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Above- and below-ground net primary productivity across ten Amazonian forests on contrasting soils

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Above- and below-ground net primary productivity across ten Amazonian forests on contrasting soils
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  Biogeosciences, 6, 2759–2778, 2009www.biogeosciences.net/6/2759/2009/ © Author(s) 2009. This work is distributed underthe Creative Commons Attribution 3.0 License. Biogeosciences Above- and below-ground net primary productivity across tenAmazonian forests on contrasting soils L. E. O. C. Arag ˜ ao 1,2 , Y. Malhi 1 , D. B. Metcalfe 1,2 , J. E. Silva-Espejo 3 , E. Jim´enez 4 , D. Navarrete 4,5 , S. Almeida 6 ,A. C. L. Costa 7 , N. Salinas 1,3 , O. L. Phillips 9 , L. O. Anderson 1 , E. Alvarez 4 , T. R. Baker 9 , P. H. Goncalvez 7,8 ,J. Huam´an-Ovalle 3 , M. Mamani-Sol´orzano 3 , P. Meir 12 , A. Monteagudo 13 , S. Pati ˜ no 4 , M. C. Pe ˜ nuela 4 , A. Prieto 14 ,C. A. Quesada 9,10,11 , A. Rozas-D´avila 3 , A. Rudas 15 , J. A. Silva Jr. 7 , and R. V´asquez 131 Environmental Change Institute, School of Geography and the Environment, University of Oxford, South Parks Road,OX1 3QY, Oxford, UK 2 Climate Change and Sustainability Group, School of Geography, University of Exeter, Amory Building, Rennes Drive,Exeter, Devon, EX4 4RJ, UK 3 Universiadad Nacional San Antonio Abad, Cusco, Peru 4 Grupo de Estudio de Ecosistemas Terrestres Tropicales, Universidad Nacional de Colombia, Leticia, Colombia 5 Fundaci´on Puerto Rastrojo, Bogot´a, Colombia 6 Museu Paraense Emilio Goeldi, 66077-530 Belem, Brazil 7 Universidade Federal do Para, Belem, Para, Brazil 8 Universidade Federal de Vicosa, Vicosa, Minas Gerais, Brazil 9 Earth and Biosphere Institute, School of Geography, University of Leeds, LS2 9JT, UK 10 Institito National de Pesquisas Amazˆonicas, Manaus, Brazil 11 Departamento de Ecologia, Universidade de Bras´ılia, Brazil 12 School of Geography, University of Edinburgh, Edinburgh, UK 13 Jardin Botanico de Missouri, Oxapampa, Pasco, Peru 14 Instituto Alexander von Humboldt, Claustro de San Agust´ın, Villa de Lleva, Boyaca, Colombia 15 Universidad Nacional de Colombia, Instituto de Ciencias Naturales, Apartado 7495, Bogota, ColombiaReceived: 18 December 2008 – Published in Biogeosciences Discuss.: 25 February 2009Revised: 11 November 2009 – Accepted: 11 November 2009 – Published: 1 December 2009 Abstract.  The net primary productivity (NPP) of tropi-cal forests is one of the most important and least quan-tified components of the global carbon cycle. Most rel-evant studies have focused particularly on the quantifica-tion of the above-ground coarse wood productivity, and lit-tle is known about the carbon fluxes involved in other el-ements of the NPP, the partitioning of total NPP betweenits above- and below-ground components and the main en-vironmental drivers of these patterns. In this study wequantify the above- and below-ground NPP of ten Amazo-nian forests to address two questions: (1) How do Ama-zonian forests allocate productivity among its above- andbelow-ground components? (2) How do soil and leaf nu-trient status and soil texture affect the productivity of Ama-zonian forests? Using a standardized methodology to mea- Correspondence to:  L. E. O. C. Arag˜ao(leocaragao@gmail.com)sure the major elements of productivity, we show that NPPvaries between 9.3 ± 1.3MgCha − 1 yr − 1 (mean ± standard er-ror), at a white sand plot, and 17.0 ± 1.4MgCha − 1 yr − 1 ata very fertile  Terra Preta  site, with an overall average of 12.8 ± 0.9MgCha − 1 yr − 1 . The studied forests allocate onaverage 64 ± 3% and 36 ± 3% of the total NPP to the above-and below-ground components, respectively. The ratio of above-ground and below-ground NPP is almost invariantwith total NPP. Litterfall and fine root production both in-crease with total NPP, while stem production shows no over-all trend. Total NPP tends to increase with soil phospho-rus and leaf nitrogen status. However, allocation of NPP tobelow-ground shows no relationship to soil fertility, but ap-pears to decrease with the increase of soil clay content.Published by Copernicus Publications on behalf of the European Geosciences Union.  