Using high-resolution X-ray imaging, researchers from the KBS LTER tested soil samples from the LTER Main Cropping System Experiment and discovered that intensive agriculture continues to influence soil porosity and carbon content for decades after restoration to native habitat. Even after 35 years, restored soils contained only about 50% of the organic carbon found in native grasslands and forests.
When it comes to agriculture, it’s not just about what’s in the soil, but also how the soil is structured. Given that much of our land is converted from native habitat to agriculture, it’s important to understand how disturbance might alter both soil composition and structure over the long term.
Previous research at the LTER has shown how different farming practices can build soil carbon over a 25 year period – but to different degrees and at different rates. Now new research continues to use long-term data to look at how decades of intensive agriculture shape the structure of soil and consequently its carbon content.
Led by Maoz Dor, a post-doctoral researcher in Sasha Kravchenko’s lab, researchers used high-resolution X-ray imaging to compare soil from a gradient of four types of land use at the LTER Main Cropping System Experiment: intensively farmed, restored early successional, untilled grasslands, and undisturbed deciduous forests. They looked at soil pore structure and soil organic carbon, and compared results across the four types of land uses after they had been under different treatments for 35 years.
The study found that decades of intensive agriculture significantly reduced soil porosity, with farmed plots having fewer medium-sized pores. This change is an important discovery, as previous work from the Kravchenko lab has shown soil pores to be crucial for microbial activity and carbon stabilization. Agricultural soils also had 42–75% lower organic carbon than undisturbed forest and grassland soils.
While restoration efforts (i.e. early successional land) improved soil structure—bringing pore characteristics closer to natural conditions—carbon recovery lagged behind. Even after 35 years, restored soils contained only about 50% of the organic carbon found in native grasslands and forests. Additionally, the type of carbon accumulating in restored soils differed chemically from that lost during agricultural use, suggesting complex recovery pathways.
These findings highlight the long timescales required for soil carbon restoration and emphasize the role of land management in preserving soil health and carbon storage. The study bridges the gap between laboratory-based science and agricultural management to provide answers about the long-term impacts of land use conversion.