CC2: Biodiversity and climate change: impacts on non-marine ecosystems

Date: Wednesday October 10, 2018

Location: Saivo, Lappia Hall

Time: 15:15-17:15

Freshwater and terrestrial ecosystems are undergoing multiple drivers of change. As the Arctic warms and the tundra greens, entire regime shifts, diversity and assemblages may change. This session explores how any why terrestrial and freshwater ecosystems are changing, the diverse responses to drivers, and the resulting implications for biodiversity and management, including the exploration of possible tipping points and surprise cascading effects.

Chairs: Arkady Tishkov, Institute of Geography, Russian Academy of Sciences; Leigh Welling, US National Park Service

Format: Series of presentations, followed by question/answer and discussion

Presentations:

1. Biodiversity in heathlands and barrens of Nova Scotia, Canada: islands of “Subarctic” vegetation in temperate and boreal zones: Jeremy Lundholm, Saint Mary's University 
2. Responses of tundra carbon cycling and storage to reindeer-induced vegetation transition: Henni Ylänne, Lund University 
3. Greening of the tundra as a driver of the current trends in the Arctic biota: Russian Perspective: Elena Belonovskaya, Institute of Geography, Russian Academy of Sciences 
4. Geomorphology shapes multidiversity patterns of Arctic vegetation: Miska Luoto, University of Helsinki 
5. Water as a resource, stress and disturbance shaping tundra vegetation: Julia Kemppinen, University of Helsinki  
6. The future of Arctic biodiversity is dependent on evolution of the snow cover: Pekka Niittynen, University of Helsinki 
7. High-potential for a future tipping-point in Arctic land surface conditions: Juha Aalto, University of Helsinki  
8. Climate and productivity forced regime shifts in subarctic lakes: Kimmo Kahilainen, UiT The Arctic University of Norway 

Abstracts

Biodiversity in heathlands and barrens of Nova Scotia, Canada: islands of “Subarctic” vegetation in temperate and boreal zones

Jeremy Lundholm, Saint Mary's University; Caitlin Porter, Saint Mary's University

Barrens in Nova Scotia, Canada are characterized by heaths dominated by low-growing Ericaceous shrubs such as Empetrum spp. and resemble tundra habitats. They represent less than 3% of provincial land area, persisting as isolated islands within a landscape that otherwise consists of temperate or boreal forest biomes. Barrens ecosystems are associated with climatic and geomorphic processes that influence biodiversity, such as frost sorting of rocks, that are more typical of Arctic environments. Inland, coastal and highland barrens contain distinctive vegetation rich in rare species, including many with Arctic or alpine biogeographic affinities, and may represent periglacial relict habitats. These habitats support over 500 species of vascular plants, bryophytes and lichens, but descriptions of the biodiversity in these ecosystems are recent and incomplete, especially in light of current threats that include off-highway vehicle use, hiking trails, housing development and invasive species. Here we describe studies that quantify vegetation patterns at multiple scales and environmental drivers of biodiversity in our region and also present a recently developed vegetation classification. We compare these plant communities with similar vegetation types found in Subarctic and Arctic North America and Europe. Fine-scale plant species richness patterns are most strongly predicted by coastal exposure and average soil moisture levels, whereas at larger spatial scales, plant diversity increases with spatial heterogeneity in elevation, soil depth and moisture. Important influences of fog, frost action, and seasonal snow and ice have yet to be quantified but likely affect the distribution of rare species. The factors that maintain open barrens vegetation in this forested region include climatic limits to soil development and wildfire, but there are also unknown contributions of past human use of the habitats including berry harvesting, sheep grazing and possible influences of extirpated animal grazers (caribou) that may affect long-term vegetation dynamics. Through this presentation we hope to make connections with researchers that study similar vegetation across the Arctic and discuss the possible value of studying climate change effects on Arctic vegetation across a range of latitudes that include the southernmost range limits of dominant plant species. This presentation contributes to Action Item 16 - better identifying drivers and stressors of vegetation change, and Policy Recommendations 12 and 13, as our projects involve quantifying ecosystem services derived from barrens habitats and we fill in major regional knowledge gaps in biodiversity inventory. It will also facilitate inter-disciplinary discussion about human influences on and benefits from Arctic vegetation.

