Nery Gaona-Jimenez

Aim of study: The study assesses the carbon potential of forests in the Peruvian Amazon, focusing on modeling carbon within a climate change mitigation framework to improve our understanding of the regional capacity to store in forest ecosystems. Area of study: San Martín Region, Peruvian Amazon. Material and methods: A total of six forest sites in the Amazonas region, located within San Martín and Loreto districts, were assessed. Structural measurements were recorded for all the trees and allometric equations were applied to estimate biomass. Additionally, altitude was recorded and its relationship with carbon storage was analyzed. Main results: The highest tree density was found in El Varillal and Ojo del Agua forests with 360 and 332 trees ha-1, respectively. Ahuihua and El Varillal forests showed the largest total height and diameter values. The accumulated carbon was greater in Ahuihua and Bajo Huallaga forests both the aboveground and belowground with values of 405.07 t ha-1 and 51.85 t ha-1, and 201.46 t ha-1 and 27.59 t ha-1, respectively. These forests also had the largest structural mean values of basal area, total height, dominant height, and diameter at breast height. The altitude variable was negatively related to aboveground and belowground carbon. Research highlights: The type of forest and the management practices play a crucial role for carbon accumulation both in the aboveground and belowground biomass. The basal area was the variable that most contributed on carbon accumulation. Understanding the carbon dynamic in forests provides essential information for the implementation of accurate management practices and conservation efforts.

La investigación sobre los patrones de las reservas de carbono en árboles es fundamental para los esfuerzos de mitigación y adaptación del cambio climático. El objetivo de este estudio fue analizar la diversidad de árboles y reservas de carbono en tres bosques primarios bajo gradientes altitudinales en la región San Martín, Perú. El estudio estuvo constituido por tres bosques entre los 2 000 - 2 100, 1 600 - 1 700 y 1 000 -1 100 msnm respectivamente. Cada parcela estuvo conformada por 1 000 m2 y se seleccionaron un total de cuatro subparcelas por cada bosque. Se midieron los árboles con una altura ≥2 m y ≥5 cm de diámetro a la altura del pecho (DAP). Asimismo, la similitud florística entre altitudes se evaluó a través de los índices de Jaccard y Sørensen. El Bosque Alto Mayo presentó valores relativamente altos y consistentes en riqueza de especies, variando entre 6 y 8 especies por parcela, con un índice de Shannon de hasta 1,972; Simpson de 0,842 y equitatividad de 0,948. El Bosque Moyobamba alcanzó el promedio más alto de almacenamiento de carbono total, con un valor de 415,95±21,95 t C ha-1; debido al mayor tamaño en diámetro y altura de los árboles. Se encontró que el mayor contenido de carbono por encima y debajo del árbol estuvo influenciado por el DAP y altura total de los árboles.

Soil organic carbon (SOC) plays a crucial role in mitigating climate change and enhancing soil fertility. Its storage and dynamics are particularly significant in agricultural ecosystems of the Peruvian Amazon, where the expansion of agriculture and livestock farming may disrupt the regional carbon balance. This study aimed to analyze SOC variability and its relationship with edaphic and nutritional properties in agricultural systems in Eastern Peru (San Martín and Loreto regions). Four representative cropping systems were evaluated: coffee grown in agroforestry and polyculture systems; maize as a monoculture; and camu‐camu and cocoa cultivated in monoculture and agroforestry systems, respectively. The highest SOC content (80.70 t·ha ⁻¹ ), phosphorus (12.03 mg·kg ⁻¹ ), and moisture (52.36%) were observed in coffee‐growing soils, likely due to the presence of shade trees that enhance organic matter inputs in soils at 0–20 cm depth. In contrast, soils under maize cultivation exhibited the highest levels of nitrogen (0.19%), potassium (364.02 mg·kg ⁻¹ ), and pH (7.61), likely due to the frequent fertilization applied to this crop. The lowest carbon saturation deficits were found in soils under camu‐camu (31.67%), cocoa (26.88%), maize (24.80%), and coffee (20.59%), with the most pronounced deficits occurring in camu‐camu and cocoa soils in Yurimaguas (Loreto), indicating a heightened vulnerability to carbon loss. These findings underscore the significant influence of crop type and management practices on carbon and nutrient dynamics in tropical soils. Long‐term studies are recommended to assess carbon sequestration over extended periods, informing sustainable soil management policies in the Peruvian Amazon.

