Marcos Fernández-Martínez, Ferran Berloso, Jordi Corbera, Joan Garcia-Porta, Ferran Sayol, Catherine Preece and Francesc Sabater
Mosses often go unnoticed due to their small size and lack of flowers. They deserve more attention, as they are amongst the oldest plants on Earth, and they played a vital role in the initial spread of plants across the land, and continue to be important to the functioning of many ecosystems today. Their extremely simple structure – no true roots, stems or leaves and no flowers – means that they are very sensitive to their environment and relatively easy to study. Therefore studying mosses is a good way to learn about the effects of environmental changes.
We looked at aquatic and semi-aquatic mosses growing in more than 300 semi-natural springs in the north-east of the Iberian Peninsula (Catalonia). These springs are small man-made structures, which collect water from natural springs and aquifers, to provide water for people and other animals, and are common in the Mediterranean. We measured characteristics of the mosses relating to their size, shape, method of reproduction and way of growing. Wouldn’t it be useful if the mosses found in a spring could tell us about the quality of the water we find there?
We wanted to see how the characteristics of the mosses change depending on their evolutionary history and the climate and water chemistry of where they live. Two mosses that are closely related to each other would be expected to be more similar to each other in their characteristics than two mosses that are distantly related. But of course, unrelated mosses living under the same environmental conditions may also show similarities in their features.
Vascular plants (more complex plants with true leaves, roots and stems) show general patterns between plant characteristics and the environment. For example, plants that grow in dry, stressful conditions often have smaller, denser leaves and grow more slowly compared with plants growing in areas with higher rainfall. We expected to find similar patterns in the mosses in the different springs, but with the chemistry of the water being the key cause of moss characteristics.
We found that mosses living in springs with hard water (high in calcium carbonate) and a warm and dry climate were mainly species with needle-like leaves, higher density and lower capacity to absorb water. The opposite was found in cold, humid and soft water springs. We think that this difference in moss characteristics is mainly due to difficulties that mosses can have growing in hard water. Patterns in the types of mosses that live in certain places should help us to answer theoretical and applied ecological questions.