Professional paper
https://doi.org/https://doi.org/10.31298/sl.150.9-10.7
Second National Forest Inventory of the Republic of Croatia (CRONFI II): Status and Changes in Forest Resources
Zdenko Bogović
; Šume – Obrt za savjetovanje u šumarstvu, Zagreb, Hrvatska
Matej Turk
; Unique forest d.o.o., Našice, Hrvatska
Abstract
The aim of this professional paper is to present the main results of the Second National Forest Inventory of the Republic of Croatia (CRONFI II) and, where methodological comparability allows, to compare them with the results of the First National Forest Inventory (CRONFI I). Particular attention has been given to forest area, growing stock and tree species composition, the relationship between increment and harvest, deadwood, disturbances, regeneration, biodiversity and carbon stock in Croatian forest ecosystems.
CRONFI II represents the second national-scale assessment within the Croatian forest monitoring system, and provides a basis for assessing changes through repeated measurements of permanent sample plots. Field measurements for CRONFI I were carried out between 2005 and 2009, whereas CRONFI II field measurements were conducted in 2024 and 2025, resulting in an average interval of approximately 17 years between measurements. Twelve field teams measured approximately 112,000 trees on 1,932 tracts and 6,366 sample plots. The second inventory retained the permanent-plot concept while expanding the set of recorded stand, ecological and disturbance variables to approximately 130 attributes. Fieldwork within CRONFI II is shown in Figure 1. The repeated measurement concept is further illustrated in Figure 2 by a panoramic comparison of the same permanent sample plot in CRONFI I in July 2009 and CRONFI II in February 2024, with QR code access to an interactive 360° panorama.
According to CRONFI II, forests and forest land cover 2,997,402 ha, corresponding to 53% of the total area of Croatia, of which 2,430,604 ha are stocked forest land. The CRONFI II estimate of stocked forest area is about 54,000 ha, or 2.27%, higher than the estimate obtained in CRONFI I. Because the two inventories used different approaches to forest area estimation, this difference should primarily be interpreted as a difference between estimates rather than as a fully homogeneous temporal trend. Selected national indicators from the two inventory cycles are summarised in Table 1.
Total growing stock in CRONFI II is estimated at 548 million m³, corresponding to 227 m³/ha, compared with 552 million m³ or 232 m³/ha in CRONFI I. At the same time, a positive net growing-stock change of 1.05 m³/ha was estimated from the consistent sample of plots measured in both inventory cycles. This apparent contrast reflects the difference between estimates of current total growing stock and estimates of change based on comparable plots. European beech remains the dominant tree species, accounting for approximately 34% of total growing stock, followed by pedunculate oak, sessile oak, European hornbeam, silver fir, narrow-leaved ash and Norway spruce. The shares of the major tree species are shown in Figure 3, while changes in growing stock of the selected species are presented in Table 2. Narrow-leaved ash showed the strongest relative decline among the principal species, whereas European hornbeam showed the largest relative increase.
Annual net increment is estimated at 13 million m³, or 5.33 m³/ha per year. Average annual harvest is 8 million m³, or 3.31 m³/ha per year, corresponding to 62.1% of annual net increment at the national level (Figure 4). Harvest intensity differs considerably among bioclimatic zones, ranging from 5.50 m³/ha per year in the lowland zone to 0.03 m³/ha per year in the Eumediterranean-Stenomediterranean zone. These differences reflect variation in site productivity, stand structure, accessibility, ownership patterns and the relative importance of productive, protective and ecological forest functions.
Average deadwood volume according to CRONFI II is 22.66 m³/ha, corresponding to 55 million m³ at the national level. Examples of lying and standing deadwood are shown in Figure 5. Lying deadwood accounts for 50% of total deadwood volume, standing dead trees for 44% and stumps for 6%, as shown in Figure 6. Deadwood volume differs markedly among bioclimatic zones, with the highest value recorded in the high-mountain and subalpine zone, where it reaches 39.93 m³/ha (Figure 7). The comparative value reported in CRONFI I is 14.81 m³/ha. However, the difference between the inventories should be interpreted with caution because stumps were not included in the same manner in CRONFI I. No specific ecological problems were recorded on 69% of the total forest area, while pests and diseases, drought, frequent fire exposure and storms were the most commonly identified pressures. A total of 94 woody species were recorded.
Carbon assessment represents one of the major extensions of CRONFI II. Total forest ecosystem carbon stock is estimated at 643 million tonnes, or 266 t C/ha. By individual carbon pools, aboveground biomass contains 80.75 t C/ha, belowground biomass 21.76 t C/ha, deadwood 6.41 t C/ha, forest litter 42.36 t C/ha and forest soil 114.45 t C/ha (Figure 8). Forest soil is therefore the largest individual carbon pool. The results demonstrate that a substantial proportion of total forest-ecosystem carbon is stored outside living aboveground biomass and that changes in growing stock alone cannot adequately describe the overall carbon status of forest ecosystems.
CRONFI II also provides a broader basis for assessing regeneration and future forest structure. The inventory estimates 27 billion trees and young plants across different developmental categories, including 1 billion trees with a diameter at breast height greater than 10 cm, 6 billion small trees up to 10 cm in diameter and 20 billion young plants up to 1.3 m in height or 11.425 trees per hectare. Young forests originate through natural regeneration in 95% of cases, while climatogenic mixed forests with two or more vertical layers occur in 97% of the area.
Overall, CRONFI II confirms the development of the Croatian National Forest Inventory from a system primarily focused on forest area and timber resources towards a multipurpose forest ecosystem monitoring framework. Repeated measurements provide a more reliable basis for distinguishing changes in the current forest condition from long-term trends, and for analysing the effects of disturbances, management and environmental change. The long-term value of the inventory will depend on continuity of measurements and preservation of comparable definitions, sampling designs and analytical procedures.
Key words: biodiversity, carbon, CRONFI II, deadwood, growing stock, harvest, increment, tree number
Keywords
biodiversity, carbon, CRONFI II, deadwood, growing stock, harvest, increment, tree number
Hrčak ID:
352073
URI
Publication date:
30.9.2026.
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