Aspect-dependent high-irradiance damage in two transplanted foliose forestlichens, Lobaria pulmonaria and Parmelia sulcata

High-irradiance damage in two epiphytic lichens was recorded as reduction i n predawn photosystem II quantum yield (F-v /F-m) measured at the end of a night with full hydration. Measurements were repeated during a 29-day trans plantation in early summer at defined aspects (north, east, south, west, pe rpendicular to the sun at noon, and shade) in an open site at 60 degreesN. These treatments included the contrasts that remaining lichens adjacent to clear-cut areas could experience subsequent to logging. The F-v /F-m values declined linearly with the mean irradiance during the previous day, with t he old-forest epiphyte Lobaria pulmonaria (L.) Hoffm. being consistently mo re severely photoinhibited than the ubiquitous Parmelia sulcata Taylor. Bot h irradiance levels and predawn F-v /F-m values decreased in the following direction: shaded controls > transplants facing north > south, east, west > transplants perpendicular to the sun. Since the transplantation period hap pened to be very rainy with favorable conditions for recovery, all transpla nts survived. Nevertheless, photoinhibition was sustained from one day to t he other, especially in the old-forest species L. pulmonaria, implying a lo ng-lasting strain, which could affect long-term performance and survival of thalli. The results are discussed in a wider context including confounding effects of irradiance in forests, with implications to facilitate lichen c onservation in managed forests.