Mudrák Ondrej discusses his recent article: Ecological significance of standing dead phytomass: Marcescence as a puzzle piece to the nutrient cycle in temperate ecosystems.
❄️ Why do some plants retain their dead tissues and others don’t?
As the winter approaches and the first freezing temperatures sweep across temperate climates, plants become dormant and shed their leaves. However, during a winter walk through the botanical gardens, we recognised that not only did some trees retain their dead, brown leaves, but also that the stalks and leaves of various grasses and herbs were erect, although already pale and without colour. You may have noticed this phenomenon, termed marcescence, yourself when walking through a snowy landscape. But does marcescence have a function in nature, or is it a remnant from the bygone summer without specific meaning?
☀️ Background
We knew that marcescence had been relatively well researched in arid ecosystems, in which solar radiation strongly degrades difficult-to-decompose compounds in retained biomass. This facilitates decomposition and nutrient release from the biomass once shed, with potential competitive advantages for the respective plants. Solar radiation can even cause direct losses of carbon fixed in marcescent biomass to the atmosphere. In temperate regions, however, research has been scarce and mainly focused on tree species, with few exceptions. Here, solar radiation is much less intense, so the photodegradation potential is likely low, and other environmental conditions acting on marcescent biomass such as freeze-thaw cycles, exposure to precipitation, or restricted access to decomposers may have higher relevance. Yet, virtually nothing is known about marcescence in the temperate herbaceous flora, although simple observations indicate that it is widespread. We thus asked ourselves, how common is marcescence in temperate herbaceous flora, and can it be linked to certain plant traits?
🍂 The experiment
Behind our exploration of marcescence was a random meeting of two of the future co-authors of our study, Jan and Tomáš. Jan asked in a deep voice: “Tomáš, you are a plant ecologist, do you know the term marcescence?” Tomáš was embarrassed and replied: “I have no idea what that is”; so Jan explained the concept and outlined a few ideas that might be tested. They then realized that some of their colleagues were also interested in marcescence, and that Renáta was already running a large common garden experiment that could directly be used to assess marcescent tissues in a large set of species.
The experiment was ideal to tackle our research question as the plants were grown in the same soil substrate and under the same climate. We thus gathered to create a battle plan. We sampled dead biomass from 127 plants shortly before the start of the subsequent growing season, determined the proportion of marcescence for each of these plants, and related this proportion to plant functional traits.
Middle: Determining the proportion of marcescence in the field (credit: Šárka Angst).
Right: Measuring plant functional traits in the laboratory (credit: Šárka Angst).
🔎 Major findings – marcescence is common in nature and may have important functions
To our surprise, almost all of the investigated plants (123 of 127) kept at least part of their biomass marcescent, indicating the commonness of marcescence in temperate flora. Marcescence particularly predominated in tall plant species with small leaves and high carbon concentrations in their tissues, and in those commonly preferring intensely disturbed sites. Marcescence may thus serve to provide advantages for certain plants in the initial stages of succession.
📚 In conclusion
Our results indicate that marcescence indeed has a function in nature, with potentially strong effects on carbon and nutrient cycling. As we are just beginning to understand the determinants and function of marcescence in temperate regions, intensified research efforts are crucially needed to disentangle the relevance of this widely overlooked phenomenon to ecosystem functioning.
Apart from providing novel insights into marcescence, our research has also changed our perception of the local flora in everyday life, and paying attention to marcescence during your next autumn or winter walk might change yours as well!
Mudrák Ondrej, Charles University, Czech Republic
Read the full article online: Ecological significance of standing dead phytomass: Marcescence as a puzzle piece to the nutrient cycle in temperate ecosystems.
