| Grasses have been playing crucial roles in helping overcome the effects of global warming,providing sustainable food production and maintaining a good environment.Cleistogenes songorica is a very important native grass distributed in arid areas in northern China.After the research and breeding efforts related to this grass by the team of Wang et al.in the college of Pastoral Agriculture Technology and science,Lanzhou University,a selection of this grass was approved as a new variety by the National Grass Variety Approval Committee in 2016,named Cleistogenes songorica'Tenggeli'.Based on previous researches,the research reported in this thesis studied the root morphology,root growth,root functions in soil including overcoming of water flow erosion,and carbon sequestration related to C.songorica 'Tenggeli'.This research was carried out in Zhangye city in Gansu province and in natural grassland located in Alashan in Inner Mongolia of northern China during the period from years of 2010 to 2014,aiming to provide the basis for better understanding of the root biology and ecology of this grass and its ecological functions.The main results are as follows:1?Each root of C.songorica originates from the base of tillers,and generally,each tiller developed 1-3 adventitious roots.The numbers of tillers and roots increased as plants became older.The relationship between tillers and roots can be formulated as:Roots=2.0048 x Tillers.The entire mother plant and the adventitious roots are connected through rhizomes.98%of C.songorica plants in natural grassland had upward step-like rhizomes,while there were only 2%of C.songorica'Tenggeli' in sown plots having such structured rhizomes.Roots of the grass have a rhizosheath that was mostly distributed in the 0-20 cm soil zone in natural grassland and in the 0-10 cm soil zone in sown plots.The maximum depth that roots can penetrate increased with plant age in cultivated conditions.At five years the maximum depth was 70-80 cm.Minirhizotrons were used to monitor root branching and root length of C.songorica 'Tenggeli' in soil 0-70 cm deep during 2013 and 2014,and this research found that 51.4%of root branches were distributed in the 30-50 cm zone,and 32.2%and 31.8%of the root length were distributed in 10-30 and 30-50 cm zones respectively.The average and median longevity of C.songorica 'Tenggeli' were 279.8 days and 405.5 days respectively.The root length of C.songorica 'Tenggeli' was significantly longer than that of tall fescue while the leaf length of tall fescue is significantly greater than that of C.songorica 'Tenggeli'each day after seed germination in a pot trial.These two grasses had different growth strategies during seedling growth;C.songorica was priority of roots while tall fescue was priority of leaves.We studied the erosion resistance of C.songorica 'Tenggeli' in sown plots under middle drought?irrigated 5 times?and severe drought?2 times?compared with tall fescue 'water save',known for having strong drought tolerance,and bare plots,from 2012 to 2013.Soil aggregates in bare plots,tall fescue and C.songorica 'Tenggeli' plots were 58.6%?74.3%and 84.1%respectively under middle drought conditions,and C.songorica "Tenggeli" was 9.8%and 25.6%higher compared with tall fescue and bare soil.Under severe drought conditions,the soil aggregate in bare plots,tall fescue and C.songorica 'Tenggeli' plots were 54.1%?66.9%and 68.8%.C.songorica 'Tenggeli' was 1.9%and 14.7%higher than of tall fescue and bare soil plots.In a rainfall simulation experiment,the scouring resistance index was 0.86 for C.songorica 'Tenggeli',0.47 for tall fescue,and 0.06 for bare soil under middle drought conditions.Under severe drought conditions,the scouring resistance index for C.songorica 'Tenggeli' was 0.33,for tall fescue was 0.18,and for bare soil it was 0.05.The scouring resistance of C.songorica 'Tenggeli' was 83.0%and 83.3%higher than tall fescue under middle and severe drought conditions,and 13.3 and 5.6 times greater than bare soil in the middle and severe drought conditions.3.Root biomass of C.songorica in natural grassland in 2011-2013 was 1.60,1.63 kg m-2,and in sown plots was 0.85,1.46 kg m-2.The fraction of biomass in 0-40 cm soil depth in natural grassland was 85.1%?87.5%,and in the sown plots was 98.5%?95.5%.The biomass of C.songorica 'Tenggeli' in the 0-70 cm profile became located deeper overtime.The fraction of biomass in the 0-10 cm zone decreased from 71.8%in 2011 to 53.7%in 2013,while the fraction of biomass in soil layers of 20-30,30-40,and 40-50 increased from 20.8%,10.4%and 4.9%in 2011 to 23.6%,12.2%and 6.2%in 2013.There were no significant differences in soil total carbon,soil organic carbon and soil inorganic carbon between 2011 and 2013 in natural grassland.The total soil carbon in sown plots of C.songorica 'Tenggeli' in the 0-70 cm soil zone increased from 17.6 kg m-2 in 2011 to 18.7 kg m-2 in 2013.The growth rate was 6.25%;and the soil organic carbon increased from 7.89 kg m 2 in 2011 to 8.39 kg m-2 in 2013,the growth rate was 6.34%.The zone in which soil organic carbon increased was in the10-30 cm soil layer.Soil inorganic carbon didn't differ significantly.After five years following the establishing of the sown plots with different plant densities?0,10,20,30 plants m 2?,soil organic carbon content in 0 plants m 2 was decreased from 3.59 g kg-1 to 2.94 g kg-1 while increased in 10,20,30 plants m-2 in 10-30 cm soil layer,soil organic carbon content increase was the greatest in plots with 10 plants m 2,while the growth rate was 17.9%. |
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