Natural restoration of flora on burned agricultural land - case study Biograd na Moru (Croatia)

A neglected arable agricultural area near the town of Vrana near Lake Vrana was burned by an induced fire. The area is located in the transition zone between evergreen (Fraxino orni - Quercetum ilicis) and deciduous vegetation (Querco- Carpinetum orientalis). The agricultural site itself, immediately around the burned area of the experiment, is dominated by Mediterranean maquis with the characteristic species Pistacia lentiscus and the monoculture community of Foeniculum vulgare. The studied area is divided into three experimental variants (average slope 18%): I. (control - anthropogenic meadow), II. (lower intensity burning, burning 10 kg/m2 of straw) and III. ( higher intensity burning, burning 10 kg/m2 of straw and 15 kg of vine wood). Fifteen rings (diameter 0.2 m2) were established on the studied area, five on each variant. The growth and development of flora and vegetation were observed monthly. All inventoried plant species were identified, herbarized, digitised, and are available in the ZAGR online herbarium (http://herbarium.agr.hr/hr_search.html). Abundant growth of plant taxa from all three functional groups that follow different ecological survival strategies was observed on the control variant: legumes, forbs, and graminoids. The most abundant species included the very species that were recorded within the experimental rings, but also included several others that were not previously recorded in the burned experimental rings (Plantago lanceolata, Urospermum picroides, Sisymbrium officinale, Silene latifolia ssp. alba). On the variant with lower fire intensity, the dominance of monocotyledons from the Poaceae family is visible: Avena sativa, Dactylis glomerata, Hordeum murinum, Elymus repens and others. On the variant with higher fire intensity, the dominance of plants from the group and family of legumes (Fabaceae) was observed, for example, Vicia cracca, Vicia sativa and Lathyrus aphaca. Compared to the control variant, abundant plants from the forage functional group grew in both burn variants (higher and lower intensity): Foeniculum vulgare, Convolvulus arvensis, and C. cantabrica, which were also the first to emerge three weeks after the 2019 induced burn. Total cover of renewed vegetation did not exceed 25% at either fire intensity after 24 months. Based on this results, we conclude that higher fire intensity does not promote survival of therophyte (monocotyledonous) life form, while hemicryptophytes and hamephytes (dicotyledonous) are more resistant to higher fire intensity and therefore have a greater possibility of survival.