Inoculation of arbuscular mycorrhizal fungi (AMF) has important benefits, not only for plant growth but also for reducing Cd absorption in Theobroma plants. This study aimed to investigate the influence of cadmium (Cd) and arbuscular mycorrhizae (AM) on growth and chlorophyll content (CC) in Theobroma plants. This experiment had a 3 × 2 × 2 factorial design with species of Theobroma cacao and Theobroma grandiflorum , AMF inoculation (mycorrhizal control and AMF inoculation), and Cd addition (0, 1, and 3 mgkg ⁻¹ ), arranged in a completely randomized design with three repetitions. The AMF inoculum consisted of applying 1500 units to each seedling. The results showed that the Cd content decreased in the stems with AMF treatment for T. cacao as well as in the soil, showing significant differences in both variables. However, a reduction of Cd could also be observed in T. grandiflorum stems without significant differences with Cd in the soil. The height, diameter, root biomass, and leaf area (LA) of the Theobroma plants increased in most of the treatments studied in comparison with treatments that received Cd, as did CC. The AMFs inoculated into Theobroma plants induced higher CC in leaves. Likewise, T. cacao presented a higher value in morphology and a lower Cd concentration in soil and shoots.

Aim of study: The loss of forest cover is a global problem that alters ecosystems, contributing to carbon emissions. This study measured the soil organic carbon (SOC) at different soil depths in tropical dry forests of the Huallaga Central in the Peruvian Amazon. Area of study: San Martín Region, Peruvian Amazon. Material and methods: A total of 24 plots of 100 m2 were selected in primary (~200 years), intervened (~50 years since intervention), and deforested forests (10 years ago), with 120 soil samples collected across five depths. Soil texture (hydrometer), bulk density (cylinder method), SOC content, SOC density, and erodibility (K parameter) were calculated. Main results: SOC content in the 0-20 cm soil horizon was 79.5±21.3 t ha-1 for the primary forest, 58.5±11.8 t ha-1 for the intervened forest, and 41.8±10 t ha-1 for the deforested forest. A soil erodibility K of 0.065 was observed for primary forests and 0.076 and 0.093 for intervened and deforested forests. In average, the SOC density obtained in this study was 7.6±5.1 t ha-1 in the primary forest, 6.2±3.6 t ha-1 in the intervened forest, and 4.7±2.7 in the deforested forest. Research highlights: Primary forests had the highest SOC content and SOC density, followed by intervened and deforested forests, while the opposite pattern was found for soil erodibility. These patterns were especially marked in the first 40 cm of soil depth.

La selva amazónica de Perú ha experimentado grandes cambios en el uso de suelos, mediante la deforestación del ecosistema forestal para la instalación de silvopasturas y cultivos agrícolas como café y cacao, lo que ha contribuido al aumento de CO2 en la atmósfera. Este estudio evaluó los niveles de glomalina y carbono en función de los agregados del suelo en estos ambientes. Se estudiaron tres tipos de ecosistemas: i) ecosistema de bosque, ii) agroecosistema de silvopastura y iii) agroecosistema de café. En cada uno se establecieron nueve parcelas de 100 m2 y se extrajeron muestras de suelos a una profundidad de 0-20 cm. Se evaluó el carbono orgánico del suelo (COS) así como la glomalina extraíble (GE) y total (GT), en cuatro diferentes rangos del tamaño de los agregados (>2 mm, 2-1 mm, 1-0,25 mm y 0,25 mm). El efecto del tipo de ecosistema y agregados sobre el COS y glomalina se analizó mediante un ANOVA, así como con una prueba de regresión. Los ecosistemas estudiados influyeron significativamente en la disponibilidad de COS y glomalina; se obtuvo mayor COS en el agroecosistema de café, seguido del ecosistema de bosque con 101,08 y 80,17 t·ha-1. El bosque presentó mayor concentración de GE y GT respecto al cafetal y las silvopasturas. El tamaño de los agregados influyó significativamente en la disponibilidad de COS, GE y GT; cuando fueron de menores dimensiones, los contenidos de COS y glomalina disminuyeron. El tipo del sistema y los agregados del suelo influyeron significativamente en la disponibilidad de COS y glomalina en los tres ambientes estudiados.

