Arctic Indigenous food systems are typified by diverse social interactions that maintain food sec... more Arctic Indigenous food systems are typified by diverse social interactions that maintain food security. Given the numerous challenges Arctic Indigenous communities face, it is important to understand diversity in these systems and how they are impacted by change. This study adopts a mixed methods approach that combines participatory methods with network analysis to assess the diversity of food-related interactions between different actor types in the mixed food system on St. Paul Island, Alaska. We conducted 36 interviews with local food system actors to identify current food security challenges and foodrelated interactions in the local food system. We used network analysis to investigate the diversity of interactions in the food system quantitatively. We simulated the effects of two key food security challenges (out-migration and knowledge loss) on food system diversity and explored interventions to increase diversity. Qualitative data from the same interviews were used to embed our results in the lived realities of the St. Paul Island community. Our approach reveals diverse interactions in the local food system, reflecting both subsistence and market-based elements of the St. Paul Island mixed economy. While both challenges threaten the system's diversity, out-migration presents a more immediate risk to food system diversity than knowledge loss. We advocate for targeting a combination of food system interventions at the community level to enhance food system diversity effectively. Our research contributes to understanding the importance of diversity for Arctic Indigenous food security and emphasizes the need to recognize the complex interactions between food system interventions and their implications for Arctic Indigenous communities.
EGU General Assembly Conference Abstracts, Apr 1, 2015
Focus and aim: Currently, lake Markermeer (680 km 2) provides poor environmental conditions for t... more Focus and aim: Currently, lake Markermeer (680 km 2) provides poor environmental conditions for the development of flora and fauna due to a thick fluffy layer that prevails at the lake's bed. To improve the conditions in the lake, large wetlands will be built from this fluffy layer, possibly mixed with sand or with the underlying Southern Sea deposit. The aim of this study is to distinguish biogeochemical processes influencing phosphorus dynamics in porewater during oxidation and desiccation of mud deposits from this lake. We focus on three important aspects that potentially influence these processes: granulometry, sediment type and modification by plants.
Invasions by non-native plant species are widely recognized as a major driver of biodiversity los... more Invasions by non-native plant species are widely recognized as a major driver of biodiversity loss. Globally, (sub-)tropical islands form important components of biodiversity hotspots, while being particularly susceptible to invasions by plants in general and vines in particular. We studied the impact of the invasive vine A. leptopus on the diversity and structure of recipient plant communities on the northern Caribbean island St. Eustatius. We used a paired-plot design to study differences in species richness, evenness and community structure under A. leptopus-invaded and uninvaded conditions. Community structure was studied through species co-occurrence patterns. We found that in plots invaded by A. leptopus, species richness was 40-50% lower, and these plots also exhibited lower evenness. The magnitude of these negative impacts increased with increasing cover of A. leptopus. Invaded plots also showed higher degrees of homogeneity in species composition. Species co-occurrence patterns indicated that plant communities in uninvaded plots were characterized by segregation, whereas recipient plant communities in invaded plots exhibited random cooccurrence patterns. These observations suggest that invasion of A. leptopus is not only associated with reduced species richness and evenness of recipient communities in invaded sites, but also with a community disassembly process that may reduce diversity between sites. Given that A. leptopus is a successful invader of (sub-)tropical islands around the globe, these impacts on plant community structure highlight that this invasive species could be a particular conservation concern for these systems.
Effective management strategies are needed to control expansion of invasive alien plant species a... more Effective management strategies are needed to control expansion of invasive alien plant species and attenuate economic and ecological impacts. While previous theoretical studies have assessed optimal control strategies that balance economic costs and ecological benefits, less attention has been paid to the ways in which the spatial characteristics of individual patches may mediate the effectiveness of management strategies. We developed a spatially explicit cellular automaton model for invasive species spread, and compared the effectiveness of seven control strategies. These control strategies used different criteria to prioritize the removal of invasive species patches from the landscape. The different criteria were related to patch size, patch geometry, and patch position within the landscape. Effectiveness of strategies was assessed for both seed dispersing and clonally expanding plant species. We found that, for seed-dispersing species, removal of small patches and removal of patches that are isolated within the landscape comprised relatively effective control strategies. For clonally expanding species, removal of patches based on their degree of isolation and their geometrical properties comprised relatively effective control strategies. Subsequently, we parameterized the model to mimic the observed spatial distribution of the invasive species Antigonon leptopus on St. Eustatius (northern Caribbean). This species expands clonally and also disperses via seeds, and model simulations showed that removal strategies focusing on smaller patches that are more isolated in the landscape would be most effective and could increase the effectiveness of a 10-yr control strategy by 30-90%, as compared to random removal of patches. Our study emphasizes the potential for invasive plant species management to utilize recent advances in remote sensing, which enable mapping of invasive species at the high spatial resolution needed to quantify patch geometries. The presented results highlight how this spatial information can be used in the design of more effective invasive species control strategies.
