Long-term effect of forest and landscape restoration practices on soil organic carbon stock in semi-arid Burkina Faso

In semi-arid areas, forest and landscape restoration (FLR) practices are being implemented to reverse the land degradation process. The objective of this study was to investigate the long-term effect of FLR practices on soil organic carbon stock (SOCs) under different land uses in the semi-arid region of Burkina Faso. The study was conducted on degraded land under rehabilitation practices for 45, 27, 18 and 11 years, which were compared to similar land without specific rehabilitation measures. The soil was collected in 2018 in 35 sampling plots of 30 m x 30 m. Soil analysis concerned bulk density, soil particle size, soil pH, soil organic carbon content, and respiratory activity of microorganisms. SOCs increased by 150%, 98% and 29% over 0-10 cm depth in 45-, 27- and 11-year of FLR practices, and decreased by 6% in 18-year of FLR practices compared to their respective control. SOCs were not linearly increased with the duration of the implementation of FLR practices because the variation of SOCs depends on several other parameters such as soil texture, and types of combination of FLR practices. The highest SOCs were recorded for 27 years (9.5 t.ha-1) and 45 years (8.5 t.ha-1) of FLR practices. This study revealed the importance of including Assisted Natural Regeneration (ANR) as one of the combined FLR practices, for improvement of SOCs

Erosão hídrica pós-plantio em florestas de eucalipto na bacia do rio Paraná, no leste do Mato Grosso do Sul

Nas regiões tropicais, o desgaste provocado no solo por ação das águas da chuva, ou seja, a erosão hídrica é a mais importante forma de degradação do solo. Visto que os plantios florestais de eucalipto estão inseridos em ecossistemas sensíveis às perturbações antrópicas em razão de ocorrência de plantações em solos com baixos teores de argila, com baixa fertilidade natural e grande parte das plantações estabelecidas em antigas áreas agrícolas e de pastagens degradadas, surge a necessidade do entendimento dos processos que regem a erosão hídrica e suas relações com as perdas de solo e água nos sistemas florestais. Objetivaram-se com este trabalho calcular os valores de erosividade da chuva (fator R - EI30), estimar a tolerância de perda de solo (T) para as classes representativas nas áreas de estudo, avaliar as perdas de solo e água por erosão hídrica e verificar a influência, por meio de análise de componentes principais (ACP), de atributos físicos e matéria orgânica do solo sobre a erosão hídrica em florestas de eucalipto no estádio de pós-plantio. Os tratamentos constituíram de diferentes sistemas de manejo dos resíduos e da disposição de plantio (nível e desnível), em dois biomas distintos, Cerrado e Floresta, e solo descoberto. Os solos foram classificados como Latossolo Vermelho distrófico típico textura média-alta fase floresta (LVd1) e Latossolo Vermelho distrófico típico textura média-baixa fase cerrado (LVd2). O estudo foi realizado em áreas experimentais de plantio de eucalipto localizadas no município de Três Lagoas, na bacia do Rio Paraná, no leste do Mato Grosso do Sul. O índice de erosividade anual obtido foi de 6.792,7 MJ mm ha-1 h-1 ano-1. Os valores de T variaram de 9,0 a 11,0 Mg ha-1 ano-1, para o LVd2 e LVd1, respectivamente. As perdas de solo apresentaram valores em torno de 0 a 0,505 Mg ha-1 no LVd1 e de 0 a 0,853 Mg ha-1, no LVd2. A ACP evidenciou-se eficiente na discriminação dos sistemas de manejo em razão da interação entre os atributos físicos e matéria orgânica do solo e suas relações com a erosão hídrica, possibilitando visualizar de forma clara a influência do manejo sobre esses atributos e a relação de ambos com as perdas de solo e água

Impact of sheet erosion mechanisms on organic carbon losses from crusted soils in the Sahel

Soil surface crusting influences water infiltration and runoff but its impact on soil organic carbon (SOC) losses by sheet erosion is largely unknown. Because there are different mechanisms of sheet erosion, from raindrop detachment and transport by raindrops interacting with flow (RIFT), to detachment and transport by flow, that require a certain slope length to be operative, this study examined the impact of slope length on SOC and nutrient losses. Field experiments were conducted on crusted soils in the Sahel region of Africa. Three replicates of micro-plots (1 m ? 1 m), plots (10 m long ? 5 m width) and long plots (25 m ? 6 m) were installed for each crust type in the area (structural, STRU; desiccation, DES; gravel, GRAV; and erosion, ERO) and followed for each rainfall event in the 2012 rainy season. Sediment, SOC content in sediments and selected nutrients (NO3?; PO43?) in the runoff were analyzed to evaluate the annual losses by sheet erosion. SOC losses decreased significantly with increasing slope length from 0.24 g C m ? 1 on micro-plots to 0.04 g C m? 1 on plots and to 0.01 g C m? 1 on long plots and similar trends were observed for NO3? and PO43? losses. This suggested a strong scale dependency of sheet erosion with the efficiency of transport by saltation and rolling by RIFT decreasing significantly with increasing slope length, by 6 folds in average between 1 and 10 m, with values between 1.8 on DES crusts and 19 on STRU crusts. These results on the relationship between soil crusting and sheet erosion should be further used to mitigate against the loss of SOC through the implementation of improved soil conservation techniques, as well as to improve soil erosion and/or SOC models