Rising global temperatures have led to Plant communities migrating upwards in mountain ranges across the globe, colonising areas formerly covered by snow and glaciers. However this process is not simply dependent on temperature, as Plants usually grow in some form of soil layer, with root structures that form complex relationships with Fungi and other micro-organisms in this soil and soil is typically absent or very limited on the snow and ice covered upper slopes of mountains, with microbial communities, if present at all, quite different to those found in Plant-supporting soils at lower altitudes.
In a paper published in the journal Microbial Ecology on 31 May 2016, Roey Angel of the Max Planck Institute for Terrestrial Microbiology and the Department of Microbiology and Ecosystem Science at the University of Vienna, Ralf Conrad, also of the Max Planck Institute for Terrestrial Microbiology, Miroslav Dvorsky and Martin Kopecky of the Institute of Botany of the The Czech Academy of Sciences, Milan Kotilínek of the Department of Botany at the University of South Bohemia, Inga Hiiesalu, also of the Institute of Botany of the The Czech Academy of Sciences, Fritz Schweingruber of the Swiss Federal Research Institute and Jiří Doležal, also of the Institute of Botany of the The Czech Academy of Sciences and of the Department of Botany at the University of South Bohemia describe the highest known Vascular Plant community yet discovered, discovered at an altitude of 6150 m above sea level on Mount Shukule II in the Ladakh Region of Jammu and Kashmie State, India, part of the southwestern spur of the Tibetan Plateau in the Northwestern Himalayas.
Angel et al. found six species of plants growing on a sparse patch of undeveloped calcareous soil on a southwest-facing small boulder field, close to the summit of Mount Shukule II. The area has an arid climate, with the summer monsoon which brings rain to much of the region blocked by the main Himalaya Range to the south and the westerly winds which bring winter rain to the Himalayas blocked by the Hindu Kush range to the west.
The first of these was Draba alshehbazii, a perenial herbaceous Brasica (the group of plants that also includes Cabbages and Rape) that forms dense cusions up to 2 cm in height and 5 cm in diameter, with a single main taproot and numerous lateral roots. This plant has previously been described in the Ladakh Region and western Xizang (Tibet) in China, at altitudes of between 5700 and 6000 m.
Draba alshehbazii, samples collected at 6150 m above sea level on Mount Shukule II in the Ladakh Region of Jammu and Kashmir. Angel et al. (2016).
The second plant found was Draba altaica, another cushion-forming perennial herbaceous Brasica, forming cushions up to 8 cm in height and 5 cm in diameter, with a similar main tap root and numerous lateral root system, which has previously been recorded widely in Central Asia, from southern Siberia and Kazakhstan to Mongolia. This species has been recorded as low as 3420 m, but appears to have an optimum altitude of about 5500 m.
Draba altaica, growing on Mount Shukule II in the Ladakh Region of Jammu and Kashmir at an altitude of 6150 m. Angel et al. (2016).
The third plant found was Ladakiella klimesii, another perennial herbaceous Brasica, which forms cushions up to 3 cm in height and 10 cm in diameter, again with a single long taproot and numerous lateral roots. This plant has previously been found in eastern Ladakh and western Xizang at altitudes of 5350 to 6150 m, with an optimum altitude of 5800 m.
Ladakiella klimesii, growing on Mount Shukule II in the Ladakh Region of Jammu and Kashmir at an altitude of 6150 m. Angel et al. (2016).
The fourth plant found was Poa attenuata, a perennial Grass forming tussocks up to 30 cm in height, with an adventitious root system (root system in which numerous roots arise from a system of underground stems). This is a widely distributed plant in Central Asia, found from southern Siberia and continental Central Asia to the humid East Himalayas, at altitudes from 3250 m to 6150 m, though it has optimum altitude of between 5000 and 5500 m.
Poa attenuata, growing on Mount Shukule II in the Ladakh Region of Jammu and Kashmir at an altitude of 6150 m. Angel et al. (2016).
