OPENLAND3: a computer program to estimate plant abundance around pollen sampling sites from vegetation maps: a necessary step for calculation of pollen productivity estimates
Summary, in English
OPENLAND3 belongs to a suite of computer programs included in the POLLSCAPE simulation model. These programs make it possible to calculate estimates of pollen loadings in lake basins or bogs using vegetation data. OPENLAND3, written in Visual Basic 6, is designed to produce appropriate vegetation data files from vegetation maps stored in a Geographical Information System. It calculates percentage cover of plant taxa in concentric circles at increasing distances from a central point, using either real digitised maps or hypothetical maps (simulated landscape designs). Such data are necessary for simulation of pollen dispersal and deposition, and for calculation of pollen productivity estimates and relevant source area of pollen using specific mathematical models developed by palynologists, such as the Prentice-Sugita model. OPENLAND3 also produces output files needed to run RS-OPEN, another program included in POLLSCAPE, in order to obtain estimates of pollen loadings in lakes or bogs. The rationale of OPENLAND3, the algorithm used, and a modification of RS-OPEN (RS-OPEN2) are described. A test of the programme capability using a detailed vegetation map from southern Sweden shows that simulations using OPENLAND3 produce coherent results. Pollen loading for species characterized by high pollen productivity is higher than for species with low pollen productivity. Altering the wind speed has also a significant effect on pollen loading. As wind speed increases, the proportions of the light pollen decrease, while the heavy pollen types increase, which is what empirical data suggest, and what the model predicts in earlier studies. (C) 2004 Elsevier B.V. All rights reserved.