Environmentalresearchweb: why did you investigate modelling of organic matter in soils?

Nell Campbell (NC): Healthy soils are a limited natural resource. People ranging from agricultural producers to policy makers are thinking about how to manage soils sustainably, in order to maintain soil health and support the diversity of important ecosystem functions that a healthy soil provides. An important question is: can soils be managed sustainably to provide food, fiber and fuel production? An important component in answering this question is the impact of land management on soil organic matter. Why? Because the quantity and characteristics of soil organic matter affects many important soil functions, including water-holding capacity, nutrient availability, and more.

An important additional consideration is the potential for soils to either contribute to or reduce atmospheric greenhouse gases. Soils have this potential because they hold an enormous reservoir of carbon in organic material. This carbon is more than the amount contained in the atmosphere plus the amount contained in all of the plant material that is aboveground on earth. However, the carbon in soil organic matter is not static. It changes through time and has the potential to be gained or lost, either through natural processes or human impacts that change natural processes. Therefore, an important additional question is: can soils be managed to increase their store of carbon in organic matter, in order to reduce greenhouse gas emissions in the atmosphere?

Answering either of these questions is difficult. Soils are very complex. Many factors affect soil organic matter dynamics, including climate, soil texture, land management history, and more. This is where models of soil organic matter play an important role: they integrate these complexities and provide a tool to evaluate these questions based on current scientific understanding of soil organic matter dynamics.

However, scientific understanding is always advancing. In addition, some of these questions may involve regions or types of land management that have not been extensively studied in the past. Therefore, results from model simulations also include uncertainties from various sources. These uncertainties may prompt new studies, or may change based on new discoveries or advancements. In either case, it is important to have a connection between how models are being applied to shape decisions for land management, and how model results reflect current scientific understanding.

This is the basis for writing our review. We wanted to investigate the current connection between the science and applications of soil organic matter models. We hoped to create a better bridge between these two areas.

Environmentalresearchweb: what surprised you as you prepared your review?

NC: One surprise when preparing this review: the power of unique names for discovering how soil organic matter models are used in scientific literature. I realized this while completing the quantitative literature review of soil organic matter model citations (section 2.2), and discussed what I learned in the Appendix. The uses of models with non-unique names were difficult to isolate. Models with unique names have the unexpected attribute of being more transparent in their uses, due to being easier to find.

As we discussed in the review, transparency is a challenge in soil organic matter model applications, where these models are often just one component of analyses that may include evaluation of economic, social, or other environmental impacts. I realized that something as simple as a unique model name would help promote transparency in these multifaceted analysis efforts.

Environmentalresearchweb: what do we still need to find out?

NC: As we discussed in Section 4, there are many ongoing areas of soil organic matter model development. These reflect scientific efforts to find out more about microbial roles in soil organic matter stabilization, the impacts of soils having a saturation point for holding organic matter, temperature controls on soil organic matter, the importance of deep soil organic matter dynamics, and the role of soil organic matter in global processes.

All of these developments could benefit by ongoing efforts to develop large-scale data collection and monitoring networks, and tools to support better data-model integration (like PEcAn). These types of efforts can help address the challenges that limited data availability pose to advancing the understanding of soil organic matter dynamics across scales. A key challenge in soil organic matter modeling is testing hypotheses and advancing understanding of soil organic matter dynamics at the ‘landscape’ or ‘ecosystem’ scale (discussed at the end of Section 2.2.2). This is an area where many uncertainties remain, in part due to difficulties in assembling enough data to develop and test soil organic matter models at this scale. There also needs to be continued focus on data-poor areas like the tropics. These efforts will help to gain a more comprehensive scientific understanding of what affects the movement and persistence of organic matter in soils, in order to better understand how to direct its dynamics through land management practices.

Environmentalresearchweb: how will you be taking your research forward?

NC: I will focus on data-model integration and the use of multi-model comparisons in ‘landscape’ scale model analyses. I will be working on projects using soil organic matter models to evaluate the impacts of land management change, with connection to stakeholders involved in land management decision making.

Environmentalresearchweb: what’s the outlook for the future?

NC: In 50 years, I believe that many of the computational infrastructure challenges may be addressed, allowing data from more dispersed sources to be leveraged to more effectively address many of the challenges in understanding soil organic matter dynamics across scales.

Ideally this infrastructure will also help forage a better connection between scientific understanding and the use of soil organic matter models to support more sustainable land management.

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