Monitoring the state and structure of representative forest communities in Krka National Park

Monitoring the state and structure of representative forest communities in Krka National Park
The multi-year monitoring of the state of forest communities within Krka National Park continues

In 2023, monitoring the state and structure of forest communities in Krka National Park was conducted by the Croatian Forestry Institute Jastrebarsko. This project is the continuation of a multi-year project to monitor the state of forests on five permanent experimental plots that encompass different forest communities: high forest of pubescent oak in the Stinice area, stand of holm oak in the Mačkovica area, stand of Aleppo pine in the Žurića Brdo area, floodplain forests of narrow-leaved ash near the Krka Monastery, and coppice wood of pubescent oak in the Donji Radići area.

The initial research of these forest communities established the floral composition and structure of the basic stand elements (tree species, number of trees (per hectare), basal area (m²/ha), average diameter at breast height (cm)). These parameters are important to assess the overall condition of forest communities. Their multi-year monitoring gives insight into the development of forest communities and their capability for natural regeneration, with special emphasis on the native tree species in this area. On the basis of the monitoring performed, it was established that the park ecosystems have high biodiversity, and guidelines for their conservation were defined.

A comparison of the most representative forest communities in the park showed that the forest stands are in progression, both in area and in the number of trees of main species, with increased values of all structural parameters. For example, in 2023, the number of trees of narrow-leaved ash in the Krka Monastery area was 1091 per hectare, with an average diameter at breast height (DBH) of 17.8 cm, as compared to 415 trees per hectare and an average DBH of 20.8 cm in 2018.

On the selected plots, the influence of biotic and abiotic factors is monitored, including the appearance of plant diseases and pests in the park. The overall state of forest health at these locations was assessed as good, with small and individual attacks by pests, and no special protection measures are currently required. It is recommended that the pest populations continue to be monitored, as a gradation of these species could cause damage to the forest communities and degrade the health condition of the trees.

In the forest community of pubescent oak and Oriental hornbeam at the location Stinice, rain meters were installed. An analysis of the collected rainwater samples (12 samples per year) tracks the influence of air pollution on the forest community. Continuous measurements at regular intervals enables us to monitor trends and the ratios of ions brought by atmospheric deposition. The analysis of samples indicates that in certain periods, there is an increased deposition of nitrogen and acidic compounds. At this time, these compounds have not reached a critical load level, though continued monitoring is recommended to measure the atmospheric deposition in the forest stands.

With the aim of protecting and conserving forests as important elements of this protected area, further monitoring of the forest ecosystems and their elements is recommended, with an emphasis on the detection of any possible pests or plant diseases and the adoption of measures to counter them.