Abstract
Young trees 0.03-1.7 m high of three coexisting Betula species were investigated in four sites of varying soil fertility, but all in full daylight, to separate nutrient and plant size controls on leaf dry mass per unit area (MA), light-saturated foliar photosynthetic electron transport rate (J) and the fraction of plant biomass in foliage (F(L)). Because the site effect was generally non-significant in the analyses of variance with foliar nitrogen content per unit dry mass (N(M)) as a covariate, N(M) was used as an explaining variable of leaf structural and physiological characteristics. Average leaf area (S) and dry mass per leaf scaled positively with N(M) and total tree height (H) in all species. Leaf dry mass per unit area also increased with increasing H, but decreased with increasing N(M), whereas the effects were species-specific. Increases in plant size led to a lower and increases in N(M) to a greater FL and total plant foliar area per unit plant biomass (LAR). Thus, the self-shading probably increased with increasing N(M) and decreased with increasing H. Nevertheless, the whole-plant average M(A), as well as M(A) values of topmost fully exposed leaves, correlated with N(M) and H in a similar manner, indicating that scaling of MA with N(M) and H did not necessarily result from the modified degree of within-plant shading. The rate of photosynthetic electron transport per unit dry mass (J(M)) scaled positively with N(M), but decreased with increasing H and M(A). Thus, increases in M(A) with tree height and decreasing nitrogen content not only resulted in a lower plant foliar area (LAR = F(L)/M(A)), but also led to lower physiological activity of unit foliar biomass. The leaf parameters (J(M), N(M) and M(A)) varied threefold, but the whole-plant characteristic FL varied 20-fold and LAR 30-fold, indicating that the biomass allocation was more plastically adjusted to different plant internal nitrogen contents and to tree height than the foliar variables. Our results demonstrate that: (1) tree height and N(M) may independently control foliar structure and physiology, and have an even greater impact on biomass allocation; and (2) the modified within-plant light availabilities alone do not explain the observed patterns. Although there were interspecific differences with respect to the statistical significance of the relationships, all species generally fit common regressions. However, these differences were consistent, and suggested that more competitive species with inherently larger growth rates also more plastically respond to N and H.
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Claims 12
Claim · model-written summary
Leaf area and dry mass per leaf increased with foliar nitrogen and tree height in all three Betula species.
- Organ / stage
- leafe0
- Outcome
- Average leaf area (S) and dry mass per leafe0
- Direction
- scaled positivelye0
- Qualifier
- in all speciese0
BetulaOrganisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Average leaf area (S) and dry mass per leaf scaled positively with N(M) and total tree height (H) in all species”
t0“Three Betula Species”
Claim · model-written summary
Leaf dry mass per area increased with tree height.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Leaf dry mass per unit area also increased with increasing H”
t0“Betula Species”
Claim · model-written summary
Leaf dry mass per area decreased with foliar nitrogen.
- Organ / stage
- Leafe0
- Outcome
- Leaf dry mass per unit areae0
- Direction
- decreasede0
- Qualifier
- increasing N(M)e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Leaf dry mass per unit area also increased with increasing H, but decreased with increasing N(M)”
t0“Betula Species”
Claim · model-written summary
Larger plants had lower foliage biomass fraction and foliar area per plant biomass.
- Outcome
- FL and total plant foliar area per unit plant biomass (LAR)e0
- Direction
- lowere0
- Qualifier
- Increases in plant sizee0
Not reportedOrgan / stage
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Increases in plant size led to a lower and increases in N(M) to a greater FL and total plant foliar area per unit plant biomass (LAR)”
t0“Betula Species”
Claim · model-written summary
Greater foliar nitrogen was associated with greater foliage biomass fraction and foliar area per plant biomass.
- Outcome
- FL and total plant foliar area per unit plant biomass (LAR)e0
- Direction
- greatere0
- Qualifier
- increases in N(M)e0
Not reportedOrgan / stage
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“increases in N(M) to a greater FL and total plant foliar area per unit plant biomass (LAR)”
t0“Betula Species”
Claim · model-written summary
Whole plant and exposed leaf M(A) correlated similarly with nitrogen and height.
- Organ / stage
- leavese0
- Outcome
- whole-plant average M(A), as well as M(A) values of topmost fully exposed leavese0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the whole-plant average M(A), as well as M(A) values of topmost fully exposed leaves, correlated with N(M) and H in a similar manner”
t0“Betula Species”
Claim · model-written summary
Electron transport per dry mass rose with foliar nitrogen.
- Outcome
- rate of photosynthetic electron transport per unit dry mass (J(M))e0
- Direction
- scaled positivelye0
- Qualifier
- N(M)e0
Not reportedOrgan / stage
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The rate of photosynthetic electron transport per unit dry mass (J(M)) scaled positively with N(M)”
t0“Betula Species”
Claim · model-written summary
Electron transport per dry mass decreased as height and leaf mass per area increased.
- Outcome
- rate of photosynthetic electron transport per unit dry mass (J(M))e1
- Direction
- decreasede0
- Qualifier
- increasing H and M(A)e0
Not reportedOrgan / stage
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“but decreased with increasing H and M(A)”
e1“The rate of photosynthetic electron transport per unit dry mass (J(M))”
t0“Betula Species”
Claim · model-written summary
Leaf traits varied threefold, while foliage fraction varied 20-fold and leaf area ratio 30-fold.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The leaf parameters (J(M), N(M) and M(A)) varied threefold, but the whole-plant characteristic FL varied 20-fold and LAR 30-fold”
t0“Betula Species”
Claim · model-written summary
The foliage biomass fraction varied 20-fold.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“whole-plant characteristic FL varied 20-fold”
t0“Betula Species”
Claim · model-written summary
Leaf area ratio varied 30-fold.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“LAR 30-fold”
t0“Betula Species”
Claim · model-written summary
Interspecific differences in relationship significance were consistent and suggested faster growing species respond more plastically to nitrogen and height.
- Outcome
- more plastically respond to N and He0
- Qualifier
- more competitive species with inherently larger growth ratese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“these differences were consistent, and suggested that more competitive species with inherently larger growth rates also more plastically respond to N and H”
t0“Betula Species”