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Synergetic effects of fire, climate, and management history on Prosopis caldenia recruitment in the Argentinean pampas
... Coetaneous forests, in relation to their age, which are the result of a disturbance (fire, deforestation, etc.) and subsequent recruitment, are common in the area (Dussart et al., 2015;Bogino et al., 2015). In the 18th century a simultaneous recruitment occurred, which could have been favoured by the massive cattle movement that helped dissemination (Dussart et al., 1998). ...
... In the 20th century, and more specifically in the 1920s, another simultaneous recruitment happened, due to land abandonment as a result of the great agricultural penury. Sheep overgrazing caused low grass availability during dry periods, which likely had a beneficial effect on recruitment due to the reduction of grass competition (Walter, 1971;Villalobos et al., 2005;Bogino et al., 2015). ...
... A simultaneous growth release linked to extensive deforestation as a result of European immigration occurred, changing the woodlands' physiognomy into a savannah-like area. The old paradigm of caldén forests being open to semi-open woodlands can be challenged in light of dendrochronological studies (Dussart et al., 2015;Bogino et al., 2015). ...
... In Argentina, some semiarid forests are dominated by "Caldén" (Prosopis caldenia Burkart, Fabaceae), a xerophilous deciduous tree species endemic in Argentina that thrives at the dry edge of the Pampas. Caldén's woodlands originally covered 169,333 km 2 in central Argentina, but these forests have been severely affected by deforestation for more than one century [5,6]. ...
... Nees) cropfields, and croplands such as corn (Zea mays L.), soybean (Glycine max (L.) Merill) and sunflower (Helianthus annuus L.) fields [7]. Only 18% of the original Caldén's woodland is still in place, covering approximately 8438 km 2 [6,7]. ...
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.
... One of the most relevant applications of a growth-ring analysis is its use to establish the relationship between annual growth and climatic variables and, consequently, the reconstruction of past climatic conditions. Previous dendrochronological studies in the arid and semi-arid environments of Argentina had analyzed the most long-lived species with the highest timber value with special emphasis on the genus Prosopis (Morales et al. 2005, Villagra et al. 2005, Dussart et al. 2011, Bogino et al. 2015. Therefore, knowing about the growth dynamics of pioneer species will complement these studies and establish the interconnection between main species and those that are codominant or intermediate in a secondary forest (Gorzelak et al. 2015). ...
... The mean radial growth of G. decorticans (3.95 mm year -1 ) is similar to that of Prosopis caldenia (2.69 -5.12 mm year -1 ) growing in the same area (Bogino and Villalba 2008) or in the province of La Pampa (2.2 -4.52 mm year -1 ) (Bogino et al. 2015, Velasco et al. 2018. These results pointed out that woody species have similar growing rates even though they are dominant (P. ...
In Prosopis caldenia forests, currently, the main activity is cattle rearing. Almost all research focuses on the herbaceous component, losing sight of the value of the forest resource and the implications of its management on the forage resource. The objective of this work is to evaluate forage availability based on forest cover, apply a model of diameter classes that allows predicting the evolution of forest mass and establish the relationship between the evolution of forest cover and forage availability. For this, forage availability was measured under and outside the projection of woody canopies, in two covers: open (10-15 m2 ha-1) and closed (25-30 m2 ha-1). Afterwards, through a model of diameter classes, it was sought to predict how the parameters of forest mass would evolve. The results of the herbaceous component showed that, up to 15 m2 ha-1 of basal area (BA), there is no significant decrease in forage availability (approximately 2,700 kg ha-1). Regarding the forestry component, in a projected period of 10 years, 6.68 m3 ha-1 would be obtained, representing 9.61 % of total standing volume. The relationship between canopy coverage and BA showed increase of 3.18 % per BA unit (R2 = 0.96). This would allow projecting their participation by diameter class to propose improvement cuts that allow conducting these systems at coverage levels that do not significantly affect forage yield.
... One of the most relevant applications of a growth-ring analysis is its use to establish the relationship between annual growth and climatic variables and, consequently, the reconstruction of past climatic conditions. Previous dendrochronological studies in the arid and semi-arid environments of Argentina had analyzed the most long-lived species with the highest timber value with special emphasis on the genus Prosopis (Morales et al. 2005, Villagra et al. 2005, Dussart et al. 2011, Bogino et al. 2015. Therefore, knowing about the growth dynamics of pioneer species will complement these studies and establish the interconnection between main species and those that are codominant or intermediate in a secondary forest (Gorzelak et al. 2015). ...
... The mean radial growth of G. decorticans (3.95 mm year -1 ) is similar to that of Prosopis caldenia (2.69 -5.12 mm year -1 ) growing in the same area (Bogino and Villalba 2008) or in the province of La Pampa (2.2 -4.52 mm year -1 ) (Bogino et al. 2015, Velasco et al. 2018. These results pointed out that woody species have similar growing rates even though they are dominant (P. ...
Arid and semiarid environments dominate the Earth's surface and are very vulnerable to global change. Chañar (Geoffroea decorticans) and brea (Parkinsonia praecox) are two ubiquitous woody species of these environments. They grow in degraded forests, strongly modified areas and as a main component of secondary forests. Despite the value of both species, little is known about their growth dynamics and their relationship with climate. The objective of this research was to determine their dendrochronological potential and the connection between growth and climate variables. Anatomical and standard dendrochronological methods were applied. First of all, we stated the anatomical characteristics that allowed us to detect tree-ring boundaries (terminal parenchyma and variation in the shape of vessels). Further, after dating and measurement of tree rings we determined significant correlation between series, which means a common growth signal among trees as a result of environmental variable effects. Trees were not older than 40 years. Mean annual radial growth was 3.37 mm (SD±0.71) and 2.16 mm (SD±0.61) for chañar and brea, respectively. Finally, chañar and brea had a negative growth-mean temperature association. Rainfall affected chañar and brea growth in summer previous to the growing season. Southern Oscillation Index (SOI) had an inverse association with growth of brea. This means, in the case of brea, a significant association with local (temperature and rainfall) and global (SOI) climate variables. These results evidenced the growth dynamics of both species and their value for dendroclimatological studies for the first time.
