| 1. |
- Amsten, Karin, et al.
(författare)
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Fire- and herbivory-driven consumer control in a savanna-like temperate wood-pasture: An experimental approach
- 2021
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Ingår i: Journal of Ecology. - : Wiley. - 0022-0477 .- 1365-2745. ; 109, s. 4103-4114
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Tidskriftsartikel (refereegranskat)abstract
- 1. Fire and herbivory are fundamental top-down processes, structuring grass-tree ratios in ecosystems across a diversity of climates. Both are plant consumers that can strongly control the recruitment of woody seedlings and saplings to taller height classes. Without consumer control, many grass-dominated ecosystems would convert into woodlands or forests. While extensively studied in savannas, few have explored the effects of these disturbance regimes on woody recruitment under temperate conditions.2. We exposed saplings of five common European tree species to fire and herbivory in a full factorial experiment in a savanna-like wood-pasture. After 3 years, we evaluated the effects of fire and herbivory on tree sapling survival and height increment. The tree species used, varying in traits and in expected response to fire and herbivory, were Scots pine Pinus sylvestris, Norway spruce Picea abies, European oak Quercus robur, Silver birch Betula pendula and Small-leaved lime Tilia cordata.3. Fire and herbivory had a negative effect on sapling survival for all species except for Q. robur, which was not affected by fire. Both processes reduced height increment of B. pendula, while only herbivory reduced the height increment of P. sylvestris and Q. robur. At the same time, B. pendula and P. sylvestris had some of the highest increments, together with P. abies, which had unaffected height increment in all treatments. T. cordata, on the other hand, had a negative height increment across all treatments. Overall, the combined effect of fire and herbivory was similar to the effect of herbivory alone on both survival and height increment, indicating no additional effect of fire when herbivores were present.4. Synthesis. Our experiment showed how fire and herbivory can strongly affect the recruitment of European temperate tree saplings on a wood-pasture, potentially leading to comparable consumer control described for ecosystems elsewhere (e.g. savannas). Two strategies to deal with fire and herbivory were identified: tolerance (Q. robur) and avoidance (P. sylvestris and B. pendula). We conclude that both fire and herbivory may have been important drivers of structure and species composition in open ecosystems in temperate Europe in the past.
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| 2. |
- Amsten, Karin, et al.
(författare)
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Pyric herbivory in a temperate European wood-pasture system
- 2024
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Ingår i: Journal of Applied Ecology. - 0021-8901 .- 1365-2664. ; 61, s. 1081-1094
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Tidskriftsartikel (refereegranskat)abstract
- The term pyric herbivory was first introduced in 2009, describing how fire shapes herbivory as burned areas attract herbivores and, simultaneously, herbivory shapes fuel load and fire behaviour. Pyric herbivory results in a mosaic of patches with varying levels of herbivory and grazing intensity fire intensity and frequency. The importance of pyric herbivory for ecosystem heterogeneity and biodiversity has been described for North American, Australian and African systems, but the concept remains largely untested in a European context. We introduced fire and herbivory in a full-factorial experiment in a temperate European wood-pasture system to test whether pyric herbivory operates in ways comparable to grassy systems elsewhere in the world. Using camera traps, we observed the behaviour of cattle in burned subplots (49 m2) compared with unburned subplots. We measured grass height and the proportion of the subplot that burned as variables affecting cattle preference and to assess how grazing affects fire behaviour. We also examined the effect on plant species and life-form composition after six seasons of treatment. Cattle spent more time grazing in burned than in unburned subplots in the most productive paddock, where a larger proportion of the subplot burned. The proportion of a subplot that burned was positively related to pre-fire grass height. Moreover, both grass height and the proportion of subplot burned declined in the burned subplots during the 6-year study period and fire and cattle grazing altered the relative cover of graminoids and shrubs (Rubus spp.), with more graminoids in grazed and/or burned subplots and more shrubs in ungrazed subplots at the end of the study. Synthesis and applications. In our temperate European wood pasture, fire and (cattle) grazing interacted in ways comparable to pyric herbivory in grassy ecosystems elsewhere in the world, especially in the most productive paddock. Fire attracted grazing, with cattle grazing longer on subplots that burned more fully. Grazing also affected fire, where over the course of our experiment cattle grazing reduced grass height and the proportion of a subplot that burned. We suggest that pyric herbivory is an interesting management method to further explore in the European context to address the loss of biodiversity in open ecosystems, particularly in more productive sites.In our temperate European wood pasture, fire and (cattle) grazing interacted in ways comparable to pyric herbivory in grassy ecosystems elsewhere in the world, especially in the most productive paddock. Fire attracted grazing, with cattle grazing longer on subplots that burned more fully. Grazing also affected fire, where over the course of our experiment cattle grazing reduced grass height and the proportion of a subplot that burned. We suggest that pyric herbivory is an interesting management method to further explore in the European context to address the loss of biodiversity in open ecosystems, particularly in more productive sites.image
