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Research focusing on energy, water vapor, and CO2 exchanges over the Caatinga Biome is recent. Consequently, there exist research gaps on this topic that limit our ability to understand and project interannual and long-term variations in the CO2 cycle of this environment. Thus, the objective of this study was to evaluate the behavior of the energy and CO2 balances of the Caatinga Biome under extreme rainfall conditions (extreme drought and intense rainfall) using simulations of the SITE model (Simple Tropical Ecosystem Model). Meteorological data from the years 2009 (heavy rainfall) and 2012 (extreme drought) obtained from an INMET automatic station were used. Relationships between monthly GPP and NEE values and rainfall were also analyzed. Although the SITE model had been previously calibrated for the region, adjustments to the calibration were necessary for our study due to the extreme climatic values of the selected years. The results highlight the impact of rainfall on energy and mass exchanges over the Caatinga, particularly evident in the partitioning of the energy balance and the CO2 balance. In 2009 (during heavy rainfall), the fraction of Rn converted into LE was nearly 6% higher compared to the values observed in 2012 (during extreme drought). Regarding CO2, it was found that the Caatinga behaved as a sink, even under extreme drought conditions (2012), with annual average values of −1.86 µmol m−2 s−1 (2009) and −0.81 µmol m−2 s−1 (2012). Relationships between monthly GPP and NEE values and rainfall were also investigated, revealing an asymptotic relationship between the components of CO2 balance and rainfall. It was evident that both the monthly values of GPP and NEE tend to stabilize when monthly rainfall volumes exceed 200 mm. [ABSTRACT FROM AUTHOR]

Desertification is defined as land degradation in arid, semiarid, and dry sub-humid regions, and it is caused primarily by human activities and climate change. The semiarid region of Northeast (NE) Brazil is a very large, populous region, and thus, it is hard to monitor the dynamics of its desertified areas; therefore, the present study aimed to develop a minimum set of biophysical indicators to qualify and monitor desertification in this region. This approach included sampling a pair of preserved forested areas and nearby degraded, non-forested areas which had no vegetation growth in the previous years. The study was developed in four stages: (a) pilot site selection; (b) quantification and analysis of soil and vegetation biophysical indicators; (c) biophysical indicator selection; and (d) elaboration of the minimum set of biophysical indicators and desertification levels. Of the analyzed 24 biophysical indicators, 11 were retained and subjected to factor analysis by its principal components. This yielded the minimum set of indicators used to estimate the desertification levels of the pilot sites, which consisted of four soil characteristics: Total Organic Carbon (TOC), cation exchange capacity, clay content, and magnesium content. Regressions were conducted using the SQI, and these indicators showed that the TOC had the highest coefficient of determination. In an exploratory analysis, high SQI (low desertification) showed a positive correlation with the normalized difference vegetation index (R = 0.70) and Aridity Index (R = 0.97). This methodological approach could form the basis of a dynamic monitoring system that is capable of supplying objective, quantitative, and easy to obtain information to decision-makers in NE Brazil and other dry ecosystems around the globe. [ABSTRACT FROM AUTHOR]

An understanding of variations in morphophysiological leaf traits of plant models in dry tropical forests is essential for quantifying C fluxes from forest ecosystems in response to climate changes. The present study evaluated the influences of seasonal rainfall and different light conditions on the gas exchange, nutrients, organic compounds and morphological traits in Croton blanchetianus Baill. trees within a fragment of Caatinga forest. Stomatal conductance (gs) and net photosynthesis (PN) demonstrated variations within the diurnal cycle, with maximum values at approximately midday and minimum values at predawn. The PN and the diurnal integrated CO2 assimilation were lower during the dry season than in the rainy season. Water use efficiency was positively correlated with PN (r = 0.73) during the dry season only. However, the correlation between PN and gs was observed during the rainy season only (r = 0.60). Thus we demonstrated that C. blanchetianus has a remarkable ability to adapt to global climatic changes and could be considered a model in studies exploring water relationships in woody plants; consequently, this species may be important in future reforestation studies. [ABSTRACT FROM AUTHOR]

Copyright of Neotropical Biology & Conservation is the property of Pensoft Publishers and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Revista Brasileira de Engenharia Agricola e Ambiental - Agriambi is the property of Revista Brasileira de Engenharia Agricola e Ambiental and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Brazilian Journal of Agricultural Sciences / Revista Brasileira de Ciências Agrárias is the property of Universidade Federal Rural de Pernambuco and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The aim of this study was to evaluate the contribution of the form and timing of application of organic fertilizers of different grades for nutrients uptake and its relation to the productivity of corn grown in Fluvic Entisol in the semiarid region of the Paraiba State, Brazil. The experiment was conducted at Vila Maria Rita Agroecological Station, in the Cariri region of the state, in a randomized complete block design with four replications. The treatments were: T1 - built-in application of 20 Mg ha-1 of soil gliricidia (GI); T2 - sidedress application of 20 Mg ha-1 of gliricidia (GC); T3 - built-in application of 10 Mg ha-1 manure and 10 Mg ha-1 biomass gliricidia (EI+ GI); T4 - application of 10 Mg ha-1 incorporated manure and 10 Mg ha-1 in sidedress, 45 days after sowing (EI + GC); T5 - built-in application of 10 Mg ha-1 manure (EI); T6 - control without application of organic manure (C). The application of gliricidia in cover (GC) in the soil led to the greatest accumulation of nutrients in corn biomass. The presence of gliricidia alone or in combination with manure favored for a greater synchronization between the soil nutrients availability and the corn demand for nutrients. The application of gliricidia alone and in combination with manure favored the increase in the nutrients export through the straw and corn grain. The use of built-in gliricidia biomass alone and in combination with manure in the Fulvic Entissol is recommended to increase corn productivity. [ABSTRACT FROM AUTHOR]

