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Aboveground and belowground biomass allocation in native Prosopis caldenia Burkart secondaries woodlands in the semi-arid Argentinean pampas
... Determining the carbon balance of the caldén woodlands is a complex task since the potential carbon sequestration of a forest depends on many factors and, in particular in these forests, patches of vegetation coexist in different states of conservation. Some patches, such as overmature woodlands in a senescent state, can behave as sources of CO 2 and others, such as grasslands, can behave as a sink (Risio et al. 2014). The constant expansion of agriculture as well as the abandonment of lands add another level of complexity to these estimations. ...
... Understanding the biomass distribution within the caldén tree is also important for these quantifications. Risio et al. (2014) found that the highest biomass percentage (46%) is in the crown (branches and leaves), followed by roots (35%) and finally the stem (19%). Furthermore, the relationship between aboveground and underground biomass showed a mean value of 0.58 with a maximum of 1.88 and a minimum of 0.065 ( Figure 13). ...
... Biomass partition within each caldén (Prosopis caldenia) tree, divided in crown, stem and roots (n=38) (modified fromRisio et al. 2014). ...
The arid and semi-arid areas in Argentina occupy more than the sixty
percent of the country. The genus Prosopis dominates these environments
with approximately 21 species. The driest part of the Argentinean Pampas
is dominated by caldén (Prosopis caldenia) forests which cover
approximately 27,000 km2. For many years, caldén woodlands were
considered as a main source of wood due to its praiseworthy quality. At the
beginning of the last century it was widely used as railroad firewood and
for paving the streets of Buenos Aires, the capital city of Argentina. As a
result, only 18% of the original area of these forests remain nowadays.
Today, new paradigms allow us to value the caldén forests not only for
their wood but also for the many services that they can provide such as
food, medicinal products, dyeing materials, apiculture, regulation of water
basins, stabilization of sandy soils, recycling of nutrients, carbon sink,
forage for livestock and recreation. In a context of global change, the fact
that these forests are a refuge for a large proportion of mammals and birds
emphasizes their value as a source of biodiversity. Despite the many
functions that these forests have and regardless of the ecosystem services
that they provide being valued at USD 2,000 ha-1, they are currently
subject to the highest deforestation rates in Argentina. Valuing these
forests is a complex task and challenge in a globalized economy that
constantly struggles between productive systems which require the
replacement of forests and the need to preserve them for the generations to
come.
... El bosque conforma un distrito fitogeográfico con predominancia del árbol del caldén en transición con sabanas de gramíneas, dunas con vegetación psamófila y suelos salinos con matorrales o estepas halófilas (Secretaría de Ambiente y Desarrollo Sustentable [SAyDS], 2007). A partir de funciones ecosistémicas determinadas, este bosque puede contribuir al desarrollo y protección del suelo (Buschiazzo, Estelrich, Aimar, Viglizzo, & Babinec, 2004); proporcionar alimentos, fibra, energía y especies medicinales (Lell, 2005); favorecer la regulación del ciclo hidrológico (Jayawickreme, Santoni, Kim, Jobbágy, & Jackson, 2011), del clima local y global (Risio, Herrero, Bogino, & Bravo, 2014); y aportar servicios culturales como identidad, enriquecimiento espiritual y recreación. ...
... The forest forms a phytogeographic district with predominance of the calden tree in transition with grass savannas, dunes with psammophyll vegetation and saline soils with shrubs or halophilic steppes (Secretaría de Ambiente y Desarrollo Sustentable [SAyDS], 2007). Based on specific ecosystem functions, this forest can contribute to the development and protection of the soil (Buschiazzo, Estelrich, Aimar, Viglizzo, & Babinec, 2004); provide food, fiber, energy and medicinal species (Lell, 2005); favor the regulation of the hydrological cycle (Jayawickreme, Santoni, Kim, Jobbágy, & Jackson, 2011), of the local and global climate (Risio, Herrero, Bogino, & Bravo, 2014); and provide cultural services such as identity, spiritual enrichment and recreation. ...
Introduction:
The native forest of calden is a natural ecosystem that produces valuable ecosystem goods and services for society; however, it has been replaced for the production of commercial, agricultural and livestock goods.
Objective:
To estimate the economic value of a conservation program for ecosystem services of the remnant of the native calden (Prosopis caldenia Burkart) forest in the south of the province of Córdoba, Argentina.
Materials and methods:
The study area corresponds to a remnant forest of 37 648 ha. The willingness to pay (WTP) was obtained from a contingent valuation survey; 361 questionnaires were applied. The sampling unit was the household. A multistage cluster sampling was used in the city of Río Cuarto and a simple random sampling in Villa Huidobro.
Results and discussion:
The estimated WTP showed goodness of fit and most of the estimated coefficients were statistically significant (P < 0.05) and consistent with what was theoretically expected. The WTP increases with household income and decreases as the consulted amount of money to pay increases. The average WTP for a conservation program of the native calden forest is 52 ± 8 ARS (11.45 ± 1.76 USD) monthly per household.
Conclusion:
The majority of the urban population of southern Córdoba does not use forest ecosystem services; however, they are willing to pay to maintain or increase forest ecosystem services.
... Root systems were either not considered in those studies or (in the last two cases) the equations were fitted without using seemingly unrelated regression (SUR). The efficacy of applying SUR to satisfy the additivity property has been emphasized in other research [43,10,11,44]. The lack of additivity creates logical inconsistency because the predicted values from the biomass equations of the tree components do not add up to the predicted value from the equation for the total tree biomass [45]. ...
... Our data also revealed that root systems comprise 15% and 35% of total biomass in planted and coppice E. globulus stands, respectively, in northern Spain. In this type of re-sprouting species, as well as in other non-productive but fragile forest ecosystems [44], careful estimation of root biomass is essential to any attempt at quantifying carbon sequestration. ...
... Los bosques almacenan carbono y el desmonte constituye una de las causas de emisión de gases de efecto invernadero. Risio et al. (2014) estimaron que la reserva promedio de carbono total del árbol de caldén (biomasa aérea y del suelo) es de 9,6 tn/ha. En este sentido, Colazo y Buschiazzo (2013) hallaron que en suelos con bosque nativo duplican el contenido de carbono orgánico total, en comparación con suelos cultivados. ...
Patrones espaciales y características de la vegetación terrestre de la provincia de Córdoba, Argentina.
... caldenia), an endemic specie in Argentina. These woodlands thrive on the edge of the driest area of the Argentinean Pampas, at 34-36 • S and 64-66 • W [8,9]. Across its natural distribution area, the total annual precipitation varies from 450 to 620 mm, and it is concentrated in the spring and summer months (78%, from October to March). The average temperature ranges from 16 to 18 • C. The area is a welldrained plain with moderate slopes produced by wind and fluvial processes [7]. ...
Arbuscular mycorrhizal fungi (AMFs, Glomeromycota) are biotrophic mutualistic symbionts of 80% of terrestrial plants. AMFs increase their hosts’ growth through their contribution to water and nutrient absorption from the soil to the plant roots. The different AMF taxa vary in their edaphic and nutritional preferences, the host species ranges and the seasonal changes in sporulation features. The increase in the world human population and the global demand for natural resources have acted as an important driving force for agricultural changes in Argentina in the last 150 years. Particularly, the Prosopis caldenia Burkart forests (or “Caldenales”) have suffered an important reduction in the last 10 years. Here, we studied AMF abundance and diversity in four land uses and their relationship with soil and vegetation characteristics. The land uses selected were native forest (Caldenales), Eragrostis curvula (Schrad.) Nees pasture, Medicago sativa L. cropfield and soybean (Glycine max (L.) Merill) cropfield. AMF spores were extracted from soil by the traditional method and were identified by their morphological features. Cluster analysis divided the land uses into two groups; Kruskal–Wallis tests showed significant differences in AMF abundance and richness between land uses; the AMF abundance and tree richness were negatively correlated, showing less abundance of AMF spores in the plots with the highest richness of tree species. Our results suggest that land use and vegetation richness have a strong influence on the AMF community. Agricultural activities would negatively influence the AMF species diversity but would not negatively affect the spore abundance.