The Slikken van Flakkee, a former tidal wetland in the Grevelingen, the Netherlands, has been cha... more The Slikken van Flakkee, a former tidal wetland in the Grevelingen, the Netherlands, has been changing under freshening conditions since 1971; in that year, the salty Grevelingen estuary was closed from the North Sea as part of the Dutch Delta Works. Our research aimed to analyse vegetation development over 1972-2016 and relates succession to quantified ecohydrogeochemical processes in the Slikken van Flakkee. We analysed succession and physico-chemical conditions at 63 monitoring locations. Based on extensive fieldwork in 2016 and 2017, we quantified the identified geochemical processes via inverse modelling and applied Canonical Correspondence Analysis (CCA) to search for interrelations with vegetation. Nine per cent of the 229 observed plant species are rare and threatened or vulnerable, according to the Dutch Red List. Succession series showed a development from saline pioneer communities towards grassland and shrub vegetation dependent on management measures (grazing and mowing versus spontaneous development), desalinisation and geochemical processes, of which dissolution of carbonates appeared to be the dominant one. During desalinisation, the water-type shifted from NaCl towards CaHCO 3. The CCA confirmed the impact of geochemical and texture variables, elevation and management on vegetation. Grazing and mowing led to species-rich grasslands and forb vegetation harbouring twice as many species than the spontaneously developed area after 50 years, demonstrating the importance of active nature management. We argue that hydrological-geochemical modelling is necessary to support policy-making before deciding on the partial re-establishment of the tide in Lake Grevelingen.
Nitrogen (N) and phosphorus (P) availability affect plant sexual reproduction performance. Seed a... more Nitrogen (N) and phosphorus (P) availability affect plant sexual reproduction performance. Seed as the main product of sexual reproduction is expected to be affected by N and P availability in parent plant. We experimentally test how parental N:P stoichiometry affected seed characteristics and performance of two grassland species. Seeds of a common species (Holcus lanatus) and an endangered species (Parnassia palustris) were collected from parent plants under two different N:P ratio growth conditions in a grassland reserve in the Netherlands. We measured the following traits of the two species from the two parental N:P ratio growth conditions: seed N concentration and content, seed P concentration and content, seed length, seed area, seed weight, seed germination, and offspring survival. No significant inter-location difference was found in seed weight of the collected seeds for either of the two species. However, the stronger P-limited conditions at the locations of the parent plants affected seed length and seed area negatively in H. lanatus and positively in P. palustris. Stronger P-limited conditions also decreased seed P concentration and content and increased seed N:P ratio of H. lanatus, but no inter-location nutrient difference was found in seeds of P. palustris. Surprisingly, contrary to what could be expected from seed P concentration and content there was no inter-location difference in seed germination for H. lanatus. For P. palustris, stronger P-limited conditions in the parental environment significantly enhanced seed germination, whereas stronger P-limited conditions in the offspring environment decreased offspring survival, suggesting that P limitation may negatively affect P. palustris rejuvenation. Our results suggest the possibility of different influences of parental N:P ratio and especially of P limitation on seed characteristics and performance of a common and an endangered species.
This is an open access article under the terms of the Creative Commons Attribution-NonCommercial ... more This is an open access article under the terms of the Creative Commons Attribution-NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.
