uid=HFR,o=lter,dc=ecoinformatics,dc=org all public read doi:10.6073/pasta/0bc6f43d7406c9c01e84a3dd4ed65193 Daniel Johnson https://orcid.org/0000-0002-8585-2143 Lukas Magee https://orcid.org/0000-0003-3124-2275 Researcher David Orwig https://orcid.org/0000-0001-7822-3560 Researcher 2026 English

The rate of tree mortality has been increasing, but why and where? Understanding the scope and scale of tree mortality is important because tree death can have a large impact on carbon dynamics and reduce biodiversity quickly. Mortality events most often occur at the scale of the individual or a small group of trees in a forest. Our ability to detect shifts in tree mortality and determine the causal factors responsible is defined by the intensity, scale, and frequency of our observations. Currently, most observations are too coarse in spatial scale and too infrequent in time to determine causal factors of mortality or how they vary across space and time and lack detail of why a tree died. Determining the uncertainty in tree mortality associated with the scale of observation is critical for making well informed estimates of carbon dynamics and predictions of forest community trajectories. The macroecological challenge lies gathering enough data on the ground to allow scaling up to broad regions with remote sensing products that can detect mortality events and changes in biomass at landscape and continental scales while minimizing uncertainty in our estimates. Our objective is to address this challenge and build scalable models of tree mortality with underlying factors associated with tree death. Each July for four years, we collected annual health and mortality data on all trees ≥10 cm diameter at breast height across the 35 ha ForestGEO megaplot at Harvard Forest. We assessed tree health by assigning any of 20 factors associated with death to all trees. We also collected crown metrics including the position in the canopy strata, percentage of crown structure intact, and percentage of crown living.

community composition forest dynamics invasive species mortality remote sensing tree maps LTER controlled vocabulary primary production populations disturbance LTER core area Harvard Forest HFR LTER USA HFR default

This dataset is released to the public under Creative Commons CC0 1.0 (No Rights Reserved). Please keep the dataset creators informed of any plans to use the dataset. Consultation with the original investigators is strongly encouraged. Publications and data products that make use of the dataset should include proper acknowledgement.

Creative Commons Zero v1.0 Universal https://spdx.org/licenses/CC0-1.0.html CC0-1.0 https://harvardforest.fas.harvard.edu/exist/apps/datasets/showData.html?id=hf453 Prospect Hill Tract (Harvard Forest). Coordinates based on WGS84 datum. -72.18 -72.18 +42.54 +42.54 340 368 meter 2021 2024 complete Information Manager Harvard Forest

324 North Main Street Petersham MA 01366 USA

(978) 724-3302 hf-im@lists.fas.harvard.edu Harvard Forest

324 North Main Street Petersham MA 01366 USA

(978) 724-3302 (978) 724-3595 https://harvardforest.fas.harvard.edu

We performed a field census to assess tree health within the 35-ha ForestGEO plot. This census involves conducting comprehensive visual examinations of all stems greater than 10 cm in diameter, focusing on indicators such as canopy condition, pests and pathogens, and physical damages. These field observations were meticulously recorded to create a detailed dataset capturing the health status of individual trees across the study area.

Harvard Forest

324 North Main Street Petersham MA 01366 USA

(978) 724-3302 (978) 724-3595 https://harvardforest.fas.harvard.edu https://ror.org/059cpzx98 pointOfContact The Harvard Forest Long-Term Ecological Research (LTER) program examines ecological dynamics in the New England region resulting from natural disturbances, environmental change, and human impacts. National Science Foundation LTER grants: DEB-8811764, DEB-9411975, DEB-0080592, DEB-0620443, DEB-1237491, DEB-1832210. Other funding: National Science Foundation Macrosystems grant: DEB-2106015 hf453-01-tree-census-2021-2024.csv tree mortality census data 2021-2024 hf453-01-tree-census-2021-2024.csv 5524386 c6be7aa99e31ded2041a0aaea07c0205 1 \r\n column , https://harvardforest.fas.harvard.edu/data/p45/hf453/hf453-01-tree-census-2021-2024.csv StemTag unique tag for each tree that can be matched to the tree census data found in the related datasets identifier year year data was collected (Always in July of that year) YYYY 1 status health status of the tree A alive with no visible health issues AU alive but has at least one health issue DC dead and down on the ground DN dead and not found DS dead and standing CP crown position in the canopy strata 1 understory with no direct light 2 understory with side light only 3 codominant with 15-90% direct light 4 dominant with 90+% direct light 5 emergent with crown well above the surrounding trees PercCI percentage of the crown woody material intact dimensionless 1 whole NA missing value PercCL percentage of the crown that is has living foliage dimensionless 1 whole NA missing value Lean angle (degrees) from vertical based on the angle from the base of the trunk to 1.3 m above the ground dimensionless 1 whole NA missing value FAD factor associated with death is a list of tree health codes that signify how a tree is unhealthy. AN: Animal damage; B: Broken bole; BB: Bark beetles; CR: Crushed; DF: Defoliation; F: Fungi; HS: Hollow stem; I: Insect infection; K: Canker; L: Lightning; LF: Leaf damage; OT: Overtopped; R: Rot; R1: Root damage; R2: Armallaria Root rot; S: Slope failure; U: unknown; UP: Up-rooted; W: Wound; Fi: Fire factor associated with death wound severity scale for any wound present 1 small damage, smaller in area than a square of DBH x DBH in shape 2 large damage, greater in area than a square of DBH x DBH in shape 3 massive damage, affecting more than 50% of the basal area (i.e., a very deep and extensive wound) or more than 50% of the living length canker severity scale for any canker present 1 small deformity area, smaller in area than a square of DBH x DBH in shape 2 big deformity, greater in area than a square of DBH x DBH in shape 3 massive deformity or canker, greater than 50% of the basal area or greater than 50% of the main axis length rot severity scale for any rot present 1 small rotting area, smaller in area than a square of DBH x DBH in shape 2 big rotting area, greater in area than a square of DBH x DBH in shape 3 massive rotting, affecting more than 50% of the basal area or more than 50% of the main axis length Lianas severity of liana infestation 0 lianas absent 1 up to 25% of the tree crown covered by lianas 2 26-50% liana cover 3 51-75% liana cover 4 76-100% liana cover DWR Boolean for dead trees if they have resprouted below DBH dead with resprout; tree is dead at 1.3m and above but has a resprout below 1.3m Notes any field notes about the tree notes 123232 conservation invasive short-term measurement https://harvardforest.fas.harvard.edu/exist/apps/datasets/showData.html?id=hf253