Journal
ECOLOGY AND EVOLUTION
Volume 8, Issue 3, Pages 1655-1672Publisher
WILEY
DOI: 10.1002/ece3.3743
Keywords
functional ratio; Huber value; isohydricity; leaf area; stomatal conductance; xylem
Categories
Funding
- Fulbright-Ministerio de Ciencia e Innovacion
- Marie Curie FP7-PEOPLE-IE
- Marie Curie International Outgoing Fellowship [PIOF-GA-2009-253277]
- Columbia University's Center for Climate and Life
- Swiss State Secretariat for Education, Research and Innovation SERI [SBFI C14.0104]
- US Department of Energy, Office of Science
- Direct For Biological Sciences
- Div Of Biological Infrastructure [1401312] Funding Source: National Science Foundation
Ask authors/readers for more resources
In the southwestern USA, recent large-scale die-offs of conifers raise the question of their resilience and mortality under droughts. To date, little is known about the interannual structural response to droughts. We hypothesized that pinon pines (Pinus edulis) respond to drought by reducing the drop of leaf water potential in branches from year to year through needle morphological adjustments. We tested our hypothesis using a 7-year experiment in central New Mexico with three watering treatments (irrigated, normal, and rain exclusion). We analyzed how variation in evaporative structure (needle length, stomatal diameter, stomatal density, stomatal conductance) responded to watering treatment and interannual climate variability. We further analyzed annual functional adjustments by comparing yearly addition of needle area (LA) with yearly addition of sapwood area (SA) and distance to tip (d), defining the yearly ratios SA:LA and SA:LA/d. Needle length (l) increased with increasing winter and monsoon water supply, and showed more interannual variability when the soil was drier. Stomatal density increased with dryness, while stomatal diameter was reduced. As a result, anatomical maximal stomatal conductance was relatively invariant across treatments. SA:LA and SA:LA/d showed significant differences across treatments and contrary to our expectation were lower with reduced water input. Within average precipitation ranges, the response of these ratios to soil moisture was similar across treatments. However, when extreme soil drought was combined with high VPD, needle length, SA:LA and SA:LA/d became highly nonlinear, emphasizing the existence of a response threshold of combined high VPD and dry soil conditions. In new branch tissues, the response of annual functional ratios to water stress was immediate (same year) and does not attempt to reduce the drop of water potential. We suggest that unfavorable evaporative structural response to drought is compensated by dynamic stomatal control to maximize photosynthesis rates.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available