A Study On Leaf Traits And Leaf Physiological Traits Of Dominant Species In Minqin Oasis

In this study, taking Populus euphratica Oliv., Elaeagnus angustifolia L., Populus simonii, Haloxylon ammodendron, Tamarix chinens, Nitraria tangutorum, Reaumuria soongorica, Phragmites australis, Suaeda salsa dominant species of Minqin Oasis as the research object, through field experiment, indoor experiment and data analysis, using the correlation analysis, one-way analysis of variance method, first, fitted the relationships between leaf traits of dominant species, explored different plant leaf traits and differences between leaf traits; then analysed the plant photosynthetic physiological characteristics and diurnal variation of photosynthetic physiological characteristics; At last, explored the relationship between leaf traits and photosynthetic physiological characteristics, verified the existence of leaf economics spectrum of dominant species in Minqin Oasis.Conclusions are as follows:(1)The LA(leaf area) has significant correlation with FW(fresh weight), DW(dry weight), SFW(saturated fresh weight) of dominant species in Minqin Oasis, FW, DW, SFW increased with the increase of LA in a certain range. The leaf traits of seven species were LA>EWT(equivalent water content)>LMA(leaf mass per area)>SLA(specific leaf area)>LDMC(leaf dry matter content)>LWC(leaf water content), the difference of LA were greatest, desert plants reduce water loss and leaf morphology to adapt to arid environment. At the level of life form, the tree average FW, DW, LA, LDMC, SLA were higher than that of the shrub, and shrub?s LWC, LMA, EWT is higher than that of trees, explained that tree use more nutrients in the construction of cell, tree?s ability of keeping nutrient was stronger than shrub, stand can bear stronger water stress and drought, which should be one of the reasons that shrub account for the advantage in the desert.(2)The peaks of net photoynthtic rate(Pn) of different plants appeared at different time, the photosynthetic “midday depression” were remarkable of 9 plants in Minqin oasis. The curves of transpiration rate(Tr) showed asymmetric two peaks, Populus euphratica Oliv.?s Tr was a single peak curve, the Pn and Tr of Haloxylon ammodendron were highest in 9 plants, it was a high photosynthesis, high transpiration type plant. The curves of stomatic conductance(Gs) of 9 plants showed asymmetric two peaks and the peaks appeared at different time. Intercellular carbon dioxide(Ci) of 9 plants showed a trend of “higher at morning and afternoon, lower at noon ”, plants appeared photosynthetic “midday depression” at noon, Ci declined at noon because plant photosynthesis required CO2 from the cell gap. The curves of water use efficiency(WUE) showed asymmetric two peaks of Populus euphratica Oliv., Elaeagnus angustifolia L., Tamarix chinens, Reaumuria soongorica, Phragmites australis, Populus simonii was a single peak curve, Haloxylon ammodendron, Nitraria tangutorum and Suaeda salsa showed a trend of increased firstly and then decreased.(3)At the species level, there are some differences between different kinds of photosynthetic physiological characteristics of 9 species in Minqin oasis(p<0.05). The coefficients of variation of Pn, Tr, Gs, Ci, WUE 5were 0.871, 0.998, 1.215, 0.043, 0.391. At the level of life form, average Pn:tree>grass>shrub, there are no significant difference in Pn(F=2.712, p=0.072); average Tr: tree>grass>shrub, the shrub?s Tr is significantly higher than grass and tree(F=4.653, p=0.012); average Gs:tree>grass>shrub, the tree?s Gs is significantly higher than grass and shrub(F=17.619, p<0.001); average Ci: grass>shrub>tree, there are no significant difference in Ci(F=0.476, p=0.622); average WUE: shrub>tree>grass, the grass?s WUE is significantly lower than tree and shrub(F=2.1, p=0.013).(4) Photosynthetic traits of plant leaf in Minqin oasis and physiological characteristics are significantly correlated. On the whole, Pn and Tr, Gs are in positive correlation. Tr and LWC are in positive correlation, LDMC and SLA are significantly negatively correlated. Different species are in different positions in the leaf economic spectrum, in the same environment, the photosynthetic characteristics of trees are superior than herbaceous and shrubs. The position of trees in leaf economic spectrum is closer to the side which has thin leaves, high carbon and nitrogen content, strong photosynthetic capacity but long life. While shrubs are closer to the end which has thick foliage, low carbon and nitrogen content, the weak photosynthetic capacity, the smaller area of the leaf but short life. Herbaceous plants have higher photosynthetic capacity and are mostly annual plants. Therefore they are the end which has thick foliage, low carbon and nitrogen content, the weak photosynthetic capacity but short lifetime. It illustrates that the leaf economic spectrum also exists in the harsh environment such as desert steppe.