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Drought dominates the interannual variability in global terrestrial net primary production by controlling semi-arid ecosystems.

Huang L, He B, Chen A, Wang H, Liu J, Lű A, Chen Z - Sci Rep (2016)

Bottom Line: Drought-dominated NPP, which mainly occurs in semi-arid ecosystems, explains 29% of the interannual variation in global NPP, despite its 16% contribution to total global NPP.More surprisingly, drought prone ecosystems in the Southern Hemisphere, which only account for 7% of the total global NPP, contribute to 33% of the interannual variation in global NPP.Our observations support the leading role of semi-arid ecosystems in interannual variability in global NPP and highlight the great impacts of long-term drought on the global carbon cycle.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of Earth Surface Processes and Resource Ecology, College of Global Change and Earth System Science, Beijing Normal University, Beijing 100875, China.

ABSTRACT
Drought is a main driver of interannual variation in global terrestrial net primary production. However, how and to what extent drought impacts global NPP variability is unclear. Based on the multi-timescale drought index SPEI and a satellite-based annual global terrestrial NPP dataset, we observed a robust relationship between drought and NPP in both hemispheres. In the Northern Hemisphere, the annual NPP trend is driven by 19-month drought variation, whereas that in the Southern Hemisphere is driven by 16-month drought variation. Drought-dominated NPP, which mainly occurs in semi-arid ecosystems, explains 29% of the interannual variation in global NPP, despite its 16% contribution to total global NPP. More surprisingly, drought prone ecosystems in the Southern Hemisphere, which only account for 7% of the total global NPP, contribute to 33% of the interannual variation in global NPP. Our observations support the leading role of semi-arid ecosystems in interannual variability in global NPP and highlight the great impacts of long-term drought on the global carbon cycle.

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Related in: MedlinePlus

Interannual variations in anomalies of total NPP and average SPEI.(a) Relationships between annual NPP and annual SPEI in both hemispheres. (b) Correlation coefficients (Pearson coefficient, R) between annual NPP and 12- to 24-month SPEI. (c) Relationship between annual NPP and 19-month SPEI in the Northern Hemisphere. (d) Relationship between annual NPP and 16-month SPEI in the Southern Hemisphere. **Denotes 95% confidence level estimated with a t-test; ***denotes 99% confidence level estimated with a t-test.
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f1: Interannual variations in anomalies of total NPP and average SPEI.(a) Relationships between annual NPP and annual SPEI in both hemispheres. (b) Correlation coefficients (Pearson coefficient, R) between annual NPP and 12- to 24-month SPEI. (c) Relationship between annual NPP and 19-month SPEI in the Northern Hemisphere. (d) Relationship between annual NPP and 16-month SPEI in the Southern Hemisphere. **Denotes 95% confidence level estimated with a t-test; ***denotes 99% confidence level estimated with a t-test.

Mentions: Figure 1a shows the relationship between annual SPEI and NPP from 2000 to 2013. A significant positive relationship (R = 0.88, P < 0.01) between annual SPEI and NPP was identified in the Southern Hemisphere (SH), whereas the relationship was weaker (R = 0.57, P < 0.05) in the Northern Hemisphere (NH), indicating that NPP is more sensitive to drought in the SH than in the NH. This is consistent with the findings of an earlier study that used PSDI as an indicator of drought2. Considering the possible lag in the response of NPP to drought caused by physiological processes, the relationship between SPEI and NPP was re-examined by using SPEI over longer timescales. Interestingly, based on this multi-timescale analysis, drought was highly correlated with NPP in both hemispheres (Fig. 1b). In the NH, the relationship between SPEI and NPP increased sharply as the SPEI timescale was extended, reached the strongest correlation at 19 months (R = 0.86, P < 0.01), and decreased with further extension of the drought timescale (Fig. 1c). In the SH, the most robust positive relationship between SPEI and annual NPP was observed on a 16-month drought timescale (R = 0.89, p < 0.01), after which the correlation steadily decreased (Fig. 1d). To examine the potential impacts from autocorrelations in SPEI or NPP series on correlation coefficients between SPEI and NPP, the autocorrelations in relevant series had also been checked by using different numbers of lags, as presented in Table S1. No significant autocorrelation (p < 0.05) was observed for SPEI or NPP series, indicating the autocorrelation contribute little to P levels between SPEI and NPP. The above analysis indicates that 1) drought is a main driver of IAV in global NPP; and 2) long-term drought can better explain IAV in NPP than annual drought. Furthermore, annual NPP in the NH is related to cumulative water deficit over longer time scales than in the SH.


