The mechanism of productivity formation of alpine meadow ecosystem

1. The mechanism of productivity formation of alpine meadow ecosystem Dr Xinquan Zhao Northwest Plateau Institute of Biology, The Chinese Academy of Sciences, Xining, 810001

2. Haibei Research Station

3. Environmental conditions of the research area The Haibei alpine meadow ecosystem research station is located with N latitude 3729'-3745' and E longitude 10112'-10123'. The altitude of area is 2900 - 3500 meters. It has a continental monsoon climate, with severe and long winters and short cool summers. The average air temperature is -1.7℃. Average annual precipitation ranges from 426 to 860 mm, 80% of which falls in the short summer growing season from May to September.

4. Vegetations and Animals Alpine meadow, dominated by Kobresia humilis and various grasses and forbs (depending on grazing density) are widely distributed in this region along the valley floor. The shrub, Potentilla fruticosa are joined by shrubby Salix species are locating on the north hill. The region marsh vegetation consists primarily of Kobresia tibetica and Pedicularis longiflora.

5. Vegetations and Animals The higher shrub lands on the mountains surrounding the valley are common summer grazing lands. The meadow vegetation is grazed in winter and is privately owned. Sheep and yaks, the major herbivorous animals in the region, live on herbage, which varies greatly with seasons.

9. Age (year) 1 2 3 4 5 6 7 Herbage consumption (HC, kg) 738 2700 4830 6060 7740 9420 11110 Carcass weight (CW, kg) 7.6 15.4 21.3 27.2 29.2 30.7 28.5 HC/CW 96.3 175.2 226.4 223.2 265.4 306.4 391.5 Table 1 the ratio of herbage consumption to kilogram carcass of different ages of sheep

12. Conclusions The monthly patterns of biomass changes of the plants are significantly different (P< 0.05) for various plants. The seasonal pattern showed that maximum (80%) above-ground production occurred during July to September when temperature and precipitation are most favorable for plant growth. The ratio of herbage intake and live weight gain is very low due to the imbalance of herbage supply, both quantity and quality. During the cold season, which lasts for more than 7 months, livestock live mainly on standing dead grasses and the livestock body weights loss is 50% to 80% of body weight gain during the warm season.

13. Case study 1 • Carbon flux in the alpine meadow (Kobresia humilis) ecosystem

17. 1.5 1200 a Clear day 1000 8/14 Fc 1.0 8/14 Rn 800 ) 0.5 -1 ) s -2 -2 600 Rn (w m 0.0 Fc (mg m 400 -0.5 200 -1.0 0 -1.5 -200 0:00 2:00 4:00 6:00 8:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00 0:00 Time 1200 1.5 b 8/29 CO2 1000 1.0 Cloudy day 8/29 Rn 800 ) 0.5 ) -1 s -2 -2 600 Rn (wm 0.0 Fc (mg m 400 -0.5 200 -1.0 0 -200 -1.5 0:00 2:00 4:00 6:00 8:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00 0:00 Time Fig.4 Daily variation of net radiation (Rn) and CO2 flux (Fc) on clear day and cloudy day

19. Net Ecosystem Exchange of CO2

20. Some preliminary conclusions The alpine meadow exhibited a fairly high daily Fc during the growing season as compared with other similar ecosystem. The decrease of Fc under the high radiation suggests the potential importance of photoinhibition and/or ecosystem respiration in the meadow. Further detailed investigation is needed to evaluate the carbon budget for the unique ecosystem.

21. Case study 2 • CLIMATIC AND GRAZING CONTROLS ON VEGETATIVE • ABOVEGROUND BIOMASS

22. Experimental Design Open top chamber Within site plot setup 30m Treatments: * control * chamber (warm) * clip (graze) * chamber x clip O O O O O O O O O O O O O O O O 40 cm 30m 1.48m *graze control High Graze History Site Low Graze History Site shrub habitat (summer rangeland) meadow habitat (winter rangeland)

24. The International Tundra Experiment (ITEX) Arctic and Subarctic Field Sites

25. Air Temperature – Treatment EffectsGrowing Season, All Sites (Klein, Xin-quan, Harte, unpublished data) * * * *

26. Soil Temperature – Treatment EffectsGrowing Season, 3 Sites * * * SHRUB MEADOW (Klein, Xin-quan, Harte, unpublished data)

27. Soil Moisture – Treatment EffectsGrowing Season, All Sites

28. Control Plots Only - Site Comparisons dry weight (g/m2) MEADOW SHRUB (Klein, Xin-quan, Harte, unpublished data)

29. Chamber Effects on Total AG Vegetative Biomass (2001) HIGH GRAZE HISTORY SHRUBLAND LOW & HIGH GRAZE MEADOWS LOW GRAZE SHRUBLAND Dry weight biomass (g/m2) * * * (Klein, Xin-quan, Harte, unpublished data)

32. Temperature and CP, EE contents of herbage grown at different altitudes

33. Temperature and ADF, ADL contents of herbage grown at different altitudes

34. Conclusions Our results suggest that the response of AG biomass to warming is mediated by habitat type and site grazing intensity history. The warming-induced reduction in plant species richness is consistent across habitats and site grazing histories. There were significant downtrends in crude protein, fat and nitrogen free extract contents of herbage along with the increase of temperature. It had a positive correlation between temperature and content of constructed carbohydrates

35. Case study 3 The influence of enhanced UV-B radiation on alpine meadow

38. Conclusions Some species were exposed to a UV-B density 15.80 kJ/m2 every day, simulating a nearly 14% ozone reduction during plant growing season. The results showed both net photosynthetic rate and photosynthetic O2 evolution rate were not decreased after long period of treatment with enhanced UV-B radiation

39. Thank you!