Linking functional diversity to resource availability and disturbance: a mechanistic approach for water‐limited plant communities

Abstract

Summary Functional diversity (FD) has become a principal concept for revealing mechanisms driving community assembly and ecosystem function. Multiple assembly processes, including abiotic filtering, competition and multi‐trophic relationships, operate simultaneously to structure FD. In water‐limited plant communities, FD is likely to reflect trade‐offs between drought resistance vs. disturbance resistance and competitive ability. We propose a mathematical mechanistic model for understanding the organization and function of water‐limited plant communities. The approach captures the interplay between abiotic filtering, below‐ and above‐ground competition and disturbance. We exploit this powerful model to uncover mechanisms underlying changes in functional diversity along stress gradients. Our approach links biomass production and FD to environmental conditions through plant resource capture ability. Functional groups are defined along a single trade‐off axis according to investment in capturing light (shoot) vs. water (root). Species growth rate is determined dynamically by the species traits, water availability and grazing stress. We derive biomass production, functional diversity and composition along precipitation and grazing gradients. Model's results revealed several regimes structuring FD along the precipitation gradient: ‘Struggle for water’ at low precipitation, ‘competition for water’ at intermediate precipitation and ‘competition for light’ at high precipitation. We observed a shift in grazing effect on FD from negative at very low precipitation, to positive at higher precipitation. Unimodal FD–grazing intensity relationship was observed under high precipitation, while under low precipitation, FD decreased moderately with increasing grazing intensity. Synthesis. Our model showcases how fundamental tradeoffs in plant traits may drive functional diversity and ecosystem function along environmental gradients. It offers a mechanism through which novel understandings can be obtained regarding the interplay between water stress, below‐ and above‐ground competition and disturbance intensity and history. We discuss further model testing possibilities as well as required empirical work.

Vegetation ring formation by water overland flow in water‐limited environments: Field measurements and mathematical modelling

“…Very few model studies, however, have been devoted to patterns that emerge at the single‐patch scale, such as spots, rings, crescent‐like shapes, and spirals, and to the biomass–water relationships associated with them (Couteron et al, ; Fernandez‐Oto, Escaff, & Cisternas, ; Meron, Yizhaq, & Gilad, ; Sheffer et al, ; Sheffer, Yizhaq, Gilad, Shachak, & Meron, ; Tlidi et al, ; Tlidi, Lefever, & Vladimirov, ). Model studies of self‐organized patchiness, at both the patch and landscape scales, are important for understanding the relationships among spatial heterogeneity, community structure, and ecosystem functioning (Nathan, Osem, Shachak, & Meron, ). In addition, field studies of patch formation are much more feasible at the single‐patch scale and can thus help in examining and explaining self‐organizing phenomena at larger spatial scales.…”

Trade-off shapes diversity in eco-evolutionary dynamics

“…Interestingly, the model shows a unimodal ("humpback") behavior of diversity as function of trade-off, with a critical trade-off at which biodiversity undergoes a phase transition, a behavior observed in nature [72][73][74][75]. ITEEM shows that diversity is a natural outcome of competition when species evolve under certain physical constraints which restrict the energy allocation in different strategies.…”

Partitioning the functional variation of tree seedlings during secondary succession in a tropical lowland rainforest

“…, Nathan et al. ). The role of functional diversity in ecosystem functioning has been a research focus in recent years (Milcu et al.…”

“…, Nathan et al. ). It has been recognized that functional diversity has different dimensions, and attempts been made to describe these dimensions through different measures (Zhang et al.…”

“…Understanding the biodiversity and ecosystem functioning relationship is a major challenge in ecology. Functional diversity is an important approach in exploring biodiversity and ecosystem functioning (Tilman et al 1996, Spasojevic et al 2014, Muscarella et al 2016, Nathan et al 2016. The role of functional diversity in ecosystem functioning has been a research focus in recent years (Milcu et al 2014, Nathan et al 2016).…”