Table 1.
Physical variables and community change on serpentine and non-serpentine study sites
| Serpentine |
Non-serpentine |
||||
|---|---|---|---|---|---|
| Mean | s.d. | Mean | s.d. | P | |
| Number of sites | 55 | 53 | |||
| Elevation (m) | 726 | 226 | 804 | 163 | 0·89 |
| Latitude (°N) | 40·62 | 7·69 | 42·13 | 0·01 | <0·001 |
| Longitude (°W) | 119·29 | 23·36 | 123·45 | 0·03 | <0·001 |
| Mean annual precipitation (cm) | 97·70 | 11·52 | 97·72 | 9·45 | 0·995 |
| Precipitation seasonality | 1488·50 | 137·59 | 1057·72 | 50·89 | <0·001 |
| Mean annual temp. (°C) | 9·77 | 1·15 | 9·77 | 0·95 | 0·995 |
| Maximum annual temp. (°C) | 27·15 | 1·97 | 29·18 | 1·43 | <0·001 |
| Temperature seasonality | 512·69 | 30·34 | 574·48 | 10·61 | <0·001 |
| Overstorey sover (%) | 87·1 | 48·0 | 194·8 | 42·8 | <0·001 |
| Mean July ground temp. (°C) | 22·4 | 2·1 | 18·9 | 0·9 | <0·001 |
| Maximum July ground temp. (°C) | 50·3 | 3·8 | 45·3 | 4·4 | <0·001 |
| Soil texture (% sand) | 52·2 | 10·0 | 58·5 | 9·5 | 0·002 |
Macroclimatic values came from BIOCLIM (http://www.worldclim.org/bioclim), while ground (=understorey) temperatures were measured in the field in July 2014. P-values are for individual t-tests comparing sites on the two soils (values in bold are significant).