The Response Of Growth And Interspecific Interaction In Three Sphagnum Species To Environmental Changes In The Changbai Mountains

Facilitative or positive interactions are encounters between organisms that beneft atleast one of the participants and cause harm to neither. The famous stress gradient hypothesisconsider that facilitation are dominant in the harsh environment. Peatland, a wetlandecosystem dominanted by Sphagnum with harsh environment, is an ideal place to studypositive interactions. Warming, nitrogen deposition, and drought are most seriousenvironmental problem in the world, is changing the cold, oligotrophic and drownedenvironmental features of peatland, and threatening the growth of Sphagnum.Through combing field and laboratory experiments, this study researched the effects ofthe increases of elevation and water level changes on the growth and interspecies interactionsof Sphagnum. I chosed three Sphagnum species including S. fallax and S. capillifolium and S.palustre as materials, and four original peatlands-Jinchuan, Hani, Yuanchi, Chichi-inChangbai Mountain as the research sites, to build Sphagnum communities. on the growth andinterspecies interactions of Sphagnum. I tried to study the effect of growth and interspeciesinteraction on Sphagnum by laboratory nitrogen deposition experiments, to verify the stressgradient hypothesis, and reveal the mechanism how the bryophytes adapt environmentalchanges. The main results and conclusions are as follows:(1) Raising temperature only affects the height growth of Sphagnum, and has nosignificant effects on the biomass of three Sphagnum. The height of S. palustre and S.capillifolium increased with the rising of temperature. However, the growth of S. fallax ismainly affected by water stress, raising temperature can’t decreased water stress to S. fallax.(2) Falling water levels inhibit the height of Sphagnum. The reduce of the height canshorten the distance between capitulum and water level, to obtain more water. It suggestedthat the reduce of height is an adaptation mechanism.(3) Nitrogen increases the absorption of Sphagnum to nitrogen, but has no significanteffects on the growth of S.capillifolium and S.palustre. Suitable nitrogen fertilizer isbeneficial to the growth of height, but a little more will lead the disappearance of advantance.(4) This experiment can verify the stress gradient hypothesis effectively. Competitions toS. palustre and S. capillifolium reduced with the increase of temperature when the neighborwas S. fallax. The interspecific interactions between S. palustre and S. capillifolium increasedafter decreased with the increase of temperature. Moreover, It existed significant positiveinteractions between S. palustre and S. capillifolium under the condition of high and lowwater levels.(5) Net result of biological interactions depends on the characteristics of species andresource availabilities. Nitrogen failed to change the interactions among Sphagnum. Throughthe behavior characteristic of reducing the height and increasing the number of branch and soon, Sphagnum can adapt to the new environment, to keep the advantage of nutrient gain.(6) Environmental changes, warming, drought and nitrogen deposition, not only canrestrain the growth of the mono-culture of S. palustre, but also change in community speciescomposition indirectly through peat decomposition, then effect the micro geomorphologicenvironment.