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A “living skin” of tiny, rootless plants and microorganisms known as biocrusts cover the soil surfaces on the Great Wall of China.
Rammed earth portions of the Great Wall of China — built by compressing natural materials with soils — have been regarded as a weak point in its structure. But these swaths of the iconic landmark developed a natural line of defense against the looming risk of deterioration, a new study has found.
These soil surfaces on the Great Wall are covered by a “living skin” of tiny, rootless plants and microorganisms known as biocrusts that are a source of the heritage site’s staying power, according to soil ecologist Matthew Bowker, a coauthor of the study published December 8 in the journal Science Advances.
“(Biocrusts) are common throughout the world on soils of dry regions, but we don’t typically look for them on human-built structures,” said Bowker, an associate professor at Northern Arizona University, in an email.
Past studies have found lichen and moss biocrusts to be a destructive threat to modern heritage stone structures due to the microbial communities’ long-term impacts on aesthetic value, production of acid and other metabolites, and alteration of microenvironments, which may cause erosion and rock weathering. Those findings have led to the removal of plants growing on the top of parts of the Great Wall. But the effects of biocrusts look different for earthen landmarks, and communities of cyanobacteria and moss actually increase the Great Wall’s stability and improve its resistance to erosion, according to the new paper.
Rammed earth portions of the Great Wall of China — built by compressing natural materials with soils — have been regarded as a weak point in its structure. But these swaths of the iconic landmark developed a natural line of defense against the looming risk of deterioration, a new study has found.
These soil surfaces on the Great Wall are covered by a “living skin” of tiny, rootless plants and microorganisms known as biocrusts that are a source of the heritage site’s staying power, according to soil ecologist Matthew Bowker, a coauthor of the study published December 8 in the journal Science Advances.
“(Biocrusts) are common throughout the world on soils of dry regions, but we don’t typically look for them on human-built structures,” said Bowker, an associate professor at Northern Arizona University, in an email.
Past studies have found lichen and moss biocrusts to be a destructive threat to modern heritage stone structures due to the microbial communities’ long-term impacts on aesthetic value, production of acid and other metabolites, and alteration of microenvironments, which may cause erosion and rock weathering. Those findings have led to the removal of plants growing on the top of parts of the Great Wall. But the effects of biocrusts look different for earthen landmarks, and communities of cyanobacteria and moss actually increase the Great Wall’s stability and improve its resistance to erosion, according to the new paper.
