Nitrogen Fixation


Part III. Ecology of nitrogen fixation


(Note: If you click on any of the pictures displayed on this page, you will be shown a larger, higher-quality version of the same image.)


Figures 1-5.

The first 5 figures are a series demonstrating the beneficial effects of interplanting N-fixing red alder and Douglas-fir in a temperate rain forest in SW Washington state. The U.S. Forest service planted seedlings of both trees around 1930 following a devastating wildfire. The alder-fir mixture was limited to a narrow strip intended to serve as a fire break. By the time these photos were taken (1990's) the alder had been almost entirely overtopped and replaced by the Douglas-fir, but the N contributed by the alder through the years continues to have very profound effects on promoting the growth of the Douglas-fir.


Figure 1. Aerial view showing a prominent green strip where the Douglas-fir has been interplanted with alder.


Figure 2. The arrows indicate a landscape view of the taller trees in the narrow strip (arrows) where alder was interplanted.


Figure 3. Typical view of Douglas-fir foliage from the alder interplanting zone (right) compared to foliage from an area immediately outside the interplanting.


Figure 4. General view of tree size (Douglas-fir) of stand that developed with alder interplanting.


Figure 5. General view of tree size (Douglas-fir) of stand that developed in an area immediately outside the interplanting.


Figure 6. Interplanting of Erythrina, a leguminous tree, in a coffee plantation in the central highlands of Costa Rica. The tree provides shade as well as beneficial N for the coffee crop.


Photo Credits
Figures 1, 2U.S. Forest Service
Figures 3, 4, 5, 6David Dalton, Reed College



Index

Nitrogen Fixation Home Page

Part I. The range of organisms that can fix nitrogen

Part II. Physiology and anatomy of nitrogen fixation

Part III. Ecology of nitrogen fixation


This page was created for David Dalton, a faculty member in the Biology Department at Reed College.

Questions or comments? Send e-mail to: david.dalton@reed.edu
Created 31July 97. Last modified 13 Aug 97.
Copyright ©1997 David Dalton