MICROCLIMATIC CONVERGENCE OF HIGH-ELEVATION TROPICAL PARAMO AND TEMPERATE-ZONE ALPINE ENVIRONMENTS

Plant microclimates of three tropical superparamo sites at 4100 - 4600 m a.s.l. in Ecuador were monitored over a five-month period and resul ts were evaluated in local and biogeographical contexts. Soil temperat ures tended to decrease with altitude, whereas quantum flux density (Q FD) exhibited no consistent altitudinal pattern. Leaf temperatures of prostrate rosette and cushion plants exhibited diurnal amplitudes of 3 0 degrees C independent of altitude, while herbaceous perennials and w oody shrubs, which were situated higher above the soil surface, had lo wer maxima and lower daily amplitudes as a result of aerodynamic coupl ing to the atmosphere. Longterm growth measurements and an analysis of a stem cross-section of the shrub Loricaria indicated that growth con ditions at 4060 m a.s.l. were constant over a 4-yr to > 25-yr period. Means and frequency distributions of QFD as well as soil and leaf temp eratures in the Ecuadorean Andes closely resemble growing season avera ges at high alpine sites in the European Central Alps at 2600 m a.s.l. Equivalent growth conditions in equatorial tropical paramo sites and seasonal temperate zone mountains extending to the arctic, suggest tha t, aside from the duration of the growing season, similar abiotic sele ction pressures operate on high elevation plants in humid mountain eco systems, which are largely independent of latitude.