Effects Of Salt Heterogeneity And Competition On The Clonal Plant Phragmites Australis In The Wetland Of The Yellow River Delta

The Yellow River Delta has a special location and is located in the sea land ecotone.The soil exhibits varying degrees of resource heterogeneity distribution and saline alkali stress due to its short soil formation time,low soil nutrients,rapid water evaporation,and high salt content.At present,the problem of soil salinization has seriously restricted the local ecology,economy and development.Soil salt heterogeneity is also widespread.Although soil salt heterogeneity will affect plant growth,development,and reproduction,there have been few studies on the effects of coupled competition on wetland plant growth and reproduction.This study used a mixture of in-situ soil and river sand in the Yellow River Delta as the matrix and selected typical wetland plants Phragmites australis and Suaeda salsa as the research objects to investigate the effects of salt homogeneous and heterogeneous habitats,clonal integration,and interspecific competition on the physiological and morphological indexes of P.australis.The following are the main contents and conclusions:(1)A comparative analysis of P.australis response differences in salt heterogeneous and salt homogeneous habitats.Under the same total salt content,salt heterogeneity promoted the growth of P.australis,which was related to habitat adaptation strategies such as foraging behavior and biomass allocation of clonal plant P.australis.That is,P.australis adapted to the heterogeneous saline habitat by increasing the distribution of aboveground and underground biomass and changing the morphology parameters,thereby promoting plant growth and development.(2)The physiology and morphology of cutting P.australis rhizome in homogeneous and heterogeneous saline habitats were compared and analyzed.Severed treatment significantly reduced the morphological indexes and biomass distribution of P.australis in heterogeneous saline habitats(p<0.05).Clonal integration,on the other hand,significantly aided the growth of P.australis in heterogeneous saline habitat.The severed treatment had no effect on homogeneous saline habitat.The rise and fall trend of photosynthetic indicators showed that P.australis was primarily dominated by non-sto matal limiting factors.(3)The ecological adaptation countermeasures of P.australis to interspecific competition of S.salsa in heterogeneous saline habitat were analyzed.The interspecific competition between S.salsa and P.australis significantly reduced the morphological indexes,leaf chlorophyll content and biomass accumulation of aboveground and unde rground organs of P.australis(p<0.05).This demonstrates that S.salsa growth had a significant inhibitory effect on the normal growth and development of P.australis,implying that P.australis grows better in a single environment.(4)The effects of severed treatment on biomass and ion content of S.salsa in heterogeneous saline habitats were compared and analyzed.In the heterogeneous saline habitat,the severed treatment significantly increased the Na⁺content in stems and leaves of S.salsa(p<0.05),indicating that when P.australis losed the ability of clonal inte gration,S.salsa will occupy a competitive advantage by increasing basal stem biomass.As a halophyte,S.salsa frequently reduces soil salt by absorbing the salt in the soil,whereas the severed treatment reduced P.australis resistance to salt,resulting in a significant increase in Na⁺content in S.salsa leaves(p<0.05).This study demonstrates that P.australis changed its phenotypic plasticity to adapt to heterogeneous salt stress habitat,resulting in increased P.australis growth in heterogeneous salt habitat.Severed treatment significantly inhibited P.australis growth in heterogeneous saline habitat but had no effect on P.australis growth in homogeneous saline habitat.At the same time,compared with the single growth treatment of P.australis,the symbiosis of P.australis and S.salsa significantly inhibited the increase of physiological and morphological indexes of P.australis.Without competition,P.australis can grow faster.In conclusion,clonal integration promoted the growth of physiological and morphological indexes of P.australis in heterogeneous habitats,which aided in the development of clonal plants'adaptive strategies under various stress conditions.