Driving Mechanism of Gross Primary Production Changes and Implications for Grassland Management on the Tibetan Plateau

doi:10.5814/j.issn.1674-764X.2019.05.002

Abstract

Abstract:

The contribution of climatic change and anthropogenic activities to vegetation productivity are not fully understood. In this study, we determined potential climate-driven gross primary production (GPPp) using a process-based terrestrial ecosystem model, and actual gross primary production (GPPa) using MODIS Approach in alpine grasslands on the Tibetan Plateau from 2000 to 2015. The GPPa was influenced by both climatic change and anthropogenic activities. Gross primary production caused by anthropogenic activities (GPPh) was calculated as the difference between GPPp and GPPa. Approximately 75.63% and 24.37% of the area percentages of GPPa showed increasing and decreasing trends, respectively. Climatic change and anthropogenic activities were dominant factors responsible for approximately 42.90% and 32.72% of the increasing area percentage of GPPa, respectively. In contrast, climatic change and anthropogenic activities were responsible for approximately 16.88% and 7.49% of the decreasing area percentages of GPPa, respectively. The absolute values of the change trends of GPPp and GPPh of meadows were greater than those of steppes. The GPPp change values were greater than those of GPPh at all elevations, whereas both GPPp and GPPh showed decreasing trends when elevations were greater than or equal to 5000 m, 4600 m and 4800 m in meadows, steppes and all grasslands, respectively. Climatic change had stronger effects on the GPPa changes when elevations were lower than 5000 m, 4600 m and 4800 m in meadows, steppes and all grasslands, respectively. In contrast, anthropogenic activities had stronger effects on the GPPa changes when elevations were greater than or equal to 5000 m, 4600 m and 4800 m in meadows, steppes and all grasslands, respectively. Therefore, the causes of actual gross primary production changes varied with elevations, regions and grassland types, and grassland classification management should be considered on the Tibetan Plateau.

Key words: alpine regions, elevation, grassland classification management, grassland types

SUN Wei, LI Meng, WANG Junhao, FU Gang. Driving Mechanism of Gross Primary Production Changes and Implications for Grassland Management on the Tibetan Plateau[J]. Journal of Resources and Ecology, 2019, 10(5): 472-480.

Figures/Tables 8

Fig. 1 Relationship between observed and simulated GPPa Note: GPPa: actual gross primary production

Slope comparison	Cause of GPPa change
Sa > 0 and abs(Sp) > abs(Sh)	GPPa increase mainly due to climatic change (ICC)
Sa > 0 and abs(Sp) < abs(Sh)	GPPa increase mainly due to human activities (IHA)
Sa < 0 and abs(Sp) > abs(Sh)	GPPa decrease mainly due to climatic change (DCC)
Sa < 0 and abs(Sp) < abs(Sh)	GPPa decrease mainly due to human activities (DHA)

Fig. 2 Interannual variations of GPPa, GPPp and GPPh Note: GPPa: actual gross primary production (GPP); GPPp: climate- driven potential GPP; GPPh: human-induced GPP; Sa: the anomaly of spatially averaged GPPa; Sp: the anomaly of spatially averaged GPPp; Sh: the anomaly of spatially averaged GPPh

Fig. 3 The change trends of (a) GPPa, (b) GPPp and (c) GPPh Note: GPPa: actual gross primary production (GPP); GPPp: climate-driven potential GPP; GPPh: human-induced GPP; Sa: the anomaly of spatially averaged GPPa; Sp: the anomaly of spatially averaged GPPp; Sh: the anomaly of spatially averaged GPPh.

Fig. 4 Spatial distribution of different drivers of alpine grassland GPP change Note: GPP: gross primary production; DCC: actual gross primary production (GPPa) decrease due to climatic change; DHA: GPPa decrease due to human activities; ICC: GPPa increase due to climatic change; IHA: GPPa increase due to human activities.

Fig. 5 Interannual variation of GPPa, GPPp and GPPh in (a) DCC, (b) DHA, (c) ICC and (d) IHA regions for meadows and steppes. Note: GPPa: actual gross primary production (GPP); GPPp: climate-driven potential GPP; GPPh: human-induced GPP; Sa: the anomaly of spatially averaged GPPa; Sp: the anomaly of spatially averaged GPPp; Sh: the anomaly of spatially averaged GPPh; DCC: actual gross primary production (GPPa) decrease due to climatic change; DHA: GPPa decrease due to human activities; ICC: GPPa increase due to climatic change; IHA: GPPa increase due to human activities.

	Steppes				Meadows
	DCC	DHA	ICC	IHA	DCC	DHA	ICC	IHA
Sa	-0.44	-0.55	1.89	0.67	-0.60	-0.80	1.68	1.20
Sp	-2.49	1.62	3.47	-1.69	-3.02	4.31	4.97	-2.18
Sh	-2.05	2.16	1.58	-2.36	-2.42	5.11	3.28	-3.38

Fig. 6 The change trends of actual Sa, Sp and Sh in (a) meadows and steppes, (b) meadows and (c) steppes. Note: Sa: the anomaly of spatially averaged actual gross primary production; Sp: the anomaly of spatially averaged climate-driven potential gross primary production; Sh: the anomaly of spatially averaged human-induced gross primary production.

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