Soil ecosystem services of biochar for sandy-textured soils

Abstract

This dissertation enhances both the theoretical and empirical understanding of biochar's influence on soil ecosystem services, particularly the nutrient and carbon cycles, and the monetary value of these changes through (1) the development of a comprehensive review method, (2) the identification of the most affected components in soil nutrient cycles after biochar through systematic review and meta-analysis, (3) the determination of the soil carbon cycle components most affected by biochar through the application of meta-analysis, and (4) the application of valuation to the enhanced components of carbon and nutrient cycles. Previous review studies on biochar's impact on soil ecosystem services have not strived to formulate a systematic review protocol with well-defined goals and review steps. Therefore, this dissertation takes a novel approach by developing a comprehensive review protocol to systematically assess and meta-analyze the influence of biochar on soil ecosystem services, namely nutrient cycling and water cycling, climate regulation, and crop/biomass production. The protocol establishes a clear research question and methodology, encompassing the development of search queries, selection of search databases, screening strategies, and quantitative synthesis methods. Although previous studies have examined the impact of biochar on soil nutrient cycling using various review and meta-analysis methods, none have used a systematic review to comprehensively examine the effects on multiple components of the nutrient cycle in sandy-textured soils. This dissertation introduces a primary systematic review and meta-analysis, specifically focusing on biochar's influence on the nutrient cycle of sandy-textured soils. This review delves into the impact of biochar on nine key components of the nutrient cycle in sandy-textured soils, encompassing soil total NPK, soil mineral nitrogen, plant nutrient levels, N2O emissions, potential and effective cation exchange capacity (CEC), nutrient use efficiency, and mineral N leaching. Moreover, the changes in food crop yield and biomass production have also been analyzed based on the same data obtained. The review also examines the influence of predictors (effect modifiers) on the responses of the nutritional cycle components using advanced meta-regression methods such as randomized LASSO (least absolute shrinkage and selection operator). In ecological studies, the correction for 3 publication bias is frequently neglected. In contrast to these oversights, we implemented one of the recommended methods to rectify any potential publication bias in our analysis. Numerous studies have attempted to examine the impact of biochar on soil carbon sequestration or CO2 emissions, but none have comprehensively investigated its effects on the carbon cycle as a whole. Leveraging a state-of-the-art review, we focused on the three pivotal components of the carbon cycle—CO2 flux, soil respiration, and carbon sequestration—and subjected them to thorough meta-analysis. This study employed advanced methodologies to ensure reliable and robust results. To unveil the influence of various predictors, akin to our earlier systematic review, we applied methods such as the LASSO method. Additionally, individual moderator analysis was also employed. Consistent with the preceding review, correction for publication bias was implemented to enhance the study's reliability. To our knowledge, no study has undertaken the task of quantifying the costs and benefits associated with the impact of biochar on soil ecosystem services. In the concluding chapter of this dissertation, we conducted a valuation of the benefits derived from biochar on soil carbon sequestration, nutrient leaching, nutrient availability, and crop yield. We also evaluated the costs associated with biochar application to discern the disparity between its cost and the benefits. This chapter aims to underscore the economic implications of integrating biochar for these soil ecosystem services. This chapter is the culmination of our research and can be a valuable tool for communicating our findings to policymakers