In this Behind the Paper blog post, Šárka Angst – a research assistant at the Czech Academy of Sciences – discusses her paper “The effect of dead standing (marcescent) biomass on litter decomposition in herbaceous flora is governed by plant functional group“. Šárka discusses the ecological relevance of marcescence, conducting fieldwork in the cold, and how she’s developed a passion for soil ecology.
About the paper
Marcescence, i.e., when plants retain their dead biomass, has been attracting the interest of our team already for more than a decade. Not only trees such as beech or oak keep their dead leaves on the treetop during the whole winter season until the beginning of spring, but a remarkable number of herbs are marcescent as well. We recognized the real extend of marcescence across temperate herbs when we visited the common-garden experiment of our colleague Renáta Schnablová in winter 2020. Renáta planted more than 200 temperate herb species in her common garden, and most of them were, at least partly, marcescent. We quantified the extent of marcescence in that experiment (summarized in the study by Mudrák et al (2023) and asked ourselves whether this phenomenon has any ecological relevance, e.g., with respect to plant tissue decomposition. We were curious about this because substantial amounts of marcescent herb biomass remains standing during the dormant season without direct contact to the soil until it is finally shed (in case of leaves) or the plant collapses (in case of stems) to the ground in spring. This may be important to decomposition because in this process, not only the chemistry of the tissues themselves, but also the environment plays a substantial role. Marcescent plant parts are more exposed to solar radiation, freeze-thaw cycles, or precipitation, while microbial colonization and decay of those tissues are strongly limited.
To clarify the impact of marcescence on decomposition, we designed a 6-month experiment in which we compared the decomposition of marcescent and directly shed plant tissues of 40 temperate herbs in soil. We found that marcescent tissue decomposed much slower than the directly shed litter. A crucial factor explaining these differences was probably microbial colonization, which was much higher for the directly shed litter, although both types of plant tissues were incubated in the same soil for the same time. The dissimilar environmental conditions the two tissue types were exposed to in the first period (i.e., when part of the biomass is already in contact with the soil and another part remains standing) seemed to have a great impact on the whole decomposition process, in which directly shed litter appeared to be more susceptible to microbial decay. Notably, the effect of marcescence was more pronounced for forbs than for grasses. We suppose that this is to plant architecture. While forbs usually shed easily decomposable litter, their more recalcitrant stems with higher lignin contents remain marcescent. In contrast, the decomposability of marcescent and directly shed plant tissues of grasses is similar, which results in minor differences in decomposition between these tissues.
We highlight that marcescence, which has been a rather overlooked phenomenon, can have a large impact on herb litter decomposition and consequently on environmental carbon and nutrient cycling. In view of how common marcescence is, its relevance for further ecological processes may be great.
About the research
For our experiment, we needed marcescent and shed plant material. We thus had to collect this material in winter after the litterfall period and before the next vegetation season. Warm clothes and a lot of tea were thus mandatory. Using the common-garden experiment of our colleague Renáta, however, made our task much easier as we did not have to sow the plants or collect them in nature ourselves. We sampled over 100 herb species, but due to limitations in available material for both marcescent and shed plant tissues, we chose 40 species for our decomposition experiment. The establishment of the experiment was quite easy, then. Using litterbags, we let the biomass decompose in soil for six months. Apart from determining microbial biomass and community composition using phospholipid fatty acid analyses, we also focused on chemical changes in the plant tissues. An interesting niche for future research would be the observation of the microbial colonization process. Only little is known about how senescing plant tissue is colonized by microorganisms and how this colonization differs between directly shed and marcescent tissues because most previous research has focused on processes in soil.
About the author
I have always loved nature and focused on environmental protection. My way to soil science and soil ecology was the result of the enthusiastic university lectures by my, at that time future, Ph.D. supervisor Jan Frouz (he was also the one who had the idea of focusing on the decomposition of marcescent litter of temperate herbs). By focusing on soil science, especially on chemical changes during litter decomposition, I for the first time recognized the relevance of ecological factors such as soil fauna and marcescence in this process. During my postdoc stay at the German Centre for Integrative Biodiversity Research (iDiv), Germany, I was involved in long-term ecological experiments, such as the Jena experiment, which inspired me to connect soil science and ecology. I have recently returned to my home institute at the Biology Centre of the Czech Academy of Sciences, Czech Republic, as a research assistant. My research focuses on the effects of plant diversity and soil biota on litter decomposition and soil organic matter stabilization. In my free time, I like to spend time with my family, especially on trips to nature.
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