Plant biodiversity and the regeneration of soil fertility

Abstract

Fertile soils have been an essential resource for humanity for 10,000 y, but the ecological mechanisms involved in the creation and restoration of fertile soils, and especially the role of plant diversity, are poorly understood. Here we use results of a long-term, unfertilized plant biodiversity experiment to determine whether biodiversity, especially plant functional biodiversity, impacted the regeneration of fertility on a degraded sandy soil. After 23 y, plots containing 16 perennial grassland plant species had, relative to monocultures of these same species, ∼30 to 90% greater increases in soil nitrogen, potassium, calcium, magnesium, cation exchange capacity, and carbon and had ∼150 to 370% greater amounts of N, K, Ca, and Mg in plant biomass. Our results suggest that biodiversity, likely in combination with the increased plant productivity caused by higher biodiversity, led to greater soil fertility. Moreover, plots with high plant functional diversity, those containing grasses, legumes, and forbs, accumulated significantly greater N, K, Ca, and Mg in the total nutrient pool (plant biomass and soil) than did plots containing just one of these three functional groups. Plant species in these functional groups had trade-offs between their tissue N content, tissue K content, and root mass, suggesting why species from all three functional groups were essential for regenerating soil fertility. Our findings suggest that efforts to regenerate soil C stores and soil fertility may be aided by creative uses of plant diversity.

The importance of biodiverse plant communities for healthy soils

“… Complementary nutrient profiles of diverse marine animal communities, with the healthier diets that they provide ( 19 ), have similarities with the complementary nutrient profiles of diverse plant communities found by Furey and Tilman ( 1 ) that generate healthier soils. Because multinutrient profiles are positively related to the richness of marine species, increases in aquatic biodiversity increase human well-being through nutritional benefits ( A–C vs. D–F ), including the number of recommended daily allowance (RDA) nutrient targets (NTs; 10 and 25% thresholds of RDA guidelines) met and smaller seafood requirements ( B , i and E , iii vs. B , ii and E , iv ).…”

“…Among these are the ongoing loss of biological diversity and threats to soil fertility. In PNAS, Furey and Tilman ( 1 ) present results from a long-term field experiment that demonstrates the importance of plant diversity for healthy soils.…”

“…These biogeochemical processes—like primary productivity—underpin human societies by providing a multitude of ecosystem services (or “nature's contributions to people”), such as the provision of food, materials, and clean water; the sequestration of atmospheric carbon; and the generation of healthy soils. Furey and Tilman ( 1 ) present results from the longest-running biodiversity experiment (it will soon celebrate its 30th anniversary in 2024) that show how ecologically diverse mixtures of plant species can generate soils that are richer in essential plant nutrients and more productive in plant biomass and that store more carbon.…”

“…Earlier studies considering multiple ecosystem functions (including some soil nutrients and conditions) have found that the more ecosystem responses that are considered, the more species are found to play a supporting role ( 11 ), something that is also true as studies consider greater spatial and temporal scales where different species seem to play functionally important roles at different times and places ( 12 ). The work of Furey and Tilman ( 1 ) suggests the same may be true when examining multiple soil processes—but how many of the prairie species are needed for a healthy soil remains an open question (to which I return below).…”

“…A constant during this period—presumably due to the initial controversy—has been the need for biodiversity to justify itself by demonstrating significantly better functioning than monocultures. Although the paper of Furey and Tilman ( 1 ) demonstrates the limitations of monocultures, it also raises the question of how many species are functionally important. Would mixtures containing just one species of grass, legume, and forb be enough as far as healthy soils are concerned?…”