Testing the importance of plant strategies on facilitation using congeners in a coastal community

Abstract. Since proposed two decades ago, the stress-gradient hypothesis (SGH), suggesting that species interactions shift from competition to facilitation with stress, has been widely examined. Despite broad support across species and ecosystems, ecologists debate whether the SGH applies to extreme environments, arguing that species interactions switch to competition or collapse under extreme stress. We show that facilitation often expands distributions on species borders. SGH exceptions occur when weak stress gradients or stresses outside of species' niches are examined, multiple stresses co-occur canceling out their effects, temporally dependent effects are involved, or results are improperly analyzed. We suggest that ecologists resolve debates by standardizing key SGH terms, such as fundamental and realized niche, stress gradients vs. environmental gradients, by quantitatively defining extreme stress, and by critically evaluating the functionality of stress gradients. We also suggest that new research examine the breadth and relevance of the SGH. More rigor needs to be applied to SGH tests to identify actual exceptions rather than those due to failures to meet its underlying assumptions, so that the general principles of the SGH and its exceptions can be incorporated into ecological theory, conservation strategies, and environmental change predictions.

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“…Functional traits (e.g., stress tolerance) have been suggested to determine the nature of species interactions (e.g., He et al 2012).…”

Section: Define or Clarify Terms Vaguely Used In The Literaturementioning

confidence: 99%

Extreme stresses, niches, and positive species interactions along stress gradients

Bertness

2014

Ecology

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234

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“…The lower limits of plants are thought to be determined by physical stress, while the upper limits of plants are determined by interspecific plant competition. This simple community assembly model has been tested in California (Pennings & Callaway, 1992), Spain (Castellanos, Figueroa, & Davy, 1994;Castillo, Fernandez-Baco, Castellanos, & Davy, 2000), Brazil (Costa, Marangoni, & Azevedo, 2003), China (He, Cui, Bertness, & An, 2012;He et al, 2009), Argentina (Alberti et al, 2010;Idaszkin, Bortolus, & Bouza, 2011, and Chile (Farina, Silliman & Bertness, 2009). …”

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confidence: 99%

Biogeography of salt marsh plant zonation on the Pacific coast of South America

Fariña

Silliman

et al. 2017

Journal of Biogeography

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Aim: The aim of this study was to investigate the biogeography of plant zonation in salt marshes on the Pacific coast of South America; to examine whether salt marsh plant zonation varies with latitude; and to explore the relative importance of climatic, tidal, edaphic and disturbance factors in explaining large-scale variation in salt marsh plant community structure.Location: A 2,000-km latitudinal gradient on the Pacific coast in Chile, with a climate shift from hyper-arid at low to hyper-humid at high latitudes.Methods: Plant zonation was quantified in field surveys of ten marshes. Climate, tidal regimes, edaphic factors and disturbances (tsunami and rainfall floods) were determined. We used multivariate analyses to explore their relative importance in explaining large-scale variation in salt marsh plant community structure.Results: Across latitude, marshes were dominated by distinct plant communities in different climate regions, especially at the extreme dry and wet latitudes. Intertidal plant species zonation was present in hyper-arid and semi-arid climates, but not in arid, humid and hyper-humid climates. Latitudinal variation in low-marsh plant communities (regularly flooded at high tide) was largely a function of precipitation, while at high marshes (never flooded at high tide) latitudinal variation was explained with precipitation, temperature, tidal cycles, soil salinity and disturbances. These patterns appear to be mechanistically explained by extrapolating experimentally generated community assembly models and have implications for predicting responses to climate change.

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“…Such experiments show the importance of facilitation between plants ( Miranda-Jácome et al 2013;Rolo et al 2013;He et al 2012;Zonneveld et al 2012), especially between legumes and grasses (Mulder et al 2002;Scherer-Lorenzen et al 2003;Spehn et al 2002). However, only a small number of articles investigated facilitation.…”

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confidence: 99%

Plant functional groups: scientometric analysis focused on removal experimentsPlant functional groups: scientometric analysis focused on removal experiments

Morais

Cianciaruso

2014

Acta Bot. Bras.

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Understanding what determines species co-occurrence and its consequences for ecosystem functioning is central to the study of plant ecology. The ecological similarity of species can explain co-occurrence patterns, species interactions, and how species affect ecosystem processes. A useful approach to answer these questions is to group similar species in functional groups and then perform removal experiments. Here, we conducted a scientometric review of articles about plant functional diversity and plant functional group removal. We identified publication patterns and impact; environmental and geographic gaps; ecological effects being tested; which groups are removed; and what the removal methods are. We analyzed articles published between 1991 and 2012 in journals indexed for the Thomson ISI Web of Science database. Although the number of articles and citations of experimental articles increased during that period, the corresponding increase for functional diversity articles was 12 times greater. This might be because field and cafeteria experiments are harder to conduct. Most studies were performed in temperate regions, where taxonomic knowledge and scientific investment is greater. Studies on herbaceous vegetation predominate, probably because short-lived species are more easily removed and manipulated than are trees. The main reason for the removal experiments was to test hypotheses related to competition, and clipping at ground level was the most common removal method. Few studies were performed in the field and in greenhouses, which could control for differential responses of natural conditions and controlled environments.

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Testing the importance of plant strategies on facilitation using congeners in a coastal community

Cited by 62 publications

References 25 publications

Extreme stresses, niches, and positive species interactions along stress gradients

Extreme stresses, niches, and positive species interactions along stress gradients

Biogeography of salt marsh plant zonation on the Pacific coast of South America

Plant functional groups: scientometric analysis focused on removal experimentsPlant functional groups: scientometric analysis focused on removal experiments

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