Resource subsidy flows across freshwater–terrestrial boundaries and influence on processes linking adjacent ecosystems

Abstract

Freshwaters receive more than water from their catchments, including a large amount of materials and biologically available energy, referred to as cross‐ecosystem resource subsidies. The passive flows of energy such as leaf litter and terrestrial invertebrate inputs, as well as dissolved organic carbon, are donor‐controlled, whereas other flows, such as between fish and fish‐eating birds, have more directly coupled feedbacks. There are also flows upstream or to the terrestrial environment in the form of adult aquatic insects, salmon carcasses and particulate carbon through overbank flooding, as well as directed foraging activities. Hypotheses about the effects of flux rates, timing, quality and physical structure of such resource subsidies on the responses of consumers have been experimentally tested at many trophic levels. Many freshwater and terrestrial consumers depend on these subsidies for at least part of their life cycle, and timing of inputs can affect growth. Developing more quantitative relations between the population and community responses across gradients of cross‐ecosystem resource subsidy input rates will require exploring the shape of the relations, as well as the effects of quality and timing on responses. The stage is now set to consider how resource subsidies might affect the stability of communities and processes such as the strength of trophic cascades. The high degree of connectivity between the land and water are essential to biodiversity conservation and to ensuring that critical aquatic ecosystem services are sustained. The management of riparian areas is a key to the security of these values. Copyright © 2014 John Wiley & Sons, Ltd.

Importance of Riparian Zone: Effects of Resource Availability at Land-water Interface

“…Moreover, we should conduct more research about newly emerged cross-system subsidies under changed environmental conditions (e.g. human-provided foods to predators, artificial light, and novel ecosystems), which are becoming more common and may have large impacts on aquatic and riparian ecosystems [143,[189][190][191], and think more about their effects on subsidy quality, quantity, and fluctuation intensity/frequency [10,36]. Also, we should not ignore the dark side of cross-ecosystem subsidies [117,152], which may also influence riparian biodiversity and ecosystem functioning through interactions of resource subsidy fluxes, consumer communities and their ecological feedbacks [192].…”

“…The flow of food resources from freshwater to terrestrial ecosystems has the potential to create the high abundance of consumers along the edge of aquatic habitats [17,[54][55][56]. Since the flux of adult aquatic insects is an important subsidy for many terrestrial consumers / predators [2,10,19,23,27], managing aquatic and riparian habitats must consider trophic linkage of aquatic resource and terrestrial organisms [1,4,17]. This section will focus on studies in the field of subsidies and their impact on specific riparian taxa, including: spiders, birds, mammals, plants, as well as aquatic predators and their particular influence on riparian zone trophic dynamics.…”

“…Plants -While most studies focused on the importance of riparian forests as donor ecosystems to transfer leaf litter, large wood, seeds, pollen and terrestrial insects to aquatic ecosystems [5,10,39,56,108,109], or as recipient ecosystems for terrestrial consumers to enjoy the aquatic subsidy feast [7,9,23,27,54], ecologists investigated effects of aquatic subsidies (e.g. organic matter, emerging aquatic insects, salmon carcasses) on riparian plants [97,100,110,111].…”

Crossing boundaries: Shigeru Nakano's enduring legacy for ecology

“…These experiences have forged new friendships and connections that span the globe (Fig. 6) and continue to foster reciprocal collaborations and new research and synthesis among Japanese researchers and western scientists that are advancing ecological research worldwide (e.g., Dunham et al 2008;Fausch et al 2010;Richardson and Sato 2015;Sato et al 2016).…”

Getting quantitative about consequences of cross-ecosystem resource subsidies on recipient consumers

“…In Richardson and Sato (2015), there were five key questions posed regarding future directions of the study of cross-ecosystem resource subsidies. These included questions of duration and magnitude (e.g., Yang et al 2008), resource quality (size, nutritional value, protective chemicals, etc.…”