Are wide aquatic moss distributions helped by flexible nutrient use?

Posted on December 18, 2015


In headwater streams, mosses and liverworts (bryophytes) are often the dominant and most productive plant forms, and they provide shelter and feeding sites for small invertebrates. However, despite their ecological significance, stream bryophytes haven’t received much attention in the research literature. To investigate how ecological variables affect bryophyte distributions and diversity, 20 m stretches of 26 streams draining the Shawangunk Mountains in the south-east of New York State, U.S.A. were sampled in spring and summer. Water samples were collected, and details of channel morphology, stream substrate, canopy cover and the abundance of bryophytes and other plants were recorded. A total of 33 bryophyte species were identified. Bryophyte distributions were closely related to stream pH and the amount of bedrock at a given site. These two factors were probably related, since the local conglomerate bedrock is known to increase stream acidity. In low-pH streams, dissolved inorganic phosphorus was relatively scarce. Laboratory assays showed that species and populations of bryophytes from acidic streams tended to have stronger phosphatase activity at lower pH than those from higher pH streams. Given that phosphatase (specifically, phosphomonoesterase) allows bryophytes to use organic P when inorganic P is in short supply, it seems that the relationship between pH and bryophyte distributions is coupled with the ability of these plants to use organic as well as inorganic nutrient sources.

Reference: Tessler, M. et al. 2014. Diversity and distribution of stream bryophytes: does pH matter? Freshwater Science 2014, 33(3), 778–787. http://www.jstor.org/stable/10.1086/676996

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