Recently, microclimate has gained significant momentum [1], as evidenced by the increasing number of studies and the emergence of a dedicated scientific community coordinating research efforts [2]. Several factors underpin this trend, including advances in technology that have made microclimate monitoring [3] and ecological contextualization [4] more accessible, as well as improvements in computational methods that facilitate modeling at unprecedented scales [5]. But the growing emphasis on microclimate is primarily driven by their ecological relevance, as microclimate represent the actual climate conditions experienced by organisms [1]. This makes them more suitable than macroclimate data for understanding and predicting biodiversity responses to climate change [6]. While macroclimate data remain a common tool in ecology, they often represent generalized climatic conditions over large spatial scales. These data are typically derived from statistical models calibrated on observations collected at meteorological stations [7], which are usually located at 2 meters above the ground in open areas and at elevations compatible with human activities. Such characteristics limit the applicability of macroclimate data for understanding biodiversity responses, particularly at finer spatial scales.

 This is especially true in forest ecosystems, where microclimate results from the filtering of macroclimate conditions by forest habitats [8]. A simple walk in a forest during summer highlights this filtering, with the cooling effect of canopy shading and tree packing being clearly perceptible. If humans can sense these variations, they likely influence forest biodiversity. In fact, microclimates are crucial for defining the thermal niches of understory plant species [9] and understanding plant community reshuffling in response to climate warming [10]. In mountainous areas, topography adds further complexity to microclimates. The drop in temperature with elevation, known as the elevation-temperature lapse rate, is familiar, but topography also drives fine-scale variations [11]. Solar radiation hitting forest varies with aspect and hillshade, creating localized temperature differences. For example, equator-facing slopes receive more sunlight, while west-facing slopes are sunlit during the warmest part of the day. Consequently, in the northern hemisphere, southwest-facing slopes generally exhibit warmer temperatures, longer growing seasons, and shorter snow cover durations [12]. Thus, both topography and forest canopy shape the understory microclimate experienced by organisms in temperate mountainous forests.

 Is biodiversity more influenced by topography- or canopy-induced temperature buffering? While this question may not seem particularly interesting at first glance, understanding the underlying mechanisms of microclimate is crucial for guiding biodiversity conservation decisions in the face of climate change [13]. Poleward-facing slopes, valley bottoms, and dense canopies buffer warm episodes by creating cooler, more humid habitats that can serve as refugia for biodiversity [12]. Both buffering processes are valuable for conservation, but topography-induced buffering is generally more stable over the long term [14]. In contrast, canopy buffering is more vulnerable to human management, disturbances, and the ongoing acceleration of climate change, which is expected to drive tree mortality and lead to canopy opening [15]. Identifying the dominant buffering process in a given area is essential for mapping biodiversity refugia and fully integrating microclimate into conservation strategies. This approach can improve decision-making and actions aimed at promoting biodiversity sustainability in a warming world.

 The work of Borderieux and colleagues [16] offers new insights into this question through an innovative approach. They focus on temperate forests in a watershed in the Vosges Mountains, where they monitor understory temperature and inventory forest plant communities in separate samplings. Aiming to disentangle the effects of topography and forest canopy on understory temperature and its impact on plant communities, the authors deployed a network of temperature sensors using stratified sampling, balanced according to topography (elevation, aspect, and slope) and canopy cover. They then correlated mean annual temperatures (daily mean and maximum) with topographic factors and canopy cover, considering their potential interactions in a linear model. The contribution of each microclimate component was computed, and their effects on temperatures were mapped. These predictions were then confronted to floristic inventories to test whether topography- and canopy-induced temperature variations explained plant diversity and assemblages.

