Modeling effects of changes in diffuse radiation on light use efficiency in forest ecosystem Wei Nan 2018.05.04 1
Outline 1. Background 2. Material and methods 3. Results & Discussion 4. Conclusion 2
1 Background 3
Background Diffuse radiation Light use efficiency (LUE) (Gu et al., 2002; Law et al., 2002). Quantitative analysis of the effect of diffuse radiation on LUE needs to be further studied (He et al., 2011). Soil-Plant-Atmosphere Continuum (SPAC) multiple layers, separated into sunlit and shaded components (Williams et al., 1996). 4
Objectives Applying the modified light response model, we analyze the initial quantum efficiency and the capacity of a canopy to resist photosynthetic saturation at high levels of photosynthetically active radiation (PAR) under direct PAR and diffuse PAR in order to clarify the effects of diffuse PAR on photosynthetic characteristics of vegetation. Furthermore, we used Soil-Plant-Atmosphere Continuum (SPAC) model to simulate LUE in different layers of canopy and analyze the impacts of changes in diffuse radiation on LUE. 5
2 Material and methods 6
Experimental Sites Sites Landscape Latitude and Longitude Altitude (m) Annual mean temperature ( ) Annual rainfall mm) Broad leaved Korean pine forest of Changbai Mountain (CBS) 42 24 N, 128 6 E 784 3.5 695 Subtropical plantation coniferous forest at Qianyanzhou (QYZ) 26 44 N, 115 03 E 60-120 18 1179.1 Coniferous and subtropical broad-leaved mixed forest in Dinghushan (DHS) 23 10 N, 112 32 E 240 28 1956 7
Material 2003-2008 30-min CO 2 flux data Routine meteorological data (S 0, PAR, T a, T s, VPD, Wspd, PAR, Rain et al.) 站点 地形 通量观测高度 (m) 辐射观测高度 ( 两层 ) (m) 降水观测高度 (m) 温度和相对湿度观测高度 (m) 土壤温度测定深度 ( 五层 ) (m) 土壤水分测定深度 ( 三层 ) (m) CBS 平坦 40 32, 2 70 2.5, 8.0, 22.0, 26.0, 32.0, 50.0, 61.8 0.05, 0.10, 0.20, 0.50, 1.0 0.05, 0.2, 0.5 QYZ 丘陵 39 42, 2 42 1.6, 7.6, 11.6, 15.6, 23.5, 31.6, 39.6 0.02, 0.05, 0.20, 050, 1.0 0.05, 0.2, 0.5 DHS 山地 27 36, 2 36 4.0, 9.0, 15.0, 21.0, 27.0, 31.0, 36.0 0.05, 0.10, 0.20, 0.50, 1.0 0.05, 0.2, 0.4 8
Light use efficiency (LUE): (1) (2) where GPP is ecosystem gross primary productivity, mg CO 2 m -2 s -1 ; PAR is photosynthetic active radiation, μmol m -2 s -1. APAR represents the total amount of photosynthetic effective radiation absorbed by the ecosystem leaves (μmol m - 2 s - 1 ). (3) R e =R ref e E 0 (1/ (T ref T 0 ) 1/ (T s T 0 )) (4) 9
