Spatial Patterns of Atmospheric Pollen Transport in a Montane Region,

Abstract

Annual pollen deposition (pollen cm−2yr−1) was sampled for 6 yr in the southern Sierra Nevada, the Owens Valley, and the Inyo Mountains of central California. Spatial pollen distributions were examined for anemophilous plants which are limited to growth sites (1) at high elevations on one or both mountain ranges, (2) on lower mountain slopes, and (3) on the Owens Valley floor, Pollen deposition values for high- and low-elevation plants changed by a factor of 5 to 10 between adjacent sample sites which straddle boundaries of the plant communities in which the source plants grow. Pollen deposition values were high and variable within communities in which the species grew. Pollen deposition beyond source populations was low and uniform despite great differences in distance of sites from pollen sources. The step function that seems to characterize pollen distribution patterns implies that pollen from distant populations may be of little value in interpreting vegetation stability and change reflected by fossil pollen stratigraphy. The physical isolation of pollen embedded in the local mountain-valley wind system from that in the prevailing westerlies may explain part of the spatial distribution of the pollen.