2. History of apothecial growth and substratal decay


A. Growth history and longevity of xerotolerant Orbiliomycetes


Apothecia of xerotolerant species are more or less perennial due to shorter or longer periods of dormancy in their life cycle during dry weather. Under temperate climate apothecia of Orbiliomycetes apparently exist up to roughly a year in the field (from immature to overmature stages) if not grazed away by animals (see below images). In the semideserts apothecia undoubtedly persist several years in the living state (being dry over most of the time). Tests with herbarium specimens showed that Orbilia apothecia from semideserts remain alive over max. 2-3 years, thereby not undergoing any maturation processes. In semideserts, the very rare but often heavy rain permits growth for a short period of time, thereby probably setting back the “inner clock” so that single apothecia, at least theoretically, may even survive for several decades.


The below experiment shows a population of Orbilia trapeziformis sp. nov. (Germany, Tübingen, on decorticated, 12-13 mm thick, broken branch of Juglans regia hanging in 1.5 m above ground in a shrub) being under observation during a period of four months. Photos were made indoor if the branch was naturally wetted by rain; then the branch was brought outside at its original position. Most of the time of observation the branch including the apothecia was completely dry. Three apothecia survived the whole period of time, thereby remaining fully alive, whilst many have disappeared, obviously by grazing of invertebrates (such damage is a well-known problem with herbarium specimens).












B. Decay history of xeric substrate: slowness of decay of dry branches under temperate climate


Decay of medium-sized dead branches in temperate areas (natural pruning) lasts over roughly 10-20 years, strongly depending on the thickness of the branch, hardness of the wood, and protection against drying wind and sunshine. In semideserts dead branches obviously persist much longer (about 50-100 years) until being completely decayed.


The below experiment shows a ca. 1 m long dead branch of Quercus robur still attached in 3.5 m above ground (Germany, Tübingen) which was accidentally documentated in Feb. 1996 and again in Sept. 2003 and Jan. 2009. It had already lost its bark before 1996, and its sapwood appears strongly decayed on the foto. During 7.5 years the complete sapwood was broken away by natural decay. Since this branch was left at its position in order to allow study of its further decay, it was not examined for fungi so far.


II.1996: bark present only at base of branch, decorticated sapwood already strongly rotten.

Same branch, IX.2003: all sapwood removed, surface of heartwood already strongly rotten.

 I.2009: very little decay occurred to the hard wood core during further 5 years.