than that for CTC,whereas the ＜ 0.25-mm size fraction was 380％ more for CTC than for NTC.The values of both MWD and GMD in soil for NTC (2.17 mm and 1.19 mm,respectively) were higher than those for CTC (1.47 and 0.72 mm,respectively) in the 0-10 cm soil layer.Macroaggregates contained 6％42％ and 13％ 43％ higher organic carbon and total nitrogen contents,respectively,than microaggregates in soil for all sites.Macroaggregates in soil for NTC contained 40％ more organic carbon and total nitrogen over microaggregates in soil for CTC.Therefore,a higher proportion of microaggregates with lower organic carbon contents created a carbon-depleted environment for CTC.In contrast,soil for NTC had more aggregation and contained higher organic carbon content within water-stable aggregates.The soil organic carbon and total nitrogen stocks (Mg ha-1) among the different sites followed the trend of NF ＞ PL ＞ NTC ＞ CTC,being 35％-46％ more for NTC over CTC.The NT practice enhanced soil organic carbon content over the CT practice and thus was an important strategy of carbon sequestration in cropland soils.     

Effects of disturbance by visitors on two woodland orchid species in Great Smoky Mountains National Park,USA

Two species of woodland orchid, showy orchis Orchis spectabilis, and pink lady slipper Cypripedium acaule, were surveyed for population density, clumping characteristics, and shoot morphology along sampling routes with easy, moderate and difficult access for visitors in Great Smoky Mountains National Park. Showy orchis populations were denser close to trails, and there were no major differences in populations attributable to visitor disturbance. The density of lady slipper populations was not clearly related to road or trail position, but there were significant differences in plant morphology between, easy, moderate and difficult access routes and some morphological characteristics gave significant regressions against road and trail distance. There was only limited evidence that environmental factors, such as slope or elevation, were influencing shoot morphology. The results indicate that visitors to the National Park will have difficulty finding blooming plants, despite the numerous lady slipper shoots along easy access routes. Rare plant monitoring efforts and further plant poaching studies should include detailed morphological information, since density may not be an adequate measure of population condition.     

Biology and establishment of mountain shrubs on mining disturbances in the Rocky Mountains,USA

The Rocky Mountains of the western United States contain many economically important natural resources. Increasing development of these resources has lead to land degradation, which often requires restoration efforts. A common type of disturbance in this region is mineral extraction and these activities often occur in zones of vegetation dominated by shrubs. These mined lands have proven to be particularly challenging to restore to native shrub cover. Mountain shrubland species such as big sagebrush (Artemisia tridentata), antelope bitterbrush (Purshia tridentata), Saskatoon serviceberry (Amelanchier alnifolia), black chokecherry (Prunus virginiana), mountain mahogany (Cercocarpus montanus), and snowberry (Symphoricarpos sp.) are crucial species for wildlife in this region due to the seasonal dependence of many wildlife species on the mountain shrubland zones. The development of successful restoration techniques for these key shrub species is therefore important for the continued and sustainable utilization of natural resources in the Rocky Mountains. The purpose of this literature review is to provide a reference to land managers working on woody plant establishment on mining disturbances in mountain shrublands in the Rocky Mountains. This review covers the biology, ecology, and propagation of six shrub species that are of primary importance for meeting regulatory compliance in this region. Based upon this survey of the published literature, we conclude that successful establishment of these species has most often involved: (1) utilization of local shrub ecotypes, varieties or subspecies in reclamation efforts, (2) protection from browsing during the establishment phase, (3) strategies for avoiding herbaceous competition, and (4) providing a source of mutualistic soil organisms. Additional specific recommendations for each of these species are discussed. Copyright © 2003 John Wiley & Sons, Ltd.     

