The Overlooked Role of Facilitation in Biodiversity Experiments

• Published in: Trends in ecology & evolution (Amsterdam) Vol. 32; no. 5; pp. 383 - 390
• Main Authors: Wright, Alexandra J., Wardle, David A., Callaway, Ragan, Gaxiola, Aurora
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01-05-2017
• Subjects: Biodiversity; Climate change; Ecosystem; Environment; Forest Science; Legumes; Microclimate amelioration; Niche complementarity; Overyielding; Pathogens; Sampling effects; Skogsvetenskap; Stress gradient hypothesis; Legumes; Pathogens; Climate change; Microclimate amelioration; Sampling effects; Niche complementarity; Stress gradient hypothesis; Overyielding
• ISSN: 0169-5347; 1872-8383; 1872-8383
• DOI: 10.1016/j.tree.2017.02.011

Past research has demonstrated that decreased biodiversity often reduces ecosystem productivity, but variation in the shape of biodiversity–ecosystem function (BEF) relationships begets the need for a deeper mechanistic understanding of what drives these patterns. While mechanisms involving competition are often invoked, the role of facilitation is overlooked, or lumped within several less explicitly defined processes (e.g., complementarity effects). Here, we explore recent advances in understanding how facilitation affects BEF relationships and identify three categories of facilitative mechanisms that can drive variation in those relationships. Species interactions underlying BEF relationships are complex, but the framework we present provides a step toward understanding this complexity and predicting how facilitation contributes to the ecosystem role of biodiversity in a rapidly changing environment.
Understanding the functional role of biodiversity in an ecosystem is an essential component of predicting the consequences of biodiversity loss. Experimental studies have consistently shown that the loss of biodiversity can lead to a loss in ecosystem functioning (BEF relationships).
Our ability to predict the consequences of biodiversity loss in understudied ecosystems, and in a global change context, requires a deeper mechanistic understanding of BEF relationships.
Here, we highlight three categories of facilitation that can be important drivers of BEF relationships: indirect biotic interactions due to pathogens and mutualists; abiotic interactions due to nutrient enrichment; and abiotic interactions due to microclimate amelioration.
We demonstrate how increased environmental severity, abundance of specialist pathogens, and biological nitrogen fixation rates likely drive increased facilitation and, thus, the strength of the BEF relationship, across ecosystems.