Effects of drought climate on the photosynthesis of Aneurolepidium chinense community in the typical steppe region of Inner Mongolia

Under the dry weather conditions in the typical steppe region of Inner Mongolia, the diurnal change curve of photosynthetic rate of Aneurolepidium chinense community is a curve of 'double peaks' with midday depression. The photosynthetic rate in the morning is height than in the afternoon, which is related to the water condition at that time. The decrease range of community photosynthetic rate at noon is closely correlated with the low air relative humidity and soil moisture, the photosynthetic rate decreases less under better water condition.The instantaneous photosynthetic rate and diurnal net photosynthesis declined in dry condition, but they rised after irrigation or nitrogen-fertilization. Thus irrigation and fertilization is a effective way to improve grasslands and to raise grassland productivity.

Genetic Diversity Analysis of Aneurolepidium chinense (Trin) Kitag by ISSR Marker

In the study,the reasonable sampling of the grey Aneurolepidium chinense of green grassland,the grey-green A.chinense of green grassland,the grey A.chinense of Wulimu and the grey-green A.chinense of Wulimu were analyzed by ISSR.Eight primers with clear and diverse products were screened out from 20 primers and 47 DNA fragments were amplified from 39 individuals.The average number of DNA fragments produced by each primer was 5.9,and polymorphic bands were 41 and the polymorphic rate was 87.23%,which could r...

Comparison of CO_(2) Effluxes and Their Driving Factors Between Two Temperate Steppes in Inner Mongolia, China

Soil respiration is a key component of the global terrestrial ecosystem carbon cycle. The static opaque chamber method was used to measure the CO2 effiuxes from soil of a semiarid Aneurolepidium chinense steppe and a Stipa krylovii steppe in the Xilin River Basin of Inner Mongolia, China from March 2002 to December 2004. The results indicated that the soil respiration rates of the semiarid Aneurolepidium chinense steppe and the Stipa krylovii steppe were both relatively high from mid-May to mid-September of each year and remained low during the rest of the year. The minimum value of soil respiration occurred in December or January and negative effiuxes of CO2 appeared for several days during the non-growing season of individual years at the two sampling sites. A high annual variation was found in the two steppes with the coefficients of variance （CV） being over 94%, even high to 131%. The annual sums of soil CO2 effiux of the Aneurolepidium chinense steppe varied between 356.4 gC m^-2 yr^-1 and 408.8 gC m^-2 yr^-1, while those of the Stipa krylovii steppe in the three years were in the range of 110.6 gC m^-2 yr^-1 to 148.6 g Cm^-2 yr^-1. The mean respiration rates of the Aneurolepidium chinense steppe were significantly higher than those of the Stipa krylovii steppe in different statistical periods with the exception of the non-growing season. About 59.9% and 80.6% of the soil respiration variations in both steppes for the whole sampling period were caused by the changes of temperature and soil water content. In the Aneurolepidium chinense steppe, the soil respiration rate has significant or extremely significant positive correlation （r = 0.58 - 0.85, p 〈 0.05 or p 〈 0.01） with air temperature and ground temperature of the topsoil except in 2002; the unique contributions of temperature change to the soil respiration variation of the three years were 53.3%, 81.0% and 58.6%, respectively. But, for the Stipa krylovii steppe in the same time interval, the soil water content （especially that of the 10-20 cm layer） has a greater effect on the change of soil respiration, and the unique contributions of the change of the 10-20 cm soil water content to the variations of soil respiration in 2002 and 2003 were 60.0% and 54.3%, respectively. In 2004, in spite of the higher contribution of temperature than soil water content, the contribution of ground temperature at a depth of 10 cm was only 46.2%, much weaker than that of any single year in the Aneurolepidium chinense steppe.

Daily variation characteristics of CO_(2) emission fluxes and contributions of environmental factors in semiarid grassland of Inner Mongolia, China

Fixed field experimental studies are carried out on daily variations of the undis-turbed community and soil respiration fluxes in different phenological phases of 2001―2002 in semiarid Aneurolepidium chinense steppe of Inner Mongolia,China using static black chamber method.Corresponding statistical analysis of the contributions of the water-heat factors(air temperature,ground temperature,surface soil water content)and ecological factors(above-ground biomass,underground biomass,litter biomass)to daily variation law of the undisturbed community and soil respiration fluxes as well as differences in daily respiration are also con-ducted.The results indicate that undisturbed community and soil respiration have apparent daily variation laws,daily variation patterns of respiration fluxes during different phenological phases are basically the same,and the variations of environmental factors only exert effect on CO_(2)emission intensities,while the effect on daily variation pattern of grassland CO_(2)emission fluxes is relatively small.The daily total respiration of the undisturbed community in different phenological phases ranges from 1.34―10.13 g·m^(-2);soil daily total respiration ranges from 0.98―5.17 g·m^(-2);both daily variations of undisturbed community and soil respiration fluxes are significantly corre-lated(p<0.05)or extremely significantly correlated(p<0.01)with air temperatures and ground surface temperatures,but the correlativity with the soil temperature at 5 and 10 cm depths is relatively weak;multiple regression analysis indicates that about 80%of the difference in daily respiration of the undisturbed community among different phenological phases is induced by the variation of the aboveground biomass,while the variations of the remaining factors can jointly explain around 20%of the daily respiration variations of the whole grassland ecosystem;about 83%of the soil daily respiration variation of the different phenological phases is caused by 0―20 cm underground biomass.Besides,surface soil water content is also an important environmental factor affecting soil daily respiration variations of the Aneurolepidium chinense steppe,but its partial correlation coefficient with soil daily respiration amount does not reach the significance level of 0.05.