... It was found to be the best variable for estimating the biomass of young Pica abies trees in Slovakia (Patek et al., 2008) and young P. pinaster saplings with a DBH less than 10 cm in Australia (Ritson and Sochacki, 2003). In some instances, basal area has also been used along with other tree or stand level variables to fit biomass equations to accommodate the specific characteristics of forests or species Risio et al., 2014). ...
The main objective of this study was to analyse biomass production and distribution among the constituent parts of 4-year-old Pinus pinaster and Pinus halepensis trees. Young trees were harvested from a Nelder wheel experimental site and their biomass weight was determined. With the Nelder design, the effect of stand density can be included in the biomass analysis. We analysed biomass production at test densities ranging from 1000 to 80 000 seedlings/ha by fitting two types of equations: (1) Dirichlet regressions to estimate the biomass proportions of constituent tree parts and (2) allometric equations to simultaneously predict the biomass content of constituent tree parts. Results from this innovative approach showed that the effect of stand density in tree-level biomass was significant for P. halepensis but not for P. pinaster. We observed a general increase of total biomass from P. halepensis at lower densities. More precisely, the proportion of root biomass increased at the expense of aboveground biomass, which is considered a positive effect in terms of resilience and adaptation. This new set of equations fills a fundamental knowledge gap for these species in central Spain and can readily be used by silviculturists and scientists to quantify carbon stocks for young planted forests.
... Plaza Behr et al. (2016) 12. da Silva Possete et al. (2015) 13. Redin et al. (2017) 14. Risio et al. (2014) 15. Streit et al. (2014) 16. ...
Questions
Park forests are shaped by extensive cattle ranching in the transition between natural riverine forests and open grasslands. The underlying mechanisms driving tree regeneration have not been studied, however, they determine biodiversity, sustainability and multifunctionality of these ecosystems. We explored patterns of tree regeneration by analyzing nurse–beneficiary interactions and tree community composition.
Location
Park forests within the departments of Rio Negro, Paysandú, Artigas and Tacuarembó, República Oriental del Uruguay, South America.
Methods
We established 205 (1 × 1 m ² ) paired plots in open microhabitat and under the tree canopy to evaluate the patterns of tree regeneration. To assess tree community composition and diversity we carried out forest inventories within one‐hectare plots of ten park forests.
Results
Scattered trees in park forests had a positive effect on tree regeneration density, whereas, dense grass coverage had a negative effect. Regeneration density increased and grass cover reduced under the canopy of nurse trees. Regeneration beneficiaries were mainly bird dispersed species with different life strategies. Tree communities varied between forest types and spatially closer forests were more similar.
Conclusions
Our study outlines the importance of park forest trees to the promotion of forest regeneration and recovery in grazed forests. Our results found a positive interaction effect between nurse trees and saplings, based on our results we suggested possible facilitation mechanisms including the provision of shade, reduction of grass competition and the attraction of seed dispersers.
... en función del área basal (Bogino y Villalba, 2008;Jové-Alcalde, 2014;Risio-Allione et al., 2014) y proveer de la información básica para la elaboración del primer plan dasocrático para la provincia de San Luis (Rollán-Martín, 2017). Las bajas tasas de crecimiento registradas antes de la ocupación europea del territorio del caldenal posteriores a la campaña del desierto, año 1882, hacen suponer la existencia de un bosque cerrado y muy denso el cual, incluso, ha sido descrito por las crónicas en época de los ranqueles como "selvas tupidas" con una fisonomía muy contrastante con la del supuesto parque (Tapia y Dussart, 2013;Velasco-Sastre et al., 2018). ...
Se presenta el estado de los bosques del Espinal, analizando la estructura y funcionamiento de los principales tipos de unidades de paisaje. Se discuten los principales cambios a nivel del paisaje relacionados con el manejo histórico del territorio y aspectos socioecológicos vinculados a los cambios en el uso de la tierra. Se presentan los tratamientos silvícolas y técnicas de manejo silvicultural que se han realizado o se realizan en esta región, evaluando los distintos factores ecológicos, sociales y económicos relacionados a la pérdida de bosque nativo. Se discuten distintas éticas ambientales en relación con valoraciones de los bosques para así analizar posibles manejos silviculturales en el bosque nativo que posibiliten la conservación de la biodiversidad en los agro-ecosistemas del Espinal. Finalmente, se presentan algunas prioridades en la generación de nuevos conocimientos necesarios para el manejo silvicultural sostenible y se incluyen recomendaciones para mejorar la conservación y la silvicultura en los bosques del Espinal y el buen vivir de la sociedad
... Accurate biomass models are key to estimate carbon stocks from forest inventories and provide comparable and verifiable information to policymakers and stakeholders ( Risio et al., 2014 ). As a result, biomass equations are frequent in ecological and forestry studies over the last 60 years ( Bi et al., 2015 ). ...
Accurate tree biomass estimation is critical and crucial for calculating carbon stocking as well as for studying climate change, forest health, productivity, nutrient cycling and budget etc. A total of 50 individuals of Shorea robusta Gaertn. f. were harvested to assess the biomass of tree components (leaf, branch, bark and stem). Carbon and nutrients (N, P and K) content in the tree components were also measured. This study adopted component biomass models with cross-validation technique. Additive biomass models were developed following the modified Gaussian maximum likelihood aggregated approach using open source software R (version 4.0.1). Component and additive biomass model used D (Diameter at Breast Height) as a sole predictor performed satisfactorily, the inclusion of total tree height (H) in Da*Hb form showed its supremacy over all the models. The best fitted additive model (AGB = 0.002056*D2.923998*H−0.69278 + 0.00848*D2.3896*H0.29648 + 0.04224*D2.06986*H0.65549 + 0.00552*D2.06723*H0.70536) and conventional model (Ln (AGB) = -2.7977 + 2.1829*ln(D) + 0.5073*ln(H)) took the lowest AIC, MPE and MAE and the highest model efficiency values. The derived species-specific additive and non-additive model showed its superiority over the frequently used pan-tropical models and suggested using this model for estimating aboveground biomass of S. robusta in Bangladesh.
... The natural range of P. caldenia extends over the Chaco-Pampa Plain, covering 48,872 km 2 (Morello et al. 2012;Oyarzabal et al. 2018) of the southern part of the Espinal ecoregion. The temperate -semiarid climate of the Caldenal has gradually increased its mean precipitation from 560 to 900 mm.year −1 in the last 50 years (Contreras et al. 2011;Risio et al. 2014), thus raising the deforestation area used for crops and shifting westward the agricultural frontier (Barbosa 2005). ...
This chapter gathers six species that have been extensively used from the natural forest, but that are not included in any domestication programme yet. These species from the Chaco region belong to genera Acacia, Prosopis and Gonopterodendron. Main characteristics of the different species such as botanical, ecological and usage features (timber and non-timber forest products) are described. Natural range of each species is also depicted. The state of knowledge of the molecular genetic diversity and reproductive biology is shown together with the available information about the mating system. Landscape genetic structure analyses among populations of different Acacia species revealed high levels of differentiation. Experiences of germination and plantation, although scarce, give promising results. Special sampling methods for conservation, management and deployment are discussed together with particular genetic considerations for their use in restoration programmes. We call attention to the relevance of these species for their future inclusion in domestication efforts.
