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

Haibei Research Station

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 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.

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.

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.

Table 1 the ratio of herbage consumption to kilogram carcass of different ages of sheep Age (year) Herbage consumption (HC, kg) Carcass weight (CW, kg) HC/CW

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. Conclusions

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

Fig.4 Daily variation of net radiation (Rn) and CO2 flux (Fc) on clear day and cloudy day

EcosystemLocationNEE （ gCO 2 m -2 day -1 ) Canopy height (cm) Leaf area index (m 2.m - 2 ) Reference Alpine meadow (Qinghai, China) 37º 29'N 101º 12'E Al. 3250m DOY DOY Ca.3? C4-dominated tall grass prairie (KS USA)39º 12'N, 396º 35'E Al. 324m 17.8 DOY DOY Ham & Knapp (1998) Larch forest (Tomakomai, Japan) 42 44'N 'E m (June) Yamamoto et al. (2001) Temperate deciduous forest (Takayama, Japan) 36º 8'N, 137º 25'E 1420m (1995) ～ (1998) Yearly average trees Ca.2.0 Bamboo Yamamoto et al. (2001) Net Ecosystem Exchange of CO 2

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.

Case study 2 CLIMATIC AND GRAZING CONTROLS ON VEGETATIVE ABOVEGROUND BIOMASS

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

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

Air Temperature – Treatment Effects Growing Season, All Sites * (Klein, Xin-quan, Harte, unpublished data)

Soil Temperature – Treatment Effects Growing Season, 3 Sites * * (Klein, Xin-quan, Harte, unpublished data) MEADOWSHRUB

Soil Moisture – Treatment Effects Growing Season, All Sites

Control Plots Only - Site Comparisons MEADOWSHRUB dry weight (g/m 2 ) (Klein, Xin-quan, Harte, unpublished data)

Chamber Effects on Total AG Vegetative Biomass (2001) LOW & HIGH GRAZE MEADOWS LOW GRAZE SHRUBLAND HIGH GRAZE HISTORY SHRUBLAND * * Dry weight biomass (g/m 2 ) (Klein, Xin-quan, Harte, unpublished data)

Species Altitude (m) T （℃） CP （ % ） （ ±SD ） EE (%) （ ±SD ） Correlation analyses T 1-2 T 3-4 T 1-2 and CPT 3-4 and CPT 1-2 and EET 3-4 and EE Festuca ovina ± ± 1.40 r = P ＜ 0.01 r = P ＜ 0.01 r = P ＜ 0.05 r = P ＜ ± ± ± ± ± ± 0.10 Poa annua ± ± 0.45 r = P ＞ 0.05 r = P ＞ 0.05 r = P ＜ 0.01 r = P ＜ ± ± ± ± ± ± 0.25 Koeleria cristata ± ± 0.05 r = P ＞ 0.05 r = P ＞ 0.05 r = P ＜ 0.01 r = P ＜ ± ± ± ± ± ± ± ± ± ± ± ± 0.21 Temperature and CP, EE contents of herbage grown at different altitudes

Species Altitude (m) T （℃） ADF (%) （ ±SD ） ADL (%) （ ±SD ） Correlation analyses T 1-2 T 3-4 T 1-2 and ADF T 3-4 and ADF T 1-2 and ADL T 3-4 and ADL Festuca ovina ± ± 0.96 r = P ＜ 0.05 r = P ＜ 0.05 r = P ＜ 0.01 r = P ＜ ± ± ± ± ± ± 1.90 Poa annua ± ± 1.28 r = P ＜ 0.01 r = P ＜ 0.01 r = P ＜ 0.01 r = P ＜ ± ± ± ± ± ± 0.87 Koeleria cristata ± ± 0.96 r = P ＜ 0.01 r = P ＜ 0.05 r = P ＜ 0.05 r = P ＜ ± ± ± ± ± ± ± ± ± ± ± ± 1.42 Temperature and ADF, ADL contents of herbage grown at different altitudes

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

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

Conclusions Some species were exposed to a UV-B density 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

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