Author: isabel

As vegetation and soil jointly regulate whole-ecosystem processes, differential sensitivity and magnitude of their carbon and nitrogen responses to environmental perturbations may have implications for the functioning of tundra ecosystems. In this study, we addressed sensitivity and magnitude of short-term carbon and nitrogen responses of vascular plants, mosses, and soil to simulated goose disturbance and warming across three habitats that differ in soil moisture in a high-Arctic ecosystem in Svalbard.

Though the system’s total carbon and nitrogen contents were relatively resistant to both perturbations, the three studied ecosystem compartments still differed in their chemical responses (vascular plants > soil > mosses), and such differential sensitivity was further exacerbated by their different responses across habitats (mesic > moist > wet).

These findings highlight the potential for environmental perturbations to have small, yet differential short-term impacts on the carbon and nitrogen contents of vascular plants, mosses, and soil, both within and between tundra-habitats. They also imply that assessments of a single ecosystem compartment in a given context cannot be extrapolated to the whole ecosystem, suggesting that addressing vegetation and soil chemical responses in different habitats can advance our predictive capability of how the biogeochemistry of tundra ecosystems respond to environmental changes.

Reference: Petit Bon, M., Böhner, H., Bråthen, K. A., Ravolainen, V. T., and Jónsdóttir, I. S.. 2021. Variable responses of carbon and nitrogen contents in vegetation and soil to herbivory and warming in high-Arctic tundra. Ecosphere 12( 9):e03746. https://doi.org/10.1002/ecs2.3746

---

Text: Matteo Petit Bon, Czech Academy of Sciences.

Picture: Pink-footed geese after their arrival in Svalbard (Photo: Matteo Petit-Bon).

Insect herbivory is a significant source of plant stress and, due to climate change, the herbivory stress is continuously increasing. In the Arctic, where climate warming proceeds with the rate twice of the global average, insect herbivory stress to vegetation is expected to become more severe. In response to herbivory, plants produce specialized metabolites to fulfil physiological and ecological functions, which include volatile organic compounds (VOCs). VOCs are highly reactive and play an important role in biosphere-atmosphere interactions. Various biotic and abiotic stressors, including insect herbivory, can enhance and/or induce the production of many VOCs and alter the composition of the overall VOC blend emitted from the plants.

Due to lack of the empirical studies in the Arctic, it is unclear how the effects of insect herbivory and changing climate such as warming and increased cloudiness, which are both predicted conditions for the future Arctic, will affect VOC emissions in the changing Arctic.

Therefore, in this study we assessed how experimental manipulations of temperature and light availability in subarctic tundra, that had been maintained for 30 years at the time of the measurements, affect the VOC emissions from a widespread dwarf birch when subjected to herbivory by local geometrid moth larvae, the autumnal moth and the winter moth.

Our study showed that whether the future subarctic tundra in Northern Fennoscandia experiences rising temperatures or increasing cloudiness, and therefore milder temperature increases, matter very little for herbivory-related VOC emissions. Under both conditions, we showed strong interactions with herbivory effects on VOC emissions with potentially positive feedbacks on cloud formation. We also show that acclimation of plants to long-term climate treatments, which has resulted in changes in anatomical traits, might strongly interact with volatile responses to insect herbivory. This finding further complicates predictions of how climate change, together with interacting biotic stresses, affects VOC emissions in the Arctic.

Full article here:  https://doi.org/10.1111/gcb.15773

Reference: Rieksta, J., Li, T., Michelsen, A., & Rinnan, R. (2021). Synergistic effects of insect herbivory and changing climate on plant volatile emissions in the subarctic tundra. Global Change Biology, 27(20), 5030-5042.

---

Text: Jolanta Rieksta, University of Copenhagen.

Picture: Measuring volatile organic compound (VOC) emissions from dwarf birch in the field using branch enclosure method where VOC are collected using custom built pull-push systems. (Photo: Jolanta Rieksta).

Have you ever been puzzled by the fact that we as ecologists often lump a range of plant species into a single functional category? In this paper the focus is to the most species rich functional grouping we often apply in grasslands, the herbaceous plants with colorful flowers, the forbs. We lump them because each single species often make up a very small abundance, yet why are there so many forb species with small abundances? And why are they in sum often inferior in abundance to the grasses? If looking at forbs in a paleoecological perspective, in the cold Mammoth steppe and in which DNA-based evidence indicates the forbs flourished, we may rethink the importance of forbs and why they often do not seem to thrive in grasslands today.

You can access the paper here: https://esajournals.onlinelibrary.wiley.com/doi/10.1002/fee.2405

Reference: Bråthen, K.A., Pugnaire, F.I. and Bardgett, R.D., 2021. The paradox of forbs in grasslands and the legacy of the mammoth steppe. Frontiers in Ecology and the Environment.

---

Text: Kari Anne Bråthen, Professor, UiT The Arctic University of Norway.
Illustration: Ernst Asbjørn Høgtun