Multiple Trophic Levels of a Forest Stream Linked to Terrestrial Litter Inputs

Abstract

The importance of terrestrial-aquatic linkages was evaluated by a large-scale, 3-year exclusion of terrestrial leaf litter inputs to a forest stream. Exclusion of leaf litter had a strong bottom-up effect that was propagated through detritivores to predators. Most invertebrate taxa in the predominant habitat declined in either abundance, biomass, or both, compared with taxa in a nearby reference stream. However, fauna in moss habitats changed little, indicating that different food webs exist in habitats of different geomorphology. Thus, the ecosystem-level consequences of excluding detrital inputs to an ecosystem were demonstrated. Inputs of riparian detritus are essential for conservation or restoration of diverse stream food webs. Detritus, or dead organic matter (I), is the major carbon pathway in most ecosystems: 70 to 90% of all primary production eventually enters the detrital food web (2). The addition of detritus to food webs complicates classical plant-herbivore-predator relationships (3). Indeed, in most headwater streams draining forests in eastern North America, inputs of detritus from the surrounding forest exceed within-stream primary production (4). One of the basic tenets of stream ecology for more than two decades has been the importance of terrestrial-aquatic linkages (5). Although details about linkages between detritivores and detritus processing in streams are well known (2, 6, 7), there is little direct evidence supporting the importance of terrestrial detrital inputs and ecosystem productivity (8) and it is limited to short-term studies in artificial channels (9). It has also been suggested that several generations of consumers are required to detect responses to detrital manipulations (10). We studied the role of detritus in ecosystem productivity by excluding inputs of terrestrial litter to a 180m-long headwater stream, using an overhead canopy and a lateral fence for 3 years (11). We evaluated the impact of the basal resource (terrestrial litter inputs) in this forest stream on abundance, biomass, and production of animals. In addition to examining numerical abundances of populations, we calculated secondary production as the flow (or flux) of mass • area" 1 • time" 1 , which incorpo

Environmental Services Provided from Riparian Forests in the Nordic Countries

“…Forests cover shade streams and moderate water temperature for the benefit of aquatic life. The litter production from the trees is important for stream food webs and stream production (Wallace et al 1997) and has similar effects in small forest lakes (Sand-Jensen and Staehr 2007). Further, plant cover reduces erosion and stabilises stream banks.…”

Benefits of riparian forest for the aquatic ecosystem assessed at a large geographic scale

“…Such benefits may include the following: addition of organic matter, diversifying the trophic conditions; thermal regulation by forest canopy cover; structuring of habitat and provision of microhabitat; and buffer for nutrients and pollutant influx to the water course (Lowrance et al, 1984;Lowrance et al, 1997;Wenger et al, 1999). These functions have been evidenced only from local studies with field measurements (Storey and Cowley, 1997;Wallace et al, 1997;Parkyn et al, 2003;Dodds and Oakes, 2006;Rios and Bailey, 2006) and from some larger scale studies in strictly agricultural watersheds (Stewart et al, 2001;Wilson et al, 2008;Arnaiz et al, 2011). The cumulative watershed impact of forested riparian zones on stream nutrient levels is also acknowledged (Newbold et al, 2010;Curie et al, 2011;Wang et al, 2011), but remains poorly understood (Weller et al, 2011).…”

Relationships of shredders, leaf processing and organic matter along a canopy cover gradient in tropical streams

“…Especially in loworder streams covered by dense riparian vegetation, allochthonous organic matter represents the main resource for aquatic fauna (Wallace et al, 1997). Leaves compose the major fraction of allochthonous organic matter entering in streams (França et al, 2009;Gonçalves et al, 2014;Bambi et al, 2017) and once in the lotic environment, fauna colonize and start the process of leaf breakdown (Gessner et al, 1999;Graça, 2001;Tank et al, 2010).…”