Growth and quality of Fagus sylvatica saplings depend on seed source, site, and browsing intensity

Abstract

2019. Growth and quality of Fagus sylvatica saplings depend on seed source, site, and browsing intensity.Abstract. Local climate and ungulate browsing are two major factors that affect tree regeneration and genetic adaptation in Central European forests. Owing to climate change and increasing ungulate numbers, the abiotic and biotic environments of trees are changing remarkably, making it necessary to investigate the separate and joint effects of seed source (i.e., location of tree population origin) and ungulate herbivory. We used a common garden experiment to study the growth and morphology of Fagus sylvatica saplings from 77 Swiss seed sources. The experiment was set up at two sites and included a clipping treatment (i.e., terminal shoot clipped at two intensities) applied before budburst to simulate winter ungulate browsing. We studied F. sylvatica sapling growth and morphology before and two years after clipping. Measured growth traits included sapling height, stem diameter, and biomass. Morphological traits included multi-stemming, stem and crown form, stem quality, and reaction to clipping. Seed source, test site, and simulated leader browsing were all important in determining the growth and quality of F. sylvatica saplings. The effects of seed source on growth and quality indicate that F. sylvatica possesses a large pool of diverse genotypes across Switzerland and thus has the potential to adapt to local conditions through gene flow. Growth and morphology differed significantly between the two test sites, indicating that local environments should be considered carefully when a new plantation is established. The effect of the single simulated browsing event disappeared over time for the growth traits, owing to growth compensation. However, sapling quality decreased after clipping, suggesting that browsing may lead to persistent quality losses in production forests. Neither the growth nor the morphological reaction after clipping depended on the effect of population, meaning that resilience to browsing was independent of seed source. Consequently, interactions with ungulate browsing do not have to be taken into account when selecting F. sylvatica populations for particular climatic and site conditions.

Growth Recovery and Phenological Responses of Juvenile Beech (Fagus sylvatica L.) Exposed to Spring Warming and Late Spring Frost

“…Our results may suggest that the heat treatment may have caused elevated photosynthesis, as warmer temperatures increase the photosynthetic processes that are associated with light [52], and that this was not invested in growth but led to an increased starch accumulation that was exploited in the following years, resulting in an enhanced post-stress growth. An analogous result was found in a simulated browsing experiment on beech saplings, where a single experimental removal of terminal buds was compensated by increased growth (in comparison to the control) in the following year [53]. Additionally, in black oak, carbohydrate storage was shown to be favored relative to growth upon experimental defoliation [54], supporting the hypothesis of enlarged stress induced carbon storage that in its turn can lead to enhanced growth.…”

Recovery of Abies alba and Picea abies saplings to browsing and frost damage depends on seed source

“…Our results would be more informative if the experiment had been carried out at two or more locations or even with a fully reciprocal experimental design. However, no interactions between treatment and site were found for morphological traits regarding the recovery of Fagus sylvatica saplings when results from our study sites were compared with those at the lowland study site Birmensdorf (Frank et al, 2019). In addition, a reciprocal common garden experiment can be performed with only a few populations and not with seeds from 90 Abies and 72 Picea seed sources.…”

“…Very few studies have been conducted to investigate the population differences in recovery following browsing. The growth trait differences in five populations of Pinus sylvestris were found to be maintained irrespective of browsing (O'Reilly‐Wapstra et al, ), and the same was found for saplings of 77 Fagus sylvatica seed sources (Frank, Heiri, & Kupferschmid, ). However, the compensation capacity of tree species in response to leader shoot browsing depends on many factors, among them the architecture of the tree saplings (cf.…”

Assessment of the Impact of Ungulate Browsing on Tree Regeneration

“…These measurements are more difficult with Larix decidua (European larch), Fagus sylvatica (European beech), Quercus petraea (sessile oak), Quercus pubescens (downy oak), Quercus robur (common oak), and Sorbus aucurparia (rowan). This is particularly true for European beech, due to the frequent formation of second to fifth flushes [48]. In principle, it is acceptable to reduce the height increment measurements to one or two preferably browsed main tree species (e.g., silver fir, maple, and ash) and one less frequently browsed species (usually spruce or, depending on the forest type, pine) to estimate the effect of browsing on speciesspecific height growth (Figure 4).…”