Niche characteristics of Cladonia lichens associated with geothermal vents in Japan

Abstract

To characterize the niche preferences of Cladonia species associated with geothermal areas, we sampled ten thermal areas in Japan. It appears from the current study and related studies that some members of the Cladonia genus can have a wide tolerance for both soil temperature and pH conditions. Cladonia mitis is the most abundant Cladonia and occurs throughout most of the vent system. Cladonia theiophila occurs most frequently at a soil pH of less than 3.5, but occurs mostly at lower soil surface temperatures (below 29~ Cladoniafloerkeana is very restricted in its distribution and is most abundant where the root zone temperature (15 cm) is above 70~ the surface temperature is above 40~ and the pH is 5-5.5. Tolerances to low pH, high soil temperatures, and low to moderate humidity permit Cladonia species to grow where vascular plants and even mosses cannot grow and thus they avoid the competition such plants would provide to these slow-growing organisms.

Vegetation change along a geothermal stress gradient at the Te Kopia steamfield

“…Sheppard (1971, fig. 21) and Glime & Iwatsuki (1994) also observed that soil pH affected the distribution of some bryophytes in geothermal Table 5 Results of second soil analysis per vegetation association. Vegetation associations (Assoc.)…”

“…Given (1980) at Karapiti, Glime & Iwatsuki (1994) at Ponponyama (Japan), Sheppard (1971) at Yellowstone National Park (U.S.A.), and Broady et al (1987) at Mt Melbourne (Antarctica) all found that geothermal vegetation zonation was closely related to soil temperature in the root zone. Similarly at Te Kopia plant species are differentially sensitive to temperature, showing gradual increase or decrease in abundance with changing soil temperatures.…”

Geothermal bryophyte habitats in the South Sandwich Islands, maritime Antarctic

“…2c, d). As suggested by these authors, this is most likely to be related to the different thermal and/or moisture tolerances of the species concerned (see also Glime & Iwatsuki 1990).…”

Distribution drivers and physiological responses in geothermal bryophyte communities

“…However, neither morning nor midday temperature is a key driver for the other species we investigated. Previous studies have indicated that temperature is key to limiting angiosperms from dominating high‐temperature geothermal sites (Glime and Iwatsuki, 1990; Stout and Al‐Niemi, 2002). The lack of belowground tissues in geothermal bryophytes (temperatures increase with soil depth in this system) and the fact that bryophytes act as thermal insulators (Casanova‐Katny and Cavieres, 2012), potentially further protecting their growing tips against high temperatures, likely gives bryophytes a significant competitive advantage compared to angiosperms in geothermal environments.…”

“…We conducted extensive surveys of geothermal bryophyte populations at Lassen Volcanic National Park (LVNP), California, USA, where midday temperatures range from 21°C to 73°C at the level of the rhizoid (the structure attaching mosses to a substrate). These geothermal bryophyte sites are atypical of many bryophyte habitats, in that they lack the shading associated with an overhead canopy, and only a few small vascular plants are able to grow in these areas because of high temperatures in the root zone (Glime and Iwatsuki, 1990; Stout and Al‐Niemi, 2002). However, we have also found that in addition to an extreme temperature gradient, an extreme moisture gradient also runs through these habitats, based on aspect and daily evapotranspiration cycles: steep slopes provide continually high‐moisture habitats, while low‐gradient habitats provide fluctuating daily wet–dry habitats.…”