Low-carbon development for Colombia

Colombia is well-positioned to pursue a low-carbon development path given the country’s already large hydropower production, a model urban transport program, and significant potential to reduce emissions from agriculture, forestry, and other land-use (AFOLU). While reducing carbon emissions through these and other activities can demonstrate Colombia’s commitment to addressing global climate change, the primary driver of such activities should be that they are part of the country’s economic and sustainable development agenda. Policymakers need to ensure that public policies for climate mitigation support projects that are economic and achieve macroeconomic goals such as generating income and employment. Given the importance of hydropower and Colombia’s huge potential for expanding agriculture and forestry, another consideration is that mitigation measures should not increase the country’s vulnerability to climate change impacts—some could actually do that—but should also increase the country’s resilience to natural and manmade disasters. These findings are based on an analysis of Colombia’s climate mitigation options made jointly by the World Bank and the Department of National Planning (DNP)

Low-carbon development for Colombia

Colombia is well-positioned to pursue a low-carbon development path given the country’s already large hydropower production, a model urban transport program, and significant potential to reduce emissions from agriculture, forestry, and other land-use (AFOLU). While reducing carbon emissions through these and other activities can demonstrate Colombia’s commitment to addressing global climate change, the primary driver of such activities should be that they are part of the country’s economic and sustainable development agenda. Policymakers need to ensure that public policies for climate mitigation support projects that are economic and achieve macroeconomic goals such as generating income and employment. Given the importance of hydropower and Colombia’s huge potential for expanding agriculture and forestry, another consideration is that mitigation measures should not increase the country’s vulnerability to climate change impacts—some could actually do that—but should also increase the country’s resilience to natural and manmade disasters. These findings are based on an analysis of Colombia’s climate mitigation options made jointly by the World Bank and the Department of National Planning (DNP)

Carbon and nutrient stocks in the litter layer of agroforestry systems in central Amazonia, Brazil

Both second-growth and agroforestry systems (AFs) have the potential for recovering thousands of abandoned pasturelands in Amazon. The AFs may do it faster and, at the same time, produce direct economic benefits for farmers. Improved nutrient recycling may be expected due to distinctive litter production in AFs, but lacks experimental data yet. The stocks of carbon and nutrients of the litter layer under different agroforestry systems (AFs) were investigated at an abandoned pasture site, 60 km north of Manaus. The experimental design consisted of three blocks, with five treatments: four different types of 5-year-old AFs and a secondary forest (CAP). Litter layer was sampled in the wet and dry seasons, sorted according to the predominant plant species and analysed for carbon and nutrient concentrations. The litter layer in the control plots was much larger than in the AFs, and thus, the carbon stocks in the litter layer of the control (wet = 489 g m 2; dry = 783 g m 2) were larger than in the AFs. However, due to a clearly higher concentration of nutrients in the litter from the AFs, some nutrient stocks were similar or even greater than in the control. The planted timber species and the green manures were important sources of K and Ca to the litter layer while the peach-palm was an important source of Mg. In general, the litter of AFs had lower C:nutrient ratios than the litter in the secondary forest control, indicating a faster nutrient recycling in the AFs. © Springer 2005

Inorganic and organic phosphorus pools in earthworm casts (Glossoscolecidae) and a Brazilian rainforest Oxisol

We compared differences in soil phosphorus fractions between large earthworm casts (Family Glossoscolecidae) and surrounding soils, i.e., Oxisols in 10 year-old upland agroforestry system (AGR), pasture (PAS), and secondary forest (SEC) in the Central Brazilian Amazon. AGR and PAS both received low-input fertilization and SEC received no fertilization. We found that earthworm casts had higher levels of organic hydroxide P than surrounding soils, whereas fertilization increased inorganic hydroxide P. Inorganic P was increased by fertilization, and organic P was increased by earthworm gut passage and/or selection of ingested materials, which increased available P (sum of resin and bicarbonate fractions) and moderately available P (sum of hydroxide and dilute acid fractions), and P fertilizer application and land-use increased available P. The use of a modified sequential P fractionation produced fewer differences between earthworm casts and soils than were expected. We suggest the use of a condensed extraction procedure with three fractions (Available P, Moderately Available P, and Resistant P) that provide an ecologically based understanding of the P availability in soil. Earthworm casts were estimated to constitute 41.0, 38.2, and 26.0 kg ha-1 of total available P stocks (sum of resin and bicarbonate fractions) in the agroforestry system, pasture, and secondary forest, respectively

