Soil quality in urban forests under different understory management practices

Abstract Forest vegetation management plays an important role in maintaining soil quality and function. In highly managed urban forests, the clearing of understory vegetation has potential to cause loss of soil nutrients, resulting in stoichiometric imbalances and a decrease in soil function. Whether the presence of ornamental understory in urban forests can mitigate the negative influences on soil quality remains highly uncertain. Here, we collected soil samples from a plantation forest in Zijin Shan National Forest Park in two stands, each with three adjacent plots with different understory management practices: one with natural understory vegetation (≥10 species), a second with managed understories of ornamental groundcover [ Reineckea carnea (Andrews) Kunth or Ophiopogon bodinieri H.Lév], and a third with cleared understory. Compared with plots with natural understories, we found lower levels of soil total carbon (C), total nitrogen (N), and microbial C and N, in plots with no understories. Correspondingly, ratios of soil C:phosphorus (P) and N:P, and microbial C:N, were lower in the absence of understories in one of the two stands. The magnitude of these effects differed between the two stands, with greater effects observed in the stand with higher soil quality. These influences were smaller with groundcover plants in both stands, particularly O. bodinieri H.Lév. While we cannot rule out the effects of other influences on soil properties, these results offer support for the hypothesis that clearing of understories is potentially detrimental to soil quality, and that maintaining ornamental groundcover can alleviate these adverse influences in urban forest.