Competition and facilitation over space and time: can N-fixing species increase forest productivity?<br />Stephanie Yeleni...
What structures plant communities?<br />
Competition: Negative interactions between individuals due to the simultaneous use of resources such as light, water, or n...
Stress Gradient Hypothesis<br />The balance between competition and facilitation will change over environmental gradients<...
The balance between competition and facilitation will also change over the lives of the plants<br />Competition<br />Facil...
How does the relationship between competition and facilitation<br />change across environmental gradients and over time?<b...
+<br />= ?<br />
Potential for facilitation:<br />Many Douglas-fir forests are nitrogen limited<br />N accretion rates under red alder are ...
Potential for competition:<br />Alder has higher growth rates than Douglas-fir <br />Light limitation<br />Water limitatio...
Potential for change in net balance across environmental gradients:<br />N – limitation of Douglas-fir forests changes acr...
Potential for change in net balance over time:<br />Alder quickly overtops Douglas-fir, but then its growth rate slows dow...
This is important because:<br />Both species are valued for timber<br />Positive effects on various ecosystem services<br ...
QUESTIONS:<br />Question 1:  Does the NET outcome of competition and facilitation change across environmental gradients an...
0.5<br />0.5<br />1.0<br />1.0<br />0.6<br />0.4<br />0.6<br />0.6<br />= 1<br />= 1.2<br />
RA 4.4 × <br />taller than <br />DF<br />Cascade Head<br />RA 1.8 × <br />taller than <br />DF<br />HJ Andrews<br />RA 1.4...
Question 1:  Does the NET outcome of competition and facilitation change across environmental gradients and over time in m...
     Assess how quickly red alder can increase soil N 		cycling rates</li></li></ul><li>
microbes<br />NH4+<br />NO3-<br />
microbes<br />N-FIXER<br />litterfall rates<br />NH4+<br />NO3-<br />N mineralization rates<br />NNN4+<br />
Question 3:  How does competition between Douglas-fir and red alder change across environmental gradients and over time?<b...
WUE = A/gs ∝ δ13C<br />gs ∝ δ18O<br />
Douglas-fir resource limitation<br />LIMITING RESOURCE:<br />N : nitrogen<br />W: water<br />L: light<br />L<br />Stand  A...
Alder Doug Fir Proposal
Alder Doug Fir Proposal
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Alder Doug Fir Proposal

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Alder Doug Fir Proposal

  1. 1. Competition and facilitation over space and time: can N-fixing species increase forest productivity?<br />Stephanie Yelenik<br />Steve Perakis<br />Dave Hibbs<br />
  2. 2. What structures plant communities?<br />
  3. 3. Competition: Negative interactions between individuals due to the simultaneous use of resources such as light, water, or nutrients<br />Facilitation: Positive interactions between individuals<br />The balance between competition and facilitation determines net interactions between species<br />
  4. 4. Stress Gradient Hypothesis<br />The balance between competition and facilitation will change over environmental gradients<br />Competition<br />Facilitation<br />Low ←resourceavailability -> High<br />Low ←stress-> High<br />
  5. 5. The balance between competition and facilitation will also change over the lives of the plants<br />Competition<br />Facilitation<br />Plant Age<br />
  6. 6. How does the relationship between competition and facilitation<br />change across environmental gradients and over time?<br />
  7. 7. +<br />= ?<br />
  8. 8. Potential for facilitation:<br />Many Douglas-fir forests are nitrogen limited<br />N accretion rates under red alder are high<br /> (50-100 kg N/ ha yr)<br />NNN4+<br />NH4+<br />NO3-<br />
  9. 9. Potential for competition:<br />Alder has higher growth rates than Douglas-fir <br />Light limitation<br />Water limitation<br />red alder<br />Douglas-fir<br />
  10. 10. Potential for change in net balance across environmental gradients:<br />N – limitation of Douglas-fir forests changes across the Pacific Northwest<br />Baseline soil N levels heterogeneous <br />Water availability can drive alder N-fixation rates<br />Competition<br />Facilitation<br />Low ←soil N availability -> High<br />
  11. 11. Potential for change in net balance over time:<br />Alder quickly overtops Douglas-fir, but then its growth rate slows down<br />Soil N levels under alder will increase over the life of the stand<br />Competition<br />Facilitation<br />Plant Age<br />
  12. 12.
  13. 13. This is important because:<br />Both species are valued for timber<br />Positive effects on various ecosystem services<br />Overall production<br />Carbon sequestration<br />Biodiversity through trophic levels<br />Ecosystem nutrient retention<br />Would be of ecological and economic value to know where and when red alder/Douglas-fir mixtures are likely to increase yields<br />
  14. 14. QUESTIONS:<br />Question 1: Does the NET outcome of competition and facilitation change across environmental gradients and over time in mixed stands of red alder and Douglas-fir?<br />Question 2: How does the provision of alder-derived N to Douglas-fir (facilitation) change across environmental gradients and over time?<br />Question 3: How does competition between Douglas-fir and red alder change across environmental gradients and over time?<br />
  15. 15. 0.5<br />0.5<br />1.0<br />1.0<br />0.6<br />0.4<br />0.6<br />0.6<br />= 1<br />= 1.2<br />
  16. 16.
  17. 17. RA 4.4 × <br />taller than <br />DF<br />Cascade Head<br />RA 1.8 × <br />taller than <br />DF<br />HJ Andrews<br />RA 1.4 × <br />taller than <br />DF<br />RA 2.7 × <br />taller than <br />DF<br />Already evidence that species interactions shift across sites, and over time.<br />
  18. 18.
  19. 19. Question 1: Does the NET outcome of competition and facilitation change across environmental gradients and over time in mixed stands of red alder and Douglas-fir?<br /><ul><li> Resample plots for tree height and dbh</li></li></ul><li>Question 2: How does the provision of alder-derived N to Douglas-fir (facilitation) change across environmental gradients and over time?<br /><ul><li>Track alder-derived N into Douglas-fir and soils with stable isotopes
  20. 20. Assess how quickly red alder can increase soil N cycling rates</li></li></ul><li>
  21. 21. microbes<br />NH4+<br />NO3-<br />
  22. 22. microbes<br />N-FIXER<br />litterfall rates<br />NH4+<br />NO3-<br />N mineralization rates<br />NNN4+<br />
  23. 23. Question 3: How does competition between Douglas-fir and red alder change across environmental gradients and over time?<br /><ul><li>Use tree rings and carbon and oxygen isotopes to look at competition for light, water, and nitrogen over the life of the experiment</li></li></ul><li>Water use efficiency = [Carbon gained] per [Water lost]<br /> = [Photosynthesis] / [Stomatal conductance]<br /> = A/gs<br />WUE = A/gs ∝ δ13C<br />
  24. 24. WUE = A/gs ∝ δ13C<br />gs ∝ δ18O<br />
  25. 25.
  26. 26. Douglas-fir resource limitation<br />LIMITING RESOURCE:<br />N : nitrogen<br />W: water<br />L: light<br />L<br />Stand Age<br />L<br />SITE:<br />N<br />H.J. Andrews (lower N, W; higher L)<br />W<br />Cascade Head (higher N, W; lower L)<br />0 % <br />100% Red Alder<br />0 %<br />100% Douglas-fir<br />Soil N increases<br />Soil N increases<br /><ul><li> Resource limitation tells us when facilitation most likely to be </li></ul>important<br /><ul><li> Can relate tree growth in given years to resource limitation:</li></ul> When individuals show strong resource limitation, but do NOT show changes in growth, we expect to find a strong signal of alder-derived N (facilitation). <br />
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