Daily dynamics of CPC and CPC deficits at Qianyanzhou station from 2003 to 2010

<p><strong>Figure 1.</strong> Daily dynamics of CPC and CPC deficits at Qianyanzhou station from 2003 to 2010. Both the CPC curve (red line) and PCPC curve (black line) were algorithmically smoothed. The CPC deficits were the difference between the CPC and PCPC (blue area).</p> <p><strong>Abstract</strong></p> <p>Increasing occurrences of climate extreme events urge us to study their impacts on terrestrial carbon sequestration. Ecosystem potential productivity deficits could characterize such impacts and display the ecosystem vulnerability and resilience to the extremes in climate change, whereas few studies have analyzed the yearly dynamics of forest potential productivity deficits. Based on a perfect-deficit approach, we used <em>in situ</em> eddy covariance flux data and meteorological observation data at Qianyanzhou station from 2003 to 2010 to explore the relationship between potential productivity and climate extremes, such as droughts in 2003 and 2007, ice rain in 2005, and an ice storm in 2008. We found (1) the monthly canopy photosynthetic capacity (CPC) deficits could be mainly explained by air temperature (Ta) deficits (<em>R</em>² = 0.45, <em>p</em> < 0.000 01); (2) a significant correlation was noted between seasonal CPC deficits and co-current Ta deficits (<em>R</em>² = 0.45, <em>p</em> < 0.000 01), especially in winter (<em>R</em>² = 0.79, <em>p</em> = 0.003); (3) drought in summer exerted a negatively lagged effect on potential productivity (<em>R</em>² = 0.59, <em>p</em> = 0.02), but at a short time scale; and (4) annual CPC deficits captured the impacts of climate extremes on the forest ecosystem potential productivity, and the two largest potential productivity deficits occurred in 2003 (relative CPC deficits = 0.34) and in 2005 (relative CPC deficits = 0.35), respectively. With the perfect-deficit approach, the forest ecosystem vulnerability to extremes was analyzed in a novel way.</p

(a) Relative monthly CPC deficits versus relative monthly Ta deficits; (b) relative monthly CPC deficits in July; (c) relative monthly CPC deficits in February versus relative monthly Ta deficits in February; (d) relative CPC deficits in August versus water balance index (P/ET) in July

<p><strong>Figure 3.</strong> (a) Relative monthly CPC deficits versus relative monthly Ta deficits; (b) relative monthly CPC deficits in July; (c) relative monthly CPC deficits in February versus relative monthly Ta deficits in February; (d) relative CPC deficits in August versus water balance index (P/ET) in July.</p> <p><strong>Abstract</strong></p> <p>Increasing occurrences of climate extreme events urge us to study their impacts on terrestrial carbon sequestration. Ecosystem potential productivity deficits could characterize such impacts and display the ecosystem vulnerability and resilience to the extremes in climate change, whereas few studies have analyzed the yearly dynamics of forest potential productivity deficits. Based on a perfect-deficit approach, we used <em>in situ</em> eddy covariance flux data and meteorological observation data at Qianyanzhou station from 2003 to 2010 to explore the relationship between potential productivity and climate extremes, such as droughts in 2003 and 2007, ice rain in 2005, and an ice storm in 2008. We found (1) the monthly canopy photosynthetic capacity (CPC) deficits could be mainly explained by air temperature (Ta) deficits (<em>R</em>² = 0.45, <em>p</em> < 0.000 01); (2) a significant correlation was noted between seasonal CPC deficits and co-current Ta deficits (<em>R</em>² = 0.45, <em>p</em> < 0.000 01), especially in winter (<em>R</em>² = 0.79, <em>p</em> = 0.003); (3) drought in summer exerted a negatively lagged effect on potential productivity (<em>R</em>² = 0.59, <em>p</em> = 0.02), but at a short time scale; and (4) annual CPC deficits captured the impacts of climate extremes on the forest ecosystem potential productivity, and the two largest potential productivity deficits occurred in 2003 (relative CPC deficits = 0.34) and in 2005 (relative CPC deficits = 0.35), respectively. With the perfect-deficit approach, the forest ecosystem vulnerability to extremes was analyzed in a novel way.</p

Variation of relative monthly CPC deficits and relative monthly air temperature (Ta) deficits

