Productivity of grassland ecosystems in the Tyva Republic, Russia

Abstract

The aim of the study. The aim of the study was to estimate biological productivity of Tyva grasslands.

Location and time of the study. The living and dead above- and belowground phytomass, as well as net primary production, were estimated in the montane ecosystems and depressions of the Tyva Republic, Russia.

Methodology. Field and laboratory studies of the biological production by grasslands were conducted using botanical, geobotanical and ecological methods.

Main results. In the montane ecosystems the aboveground phytomass production was shown to range from 1.3 to 3.6 Mg ha^-1 yr^-1, whereas the belowground production was evaluated as ranging 10-65 Mg ha^-1 yr^-1. The belowground production was found to vary widely, being associated with location of mountain ridges, slope geomorphology and grazing, but no association was found with the altitude. In depressions the average green phytomass stock changed from 0.7 to 1.9 Mg ha^-1, living belowground phytomass varied 3.4 to 19.3 Mg ha^-1. From the meadow steppes to the deserted ones the living above- and belowground stocks decreased 2.7 and 5.7 fold, respectively, whereas the above- and belowground production was estimated to decrease 3 and 4 times, respectively. Several indices to characterize the growth and development, hence the productivity, of herbaceous plants was proposed. The values of the indices calculated for the Tyva grasslands suggested high photosynthetic activity: all studied steppes had the same share of belowground production in the total ecosystem production, i.e. 90%. The turnover rate of the living belowground phytomass was estimated to increase from meadow steppes to the deserted ones, whereas green phytomass increment, as related to its stock, slightly decreased.

Conclusions. The living belowground phytomass stock was found to exceed the green phytomass stock by 5-8 times, both in montane ecosystems and depressions. Preservation of living belowground organs during hot dry summers and cold winters, when soil freezes through, is apparently indispensable for grassland survival under any climatic conditions.