Copyright of Revista Brasileira de Engenharia Agricola e Ambiental - Agriambi is the property of Revista Brasileira de Engenharia Agricola e Ambiental and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Although seasonally dry tropical forests are considered invaluable to a greater understanding of global carbon fluxes, they remain as one of the ecosystems with the fewest observations. In this context, ecological and ecosystem models can be used as alternative methods to answer questions related to the interactions between the biosphere and the atmosphere in dry forests. The objective of this study was to calibrate the simple tropical ecosystem model (SITE) and evaluate its performance in characterizing the annual and seasonal behavior of the energy and carbon fluxes in a preserved fragment of the Caatinga biome. The SITE model exhibited reasonable applicability to simulate variations in CO2 and energy fluxes (r > 0.7). Results showed that the calibrated set of vegetation parameters adequately simulated gross primary productivity (GPP) and net ecosystem CO2 exchange (NEE). The SITE model was also able to accurately retrieve the time at which daily GPP and NEE peaked. The model was able to simulate the partition of the available energy into sensible and latent heat fluxes and soil heat flux when the calibrated parameters were used. Therefore, changes in the dynamics of dry forests should be taken into consideration in the modeling of ecosystem carbon balances. [ABSTRACT FROM AUTHOR]

Biochar has been used to reuse the agro-industrial wastes and improve soil quality. Several studies have been carried out to show the impact of biochar on physical and chemical soil attributes. However, there are still gaps regarding the effects on as microbial biomass and enzymatic activities that are important to determine sensitive indicators to evaluate changes in management practices. The objective of this study was to assess the effect of two biochars on the chemical, microbial biomass carbon, and the enzymatic activities in an Entisol cultivated with bean. We evaluate two types of coffee biochar: ground and husks, four doses (4, 8, 12, and 16 Mg ha-1) and control. All treatments received organic fertilization with cow manure. Husks biochar increase the soil pH, Ca, and K, also contributing to the reduction of toxic aluminum contents and raising the concentrations of P labile. The treatments that received ground biochar showed higher soil organic carbon, microbial biomass, β-glucosidase, and fluorescein diacetate. Biochar produced from coffee residues increased sandy soil quality. We showed the first report on the beneficial impact of coffee biochar on enzymatic and microbiological quality of sandy soil cultivated with the bean.

Organic fertilizers are a viable alternative to increase oilseed productivity in family agriculture systems. The study aimed to evaluate the effects of timing and placement of cattle manure and/or gliricidia (Gliricidia sepium Jacq. Walp) prunings on cotton (Gossipium hirsutum L.) and sunflower (Helianthus annuus L.) nutrient accumulation and biomass productivity. Experiments were carried out in 2010 and 2011 in Taperoá, Paraíba, Brazil. The organic fertilization treatments were: GI - gliricidia incorporated before planting; GS - gliricidia applied on surface 45 days after planting (DAP); MI + GI - manure and gliricidia incorporated before planting; MI + GS - manure incorporated before planting and gliricídia applied on the surface 45 DAP; MI - manure incorporated before planting; and T - with no organic fertilization. In 2010, treatment MI + GS increased N, P, and K accumulation in cotton (12 and 7 kg ha-1) as well as in sunflower (20 and 29 kg ha-1). In 2011, GI and GS treatments resulted in higher N, P, K accumulations in both crops. The highest cotton productivity in 2010 was obtained with MI + GS treatment (198 kg ha-1) and in 2011 with GS treatment (594 kg ha-1). For sunflower, MI + GS treatment yielded the highest productivity in 2010 (466 kg ha-1) and GI treatment in 2011 (3542 kg ha-1). GI and MI + GS treatments increased total biomass productivity for cotton and sunflower. The treatment that combined both cattle manure incorporated into the soil before planting and gliricidia applied on the surface 45 days after planting was the most viable management strategy.

This study used (15)N natural abundance techniques to investigate whether elk herbivory affects the capability of willow (Salix spp.) and reed-grass (Carex spp.) to access N from groundwater in upper and lower landscape positions within riparian areas of the Rocky Mountain National Park. For this, delta(15)N values of plant, soil, rainfall and groundwater samples were measured within a replicated field experiment. Despite the relatively high variability in the (15)N data, it provided evidence of the effects of grazing and lanscape position on plant N sources. Carex seemed to acquire less groundwater N in upper landscape positions compared to Salix, maybe due to the deeper willow rooting system. However, grazed willows in upper landscape positions seemed to acquire less groundwater N as compared to willows protected from herbivory. These findings were in accordance with other isotopic and non-isotopic studies conducted in the same experimental site.