25 Jun 2024
 | 25 Jun 2024
Status: this preprint is open for discussion.

Causal relationships between vegetation productivity, water availability, and atmospheric dryness at the catchment scale

Guta Wakbulcho Abeshu, Hong-Yi Li, Mingjie Shi, and Ruby Leung

Abstract. This study explores the causal relationships between catchment water availability, vapor pressure deficit, and gross primary productivity across 341 catchments in the contiguous US. Seasonal climatic, hydrological, and vegetation characteristics were represented using the Horton index, ecological aridity index, evaporative fraction index, and carbon uptake efficiency. Statistical methods, including circularity statistics, correlation analysis, and causality tests, were employed to determine the complex interactions between catchment wetness, atmospheric dryness, and vegetation carbon uptake. The results revealed a maximum lag of two months in the intra-annual variability of catchment water supply-productivity and atmospheric water demand-productivity relationships, with hysteresis patterns varying with the catchment’s hydrological characteristics. In catchments not permanently under water-limited or energy-limited conditions, vegetation experiences hydrological stress during the peak growing period, coinciding with the highest gross primary productivity and carbon uptake efficiency being out of phase with Horton index and in phase with evaporative fraction index. Causality analysis highlights strong temporal continuity in GPP seasonal characteristics, with a cause-effect relationship between catchment water supply, atmospheric demand, and vegetation productivity spanning a maximum of two months. These findings underscore the need for a comprehensive functional framework that integrates catchment water supply, atmospheric demand, and vegetation productivity to enhance our understanding and predictive capabilities of ecosystem responses to climate change.

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Guta Wakbulcho Abeshu, Hong-Yi Li, Mingjie Shi, and Ruby Leung

Status: open (until 20 Aug 2024)

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  • RC1: 'Comment on egusphere-2024-1748', Anonymous Referee #1, 10 Jul 2024 reply
Guta Wakbulcho Abeshu, Hong-Yi Li, Mingjie Shi, and Ruby Leung
Guta Wakbulcho Abeshu, Hong-Yi Li, Mingjie Shi, and Ruby Leung


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Short summary
This study examined how water availability, climate dryness, and plant productivity interact at the catchment scale. Using various indices and statistical methods, it found a 0–2-month lag in these interactions. Strong correlations during peak productivity months were observed, with a notable hysteresis effect in vegetation response to changes in water availability and climate dryness. The findings help better understand catchment responses to climate variability.