Regeneration in European beech forests after drought: the effects of microclimate, deadwood and browsing

Abstract

With progressing climate change, increasing weather extremes will endanger tree regeneration. Canopy openings provide light for tree establishment, but also reduce the microclimatic buffering effect of forests. Thus, disturbances can have both positive and negative impacts on tree regeneration. In 2015, three years before an extreme drought episode hit Central Europe, we established a manipulation experiment with a factorial block design in European beech (Fagus sylvatica L.)-dominated forests. At five sites located in southeastern Germany, we conducted three censuses of tree regeneration after implementing two different canopy disturbances (aggregated and distributed canopy openings), and four deadwood treatments (retaining downed, standing, downed + standing deadwood and removing all deadwood), as well as in one untreated control plot. In addition, we measured understory light levels and recorded local air temperature and humidity over five years. We (i) tested the effects of experimental disturbance and deadwood treatments on regeneration and (ii) identified the drivers of regeneration density as well as seedling species and structural diversity. Regeneration density increased over time. Aggregated canopy openings supported species and structural diversity, but reduced regeneration density. Tree regeneration was positively associated with understory light levels, while maximum vapor pressure deficit influenced tree regeneration negatively. Deadwood and browsing impacts on regeneration varied and were inconclusive. Our study indicates that despite the drought episode regeneration in beech-dominated forests persisted under moderately disturbed canopies. However, the positive effect of increased light availability on tree regeneration might have been offset by harsher microclimate after canopies have been disturbed.

Microclimate, an important part of ecology and biogeography

“…Water availability is another factor that has been shown to affect the growth and mortality of plants (Liu et al, 2018), and water availability also controls the regeneration of trees after disturbances (Lloret et al, 2004;Thom et al, 2022). Besides affecting many physiological processes, microclimates also influence behavioural responses across taxa.…”

“…Plant populations are a great example of this, as recent discoveries show that crucial processes like seed germination and seedling establishment depend on specific temperature, humidity and light conditions (Davis et al., 2016; Graae et al., 2022). Water availability is another factor that has been shown to affect the growth and mortality of plants (Liu et al., 2018), and water availability also controls the regeneration of trees after disturbances (Lloret et al., 2004; Thom et al., 2022). Besides affecting many physiological processes, microclimates also influence behavioural responses across taxa.…”

“…Forestry is an excellent example of how ecosystem management affects microclimate heterogeneity (Menge et al., 2023; Scheffers et al., 2017). In forestry, microclimates are managed to reduce insect outbreaks (Kautz et al., 2013), support tree regeneration (Thom et al., 2022) and reduce frost damage (Örlander, 1993). Forest microclimates are affected by the diversity in tree species, forest structures, management practices (e.g.…”

­Decametric-scale buffering of climate extremes in forest understory within a riparian microrefugia: the key role of microtopography

“…For each microclimate sensor and the reference weather station, we computed half-hourly vapour pressure de cits (VPD, expressed in kPa) from air temperature and relative humidity (RH) data using classical formula of vapour pressure at saturation (Gueymard 1993). We included VPD in our analysis because VPD is a better measure of the evaporative demand, and usually a better predictor of the distribution and regeneration potential of European beech (Hohnwald et al 2020;Thom et al 2022).…”

Стан І Продуктивність Штучних Дубових Насаджень Лівобережного Лісостепу України

“…Нині в окремих регіонах країни внаслідок кліматичних змін, а також антропотехногенного впливу та певних недоліків у веденні лісового господарства виникають осередки ослаблення та всихання лісів, зокрема штучних дубових. Це може погіршити успішність надання лісами комплексу різноманітних екосистемних послуг, а також збереження біорізноманіття лісових екосистем (Thom et al 2022).…”