Comparison Of African And Australian Savanna Tree Species' Seedlings In A Greenhouse Experiment

Savanna is an important ecosystem throughout the world, characterized by the co-occurrence of trees and grasses. Savanna vegetation has variable physiognomy and floristic composition, the result of independent evolution on different continents from a host of plant genera in response to local environmental conditions. Water, nutrient, fire and herbivory are key environmental determinants. Tree seedling recruitment and establishment is the critical stage to long-term balance and dynamics in savanna.However, the questions of whether and how species have adapted to differences in environmental variables expressed at continental scales and whether these adaptations have affected their abilities to grow in competition with grasses remain elusive. In order to access this, I conducted a greenhouse pot trial experiment to test the effect of resource availability and competition with grass on the growth of tree seedlings of species that are dominant in semi-arid and humid savannas in Africa and Australia. Various plant functional traits in relation to treatments, continents and savanna types have been evaluated using General Linear Model; correlations between these traits are further calculated by Spearman's correlation.Main findings are: (1) Biomass allocation pattern is a major factor in the response of plants to limited resource supply and disturbance; (2) The trade-off between relative growth rate and nutrient acquisition and conservation is affected by plant developmental stage and environmental stress; (3) Seedling growth is positively correlated with water and nutrient availability and inhibited by tree-grass competition. Growing pattern reflects local environmental conditions and is modified by independent flora evolution across continents; (4) Species'seedlings show convergent traits for environmental conditions. The association of plant functional traits and trait-environment linkage affect and reflect the ecological interaction between plant community and their ecosystem.