... The natural range of P. caldenia extends over the Chaco-Pampa Plain, covering 48,872 km 2 ) of the southern part of the Espinal ecoregion. The temperate -semi-arid climate of the Caldenal has gradually increased its mean precipitation from 560 to 900 mm.year -1 in the last 50 years (Contreras et al. 2011;Risio et al. 2014), thus raising the deforestation area used for crops and shifting westward the agricultural frontier (Barbosa 2005). Caldén is a heliophilous and deciduous tree, 12-15 meters high, with a superficial radical system. ...
Nothofagus obliqua forests in Argentina extend over a wide latitudinal gradient but highly fragmented and locally restricted. The relevance of this species relies in its high wood quality and tolerance to warmer niches, as those predicted under climate change. In this chapter, we describe the species characteristics and natural distribution range as well as the natural hybridisation process that occurs frequently with other Nothofagus species. Genetic variation patterns based on neutral genetic markers (isozymes, cpDNA and microsatellites) allowed inferring past demographic changes during the Pleistocene glaciations. In addition, the level of genetic diversity was used as an indicator for conservation and for the definition of genetic zones as seed sources for breeding and restoration. Quantitative genetic variation and phenotypic plasticity measured at seeds, seedling and juvenile states on nursery and field trials gave insights about adaptation. The first steps towards breeding of roble pellín in Argentina are fully described: provenance and progeny tests and seed producing areas, both natural and cultivated ones. Intra- and interspecific-controlled crossings of N. obliqua represent a fundamental step towards the breeding of this species, and the first achievements are described.
... Accurate biomass models are key for estimating forest carbon stocks from forest inventories and provide comparable and verifiable information to policymakers and stakeholders [59,60]. ...
Accurate estimates of tree component and aboveground biomass strongly depend on robust and precise allometric equations. However, site-specific and suitable biomass equations are currently scarce for natural Larix gmelinii forests in the western Daxing’anling Mountains, northeastern China. This study aimed to evaluate the biomass allocation patterns within tree components and develop additive allometric biomass equations for species of L. gmelinii. A total of 58 trees were destructively sampled and measured for wood (inside bark), bark, branch and leaf biomass. For each component, we assessed the share of biomass allocated to different components by computing its ratio; we also tested two allometric equations based on diameter at breast height (dbh) alone, and dbh fitted with height (h) as independent variables. Seemingly unrelated regression methodology was used to fit an additive system of biomass allometric equations. We performed an independent dataset to evaluate the predictive ability of the best model system. The results revealed that wood biomass accounted for approximately 60% of the aboveground biomass. Wood and branch biomass ratios increased with increasing dbh, while a reverse trend was observed for bark and leaf biomass ratios. All models showed good fitting results with Adj.R2 = 0.958–0.995. Tree dbh provided the lowest estimation errors in the regressions associated with branches and leaves, while dbh2 × h generated the most precise models for stems (wood and bark). We conclude that these allometric equations will accurately predict biomass for Larix trees in the western Daxing’anling Mountains.
... El bosque de caldén (Prosopis caldenia) -al igual que otros bosques del mundo-brinda múltiples servicios ecosistémicos (SE) a la sociedad. Este bosque provee de alimentos, leña y especies medicinales (Cisneros et al., 2002;Lell, 2004), asiste en la regulación del clima (Risio, Herrero Bogino y Bravo, 2014), en la regulación del ciclo hidrológico (Santoni, Jobbágy y Contreras, 2010), en la protección del suelo ante adversidades climáticas (Adema, Babinec, Buschiazzo, Martín y Peinemann, 2003) y es apreciado culturalmente por su carácter endémico (Rosacher, 2002). ...
El objetivo de este trabajo es desarrollar un análisis beneficio-costo que permita identificar el incentivo económico a la deforestación del bosque de Caldén y el impacto económico de diferentes alternativas políticas. Los resultados indican que, de mantenerse las condiciones de precios y rendimientos actuales, existe un incentivo económico a la deforestación en más de 70 % de la superficie actual de bosque. A partir del aprovechamiento múltiple del bosque, junto a la política actual de bosques, se podría conservar la superficie actual, así como reducir los esfuerzos del Estado en términos de transferencias y el costo de oportunidad del productor que incentiva a la deforestación.
... En Uruguay, la cantidad de carbono orgánico del suelo puede variar entre 50 y 150 toneladas por hectárea dependiendo del sitio de estudio (Paruelo et al., 2010). Esto es inverso a lo que sucede con las forestaciones y los bosques que concentran más de la mitad de su biomasa encima del suelo (Jobbágy et al., 2006;Risio et al., 2012). La acumulación de materia orgánica por encima del suelo en forestaciones ofrece combustible para incendios que pueden provocar la pérdida de importantes cantidades de suelo (Jobbágy et al., 2006). ...
... En Uruguay, la cantidad de carbono orgánico del suelo puede variar entre 50 y 150 toneladas por hectárea dependiendo del sitio de estudio (Paruelo et al., 2010). Esto es inverso a lo que sucede con las forestaciones y los bosques que concentran más de la mitad de su biomasa encima del suelo (Jobbágy et al., 2006;Risio et al., 2012). La acumulación de materia orgánica por encima del suelo en forestaciones ofrece combustible para incendios que pueden provocar la pérdida de importantes cantidades de suelo (Jobbágy et al., 2006). ...
Introducción El pastizal o campo natural es la formación vegetal más extensa y diversa de la región. Es la base sobre la cual se sustenta una de las actividades productivas más importantes de nuestro país: la ganadería extensiva. Además, provee otros beneficios a la sociedad como el secuestro de carbono, el ciclado de nutrientes y la prevención de la erosión del suelo. La influencia del pastizal natural en la historia, la cultura y las tradiciones del país y de la región se ve reflejada en los hechos históricos que ocurrieron luego de la introducción de la ganadería y que marcaron para siempre el destino de la región. En este capítulo se señalarán los principales servicios ecosistémicos que el pastizal natural le brinda a la sociedad y se analizará el efecto de la resiliencia para la producción de forraje y otros beneficios al absorber perturbaciones y evitar que pierda la capacidad de seguir proveyendo dichos beneficios. Servicios ecosistémicos del pastizal natural El pastizal natural es el bioma de nuestro país. Es la formación vegetal determinada por la temperatura y la precipitación promedio de la región. Según Soriano (1991), nuestro país forma parte de los pastizales del Río de la Plata, una de las regiones más vastas de pastizales naturales del mundo que se extiende desde el centro este de Argentina hasta el sur de
... inappropriate livestock management have altered forest appearance and structure by stimulating vegetative reproduction, increasing density, colonizing new areas and changing allometric tree relationships (Dussart et al., 1998;Medina et al., 2000;Risio et al., 2014). ...
... Root abiotic factors such as soil texture, soil nutrient levels and available soil moisture (Cavelier 1992;Gerhardt and Fredriksson 1995;Mokany et al. 2006;Ruiz-Peinado et al. 2012;Risio et al. 2014). Nursery tests of other African hardwoods partially agree with the results of this study. ...
Rural communities in West Africa value Prosopis africana for its wood and other essential products and environmental services. The climate is becoming hotter and drier with more variable rainfall, so it is important to identify provenances that are better adapted to a hotter, drier climate. Some tree improvement research programs use nursery tests to identify better adapted provenances, but are conclusions comparable to those from field tests? We analyzed data (height, root dry weight, shoot dry weight, root/shoot ratio, survival) from a provenance/progeny nursery test of P. africana at 8 months, and compared the results with a field test at 11 and 13 years. The tests included 275 families from 28 provenances in the Sahelian and Sudanian ecozones of Burkina Faso and Niger, and were established at one relatively dry site in Niger. The proportion of total variance due to provenances and families within provenances was greatest for root/shoot ratio, and root/shoot ratio had the highest heritability of growth variables in the nursery. Provenances with smaller seedlings and larger root/shoot ratios in the nursery had better growth and survival in the field, and were from drier locations. Mean annual rainfall of provenances was the best predictor of provenance growth and survival in the field, followed by provenance height and root/shoot ratio in the nursery. We recommend that tree improvement research programs in the Sahelian and Sudanian ecozones of West Africa identify P. africana provenances that are from drier locations and have smaller seedlings and larger root/shoot ratios in the nursery for planting in agroforestry projects in rural communities.
