Growth sensitivity to drought of co-occurring Pinus Spp. along an elevation gradient in northern Mexico

Bickford, Isaac N. and Fule, Peter Z. and Kolb, Thomas E. (2011) Growth sensitivity to drought of co-occurring Pinus Spp. along an elevation gradient in northern Mexico. Western North American Naturalist, 71 (3). pp. 338-348. ISSN 1944-8341

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Abstract

Climate change is predicted to increase the frequency of severe drought, yet little information exists on the impacts of drought on dominant trees of Mexican pine forests, which are among the most biologically diverse forests in the world. We conducted the first comparison of growth sensitivity to drought of two co-occurring Pious species in Mexico to understand whether growth of dominant pines of the Sierra Madre Occidental in northern Mexico is sensitive to drought and temperature variation and to understand how sensitivity differs between tree species and elevations. We sampled and analyzed tree-ring data across a 400-m elevation gradient for the years 1945-2004 for co-occurring Pinus engelmannii and Pious lumholtzii at Basaseachi National Park, Chihuahua, Mexico. We hypothesized that growth sensitivity to drought would be highest at low elevations, annual basal area increment (BAI) would be lowest at low elevations, and winter precipitation would covary positively with BAI at all elevations. Growth sensitivity to drought, as measured by a wet-dry ring-width index ratio (W:D), was significantly higher for both species at low elevations (W:D range 2.2-2.8) than at intermediate and high elevations (W:D range 1.5-1.9). Pious engelmannii had significantly higher W:D (2.2) than P. lumholtzii (1.8). Annual BAI did not differ between elevations or species. Annual ring width index was positively and significantly associated with winter (December April) precipitation. This association was stronger at low elevations than at high elevations. Other seasons of precipitation and other climatic variables were not significantly associated with annual growth. Our results suggest that the increasing frequency and severity of drought predicted for this region in the coming decades will reduce growth of P. engelmannii and P lumholtzii, with greater impacts on low-elevation populations and on P engelmannii.

Item Type:	Article
ID number or DOI:	10.3398/064.071.0302
Keywords:	Climate change; drought; pine trees; temperature variation; lower precipitation; adaptation; plant growth
Subjects:	S Agriculture > SD Forestry
NAU Depositing Author Academic Status:	Faculty/Staff
Department/Unit:	College of Engineering, Forestry, and Natural Science > School of Forestry
Date Deposited:	16 Oct 2015 21:55
URI:	http://openknowledge.nau.edu/id/eprint/1379

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