Maintenance of urban green infrastructure generates a large amount of biomass that can be conside... more Maintenance of urban green infrastructure generates a large amount of biomass that can be considered a valuable feedstock for biogas production. This study aims to determine the effect of the cutting time and method of substrate preservation on the specific methane yield (SMY) of urban grass collected from road verges and median strips between roadways in wet (WF) and dry fermentation (DF) technology. The grass was collected three times in a growing season, including in spring, summer, and autumn. The biochemical methane potential (BMP) test was performed on fresh grass, grass ensiled without additives, and grass ensiled with microbiological additives. In addition, the energy potentially produced from biogas and the avoided CO2 emissions were calculated. The highest SMY (274.18 ± 22.59 NL kgVS−1) was observed for the fresh grass collected in spring and subjected to WF. At the same time, the lowest CH4 production (182.63 ± 0.48 NL kgVS−1) was found in the grass ensiled without additi...
Despite the importance of non-timber forest products (NTFPs) for local livelihoods in tropical co... more Despite the importance of non-timber forest products (NTFPs) for local livelihoods in tropical countries and the increasing attention for biodiversity-ecosystem services relationships, it remained unclear how the ecosystem service of NTFP provisioning is related to plant diversity. Although it is generally assumed that plant diversity is positively related to ecosystem services, this had not been assessed for NTFP provisioning. We applied bivariate and multiple regression models to explore the relationships between the abundance of 58 commercially relevant NTFP species and woody plant diversity across 287 plots of tropical forests in Northern Suriname. We found that NTFP abundance showed both positive and negative relationships to plant diversity indicators. In contrast to expectations, NTFP abundance was negatively related to woody species richness. In addition, across the plots disproportionately few (2-6) NTFP species determined >50% of NTFP abundance. The occurrence and the identity of these 'NTFP oligarchs' was associated to specific floristic compositions. Overall, more than half, i.e. 55.9%, of the observed variation in NTFP abundance could be explained by a combination of taxonomic and structural plant diversity indicators. Our case study findings are relevant for conservation policies in general. In most countries NTFPs are not on the agenda of governments and current tropical conservation policies often focus on forests with high species richness and/or carbon stocks. Our findings indicate that current policies may not cover valuable forests in terms of high NTFP abundance. To support sustainable NTFP provisioning, additional conservation efforts would need to include those vegetation types with high NTFP abundance.
Arctic Indigenous food systems are typified by diverse social interactions that maintain food sec... more Arctic Indigenous food systems are typified by diverse social interactions that maintain food security. Given the numerous challenges Arctic Indigenous communities face, it is important to understand diversity in these systems and how they are impacted by change. This study adopts a mixed methods approach that combines participatory methods with network analysis to assess the diversity of food-related interactions between different actor types in the mixed food system on St. Paul Island, Alaska. We conducted 36 interviews with local food system actors to identify current food security challenges and foodrelated interactions in the local food system. We used network analysis to investigate the diversity of interactions in the food system quantitatively. We simulated the effects of two key food security challenges (out-migration and knowledge loss) on food system diversity and explored interventions to increase diversity. Qualitative data from the same interviews were used to embed our results in the lived realities of the St. Paul Island community. Our approach reveals diverse interactions in the local food system, reflecting both subsistence and market-based elements of the St. Paul Island mixed economy. While both challenges threaten the system's diversity, out-migration presents a more immediate risk to food system diversity than knowledge loss. We advocate for targeting a combination of food system interventions at the community level to enhance food system diversity effectively. Our research contributes to understanding the importance of diversity for Arctic Indigenous food security and emphasizes the need to recognize the complex interactions between food system interventions and their implications for Arctic Indigenous communities.
EGU General Assembly Conference Abstracts, Apr 1, 2015
Focus and aim: Currently, lake Markermeer (680 km 2) provides poor environmental conditions for t... more Focus and aim: Currently, lake Markermeer (680 km 2) provides poor environmental conditions for the development of flora and fauna due to a thick fluffy layer that prevails at the lake's bed. To improve the conditions in the lake, large wetlands will be built from this fluffy layer, possibly mixed with sand or with the underlying Southern Sea deposit. The aim of this study is to distinguish biogeochemical processes influencing phosphorus dynamics in porewater during oxidation and desiccation of mud deposits from this lake. We focus on three important aspects that potentially influence these processes: granulometry, sediment type and modification by plants.