... Mean annual rainfall varies considerably both spatially and temporally in Burkina Faso and Niger (Sivakumar and Gnoumou 1987; Sivakumar et al. 1993), and this could produce spatially and temporally variable selection pressures on root growth, resulting in extensive genetic variation. Root/shoot ratio is affected by stand development such as tree age and tree density, and abiotic factors such as soil texture, soil nutrient levels and available soil moisture (Cavelier 1992; Gerhardt and Fredriksson 1995; Mokany et al. 2006; Ruiz-Peinado et al. 2012; Risio et al. 2014). ...
Rural communities in West Africa value Prosopis africana for its wood and other essential products and environmental services. The climate is becoming hotter and drier with more variable rainfall, so it is important to identify provenances that are better adapted to a hotter, drier climate. Some tree improvement research programs use nursery tests to identify better adapted provenances, but are conclusions comparable to those from field tests? We analyzed data (height, root dry weight, shoot dry weight, root/shoot ratio, survival) from a provenance/progeny nursery test of P. africana at 8 months, and compared the results with a field test at 11 and 13 years. The tests included 275 families from 28 provenances in the Sahelian and Sudanian ecozones of Burkina Faso and Niger, and were established at one relatively dry site in Niger. The proportion of total variance due to provenances and families within provenances was greatest for root/shoot ratio, and root/shoot ratio had the highest heritability of growth variables in the nursery. Provenances with smaller seedlings and larger root/shoot ratios in the nursery had better growth and survival in the field, and were from drier locations. Mean annual rainfall of provenances was the best predictor of provenance growth and survival in the field, followed by provenance height and root/shoot ratio in the nursery. We recommend that tree improvement research programs in the Sahelian and Sudanian ecozones of West Africa identify P. africana provenances that are from drier locations and have smaller seedlings and larger root/shoot ratios in the nursery for planting in agroforestry projects in rural communities.
Prosopis genus comprises 44 species which grow in arid and semiarid environments of America, Asia and Africa and in Oceania as introduced species. Of those 44 species, 30 grow in America. Argentina is supposed to be the origin center of the genus Prosopis, and that could explain the fact that this country has the highest species variability. Prosopis species are of great ecological and social value providing goods such as firewood, food, feed for livestock and medicines as well as services acting as watershed stabilizers and nitrogen and carbon sequesters. In this chapter, we address the new insights that dendrochronological studies have provided about Prosopis genus worldwide with main emphasis in Latin America. Many studies provide information about growth dynamics which are later on applied to develop management plans, to quantify the increment in dead and alive biomass throughout time or to estimate growth changes linked to social and political events. Rainfall is the main growth driver of Prosopis throughout the Andes from Peru to central Argentina, whereas in the flat Pampas temperature is the main tree-ring width driver. Climate variables are hard to separate from other factors affecting growth such as geomorphology, anthropogenic impact and groundwater depth. Outside of Latin America, dendrochronology of Prosopis has been used for the analysis of anthropogenic contamination. Fire, the main disturbance factor in arid and semiarid environments, showed a regional dynamic as a result of human activities. Most dendroecological studies on Prosopis species, which allowed determining these species dynamics, concluded that Prosopis do not present an encroaching behavior. This review demonstrates the avant-garde and influential value of Prosopis genus for dendroecological research as it allows reconstructing past disturbances as fire, anthropogenic impact and changes in groundwater depth for the last 50–100 years and up to 356 years in the case of Prosopis caldenia Burkart in the Pampean Region.
Difficulty in quantifying rates of biological N fixation (BNF), especially over long time scales, remains a major impediment to defining N budgets in many ecosystems. To estimate N additions from BNF, we applied a tree-scale N mass balance approach to a well-characterized chronosequence of woody legume (Prosopis glandulosa) encroachment into subtropical grasslands. We defined spatially discrete single Prosopis clusters (aged 28–99 years), and for each calculated BNF as the residual of: soil N (0–30 cm), above- and below-ground biomass N, wet and dry atmospheric N deposition, N trace gas and N2 loss, leaching loss, and baseline grassland soil N at time of establishment. Contemporary BNF for upland savanna woodland was estimated at 10.9 ± 1.8 kg N ha−1 y−1, equal to a total of 249 ± 60 kg N ha−1 over about 130 years of encroachment at the site. Though these BNF values are lower than previous estimates for P. glandulosa, this likely reflects lower plant density as well as low water availability at this site. Uncertainty in soil and biomass parameters affected BNF estimates by 6–11%, with additional sensitivity of up to 18% to uncertainty in other scaling parameters. Differential N deposition (higher rates of dry N deposition to Prosopis canopies versus open grasslands) did not explain N accrual beneath trees; iterations that represented this scenario reduced estimated BNF estimates by a maximum of 1.5 kg N ha−1 y−1. We conclude that in this relatively well-constrained system, small-scale mass balance provides a reasonable method of estimating BNF and could provide an opportunity to cross-calibrate alternative estimation approaches.
Difficulty in quantifying rates of biological N fixation (BNF), especially over long time scales, remains a major impediment to defining N budgets in many ecosystems. To estimate N additions from BNF, we applied a tree-scale N mass balance approach to a well-characterized chronosequence of woody legume (Prosopis glandulosa) encroachment into subtropical grasslands. We defined spatially discrete single-Prosopis clusters (aged 28-99 years), and for each calculated BNF as the residual of: soil N (0-30 cm), above- and below-ground biomass N, wet and dry atmospheric N deposition, N trace gas and N2 loss, leaching loss, and baseline grassland soil N at time of establishment. Contemporary BNF for upland savanna woodland was estimated at 10.9 kg N ha-1 yr-1, equal to a total of 249 kg N ha-1 over ~130 years of encroachment at the site. Though these BNF values are lower than previous estimates for P. glandulosa, this likely reflects lower plant density as well as low water availability at this site. Uncertainty in soil and biomass parameters affected BNF estimates by 6-11%, with additional sensitivity of up to 18% to uncertainty in other scaling parameters. Differential N deposition (higher rates of dry N deposition to Prosopis canopies versus open grasslands) did not explain N accrual beneath trees; iterations that represented this scenario reduced estimated BNF estimates by a maximum of 1.5 kg N ha-1 yr-1. We conclude that in this relatively well-constrained system, small-scale mass balance provides a reasonable method of estimating BNF and could provide an opportunity to cross-calibrate alternative estimation approaches.
Efectos del Fuego en la Madera de Prosopis alba Griseb. y Prosopis nigra (Griseb.) Hieron, Mimosaceae Se evaluó el efecto de incendios forestales sobre el fuste y ramas principales de ejemplares de Prosopis alba y Prosopis nigra de las localidades Sachayoj y Coronel Rico, provincia de Santiago del Estero, pertenecientes al Chaco Seco de Argentina. Las lesiones por fuego identificadas se categorizaron en cicatrices y marcas. Las primeras corresponden a alteraciones más frecuentes y severas que las segundas. Estas lesiones originan defectos en los fustes que incluyen la formación de costillas, acebolladuras, fendas y corteza inclusa. El porcentaje más frecuente de pérdida o alteración de anillo cambial es el comprendido entre 1 y 20 % del perímetro. En sentido longitudinal, el mayor número de lesiones se identificaron hasta una altura de 2,30 m, que representa casi la totalidad de los fustes tecnológicamente aprovechables. El leño decolorado es el leño formado antes del daño por fuego, que sufre la impregnación de vasos, fibras y radios con contenidos. El leño formado después del fuego manifiesta cambios en el patrón normal de tejidos, tales como el incremento en el porcentaje de parénquima axial y radial, la disminu-ción el porcentaje fibras y vasos y la desorientación de los elemento axiales. Todos los cambios observados reducen el volumen y la calidad de la madera potencialmente aprovechable in P. alba y P. nigra.
