Abteilung Aquatische Ökologie

Gemeinschaftsökologie und Saisonalität der Laubstreu-Dynamik in kleinen Fliessgewässern

Foto: Altermatt lab

Laubfall bildet die Grundlage vieler aquatischer Ökosysteme und stellt einen wichtigen Weg für den Ressourcentransfer von terrestrischen in aquatische Umgebungen dar. In kleinen Fliessgewässern sorgt eine vielfältige Gruppe von Organismen, die als Zersetzer bezeichnet werden, für den Abbau dieses Materials, indem sie Blätter verzehren und so Nährstoffe freisetzen. Durch diesen Prozess werden Kohlenstoff und Stickstoff auf höhere trophische Ebenen übertragen, da die Zersetzer von Fischen gefressen werden und feine organische Partikel produzieren, die wiederum von filternden Organismen verzehrt werden können.

Die Geschwindigkeit, mit der Zerkleinerer Laubstreu verzehren, hat einen starken Einfluss auf das Ausmass des Nährstoffkreislaufs innerhalb der Nahrungsnetze von Gewässern und wird sowohl von der Qualität als auch von der Quantität des Falllaubs bestimmt. In gemässigten Zonen verändert der Klimawandel den Zeitpunkt des Laubfalls und beeinträchtigt damit die Verfügbarkeit und Nährstoffqualität des Laubstreus für aquatische Konsumenten und stört möglicherweise diese wichtigen Nährstoffwege.

Unsere Forschung konzentriert sich darauf, zu verstehen, wie saisonale Veränderungen in der Dynamik des Laubstreus den Nährstoffkreislauf in kleinen Fliessgewässern beeinflussen. Wir verwenden zeitlich und räumlich replizierte Laubstreu-Beutel und Laubstreu-Fallen, um die Muster der Laubstreu-Zersetzung zu quantifizieren und Laubstreu-Bilanzen zu erstellen. Darüber hinaus verwenden wir Mesokosmos-Experimente, um zu bewerten, wie sich veränderte Laubfallzeiten auf die Verzehrraten von Wasserorganismen auswirken, wobei wir uns insbesondere auf den häufig vorkommenden zerkleinernden Flohkrebs Gammarus fossarum konzentrieren. Dabei untersuchen wir, wie Veränderungen des Zeitpunkts des Laubfalls die Verzehr- und die Wachstumsraten von aquatischen Wirbellosen beeinflussen, sodass wir beurteilen können, wie sich klimabedingte Veränderungen der Laubstreu-Saisonalität auf die Vernetzung von aquatischen und terrestrischen Ökosystemen auswirken können.

Publikationen

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      authors => protected'Cereghetti, E.; Altermatt, F.' (39 chars)
      title => protected'The phenology of leaf litter decomposition in aquatic and terrestrial compar
         tments of headwater catchments' (106 chars)
      journal => protected'American Naturalist' (19 chars)
      year => protected2025 (integer)
      volume => protected206 (integer)
      issue => protected'2' (1 chars)
      startpage => protected'89' (2 chars)
      otherpage => protected'100' (3 chars)
      categories => protected'ecosystem function and services; detritus cycling; seasonality; metaecosyste
         m' (77 chars)
      description => protected'The decomposition of leaf litter is a major ecological process in terrestria
         l and aquatic ecosystems worldwide. Leaf litter generally enters ecosystems 
         in annual pulses and is subsequently decomposed across many seasons. Yet inv
         estigations into this process are rarely conducted in parallel in aquatic an
         d terrestrial ecosystems and over the full year, limiting our understanding 
         of its phenological context across the blue-green interface. Here, we assess
         ed the decomposition of three litter species by microorganisms and macroinve
         rtebrates in temperate streams and forests across a year using repeated litt
         erbag assays at 6-week intervals. We observed higher decomposition rates in 
         summer in most combinations of ecosystem, litter species, and decomposer typ
         e, indicating positive effects of higher temperatures and low standing crops
          of labile litter. Furthermore, forests showed lower decomposition rates tha
         n streams. Last, we found that the relative litter species effects on both m
         icrobial and invertebrate decomposition were consistent across environments,
          suggesting that the fast microbial activity decreased the quality of the re
         maining tissue mass for invertebrates. Overall, our work places known driver
         s of the decomposition of leaf litter into a phenological context, providing
          evidence that changes in the timing or strength of these drivers could driv
         e temporal shifts of this central ecological process.' (1421 chars)
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      authors => protected'Cereghetti, E.; Peller, T.; Kaeser, S.; Gounand, I.; Alt
         ermatt, F.' (91 chars)
      title => protected'Seasonal dynamics of detritus flows and decomposition across ecosystem bound
         aries' (81 chars)
      journal => protected'Current Biology' (15 chars)
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      issue => protected'9' (1 chars)
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      description => protected'Material fluxes are ubiquitous in nature within and across ecosystems, conne
         cting habitats with vastly different characteristics, like forests to rivers
          and lakes.<sup>1</sup><sup>,</sup><sup>2</sup><sup>,</sup><sup>3</sup> Alth
         ough individual fluxes and their cascading effects are well known,<sup>4</su
         p><sup>,</sup><sup>5</sup><sup>,</sup><sup>6</sup> very few studies address 
         the intra-annual phenology of ecosystem processes, despite the pronounced se
         asonality of fluxes. Here, we empirically quantified and resolved fluxes of 
         recalcitrant and labile types of leaf litter in temperate riparian forests a
         nd streams across a year, representing one of the most emblematic examples o
         f seasonal systems. We quantified intra-annual variation in litter inputs fr
         om terrestrial plants to forest floors and streams and estimated aquatic and
          terrestrial decomposition rates across the year at 6-week intervals. Our da
         ta show that the autumn pulse of leaf litter is complemented by smaller magn
         itude but more constant-through-the-year lateral flows to the stream ecosyst
         ems. Decomposition of labile litter fluctuated seasonally, on a different ph
         enology, with generally higher rates in summer, but rates of recalcitrant li
         tter decomposition remained largely constant. Microorganisms were the main c
         ontributors to the decomposition process in both forests and streams. Overal
         l, our work highlights the asynchronous and seasonally variable changes in d
         ecomposition rates between recalcitrant and labile detritus despite their in
         itial synchronized availability and suggests that the dominating presence of
          recalcitrant litter buffers ecosystem responses to the concentrated tempora
         l distribution of litter resources.<sup>7</sup><sup>,</sup><sup>8</sup> Inve
         stigating such ecological processes both across ecosystem borders and at fin
         e intra-annual resolutions is imperative to understand complex system respon
         ses in the context of species’ shifts in phenologies and resource quality.
         <sup>9</sup><sup>,</sup>...' (2038 chars)
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The phenology of leaf litter decomposition in aquatic and terrestrial compartments of headwater catchments