... Prosopis species like P. caldenia offer outstanding accuracy for dendrochronological research on growth dynamics and productivity (Dussart et al., 1998;Villalba et al., 2000;Bogino and Villalba, 2008;Bogino et al., 2015), growth, ground water table and climate association (Bogino and Jobbágy, 2011), and fire effect (Medina et al., 2000;Medina, 2008;Bogino et al., 2015).The first South American dendrochronological study was conducted on caldén to determine its potential as a drought indicator (Krebs and Fisher, 1931). ...
... Prosopis species like P. caldenia offer outstanding accuracy for dendrochronological research on growth dynamics and productivity (Dussart et al., 1998;Villalba et al., 2000;Bogino and Villalba, 2008;Bogino et al., 2015), growth, ground water table and climate association (Bogino and Jobbágy, 2011), and fire effect (Medina et al., 2000;Medina, 2008;Bogino et al., 2015).The first South American dendrochronological study was conducted on caldén to determine its potential as a drought indicator (Krebs and Fisher, 1931). ...
... However, likely due to the disagreement about the role of competition in shaping the desert tree growth (e.g.: Grime, 1977;Fowler, 1986), it has been recent that the application of dendrochronological methods proved its utility in analyzing semi-arid forest disturbances. Nevertheless, tree-ring studies of forest disturbance in drylands are still scarce and, with few exceptions (Dussart et al., 1998;Bogino et al., 2015), mainly performed on conifer forests from the Northern Hemisphere (e.g. Black and Abrams, 2005;Py et al., 2006;Rozas et al., 2011). ...
... releases are related to influence of disturbances (fire) rather than climatic variability (Bogino et al., 2015). ...
Anthropogenic disturbance acts globally as an ecological process with long-term implication on the ecosystem equilibrium. In the central-western Argentina (Desierto del Monte Central: DMC), the desert Prosopis flexuosa woodlands has been intervened by man with differential incidence, e.g. through logging, fire and grazing. Despite recognizing a history of disturbances in these forests, the local removal of trees and its incidence in the stem growth of the surviving trees is still poorly known. Dendroecological methods were applied to 10 plots distributed along a landform gradient, aiming to analyze how disturbance, together with possible modulation effects on the spatial variability of growth, can influence forest dynamics. Tree removal was an intensive practice during the second half of the 20th century in the DCM, in synchrony with the expansion of wine-growing activity. Our results suggest that removal of P. flexuosa individuals in any considered plot was the main driver of changes in the forest dynamics. This argument is based on the weak climatic incidence in years considered critical with respect to the beginning of abrupt tree-growth releases. This disturbance impact seemed to be landform-dependent, as suggested by the higher relative basal area values at mesic sites in relation to sites linked to drier landforms. The presented findings represent the first attempt in reconstructing the disturbance regime experienced by the DMC P. flexuosa woodlands. Our research contributes to interpret how logging practices coupled with landform-related heterogeneities may influence the forest dynamics at desert environments, providing elements for implementing policies for conservation and management of these natural resources.
... Esta revisión comienza con el estudio pionero de Krebs y Ficher (1931) donde un evento climático catastrófico los motivó a comparar el crecimiento del caldén con las variables climáticas, hasta los estudios más recientes que abordan la dinámica de crecimiento y las tasas de regeneración para su aplicación en la elaboración de planes de manejo (Dussart et al 1998;Bogino y Villalba 2008;Amieva-García et al. 2013), el análisis del fuego el disturbio más significativo de esta área, a través de la estimación de su frecuencia y su efecto sobre las tasas de crecimiento (Medina 2007;; la asociación sinergética entre la tasa de regeneración, los fuegos y la presencia de ganado vacuno y ovino (Dussart et al 1998;Bogino et al. 2015), la asociación del crecimiento con disturbios de baja frecuencia como, por ejemplo, el incremento de la napa freática y la respuesta poblacional o individual del crecimiento al clima (Bogino y Jobbágy 2011; Jové-Alcalde 2014) y la reconstrucción del paisaje histórico que permitió suponer que los bosques de la zona más seca de la pampa argentina no tendrían la fisonomía tipo sabana que normalmente se les atribuye (Dussart et al. 2011). ...
... Posteriormente, otro estudio del mismo tipo, pero con más muestras y amplitud geográfica (ocho sitios desde el norte de San Luis hasta el centro de La Pampa) confirmó estos resultados. En este caso, además se detectó una fuerte coincidencia entre periodos de fuegos frecuentes y las edades de las muestras, es decir que los incendios indujeron pulsos de regeneración dentro de estos rodales añejos, tal como se había demostrado en los estudios de estructuras de edades de formaciones secundarias actuales en La Pampa, en ausencia de influencias climáticas directas (Bogino et al. 2015). ...
The Argentinean pampas are natural flatlands that cover about 520 000 km2 being considered as the most characteristic landscape of Argentina. Even though the pampa is considered as a land without trees the driest southernmost distribution limit is covered by xerophyte woodlands mainly dominated by caldén (Prosopis caldenia Burkart, Fabaceae). In 1931, two agronomists, Krebs and Fischer, published one study of tree rings of caldén that can be considered as the first dendrochronological study in South America. Dendrochronological studies on this species restarted in the 90s in order to explain the woodland degradation and to propose management strategies. In the last three decades several studies have been made in order to address ecological, climatological and anthropological processes, as: recruitment rates and their association with growth dynamics of adult trees, anthropic disturbances linked with changes in the soil use, fire impact, growth dynamics and water table deep changes, etc. Considering that caldén is the most important woody species in the Argentinean pampas these studies reconfirm its dendroecological potential and new challenges are stated for the future in order to determine synergetic factors that would affect these ecosystems under the current ecological and social changes.
... In the central area of Argentina, three phytogeographic provinces are represented (Espinal, Monte and Pampean) belonging to the Chacoan subregion and South American transition zone, respectively (Morrone, 2014). The central human activities such as deforestation, erosion, and domestic sewage disposal have impacted this region over the past, mostly due to the increasing immigration from other parts of Argentina to Patagonia (Massaferro et al., 2005;Dussart et al., 2011;Bogino et al., 2015). The knowledge of terrestrial Heteroptera in this region is poor and is limited to a few contributions (e.g.; Diez & Coscarón, 2015;Diez et al., 2016). ...
