Invertebrates and microorganisms are important but climate-dependent agents of wood decomposition globally. In this meta-analysis, we investigated what drives the invertebrate effect on wood decomposition worldwide. Globally, we found wood decomposition rates were on average approximately 40% higher when invertebrates were present compared to when they were excluded. This effect was most pronounced in the tropics, owing mainly to the activities of termites. The invertebrate effect was stronger for woody debris without bark as well as for that of larger diameter, possibly reflecting bark- and diameter-mediated differences in fungal colonisation or activity rates relative to those of invertebrates. Our meta-analysis shows similar overall invertebrate effect sizes on decomposition of woody debris derived from angiosperms and gymnosperms globally. Our results suggest the existence of critical interactions between microorganism colonisation and the invertebrate contribution to wood decomposition. To improve biogeochemical models, a better quantification of invertebrate contributions to wood decomposition is needed.
Tag: meta analysis
Effect of rewetting degraded peatlands on carbon fluxes: a meta-analysis
Numerous studies claim that rewetting interventions reduce CO2 and increase CH4 fluxes. To verify the claim, we conducted a systematic review and meta-analysis of the effects of rewetting on CO2 and CH4 fluxes and dissolved organic carbon (DOC). We identified 28 primary articles eligible for meta-analysis, from which we calculated 48 effect sizes for CO2 emissions, 67 effect sizes for CH4 emissions, and 5 effect sizes for DOC. We found that rewetting significantly decreased CO2 fluxes, with temperate zones showing the highest Hedges’ g effect size (−0.798 ± 0.229), followed by tropical (−0.338 ± 0.269) and boreal (−0.209 ± 0.372) zones. Meanwhile, rewetting increased CH4 fluxes, with the highest Hedges’ g effect size shown in temperate zones (1.108 ± 0.144), followed by boreal (0.805 ± 0.183) and tropical (0.096 ± 0.284) zones. In addition, based on yearly monitoring after rewetting, the CH4 emissions effect size increased significantly over the first 4 years (r2 = 0.853). Overall, the rewetting intervention reduced CO2 emissions by −1.43 ± 0.35 Mg CO2–C ha−1 year−1, increased CH4 emissions by 0.033 ± 0.003 Mg CH4–C ha−1 year−1, and had no significant impact on DOC. To improve the precision and reduce the bias of rewetting effect size quantification, it is recommended to conduct more experimental studies with extended monitoring periods using larger sample sizes and apply the before-after control-impact study design, especially in boreal and tropical climate zones.
Regenerative fertilization strategies for climate-smart agriculture: Consequences for greenhouse gas emissions from global drylands
Cultivated drylands are significant sources of greenhouse gases (GHGs), with declining yields. Regenerative practices are vital to achieve joint goals of boosting yields and mitigating GHGs emissions. Nevertheless, studies usually consider crop yields and soil properties, often lacking quantitative analysis of GHGs. This meta-analysis used log response ratio (lnRR) to perform effect size statistics; assessing impacts of major regenerative (manure, biochar, and two integrated applications) and inorganic fertilizers on GHGs emissions. The results reveal that GHGs emissions were increased by fertilizer or manure addition, but biochar decreased GHGs emissions, with greatest benefit at 50 t ha−1. Combining biochar or manure application with fertilizer emitted CO2 and/or N2O. Applying biochar alone led to 144% reduction in global warming potential (GWP). Paddy-rice with fertilizer emitted N2O and CH4, whereas these were mitigated by wheat with biochar. Fine-textured soils with manure emitted all three GHGs, whereas biochar with coarse-textured soils reduced emissions. Medium-textured soils had reduced N2O (18%) and CH4 (25%) emissions with integrated biochar and fertilizer. CO2 and N2O emissions were highest for neutral and acidic soils with fertilizer but lowest for alkaline soils after biochar application. Soil C:N ratios affected the best strategy to minimize GHGs: for high C:N ratio, fertilizer or manure should be avoided, in favour of biochar. Yet integrated biochar and fertilizer should be avoided for soils with low C:N ratio. We conclude that regenerative strategies using manure risk converting global drylands into major GHGs emitters. However, strategies incorporating biochar could mitigate dryland GHGs emissions and minimize GWP.
Developing holistic assessments of food and agricultural systems: A meta‑framework for metrics users
Food and agricultural (agrifood) systems feed the world and form the basis of our economic, political and cultural systems. At the same time, they are also drivers of environmental change at local and global levels. Given how central agrifood systems are to lives and livelihoods and the environment, it is not surprising that we try to measure, monitor and assess how they are performing.
Considering the diversity of agrifood systems globally, as well as the diversity in objectives of those who wish to collect data on the performance of those systems, there can be no single assessment framework which can meet every objective in all possible contexts. Any group that finds a need for holistic system assessment data has the challenge then, of selecting from available frameworks, adapting them to their needs, or innovating when there is nothing that meets those needs.
Hence, we need a guide through the maze of frameworks to help choose an approach, metrics and process that meet specific objectives. We therefore propose the development of a meta-framework, a scheme to guide or support those groups planning or promoting holistic agrifood systems measurement.
In this document, we put forward general steps for developing a holistic agrifood system assessment, as well as principles to guide decision making at each step of the design process, intended to support metrics-users in navigating the jungle of available approaches and selecting something that meets their needs. By developing a guiding framework for the design of holistic assessment and metrics, we aim to support their wider use, levelling the playing field for sustainable agrifood systems.
Application Module: Systematic Review and Meta-analysis
The first training series focused on research methodologies and techniques based on the realization that researchers have important knowledge and skills to create robust research products in the topic of sustainable development, which is always complex, and had become even more so in the midst of the pandemic. Material from the training has now been compiled into book form to improve accessibility to this knowledge product.