Variation in whole-rotation yield among Eucalyptus genotypes in response to water and heat stresses: The TECHS project

Made available in DSpace on 2020-12-12T01:16:20Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-04-15 Colorado State University North Carolina State University Universidade Federal de Lavras Universidade Federal do Rio Grande do Norte U.S. Forest Service Universidade de São Paulo The TECHS project spanned a 3500 km gradient from the Amazon to Uruguay, examining the influence of stresses from temperature and water supply on clonal plantations of Eucalyptus, with and without rain reduction, and across a stocking gradient. The whole-rotation mean annual increment (MAI) showed a humped pattern in relation to temperature, rising from about 18 Mg ha−1 yr−1 of stemwood production when mean annual temperatures were near 16 °C, to 27 Mg ha−1 yr−1 at 20 °C, and then falling to less than 15 Mg ha−1 yr−1 above 24 °C. The age trend in growth showed a steeper initial rise in the warmer tropical sites (reaching a peak current annual increment, CAI, of 27 Mg ha−1 yr−1, at age 2–3 years), but the slower early growth in the cooler subtropical sites had a higher peak (CAI of 32 Mg ha−1 yr−1, at 4 years) and slower decline, giving 15% higher MAI for the cooler region. Whole-rotation MAI declined by about 2.2 Mg ha−1 yr−1 for each 1 °C increase in temperature (in the range between 19.5 and 23.5 °C), and MAI declined by 0.5 Mg ha−1 yr−1 for each 100 mm yr−1 decline in rain. The effect of reducing ambient rain was also a loss of 0.5 Mg ha−1 yr−1 for each 100 mm yr−1 reduction in rain, though the effect was small on low productivity sites (