4.8 Article

Thermal optima of gross primary productivity are closely aligned with mean air temperatures across Australian wooded ecosystems

期刊

GLOBAL CHANGE BIOLOGY
卷 27, 期 19, 页码 4727-4744

出版社

WILEY
DOI: 10.1111/gcb.15760

关键词

air temperature; broadleaved evergreen tree; climate change; Eddy covariance; forest; gross primary production; savanna; thermal optima

资金

  1. Terrestrial Ecosystem Research Network (TERN)
  2. Australian Government National Collaborative Infrastructure Strategy (NCRIS)
  3. Australian Government Research Training Program Scholarship by the Australian Commonwealth Government
  4. Integrated Forest Ecosystem Research Program (Victorian Department of Environment, Land, Water and Planning
  5. LTB)
  6. Australian Research Council DECRA Fellowship [DE190101182]
  7. Australian Research Council [DE190101182] Funding Source: Australian Research Council

向作者/读者索取更多资源

The study found that the relationship between GPP and air temperature in Australian wooded ecosystems is a convex parabola, influenced by factors such as daytime temperature range, mean daytime temperature, and maximum GPP. The shape of the GPP-Ta curves is largely determined by these factors, with upslope influenced by Fsd and downslope influenced by VPD. There is a strong positive linear relationship between T-opt and MDTa, with T-opt exceeding MDTa in most ecosystems.
Gross primary productivity (GPP) of wooded ecosystems (forests and savannas) is central to the global carbon cycle, comprising 67%-75% of total global terrestrial GPP. Climate change may alter this flux by increasing the frequency of temperatures beyond the thermal optimum of GPP (T-opt). We examined the relationship between GPP and air temperature (Ta) in 17 wooded ecosystems dominated by a single plant functional type (broadleaf evergreen trees) occurring over a broad climatic gradient encompassing five ecoregions across Australia ranging from tropical in the north to Mediterranean and temperate in the south. We applied a novel boundary-line analysis to eddy covariance flux observations to (a) derive ecosystem GPP-Ta relationships and T-opt (including seasonal analyses for five tropical savannas); (b) quantitatively and qualitatively assess GPP-Ta relationships within and among ecoregions; (c) examine the relationship between T-opt and mean daytime air temperature (MDTa) across all ecosystems; and (d) examine how down-welling short-wave radiation (Fsd) and vapour pressure deficit (VPD) influence the GPP-Ta relationship. GPP-Ta relationships were convex parabolas with narrow curves in tropical forests, tropical savannas (wet season), and temperate forests, and wider curves in temperate woodlands, Mediterranean woodlands, and tropical savannas (dry season). Ecosystem T-opt ranged from 15celcius (temperate forest) to 32celcius (tropical savanna-wet and dry seasons). The shape of GPP-Ta curves was largely determined by daytime Ta range, MDTa, and maximum GPP with the upslope influenced by Fsd and the downslope influenced by VPD. Across all ecosystems, there was a strong positive linear relationship between T-opt and MDTa (Adjusted R-2: 0.81; Slope: 1.08) with T-opt exceeding MDTa by >1celcius at all but two sites. We conclude that ecosystem GPP has adjusted to local MDTa within Australian broadleaf evergreen forests and that GPP is buffered against small Ta increases in the majority of these ecosystems.

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