Responses of tundra carbon cycling and storage to reindeer-induced vegetation transition

Henni Ylänne, Lund University

In this presentation, I will summarize our findings on the effects of reindeer-induced vegetation transitions on carbon cycling processes and storage. These are monitored in subarctic Northern Norway alongside reindeer pasture rotation fences. At these sites, a yearly pulse of intensive reindeer grazing has turned the vegetation from shrub-dominated towards graminoid-dominated. We monitor the development of ecosystem carbon storage and demonstrate how reindeer grazing can alter the location and total amount of ecosystem carbon. At one of the sites, we also monitor carbon cycling processes on a zone that has recently become graminoid-dominated and show that many of the processes in soils respond to changes in grazing intensity even faster than vegetation-driven processes. The presented data acts as evidence of the potential of grazers to shape tundra processes and carbon storage. It also highlights the need for further studies on the site-specific carbon cycling responses to grazing. This could improve predictions of ecosystem changes across the tundra. Grazer-induced differences in carbon sequestration rates could be incorporated into land-use management, which aims to increase carbon sequestration in tundra soils.

Greening of the tundra as a driver of the current trends in the Arctic biota: Russian Perspective

Elena Belonovskaya, Institute of Geography, RAS; Arkadiy Tishkov, Institute of Geography, RAS

In the beginning of the XXI century in tundra growth of plant productivity and vegetative index (NDVI) was revealed (Walker, et. al. 2012; Bhatt, et. al. 2013; Belonovskaya et al., 2016; Tishkov et al., 2016). Comparing of the results of remote sensing and terrestrial investigation in the beginning of the century (2000) and our time (2015) in Russian Arctic shows progressive expansion of the forest vegetation at the northern limit. According to the analysis of satellite images the trend of growth of productivity (more than 25-30%) and increasing of herbaceous plants’ share in the tundra communities were observed. Over the past decade the average value of the NDVI index increased, which reflected the degree of "greening" of the territory, due to an increase in the number and length of the growing period. The main cause of this process is synergism of climatic (permafrost melting, changes in rainfall and snow accumulation) and anthropogenic impact changes. Growing season’s increasing, active temperature sum’s raising and soil melting depth’s deepening result the artic vegetation communities’ structure and life forms spectrum transformation. First of all, the trend of scrub vegetation invasion was recognized for various treeless biomes. This process concerns the increasing of biomass, abundance and cover of tundra shrubs: Betula, Salix, Dusсhekia, Pinus, Juniperus, etc. genera spreading in Russian tundra (Kola Peninsula, Lower Pechora-river, Yakutia). Also the reducing of lichens and mosses, and increasing of grasses coverage were recorded there. The so called "greening" of tundra was also associated with fires and overgrazing of domestic reindeer. Identified current trends in artic vegetation coincided with the changes of distribution and abundance of indicators in terrestrial fauna of Russian Arctic (geese, sandpipers, reindeer, lemmings, polar fox), which could be interpreted as the effects of tundra habitat’s “greening”: for example, the increasing in the abundance and changes in migration routes for geese, stopping 3-4 years oscillates of the lemmings’ population in some regions, the transformation of continuous distribution of reindeer. The obtained results are important for the Artic biodiversity conservation.

Geomorphology shapes multidiversity patterns of Arctic vegetation

Miska Luoto, University of Helsinki

Physical disturbances resulting from different earth surface processes (ESP) are often intense in high-latitude systems, affecting the distribution of many species and thereby potentially also the multidiversity patterns of Arctic vegetation. Here, we test whether incorporating field-quantified estimates of five dominant ESPs into baseline species distribution models (based on six climate-topography-soil variables) significantly improves the accuracy of species occurrence and community-level predictions. Species data were recorded in 1200 study sites covering a wide range of environmental conditions characteristic of mountain systems at high-latitudes. Data were collected in northernmost Norway for 460 species from three ecologically different taxonomical groups: vascular plants, mosses, and lichens. Here, we offer multiple lines of evidence that several individual geomorphic processes partly control vegetation characteristics of three species groups, affecting the plot-scale occurrence patterns of individual species, species richness and community composition. Models including geomorphic predictors had higher predictive power than corresponding models without these variables, allowing more realistic estimation of multiple vegetation properties across broad environmental gradients in a high-latitude environment. Our results indicate that different species groups can show a wide variety of responses to warming climate and changing ground-surface conditions depending on species’ ecological and evolutionary characteristics. Multidiversity patterns of Arctic vegetation may be concurrently affected by both increasing temperatures and decreasing disturbance frequency. Our results highlight the need for explicitly including data on earth surface processes in biodiversity models to achieve realistic predictions of vegetation assemblage properties, particularly in areas of varying geomorphological conditions. These findings call for integrated ecological and geophysical approaches to advance our understanding of the long-term impacts of global change on high-latitude systems, enabling realistic forecasts of future Arctic biodiversity. Our results contribute to the implementation of several Arctic Biodiversity Assessment policy recommendations, especially (5) “Advance the protection of large areas of ecologically important marine, terrestrial and freshwater habitats, taking into account ecological resilience in a changing climate”; (13) “Increase and focus inventory, long-term monitoring and research efforts to address key gaps in scientific knowledge identified in this assessment to better facilitate the development and implementation of conservation and management strategies” and (16) “Research and monitor individual and cumulative effects of stressors and drivers of relevance to biodiversity, with a focus on stressors that are expected to have rapid and significant impacts and issues where knowledge is lacking”.

