The study of mosses could help understand environmental impacts

Mosses are an important but sometimes overlooked group of plants, which play a significant role in cycling in carbon and nitrogen between the land and the air. A new study proposes that scientists could use mosses as a model to investigate the impacts of environmental change on biodiversity and nature.

Over 10,000 different species of moss grow around the world, from the tropics to the arctic, in water and on land, varying from tree-like stalks to dense mats. They play an important role in nutrient cycling and in carbon sequestration and also provide habitat to a large diversity of flora and fauna. However, despite the existence of so many important processes in such a small system, there are few attempts to use mosses to study the impacts of environmental change, such as the effects of climate change.

The study reviewed existing research on mosses and proposed a formal definition of the 'bryosphere' as 'the combined complex of living and dead moss tissue and associated organisms, representing a tightly coupled system of both above and below ground processes'.

The bryosphere consists of the above ground zone, which is alive and growing, and the below ground zone, which is dead and includes decaying moss and litter. The linkages between these two ecosystems make the bryosphere potentially useful as a model to study the interactions between above and below ground processes.

The bryosphere hosts a diverse community of microorganisms and invertebrates. For example, there are 158 types of fungi living on moss in Northern forests. Less is known about the bacteria that inhabit the bryosphere apart from the cyanobacteria which work together with the moss to 'fix' nitrogen - a process that makes this essential nutrient (nitrogen) available to plants. There are also a range of larger wildlife that inhabit the moss including mites, insects and spiders.

Like other plants, the bryosphere uses and produces CO₂ through respiration and decomposition. However, because it decomposes more slowly than most plants, it tends to store carbon for longer before releasing it. In addition, the bryosphere has been shown to capture an estimated 10-36 per cent of the CO₂ produced from decomposition and respiration from the forest floor. As the bryosphere stores a significant amount of carbon it is likely to be affected by climate change, which will increase CO₂ levels. Land use change will also have consequences for the bryosphere carbon cycle.

The properties of the bryosphere offer opportunities to study many ecosystem processes. Due to its layered and compact structure it can be sampled and manipulated as a whole system in the field or transported to the laboratory. In other words, it could be used as a Natural Model System (NMS) to study its response to changes in environmental conditions, such as climate change, CO₂ change or land use change. However, as the bryosphere is small-scale, it may not always be possible to transfer findings to larger scale systems. The study suggested it may be beneficial to combine its use with larger-scale research, for example, using the bryosphere to test predictions from models that forecast environmental changes at a larger scale.

Source: Lindo, Z. & Gonzalez, A. (2010) The Bryosphere: An Integral and Influential Component of the Earth's Biosphere. Ecosystems. 13:612-627.

Contact: zoe.lindo@mcgill.ca