Roots reveal functional differences between arid zone species

Irene Vega

Despite having limited availability of water and nutrients, arid Mediterranean environments are characterized by hosting a large number of plant species. In these ecosystems, plant-soil interactions are very important, since both herbaceous and woody species coexist, with known functional differences in the aerial part, stem structure and growth patterns. However, the role played by roots is little studied and is a key element to understand the coexistence processes between species.

A novel study, conducted by the Global Change Research Institute (IICG) of the Rey Juan Carlos University, has explored the possible functional differences between herbaceous and woody species that coexist in the same Mediterranean plant community, focusing especially on root characteristics related to nutrient use and growth.

The results obtained, published in the journal functional ecology, show that the growth of all species is closely associated with functional traits of the roots. “For example, a lower density of root tissue appears to be related to faster growth. We also highlighted many functional differences at the root level between herbaceous and woody species,” explains Angela Illuminati, researcher at the IICG and co-author of the study. “Our results suggest that the constant coexistence of the two functional groups is potentially associated with a diversification of strategies for capturing and using soil resources,” she adds.

To carry out the research, the IICG scientific team conducted a common garden experiment with a total of 23 species, of which 7 were herbaceous and 16 woody. In total, 17 functional traits were measured - aerial and root such as their diameter or tissue density - related to growth, nutrient use and size.

a) Experimental tubes buried in soil for individual root growth, b) Longitudinal section of one of the tubes (first 15 cm). c) Image of scanned roots and measurement of traits with WinRHIZO software (each color identifies the total root length (cm) by different diameter classes). Image credit: Angela Illuminati.

This work represents a step forward in the knowledge of the functional characteristics of plants in arid Mediterranean environments and, consequently, of the processes that regulate their coexistence. “A better understanding of the functioning of Mediterranean arid ecosystems is of special interest for the management and conservation of natural heritage in the context of climate change,” concludes the URJC researcher.