The effects of experimental forestry treatments on site conditions: short response study from an oak-hornbeam forest
Authors: Kovács Bence , Tinya Flóra , Guba Erika , Németh Csaba , Sass Vivien , Bidló András , Ódor Péter 
Published: March 2018

Background

Forest management alters the forest site, however, information is still limited about how different silvicultural treatments modify these conditions. In the past decades, besides rotation forestry, new silvicultural systems were introduced, fulfilling the requirements of multipurpose forestry. In this study we investigated the short-term effects of different forestry treatments on microclimate, litter and soil conditions in a European oak-dominated forest.

Methods

A forest ecological experiment was established in a homogenous, managed, 80 years old, Quercus petraea and Carpinus betulus dominated forest, in 2014. Five treatments of three different forestry systems were installed following a complete block design in six replicates: clear-cutting with a circular retention tree group as typical elements of the clear-cutting system, preparation cutting (partial harvest) belonging to the shelterwood system, gap-cutting as a common tool of continuous cover forestry in Europe and uncut control. Microclimate, litter and soil variables were measured systematically since 2014. Here we present the results of the analyses of the first growing season following the interventions (2015).

Results

We found that there is strong treatment effect in the case of microclimate and litter varibles, but for soil characteristics the impacts will presumably appear in longer term. The increment of total and diffuse light was the greatest in clear-cutting, in gap-cutting the illuminance was intermediate, while light-levels were lower and less variant in preparation cutting and retention tree group. Air and soil temperature as well as vapor pressure deficit increased the most in clear-cutting; both means and variances were the highest in this treamtment. Retention tree group could not buffer the means of the temperature variables, but a small group of tree individuals was able to ameliorate the extremes of the microclimate. Significant increase of soil moisture was measured as a consequence of gap-cutting and less pronouncedly in clear-cutting. Similarly, litter pH and moisture were the highest in these treatment types. Significant increment in soil pH was detected in retention tree group. Through the analysis of microclimate variables during the growing season, we could demonstrate the buffering effect of forest canopy: differences between treatments were the greatest in summer for all microclimate variables.

Discussion

We can conclude that in oak–hornbeam forest, only less intensive and spatially heterogeneous silvicultural treatments could preserve the stable, cooler and humid below-canopy microclimate, therefore, group selection using gaps and irregular shelterwood systems are favourable. Our findings can support the mitigation of the negative impacts of climate change in managed forest. Moreover, besides basic research we can formulate implications for foresters and conservationists to preserve biodiversity in temperate forests.