The Spatiotemporal Differences Of Biomass Allocation Pattern Of Melica Przewalskyi In Degraded Grassland

It is an important ecological and evolutionary significance that the change and feedbackplant biomass distribution model have a significant impact on the plant life history strategy,community structure and evolutionary strategies. Research on biomass allocation patterns formultiple views including space redistribution of solar radiation and precipitation by terraincontrolled neighborhood competition between light and water, mineral nutrients and changingenvironmental conditions of internal. Communities have an important theoretical significanceto reveal the resource allocation strategy of species in heterogeneous habitats. Melicaprzewalskyi is a grassy perennial intensive clonal plant, and in the middle area of the QilianMountain, Melica przewalskyi form single dominant population patches with massivedifferent sizes and lush growth, depending on their biological characteristics, plasticity andadaptation to the environment. Research on biomass allocation patterns contributes tounderstanding the risk aversion of environmental adaptation mechanisms and populationupdate strategy of Melica przewalskyi in Gansu with single superiority. Given all this, thepaper build a digital elevation model(DEM) by using ArcGIS, and extract sample plot aspect,slope data to divide grassland degradation gradient, using a combination of methods withCommunity surveys, generalized additive models (GAM) and standardized major axis (SMA)to analyze Melica przewalskyi population biomass characteristics and distribution patternsunder different spatial and temporal gradients. The results show that:(1) In a different aspect, slope and degradation stages, biomass characteristics Melicaprzewalskyi populations showed some differences: from the southern slope to the North Slope,aboveground biomass and total biomass decreased; with the slope increasing, abovegroundbiomass and total biomass was also decreasing; with the patch from the formation to therecession, aboveground biomass and total biomass increased first and then decreased.(2) With turning the aspect from north to east, west and south, soil moisture, density andaboveground biomass of grassland community were on the rise. The Melica przewalskyi inthe east and west had maximal underground biomass and root-shoot ratio, while the southpopulation had maximal total biomass. From south aspect to north aspect, root biomassallocation decreased from54%to27%, while rhizome biomass allocation increased from46%to73%. Melica przewalskyi in the east and west had the lowest stem biomass allocation;however it had the largest leaf and leaf sheath allocation. The flower biomass allocation ofMelica przewalskyi in north and south was relatively large.(3)With the slope increasing, coverage, height and aboveground biomass of grasslandcommunities decreased, and soil moisture also showed a downward trend, then the magnitudeof Melica przewalskyi increased first and then decreased; within each slope gradient, rootbiomass and aboveground biomass Melica przewalskyi showed allometric relationship; as theslope increased, Melica przewalskyi root biomass and aboveground biomass slope increased;with slope showing an increasing trend, flower biomass and stem biomass increased, whilethe leaves and leaf sheath biomass decreased.(4) As the degraded grassland, Melica przewalskyi patches height rise, coverage anddensity after the first increased and then decreased, soil moisture decreased; in addition, asgrassland degradation, the root biomass allocation was on the rise, rhizome biomass allocationdecreased, the root biomass allocation and stem biomass allocation was on the rise, leaves andleaf sheaths biomass allocation showed a downward trend. Optimal allocation theory is only applicable in the case without competition, whileresource competition between the neighborhoods intensified, community environment andregulation of its density conditionality are key factors to determine biomass allocation pattern.Melica przewalskyi as a dominant species of "poisonous weed type" degraded grassland, inthe case of changes in the level of resources its aboveground and underground parts have astrong phenotypic plasticity, and cloning trait can improve fitness to adapt to changes in theenvironment by optimizing their own allocation of resources continuously.