El conocimiento actual de Heteroptera en el norte de la Patagonia y la región central de Argentina es muy disperso y ciertamente muy incompleto. En el presente trabajo proporcionamos una lista de 17 especies del norte de la Patagonia y la región central de Argentina, incluyendo 16 nuevos registros para provincias, y un nuevo registro para el país. ABSTRACT. The present knowledge of Heteroptera in northern Patagonia and central region of Argentina is widely scattered and admittedly very incomplete. In the present work we provide a checklist of 17 species from northern Patagonia and the central region of Argentina, including 16 new records for provinces and one new record for the country.
... Establishment of R. girolae during the first decade of the 20th century coincides with that of species from other semi-arid environments such as Prosopis caldenia Burkart (Bogino et al. 2015). However, anthropogenic factors such as the construction of railways and the changes in land tenure that impacted the growth dynamics of these species were not identified as a factor in the case of R. girolae. ...
Chica (Ramorinoa girolae, Fabaceae) is an endemic species with a valuable ecological role in arid environments of Argentina, protecting watersheds and wildlife and providing food for humans. The aim of this study was to describe its woody anatomy, growth dynamics, recruitment and relation to climate. Samples from three sites were collected, and anatomical woody analysis and standard dendrochronological techniques were applied. After dating the samples, residual tree-ring chronology was compared with two climate variables, temperature and southern oscillation index (SOI). Results show that chica has variable porosity (diffused, semicircular or circular) with single or grouped vessels. Vessel density varies among the annual growth rings. The storied rays are considered characteristics of a specialized wood. Wider vessels in the beginning of the growing season and terminal parenchyma allowed us to detect tree-ring boundaries. Missing rings and lenses were common, making the dating process difficult. Mean radial growth was 1.2 mm year-1 (SD ± 0.25; 1605 - 2009 period). Temperature and SOI have a positive impact on growth. Results showed the anatomical adaptations of chica wood to arid conditions and its potential to provide data from more than 400 years to environmental and temporal studies.
... Una especie muy interesante para la región es el caldén (Prosopis caldenia). Se ha estudiado cómo distintos factores (fuego, clima, napas freáticas, dispersores y predadores de semillas, etc.) afectan procesos biológicos importantes para su regeneración, reclutamiento o mortalidad en esta especie clave de los bosques en el sudoeste del Espinal (por ejemplo; Peinetti et al., 1993;Lerner y Peinetti 1996;Bogino y Jobbagy 2011;Matula et al., 2014;Bogino et al., 2015;Svátek 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
... Many plant and animal species have been displaced or are extinct as a result of the changes in their habitats. Furthermore, at a systemic level, the rates of nutrient circulation, the infiltration capacity, the water retention and the fire dynamics have been modified (Medina 2008;Bogino et al. 2015;Velasco et al. 2018). Even though the National Law No. 26,331 was enacted in order to regulate the use and management of the woodlands, its implementation is of regional jurisdiction, which means that the interpretation of its scope is diverse and in some cases can result in contradictory regulations. ...
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.
... We hypothesize that: (i) P. pugionata has distinctive growth rings, allowing for the accurate dating of tree rings, (ii) P. pugionata forms identifiable fire scars in the wood, and (iii) the bark of P. pugionata sufficiently protects the cambial tissue to resist wildfires, and plant size influences the cambial damage percentage on bole. These considerations are based on: (i) the literature that reports that other Prosopis species form annual growth rings, identifiable fire wounds suitable for dating wildfires and feasible tree ring dating Morales et al. 2001;Medina 2003;2008;Bravo et al. 2008;Bogino et al. 2015), and (ii) in other Prosopis species, the bark thickness protects cambial tissue, allowing them to survive low to medium fire severity wildfires (Bravo et al. 2001b;2008). However, the exceptional environmental conditions of the distribution area of P. pugionata (dryness, saline soils, scarce seasonal thermal amplitude) may produce different wood anatomy than other Prosopis species. ...
Prosopis pugionata (Fabaceae) is a halophyte tree species that grows exclusively in Argentina's arid environments, whose woodlands are mainly affected by fires and overgrazing. Here, we describe the wood anatomy and fire wounds of P. pugionata and their relationship with plant size and bark thickness. Besides, we attempt to determine the potential of P. pugionata for dendrochronological studies in order to date fire events throughout time. We tested the hypothesis that P. pugionataforms datable fire wounds, allowing its use for dendrochronological studies. The study area is located in the arid Argentine Chaco region. Seventeen individuals, varying from 15 to 65 years of age, were randomly sampled and bole disks were taken at 0.3, 1.3 and 2.3 m high. P. pugionatais a diffuse and semi-ring-porous hardwood species with growth rings delimited by marginal parenchyma bands. The bark is longitudinally fissured, with an average thickness of 0.19 cm, and a scarce increase with age. Seventy-seven percent of the samples showed fire wounds (n = 46). We identified fire scars (70%) and marks (30%), and differentiated them by wood growth interruption in the former. Sixty-one percent of fire wounds affected less than 20% of the cambial perimeter and there were no significant effects of age, bole diameter, bole height and bark thickness on the cambial damage percentage. After cross-dating, P. pugionata showed a mean correlation value between series of 0.5, which represents an accurate potential for dendrochronological studies. Twenty wildfires were dated from 1943 to 2007 in the study area with a fire frequency of 0.40 fires/year and a mean fire interval of 2.5 years. Wildfires frequency increased from 1980 to 0.48 fires/year and a mean fire interval of 2 years. Our results indicate that P. pugionata has the potential to date fires, considering its potential for dendrochronological studies, its ability to survive recurrent fires and forms identifiable wound scars in the wood.
... Previous studies determined the suitability of Prosopis species en general, and of P. caldenia in particular, for dendrochronological analysis (Villalba et al., 2000;Bogino et al., 2015, Velasco-Sastre et al., 2018, being caldén the first species to be dated in South America at the beginning of the 20th century (Bogino, 2014). These investigations stated the longevity of Prosopis trees to around 250-300 years and provided evidence to go back up to the first half of the 18th century. ...
