Studies On The Comparison Of Biological Characteristics And Eco-Physiology Between The Alien Species Of Conyza Canadensis And Erigeron Annus And Its Companion Species

Conyza canadensis and Erigeron annus which were belonged to the family Compositae,genus Conyza, was originated in north America, and spread to China at the end of 19centuries. They were annual herbaceous plants, and had strong reproductive capacity and highpropagation rate. They had made certain of threat to the agricultural production and theecological environment because they could displace native plants after their invasions, andthey made more influence on the composition and structure of natural ecosystem and cropsgrowth in the farmland ecosystem, destroyed biodiversity, affected the land utilization, andthey had a tendency of further spreading in Jilin province.The above-ground biomass assignment, seed output and the growth characteristics, as wellas the photosynthesis, the transpiration and the moisture content of the species of Conyzacanadensis and their accompanying species of Polygonum bungeanum, Plantago asiatica,Cephalanoplos segetum, Crepis rigescens, and Erigeron annus and its accompanying speciesof Glycine soja, Agrimonia pilosa, Oenothera erythrosepala, Artemisia mongolica werestudied by the methods of sample plot survey, biology characteristic analysis andphysiological ecology characteristics observation. Then expounded the difference of biologycharacteristics and physiological ecology function between the alien species of Conyzacanadensis, Erigeron annus and native species, then provided a scientific basis to understandinvasive mechanism and effectively guard against of Conyza canadensis and Erigeron annus.The results show that:The above-ground biomass, leaf biomass, stem biomass of individual plants of Conyzacanadensis was maximum on 26th July, and inflorescence biomass was maximum on 26thAugust. At early stage of growth, 80ï¼…of all the biomass of plant was Conyza canadensis insample, and it was 99ï¼…on 9th August. Change of each module and plant height were that:plant height, number of leaves, growth height up to peak on 26th July, after that plant height,number of inflorescence continue increase, number of leaf decreased rapidly. The number ofleaves, area of leaves and biomass of Conyza Canadensis individual were far greater thanother species on 26th June at the middle of growth period, the number of seeds of Conyza canadensis individual was average 32675 in terms of propagation. The single seed weight was0.45g. It had a great seed yield and the seed has little weight, great diffusivity.The daily changes of photosynthetic rate of Conyza canadensis was a kind of double-peaks curve. Cephalanoplos segetum, Crepis rigescens, Plantago asiatica all had "noon break" at about 12:00. And Conyza Canadensis up to a peak at 12:00, and its "noon break" at 14:00. The photosynthetic rate of Conyza canadensis was up to maximum at 16:00 on 2nd July. It was 12.93μmolCO₂·m^-2·s^-1. And it was 19.49μmol CO2·m^-2·s^-1 at 12:00 on 23rd July. The numerical value was far than the maximum of photosynthetic rate of other species. The average of photosynthetic rate on 23th July was that: Conyza canadensis＞Polygonum bungeanum＞Cephalanoplos segetum＞Crepis rigescens＞Plantago asiatica Compared with other plants, Conyza canadensis had obvious higher photosynthetic rate. So it had obvious faster growth capability. On the aspect ofwater utilization efficiency, Conyza canadensis superior other species, It could progressive photosynthesis effectively, progressive material accumulates also. These could afford nutrient elements for seed growth, improve maturity degree of seed, in favor of diffusion of plant population.Plant height of Erigeron annus was relatively high, it can form gloomy closedenvironment rapidly though it was lower than Artemisia mongolica and Oenotheraerythrosepala, and it can acquire dominant position in the competitive progress with otherspecies. Plant's height could up to 90.8cm on 23rd July, and it was obvious higher than otheraccompanying species Glycine soja and Agrimonia pilosa. The population density of Erigeronannus relatively big, stem relatively tenuity, reproduction organs developed, so it could createpreconditions for seed diffusion.Erigeron annus had obvious higher photosynthetic rate, So its growth ability was betterthan other plants Erigeron annus. The daily changes of photosynthetic rate of Erigeron annuswas a kind of variation curve, it can reach maximum value at 9:00am, it is15.8μmolCO₂·m^-2·s^-1, at 13::00pm reach minimum, it is 4μmol CO₂·m^-2·s^-1, daily average netphotosynthetic rate was that; Erigeron annus＞Oenothera erythrosepala＞Artemisiamongolica＞Agrimonia pilosa＞Glycine soja. So, its growth ability was better than otherplants. It can form close canopy environment rapidly, in the processes of competitive withother plants, it could get overwhelming predominance. These were necessary conditions whyErigeron annus could invade successfully.