Effect of diffuse radiation on gross primary productivity of typical planted forests in eastern China

doi:10.17521/cjpe.2021.0416

Abstract

Abstract:

Aims Diffuse radiation is one of the important factors affecting forest carbon uptake. However, the response of gross primary productivity (GPP) of planted forest ecosystems to diffuse radiation in China is still unclear. We explored the effects of diffuse radiation on GPP at 6 plantation ecosystems in eastern China during the growing season.

Methods Based on carbon flux data and meteorological data during the growing season of 2019-2020, we estimated the diffuse radiation and identified the direct and diffuse conditions. The important light response parameters of plantation ecosystems were obtained by the rectangular hyperbolic curve. Meanwhile, we quantified the variations of GPP responding to diffuse and direct radiation. The contribution of light and environmental factors to the diurnal variation of GPP was analyzed by partial correlation method.

Important findings Diffuse radiation can effectively promote canopy photosynthesis. The values of light response parameter canopy quantum efficiency (α) and photosynthesis at photosynthetically active radiation of 1 000 µmol·m^-2·s^-1 (P₁₀₀₀)increased by 47%-150% and 2%-65%, respectively. Compared with direct sky conditions, GPP increased by 0.86%-1.70% in response to 1 μmol·m^-2·s^-1 enhancement of photosynthetically active radiation (PAR) under diffuse sky conditions, which was affected by forest type and vegetation phenology. In diffuse skies, the increment of the variation of GPP under increasing per unit PAR (0.86%-1.00%) at Pinus sylvestrisvar. mongolica and P. tabuliformissites with lower normalized difference vegetation index (NDVI) value was significantly lower than other plantation sites (1.04%-1.70%), and there was a significant positive correlation between NDVI and P₁₀₀₀. Under low light level, PAR controlled the averaged gross primary productivity (GPP_a), but diffuse fraction (DF) mainly regulated GPP_ain middle and high light level. The photosynthesis corresponding to diffuse radiation under moderate light was roughly equal to photosynthesis corresponding to total radiation under high light. Under middle light conditions, the GPP_a value in medium and high DF (≥0.5) at Cunninghamia lanceolata, Populusspp., Quercus variabilis and Larix gmeliniiwas about 27%-50% higher than under low DF condition (<0.5), and the GPP_a value at high DF was about 2% more than under low DF conditions at Pinus sylvestrisvar. mongolica and P. tabuliformis sites. Under diffuse radiation conditions, diffuse photosynthetically active radiation (PAR_dif) explained 16%-45% of the variation of GPP. Air temperature (T_a) and vapor pressure deficit (VPD) explained 10%-19% of the variation of GPP at Cunninghamia lanceolata, Quercus variabilis and Larix gmelinii sites. Under diffuse radiation conditions, the P₁₀₀₀ will be the highest when T_a is 15-25 °C and VPD is 0-1 kPa.

Key words: plantation, diffuse radiation, gross primary productivity, vapor pressure deficit

LIU Pei-Rong, TONG Xiao-Juan, MENG Ping, ZHANG Jin-Song, ZHANG Jing-Ru, YU Pei-Yang, ZHOU Yu. Effect of diffuse radiation on gross primary productivity of typical planted forests in eastern China[J]. Chin J Plant Ecol, 2022, 46(8): 904-918.

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URL: https://www.plant-ecology.com/EN/10.17521/cjpe.2021.0416

https://www.plant-ecology.com/EN/Y2022/V46/I8/904

Figures/Tables 12

Table 1 Description of flux sites of six typical planted forests in eastern China

站点 Site	位置 Location	海拔 Elevation (m)	树种 Species	冠层高度 Canopy height (m)	生长季 Growing season (Month)	土壤类型 Soil type	开路红外分析仪 Open-path infrared gas analyzer	三维超声风速仪 3-D sonic anemometer	仪器高度 Height of instrument (m)
金寨 Jinzhai	31.28° N, 115.68° E	1 100	杉木 Cunninghamia lanceolata	9.0	4-10	砂壤土 Sandy loam	LI-7500	CSAT3	18
民权 Minquan	34.72° N, 115.08° E	100	杨树 Populus spp.	17.0	4-9	砂壤土 Sandy loam	LI-7500	CSAT3	34
济源 Jiyuan	35.02° N, 112.47° E	410	栓皮栎 Quercus variabilis	12.5	4-10	棕壤土 Brown loam	LI-7500	CSAT3	25
黑水₁Heishui₁	41.97° N, 119.42° E	550	樟子松 Pinus sylvestris var. mongolica	10.0	6-9	灰棕壤 Grey brown earths	LI-7500	CSAT3	20
塞罕坝 Saihanba	42.30° N, 117.42° E	1 700	落叶松 Larix gmelinii	9.0	5-9	棕壤土 Brown loam	LI-7500	CSAT3	18
黑水₂Heishui₂	42.10° N, 119.48° E	650	油松 Pinus tabuliformis	8.0	6-9	灰棕壤 Grey brown earths	LI-7500	CSAT3	16

Fig. 1 Monthly variations of photosynthetically active radiation (PAR), vapor pressure deficit (VPD), air temperature (Ta), precipitation (P) and normalized difference vegetation index (NDVI) during growing season of typical planted forests in eastern China (mean ± SD). A, Cunninghamia lanceolata forest. B, Populus spp. forest. C, Quercus variabilis forest. D, Pinus sylvestris var. mongolica forest. E, Larix gmelinii forest. F, Pinus tabuliformis forest.

