Victoria Gonzalez

Adviser

(+47) 916 84 166
victoria.gonzalez@nibio.no

Place
Svanhovd

Visiting address
Svanhovd, NO-9925 Svanvik

To document

Abstract

1. Altered species composition caused by environmental and climatic change can affect the transfer of plant residues among communities. Whereas transferred residues are typically considered a resource in recipient systems, residues of allelopathic species may instead cause interference. 2. Evergreen dwarf shrubs, specifically the allelopathic species Empetrum nigrum are increasing in abundance in response to a warming climate. Empetrum has small, evergreen leaves that can be transferred to other communities when withered and lost from the plant. 3. We hypothesize that Empetrum can have allelopathic effects in the recipient communities of the withered leaves. We call this allochthonous allelopathy as opposed to autochthonous allelopathy, which is well documented in communities where the plant grows. 4. We measured influx of allochthonous Empetrum leaves onto snow-covered snowbeds, where they are easily identified within the debris. Next, we compared the bioactivity of allochthonous withered leaves with that of green Empetrum leaves. Finally, we conducted an experiment testing the germination and seedling growth of 10 tundra species in snowbed soil supplemented with no (control) and three densities of allochthonous Empetrum leaves. 5. We found Empetrum leaves to be common on the snow cover of snowbeds. We found Empetrum leaves collected on snowbeds to be as bioactive as green leaves. Finally, we found forb species to have reduced germination and all 10 species to have delayed seedling development when growing in snowbed soil supplemented with withered Empetrum leaves. Seedlings under the control treatment were 2.3 times longer and had 3.2 times more leaves in comparison to seedlings grown under the strongest allochthonous leaf treatment. 6. Results from our study imply that Empetrum is allelopathic in recipient systems of its allochthonous leaves. The abundant nature of Empetrum in the tundra suggests that allochthonous allelopathy is a common phenomenon, causing biotic stress in snowbeds and potentially other parts of the tundra. Exemplifying the ability of a plant to interfere in neighbouring communities, our study demonstrates a plant trait that may provide insight to other study systems.

Abstract

Citizen science can facilitate in‐depth learning for pupils and students, contribute to scientific research, and permit civic participation. Here, we describe the development of the transnational school‐based citizen science project Phenology of the North Calotte. Its primary goal is to introduce pupils (age 12–15; grades 7–10) in northern Norway, Russia, and Finland to the local and global challenges of climate change resulting in life cycle changes at different trophic and ecosystem levels in their backyards. Partnerships between regional scientists and staff from NIBIO Svanhovd, State nature reserves, national parks, and teachers and pupils from regional schools aim to engage pupils in project‐based learning. The project uses standardized protocols, translated into the different languages of participating schools. The phenological observations are centered around documenting clearly defined life cycle phases (e.g., first appearance of species, flowering, ripening, leaf yellowing, snow fall, and melt). The observations are collected either on paper and are subsequently submitted manually to an open‐source online database or submitted directly via a newly developed mobile app. In the long term, the database is anticipated to contribute to research studying changes in phenology at different trophic levels. In principle, guided school‐based citizen science projects have the potential to contribute to increased environmental awareness and education and thereby to transformative learning at the societal level while contributing to scientific progress of understudied biomes, like the northern taiga and (sub)arctic tundra. However, differences in school systems and funding insecurity for some schools have been major prohibiting factors for long‐term retention of pupils/schools in the program. Project‐based and multidisciplinary learning, although pedagogically desired, has been partially difficult to implement in participating schools, pointing to the need of structural changes in national school curricula and funding schemes as well as continuous offers for training and networking for teachers.

To document

Abstract

Climate change is modifying temperature and precipitation regimes across all seasons in northern ecosystems. Summer temperatures are higher, growing seasons extend into spring and fall and snow cover conditions are more variable during winter. The resistance of dominant tundra species to these season-specific changes, with each season potentially having contrasting effects on their growth and survival, can determine the future of tundra plant communities under climate change. In our study, we evaluated the effects of several spring/summer and winter climatic variables (i.e., summer temperature, growing season length, growing degree days, and number of winter freezing days) on the resistance of the dwarf shrub Empetrum nigrum. We measured over six years the ability of E. nigrum to keep a stable shoot growth, berry production, and vegetative cover in five E. nigrum dominated tundra heathlands, in a total of 144 plots covering a 200-km gradient from oceanic to continental climate. Overall, E. nigrum displayed high resistance to climatic variation along the gradient, with positive growth and reproductive output during all years and sites. Climatic conditions varied sharply among sites, especially during the winter months, finding that exposure to freezing temperatures during winter was correlated with reduced shoot length and berry production. These negative effects however, could be compensated if the following growing season was warm and long. Our study demonstrates that E. nigrum is a species resistant to fluctuating climatic conditions during the growing season and winter months in both oceanic and continental areas. Overall, E. nigrum appeared frost hardy and its resistance was determined by interactions among different season-specific climatic conditions with contrasting effects.

To document

Abstract

Organisms that modify the environment (niche constructors) are likely candidates to mediate the effects of climate warming. Here we assess tundra plant community changes along a temperature gradient and how these are modified in the presence of the common allelopathic dwarf shrub Empetrum nigrum and the large herbivore Rangifer tarandus. We developed a structural equation model based on data from a field-based study of 1450 tundra plant communities across Northern Fennoscandia, covering a temperature gradient of 3.5 °C, contrasting Rangifer densities, a range of Empetrum abundances in addition to gradients in topography and bedrock. We found temperature to be a significant positive predictor of Empetrum, herbaceous and woody plant abundances. However, the effect of temperature as predictor for herbaceous plant abundance was significantly reduced in communities with Empetrum present. For woody plant abundance Empetrum was a stronger predictor than temperature. In comparison, we found Rangifer density to have marginal or no effect on either herbaceous or woody plant abundance. These findings were not modified by either topography or bedrock. Results from this study indicate that herbaceous plant responses to climate warming are currently reduced in communities where Empetrum is present, whereas the abundance of Empetrum and other woody plants is promoted. Results also indicate that any future Empetrum encroachment is likely to drive tundra communities towards slower process rates and lower biodiversity. As such our results substantiate the importance of understanding the dynamics of niche constructor species and include them in predictive models of climate change.