DOI: 10.5061/dryad.fbg79cp2n
title: Data from: Effects of deer browsing on eastern hemlock growth and survival

description: Studies during the past six decades convincingly demonstrate that
 persistent browsing by native white-tailed deer (Odocoileus virginianus)
 eliminates the ability of eastern hemlock (Tsuga canadensis), white cedar
 (Thuja occidentalis), yellow birch (Betula alleghaniensis), and several
 other long-lived tree species to regenerate in forests of the upper
 Midwest and northeastern United States. The data shared here were used for
 three publications to date (see the Related Works section, below): The
 first is Alverson et al. 2019, which critically examined the relative
 contributions of deer versus snowshoe hare in reducing the growth and
 survival of eastern hemlock. The second is Alverson et al. 2024, a more
 detailed examination of growth and mortality rates of eastern hemlock, and
 the relationship of those two variables. The third is Waller et al. 2024,
 which explores the Regeneration Ratio, a new metric that integrates growth
 ("transit time" through the zone of vulnerability to browsing by
 deer and other herbivores) and mortality (half-life), and can be used to
 assess regeneration potential in populations of other tree species. (We
 are interested in collaborations to further test this metric for
 additional temperate and tropical species.) This is a rich data set from
 extensive fieldwork in northern Wisconsin and the western Upper Peninsula
 of Michigan, USA, from 1991 to 2011. It will be useful to others who wish
 to check our results, or examine specific subsets of data, e.g., the
 growth and mortality of specific size classes of hemlocks, behaviour of
 cohorts during a specific decade relative to regional changes in deer or
 hare abundance, or the characteristics of cohorts growing in specific
 ownerships. Although we examined the relationship of diameter and height,
 we did not consider allometry in detail in these publications. We
 encourage others to explore the allometry of these indigenous, juvenile
 hemlocks and would be happy to share the limited additional data that we
 have, upon request.
description: Site selection, study plot location, assignment of individual
 hemlocks to plots and exclosure treatment, and protocols for growth and
 mortality data, and for pellet counts, are fully described in W.S.
 Alverson and D.M. Waller, 1997. Deer populations and the failure of
 hemlock regeneration in northern forests. Pp. 280-297 in W.J. McShea et
 al., eds. <em>The science of overabundance: Deer ecology and
 population management.</em> Smithsonian Institution Press,
 Washington, DC. A description of the analyses, and a
 summary of protocols, are provided in W.S. Alverson, D.A. Riege, and D.M.
 Waller. 2024. Losing the slow race: How deer hinder growth, survival, and
 regeneration of juvenile hemlocks (<em>Tsuga canadensis</em>).
 Forest Ecology and Management.
 [https://doi.org/10.1016/j.foreco.2023.121466]
description: # Effects of deer browsing on eastern hemlock growth and survival
 This is a rich data set
 from extensive fieldwork in northern Wisconsin and the western Upper
 Peninsula of Michigan, USA, from 1991-2011. It will be useful to others
 who wish to check our results, or examine more specific subsets of data,
 e.g., growth and mortality of specific size classes of hemlocks, cohorts
 during a specific decade relative to regional changes in deer or hare
 abundance, or cohorts growing in specific ownerships. In particular,
 although we examined allometric relationships between diameter and height,
 we included little about this in our publications. We encourage others to
 explore this, and we have a limited amount of additional data on the ages
 of some of the indigenous hemlock juveniles (seedlings and saplings) that
 we are willing to share. ## Description of the data and file structure The
 dataset comprises 936 rows and 117 columns. Each row corresponds to a
 unique hemlock individual that was tagged and followed throughout the
 study (or until death). The sets of columns describe (1) seedling and site
 identity, and whether the seedling was transplanted or protected by a
 deer-proof "exclosure" cage; (2) site location; (3) diameter
 growth; (4) height growth; (5) browse and pellet-count data for hare and
 white-tailed deer at the study sites; and, (6) mortality data relevant to
 Cox proportional hazard analysis. Empty cells signify that we have no data
 for a particular hemlock individual for the specified census period, as a
 result of one of these three conditions: (1) The individual died since the
 previous census, so it has no living tissue on which to measure height or
 diameter. An examination of the mortality data in the rightmost columns of
 the dataset clearly indicate when individuals died.; (2) The study site
 where this individual grew was not visited during that census period. This
 mostly applies to sites on Menominee tribal lands, which were not visited
 after 1997 and sites in the Ottawa National Forest, which were not visited
 after 2007. In all cases, the mortality data in the rightmost columns of
 the dataset will indicate the year that that individual was
 "censored" (cf. Cox proportional hazards analysis), i.e., was
 lost to the study with an unknown fate; (3) In a very few cases, we simply
 missed a measurement on that individual in the field during a given
 census. Description of columns in Alverson.HemlockForDryad.18dec2023.xslx
 (and .csv): SEENO - Unique number assigned to each seedling; each was
 stamped onto a stainless steel tag, loosely attached with a stainless wire
 at base of stem at soil surface. SITE - Study site number. OWN - Ownership
 of site as of 1991. CNF, Chequamegon National Forest; LDF, Lac du Flambeau
 Reservation (First Nation lands); MEN, Menominee Reservation (First Nation
 lands); NNF, Nicolet National Forest (all in Wisconsin); ONF, Ottawa
 National Forest (Michigan). The Chequamegon and Nicolet National Forests
 later merged into the Chequamegon-Nicolet National Forest. ORIGN - Source
 of hemlock seedlings. All individuals here are “WI,” which means they were
 seedlings indigenous to Wisconsin or the Upper Peninsula of Michigan.