Fig. 2 Relationship between photosynthetically active radiation (PAR), diffuse photosynthetically active radiation (PARdif), direct photosynthetically active radiation (PARdir) and diffuse fraction (DF) at midday period (10:00-15:00) in growing season of typical planted forests in eastern China (mean ± SD). A, Cunninghamia lanceolata forest. B, Populus spp. forest. C, Quercus variabilis forest. D, Pinus sylvestris var. mongolica forest. E, Larix gmelinii forest. F, Pinus tabuliformis forest.

Fig. 3 Frequency distribution of diffuse fraction (DF) in growing season of typical planted forests in eastern China. A, Cunninghamia lanceolata forest. B, Populus spp. forest. C, Quercus variabilis forest. D, Pinus sylvestris var. mongolica forest. E, Larix gmelinii forest. F, Pinus tabuliformis forest.

Fig. 4 Diurnal variation of diffuse fraction (DF) during growing season of typical planted forests in eastern China (mean ± SD). A, Cunninghamia lanceolata forest. B, Populus spp. forest. C, Quercus variabilis forest. D, Pinus sylvestris var. mongolica forest. E, Larix gmelinii forest. F, Pinus tabuliformis forest.

Fig. 5 Relationship between gross primary productivity (GPP) and photosynthetically active radiation (PAR) under different radiation conditions of typical planted forests in eastern China (mean ± SD). GPP is 0.5 h averaged for every 100 μmol·m-2·s-1 of PAR. A, Cunninghamia lanceolata forest. B, Populus spp. forest. C, Quercus variabilis forest. D, Pinus sylvestris var. mongolica forest. E, Larix gmelinii forest. F, Pinus tabuliformis forest.

Table 2 Under different radiation conditions, canopy quantum efficiency (α), maximum canopy photosynthesis (Pmax) and gross primary productivity at high photosynthetically active radiation of 1 000 µmol·m-2·s-1 (P1000) of typical planted forests in eastern China

人工林 Plantation	辐射条件 Radiation condition	α	P_max(mg·m²·s^-1)	P₁₀₀₀(mg·m²·s^-1)	决定系数 Coefficient of determination	样本数 Number of samples
杉木 Cunninghamia lanceolata	散射辐射 Diffuse radiation condition	0.045	1.94	0.70	0.61	3 611
杉木 Cunninghamia lanceolata	直接辐射 Direct radiation condition	0.020	1.97	0.61	0.45	891
杨树 Populus spp.	散射辐射 Diffuse radiation condition	0.024	1.57	0.48	0.52	5 000
杨树 Populus spp.	直接辐射 Direct radiation condition	0.011	0.49	0.24	0.35	649
栓皮栎 Quercus variabilis var. mongolica	散射辐射 Diffuse radiation condition	0.020	1.44	0.42	0.44	5 042
栓皮栎 Quercus variabilis var. mongolica	直接辐射 Direct radiation condition	0.008	1.44	0.29	0.33	1 270
樟子松 Pinus sylvestris	散射辐射 Diffuse radiation condition	0.026	0.78	0.32	0.42	1 636
樟子松 Pinus sylvestris	直接辐射 Direct radiation condition	0.015	0.52	0.29	0.35	943
华北落叶松 Larix gmelinii	散射辐射 Diffuse radiation condition	0.021	2.37	0.55	0.56	1 705
华北落叶松 Larix gmelinii	直接辐射 Direct radiation condition	0.013	1.65	0.43	0.59	679
油松 Pinus tabuliformis	散射辐射 Diffuse radiation condition	0.025	1.00	0.38	0.53	1 841
油松 Pinus tabuliformis	直接辐射 Direct radiation condition	0.017	0.73	0.37	0.39	951

Fig. 6 Response of gross primary productivity to changes in per photosynthetically effective radiation under different radiation conditions of typical planted forests in eastern China. A, Cunninghamia lanceolata forest. B, Populus spp. forest. C, Quercus variabilis forest. D, Pinus sylvestris var. mongolica forest. E, Larix gmelinii forest. F, Pinus tabuliformis forest.

Fig. 7 Relationship between gross primary productivity at high photosynthetically active radiation of 1 000 µmol·m-2·s-1 (P1000) and normalized difference vegetation index (NDVI) under diffuse sky radiation conditions of typical planted forests in eastern China. A, Cunninghamia lanceolata forest. B, Populus spp. forest. C, Quercus variabilis forest. D, Pinus sylvestris var. mongolica forest. E, Larix gmelinii forest. F, Pinus tabuliformis forest.

Fig. 8 Relationship among average gross primary productivity (GPPa), diffuse radiation fraction (DF) and photosynthetically effective radiation (PAR) of typical planted forests in eastern China. The region with no data in upper right indicates that there cannot be high magnitudes of PAR at high levels of DF because diffuse radiation reduces the magnitude of PAR. A, Cunninghamia lanceolata forest. B, Populus spp. forest. C, Quercus variabilis forest. D, Pinus sylvestris var. mongolica forest. E, Larix gmelinii forest. F, Pinus tabuliformis forest.

Fig. 9 Under diffuse conditions, diurnal variation of gross primary productivity (GPP) explained by diffuse photosynthetically active radiation (PARdif), temperature (Ta) and vapor pressure difference (VPD) of typical planted forests in eastern China. A, Cunninghamia lanceolata forest. B, Populus spp. forest. C, Quercus variabilis forest. D, Pinus sylvestris var. mongolica forest. E, Larix gmelinii forest. F, Pinus tabuliformis forest.

Fig. 10 Under diffuse conditions, effects of temperature (Ta) and vapor pressure difference (VPD) on gross primary productivity at high photosynthetically active radiation of 1 000 µmol·m-2·s-1 (P1000) of typical planted forests in eastern China. A, Cunninghamia lanceolata forest. B, Populus spp. forest. C, Quercus variabilis forest. D, Pinus sylvestris var. mongolica forest. E, Larix gmelinii forest. F, Pinus tabuliformis forest.

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