Effects of sowing date on photosynthetic characteristics, chlorophyll fluorescence and yield of different Echium plantagineum L. cultivars.

The seed oil of Echium plantagineum L. is rich in unsaturated fatty acids. With the gradual development of the value of echium oil in food, medical care and cosmetics, the corresponding market demand has also increased. The selection of suitable cultivars and the increase of yield per unit area has also become one of the main objectives of current breeding and cultivation of E. plantagineum. To effectively use the local photothermal resources, to improve the use of light energy by E. plantagineum, and to enhance the growth and yield of E. plantagineum. E. plantagineum cultivars Blue Bedder and Mixed Bedding were used as research subjects to study the effects of different sowing dates (1 May, 8 May, 15 May, 22 May and 29 May) on the photosynthetic characteristics and yield of E. plantagineum. Under the same cultivar conditions, with the delay in sowing date, the leaf chlorophyll content (SPAD), photosynthetic rate (Pn), transpiration rate (Tr), stomatal limitation value (Ls), photochemical quenching (qP), electron transfer rate (ETR), actual photochemical efficiency (ΦpsII) and yield of Blue Bedder decreased and reached a maximum at T1, while the SPAD, Pn, Tr, water use efficiency (WUE), Ls, initial fluorescence (Fo), maximum fluorescence (Fm), qP, ETR, ΦpsII and yield of Mixed Bedding reached the maximum at T4. Blue Bedder should be sown early at T1 and Mixed Bedding late at T4 during planting, which will help to improve the photosynthetic characteristics and grain yield of E. plantagineum.

Effects of pyrogenic carbon addition after fire on soil carbon mineralization in the Great Khingan Mountains peatlands (Northeast China).

Wildfires play a critical role in regulating soil carbon (C) budgets in peatland ecosystems, and their frequency and intensity are increasing owing to climate change and human activities. Wildfires not only emit CO2 during the combustion process but also produce pyrogenic carbon (PyC), which accumulates in the soil C pool and influences soil C decomposition. However, the role of PyC after a fire in peatland soil C mineralization has rarely been examined. This study investigated the effects of PyC addition on peatland soil C mineralization and its potential driving mechanisms using an anaerobic/aerobic incubation experiment with peat soils collected from typical peatlands in the Great Khingan Mountains, Northeast China. The effect of PyC was more pronounced under aerobic conditions than under anaerobic conditions. The mean C- mineralization rates of soil were significantly increased by 45.2 ± 15.5 % and 87.6 ± 14.3 % with 10 % PyC250°C addition after the initial stage (D7) of aerobic and anaerobic incubation, but PyC600°C addition caused a to decrease. Compared with PyC600°C, PyC250°C addition significantly increased the available N content and altered the soil microbial activities, which may be the primary reason for the increase in C mineralization rates. Furthermore, adding a high concentration of PyC (10 %) reduced the concentration of phenolics but increased phenol oxidase activity, which promoted C mineralization rates. Thus, PyC250°C addition to peat soils mainly influences the microbial biomass C content through the accumulation of available N and phenolics, which ultimately positively affects C mineralization rates.