Esta pequeña obra procura esclarecer algunos interrogantes y controversias acerca de la relación compleja entre agricultura y ambiente en la Argentina. A menudo somos testigos de posiciones dogmáticas o interesadas que hoy requieren ser abordadas con el mejor conocimiento científico disponible ¿Cuánto hay de mito y de realidad en los impactos ambientales de la expansión agrícola? ¿Es progresiva la expansión de la frontera agrícola, o hay avances y retrocesos territoriales? ¿Aumenta la contaminación por plaguicidas? ¿Aumenta la erosión de los suelos por el mayor cultivo? ¿Se deforesta en Argentina a tasas tan altas como denuncian las organizaciones ambientalistas? ¿Se pierden áreas de pastizales y pasturas? ¿Cuán afectados están el hábitat y la biodiversidad? ¿Hay una pérdida desmedida de minerales esenciales como el carbono, el nitrógeno y el fósforo? ¿Cuál es el impacto real del cultivo de soja sobre la ecología y el ambiente? ¿Qué muestran nuestros indicadores ecológicos y ambientales respecto a otros países del mundo? Ninguno de estos interrogantes tiene una respuesta sencilla, pero sí es posible aproximarla a través del análisis de 50 años de avance de nuestra frontera agropecuaria.
Los cambios más importantes registrados en la distribución del caldén (Prosopis caldenia Burkart) en la región semiárida central de Argentina, Incluyen el aumento de la densidad de esta especie y la invasión de pastizales naturales. Los factores causales y la dinámica de estos cambios no han sido detalladamente estudiados. En este trabajo se relaciona la dinámica de dos poblaciones de caldén con factores tales como manejo, fuego y precipitaciones. Se eligieron como áreas de estudios una planicie cuya vegetación original era un pastizal (sitio 1) y un bosque de caldén que originalmente fue una sabana (sitio 2). En cada sitio se determinaron los patrones espaciales en base a transectas y las tasas de Implantación las cuales fueron inferidas por dendroecologia. Las densidades estimadas fueron 586 y 1259 plantas/ha, para el sitio 1 y 2 respectivamente. No se encontraron evidencias de agrupamiento para la escala espacial de este estudio (p=0.52, sitio 1 y p=0.08, sitio 2 para n=112). Las edades de los individuos muestreados comprendieron un rango de 3 a 65 años en el sitio 1 y de 8 a 55 años en el sitio 2 (en este sitio 2 solo fueron muestreadas las plantas con diámetro menor de 30 cm). Primariamente los dos sitios fueron utilizados para erra de ovinos; durante ese periodo, las tasas de establecimiento fueron 0.99 plantas/ha/año (16 años) en el sitio 1, Y 10 plantas/ha/año (15 años) en el sitio 2. Posteriormente luego de diez años desde la introducción del ganado vacuno, las tasas ascendieron a 12.7 y 48.5 plantas/ha/año respectivamente. Un evento de fuego fue registrado en cada sitio (1980 en el sitio 1 y 1964 en el sitio 2) pero este factor no alteró la tendencia ascendente de la densidad. En el sitio 2 el Incendio fue contemporáneo con la introducción del ganado y coincide a su vez con un importante incremento en el establecimiento. No se encontró relación entre la dinámica de la población de caldén y las fluctuaciones en la precipitación anual o estacional. Las variaciones registradas en las tasas de establecimiento coincidieron con cambios en el manejo ganadero, confirmando la Importancia del ganado en la dispersión de las semillas de caldén.
Resúmenes de Trabajos presentados en otras publicaciones (por docentes de la U.N.L.Pam.) Publicado en JOURNAL OF RANGE MANAGEMENT, 51 (6), November 1998
La estimación alométrica de la biomasa foliar arbórea es necesaria para determinar la producción primaria y para analizar algunas de las interacciones ecológicas entre los árboles y los demás componentes de la vegetación. El objetivo del trabajo fue ajustar y seleccionar modelos para estimar la biomasa foliar de Prosopis flexuosa a partir de variables dendrométricas. Se apearon seis árboles, se midió su diámetro y se calculó el área de albura de muestras transversales de leño, en cuatro niveles: en los órdenes de ramificación dentro de la copa viva (ramas secundarias, terciarias y cuaternarias agrupadas), en el extremo distal de las ramas primarias y en los extremos distal y basal del fuste. Se recolectaron las hojas correspondientes a cada nivel y se obtuvo el peso seco. El área de albura fue la mejor variable predictora de biomasa foliar, aunque el diámetro tuvo buen ajuste en ramas dentro de la copa viva y en ramas primarias. Los modelos calculados con variables de fuste tuvieron menor ajuste. Se concluye que para la estimación no destructiva de la biomasa foliar de plantas adultas de Prosopis flexuosa es recomendable utilizar el modelo basado en el diámetro distal de las ramas primarias.
Efectos del Fuego en la Madera de Prosopis alba Griseb. y Prosopis nigra (Griseb.) Hieron, Mimosaceae Se evaluó el efecto de incendios forestales sobre el fuste y ramas principales de ejemplares de Prosopis alba y Prosopis nigra de las localidades Sachayoj y Coronel Rico, provincia de Santiago del Estero, pertenecientes al Chaco Seco de Argentina. Las lesiones por fuego identificadas se categorizaron en cicatrices y marcas. Las primeras corresponden a alteraciones más frecuentes y severas que las segundas. Estas lesiones originan defectos en los fustes que incluyen la formación de costillas, acebolladuras, fendas y corteza inclusa. El porcentaje más frecuente de pérdida o alteración de anillo cambial es el comprendido entre 1 y 20 % del perímetro. En sentido longitudinal, el mayor número de lesiones se identificaron hasta una altura de 2,30 m, que representa casi la totalidad de los fustes tecnológicamente aprovechables. El leño decolorado es el leño formado antes del daño por fuego, que sufre la impregnación de vasos, fibras y radios con contenidos. El leño formado después del fuego manifiesta cambios en el patrón normal de tejidos, tales como el incremento en el porcentaje de parénquima axial y radial, la disminu-ción el porcentaje fibras y vasos y la desorientación de los elemento axiales. Todos los cambios observados reducen el volumen y la calidad de la madera potencialmente aprovechable in P. alba y P. nigra.
In a semiarid sedimentary catchment of central Argentina, we describe a recent process of landscape dissection, abrupt canyon and watercourse formation and soil salinization. We link these adverse hydrological and geomorphological transformations to three potentially important drivers: precipitation increase, seismic activity and deforestation. Remote sensing imagery in the last 48 years showed an exponential increase in the length of streams, with drainage density values tripling to reach 0.22 km km 2 . During the same period, forest area declined from 47% to 10%, at the expense of agriculture expansion. A 3.4-fold expansion of surface water bodies and water table level raise of 0.15 m y À1 over the last 35 years was observed. Discharge of a new stream at the middle of the basin ranged between 0.25 and 0.45 m 3 s À1 accompanied by a large and stable load of salts (~0.7 g l À1). Nil recharge and large vadose accumulation of salts in dry forests stands contrasted with recharge rates of ~16 mm y À1 and salt-leached profiles under agriculture. Although the process of landscape dissection occurred during decades of higher than average precipitation, extreme rainfall events and seismic activity were not exceptional in that period. Results suggest that the replacement of forests by annual crops played a more important role, reducing evapotranspiration, triggering the onset of groundwater recharge and favouring subsurface through piping/ sapping processes. The abrupt landscape dissection shows no signs of stabilization at the present and may only be ameliorated through changes in vegetation that restore the original non-flow condition of the forest.
