Harvard Forest

Data Archive

HF285

Maple Reproduction and Sap Flow at Harvard Forest since 2011

Related Publications

Data

• hf285-01: maple tapping data (preview)
• hf285-02: sap collection data (preview)
• hf285-03: flowering data, whole tree (preview)
• hf285-04: flowering data, twigs (preview)
• hf285-05: spring branch growth (preview)
• hf285-06: fall leaf and twig growth and samara production (preview)
• hf285-07: samara evaluation (preview)
• hf285-08: samara evaluation, pollinator exclusion bag (preview)
• hf285-09: samara pairs count (preview)
• hf285-10: leaf removal data (preview)
• hf285-11: leaf removal treatment, twig growth data (preview)
• hf285-12: leaf and seed removal data (preview)
• hf285-13: leaf and seed removal, branches data (preview)
• hf285-14: branches data (preview)

Overview

• Lead: Joshua Rapp, Elizabeth Crone, Kristina Stinson
• Investigators: Iris Le Ronce
• Contact: Information Manager
• Start date: 2011
• End date: 2024
• Status: ongoing
• Location: Prospect Hill Tract (Harvard Forest)
• Latitude: +42.53 degrees
• Longitude: -72.19 degrees
• Elevation: 340 meter
• Datum: WGS84
• Taxa: Acer rubrum (red maple), Acer saccharum (sugar maple)
• Release date: 2025
• Language: English
• EML file: knb-lter-hfr.285.7
• DOI: digital object identifier
• EDI: data package
• DataONE: data package
• Related links:
• Study type: long-term measurement
• Research topic: physiological ecology, population dynamics and species interactions
• LTER core area: primary production, population studies
• Keywords: flowering, leaves, maple, masting, seed production
• Abstract:

  Seed production assures the persistence of tree populations and forest cover over the long-term, and so has long interested plant demographers and foresters. Many forest tree species produce seeds synchronously and at irregular intervals across large areas, a phenomenon known as masting. Initiated in spring 2011, this study addresses the mechanisms of mast seeding in sugar maple (Acer saccharum), and its impact on pollinators, seed consumers, and forest carbon dynamics at the Harvard Forest. We monitor seed production (via counts of seeds on trees), flower production, and resource status (via sap collection) on 20 trees. Pollinator dynamics and seed predation (by weevils) are also monitored. In 2015, we added sap and seed monitoring of red maple (Acer rubrum) trees to explore the hypothesis that this non-masting species would have muted dynamics compared to its masting congener.

• Methods:

  Sap monitoring

  We have monitored reproductive effort since 2011 and NSC in xylem sap since 2012 at Harvard Forest. We monitor nonstructural carbohydrates in xylem sap by tapping 20 trees using traditional gravity tapping methods, following accepted guidelines (Heiligmann et al. 2006). In late February when temperatures rise above freezing during the day, 5/16 inch diameter holes are drilled into trees and 5/16” spiles inserted into the holes. Trees greater than 20 inches in diameter are fitted with two spiles, located on opposite sides of the tree. Xylem sap is collected from February through early April, on all days when there is sap flow (generally when temperatures during the day rise above the freezing point of water). At each collection, sap is weighed and the sugar content measured for each tap hole.

  Reproductive monitoring

  Reproductive effort is evaluated are both flowering and fruiting stages. During flowering (late-April through early May) we qualitatively evaluate flowering effort of each tree (low - fewer than 1,000 flowering buds; medium – 1000-10000 flowering buds; high - more than 10,000 flowering buds) and evaluate whether trees have only male flowers or have both male and female flowers, and if so, which sex is mature first on the tree. From 2011-2014 we also sampled 9 branches from each tree (3 from upper canopy, 3 from mid-canopy, and 3 from lower-canopy) and counted the number of male and female flowers in each bud originating from the last two year’s growth of the main twig. We also counted the number of leaves originating from each bud. For these collections we also measured the length in millimeters of the last two year’s growth of the main twig.

  In the spring of 2011-2014 we also marked branches with and without flowers that we returned to in the fall. When seeds were mature, we collected these branches and counted the number of leaves on the terminal twig, the total leaf area, the length of twig growth, and the number of samaras for flowering twigs. We also examined the status of the samaras collected and seed predation by evaluating whether they were empty, or contained a filled seed, grub, exit hole, or a non-viable seed that was wrinkled, small, or moldy.

  We examine pollination by insects (mainly andrenid bees) by installing pollinator exclusion bags on 3 branches of 3-5 trees each spring during flowering. In the fall, we collect the bagged twigs, as well as nearby control twigs (marked in the spring) and evaluate samaras as above.

  To evaluate whole tree seed production, we make timed counts of seeds across the canopy using binoculars in late summer (Koenig et al. 1994). Crone and Rapp each count the number of seeds they observe in 15 seconds. The two counts are summed and used as a metric of seed production for that tree.

• Organization: Harvard Forest. 324 North Main Street, Petersham, MA 01366, USA. Phone (978) 724-3302. Fax (978) 724-3595.

• Project: 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. (ROR).

