Soil Respiration Of Punica Granatum-Crop Intercropping System In Hilly Area Of North China

Soil respiration is the process of soil CO2 and an important source of atmospheric CO2. As ecosystems and land uses are various,comprehensive research of the processes and influencing factors of soil respiration in variety of terrestrial ecosystem or different land-uses conditions has great significance. In this study, soil respiration under the Punica granatum-Triticum aestivum intercropping, Triticum aestivum monoculture, Punica granatum- Vigna radiata intercropping and Vigna radiata monoculture systems were measured by Li-8100 in Jiyuan city of Henan province during the growing season of March–September 2010. The relationship between the time variation of the soil respiration and soil temperature in 15cm depth and soil moisture in the 0^-20cm soil layer were analyzed. The results were shown as follows:The dynamic variation of the soil respiration showed a single peak curve in the P. granatum-T. aestivum intercropping, P. granatum-V. radiata intercropping, T. aestivum monoculture and V. radiata monoculture systems. The soil respiration of the four cropping systems were increased with increasing soil temperature in the morning, reached a peak at noon and decreased with decreasing soil temperature in the night. The soil respiration in sunny-cloudy showed a significant diurnal variation at both four cropping systems and the fluctuations at the cloudy day showed little change. The change were consistent with the variation of soil temperature. The highest soil respiration of the four cropping systems were observed at 15pm in sunny-cloudy,and 16pm at the cloudy day,with a hysteresis of 3 hour with soil temperature, the soil respiration of the P. granatum-T.aestivum and P.granatum- V. radiata intercropping were higher than that in the T.aestivum and V.radiata monoculture systems. During the study period, the average soil respiration were 1.813μmol·m^-2·s^-1 and 1.642μmol·m^-2·s^-1 for the P. granatum-T. aestivum intercropping and T. aestivum monoculture systems, the average soil respiration were 2.996μmol·m^-2·s^-1 and 2.378μmol·m^-2·s^-1 for P. granatum- V. radiata intercropping and V. radiata monoculture systems respectively.During the study period, soil respiration of the P. granatum-T. aestivum intercropping, P. granatum-V. radiata intercropping, T. aestivum monoculture and V. radiata monoculture systems had significant apparent seasonal variation. The highest soil respiration rate of P. granatum-T. aestivum intercropping and T. aestivum monoculture systems in the study period observed in May were 2.771μmol·m^-2·s^-1 and 2.517μmol·m^-2·s^-1. The lowest soil respiration were observed in March, followed by May> June> April> March. The amplitude of average soil respiration rate of P. granatum-T. aestivum intercropping and T. aestivum monoculture systems were 1.446μmol·m^-2·s^-1 and 1.246μmol·m^-2·s^-1. The highest soil respiration rate of P. granatum-V. radiata intercropping and V. radiate monoculture systems were 5.012μmol·m^-2·s^-1and 4.513μmol·m^-2·s^-1, and the lowest soil respiration observed in June, followed by July>August>September>June. The amplitude of average soil respiration rate of P. granatum- V. radiata intercropping and V. radiata monoculture systems were 3.652μmol·m^-2·s^-1 and 3.371μmol·m^-2·s^-1. Both the highest monthly average soil respiration rate and the average soil respiration rate, the soil respiration of intercropping system are larger than that of monoculture systems in the experiment period.Soil respiration of the P. granatum-T. aestivum intercropping, P. granatum-V. radiata intercropping, T. aestivum monoculture and V. radiata monoculture systems had significant relationship with soil temperature at 15cm depth. Soil temperature could explain 53.35% and 52.04% of various of soil respiration in P. granatum-T. aestivum intercropping and T. aestivum monoculture systems. The Q10 of P. granatum-T. aestivum intercropping and T. aestivum monoculture systems were 1.732 and 1.491 respectively. Soil temperature could explain 59.68% and 55.51% of soil respiration various of P. granatum- V. radiata intercropping and V. radiata monoculture systems. The Q10 of P. granatum- V. radiata intercropping and V. radiata monoculture systems were 2.462 and 1.793 respcectively. Soil respiration of intercropping system was more sensitive to temperature than monoculture system.There was no significant relationship between soil respiration and soil moisture at 20cm deep content for the P. granatum-T. aestivum intercropping, P. granatum-V. radiata intercropping, T. aestivum monoculture and V. radiata monoculture systems in this study. Soil moisture is not the limiting factor affecting soil respiration rate.Double factors relative models were built, the result shows that soil temperature and soil moisture together accounted for 51.8% and 51.1% of various soil respiration in P. granatum-T. aestivum intercropping and T. aestivum monoculture systems. Soil temperature and soil moisture together accounted for 62.8% and 56.6% of various soil respiration in P. granatum-V. radiata intercropping and V. radiata monoculture systems. The partial correlation coefficient of soil temperature and soil moisture were analyzed. Correlation of soil temperature with soil respiration was better than soil moisture with soil respiration, which showed that soil temperature was the most important environmental factor of soil respiration.