Table 1. Three organisational levels of BSCs as a functional unit, their traits, units and possible drivers or anticipated drivers of change.
|
Functional unit: BSC | |||
|---|---|---|---|
| Level | Trait | Unit | Driver |
| BSC community members | Lichen species | Name | Genetic limits to phenotypic/metabolic plasticity |
| Number of species | Number | Overall metabolic fate: growth versus survival | |
| Functional group (mosses, lichens, cyanobacteria, green algae) | Occurrence/number | Succession state/habitat suitability | |
| Carbon gain | NP | μmol m−2 s−1 | Carbon gain |
| Dark respiration | μmol m−2 s−1 | Maintenance/growth | |
| Carbon gain efficiency | ratio | Overall gain efficiency | |
| Light level to saturate photosynthesis | μmol photons m−2 s−1 | Light use/Protection against excess light | |
| Light level to achieve NP compensation | μmol photons m−2 s−1 | Low light use efficiency | |
| Thallus water content | gH2O gDW−1 | Water availability | |
| Optimal temperature for NP | °C | Active temperature | |
| Carbon allocation | Small sugars | % Fixed carbon | Stress protection/Respiratory substrate |
| Polysaccharides | % Fixed carbon | Intermediate storage for growth support versus respiratory backup | |
| Insolubles | % Fixed carbon | Growth versus survival | |
Abbreviations: BSC, biological soil crust; NP, net photosynthesis.