Meng Ping

Autotrophic and heterotrophic components of soil respiration caused by rhizosphere priming effects in a plantation

Song W.C., Tong X.J., Zhang J.S., Meng P., Li J. (2017): Autotrophic and heterotrophic components of soil respiration caused by rhizosphere priming effects in a plantation. Plant Soil Environ., 63: 295–299. Root-exudate inputs can stimulate the decomposition of soil organic carbon by priming microbial activity, but its ecological significance is still not fully understood. This study evaluated autotrophic respiration and heterotrophic respiration driven by roots using the 13C natural abundance method in a Robinia pseudoacacia plantation. The results showed that the priming effect existed in deep soil of the plantation. The proportions of autotrophic respiration and heterotrophic respiration deriving from priming effect to total soil respiration varied with soil depth. Rhizomicrobial respiration (RMR) accounted for about 15% of the total soil respiration, and the rate of priming decomposition of soil organic matter (PSOM) was only about 5% of the total soil respiration. RMR was significantly positively correlated with PSOM. Heterotrophic respiration derived by the priming effect was too weak to have a positive impact on atmospheric CO2.

Effects of a nitrogen fixing plant Vigna radiata on growth, leaf stomatal gas exchange and hydraulic characteristics of the intercropping Juglans regia seedlings

Aims Our main purposes were to determine the effects of Vigna radiata, a nitrogen fixing plant, on growth, water balance and gas exchange of the intercropping Juglans regia seedlings and to investigate the hydraulic mechanism involved in photosynthesis and growth. Methods We measured growth, hydraulic characteristics, and rate of gas exchange in J. regia seedlings, and analyzed the effects of the intercropping nitrogen fixing V. radiata on xylem anatomic structure, water balance and photosynthetic characteristics of J. regia seedlings under conditions of nitrogen deprivation and enrichment. Important findings Under conditions of nitrogen deficiency, the nitrogen fixing V. radiata facilitated the growth of the intercropping J. regia seedlings by improving xylem development, water transport and hydraulic characteristics in high transpiration demand. However, with nitrogen addition, the occurrence of V. radiata inhibited the growth of J. regia seedlings, likely by competing for water and other elements.