• Funding: National Science Foundation LTER grants: DEB-8811764, DEB-9411975, DEB-0080592, DEB-0620443, DEB-1237491, DEB-1832210.

• Use: 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.

• License: Creative Commons Zero v1.0 Universal (CC0-1.0)

• Citation: Rapp J, Crone E, Stinson K. 2025. Maple Reproduction and Sap Flow at Harvard Forest since 2011. Harvard Forest Data Archive: HF285 (v.7). Environmental Data Initiative: https://doi.org/10.6073/pasta/2ad66d124f043c7326ca2b607447c518.

Detailed Metadata

hf285-01: maple tapping data

1. date: date of data collection
2. tree: tree identification number; prefix is either HF (for sugar maples) or HFR (for red maples)
3. tap: A or B for trees with 2 taps; consistent within years but not between years
4. species: tree species
   • ACSA: Acer saccharum
   • ACRU: Acer rubrum
5. dbh: diameter at 1.4 m above ground (unit: centimeter / missing value: NA)
6. tap_bearing: compass bearing of tap hole, facing into the tree (unit: degree / missing value: NA)
7. tap_height: tap height above ground (unit: centimeter / missing value: NA)

hf285-02: sap collection data

1. date: date of data collection
2. tree: tree identification number; prefix is either HF (for sugar maples) or AR (for red maples)
3. tap: A or B for trees with 2 taps; consistent within years but not between years
4. time: time of sap collection; recorded for each tap in 2012, at beginning and end of collection period thereafter
5. datetime: date and time of sap collection; recorded for each tap in 2012, at beginning and end of collection period thereafter
6. sugar: sugar concentration measured in Brixx (weight percent) with Misco digital refractometer of sap collected directly from tap (unit: dimensionless / missing value: NA)
7. species: tree species
   • ACSA: Acer saccharum
   • ACRU: Acer rubrum
8. sap_wt: weight of sap collected (unit: kilogram / missing value: NA)

hf285-03: flowering data, whole tree

1. year: year of observation
2. tree_num: tree identification number
3. first_sex: first flower sex to mature on tree
   • F: female
   • M: male
   • NF: nonflowering
   • MO: male-only
4. flowering_intensity: qualitative evaluation of whole-tree flowering
   • low: generally <1,000 flowering buds
   • medium: generally 1,000-10,000 flowering buds
   • high: generally >10,000 flowering buds
   • none: no flowering buds

hf285-04: flowering data, twigs

1. date: data twig sample collected
2. tree: tree identification number
3. branch: branch identification code (A-I)
4. canopy_strata: location in the canopy (lower, middle, upper)
5. internode_year: age of main twig internode from which the focal twig/bud originated (unit: number / missing value: NA)
6. internode_num: when 2 terminal twigs (i.e. a bifurcation), identification code to differentiate the two
7. bud_num: bud identification number, ordered sequentially from terminal bud in
8. bud_pos: position of bud on twig - terminal, sub-terminal, side (S# indicates number of side bud pair from terminal)
   • T: terminal
   • ST: sub-terminal
9. num_male: count of male flowers in bud (unit: number / missing value: NA)
10. num_female: count of female flowers in bud (unit: number / missing value: NA)
11. num_unknown: count of flowers for which sex could not be determined (unit: number / missing value: NA)
12. leaves: whether or not leaves were present
    • Y: leaves present
    • N: leaves not present
13. num_leaves: number of leaves originating in bud (unit: number / missing value: NA)

hf285-05: spring branch growth

1. year: year of observation
2. tree: tree identification number
3. branch: branch identification code (A-I)
4. internode_year: age of main twig internode from which the focal twig/bud originated (unit: number / missing value: NA)
5. internode_num: when 2 terminal twigs (i.e. a bifurcation), identification code to differentiate the two
6. internode_length: length of main twig internode (unit: millimeter / missing value: NA)
7. num_buds: number of buds originating from that internode (unit: number / missing value: NA)

hf285-06: fall leaf and twig growth and samara production

1. date: data branches collected
2. tree: tree identification number
3. branch: branch identification code (A-I)
4. treatment: treatment
   • FL: flowering
   • NF: non-flowering
   • FR: flowers removed, 2013 only
5. internode_year: age of main twig internode from which the focal twig/bud originated (unit: number / missing value: NA)
6. internode_num: when 2 terminal twigs (i.e. a bifurcation), identification code to differentiate the two
7. internode_length: length of main twig internode (unit: millimeter / missing value: NA)
8. leaves: number of leaves on terminal twig (unit: number / missing value: NA)
9. leaves_missing: number of pedicel scars indicating missing leaves (unit: number / missing value: NA)
10. leaf_area: total leaf area measured using a LI-3100 (unit: squareCentimeters / missing value: NA)
11. num_samaras: number of samaras on terminal twig (unit: number / missing value: NA)