Clearness index, k t : k t = S 0 S e S e =S sc [1+0.033cos 2 (360t d /365)]sinh (5) (6) Diffuse radiation: 0 k S k t 0.3; Sf / S f / Se = kt (1.020 0.254kt + 0.0123sinh) 0.3< kt < 0.78; 0.1k t Sf / Se 0.97k t S S = k (1.400 1.749k 0.177sin h) f / e t t + kt Sf / Se 0.1 Sf / Se = kt (0.486k t 0.78; k e t t 0.182sin h) (7) (8) (9) (10) (11) (12) 10
Light Responsive Curve Models NEE= αparβ αpar R e (13) NEE= (α f I f+α r I r ) (β f I f +β r I r ) (β f I f +β r I r )+ (α f I f +α r I r )I t R e (14) where α f (mgco 2 μmol -1 photon) and α r are the initial canopy quantum yield for diffuse (I f ) and direct (I r ) PAR, respectively, and β f (mgco 2 m 2 s 1 ) and β r are the capacity of a canopy to resist photosynthetic saturation at high levels of PAR for diffuse and direct PAR, respectively. (Gu et al., 2002) 11
SPAC model 12
Input parameters Table2-1 Layers of canopy in SPAC Canopy layers site 1 2 3 4 5 6 7 8 9 10 la_frac CBS/QYZ 0.02 0.02 0.02 0.13 0.13 0.14 0.14 0.12 0.12 0.12 3 7 7 4 4 5 5 2 2 2 nit_frac CBS/QYZ 0.02 0.02 0.02 0.13 0.13 0.14 0.14 0.12 0.12 0.12 3 7 7 4 4 5 5 2 2 2 CBS 26.5 24.5 22.5 20.5 18.5 16.5 14.5 12.5 10.5 8.5 ht(m) QYZ 12 11 10 9 8 7 6 5 4 3 Table2-2 Layers of soil in SPAC in CBS Soil layers 1 2 3 4 5 6 core Layer_thickness(m) 0.1 0.1 0.1 0.1 0.1 0.1 0.1 Organic_fraction 0.34 0.12 0.12 0.08 0.08 0.08 0.08 Mineral_fraction 0.1 0.2 0.2 0.3 0.4 0.45 1 Initial_water_fraction 0.3 0.3 0.3 0.3 0.3 0.3 0.3 Initial_soil_temp (K) 289 288 287 286 285 284 283 rootfrac 0.412 0.277 0.186 0.125 0 0 0 13
Soil layers 1 2 3 4 5 6 7 8 9 10 core Layer_thickness(m) 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 Organic_fraction 0.34 0.34 0.34 0.12 0.12 0.12 0.08 0.08 0.08 0.08 0.08 Mineral_fraction 0.1 0.2 0.2 0.3 0.3 0.4 0.45 0.45 0.45 0.45 1 Initial_water_fraction 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 Initial_soil_temp (K) 300 299 298 297 296 295 294 293 292 291 290 rootfrac 0.38 0.26 0.17 0.12 0.08 0 0 0 0 0 0 Parameters Input values CBS QYZ Source totla (m 2 m -2 ) 5.5 4.5 observed value totn (gn m -2 ) 1.4 6.3 observed value gplant (mol m -1 s -1 MPa -1 ) 10 10 Default value minlwp(mpa) -1.5-2.5 Optimal value iota(n/a) 1.01 1.01 Optimal value capac(mol m -2 MPa -1 ) 5000 3000 Optimal value rootresist(mpa s g mol -1 (biomass based)) Table2-3 Layers of soil in SPAC in QYZ Table2-4 Parameters of vegetation in SPAC 300 150 Optimal value kappac(mol g -1 s -1 ) 46 50 literature(zhang,2006) kappaj(mmol g -1 s -1 ) 71 88 literature(zhang,2006) 14
