Differences in early seasonal growth efficiency and productivity of eucalyptus genotypes

Abstract

Understanding the changes in early growth efficiency (GE, growth/leaf area) may improve forest production through the selection of appropriate genotypes at early stages. We investigated different early growth responses of genotypes of Eucalyptus globulus (7), E. nitens (3), and E. nitens × E globulus (E. gloni) (7) in south-central Chile. To evaluate seasonal growth, plants of each genotype were established in a completely randomized block design in coarse sandy soil (i.e., low water holding capacity), with spring and summer irrigation. The current monthly increment (CMI) in wood volume (cm 3 tree −1 month −1 ), and leaf area index (LAI, m 2 m −2 ) were used to calculate GE at 4.1, 7.5, 10.4, 13.4, and 15.4 months of age, corresponding to five growing seasons (first summer, fall, winter, spring, and second summer). The interaction between genotype and season had a significant effect (p < 0.001) on LAI and GE, but not on CMI. In general, CMI values declined in winter, but increased greatly in the second summer. LAI values were stable during the first three seasons, increased in spring, and peaked in the second summer. During all seasons, a significant (p < 0.001) relationship between growth and LAI was observed, with differences in model coefficients among taxa. The highest GEs were observed mainly for E. globulus, which grew with small changes in the LAI. In general, our findings showed that eucalyptus genotypes with higher annual GEs presented higher seasonal GEs, except for some E. globulus genotypes. Changes in seasonal GEs among genotypes suggest that the same environment drives a significant response in the early growth stage as a consequence of climate influences on carbon allocation among different eucalyptus genotypes.

Water and Temperature Ecophysiological Challenges of Forests Plantations under Climate Change

“…The growth response to water stress over time and its genetic variation in Eucalytpus genotypes has been analyzed using the water stress integral concept [79,80] (Figure 3). Low productivity varieties showing higher levels of accumulated stress response over time may represent the responses of sensitive species to seasonal water stress (Figure 3a) [81]. For example, Waghorn et al [82], researching juvenile Pinus radiata, concluded that lateseason drought (higher WSI levels) is more detrimental to diameter growth and biomass accumulation compared to early-season drought (Figure 3b).…”

“…time may represent the responses of sensitive species to seasonal water stress (Figure 3a) [81]. For example, Waghorn et al [82], researching juvenile Pinus radiata, concluded that late-season drought (higher WSI levels) is more detrimental to diameter growth and biomass accumulation compared to early-season drought (Figure 3b).…”

“…Considering the relevance and caution of sustaining forest biodiversity, robust scientific studies have shown the importance of considering fast-growing forest plantations to reach high C sequestration rates, and at the same time, the importance of maintaining long-term large C stocks accumulated over decades or centuries by old and natural forests. From a soil carbon sequestration point of view, and in particular considering degraded or low fertility soils with agricultural abandonment, plantations with fast-growing species undoubtedly show faster and larger positive effects on soil C sequestration and stocks [81,119]. The C sequestration potential of a given soil depends strongly on belowground biomass growth and decay, up until reaching a physical maximum potential of organic matter accumulation associated with soil porosity.…”