 First, the authors demonstrated that local topographic variations, which determine the amount of solar radiation reaching forests in mountainous areas, outweigh the contribution of canopy shading to understory temperatures. This result is surprising, as many previous studies have emphasized the importance of canopy buffering in shaping forest microclimate conditions [8]. However, these studies mostly focused on lowland areas or large scales, where terrain roughness has less influence. It is also unexpected because the authors observed that canopy cover varies at a smaller scale than aspect or topographic position in their study area, creating habitat heterogeneity that could reasonably drive local temperature variations. Nevertheless, the authors found that aspect, heat load, and topographic position induced more variation in microclimate than canopy filtering, significantly allowing deviations from the expected elevation-temperature lapse rate. Second, the topographic effect on understory temperature propagated to biodiversity. The authors found that topography-induced temperature offset explained plant diversity and composition, while canopy-induced temperature offset did not. Specifically, cold topoclimates harbored 30% more species than the average species richness across the inventoried plots. This increase in species richness was primarily due to an increase in cold-adapted species, highlighting the role of cold topoclimates as refugia.

 It is difficult to assess the extent to which these results are influenced by the specific forest context of the study area chosen by the authors, as there is no clear consensus in previous research regarding the role of topoclimate. For example, Macek et al. (2019) [17] highlighted the predominance of topography in controlling temperature and, consequently, forest community structure in the Czech Republic, while Vandewiele et al. (2023) [18] demonstrated the dominance of canopy control in the German Alps. The forest conditions investigated by Borderieux et al. (2025) were narrow, as they focused mainly on closed forests (more than 80% of the study area and sampling sites exhibiting canopy cover greater than 79%). Given that the canopy buffering effect on temperature increases with canopy cover until plateauing at around 80% [19], this may explain why the authors did not find a strong contribution from the canopy. Nevertheless, the methodology and case presented in their study are both innovative and applicable to other mountainous regions. The work of Borderieux et al. (2025) deserves attention for highlighting a frequently overlooked component of forest microclimate, as canopy filtering is typically regarded as the dominant driver. Topoclimate is a critical factor to consider when protecting cold-adapted forest species in the context of global warming, especially since topographic features are less subject to change than canopy cover. Future research should aim to test this hypothesis across a broader range of forest and topography conditions to identify general patterns, as well as assess the long-term effectiveness of these topographic refugia for biodiversity. It remains unclear whether the cooling effect provided by topoclimate will be sufficient to stabilize climate conditions despite the expected acceleration of climate warming in the coming decades, and whether it will be able to preserve cold-adapted species, which are among the most unique but threatened components of mountain biodiversity.

References

[1] Kemppinen, J. et al. Microclimate, an important part of ecology and biogeography. Global Ecology and Biogeography 33, e13834 (2024). https://doi.org/10.1111/geb.13834

[2] Lembrechts, J. J. et al. SoilTemp: A global database of near-surface temperature. Global Change Biology 26, 6616–6629 (2020). https://doi.org/10.1111/gcb.15123

[3] Wild, J. et al. Climate at ecologically relevant scales: A new temperature and soil moisture logger for long-term microclimate measurement. Agricultural and Forest Meteorology 268, 40–47 (2019). https://doi.org/10.1016/j.agrformet.2018.12.018

[4] Zellweger, F., Frenne, P. D., Lenoir, J., Rocchini, D. & Coomes, D. Advances in Microclimate Ecology Arising from Remote Sensing. Trends in Ecology & Evolution 34, 327–341 (2019). https://doi.org/10.1016/j.tree.2018.12.012

[5] Haesen, S. et al. ForestTemp – Sub-canopy microclimate temperatures of European forests. Global Change Biology 27, 6307–6319 (2021). https://doi.org/10.1111/gcb.15892

[6] Lembrechts, J. J. et al. Comparing temperature data sources for use in species distribution models: From in-situ logging to remote sensing. Global Ecology and Biogeography 28, 1578–1596 (2019). https://doi.org/10.1111/geb.12974

[7] Fick, S. E. & Hijmans, R. J. WorldClim 2: new 1-km spatial resolution climate surfaces for global land areas. International Journal of Climatology 37, 4302–4315 (2017). https://doi.org/10.1002/joc.5086

[8] De Frenne, P. et al. Global buffering of temperatures under forest canopies. Nat Ecol Evol 3, 744–749 (2019). https://doi.org/10.1038/s41559-019-0842-1

[9] Haesen, S. et al. Microclimate reveals the true thermal niche of forest plant species. Ecology Letters 26, 2043–2055 (2023). https://doi.org/10.1111/ele.14312