Development of the soil macrofauna community under silvopastoral and agrosilvicultural systems in Amazonia

In the Brazilian Amazon region, millions of hectares of forest land have been converted into cattle pastures and then been abandoned. Agroforestry is a potential option for the transformation of in parts degraded lands into productive agricultural systems. The re-establishment of a diversified soil macrofauna can help in the process of recuperation of the often compacted soil structure of the pastures. The soil macrofauna community was studied during the rainy season in four different agroforestry systems near Manaus in Central Amazonia: 1. a high-input silvopastoral system (ASPh), 2. a low-input silvopastoral system (ASPI), 3. a palm based system with four tree crop species (AS1) and 4. a high-diversity tree crop system with ten tree crop species (AS2), plus a spontaneous fallow for comparison. The sampling method recommended by the Tropical Soil Biology and Fertility Programme was used. The highest diversity of fauna groups was observed in the ASPh and ASPI where trees were associated with the leguminous cover crop, Desrnodiurn ovalifoliurn. The cover crop exerted a favorable effect on the soil fauna presumably by maintaining the soil moist and shaded and providing litter as a substrate. Of the 15 soil fauna groups that were found in all systems, four were absent from AS1. Within the AS2 system a significantly greater density of the soil fauna was observed under peach palm (Bactris gasipaes) and cupuaçu (Theobroma grandiflorum) (3107 and 524 ind.m-2, respectively) than under the other three tree species. The soil under peach palm and cupuaçu also tended to have a higher number of soil fauna groups. In AS1, the soil under peach palm had a higher fauna density than the soil under cupuaçu, probably caused by the abundant residues of the heart of palm harvest on the soil. The earthworm biomass was particularly high in AS1. Under cupuaçu approximately 7 times more earthworms were found in AS1 (17.9) than in AS2 (2.4). The study of the macrofauna community, including both the litter layer and the superficial soil layers, allows to identify the plant species/management combinations which favour the increase of the diversity of the invertebrates

Nitrogen transfer between high- and low-quality leaves on a nutrient-poor Oxisol determined by 15N enrichment

It has been proposed that the C/N ratio, or quality, of litter or mulch mixtures affects N release. Although total N release from these mixtures and the effects on soil N are relatively well understood, a mechanistic understanding of the interactions between litter species with respect to their N release is still lacking. This study examines decomposition and N dynamics in mixtures of high-quality leguminous mulch, gliricidia [Gliricidia sepium (Jacq.) Kunth. ex Walp.] with a C/N ratio of 13, and low-quality cupuaçu [Theobroma grandiflorum (Wild. ex Spring) Schumann] litter with a C/N ratio of 42, which occur in combination in agroforestry systems. Ratios of 100:0, 80:20, 50:50, 20:80, 0:100 of fresh 15N-enriched gliricidia leaves and senescent cupuaçu leaves, totaling the same dry weight of 6.64 t ha-1, were applied to an Oxisol and sampled at 6, 14, 38, and 96 days after application. After more than 40% of the N in the gliricidia leaves had been released and the microbial biomass N reached its peak, a significant increase in available soil N occurred at day 14, which was more pronounced with greater amounts of gliricidia in the leaf mixture. However, relative to the N applied in the leaf mixture, there was no significant difference in available soil N with greater proportions of gliricidia. Total N release from the mixtures corresponded to the total N applied by gliricidia. Until day 38, cupuaçu C mineralization was significantly faster in the presence of the highest proportion of gliricidia compared to lower proportions. This faster C mineralization of more than 0.5% per day, however, did not increase total C loss or N release from cupuaçu leaves after 96 days. The use of 15N tracers identified an N transfer from gliricidia leaves and the soil to cupuaçu leaves and consequently, a lower N release from gliricidia to the soil in the presence of cupuaçu leaves. Though we expected that available N in the soil would also decrease with greater amounts of cupuaçu litter in the mixture, our results indicated an additive effect of the two species on N release and soil mineral N, with gross interactions between them canceling net interactive effects. Therefore, N release of leaf mixtures behaved as predicted from a calculated sum of individual release patterns, in spite of a transfer of N from the high- to the low-quality leaves. © 2004 Elsevier Ltd. All rights reserved