2760 L. E. O. C. Arag˜ao et al.: Net primary productivity in Amazonian forests 1 Introduction Plants are able to capture and accumulate atmospheric car-bon via photosynthesis or gross primary productivity (GPP),and synthesis of organic compounds. The amount of organiccarbon retained in plant biomass over time, which resultsfrom the difference between GPP and autotrophic respiration( R a ) , is known as net primary productivity (NPP). Globally,it has been estimated that the terrestrial biosphere fixes annu-ally between 46Pg C (Del Grosso et al., 2008) and 63Pg C(Grace, 2004) through NPP, approximately the same amountthat is fixed by oceans (Field et al., 1998). Despite coveringonly around 13% of the total land cover area (Bartholom´eand Belward, 2005; Del Grosso et al., 2008), tropical forestsalone have a major impact on global carbon cycling, account-ing for about a third of overall terrestrial NPP (Field et al.,1998; Malhi and Grace, 2000; Grace, 2004; Del Grosso etal., 2008).Detailed understanding of the total NPP of tropicalforests, including both above- and below-ground productiv-ity(NPP AG  andNPP BG , respectively), islimitedbychalleng-ing logistics and elevated research costs. Hitherto, most of the on-site measurements of NPP for tropical forests havebeen based on few sites and do not present adequate data onbelow-ground NPP (Clark et al., 2001a). Amazonia, home toover half of the world’s tropical forest area, is no exception.Most studies that attempted to measure NPP in this ecosys-tem focused exclusively on above-ground wood productivity(e.g. Chambers et al., 2001; Malhi et al., 2004; Quesada etal., 2009a). Malhi et al. (2009) compiled a synthesis of car-bon production for three Amazonian forests (key sites of theLarge Scale Biosphere-Atmosphere Experiment in Amazo-nia – LBA) based on detailed measurements of the individ-ual above and below-ground C cycling components. GPPestimate from the component studies was in agreement withestimates derived from ecosystem flux measurements, giv-ing increased confidence in both approaches to estimatingtropical forest’s GPP. Moreover, this study indicated that old-growth or infertile tropical forests may have low carbon useefficiency (CUE ∼= 0.3) in comparison to recently disturbed orfertile tropical forests (CUE ∼= 0.5), highlighting the hetero-geneity of forest processes in the Amazon.In order to improve our understanding of the biogeochem-ical function of Amazonian forests, and model simulationsof their vulnerability to climate change and human-inducedimpacts, there is a need to expand our knowledge on the pri-mary productivity of these ecosystems, taking into accounttheir spatial heterogeneity. The understanding of how theseprocesses vary across the region and across soil types wouldtherefore assist in planning the development of the Amazonregion within the global climate change mitigation and adap-tation framework.Based on the analysis of 104 forest plots across Amazo-nia from the RAINFOR network (Amazon Forest InventoryNetwork; Malhi et al., 2002), Malhi et al. (2004) demon-strated that wood production varies by up to a factor of threeacross Amazonian forests. The lowest wood productivitiesare found on heavily weathered oxisols (United States De-partment of Agriculture soil classification – USDA), or fer-ralsols (World Reference Base soil classification – WRB)in lowland eastern Amazonia; the highest on fertile alluvialsoils and inceptsols (USDA classification system) or fluvi-sols and cambisols (WRB classification system) in westernAmazonia (Ecuador and Peru). More fertile sites in west-ern Amazonia tend to favour fast growing, low wood den-sity species (Baker et al., 2004), which are likely to allo-cate relatively more to wood and leaf production and less tostructural and chemical defences and their associated con-struction and maintenance metabolic costs. A companionpaper in this issue (Chave et al., 2009) examines patterns of canopy NPP across Amazonia in greater detail. This studysuggests that soil