| The life history characteristics of plants are all indicators related to their survival,growth,and reproduction in each life history stage of the plant population,and they are also the specific manifestations of the plant's long-term adaptation to the environment and the interference it receives.Seed germination is the beginning of plant life history.The time of germination directly affects the life history characteristics of the plant such as growth period,growth,reproduction and biomass distribution.The annual plants Chenopodium album and Amaranthus retroflexus in temperate arid and semi-arid areas can form a germination series during the growing season.Mowing affects the morphological structure,reproductive growth and other life history characteristics of plants.The study of the effects of sowing time and different mowing treatments on the life history characteristics of annual plant populations is of great significance for revealing the strategies of life history regulation of annual plants and the adaptation theories of enriching plant populations.In this study,control and simulation experiments were carried out in the plot for two consecutive growth seasons(2018,2019),and the growth was carried out at different sowing times(May 12,June 1,June 21,and July 11).Of C.album and A.retroflexus for mowing intensity(control,plant height ?,plant height ?)and mowing frequency(control,1 time,2 times,3 times)The treatment and analysis of the growth period,growth characteristics,biomass,and biomass distribution characteristics of the two plants were analyzed.Results were as follows:(1)The effects of sowing time on the growth periods of C.album and A.retroflexus are consistent and different.Consistent performance is: the total life history and vegetative growth period of the two plants are shortened,and the proportion of flowering period is increased under different planting times;the difference is as follows: C.album increased seed maturity and proportion,while A.retroflexus shortened seed maturity and proportion.(2)Sowing time and mowing disturbance had different effects on the growth characteristics of C.album and A.retroflexus.In 2018,their interactions significantly affected the plant height,crown width,and 2nd branch length of C.album and A.retroflexus.The interactions in 2019 had a significant effect on the plant height and crown width of the C.album and 1st branch number of A.retroflexus.The height,crown width,1st branch length,2nd branch length,1st branch number,2nd branchnumber of C.album were 2.2 times,1.6 times,1.3 times,2.7 times,3.1 times,2.7times of the 4th sowing in 2018,and 4.4 times,4.7 times,7.7 times,3.5 times,1.7times,12.3 times in 2019.As for A.retroflexus,they were 3.5 times,1.9 times,1.1times,2.5 times,5.4 times,11.9 times in 2018,and 3.6 times,2.5 times,6.3 times,1.7times,1.4 times,24.0 times in 2019.The two plants responded similarly to castration disturbances.The height,1st branch length,1st branch number,and 2nd branch length of C.album and A.retroflexus gradually increased with the increase in the intensity and frequency of mowing in 2018 and 2019.The response to growth characteristics was the most significant under moderate mowing intensity,and the frequency of 1time and 2 times mowing treatments.(3)Sowing time and mowing disturbance have different effects on the biomass accumulation of C.album and A.retroflexus.The interactions had significant effects on the root biomass,stem biomass,inflorescence biomass,and total biomass of A.retroflexus in 2018.The root biomass,stem biomass,leaves biomass,inflorescence biomass,and total biomass of C.album were 5.6 times,9.6 times,6.9 times,4.3 times,6.1 times of the 4th sowing in 2018,and19.8 times,25.3 times,13.6 times,17.9 times,20.1 times in 2019.As for A.retroflexus,they were 13.4 times,18.4 times,11.1 times,6.6 times,9.9 times in 2018,and 7.2 times,12.8 times,5.2 times,11.3 times,10.3times in 2019.Castration disturbance has similar effects on C.album and A.retroflexus.Root biomass,stem biomass,leaf biomass,inflorescence biomass,and total biomass all increased at a moderate mowing intensity,with the 1 time and 2times mowing frequencies increasing most significantly.(4)Sowing time and mowing disturbance have different effects on the biomass allocation of C.album and A.retroflexus.The interaction had a significant impact on C.album's leaf biomass allocation in 2018,and root biomass allocation,stem biomass allocation,inflorescence biomass allocation in 2019.The interaction had a significant impact on A.retroflexus' s root biomass allocation,stem biomass allocation,and inflorescence biomass allocation in 2018,and root biomass allocation and leaf biomass allocation had significant effects in 2019.With the delay of sowing time in2018 and 2019,inflorescence biomass allocation and root biomass allocation showed an increasing trend,while stem biomass allocation showed a decreasing trend.The effect of castration disturbance on C.album and A.retroflexus biomass allocation is that as the intensity and frequency of mowing increase,leaf biomass allocation and inflorescence biomass allocation gradually increase.The increase of C.album's biomass distribution was the most obvious in the 2nd and 4th seeding in 2018 and the2 nd and 3rd seeding in 2019,and it was significantly different from the control group.A.retroflexus' s biomass allocation responds relatively weakly to castration disturbances. |
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