Management effects on C accumulation and loss in soils of the southern Appalachian Piedmont of Georgia

Soil conservation management practices can impact on soil C storage. Long- and short-term data sets from three research sites were used to assess effects of management on C content of soils on the southern Appalachian Piedmont of Georgia. Intensive cultivation resulted in no observable change in total C content at the end of 3 yr, but at the end of 16 yr there were 40% and 18% declines in C in conventional tillage (CT) and no-tillage (NT) soils, respectively, at the Horseshoe Bend site. No significant changes in soil C were observed in either CT or NT soils at the end of 16 yr at Griffin. Higher clay content of Griffin soils may have contributed to this difference. Newly established NT plots on C-depleted soils on Dawson Field showed no change in C content at the end of 3 yr on both a highly eroded Pacolet sandy clay loam and a slightly eroded Cecil sandy loam. A soil under long-term NT accumulated C at a mean rate of ca. 0.6 Mg C ha⁻¹ yr⁻¹, reaching 29 Mg C ha⁻¹ after 20 yr. Steady-state levels of C in soils of the region may approach 40 Mg C ha⁻¹ (0–20 cm depth). Long-term forested and sod-based soils at Griffin showed C contents approximating this steady-state, while fertilized NT soils exceeded the estimated steady-state level.     

Spatial structure of multispecies distributions in southern California, USA

Analysis of the spatial distribution of all species of conservation importance within a region is necessary to augment reserve selection strategies and habitat management in biodiversity conservation. In this study, we analyzed the spatial aggregation, spatial association, and vegetation types of point occurrence data collected from museum and herbaria records for rare, special concern, threatened, and endangered species of plants, reptiles, mammals, and birds in western Riverside County in southern California, USA. All taxa showed clumped distributions, with aggregation evident below 14 km for plants, 12 km for reptiles, 2 km for mammals, and 10 km for birds. In addition, all combinations of the different species groups showed high positive spatial association. The Santa Rosa Plateau exhibited the highest number of rare, special concern, threatened, and endangered species, and shrubland (coastal sage and chaparral) was the vegetation type inhabited by the most species. Local land use planning, zoning and reserve design should consider the spatial aggregation within and between species to determine the appropriate scale for conservation planning. The higher spatial association between species groups in this study may indicate interdependence between different species groups or shared habitat requirements. It is important to maintain diverse communities due to potential interdependence. The results of the study indicate that concentrating preservation efforts on areas with the highest number of species of concern and the restoration of native shrublands are the most appropriate actions for multiple species habitat conservation in this area.     

Factors affecting streamwater chemistry in The Great Smoky Mountains,USA

The Great Smoky Mountains in the southeastern U.S. receive high total atmospheric deposition of sulphur and nitrogen (N) and contain large areas of shallow, poorly buffered soils. Results from extensive surveys conducted in October 1993 and March 1994 showed mat stream pH values were near or below 5.5 and Acid Neutralizing Capacity (ANC) was below SO μeq·L^?1 at high elevations. Mechanisms of acidification varies among stream systems in the study. We classified each study catchment into one of five water quality districts based upon within-basin elevational gradients of streamwater quality. Geologic factors, cf. the presence of calcareous or pyritic bedrock types exhibited a major influence on water quality and within-basin elevational gradients. Atmospheric deposition is an important factor affecting water quality at high elevations in all districts. Nitrate was the dominant strong acid anion in streamwater in many catchments, particularly at high elevation and especially in basins draining old growth forests. Most high elevation catchments appear to be N saturated. Continued high atmospheric loadings of N will likely spread N saturation of catchments downslope into areas where second growth forests are now maturing. Stream sulphate concentrations were lower than expected at higher elevations and may be related to the N saturation status of fliese systems.     

Distribution and environmental limitations of an amphibian pathogen in the Rocky Mountains, USA

Amphibian populations continue to be imperiled by the chytrid fungus (Batrachochytrium dendrobatidis). Understanding where B. dendrobatidis (Bd) occurs and how it may be limited by environmental factors is critical to our ability to effectively conserve the amphibians affected by Bd. We sampled 1247 amphibians (boreal toads and surrogates) at 261 boreal toad (Bufo boreas) breeding sites (97 clusters) along an 11° latitudinal gradient in the Rocky Mountains to determine the distribution of B. dendrobatidis and examine environmental factors, such as temperature and elevation, that might affect its distribution. The fungus was detected at 64% of all clusters and occurred across a range of elevations (1030-3550 m) and latitudes (37.6-48.6°) but we detected it in only 42% of clusters in the south (site elevations higher), compared to 84% of clusters in the north (site elevations lower). Maximum ambient temperature (daily high) explained much of the variation in Bd occurrence in boreal toad populations and thus perhaps limits the occurrence of the pathogen in the Rocky Mountains to areas where climatic conditions facilitate optimal growth of the fungus. This information has implications in global climate change scenarios where warming temperatures may facilitate the spread of disease into previously un- or little-affected areas (i.e., higher elevations). This study provides the first regional-level, field-based effort to examine the relationship of environmental and geographic factors to the distribution of B. dendrobatidis in North America and will assist managers to focus on at-risk populations as determined by the local temperature regimes, latitude and elevation.     

