Analysis Of Soil Respiration And Its Influencing Factors In The Semi-arid Areas In The Loess Plateau

Based on a long-term experiment implemented in Lijiabu town of Dingxi from Gansu province, an experiment was conducted to study the effects of different tillage measures on soil respiration in the semi-arid areas of the loess plateau and attempt to analyze the effect of differerent tillage measures from a perspective of carbon cycle in order to provide scientific basis for agricultural production and choose the tillage measures that more adapt to circumstances of the dry farmland of the loess plateau.The examined tillage treatments were T(Conventional tillage with no straw ) , NT ( No–till with no straw cover),NTS(No-till with straw cover),TS(Conventional tillage with straw incorpo), TP (Conventional tillage with plastic mulch), NTP (No-till with plastic mulch).Basically,the experiment was designed with rotation.The rotation sequencewas spring wheat(w)followed by field pea(p). The soil respiration,canopy temperature,soil moisture content and CO2 Concentration were determined in a phased rotation systems with spring wheat and field pea, in2008.1 Diurnal variation of soil respiration under T and NTS of spring wheat and field peaThere was obvious daily variation in soil respiration for spring wheat under no-till with stubble retention (NTS) and conventional tillage (T), and the soil respiration rate under NTS is lower than that under T. However daily variation of soil respiration for field pea was not apparent.2 Seasonal variation of soil respiration of spring wheat and field pea under different tillage measuresThe results showed that the soil respiration had different wariation during the whole growth stages of spring wheat and field pea. The peak of soil respiration appeared at jointing, filling and harbested for spring wheat, and that appeared at 5-leaf, ipecacing, poding and harvested for field pea.3 The effects of soil temperature on soil respiration of dry farmland in the southeast Loess Plateau Among the six treatments of spring wheat land, there are remarkable Relations between soil respiration rate and temperature of different depth and land surface temperature, which was most significant to land surface temperature. The correlation coefficient between Soil respiration rate and land surface temperature under no-till with stubble retention (NTS) is 0.779, and the correlation coefficient is 0.728 between Soil respiration rate and soil temperature of 5 cm depth under no-till with no stubble (NT). The correlation coefficients between Soil respiration rate and the soil temperature were highest under the NTS treatment and that is lowest under NT treatment among six treatments for both spring wheat and field pea land. For spring wheat land the effects of the soil temperature on Soil respiration rate are significant, and the value is 0.867 under NTS and 0.811 under NT. for field pea, the correlation coefficients are 0.818 and 0.738 under NTS and NT respectively, so soil temperature exhibits a positive correlation with Soil respiration rate.4 Relationship between soil respiration and canopy temperatureSoil respiration rate was linearly correlated with canopy temperature of both spring wheat and field pea, which was most significant at booting and poding, and relatively significant at filling and branching for spring wheat and field pea respectively.5 Relationship between soil respiration and soil moisture contentSignificant relationships were found between soil respiraion under different tillage measures and soil moisture content, which could be desvribed by protruding parabolas. The correlation coefficients under conservation tillage measures were higher than conventional tillage and the correlation coefficient under NTS is higher than that under other conservation tillage. Especially, correlation coefficients reached the maximum at the depth of 10-30cm and 5-10cm for spring wheat and field pea respectively.6 The effects of hydro-thermal factors on soil respiration of dry farmlandThe effects of hydro-thermal factors(temperature, land surface temperature, soil temperature from different layers: 5cm dept, 10cm dept, soil moisture content from different depth: 10-30cm, 5-10cm and 10-30cm)on soil respiration were analyzed. The results showed that Soil respiration rate is significantly correlate to the soil surface temperature and different layers of soil temperature for both spring wheat and field pea, which was most significant at 5cm depth. And the correlation coefficient under NTS between soil respiration rate and temperature is higher than that under T for both spring wheatand field pea.7 The effects of the atmosphere CO2 concentration on soil respiration of dry farmlandThe atmosphere CO2 concentration exhibits a negative correlation with soil respiration rate, namely soil respiration rate will accelerate when the atmosphere CO2 concentration decreases.8 The effects of different tillage measures on soil respiration of Spring wheat and field peaCompared with conventional tillage (T), the soil respiration decreased to varying degree under conservation tillage measures such as no-till with stubble retention (NTS), no-till with no stubble (NT), conventional tillage with stubble incorporating (TS), conventional tillage with plastic mulching (TP), no-till with plastic mulching (NTP) , and the soil respiration rate under NTS is slower than others.