The Pampas is a natural flat region that covers 750 000 km ² in Brazil, Uruguay and Argentina. The driest part of the Argentinean Pampas is occupied by thorny forests dominated by Fabaceae species, mainly by caldén (Prosopis caldenia Burkart). The caldén's area was affected by large human immigration processes that started in the 18th century up to the last century. Semiarid climate in caldén's area has made water a critical source for the development of biotic communities and human settlements. Native people dug wells, lined by wooden poles, commonly named jagüeles, in order to have access to drinkable groundwater. Such poles, preserved in the subsoil, were submitted to wood anatomical and dendrochronological analysis, and 18 were collected from three archeological sites. Because the poles were undated, they were compared with two master chronologies of P. caldenia that belong to the area. Anatomical studies determined that the poles belonged to P. caldenia and Prosopis flexuosa. Poles of one of the sampling sites had their last tree rings between 1799 and 1838, which coincided with indigenous occupation period. On the contrary, the samples from the other two sites were placed chronologically between 1885 and 1918, which coincided with the first creole and European occupation. These results show the use of native people's traditional building strategies by other cultural groups such as the creole and European settlers since the strategies were useful in the semiarid environments.
... Thicketization in the absence of fire is represented as the transition to a "closed forest/herbaceous understory" state characterized by a high density of trees (up to 2 000 plants ha −1 ) and low shrub density (T1, see Box 1). Thicketization combined with limited fires (T2, see Box 1) favors P. caldenia shrubs, creating a "closed forest/shrubby understory" state (Bóo et al., 1997;Dussart et al., 1998;Bogino et al., 2015). Fire damage on young P. caldenia trees stimulates resprouting from basal buds and the development of several vigorous stems, none of which becomes the leader. ...
Management impacts and natural events can produce ecosystem state changes that are difficult to reverse. In such cases, a detailed understanding of drivers, thresholds, and feedback mechanisms are needed to design restoration interventions. The Caldenal ecoregion in central Argentina has undergone widespread state change, and restoration is urgently needed, but as yet there has been no knowledge synthesis to support restoration actions. In this paper, we provide evidence-based guidelines for ecological restoration of the Caldenal forest derived from a general to local conceptual understanding of ecosystem dynamics. We develop a Caldenal forest state transition model based on a generalized fire-mediated savanna-woodland transition model. The generalized model depicts global similarities in fire-grass feedback loops as a primary factor controlling savanna to woodland transition (thicketization) in semiarid savannas around the world. An open forest is considered to be the reference state of the Caldenal that developed under a historical regime of frequent low-intensity fire. The introduction of large livestock herds in the region disrupted the positive fire-grass feedback loop and increased dispersal and recruitment of Prosopis caldenia, creating conditions for thicketization of the forest. Controlled, low-intensity fire can be used to build the resilience of an open forest state. Restoring open forest states from woodland states requires a large-scale selective thinning and pruning operation. Long-term restoration requires breaking the positive livestock-thicketization − high-intensity fire feedback and reestablishing the positive grass-low intensity fire feedback to ensure the persistence of a restored open forest state.
... Un fuego fuerte, sin embargo, no dejará prácticamente nada, requiriéndose un largo tiempo para recomponer una cubierta vegetal y acumular material combustible. Esto favorece la implantación de nuevas leñosas y las sobrevivientes rebrotan de forma arrosetada, lo cual es coincidente con lo mencionado por varios autores (Llorens 1995;Medina et al. 2000;Dussart et al. 2011;Dudinszky and Ghermandi 2013, Matula et al. 2014, Bogino et al. 2015. ...
El presente libro contiene los trabajos donde profesionales de diversas instituciones aplicaron el uso de la teledetección y los sistemas de información geográfica en la resolución de problemas.
Los trabajos se realizaron en el ámbito de la provincia de La Pampa en problemáticas asociadas a los territorios circunscriptos en los proyectos regionales con enfoque territorial PRET.
El abordaje contempla aspectos productivos, medioambientales, cambio climático y socioeconómico en escalas regionales, locales y prediales utilizando las herramientas propias acordes de resolución.
En una primera etapa se explica de manera concisa y concreta los aspectos básicos de la significancia de los conceptos relacionados con la temática. Posteriormente se esbozan los trabajos que manifiestan las resoluciones en diferentes escalas.
Los trabajos presentados generan aportes diversos desde su especificidad y, seguramente serán de gran utilidad para aquellos que deseen profundizar en la temática, dado que permiten explorar, caracterizar y comprender los aspectos que tiene fuerte implicancias con los territorios.
... Un fuego fuerte, sin embargo, no dejará prácticamente nada, requiriéndose un largo tiempo para recomponer una cubierta vegetal y acu-mular material combustible. Esto favorece la implantación de nuevas leñosas y las sobrevivientes rebrotan de forma arrosetada, lo cual es coincidente con lo mencionado por varios autores (Llorens 1995;Medina et al. 2000;Dussart et al. 2011;Dudinszky and Ghermandi 2013, Matula et al. 2014, Bogino et al. 2015. ...
Se desarrolló un modelo para estimar productividad primaria neta aérea de herbáceas forrajeras (PPNA) en el árido-semiárido de La Pampa, Argentina, considerando a la densidad de plantas y la precipitación antecedente como principales componentes
de rendimiento. El modelo fue construido a partir de información proveniente de un ensayo llevado a cabo en la localidad de Chacharramendi entre los años 2001 y 2011. La densidad de herbáceas forrajeras al final de la estación de crecimiento fue modelada considerando el índice verde normalizado (IVN), la precipitación acumulada de una y dos
estaciones de crecimiento antecedentes como predictores (R2=0.98, RMSE=1.43). La PPNA fue modelada a partir de la precipitación acumulada durante las dos estaciones de crecimiento previas a la evaluada y la densidad de herbáceas modelada al final de ciclo (R2=0.84, RMSE=1048). Para corregir esta estimación de oferta forrajera y aproximarlo a valores más reales a las observadas a campo, se modeló la presencia de procesos de lignificación en la provincia de La Pampa a partir de series temporales de índice verde normalizado (IVN) provenientes del sensor MODIS Terra y el algoritmo Seasonal Trend Decomposition - LOESS (STL) durante el período 2000-2013. Se relacionó la ocurrencia
de estos procesos con la razón entre la estacionalidad (ΣIVNh) y la tendencia (ΣIVNw) acumuladas durante todo el período , y la frecuencia de fuegos observadas durante el mismo período. Las áreas afectadas se caracterizaron por presentar una relación ≤ 0.8. El 38% de la superficie provincial (5400000 millones de hectáreas) fue clasificada en proceso de lignificación con un índice de certeza de 0.81. El 90% de las áreas afectadas por el fuego en estos sitios fueron quemadas entre 1 y 3 veces por fuegos muy fuertes durante el período estudiado.
