The microbial decomposition of six species of New Zealand bryophytes
Degree GrantorUniversity of Canterbury
Degree NameMaster of Science
Nutrient cycling and energy flow within various ecosystems has been the subject of many studies in the past. The influence bryophyte litter has on nutrient cycling has not been investigated extensively and research on nitrogen flow, in particular, is limited. In the following study the litter quality and decomposition characteristics of material from six New Zealand moss species was investigated using both laboratory and field studies. Ptychomnion aciculare, Hypnodendron comatum and Dicranoloma dicarpum were collected from Maruia Springs in the Lewis Pass Reserve and Hypnum cupressiforme, Breutelia pendula and Racomitrium pruinosum came from Cass near Arthur's Pass. Differences between the six species and between the green (younger) and brown (older) fractions of the litter were investigated with respect to litter quality, decay rates and nitrogen mobilisation. Due to the lack of an obvious senescence cycle naturally dead moss litter was difficult to determine therefore comparisons between the older and younger material were made. Moss litter is thought to be resistant to microbial degradation due to the chemical characteristics of the material Chemical analysis of the species showed a range of high C:N and C:P ratios (53-188 and 206-815 respectively), and that approximately 90% of the acid soluble nitrogen was derived from amino acids and proteinaceous compounds. The high percentage of amino acid and proteinaceous nitrogen indicates that the litter may be of high quality if the nitrogen is not complexed with other compounds causing it to become recalcitrant. Decay rates (k) were determined from weight loss experiments giving a range of 0.23- 1.3. There was an observed increase in weight loss over time for all the litter types. Nitrogen mineralisation studies indicated that nitrogen was released (generally in the form of ammonium ions) by microbial activity over 180 days incubation. Nitrate was also observed which in some cases exceeded ammonium levels. Leaching of the litter yielded water-soluble compounds including high nitrogen levels. Water-soluble extracts were shown to support microbial growth.