Ondřej Mudrák, Epp Maria Lillipuu, Kateřina Čápová, Tomáš Cajthaml, Jan Frouz
This is a plain language summary of a Functional Ecology research article which can be found here.
At the end of the vegetation season plants regularly shed their senescent leaves and other tissues, which affect soil conditions during decomposition. A large proportion of the dead plant biomass however also remain standing and thus unavailable to soil decomposers. Despite that, this standing or unshed dead, so called marcescent, plant biomass undergoes important changes. Structures responsible for its stability, like lignin, are partly decomposed by UV radiation and weathering. When the marcescent biomass reaches the ground, it is therefore more decomposable. Its nutrients and carbon are more accessible to decomposers than they were originally. This may stimulate the soil organisms, as they generally need organic carbon as a source of energy. At the same time plants can exert a variety of other effects on soil, like nutrient extraction or root exudation, which also have strong effects on both soil chemical composition and biota. Soil affected by such effects also significantly feeds back on plants.
We tested these interactions in a pot experiment where we explored the effect of marcescent and shed litter on three grassland species (grass Bromus erectus, and forbs Plantago media and Filipendula vulgaris). To test also the effect of soil conditions we grew these plants in soil from ancient long-term stable grassland and in contrasting soil from restored grassland, which was sown on arable land 20 years ago. Restored grassland soil was therefore disturbed by former tillage.
We found that marcescent biomass had a different effect than shed litter only on one plant species (F. vulgaris). It increased its biomass but only in the disturbed soil of restored grassland, likely due to nutrient mobilization. At the same time, in ancient grassland soil plant species affected differentially both soil chemical composition and the community of soil organisms. However, in restored grassland soil plant species modified only the soil chemical composition, which indicates differential plant-soil feedback in tilled and untilled soils.
The phenomenon of marcescence is poorly studied, but we have found that it may exert a complex effect on soil, which interacts with living plants in a species specific manner. This may play an important role in grassland restoration.