Las áreas no quemadas o con alta frecuencia de fuegos no presentaron procesos de lignificación, coincidiendo con lo observado por varios autores. La carga animal fue otro elemento significativo presente en sitios arbustizado, siendo un 40% más alta que
en los sitios sin la presencia de este proceso p=0.0001). La estructura del modelo permite generar predicciones de PPNA con un año de anticipación, constituyendo
esto una herramienta fundamental al momento de la planificación ganadera y el aprovechamiento racional de los recursos naturales.
Palabras clave: monte - arbustal, precipitación, fuego, carga animal, teledetección
... Un fuego fuerte, sin embargo, no dejará prácticamente nada, requiriéndose un largo tiempo para recomponer una cubierta vegetal y acumular material combustible. Esto favorece la implantación de nuevas leñosas y las sobrevivientes rebrotan de forma arrosetada, lo cual es coincidente con lo mencionado por varios autores (Llorens 1995;Medina et al. 2000;Dussart et al. 2011;Dudinszky and Ghermandi 2013, Matula et al. 2014, Bogino et al. 2015. ...
La información generada en este libro ha sido desarrollada en el ámbito de la provincia de La Pampa en problemáticas asociadas a los territorios circunscriptos en los proyectos regionales con enfoque territorial (PRET). El abordaje contempla aspectos productivos, medioambientales, cambio climático y socioeconómico en escalas regionales, locales y prediales utilizando las herramientas propias acordes de resolución. El contenido de este libro es un trabajo conjunto entre profesionales del INTA Anguil, INTA Castelar, UNLPam, UNS, Gobierno de la Provincia de La Pampa y Asesores privados. En el primer capítulo se abordan conceptos de las nuevas tecnologías como SIG, escala, GPS, IDE y una discusión de servicios y aplicaciones, con el objetivo de dotar al lector con la terminología básica que le permita aprovechar los capítulos sucesivos donde se presentan estudios de caso en diferentes escalas.
... The objectives of this paper were to 1) quantitatively characterize alternative vegetation states and 2) determine if the occurrence of different vegetation states was related to climoedaphic variations within the Caldenal region. Disturbance and management history are the most widely accepted explanations for differences in vegetation (Bogino et al., 2015;Busso, 1997;Distel and Boo, 1996;Dussart et al., 1998Dussart et al., , 2011Llorens, 1995). However, variation in climoedaphic conditions may result in distinct vegetation states under similar management and disturbance regimes, due to variations in resistance to shrub encroachment (Bestelmeyer et al., 2006). ...
Woody plant encroachment is widespread throughout drylands of the world, but rates and patterns of encroachment at the regional scale can be mediated by soil and climate. Climoedaphic properties may therefore help to explain patterns of woody plant dominance. In the Caldenal region of central Argentina, which is experiencing widespread woody plant encroachment, we used stratified and targeted inventory of vegetation and soils alongside climate data to classify vegetation states and then identify factors indicating resistance to woody plant encroachment. We found that three climoedaphic contexts differed in the degree of woody plant dominance. Sandsheet landforms had the lowest likelihood of a shrub thicket state. Within loamy soils, sites with deep soil carbonates in warmer and wetter climates were less likely to feature a shrub thicket state than sites with shallow carbonates in cooler and drier climates. These contexts serve as a basis for recognizing different ecological sites to assist mapping and prioritization of management interventions in the Caldenal region. Simple inventory-based approaches can be helpful for designing land management recommendations in other ecosystems.
... El fechado de marcas de incendio en secciones transversales de diferentes especies de árboles ha permitido determinar la frecuencia y estacionalidad de fuegos pasados, así como la diferenciación entre fuegos de gran magnitud y fuegos de pequeña extensión (Medina et al. 2000, Fule et al. 2008, Cerano Paredes et al. 2010). Asimismo, la estimación de fechas de establecimiento de árboles, junto al fechado de cicatrices de incendios, ha permitido estudiar los efectos sinérgicos entre la ocurrencia de incendios y otros factores como clima (Grau y Veblen 2000, González y Veblen 2006, Mundo et al. 2013) y/o historias de manejo sobre las comunidades leñosas (Bogino et al. 2015). Por otra parte, el desarrollo de robustas cronologías de fuego, ha permitido determinar la manera en que la frecuencia de fuego refleja los cambios en las actividades humanas en un contexto histórico, así como la influencia de las condiciones físicas que impone el ambiente donde ocurren (Kitzberger et al. 1997, Veblen et al. 1999, González 2005). ...
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.
In open woodlands and savannas, fire is often the dominant disturbance that shapes and maintains their structure and dynamics. Numerous studies have explored tree-grass coexistence under different fire regimes in these ecosystems; however, there is a lack of research on the tree-tree relationship in the presence or absence of fire. In the present study, we explored the effects of fire regime on tree spatial pattern, mortality and regeneration in the Argentine Caldenal, which is one of the most endangered and least studied open woodlands in the Neotropics. While there was no significant difference in the overall tree density between frequently burned and fire-excluded regimes, we found clear divergences between fire regimes in the within-stand spacing of not only all trees, but also of large and small trees in addition to their spatial interactions. In contrast with previous results from other frequently burned open forests, trees in the Caldenal were randomly distributed in burned plots whereas both mid- and long-term fire exclusion lead to the strong short-scale aggregation of trees. In the absence of fire, both large and small trees were significantly clumped, but in the frequently burned woodlands, large and small trees had a tendency to repulsion and aggregation, respectively. Fire regime also significantly affected tree mortality and regeneration mechanisms in the Caldenal. Our mortality analysis indicated that fire suppression led to the shift from fire-induced to competition-driven mortality of trees. When analysing tree regeneration, we found a lack of seedlings in any of the fire regimes but the presence of vigorous sprouting only in frequently burned plots. The present study thus revealed the key role of frequent fires in the Caldenal open woodlands because recurrent burning not only shaped the spatial arrangement of trees, but fire-induced mortality also triggered an essential tree recruitment mechanism in these ecosystems.
