Biology subjects

Maliniemi, T.

Publications and source records attributed to Maliniemi, T..

4 recordsLinked to original sources

bioRxiv2026

Intertwined degradation of plant diversity and permafrost in sub-Arctic palsa mires

Plant communities of sub-Arctic and Arctic regions are undergoing changes due to rapid climate change. Permafrost degradation is one of the key drivers of habitat change in these environments and it is considered to impact the biodiversity of northern peatlands. However, the empirical evidence linking permafrost thaw to biodiversity change remains limited. Here, we conducted a vegetation survey of the plant communities (including vascular plants, bryophytes, and lichens) of 14 palsa mires to quantify biodiversity change along different stages of permafrost degradation. We quantified changes in community composition, indicator species, alpha- and beta diversity as well as in two biodiversity indicators. Our results showed that permafrost degradation significantly affected both the plant community composition and the biodiversity of palsa mires. The most pronounced changes in biodiversity were associated with mires from which the permafrost had thawed completely. However, those mires that represented high stage of degradation but still retained remnant permafrost features, were still maintaining plant communities comparable to palsas with low stages of degradation. Thus, our results indicate that collapsing palsas are a clear tipping point for local biodiversity. Almost a complete loss of lichens was observed in completely thawed mires. Furthermore, the shifts in the vascular plant community were recognized to have potential to affect the biodiversity of palsa mires beyond vegetation. This study underscores the role of permafrost sustaining the compositional and taxonomic diversity of plants in palsa mires while also highlighting the varying responses of vascular plants, bryophytes, and lichens to permafrost degradation. Overall, our findings illustrate how the climate-induced changes in habitats and loss of environmental heterogeneity impact the biodiversity and the ecological resilience of the permafrost peatlands.

ecology↗

bioRxiv2024

Long-term homogenization of vascular plant and lichen communities across Fennoscandian heathlands and tundra is connected to the expansion of an allelopathic dwarf shrub

Boreal and tundra plant communities are expected to change in biodiversity due to increasing global change pressures such as climate warming. One long-term scenario is increasing compositional similarity, i.e., biotic homogenization, which has been relatively little studied in high-latitude plant communities. Here, we study how the composition and diversity of heathland and tundra plant communities have changed in northern Fennoscandia over several decades. In 2013-2023, we resurveyed 275 historic vegetation plots, originally surveyed in 1964-1975, with percentage covers for vascular plant, bryophyte and lichen species. We analyzed temporal changes in community composition and diversity across the study area and in different habitat types, biogeographic zones, and along the continentality-humidity gradient. We found a strong trend across the study area, with plant communities becoming more similar in composition over the decades. The observed homogenization was associated with compositional changes in vascular plant and lichen communities, and in particular with the encroachment of the evergreen dwarf shrub Empetrum nigrum. In comparison to vascular plants and lichens, the diversity of bryophytes generally remained more stable over time. Our findings suggest that Fennoscandian heathland and tundra vegetation is transforming towards a more homogenous evergreen dwarf shrub dominated system, which may threaten ecosystem multifunctionality. Our results highlight the importance of exploring biodiversity among different metrics and growth forms to understand the overall changes in heathland and tundra biodiversity.

ecology↗

bioRxiv2024

A Gridded Microclimate Dataset from a Sub-Arctic Biodiversity Hotspot in Finland

Microclimate measurements are crucial for explaining and predicting functions and patterns in nature, yet the availability of microclimate data often poses a challenge. This study introduces a dataset comprising 63 spatially continuous microclimate surfaces for the Kilpisjarvi region in northwestern Finland. The study region is a biodiversity hotspot for arctic-alpine flora and fauna and one of the most extensively investigated regions in Northern Europe. The data were gathered through a collaborative network of microclimate loggers, encompassing 430 measurement locations that comprehensively cover the 300 km2 landscape under study. We employed predominantly well-performing Random Forest models to project microclimate variables across the study area at a 3-metre spatial resolution. The high-resolution and extensive spatial coverage of the dataset facilitates examination of microclimate characteristics and variability across this sub-Arctic region, providing a valuable resource for both theoretical and applied research, as well as for biodiversity conservation.

ecology↗

bioRxiv2020

Trait-based responses to forestry and grazing modify long-term changes in biodiversity hot-spots of boreal forests

AimLand use is the foremost cause of global biodiversity decline, but species do not respond equally to land-use practices. Instead, it is suggested that responses vary with species traits, but long-term data on the trait-mediated effects of land-use on communities is scarce. Here we study how forest understory communities have been affected by two land-use practices during 4-5 decades, and whether changes in plant diversity are related to changes in functional composition. LocationFinland Time period1968-2019 Major taxa studiedVascular plants MethodsWe resurveyed 245 vegetation plots in boreal herb-rich forest understories, and used hierarchical Bayesian linear models to relate changes in diversity, species composition, average plant size, and leaf economic traits to reindeer abundance, forest management intensity, and changes in climate, canopy cover and composition. ResultsIntensively managed forests decreased in species richness and had increased turnover, but management did not affect functional composition. Increased reindeer densities corresponded with increased leaf dry matter content, evenness and diversity, and decreased height and specific leaf area. Successional development in the canopy was associated with increased specific leaf area and decreased leaf dry matter content and height in the understory over the study period. Effects of reindeer abundance and canopy density on diversity were partially mediated by vegetation height, which had a negative relationship with evenness. Observed changes in climate had no discernible effect on any variable. Main conclusionsFunctional traits are useful in connecting vegetation changes to the mechanisms that drive them, and provide unique information compared to turnover and diversity metrics. These trait-dependent selection effects could inform whether species benefit or suffer from land use changes and explain observed biodiversity changes under global change.

ecology↗