Comparative leaf morphology spectra of plant communities in New Zealand, the Andes and the European Alps

Wellington

1996

S. 41-78

Bandaufführung

9850S

132414

Leaf morphology of native vegetation has often been interpreted as a sensitive indicator of enviromental conditions, presumably as a result of natural selection.If environmental pressures act as a selective force on community leaf morphology, then we wouid expect a high degree of similary in similar envirooments, regardlrss of biogeographie origin of the flora.A comparative studdy of full regional flors of alpine vascular plants was undertaken to test the sensivity of leaf morpholigy to macro-enviromental conditions.Five alpine sies and one lowland (control) site were selected in southern New Zealand spanning 1.5 latitude and 2323 m. Three sites with equivalent alpine environments werw selected in South America across a 60 latitudinal and 4200 m altitudinal span with subtropicaö forest used as a control. A further alpine sie from the European Alps was included as an outlier. Twenty leaf parameters were obtained for 2143 taxonomic entities x sites.Both the mean and the frequency distribution of leaf size and shape parameterswere distinctive for each locality Several morphological trends were ffound. Means of New Zealand contiguous low-alpine and high-alpine site pairs differed in : length- 33% width-14%, length/ width -20%, leaf area -44%, entire margin -2% (variable), coriaceousness- 18%, folded +22%, pubescence +40%. At higher elevations, leaves become smaller but rounder, considerably softer, are more often folded in to crypts or similar structures and are more often pubescent.these changes corresponded to reductions of 2-3 C in mean annual air temperature,c. 10% in mean minimum relative humidity and 7% in CO2 partial pressure. Despite hte biogeographie and enviromental differences, New Zealand and South American low-alpine sites were consistently similar in their morphological parameters and consistenly different from high-alpine sites ( execept in Tierra del Fuego). High alpine sites were also consistenly similar across the Pacific. Seveeral parameters were found to have multimodal frequency distributions that were not significsntly different in widly separate localities with different floras.The resultalts suggest that plant community morphology is an emergent property,the magnitude of which is environmentally constrained.