Abstract
This study assessed intrinsic differences in tissue quality and growth rate among populations of Metrosideros polymorpha native to sites with a range of soil fertilities. We collected seedlings from three Hawaiian mesic forests that were either phosphorus-limited, nitrogen-limited, or relatively fertile. These individuals were grown in a common garden under a factorial high/low, N/P fertilization regime for 1.5years and then harvested to determine genetic divergence; aboveground growth rate; and lignin, N, and P concentrations in leaves and roots. Allozyme analyses indicated that the three groups had genetically diverged to some degree (genetic distance = 0.036-0.053 among populations). Relative growth rate did not differ significantly among the populations. Senescent leaves from the fertile-site population had the highest N concentrations (due to low N resorption) and had lower lignin concentrations than plants from the N-limited site. Across treatments, P concentrations in senescent leaves were highest in plants from the fertile and P-limited site. Root tissue quality did not generally differ significantly among populations. Since decomposition rate of senescent leaves in this system is related positively to N concentration and negatively to lignin concentration, senescent leaves from the fertile-site population may have a genetic tendency toward faster decay than the others. The intrinsic qualities of the three populations may provide positive feedbacks on nutrient cycling at each site-nutrient availability may be raised to some degree at the fertile site, and reduced at the N- or P-limited sites. Our results suggest that even a small degree of genetic differentiation among groups can influence traits related to nutrient cycling.
Highlights
The composition of plant communities has long been recognized as an important factor in nutrient dynamics (Jenny 1941, 1980), and much recent attention has been focused on the roles of different species or functional groups (e.g. Wedin and Tilman 1990; Hobbie 1992; Binkley 1995; Chapin et al 1997; Steltzer and Bowman 1998)
We examined intrinsic differences in plant populations from sites that varied in soil nutrient availability, and focused on traits that should feed back to affect nutrient cycling
Plant traits that vary among species and could potentially vary among populations include nitrogen (N), phosphorus (P), and lignin concentrations of plant tissue; nutrient resorption upon tissue senescence; relative growth rates; and allocation strategies (e.g. Grime 1977, 1979; Chapin 1980; Coley et al 1985; Chapin et al 1986, 1990, 1993; Chapin 1991)
Summary
The composition (i.e. genotypes) of plant communities has long been recognized as an important factor in nutrient dynamics (Jenny 1941, 1980), and much recent attention has been focused on the roles of different species or functional groups (e.g. Wedin and Tilman 1990; Hobbie 1992; Binkley 1995; Chapin et al 1997; Steltzer and Bowman 1998). Intrinsic differences in plant traits that could affect ecosystem processes (such as morphology, physiology, and allocation) occur among populations within species Plant traits that vary among species and could potentially vary among populations include nitrogen (N), phosphorus (P), and lignin concentrations of plant tissue; nutrient resorption upon tissue senescence; relative growth rates; and allocation strategies Grime 1977, 1979; Chapin 1980; Coley et al 1985; Chapin et al 1986, 1990, 1993; Chapin 1991) Each of these characteristics is known to affect nutrient dynamics through influences on tissue decomposition and/or ecosystem productivity
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