Quantity and dynamics of dead wood in managed and unmanaged dry-mesic oak forests in the Hungarian Carpathians

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Dead wood (DW) has great importance for many wildlife species and ecological processes. The volume of DW is considered a useful indicator of the sustainability and maintenance of biodiversity in forests. Though dry-mesic oak forests cover large areas in Hungary, little is known about DW quantities or dynamics in these forests. We investigated DW conditions in five age classes of dry-mesic Quercus petraea and Q. cerris dominated forests in the Hungarian Carpathians. Stands of the first four age classes (age class 1: 40–59, age class 2: 60–79, age class 3: 80–99, age class 4: 100–119years old) were managed and stands at least 120years old were unmanaged at least for 30years (age class 5). We measured the volume, density, dominance and size distribution of standing DW and volume of downed DW. We also evaluated the decay stages of DW on an ordinal scale (I-V, intact to well-decayed). The effect of age class on the derived variables such as density, dominance, volume or proportion of DW was analysed with general linear mixed models using age class as a fixed and region as a random effect. Mean total DW volume did not reach 15m3/ha in age class 1, 2 and 3. A much larger volume of DW was found in age class 4 and 5, where the mean total volume of DW was 36.9 and 45.1m3/ha, respectively. Volume and proportion of total DW over 30cm in diameter were markedly lower in age classes 1, 2 and 3 than in age classes 4 and 5, moreover standing and downed DW over 30cm in diameter were totally absent in stands under 100years old. The proportion of well-decomposed (decay stage IV and V) DW was much lower (3–18% of the volume) in all five age classes than in old-growth stands of dry-mesic oak forests. After three decades of non-intervention (age class 5), the volume of DW can approach that of old-growth forests. The 40–99-year old stands contained a similarly low percentage of DW as other managed dry-mesic oak forests in Europe. Based on the results, it is likely that stands greater than 100years old will support much higher biodiversity of saproxylic organisms compared to younger stands.