Table 1.
Soil characteristics of the C. lanceolata plantations at the Huitong National Forest Ecosystem Research Station, Hunan Province, China.
Figure 1.
The model was validated by fitting the predicted and observed values.
(A) Stand height (H, m). (B) Diameter at breast height (DBH, cm). (C) Stand stocking (stems per ha). (D) Stem woody biomass in tone dry matter per hector (t DM ha−1). Gray dashed lines represent a 1∶1 relationship; solid lines are linear regressions. NSE for “Nash-Sutcliffe efficiency”.
Figure 2.
Simulated increased N deposition impacts on forest productivity as stand development.
(Panel A) The magenta solid line stands for the stem wood biomass production in tone dry matter per hector (t DM ha−1), and green solid line refers to the net primary production in tone dry matter per hector (NPP, t DM ha−1 year−1). (Panel B) Annual increment of ANR (red solid line, ANR, kg N ha−1 year−1). (Panel C) The blue solid line represents current status of soil available N for growth in kg N per hector (kg N ha−1), olive solid line refers to soil organic C (SOC, t C ha−1) of C. lanceolata plantation in southern China from seedling to 120 years of age. In panels A, B, and C, a0, b0 and c0 represent growth trends from the basic, under initial level of N deposition (N4.9) and without rotation practice (RL120), simulation that made up the baseline data set; and a1–5, b1–5, as well as c1–5 represent predicted growth response trends generated under increased N deposition. The dashed lines represent growth constraint equilibrium state.
Figure 3.
Simulated interactive effects of increased N deposition and short-rotation management as stand development.
(A) The stem wood biomass production in tone dry matter per hector (t DM ha−1). (B) The net primary production in tone dry matter per hector (NPP, t ha−1 year−1). (C) Annual increment of ANR (kg N ha−1 year−1). (D) The current status of soil available N for growth in kg N per hector (soil available N, kg N ha−1). (E) Soil organic C (SOC, t C ha−1). Over the 120-year period coupling chronic levels of atmosphere N depositions of N4.9, N18, N30, N50, N70, and N90 with different rotation intervals (RL40, RL30, RL20, and RL15). RL40, RL30, RL20, and RL15 represent rotation cycles with intervals of 40, 30, 20, and15 years, respectively. N4.9 (black solid line) = 4.9 kg N ha−1 year−1, N18 (gray solid line) = 18 kg N ha−1 year−1, N30 (light gray solid line) = 30 kg N ha−1 year−1, N50 (black dash) = 50 kg N ha−1 year−1, N70 (gray dash) = 70 kg N ha−1 year−1, and N90 (light gray dash) = 90 kg N ha−1 year−1.
Figure 4.
The summary of simulated interactive effects of increased N deposition and short-rotation management over successive rotations.
It displays the accumulative statues, (A) Stem wood biomass at the end-of-rotation, and rotation-average values for flux or rates, (B) NPP and (C) ANR. RL40, RL30, RL20, and RL15 represent rotation cycles with intervals of 40, 30, 20, and 15 years, respectively. The effects of atmosphere N deposition levels: N4.9 (solid squares) = 4.9, N18 (hollow squares) = 18, N30 (solid upward triangles) = 30, N50 (hollow upward triangles) = 50, N70 (hollow leftward triangles) = 70, and N90 (hollow rightward triangles) = 90 kg N ha−1 year−1.
Figure 5.
The long-term (total 120-year period) summary of interactive effects of increased N deposition and short-rotation management over successive rotations.
It shows the sum of accumulative statues at the end-of-rotations, (A) stem wood biomass, and 120-year-average values for flux or rates, (B) NPP and (C) ANR.