Invasions by non-native plant species are widely recognized as a major driver of biodiversity los... more Invasions by non-native plant species are widely recognized as a major driver of biodiversity loss. Globally, (sub-)tropical islands form important components of biodiversity hotspots, while being particularly susceptible to invasions by plants in general and vines in particular. We studied the impact of the invasive vine A. leptopus on the diversity and structure of recipient plant communities on the northern Caribbean island St. Eustatius. We used a paired-plot design to study differences in species richness, evenness and community structure under A. leptopus-invaded and uninvaded conditions. Community structure was studied through species co-occurrence patterns. We found that in plots invaded by A. leptopus, species richness was 40-50% lower, and these plots also exhibited lower evenness. The magnitude of these negative impacts increased with increasing cover of A. leptopus. Invaded plots also showed higher degrees of homogeneity in species composition. Species co-occurrence patterns indicated that plant communities in uninvaded plots were characterized by segregation, whereas recipient plant communities in invaded plots exhibited random cooccurrence patterns. These observations suggest that invasion of A. leptopus is not only associated with reduced species richness and evenness of recipient communities in invaded sites, but also with a community disassembly process that may reduce diversity between sites. Given that A. leptopus is a successful invader of (sub-)tropical islands around the globe, these impacts on plant community structure highlight that this invasive species could be a particular conservation concern for these systems.
Effective management strategies are needed to control expansion of invasive alien plant species a... more Effective management strategies are needed to control expansion of invasive alien plant species and attenuate economic and ecological impacts. While previous theoretical studies have assessed optimal control strategies that balance economic costs and ecological benefits, less attention has been paid to the ways in which the spatial characteristics of individual patches may mediate the effectiveness of management strategies. We developed a spatially explicit cellular automaton model for invasive species spread, and compared the effectiveness of seven control strategies. These control strategies used different criteria to prioritize the removal of invasive species patches from the landscape. The different criteria were related to patch size, patch geometry, and patch position within the landscape. Effectiveness of strategies was assessed for both seed dispersing and clonally expanding plant species. We found that, for seed-dispersing species, removal of small patches and removal of patches that are isolated within the landscape comprised relatively effective control strategies. For clonally expanding species, removal of patches based on their degree of isolation and their geometrical properties comprised relatively effective control strategies. Subsequently, we parameterized the model to mimic the observed spatial distribution of the invasive species Antigonon leptopus on St. Eustatius (northern Caribbean). This species expands clonally and also disperses via seeds, and model simulations showed that removal strategies focusing on smaller patches that are more isolated in the landscape would be most effective and could increase the effectiveness of a 10-yr control strategy by 30-90%, as compared to random removal of patches. Our study emphasizes the potential for invasive plant species management to utilize recent advances in remote sensing, which enable mapping of invasive species at the high spatial resolution needed to quantify patch geometries. The presented results highlight how this spatial information can be used in the design of more effective invasive species control strategies.
The Slikken van Flakkee, a former tidal wetland in the Grevelingen, the Netherlands, has been cha... more The Slikken van Flakkee, a former tidal wetland in the Grevelingen, the Netherlands, has been changing under freshening conditions since 1971; in that year, the salty Grevelingen estuary was closed from the North Sea as part of the Dutch Delta Works. Our research aimed to analyse vegetation development over 1972-2016 and relates succession to quantified ecohydrogeochemical processes in the Slikken van Flakkee. We analysed succession and physico-chemical conditions at 63 monitoring locations. Based on extensive fieldwork in 2016 and 2017, we quantified the identified geochemical processes via inverse modelling and applied Canonical Correspondence Analysis (CCA) to search for interrelations with vegetation. Nine per cent of the 229 observed plant species are rare and threatened or vulnerable, according to the Dutch Red List. Succession series showed a development from saline pioneer communities towards grassland and shrub vegetation dependent on management measures (grazing and mowing versus spontaneous development), desalinisation and geochemical processes, of which dissolution of carbonates appeared to be the dominant one. During desalinisation, the water-type shifted from NaCl towards CaHCO 3. The CCA confirmed the impact of geochemical and texture variables, elevation and management on vegetation. Grazing and mowing led to species-rich grasslands and forb vegetation harbouring twice as many species than the spontaneously developed area after 50 years, demonstrating the importance of active nature management. We argue that hydrological-geochemical modelling is necessary to support policy-making before deciding on the partial re-establishment of the tide in Lake Grevelingen.
