Effect of Water Availability on Radial and Height Growth of Nothofagus pumilio

Soil water availability is one of the most relevant environmental factors for plant growth. For Nothofagus pumilio , the most widely distributed temperate tree in the southern hemisphere, the effects of soil water availability on radial and height growth were analyzed by means of an open‐air nursery experiment. In the present study, 5‐year‐old saplings growing under nursery field conditions were assigned to three irrigation treatments: no irrigation, intermediate irrigation, and high irrigation. The irrigation treatments were aimed at emulating three levels of rainfall —dry, mesic, and wet—occurring within the natural distribution of N. pumilio in north‐western Patagonia. Increased water availability resulted in longer shoots with more internodes and taller plants with wider trunks. Also, higher soil moisture availability extended the period of trunk diameter growth. Although the growth of N. pumilio stands is strongly controlled by light availability, this study shows that microenvironmental differences in soil water induce differences in the length and diameter of the trunk. The effect of water availability would be more pronounced during the driest season of the year.