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| 3. |
- Cromsigt, Joris
(författare)
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A network to understand the changing socio-ecology of the southern African woodlands (SEOSAW): Challenges, benefits, and methods
- 2021
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Ingår i: Plants, People, Planet. - : Wiley. - 2572-2611. ; 3, s. 249-267
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Tidskriftsartikel (refereegranskat)abstract
- Societal Impact StatementThe sustainable management of the southern African woodlands is closely linked to the livelihoods of over 150 M people. Findings from the Socio-Ecological Observatory for the Southern African Woodlands (SEOSAW) will underpin the sustainability of two of the largest industries on the continent: woodfuels and timber. SEOSAW will also improve our understanding of how human use shapes the biogeography and functioning of these ecosystems.SummaryHere we describe a new network of researchers and long-term, in situ, measurements that will characterize the changing socio-ecology of the woodlands of southern Africa. These woodlands encompass the largest savanna in the world, but are chronically understudied, with few long-term measurements. A network of permanent sample plots (PSPs) is required to: (a) address management issues, particularly related to sustainable harvesting for energy and timber; (b) understand how the woodlands are responding to a range of global and local drivers, such as climate change, CO2 fertilization, and harvesting; and (c) answer basic questions about biogeography, ecosystem function, and the role humans play in shaping the ecology of the region. We draw on other successful networks of PSPs and adapt their methods to the specific challenges of working in southern African woodlands. In particular we suggest divergences from established forest monitoring protocols that are needed to (a) adapt to a high level of ecosystem structural diversity (from open savanna to dry forest); (b) quantify the chronic disturbances by people, fire, and herbivores; (c) quantify the diversity and function of the understory of grasses, forbs, and shrubs; (d) understand the life histories of resprouting trees; and (e) conduct work in highly utilized, human-dominated landscapes. We conclude by discussing how the SEOSAW network will integrate with remote sensing and modeling approaches. Throughout, we highlight the challenges inherent to integrating work by forest and savanna ecologists, and the wide range of skills needed to fully understand the socio-ecology of the southern African woodlands.
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| 4. |
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| 5. |
- Cromsigt, Joris
(författare)
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Animal body size distribution influences the ratios of nutrients supplied to plants
- 2020
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 117, s. 22256-22263
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Tidskriftsartikel (refereegranskat)abstract
- Nutrients released through herbivore feces have the potential to influence plant-available nutrients and affect primary productivity. However, herbivore species use nutrients in set stoichiometric ratios that vary with body size. Such differences in the ratios at which nutrients are used leads to differences in the ratios at which nutrients are deposited through feces. Thus, local environmental factors that affect the average body size of an herbivore community (such as predation risk and food availability) influence the ratios at which fecal nutrients are supplied to plants. Here, we assess the relationship between herbivore body size and the nitrogen-to-phosphorus ratios of herbivore feces. We examine how shifts in the average body size of an herbivore community alter the ratios at which nitrogen and phosphorus are supplied to plants and test whether such differences in the stoichiometry of nutrient supply propagate through plants. We show that dung from larger-bodied herbivores contain lower quantities of phosphorus per unit mass and were higher in N:P ratio. We demonstrate that spatial heterogeneity in visibility (a proxy for predation risk and/or food availability) and rainfall (a proxy for food availability), did not affect the overall amount of feces deposited but led to changes in the average body size of the defecating community. Feces deposited in areas of higher rainfall and reduced visibility originated from larger herbivores and were higher in N:P ratios. This indicates that processes that change the size distribution of herbivore communities, such as predation or size-biased extinction, have the potential to alter the nutrient landscape for plants.
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| 6. |
- Cromsigt, Joris, et al.