Dendrochronological analysis of basalcross-sections of 22 dominant Prosopis caldenia (Burk.) trees from a woodlandof 200 ha in the Estancia La Verde, southof San Luis province, allowed the con-struction of a fire chronology spanning rom 1.787 to 1.993, who show a meanfire interval(MFI) of 13,14 years for theNative American ocupation period(1.787-1.879), of 15 years for the follow-ing transition period (1.880-1.910), andof 7,25 years for the final period(1.911-1.993).To differentiate between wide-spread fires and smaller ones we com-puted fire intervals for years during whichat least 10% of our samples were fire-scarred simultaneously. The frequencyand extension of fire incremented from1.910, when colonization began in thesite, with changes in land management.Fire occurrence during the twentieth cen-tury coincides with periods of intensivelogging and management of prescribedfire in the area.Fire seasonality registred in the area,mainly of summer and spring fires, coin-cides with the annual period of majorhidric deficit and accumulation of flam-mable material in the lower vegetationstratum of this forest.
Tree rings are a useful tool to quantify the rate of radial growth of trees at different
environments and to determine differences in stand population structures in responses
to factors such as soil, disturbance and climate. However, to precisely date a piece of
wood, tree rings need to be clearly identified. The determination of tree rings in
Prosopis species vary between species, between individuals of the same species, and
sometimes between radii from the same tree. This large variability likely reflects the
broad plasticity and adaptability of Prosopis trees to different environmental conditions.
Tree rings in Prosopis species are determined by several patterns or anatomical
arrays such as larger vessels in the earlywood tending to produce circular to
semi-circular porosity, and the presence of strands of terminal parenchyma. In Prosopis
species with clear bands, long-term studies of cambial activity and the dating of trees
of known ages have allowed to determine the annual nature of tree rings.
Although the number of studies on forest ecology and dendroclimatology using
Prosopis species is increasing, the application of Prosopis wood in these fields is still
limited to few cases. However, the material reviewed in this paper indicated that
Prosopis species show a high potential as a source of information on past climate
fluctuations, forest ecology and human-environment relationships in the extended
arid and semiarid regions of South America.
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
Current calden forests (caldenal) in La Pampa are understood as derived from pristine savannas. It is also usually accepted that the degradation of these open formations started following two deforestation periods locally known as Grandes Hachadas and linked to the World War periods. This outline for the landscape history disregard any significant impact during the Indian occupation period prior to 1879 and the re-settlement period that took place right afterwards. Both assumptions are questioned by modern historical investigations. In this study, we used dendroecological techniques to reconstruct the evolution of the forest landscape in La Pampa. Our results show that most of the study sites were closed forests at least since the middle the XVIIIth century, in coincidence with intense indigenous cattle ranging and transhumance activities between the wet pampas in Argentina and southern Chile. The opening of these formations occurred synchronously at the end of the XIXth century together with the introduction of sheep raising activities. The woodlands closed again when cattle supplanted sheep ranching by the 1940s. These results show a high degree of human impact on the caldenal during the last 250 years.
Prosopis caldenia Burk. is one of the woody species that is increasing in abundance due to poor grazing management in the semi-arid phytogeographic region of central Argentina, commonly known as the Caldenal. The objective of this study was to evaluate the effect of herbaceous cover, cattle dung, soil disturbance, and water supply on emergence and survival of P. caldenia seedlings on sites with different grazing histories: (i) a site exposed to long-term continuous grazing by cattle (grazed site), and (ii) a long-term exclosure to domestic livestock (ungrazed site). Removal of grass cover, addition of cattle dung, and water supply enhanced seedling emergence and survival, especially in the grazed site. Results suggest that factors (direct and indirect) associated with prolonged grazing history markedly affect P. caldenia establishment. This in turn alters the grass-woody plant balance, which might reduce the potential capacity of livestock production in the Caldenal.
El fuego es un componente significativo del régimen de disturbios que afecta a los bosques de Prosopis caldenia (caldén), con importancia tanto ecológica como económica en los mismos. Contar con información sobre su dinámica, tanto temporal como espacial, resulta de gran importancia para la planificación del manejo y el uso racional del caldenal. El fechado de cicatrices de fuego registradas en los troncos es una metodología ampliamente utilizada para reconstruir regímenes de fuego en áreas boscosas. En este trabajo se analizaron las cicatrices de fuego registradas en el leño de caldenes de un bosque afectado por una serie de fuegos realizados con fines de manejo ganadero-pastoril y se describen otras marcas, anillos de crecimiento y estructuras asociadas a este disturbio. Si bien las cicatrices de fuego permiten conocer en forma precisa la frecuencia y la estacionalidad de los fuegos pasados, incluir el análisis de otras estructuras asociadas a la influencia del fuego, tales como separación de anillos, marcas de fuego, microanillos y anillos con bandas de tejido parenquimático, aportaría mayor información acerca de algunas de las características inmediatas del régimen de fuego, tales como su intensidad y extensión espacial.
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.
Grasslands provide a number of ecosystem services that have been essential to human well-being since pre-historical times (Gibson 2009). Yet they also represent the most endangered terrestrial biome due to conversion into agricultural systems (Sala 2001). The grassland biome covers 15 million km2 (11 %) of the Earth's surface with non-woody vegetation, excluding deserts and savannas (Sala 2001). Natural grasslands encompass vast regions including the North American Great Plains, the Eurasian steppes of Russia, China and Mongolia, and the South American Pampas (Gibson 2009). © 2012 Springer Science+Business Media New York. All rights are reserved.
Large increases in the density of woody plants in former grasslands have been documented globally over the past two centuries. Prosopis velutina (velvet mesquite) has recently expanded on over 38 million ha in the grasslands of the American southwest.Mesquite establishment and expansion is potentially influenced by competitive interactions with grasses, particle size distribution (texture) of soil and changes in the amount and/or seasonality of precipitation, amongst other factors.To investigate the relative importance of precipitation seasonality, grass competition, and soil texture on mesquite seedling and establishment, we experimentally manipulated seasonality of precipitation across 72 1.5 m × 1.7 m plots that we planted with two grasses from contrasting functional groups (or left unvegetated) across two highly contrasting soil textures within a semi-desert grassland in Arizona, USA, wherein we followed the demography of 8640 planted mesquite seeds between 2002 and 2006. Up to 70% of the variance in seedling emergence was explained by soil water content, and seedling mortality was more dependent on summer than on winter precipitation.Mortality of less drought tolerant grasses after drought in coarse textured soils created conditions most favorable for seedling establishment, whereas lower rates of seedling establishment were observed in finer textured soils or in plots dominated by more drought tolerant grasses.We conclude that mesquite encroachment is episodic, based on discontinuous patterns of seedling establishment, favored on coarse textured soils and associated with unique conditions of high summer water availability when precipitation is not limiting and when competition from grasses is lowered.
