Overall grazing tolerance index (overall GTI) is not an ideal predictor for describing a single‐species tolerance to grazing
| Autor: | Gang Liu, Xiaoan Wang, Zengqiang Qian, Yingnian Li, Lulu Zhang, Zhihong Zhu |
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| Rok vydání: | 2019 |
| Předmět: |
0106 biological sciences
0303 health sciences Multivariate statistics Ecology Field experiment effective predictor Elymus nutans Biology tolerance expression 010603 evolutionary biology 01 natural sciences 03 medical and health sciences Single species Random error Grazing Statistics alpine meadow clipping Compensatory growth (organism) Aboveground biomass Ecology Evolution Behavior and Systematics Original Research 030304 developmental biology Nature and Landscape Conservation |
| Zdroj: | Ecology and Evolution |
| ISSN: | 2045-7758 |
| Popis: | Plants' pattern of compensatory growth is often used to intuitively estimate their grazing tolerance. However, this tolerance is sometimes measured by the overall grazing tolerance index (overall GTI), which assumes that tolerance is a multivariate linear function of various underlying mechanisms. Because the interaction among mechanisms is not independent, the grazing tolerance expression based on overall GTI may be inconsistent with that based on compensatory growth. Through a manipulative field experiment from 2007 to 2012, we measured the responses of 12 traits of Elymus nutans to clipping under different resource availabilities in an alpine meadow and explored the compensatory aboveground biomass and the overall GTI to assess the possible differences between the two expressions of tolerance. Our results showed that these two expressions of tolerance were completely opposite. The expression based on overall GTI was over‐compensatory and did not vary with clipping and resource availability, while the expression based on compensatory aboveground biomass was under‐compensatory and altered to over‐compensation after fertilization. The over‐expression of highly variable traits with extremely high negative mean GTI to defoliation damage, the influence of random errors contained in traits considered, and the doubling weight of functional redundant traits greatly inflated the overall GTI, which leads to the inconsistency of the two tolerance expressions. This inconsistency is also associated with the different determining mechanisms of the two tolerance expressions. Our data suggest that plants' grazing tolerance is not a multivariate linear function of traits or mechanisms that determine grazing tolerance; the overall GTI is only a measure of traits' variability to defoliation damage. Our findings highlight that the tolerance of E. nutans mainly depends on the response of traits with lower variability to defoliation, and the overall GTI is not an ideal predictor for describing a single‐species tolerance to grazing. |
| Databáze: | OpenAIRE |
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