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Foliar resorption is a principal nutrient conservation mechanism in terrestrial vegetation that could be sensitive to ongoing changes in climate and atmospheric nitrogen (N) deposition. We quantified N resorption in northern hardwood forests along an elevation gradient of decreasing temperature and increasing soil N availability to evaluate how this critical nutrient cycling process can be expected to respond to global and regional environmental changes. Foliar N resorption proficiency (NRP) increased significantly at lower elevations for both sugar maple and American beech, the dominant species in these forests. Foliar N resorption efficiency (NRE) also decreased with increasing elevation, but only in one year. Both species exhibited strong negative relationships between NRP and soil N availability. Thus, we anticipate that with climate warming and decreasing N inputs, northern hardwood forests can be expected to exhibit stronger N conservation via foliar resorption. Both species also exhibited strong correlations between resorption efficiency of N and C, but resorption of both elements was much greater for beech than sugar maple, suggesting contrasting mechanisms of nutrient conservation between these two widespread species. 

Marked individual northern red oak seedlings were individually marked and mapped at 20 valleywide transects starting in summer 2011. This data set includes detailed seedling measures starting in summer 2014. The data were used to examine the impact of previous year seedling condition on whether the seedling survived in the next season. These data were gathered as part of the Hubbard Brook Ecosystem Study (HBES). The HBES is a collaborative effort at the Hubbard Brook Experimental Forest, which is operated and maintained by the USDA Forest Service, Northern Research Station. 

Overview: These data sets are the culmination of a five-year community science project done in collaboration with the Society for Protection of NH Forests. Co-authors on the resulting paper were: Carrie Deegan, Sarah Thorne, Ana Suppé, Kimberly L. Colson and Wanda Rice. Funding was provided by: Engaged Research Grant from the Einhorn Center for Community Engagement at Cornell University 2019 - 2023; Public Engagement with Science Grant (NSF grant #1713204) subcontract from Hubbard Brook Research Foundation; USDA Climate Hub; NSF-REU supplement under the HBR LTER (NSF grant #1637685) in 2021 and 2022 and HBR LTER in 2023 (NSF grant #2224545 ). Undergraduate students who helped on the project: Katie Sims, Alex Ding, Esmée deCortie, Sage Wentzell-Brehme, Colin Craig, Linda Mahecha, Roxy Moore. Community volunteers who contributed to field data collection and project meetings: Paul Doscher, Dave Heuss, Kim Sharp, Chris Brown, Tim Kendrick, Dan Poor, Rickey Poor, and Blaine Kopp. The study was conducted in four mature forest stands with a notable sugar maple component owned and managed by the Society for Protection of New Hampshire Forests (Forest Society) and spanning most of the latitudinal gradient in the state. Plots were established in autumn of 2018. In general, 12 plot locations were established for each of the four forest stands. Plots are spatially-uniform and placed as close to a 100 m grid system as possible with the restriction that the plot had to include three canopy sugar maple trees. The plots are 0.05 hectares or 500 m2 in size measured in a 12.62 m radius circular plot. Marked_sdlg_site_EDI: This data set contains survival, leaf area and leaf damage for 1191 sugar maple seedlings at four sites in New Hampshire. The sugar maple seedlings were two years old at the time of marking in 2019 and were from the 2017 mast year. The study followed the seedlings on 12 plots per site for 5 years (2019-2023). The data file also contains plot and site variables for topography, soil chemistry and tree density and sugar maple dominance. Some of the main findings from the study were the importance of site, initial leaf area and leaf damage to seedling survival. Litter_coll_ForestSoc_2yr: Leaves and seeds were collected from half of the plots (N=6) per site using three collectors. Count and dry weight were obtained for the leaves and counts for any seeds. This data set contains the main autumn collection data for 2019 and 2020. The were 20 tree species included over the four sites. There was a pattern of greater productivity in the southern site (greatest number of leaves) and decreased productivity in the northern site (lowest dry mass of leaves). Seed production for sugar maple was higher in 2019. Sweep_ForestSoc: Sapling layers were generally open with only 281 saplings from all plots. Kauffmann had the densest and most diverse sapling layer. The saplings were only measured once in 2019. Tagged_trees_ForestSoc: The data set includes growth (4 year) and vigor data (every other year) for 1335 trees in four study sites in New Hampshire. The data set includes data for 16 tree species tagged in 2019 and assessed in 2021 and 2023. At all sites, sugar maple growth was slower than average tree growth and mortality for sugar maple was higher than the average tree. This data set does not include data for trees that died during the study and therefore do not have growth data (96 trees). Common_garden_sdlgs: This data set includes harvest data for 50 sugar maple seedlings grown in a common garden experiment with soil from the four study sites taken from two microsites: sugar maple dominated and dominated by other species. The experimental setup had two controls. One control was the live soil from the site where the seedlings were obtained (native soil control). A second control contained a mix of sugar maple soil from the four sites that had been sterilized (pathogen free control). The experiment did not demonstrate a microsite difference for seedling growth but rather sites differed with the most nutrient rich soil resulting in larger seedlings. Overall, the experiment did not support a significant role of soil pathogens in explaining seedling survival differences between sites. ACSA_samaras_2019: This data table gives counts and condition of the samaras collected at the four study sites in autumn 2019, which represented the largest seed year during the study time. This data is useful for comparing differences in pre-dispersal damage to the seeds and seed production across sites. 2020_germinant_counts: This data table gives counts of newly germinated sugar maple seedlings at the plots with collectors (odd numbered plots). Sites were visited 14-18 May 2020. These data are used for comparing initial seedling densities across sites and the number of seedlings compared to the number of seeds for those plots, which gives an idea of post-dispersal survival. 

