The seasonal changes in the energy balance after the substitution of a herbaceous savanna by a Br... more The seasonal changes in the energy balance after the substitution of a herbaceous savanna by a Brachiaria field located in the Orinoco lowlands were assessed over an entire year using the eddy covariance technique. Simultaneously, an herbaceous savanna was monitored as a control. This work provides evidence that the vegetation replacement lead to different patterns of energy and water balance. The seasonal trends of the latent heat flux (λE) to available energy (Ra) ratio tended to decrease as senescence increased due to seasonal influence of air humidity mole fraction deficit and soil water content on leaf area index (LAI) and surface conductance (gs). Therefore, the partitioning of the available energy depended on both climatological (i.e., solar radiation, volumetric soil water content and air humidity mole fraction deficit) and biological variables (i.e., conductance behavior and LAI) which were stress-induced. For the wet season, the seasonally averaged daily λE in the Brachia...
Figure 1. Locations of Trachypogon savannas at the Orinoco Llanos (Venezuela). The scale = 1:4,00... more Figure 1. Locations of Trachypogon savannas at the Orinoco Llanos (Venezuela). The scale = 1:4,000,000. We analyzed the ecological factors affecting the oc-currence of termite mounds within and among physio-nomie types of Trachypogon savannas from the central and ...
... 11. Nitrogen content and nitrogen RUBEN A. MONTES? ... Can. J. Bot. 61: 2 159-2 168. The effe... more ... 11. Nitrogen content and nitrogen RUBEN A. MONTES? ... Can. J. Bot. 61: 2 159-2 168. The effects of chronic doses of ozone (03) and rates of nitrogen (N) fertilizer on N content of ladino clover (Trifoliurn r-epens L. cv. Tillman) and tall fescue (Festuca arunrlinacea Schreb. cv. ...
Water relations were analysed in a semi-deciduous forest grove occurring in the oxisols of the Or... more Water relations were analysed in a semi-deciduous forest grove occurring in the oxisols of the Orinoco savannas. This grove has a shallow unconsolidated ironstone cuirass, which is overlaid by a sandy loam layer (0.0-0.5 m) that contains more than 90% of the grove forest root phytomass. Evapotranspiration and through drainage were calculated by using data from the soil profile as related to physical characteristics of the site root zone, hydraulic conductivity, volumetric water content and potential hydraulic gradient. Mean annual evapotranspiration was 783 mm year(-1) and annual through drainage below the root zone was 14% (162 mm year(-1)) of the gross rainfall. This drainage recharged the 42% of the annual saturation deficit of the water table. Similar mean annual evapotranspiration (770 mm year(-1)) was also calculated by using the water balance components. The mean daily coupling omega factor (Ω) between the grove canopy and the surrounding atmosphere indicated that a high degree of coupling (Ω=0.14±0.16) occurs in the grove and evapotranspiration was mainly controlled by surface conductance. As the dry season proceeded, the soil saturation deficit (δθ) increased rapidly resulting in a threshold surface conductance (0.030-0.005 m s(-1)) for δθ ranging from 0.05 to 0.10. Hypotheses to explain the omnipresence of perennial species in the wide range of physical conditions in neotropical savannas are discussed.
Communications in Soil Science and Plant Analysis, 2007
Field measurements showed the nitrogen (N) inputs and output of a fertilized pineapple crop [Anan... more Field measurements showed the nitrogen (N) inputs and output of a fertilized pineapple crop [Ananas comosus (L.) Merr. c.v. Red Spanish] growing in the Orinoco llanos during consecutive seasonal courses. The process rate changed with growth life‐cycle stages and seasonal conditions. The N accumulated by pineapple over the growing period was 226 kg N ha. It depended on the available N in the soil and the timing of split application of N fertilizer. Detailed monitoring of plant N‐accumulation rate showed a maximum rate (3.20 kg N ha d) at the harvesting time. The N‐harvested ratio and N‐use efficiency were 0.27 and 138 g g, respectively. The calculated N‐mineralization rate of the soil was 167 kg N ha over the life cycle. The fate of fertilizer N applied to pineapple was determined in microplots using urea labelled with 9.634% atom excess N. Fertilizer N recovery accounted for 48% of the applied N. The corresponding fractions of N recovered in the soil were 0.16 for the 0.0‐ to 0.3‐m depth and 0.01 for the 0.3‐ to 0.7‐m depth. The unrecovered fertilizer N in this study (34%) was largely due to volatilization (20% of the fertilizer) and denitrification (1.2%). Volatilization was shown to be greatly influenced by the seasonal conditions, namely the volumetric soil water content. In the pineapple field, monitored N input exceeded N output by 134 kg N ha, which is likely to lead to maintenance of soil N. Furthermore, utilization of N from crop residues input (164 kg N ha) has repercussions for the sustainable use of the Savanna Oligotrophic soils.
