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Plant growth - stoichiometry and competition

theory development in ecosystem ecology

Knecht Billberger, Magnus (2006). Plant growth - stoichiometry and competition. Diss. (sammanfattning/summary) Uppsala : Sveriges lantbruksuniv., Acta Universitatis Agriculturae Sueciae, 1652-6880 ; 2006:24
ISBN 91-576-7073-0
[Doctoral thesis]

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In four different studies, this thesis addresses issues concerning plant nutrition and growth from a theoretical perspective. Terrestrial plants require nutrients, water, light and space for their existence. All of these resources may be limiting for growth, however in this thesis the main focus is on the nutrients. The first paper is part of an environmental impact assessment on introducing logdepole pine (pinus contorta) as a replacement for the domestic Scots pine (pinus sylvestris) in Swedish forests. The long-term development of carbon and nutrient pools was simulated in a mathematical model. Higher yield of P. contorta meant higher acidification of the soil. Lower decomposability of P. contorta litter had minor impact on the soil carbon pool after one rotation, but lead to significantly larger storage at steady state. The subject of paper II was plant nutrient ratios. Lab experiments have suggested that nutrients are required in similar proportions for a number of species. We wanted to know if the same proportions could be detected also in the field. We first made the assumption that nitrogen is either limiting growth or when available in larger amounts, only taken up moderately in excess of requirements for growth. Then we found that nutrient ratios determined from field data corresponded well to the optimum ratios determined in the lab. In paper III we addressed the competitive exclusion principle, which predicts that for plants occupying the same niche and competing for a single limiting nutrient, the stronger competitor will outcompete all the others. The competitive exclusion relies on the assumption that growth is proportional to biomass. However, growth is commonly assumed proportional to the concentration of the limiting nutrient. We showed that it is highly unlikely that potential nutrient uptake increases proportionally to plant biomass, but rather at a slower rate. When this scaling relation is included in a competition model, plants are allowed to coexist without niche separation. Finally, in paper IV, feedback of carbon was added to plant nitrogen and phosphorus relations in an ecosystem model. For nutrient acquirement, plant carbon can be invested in roots, be exchanged for nutrients in the symbiotic relation with myccorhiza or exudated, where the exudates stimulate nutrient availability in different ways. We suggest that the plant partly can direct this carbon investment to the nutrient most limiting growth. We also suggest that a smaller fraction of available carbon is invested as nutrient availabilities increase. The model then predicts 1) The plant nutrient ratio partly reflects availabilities and partly plant requirements. 2) When co-limited by N and P, plant growth will increase at increased availability of either of these, because a larger fraction of carbon can be directed for uptake of the more limiting nutrient.

Authors/Creators:Knecht Billberger, Magnus
Title:Plant growth - stoichiometry and competition
Subtitle:theory development in ecosystem ecology
Series Name/Journal:Acta Universitatis Agriculturae Sueciae
Year of publishing :March 2006
Number of Pages:20
ALLI. Ågren G I, Knecht M F. 2001. Simulation of soil carbon and nutrient development under Pinus sylvestris and Pinus contorta. Forest Ecology and Management 141, 117-129. II. Knecht M F, Göransson A. 2004. Terrestrial plants require nutrients in similar proportions. Tree Physiology 24. 447-460. III. Billberger M F K, Ågren G I. 2005. Allometric constraints on nutrient uptake in an ecosystem model allow plants to coexist without niche separation. (Submitted to Oikos) IV. Billberger M F K, Wetterstedt J Å M, Ågren G I. 2006. Coupling limitations from energy and nutrients on plant growth. (Manuscript).
Place of Publication:Uppsala
ISBN for printed version:91-576-7073-0
Publication Type:Doctoral thesis
Full Text Status:Public
Agris subject categories.:F Plant production > F40 Plant ecology
Subjects:Not in use, please see Agris categories
Agrovoc terms:plant nutrition, nitrogen, plant soil relations, forest soils, carbon, mathematical models, sweden
Keywords:nutrient ratios, optimum nutrition, ecosystem ecology, competition, coexistence, ecosystem modelling
Permanent URL:
ID Code:1059
Department:(NL, NJ) > Department of Ecology and Environmental Research (until 20061231)
Deposited By: Magnus Billberger
Deposited On:13 Mar 2006 00:00
Metadata Last Modified:02 Dec 2014 10:09

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