Los bosques de Prosopis caldenia (caldén) han sufrido grandes cambios estructurales a partir de la introducción de las actividades silvopastoriles en los mismos. El fuego ha jugado un rol importante en tales cambios aunque las relaciones de causa-efecto no han sido aún demostradas en forma conclusiva. En este trabajo se reconstruyen los regímenes de fuego ocurridos en un bosque de caldén de la estancia Bajo Verde, en la provincia de La Pampa, Argentina, mediante el análisis dendrocronológico de cicatrices de fuego registradas en el leño de los mismos. El régimen de fuego en el área de estudio ha sido muy dinámico durante los siglos XIX y XX. Tanto la frecuencia como la extensión de los fuegos han experimentado importantes cambios probablemente en relación a cambios en el tipo de ocupación y de uso del área. Esta información será de gran importancia a la hora de evaluar el grado de influencia del fuego en la variación espacio-temporal de los patrones de los bosques de caldén.
The objective of this work was to study the effects of different fire intensities and season of burning on five important woody species in the central semi-arid rangelands of Argentina. Overall results in this experiment indicate that a single fire reduces woody species abundance. This effect persists for several growing seasons after the fire and is related to fire intensity. Mortality rates, with the exception ofLarrea divaricata, were low and all the species produced new sprouts after the fire. This sprouting capacity may be the key to the abundance and persistence of woody species in these communities. A single fire does not start a replacement sequence and the plant community persists with some variation in the abundance of the principal woody species.
As much as 40% of live biomass in coniferous forests is located belowground, yet the effect of tree density on biomass allocation is poorly understood. We developed allometric equations using traditional harvesting techniques to estimate coarse root biomass for approximate to13-year-old postfire lodgepole pine trees (Pinus contorta Dougl. ex Loud. var. latifolia Engelm.). We then used these equations, plus estimates of fine root and aboveground biomass, to estimate total tree biomass and belowground to aboveground biomass ratios in young postfire lodgepole pine stands with a wide range of tree densities. Belowground biomass allocation increased with tree density, but the increase was largely determined by inherent differences associated with tree size, not competition. Stand biomass in trees ranged from 46 to 5529 kg.ha(-1) belowground, from 176 to 9400 kg.ha-1 aboveground, and from 222 to 13 685 kg.ha(-1) for total biomass. For individual trees, the ratio of belowground to total biomass declined with tree size from 0.44 at a basal diameter of 0.5 cm to 0.11 at a basal diameter of 8 cm. This shift in individual tree allocation caused the proportion of total stand biomass in belowground tissues to increase from 19% in low-density stands with larger trees to 31% in high-density stands with small trees.
To estimate forest carbon pools from forest inventories it is necessary to have biomass models or biomass expansion factors. In this study, tree biomass models were developed for the main hardwood forest species in Spain: Alnus glutinosa, Castanea sativa, Ceratonia siliqua, Eucalyptus globulus, Fagus sylvatica, Fraxinus angustifolia, Olea europaea var. sylvestris, Populus x euramericana, Quercus canariensis, Quercus faginea, Quercus ilex, Quercus pyrenaica and Quercus suber. Different tree biomass components were considered: stem with bark, branches of different sizes, above and belowground biomass. For each species, a system of equations was fitted using seemingly unrelated regression, fulfilling the additivity property between biomass components. Diameter and total height were explored as independent variables. All models included tree diameter whereas for the majority of species, total height was only considered in the stem biomass models and in some of the branch models. The comparison of the new biomass models with previous models fitted separately for each tree component indicated an improvement in the accuracy of the models. A mean reduction of 20% in the root mean square error and a mean increase in the model efficiency of 7% in comparison with recently published models. So, the fitted models allow estimating more accurately the biomass stock in hardwood species from the Spanish National Forest Inventory data.
Biomass additivity is a desirable characteristic of a system of equations for predicting component as well as total tree biomass since it eliminates the inconsistency between the sum of predicted values for components such as stem, bark, branch and leaf and the prediction for the total tree. Besides logical consistency, a system of additive biomass equations when estimated by taking into account the inherent correlation among the biomass components has greater statistical efficiency than separately estimated equations for individual components. Using mostly small sample data from both published and unpublished sources, a system of non-linear additive biomass equations was developed for 15 native eucalypt forest tree species of temperate Australia. Diameter at breast height was used as the independent variable for all 15 species, while the combined variable of diameter and tree height was used for 14 species with height data. The system of additive equations provided more accurate biomass estimates than the common approach of separately fitting total tree and component biomass equations using log transformed data through least squares regression. Residual error variances were collectively estimated for each species by pooling small sample data across species and using indicator variables to represent the scale factor for each species in a residual variance function. This method overcame a common problem in estimating heteroscedastic error variance in non-linear biomass equations with additive error terms for small samples. From the estimated residual variance functions, approximate confidence bands containing about 95% of the observed data about the mean curve of predicted biomass were derived for all biomass components of each species. This system of additive biomass equations will prove to be useful for biomass estimation of native eucalypt forests of temperate Australia.
Because the world's forests play a major role in regulating nutrient and carbon cycles, there is much interest in estimating
their biomass. Estimates of aboveground biomass based on well-established methods are relatively abundant; estimates of root
biomass based on standard methods are much less common. The goal of this work was to determine if a reliable method to estimate
root biomass density for forests could be developed based on existing data from the literature. The forestry literature containing
root biomass measurements was reviewed and summarized and relationships between both root biomass density (Mg ha−1) and root:shoot ratios (R/S) as dependent variables and various edaphic and climatic independent variables, singly and in
combination, were statistically tested. None of the tested independent variables of aboveground biomass density, latitude,
temperature, precipitation, temperature:precipitation ratios, tree type, soil texture, and age had important explanatory value
for R/S. However, linear regression analysis showed that aboveground biomass density, age, and latitudinal category were the
most important predictors of root biomass density, and together explained 84% of the variation. A comparison of root biomass
density estimates based on our equations with those based on use of generalized R/S ratios for forests in the United States
indicated that our method tended to produce estimates that were about 20% higher.
In this paper a method of estimating the parameters of a set of regression equations is reported which involves application of Aitken's generalized least-squares [1] to the whole system of equations. Under conditions generally encountered in practice, it is found that the regression coefficient estimators so obtained are at least asymptotically more efficient than those obtained by an equation-by-equation application of least squares. This gain in efficiency can be quite large if “independent” variables in different equations are not highly correlated and if disturbance terms in different equations are highly correlated. Further, tests of the hypothesis that all regression equation coefficient vectors are equal, based on “micro” and “macro” data, are described. If this hypothesis is accepted, there will be no aggregation bias. Finally, the estimation procedure and the “micro-test” for aggregation bias are applied in the analysis of annual investment data, 1935–1954, for two firms.
La reintroducción del fuego en el ecosistema bosque de caldén
The estimation of leaf biomass, usually performed by alometric relations, is important for the interpretation of primary production and for the assessment of ecological interactions between trees and the rest of the components in a wood vegetation. The goal for the present work was to adjust and to select allometric models for the estimation of leaf biomass Prosopis flexuosa based on dendrometric variables. Six trees were surveyed. The diameter and sapwood area of transversal samples of wood were determined at four different levels: in the orders of ramification within living crown (secondary, tertiary and quaternary grouped branches), at the distal portions of primary branches and in the apical and basal portions of bole. The leaves were collected according to each level and dry mass was obtained. The sapwood area was the best predictor of leaf biomass, although diameter provided accurate estimations within crown and at the distal portions of primary branches. The models based on trunk dimensions were less precise. It is concluded that the obtained regression model based on the diameter of the distal portions of primary branches can be applied for the non-destructive estimation of leaf biomass in Prosopis flexuosa adult trees.