<p><strong>Figure 2.</strong> Variation of relative monthly CPC deficits and relative monthly air temperature (Ta) deficits. CPC deficits monthly dynamics (black line) and Ta deficits monthly dynamics (blue line). Ta deficits were calculated by corresponding half-hourly meteorological data with the perfect-deficit approach. The relative deficits were the values of CPC and Ta deficits normalized by the total area of their perfect curve integrated over each month, respectively.</p> <p><strong>Abstract</strong></p> <p>Increasing occurrences of climate extreme events urge us to study their impacts on terrestrial carbon sequestration. Ecosystem potential productivity deficits could characterize such impacts and display the ecosystem vulnerability and resilience to the extremes in climate change, whereas few studies have analyzed the yearly dynamics of forest potential productivity deficits. Based on a perfect-deficit approach, we used <em>in situ</em> eddy covariance flux data and meteorological observation data at Qianyanzhou station from 2003 to 2010 to explore the relationship between potential productivity and climate extremes, such as droughts in 2003 and 2007, ice rain in 2005, and an ice storm in 2008. We found (1) the monthly canopy photosynthetic capacity (CPC) deficits could be mainly explained by air temperature (Ta) deficits (<em>R</em>² = 0.45, <em>p</em> < 0.000 01); (2) a significant correlation was noted between seasonal CPC deficits and co-current Ta deficits (<em>R</em>² = 0.45, <em>p</em> < 0.000 01), especially in winter (<em>R</em>² = 0.79, <em>p</em> = 0.003); (3) drought in summer exerted a negatively lagged effect on potential productivity (<em>R</em>² = 0.59, <em>p</em> = 0.02), but at a short time scale; and (4) annual CPC deficits captured the impacts of climate extremes on the forest ecosystem potential productivity, and the two largest potential productivity deficits occurred in 2003 (relative CPC deficits = 0.34) and in 2005 (relative CPC deficits = 0.35), respectively. With the perfect-deficit approach, the forest ecosystem vulnerability to extremes was analyzed in a novel way.</p

The relationship between relative CPC deficits in a specific month and P/ET in previous months

<p><b>Table 1.</b>  The relationship between relative CPC deficits in a specific month and P/ET in previous months. In general, summer droughts lasted from June to August, and we will focus only on the monthly CPC deficits in those three months. </p> <p><strong>Abstract</strong></p> <p>Increasing occurrences of climate extreme events urge us to study their impacts on terrestrial carbon sequestration. Ecosystem potential productivity deficits could characterize such impacts and display the ecosystem vulnerability and resilience to the extremes in climate change, whereas few studies have analyzed the yearly dynamics of forest potential productivity deficits. Based on a perfect-deficit approach, we used <em>in situ</em> eddy covariance flux data and meteorological observation data at Qianyanzhou station from 2003 to 2010 to explore the relationship between potential productivity and climate extremes, such as droughts in 2003 and 2007, ice rain in 2005, and an ice storm in 2008. We found (1) the monthly canopy photosynthetic capacity (CPC) deficits could be mainly explained by air temperature (Ta) deficits (<em>R</em>² = 0.45, <em>p</em> < 0.000 01); (2) a significant correlation was noted between seasonal CPC deficits and co-current Ta deficits (<em>R</em>² = 0.45, <em>p</em> < 0.000 01), especially in winter (<em>R</em>² = 0.79, <em>p</em> = 0.003); (3) drought in summer exerted a negatively lagged effect on potential productivity (<em>R</em>² = 0.59, <em>p</em> = 0.02), but at a short time scale; and (4) annual CPC deficits captured the impacts of climate extremes on the forest ecosystem potential productivity, and the two largest potential productivity deficits occurred in 2003 (relative CPC deficits = 0.34) and in 2005 (relative CPC deficits = 0.35), respectively. With the perfect-deficit approach, the forest ecosystem vulnerability to extremes was analyzed in a novel way.</p

Relationship between relative seasonal CPC deficits and relative seasonal Ta deficits

<p><strong>Figure 5.</strong> Relationship between relative seasonal CPC deficits and relative seasonal Ta deficits. (a) Relative deficits of all the 4 seasons; (b) relative deficits of winter.</p> <p><strong>Abstract</strong></p> <p>Increasing occurrences of climate extreme events urge us to study their impacts on terrestrial carbon sequestration. Ecosystem potential productivity deficits could characterize such impacts and display the ecosystem vulnerability and resilience to the extremes in climate change, whereas few studies have analyzed the yearly dynamics of forest potential productivity deficits. Based on a perfect-deficit approach, we used <em>in situ</em> eddy covariance flux data and meteorological observation data at Qianyanzhou station from 2003 to 2010 to explore the relationship between potential productivity and climate extremes, such as droughts in 2003 and 2007, ice rain in 2005, and an ice storm in 2008. We found (1) the monthly canopy photosynthetic capacity (CPC) deficits could be mainly explained by air temperature (Ta) deficits (<em>R</em>² = 0.45, <em>p</em> < 0.000 01); (2) a significant correlation was noted between seasonal CPC deficits and co-current Ta deficits (<em>R</em>² = 0.45, <em>p</em> < 0.000 01), especially in winter (<em>R</em>² = 0.79, <em>p</em> = 0.003); (3) drought in summer exerted a negatively lagged effect on potential productivity (<em>R</em>² = 0.59, <em>p</em> = 0.02), but at a short time scale; and (4) annual CPC deficits captured the impacts of climate extremes on the forest ecosystem potential productivity, and the two largest potential productivity deficits occurred in 2003 (relative CPC deficits = 0.34) and in 2005 (relative CPC deficits = 0.35), respectively. With the perfect-deficit approach, the forest ecosystem vulnerability to extremes was analyzed in a novel way.</p