This data set was built from a larger data set of marked northern red oak seedlings surveyed from 2011-2023. In this data set, only seedlings marked in their year of germination with full environmental and seedlings measures were kept (N = 937). The data set was built for an accelerated failure time model of seedling survival that found year of germination, seedling density, shrub cover and elevation to have the largest effect on survival time. The status of the seedling acorn (attached or missing) was also important. These data were gathered as part of the Hubbard Brook Ecosystem Study (HBES). The HBES is a collaborative effort at the Hubbard Brook Experimental Forest, which is operated and maintained by the USDA Forest Service, Northern Research Station. 

This data set encompasses leaf area and dry weights for collected freshly shot leaves (early August) and fallen leaves (entire leaf fall period) along the elevation gradient of 14 sites used for the nitrogen oligotrophication study at Hubbard Brook Experimental Forest. This data will be used to calculate nutrient resorption along the elevation gradient for sugar maple (collection years: 2020-2022) and American beech (2021-2022). These data were gathered as part of the Hubbard Brook Ecosystem Study (HBES). The HBES is a collaborative effort at the Hubbard Brook Experimental Forest, which is operated and maintained by the USDA Forest Service, Northern Research Station. 

We quantified nitrogen (N) resorption of the two dominant tree species of northern hardwood forests along an elevation gradient using 14 sites at Hubbard Brook Experimental Forest, NH. For these calculations, we also quantified the leaf mass per area for both species, sugar maple and American beech. The original data before averaging for combining with chemistry data is available in an earlier revision of this dataset. Foliar N of sugar maple increased, and N resorption proficiency (NRP) decreased with increasing elevation. In contrast, foliar N and NRP of American beech did not vary significantly with elevation, suggesting that the mechanisms driving patterns of N resorption were distinct between these co-occurring species. While both species exhibited strong correlations between resorption efficiency of C and N, resorption of both elements was much greater for beech than maple. These data were gathered as part of the Hubbard Brook Ecosystem Study (HBES). The HBES is a collaborative effort at the Hubbard Brook Experimental Forest, which is operated and maintained by the USDA Forest Service, Northern Research Station. 

Upslope shifts in plant distributions are often attributed to warming climate and lengthening of the growing season; however, biotic interactions may also contribute. The impacts of pests and pathogens are often sensitive to climate change and can vary along the climatic gradient associated with elevation. American beech ( Fagus grandifolia) has moved upslope throughout the northeastern United States. Meanwhile, beech growth and longevity have decreased as a result of beech bark disease (BBD), a decline disease caused by the introduced European felted beech scale insect ( Cryptococcus fagisuga) and native fungi from the genus Neonectria. Within a forested landscape spanning 250–1150 m elevation, we examined the relationships between elevation, beech demography and BBD to explore whether release from BBD at higher elevation may contribute to the upslope expansion of beech. Beech has shifted upslope at a rate of 1 m⋅year −1 coincident with lower mortality, higher recruitment, faster growth, lower BBD severity, and higher sapling densities at higher elevations. We suggest that climatic constraints on the beech scale insect at high elevations has led to a lower impact of BBD, which contributed to higher rates of beech growth, survival, and recruitment and in turn facilitated the regional upslope shift of beech.