The fifth plant found was Saussurea gnaphalodes, a perennial herbaceous Aster (the group of Plants that also includes Daisies, Sunflowers and Thistles), which reaches 6 cm in height and forms low density stands, with rosettes connected by a system of underground stems connected to a single deep tap root. This Plant is found across Central Asia from East Kazakhstan to Tibet, at altitudes of 4650 to 6150 m, with an optimum altitude of between 5200 and 5600 m.
Saussurea gnaphalodes, growing on Mount Shukule II in the Ladakh Region of Jammu and Kashmir at an altitude of 6150 m. Angel et al. (2016).
The final plant found was Waldheimia tridactylites, another herbaceous perennial Aster, reaching 5 cm in height, which grows from a thick woody rhizome (underground stem), which puts out many prostrate branches and few adventitious roots. This Plant is found across Central Asia from Kazakhstan to Mongolia at altitudes of 3600 to 6150 m, with an optimum altitude of 4500 to 5000 m.
Waldheimia tridactylites, growing on Mount Shukule II in the Ladakh Region of Jammu and Kashmir at an altitude of 6150 m. Angel et al. (2016).
A TMS data logger was used to record the soil (10 cm bellow ground level) and air temperature (10 cm above ground level), as well as soil moisture and air humidity at 6150 m on Mount Shukule II from August 2011 to September 2012. In addition the air temperature (3 cm above ground) and humidity were recorded at 5900 m on the mountain from August 2008 to June 2013 using a HOBO U23 Pro v2 logger.
The average soil temperature at 6150 m on Mount Shukule II between August 2011 and September 2012 was −8.7 °C. The lowest air temperature recorded was on 10 January 2016, when it fell to −36 °C, the highest air temperature was recorded on 15 June 2012, when the air reached 28.2 °C; this was also the day with the greatest range of air temperatures recorded (42.4 °C), with the lowest temperature that day being −14.1 °C. The vegation season (when the soil, surface and air temperature was above 0 °C, and vegetative growth therefore theoretically possible) lasted from mid May to mid September, with an average soil temperature of 2.71 °C, an average surface temperature of 3.62 °C and an average air temperature of 2.97 °C. However it is likely that growth was restricted to a far shorter season when temperatures rose above 5 °C; this lasted 12 days in the soil and 17 days above ground level. Throughout the vegetation season the nighttime air temperature regularly fell to -7 °C, with a minimum vegetation season air temperature of -16.2 °C recorded on 17 June 2012. However the soil retained more heat during this period, seldom falling below 0 °C and often staying as warm as 3 °C.
Above 5800 m all precipitation typically falls as snow, with soil moisture derived from melting snow. Based upon soil moisture measurements at 5800 m, the study area is thought to have had snowfall or snow-cover for 273 days in 2009, 228 days in 2010, 132 days in 2011 and 141 days in 2012.
All of the Plants were growing under stressful, sub-optimal conditions, but appeared to be stable and, in a way thriving. All of these Plants produce woody tissues, with four (Ladakiella klimesii, Draba altaica, Waldheimia tridactylites and Saussurea gnaphalodes) producing anular growth rings on their tap roots that can be used to estimate their age. Of the plants examined the Ladakiella klimesii Plants had an average age of 15 years, while all the others were under 10 years old. This suggests that the colonies were of fairly recent origin, having migrated upslope in response to rising temperatures.
The soil in which the Plants were growing was poorly developed and had only a rather limited Bacterial community dominated by by members of the order Sphingomonadales (Alphaproteobacteria). However the soil around the roots of the Plants hosted a much more diverse Bacterial community, comparable in diversity to that found around plants at much lower altitudes, still dominated by the Sphingomonadales, but joined by significant levels of Sphingobacteriales (Bacteroidetes), Rhizobiales (Alphaproteobacteria) and Burkholderiales (Betaproteobacteria). This Bacterial community is similar to that seen in desert communities found in deserts (hot and cold) at lower altitudes, but is quite different to that seen in the temperate soils found in lower high-altitude soils in the Himalayas. Since the Plants lacked any mycorrhizal (Fungal) root associations, they were presumed to be dependent on associations with these soil Bacteria to recover nutrients from the sparse soil.
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