tailieunhanh - Climate Change and Variability Part 9

Tham khảo tài liệu 'climate change and variability part 9', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 228 Climate Change and Variability Percentage of parent rock outcrops on the plot 4 Water holding capacity of earth mm cm based on soil texture 3 Percentage of coarse fragments in the sod 4 Total soil depth 4 Table 1. variables describing site conditions and used for the model Coef. Partial regression coefficient in the PLS regression model. All theses coefficients are highly significant P . They sort variable by their relative weight in the model. The initial CA using the flora census of 1996-98 was computed with the climate of the period 1961-1996. Simulation of climate change impact on plant turnover The simulation used the two steps of the model First we considered that an increasing mean annual temperature or decreasing spring or summer rainfall would favour xero-thermophilous species and stress mesophilous ones. We simulated this impact Figure 3 changing at plant distribution margins of each plot the composition 3b or the abundance-dominance 3c . Using these modified plots as supplementary observations in the initial CA we computed the new coordinates of each plot on axis 1 Figure 3 which means new and smaller Fi indices modified plots shifted to the left in the CA plane . In the second step we simulated various climate change scenarios with lessening summer or spring rainfall -10 to -30 and raising temperatures 1 to 2 C . We also used in the model the mean climate observed over respectively the last 10 20 and 30 years 1978-2007 . New and smaller Bi indices for each plot were computed. The good correlation between Fi and Bi indices enabled linking their respective shift with the flora and climate change simulations and therefore assessing the plant composition turnover expected for each climate scenario. We did not consider the future of individual or specific plants but the global turnover as a percentage of plant composition. Validation with the new flora census This census was performed in spring 2008 by the same .

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