Biology subjects

Oester, R.

Publications and source records attributed to Oester, R..

3 recordsLinked to original sources

bioRxiv2024

A global synthesis on land-cover changes in watersheds shaping freshwater detrital food webs

Anthropogenic land-cover changes are among the most pressing global threats to both aquatic and terrestrial ecosystems, jeopardising biodiversity and the critical connections between these systems. Resource flows and trophic interactions intricately link aquatic and terrestrial ecosystems, with terrestrial-derived detritus playing a foundational role in supporting aquatic food webs. These detrital inputs form essential cross-ecosystem linkages, underpinning key ecological processes and providing vital resources for aquatic communities. Yet, little research has focused on how land-cover changes cascade across this linkage. To better understand how land-cover changes in the watershed influence freshwater detrital food webs, we conducted a meta-analysis of field studies reporting the effects of vegetation changes on freshwater detrital consumers and organic matter decomposition. The results from 144 studies, reporting 1235 comparisons, showed that, overall, land-cover changes in the watershed vegetation, especially through harvest and land-use conversion, have negative effects on aquatic biodiversity and ecosystem processes. These vegetation changes reduced diversity, abundance, and biomass across multiple trophic levels in freshwater detrital food webs. Studies examining multiple organism groups most often observed negative responses across multiple trophic levels, suggesting that the land-cover changes negatively affected multiple detrital food web components simultaneously. Our results also show that outcomes of restoration of watershed vegetation were context-dependent, and no clear trend of improvement was visible. Therefore, conservation of natural riparian and catchment vegetation are key to maintain freshwater ecosystem processes and aquatic biodiversity worldwide, and more efficient and evidence-based restoration measures are urgently needed. As our global synthesis shows that direct human-induced alterations of vegetation type in watersheds have significant negative effects on freshwater detrital food webs, there is a pressing need to consider cross-ecosystem consequences of land-cover changes in conservation and ecosystem management.

ecology↗

bioRxiv2024

Biodiversity and riparian forests are mutual biological drivers of ecosystem functions in temperate and tropical streams

Fluxes of energy, matter, and organisms sustain linkages and functions within and between ecosystems. Yet, how biological drivers influence interactions and functions at the interface between aquatic and terrestrial environments (i.e., aquatic-terrestrial ecosystem functions) locally and across regions has received little attention. To test the relative importance of biological drivers on multiple aquatic-terrestrial ecosystem functions, we subsidised local terrestrial detritus in forested and non-forested stream sites in a temperate and tropical region. We also manipulated leaf litter diversity (horizontal biodiversity of resources) and macroinvertebrate access (vertical biodiversity of consumers). We measured secondary production of aquatic fungi, in-stream leaf litter nitrogen loss, and decomposition rates. The simultaneous provision of all three ecosystem functions (i.e., multifunctionality) was positively driven by vertical biodiversity and riparian forests in both regions. In both tropical and temperate streams, nitrogen loss was associated with vertical biodiversity. Decomposition rates were also enhanced by vertical biodiversity and linked to other ecosystem functions. These results reveal strong and consistent effects of biodiversity and riparian forests on aquatic-terrestrial ecosystem functions in freshwater detrital food webs in both temperate and tropical headwater streams. Thus, disentangling the drivers of ecosystem functions in these systems requires an understanding of underlying mechanisms beyond ecosystem borders.

ecology↗

bioRxiv2023

Riparian forests shape trophic interactions in detrital stream food webs

Freshwater and terrestrial biodiversity is linked through resource flows. For example, subsidies from the riparian vegetation form the base of food webs in small streams. Despite the key role of detritivores in these food webs, consequences of altered resource availability and riparian vegetation type on their trophic strategies are largely unknown. Therefore, we experimentally tested direct and indirect effects of riparian vegetation type on trophic interactions and dietary imbalances of detritivores. We used stoichiometric and isotopic differences between consumers and resources as functional measures of trophic link strength. Our results show that the lack - compared to the presence - of riparian forests directly affected both stoichiometric and isotopic differences in detrital food webs, yet with diverging patterns between resources and consumers, ultimately leading to aquatic-terrestrial decoupling. Consequently, our findings demonstrate that riparian forests are essential for aquatic food webs by influencing both organisms and interactions networks.

ecology↗