Effects Of Simulated Precipitation Changes And Increased N Deposition On The Phenology And Biomass Of Plants In An Alpine Meadow

By artificially controlling precipitation and N deposition, we observed the change of phenology and biomass of the several plants in an alpine meadows of Tibetan plateau during a whole growing season, discussing potential changes of dynamics and resources utilization of the plant community under the future background of change of precipitation and increased N deposition in an alpine meadow. There are five precipitation treatments: control treatment (AO), springO summer-autumn and winter+(A1), spring-summer-autumn and winter+(A2), spring+summer-autumn and winter0(A3) and spring-summer+autumn and winter-(A4). N decoposition treatments included control and N adding level. By researching the effects of dynamic of precipitation and increasing N deposition, we gained the following results:1. Effects of Simulated precipitation changes on the plant phenology:In the treatment of A3, the flowering duration period of Leontopo diumnanum, Macrofloral Kobresia, Kobresia setchwanensis and Gentiana squarrosa significantly lengthen, between6.6d to11.8d; But in the treatment of A2and A4, the flowering duration of which significantly shorten, between4.8d to8.2d. In the treatment of A2and A4, the seeding duration of Leontopo diumnanum, Macrofloral Kobresia and Kobresia setchwanensis notably shorten, between8.6-12.8d and3.8-6.5d; In the treatment of A3the seeding duration of them have no significant change. The effects of precipitation changes have no significant change on the reproductive phenology of Gentianopsis paludosa, Potentilla bifurca, Gueldenstaedtia diversfolia, Euphrasia regelii and Potentilla ansrina.The dynamic of precipitation in the spring have significant change on the biotemperature of plants; But the dynamic of precipitation in the summer have no significant change on the biotemperature of plants to some extent, because there is enough precipitation in summer.2. Effects of simulated increased N deposition on plants phenology and biomass:The increased N deposition makes the flowering duration and the seeding duration of Kobresia setchwanensis shorten between5.2-7.4d and8.4-9.2d; The biotemperature of Gentianopsis paludosa, Potentilla bifurca, Gentiana squarrosa, Gueldenstaedtia diversfolia, Potentilla bifurca and Leontopodiumnanum significantly lengthen; The biotemperature of Euphrasia regelii and Macrofloral Kobresia have no significant change. The increasing N deposition makes the biotemperature of plants lengthen.3. Effect of Simulated dynamic of precipitation on plants aboveground biomass:Under the condition of the natural and increased N deposition, in the treatment of A3the total aboveground biomass reach maximum and has significant change compared with the other4treatments. The increased precipitation in the spring has important effects on the accumulation of aboveground biomass in the alpine meadow, increased75.4g/m2; The reduced precipitation in the spring has important effects on the accumulation of aboveground biomass in the alpine meadow, reduced44.8g/m2. It illustrates that the dynamic of precipitation in the spring has important effects on the accumulation of aboveground biomass, whereas the dynamic of precipitation in the summer is not the key factor, and have no significant effects on the accumulation of aboveground biomass to some extent. The dynamic of precipitation in the spring is the key factor of the growing of plants in the alpine meadow.4. Effect of simulated increased N deposition on plant aboveground biomassIn the five precipitation treatments, the increased N deposition makes the aboveground biomass of graminoid, sedge and the total aboveground biomass significantly increase, which has no significant of dicotylion weeds. Hence, if the N deposition increases in this area, the total plant community biomass will ascend the proportion of graminoid and sedge will rise, the dicotylion weeds will have no significant change. Therefore, the increased N deposition will be of the benefit to the local animal husbandry in the short run.All in all, the increased precipitation in spring and increased N deposition could significantly lengthen the reproductive phenology and enhance the total aboveground biomass of plant community in the alpine meadow. Through the study of relationship between dynamic of precipitation, increasing N deposition and the phenology, biomass, the tendency of the plant species composition and its respective proportion may be appraised in the future under the condition of global changes.