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Below you find a description of the awarded papers.

How Future Global Changes Will Impact Grasslands’ Greenness?

Grasslands are under pressure from climate change, including warming, elevated CO2, and
drought. In this study, we explored how these changes individually and together affect grassland
growth and phenology characterised by greenness indices. Using three years of data from an
Alpine grassland experiment, we found:
• Warming sped up spring growth and greenness.
• Elevated CO2 boosted growth rates.
• Drought had no immediate impact but caused faster growth in the next spring due to a
"memory effect."
• Combined effects amplified shifts, causing earlier summer greenness decline and faster
spring growth in the following year.
These findings reveal that grasslands will respond more dramatically to combined global
change factors than to individual ones, posing challenges for future management and
conservation.

Graphical summary of statistically significant treatment effects on grassland phenology, as
based on the greenness index derived from the phenocam images across the six treatments
(A=ambient control, C=elevated CO2 (+300 ppm), T=warming (+3° C), D=summer drought,
CT=elevated CO2 combined with warming, CTD=elevated CO2, warming and summer
drought.) Grassland management involves three cuts at the end of May, July and September.
The four important phenological stages 1) Start of growth (Upturn date), 2) Peak growth
(Maximum greenness), 3) Start of senescence (Downturn date), and 4) End of senescence are
represented using the respective icons provided in the lower legend. Open symbols on the
right-hand side legend for the treatments indicate that these treatments did not cause
statistically significant effects and are therefore not included in the graphical summary.

Joseph, L.; Cremonese, E.; Migliavacca, M.; Schaumberger, A.; Bahn, M. (2025): Warming, elevated CO2 and drought in combination amplify shifts in canopy greenness dynamics in managed grassland.
In: Agriculture, Ecosystems & Environment 378, No. 109304. (DOI)

When water turns to ice: Control of ice volume and freezing dynamics as important aspects of cold acclimation

In the cold acclimated (CA) state, a reduced tissue water content is considered important to survive subzero temperatures. However, the causal relationship between the reduced water content and increased frost hardiness is unclear. Our aim was to assess whether the seasonally reduced water content affects the freezing dynamics and the amount of ice formed in evergreen leaves: Xeromorph leaves of the woody species Buxus sempervirens and Hedera helix were compared with the herbaceous, soft-leaved Bellis perennis in the non-acclimated (NA) state in summer, during cold acclimation and in the fully CA state in winter. Freezing dynamics were studied using differential scanning calorimetry in addition to the volume fraction of ice and related to water content, osmotic potential and frost hardiness.

In the CA state, freezing dynamics were slower than in NA state. In xeromorph leaves, displacement from ideal equilibrium freezing was higher than in B. perennis. Freeze dehydration was lower in CA state. In the CA state, water content and osmotic potential were reduced, except for B. sempervirens, where the water content remained unchanged. Active osmoregulation and controlled dehydration (only found in two species), are supporting cellular water retention against the dehydrative force of extracellular ice. B. perennis had the highest water content and the least negative osmotic potential, and was the most frost susceptible species (LT10: ‒8.4 °C CA). The leaves froze at ideal equilibrium. 83% of the total water froze, occupying more than 60 vol%. H. helix (LT10: ‒18.4 °C CA) was frost hardier and B. sempervirens (LT10: ‒28.8 °C CA) the frost hardiest species, but in contrast to the other species tested got frost killed by intracellular freezing. The xeromorph leaves froze at non-ideal equilibrium and had lesser ice masses. Despite an increase in frost hardiness with CA, the volume fraction of ice at LT10 was the same (30-40 vol%). In the CA state, slower freeze dehydration and at the same subzero temperature lesser ice masses appeared to be important for higher frost hardiness.

Overall, an important component of cold acclimation in evergreen leaves was the slowing of freezing dynamics, which, depending on the species, involved a specific cell architecture, osmoregulation and a reduction in water content.

