Spatial and temporal variability of key bio-temperature indicators on the Qinghai-Tibetan Plateau for the period 1961-2013

The ecosystems of the Qinghai-Tibetan Plateau (QTP) are highly sensitive to climate change, the effects of which can be expressed through alterations to some key thresholds, including bio-temperature. However, to date, few studies have investigated variations in bio-temperature on the QTP in the context of climate change. To address this, the present study selected the following key indicators of bio-temperature: mean temperature of the warmest month (TWM); mean temperature of the coldest month (TCM); accumulated temperature above 10 degrees C (AT(10)), 5 degrees C (AT(5)), and 0 degrees C (AT(0)); and number of days with daily mean temperature above 10 degrees C (DT10), 5 degrees C (DT5), and 0 degrees C (DT0). These indicators were selected owing to their roles in the growth and distribution of vegetation on the QTP. The trends exhibited by these indicators were examined on basis of the data obtained from 71 observation stations on the QTP from 1961 to 2013. The results demonstrate that both TWM and TCM at the regional scale exhibited significant rising trends over this period, although TCM increased at a considerably faster rate. Spatially, the greatest increases in TWM and TCM were observed in the Qaidam basin desert and Guoluo-Naqu alpine shrub meadow regions. Additionally, AT(10), AT(5), and AT(0) exhibited increasing trends, with AT(0) increasing most rapidly and exhibiting the most significant changes, followed by AT(5) and then AT(10). Similarly, DT0 exhibited a greater overall increase than DT10 and DT5. Spatially, AT and DT exhibited asymmetrical change, i.e. large increases in AT did not correspond to large increases in DT. In general, all the bio-temperature indicators considered indicate pronounced rising trends over this recent five decades. This was likely due to rising air temperatures across the QTP, which have affected the structures and functions of alpine ecosystems