Abstract
BACKGROUND AND AIMS: Plant species composition in wetlands and on lakeshores often shows dramatic zonation, which is frequently ascribed to differences in flooding tolerance. This study compared the growth responses to water depth of three species (Phormium tenax, Carex secta and Typha orientalis) differing in depth preferences in wetlands, using non-linear and quantile regression analyses to establish how flooding tolerance can explain field zonation. METHODOLOGY: Plants were established for 8 months in outdoor cultures in waterlogged soil without standing water, and then randomly allocated to water depths from 0 to 0.5 m. Morphological and growth responses to depth were followed for 54 days before harvest, and then analysed by repeated-measures analysis of covariance, and non-linear and quantile regression analysis (QRA), to compare flooding tolerances. PRINCIPAL RESULTS: Growth responses to depth differed between the three species, and were non-linear. Phormium tenax growth decreased rapidly in standing water >0.25 m depth, C. secta growth increased initially with depth but then decreased at depths >0.30 m, accompanied by increased shoot height and decreased shoot density, and T. orientalis was unaffected by the 0- to 0.50-m depth range. In P. tenax the decrease in growth was associated with a decrease in the number of leaves produced per ramet and in C. secta the effect of water depth was greatest for the tallest shoots. Allocation patterns were unaffected by depth. CONCLUSIONS: The responses are consistent with the principle that zonation in the field is primarily structured by competition in shallow water and by physiological flooding tolerance in deep water. Regression analyses, especially QRA, proved to be powerful tools in distinguishing genuine phenotypic responses to water depth from non-phenotypic variation due to size and developmental differences.
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Claims 12
Claim · model-written summary
Phormium tenax growth decreased rapidly in standing water deeper than 0.25 m.
- Taxon
- Phormium tenax
Phormium tenaxe0 - Treatment
- standing water >0.25 m depthe0
- Outcome
- growthe0
- Direction
- decreasede0
- Qualifier
- rapidlye0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Phormium tenax growth decreased rapidly in standing water >0.25 m depth”
Claim · model-written summary
Carex secta growth increased initially with depth.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“C. secta growth increased initially with depth but then decreased at depths >0.30 m, accompanied by increased shoot height and decreased shoot density”
Claim · model-written summary
Carex secta growth decreased at depths >0.30 m.
- Taxon
- C. secta
Carex sectae0
- Treatment
- depths >0.30 me0
- Outcome
- growthe0
- Direction
- decreasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“C. secta growth increased initially with depth but then decreased at depths >0.30 m, accompanied by increased shoot height and decreased shoot density”
Claim · model-written summary
Carex secta shoot height increased with water depths >0.30 m.
- Taxon
- C. secta
- Treatment
- depths >0.30 me0
- Outcome
- shoot heighte0
- Direction
- increasede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“C. secta growth increased initially with depth but then decreased at depths >0.30 m, accompanied by increased shoot height and decreased shoot density”
Claim · model-written summary
Carex secta shoot density decreased with water depths >0.30 m.
- Taxon
- C. secta
- Treatment
- depths >0.30 me0
- Outcome
- shoot densitye0
- Direction
- decreasede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“C. secta growth increased initially with depth but then decreased at depths >0.30 m, accompanied by increased shoot height and decreased shoot density”
Claim · model-written summary
Tenax-free growth of T. orientalis was unaffected across the 0- to 0.50-m depth range.
- Taxon
- T. orientalis
Typha orientalise1 - Treatment
- 0- to 0.50-m depth rangee1
- Outcome
- growthe2
- Direction
- unaffectede1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“T. orientalis was unaffected by the 0- to 0.50-m depth range”
e2“Growth responses to depth differed between the three species, and were non-linear”
Claim · model-written summary
In Phormium tenax the decrease in growth was associated with a decrease in the number of leaves produced per ramet.
- Taxon
- P. tenaxPhormium tenaxe3
- Organ / stage
- ramete3
- Outcome
- number of leaves produced per ramete3
- Direction
- decreasee3
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e3“In P. tenax the decrease in growth was associated with a decrease in the number of leaves produced per ramet”
Claim · model-written summary
In Carex secta the effect of water depth was greatest for the tallest shoots.
- Taxon
- C. secta
- Organ / stage
- tallest shootse7
- Outcome
- effect of water depthe7
- Direction
- greateste7
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e7“in C. secta the effect of water depth was greatest for the tallest shoots”
Claim · model-written summary
Allocation patterns were unaffected by water depth.
Not reportedComparator
Verbatim
t0“in three wetland plant species”
e4“Allocation patterns were unaffected by depth”
Claim · model-written summary
Quantile regression analysis distinguished genuine phenotypic responses to water depth from non-phenotypic variation.
Verbatim
t0“in three wetland plant species”
e5“Regression analyses, especially QRA, proved to be powerful tools in distinguishing genuine phenotypic responses to water depth from non-phenotypic variation due to size and developmental differences”
Claim · model-written summary
Zonation of wetland plants in the field is primarily structured by competition in shallow water and by physiological flooding tolerance in deep water.
Verbatim
t0“in three wetland plant species”
e6“zonation in the field is primarily structured by competition in shallow water and by physiological flooding tolerance in deep water”
Claim · model-written summary
Growth responses to depth differed between the three wetland plant species and were non-linear.
Verbatim
t0“in three wetland plant species”
e2“Growth responses to depth differed between the three species, and were non-linear”