... 11. Nitrogen content and nitrogen RUBEN A. MONTES? ... Can. J. Bot. 61: 2 159-2 168. The effe... more ... 11. Nitrogen content and nitrogen RUBEN A. MONTES? ... Can. J. Bot. 61: 2 159-2 168. The effects of chronic doses of ozone (03) and rates of nitrogen (N) fertilizer on N content of ladino clover (Trifoliurn r-epens L. cv. Tillman) and tall fescue (Festuca arunrlinacea Schreb. cv. ...
... José San-José Æ Rubén Montes Æ Miguel Angel Mazorra Æ Ernesto Aguirre Ruiz Æ Nathaly Matute .... more ... José San-José Æ Rubén Montes Æ Miguel Angel Mazorra Æ Ernesto Aguirre Ruiz Æ Nathaly Matute ... histosols are important in the global carbon cycle, although covering little more than 1% of the world's land surface, they hold about 20% of global soil carbon (Brady and Weil ...
Page 1. Heterogeneity of the inland waterland palm ecotones (morichals) in the Orinoco lowlands,... more Page 1. Heterogeneity of the inland waterland palm ecotones (morichals) in the Orinoco lowlands, South America José San-José Rubén Montes Miguel Angel Mazorra Nathaly Matute Received: 8 May 2009 / Accepted: 13 ...
The seasonal changes in the energy balance after the substitution of a herbaceous savanna by a Br... more The seasonal changes in the energy balance after the substitution of a herbaceous savanna by a Brachiaria field located in the Orinoco lowlands were assessed over an entire year using the eddy covariance technique. Simultaneously, an herbaceous savanna was monitored as a control. This work provides evidence that the vegetation replacement lead to different patterns of energy and water balance. The seasonal trends of the latent heat flux (λE) to available energy (Ra) ratio tended to decrease as senescence increased due to seasonal influence of air humidity mole fraction deficit and soil water content on leaf area index (LAI) and surface conductance (gs). Therefore, the partitioning of the available energy depended on both climatological (i.e., solar radiation, volumetric soil water content and air humidity mole fraction deficit) and biological variables (i.e., conductance behavior and LAI) which were stress-induced. For the wet season, the seasonally averaged daily λE in the Brachia...
Figure 1. Locations of Trachypogon savannas at the Orinoco Llanos (Venezuela). The scale = 1:4,00... more Figure 1. Locations of Trachypogon savannas at the Orinoco Llanos (Venezuela). The scale = 1:4,000,000. We analyzed the ecological factors affecting the oc-currence of termite mounds within and among physio-nomie types of Trachypogon savannas from the central and ...
... 11. Nitrogen content and nitrogen RUBEN A. MONTES? ... Can. J. Bot. 61: 2 159-2 168. The effe... more ... 11. Nitrogen content and nitrogen RUBEN A. MONTES? ... Can. J. Bot. 61: 2 159-2 168. The effects of chronic doses of ozone (03) and rates of nitrogen (N) fertilizer on N content of ladino clover (Trifoliurn r-epens L. cv. Tillman) and tall fescue (Festuca arunrlinacea Schreb. cv. ...
