Effect of artificially simulated moisture regimes on growth attributes of different Eucalyptus clones in sub-tropics of north-western India

Eucalyptus clones respond differentially under variable moisture regimes with considerable differences in net primary production due to changed rates of photosynthesis which eventually influence plant growth attributes due to change in stomatal conductance and transpiration rate. We studied the growth attributes of five different Eucalyptus clones (PE-17, C-2045, PE-11, PE-1 and C-413) in response to varying moisture regimes viz. optimal (100% Cumulative Pan Evaporation; CPE100), sub-optimal (75% CPE; CPE75) and super-optimal (125 and 150% CPE; CPE125/150). Plant establishment under CPE100 resulted in significantly (p < 0.05) higher plant height (by ~ 8.9%), collar diameter (by ~ 9.3%) and number of branches plant−1 (by ~ 63.6%) at 90 days after their establishment, compared with those established under CPE75. Conversely, there was a non-significant (p < 0.05) difference in number of roots plant−1 as well as root length of Eucalyptus clones at 120 days after establishment under CPE75 and CPE100. However, these root growth attributes were significantly decreased under super-optimal moisture (CPE125-150; by ~ 30.2 to 37.5% for number of roots plant−1 and ~ 15.0 to 17.6% for root length) as compared to those under optimal moisture regime (CPE100). Regardless of the moisture regimes, PE-1 clone has significantly higher collar diameter, number of branches/roots plant−1, and dry branches + leaves and roots biomass, compared with other clones. The CPE100 helped increase the net primary production significantly in different components viz. dry biomass of branches + leaves (by ~ 25.1%), stems (by ~ 24.1%) and roots (by ~ 32.2%), compared with CPE75. The branches + leaves biomass of Eucalyptus was significantly related to the stems biomass (0.9096**; p < 0.01). The rate of photosynthesis was significantly decreased by ~ 56.6 to 80.6% under super-optimal (CPE125-150), compared with under optimal (CPE100) moisture regime. Similarly, the stomatal conductance was decreased by ~ 46.5 to 71.8% under CPE125–150 than CPW100. The stomatal conductance increased with increased rates of photosynthetic activity (R2 = 0.888), regardless of the clone and moisture regime. The transpiration rate of Eucalyptus clones was increased by ~ 58.2% under CPE100 than under CPE75, but was decreased significantly (by ~ 34.9 to 79.6%) with increase in moisture regime from CPE100 to CPE125–150. Therefore, it can be concluded these Eucalyptus clones has considerable potential for increased productivity at CPE100; although PE-1 outperformed based on growth attributes and rates of photosynthesis, transpiration and stomatal conductance to yield higher net primary production.