| 1. |
- Christiansen, Ditte Marie, 1990-, et al.
(author)
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Effects of past and present microclimates on northern and southern plant species in a managed forest landscape
- 2023
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In: Journal of Vegetation Science. - 1100-9233 .- 1654-1103. ; 34:4
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Journal article (peer-reviewed)abstract
- Questions: Near-ground temperatures can vary substantially over relatively short distances, enabling species with different temperature preferences and geographical distributions to co-exist within a small area. In a forest landscape, the near-ground temperatures may change due to management activities that alter forest density. As a result of such management activities, current species distributions and performances might not only be affected by current microclimates, but also by past conditions due to time-lagged responses.Location: Sweden.Methods: We examined the effects of past and current microclimates on the distributions and performances of two northern, cold-favoured, and two southern, warm-favoured, plant species in 53 managed forest sites. Each pair was represented by one vascular plant and one bryophyte species. We used temperature logger data and predictions from microclimate models based on changes in basal area to relate patterns of occurrence, abundance, and reproduction to current and past microclimate.Results: The two northern species were generally favoured by microclimates that were currently cold, characterised by later snowmelt and low accumulated heat over the growing season. In contrast, the two southern species were generally favoured by currently warm microclimates, characterised by high accumulated heat over the growing season. Species generally had higher abundance in sites with a preferred microclimate both in the past and present, and lower abundance than expected from current conditions, if the past microclimate had changed from warm to cold or vice versa, indicating time-lags in abundance patterns of the species.Conclusions: Our results show a potential importance of past and present microclimate heterogeneity for the co-existence of species with different temperature preferences in the same landscape and highlight the possibility to manage microclimates to mitigate climate change impacts on forest biodiversity.
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| 2. |
- De Lombaerde, Emiel, et al.
(author)
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Maintaining forest cover to enhance temperature buffering under future climate change
- 2022
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In: Science of the Total Environment. - : Elsevier BV. - 0048-9697 .- 1879-1026. ; 810
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Journal article (peer-reviewed)abstract
- Forest canopies buffer macroclimatic temperature fluctuations. However, we do not know if and how the capacity of canopies to buffer understorey temperature will change with accelerating climate change. Here we map the difference (offset) between temperatures inside and outside forests in the recent past and project these into the future in boreal, temperate and tropical forests. Using linear mixed-effect models, we combined a global database of 714 paired time series of temperatures (mean, minimum and maximum) measured inside forests vs. in nearby open habitats with maps of macroclimate, topography and forest cover to hindcast past (1970–2000) and to project future (2060–2080) temperature differences between free-air temperatures and sub-canopy microclimates. For all tested future climate scenarios, we project that the difference between maximum temperatures inside and outside forests across the globe will increase (i.e. result in stronger cooling in forests), on average during 2060–2080, by 0.27 ± 0.16 °C (RCP2.6) and 0.60 ± 0.14 °C (RCP8.5) due to macroclimate changes. This suggests that extremely hot temperatures under forest canopies will, on average, warm less than outside forests as macroclimate warms. This knowledge is of utmost importance as it suggests that forest microclimates will warm at a slower rate than non-forested areas, assuming that forest cover is maintained. Species adapted to colder growing conditions may thus find shelter and survive longer than anticipated at a given forest site. This highlights the potential role of forests as a whole as microrefugia for biodiversity under future climate change.
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| 3. |
- Greiser, Caroline, 1987-, et al.
(author)
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Archive value : measuring the palaeo-information content of peatlands in a conservation and compensation perspective
- 2018
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In: International Journal of Biodiversity Science, Ecosystem Services & Management. - : Informa UK Limited. - 2151-3732 .- 2151-3740. ; 14:1, s. 209-220
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Journal article (peer-reviewed)abstract
- The value of peatlands as archives for vegetation, landscape, climate, and human history is well known, but often neglected in conservation planning. Archive value is the potential to satisfy future (yet unknown) demands for information about the past. This study aims at assessing the comparative archive value of a set of peatlands, to identify the most similar alternatives for three peatlands and to estimate the archive loss in case of their destruction. Representative cores from 49 peatlands in the region were assessed with respect to age, depth, resolution, (in)completeness, evenness, and diversity of substrates, peat accumulation status, and thickness of every single substrate type. After using cluster analysis to identify archive types and the relatedness among peatlands, the archive value of each peatland was expressed as a proportion of the total regional archive. We found candidates for compensating the three threatened peatlands, but also identified other archives of high conservation interest according to our criteria. The outcomes appeared rather robust but were determined by the criteria, resolution, and algorithms chosen. This work presents a first step towards developing an objective and consistent evaluation procedure of peatland archives, allowing the archive value to be considered in conservation and management decisions.
