Post-fire dynamics in a mesotrophic pine forest: the third year after fire

anglais. Monitoring of forest structures in three successive years (2015–2017) after forest surface fire reveal most likely development scenarios after this type of disturbance. The dynamics of ground vegetation (species composition and cover) reflects the dominant process – graminification of the ground cover. Indirect assessment of soil and climatic factors (Ellenberg’s values) indicates increase of biologically available nitrogen. Therefore, further impact of the nutrient cycling processes on the yield of the forest stand in the future is of high interest. The change in the composition of ground vegetation species highlights trends of ruderalisation and hygrofitisation as well, but these processes are currently of minor importance compared to graminification. The number of pine individuals in the fire-disturbed forest stand has decreased by 40.4% compared to the year before the disturbance. As the process of decline of the forest stand is continuing, it is likely that pines, so far dominant species in the overstorey, will be replaced in near future. In the third year following the forest fire, gradual stabilisation of dwarf shrubs and mosses is continuing; compared to the previous year, no significant changes in the cover of these structures have been observed. As in the previous two years following the forest fire, spontaneous establishment of certain vascular plant species is taking place. On average, 4.7 new vascular plant species have spontaneously established into the forest stand annually, with 0.7 species disappearing. Thus, in the first years after the forest fire, the number of species has increased, i.e. the biodiversity of forest stands increasing at taxon level.

letton. Darbā analizētas meždegas skartās mežaudzes sugu sastāva, zemsedzes acumēra un stratificētā projektīvā seguma, kokaudzes atmiruma un veselības stāvokļa, kā arī dabiskās atjaunošanās parametru izmaiņas, aprēķinātas Ellenberga ekoloģisko faktoru vērtības. Augāja sugu sastāva un ekoloģisko faktoru sakarības traucētajā mežaudzē atspoguļo pašlaik vadošo transformācijas procesu mežaudzē – graudzāļošanos jeb graminifikāciju. Graudzāļošanās process zemsedzē ir saistīts ar bioloģiski aktīvā slāpekļa uzkrāšanos augsnes virskārtā, kas nākotnē būtiski var ietekmēt vielas un enerģijas apriti mežaudzē. Meždegas skartajā audzē priedes indivīdu skaits, salīdzinot ar gadu pirms traucējuma, ir samazinājies par 40,4%. Turpinoties kokaudzes sabrukšanas procesam, jau tuvākajos gados varētu notikt priedes, līdz šim koku stāvā valdošās sugas, nomaiņa.