(författare)
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Camtrap DP: an open standard for the FAIR exchange and archiving of camera trap data
- 2023
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Ingår i: Remote sensing in ecology and conservation. - 2056-3485. ; 10, s. 283-295
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Tidskriftsartikel (refereegranskat)abstract
- Camera trapping has revolutionized wildlife ecology and conservation by providing automated data acquisition, leading to the accumulation of massive amounts of camera trap data worldwide. Although management and processing of camera trap-derived Big Data are becoming increasingly solvable with the help of scalable cyber-infrastructures, harmonization and exchange of the data remain limited, hindering its full potential. There is currently no widely accepted standard for exchanging camera trap data. The only existing proposal, "Camera Trap Metadata Standard" (CTMS), has several technical shortcomings and limited adoption. We present a new data exchange format, the Camera Trap Data Package (Camtrap DP), designed to allow users to easily exchange, harmonize and archive camera trap data at local to global scales. Camtrap DP structures camera trap data in a simple yet flexible data model consisting of three tables (Deployments, Media and Observations) that supports a wide range of camera deployment designs, classification techniques (e.g., human and AI, media-based and event-based) and analytical use cases, from compiling species occurrence data through distribution, occupancy and activity modeling to density estimation. The format further achieves interoperability by building upon existing standards, Frictionless Data Package in particular, which is supported by a suite of open software tools to read and validate data. Camtrap DP is the consensus of a long, in-depth, consultation and outreach process with standard and software developers, the main existing camera trap data management platforms, major players in the field of camera trapping and the Global Biodiversity Information Facility (GBIF). Under the umbrella of the Biodiversity Information Standards (TDWG), Camtrap DP has been developed openly, collaboratively and with version control from the start. We encourage camera trapping users and developers to join the discussion and contribute to the further development and adoption of this standard.We present a new data exchange format for camera trap data, the Camera Trap Data Package (Camtrap DP; ), designed to allow users to easily exchange, harmonize and archive camera trap data at local to global scales. Camtrap DP is being developed under the umbrella of the Biodiversity Information Standards (TDWG), and through outreach and collaboration, it is now supported by GBIF. Importantly, Camtrap DP is the consensus of a long, in depth consultation process among the main existing camera trap data management platforms, as well as some of the major global players in the field of camera trapping. As an open, evolving standard for the FAIR exchange and archive of camera trap data, Camtrap DP represents an important step towards a global data sharing workflow with rapid results and thus more timely science based wildlife management recommendations.image
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| 7. |
- Cromsigt, Joris
(författare)
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Environmental controls on African herbivore responses to landscapes of fear
- 2021
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Ingår i: Oikos. - : Wiley. - 0030-1299 .- 1600-0706. ; 130, s. 171-186
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Tidskriftsartikel (refereegranskat)abstract
- Herbivores balance forage acquisition with the need to avoid predation, often leading to tradeoffs between forgoing resources to avoid areas of high predation risk, or tolerating increased risk in exchange for improved forage. The outcome of these decisions is likely to change with varying resource levels, with herbivores altering their response to predation risk across heterogeneous landscapes. Such contrasting responses will alter the strength of non-consumptive predation effects, but are poorly understood in multiple-predator/multiple-prey systems. We combined fine-scaled spatial information on two predator and 11 herbivore species with remotely-sensed measurements of forage quantity and vegetation structure to assess variation in herbivore response to predation risk with changing environmental context, herbivore body size, herbivore foraging strategy (browsers versus grazers), predator type (ambush versus coursing hunters) and group size across a South African savanna landscape. Medium-sized herbivore species were more likely to adjust their response to risk with a changing resource landscape: warthog, nyala and wildebeest tolerated increased long-term predator encounter risk in exchange for abundant (warthog and nyala) or preferred (wildebeest) forage, and nyala selected areas with higher visibility only in landscapes where food was abundant. Impala were more likely to be observed in areas of high visibility where wild dog risk was high. In addition, although buffalo did not avoid areas of high lion encounter risk, large buffalo groups were more frequently observed in open areas where lion encounter risk was high, whereas small groups did not alter their space use across varying levels of risk. Our findings suggest that risk effects are not uniform across landscapes for medium-sized herbivores and large buffalo groups, instead varying with environmental context and leading to a dynamic landscape of fear. However, responses among these and other prey species were variable and not consistent, highlighting the complexities inherent to multi-predator/multi-prey systems.
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| 8. |
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| 9. |
- Cromsigt, Joris
(författare)
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Floristic evidence for alternative biome states in tropical Africa
- 2020
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 117, s. 28183-28190
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Tidskriftsartikel (refereegranskat)abstract
- The idea that tropical forest and savanna are alternative states is crucial to how we manage these biomes and predict their future under global change. Large-scale empirical evidence for alternative stable states is limited, however, and comes mostly from the multimodal distribution of structural aspects of vegetation. These approaches have been criticized, as structure alone cannot separate out wetter savannas from drier forests for example, and there are also technical challenges to mapping vegetation structure in unbiased ways. Here, we develop an alternative approach to delimit the climatic envelope of the two biomes in Africa using tree species lists gathered for a large number of forest and savanna sites distributed across the continent. Our analyses confirm extensive climatic overlap of forest and savanna, supporting the alternative stable states hypothesis for Africa, and this result is corroborated by paleoecological evidence. Further, we find the two biomes to have highly divergent tree species compositions and to represent alternative compositional states. This allowed us to classify tree species as forest vs. savanna specialists, with some generalist species that span both biomes. In conjunction with georeferenced herbarium records, we mapped the forest and savanna distributions across Africa and quantified their environmental limits, which are primarily related to precipitation and seasonality, with a secondary contribution of fire. These results are important for the ongoing efforts to restore African ecosystems, which depend on accurate biome maps to set appropriate targets for the restored states but also provide empirical evidence for broad-scale bistability.
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| 10. |
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