Nhận biết (M1)

Gross primary productivity (GPP), the rate of carbon fixation by plants during photosynthesis, is typically inferred from carbon flux observations. Since seasonal onset and cessation of photosynthesis correspond with changes in GPP, GPP data sets derived from carbon flux observations, including FLUXNET, FLUXCOM, and RF-GPP, can be used to estimate growing-season length. In a study exploring the use of another proxy for photosynthesis—solar-induced chlorophyll fluorescence (SIF), solar radiation reemitted by plants that can be detected via satellite—to determine growing-season length, Zhe Wang et al. calculated correlations between estimates from several SIF data sets (a sample of which are represented in the graph) and estimates from GPP data sets (values closer to 0 indicate weaker correlations).

The information in the text and the graph best supports which conclusion about the data sets used in Wang et al.’s study?

• A.

  The stronger correlations between all three SIF data sets and the FLUXCOM and RF-GPP data sets relative to those between all three SIF data sets and FLUXNET suggest that FLUXCOM and RF-GPP enable more accurate estimates of growing-season length than FLUXNET does.

• B.

  In comparison to the more limited range of FLUXNET values, the greater range between the highest and lowest FLUXCOM values suggests that FLUXCOM-derived estimates of growing-season length vary more widely than FLUXNET-derived estimates do.

• C.

  Length-of-season estimates derived from RF-GPP data were generally more similar to those derived from FLUXCOM data than they were to those derived from FLUXNET data.

• D.

  The weaker correlations between SIF data set F and all three GPP data sets relative to those of the other SIF data sets suggest that data set F systematically underestimates the length of the growing season.