[10] Zellweger, F. et al. Forest microclimate dynamics drive plant responses to warming. Science 368, 772–775 (2020). https://doi.org/10.1126/science.aba6880

[11] Rolland, C. Spatial and Seasonal Variations of Air Temperature Lapse Rates in Alpine Regions. Journal of climate, 16(7), 1032-1046 (2003). https://doi.org/10.1175/1520-0442(2003)016%3C1032:SASVOA%3E2.0.CO;2

[12] Rita, A. et al. Topography modulates near-ground microclimate in the Mediterranean Fagus sylvatica treeline. Sci Rep 11, 1–14 (2021). https://doi.org/10.1038/s41598-021-87661-6

[13] Bertrand, R., Aubret, F., Grenouillet, G., Ribéron, A. & Blanchet, S. Comment on “Forest microclimate dynamics drive plant responses to warming”. Science 370, eabd3850 (2020). https://doi.org/10.1126/science.abd3850

[14] Hylander, K., Greiser, C., Christiansen, D. M. & Koelemeijer, I. A. Climate adaptation of biodiversity conservation in managed forest landscapes. Conservation Biology 36, e13847 (2022). https://doi.org/10.1111/cobi.13847

[15] McDowell, N. G. & Allen, C. D. Darcy’s law predicts widespread forest mortality under climate warming. Nature Clim Change 5, 669–672 (2015). https://doi.org/10.1038/nclimate2641

[16] Borderieux, J. et al. Cool topoclimates promote cold-adapted plant diversity in temperate mountain forests. Ecoevorxiv, ver. 3( 2024). Peer-reviewed and recommended by PCI Ecology https://doi.org/10.32942/X2XC8T

[17] Macek, M., Kopecký, M. & Wild, J. Maximum air temperature controlled by landscape topography affects plant species composition in temperate forests. Landscape Ecol 34, 2541–2556 (2019). https://doi.org/10.1007/s10980-019-00903-x

[18] Vandewiele, M. et al. Mapping spatial microclimate patterns in mountain forests from LiDAR. Agricultural and Forest Meteorology 341, 109662 (2023). https://doi.org/10.1016/j.agrformet.2023.109662

[19] Zellweger, F. et al. Seasonal drivers of understorey temperature buffering in temperate deciduous forests across Europe. Global Ecology and Biogeography 28, 1774–1786 (2019). https://doi.org/10.1111/geb.12991

Urban ecology, the study of ecological systems in our increasingly urbanized world, is crucial to planning and redesigning cities to enhance ecosystem services (Kremer et al. 2016), human health and well-being and further conservation goals (Dallimer et al. 2012). Urban trees are a crucial component of urban streets and parks that provide shade and cooling through evapotranspiration (Fung and Jim 2019), improve air quality (Lai and Kontokosta 2019), help control storm water (Johnson and Handel 2016), and conserve wildlife (Herrmann et al. 2012; de Andrade et al. 2020).
Ideally, management of urban forests strikes a balance between maintaining the health of urban trees while retaining those organisms, such as herbivores, that connect a tree to the urban ecosystem. Herbivory by arthropods can substantially affect tree growth and reproduction (Whittaker and Warrington 1985), and so understanding factors that influence herbivory in urban forests is important to effective management. At the same time, herbivorous arthropods are important as key components of urban bird diets (Airola and Greco 2019) and provide a backyard glimpse at forest ecosystems in an increasingly built environment (Pearse 2019). Maintenance of arthropod predators may be one way to retain arthropods in urban forests while keeping detrimental outbreaks of herbivores in check. In “Insect herbivory on urban trees: Complementary effects of tree neighbors and predation” Stemmelen and colleagues (Stemmelen et al. 2020) use a clever sampling design to show that insect herbivory decreases as the diversity of neighboring trees increased. By placing artificial larvae out on trees, they provide evidence that increased predation in higher diversity urban forest patches might drive patterns in herbivory. The paper also demonstrates the importance of tree species identity in determining leaf herbivory.
The implications of this research for urban foresters is that deliberately planting diverse urban forests will help manage insect herbivores and should thus improve tree health. Potential knock-on effects could be seen for the ecosystem services provided by urban forests. While it might be tempting to simply plant more of the species that are subject to low current rates of herbivory, other research on the long-term vulnerability of monocultures to attack by specialist pathogens and herbivores (Tooker and Frank 2012) cautions against such an approach. Furthermore, the importance of urban forest insects to birds, including migrating birds, argues for managing urban forests more holistically (Greco and Airola 2018).
Stemmelen et al. (2020) used an observational approach focused on urban forests in Montreal, Canada in their research. Their findings suggest follow-up research focused on a broader cross-section of urban forests across latitudes, as well as experimental research. Experiments could, for example, exclude avian predators with netting (e.g. (Marquis and Whelan 1994)) to evaluate the relative importance of birds to managing urban insects on trees, as well as the flip side of that equation, the important to birds of insects on urban trees.
In summary, Stemmelen and colleague’s manuscript illustrates clever sampling and use of observational data to infer broader ecological patterns. It is worth reading to better understand the role of diversity in driving plant-insect community interactions and given the implications of the findings for sustainable long-term management of urban forests.

