Biological Characteristics And Spreading Trend Of Phragmites Australis In Caohai,Guizhou Province

P.australis is a typical hermaphrodite plant,which is widely distributed all over the world.In the asexual propagation of reed in Caohai,there are two ways:one is to germinate at the base of withered old stem to produce new plants,often one base to produce multiple plants;the other is to germinate at the internode of P.australis root tiller to produce new plants,and only one plant.There are differences in the supply and utilization of resources between the two ways of reproduction,the latter is the main way of P.australis diffusion.In order to understand the dynamic changes of plant factors and the biological characteristics of Phragmites australis in the process of growth and expansion,and to observe the spread rule of P.australis in Caohai area,this paper provides a theoretical basis for the rational and effective utilization of P.australis.The main results are as follows:(1)The total diffusion area of P.australis in Caohai is 147.17 hm²,including 89.87 hm² in 2016and before,45.38 hm² in 2017 and 11.92 hm² in 2018,showing a decreasing trend;the diffusion direction is mainly concentrated in the north and east of Caohai,showing a trend of South expansion;At 30?,the germination rate(43.3%)and germination rate(27.0%)of P.australis seeds in Caohai are the highest,and at the same temperature,the germination rate and germination rate of P.australis seeds in the 0-1a age group are higher than those in the>2a age group;the length of root tiller is up to 3.57m,and the shortest is 1.36m,and the number of plants changes linearly with the length of root tiller The number of P.australis is larger than that of 0-1a age group;the length of tillering on the main root tiller is mainly concentrated in 10-20cm,the shortest is 2.80cm,the longest is 88.90cm;the species between the P.australis community and the open space are similar,Cultivation,grazing and the dense growth of Juncus effusus,Chenopodium ambrosioides and other plants will affect the growth and reproduction of Phragmites australis.(2)In April to may,the elongation rate was the highest,3.105cm in the 0-1a age group,3.187cm in the>2a age group,2.879cm in the 0-1a age group,1.635cm in the>2a age group,slightly lower than that in the 0-1a age group in the early growth period,and 3.105cm in the 0-1a age group The number of P.australis in different age groups changed with time in a power function,and showed a very high significance(P<0.01),and the number of P.australis in the 0-1a age group increased for a longer time.(3)The number of P.australis in Caohai age group was normal distribution;the number of16-18 internodes was the most in the 0-1a age group,and then decreased with the increase or decrease of internodes;no more than 22 internodes were found in the 0-1a age group,and only one plant below7 internodes was found;Among the P.australis of the age group>2a,the number of internodes was16-18 nodes,up to one third of the samples;the change rule of internode length was"short-long-short",and the length of the 5th-6th nodes reached the maximum.(4)The height of P.australis communis and the biomass of each component showed a high degree of fit,and the biomass of each component was positively correlated with the height of P.australis communis;the height of P.australis communis in different years was 250cm,which was lower than 250cm,and the biomass was relatively gentle with the increase of height.When the height reached 250cm,the growth trend of biomass was relatively accelerated;the number of internode and the biomass of component had a very significant relationship The relationship was exponential(P<0.01).(5)The photosynthetic characteristics of P.australis communis were different with the change of leaf position;the stomatal conductance increased with the increase of leaf position,and the transpiration rate of strong leaves in the middle was the largest,and the transpiration rate and leaf position of P.australis communis in different age groups showed a second power function change rule,and reached the peak value in the ninth leaf position;in the intercellular CO₂ concentration,P.australis communis in the 0-1a age group showed an exponential function decline with the increase of leaf position,and those in the>2a age group showed a linear trend The net photosynthetic rate was the highest and the accumulation rate was the fastest.(6)In the 0-1a age group,the amount of material accumulation was larger than that in the 2 a age group,but showed consistency with the change of leaf position;there was significant difference in material accumulation and utilization between leaves in different leaf positions;the starch in the middle leaf position was the most,the soluble sugar content in the high leaf position was the highest,and the starch and soluble sugar content in the low leaf position were lower,indicating that from the high leaf position to the low leaf position,the rule of material use was:"transformation-accumulation-use".