 TRANS - Transplant status. “N” indicates an individual growing in situ;
 “T” indicates that it was transplanted from a nearby location in northern
 Wisconsin or the western Upper Peninsula of Michigan. EXCLO - Exclosure
 status. “C” indicates an individual growing inside a deer-proof cage that
 was permeable to hare, rabbits, and other small mammals; “U” indicates
 that it was not protected by an exclosure cage. DegN - Degrees of north
 latitude. All locality data were recorded with a handheld GPS in 2007,
 with the exception of the Menominee (MEN) data, which were estimated in
 2023 using paper maps from our field work and GoogleEarth. MinN - Minutes
 of north latitude. DegW - Degrees of west longitude. MinW - Minutes of
 west longitude. Acc - Accuracy (meters) of locality information. These
 were derived from a handheld GPS except in the case of the Menominee (MEN)
 data, which were assigned very conservative values based on our review of
 paper maps of those sites in 2023. D91S - Diameter (mm) of individual
 seedling at base of stem in spring 1991. D92S, D93S, … D11S - Diameter
 (mm) at base of stem in spring 1992, 1993, … 2011. D.y0 - Diameter (mm) at
 base of stem the first spring that the individual was measured. D.y1,
 D.y2, … D.y20 - Diameter (mm) at base of stem in spring 1 year, 2 years, …
 20 years after the individual was first measured. H91S - Height of
 individual (cm) from ground level to highest living foliage in spring
 1991. H92S, H93S, … H11S - Height (cm) from ground level to highest living
 foliage in spring 1992, 1993, … 2011. H.y0 - Height (cm) from ground level
 to highest living foliage the first spring that the individual was
 measured. H.y1, H.y2, … H.y20 - Height (cm) from ground level to the
 highest living foliage in spring 1 year, 2 years, … 20 years after the
 individual was first measured. B92S, B93S, … B11S - “Recent” browse. If an
 individual appeared to have been browsed since the prior census, it was
 scored as “1” and if not, as “0”. An imperfect metric, in part because the
 census periods were not evenly spaced and we didn’t critically assess of
 how long prior to a census the browse occurred and could still appear as
 “new.” Note that we didn’t distinguish between deer and hare browse,
 although typically the difference was quite obvious. 0-BrowseCensuses -
 The number of censuses (spring visits) during which “recent” browse on
 that individual was NOT detected. 1-BrowseCensuses - The number of
 censuses during which “recent” browse on that individual WAS detected.
 \#BrowseCensuses - The number of censuses that individual hemlock was
 observed and scored for browse. AnyBrowse - Whether any browse was
 detected on that individual during the entire period of its observation; 1
 = yes, 0 = no. N91 - Number of new deer pellet groups at site during the
 survey in spring 1991. Specifically, these are the number of new
 deer-pellet groups in eight circular 0.01-acre sampling points (totaling
 323.9m2/site). Careful preliminary trials were made to avoid counting
 pellets deposited in previous years: see Alverson and Waller 1997 for
 details of the trials and sampling protocol. N92, N93, … N11 - Number of
 new deer pellet groups at site in spring 1992, 1993, … 2011. SumDeer -
 Total number of deer pellet groups at the site across all spring pellet
 surveys. \#DeerCensuses - Number of spring censuses for deer pellets at
 the site. MaxDeer/Census - The maximum number of deer pellet groups at the
 site in any census. HPEL91 - Number of individual hare pellets at site
 during spring survey in 1991. Specifically, these are the number of new
 hare pellets in eight circular 0.01-acre sampling points (totaling
 323.9m2/site) at the site. See Alverson and Waller 1997 for the detailed
 protocol. HPEL92, HPEL93, …. HPEL07 - Number of individual hare pellets at
 site during spring surveys in 1992, 1993, … 2007. SumHPEL - Total number
 of hare pellets at the site across all spring pellet surveys.
 \#HPELCensuses - Number of spring censuses for hare pellets at the site.
 MaxHPEL/Census - The maximum number of hare pellets at the site in any
 census. HAR91 - An alternative metric for hare presence at the site,
 specifically the number of circular, 0.01-acre sampling points in which
 hare pellets were detected during the spring survey in 1991. HAR92, HAR92,
 …HAR07 - Number of sampling points in which hare pellets were detected
 during the spring surveys in 1992, 1993, … 2007. SumHAR - Total number of
 sampling points with hare points at the site, across all spring pellet
 surveys. \#HARCensuses - Number of spring censuses for hare pellets at the
 site. MaxHAR/Census - The maximum number of sampling points within site
 that had hare pellets in any given census. AliveYR - The first calendar
 year that the living seedling was observed and measured. (This and the
 remaining columns are useful for Cox proportional hazards analyses.) DIED
 - Whether the individual was observed dead (1) or not (0) during the
 study. Note that a score of “0” can mean either that the individual lived
 to the end of the study or that we ceased following it when it was still
 alive and don’t know its fate at the end of the study. DeadYR - The first
 census year in which the individual was observed dead. LastYR - The last
 census year in which the individuals was observed alive. TimeAlive - The
 number of years the individual was alive during the study. Censor -
 Indicates whether we knew the fate of the individual throughout the study
 (Censor = 0); or if we were unable to ascertain its fate after the last
 time we observed it alive, i.e., it was “lost” to the study (Censor = 1).
 ## Sharing/Access information The authors can be contacted to clarify, or
 to share additional data (including the dataset used in earlier
 publications, which also included non-native hemlocks that were used as
 "phytometers" to assess browsing pressure early in the
 twenty-year field experiment.)