Abstract
The growth and mortality patterns of the clonal forb Urtica dioica were investigated at the level of the individual shoot in two growing seasons, 1991 and 1992, in a natural stand. Shoot height and diameter at ground level of each shoot tagged in spring were measured repeatedly five times during the growing season. Dry weights of these repeatedly measured shoots were estimated using an allometric relationship between dry weight, height and diameter of harvested shoots. A large decrease in shoot density occurred with stand development from the beginning of the growing season in both the years: (1) shoot survival rate was about 30% at the end of the growing season; (2) shoot mortality rate per 10 × 10 cm subplot between censuses was positively dependent on shoot density per subplot; (3) the mortality rate of individual shoots was negatively dependent on shoot size (height, diameter and weight) at each growing stage, suggesting one-sided competition between living and dying shoots; (4) shoot size (height, diameter and weight) variability in terms of the coefficient of variation and skewness decreased in accordance with shoot mortality. Symmetric competition between living shoots was detected by regression analysis based on a model for individual shoot growth considering the degree of competitive asymmetry. However, the competitive effect on individual shoot growth was very small (nearly absent). The mortality pattern of Urtica dioica indicates that shoot self-thinning occurred from the early growing stage as in non-clonal crowded monospecific stands, and contrasts with many clonal plants where shoot self-thinning rarely occurs or, if any, is confined only to a short period of the later growing stage. The pattern of growth and competition between living shoots of Urtica dioica contrasts with non-clonal crowded plants undergoing intense competition (usually asymmetric) between individuals, but is a common feature of many clonal plants where shoot competition is supposed to be reduced by 'physiological integration' between shoots. These form a new pattern not reported yet for clonal plants. It is pointed out that clonal plants show a wider spectrum of the growth, competition and mortality patterns of shoots than non-clonals. Some possible mechanisms for the pattern of Urtica dioica are discussed.Copyright 1995, 1999 Academic Press
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Claims 8
Claim · model-written summary
Shoot survival rate was about 30% at the end of the growing season.
- Taxon
- Urtica dioica
.jpg?width=60)
Urtica dioicat0 - Outcome
- shoot survival ratee0
- Value
- about 30%e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
.jpg?width=500)
Verbatim
t0“Urtica dioica”
e0“shoot survival rate was about 30% at the end of the growing season”
Claim · model-written summary
Shoot mortality rate between censuses was positively dependent on shoot density per subplot.
- Taxon
- Urtica dioicaUrtica dioicat0
- Treatment
- shoot density per subplote1
- Outcome
- shoot mortality ratee1
- Direction
- positively dependente1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Urtica dioica”
e1“shoot mortality rate per 10 × 10 cm subplot between censuses was positively dependent on shoot density per subplot”
Claim · model-written summary
The mortality rate of individual shoots was negatively dependent on shoot size.
- Taxon
- Urtica dioicaUrtica dioicat0
- Treatment
- shoot size (height, diameter and weight)e2
- Outcome
- mortality rate of individual shootse2
- Direction
- negatively dependente2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Urtica dioica”
e2“the mortality rate of individual shoots was negatively dependent on shoot size (height, diameter and weight) at each growing stage”
Claim · model-written summary
Shoot size variability decreased in accordance with shoot mortality.
- Taxon
- Urtica dioicaUrtica dioicat0
- Treatment
- shoot mortalitye3
- Outcome
- shoot size (height, diameter and weight) variabilitye3
- Direction
- decreasede3
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Urtica dioica”
e3“shoot size (height, diameter and weight) variability in terms of the coefficient of variation and skewness decreased in accordance with shoot mortality”
Claim · model-written summary
Symmetric competition between living shoots was detected.
- Taxon
- Urtica dioicaUrtica dioicat0
- Outcome
- Symmetric competition between living shootse4
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Urtica dioica”
e4“Symmetric competition between living shoots was detected by regression analysis based on a model for individual shoot growth considering the degree of competitive asymmetry”
Claim · model-written summary
The competitive effect on individual shoot growth was very small, nearly absent.
- Taxon
- Urtica dioicaUrtica dioicat0
- Outcome
- competitive effect on individual shoot growthe5
- Qualifier
- very small (nearly absent)e5
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Urtica dioica”
e5“However, the competitive effect on individual shoot growth was very small (nearly absent)”
Claim · model-written summary
Shoot self-thinning occurred from the early growing stage, as in non-clonal crowded monospecific stands.
- Taxon
- Urtica dioicaUrtica dioicat0
- Organ / stage
- early growing stagee6
- Outcome
- shoot self-thinninge6
- Qualifier
- as in non-clonal crowded monospecific standse6
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Urtica dioica”
e6“shoot self-thinning occurred from the early growing stage as in non-clonal crowded monospecific stands”
Claim · model-written summary
Shoot density showed a large decrease with stand development in both years.
- Taxon
- Urtica dioicaUrtica dioicat0
- Outcome
- shoot densitye7
- Qualifier
- A large decreasee7
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Urtica dioica”
e7“A large decrease in shoot density occurred with stand development”