type is not a major determinat of litterfallpatterns across Amazonia, however, infertile white sand soils(5.42 ± 1.91Mgha − 1 yr − 1 )  have significantly lower litterfallproduction than other soil types and seems to prioritize car-bon allocation to photosynthetic organs over that to repro-duction.Another (Quesada et al., 2009a) relates Amazon above-ground productivity to its potential edaphic and climatedrivers. This analysis revealed that forest structure and dy-namics are strongly related to physical and chemical edaphicconditions. On one hand tree turnover rates were mostlyinfluenced by soil physical properties, on the other hand,forest growth rates were mainly related to available soilphosphorus, suggesting that soils may be a determinant fac-tor on forest functioning and composition at a Basin widescale. However, beyond the stand-level wood and leaf pro-duction pattern across the region, almost nothing is knownabout the amount of carbon being allocated by other compo-nents of the NPP, the partitioning of total NPP (NPP total ) be-tween its above- and below-ground components, NPP AG  andNPP BG  respectively, and the main environmental drivers of any site-to-site variation. Therefore, in this paper we providethe first inter-site quantification of the major components of NPP total  for Amazonian forest stands on contrasting soils us-ing standardized on-site measurements of the major above-and below-ground components of forest NPP.The total NPP of a tropical forest stand can be brokendown as:NPP total =NPP AG + NPP BG  (1)Each of the components of NPP total  can be described as thesum of its subcomponents (Clark et al., 2001a; Malhi et al.,2009). Thus, NPP AG  can be expressed as:NPP AG =NPP canopy + NPP branch + NPP stem + NPP VOC  (2)where NPP canopy  is the canopy production (leaves, twigs < 2cm diameter, flowers and fruits), NPP branch  is the pro-duction of branches > 2cm diameter, NPP stem  is the produc-tion of coarse woody biomass, calculated as the change inBiogeosciences, 6, 2759–2778, 2009 www.biogeosciences.net/6/2759/2009/   L. E. O. C. Arag˜ao et al.: Net primary productivity in Amazonian forests 2761the stem biomass of trees > 10cm diameter plus the biomassrecruited during the measurement interval. NPP VOC  is theemission of volatile organic carbon compounds (see Malhi etal., 2009, for greater discussion of these terms). The canopyproduction, NPP canopy  is estimated to be equal to the rate of litterfall; this assumes the forest is in near-steady state andthat there is little loss of this production through insect her-bivory or decomposition before the litter hits the ground.NPP BG  can be divided into three major subcomponents(Eq. 3):NPP BG =NPP fineroot + NPP coarseroot + NPP exudates  (3)Where NPP fineroot  is the fine root ( < 2mmdiameter) pro-duction, NPP coarseroot  is the production of coarse roots( > 2mmdiameter) and NPP exudates  is the carbon loss throughexudates and mycorrhizae, which is challenging to measureand is not considered here.In this study we quantify the above- and below-groundNPP of ten Amazonian forests to address two general ques-tions: (1) how do Amazonian forests allocate productivityamong its above- and below-ground components? (2) Howdo soil and leaf nutrient status and soil texture affect the pro-ductivity of Amazonian forests?Based on the concepts above, these two questions can bedecomposed into five specific questions, which we tackle inthis paper:1. How do NPP AG  and NPP BG  and their subcomponentsvary with NPP total ?2. Is the partitioning between NPP AG  and NPP BG  invariantwith changes in NPP total ?3. Is the partitioning between NPP stem  and NPP canopy  con-stant?4. How does NPP vary with soil and leaf nutrients status?5. How does the partitioning of NPP vary with soil andleaf properties?WethereforeaimtoinvestigateinthisstudyhowNPP total  andits subcomponents vary across a wide range of Amazonianforests on different soil types. Specifically, our objectivesare to:1. Quantify and describe the patterns of NPP total  across agradient of soil conditions.2. Quantify the partitioning of NPP total  among its majorabove and below-ground components.3. Investigate if the partitioning between NPP canopy  andNPP stem  is constant.4. Determine how soil fertility and texture, based on avail-able soil phosphorus, nitrogen and clay content data(Quesada et al., 2009a, b) influence NPP in Amazonianforests. Fig. 1.  