Water relations were analysed in a semi-deciduous forest grove occurring in the oxisols of the Or... more Water relations were analysed in a semi-deciduous forest grove occurring in the oxisols of the Orinoco savannas. This grove has a shallow unconsolidated ironstone cuirass, which is overlaid by a sandy loam layer (0.0-0.5 m) that contains more than 90% of the grove forest root phytomass. Evapotranspiration and through drainage were calculated by using data from the soil profile as related to physical characteristics of the site root zone, hydraulic conductivity, volumetric water content and potential hydraulic gradient. Mean annual evapotranspiration was 783 mm year(-1) and annual through drainage below the root zone was 14% (162 mm year(-1)) of the gross rainfall. This drainage recharged the 42% of the annual saturation deficit of the water table. Similar mean annual evapotranspiration (770 mm year(-1)) was also calculated by using the water balance components. The mean daily coupling omega factor (Ω) between the grove canopy and the surrounding atmosphere indicated that a high degree of coupling (Ω=0.14±0.16) occurs in the grove and evapotranspiration was mainly controlled by surface conductance. As the dry season proceeded, the soil saturation deficit (δθ) increased rapidly resulting in a threshold surface conductance (0.030-0.005 m s(-1)) for δθ ranging from 0.05 to 0.10. Hypotheses to explain the omnipresence of perennial species in the wide range of physical conditions in neotropical savannas are discussed.
Communications in Soil Science and Plant Analysis, 2007
Field measurements showed the nitrogen (N) inputs and output of a fertilized pineapple crop [Anan... more Field measurements showed the nitrogen (N) inputs and output of a fertilized pineapple crop [Ananas comosus (L.) Merr. c.v. Red Spanish] growing in the Orinoco llanos during consecutive seasonal courses. The process rate changed with growth life‐cycle stages and seasonal conditions. The N accumulated by pineapple over the growing period was 226 kg N ha. It depended on the available N in the soil and the timing of split application of N fertilizer. Detailed monitoring of plant N‐accumulation rate showed a maximum rate (3.20 kg N ha d) at the harvesting time. The N‐harvested ratio and N‐use efficiency were 0.27 and 138 g g, respectively. The calculated N‐mineralization rate of the soil was 167 kg N ha over the life cycle. The fate of fertilizer N applied to pineapple was determined in microplots using urea labelled with 9.634% atom excess N. Fertilizer N recovery accounted for 48% of the applied N. The corresponding fractions of N recovered in the soil were 0.16 for the 0.0‐ to 0.3‐m depth and 0.01 for the 0.3‐ to 0.7‐m depth. The unrecovered fertilizer N in this study (34%) was largely due to volatilization (20% of the fertilizer) and denitrification (1.2%). Volatilization was shown to be greatly influenced by the seasonal conditions, namely the volumetric soil water content. In the pineapple field, monitored N input exceeded N output by 134 kg N ha, which is likely to lead to maintenance of soil N. Furthermore, utilization of N from crop residues input (164 kg N ha) has repercussions for the sustainable use of the Savanna Oligotrophic soils.
... 11. Nitrogen content and nitrogen RUBEN A. MONTES? ... Can. J. Bot. 61: 2 159-2 168. The effe... more ... 11. Nitrogen content and nitrogen RUBEN A. MONTES? ... Can. J. Bot. 61: 2 159-2 168. The effects of chronic doses of ozone (03) and rates of nitrogen (N) fertilizer on N content of ladino clover (Trifoliurn r-epens L. cv. Tillman) and tall fescue (Festuca arunrlinacea Schreb. cv. ...
... José San-José Æ Rubén Montes Æ Miguel Angel Mazorra Æ Ernesto Aguirre Ruiz Æ Nathaly Matute .... more ... José San-José Æ Rubén Montes Æ Miguel Angel Mazorra Æ Ernesto Aguirre Ruiz Æ Nathaly Matute ... histosols are important in the global carbon cycle, although covering little more than 1% of the world's land surface, they hold about 20% of global soil carbon (Brady and Weil ...
Page 1. Heterogeneity of the inland waterland palm ecotones (morichals) in the Orinoco lowlands,... more Page 1. Heterogeneity of the inland waterland palm ecotones (morichals) in the Orinoco lowlands, South America José San-José Rubén Montes Miguel Angel Mazorra Nathaly Matute Received: 8 May 2009 / Accepted: 13 ...
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