Effects Of Drought Stress And Interspecific Competition On Growth And Physiological Characteristics Of Two Sphagnum Species

Sphagnum,a major group of peat-forming plants in peatland,has important influence on the development and maintenance of peatland.The frequency and intensity of drought stress increase as the global change intensifies,and the physiological response mechanisms of Sphagnum under drought stress need to be studied.Interspecific competition,an important factor in the construction of plant communities,study of which in Sphagnum is rather few,especially limited under environmental stress.In addition,allelopathy,as an important way of interspecific competition,study of which in the same genus is rather few and its status in interspecific competition is ambiguous.In this study,two typical Sphagnum species,S.fuscum(Schim P.)Klinggr.and S.magellanicum Brid.,in Dongfanghong forest farm peatland,were selected as study species.In order to uncover the growth and physiological responses of Sphagnum to drought stress and interspecific competition,effects of drought stress and interspecific competition on the biomass production,height increment,side-shoots production,total carbon,total nitrogen,soluble carbohydrates were measured,during a transplantation experiment in the field and a control experiment in the laboratory.At the same time,we tried to separate the resource competition and allelopathy,using the method of activated carbon addition,to explore the role of allelopathy of Sphagnum in its interspecific competition.The main results and conclusions of this study are as follows:(1)The growth of both Sphagnum species were significantly inhibited,under short-term continuous drought stress in laboratory.Biomass production of S.magellanicum and S.fuscum respectively decreased by approximately 13% and 15%,and height increment of both respectively decreased by approximately 37%,30%.Soluble sugar content and non-structural carbohydrate content of both Sphagnum species increased by at least 5 mg/g.Two Sphagnum species have osmotic adjustment function.Due to the existing of osmotic adjustment,Fv / Fm,the maximum quantum yield of photosynthetic systems II,of the two Sphagnum species were not significantly damaged,and the total carbon content,total nitrogen content and C:N were not significantly affected by drought stress.Both Sphagnum species could maintain its own elemental balance.(2)Under the intermittent long-term drought stress in the field,the growth and physiology of S.magellanicum were inhibited,but S.fuscum had stronger drought tolerance.The osmotic adjustment function of S.magellanicum disappeared,and it is difficult to maintain the balance of elements by itself.Biomass production,height increment and soluble sugar content of S.magellanicum decreased respectively by approximately 37%,31% and 22%.(3)In the competition model constructed in the field,S.fuscum significantly inhibited the biomass production and height increment of S.magellanicum under the high water levels,respectively reducing them by 20% and 25%.As the water level declines,interspecific inhibition disappeared and results of competition were regulated by drought stress.(4)In the competition model constructed in the field,there was no significant change in the release of allelochemicals for the emergence of neighboring Sphagnum,and the addition of activated carbon did not play a role in adsorbing allelochemicals.It was difficult to clarify the role of allelopathy of Sphagnum in its interspecific competition position in this study.