Nitrogen (N) and phosphorus (P) availability affect plant sexual reproduction performance. Seed a... more Nitrogen (N) and phosphorus (P) availability affect plant sexual reproduction performance. Seed as the main product of sexual reproduction is expected to be affected by N and P availability in parent plant. We experimentally test how parental N:P stoichiometry affected seed characteristics and performance of two grassland species. Seeds of a common species (Holcus lanatus) and an endangered species (Parnassia palustris) were collected from parent plants under two different N:P ratio growth conditions in a grassland reserve in the Netherlands. We measured the following traits of the two species from the two parental N:P ratio growth conditions: seed N concentration and content, seed P concentration and content, seed length, seed area, seed weight, seed germination, and offspring survival. No significant inter-location difference was found in seed weight of the collected seeds for either of the two species. However, the stronger P-limited conditions at the locations of the parent plants affected seed length and seed area negatively in H. lanatus and positively in P. palustris. Stronger P-limited conditions also decreased seed P concentration and content and increased seed N:P ratio of H. lanatus, but no inter-location nutrient difference was found in seeds of P. palustris. Surprisingly, contrary to what could be expected from seed P concentration and content there was no inter-location difference in seed germination for H. lanatus. For P. palustris, stronger P-limited conditions in the parental environment significantly enhanced seed germination, whereas stronger P-limited conditions in the offspring environment decreased offspring survival, suggesting that P limitation may negatively affect P. palustris rejuvenation. Our results suggest the possibility of different influences of parental N:P ratio and especially of P limitation on seed characteristics and performance of a common and an endangered species.
This is an open access article under the terms of the Creative Commons Attribution-NonCommercial ... more This is an open access article under the terms of the Creative Commons Attribution-NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.
Maintenance of urban green infrastructure generates a large amount of biomass that can be conside... more Maintenance of urban green infrastructure generates a large amount of biomass that can be considered a valuable feedstock for biogas production. This study aims to determine the effect of the cutting time and method of substrate preservation on the specific methane yield (SMY) of urban grass collected from road verges and median strips between roadways in wet (WF) and dry fermentation (DF) technology. The grass was collected three times in a growing season, including in spring, summer, and autumn. The biochemical methane potential (BMP) test was performed on fresh grass, grass ensiled without additives, and grass ensiled with microbiological additives. In addition, the energy potentially produced from biogas and the avoided CO2 emissions were calculated. The highest SMY (274.18 ± 22.59 NL kgVS−1) was observed for the fresh grass collected in spring and subjected to WF. At the same time, the lowest CH4 production (182.63 ± 0.48 NL kgVS−1) was found in the grass ensiled without additi...
Despite the importance of non-timber forest products (NTFPs) for local livelihoods in tropical co... more Despite the importance of non-timber forest products (NTFPs) for local livelihoods in tropical countries and the increasing attention for biodiversity-ecosystem services relationships, it remained unclear how the ecosystem service of NTFP provisioning is related to plant diversity. Although it is generally assumed that plant diversity is positively related to ecosystem services, this had not been assessed for NTFP provisioning. We applied bivariate and multiple regression models to explore the relationships between the abundance of 58 commercially relevant NTFP species and woody plant diversity across 287 plots of tropical forests in Northern Suriname. We found that NTFP abundance showed both positive and negative relationships to plant diversity indicators. In contrast to expectations, NTFP abundance was negatively related to woody species richness. In addition, across the plots disproportionately few (2-6) NTFP species determined >50% of NTFP abundance. The occurrence and the identity of these 'NTFP oligarchs' was associated to specific floristic compositions. Overall, more than half, i.e. 55.9%, of the observed variation in NTFP abundance could be explained by a combination of taxonomic and structural plant diversity indicators. Our case study findings are relevant for conservation policies in general. In most countries NTFPs are not on the agenda of governments and current tropical conservation policies often focus on forests with high species richness and/or carbon stocks. Our findings indicate that current policies may not cover valuable forests in terms of high NTFP abundance. To support sustainable NTFP provisioning, additional conservation efforts would need to include those vegetation types with high NTFP abundance.
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