Abstract
Summary Interspecific variation in leaf life span of woody plants should have important consequences for ontogenetic variation in biomass distribution, and hence carbon balance, in low light. This proposal was examined by measuring foliage turnover, growth, biomass allocation and biomass distribution of juveniles (25–1180 mm tall) of four evergreens differing in shade tolerance, growing in low light (2–5% canopy openness) in temperate rainforest understoreys in south‐central Chile. As predicted, ontogenetic trends in leaf area ratio (LAR) of two very shade‐tolerant species with long‐lived leaves ( Aextoxicon punctatum and Myrceugenia planipes ) contrasted strongly with those of mid‐tolerant Eucryphia cordifolia and intolerant Aristotelia chilensis . Low‐light LAR fell rapidly with increasing plant size in Eucryphia and Aristotelia , but was size‐invariant in the two shade‐tolerant taxa. As a result, although small seedlings of Eucryphia and Aristotelia displayed more leaf area than shade‐tolerant seedlings of similar size (largely because of differences in specific leaf area), this relationship was reversed for plants over ≈500 mm tall. Although the slower foliage turnover of the shade‐tolerant species at least partly explains this reversal, allocational differences may also be involved. Root mass fraction of both shade‐tolerant species was significantly negatively correlated with size, possibly reflecting declining allocation to roots in larger plants. In contrast, root mass fraction was not correlated with size in Eucryphia or Aristotelia . Above‐ground relative growth rate in low light followed similar ontogenetic trends to LAR, declining more quickly in light‐demanding species than in shade‐tolerant associates. As a result, large seedlings (>400 mm tall) of shade‐tolerant Myrceugenia and Aextoxicon grew more quickly than their light‐demanding associates at the same height. The steeply declining LAR and growth of Eucryphia and Aristotelia suggest that these taxa will eventually die of energy starvation in low light. Results are consistent with the idea that accumulation of an extensive leaf area eventually gives juvenile shade‐tolerant evergreens a net carbon gain advantage over their light‐demanding associates in low light. Awareness of long‐term ontogenetic trends will enhance understanding of relationships of shade‐tolerance variation with morphology and growth of woody evergreens.
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Claims 7
Claim · model-written summary
Leaf area ratio declined with size in Eucryphia and Aristotelia but remained size-invariant in two shade-tolerant taxa.
- Taxon
- Eucryphia and Aristotelia
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Eucryphia
Aristoteliae0 - Organ / stage
- plant sizee0
- Outcome
- LARe0
- Direction
- fell rapidlye0
- Comparator
- the two shade‐tolerant taxae0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
.jpg?width=500)
Verbatim
e0“Low‐light LAR fell rapidly with increasing plant size in Eucryphia and Aristotelia , but was size‐invariant in the two shade‐tolerant taxa.”
Claim · model-written summary
Small Eucryphia and Aristotelia seedlings had more leaf area than equally sized shade-tolerant seedlings.
- Taxon
- Eucryphia and AristoteliaEucryphiaAristoteliae0
- Outcome
- leaf areae0
- Direction
- moree0
- Comparator
- shade‐tolerant seedlings of similar sizee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“small seedlings of Eucryphia and Aristotelia displayed more leaf area than shade‐tolerant seedlings of similar size”
Claim · model-written summary
Above roughly 500 mm, shade-tolerant species had more leaf area than Eucryphia and Aristotelia.
Verbatim
e0“this relationship was reversed for plants over ≈500 mm tall.”
t0“juvenile temperate evergreens”
Claim · model-written summary
Root mass fraction declined significantly with size in both shade-tolerant species.
Verbatim
e0“Root mass fraction of both shade‐tolerant species was significantly negatively correlated with size”
Claim · model-written summary
Root mass fraction was unrelated to size in Eucryphia or Aristotelia.
- Taxon
- Eucryphia or AristoteliaEucryphiaAristoteliae0
- Organ / stage
- sizee0
- Outcome
- root mass fractione0
- Direction
- not correlatede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“root mass fraction was not correlated with size in Eucryphia or Aristotelia”
Claim · model-written summary
Low-light above-ground relative growth rate declined more rapidly with size in light-demanding than shade-tolerant species.
Verbatim
e0“Above‐ground relative growth rate in low light followed similar ontogenetic trends to LAR, declining more quickly in light‐demanding species than in shade‐tolerant associates.”
Claim · model-written summary
Large Myrceugenia and Aextoxicon seedlings grew faster than light-demanding associates at equal height.
- Taxon
- Myrceugenia and AextoxiconAextoxicon
Myrceugeniae0 - Outcome
- grew more quicklye0
- Direction
- more quicklye0
- Value
- >400 mme0
- Comparator
- light‐demanding associatese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“large seedlings (>400 mm tall) of shade‐tolerant Myrceugenia and Aextoxicon grew more quickly than their light‐demanding associates at the same height.”