Response Of Plant Community And Functional Traits To Salt And Mowing In The Yellow River Delta

Yellow River Delta is the world’s fastest-growing delta, located in Dongying in Shandong Province shaped by large amounts of sediment. Plant functional traits can reflect the response of plants to growth environment, and link up environmental factors, individual plants, and ecological communities with the structure, processes and functions of ecosystem. Researching the response of plants to growing environment contributes to a better understanding of the relationship between environment and plants during the growth process.I conducted the community research in coastal meadow of Yellow River Delta in August 2013, obtained 104 quadrats, collected surface soil samples and leaves of plants within every quadrat to do determination. Conducted the cluster analysis and the 104 samples were divided into four different salinity gradients, using SPSS 20.0 and PCA gradation to find the response of communities and functional traits of Phragmites australis in Yellow River Delta to soil salinity. The study found that coverage of plant communities, species diversity are negatively correlated with soil salinity. Compared with community characteristic, functional traits of P.australis have more sensitive response to changed soil salinity, which mainly reflected, that P.australis leaf size, stem diameter and number of sections have most significant negative correlation with soil salinity. Meanwhile P.australis height and special leaf area also have a negative correlation with soil salinity; Moreover leaf thickness and chlorophyll content of P.australis have significant positive correlation with soil salinity. We found out that most indicators of P.australis are increased first and then decreased, and got a faster growth before the mature stage in lower soil salinity. In higher soil salinity, P.australis stems, leaf traits has greater variation width after mature stage than other groups.I conducted mowing experiments of P.australis communities between April to August 2014, according to the soil salinity gradients in 2013, separately denoted as Ml (mowing at germination period, growth period, mature period and stable period), M2 (mowing at germination period and stable period), M3 (mowing at germination period), M4 (cutting at stable period) and UN(control group, without mowing), recorded traits of communities and P.australis of each growth period to analyze their response to mowing. Study showed that the community coverage, community height, and aboveground biomass got a certain reduction because of mowing, but degree of reduction got increased with the stronger mowing intense. We found the least deduction degree in plots that got one-time cut at germination period. Mowing lead to a rise of P.australis leaf size, specific leaf area, leaf nitrogen and phosphorus content and a reduction of leaf dry matter content, which mainly reflected in Ml, M2 and M4, except plots in Soil salinity content of S4. P.australis leaf size, specific leaf area, dry matter content, leaf nitrogen and phosphorus content can be used as dominant trait combinations in responsed to mowing. Moreover numbers of P.australis sections and section height also can be used as intuitive traitsBy analyzing changes of community traits at each salinity gradient and the response of P.ausiralis to different mowing methods, we found out that mowing can reduce the community coverage and increase species diversity at low salinity, P.australis average height and aboveground biomass also got a certain reduction because of mowing. Meanwhile P.australis leaf size, specific leaf area, dry matter content, leaf nitrogen and phosphorus content can be used as dominant trait combinations in response to mowing. For example, mowing leads to an increased leaf area and special leaf area. But at high soil salinity the response of special leaf area to mowing is less significant, which mainly because that special leaf area has a negative correlation with soil salinity, so at higher soil salinity mowing has a weaker effect than plants than soli salinity. Moreover numbers of P.australis sections and section height also can be used as intuitive traits in responding mowing, except plants in high soil salinity, mowing all led to a reduced number of sections and section height. Under lower soil salinity, S1, S2 and S3, we suggest taking M3 method, and under higher soil salinity S4, it is better for P.australis’growth to take M2 and M4.Researching the response of plants to growing environment and the relationship between the plant functional traits contributes to a better understanding of the relationship between environment and plants during the growth process, and the relationship of plants with plants communities and ecosystem, thus we can simulate large-scale (community or ecosystem) changes by researching small scale (plant functional traits) changes. We put forward a proposal about mowing to predict the adaptation strategies in response to vegetation and varied habitats and provide a scientific development of regional conservation and development decisions.