Drought dominates the interannual variability in global terrestrial net primary production by controlling semi-arid ecosystems.

Huang L, He B, Chen A, Wang H, Liu J, Lű A, Chen Z - Sci Rep (2016)

Interannual variations in anomalies of total NPP and average SPEI.(a) Relationships between annual NPP and annual SPEI in both hemispheres. (b) Correlation coefficients (Pearson coefficient, R) between annual NPP and 12- to 24-month SPEI. (c) Relationship between annual NPP and 19-month SPEI in the Northern Hemisphere. (d) Relationship between annual NPP and 16-month SPEI in the Southern Hemisphere. **Denotes 95% confidence level estimated with a t-test; ***denotes 99% confidence level estimated with a t-test.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4835775&req=5

f1: Interannual variations in anomalies of total NPP and average SPEI.(a) Relationships between annual NPP and annual SPEI in both hemispheres. (b) Correlation coefficients (Pearson coefficient, R) between annual NPP and 12- to 24-month SPEI. (c) Relationship between annual NPP and 19-month SPEI in the Northern Hemisphere. (d) Relationship between annual NPP and 16-month SPEI in the Southern Hemisphere. **Denotes 95% confidence level estimated with a t-test; ***denotes 99% confidence level estimated with a t-test.
Mentions: Figure 1a shows the relationship between annual SPEI and NPP from 2000 to 2013. A significant positive relationship (R = 0.88, P < 0.01) between annual SPEI and NPP was identified in the Southern Hemisphere (SH), whereas the relationship was weaker (R = 0.57, P < 0.05) in the Northern Hemisphere (NH), indicating that NPP is more sensitive to drought in the SH than in the NH. This is consistent with the findings of an earlier study that used PSDI as an indicator of drought2. Considering the possible lag in the response of NPP to drought caused by physiological processes, the relationship between SPEI and NPP was re-examined by using SPEI over longer timescales. Interestingly, based on this multi-timescale analysis, drought was highly correlated with NPP in both hemispheres (Fig. 1b). In the NH, the relationship between SPEI and NPP increased sharply as the SPEI timescale was extended, reached the strongest correlation at 19 months (R = 0.86, P < 0.01), and decreased with further extension of the drought timescale (Fig. 1c). In the SH, the most robust positive relationship between SPEI and annual NPP was observed on a 16-month drought timescale (R = 0.89, p < 0.01), after which the correlation steadily decreased (Fig. 1d). To examine the potential impacts from autocorrelations in SPEI or NPP series on correlation coefficients between SPEI and NPP, the autocorrelations in relevant series had also been checked by using different numbers of lags, as presented in Table S1. No significant autocorrelation (p < 0.05) was observed for SPEI or NPP series, indicating the autocorrelation contribute little to P levels between SPEI and NPP. The above analysis indicates that 1) drought is a main driver of IAV in global NPP; and 2) long-term drought can better explain IAV in NPP than annual drought. Furthermore, annual NPP in the NH is related to cumulative water deficit over longer time scales than in the SH.

Bottom Line: Drought-dominated NPP, which mainly occurs in semi-arid ecosystems, explains 29% of the interannual variation in global NPP, despite its 16% contribution to total global NPP.More surprisingly, drought prone ecosystems in the Southern Hemisphere, which only account for 7% of the total global NPP, contribute to 33% of the interannual variation in global NPP.Our observations support the leading role of semi-arid ecosystems in interannual variability in global NPP and highlight the great impacts of long-term drought on the global carbon cycle.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of Earth Surface Processes and Resource Ecology, College of Global Change and Earth System Science, Beijing Normal University, Beijing 100875, China.

ABSTRACT
Drought is a main driver of interannual variation in global terrestrial net primary production. However, how and to what extent drought impacts global NPP variability is unclear. Based on the multi-timescale drought index SPEI and a satellite-based annual global terrestrial NPP dataset, we observed a robust relationship between drought and NPP in both hemispheres. In the Northern Hemisphere, the annual NPP trend is driven by 19-month drought variation, whereas that in the Southern Hemisphere is driven by 16-month drought variation. Drought-dominated NPP, which mainly occurs in semi-arid ecosystems, explains 29% of the interannual variation in global NPP, despite its 16% contribution to total global NPP. More surprisingly, drought prone ecosystems in the Southern Hemisphere, which only account for 7% of the total global NPP, contribute to 33% of the interannual variation in global NPP. Our observations support the leading role of semi-arid ecosystems in interannual variability in global NPP and highlight the great impacts of long-term drought on the global carbon cycle.

No MeSH data available.


Related in: MedlinePlus