Visible Ozone Injury on Forest Trees in Great Smoky Mountains National Park, USA

During the summer of 1991 ozone injury trend plots in Great Smoky Mountains National Park, USA, consisting of mature black cherry, sassafras and yellow-poplar were established near three ozone monitors, ranging in elevation from 597-1265 m. Beginning in mid-August 1991-1993, three exposed branches each from the upper- and mid- to lower-crown of each tree were collected and evaluated for ozone injury. Of the trees examined, 63%, 52% and 36% exhibited some amount of foliar injury in 1991, 1992 and 1993, respectively. Ozone injury across species was the greatest at Cove Mountain in all three years of the study. Overall, across sites and years, 11, 12 and 11% of all leaves examined exhibited visible injury for black cherry, sassfras and yellow-poplar, respectively. The percentage of injured leaves per branch was greater in the mid- to lower-canopy for black cherry, across all sites. Trees for each species that exhibited the greatest or least amounts of visible injury did so in all three years of the study, indicating a differential sensitivity within each species population. No significant ozone exposure-tree response relationships were observed with any variable tested. These data indicate that ozone concentrations are high enough to cause visible symptoms to selected trees within Great Smoky Mountains National Park, USA.     

Effects of ecological restoration on microbial activity,microbial functional diversity,and soil organic matter in mixed-oak forests of southern Ohio,USA

As a result of many decades of fire suppression and atmospheric deposition the deciduous forests of eastern North America have changed significantly in stem density, basal area, tree size-frequency distribution, and community structure. Consequently, soil organic matter quality and quantity, nutrient availability, and microbial activity have likely been altered. This study evaluated the effects of four alternative forest ecosystem restoration strategies on soil microbial activity, microbial functional diversity, soil organic C, and soil N status in two mixed-oak (Quercus spp.) forests in southern Ohio, USA. The soils of these forests were sampled during the fourth growing season after application of (1) prescribed fire, (2) thinning of the understory and midstory to pre-settlement characteristics, (3) the combination of fire and thinning, and (4) an untreated control. Prescribed fire, with or without thinning, resulted in increased bacterial but not fungal activity when assessed using Biolog^®. In contrast, assays of acid phosphatase and phenol oxidase activity indicated greater microbial activity in the thinning treatment than in the other three treatments. Functional diversity of both bacteria and fungi was affected by restoration treatment, with the bacterial and fungal assemblages present in the thin + burn sites and the fungal assemblage present in the thinned sites differing significantly from those of the control and burned sites. Treatments did not result in significant differences in soil organic C content among experimental sites; however, the soil C:N ratio was significantly greater in thinned sites than in sites given the other three treatments. Similarly, there were no significant differences in dissolve inorganic N, dissolved organic N, or microbial biomass N among treatments. Bacterial and fungal functional diversity was altered significantly. Based on Biolog^® utilization treatments the bacterial assemblage in the thin-only treatment appeared to be relatively N-limited and the fungal assemblage relatively C-limited, whereas in the thin + burn treatment this was reversed. Although effects of restoration treatments on soil organic matter and overall microbial activity may not persist through the fourth post-treatment year, effects on microbial functional diversity are persistent.     

Current and predicted long-term effects of deer browsing in hemlock forests in Michigan,USA

Remnants of virgin hemlock Tsuga canadensis (L.) Carr. forest in the Porcupine Mountains, Michigan, USA, have experienced inadequate hemlock regeneration lasting several decades. White-tailed deer Odocoileus virginianus Zimmermann browsing seems to be the major cause of the observed decline of hemlock regeneration, rather than poor seedbed conditions or changing climate. In some areas, significant changes in the size-structure of the forest have already occurred, with a shift of dominance from hemlock to sugar maple Acer saccharum Marsh. taking place. A simulation of forest development is used to predict the changes in forest structure that will occur if no action is taken to control browsing. From this simulation it is estimated that in less than 150 years, hemlock will become only a minor component of the forest over large areas where it is currently the major dominant.     