Since the introduction of forestry and livestock actitvities Prosopis caldenia (caldén) woodlands have undergone drastic structural changes. Fire has played an important role in such changes although cause-effect relationships have not been established conclusively. In this paper the fire regime that ocurred in a caldén woodland in estancia Bajo Verde, La Pampa Province, Argentina, is reconstructed, through dendrochronological analysis of fire scars recorded in sections of the trunk. The fire regime in the study area has been very dynamic during the 19th and 20th centuries. The important changes in frequency and areal extent that fires have experienced are probably related to changes in human occupation and land use patterns. This information would be useful for assessing the degree of influence of fire in the spatio-temporal variations in caldén woodlands.
Fine root biomass was estimated for two Costa Rican broad-leaf evergreen forests with apparent differences in soil nutrient status. Live fine root biomass (<5 mm diameter) for the two sites was 187 and 125 g$\cdot$m$^{-2}$ while total fine root biomass was 662 and 369 g$\cdot$m$^{-2}$. The greater fine root biomass occurred on the site with the lowest soil phosphorus and calcium content. Reviews of the tropical literature suggest that total fine root biomass is inversely related to phosphorus and calcium availability. No apparent relationship was observed between fine root biomass and nitrogen availability in tropical forests.
Two procedures that guarantee the property of additivity among the components of tree biomass and total tree biomass utilizing nonlinear functions are developed. Procedure 1 is a simple combination approach, and procedure 2 is based on nonlinear joint-generalized regression (nonlinear seemingly unrelated regressions) with parameter restrictions. Statistical theory is given for construction of confidence and prediction intervals for the two procedures. Specific examples using slash pine (Pinus elliottii Engelm. var. elliottii) biomass data are presented to demonstrate and clarify the methods behind nonlinear estimation, additivity, error modeling, and the formation of confidence and prediction intervals. Theoretical considerations and empirical evidence indicate procedure 2 is generally superior to procedure 1. It is argued that modeling the error structure is preferable to using the logarithmic transformation to deal with the problem of heteroscedasticity. The techniques given are applicable to any quantity that can be disaggregated into logical components.Deux procédés qui assurent l'additivité entre la biomasse totale d'un arbre et ses composantes ont été développés en utilisant des fonctions non linéaires. Le procédé 1 est une simple approche de combinaison et le procédé 2 est basé sur la méthode non linéaire des moindres carrés unifiés et généraux (la méthode des régressions apparemment indépendantes et non linéaires) avec des restrictions sur les paramètres. La théorie statistique utilisée pour construire les intervalles de confiance et de prédiction est présentée pour chaque procédé. Des exemples spécifiques utilisant des données de biomasse du pin de Floride (Pinus elliottii Engelm. var. elliottii) sont présentés afin de démontrer et de clarifier les méthodes sur lesquelles reposent l'évaluation non linéaire, l'additivité, la modélisation des erreurs et la détermination des intervalles de confiance et de prédiction. Des considérations théoriques et l'évidence empirique indiquent que le procédé 2 est généralement meilleur que le procédé 1. L'auteur soutient qu'il est préférable de modeler la structure des erreurs plutôt que d'employer la transformation logarithmique pour solutionner le problème de l'hétéroscédacité. Les méthodes suggérées sont applicables à n'importe quelle quantité qui peut être désagrégée en composantes logiques.[Traduit par la Rédaction]
Indicators for sustainable forest management are considered to be key tools for the implementation of regional, national and international forest policies. The Montreal process identified the “maintenance of forest contribution to global carbon cycles” as an essential component in sustainable management of forest ecosystems. Carbon sink evaluations provide reference information to policy-makers, stakeholders, resource managers and concerned citizens about the sustainable use of our forests for present and future generations. Two forest areas in northern and central Spain (‘Páramos y Valles’ and Central Mountain Range) were chosen as pilot areas to test the use of the National Forest Inventory to calculate carbon biomass forest sink at operational level.Data from the Second and Third National Forest Inventory (2NFI and 3NFI, respectively), together with biomass equations were used. Total carbon biomass sink was calculated as a balance between carbon dioxide inputs and outputs in forest biomass. Tree growth between 2NFI and 3NFI, new plots and ingrowth (recruitment and upgrowth) biomass were considered as inputs, while forest harvesting and natural mortality were considered as outputs. In ‘Páramos y Valles’, 2.46 Mg CO2 ha−1 year−1 was fixed in the tree biomass of forest ecosystems from 2NFI to 3NFI, whereas in the Central Mountain Range the fixation was 0.72 Mg CO2 ha−1 year−1 in the period between inventories. The balance of CO2 in the two areas was positive in 3NFI, with more than four million Mg of CO2 accumulated in ‘Páramos y Valles’ and more than 72 million Mg of CO2 fixed in the Central Mountain Range. Forest ecosystems are carbon sinks in the tree biomass in the two areas considered.
Two procedures that guarantee the property of additivity among the components of tree biomass and total tree biomass utilizing nonlinear functions are developed. Procedure 1 is a simple combination approach, and procedure 2 is based on nonlinear joint-generalized regression (nonlinear seemingly unrelated regressions) with parameter restrictions. Statistical theory is given for construction of confidence and prediction intervals for the two procedures. Specific examples using slash pine (Pinus elliottii Engelm. var. elliottii) biomass data are presented to demonstrate and clarify the methods behind nonlinear estimation, additivity, error modeling, and the formation of confidence and prediction intervals. Theoretical considerations and empirical evidence indicate procedure 2 is generally superior to procedure 1.(1) It is argued that modeling the error structure is preferable to using the logarithmic transformation to deal with the problem of heteroscedasticity. The techniques given are applicable to any quantity that can be disaggregated into logical components.
Little is known about the contribution of arid and semiarid regions to the carbon balance at a global scale. The lack of information is especially noticeable for the Gran Chaco, which covers an area of about 1,200,000km2 in South America. This study quantified carbon pools and their changes along a land-use gradient in the Dry Chaco, the driest portion of the Gran Chaco, measured in the aboveground biomass and in soils (20cm depth). The work was conducted in the Chancaní reserve, where the best preserved forests of the region are found, and in surrounding areas, including a primary forest, a secondary forest and shrubby grasslands. Previous works indicate that the entire area was originally covered by forests similar to those found at the Chancaní reserve, and that the land-use changes occurred at least 30 years prior to this study. Total aboveground carbon stock, which comprises the total amount of living organic matter in trees and shrubs, was 30.31MgCha−1 in the primary forest, which was reduced to 8.38MgCha−1 in the secondary forest and to 1.37MgCha−1 in shrubby grasslands. Carbon stock in the tree component decreased drastically between the primary and the secondary forests from 25.40 to 5.11MgCha−1. The component described as saplings of trees and shrubs also decreased significantly among the three communities from 4.91MgCha−1 in the primary forest to 3.27MgCha−1 in the secondary forest and to only 1.37MgCha−1 in the shrubby grasslands. No significant differences were detected in the carbon content per unit area of soil, although it decreased from 34.59MgCha−1 in the primary forest to 28.04MgCha−1 in the secondary forest and to 22.93MgCha−1 in the shrubby grassland, with a significant increase in soil bulk density in the disturbed communities. Therefore, differences in carbon stocks between communities were primarily the result of differences in vegetation biomass, whereas changes in the land-use gradient analyzed had a lower impact on soils. Nevertheless, soil constitutes the largest pool, and more severe ecological disturbances could lead to important changes in net carbon storage.
