“Soil respiration” refers to the flow of carbon dioxide, mostly generated by plant roots and microbes, from the soil to the atmosphere. This flux is large and highly uncertain, and understanding it has significant implications for our ability to predict the effects of land use and climate change. This review summarizes advances, insights, and challenges in soil respiration science. It examines laboratory approaches and findings; documents changes in how researchers measure and understand soil respiration in the natural world; and describes efforts to estimate the global dynamics of soil respiration from openly-available databases of observations. We conclude by discussing the most compelling challenges and opportunities for the future.

Climate change and the consequent thawing of permafrost threatens to transform the permafrost region from a carbon sink into a carbon source, posing a challenge to global climate goals. Numerous studies over the past decades have identified important factors affecting carbon cycling, including vegetation changes, periods of soil freezing and thawing, wildfire, and other disturbance events. Overall, studies show high wetland methane emissions and a small net carbon dioxide sink strength over the terrestrial permafrost region but results differ among modeling and upscaling approaches. Continued and coordinated efforts among field, modeling, and remote sensing communities are needed to integrate new knowledge from observations to modeling and predictions and finally to policy.

Inland waters (e.g., streams, rivers, lakes, reservoirs, and ponds) are important sources of greenhouse gases (i.e., CO₂ and CH₄) for the atmosphere, affecting the earth's carbon balance. With a vast land area (∼9.6 million km²) and diverse climate regions, China contains numerous natural and man-made water bodies. Dissolved carbon dioxide (CO₂) and methane (CH₄) emissions from these inland water systems have been significantly disturbed by global climate change and human activities. This review focuses on the current research progress of CO₂ and CH₄ emissions from China's inland waters. Major factors controlling dissolved CO₂ and CH₄ emission dynamics are examined. Furthermore, we discuss the shortcomings of current research on inland water carbon emissions in climate-sensitive regions and anthropogenically disturbed regions of China. There is a pressing need to strengthen the monitoring of aquatic CO₂ and CH₄ emissions over space and time and to gain a deeper understanding of the underlying mechanisms.

Soil organic matter, the remains of plants, animals, and microbes in the soil, performs many important functions for humans and ecosystems, providing habitat for animals, nutrients for plants, climate change buffering, and structure for soil animals and human structures. Thus, it is important to understand how soil organic matter is formed, stabilized, and lost. Here, we review conceptual frameworks that have contributed to our understanding of soil organic matter over the past 20 years. We evaluate their support in experiments and also how well represented they are in computer models. We find the least support and representation for controls of soil organic matter associated with properties of microbes and physical barriers between microbes and soil organic matter. These and novel soil organic matter controls require more research for better understanding of soil organic matter functions.

Beavers are ecosystem engineers that can dramatically change the shape of the landscape and how water moves through it. They create and maintain wetland environments across North America in a wide variety of places, including mountains, deserts, coasts, forests, grasslands, shrublands, etc. Despite their large influence on the landscape, there are very few programs that monitor them at the landscape scale. This is partially due to how much time it takes to find and identify beaver dams in satellite and aerial images. To make it easier for us to find and understand the influence of beavers at larger scales, we built a model that can automatically find beaver dams in satellite and aerial imagery. While our model is trained to find beaver dams, this type of model has promise for finding other landscape features too.

Fungi are an important yet often overlooked member of marine food webs, especially in the water column. This review highlights the important ecological roles fungi play in the ocean water column, such as the recycling of dead organic matter and acting as parasites of microalgae in the ocean. We provide a summary of state-of-the-art methods for studying planktonic marine fungi and making discoveries in the future.

A greenhouse gas which contributes significantly to global warming is methane (CH₄). Atmospheric concentrations of CH₄ have more than doubled since the pre-industrial era primarily due to emissions from human activities. Inland waters (i.e., wetlands, lakes, rivers, and reservoirs) are significant CH₄ emitters yet still represent a major challenge in quantifying the global CH₄ budget. This investigation presents an observation-based analysis of global lake area and CH₄ emissions and addresses multiple uncertainties and gaps in recent global estimates of CH₄ emission from lakes. We show that lakes occupy a global area of around 2,800,000 km² (comparable to the size of Argentina) and release ∼42 million tons of CH₄ per year to the atmosphere. This study identifies both methods and data sources from other recent studies that contribute to overestimating lake emissions. We produce a suite of global gridded data sets representing lake area and distribution, lake type, observed freeze-thaw periods, and daily CH₄ emissions for a full annual cycle.