Aspects of litter dynamics in semi-arid environments in eastern Australia

Abstract

Leaf litter is an important resource and a fundamental component of all terrestrial ecosystems. The senescence and decay of leaves, bark and other organic material provides a mechanism for carbon, nitrogen and other critical elements to be transported and incorporated into the soil. This process is particularly important in arid and semi-arid ecosystems where resources are limited and unevenly distributed spatially and temporally. There are many drivers that modulate surface litter accumulation, litter fall rates and litter decay rates. This thesis examines how these aspects of litter dynamics are moderated by abiotic (e.g. soil, landform, fire, rainfall) and biotic (e.g. vegetation communities, individual species) factors in semi-arid woodlands and shrublands in eastern Australia. Chapter 1 provides an overview of the importance of litter in semi-arid woodlands, describing previous research on leaf litter dynamics in arid and semi–arid ecosystems. Chapter 2 examines litter fall rates in response to abiotic conditions, with a focus on the fall rates of reproductive structures (seeds, flowers and fruits) from three species that differ in their life histories. Chapter 3 and 4 focus on the accumulation and spatial arrangement of surface litter. Chapter 3 describes the shift in litter bed size and composition under two Eucalypt Mallee species (Eucalyptus socialis, E. dumosa) along a 42 year chronosequence of fire histories. Chapter 4 examines properties of spatial self-organisation exhibited by litter patches, assessing litter patch cover, size and degree of spatial association between surface litter and perennial vegetation across four different landscapes. Chapters 5 and 6 focus on aspects and implications of litter decomposition in the foraging pits of mammals. Chapter 5 examines the relative importance of biotic and abiotic factors during the decomposition process of substrates in the foraging pits of short-beaked echidnas (Tachyglossus aculeatus), greater bilbies (Macrotis lagotis) and burrowing bettongs (Bettongia lesueur). Chapter 6 examines the conditions under which litter decomposition in echidna foraging pits facilitates seedling growth by assessing water stress and the proximity of foraging pits to large trees. Chapter 7 is a summation of the previous chapters, highlighting the implications and limitations of these novel studies, and providing direction for future work in this field.