A balance between forest production and protection is hard to achieve in arid zones due to their low potential for wood production. Prosopis flexuosa woodlands are the major woody formations in the Monte desert and are currently in a degraded state due to intense use. The main degradation factors in the study area are overgrazing and firewood extraction. We developed allometric models to estimate the aerial biomass of P. flexuosa, compared annual growth rates of one-and multi-stemmed individuals through dendrochronological methods, and estimated the productivity of four structurally different woodlands in the central Monte. Total dry weight was best estimated by power equations. Annual increments in basal area and dry weight were initially larger for multi-than one-stemmed individuals. However, whereas multi-stemmed individuals rapidly decreased their growth rates after 60 years of age, one-stemmed trees maintained steady growth rates during the first 100 years. Depending on woodland density and tree size, total woodland biomass varied between 4000 and 15 000 kg ha -1 . Wood productivity was similar in all four woodlands studied (121.6e173.7 kg ha -1 year -1). Our results reveal the importance of tree growth habit to productivity, and suggest that regulated extraction of firewood and poles from old multi-stemmed individuals could optimize wood productivity and contribute to the sustainable use and conservation of these woodlands.
Export Date: 2 July 2013, Source: Scopus, Article in Press
The authors begin by outlining the role of the dendrochronologists both in the field and in the laboratory. The basic principles of tree-ring dating are then explained in detail, followed by a guide to the collection of archaeological and modern specimens from the field. The final section deals with the laboratory techniques used: the preliminary processing and preparation of archaeological and modern specimens; the process of dating specimens; and finally the compilation of a master chronology.
Semiarid woodlands dominated by Prosopis caldenia thrive at the dry edge of the Argentinean Pampas. Deforestation and increased precipitation have driven sustained water table level rise in the region that are likely to affect the dynamics of remnant woody vegetation patches. Here we analyze the effect of climate and groundwater level on the establishment, growth and death of P. caldenia located on lowland (current water table
Above- and below-ground net primary production was estimated for 40-year-old Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) stands growing on sites with apparently large differences in productivity potential. Aboveground net production was estimated from direct measurements of tree growth; belowground productivity was derived from data obtained by sorting live and dead roots from soil cores used in combination with measurements of root growth on observation windows.Aboveground net production was 13.7 t•ha−1 on the high productivity site and 7.3 t•ha−1 on the low productivity site. Belowground dry matter production on the high productivity site was 4.1 t•ha−1 compared with 8.1 t•ha−1 for the poorer site. On the more productive site, 8% of total stand dry matter production was in fine roots in contrast to over 36% on the poorer site. The difference in total net production (aboveground plus belowground) between the two sites was small (2.4 t•ha−1). Apparent differences in aboveground productivity may, to a large extent, result from the need for a greater investment in the fine roots on harsher sites.
In this paper a method of estimating the parameters of a set of regression equations is reported which involves application of Aitken's generalized least-squares [1] to the whole system of equations. Under conditions generally encountered in practice, it is found that the regression coefficient estimators so obtained are at least asymptotically more efficient than those obtained by an equation-by-equation application of least squares. This gain in efficiency can be quite large if “independent” variables in different equations are not highly correlated and if disturbance terms in different equations are highly correlated. Further, tests of the hypothesis that all regression equation coefficient vectors are equal, based on “micro” and “macro” data, are described. If this hypothesis is accepted, there will be no aggregation bias. Finally, the estimation procedure and the “micro-test” for aggregation bias are applied in the analysis of annual investment data, 1935–1954, for two firms.
To improve estimates of the state and change in C pools due to changes in land use in tropical forests of Africa, we combined spatially explicit estimates of biomass C density, obtained by modelling in a geographical information system (GIS), with new data on the area of forests (woody formations with a minimum of 10% crown cover) reported at subnational units for 1980 and 1990 by the Food and Agriculture Organization (FAO). Estimates of the biomass C densities for grass/shrub savannas were also included using a simple model based on precipitation. The total C pool in above– and below–ground forests and grass/shrub savannas of Africa for 1980 was 50.8 Pg (1015g), with aboveground forest biomass accounting for 75% of the total, below–ground forest biomass for 21%, and grass/shrub savannas for 4%. Area weighted mean biomass C densities were about 180 Mg ha–1 for lowland moist forests, 82 Mg ha–1 for all forests, and 6 Mg ha–1 for grass savannas. The total change in the aboveground forest C pool for the decade 1980–90 due to changes in land cover and use was estimated to be a decrease of 6.6 Pg C. Of this total, 43% was due to deforestation and 57% due to biomass reduction by other human activities. Six countries, mostly in central Africa, accounted for more than 73% of the total change in the C pool. The difference between state and change of C pool estimates made at the subnational scale and those made at the national scale proved to be insignificant across the region as a whole (2% for pools and – 1% for change in pool) but potentially important to individual countries (from + 36% to – 39% for pools and from + 43% to – 57% for change in pool). The differences between the two approaches may reflect a better match of the areas being deforested with the biomass C density of forests being cleared.
One of the most common descriptors of the relationship between root and shoot biomass is the root : shoot ratio, which has become a core method for estimating root biomass from the more easily measured shoot biomass. Previous reviews have examined root : shoot ratio data, but have only considered particular vegetation types and have not always critically reviewed the data used. Reliable root : shoot ratios are needed for a wide range of vegetation types in order to improve the accuracy of root biomass estimates, including those required for estimating the effects of land management and land use change in National Greenhouse Gas Inventories.
This study reviewed root : shoot ratios in terrestrial biomes. A key facet of our analysis was a critical methodological review, through which unreliable data were identified and omitted on the basis of specific criteria. Of the 786 root : shoot ratio observations collated, 62% were omitted because of inadequate or unverifiable root sampling methods. When only the reliable data were examined, root : shoot ratios were found to be negatively related to shoot biomass, mean annual precipitation, mean annual temperature, forest stand age, and forest stand height.
Although a single allometric equation derived in this study reliably predicted root biomass from shoot biomass for forests and woodlands, in general, the use of vegetation-specific root : shoot ratios were found to be a more accurate method for predicting root biomass. When the root : shoot ratio data collated here were applied to an analysis of the global carbon budget, there was a 50% increase in estimated global root carbon stock, and a 12% increase in estimated total carbon stock of terrestrial vegetation. The use of the vegetation-specific root : shoot ratios presented in this study is likely to substantially improve the accuracy of root biomass estimates for purposes such as carbon accounting and for studies of ecosystem dynamics.
The distribution of root biomass and physical and chemical properties of the soils were studied in a semideciduous and in
a lower montane rain forest in Panama. Roots and soil samples were taken by means of soil cores (25 cm deep) and divided into
five, 5-cm deep sections. Soils were wet-sieved to retrieve the roots that were classified in four diameter classes: very
fine roots (<1 mm), fine roots (1–2 mm), medium roots (2–5 mm) and coarse roots (5–50 mm). Soil samples were analyzed for
organic carbon, total nitrogen, available phosphorus, exchangeable bases, cation exchange capacity, pH, aluminium and exchangeable
acidity. Total root biomass measured with the soil corer (roots <50 mm in diameter) was not different between the forests
(9.45 t ha-1), while biomass of very fine roots was larger in the mountains (2.00 t ha-1) than in the lowlands (1.44 t ha-1). The soils in the semideciduous forest were low in available phosphorus, while in the mountains, soils had low pH, high
exchangeable aluminium and exchangeable acidity, and low concentration of exchangeable bases. Phosphorus was in high concentration
only in the first 5 cm of the soil. In both forests, there was an exponential reduction of root biomass with increasing depth,
and most of the variation in the vertical distribution of roots less than 2 mm in diameter was explained by the concentration
of nitrogen in the soils. The results of this study support the hypothesis that a large root biomass in montane forests is
related to nutrients in low concentration and diluted in organic soils with high CEC and low bulk density, and that fine root
biomass in tropical forests in inversely related to calcium availability but not a phosphorus as has been suggested for other
forests.