Seasonal variations of leaf traits and drought adaptation strategies of four common woody species in South Texas, USA

Understanding physiological responses and drought adaptation strategies of woody plant leaf traits in sub-humid to semi-arid regions is of vital importance to understand the interplay between ecological processes and plant resource-allocation strategies of different tree species.Seasonal variations of leaf morphological traits, stoichiometric traits and their relationships of two drought tolerant woody species, live oak(Quercus virginiana) and honey mesquite(Prosopis glandulosa) and two less drought tolerant species, sugarberry(Celtis laevigata) and white ash(Fraxinus americana) were analyzed in a sub-humid to semi-arid area of south Texas, USA. Our findings demonstrate that for the two drought tolerant species, the leguminous P. glandulosa had the highest specific leaf area,leaf N, P, and lowest leaf area and dry mass, indicating that P. glandulosa adapts to an arid habitat by decreasing leaf area, thus reducing water loss, reflecting a resource acquisition strategy. While the evergreen species Q. virginiana exhibited higher leaf dry mass, leaf dry matter content, C content, C:N, C:P and N:P ratios, adapts to an arid habitat through increased leaf thickness and thus reduced water loss, reflecting a resource conservation strategy in south Texas. For the two less drought tolerant deciduous species, the variations of leaf traits in C. laevigata and F. americana varied between Q. virginiana and P.glandulosa, reflecting a trade-off between rapid plant growth and nutrient maintenance in a semi-arid environment.