Cross sections from coast redwood trees (Sequoia sempervirens (D.Don.)Endl.) in and near Redwood National Park were dendrochronologically cross-dated and used to develop a fire history from 1714 to 1985. A master chronology for the study area was first developed from old-growth trees and provided dating control for fire-scarred samples. Redwood offers a challenge for dendrochronology owing to partially absent rings (ring wedging) and uniform ring widths (complacency). Cross dating was successful in portions of 12 of 24 fire-scarred trees. Fire events were dated by noting the position of fire scars and other fire-associated ring structures (resin ducts, double latewood, growth releases, and ring separations) in the cross-dated ring series. Using only dates of fire scars, the mean fire interval (MFI) was 9.9 years from the first recorded fire in 1714 to the last in 1962. The MFI was 8.0 years for the best represented (greatest sample depth) presettlement period from 1714 to 1881. Using dates for all fire-associated ring features, the MFI from 1714 to 1962 was 7.0 years and from 1714 to 1881 was 6.0 years. Use of all fire-associated ring characteristics is argued to be a more complete representation of past fire frequency due to possible under-representation of fire-scar records from stump-top samples. Based upon scar positions within annual rings, fires occurred predominately late in the growing season or after growth ceased for the year. The mean fire intervals determined are shorter than those reported in all except one other fire history study from coast redwood and suggest that fire frequency in redwood may have been underestimated in many past studies.
Trees act as ecosystem engineers and invasions by exotic tree species profoundly impact recipient communities. Recently, research
on invasive trees has dramatically increased, enabling the assessment of general trends in tree invasion. Analysing 90 studies
dealing with 45 invasive tree species, we conducted a quantitative review and a meta-analysis to estimate the relevance of
eight leading hypotheses for explaining tree invasions. We also tested whether species functional traits (growth rate, density/cover,
germination, biomass and survival) equally promote tree invasiveness. Overall, our results suggest that several hypotheses,
linked to invasibility or invasiveness, are pertinent to explain tree invasions. Furthermore, more than one hypothesis has
been supported for a given species, which indicates that multiple factors lead to the success of invasive tree species. In
addition, growth rate appears to be the most efficient predictor of invasiveness for invasive trees and could thus be used
as a means to identify potential alien tree invasions. We conclude that further investigations are needed to test the consistency
of some hypotheses across a broader pool of invasive tree species, whilst experimental studies with the same tree species
across a larger range of sites would help to reveal the full suite of factors that affect tree invasions.
KeywordsTree invasion–Systematic review–Meta-analysis–Invasiveness–Invasibility–Functional traits
Fire is a significant component of the disturbance regime that affects Prosopis caldenia (caldén) woodlands with ecological and economical importance. Obtaining information on its temporal and spatial dynamics would be of great importance for management planning and rational use of these forests. The dating of fire scars registered in tree trunks is a widely used method for reconstructing fire regimes in. forested areas. In this paper fire scars registered in the wood of caldén trees were analyzed from an area that was affected by prescribed fires to enhance pastures for livestock. Other marks, tree growth rings and structures associated to this disturbance are described. Although fire scars allow precise knowledge of the frequency and seasonality of past fires, the analysis of other structures associated to the influence of fire, such as ring separation, fire marks, "micro-rings" and rings with bands of parenchymatous tissue, would provide greater information on some immediate characteristics of fire regimes, such as intensity and spatial extent.
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.
Calden (Prosopis caldenia) seeds not dispersed by animals sometimes constitute a considerable number of seeds to the seed bank which may contribute to the species' dissemination. The monthly change in the number of viable non-animal dispersed seeds was evaluated over a one-year period. We determined the percentage germination of seeds and the amount of predation by bruchid beetles to learn how those factors influence seed longevity. Forty eight bags containing 10 fruits were placed in 4 sites below calden tree canopies at the time of shedding (March). To monitor seed losses we randomly removed 1 bag per site every 25-35 days during a year. At the time of shedding, fruits contained 29 seeds, 73 ± 5.0% which were viable and 9 ± 2.2% attacked by bruchids. Viability decreased to 33 ± 22.3% one year later. Loss of viability was described by a polynomial quadratic (y = 70.12 + 0.0238 t-0.0004 t2 (r2 = 0.62)). Bags with germinated seeds were observed beginning in November. Percentage germinated seed increased 4.8 ± 3.7% in the last month of sampling. Consumption of seeds by bruchids also increased in November, but the effect was highly variable. In the last month of sampling (March in the following year), 35 ± 18.0% of seeds were affected by bruchids. A predictive seed longevity model was developed considering climatic variables, but data were well described only until January (y = 81.50-0.097 time-3.94 precipitation (r2 = 0.66)). Undispersed seeds had a high rate of decoy and low germination. Longevity was strongly affected by bruchid attack.
Reviews the discipline of fire ecology under the following chapter headings: introduction (global importance, methods, ecological concepts); why and how do ecosystems burn (the fire regime, prerequisites for fire, temperatures of fires and survival of plant tissue); surviving fires - vegetative and reproductive responses; plant demography and fire interval-dependent effects (types of population growth, modelling population growth, demography and the fire interval hypothesis, density dependence and population regulation - the self-reegulatory hypothesis) and event-dependent effects (effects of fire intensity and season on survival and recruitment, effects of ground fires and fire area); fire and the evolutionary ecology of plants; fire, competition and the organization of communities; fire and management; and fire and the ecology of a changing world. -S.R.Harris
In 1931, Krebs and Fischer, published El pluviómetro secular (The centenary pluviometer) an analysis of tree rings of Prosopis caldenia Burkart (caldén) in the central Argentinean Pampas which, according to the date, may be considered as one of the first dendrochronological studies in South America.
