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Forests, Functions, and Food Webs: Riparian processes through an ecological and molecular lens
Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Environmental and Life Sciences (from 2013).ORCID iD: 0000-0002-6011-8540
2023 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Riparian systems are critical ecological interfaces that have a significant impact on the surrounding aquatic and terrestrial ecosystems. The riparian and surrounding systems have significant roles in regulating energy flow, providing essential nutrients, and supporting unique species, making them important for ecosystem function. Both the aquatic and terrestrial ecosystems are reliant on the reciprocal exchange of energy subsides to maintain productive and stable food webs. Retention of forested buffers along streams during tree felling operations is a common management technique used to protect aquatic resources and conserve the surrounding ecosystem processes. Measuring the effects of forestry practices on the function and food webs of riparian predators is vital to making forest management decisions that strengthen and protect these fundamental services. Insight into predator function and predator-prey interactions using powerful molecular techniques can further the understanding of these complex systems and help to mitigate the effects of forestry practices.

This thesis explores the functional diversity, food webs, and predator-prey interactions in riparian systems impacted by forestry felling practices. I have studied the effects of clear-cutting and forested buffer zones on riparian functional diversity through the assessment of functional richness and redundancy of spider and plant communities. In addition, I have both validated and used stable isotope analysis and DNA metabarcoding to investigate the primary food sources and prey choices of riparian predators. Riparian buffer size had no direct effect on the functional richness or redundancy of riparian spiders and vascular plants. However, riparian buffer variables such as canopy closure, buffer density, and vegetation coverage did have direct impacts on both spider and plant function. Most riparian spiders and brown trout received a significant majority of their food source from the terrestrial environment and the presence or absence of a riparian buffer did not effect this outcome. However, web-weaving spiders in unbuffered systems were more likely to exploit aquatic resources as a primary food source. Overall, the responses of predator function and food webs to forestry practice are site-specific.

Abstract [en]

This thesis investigates the role of riparian systems impacted by forestry practices, examining their functional diversity, food webs, and predator-prey interactions. Clear-cutting and forested buffer zones' effects on riparian functional diversity, as well as the primary food sources of riparian predators, were studied using stable isotope analysis and metabarcoding. While buffer size did not directly impact the functional diversity of riparian spiders, brown trout, or plants, factors such as canopy closure and vegetation coverage did. Additionally, unbuffered systems impacted the prey source of web-weaving spiders.

Place, publisher, year, edition, pages
Karlstad: Karlstads universitet, 2023. , p. 61
Series
Karlstad University Studies, ISSN 1403-8099 ; 2023:34
Keywords [en]
Riparian systems, functional diversity, stable isotope analysis, metabarcoding, Tetragnathidae, Lycosidae, forestry management, prey subsidies
National Category
Ecology
Research subject
Biology
Identifiers
URN: urn:nbn:se:kau:diva-97332ISBN: 978-91-7867-418-3 (print)ISBN: 978-91-7867-419-0 (electronic)OAI: oai:DiVA.org:kau-97332DiVA, id: diva2:1810319
Public defence
2023-12-08, 21A342, Eva Erikssonsalen, Universitetsgatan 2, Karlstad, 10:00 (English)
Opponent
Supervisors
Funder
Swedish Research Council FormasKarlstad UniversityAvailable from: 2023-11-17 Created: 2023-11-07 Last updated: 2023-11-17Bibliographically approved
List of papers
1. Forested riparian buffer environmental variables are more important than size for species functional diversity in production forests
Open this publication in new window or tab >>Forested riparian buffer environmental variables are more important than size for species functional diversity in production forests
2022 (English)In: Forest Ecology and Management, ISSN 0378-1127, E-ISSN 1872-7042, Vol. 526, article id 120599Article in journal (Refereed) Published
Abstract [en]

Retention of forested buffers around streams following forest cutting operations is a common managementtechnique used to protect aquatic resources and conserve the surrounding ecosystem services. Species richness,or α-diversity, is commonly used as an indicator of the effects of forestry management although it provides verylittle information about those effects on ecosystem processes and function. Functional diversity links speciestraits and ecosystem function incorporating species diversity, community composition, and functional guild andis more suitable to investigate the direct and indirect effects of forestry on ecosystem function. We sampledspiders and vascular plants in buffered and unbuffered stream-forest systems in southern Sweden and used atrait-based approach to assess the effects of buffer size and environmental variables on functional diversity. Weused structural equation modeling (SEM) to explore the effects of buffer size and condition on spider and vascularplant diversity. We found no effect of buffer size on the functional richness or functional redundancy for spidersor vascular plants. Buffer size had a slight effect on the α-diversity of spiders within small buffers and fullyforested sites but the effect was small. Other buffer variables including canopy closure, buffer density, bareground coverage, and soil fertility had direct effects on spider and vascular plant functional diversity. The maindriver of functional richness was α-diversity, but our SEM analysis illustrated other environmental variablesworking jointly to drive functional diversity. Using a trait-based approach, we showed that forested buffers havea minimal overall impact on spider and vascular plant functional diversity. However, it is important to maintainhigh levels of α-diversity to preserve and promote both spider and plant functional richness in production forestsand we suggest that forest management conserves and encourages high levels of α-diversity to increase overallfunctional diversity.

