Browsing by Autor "Walter Huaraca Huasco"

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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.
Drought impact on forest carbon dynamics and fluxes in Amazonia
(Nature Portfolio, 2015) Christopher E. Doughty; D. B. Metcalfe; Cécile Girardin; Filio Farfán Amézquita; Darcy Galiano Cabrera; Walter Huaraca Huasco; Javier E. Silva‐Espejo; Alejandro Araujo‐Murakami; Mauricio C. da Costa; Wellington Willian Rocha
Fine root dynamics across pantropical rainforest ecosystems
(Wiley, 2021) Walter Huaraca Huasco; Terhi Riutta; Cécile A. J. Girardin; Fernando Hancco Pacha; Beisit L. Puma Vilca; Sam Moore; Sami W. Rifai; Jhon del Águila Pasquel; Alejandro Araujo Murakami; Renata Freitag
Fine roots constitute a significant component of the net primary productivity (NPP) of forest ecosystems but are much less studied than aboveground NPP. Comparisons across sites and regions are also hampered by inconsistent methodologies, especially in tropical areas. Here, we present a novel dataset of fine root biomass, productivity, residence time, and allocation in tropical old-growth rainforest sites worldwide, measured using consistent methods, and examine how these variables are related to consistently determined soil and climatic characteristics. Our pantropical dataset spans intensive monitoring plots in lowland (wet, semi-deciduous, and deciduous) and montane tropical forests in South America, Africa, and Southeast Asia (n = 47). Large spatial variation in fine root dynamics was observed across montane and lowland forest types. In lowland forests, we found a strong positive linear relationship between fine root productivity and sand content, this relationship was even stronger when we considered the fractional allocation of total NPP to fine roots, demonstrating that understanding allocation adds explanatory power to understanding fine root productivity and total NPP. Fine root residence time was a function of multiple factors: soil sand content, soil pH, and maximum water deficit, with longest residence times in acidic, sandy, and water-stressed soils. In tropical montane forests, on the other hand, a different set of relationships prevailed, highlighting the very different nature of montane and lowland forest biomes. Root productivity was a strong positive linear function of mean annual temperature, root residence time was a strong positive function of soil nitrogen content in montane forests, and lastly decreasing soil P content increased allocation of productivity to fine roots. In contrast to the lowlands, environmental conditions were a better predictor for fine root productivity than for fractional allocation of total NPP to fine roots, suggesting that root productivity is a particularly strong driver of NPP allocation in tropical mountain regions.
Source and sink carbon dynamics and carbon allocation in the Amazon basin
(Wiley, 2015) Christopher E. Doughty; Daniel B. Metcalfe; Cécile Girardin; Filio Farfán Amézquita; Lucile Durand; Walter Huaraca Huasco; Javier E. Silva‐Espejo; Alejandro Araujo‐Murakami; Mauricio C. da Costa; Antônio C. L. da Costa
Abstract Changes to the carbon cycle in tropical forests could affect global climate, but predicting such changes has been previously limited by lack of field‐based data. Here we show seasonal cycles of the complete carbon cycle for 14, 1 ha intensive carbon cycling plots which we separate into three regions: humid lowland, highlands, and dry lowlands. Our data highlight three trends: (1) there is differing seasonality of total net primary productivity (NPP) with the highlands and dry lowlands peaking in the dry season and the humid lowland sites peaking in the wet season, (2) seasonal reductions in wood NPP are not driven by reductions in total NPP but by carbon during the dry season being preferentially allocated toward either roots or canopy NPP, and (3) there is a temporal decoupling between total photosynthesis and total carbon usage (plant carbon expenditure). This decoupling indicates the presence of nonstructural carbohydrates which may allow growth and carbon to be allocated when it is most ecologically beneficial rather than when it is most environmentally available.
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 .