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Deakin University (2014)

Moss distribution along a rainfall gradient in semiarid, non-Eucalypt woodland of Victoria, Australia

Tyshing, Christine Lorraine

Titre : Moss distribution along a rainfall gradient in semiarid, non-Eucalypt woodland of Victoria, Australia

Auteur : Tyshing, Christine Lorraine

Université de soutenance : Deakin University

Grade : Doctor of Philosophy (PhD) 2014

Résumé
This thesis examines the distribution of moss assemblages of non-Eucalypt woodland along a rainfall gradient in semi-arid natural parkland of north-western Victoria, Australia to determine : 1. whether the moss flora showed a sequential change in species assemblage along the rainfall gradient and to identify the environmental factors that explained this ; 2. the habitat exploitation of the moss flora along the rainfall gradient and to determine the environmental factors that explain this ; 3. whether life-form, leaf architecture or life strategies contribute to the explanation of moss distribution along the rainfall gradient. Seventy-four species were identified with those of the Pottiaceae and Bryaceae dominating as is characteristic of arid and semi-arid regions across the globe. Seriation of moss assemblages occurred at the site level with rainfall, areal actual evapotranspiration, average maximum summer temperature and pH being pivotal factors determining moss distribution. This suggested the moss assemblages could be used as indicators of climate change within non-Eucalypt Woodland, and could be monitored to show which species were disappearing, which were surviving and whether migration of species occurred as conditions became hotter and drier. Examination of the moss flora at the habitat level also showed variation along the rainfall gradient within each habitat but soil texture also assumed a significant proportion of the explanation of moss distribution, suggesting habitat amelioration of conditions. Three habitats were examined : soil exposed to the sun, shaded soil and tree trunks. Soil exposed to the sun had greatest species richness while epiphytic species were very few. The contribution of leaf architecture and life-form to distribution of moss assemblages was investigated. Both life-form and leaf architecture contributed to the explanation of the distribution of moss assemblages along the rainfall gradient with affiliation of specific adaptations occurring. Short turfs or small tufts were most common in the wetter regions while herd species were most prevalent in the driest regions, although both occurred throughout the length of the rainfall gradient. The most important adaptations were concave leaves, dry leaves that curve towards the stem, short turfs or small tufts, papillae/mammillae, dry leaves that twist and/or overlap, herds, specialised cells on borders of leaves and incrassate cells. Each moss was assigned a life strategy and colonists were found to dominate along the length of the rainfall gradient although annual shuttles also formed a strong component. Life strategies did not explain the distribution of moss assemblages along the rainfall gradient although other studies found life strategies were environmentally driven. In the process of examining life strategies, a novel method of spore dispersal was identified for Goniomitrium acuminatum Hook.f. & Wilson. Studies that examine the ecology of the moss flora of native vegetation in semi-arid Victoria, Australia are limited, other than what has been completed for the rangelands. The work presented in this thesis, therefore, fills an important knowledge gap and is all the more pertinent in this current time of climate change, particularly as much of Australia is arid and semi-arid.

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Page publiée le 30 novembre 2014, mise à jour le 10 juillet 2017