Location of the study area within South America (lower-right panel) and location of the studied plots within the studied area.Plot locations are approximated in order to display all plots. 2 Study sites We analysed the NPP total  and its above- and below-groundsubcomponents for ten forest plots across Amazonia (Fig. 1).We directly quantified NPP employing a consistent method-ology in eight plots: three plots at Caxiuan˜a, Brazil (CAX-03, CAX-06 and CAX-08), two at Tambopata, Peru (TAM-05 and TAM-06), two at Amacayacu, Colombia (AGP-01and AGP-02) and one at Zafire, Colombia (ZAR-01). Inaddition, we used published data compiled from two otherBrazilian sites in Manaus (MAN-05) and Tapaj´os (TAP-04)(Malhi et al., 2009) to support our analysis.These sites are part of the intensive surveyed plots withinthe RAINFOR network where measurements of all the ma- jor components of the C cycle are being measured since theend of 2004 or beginning of 2005 (see methods section), andwhere stem productivity has been measured since as early asthe 1980s. All directly studied plots were one-hectare (ha)in area; the results from Manaus and Tapaj´os were a synthe-sis from several study plots (Malhi et al., 2009). A summaryof plots name, location and basic climate data (Malhi et al.,2004) is given in Table 1.Allforestssurveyedinthisstudyare“primary”old-growthrainforests with the exception of CAX-08, which is a wellpreserved late successional forest growing on a very fer-tile Indian Dark Earth (or  Terra Preta do Indio ) soil (HorticArcheo-Anthrosol, Kampfetal., 2003). Thissoilwasformedby human activities from ancient inhabitants that have occu-pied this area between 720–300 years BP (Ruivo and Cunha,2003; Lehmann et al., 2003). This was selected as one of the few  Terra Preta  sites in the region covered by forest thathas remained largely undisturbed for at least 40 years sincethe creation of Caxiuan˜a National Forest reserve. More de-tails about each site surveyed are given below. For each sitewww.biogeosciences.net/6/2759/2009/ Biogeosciences, 6, 2759–2778, 2009  2762 L. E. O. C. Arag˜ao et al.: Net primary productivity in Amazonian forests Table 1.  Site codes, locations and climatic characteristics of the ten Amazonian sites evaluated in this study. The climate data presented inthis table are mean values from 1960–1998 derived from the University of East Anglia Observational Climatology (New et al., 1999) andpublished in Malhi et al. (2004). Cumulative annual rainfall is given in mmyr − 1 , dry season length (DSL) in months, corresponds to thesum of consecutive months with rainfall < 100mm month − 1 , and temperature is the mean annual temperature (MAT) in Celsius degrees. Study sites ClimateRAINFOR sites code Name Country Location Rainfall DSL MATLat Long mmyr − 1 months Celsius degreesAGP-01 Agua Pudre plot E Colombia  − 3.72  − 70.3 2723 0.0 25.5AGP-02 Agua Pudre plot U Colombia  − 3.73  − 70.4 2723 0.0 25.5CAX-03 Caxiuan˜a drought experiment control plot Brazil  − 1.72  − 51.5 2314 4.0 26.9CAX-06 Caxiuan˜a flux tower site Brazil  − 1.72  − 51.5 2314 4.0 26.9CAX-08 Caxiuan˜a Terra Preta site Brazil  − 1.72  − 51.5 2314 4.0 26.9MAN-05 Manaus Brazil  − 2.5  − 60.0 2272 3.0 27.1TAM-05 Tambopata RAINFOR plot 3 Peru  − 12.8  − 69.7 2417 3.5 25.2TAM-06 Tamboapata RAINFOR plot 4 Peru  − 12.9  − 69.8 2417 3.5 25.2TAP-04 Tapaj´os flux tower site Brazil  − 2.5  − 55.0 1968 4.5 26.1ZAR-01 Zafire, Varillal Colombia  − 4.0  − 69.9 2723 0.0 25.5 we also compiled data on leaf nitrogen and phosphorus con-centrations (N leaf   and P leaf  , respectively; Fyllas et al., 2009),soil types, following the WRB soil taxonomy to be consistentwith Quesada et al. (2009b), soil texture (clay content), andsoil nitrogen and phosphorus concentrations (N soil  and P soil ,respectively; Quesada et al., 2009a). These data are shownin Table 2.At Caxiuan˜a, Brazil, we