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| 4. |
- Greiser, Caroline, 1987-, et al.
(author)
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Higher soil moisture increases microclimate temperature buffering in temperate broadleaf forests
- 2024
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In: Agricultural and Forest Meteorology. - 0168-1923 .- 1873-2240. ; 345
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Journal article (peer-reviewed)abstract
- Forest canopies can buffer the understory against temperature extremes, often creating cooler microclimates during warm summer days compared to temperatures outside the forest. The buffering of maximum temperatures in the understory results from a combination of canopy shading and air cooling through soil water evaporation and plant transpiration. Therefore, buffering capacity of forests depends on canopy cover and soil moisture content, which are increasingly affected by more frequent and severe canopy disturbances and soil droughts. The extent to which this buffering will be maintained in future conditions is unclear due to the lack of understanding about the relationship between soil moisture and air temperature buffering in interaction with canopy cover and topographic settings. We explored how soil moisture variability affects temperature offsets between outside and inside the forest on a daily basis, using temperature and soil moisture data from 54 sites in temperate broadleaf forests in Central Europe over four climatically different summer seasons. Daily maximum temperatures in forest understories were on average 2 °C cooler than outside temperatures. The buffering of understory temperatures was more effective when soil moisture was higher, and the offsets were more sensitive to soil moisture on sites with drier soils and on sun-exposed slopes with high topographic heat load. Based on these results, the soil–water limitation to forest temperature buffering will become more prevalent under future warmer conditions and will likely lead to changes in understory communities. Thus, our results highlight the urgent need to include soil moisture in models and predictions of forest microclimate, understory biodiversity and tree regeneration, to provide a more precise estimate of the effects of climate change.
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| 5. |
- Greiser, Caroline, 1987-
(author)
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Microclimate at range margins : Consequences for boreal forest understory species
- 2020
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Doctoral thesis (other academic/artistic)abstract
- A warmer climate will shift species distributional range margins poleward, but near-ground microclimates may modify these shifts. Cold-adapted northern species at their rear edge may survive locally in microrefugia with a colder microclimate, and warm-adapted southern species at their leading edge may colonize stepping stone habitats with a warmer microclimate. However, we do not always know if species ranges are limited by climate and which role microclimate variation plays in modifying range margins. This is especially true for lowland forests, where forest structure and composition have relatively large influences on near-ground microclimates.In this thesis, I explored patterns and drivers of forest microclimate at the southern margin of the boreal zone in central Sweden, where many northern and southern species meet. First, I measured, modelled and mapped near-ground temperatures across ca. 20 000 km2 of forested land (Paper I). Second, I tested if cold and warm microclimates favour northern and southern understory species, respectively. To answer this, I investigated the occurrence and performance patterns of understory vascular plants, bryophytes and lichens across microclimate gradients at the species’ northern or southern range margins (Paper II-IV). I performed both correlational analyses on natural populations and experimental testing with transplanted populations. Third, I derived recommendations and tools for biodiversity conservation and forest management (Paper I-IV).I found high spatial and temporal variation of forest microclimate, which was in the summer mainly linked to differences in forest density and in the cold season to terrain effects (Paper I). Cold and warm microclimates were occupied by natural edge populations of northern and southern species, respectively (Paper II and IV). However, in the transplant experiments with removed competition other factors were more important for the species performance. The southern herb appeared to cope well with the range of microclimate at its current northern range margin and instead seems to be limited by soil and light in northern conifer-dominated forests (Paper IV). The northern transplanted bryophytes and lichens showed no or a positive response to warmer temperature, but also to higher moisture, to more conifers in the overstory and to less gastropod grazing (Paper III). The results indicate that competition with southern species, herbivory, leaf litter and water scarcity might be more important than temperature as direct limiting factors at the species’ current southern range margin. To conclude, microclimate influences the occurrence and performance of range edge populations, but it likely does so indirectly via effects on water availability and biotic interactions.Forest management heavily modifies near-ground temperature and humidity and hence likely impacts the climate-driven range shifts of understory species. I call for considering these effects in conservation and management actions, e.g. by protecting valuable microclimates, moving from clear-cutting to selective logging, reducing forest fragmentation and drainage and favouring either broad-leaved or coniferous trees in the overstory - depending on the local conservation target (Paper I-IV). Climate-change induced biodiversity loss may thus be slowed down by responsible forest management that provides stepping stone habitats for advancing southern species as well as microrefugia for retreating northern species.
