Accidental epiphytism in the Harz Mountains, Central Europe

Abstract

Questions: Vascular epiphytes make up about 9% of all vascular plants globally but are clearly underrepresented in the temperate zones. The accidental epiphytic occurrence of terrestrial species, in contrast, is common at these latitudes and can provide important insights in the evolution of obligate epiphytes. Here, we present the results of the first two annual censuses of a planned long-term study on accidental epiphytes. We particularly aim to identify: (a) the abundance and species richness of accidental epiphytes; (b) the dynamics of accidental epiphytism; (c) occupied substrates and microsites; and (d) suitable host tree species. Location: Harz Mountains, Germany, Central Europe. Methods: We surveyed more than 1,200 trees in a low mountain range in two consecutive years for epiphytic individuals of vascular plants, considering host tree species and occupied microsites. Results: About one quarter of the surveyed trees hosted epiphytic plants, totalling 1 450 (2016) and 1 350 (2017) individuals, respectively. These belonged to more than 100 species and 39 different families. The majority of epiphytic individuals newly emerged in 2017, whereas one-third persisted since 2016 (or earlier) and a smaller proportion even reproduced in the epiphytic habitat. Accidental epiphytes were mostly restricted to host tree species providing water-storing substrates such as extensive moss pads or arboreal soil accumulated in crotches. Compared to tropical epiphyte communities, accidental epiphytes in the temperate zones show a higher turnover, as they are less consistent in species abundance and composition in time.Conclusion: For the majority of the observed species, epiphytism indeed is an accidental phenomenon. Undoubtedly, abiotic conditions limit the occurrence of obligate epiphytes at higher latitudes, but the presence and persistence of numerous epiphytic individuals illustrate that abiotic conditions do not per se preclude epiphytic occurrence of vascular plants in the north-temperate zone. Besides water shortage, the availability of suitable host trees is a decisive environmental factor that contributes to limit epiphytism of vascular plants in Central Europe.

Diversity of Vascular Epiphytes in Urban Green Areas of Juiz de Fora, Minas Gerais, Brazil

“…Similarly, we could associate the high occurrence of palm trees found in the squares studied in Juiz de Fora with the number of AE species being higher than CHL, since several AE (although not necessarily ferns) were observed in the same condition highlighted by Benzing (1990). However, further discussion is not possible due to the scarcity of systematic data on accidental epiphytes (Hoeber et al, 2019).…”

Facultative hemiepiphytism as a recruitment strategy in small‐seeded tree species

“…Epiphytism is an ecological condition that exists on a spectrum (Burns, 2010), and as such the number of plant species which utilise either facultative or accidental epiphytism to some extent may be severely underestimated (Zotz and List, 2003). Recent evidence concurs that accidental epiphytism appears to be more widespread than previously thought, including in temperate regions (Hofstede et al ., 2001; Zotz, 2005; Hoeber et al ., 2019). Furthermore, our arboreality score (used with a survey approach controlling for substrate area) is an easily applicable way of quantifying the degree to which species occur epiphytically.…”

“…Furthermore, our arboreality score (used with a survey approach controlling for substrate area) is an easily applicable way of quantifying the degree to which species occur epiphytically. Accidental epiphytes are also known to relatively frequently reach reproductive maturity (Sharp, 1957; Hoeber et al ., 2019).…”

Advanced canopy regeneration: an unrecognized mechanism of forest dynamics

“…1). First, we considered these observations resulted from the accidental epiphytic habit of tree seedlings (e.g., Hoeber et al 2019); however, in a later visit to the Guabún forest in 2014, we found a large recently fallen tree (less than one year ago) covered with numerous tree seedlings and saplings up to 2 m tall. A close examination revealed that most seedlings were rooted in the thick arboreal soil held on the crown branches and the main trunk.…”

“…In old‐growth forests of the Smoky Mountains (USA), Sharp (1957) described that the epiphytic habit was frequent in five species of trees, also indicating that some epiphytic individuals had over three inches in diameter and were able to reproduce. In European temperate rainforests, Hoeber et al (2019) reported that at least 10 tree species had seedlings occurring in forest canopies, while in Canadian forests, Burns (2010) classified seedlings from two tree species as facultative epiphytes. In New Zealand, trees often regenerate on stems of tree‐ferns, evidencing their ability to recruit on canopies (Gaxiola et al 2008).…”