Ecology and Morphology of Globular Mosses of Grimmia Longirostris in the Paramo De Piedras Blancas, Venezuelan Andes

Abstract

A population of 172 moss balls of Grimmia longirostris Hook, was studied in the Páramo de Piedras Blancas (Venezuelan Andes) at 4380 m. Moss ball transport in the paramo is caused primarily by needle-ice activity, with wind being a secondary agent. Moss ball size and shape varied widely, but were closely correlated. Larger globoids were significantly less spheroidal than smaller ones. This occurs because heavier moss balls rest for increasingly long periods of time on one side, thus becoming flattened. Several moss forms are described, including a type (pedestal mosses) attached to pebbles. Globular mosses lacked pebbles at their core, which was formed by silty soil and organic matter. Moss balls had a high content of organic matter (19%) and fine mineral grains (69.3%); the last is nearly four times higher than in site soils. This concentration of silt and clay results from moss balls trapping fine eolian dust and soil material as globoids roll over the ground. Due to their composition, globular mosses have a superior ability to store water compared to paramo soils. Larger moss balls had a greater water-holding capacity than smaller ones; they also lost water at considerably slower rates. This may be ecologically significant for moss ball growth and survival during dry periods.