Growth stage-dependant variability in water vapor and CO2 exchanges over a humid alpine shrubland on the northeastern Qinghai-Tibetan Plateau

NWIPB OpenIR

	Growth stage-dependant variability in water vapor and CO2 exchanges over a humid alpine shrubland on the northeastern Qinghai-Tibetan Plateau
	Li, Hongqin; Zhu, Jingbin; Zhang, Fawei; He, Huidan; Yang, Yongsheng; Li, Yingnian; Cao, Guangmin; Zhou, Huakun
	2019
发表期刊	AGRICULTURAL AND FOREST METEOROLOGY
卷号	268
摘要	Large uncertainties exist in carbon-water-climate feedbacks in cold regions, partly due to an insufficient understanding of the simultaneous effects of climatic and biotic controls on water and carbon dynamics. The 10-year growing season flux data were analyzed to evaluate the relative contributions of climatic and biotic effects on the variability of water vapor (ET) and net ecosystem CO2 (NEE) exchanges over a humid alpine deciduous shrubland on the northeastern Qinghai-Tibetan Plateau. The results showed that the alpine shrubland ecosystem acted as a water source and a carbon sink during the growing season, and its potential ET and NEE ranged from 161.4 mm and -41.0 g Cm-2 to 408.0 mm and -278.4 gCm(-2) at a 95% confidence interval, respectively. The average 8-day ET and NEE during the early growing season (June to July) were both significantly (P < 0.05) more than those of the late growing season (August to September). And the slopes of ET and NEE against the Julian day during the two growth stages also changed significantly (P < 0.01). Such asymmetric manners of ET and NEE during the two growth stages were probably related to the seasonal variations of net radiation (Rn) and vegetation growth (satellite-derived enhanced vegetation index: EVI), respectively. The structural equation models showed that the seasonal variations of 8-day ET were jointly determined by Rn and vapor pressure deficit (VPD), as partly indicated by a modest decoupling coefficient (0.54 +/- 0.03). The seasonal variability in 8-day NEE was controlled by the combinations of EVI and growing season degree days (GDD). The standardized coefficient of the direct effect of EVI on ET was 0.16, much less than the corresponding value (0.51) on NEE, suggesting that a weak coupling between ET and NEE arose likely because water vapor loss were about half controlled by surface evaporation, whereas CO2 flux were largely regulated by vascular plant activity. Our results highlighted the asymmetric sensitivities of ET and NEE during the early and the late growing season, and the weak coupling of water loss and carbon fixation during the whole growing season. These findings would provide a new sight to understand the growth stage-dependent responses of water budget and carbon sequestration to grazing management and climate change in humid alpine shrublands.
关键词	Net ecosystem CO2 exchange Evapotranspiration Biotic controls Structural equation models Eddy covariance techniques Humid alpine shrubland
文献类型	期刊论文
条目标识符	http://210.75.249.4/handle/363003/59815
专题	中国科学院西北高原生物研究所
推荐引用方式 GB/T 7714	Li, Hongqin,Zhu, Jingbin,Zhang, Fawei,et al. Growth stage-dependant variability in water vapor and CO2 exchanges over a humid alpine shrubland on the northeastern Qinghai-Tibetan Plateau[J]. AGRICULTURAL AND FOREST METEOROLOGY,2019,268.
APA	Li, Hongqin.,Zhu, Jingbin.,Zhang, Fawei.,He, Huidan.,Yang, Yongsheng.,...&Zhou, Huakun.(2019).Growth stage-dependant variability in water vapor and CO2 exchanges over a humid alpine shrubland on the northeastern Qinghai-Tibetan Plateau.AGRICULTURAL AND FOREST METEOROLOGY,268.
MLA	Li, Hongqin,et al."Growth stage-dependant variability in water vapor and CO2 exchanges over a humid alpine shrubland on the northeastern Qinghai-Tibetan Plateau".AGRICULTURAL AND FOREST METEOROLOGY 268(2019).