Place, publisher, year, edition, pages
Elsevier, 2022
Keywords
Aquatic ecosystems, Aquatic organisms, Conservation, Plant shutdowns, Redundancy, Timber, Buffer sizes, Environmental variables, Forestry management, Functional diversity, Functional redundancy, Functional richness, Riparian zones, Species richness, Structural equation models, Vascular plant, Forestry, Ecosystem function, Forest management, Riparian zone, Soil fertility, Species richness, Arachnids, Buffers, Conservation, Forest Management, Forestry, Production, Variables, Vascular Plants, Sweden
National Category
Ecology Forest Science
Research subject
Biology
Identifiers
urn:nbn:se:kau:diva-92498 (URN)10.1016/j.foreco.2022.120599 (DOI)000878593200004 ()2-s2.0-85140344645 (Scopus ID)
Funder
Swedish Research Council Formas, 2018-00412
Available from: 2022-11-16 Created: 2022-11-16 Last updated: 2023-11-08Bibliographically approved
2. Small stream predators rely heavily on terrestrial matter energy input in the fall, regardless of riparian buffer size
Open this publication in new window or tab >>Small stream predators rely heavily on terrestrial matter energy input in the fall, regardless of riparian buffer size
2023 (English)In: Food Webs, E-ISSN 2352-2496, Vol. 36, article id e00302Article in journal (Refereed) Published
Abstract [en]

Stream ecosystems are reliant on the reciprocal exchange of terrestrial and aquatic energy subsides to maintain a productive and stable food web. Land use around streams can have strong effects on the size and availability of resource subsidies for stream and riparian predators such as fish and spiders. A common forestry technique around streams is the establishment of forested buffers to protect aquatic and riparian ecosystems from upland disturbances. Buffer size may determine prey abundance, richness, and spatial extent of prey reach into both the aquatic and terrestrial systems. To test the effects of forested buffers subsidy direction, we explored the carbon and nitrogen stable isotope signatures of brown trout (Salmo trutta), Tetragnathidae and Lycosidae spiders, and their aquatic and terrestrial prey sources around twelve streams in southern Sweden. For both predator groups, buffer presence showed no effect on resource subsidy source. We found that both brown trout and spiders are significantly reliant on terrestrial sources of prey for their diets in the fall. To support the terrestrial subsidy into small streams it is vital to maintain ecologically functional riparian zones by conserving complex surrounding habitats that optimize habitat and both terrestrial and aquatic prey diversity.

Place, publisher, year, edition, pages
Elsevier, 2023
Keywords
Allochthonous resources, Aquatic subsidies, Forested buffers, Riparian, Stable isotopes, Terrestrial subsidies
National Category
Ecology Environmental Sciences related to Agriculture and Land-use
Research subject
Biology
Identifiers
urn:nbn:se:kau:diva-96326 (URN)10.1016/j.fooweb.2023.e00302 (DOI)001050735300001 ()2-s2.0-85165632660 (Scopus ID)
Funder
Swedish Research Council Formas, 2018-00412
Available from: 2023-08-10 Created: 2023-08-10 Last updated: 2023-11-08Bibliographically approved
3. Riparian clear-cuts affect the source of riparian spider prey depending on capture stategy
Open this publication in new window or tab >>Riparian clear-cuts affect the source of riparian spider prey depending on capture stategy
(English)Manuscript (preprint) (Other academic)
Identifiers
urn:nbn:se:kau:diva-97413 (URN)
Available from: 2023-11-17 Created: 2023-11-17 Last updated: 2023-11-17Bibliographically approved
4. Greater than the sum of your parts: Nonlethal stable isotope sampling methods in spiders
Open this publication in new window or tab >>Greater than the sum of your parts: Nonlethal stable isotope sampling methods in spiders
2022 (English)In: Ecosphere, ISSN 2150-8925, E-ISSN 2150-8925, Vol. 13, no 1, article id e3903Article in journal (Refereed) Published
Abstract [en]

As top consumers and generalist predators, spiders are ideal organisms to study food webs and complex ecological functions using stable isotopes. Most researchers use whole-body samples to analyze stable isotope ratios in spiders. Spiders can regrow lost legs and produce multiple molts during a life cycle, and nonlethal sampling utilizing legs and molts may provide a useful alternative to whole-body sampling especially in larger bodied or threatened species. Furthermore, removing spider abdomens and thus leftover prey in the gut contents may provide a more accurate isotopic value. We tested the hypothesis that the delta N-15, delta C-13, or delta H-2 isotopic values in spider legs are reliable proxies for spider prosomas, abdomens, or whole bodies. We used laboratory-reared large-bodied spiders (Pterinochilus murinus) and field-collected Lycosidae to compare lethal and nonlethal tissue isotopic values. We found that nonlethal samples of spider legs and molts are acceptable alternatives to lethal whole-body samples to determine delta C-13 and delta N-15 stable isotope signatures. Nonlethal samples are not suitable proxies for whole-body samples to determine delta H-2 isotopic values. Using nonlethal leg or molts samples in stable isotope investigations of spiders will allow researchers to promote conservation efforts and study threatened species while ensuring accurate and repeatable results.

Place, publisher, year, edition, pages
John Wiley & Sons, 2022
Keywords
discrimination values, hydrogen, Lycosidae, nonlethal sampling, Theraphosidae, trophic shift
National Category
Ecology
Research subject
Biology
Identifiers
urn:nbn:se:kau:diva-88756 (URN)10.1002/ecs2.3903 (DOI)000747491800017 ()2-s2.0-85123717955 (Scopus ID)
Available from: 2022-02-25 Created: 2022-02-25 Last updated: 2023-11-08Bibliographically approved
5. Molecular gut content analysis results are determined by various biotic factors in wolf spiders (Aranae: Lycosidae)
Open this publication in new window or tab >>Molecular gut content analysis results are determined by various biotic factors in wolf spiders (Aranae: Lycosidae)
(English)Manuscript (preprint) (Other academic)
Identifiers
urn:nbn:se:kau:diva-97415 (URN)
Available from: 2023-11-17 Created: 2023-11-17 Last updated: 2023-11-17Bibliographically approved

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