Figure 5
The main effects used within a three-level growth model to predict grassland NPP. All coefficients were standardized in terms of proportional change in grassland NPP with respect to one SD change in precipitation, temperature, sunlight, grassland area percentage (grassland_pct), DEM, slope, soil nutrient percentage (i.e. potassium, K, nitrogen, N, phosphorus, P), the average distance from the small watershed to the nearest water source (D2Water), highway (D2Highway), and village (D2Village), as well as gross domestic product (GDP), human population density (HPD), and meat production (Meat). The values used for this analysis were: precipitation, 158.5 mm; temperature, 2.28 °C; sunlight, 201.05 h; percentage of grassland, 23.99%; DEM, 395.18 m; slope, 5.8°; soil K, 37.17%; soil N, 0.17%; soil P, 0.01%; D2Water, 28.12 km; D2Highway, 196.65 km; D2Village, 55.76 km; GDP: 149 million CNY; HPD, 30.6 thousand people·km−2; Meat, 2.66 thousand tons. The t-statistics are in the parenthesis. ***, ** and * denote 1%, 5% and 10% significant level. The solid line in this figure marks the 95% confidence interval (CI) for the estimated effect of variables at the three-level model; thus, those that do not overlap this line can be considered significantly different from zero. The dots denote point estimates for parameter values47,48,93. This figure was created using the software R (http://www.Rproject.org/)94 and the library sjPlot93.