In temperate semi-arid rangelands of Argentina grazing by domestic livestock is apparently linked with the conversion of open grasslands to dense shrublands.Prosopis caldeniaandStipa tenuisare dominant species of the shrub and grass life-forms, respectively. Research was conducted to determine the growth responses ofP. caldeniaseedlings to grazing history of the site and competition fromS. tenuis, at different levels of water availability. TheProsopisseedlings grew better (p<0·05) in long-term protected than in long-term grazed sites, and at low rather than high levels of competition fromS. tenuis. Both overgrazing and high levels of grass competition may limit the establishment ofP. caldeniaseedlings in grasslands, particularly under conditions of water shortage.
COFECHA is a computer program that assesses the quality of crossdating and measurement accuracy of tree-ring series. Written by Richard L. Holmes in 1982, the program has evolved into one of the most important and widely used in dendrochronology. It is important to note that COFECHA does not perform all the necessary steps in crossdating. Rather, the program is a tool that helps the dendrochronologist assess the quality of crossdating and measurement accuracy. The ultimate decision whether or not a tree-ring series is successfully crossdated must lie with the dendrochronologist and not with the software. Therefore, the program is most useful after initial crossdating is accomplished using visual or graphical techniques (such as skeleton plots), and the rings have been measured. The proper use of COFECHA adds a high degree of confidence that tree-ring samples have been crossdated correctly and measured accurately, ensuring that the environmental signal is maximized. In this paper, I describe the use of COFECHA through all necessary steps, and discuss the meaning of the initial questions posed at program start-up, the various options available in the main menu, the various sections of the output from COFECHA, and interpretation of the diagnostics of crossdating and measurement accuracy. I demonstrate methods used to help crossdate undated series, and offer tips on taking full advantage of the various options available in the program.
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.
Crossdating is the core principle of dendrochronology. Our study compared two techniques for measuring and crossdating tree rings using Juniperus virginiana L. (eastern redcedar) as a case study. We used a pseudo 2×2 study design comparing the traditional skeleton plot/sliding measuring stage technique to a semi-automatic image analysis program across two technicians. Crossdating was evaluated in COFECHA. Raw measurements of total, earlywood, and latewood widths from the two methods were analyzed using the Verify for Windows program, ANOVA, and correlation matrices. Total ring width and earlywood width were well correlated between techniques and technicians but questionable ring boundaries from image analysis program should be checked under a stereoscope. Juniperus virginiana latewood widths were significantly different between techniques and technicians; therefore, we do not recommend combining latewood measurements from species with limited latewood variability for dendrochronological analysis. A standard definition of the earlywood-latewood boundary that can be replicated across technicians is needed to combine latewood measurements from the sliding measuring stage and image analysis systems.
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
Abstract The objective of this work was to evaluate postfire environmental effects on the emergence, survival and growth of Prosopis caldenia seedlings in relation to different controlled fire frequencies, seed scarification methods, and planting site. Seedling emergence was significantly higher in experimental units exposed twice and three times to controlled fire than in unburned experimental units. The highest average seedling survival was recorded with triple exposure to controlled fires. Emergence, survival and growth of seedlings from seeds exposed to acid scarification and 600°C for 5 min were higher in the burned experimental units than in the unburned ones. In the former, seedling survival was higher beneath a P. caldenia canopy than in an adjacent open site, though seedling emergence was similar in both planting sites. Our results suggest that postfire conditions characterized by a reduction in the vegetative cover and competition interference and an increase in soil temperatures and nutrients levels (e.g. nitrogen and phosphorus) may facilitate the establishment of P. caldenia seedlings in the Caldenal.
Prosopis caldenia Burkart (caldén) is the most important woody species in the caldenales, the open xerophytic woodlands covering approximately 33 000 km2 in the semiarid central region of Argentina. Dendrochronological techniques were used to estimate mean radial growth and the biological rotation age of P. caldenia in San Luis, Central Argentina. Inter-annual variations in ring widths were measured on cross-sections from dominant and co-dominant trees at four sampling sites from across the natural distribution of P. caldenia in the province of San Luis. For a period of 65 years, the mean cumulative radial growth between these four stands varied from 174.9 to 246.09 mm, whereas the mean annual radial growth ranged from 2.7 to 4.0 mm yr−1. Biological rotation ages were estimated based on the temporal evolution of the annual basal area mean and current increments. At the four stands, the biological rotation age occurs at ages equal to or greater than 66 years. In comparison with the introduced species presently used for commercial reforestation in the region, P. caldenia shows similar rates of radial growth, is better-adapted to the extreme climatic variability of semiarid Central Argentina, and its wood largely exceeds in quality the wood of those species used for commercial reforestation.
Soil nutrient availability influences plant invasions. Resin capsules were used to examine soil nutrient bioavailability along 2 sagebrush-grassland elevation transects in the east Tintic Range (Utah) and Shoshone Range (Nevada). In the fall of 2001, treatments were applied to 3 replicate plots at each site, which included prescribed burning, herbaceous vegetation removal, and controls. Cheatgrass (Bromus tectorum L.) was overseeded in small subplots within each treatment. Following treatments in each plot, resin capsules were installed at 15-cm depth in a shrub interspace and a B. tectorum-overseeded area. Nutrient availability was integrated during late fall to spring and spring to late fall for 2 years. Herbaceous vegetation removal increased availability of nitrate (Nevada and Utah) and Ca and Mg (Nevada only) but only during the second sampling period (growing season). Availability of K and ortho-P (Nevada and Utah) and nitrate (Nevada only) was greater on prescribed burned plots. For Utah, availability of ortho-P, K, Ca, Mg, and Fe generally increased with increasing elevation. Availability of Ca, Mg, K, and Fe was greatest during late fall to spring integration periods for Nevada. Overseeding with B. tectorum interacted with the burn treatment to influence availability of Ca, Mg, and Fe (Nevada sites only). Patterns of nutrient availability can be explained by a combination of decreased root uptake in relation to mineralization, differences in soil water content with season and elevation, and nutrient release from vegetation and soil as a consequence of prescribed burning. Herbaceous vegetation removal and burning can raise nitrate availability and increase risk of invasion by nitrophilic species such as B. tectorum. Nutrient availability can be out of phase with plant growth; plants capable of taking up nutrients during cold periods may have a competitive advantage. Resin capsules have utility in quantifying the effects of treatments on the availability of many soil nutrients.
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