Water as a resource, stress and disturbance shaping tundra vegetation

Julia Kemppinen, Department of Geosciences and Geography, University of Helsinki, Finland – Pekka Niittynen, Department of Geosciences and Geography, University of Helsinki, Finland – Juha Aalto, Department of Geosciences and Geography, University of Helsinki, Finland, and Finnish Meteorological Institute, Finland – Peter C. le Roux, Department of Plant and Soil Sciences, University of Pretoria, South Africa – Miska Luoto, Department of Geosciences and Geography, University of Helsinki, Finland | Corresponding author: J. Kemppinen,

The Arctic biodiversity is on the verge of a great change. The hydrological cycle of the Arctic has intensified and the impacts are experienced by vegetation. Plant-available water mediates climate change impacts, namely against rising temperatures and changing snow dynamics. Vegetation is limited by water resources, but water forms also major stress and disturbance. However, climate change impact studies on fine-scale vegetation patterns often cover water inadequately in the Arctic, which is considered as an energy-limited ecosystem. This key gap in knowledge must be addressed for better understanding of the impacts of changing hydrology on the Arctic biodiversity. Thus, we investigated if the inclusion of different water factors improved species distribution models of vascular plants, mosses, and lichens – the cornerstone taxa of the Arctic biodiversity. We collected occurrence data of 289 species on 378 1 m² plots in Fennoscandian mountain tundra. We also recorded eight environmental predictors comprising of direct and resource predictors of the species. The predictors consisted of three water-related factors – namely water resources (soil moisture level), water stress (soil moisture change), and water disturbance (fluvial accumulation and erosion) – and five other factors, namely temperature (growing degree day), nutrients (soil pH), light (radiation), cryogenic processes (solifluction and cryoturbation), and biota (dominant species coverage). The predictive performance of the species distribution models improved, after considering the water-related predictors in the models: the average AUC values for vascular plants increased from 0.807 to 0.836 (P ≤ 0.01), for mosses from 0.687 to 0.727 (not significant), and lichens from 0.667 to 0.668 (not significant). All water aspects represented independent hydrological gradients of the landscape, with evidently differing responses between and within each taxonomical group. Our results highlight the role of water as a multifaceted driver of fine-scale tundra vegetation patterns. While controlling all other key environmental gradients (e.g. temperature), the three water aspects proved to be crucial. Each water aspect had different impacts on the distribution of individual species. Acknowledging the uncertainties in the anticipated rapid and significant changes in tundra hydrology, there are possibly ecological surprises ahead of us. Thus, we stress the inclusion of ecologically meaningful water aspects for improving our knowledge on the fine-scale vegetation patterns in the Arctic.

The future of Arctic biodiversity is dependent on evolution of the snow cover

Pekka Niittynen, Risto K. Heikkinen, Miska Luoto, University of Helsinki

Snow is one of the most important ecosystem drivers in Arctic areas, but its effects are often ignored in climate change impact studies. The Arctic warming has been especially strong during the winter months and drastic changes in snow cover dynamics has already been documented through the northern high-latitudes. Yet, it is largely unexplored question whether the local snow conditions can buffer or catalyst the warming induced changes in Arctic biodiversity. Here, we utilized species distribution models for 273 vascular plant, moss and lichen species to test what are the impacts of different rate of change in summer temperatures and snow cover duration (SCD) on Arctic biodiversity. We fitted the models in current conditions and projected the species occurrences across 38 different temperature and snow cover scenarios. We conducted this study in mountainous tundra in northern Norway using plot-scale vegetation data from 1200 study sites. Based on our models, warming increased local species richness but the rate of species losing all suitable habitat was strongly dependent on the degree of change in SCD. The number of local extinctions increased rapidly after a tipping point at 20-30% SCD decrease regardless of the temperature scenario. All three species groups showed similar extinction rates, but contrasting species richness responses, lichens showing a decreasing trend in local species richness. Our results indicate that the future biodiversity in Arctic is dependent on the evolution of snow conditions, which should be carefully considered in climate change impact studies of high-latitude ecosystems. This work is highly relevant in respect to the first of the three cross-cutting themes raised by CAFF: “1) the significance of climate change as the most serious underlying driver of overall change in biodiversity”. In addition, the results are very important to take into account when the implementation of a number of Arctic Biodiversity Assessment policy recommendations are considered in practice, especially:(5) “Advance the protection of large areas of ecologically important marine, terrestrial and freshwater habitats, taking into account ecological resilience in a changing climate”: (7) “Develop and implement mechanisms that best safeguard Arctic biodiversity under changing environmental conditions, such as loss of sea ice, glaciers and permafrost”; (16) “Research and monitor individual and cumulative effects of stressors and drivers of relevance to biodiversity, with a focus on stressors that are expected to have rapid and significant impacts and issues where knowledge is lacking”.

