| In order to determine the physiology and growth characteristics of Bothriochloa ischaemum and Lespedeza davurica in different mixture ratios and find the better ratio at the semiarid Loess Plateau in China, B.ischaemum and L.davurica ware planted in the same plot using replacement series in the terrace land at different mixture ratios of 10:0, 8:2, 6:4, 5:5, 4:6, 2:8, and 0:10. The response of the species to drought resistant was evaluated by the photosynthetic physiological and leaf water potential at vigorous growth period. The response of root spatial-temporal distribution and root system characteristics to their mutual presence at the different ratios was calculated from the dry shoot, root and total biomass data. The aims were to provide scientific theory basis for planting high and stable yield of high quality mixture artificial grassland in Loess hilly-gully region. The main results were as follows:(1) Compared to L.davurica, the diurnal variation of LWP was higher of B.ischaemum, and daily mean value of LWP was lower, which showed that B.ischaemum was more sensitive to the change of water, it reflect that B.ischaemum can resist drought stress through low leaf potential. Daily mean value of LWP of L.davurica in mixture was higher than monoculture, whereas B.ischaemum showed an opposite trend, the possible reason was that the root distribution was affected in mixture; The Pn of B.ischaemum was higher than L.davurica, and the jointing stage was higher than blossom stage, which showed the photosynthetic ability of B.ischaemum is stronger than L.davurica, When the mixture ratio was 6:4 and 2:8, B.ischaemum and L.davurica had higher daily average Pn, revealed that the complementary effect was higher than other ratios.(2) The RB of B.ischaemum and L.davurica was decreased gradually with the vertical direction, and was increased during the year, the RB of two species taked 78.85%, 14.38%,6.76% and 88.62%, 7.09%, 4.28% of total RB, in 0~20, 20~40, 40~60 cm soil layer, respectively, and the FRB of L.davurica taked 70.68%, 12.79%, 16.52% of total RB in the three soil layer, respectively. When the mixture ratio was 6:4, the RB of B.ischaemum was 47.26% higher than monoculture; and the RB of L.davurica was 32.95% higher than monoculture when it was 2:8, the FRB was 96.56% in 0~40cm soil layer, and was 9.09% higher than monoculture, the SRL and SRA were higher in this ratio, significantly. the results showed that nutrient use efficiency of L.davurica was improved significantly in the 0~40 soil layer when the ratio was 2:8. The annual growth of total root biomass was 13.00% ~ 41.97%, and when the mixture was 2:8, the growth was higher than other ratios.(3) The RSR of L.davurica was lower than monoculture, photosynthate of aerial part was increased and underground part was decreased in mixture, showed that there have complementary effects between the two species. When the mixture ratio was 6:4, the biomass and RYT of aerial and underground part were higher than other ratios, revealed that the complementary effect was higher than other ratios.In summary, there have different complementary effects under different mixture ratio of B.ischaemum and L.davurica. Considering the higher Pn and LWP in crucial period, RB, and RYT, etc, the results showed that the B6D4 was the best mixture ratio to establish B.ischaemum and L.davurica mixture grassland at semiarid loess hilly-gully region on the Loess Plateau. |
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