Plant Diversity Pattern And Interface Characteristics Of Shrubland-Grassland Ecotone In Eastern Qilian Mountains

Ecotone of Shrubland-Grassland in Eastern Qilian Mountains were studied aboutcommunity features, microhabitat factor and soil physical and chemical characteristics. Theinterrelation among community diversity pattern, soil CO₂flux and environment factor werealso analyzed for revealing the ecology process of Shrubland-Grassland Ecotone ofcommunity and soil gradient variation rule. The main conclusions are as follows:1. Along the altitudinal vertical gradient from2950m to3250m of typical Shrubland-Grassland community ecotone in Eastern Qilian Mountains, Polygonum viviparum meadow,Polygonum viviparum meadow-Potentilla fruticosa shrub ecotone, the core area of Potentillafruticosa community, Potentilla fruticosa-Rhododendron shrub ecotone, the core area ofRhododendron shrub were appeared successively.2. Microhabitat factor of typical shrubland-Grassland community ecotone along elevationgradient vertical upward changed regularly. Air and soil temperature in community dropped, airhumidity tended to increase and temperature rising slow down during daytime; variation rangeof soil temperature and humidity were1.6⁴.0℃and2.7⁶.4%respectively; and soilmoisture showed that shade slope> semi-shady slope> semi-sunny slope at horizontal attitudeof3200m for aspect and slope reasons.3. Soil physical and chemical characteristics spatial variability of shrubland-Grasslandcommunity ecotones were significant. Along the altitudinal vertical gradient upward, soilcompaction declined, porosity increased, and water conservation ability of shrub strengthened.Carbon and nitrogen density of higher attitude Rhododendron shrub was significantly higherthan low attitude Polygonum viviparum meadow, and declined with attitude rising; soil organicmatter and nutrient of horizontal gradient had significant difference as aspect and slopesunshine hours influence.4. Soil respiration rate had a significant change of community ecotone along elevationgradient vertical upward. It descended by7.11umol. m^-2. s^-1to2.25umol. m^-2. s^-1fromPolygonum viviparum meadow to Rhododendron shrubland. Diurnal variation amplitude ofRhododendron dense shrub soil respiration rate was relatively stable, meanwhile, Polygonumviviparum meadow diurnal dynamics showed a single peak curve, and dairy amplitude was up to1.8umol. m^-2. s^-1. Soil respiration peak was almost synchronous with sunlight time in thehorizontal transect in the horizontal transect, soil CO₂flux and5cm soil temperature were linearfitting; temperature sensitivity Q value were3.9⁴.4, it had index regression relationship withsoil moisture.5. Along elevation gradient upward, shrub abundance increased, herbaceous species wasthe Maximum in Polygonum viviparum Meadow–Potentilla shrubland ecotone. Simpson indexand Shannon-Wiener index of shrub increased monotonously with elevation ascend. However,herbage showed regular pattern of first increased then decreased; adjacent shrub Cody indexincreased along vertical transect upward. Shrub Simpson index and Shannon-Wiener index wasshade slope> semi-shady slope> semi-sunny slope along horizontal transect, but herbaceousdiversity of semi-sunny slope was the maximun, and evenness of Rhododendron shrub washighest of shade slope. Ecotone boundaries were quantitative determinated using movingsplit-window technology, the results showed that8¹0window sizes could better reflected thewidth and position of the ecotone. There were highly significant correlation among speciesdiversity and altitude, soil total phosphorus, soil respiration and soil moisture content.