hf285-07: samara evaluation

1. year: year of observation
2. tree: tree identification number
3. branch: branch identification code (A-I)
4. num_filled: count of samaras with mature (or near-mature) seeds (unit: number / missing value: NA)
5. num_empty: count of empty samaras (no seeds) (unit: number / missing value: NA)
6. num_grub: count of samaras with grub present (likely had a seed that the grub ate; samara pair usually has frass) (unit: number / missing value: NA)
7. num_wrinkle: count of samaras with deformed seeds (likely still pollinated) (unit: number / missing value: NA)
8. num_small: count of samaras with small seeds (could be lumped with wrinkled) (unit: number / missing value: NA)
9. num_moldy: count of samaras that are moldy inside (likely because grub exited and frass colonized by mold) (unit: number / missing value: NA)
10. num_exit: count of samaras with evidence of weevils (frass, exit hole) but no weevil currently) (unit: number / missing value: NA)

hf285-08: samara evaluation, pollinator exclusion bag

1. year: year of observation
2. tree: tree identification number
3. branch: branch identification code (A-I)
4. treatment: treatment
   • control: open pollination
   • exclusion: pollinator exclusion bag installed during flowering
5. num_filled: count of samaras with mature (or near-mature) seeds (unit: number / missing value: NA)
6. num_empty: count of empty samaras (no seeds) (unit: number / missing value: NA)
7. num_grub: count of samaras with grub present (likely had a seed that the grub ate; samara pair usually has frass) (unit: number / missing value: NA)
8. num_wrinkle: count of samaras with deformed seeds (likely still pollinated) (unit: number / missing value: NA)
9. num_small: count of samaras with small seeds (could be lumped with wrinkled) (unit: number / missing value: NA)
10. num_moldy: count of samaras that are moldy inside (likely because grubl exited and frass colonized by mold) (unit: number / missing value: NA)
11. num_exit: count of samaras with evidence of weevils (frass, exit hole) but no weevil currently) (unit: number / missing value: NA)
12. num_missing: in 2012, seeds were collected in late September, and some samaras were missing (i.e. only one of a pair present) (unit: number / missing value: NA)

hf285-09: samara pairs count

1. tree: tree identification number
2. date: date counts occurred
3. ec_count: Elizabeth Crone's samara pairs count for the tree (unit: number / missing value: NA)
4. jr_count: Josh Rapp's samara pairs count for the tree (unit: number / missing value: NA)
5. total_count: EC and JR samara pairs counts added together (unit: number / missing value: NA)
6. note: note

hf285-10: leaf removal data

1. year: year of measurements
2. tree: tree identification number
3. branch: branch identification code (1-3)
4. treatment: treatment
   • control: control
   • leaf.removal: leaf removal
5. num_flowering: number of buds on twig without flowers (measured in spring) (unit: number / missing value: NA)
6. num_notflowering: number of buds on twig without flowers (measured in spring) (unit: number / missing value: NA)
7. num_buds_w_samaras: number of buds on twig with samaras (measured in fall) (unit: number / missing value: NA)
8. num_samaras: number of samaras on twig (measured in fall) (unit: number / missing value: NA)
9. num_petioles: number of samara petioles missing the samaras (measured in fall) (unit: number / missing value: NA)

hf285-11: leaf removal treatment, twig growth data

1. tree: tree identification number
2. branch: branch identification code (1-3)
3. treatment: treatment
   • control: control
   • leaf removal: leaf removal
4. growth_year: year of twig growth the length measurement corresponds to
5. internode_length: length of the twig internode (unit: millimeter / missing value: NA)

hf285-12: leaf and seed removal data

1. year: year of measurements
2. tree: tree identification number
3. branch: branch identification code (1-3)
4. treatment: treatment
   • control: control
   • leaf removal: leaf removal
   • seed removal: seed removal
5. num_flowering: number of buds on twig with flowers (measured in spring) (unit: number / missing value: NA)
6. num_notflowering: number of buds on twig without flowers (measured in spring) (unit: number / missing value: NA)
7. num_buds_w_samaras: number of buds on twig with samaras (measured in fall) (unit: number / missing value: NA)
8. num_samaras: number of samaras on twig (measured in fall) (unit: number / missing value: NA)
9. num_petioles: number of samara petioles missing the samaras (measured in fall) (unit: number / missing value: NA)

hf285-13: leaf and seed removal, branches data

1. tree: tree identification number
2. branch: branch identification code (1-3)
3. treatment: treatment
   • control: control
   • leaf removal: leaf removal
   • seed removal: seed removal
4. growth_year: year of twig growth the length measurement corresponds to
5. internode_length: length of the twig internode (unit: millimeter / missing value: NA)

hf285-14: branches data

1. year: year of measurements
2. tree: tree identification number
3. branch: branch identification code (A-C, new twigs to replace old twigs received new codes D-E)
4. num_flowering: number of buds on twig with flowers (measured in spring) (unit: number / missing value: NA)
5. num_notflowering: number of buds on twig without flowers (measured in spring) (unit: number / missing value: NA)
6. num_buds_w_samaras: number of buds on twig with samaras (measured in fall) (unit: number / missing value: NA)
7. num_samaras: number of samaras on twig (measured in fall) (unit: number / missing value: NA)
8. num_petioles: number of samara petioles missing the samaras (measured in fall) (unit: number / missing value: NA)