Response Of δ¹³C Values Of Wetland Ecosystem Plants To Soil Salinity In Yellow River Delta

Stable carbon isotope composition (δ¹³C) is a comprehensive actions of environment andbiological factors and the δ¹³C information in plants can reveals eco-physiologicalcharacteristics of plants. So analysis of δ¹³C composition feature can reveal the change ofexternal environment factors. Soil salinity content is high in salty land and coastal wetlandand salinity is an important factor which influences δ¹³C of plants. Discussing the relationshipbetween soil salinity and δ¹³C of plants and judging plant δ¹³C whether can as an indicator ofplant salt-tolerant to study plant salt resistance, the improvement of salty land and protectionand recovery of the ecological environment in coastal wetland has important significance intheory and practice. Based on the hot spot of protection and restoration of the Yellow Riverdelta wetland ecological system and weak domestic study on the relationship between soilsalinity and δ¹³C value of plants, in order to study deeply about the change rule andmechanism of δ¹³C value of plants with salinity, In this paper, the composition feature, spatialdifferentiation and influencing factors of C₃and C₄plants δ¹³C value of the Yellow Riverdelta wetland ecological system were discussed, the response of plant δ¹³C value to varianceof salinity was analyzed, and the mechanism of plant δ¹³C value to variance of salinity wasseeked from plant nitrogen content and soil conditions.The main conclusions were drawn asfollows:1. The value range of C₃plants δ¹³C from-31.97‰to-22.16‰and within acquiredproduction, the average value was-28.73‰and more slightly negative than the researchresults of the pioneers, which have some connection with difference on temperature andmoisture in different study areas.While the value intervals of C₄plants δ¹³C were-18.2‰^-12‰and average value was-14.46‰, which were more slightly negative than acquiredresult and may have to do with soil environment and the amount of plant species. C₃plantsδ¹³C value showed a weak negative correlation with elevation in the Yellow River deltawetland study area,but no significant correlation with longitude and latitude. However, C₄plants δ¹³C value showed no significant correlation with three geographic variables （altitude,longitude and latitude）.So the spatial disparity of plants δ¹³C value on the whole in studyarea.The relativity of soil salinity and δ¹³C value achieveed a significant level,but the soilwater, pH and organic matter contents had no significant effect on plants δ¹³C value. Therefore, soil salinity is main environment factor of distribution and variation of plants δ¹³C value in Yellow River delta wetland.2. A significant positive relationship was found between δ¹³C value in C₃plants andsalinity on the whole, but salinity coefficient was different from the previous results and rangeof study area and plant life form are probably main reason. The changing trend of δ¹³C valuewith salinity of individual species in two sampling belts were variant.There were significantpositive correlation between δ¹³C in four C₃plants species and soil salinity in the secondsampling belt, while the δ¹³C values of Suaeda glauca and Phragmites australis only showedpositive correlation with salinity and Artemisia capillaris and Artemisia kanashiroi were notresponsive to salinity in the first sampling belt,Which have some connection with salinitydifference, different salt-tolerance of plant, hereditary factor and influence of microhabitatsbetween different sampling belts. For C₄plants, there were no significant correlation betweenδ¹³C values and salinity, and the δ¹³C values depend on the values of ci/caand φ. Soenvironmental influences to δ¹³C in C₄plants more complex than C₃.3. No significant correlationship was found between leaf N content and salinity on thewhole, and leaf N content of Suaeda glauca only showed positive correlation with salinity insingle species. The leaf N content showed no significant correlation with δ¹³C values, thereason might be plant have minor N use efficiency in photosynthesis. The δ¹³C values ofSuaeda glauca of the second sampling belt only decreased with leaf N content increased insingle species and soil salinity had no influence on the relationship between δ¹³C values andleaf N content. The effect of soil salinity on δ¹³C value of C₃plants was mainly by osmosisand affecting changes in stomatal conductance and photosynthetic rate of plant photosynthesis.For C₄plants, further study is needed to determine the φ value to have a reasonableexplanation for the mechanism of soil salinity affecting δ¹³C value.