Browsing by Autor "Gregory R. Goldsmith"

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Data from: What controls variation in carbon use efficiency among Amazonian tropical forests?
(Chapman University, 2017) Christopher E. Doughty; Gregory R. Goldsmith; Nicolas Raab; Cécile Girardin; Filio Farfan‐Amezquita; Walter Huaraca Huasco; Javier E. Silva‐Espejo; Alejandro Araujo‐Murakami; Antônio C. L. da Costa; Wanderley Rocha
Why do some forests produce biomass more efficiently than others? Variations in Carbon Use Efficiency (CUE: total Net Primary Production (NPP)/ Gross Primary Production (GPP)) may be due to changes in wood residence time (Biomass/NPPwood), temperature, or soil nutrient status. We tested these hypotheses in 14, one ha plots across Amazonian and Andean forests where we measured most key components of net primary production (NPP: wood, fine roots, and leaves) and autotrophic respiration (Ra; wood, rhizosphere, and leaf respiration). We found that lower fertility sites were less efficient at producing biomass and had higher rhizosphere respiration, indicating increased carbon allocation to belowground components. We then compared wood respiration to wood growth and rhizosphere respiration to fine root growth and found that forests with residence times <40 yrs had significantly lower maintenance respiration for both wood and fine roots than forests with residence times >40 yrs. A comparison of rhizosphere respiration to fine root growth showed that rhizosphere growth respiration was significantly greater at low fertility sites. Overall, we found that Amazonian forests produce biomass less efficiently in stands with residence times >40 yrs and in stands with lower fertility, but changes to long-term mean annual temperatures do not impact CUE.
The linkages between photosynthesis, productivity, growth and biomass in lowland Amazonian forests
(Wiley, 2015) Yadvinder Malhi; Christopher E. Doughty; Gregory R. Goldsmith; Daniel B. Metcalfe; Cécile Girardin; Toby R. Marthews; Jhon del Águila Pasquel; Luiz E. O. C. Aragão; Alejandro Araujo‐Murakami; Paulo Brando
Understanding the relationship between photosynthesis, net primary productivity and growth in forest ecosystems is key to understanding how these ecosystems will respond to global anthropogenic change, yet the linkages among these components are rarely explored in detail. We provide the first comprehensive description of the productivity, respiration and carbon allocation of contrasting lowland Amazonian forests spanning gradients in seasonal water deficit and soil fertility. Using the largest data set assembled to date, ten sites in three countries all studied with a standardized methodology, we find that (i) gross primary productivity (GPP) has a simple relationship with seasonal water deficit, but that (ii) site-to-site variations in GPP have little power in explaining site-to-site spatial variations in net primary productivity (NPP) or growth because of concomitant changes in carbon use efficiency (CUE), and conversely, the woody growth rate of a tropical forest is a very poor proxy for its productivity. Moreover, (iii) spatial patterns of biomass are much more driven by patterns of residence times (i.e. tree mortality rates) than by spatial variation in productivity or tree growth. Current theory and models of tropical forest carbon cycling under projected scenarios of global atmospheric change can benefit from advancing beyond a focus on GPP. By improving our understanding of poorly understood processes such as CUE, NPP allocation and biomass turnover times, we can provide more complete and mechanistic approaches to linking climate and tropical forest carbon cycling.
What controls variation in carbon use efficiency among Amazonian tropical forests?
(Wiley, 2017) Christopher E. Doughty; Gregory R. Goldsmith; Nicolas Raab; Cécile Girardin; Filio Farfan‐Amezquita; Walter Huaraca Huasco; Javier E. Silva‐Espejo; Alejandro Araujo‐Murakami; Antônio C. L. da Costa; Wanderley Rocha
Abstract Why do some forests produce biomass more efficiently than others? Variations in Carbon Use Efficiency ( CUE : total Net Primary Production ( NPP )/ Gross Primary Production ( GPP )) may be due to changes in wood residence time (Biomass/ NPP wood ), temperature, or soil nutrient status. We tested these hypotheses in 14, one ha plots across Amazonian and Andean forests where we measured most key components of net primary production ( NPP : wood, fine roots, and leaves) and autotrophic respiration (R a ; wood, rhizosphere, and leaf respiration). We found that lower fertility sites were less efficient at producing biomass and had higher rhizosphere respiration, indicating increased carbon allocation to belowground components. We then compared wood respiration to wood growth and rhizosphere respiration to fine root growth and found that forests with residence times <40 yrs had significantly lower maintenance respiration for both wood and fine roots than forests with residence times >40 yrs. A comparison of rhizosphere respiration to fine root growth showed that rhizosphere growth respiration was significantly greater at low fertility sites. Overall, we found that Amazonian forests produce biomass less efficiently in stands with residence times >40 yrs and in stands with lower fertility, but changes to long‐term mean annual temperatures do not impact CUE .