Comparison of gas exchange characteristics between two invasive plants and a co-occurring native plant in Liaoning Province

Biological invasion is one of the century's most serious environmental problems.A comparative study of invaders and co-occurring natives is an effective approach to gaining insights into the invasiveness of exotic plants.Ambrosia artemisiifolia L.and A.trifida L.are two aggressive North American annual weeds in China, whereas A.trifida occurs mainly in Northeast China.They usually invade cultivated fields and reduce crop productivity, causing significant ecological and socio-economic impacts in introduced areas.Besides its economic impact on crop yield, A.artemisiifolia also represents a major health problem since its pollen is a strong allergen and one of the main causes of hay fever.To explore the traits contributing to invasiveness of A.artemisiifolia and A.trifida and to test the relationship between plasticity of these traits and invasiveness, we conducted a comparative study of two invasive species and their co-occurring native Asteraceae plant, Aster tataricus, in tataricus in terms of gas exchange and efficiencies in resource utilization.We tested the hypothesis that A.artemisiifolia and A.trifida had growth-related ecophysiological advantages over the natives in its non-native range, which resulted in its rapid growth and enhanced its invasiveness.Photosynthesis, specific leaf area (SLA), and the efficiency of resource use (light, phosphorus, and nitrogen) were examined in field.Leaf construction cost (CC) is considered as a quantifiable measure of energy demand for biomass production and is related to energy use efficiency as it includes component of both morphological and physiological traits.The results showed that the light saturation point (LSP) of A.artemisiifolia, A.trifida were significantly higher than that of the native species A.tataricus.The order of P_nmax was that A.artemisiifolia > A.trifida > A.tataricus, and this parameter of two invasive species were significantly higher than that of A.tataricus by 151.28%, 82.80%, respectively.The specific leaf area (SLA), leaf N content per unit mass (N_mass), leaf P content per unit mass (P_mass), photosynthetic energy use efficiency (PEUE), photosynthetic nitrogen use efficiency (PNUE) of two invasive plants were significantly higher than those of the native, but the difference of leaf construction cost per unit mass (CC_mass) between the three plant species was not significant.In summary, the two Asteraceae invasive plant species has higher gas exchange characteristics and leaf traits as compared with co-family non-invasive plant species, and their photosynthetic characteristics and leaf characteristics were closely linked.The two Asteraceae invasive plant species had higher photosynthetic characteristics and energy use parameters, including P_nmax, PNUE, PEUE, water use efficiency (WUE), leading to more effectively resources capturing and utilization efficiency, which may be one of the reasons for successful invasion of these Asteraceae invasive plants in the studied area.