How Plants Enhance Weathering and How Weathering is Important to Plants

Abstract

Since land plants emerged from swampy coastlines over 400 million years ago, they have played a fundamental role in shaping the Earth system. Roots and associated fungi increase rock weathering rates, providing access to nutrients, while altering atmospheric CO2. As soils weather, the dissolution of primary minerals forces plants to rely on recycling and atmospheric deposition of rock-derived nutrients. Thus, for many terrestrial ecosystems, weathering ultimately constrains primary production (carbon uptake) and decomposition (carbon loss). These constraints are most acute in agricultural systems, which rely on mined fertilizer rather than the recycling of organic material to maintain production. Humans now mine similar amounts of some elements as weather out of rocks globally. This increase in supply has myriad environmental consequences.

Vellozioid roots allow for habitat specialization among rock‐ and soil‐dwelling Velloziaceae in campos rupestres

“…We found that vellozioid roots were prevalent in rock‐dwelling species and rhizosheaths in soil‐dwelling species, indicating that habitat specialization is associated with root morphological and physiological differentiation. The ability of the Velloziaceae to grow on bare rocks accelerates soil formation, releases rock‐derived nutrients to the ecosystem and allows, in the long term, the establishment of other species (Porder, ). We only observed dark‐septate fungi in roots of soil‐dwelling species, probably related to the greater amount of organic N in soil.…”

“…Vellozioid roots appear essential to grow on rocks due to their capacity to penetrate the rock matrix by dissolving the quartzite (Teodoro et al, ). The ability of these species to settle in rocky habitats by dissolving rocks by root‐exuded carboxylates increases the porosity of rocks and accelerates soil formation (Kelly, Chadwick, & Hilinski, ; Porder, ; Thiry, Fernandes, Milnes, & Raynal, ). These plants can therefore contribute to weathering and soil formation within rock cracks and the mobilization of nutrients from the rock, rendering them available in the future to other organisms, and slowly creating new microhabitats for plant establishment (Alves & Kolbek, ; Jacobi et al, ).…”

“…Since crop plants require, on average, 50 mg Mn/kg (Epstein & Bloom, ), and soil and rock [Mn] were low, the very high leaf [Mn] in some Velloziaceae is likely due to the release of carboxylates into the substrate (Lambers et al, ), as demonstrated for Barbacenia tomentosa and B. macrantha (Teodoro et al, ). This process plays an important role in rock weathering (Benites et al, ; Teodoro et al, ), in quartzite dissolution (arenization) and the formation of soils (Drever, ; Sauro, ), creating new niches and allowing the establishment of other species (Conceição & Pirani, ; Porder, ).…”

“…Rhizosheaths are soil sheaths strongly bound to the roots, associated with long root hairs that increase root–soil contact and mucilage release (Brown, George, Neugebauer, & White, ; North & Nobel, ; Pang, Ryan, Siddique, & Simpson, ), which enhances the uptake of poorly mobile P (Brown et al, ; Kidd et al, ; McCully, ; Zhang et al, ). Vellozioid roots (Figure c) were described in rock‐dwelling Velloziaceae, which is an ubiquitous plant family in campos rupestres ; they are capable of dissolving the quartzite rocks, releasing strongly bound P through carboxylate release and contributing to biological weathering of rocks (Porder, ; Teodoro et al, ). These vellozioid roots are therefore expected to be more effective in rocks than in soils.…”

Do degree and rate of silicate weathering depend on plant productivity?

“…Studies along a Hawaiian chronosequence (soils of variable discrete initial formation age) have evaluated the role of soil age in weathering and the distribution and cycling of cations through plants. These studies revealed the dependency of nutrient cycling on the degree of weathering (e.g., Bullen and Chadwick, 2016;Chadwick et al, 1999;Laliberte et al, 2013;Porder and Chadwick, 2009;Vitousek, 2004). Studies along a climosequence (gradients in climate while minimizing other environmental differences) have evaluated the effect of climate on ecological and pedogenic processes (Bullen and Chadwick, 2016;Calmels et al, 2014;Dere et al, 2013;Egli et al, 2003;Ferrier et al, 2012).…”