References

Airola, D. and Greco, S. (2019). Birds and oaks in California’s urban forest. Int. Oaks, 30, 109–116.
de Andrade, A.C., Medeiros, S. and Chiarello, A.G. (2020). City sloths and marmosets in Atlantic forest fragments with contrasting levels of anthropogenic disturbance. Mammal Res., 65, 481–491. doi: https://doi.org/10.1007/s13364-020-00492-0
Dallimer, M., Irvine, K.N., Skinner, A.M.J., Davies, Z.G., Rouquette, J.R., Maltby, L.L., et al. (2012). Biodiversity and the Feel-Good Factor: Understanding Associations between Self-Reported Human Well-being and Species Richness. Bioscience, 62, 47–55. doi: https://doi.org/10.1525/bio.2012.62.1.9
Fung, C.K.W. and Jim, C.Y. (2019). Microclimatic resilience of subtropical woodlands and urban-forest benefits. Urban For. Urban Green., 42, 100–112. doi: https://doi.org/10.1016/j.ufug.2019.05.014
Greco, S.E. and Airola, D.A. (2018). The importance of native valley oaks (Quercus lobata) as stopover habitat for migratory songbirds in urban Sacramento, California, USA. Urban For. Urban Green., 29, 303–311. doi: https://doi.org/10.1016/j.ufug.2018.01.005
Herrmann, D.L., Pearse, I.S. and Baty, J.H. (2012). Drivers of specialist herbivore diversity across 10 cities. Landsc. Urban Plan., 108, 123–130. doi: https://doi.org/10.1016/j.landurbplan.2012.08.007
Johnson, L.R. and Handel, S.N. (2016). Restoration treatments in urban park forests drive long-term changes in vegetation trajectories. Ecol. Appl., 26, 940–956. doi: https://doi.org/10.1890/14-2063
Kremer, P., Hamstead, Z., Haase, D., McPhearson, T., Frantzeskaki, N., Andersson, E., et al. (2016). Key insights for the future of urban ecosystem services research. Ecol. Soc., 21: 29. doi: http://doi.org/10.5751/ES-08445-210229
Lai, Y. and Kontokosta, C.E. (2019). The impact of urban street tree species on air quality and respiratory illness: A spatial analysis of large-scale, high-resolution urban data. Heal. Place, 56, 80–87. doi: https://doi.org/10.1016/j.healthplace.2019.01.016
Marquis, R.J. and Whelan, C.J. (1994). Insectivorous birds increase growth of white oak through consumption of leaf-chewing insects. Ecology, 75, 2007–2014. doi: https://doi.org/10.2307/1941605
Pearse, I.S. (2019). Insect herbivores on urban native oak trees. Int. Oaks, 30, 101–108.
Stemmelen, A., Paquette, A., Benot, M.-L., Kadiri, Y., Jactel, H. and Castagneyrol, B. (2020) Insect herbivory on urban trees: Complementary effects of tree neighbours and predation. bioRxiv, 2020.04.15.042317, ver. 5 peer-reviewed and recommended by PCI Ecology. doi: https://doi.org/10.1101/2020.04.15.042317
Tooker, J. F., and Frank, S. D. (2012). Genotypically diverse cultivar mixtures for insect pest management and increased crop yields. J. Appl. Ecol., 49(5), 974-985. doi: https://doi.org/10.1111/j.1365-2664.2012.02173.x
Whittaker, J.B. and Warrington, S. (1985). An experimental field study of different levels of insect herbivory induced By Formica rufa predation on Sycamore (Acer pseudoplatanus) III. Effects on Tree Growth. J. Appl. Ecol., 22, 797. doi: https://doi.org/10.2307/2403230

