| Empirical classification |
Subjective opinions of researchers |
No field work required |
Lack of standardized procedures difficult to separate shade tolerance if there are many species |
Baker (1949), Ellenberg (1974)
|
| Abundance of species along light gradient |
Low-light abundance or sapling ratio |
Abundance data are widely available and easy to collect |
Abundance is often affected and confounded by other resources, such as drought and waterlogging |
Lorimer (1983), Poorter & Arets (2003)
|
| Demographic performance |
Mortality or/and growth rates |
Demographic rates are considered to be good indicators of plant’s performance in response to environment |
Require temporal, sometimes long-term data for calculating demographic rates. Relationships between shade tolerance and growth/mortality rates are often not as strong |
Kobe et al. (1995), Weber et al. (2017), Walters & Reich (1996), Sendall, Lusk & Reich (2016)
|
| Light environment |
Light level around target trees |
Reflect the preference of actual light environment of species. Data are relatively easy to collect |
Surrounding light level is often insufficient to determine light preference of species. Hard to distinguish shade tolerance if there are many species |
Lusk & Reich (2000), Figueroa & Lusk (2001), Lusk et al. (2008)
|
| Plant traits |
Organ- or sub-organ-level plant traits |
Functional trait database is often available |
Traits often have poor predictive power for responses to environmental conditions |
Valladares & Niinemets (2008), Craine et al. (2012)
|
| Light-response curves |
Light-response curves across light gradient |
Describe whole plant’s performance across light gradient; accurately reflect plant’s minimum light requirement |
Costly in labor |
Poorter et al. (2010) |
| Successional seral stage |
Successional scores of species |
No field work required |
Successional data are often not available or difficult to determine |
Poorter & Arets (2003), Niinemets & Valladares (2006)
|