The decomposition of leaf litter is a major ecological process in terrestrial and aquatic ecosystems worldwide. Leaf litter generally enters ecosystems in annual pulses and is subsequently decomposed across many seasons. Yet investigations into this process are rarely conducted in parallel in aquatic and terrestrial ecosystems and over the full year, limiting our understanding of its phenological context across the blue-green interface. Here, we assessed the decomposition of three litter species by microorganisms and macroinvertebrates in temperate streams and forests across a year using repeated litterbag assays at 6-week intervals. We observed higher decomposition rates in summer in most combinations of ecosystem, litter species, and decomposer type, indicating positive effects of higher temperatures and low standing crops of labile litter. Furthermore, forests showed lower decomposition rates than streams. Last, we found that the relative litter species effects on both microbial and invertebrate decomposition were consistent across environments, suggesting that the fast microbial activity decreased the quality of the remaining tissue mass for invertebrates. Overall, our work places known drivers of the decomposition of leaf litter into a phenological context, providing evidence that changes in the timing or strength of these drivers could drive temporal shifts of this central ecological process.
Cereghetti, E.; Altermatt, F. (2025) The phenology of leaf litter decomposition in aquatic and terrestrial compartments of headwater catchments, American Naturalist, 206(2), 89-100, doi:10.1086/736356, Institutional Repository

Seasonal dynamics of detritus flows and decomposition across ecosystem boundaries

Material fluxes are ubiquitous in nature within and across ecosystems, connecting habitats with vastly different characteristics, like forests to rivers and lakes.1,2,3 Although individual fluxes and their cascading effects are well known,4,5,6 very few studies address the intra-annual phenology of ecosystem processes, despite the pronounced seasonality of fluxes. Here, we empirically quantified and resolved fluxes of recalcitrant and labile types of leaf litter in temperate riparian forests and streams across a year, representing one of the most emblematic examples of seasonal systems. We quantified intra-annual variation in litter inputs from terrestrial plants to forest floors and streams and estimated aquatic and terrestrial decomposition rates across the year at 6-week intervals. Our data show that the autumn pulse of leaf litter is complemented by smaller magnitude but more constant-through-the-year lateral flows to the stream ecosystems. Decomposition of labile litter fluctuated seasonally, on a different phenology, with generally higher rates in summer, but rates of recalcitrant litter decomposition remained largely constant. Microorganisms were the main contributors to the decomposition process in both forests and streams. Overall, our work highlights the asynchronous and seasonally variable changes in decomposition rates between recalcitrant and labile detritus despite their initial synchronized availability and suggests that the dominating presence of recalcitrant litter buffers ecosystem responses to the concentrated temporal distribution of litter resources.7,8 Investigating such ecological processes both across ecosystem borders and at fine intra-annual resolutions is imperative to understand complex system responses in the context of species’ shifts in phenologies and resource quality.9,10,11
Cereghetti, E.; Peller, T.; Kaeser, S.; Gounand, I.; Altermatt, F. (2025) Seasonal dynamics of detritus flows and decomposition across ecosystem boundaries, Current Biology, 35(9), 2139-2145, doi:10.1016/j.cub.2025.03.019, Institutional Repository

Kontakt

Prof. Dr. Florian Altermatt Tel. +41 58 765 5592 E-Mail senden
Dr. Roman Alther Senior scientist (er/ihm) Tel. +41 58 765 5638 E-Mail senden
Luke Ireland Tel. +41 58 765 6747 E-Mail senden

Weitere Informationen

www.altermattlab.ch