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The project reports the flux of biomass and nutrients in leaf litterfall in 14 stands (the “Federer Chronosequence”) of northern hardwood forests. These 14 stands are located in the White Mountains of New Hampshire. Monitoring occurred from August 1993 through summer 1997 and again from August 2003 through summer 2006. The litterfall year is defined as starting in August (when we first set out baskets) and ending in August of the following year, years are named by the fall (in which most litter falls). In some years, we have litter mass by basket (3 per transect): 1993, 1994, 1995, 2003, 2005. In other years, we have only transect means: 1996, 2004. Seasonal masses are provided for 2005. Litterfall was sorted by species in all years except for 2005. Twig mass is reported only for 2005. Litter chemistry was measured in fresh litter samples collected in the same stands from 1994 through 2004. Raw, unedited data sorted by season can be found in “Other Entities”, though note the substantial changes that occurred between these values and the processed values published in this dataset. 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. Related publications: Yanai, R. D., Arthur, M. A., Acker, M., Levine, C. R., & Park, B. B. (2012). Variation in mass and nutrient concentration of leaf litter across years and sites in a northern hardwood forest. Canadian Journal of Forest Research, 42(8), 1597-1610. Acker, M. 2006.Base cation concentration and content in litterfall and woody debris across a northern hardwood forest chronosequence. MS Thesis. Lexington, KY: University of Kentucky. Yang, Y., Yanai, R. D., See, C. R., & Arthur, M. A. (2017). Sampling effort and uncertainty in leaf litterfall mass and nutrient flux in northern hardwood forests. Ecosphere, 8(11), e01999. 

Freshly senesced leaf litter was collected during autumn in New Hampshire at the Bartlett Experimental Forest, Hubbard Brook Experimental Forest, and Jeffers Brook as part of the Multiple Elementation Limitation in Northern Hardwood Ecosystems (MELNHE) study. Leaf litter was collected in October 2021 and 2022 at peak litterfall (i.e., mid-October) during a rain-free period. These leaf-litter samples were analyzed for nutrient concentrations for use in resorption analyses. This dataset includes photos of all of the leaf-litter samples used for chemical analysis. For the corresponding chemistry data, please see the following data package: Zukswert, J., K. Gonzales, S. Hong, C. See, B. Quintero, and R.D. Yanai. 2025. Multiple Element Limitation in Northern Hardwood Ecosystems (MELNHE): Fresh Litter Chemistry ver 3. Environmental Data Initiative. https://doi.org/10.6073/pasta/f52a613213855e4b4a03fa4a0e2f2922 (Accessed 2025-01-14). These leaf litter samples correspond with green foliage samples collected in late July and early August of the same years: the green foliage data can be found in the following data package: Zukswert, J.M., S.D. Hong, K.E. Gonzales, C.R. See, and R.D. Yanai. 2025. Multiple Element Limitation in Northern Hardwood Ecosystems (MELNHE): Foliar Chemistry 2008-2022 in Bartlett, Hubbard Brook, and Jeffers Brook ver 4. Environmental Data Initiative. https://doi.org/10.6073/pasta/ef3696a753150d0a420fd9009f73b1e9 (Accessed 2025-01-14). Photos of the corresponding foliage samples can be found in the following data package: Zukswert, J.M. 2024. Multiple Element Limitation in Northern Hardwood Ecosystems (MELNHE): Foliage Scans and Photographs ver 2. Environmental Data Initiative. https://doi.org/10.6073/pasta/7d93f50f9f2e848805b4aac9ed24689c (Accessed 2025-01-14). Additional detail on the MELNHE project, including a datatable of site descriptions and a pdf file with the project description and diagram of plot configuration can be found in this data package: https://portal.edirepository.org/nis/mapbrowse?scope=knb-lter-hbr&identifier=344 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. 

Stomatal density and length were measured on leaves of sugar maple (Acer sacharrum Marsh.) and yellow birch (Betula alleghaniensis Britton.) trees in New Hampshire at the Bartlett Experimental Forest, Hubbard Brook Experimental Forest, and Jeffers Brook as part of the Multiple Elementation Limitation in Northern Hardwood Ecosystems (MELNHE) study. Leaves were collected in late July and early August in 2021 and 2022 from the tops of dominant and codominant trees using a shotgun. These measurements were made on 3 leaves from each tree. These data correspond with other foliar trait data collected from the same trees in 2021 and 2022. That EDI package is as follows: Hong, S.D., K.E. Gonzales, C.R. See, and R.D. Yanai. 2021. MELNHE: Foliar Chemistry 2008-2016 in Bartlett, Hubbard Brook, and Jeffers Brook (12 stands) ver 1. Environmental Data Initiative. https://doi.org/10.6073/pasta/b23deb8e1ccf1c1413382bf911c6be19 This data package contains the raw images underlying the data reported in a separate data package on stomatal density and length: https://portal.edirepository.org/nis/mapbrowse?scope=knb-lter-hbr&identifier=372 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. 

