Alt: Stable nutrient patches in the field seem attractive for plant roots

In this new post Hana Skálová, from the Institute of Botany in Průhonice (Czech Republic), presents her recently published article “Cations make a difference: Soil nutrient patches and fine-scale root abundance of individual species in a mountain grassland.” She discusses the importance of overlooked nutrients on plant roots, highlights how new technology enables the advancing of ecological research, and celebrates the people who accompanied her along her research career.

About the paper

The ability of roots to proliferate in nutrient rich patches in artificial settings is well known. The relevance of these findings under field conditions remain uncertain, however, as we do not know how stable these nutrient patches are in the field. The scarce data available indicate that nutrient patches in the field likely appear and disappear too fast to be exploited by root growth. Yet the existing data address only the most essential nutrient, namely ammonium and nitrate nitrogen—other essential nutrients have been largely overlooked. We therefore decided to examine the patch stability of a spectrum of main nutrients: phosphates, potassium, calcium, magnesium, together with nitrates and ammonium, and linked it to presence of roots of the twelve most frequent species at our field site.

We confirmed the brief persistence of nitrogen but found considerable patch stability of elements with low mobility in the soil: all three cations (calcium, magnesium, potassium) as well as phosphorus. This breakthrough finding can change our thinking about root placement in nutrient patches. Indeed, nutrient patches were associated with high root biomass and the occurrence of roots of several species. The relationship was most pronounced for the bivalent cations, calcium and magnesium. As these elements affect a number of plant functions, their association with higher root densities confirms their role in the growth dynamics of terrestrial ecosystems.

Our main finding “patches of some nutrients are stable enough to be explored and some species do it”, opens many questions on the mechanisms and consequences that could be addressed by manipulative field and mesocosm experiments.

About the research

We conducted the study in “our” meadow in the Krkonoše Mts, North-eastern Bohemia, where some of us have been working since the early 1980s. Until fairly recently, we were unable to address belowground processes with a resolution comparable with research on aboveground plant parts. Two factors made this particular work possible.

First, it was Rhizon SMS samplers that have become commercially available and turned out to be a wonderful tool to get soil nutrient solution at a fine scale. Placing the samplers into the soil and taking them out—together with roots that surround them—turned out to be a monumental task in itself.  We gathered many tools from our households, from well sharpened kitchen knives and tubes, to knitting needles—which turn out to be the best thing to make tiny holes into which the samplers could be placed—and a special type of garden paddle that survived ceaseless hammering and prying through stony soil.

The second was the progress of molecular techniques, mainly the development of species-specific markers to identify plant roots. All roots look the same and determining/differentiating species has been nearly impossible until very recently. Owing to the tremendous preparatory molecular work of our colleagues, Karol and Tereza, we now possess quantitative assays for more than a dozen of the common species there, and we were thus able to tell which of them were associated with which nutrient patch in the soil.

About the author

My mother, a chemical engineer by profession, was the person who provided my first contact with botany. To ensure intellectual entertainment for the holidays, she bought a plant atlas and we collected plants together that we later identified. As a Masters student I was invited by a group that just started their investigation on the mountain grassland that became a part of our scientific lives. At that time the group included František Krahulec who was familiar with the mountain meadows at a landscape scale, Tomáš Herben who was interested primarily in the fine scale processes in plant communities, and Věra Hadincová and Marcela Kovářová who were interested in soil nutrients. Two years after my arrival, the group was joined by Sylva Pecháčková who studied plant underground structures.

My first contribution was a paper on the response of one of the dominants, Festuca rubra, to changes in light quality reflecting results of my master thesis. I developed this topic in my PhD thesis by describing radiation conditions in the grassland canopy and variability in the plant response. In the 1990s, the mountain grassland study was the main research topic for all of us. Later I partly switched to plant invasions and studied their mechanisms and impacts using model species such as the complex of European native and invasive Impatiens and Ambrosia artemisiifolia; even more recently I participated in a study of cryptic invasion of Phragmites australis, hybridisation and spread of Carpobrotus species, seed banks of non-native species ,and similar invasion-related topics. However, the montane meadows of my earliest scientific steps are still deep in my heart. Just like my colleagues, I am still fascinated by the multitude of processes driving them.  I am honoured to participate in their study, especially now that new techniques have appeared that enable us to examine the community belowground, and our working group which includes fantastic people with diverse skills and expertise, driven by a desire to cooperate.

Enjoyed the blogpost? Read the research here!