surveyed three 1-ha plots(100m × 100m). All plots are located at the Caxiuan˜a Na-tional Forest in Par´a State. The plot CAX-06, is a tall pri-mary forest (35m height canopy) situated on a clay ferral-sol (oxisol in USDA soil taxonomy) near a flux tower site(Malhi et al., 2009). The CAX-03 plot is a sandier site lo-cated 2km to further south, which was the control plot for adrought experiment (Metcalfe et al., 2007a). The  Terra Preta site (CAX-08) is a late successional forest on an Archaeo-Anthrosol (this classification was modified from the WRBsoil taxonomy by Kampf et al. (2003) to encompass the vari-ability of   Terra Preta  soils in Amazonia). The CAX-08 siteis located about 15km to the south of the primary study area,by the edge of a large river bay.At Tambopata, Peru, we surveyed two pre-existing long-term 1-ha plots (100m × 100m) located at the Tambopata Bi-ological Reserve, in Madre de Dios Region. The plot TAM-05 was set up on relatively infertile Pleistocene cambisols(inceptsols in USDA soil taxonomy), with an average canopyheight of 30m. The plot TAM-06 was on alisols (ultisols inUSDA soil taxonomy) on a fertile Holocene alluvial terrace.The canopy in this plot has the same average height as TAM-05, but a greater density of palms.At Amacayacu, Colombia, our focus was on two 1-ha terra firme  forest plots AGP-01 and AGP-02 (Jim´enez et al.,2009). Both are located at the Amacayacu National Nat-ural Park, near the border between Colombia, Brazil andPeru. The plots were set up in an area of primary old-growthforest, with a 25m height canopy, on relatively fertile clayplinthosols (aquic entisols in USDA soil taxonomy).At Zafire, Colombia our focus was on a 1-ha plot locatedon a white sand site, ZAR-01 (Jim´enez et al., 2009). This ispart of the Rio Calder´on Forest Reserve, around 50km eastof the Amacayacu site. The plot was set up in an area of pri-mary forest on white sand podzol (spodosol in the USDA soiltaxonomy), locally known as  Varillal . This forest is shorterthantheforestatAmacayacu, withanaverageheightof20m.This forest type is scarce in western Amazonia but more fre-quent in the Guyana Shield and is similar to the formationsalong the  Rio Negro . The soil in our plot has an impermeablehardpan layer at ∼ 100cm depth (Jim´enez et al., 2009).At Tapaj´os, Brazil, we focus on the sites reported by Malhiet al. (2009). The main site is the km 67 flux tower (TAP-04, Hutyra et al., 2007; Saleska et al., 2003) and its vicin-ity. This site is located within the boundaries of the Tapaj´osNational Forest in Par´a State. The plots are established inold-growth forest with canopy height around 35m. The soilsare very clay-rich Belterra clay ferralsols, interspersed withsandier soil patches. The key plots are four 1-ha transects es-tablished in 1999 immediately to the east of the tower (Riceet al., 2004; Pyle et al., 2008).At Manaus, Brazil, the study sites were also focus on thesites reported in Malhi et al. (2009). The main sites are theK34 flux tower site (Ara´ujo et al., 2002), and the variousstudies that have been conducted in its vicinity. The plotsare stablished in old-growth  Terra Firme  forests on clay-richferrasols, extensively dissected by river valleys hosting lowerbiomass forest on frequently waterlogged podzols. The keyforestplotsintheareaarethethree1-ha“Bionte”plotsontheplateaux, providing annual census data since 1989, and thetwo 5-ha (20 × 2500m) “Jacaranda” transect plots that drapeacross the plateau-valley landscape.Biogeosciences, 6, 2759–2778, 2009 www.biogeosciences.net/6/2759/2009/   L. E. O. C. Arag˜ao et al.: Net primary productivity in Amazonian forests 2763 Table 2.  