Dynamics of ground vegetation after surface fires in hemiboreal Pinus sylvestris L. forests

The aim of this work was to investigate the changes of ground vegetation (field layer: mosses, lichens, and ground layer: herbs, shrubs, tree seedlings and saplings) and regeneration of tree species in pine forests after surface fires. The study area was located in Southern part of Lithuania in hemiboreal zone of Europe. The field and ground vegetation was recorded in forest stands burned in 1992 and 1994-2002 years and compared with the nearby control fire untouched areas. We selected 5 burned areas for each year (total 50 burned stands). Vegetation sampling was conducted during July and August of 2003. For vegetation description in each stand we systematically placed twenty 1x1 m plots. Mann-Whitney nonparametric test was used to identify significant differences in vegetation between burned and untouched areas. It was determined that species richness increased after fire. Early successional species such as Agrostis capillaris L., Calamagrostis epigejos (L.) Roth, Chamerion angustifolium (L.) Holub, Festuca ovina L. and Melampyrum pratense L. invaded in burned areas immediately after fire. Abundance of dominant species (Vaccinium myrtillus L. and Vaccinium vitis-idaea L.) recovered after 5 years. Pioneer moss species (Polytrichum piliferum Hedw. and Polytrichum juniperinum Hedw.) replaced late successional mosses (Dicranum polysetum Sw., Dicranum scoparium Hedw., Hylocomium splendens (Hedw.) Schimp. and Pleurozium schreberi (Brit.) Mitt.). Species number in the shrub layer decreased. Juniperus communis L. was killed by fire. Amount of undergrowth decreased first four years after fire. Saplings of Picea abies (L.) Karst., disappeared at all. Fire stimulated regeneration of Pinus sylvestris L., especially first four years after fire. Herbaceous and dwarf shrubs recovered 5-6 years after fire, moss cover - 9 years after fire. Differences in moss species composition still remained 11 years after fireVytauto Didžiojo universitetasŽemės ūkio akademij