Stomatal density and length were measured on leaves of sugar maple (Acer sacharrum Marsh.) and yellow birch (Betula alleghaniensis Britton.) trees in New Hampshire at the Bartlett Experimental Forest, Hubbard Brook Experimental Forest, and Jeffers Brook as part of the Multiple Elementation Limitation in Northern Hardwood Ecosystems (MELNHE) study. Leaves were collected in late July and early August in 2021 and 2022 from the tops of dominant and codominant trees using a shotgun. These measurements were made on 3 leaves from each tree. These data correspond with other foliar trait data collected from the same trees in 2021 and 2022. That EDI package is as follows: Hong, S.D., K.E. Gonzales, C.R. See, and R.D. Yanai. 2021. MELNHE: Foliar Chemistry 2008-2016 in Bartlett, Hubbard Brook, and Jeffers Brook (12 stands) ver 1. Environmental Data Initiative. https://doi.org/10.6073/pasta/b23deb8e1ccf1c1413382bf911c6be19 This data package contains the stomatal density and length derived from the raw images in a separate EDI data package: https://portal.edirepository.org/nis/mapbrowse?scope=knb-lter-hbr&identifier=321 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 are conducting nutrient manipulations in three study sites in the White Mountain National Forest in New Hampshire: Bartlett Experimental Forest, Hubbard Brook Experimental Forest, and Jeffers Brook. We monitored foliar chemistry in 13 of our stands (including HBCa and excluding C3) pre-treatment (2008-2010) and post-treatment (2014-2016 and 2021-22). In 2021-22, we also measured specific leaf area, leaf dry matter content, carbon isotope composition, and stomatal density. We found that foliar N concentrations were higher with N addition and foliar P concentrations were higher with P addition. More interestingly, P addition reduced foliar N concentrations and N addition reduced foliar P concentrations. Some interactive effects were observed (i.e. NxP, Species x N, Species x P, Species x N x P). This dataset contains pre- and post- treatment foliar chemistry and trait data, and data from the analysis of quality control standard samples. Changes to pre-treatment data from version 1 include switching white birch trees #8272 and #8252 in stand JBM plots 2 and 3 (8272 is now in the nitrogen plot and 8252 is now in the control plot), correcting the species of tree #1628 in stand HBCa plot 1 (changed from red maple to sugar maple) and tree #8457 in stand HBO plot 3 (changed from sugar maple to red maple), and updating nutrient concentrations for C8 plot 3 sugar maple trees #28 and #30 to include averages of subsamples re-run in 2022. Tree tags were also updated to the tag ID present during the 2023 tree inventory. Additional detail on the MELNHE project, including a datatable of site descriptions and a pdf file with the project description and diagram of plot configuration can be found in this data package: https://portal.edirepository.org/nis/mapbrowse?scope=knb-lter-hbr&identifier=344 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. 

In the MELNHE project, we are conducting nutrient manipulations in three study sites in the White Mountain National Forest in New Hampshire: Bartlett Experimental Forest, Hubbard Brook Experimental Forest, and Jeffers Brook. We monitored foliar chemistry in 11 of our stands pre-treatment (2008-2010) and post-treatment (2014-2016 and 2021-22). In 2021-22 , we also measured specific leaf area, leaf dry matter content, carbon isotope composition, and stomatal density. This dataset includes scans of the foliage sampled in 2021-22, used to measure leaf area, and photos of all foliage samples used for trait measurements and chemical analysis. For the corresponding trait and chemistry data, please see the following dataset: https://portal.edirepository.org/nis/mapbrowse?packageid=knb-lter-hbr.313.1 Additional detail on the MELNHE project, including a datatable of site descriptions and a pdf file with the project description and diagram of plot configuration can be found in this data package: https://portal.edirepository.org/nis/mapbrowse?scope=knb-lter-hbr&identifier=344 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. Some of these data have been published in: Jenna M Zukswert, Matthew A Vadeboncoeur, Ruth D Yanai, Responses of stomatal density and carbon isotope composition of sugar maple and yellow birch foliage to N, P and CaSiO3 fertilization, Tree Physiology, Volume 44, Issue 1, January 2024, tpad142, https://doi.org/10.1093/treephys/tpad142 

Abstract Stomatal density, stomatal length and carbon isotope composition can all provide insights into environmental controls on photosynthesis and transpiration. Stomatal measurements can be time-consuming; it is therefore wise to consider efficient sampling schemes. Knowing the variance partitioning at different measurement levels (i.e., among stands, plots, trees, leaves and within leaves) can aid in making informed decisions around where to focus sampling effort. In this study, we explored the effects of nitrogen (N), phosphorus (P) and calcium silicate (CaSiO3) addition on stomatal density, length and carbon isotope composition (δ13C) of sugar maple (Acer saccharum Marsh.) and yellow birch (Betula alleghaniensis Britton). We observed a positive but small (8%) increase in stomatal density with P addition and an increase in δ13C with N and CaSiO3 addition in sugar maple, but we did not observe effects of nutrient addition on these characteristics in yellow birch. Variability was highest within leaves and among trees for stomatal density and highest among stomata for stomatal length. To reduce variability and increase chances of detecting treatment differences in stomatal density and length, future protocols should consider pretreatment and repeated measurements of trees over time or measure more trees per plot, increase the number of leaf impressions or standardize their locations, measure more stomata per image and ensure consistent light availability. 

