Weidong Gu, Mikko Kuusinen, Tuija Konttinen and Ilkka Hanski
University of Helsinki
The analysis of spatial pattern can provide information on underlying spatial processes. In this study several cyanobacterial lichen species, known to specialize on old deciduous trees (especially on aspen and goat willow), have been surveyed in an old-growth boreal forest landscape in Kuhmo, in the east central part of Finland.
The study area ( 9 km 2 ) was divided into 100 m x 100 m square grid. The occurrence of the lichen species and the number of suitable trees were recorded in each cell.
Assessment of the spatial clustering of the lichens was accomplished using an approach developed by Diggle and Chetwynd (1991). The values of the statistic D were calculated for evenly spaced distances (s) to measure departure from the random labelling hypothesis. The variances of D were calculated to obtain confidence limits.
Our preliminary results (Fig.1.) showed that Lobaria pulmonaria, Nephroma bellum, N. parile, and Peltigera canina displayed similar spatial patterns and showed clustering within the scale up to 800 m. On the other hand, the spatial pattern of N. resupinatum was not significantly different from a random distribution. These results suggest that the spatial process underlying the spatial patterns of the former four lichen species may be similar, whereas different processes may be involved in generating the spatial pattern of N. resupinatum.