The Editor’s Choice for our July issue is “Plant diversity effects on plant longevity and their relationships to population stability in experimental grasslands” by Roeder et al. The findings of this article show that the diversity of a grassland community can directly affect the longevity of the forbs, and thereby the temporal stability of populations of these species.
Here Senior Editor, David Gibson, explains the importance of this article, which he selected as this month’s Editor’s Choice.
As a grassland ecologist I’ve often had a bit of forest ecologist envy as these researchers can often quite accurately learn the ages of the woody species they study. Foresters are quite used to taking tree cores and counting annual growth rings, at least in temperate forests.
Cross section of Plantago lanceolata in polarized light showing growth rings. Photo: Anna Roeder.
It turns out that many herbaceous forbs also have annual growth rings that can be counted from tissue collected at the top of the tap root (image above). However, this approach is not quite the silver bullet for aging all species in an herbaceous community such as a grassland. The primary root of a clonal species often decays or can’t be found. In addition, genetic individuals are often difficult to identify in clonal species.
Notwithstanding the difficulties in identifying individuals and finding old tissues with growth rings, Roeder and colleagues took advantage of the Jena Experiment in Germany to investigate age/community diversity/stability relationships. The 12 year-old Jena Experiment was established with experimental treatments controlling plant species richness (1, 2, 4, 5, 8 and 16 species) and functional group number (1,2, 3, and 4 functional groups).
(Left) Field site of the Jena Experiment, Germany. (Right) Flowering individual of Plantago media L. on the plot. Photos: Anna Roeder.
Roeder and her team sampled herbaceous plants from the experimental plots and asked three questions: (1) Do forb species representing different functional groups or growth forms differ in plant age? (2) Does plant diversity affect plant age? and (3) Is plant age positively related to population stability? The answers to these questions was essentially “yes”, but the response of clonal versus taproot species were opposite highlighting the relevance of herbaceous plant age and growth form for a better understanding of community diversity.
(Left) Individual of Plantago media L. with washed root, an example of a species with taproot. (Centre) Individual of Heracleum sphondylium L. with washed root, an example of a species with taproot. (Right) Individual of Ajuga reptans L. with washed root, an example of a species with clonal growth. Oldest plant part is on the right side. Photos: Anna Roeder.
Overall, I found this to be a novel and intriguing study that makes me want to dig up some herbaceous plants and count their growth rings!
David Gibson Senior Editor, Journal of Ecology
You can read the full article by Roeder, Schweingruber, Ebeling, Eisenhauer, Fischer, & Roscher here: Plant diversity effects on plant longevity and their relationships to population stability in experimental grasslands