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  • Open Daily: 10am - 10pm
    Alley-side Pickup: 10am - 7pm

    3038 Hennepin Ave Minneapolis, MN
    612-822-4611

Open Daily: 10am - 10pm | Alley-side Pickup: 10am - 7pm
3038 Hennepin Ave Minneapolis, MN
612-822-4611
The Ecology and Evolution of Nitrogen Fixation and Nutrient Limitation at Multiple Time Scales.

The Ecology and Evolution of Nitrogen Fixation and Nutrient Limitation at Multiple Time Scales.

Menge, Duncan Nicholas Lubchenco

Paperback

Biology

Currently unavailable to order

ISBN10: 1243454776
ISBN13: 9781243454775
Publisher: Proquest Umi Dissertation Pub
Pages: 166
Weight: 0.75
Height: 0.43 Width: 7.99 Depth: 10.00
Language: English
In this thesis I use mathematical modeling and field-based studies to investigate two of the most intriguing patterns in ecosystem ecology: (i) The absence of symbiotic nitrogen (N) fixing trees in mature temperate/boreal forests despite sustained N limitation and (ii) N richness in tropical forests, where symbiotic N fixing plants are ubiquitous. Both patterns seem to be paradoxes: (i) Why do symbiotic N fixers not invade forests where soil N availability is low and N limits plant production? (ii) If the excess N in tropical forests comes from biological N fixation (BNF), why are N fixers fixing so much? The first chapter explains these patterns in more detail, discusses major findings of the following chapters, and speculates about their implications. The second chapter uses a model to show that (i) Nutrient limitation cannot be sustained at equilibrium unless nutrients are lost from a plant-inaccessible pool, but that (ii) Nutrient limitation can be sustained for centuries without these losses. The third chapter incorporates BNF and evolution into this model, finding that realistic tradeoffs between BNF and plant traits can select against N-limited N fixers. The fourth chapter presents BNF data from four sources along the 120,000-year Franz Josef soil chronosequence, finding that (i) The symbiotic plant Coriaria arborea fixed at the same rate at the 7 and 60 year old (y.o.) sites, but is excluded from the community thereafter, acting as a poorly-tuned negative feedback to soil N availability, whereas (ii) BNF from bryophytes acted as a positive feedback to soil N availability, likely due to the increased epiphytic surface area and increasingly moist sub-canopy conditions in fertile soils due to increased tree biomass. The fifth chapter uses a model to investigate how different symbiotic BNF strategies compete against each other and influence N losses, finding that (i) All else equal, facultative N fixers always outcompete obligate N fixers, and never produce large N losses, but that (ii) Costs of being facultative and time lags inherent to BNF can inhibit facultative N fixers and yield large N losses.

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