干旱区生态环境知识资源中心

We examined how the measurement of stable carbon and nitrogen isotopes in soils, vegetation and invertebrates can contribute to understanding landscape processes in mulga Acacia aneura ecosystems characterised by alternating wooded groves and intergroves. Our analyses showed that greater leakiness of water from intergroves at the landscape scale tended to promote more conserving physiology at the plant scale. Thus isolated mulga trees in intergroves probably have higher water use efficiency than those in groves. Both trees and grasses in the intergroves have a greater reliance on recycled nitrogen than plants in the groves for which recently fixed N was a substantial source. Grasses in the intergroves had higher N concentrations than those in the groves despite the soil having lower N concentrations. A lack of variation in the isotopic signature of surface soil N suggested that the lower N concentrations in soils of intergroves than groves is due to lower rates of input and not shorter residence times. Stable isotopic signatures of invertebrates showed a diversity of feeding strategies amongst termite species and indicated symbiotic N fixation in two species. There was no relationship between the dependence on N fixation and the habitat preference or diet of termites. Our results suggest that with cautious interpretation, stable isotope signatures could contribute to understanding other ecosystems where patch-interpatch functioning is an important landscape process.