Short-term Recurring Drought Affects Growth and Photosynthetic Capacity of Four Conifer Species

Abstract

The Midwest and southern Great Plains are known for historic and severe droughts. More common, however, are short-term recurring drought events that can limit tree survival. The pressure of environmental stress combined with numerous diseases and pests are decimating existing Pinus L. spp. (pine) plantings and driving the effort to identify alternative species. Four species of conifer were subjected to recurring moderate or severe drought to observe the effects on growth and photosynthesis. Species evaluated were: Abies nordmanniana (Nordmann fir), Cupressus arizonica (Arizona cypress), Picea engelmannii (Engelmann spruce), and Thuja × ‘Green Giant’ (‘Green Giant’ arborvitae). Recurring drought reduced height and growth index of T. × ‘Green Giant’. However, photosynthesis and root growth were unaffected by drought treatments. In contrast, reduced Pnet was the only detectable effect of recurring drought in P. engelmannii. Growth of A. nordmanniana was not affected by drought. When subjected to drought, C. arizonica reduced shoot dry weight, while maintaining photosynthesis and root growth. Overall, C. arizonica was able to maintain growth of roots and shoots as well as maintain photosynthesis which may be an advantage in the harsh climate of the Midwest and southern Great Plains.