Abstract
Measurements of photosynthetic photon flux density (PPFD; global, diffuse, and direct: 400–700 nm) and red:far-red ratio (660:730 nm) were made above and below an understory of salal (Gaultheriashallon Pursh) within three western red cedar (Thujaplicata Donn)–western hemlock (Tsugaheterophylla (Raf.) Sarg.) stands on the northern end of Vancouver Island, British Columbia. These stands were chosen to represent a wide range of canopy closure and understory salal cover. The measurements were repeated under both clear and overcast sky conditions. Within each stand, the percent cover, height, number of stems per hectare, and leaf morphology of the salal were measured. As expected, there was a decrease in both the salal cover and in the global PPFD and red:far-red ratio measured directly above salal as the percent tree cover increased. Salal leaf thickness and specific leaf weight decreased, whereas its leaf area increased, as global PPFD and red:far-red ratio decreased. The results indicate that the minimum light requirement for salal survival is between 3.9 and 11.1 μmol•m −2 •s −1 (1.2 to 3.3% of global PPFD measured in an adjacent clearing) and 4.5 and 27.2 μmol•m −2 •s −1 (0.3 to 1.8% of global PPFD measured in the clearing) under overcast and clear sky conditions, respectively. The global PPFD and red:far-red ratio measured 30 cm above the forest floor (beneath the salal) did not vary widely among the three stands. At this level, global PPFD values were very low, ranging from 0.15 to 0.35% and 0.58 to 0.75% of the global PPFD measured in the clearing under clear and overcast sky conditions, respectively. Red:far-red ratios at the forest floor level varied from 0.13 to 0.25 and 0.40 to 0.58 under clear and overcast sky conditions, respectively. The silvicultural implications of the results are discussed.
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Claims 10
Claim · model-written summary
Salal cover and above salal PPFD and red:far red ratio declined with greater tree cover.
- Taxon
- salal
Gaultheria shallone0 - Outcome
- salal covere0
- Direction
- decreasee0
- Comparator
- percent tree covere0
Not reportedSetting
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“there was a decrease in both the salal cover and in the global PPFD and red:far-red ratio measured directly above salal as the percent tree cover increased”
Claim · model-written summary
Salal leaf thickness and specific leaf weight declined as light and red:far red ratio declined.
- Taxon
- SalalGaultheria shallone0
- Organ / stage
- leafe0
- Outcome
- leaf thickness and specific leaf weighte0
- Direction
- decreasede0
- Comparator
- global PPFD and red:far-red ratioe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Salal leaf thickness and specific leaf weight decreased, whereas its leaf area increased, as global PPFD and red:far-red ratio decreased”
Claim · model-written summary
Salal leaf area increased as light and red:far red ratio decreased.
- Taxon
- SalalGaultheria shallone0
- Organ / stage
- leafe0
- Outcome
- leaf areae0
- Direction
- increasede0
- Comparator
- global PPFD and red:far-red ratioe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Salal leaf thickness and specific leaf weight decreased, whereas its leaf area increased, as global PPFD and red:far-red ratio decreased”
Claim · model-written summary
Estimated minimum light for salal survival under overcast sky was 3.9 to 11.1 μmol per square meter per second.
- Taxon
- salalGaultheria shallone0
- Outcome
- minimum light requirement for salal survivale0
- Value
- 3.9 and 11.1 μmol•m −2 •s −1e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“minimum light requirement for salal survival is between 3.9 and 11.1 μmol•m −2 •s −1 (1.2 to 3.3% of global PPFD measured in an adjacent clearing)”
Claim · model-written summary
Estimated minimum light for salal survival under clear sky was 4.5 to 27.2 μmol per square meter per second.
Verbatim
e0“4.5 and 27.2 μmol•m −2 •s −1 (0.3 to 1.8% of global PPFD measured in the clearing) under overcast and clear sky conditions, respectively”
t0“Gaultheriashallon”
Claim · model-written summary
Beneath salal, global PPFD and red:far red ratio varied little among three stands.
- Taxon
- salalGaultheria shallone0
- Outcome
- global PPFD and red:far-red ratioe0
- Direction
- did not vary widelye0
- Value
- 30 cme0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The global PPFD and red:far-red ratio measured 30 cm above the forest floor (beneath the salal) did not vary widely among the three stands”
Claim · model-written summary
Forest floor PPFD ranged from 0.15 to 0.35% of clearing values under clear sky.
Verbatim
e0“ranging from 0.15 to 0.35% and 0.58 to 0.75% of the global PPFD measured in the clearing under clear and overcast sky conditions, respectively”
t0“Gaultheriashallon”
Claim · model-written summary
Forest floor PPFD ranged from 0.58 to 0.75% of clearing values under overcast sky.
Verbatim
e0“ranging from 0.15 to 0.35% and 0.58 to 0.75% of the global PPFD measured in the clearing under clear and overcast sky conditions, respectively”
t0“Gaultheriashallon”
Claim · model-written summary
Forest floor red:far red ratio ranged from 0.13 to 0.25 under clear skies.
Verbatim
e0“Red:far-red ratios at the forest floor level varied from 0.13 to 0.25 and 0.40 to 0.58 under clear and overcast sky conditions, respectively”
t0“Gaultheriashallon”
Claim · model-written summary
Forest floor red:far red ratio ranged from 0.40 to 0.58 under overcast skies.
Verbatim
e0“Red:far-red ratios at the forest floor level varied from 0.13 to 0.25 and 0.40 to 0.58 under clear and overcast sky conditions, respectively”
t0“Gaultheriashallon”