3 Results & Discussion 15
光能利用率 (gco 2 mol -1 photon) 气温 ( ) 饱和水气压差 (kpa) Environmental factors : 30 20 10 0-10 -20 CBS QYZ DHS 2 4 6 8 10 12 月份 1.8 1.5 1.2 0.9 0.6 0.3 0.0 CBS QYZ DHS 2 4 6 8 10 12 月份 1.25 1.00 0.75 0.50 0.25 CBS QYZ DHS CBS 趋势线 R 2 =-0.1 P=0.5 QYZ 趋势线 R 2 =0.3 P=0.2 DHS 趋势线 R 2 =0.2 P=0.2 2003 2004 2005 2006 2007 2008 年份 16
光能利用率 (gco 2 mol -1 ) 光能利用率 (gco 2 mol -1 ) 光能利用率 (gco 2 mol -1 ) The variation of LUE in forest ecosystem with the ratio of diffuse radiation to global solar radiation: 4 3 R 2 =0.61 P<0.05 2006 年 CBS 4 3 R 2 =0.60 P<0.05 2006 年 QYZ 4 3 R 2 =0.50 P<0.05 2006 年 DHS 2 2 2 1 1 1 0 0.2 0.4 0.6 0.8 1.0 散射辐射占总辐射的比例 0 0.2 0.4 0.6 0.8 1.0 散射辐射占总辐射的比例 0 0.2 0.4 0.6 0.8 1.0 散射辐射占总辐射的比例 The increase of LUE in the ratio of diffuse radiation to global solar radiation (S f / S 0 ) range of 70% to 85% than that in the S f / S 0 range of 55% to 70%: 2003 2004 2005 2006 2007 2008 CBS 19.7% 3.9% 6.6% 21.9% 16.5% 15.6% QYZ 6.3% 12.8% 13.2% -0.7% 29.3% -0.5% DHS 13.0% 23.1% -3.6% 11.7% 32.2% 19.7% 17
初始量子效率 (gco 2 mol -1 ) 光饱和时最大潜在光合速率 (mgco 2 m -2 s -1 ) 净生态系统生产力 NEE(mg CO 2 m -2 s -1 ) Photosynthetic efficiency of three typical forest ecosystems under cloudy and clear sky conditions and direct and diffuse radiation conditions: CBS 2 多云条件晴空条件多云条件下的拟合曲线 R 1 2 =0.62 P<0.05 晴空条件下的拟合曲线 R 2 =0.49 P<0.05 0-1 6 r 5 4 3 2 1 f CBS 2006 年 -2 0 500 1000 1500 2000 光合有效辐射 PAR( mol m -2 s -1 ) 5 4 3 2 1 r f CBS 2006 年 0 6/5 6/25 7/15 8/4 8/24 日期 0 6/5 6/25 7/15 8/4 8/24 日期 18
初始量子效率 (gco 2 mol -1 ) 光饱和时最大潜在光合速率 (mgco 2 m -2 s -1 ) 初始量子效率 (gco 2 mol -1 ) 净生态系统生产力 NEE(mg CO 2 m -2 s -1 ) RESEARCH RESULTS 2 多云条件晴空条件多云条件下的拟合曲线 1 R 2 =0.56 P<0.05 晴空条件下的拟合曲线 R 2 =0.42 P<0.05 0 QYZ 6 5 4 3 2 1 r f QYZ 2006 年 -16 r 5 f QYZ 2003 年 -2 40 500 1000 1500 2000 光合有效辐射 PAR( mol m -2 s -1 ) 3 2 1 5 0 6/5 6/25 7/15 4 8/4 8/24 日期 3 2 1 r f QYZ 2006 年 0 6/5 6/25 7/15 8/4 8/24 日期 0 6/5 6/25 7/15 8/4 8/24 日期 19
初始量子效率 (gco 2 mol -1 ) 光饱和时最大潜在光合速率 (mgco 2 m -2 s -1 ) 净生态系统生产力 NEE(mg CO 2 m -2 s -1 ) DHS 6 5 4 3 2 1 r f 2 1 0 多云条件晴空条件多云条件下的拟合曲线 R 2 =0.53 P<0.05 晴空条件下的拟合曲线 R 2 =0.62 P<0.05 The initial -1 quantum efficiency under diffuse PAR condition (α f ) is higher than that (α r ) under direct PAR condition by averaged 0.29-2 g CO 0 500 2 mol -1 photon, 0.26gCO 1000 1500 2000 2 mol -1 photon and 0.31gCO 2 mol光合有效辐射 -1 photon in PAR( mol m CBS, QYZ -2 and s -1 ) DHS respectively without drought stress from June to August from 2003 to 2008. Compared with diffuse PAR condition, 5 the capacity of canopy to r resist photosynthetic saturation at high levels of PAR (β f ) is DHS 2006 more DHS 2006 年年 than that (β r ) under direct PAR condition in CBS, QYZ, and DHS by averaged about 0.4 mg 3 CO 2 m -2 s -1 approximately during study period. 4 2 1 f 0 6/5 6/25 7/15 8/4 8/24 日期 0 6/5 6/25 7/15 8/4 8/24 日期 20
生态系统总初级生产力 GPP(mgCO 2 m -2 s -1 ) GPP 模拟值 (mgco 2 m -2 s -1 ) 生态系统总初级生产力 GPP(mgCO 2 m -2 s -1 ) GPP 模拟值 (mgco 2 m -2 s -1 ) The comparison between the simulated and measured GPP: CBS 2.5 2.0 GPP 观测值 GPP 模拟值 CBS 2006 年 2.0 1.5 y=1.02x R 2 =0.86 P<0.05 CBS 2006 年 0.0 150 160 170 180 190 200 210 220 230 240 日序 2.5 2.0 1.5 1.0 0.5 1.5 1.0 0.5 QYZ GPP 模拟值 GPP 观测值 QYZ 2006 年 0.0 150 160 170 180 190 200 210 220 230 240 日序 1.0 0.5 0.0 0.0 0.5 1.0 1.5 2.0 GPP 观测值 (mgco 2 m -2 s -1 ) 2.0 y=1.2x R 2 =0.68 P<0.05 1.5 1.0 0.5 QYZ 2006 年 0.0 0.0 0.5 1.0 1.5 2.0 GPP 观测值 (mgco 2 m -2 s -1 ) 21
RESEARCH RESULTS Assessment index between simulated and observed values for GPP Year r R 2 RMSE (mgco 2 m -2 s -1 ) MBE (mgco 2 m -2 s -1 ) CBS QYZ CBS QYZ CBS QYZ CBS QYZ CBS QYZ NS 2004 0.74 0.64 0.3 0.15 0.3 0.43 0.06 0.07 0.49 0.96 2005 0.79 0.8 0.44 0.5 0.29 0.31 0.09 0.12 0.99 0.98 2006 0.8 0.83 0.45 0.52 0.26 0.31 0.09 0.08 0.95 0.85 2007 0.76 0.81 0.42 0.47 0.31 0.31 0.16 0.08 0.99 0.87 2008 0.76 0.82 0.39 0.49 0.3 0.29 0.12 0.07 0.02 0.99 22
Sensitivity of SPAC model parameters parameters effect on GPP when ±10% bias is applied (CBS) effect on GPP when ±10% bias is applied (QYZ) parameters effect on GPP when ±10% bias is applied (CBS) effect on GPP when ±10% bias is applied (QYZ) iota(n/a) 43.60% 19.40% VPD(kpa) 2.80% 3.40% CO 2 (ppm) 12.80% 12.80% capac(mol m-2 MPa-1) 1.80% 0.50% minlwp(mpa) 6.50% 3.10% Dimen(m) 0.80% 0.20% fdiff (μmol m-2 s-1) 5.00% 4.40% WSPD(m/s) 0.40% 0.10% PAR(μmol m-2 s-1) 4.20% 5.30% kappac(mol g-1 s-1) 0.30% 1.70% T( ) 3.80% 11.70% lai(m m-2) 2.50% 4.40% rootresist(mpa s g mol-1 (biomass based)) kappaj(mmol g-1 s-1) 3.00% 2.90% gplant(mol m-1 s-1 MPa-1) 3.70% 2.20% N 8.20% 4.90% 0.10% 2.90% Initial_water_fracti on 0.80% 3.80%