Decomposition of leaf litter is a major source of nutrient transfer from vegetation to soils and an important carbon flux. In northern hardwood forests, litter decomposition might be affected by nutrient availability, species composition, stand age or structure, or access by soil decomposers. We investigated these factors in four stands at the Bartlett Experimental Forest in New Hampshire that have had nitrogen and phosphorus added in full factorial design since 2011. Leaf litter of early and late successional species was collected in 2012 and deployed in bags of two mesh sizes (63 µm and 2 mm) in two young and two mature stands and collected three times over the next 2 years. Decomposition was evaluated by fitting mass loss as an exponential function of time represented by growing degree days. Litter decomposed more quickly in the small mesh bags (p < 0.001), which excluded mesofauna. This result was surprising, but might be explained by the greater rigidity of the large mesh material making poor contact with the soil. The litter with a species composition characteristic of our young stands decomposed more quickly than the litter representing mature stands (p = 0.01 for species mix in the full model). The environment in which is was placed was not as important: Neither the age of the stand in which it was placed (p = 0.31), nor N addition (p = 0.59), P addition (p = 0.41), or the interaction of N and P addition (p = 0.13) were significant predictors of the decomposition rate, defined by fitting an exponential decay constant. Additional detail on the MELNHE project, including a datatable of site descriptions and a pdf file with the project description and diagram of plot configuration can be found in this data package: https://portal.edirepository.org/nis/mapbrowse?scope=knb-lter-hbr&identifier=344 Litter was collected by Rick Bicher and sorted by species by middle school students. Litterbags were made, filled, and weighed by middle school students. Gracie Gilcrist and Jeff Merriam generated data for the chemical analyses. 

This dataset describes litterfall mass collected in the Multiple Element Limitation in Northern Hardwood Ecosystems (MELNHE) study in New Hampshire from fall 2009 through summer 2022. Litter was collected three times per year: fall (late October or early November), spring (June), and summer (August). Fall litter was sorted by species in a subset of stands. This data package also includes the R code used to impute missing data for analysis, a manually edited data file used in the R code flow, and a file matching the labels for litterfall collectors from the original (pre Fall 2011) and current (Fall 2011 and onwards) labeling systems. All collectors have the most current label if known for all years of data. Additional detail on MELNHE, including a table of stand descriptions, project description, and a diagram of plot configuration can be found in this data package: Yanai, R.D., M. Fisk, and T.J. Fahey. 2024. Multiple Element Limitation in Northern Hardwood Ecosystems (MELNHE): Project description, plot characteristics and design ver 2. Environmental Data Initiative. https://doi.org/10.6073/pasta/6cc8a39d052834c030650fb29937bf4f (Accessed 2024-10-17). Litterfall chemistry data for a subset of these samples can be found in the following data package: Fisk, M.C., R.D. Yanai, S.D. Hong, C.R. See, and S. Goswami. 2022. Litter chemistry and masses for the MELNHE NxP fertilization experiment ver 1. Environmental Data Initiative. https://doi.org/10.6073/pasta/8b2975a3a02cbcfb1b0a12ac954576d4 (Accessed 2024-06-09). 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. 

Stomatal density and length were measured on leaves of sugar maple (Acer sacharrum Marsh.) and yellow birch (Betula alleghaniensis Britton.) trees in New Hampshire at the Bartlett Experimental Forest, Hubbard Brook Experimental Forest, and Jeffers Brook as part of the Multiple Elementation Limitation in Northern Hardwood Ecosystems (MELNHE) study. Leaves were collected in late July and early August in 2021 and 2022 from the tops of dominant and codominant trees using a shotgun. These measurements were made on 3 leaves from each tree. These data correspond with other foliar trait data collected from the same trees in 2021 and 2022. That EDI package is as follows: Hong, S.D., K.E. Gonzales, C.R. See, and R.D. Yanai. 2021. MELNHE: Foliar Chemistry 2008-2016 in Bartlett, Hubbard Brook, and Jeffers Brook (12 stands) ver 1. Environmental Data Initiative. https://doi.org/10.6073/pasta/b23deb8e1ccf1c1413382bf911c6be19 This data package contains the raw images underlying the data reported in a separate data package on stomatal density and length: https://portal.edirepository.org/nis/mapbrowse?scope=knb-lter-hbr&identifier=372 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.