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.
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Hubbard Brook Experimental Forest: Oak seedling demography, 2011 - ongoing
Marked seedlings. Our dataset includes 1463 marked individual oak seedlings in 535 5m2 plots over the 20 transects. Overall, oak seedlings occurred in a third of the searched plots. Most plots had only one seedling (236 plots) and only 3% (16 plots) of the plots had 10 or more seedlings, with a maximum density of 3.4 seedlings m2. Cohort years 2011, 2015, 2017 and 2022 had a greater influx of seedlings, and our oldest seedling is estimated to be 30 years or older. For seedlings where initial height was measured in their year of germination (i.e., in 2011 or later) mean initial seedling height was 14.8 cm (SD = 6.51 cm) and there was a small but significant decline in initial seedling height with time (-0.23 cm/year, F1,1298 = 19.97, p=<0.0001). The size of first year seedlings as measured by both initial height (F1,760 = 25.2, p<0.001) and leaf number (F1,752 = 11.1, p=0.009) increased on average with distance into the valley. The mean distance of oak seedlings into the valley has not increased over the course of the study and remains centered around 800m from the east entrance.
Plot environment. Study transects encompassed a full range of topographic positions in the lower valley. Hemlock dominance ranged from absent (5 transects) to dominant (greater than 50% of trees; 3 transects). Tree basal area around the plots ranged from 18.8 – 43.5 m2 ha-1. Light transmission was universally low (all ≤13% TT). Light transmission (F1,5916 = 139.3; r2: 0.157, p<0.0001), hemlock dominance (F1,5916 = 2024; r2: 0.255, p<0.0001), and oak seedling density (F1,5916 = 73.9; r2: 0.126, p<0.0001) all decreased with distance further west into the valley.
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.
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- PAR ID:
- 10491736
- Publisher / Repository:
- Environmental Data Initiative
- Date Published:
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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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.more » « less
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Abstract Global change has created less stable forest systems and given urgency to understanding limitations to the establishment of tree seedlings beyond current range boundaries. We quantified trends in 13 years of annual northern red oak (QURU) seedling survival data for 1733 marked individuals at a local species distribution boundary within the northern hardwood forest in New Hampshire, USA. Over the study period, the median distance of seedlings into the valley did not change, although there was a net gain of 89 plots (5 m2) occupied. For a subset of seedlings that were marked in their year of birth (
N = 937), we examined relationships among terrain, vegetation community, and initial individual seedling traits, and evaluated their effects on time to seedling mortality using a parametric accelerated failure time model. The year of seedling germination had the largest effect on survival with increasing mortality rates for seedlings from more recent cohorts. Seedlings had longer survival times where oak seedling densities were lower, shrub cover was higher, and when the acorn remained attached. Additionally, survival time was increased in higher elevation plots, which were also located further into the valley. Interannual seedling survival (N = 1580) was strongly impacted by seedling condition in the previous year, particularly leaf number and amount of leaf damage. Most seedling deaths occurred over winter, and seedlings failed to break bud the following spring. Interannual variation in seasonal climate, particularly deep, heavy snowpack in 2019 followed by drought conditions in 2020, coincided with recent elevated mortality. Overall, the median survival time of 3–4 years and the rapid turnover of the oak seedling population currently limit ability for expansion, although the net gain of occupied plots and increase in survival at higher elevation plots with lower QURU densities present some mechanisms that could promote expansion if the current suboptimal understory conditions shift to favor QURU. -
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.more » « less
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The valley-wide plots are a grid of 431 sites along fifteen N–S transects established at 500-m intervals spanning the entire Hubbard Brook Valley. The plot network was designed by Paul Schwarz for spatial analysis of tree species distribution patterns within the valley. Multiple above- and below-ground attributes have been measured on these plots. This dataset includes forest inventory data at 10 year intervals, for 1995, 2005, and 2015. The full survey takes three seasons to complete, with the datatable listing the exact measurement interval for each tree. Data are included for both trees and saplings on 371 core plots (all surveys) and 60 densified plots (1998, 2008). Locations of plots in this study can be found in the following dataset: Hubbard Brook Experimental Forest Valleywide Plots: GIS Shapefile (2022.) https://doi.org/10.6073/pasta/440b176372e0cdeb341731aea816b67c 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. These data have been used in a number of publications including: Schwarz, P.A., Fahey, T.J., Martin, C.W., Siccama, T.G., and Bailey, A. 2001. Structure and composition of three northern hardwood–conifer forests with differing disturbance histories. For. Ecol. Manage. 144(1–3): 201–212. doi:10.1016/S0378-1127(00)00371-6. Schwarz, P.A., Fahey, T.J., and McCulloch, C.E. 2003. Factors controlling spatial variation of tree species abundance in a forested landscape. Ecology, 84(7): 1862–1878. doi:10.1890/0012-9658(2003)084[1862:FCSVOT]2.0.CO;2. van Doorn, N.S., Battles, J.J., Fahey, T.J., Siccama, T.G., and Schwarz, P.A. 2011. Links between biomass and tree demography in a northern hardwood forest: a decade of stability and change in Hubbard Brook Valley, New Hampshire. Can. J. For. Res. 41(7): 1369–1379. doi:10.1139/X11-063. Cleavitt, NL; AB Clyne and TJ Fahey. 2019. Epiphytic macrolichen patterns along an elevation gradient in the White Mountain National Forest, New Hampshire. J. Torrey Bot. Soc. 146(1): 8-17. Cleavitt, NL; Battles, JJ, Fahey, TJ, and Blum, J. 2014. Determinants of survival over seven years for a natural cohort of sugar maple seedlings in a northern hardwood forest. Can. J. For. Res.44 (9): 1112-1121.more » « less
