| 1. |
- Amsten, Karin, et al.
(författare)
-
Fire- and herbivory-driven consumer control in a savanna-like temperate wood-pasture: An experimental approach
- 2021
-
Ingår i: Journal of Ecology. - : Wiley. - 0022-0477 .- 1365-2745. ; 109, s. 4103-4114
-
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.
|
|
| 2. |
- Cromsigt, Joris
(författare)
-
A network to understand the changing socio-ecology of the southern African woodlands (SEOSAW): Challenges, benefits, and methods
- 2021
-
Ingår i: Plants, People, Planet. - : Wiley. - 2572-2611. ; 3, s. 249-267
-
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.
|
|
| 3. |
- Cromsigt, Joris
(författare)
-
A sharp floristic discontinuity revealed by the biogeographic regionalization of African savannas
- 2019
-
Ingår i: Journal of Biogeography. - : Wiley. - 0305-0270 .- 1365-2699. ; 46, s. 454-465
-
Tidskriftsartikel (refereegranskat)abstract
- Aim In tropical Africa, savannas cover huge areas, have high plant species richness and are considered as a major natural resource for most countries. There is, however, little information available on their floristics and biogeography at the continental scale, despite the importance of such information for our understanding of the drivers of species diversity at various scales and for effective conservation and management. Here, we collated and analysed floristic data from across the continent in order to propose a biogeographical regionalization for African savannas. Location We collated floristic information (specifically woody species lists) for 298 samples of savanna vegetation across Africa, extending from 18 degrees N to 33 degrees S and from 17 degrees W to 48 degrees E. Taxa We focused on native woody species. Methods We used ordination and clustering to identify the floristic discontinuities and gradual transitions across African savannas. Floristic relationships, specificity and turnover, within and between floristic clusters, were analysed using a (dis-)similarity-based approach. Results We identified eight floristic clusters across African savannas which in turn were grouped into two larger macro-units. Ordinations at species and genus levels showed a clear differentiation in woody species composition between the North/West macro-unit and the South/East macro-unit. This floristic discontinuity matches to the High (i.e. N&W) and Low (S&E) division of Africa previously proposed by White () and which tracks climatic and topographical variation. In the N&W savannas, the floristic gradient determined by rainfall was partitioned into the Sudanian (drier) and Guinean (wetter) clusters. Within the highly heterogeneous S&E savannas and woodlands, six clusters were identified: Ugandan, Ethiopian, Mozambican, Zambezian, Namibian and South African. Main conclusions The proposed pan-African classification of savannas and woodlands might assist the development of coordinated management and conservation policies.
|
|
| 4. |
|
|
| 5. |
- Cromsigt, Joris
(författare)
-
Animal body size distribution influences the ratios of nutrients supplied to plants
- 2020
-
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
-
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.
|
|
| 6. |
|
|
| 7. |
- Cromsigt, Joris
(författare)
-
Brown world forests: increased ungulate browsing keeps temperate trees in recruitment bottlenecks in resource hotspots.
- 2017
-
Ingår i: New Phytologist. - : Wiley. - 0028-646X .- 1469-8137. ; 214, s. 158-168
-
Tidskriftsartikel (refereegranskat)abstract
- * Plant biomass consumers (mammalian herbivory and fire) are increasingly seen as major drivers of ecosystem structure and function but the prevailing paradigm in temperate forest ecology is still that their dynamics are mainly bottom-up resource-controlled. Using conceptual advances from savanna ecology, particularly the demographic bottleneck model, we present a novel view on temperate forest dynamics that integrates consumer and resource control. * We used a fully factorial experiment, with varying levels of ungulate herbivory and resource (light) availability, to investigate how these factors shape recruitment of five temperate tree species. We ran simulations to project how inter- and intraspecific differences in height increment under the different experimental scenarios influence long-term recruitment of tree species. * Strong herbivore-driven demographic bottlenecks occurred in our temperate forest system, and bottlenecks were as strong under resource-rich as under resource-poor conditions. Increased browsing by herbivores in resource-rich patches strongly counteracted the increased escape strength of saplings in these patches. * This finding is a crucial extension of the demographic bottleneck model which assumes that increased resource availability allows plants to more easily escape consumer-driven bottlenecks. Our study demonstrates that a more dynamic understanding of consumer-resource interactions is necessary, where consumers and plants both respond to resource availability.