Spatial Distribution of Acid-sensitive and Acid-impacted Streams in Relation to Watershed Features in the Southern Appalachian Mountains

A geologic classification scheme was combined with elevation to test hypotheses regarding watershed sensitivity to acidic deposition using available regional spatial data and to delimit a high-interest area for streamwater acidification sensitivity within the Southern Appalachian Mountains region. It covered only 28% of the region, and yet included almost all known streams that have low acid neutralizing capacity (ANC ≤20 μeq l^?1) or that are acidic (ANC ≤0). The five-class geologic classification scheme was developed based on recent lithologic maps and streamwater chemistry data for 909 sites. The vast majority of the sampled streams that had ANC ≤20 μeq l^?1 and that were totally underlainby a single geologic sensitivity class occurred in the siliceous class, which is represented by such lithologies as sandstone and quartzite. Streamwater acid-base chemistry throughout the region was also found to be associated with a number of watershed features that were mapped for the entire region, in addition to lithology and elevation, including ecoregion, physiographic province, soils type, forest type and watershed area. Logistic regression was used to model the presence/absence of acid-sensitive streams throughout the region.     

Browsing by red deer negatively impacts on soil nitrogen availability in regenerating native forest

Herbivores can have important indirect effects on belowground properties and processes that govern ecosystem form and productivity. A major way that herbivores affect ecosystem productivity is by modifying feedbacks that occur between dominant plants and belowground properties, and especially by changing the rates of nutrient mineralisation. In this study, we examine the effects of browsing by red deer, relative to landscape factors such as variations in microclimate and topography, on soil biological properties and N cycling in regenerating forest in an upland region of the Scottish Highlands. The site at Creag Meagaidh in the Scottish Highlands was sampled three times over the growing season of 2001 and soil cores were taken from four exclosures. Measures of soil biological properties and nitrogen availability were made. The results presented here suggest that although spatial and temporal variation were the dominant factors affecting soil biological properties and nitrogen dynamics in this ecosystem, herbivory also had consistent and significant effects on these measures. Browsing significantly reduced measures of DOC (27%), NO₃⁻ (48%), NH₄⁺ (49%) and N-mineralisation (53%). The microbial C:N ratio was also significantly greater (89%) in browsed than un-browsed areas, suggesting that the removal of deer reduced the extent that the microbial community was N-limited. These significant negative effects of browsing on soil nitrogen cycling have the potential to reduce ecosystem productivity. We conclude that removal of browsing over 14 years has accelerated native woodland regeneration, leading to subsequent increases in soil C- and N-mineralisation, further increasing plant N supply and tree growth in this ecosystem.     

Elevational trends in the fluxes of sulphur and nitrogen in throughfall in the Southern Appalachian Mountains: Some surprising results

From 1986–1989, a team of scientists measured atmospheric concentrations and fluxes in precipitation and throughfall, and modeled dry and cloudwater deposition in a spruce-fir forest of the Great Smoky Mountains National Park which is located in the Southern Appalachian Region of the United States. The work was part of the Integrated Forest Study (IFS) conducted at 12 forests in N. America and Europe. The spruce-fir forest at 1740 m consistently received the highest total deposition rates (～2200, 1200, and 700 eq ha^?1 yr^?1 for SO₄ ^2?, NO₃ ^?, and NH₄ ⁺). During the summers of 1989 and 1990 we used multiple samplers to measure hydrologie, SO₄ ^2?, and NO₃ ^? fluxes in rain and throughfall events beneath spruce forests above (1940 m) and below (1720 m) cloud base. Throughfall was used to estimate total deposition using relationships determined during the IFS. Although the SO₄ ^2? fluxes increased with elevation by a factor of ～2 due to higher cloudwater interception at 1940 m, the NO₃ ^? fluxes decreased with elevation by ～30%. To investigate further, we began year round measurements of fluxes of all major ions in throughfall below spruce-fir forests at 1740 m and at 1920 m in 1993–1994. The fluxes of most ions showed a 10–50% increase with elevation due to the ～70 cm yr^?1 cloudwater input at 1920 m. However, total inorganic nitrogen exhibited a 40% lower flux in throughfall at 1920 m than at 1740 m suggesting either higher dry deposition to trees at 1740 m or much higher canopy uptake of nitrogen by trees at 1920 m. Differential canopy absorption of N by trees at different elevations would have significant consequences for the use of throughfall N fluxes to estimate deposition. We used artificial trees to understand the foliar interactions of N.