A matter of size and shape: Microclimatic changes induced by experimental gap openings in a sessile oak–hornbeam forest

• Published in: The Science of the total environment Vol. 873; p. 162302
• Main Authors: Horváth, Csenge Veronika, Kovács, Bence, Tinya, Flóra, Schadeck Locatelli, Julia, Németh, Csaba, Crecco, Lorenzo, Illés, Gábor, Csépányi, Péter, Ódor, Péter
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 15.05.2023
• Subjects: Artificial gaps; Continuous cover forestry; Forest management; Forest microclimate; Quercus petraea; Spatial pattern analysis; Forest microclimate; Forest management; Artificial gaps; Spatial pattern analysis; Continuous cover forestry; Quercus petraea
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2023.162302

Forest management integrating nature conservation aspects into timber production focuses increasingly on small-scale interventions. However, the ecological consequences of gap cuttings remain ambiguous in oak-dominated forests. In the Pilis Gap Experiment, we analyze how combinations of different gap shapes (circular and elongated), and gap sizes (150 m2 and 300 m2) affect the microclimate and biota of a mature sessile oak-hornbeam forest in Hungary. We first report the changes in direct and diffuse light, soil moisture, daily air and soil temperatures, and relative air humidity in the experimental cuttings in the vegetation season directly following their implementation. Diffuse light had a central maximum and a concentric pattern. Direct light was distributed along a north-south gradient, with maxima in northern gap parts. Soil moisture was determined by gap shape: it increased significantly in the center of circular gaps, with multiple local maxima in the southern-central parts of large circular gaps. Its pattern was negatively related to direct light, and larger spatial variability was present in circular than in elongated gaps. The daily mean air temperatures at 1.3 m increased in all, especially in large gaps. Soil and ground-level temperatures remained largely unchanged, reflecting on light and soil moisture conditions affecting evaporative cooling. Relative humidity remained unaltered. Even though the opening of experimental gaps changed microclimatic conditions immediately, effect sizes remained moderate. Gap size and gap shape were both important determinants of microclimate responses: gap size markedly affected irradiation increase, gap shape determined soil moisture surplus, while soil and air temperatures, and air humidity depended on both components of the gap design. We conclude that 150–300 m2 sized management-created gaps can essentially maintain forest microclimate while theoretically providing enough light for oak regeneration; and that the manipulation of gap shape and gap size within this range are effective tools of adaptive management. [Display omitted] •Scientifically based multipurpose forestry needs comparative studies on canopy gaps.•We studied the microclimate of two gap size and shape types at two spatial scales.•Light increment was driven by gap size, and shape determined soil moisture patterns.•Daily means of air temperature increased at 1.3 m yet decreased near the ground.•Gaps up to one tree height per diameter ratio can maintain forest conditions.