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Tree seeds sorted and counted from long-term reference area litter traps are presented for 1993 until the present. These data are part of the LTER funded quantification of tree annual productivity. Our focal species for seed counts have been sugar maple, American beech and white ash. This data set allows comparison between seed production in reference sites (BB and TF) and the calcium addition watershed (W1) for these species. 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. 

Coarse litterfall (woody litter greater than 2 cm diameter) was collected from cleared plots in the same sites as fine litterfall to quantify total aboveground litterfall in the reference forest. These collections are for quantifying CWD inputs from live standing trees rather than all CWD inputs. Tree mortality and fall rates are used for dead tree inputs. All together these data are used to calculate aboveground production and forest carbon and nutrient budgets. 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. 

Overstory foliage is collected in late summer from a reference forest to the west of Watershed 6 (also referred to as Bear Brook Watershed). Concentrations of C, N, P, K, Ca, Mn, Mg, and the natural abundance of N and C isotopes (delta-15N and delta-13C) in foliage are measured. These measurements, in combination with litterfall estimates of foliar biomass, allow us to estimate the pool of nutrients in foliage. They also allow us to estimate nutrient retranslocation, using measurements of leaf litterfall chemistry. Long-term measurements continue with the aim of detecting disturbances in nutrient cycling and trends in foliar chemistry over long time scales. 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. 

Fine litterfall (leaves, twigs, fruits, seeds, etc.) is collected in Watershed 1, Watershed 5, the Throughfall plots and the Bear Brook Watershed reference forest, located to the west of Watershed 6, to quantify carbon and nutrient flux associated with this important pathway. These measurements have facilitated quantification of ice storm effects and species declines (paper birch, sugar 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. 

Declining nitrogen (N) availability relative to plant demand, known as N oligotrophication, is a widespread phenomenon that has been particularly well documented in northern hardwood forests of the northeast U.S. It is hypothesized that later fall senescence contributes to this trend by increasing tree resorption of N, resulting in higher carbon:nitrogen ratios (C:N) in litterfall and reduced N availability in soil. To examine the effects of litterfall C:N on soil N cycling, we conducted a litter quality manipulation experiment comparing low C:N and high C:N litter with native litter along an elevation and aspect gradient at Hubbard Brook Experimental Forest, NH, USA. We found that potential net ammonification and mineralization rates were positively correlated with litter N and negatively correlated with litter C:N under high C:N litter, but these relationships were not present under native or low C:N litter. Differences in nitrate pools and net mineralization rates between high- and low-quality litter treatments were greater at colder sites, where native litterfall tends to have lower C:N than at low-elevation sites. Together, these results demonstrate that higher C:N litter and a warming climate may contribute to N oligotrophication through effects on microbially driven N cycling rates in organic soils. 

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. 

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. 

Tree seeds sorted and counted from long-term reference area litter traps are presented for 1993 until the present. These data are part of the LTER funded quantification of tree annual productivity. Our focal species for seed counts have been sugar maple, American beech and white ash. This data set allows comparison between seed production in reference sites (BB and TF) and the calcium addition watershed (W1) for these species. 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.