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| 6. |
- Greiser, Caroline, 1987-, et al.
(author)
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Microclimatic variation affects developmental phenology, synchrony and voltinism in an insect population
- 2022
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In: Functional Ecology. - : Wiley. - 0269-8463 .- 1365-2435. ; 36:12, s. 3036-3048
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Journal article (peer-reviewed)abstract
- Temperature influences the rate of most biological processes. Nonlinearities in the thermal reaction norms of such processes complicate intuitive predictions of how ectothermic organisms respond to naturally fluctuating temperatures, and by extension, to climate warming. Additionally, organisms developing close to the ground experience a highly variable microclimate landscape that often is poorly captured by coarse standard climate data.Using a butterfly population in central Sweden as a model, we quantified the consequences of small-scale temperature variation on phenology, emergence synchrony and number of annual reproductive cycles (voltinism). By combining empirical microclimate and thermal performance data, we project development of individual green-veined white butterflies (Pieris napi) across 110 sites in an exceptionally high-resolved natural microclimate landscape.We demonstrate that differences among microclimates just meters apart can have large impacts on the rate of development and emergence synchrony of neighbouring butterflies. However, when considering the full development from egg to adult, these temporal differences were reduced in some scenarios, due to negative correlations in development times among life stages. The negative correlations were caused by temperatures at some sites beginning to exceed the optimum for development as the season progressed. Indeed, which sites were optimal for fast development could change across the lifetimes of individual butterflies, that is, ‘fast’ sites could become ‘slow’ sites. Thus, from a thermal point of view, there seem to be no consistently optimal microsites. Importantly, the fast sites were not always the warmest sites. We showed that such unintuitive effects could play an important role in the regulation of phenological synchrony and voltinism in insects, as most sites consistently favoured two generations. The results were generally robust across years and three different egg-laying dates.Using high-resolved empirical climate data on organism-relevant temporal and spatial scales and considering nonlinear responses to temperature, we demonstrated the large and unintuitive population-level consequences of locally and temporarily high temperatures. We suggest to—whenever possible—incorporate species- and life stage-specific nonlinear responses to temperature when studying the effects of natural microclimate variation and climate change on organisms.
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| 7. |
- Greiser, Caroline, 1987-, et al.
(author)
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Southern margin of boreal bryophytes and lichens not directly limited by warmer temperatures
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Other publication (other academic/artistic)abstract
- Species at their warm range margin are potentially threatened by a warmer climate, but may escape regional warming in locally colder microclimates. We evaluated whether boreal understory bryophytes and lichens show signs of climate limitation, i.e. whether they perform better in cold and/or humid microclimates at their warm range margin. We transplanted a moss, a liverwort, and a lichen to 58 boreal forest sites with different microclimates at the species’ southern range margin in central Sweden. Species were grown in garden soil to exclude effects of competition and soil quality. We followed the transplants over three growing seasons (2016-2018) and modelled growth and vitality for each species and year as a function of sub-canopy temperature, soil moisture, air humidity and forest type. We expected a negative response to warmer temperatures and drier conditions if the species were directly climate-limited. Transplant performance increased with warmer temperatures and at sites with more conifers. Soil moisture had a positive effect, especially on the moss in the last year 2018, which was extremely hot and dry. The lichen was negatively affected only by gastropod grazing. The results indicate that competition, herbivory, leaf litter and water scarcity might be more important than temperature for performance at the species’ warm range margin. Forest microrefugia, habitats were these species could persist regional warming, may therefore mainly be sites with less competitors and enemies, and with sufficient moisture and more conifers in the overstory. Our study illustrates that transplant experiments are a powerful tool to study range dynamics and the multiple environmental factors that influence them. Our results also suggest that multi-year experiments are valuable for identifying potential range-limiting effects that occur only after some time, or under extreme weather conditions e.g. in very dry years.
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| 8. |
- Gril, Eva, et al.