Uncertainty analysis and relative error contribution of parameters of SPAC model parameters parameters effect on GPP by situ uncertainty (CBS) Relative error contribution (CBS) effect on GPP by situ uncertainty (QYZ) Relative error contribution (QYZ) PAR(μmol m -2 s -1 ) 39.8% 39.2% 34.3% 39.9% fdiff (%) 31.6% 39.5% 27.1% 4.0% CO 2 (ppm) 17.4% 0.1% 7.2% 3.3% VPD(kpa) 9.9% 68.4% 3.4% 40.8% minlwp(mpa) 6.5% 5.8% 3.1% 0.1% iota(n/a) 3.9% 37.4% 1.7% 68.2% T( ) 3.9% 0.5% 11.2% 3.6% rootresist(mpa s g mol -1 3.7% 2.0% 2.2% 0.5% (biomass based)) kappaj(mmol g -1 s -1 ) 3.0% 2.4% 2.9% 4.7% capac(mol m -2 MPa -1 ) 1.8% 0.4% 0.5% 0.03% WSPD(m/s) 1.7% 5.6% 0.3% 8.7% lai 17.7% 38.6% 1.1% 102.9% N 22.9% 6.2% 34.9% 23.7% Initial_water_fraction 6.3% 24.1% 10.0% 87.4% Dimen (m) 0.8% 0.06% 0.2% 2.7% kappac(mol g -1 s -1 ) 0.3% 4.0% 1.7% 0.3% gplant(mol m -1 s -1 MPa -1 ) 0.1% 0.2% 0.1% 0.05% 24
The results of the ten layers LUE (gco 2 mol -1 photon)in CBS Layers 2006 2007 2008 June July August June July August June July August 1 0.03 0.02 0.05 0.02 0.04 0.05 0.02 0.04 0.04 2 0.04 0.03 0.05 0.03 0.04 0.06 0.02 0.04 0.05 3 0.04 0.03 0.05 0.03 0.05 0.06 0.02 0.04 0.05 4 0.23 0.16 0.29 0.17 0.27 0.32 0.15 0.26 0.27 5 0.28 0.2 0.30 0.20 0.31 0.33 0.18 0.30 0.29 6 0.34 0.26 0.33 0.25 0.39 0.36 0.24 0.37 0.31 7 0.37 0.31 0.32 0.29 0.42 0.35 0.28 0.40 0.30 8 0.32 0.28 0.25 0.26 0.36 0.28 0.25 0.34 0.24 9 0.31 0.28 0.22 0.27 0.35 0.26 0.24 0.33 0.21 10 0.29 0.25 0.19 0.26 0.32 0.27 0.23 0.30 0.18 Entire canopy 0.17 0.14 0.18 0.14 0.20 0.20 0.13 0.19 0.17
The results of the ten layers LUE (gco 2 mol -1 photon)in QYZ Layers 2006 2007 2008 June July August June July August June July August 1 0.04 0.03 0.04 0.06 0.01 0.04 0.07 0.04 0.04 2 0.05 0.04 0.05 0.07 0.02 0.05 0.08 0.05 0.05 3 0.05 0.04 0.05 0.07 0.02 0.05 0.08 0.05 0.05 4 0.29 0.23 0.26 0.46 0.12 0.28 0.42 0.27 0.24 5 0.31 0.28 0.26 0.53 0.14 0.28 0.42 0.29 0.24 6 0.35 0.34 0.27 0.60 0.18 0.28 0.45 0.33 0.25 7 0.34 0.34 0.25 0.55 0.20 0.24 0.43 0.34 0.23 8 0.27 0.28 0.18 0.41 0.16 0.17 0.33 0.27 0.18 9 0.25 0.25 0.16 0.35 0.15 0.14 0.30 0.26 0.16 10 0.22 0.22 0.14 0.28 0.14 0.12 0.27 0.23 0.13 Entire canopy 0.19 0.17 0.15 0.27 0.10 0.15 0.23 0.15 0.15 26
