Plant species richness on the Tibetan Plateau: Patterns and determinants

Whether current hypotheses for geographic patterns of species richness
(SR) have a strong explanatory power for the Tibetan Plateau (TP) with
extreme climatic conditions remains unclear. In comparison with the
classic “water–energy dynamics hypothesis”, the unique climate factors
(e.g., extreme low temperature and low oxygen partial pressure) on the TP
likely significantly affect the spatial variation of SR. Here, we
investigate geographic patterns and determinants of SR on the TP through a
systematic field investigation. We systematically analyzed a total of
2,013 plant communities covering 11 different vegetation types on the TP.
 The SR per 400 m2 in the forests and shrubs and that per 1 m2 in
alpine grasslands and deserts was 62.76 (±1.80 SE), 44.53 (±7.57 SE),
16.84 (±0.39 SE), and 3.62 (±0.55 SE), respectively. Unique climate
factors, such as extremely low temperature, mean diurnal temperature, and
oxygen partial pressure, act synergistically with water–energy dynamics
and influence the spatial pattern of SR on the TP. Our findings provide
novel insights into the mechanisms underlying the spatial variation in
plant diversity, especially on plateaus and in high-latitude regions. Our
findings and the SR map with 1 km resolution provide important benchmarks
for biodiversity conservation and may help to improve predictions of the
effect of climate change on biodiversity.