CARBON STORAGE AND ALLOCATION PATTERN IN PLANT BIOMASS UNDER DROUGHT STRESS AND NITROGEN SUPPLY

Abstract

Climate change may have multi-faceted adverse effects on forests worldwide such as pest outbreaks, fires, heat waves and drought. These stresses including changes in water and nutrient availability, cause imbalance in carbon uptake by plants. In this study, two species Eucalyptus camaldulensis (evergreen) and Populus deltoides (deciduous) were selected for carbon content and allocation analysis with the application of nitrogen fertilizer and water stress treatments. Pot experiment was done by planting 2 years old seedlings in 5kg pots in a glasshouse for four weeks. Experiment was a 2-factor factorial completely randomized design having three water stress levels D0, D1, D2 (1000, 500 and 250 mL) and three nitrogen treatments N0, N1, N2 (0, 0.5 and 1 gNkg-1). Significant and non-significant Nitrogen into Drought interactions (NxD) were observed for each treatment. Results showed that in Populus deltoides, at N2D2 treatment, shoot carbon content increased up to 63% to 75%. Whereas in Eucalyptus camaldulensis, shoot carbon content increased up to 51% to 52% at N0D2 treatment. Leaf carbon content increased 23% to 44% in E. camaldulensis and 0.3% to 4% in P. deltoides, at N1D1 treatment respectively. Dry shoot biomass increased 3.8g to 7g at N2D2 treatment in E. camaldulensis whereas 45g to 81g at N1D2 in P. deltoides. Increased root biomass production was observed in N1D0 of P. deltoides (31.96g) and E. camaldulensis (2.73g). Leaf biomass was more observable in E. camaldulensis, at N1D2, up to 4.72g and in P. deltoides at N2D1 up to 3.4g. A significant increase at NxD interactions was observed in root carbon content, shoot length, root length, root biomass and Relative Water Content (RWC) in E. camaldulensis. Likewise, root length, shoot biomass, root biomass, Water Use Efficiency (WUE) and RWC was significantly increased in P. deltoides at NxD interactions. These significant improvements related to carbon allocation and physiological growth, with NxD interactions, can be attributed to improved acquisition of nutrients by these species in the drought stressed environments.