Increasing proportion of the ten layers LUE when the diffuse radiation increased by 10% in CBS Layers 2006 2007 2008 June July August June July August June July August 1 15.7% 10.3% 15.5% 6.5% 14.1% 17.0% 4.0% 11.2% 13.0% 2 15.8% 10.3% 15.7% 6.6% 14.3% 17.1% 4.2% 11.5% 13.1% 3 15.9% 10.4% 15.9% 6.8% 14.4% 17.3% 4.4% 11.6% 13.2% 4 16.3% 11.1% 16.2% 7.5% 14.7% 17.6% 4.9% 12.0% 13.5% 5 17.2% 12.1% 16.7% 8.8% 15.8% 17.9% 6.3% 13.0% 14.0% 6 18.3% 13.2% 17.3% 10.4% 16.9% 18.3% 8.0% 14.2% 14.5% 7 19.4% 14.7% 18.0% 12.1% 18.2% 18.8% 10.1% 15.5% 15.4% 8 20.2% 16.3% 18.9% 13.7% 19.3% 19.8% 12.0% 16.6% 16.2% 9 21.2% 17.9% 19.4% 15.2% 20.3% 20.4% 13.8% 17.9% 17.0% 10 22.1% 19.0% 20.2% 16.8% 21.4% 21.2% 15.4% 18.9% 17.6% Entire canopy 17.4% 25.3% 16.2% 11.2% 22.1% 17.1% 8.7% 16.2% 13.5% 27
Increasing proportion of the ten layers LUE when the diffuse radiation increased by 10% in QYZ Layers 2006 2007 2008 June July August June July August June July August 1 14.0% 2.9% 10.1% 11.8% -1.0% 10.2% 21.3% 5.3% 10.5% 2 14.1% 3.0% 10.2% 11.8% -0.2% 10.3% 21.3% 5.4% 10.6% 3 14.0% 3.2% 10.2% 12.2% 0.0% 10.4% 21.3% 5.5% 10.6% 4 14.2% 3.9% 10.5% 13.3% 0.0% 10.6% 21.4% 5.9% 10.8% 5 14.5% 6.2% 10.9% 14.7% 3.1% 11.0% 21.4% 7.0% 11.1% 6 14.7% 7.8% 11.1% 16.6% 4.5% 11.3% 21.5% 8.7% 11.3% 7 14.7% 9.4% 11.3% 18.0% 6.6% 11.5% 21.3% 9.7% 11.4% 8 14.6% 10.4% 11.5% 19.4% 7.7% 11.9% 21.2% 10.8% 11.5% 9 14.4% 11.3% 11.7% 20.4% 8.7% 12.4% 21.2% 11.2% 11.8% 10 14.3% 12.2% 11.9% 23.5% 9.6% 12.9% 20.9% 11.7% 11.8% Entire canopy 14.6% 6.5% 11.1% 14.7% 3.6% 11.3% 21.6% 7.9% 11.3% 28
The change of the LUE for entire canopy when the diffuse radiation increased by 10% For the entire canopy, the gross primary productivity (GPP) and LUE increase respectively by average of 2.8 % and 11.4 % from June to August from 2006 to 2008 in QYZ. For the entire canopy, the gross primary productivity (GPP) and LUE increase respectively by average of 3.4 % and 16.4 % from June to August from 2006 to 2008 in CBS. 29
4 Conclusion 30
Conclusion (1)The increase of diffuse radiation fraction in global solar radiaton can enhance light use efficiency (LUE) in CBS, QYZ and DHS. (2)The diffused PAR can enhance LUE than the direct PAR under weak light conditions without air temperature and water stress. The diffuse PAR was more benefit to improve the photosynthetic capacity of forest ecosystem compared to direct radiation. (3)When the other environmental factors kept normal daily variation and the diffuse radiation in global solar radiation increased by 10 %, for the entire canopy, the gross primary productivity (GPP) and LUE increase by average of 3.4 % and 16.4 % in CBS, and GPP and LUE increase by average of 2.8 % and 11.4 % in QYZ, respectively. 31
Thank you for your attention! 32