Grand, S. | bioRxiv Science

bioRxiv2025

Long-term impacts of tree monoculture plantations on biodiversity are mediated by soil acidification

Reforestation efforts have sought to counteract deforestation and to provide a nature-based solution against climate change. However, they often involve monoculture plantations of non-native species, which may have unintended ecological consequences. Yet, the long-term impacts of planting trees have been poorly estimated. Leveraging historical reforestation conducted in northern Italy during the 1920s by the fascist regime, we assessed the long-term impacts of red spruce (Picea abies) monoculture plantations on biodiversity of plants and soil fauna. We found that plant diversity in tree plantations was 50.3% lower than in native forests and 74.5% lower than in grasslands. Additionally, functional evenness was reduced by 30% in spruce plantations, suggesting lower ecological stability. In tree plantations, soil pH was significantly more acid and organic carbon content was 25% higher due to litter deposition and slower decomposition rates. Soil fauna diversity was marginally less affected, suggesting a faster recover over the last one-hundred years of arthropods as compared to plants. These findings highlight the need for monitoring reforestation interventions, suggesting strategies that incorporate diverse tree species rather than planting tree monocultures to support functionally and resilient ecosystems.

ecology↗

bioRxiv2025

Ecological indicators predict functional diversity dynamics following glacier retreat

The retreat of glaciers due to climate change is reshaping mountain landscapes and biodiversity. While previous research has documented vegetation succession after glacier retreat, our understanding of functional diversity dynamics is still limited. In this case study, we address the effects of glacier retreat on plant functional diversity by integrating plant traits with ecological indicator values across a 140-year chronosequence in a subalpine glacier landscape. We reveal that functional richness and functional dispersion decrease with glacier retreat, while functional evenness and functional divergence increase, suggesting a shift towards more specialized and competitive communities. Our findings highlight the critical role of ecological factors related to soil moisture, soil nutrients, and light availability in shaping plant community dynamics. The integrative approach of this case study provides novel insights into the potential response of alpine plant communities to climate change, offering a deeper understanding of how to predict and anticipate the effects of glacier extinction on biodiversity in rapidly changing environments.

ecology↗

bioRxiv2024

Glacier Retreat Effects On Ecosystem Development And Carbon Dynamics

One of the clearest indicators of global warming is the retreat of Alpine glaciers. Organisms rapidly colonize bare ground free from ice, and in less than a century complex ecosystems can develop in a process of primary succession, where community changes as terrain age increases and interactions within species change over time. When glaciers retreat the resulting ice-free soil is exposed to new forms of chemical and biological weathering, with initiating soil formation as an important driver of evolving ecosystems. Soils play an important role in the global carbon (C) cycle, serving as the largest reservoir of carbon. CO2 is removed from the atmosphere by plant photosynthesis, then stored in biomass and soils, and released again to the atmosphere via plant and soil respiration. Soil respiration includes CO2 production by heterotrophic soil organisms (e.g., bacteria, fungi, invertebrates) that metabolize plant litter and soil organic matter, and autotrophs (e.g. plant roots). However, little is known about the development of soils, their physico-chemical changes, and their influence on plant diversity and soil carbon emission (CO2) after glacier retreat. This study aims to investigate how the retreat of the Mont Mine and Ferpecle glaciers (Valais Alps, Switzerland) influences soil functioning and vegetation development. For this purpose, we carried out soil analyses and vegetation surveys on 5 ice-free stages deglaciated between 1864 and 2023. Soil physico-chemical properties (pH, soil organic matter, organic carbon and nitrogen, granulometry, available elements, total elements), soil CO2 respiration fluxes, and plant communities (composition, diversity, richness, biomass) were studied in 20 plots along the glacier forefield. Our results show that vegetation develops according to the principles of primary succession, going further from glacier front: from pioneer vegetation 7 years after glacier retreat, progressing through early vegetation at 20 years, then to intermediate vegetation, and ultimately culminating in a climax coniferous forest, 140 years after glacier retreat. Over 140 years, the increase in vegetation productivity results in a greater transfer of organic matter (SOM) to the soil, which increases organic carbon, nitrogen, and nutrient levels, and decreases pH values as it releases organic acids. Aboveground plant biomass (i.e. carbon storage) increases over the succession, however, plant diversity and richness peak at the intermediate stages and then level off due to the dominance of few species in the late stages. At the intermediate stage, there is also a peak observed in soil respiration (CO2 flux), which in turn promotes plant colonization and diversity. Thus, the soil, along with its development stages and properties, plays a critical role in carbon accumulation, leading to an increased potential for carbon release as organic matter storage increases. This project aims to contribute to the understanding of the consequences of global warming on recently deglaciated ecosystems, which remain still poorly overlooked.

ecology↗