Annual dynamics of relative CPC deficits at QYZ site

<p><strong>Figure 6.</strong> Annual dynamics of relative CPC deficits at QYZ site.</p> <p><strong>Abstract</strong></p> <p>Increasing occurrences of climate extreme events urge us to study their impacts on terrestrial carbon sequestration. Ecosystem potential productivity deficits could characterize such impacts and display the ecosystem vulnerability and resilience to the extremes in climate change, whereas few studies have analyzed the yearly dynamics of forest potential productivity deficits. Based on a perfect-deficit approach, we used <em>in situ</em> eddy covariance flux data and meteorological observation data at Qianyanzhou station from 2003 to 2010 to explore the relationship between potential productivity and climate extremes, such as droughts in 2003 and 2007, ice rain in 2005, and an ice storm in 2008. We found (1) the monthly canopy photosynthetic capacity (CPC) deficits could be mainly explained by air temperature (Ta) deficits (<em>R</em>² = 0.45, <em>p</em> < 0.000 01); (2) a significant correlation was noted between seasonal CPC deficits and co-current Ta deficits (<em>R</em>² = 0.45, <em>p</em> < 0.000 01), especially in winter (<em>R</em>² = 0.79, <em>p</em> = 0.003); (3) drought in summer exerted a negatively lagged effect on potential productivity (<em>R</em>² = 0.59, <em>p</em> = 0.02), but at a short time scale; and (4) annual CPC deficits captured the impacts of climate extremes on the forest ecosystem potential productivity, and the two largest potential productivity deficits occurred in 2003 (relative CPC deficits = 0.34) and in 2005 (relative CPC deficits = 0.35), respectively. With the perfect-deficit approach, the forest ecosystem vulnerability to extremes was analyzed in a novel way.</p

Seasonal dynamics of: (a) relative CPC deficits at QYZ station from 2003 to 2010; (b) mean relative CPC and Ta deficits

<p><strong>Figure 4.</strong> Seasonal dynamics of: (a) relative CPC deficits at QYZ station from 2003 to 2010; (b) mean relative CPC and Ta deficits. Error bars denote the standard deviation of deficits in each season. The subtropical coniferous forest ecosystem at Qianyanzhou station was divided into four seasons: spring (March, April and May); summer (June, July and August); autumn (September, October and November); winter (December, January and February) in regard to episodic summer drought attributable to the Asian monsoon climate.</p> <p><strong>Abstract</strong></p> <p>Increasing occurrences of climate extreme events urge us to study their impacts on terrestrial carbon sequestration. Ecosystem potential productivity deficits could characterize such impacts and display the ecosystem vulnerability and resilience to the extremes in climate change, whereas few studies have analyzed the yearly dynamics of forest potential productivity deficits. Based on a perfect-deficit approach, we used <em>in situ</em> eddy covariance flux data and meteorological observation data at Qianyanzhou station from 2003 to 2010 to explore the relationship between potential productivity and climate extremes, such as droughts in 2003 and 2007, ice rain in 2005, and an ice storm in 2008. We found (1) the monthly canopy photosynthetic capacity (CPC) deficits could be mainly explained by air temperature (Ta) deficits (<em>R</em>² = 0.45, <em>p</em> < 0.000 01); (2) a significant correlation was noted between seasonal CPC deficits and co-current Ta deficits (<em>R</em>² = 0.45, <em>p</em> < 0.000 01), especially in winter (<em>R</em>² = 0.79, <em>p</em> = 0.003); (3) drought in summer exerted a negatively lagged effect on potential productivity (<em>R</em>² = 0.59, <em>p</em> = 0.02), but at a short time scale; and (4) annual CPC deficits captured the impacts of climate extremes on the forest ecosystem potential productivity, and the two largest potential productivity deficits occurred in 2003 (relative CPC deficits = 0.34) and in 2005 (relative CPC deficits = 0.35), respectively. With the perfect-deficit approach, the forest ecosystem vulnerability to extremes was analyzed in a novel way.</p

Cumulative ET for each year of 2003–2010 respectively (panel a); cumulative ET averaged over the observation periods and its standard deviation (black line) and monthly variations in standard deviation (red line and the axis on right) (panel b).

<p>Cumulative ET for each year of 2003–2010 respectively (panel a); cumulative ET averaged over the observation periods and its standard deviation (black line) and monthly variations in standard deviation (red line and the axis on right) (panel b).</p

Air temperature (T_a °C) and growing season length (GSL, in days T_a≥5°C) during 2003–2010.

<p>Air temperature (T_a °C) and growing season length (GSL, in days T_a≥5°C) during 2003–2010.</p

Coefficient of variation (CV) of ET at flux sites with over 3 years' observations.

<p>Coefficient of variation (CV) of ET at flux sites with over 3 years' observations.</p