Leaf nutrient concentration (mgg − 1 )  and soil available phosphorus concentration (mgkg − 1 ) , nitrogen concentration (%) and claycontent (%) for the ten Amazonian sites evaluated in this study. Leaf data are derived from Fyllas et al. (2009) and soil data from Quesada etal. (2009b). Note that the soil type is in accordance with the World Reference Base soil classification system (WRB). RAINFOR code Leaf nutrient SoilNitrogen Phosphorus Type Clay Nitrogen PhosphorusAGP-01 20.87 1.06 Endostagnic Plinthosol (Alumic, Hyperdystric) 42.12 0.16 25.36AGP-02 19.17 0.96 Endostagnic Plinthosol (Alumic, Hyperdystric) 43.10 0.16 25.43CAX04 20.63 0.55 Vetic Acrisol (Alumic, Hyperdystric) 16.30 0.07 b 12.31 b CAX-06 19.13 0.53 Geric Acric Ferralsol (Alumic, Hyperdystric,Clayic) 47.53 0.13 12.31 b CAX-08 Hortic Archaeo-Anthrosol (Ebonic, Clayic, Mesothropic, Mesic, Ferralic) 41.41 0.17 80.00MAN-05 19.89 a 0.54 a Geric Ferralsol (Alumic, Hyperdystric, Clayic) 66.21 a 0.16 a 7.28 a TAM-05 23.99 1.05 Haplic Cambisol (Alumic, Hyperdystric, Clayic) 7.41 0.16 32.34TAM-06 24.80 1.88 Haplic Alisol (Hyperdystric, Siltic) 9.66 0.17 33.06TAP-04 22.58 0.75 Geric Ferralsol (Alimic, Hyperdystric, Clayic, Xanthic) 89.25 0.14 15.45ZAR-01 Ortseinc Podzol (Oxyaquic) 0.64 0.11 14.36 a Values are from MAN-05 plot. b Values are averages from nearby plots CAX-01 and CAX-02. For a more detailed view of the landscape attributes, suchas vegetation type and structure, topography and plot loca-tions, of many of these plots see Anderson et al. (2009). 3 Materials and methods3.1 Aboveground NPP3.1.1 Litterfall At Caxiuan˜a and Tambopata, one litter trap with an area of 0.25m 2 (0.5m × 0.5m) was installed in the centre of eachof the twenty-five 20 by 20m subplots in the plots CAX-06 and CAX-08 in August 2004. In January 2005 the samedesign was installed at Tambopata (TAM-05 and TAM-06).Litterfall in these four plots was collected every fifteen daysfrom September 2004 to December 2006 in Caxiuan˜a andfrom February 2005 to December 2006 in Tambopata. Lit-terfall in the third 1-ha plot in Caxiuan˜a (CAX-03) wasrecorded monthly from November 2001 to December 2006using twenty circular traps (area=1m 2 )  randomly placed inNovember 2001.At Amacayacu and Zafire one litter trap with an area of 0.50m 2 (0.5m × 1.0m) was installed in 2005 in the centreof each of the twenty-five 20 by 20m subplots in the plotsAGP-01, AGP-02 and ZAR-01. In all three sites litterfallwas collected biweekly for two years at AGP-01 and AGP-02, and for 1.5 years at ZAR-01.For all of these sites sites, traps were made with a PVCframe and a 1mm nylon mesh and were placed at 1m abovethe ground surface. Litter retrieved from the traps was im-mediately sun dried and subsequently dried in the laboratoryoven at 60 ◦ C until constant weight. Each dried sample wasseparated into leaves, twigs ( < 2cm diameter), reproductivestructures(flowers, fruitandseeds)andunidentifiedmaterial,and weighed.At Tapaj´os, litterfall values compiled by Malhi etal. (2009) were from: (1) Rice et al. (2004), who calculatedfine litterfall from 30 circular mesh traps (0.43m diameter,0.15m 2 ) , randomly located throughout the 19.75-ha surveyarea; (2)Silveretal.(2000), whoestimatedfinelitterfallratesin six to ten 4m × 12m plots, using six 0.9m 2 baskets perplot; and (3) Nepstad et al. (2002), who used 0.5m 2 traps at100 points arranged as a regular grid within two 1-ha plots.At all sites litter was collected at biweekly intervals. ForManaus, following Malhi et al. (2009), we used the meanvalues from Luiz˜ao et al. (2004). 3.1.2 Branch production The production of large branches was not measured in thisexperiment. For completeness of our NPP estimate we useda branchfall average rate for all plots of 1MgCha − 1 yr − 1 based upon data from two studies carried out in Amazonia:one in Manaus that reported a rate of 0.4MgCha − 1 yr − 1 (Chambers et al., 2001) and a second one in the Tapaj´os thatestimated a branchfall rate of 1.6 ± 0.8MgCha − 1 yr − 1 (Nep-stad et al., 2002). For the analysis of error propagation (seebelow) we used a conservative uncertainty ± 100% (Malhi etal., 2009). It is possible that sites with higher NPP stem  andalso higher stem breakage in western Amazonia would havehigher NPP branch  rates. 3.1.3 Coarse woody biomass production Wood productivity (NPP stem )  was estimated by repeated cen-suses of tree diameters and stems newly recruiting into the10cm diameter size-class, taking into account taxon-specificvariation in wood density.www.biogeosciences.net/6/2759/2009/ Biogeosciences, 6, 2759–2778, 2009
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