Leaf-associated macroinvertebrate assemblage and leaf litter breakdown in headwater streams depend on local riparian vegetation

Abstract

Headwater streams harbor diverse macroinvertebrate communities and are hotspots for leaf litter breakdown. The process of leaf litter breakdown mediated by macroinvertebrates forms an important link between terrestrial and aquatic ecosystems. Yet, how the vegetation type in the local riparian zone influences leaf-associated macroinvertebrate assemblages and leaf litter breakdown rates is still not resolved. We investigated how leaf-associated macroinvertebrate assemblages and leaf litter fragmentation rates differ between forested and non-forested sites using experimental leaf litter bags in sixteen sites paired across eight headwater streams in Switzerland. Our results show that sensitive taxa of the invertebrate orders Ephemeroptera, Plecoptera and Trichoptera (EPT) and the functional group of shredders were strongly associated with forested sites with overall higher values of abundance, diversity, and biomass of EPTs in forested compared to non-forested sites. However, the importance of riparian vegetation differed between study regions, especially for shredders. Fragmentation rates, which are primarily the result of macroinvertebrate shredding, were on average three times higher in forested compared to non-forested sites. Our results demonstrate that not only the composition of the aquatic fauna but also the functioning of an essential ecosystem process depend on the vegetation type in the local riparian zone.

Variables de hábitat que regulan la estructura de las comunidades de macroinvertebrados en corrientes de montaña del Oriente antioqueño (Colombia)

“…Acompañando las variables hidráulicas, la cobertura vegetal aparece como un elemento importante en el establecimiento de los macroinvertebrados en las corrientes estudiadas. La diversidad y abundancia de macroinvertebrados es mayor en los sitios que presentan más variabilidad en el sustrato y mejores condiciones de cobertura vegetal, afectando especialmente su composición funcional, tal como se ha documentado en Colombia (Barros-Núñez, 2020;Galeano-Rendón & Mancera-Rodríguez, 2018;Meza-Salazar et al, 2012;Vera-Sánchez & Pinilla-Agudelo, 2020;Walteros-Rodríguez & Castaño-Rojas, 2020) y en otros países (Fierro et al, 2017;Oester et al, 2022;Ono et al, 2020). Esta dependencia entre las características de la ribera y la estructura de la comunidad de macroinvertebrados obedece a que la entrada de material alóctono como hojarasca, semillas, ramas y troncos representa una fuente fundamental de energía y nutrientes para los macroinvertebrados, especialmente los trituradores (Vimos-Lojano, 2017).…”

Riparian forests shape trophic interactions in detrital stream food webs

“…We studied detritus-based communities and their trophic interactions in eight 1 st to 3 rd order headwater streams in Switzerland in autumn/winter 2020/2021. We selected eight streams with a forested section (mixed deciduous trees) and a non-forested section (grassland and/or extensively used pasture) in a paired design of approximately 500 m apart (Oester et al 2023). The herein-studied contrast of forested vs. non-forested stream sections is a commonly found pattern at landscape scales, with well-documented effects on the composition of aquatic detritivore communities, and representative for the studied stream systems (Cereghetti & Altermatt 2023; Little & Altermatt 2018).…”

“…The herein-studied contrast of forested vs. non-forested stream sections is a commonly found pattern at landscape scales, with well-documented effects on the composition of aquatic detritivore communities, and representative for the studied stream systems (Cereghetti & Altermatt 2023; Little & Altermatt 2018). The two sites and tributaries of each of the eight streams showed no to minor anthropogenic impacts and did not substantially differ in average water temperature (forested: 4.2 °C ± 1.1; non-forested: 4.4 °C ± 1.4), nitrate concentrations (forested: 2.4 mg/l ± 2.1; non-forested: 2.2 mg/l ± 2.1), or DOC (forested: 2.7 mg/l ±1.9; non-forested: 2.7 mg/l ± 2.0) (for more details on the site characteristics and invertebrate communities see Table S2 and Oester et al . (2023)).…”

Ecological Significance of Aquatic Macroinvertebrates in Headwater Streams

“…The headwaters consist of various microhabitats that harbor an array of both fauna and flora (Meyer et al, 2007), while many of these organisms are bioindicators of those unique habitats (Jandry et al, 2014, Pond et al, 2014, Machado et al, 2021. Among these fauna, macroinvertebrates play a crucial ecological role in keeping the ecological balance not only in the headwaters themselves but also in the entire river network (Heino 2005, Oester et al, 2023. Aquatic macroinvertebrates are animals without a backbone that are living in aquatic habitats and visible under the naked eye.…”