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This chapter examines the influence of biological lags on consumer–resource dynamics, with particular emphasis on how consumer–resource cycles, or the lack thereof, interact with population level dynamical phenomena. It first considers discrete consumer–resource interactions before discussing the dynamics of stage-structured consumer–resource interactions. It then explains how stage structure promotes the possibility of alternative stable states and changes consumer–resource interaction strength. It also shows how a change in population structure affects food web interactions and/or the strengths of food webs. Finally, it reviews empirical results that show how stage structure and food web interaction influence ecological stability. The chapter argues that weak and inherently stable consumer–resource interactions can mute a potentially unstable population level phenomenon, and that a dynamically decoupled stable stage class can strongly stabilize other stages and the consumer–resource interaction.

Climate sets the potential biomass of trees and physiologists have made considerable progress in understanding and predicting that potential and applying it in global vegetation models. The problem is in understanding and predicting tree cover where it is far from the climate potential. Vast areas of non-forested vegetation occur where climates are suitable for forests. Arguments over why forests are absent, ongoing for over a century, are generally polarized between favouring bottom-up factors (resource constraints) or top-down factors (herbivory, predation, fire). There is increasing support for hypotheses invoking the interaction between the two. This chapter introduces the key hypotheses, their assumptions and predictions. Trophic ecology is a useful framework for exploring departures from the climate potential for trees, focussing explicitly on regulation by consumers, including fire. Alternative stable state theory is emerging as particularly appropriate for explaining forest/non-forest mosaics with each state maintained by positive feedbacks to the preferred environment.

This chapter on food web interactions connects the organisms and their interactions with the abiotic frame and provides a helicopter perspective on the function of freshwater ecosystems. Initially, the theoretical basis for an ecosystem approach is outlined, including food web theory, the bottom-up and top-down concepts and how these have evolved in concert with empirical advances. Specifically, the concepts of cascading trophic interactions and alternative stable states are discussed both from a theoretical and empirical viewpoint, as well as in both benthic and pelagic habitats. This chapter links all components, from microbes to vertebrates, to temporal and spatial changes in abiotic features leading to successional patterns in populations and communities.

Mechanisms of abiotic environmental factors influencing basic community properties like standing biomass, productivity, species diversity, structure, fluctuations, persistence, and resilience are discussed on the global, regional, and local spatial scales, encompassing timescales from the ecological to the evolutionary. The geographic distribution of species diversity and of plant strategies is related to environmental conditions, mainly to light and water availability. Effects of diversity on ecosystem functioning are addressed through comparative and experimental studies. The effects of species pool size and composition—which have evolved on an evolutionary timescale—are also considered in relation to their influence on the composition and the dynamics of communities at the ecological timescale. Finally, possible causes of the changes in community composition (β‎-diversity) are discussed, exemplifying the role of self-organizing patterns and alternative stable states.