[Show abstract][Hide abstract] ABSTRACT: Based on an entire year continuous measurement of surface fluxes by eddy covariance (EC) tower and micro-climate gradient observation system, the diurnal and seasonal dynamics of net ecosystem fluxes including carbon, water, and heat fluxes over Stipa krylovii steppe in Inner Mongolia were investigated. The results indicated that the diurnal pattern of carbon fluxes during growing season could be expressed as U curve. S. krylovii steppe ecosystem emitted CO2 before the sunrise and absorbed CO2 after the sunrise, with the maximum CO2 uptake around noon. The ecosystem had weaker CO2 uptake after the noon, and turned to emit CO2 after sunset. The CO2 uptake by S. krylovii steppe ecosystem reached the maximum in September, followed in August, and got the minimum in October. The diurnal dynamic patterns of sensible heat flux (Hs) and latent heat flux (LE) could be expressed as inverse U curves. The Hs and LE over S. krylovii steppe ecosystem were positive during the daytime, while Hs was negative and LE was close to zero during the nighttime. The ecosystem had the highest Hs and LE in May and September, respectively. In winter, the steppe acted as a weak carbon source, with the CO2 flux being small; while in summer, it became an obvious carbon sink.
No preview · Article · Apr 2008 · Ying yong sheng tai xue bao = The journal of applied ecology / Zhongguo sheng tai xue xue hui, Zhongguo ke xue yuan Shenyang ying yong sheng tai yan jiu suo zhu ban
[Show abstract][Hide abstract] ABSTRACT: Based on a greenhouse simulation experiment, this paper studied the dynamics of the above- and below-ground biomass of Leymus chinensis populations with four planting densities (120, 240, 360 and 480 plants x m(-2)). The results showed that the above- and below-ground biomass of L. chinensis populations had an increasing trend with the growth, and increased with increasing planting density. However, the relative growth rates (RGRs) of the above- and below-ground biomass did not show significant difference among the L. chinensis populations. The ratio of root to shoot (RRS) of the L. chinensis populations increased with their growth, but did not show significant difference among the planting densities, implying that environmental factors were the controlling factors for RRS. There existed significant power function relationships between the above- and below-ground biomass of L. chinensis individuals and populations, but the power function indices and coefficients varied with the planting density. It was suggested that the difference of microenvironment resulted from resources competition could induce the changes of L. chinensis RRS, and the latter could be used as a reference to quantitatively study the allocation of photosynthetic products.
No preview · Article · Jan 2008 · Ying yong sheng tai xue bao = The journal of applied ecology / Zhongguo sheng tai xue xue hui, Zhongguo ke xue yuan Shenyang ying yong sheng tai yan jiu suo zhu ban
[Show abstract][Hide abstract] ABSTRACT: Based on two-year soil respiration observing data at fenced and grazing typical Leymus chinensis steppe, Nei Monggol by the enclosed chamber method, soil respiration and its relationships with various affecting factors were analyzed. The major results include: (1) The diurnal and seasonal dynamics of soil respiration are similar at fenced and grazing typical Leymus chinensis steppe, but soil respiration rate is larger at the fenced plots than that at the grazing plots, and their values were 219.18 mg x (m2 x h)(-1) and 111.27 mg x (m2 x h)(-1), respectively. The reason of soil respiration rate increasing in the fenced plots might be the increases of biomass in the belowground and soil water content. (2) Among the influencing factors on soil respiration, grazing decreases the effects of soil water content and relative humidity and increases the effect of photosynthetic rate, and has no significant effects on other factors. (3) At the fenced plots, the correlation of soil respiration rate with soil water content is largest, followed by photosynthetic rate, air temperature, relative humidity, air CO2 concentration, intercellular CO2 concentration, stomatal conductance and the lowest being photosynthetically active radiation. Soil water content and air temperature are the main environmental factors, and photosynthetic rate is the critical biotic factor. The affecting factors on soil respiration are the same at the fenced and grazing plots, however the importance of those influencing factors is changed quantitatively.
No preview · Article · Dec 2005 · Huan jing ke xue= Huanjing kexue / [bian ji, Zhongguo ke xue yuan huan jing ke xue wei yuan hui "Huan jing ke xue" bian ji wei yuan hui.]