Highlights

* In evergreen leaves, cold acclimation leads to slower freezing

* Cold acclimation reduces the extent of cellular freeze dehydration

* The total amount of ice masses becomes reduced during cold acclimation

* Xeromorph leaves freeze at non-ideal equilibrium, soft leaves at ideal equilibrium

* Osmoregulation, cell architecture and partly dehydration affect freezing dynamics

Ralser, Maria; Stegner, Matthias; Neuner, Gilbert (2024): When water turns to ice: Control of ice volume and freezing dynamics as important aspects of cold acclimation.
In: Environmental and Experimental Botany 227, Nr. 105957. (DOI)

Meadow orchards as a good practice example for improving biodiversity in intensive apple orchards

Agricultural land use and intensification of management practices are key drivers of the current global biodiversity crisis. To conserve life in and around agricultural areas and ensure the delivery of essential ecosystem services, changes in management practices are needed. A promising approach is to consider traditional, extensive agricultural management practices, that have been developed and implemented over a long time. Comparing intensive land-use forms with their extensive and traditional counterparts can help define a good practice example for integrated conservation.

In this study, we compared the biodiversity of traditional meadow orchards with intensively managed apple orchards in a mountain region. We adopted a multi-taxon approach, examining seven taxa (vascular plants, wild bees, diurnal butterflies, orthopterans, spiders, birds, and bats) considered important bioindicators of biodiversity and different ecosystem functions. Additionally, we assessed macro-invertebrates across four orchard habitat strata (soil, ground-dwelling, herb, and tree layer), identifying them to higher taxonomic levels. Each group and stratum was sampled using a target sampling method.

Our findings showed consistently higher abundance, diversity, and presence of threatened species in meadow orchards compared to apple orchards. Specifically, wild bees, butterflies, orthopterans, and birds exhibited significantly lower diversity in intensive apple orchards across different diversity indices. Despite differences in species’ habitat and landscape requirements, the results consistently point to the overall impact of management practices. Furthermore, multi-taxonomic indices of all taxa and most habitat strata reinforced this trend, supporting the conclusion that these findings are applicable to the whole orchard ecosystem.

We conclude that traditional agroforestry systems, such as meadow orchards, could represent a well-suited good-practice example for integrated biodiversity conservation in the agricultural landscape. Finally, we emphasize the importance of maintaining traditional management practices through effective conservation measures such as subsidies as part of agri-environmental schemes.

Guariento, E.; Obwegs, L.; Anderle, M.; Bellè, A.; Fontana, P.; Paniccia, C.; Plunger, J.; Rüdisser, J.; Stifter, S.; Giombini, V.; Egarter Vigl, L.; Tappeiner, U.; Hilpold, A. (2024): Meadow orchards as a good practice example for improving biodiversity in intensive apple orchards.
In: Biological Conservation 299, Nr. 110815. (DOI)

Individual versus combined effects of warming, elevated CO2 and drought on grassland water uptake and fine root traits

Projected future conditions, involving increased temperatures, atmospheric CO2 levels, and drought, are expected to modify the water dynamics of terrestrial ecosystems. Grasslands, which are highly sensitive to water shortage, are likely to be particularly affected by these global change factors. Despite the relatively well-understood individual effects of these factors, limited understanding exists about their interactive effects on grassland water uptake and whether adaptations in fine root production and traits can alter the capacity of grassland to take up water. This knowledge gap has limited our ability to predict the ecohydrological responses of grassland systems tto projected future conditions.

In this study, we addressed this knowledge gap by testing the individual and combined impacts of warming, elevated CO2, and drought on root water uptake and the production and traits of fine roots across the soil profile in a managed C3 grassland, as well as ratios of fine-root-to-shoot production. We also examined the relationships between these fine root properties and the capacity of the grassland to take up water. We found that high temperatures, amplified by warming, exacerbate reductions of root water uptake under drought, with negligible water‐sparing effects from elevated CO2. Our findings additionally provide clear evidence that drought, both under current and future (warming and elevated CO2) conditions, shifts root water sourcing towards deeper soil layers. Finally, the overall relationships of grassland water uptake capacity to specific root length and root diameter highlight a so‐far underappreciated role of root traits for grassland water uptake capacity. This study concludes that under warmer future conditions, irrespective of shifts in water sourcing, hot droughts will lead to increasingly severe restrictions of grassland water dynamics.

Radolinski, J.; Vremec, M.; Wachter, H.; Birk, S.; Brüggemann, N.; Herndl, M.; Kahmen, A.; Nelson, D.B.; Kübert, A.; Schaumberger, A.; Stumpp, C.; Tissink, M.; Werner, C.; Bahn, M. (2025): Drought in a warmer, CO2-rich climate restricts grassland water use and soil water mixing.
In: Science 387/6731, S. 290 - 296. (DOI)