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Precipitation has been measured at the Hubbard Brook Experimental Forest using rain gauges located in or around each watershed since 1956. Three types of rain gauges have been used: standard, mechanical weight recording, and electronic weight recording. Between 1956 and 2014, precipitation was measured weekly at standard gages located at 24 stations in or near gauged watersheds and at the headquarters building. Weight-recording gauges were located at 7 of the 24 stations and capture a continuous strip-chart record. Weekly totals were prorated using daily totals from the nearest recording gauges. Beginning in 2011, electronic weighing rain gauges were implemented to measure 15-minute precipitation. The number of precipitation stations was reduced to 10, when each station was fully converted to an electronic gauge for measuring 15-minute and daily precipitation beginning in 2015. These data were gathered at the Hubbard Brook Experimental Forest in Woodstock, NH, which is operated and maintained by the USDA Forest Service, Northern Research Station. 

From 1956 to 2014, watershed precipitation was estimated using the Thiessen Means weighting method. Daily watershed precipitation values were a weighted average of daily precipitation from standard gauges in or near the watershed. The weighting factor for each gauge was the fraction of the watershed area nearest that gauge. Beginning in 2015, a similar system was implemented using the 10 remaining rain gauges, however Inverse Distance Weighting was used to estimate the weighting of each gauge instead of the Theissen polygon approach. These data were gathered at the Hubbard Brook Experimental Forest in Woodstock, NH, which is operated and maintained by the USDA Forest Service, Northern Research Station. 

From 2011 to 2017, ten electronic weighing rain gauges were progressively implemented at the Hubbard Brook Experimental Forest to measure precipitation at 15-minute intervals. 15-minute resolution watershed precipitation values for nine research watersheds are calculated as a weighted average of precipitation using Inverse Distance Weighting. These data were gathered at the Hubbard Brook Experimental Forest in Woodstock, NH, which is operated and maintained by the USDA Forest Service, Northern Research Station. 

Beginning in 2011, ten electronic weighing rain gauges were progressively implemented at the Hubbard Brook Experimental Forest to measure precipitation at 15-minute intervals. These data were gathered at the Hubbard Brook Experimental Forest in Woodstock, NH, which is operated and maintained by the USDA Forest Service, Northern Research Station. 

Air temperature is measured at 15-minute intervals in six clearings throughout the Hubbard Brook experimental watersheds and at the Headquarters Station. Beginning in 2014, digital sensors housed in aspirated solar radiation shields collected air temperature measurements. These data are gathered at the Hubbard Brook Experimental Forest in Woodstock, NH, which is operated and maintained by the USDA Forest Service, Northern Research Station. 

Air temperature is measured at seven locations in rain gauge clearings throughout the experimental watersheds and at Headquarters. The oldest air temperature record dates back to October 20,1955 at Station 1. From 1955 - 2014, temperature measurements were made continuously using hygrothermographs housed in standard shelters. Beginning in 2014, digital sensors housed in solar radiation shields collected daily minimum and maximum temperature measurements. Measurements made by the hygrothermographs have been corrected for screen bias to match the current aspirated radiation shields. These data are gathered at the Hubbard Brook Experimental Forest in Woodstock, NH, which is operated and maintained by the USDA Forest Service, Northern Research Station. 

Tree growth is a key mechanism driving carbon sequestration in forest ecosystems. Environmental conditions are important regulators of tree growth that can vary considerably between nearby urban and rural forests. For example, trees growing in cities often experience hotter and drier conditions than their rural counterparts while also being exposed to higher levels of light, pollution, and nutrient inputs. However, the extent to which these intrinsic differences in the growing conditions of trees in urban versus rural forests influence tree growth response to climate is not well known. In this study, we tested for differences in the climate sensitivity of tree growth between urban and rural forests along a latitudinal transect in the eastern United States that included Boston, Massachusetts, New York City, New York, and Baltimore, Maryland. Using dendrochronology analyses of tree cores from 55 white oak trees (Quercus alba), 55 red maple trees (Acer rubrum), and 41 red oak trees (Quercus rubra) we investigated the impacts of heat stress and water stress on the radial growth of individual trees. Across our three‐city study, we found that tree growth was more closely correlated with climate stress in the cooler climate cities of Boston and New York than in Baltimore. Furthermore, heat stress was a significant hindrance to tree growth in higher latitudes while the impacts of water stress appeared to be more evenly distributed across latitudes. We also found that the growth of oak trees, but not red maple trees, in the urban sites of Boston and New York City was more adversely impacted by heat stress than their rural counterparts, but we did not see these urban–rural differences in Maryland. Trees provide a wide range of important ecosystem services and increasing tree canopy cover was typically an important component of urban sustainability strategies. In light of our findings that urbanization can influence how tree growth responds to a warming climate, we suggest that municipalities consider these interactions when developing their tree‐planting palettes and when estimating the capacity of urban forests to contribute to broader sustainability goals in the future.

 

Stream fluxes are commonly reported without a complete accounting for uncertainty in the estimates, which makes it difficult to evaluate the significance of findings or to identify where to direct efforts to improve monitoring programs. At the Hubbard Brook Experimental Forest in the White Mountains of New Hampshire, USA, stream flow has been monitored continuously and solute concentrations have been sampled approximately weekly in small, gaged headwater streams since 1963, yet comprehensive uncertainty analyses have not been reported. We propagated uncertainty in the stage height–discharge relationship, watershed area, analytical chemistry, the concentration–discharge relationship used to interpolate solute concentrations, and the streamflow gap‐filling procedure to estimate uncertainty for both streamflow and solute fluxes for a recent 6‐year period (2013–2018) using a Monte Carlo approach. As a percentage of solute fluxes, uncertainty was highest for NH₄⁺(34%), total dissolved nitrogen (8.8%), NO₃⁻(8.1%), and K⁺(7.4%), and lowest for dissolved organic carbon (3.7%), SO₄²⁻(4.0%), and Mg²⁺(4.4%). In units of flux, uncertainties were highest for solutes in highest concentration (Si, DOC, SO₄²⁻, and Na⁺) and lowest for those lowest in concentration (H⁺and NH₄⁺). Laboratory analysis of solute concentration was a greater source of uncertainty than streamflow for solute flux, with the exception of DOC. Our results suggest that uncertainty in solute fluxes could be reduced with more precise measurements of solute concentrations. Additionally, more discharge measurements during high flows are needed to better characterize the stage‐discharge relationship. Quantifying uncertainty in streamflow and element export is important because it allows for determination of significance of differences in fluxes, which can be used to assess watershed response to disturbance and environmental change.

 

Snow and frost measurements have been collected approximately weekly during the winter season at the Hubbard Brook Experimental Forest using transects underneath the forest canopy adjacent to the established network of standard rain gages from 1956 to the present. Maximum snow depth, snow water content, frost occurrence, and frost depth data are recorded at points along a transect known as a snow course, which includes 10 points spaced at 2-m intervals within a designated 0.25 ha area. Data from one course are averaged for each collection date. These data were gathered at the Hubbard Brook Experimental Forest in Woodstock, NH, which is operated and maintained by the USDA Forest Service, Northern Research Station. 

Relative humidity has been measured at 15-minute intervals in two clearings throughout the Hubbard Brook experimental watersheds and at the Headquarters Station since 2011. Data were collected at two additional sites from 2011-2019. These data are gathered at the Hubbard Brook Experimental Forest in Woodstock, NH, which is operated and maintained by the USDA Forest Service, Northern Research Station.