|
|
| 8. |
- Cromsigt, Joris
(författare)
-
Coarse woody debris facilitates oak recruitment in Białowieża Primeval Forest, Poland
- 2012
-
Ingår i: Forest Ecology and Management. - : Elsevier BV. - 0378-1127 .- 1872-7042. ; 284, s. 133-141
-
Tidskriftsartikel (refereegranskat)abstract
- While oaks contribute to the ecology and economy of temperate lowland forests, recruitment into largersize classes is generally scarce. Ungulate herbivory is a limiting factor for tree recruitment, thus naturalstructures protecting against ungulates may be important for recruitment success. We studied oakrecruitment in relation to coarse woody debris (CWD) in the Białowie_za National Park, Poland, one ofthe last remaining reference sites for undisturbed temperate lowland forests in Europe that containsthe full natural assemblage of large ungulate species and their predators. We compared two contrastingmanagement types: one that excludes all forestry activities (the strict reserve) and one where sanitarycutting and removal of bark-beetle infested Picea abies occurs to prevent further spread.We sampled 4 m wide transects (19 ha in total, of which 15.8 ha in the strict reserve) and recorded saplingheight and sapling browsing, distance from, height of and CWD encirclement, distance to and diameterof mature oaks, tree composition, distance to and diameter of nearest trees, canopy openness andcover of herbs, mosses, bare soil and litter in an equal number of plots with and without saplings. Wefound 161 oak saplings (8.5/ha). CWD was predominantly formed by P. abies. Sapling plots containedmore often CWD than plots without saplings. Also, the distance to CWD was smaller and the CWD encirclementwas higher in sapling plots, while canopy cover did not differ. Sapling height increased and saplingbrowsing decreased with increasing presence of CWD. Both CWD and recruitment beyond 50 cmwere reduced in the managed zone.Our study shows that CWD plays an essential role for the recruitment of oaks in old-growth temperateforest systems, predominantly via protection against ungulate browsing. Sanitary cutting of infestedtrees, a common management practice in temperate forests, prevents the natural accumulation of CWD and so can be counter-productive for the recruitment of appreciated species.
|
|
| 9. |
- Cromsigt, Joris
(författare)
-
Comparing the impact of a grazing regime with European bison versus one with free-ranging cattle on coastal dune vegetation in the Netherlands
- 2018
-
Ingår i: Mammal Research. - : Springer Science and Business Media LLC. - 2199-2401 .- 2199-241X. ; 63, s. 455-466
-
Tidskriftsartikel (refereegranskat)abstract
- Woody plant encroachment has increased across the globe and threatens biodiversity associated with open habitats. In order to prevent or reduce woody encroachment, conservation managers across Europe introduce large mammalian herbivores. While up to recently, managers were mostly using free-ranging domestic cattle and horses for this, there is an increasing interest in the use of European bison for nature management. However, we lack studies that compare the impact of these different grazers on vegetation. We report results from a unique grazing pilot in the National Park Zuid-Kennemerland, a heterogeneous coastal dune landscape in the Netherlands, where European bison, horses, and cattle were introduced to reverse the encroachment of grass and shrub species. We present results of an 8-year study on the development of woody and grassy vegetation on fixed transects in three different grazing areas within the national park; one area with European bison and horses, one area with cattle and horses, and one area where these large grazers were excluded. In all three areas, rabbit, fallow deer, and roe deer were present. Over time, we observed strong reductions in the vitality of several woody species, such as spindle tree, and this decline was similar across all areas. Grass height and cover also declined and the proportion of herbs increased in all three grazing areas in similar ways. However, the type of herbivore use (debarking, foraging on buds, branches) of several woody species differed significantly among areas. For instance, maple tree was only debarked in the E. bison area, while hawthorn branches were eaten significantly more in the cattle than in the bison area. Due to differences in herbivore densities among areas, it was difficult to draw strong conclusions on how the different herbivore species differed in their impact, but, importantly, we found that grazing regimes with bison can lead to as strong effects on vegetation structure and composition as grazing regimes with cattle. This is an important result since certain conditions, such as legal aspects, may motivate managers to introduce a wild large grazer rather than a domesticated one.
|
|
| 10. |
- Cromsigt, Joris
(författare)
-
Conservation implications of the refugee species concept and the European bison: king of the forest or refugee in a marginal habitat?
- 2012
-
Ingår i: Ecography. - : Wiley. - 0906-7590 .- 1600-0587. ; 35, s. 519-529
-
Tidskriftsartikel (refereegranskat)abstract
- The concept of refugee species provides a theoretical framework towards increasing the predictive power of the declining population paradigm through identifying species which are expected to suffer from a declining population syndrome. Using a simple habitat model as a framework, refugee species are defined as those that can no longer access optimal habitat, but are confined to suboptimal habitats, with consequences of decreased fitness and density, and attendant conservation risks. Refugee species may be difficult to detect in the absence of information on prior habitat use and fitness and their observed ecology will be constrained by the habitat limits forced on them. Identification of refugee species, characterisation of pre-refugee ecology and the restoration of such species to optimal habitat is critical to their successful conservation. The concept is showcased by addressing the conundrum of a large grazing bovid, the European bison Bison bonasus, being managed as a forest specialist, despite its evolutionary background, dental morphology, neonatal behaviour, diet and microhabitat selection being characteristic of a grazing species inhabiting open, grass-rich habitats. It is hypothesized that a combination of increasing replacement of open steppe by forest cover after the last postglacial period and increasing human pressure forced bison into forests as a refuge habitat. This process was then reinforced through active management of bison in forests as managers committed themselves to the bison as forest species paradigm. A research agenda to test this hypothesis using an experimental approach in the conservation management of European bison by introducing populations into diverse habitat types is suggested.
|
|