The Peruvian Amazon has experienced large losses of forest cover due to changes in land use, contributing to increases in CO₂ in the atmosphere. This study estimated the organic carbon content of forest soil in two forests “Ojos de Agua” and “El Quinillal” in the Central Huallaga of Peru, establishing three types of cover: (i) primary, (ii) intervened, and (iii) deforested. For this purpose, 24 plots of 100 m² were established and samples were extracted at a depth of 0–20 cm. The effect of the type of forest cover on soil carbon (Organic Carbon‐SOC, Inorganic Carbon‐SIC, Saturated Carbon‐SC, Critical Carbon‐CC, Saturated Carbon Deficit‐SCD, and Organic Carbon‐OC) was analyzed by means of an Analysis of Variance, correlation. Likewise, the relationship between carbon (C) and soil properties was evaluated by principal component analysis and correlation network. The results indicated that the highest SOC averages were found in the primary forests of Ojos de Agua and El Quinillal with 3.54% and 2.51%. The lowest values were found in the deforested forests with 1.34% and 1.46%. The calculation of the saturated C levels of the soil showed an average of 28.63% ± 2.14% and the saturated carbon deficit of 26.63% ± 2.45%, whereas the critical threshold of C showed an average of 2.21% ± 0.18%. The highest SOC content found in the Ojos de Agua primary forest is due to the presence of dominant forest species such as Manilkara bidentata and Brosimum alicastrum. Likewise, the C deficit in the soils of the study area is very alarming because it is very close to saturation levels, especially in deforested forests.

The production system influences the cadmium (Cd) content and mycorrhization in cocoa plantations. The objective of this study was to determine the effects of different production systems on Cd uptake and the presence of mycorrhizas in cacao clones in field conditions, in the Peruvian Amazon. Twelve subplots of 108 m2 were selected in representative cocoa cultivation systems under agroforestry (AF) and monoculture (MON), with the cocoa clones ICS and CCN. Significant differences and data distribution were evaluated using ANOVA, principal component analysis, and Tukey's tests. Mycorrhizal colonization was higher in the AF_ICS system (71.11%) while the length of the extraradical mycelium was higher in the AF_CCN system (17.23%). The highest Cd content in soils was found under the AF_CCN and AF_ICS systems, both with 0.39 mg kg-1. The Cd content in cacao roots, leaves, and beans were higher in the MON_CCN system with 1.87, 2.06, and 1.12 mg kg-1 respectively. Cocoa monocultures (with both clones) generally showed lower levels of mycorrhizal colonization than agroforestry systems, which in turn (also for both clones) presented higher Cd content in beans, even exceeding the limit established by the world health authorities.

La multiplicación de esporas de hongos micorrízicos arbusculares (HMA) es una limitante para las aplicaciones agrícolas como biofertilizantes. En el presente estudio se realizó la multiplicación masiva de HMA procedentes de fincas de cacao (Theobroma cacao L.) en la región de San Martín, Perú, para optimizar su manejo y producción de esporas en condiciones ambientales controladas. Se diseñó un experimento en condiciones de invernadero, con un diseño completamente al azar, considerando tres fuentes de inoculo de HMA obtenidas en las provincias de Mariscal Cáceres, Lamas y Rioja, en dos periodos de tiempo (110 y 220 días) y dos cultivos hospedantes (maíz y arroz). Este material fue mezclado con un volumen de arena y tres de tierra agrícola, que fueron colocadas en cajones; transcurrido el periodo de tiempo se evaluó la población de esporas, colonización micorrícica, altura de la planta hospedante y peso seco de la parte aérea y de la raíz. La multiplicación de HMA a los 220 días, procedente de Mariscal Cáceres usando arroz como planta hospedante, demostró ser la más adecuada para la multiplicación de los HMA. El arroz actuó como un huésped adecuado y pudo multiplicar un mayor número de esporas. Se concluye que esta combinación puede ser utilizada como una metodología de propagación masiva de HMA debido a su gran capacidad para reproducirse.