High-potential for a future tipping-point in Arctic land surface conditions

Aalto, J., Riihimäki, H., Niittynen, P., Luoto, M, University of Helsinki

Arctic vegetation patterns are strongly constrained by cryogenic land surface processes (LSP), potentially limiting climate change -induced vegetation redistributions. However, the effect of LSP on productivity has not been previously studied. Here by making use of extensive field-quantified data of LSP (i.e. cryoturbation, solifluction and nivation) and above-ground biomass from the northernmost Fennoscandia, fine-scale (50 m x 50 m) climate and environmental information, we show that LSP are strong controls of Arctic biomass patterns. The three surveyed LSP were found to collectively cause a substantial reduction in above-ground biomass compared to sites not associated with cryogenic disturbance. Importantly, the effect was significant over the productivity gradient, being especially pronounced in climatically sensitive snow-pack environments, where mean reduction of 47 % in biomass was estimated. These findings are important because significant decay of cryogenic processes is expected due to climate change. These changes can lead to a stabilization of ground surface and further allowing for an establishment of vegetation (i.e. Arctic shrubification). Therefore, the disappearance of cryogenic disturbance could trigger highly non-linear change in vegetation productivity and composition suggesting a future tipping-point Arctic land surface conditions. Cryogenic component is critical in future ecosystem and land surface models to understand the Arctic vegetation’s response to climate change and consequent alterations in land surface – atmosphere feedbacks. By providing new understanding of the role of cryogenic land surface processes in controlling Arctic vegetation patterns, our findings promote monitoring and modeling of Arctic biodiversity. They contribute to the implementation of multiple Arctic Biodiversity Assessment policy recommendations, especially (5) “Advance the protection of large areas of ecologically important marine, terrestrial and freshwater habitats, taking into account ecological resilience in a changing climate”; (13) “Increase and focus inventory, long-term monitoring and research efforts to address key gaps in scientific knowledge identified in this assessment to better facilitate the development and implementation of conservation and management strategies” and (16) “Research and monitor individual and cumulative effects of stressors and drivers of relevance to biodiversity, with a focus on stressors that are expected to have rapid and significant impacts and issues where knowledge is lacking

Climate and productivity forced regime shifts in subarctic lakes

Kahilainen, K.K.7,2, Harrod C.3,4, Thomas S.M.5, Eloranta A.P.6, Myllykangas, J-P.2, Siwertsson, A.7, Præbel, K.7, Knudsen, R.7, Amundsen, P-A.7 & Hayden, B.1,2.
1Canadian Rivers Institute, Biology Department, University of New Brunswick, New Brunswick, Canada
2Kilpisjärvi Biological Station, University of Helsinki, Finland
3 Instituto de Ciencias Naturales Alexander von Humboldt, Universidad de Antofagasta, Antofagasta, Chile
4 Núcleo Milenio INVASAL, Concepción, Chile.
5EAWAG, Switzerland
6NINA, Trondheim, Norway
7UiT The Arctic University of Norway, Tromsø, Norway

Subarctic habitats are warming faster than any other biome on Earth. Increased temperature and nutrient availability are changing subarctic lakes from pristine, cold, oligotrophic environments to warmer and productive ecosystems often followed increasing biodiversity by range expansion of warmer adapted species. Deciphering the joint effects of temperature and productivity on functioning of these sentinel ecosystems provides an opportunity to predict its effects across the wider subarctic. We made a space for time substitution study composing of stable isotope (δ13C, δ15N), diet and abundance datasets of 30 subarctic lakes food webs spanning a temperature (+3˚C), precipitation (+30%) and nutrient (+45 µg/L total phosphorus) gradient equating to predicted future climate scenarios for subarctic Europe. The results show that increasing temperature and productivity changed the energy pathways causing a regime shift from benthic to pelagic resource reliance in subarctic lake food webs. Actually, the largest increases were evident in benthic feeding taxa, indicating that pelagic-benthic coupling becomes increasingly important to benthic consumers. The results indicate the ecosystem level change is not only run by increased biodiversity originating from range expansion of more pelagic species, but is rather reinforced by regime shift from benthic to pelagic energy fuelling the food webs.