Spotlight on forest soils - Monitoring and challenges

Around 40% of the EU's land area is covered by forest. The soils of these forests make an important contribution to key ecosystem functions and play a central role in the stability of ecosystems and Europe's carbon balance.

Forest soils differ significantly from agricultural soils: they are often rockier, less fertile, located on steeper slopes and experience less disturbance. They are managed over decades to centuries. As a result, they develop an organic layer that contains large amounts of organic matter and is crucial for carbon storage.

In a new article in the European Forest Institute's “Forest Series,” Thünen researchers and colleagues from the Natural Resource Institute Finland share their findings from the HoliSoils project on forest soil monitoring. The HoliSoils project addresses knowledge gaps on processes in forest soils, the harmonization of available soil data, and sustainable soil management practices.

Monitoring for healthy soils

Healthy soils are essential for our environment and society: they store carbon, regulate greenhouse gases, provide clean water, filter nutrients and pollutants, provide habitats for a wide variety of species and help regulate temperature.

Around 33% of the world's soils are classified as degraded. Forest soils are threatened by various natural and man-made influences, such as nitrogen deposition, heavy metals, and acid rain. Soil and forest management and climate change also influence the ecosystem functions of soils.

Regular monitoring allows for the dection and understanding of changes in the physical, chemical, and biological properties of soils. This also enables us to make predictions for the future and identify potential hazards at an early stage.

European Monitoring Programs

In addition to national surveys, there are two large-scale monitoring programs at the European level: EU LUCAS (since 2015) and UNECE ICP Forests (since 1990). Some EU regulations, such as the LULUCF Regulation, the NEC Directive, the European Regulation on Nature Restoration, and the EU Soil Monitoring Act, require the monitoring of carbon stocks in the soil and other soil variables such as pH-values or nitrogen content.

Complex monitoring and lack of harmonization

Sampling forest soils is technically challenging because they vary from dry mineral soils to wet peatland sites. Depending on the soil type, appropriate sampling methods are used to obtain representative and comparable results. Since soils change only slowly, sampling is repeated at the same points over many years. This requires fixed markers and exact coordinates to identify long-term trends.

Due to high spatial and temporal variability of forest soils, monitoring is costly. Different national methods and a lack of harmonization in sampling and analysis make it difficult to compare data. In addition, long-term studies are costly and resource-intensive, as many areas have to be sampled at long intervals.

Despite all the challenges, the monitoring of forest soils makes a relevant contribution to the preservation of these important ecosystems. In order to better assess and preserve the health and functionality of soils, thresholds for healthy soils and land use as well as guidelines for sustainable land use must be developed in the future.

View the whole article here: 

https://efi.int/forestquestions/q25