(author)
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Slope and equilibrium : A parsimonious and flexible approach to model microclimate
- 2023
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In: Methods in Ecology and Evolution. - 2041-210X. ; 14:3, s. 885-897
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Journal article (peer-reviewed)abstract
- Most statistical models of microclimate focus on the difference or ‘offset’ between standardized air temperatures (macroclimate) and those of a specific habitat such as forest understorey, grassland or under a log. However, these offsets can fluctuate from positive to negative over a single day such that common practice consists in aggregating data into daily mean, minimum and maximum before modelling monthly offsets for each summary statistic. Here, we propose a more parsimonious and flexible approach relying on just two parameters: the slope and equilibrium. The slope captures the linear relationship between microclimate and macroclimate, while the equilibrium is the point at which microclimate equals macroclimate. Although applicable to other habitats, we demonstrate the relevance of our method by focusing on forest understoreys.We installed temperature sensors at 1-m height inside forest stands and in nearby open grasslands equipped with standardized weather stations, across 13 sites in France spanning a wide climatic gradient. From a year of hourly temperatures and for each sensor, we established relationships between microclimate and macroclimate temperatures using two linear mixed-effects models, during the leaf-on (May–November) and leaf-off period (December–April). We extracted the monthly equilibrium and slope for each sensor, and used another set of linear mixed-effects models to investigate their main determinants.The slope was chiefly determined by stand structure variables interacting with the leaf-on/leaf-off period: stand type (conifer vs broadleaf); shade-casting ability; stand age; dominant height; stem density; and cover of the upper and lower shrub layer. In contrast, forest structure had no explanatory power on the equilibrium. We found the equilibrium to be positively related to mean macroclimate temperature, interacting with the open/forest habitat.The method introduced here overcomes several shortcomings of modelling microclimate offsets. By demonstrating that the slope and equilibrium vary in predictable ways, we have established a general linkage between microclimate and macroclimate temperatures that can be applied to any location or time if we know the mean macroclimate temperature (equilibrium) and buffering or amplifying capacity of the habitat (slope). We also warn about methodological biases due to the reference used for macroclimate.
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| 9. |
- Haesen, Stef, et al.
(author)
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ForestClim : Bioclimatic variables for microclimate temperatures of European forests
- 2023
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In: Global Change Biology. - : John Wiley & Sons. - 1354-1013 .- 1365-2486. ; 29:11, s. 2886-2892
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Journal article (peer-reviewed)abstract
- Microclimate research gained renewed interest over the last decade and its importance for many ecological processes is increasingly being recognized. Consequently, the call for high-resolution microclimatic temperature grids across broad spatial extents is becoming more pressing to improve ecological models. Here, we provide a new set of open-access bioclimatic variables for microclimate temperatures of European forests at 25 x 25 m2 resolution.
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| 10. |
- Kemppinen, Julia, et al.
(author)
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Microclimate, an important part of ecology and biogeography
- 2024
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In: Global Ecology and Biogeography. - 1466-822X .- 1466-8238.
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Journal article (peer-reviewed)abstract
- Brief introduction: What are microclimates and why are they important? Microclimate science has developed into a global discipline. Microclimate science is increasingly used to understand and mitigate climate and biodiversity shifts. Here, we provide an overview of the current status of microclimate ecology and biogeography in terrestrial ecosystems, and where this field is heading next.Microclimate investigations in ecology and biogeography: We highlight the latest research on interactions between microclimates and organisms, including how microclimates influence individuals, and through them populations, communities and entire ecosystems and their processes. We also briefly discuss recent research on how organisms shape microclimates from the tropics to the poles.Microclimate applications in ecosystem management: Microclimates are also important in ecosystem management under climate change. We showcase new research in microclimate management with examples from biodiversity conservation, forestry and urban ecology. We discuss the importance of microrefugia in conservation and how to promote microclimate heterogeneity.Methods for microclimate science: We showcase the recent advances in data acquisition, such as novel field sensors and remote sensing methods. We discuss microclimate modelling, mapping and data processing, including accessibility of modelling tools, advantages of mechanistic and statistical modelling and solutions for computational challenges that have pushed the state-of-the-art of the field.What's next? We identify major knowledge gaps that need to be filled for further advancing microclimate investigations, applications and methods. These gaps include spatiotemporal scaling of microclimate data, mismatches between macroclimate and microclimate in predicting responses of organisms to climate change, and the need for more evidence on the outcomes of microclimate management.
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