Abstract Detail



Physiology

Marquardt, Paula [1], Miranda, Brian [1], Telewski, Frank [2].

Climate-growth relationships of the Sky Island Ponderosae.

Background:  Dendrochronology plays a major role in the study of relationships between patterns of annual growth and the environmental factors influencing growth.  In the desert Southwestern United States, the climate is warm and semiarid with two rainy seasons – the summer monsoon and winter precipitation – and the variation in ring width is more dependent on precipitation than temperature.  The high elevation pine forests of Southeast Arizona consist predominantly of two partially sympatric species, the well characterized five-needle Pinus arizonica, and Pinus ponderosa var. brachyptera that exists as two morphotypes (three- and mixed-needle).
Methods: Reproductively mature trees of both species were selected for coring in natural stands where the two species coexist on two south facing slopes.  After crossdating and assigning the calendar year of formation for each tree ring, response function, moving window, and partial correlations were conducted to examine the climatic sensitivity of the two pine species, identify the environmental factors limiting to growth, and determine the temporal stability of growth-climate relationships.  Predictor variables were seasonal temperature, precipitation, and Palmer drought severity index (a cumulative measure of drought stress).
Results:  The response function analysis of P. ponderosa var. brachyptera [sampled on two sites near its lower (and drier) elevation limit] indicated that tree rings correlated strongly with spring precipitation.  In comparison, the annual growth of P. arizonica [sampled near its upper (and moister) elevation limit] correlated with spring precipitation at both sites, and to winter precipitation at the more mesic site.  Partial correlation analysis revealed that P. arizonica was sensitive to longer periods of drought than P. ponderosa var. brachyptera at the more mesic site only.  Interestingly, the two species were responding differently to water balance requirements.  Correlation analysis indicated that P. arizonica’s growth was limited by increased growing season moisture stress and temperature (+ PDSI, - TAVG; an indication of increased respiration) and P. ponderosa var. brachyptera was limited by increased winter respiration.
Conclusion: The seasonally cool and moist conditions of spring are favorable growth conditions for both species.  P. arizonica’s growth correlates also with winter precipitation, and to longer periods of drought than P. ponderosa var. brachyptera under mesic site conditions.  These findings suggest that the two species have different seasonal climate requirements and sensitivity to moisture stress at different temporal scales.  Data will also be presented on temporal stability in climate-growth relationships of the three different needle types.


1 - USDA Forest Service Northern Research Station, 5985 Hwy K, Rhinelander, WI, 54501, United States
2 - Michigan State University, Department of Plant Biology, East Lansing, , MI , 48824 , USA

Keywords:
dendroecology
drought stress
Pinaceae
response function
tree-ring.

Presentation Type: Oral Paper
Number:
Abstract ID:512
Candidate for Awards:None


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