The study titled “General mechanisms for a top-down origin of the predator-prey power law” provides a fresh perspective on the classic predator-prey biomass relationship often observed in ecological communities. Traditionally, predator-prey dynamics have been examined through a bottom-up lens, where prey biomass and energy availability dictate predator populations. However, this study, which instead explores the possibility of a top-down origin for predator-prey power laws, offers a new dimension to our understanding of ecosystem regulation and raises questions about how predator-driven interactions might influence biomass scaling laws independently of prey abundance.

Ecologists have long noted that ecosystems often exhibit sublinear scaling between predator and prey biomasses. This pattern implies that predator biomass does not increase proportionally with prey biomass but at a slower rate, leading to a power-law relationship. Traditional explanations, such as those discussed by Peters (1983) and McGill (2006), have linked this to bottom-up processes, suggesting that increases in prey availability support, but do not fully translate to, larger predator populations due to energy losses in the trophic cascade. However, these explanations assume prey abundance as the principal driver. This new work raises an intriguing question: could density-dependent predator interactions, such as competition and interference, be equally or more important in creating this observed power law?

The authors hypothesized that density-dependent predator interactions might independently control predator biomass, even when prey is abundant. To test this, they combined predator and prey biomass dynamics equation based on a modified Lotka-Volterra model with agent-based models (ABMs) on a spatial grid, simulating predator-prey populations under varying environmental gradients and density-dependent conditions. These models allowed them to incorporate predator-specific factors, such as intraspecific competition (predator self-regulation) and predation interference, offering a quantitative framework to observe whether these top-down dynamics could indeed explain the observed biomass scaling independently of prey population changes.

Their results show that density-dependent predator dynamics, particularly at high predator densities, can yield sublinear scaling in predator-prey biomass relationships. This aligns well with empirical data, such as African mammalian ecosystems where predators seem to self-regulate under high prey availability by competing amongst themselves rather than expanding in direct proportion to prey biomass. Such findings support a shift from bottom-up perspectives to a model where top-down processes drive population regulation and biomass scaling.

I think that the work by Mazzarisi and collaborators (2024) offers a thought-provoking twist on predator-prey dynamics and suggests that our traditional frameworks may benefit from a broader, more predator-centered focus.

References

1. Onofrio Mazzarisi, Matthieu Barbier, Matteo Smerlak (2024) General mechanisms for a top-down origin of the predator-prey power law. bioRxiv, ver.2 peer-reviewed and recommended by PCI Ecology https://doi.org/10.1101/2024.04.04.588057

2. Peters, R. H. (1986). The ecological implications of body size (Vol. 2). Cambridge university press.

3. McGill, B. J. (2006). “A renaissance in the study of abundance.” Science, 314(5801), 770-772. https://doi.org/10.1126/science.1134920

Stochastic Cellular Automata (SCA) are a popular modelling tool because in, spite of their simplicity, they can generate a variety of spatial patterns. This makes them particularly appreciated, for instance, to validate the insights of analytical or semi-analytical spatial models that make simplifying assumptions, e.g. moment equations models. A first limit to SCA are that as soon as details are added to the model, reproducibility issues may occur. Computation speed is also an issue, especially for large populations. The work by Génin et al. addresses these two issues through the development of an R package, chouca.

The use of the package is designed to be as smooth as possible: users only need to define the type of possible transitions along with their rates, the parameter values, the number of neighbours, and the initial state of the landscape. The main function returns the population dynamics of each state and even the final state of the landscape.

In addition to its flexibility, an asset of chouca resides in its use of the Rcpp package, which compiles the model designed by the user in C++. This allows for high computation speed, which can be further boosted by using parallelising options from R.

In their manuscript, the authors use ecological models to illustrate the more advanced possibilities opened by chouca, e.g. in terms of graphical interpretation or even to estimate parameter values by computing likelihood functions (the implementation in R does make it very appropriate for statistical inference in general). The package still has some limitations, and, for example, it currently only applied to 2D rectangular grids and it cannot include elaborate movement processes. However, some of these could be addressed in future releases and chouca already has the potential to become central for SCA modelling, both for beginners and expert users, especially in ecology.

References

Alexandre Génin, Guillaume Dupont, Daniel Valencia, Mauro Zucconi, M. Isidora Ávila-Thieme, Sergio A. Navarrete, Evie A. Wieters (2024) Easy, fast and reproducible Stochastic Cellular Automata with chouca. bioRxiv, ver.6 peer-reviewed and recommended by Peer Community in Ecology https://doi.org/10.1101/2023.11.08.566206

Among vertebrates, amphibians are one of the most diverse groups with more than 7,000 known species. Amphibians occupy various ecosystems, including forests, wetlands, and freshwater habitats. Amphibians are known to be highly sensitive to changes in their environment, particularly to water quality and habitat degradation, so that monitoring abundance of amphibian populations can provide early warning signs of ecosystem disturbances that may also affect other organisms including humans (Bishop et al., 2012). Accordingly, efforts in habitat preservation and sustainable land and water management are necessary to safeguard amphibian populations.

In this context, Matutini et al. (2023) compared ecological requirements of amphibian species with the quality of agricultural landscape mosaics. Doing so, they identified critical gaps in existing conservation tools that include protected areas, green infrastructures, and inventoried sites. Matutini et al. (2023) focused on nine amphibian species in the Pays-de-la-Loire region where the landscape has been fashioned over the years by human activities. Three of the chosen amphibian species are living in a dense hedgerow mosaic landscape, while five others are more generalists.

Matutini et al. (2023) established multi-species habitat suitability maps, together with their levels of confidence, by combining single species maps with a probabilistic stacking method at 500-m resolution. From these maps, habitats were classified in five categories, from not suitable to highly suitable. Then, the circuit theory was used to map the potential connections between each highly suitable patch at the regional scale. Finally, comparing suitability maps with existing conservation tools, Matutini et al. (2023) were able to assess their coverage and efficiency.

Whatever their species status (endangered or not), Matutini et al. (2023) highlighted some discrepancies between the ecological requirements of amphibians in terms of habitat quality and the conservation tools of the landscape mosaic within which they are evolving. More specifically, Matutini et al. (2023) found that protected areas and inventoried sites covered only a small proportion of highly suitable habitats, while green infrastructures covered around 50% of the potential habitat for amphibian species. Such a lack of coverage and efficiency of protected areas brings to light that geographical sites with amphibian conservation challenges are known but not protected. Regarding the landscape fragmentation, Matutini et al. (2023) found that generalist amphibian species have a more homogeneous distribution of suitable habitats at the regional scale. They also identified two bottlenecks between two areas of suitable habitats, a situation that could prove critical to amphibian movements if amphibians were forced to change habitats to global change.

In conclusion, Matutini et al. (2023) bring convincing arguments in support of land-use species-conservation planning based on a better consideration of human-dominated landscape mosaics in full compliance with ecological requirements of the species that inhabit the regions concerned.

References

Bishop, P.J., Angulo, A., Lewis, J.P., Moore, R.D., Rabb, G.B., Moreno, G., 2012. The Amphibian Extinction Crisis - what will it take to put the action into the Amphibian Conservation Action Plan? Sapiens - Surveys and Perspectives Integrating Environment and Society 5, 1–16. http://journals.openedition.org/sapiens/1406

Matutini, F., Baudry, J., Fortin, M.-J., Pain, G., Pithon, J., 2023. Conservation networks do not match ecological requirements of amphibians. bioRxiv, ver. 3 peer-reviewed and recommended by Peer Community in Ecology. https://doi.org/10.1101/2022.07.18.500425