Medium, Vector, and Connector: Fog and the Maintenance of Ecosystems

Abstract

Fog and low-lying cloud (fog) play a significant role in the maintenance of ecosystems, from desert to alpine and from coastal to inland systems. Our central thesis is that fog provides ecosystems with critical water and nutrient subsidies, and also delivers pollutants, that often control ecosystem function. Fog is a medium, vector, and connector. In this mini-review, we synthesize recent research advances that reveal the diverse ways that fog shapes ecosystem processes. Crown wetting, elemental deposition, and light scattering and absorption are fundamental mechanisms by which fog has been shown to influence water fluxes, productivity, and decomposition in hyper-arid to ever-wet regions. These impacts are ultimately mediated by the structure and composition of biological systems that allow fog capture and utilization of resource subsidies. Climate change, and changes in land use, ocean circulation, and atmospheric pollution are simultaneously altering the nature of fog itself, and the architecture of the ecosystems adapted to capture it. The coupling between atmosphere and biosphere in fog-enshrouded areas raises new questions about past and future fog-dominated ecosystems, and their maintenance and diversity, in the face of global change.

Idioblasts and peltate hairs as distribution networks for water absorbed by xerophilous leaves

“…Leaf water absorption has been widely studied in the major groups of angiosperms, including magnoliids (eight genera), monocots (seven genera) and eudicots (67 genera) (reviewed by Berry et al, 2019, and by Dawson & Goldsmith, 2018), pointing to foliar water uptake as a key factor affecting plant function in most ecosystems (Weathers et al, 2019). However, the effect of foliar hydration in the overall plant physiology is stronger in dry or semi‐dry environments (Schreel et al, 2019), such as the dryland tropical areas where C. odoratissima grows, where the water in the soil is often a limiting resource, and foliar water uptake may become pivotal for plant growth and survival.…”

“…Foliar water uptake has direct consequences on plant function, relaxing tension in the water column of the xylem, enhancing turgor‐driven growth and increasing the productivity of agricultural and natural ecosystems (Aguirre‐Gutiérrez et al, 2019; Mayr et al, 2014; Steppe et al, 2018). The key conditions for foliar water uptake are met in fog‐dominated environments (Tognetti, 2015; Weathers, Ponette‐González, & Dawson, 2019), where high atmospheric humidity enhances night‐time dew formation on leaf surfaces, thus increasing the possibility of foliar water absorption. Indeed, studies in montane cloud forests of Brazil (Eller, Lima, & Oliveira, 2016), coastal California redwood forests in the USA (Burgess & Dawson, 2004) and cloud forests in Mexico (Gotsch et al, 2014) have demonstrated that foliar water uptake has an important impact on plant functioning, especially during dry periods (Breshears et al, 2008).…”

Idioblasts as pathways for distributing water absorbed by leaf surfaces to the mesophyll inCapparis odoratissima

“…To understand whether water uptake is possible with zero cuticular conductance, we exposed the leaves to a water-saturated environment, revealing a linear uptake of water without cuticle evapotranspiration, gaining up to 40% of the initial water content of the leaves. Leaf water absorption has been widely studied in the major groups of angiosperms, including magnoliids (8 genera), monocots (7 genera), and eudicots (67 genera) (reviewed by Berry et al, 2019 and Dawson and Goldsmith, 2018), pointing to FWU as a key factor affecting plant function in most ecosystems (Weathers et al, 2019). However, this effect is stronger in dry or semi-dry environments (Schreel et al, 2019), such as the dryland tropical areas where C. odoratissima grows, where the water in the soil is a limiting resource, and aerial water becomes pivotal for plant growth and survival.…”

“…FWU has direct consequences on plant function, relaxing tension in the water column of the xylem, enhancing turgor-driven growth, and influencing the hydraulic dynamics of agro and ecosystems (Mayr et al, 2014; Steppe et al, 2018; Aguirre-Gutiérrrez et al, 2019). The key conditions for FWU are met in fog-dominated environments (Tognetti, 2015; Weathers et al, 2019), where high atmospheric humidity enhances nighttime dew formation on leaf surfaces, thus increasing the possibility of foliar water absorption. Indeed, studies in montane cloud forests of Brazil (Eller et al, 2016), coastal California redwood forests in the USA (Burgess and Dawson, 2004), or cloud forests in Mexico (Gotsch et al, 2014), have demonstrated that aerial water is an important input contributing to plant function, especially during the dry periods of the year.…”

Estimates of the contribution of fog to wet atmospheric deposition in Czech mountain forests based on its stable hydrogen and oxygen isotope composition: preliminary results

“…Fog plays a significant role generally in the maintenance of ecosystems (Weathers et al 2020) and specifically in the CR, based both on direct measurements (Tesař et al 2000;Bridges et al 2002;Bridgman et al 2002;Fišák et al 2002;Křeček et al 2017;Palán and Křeček 2018) and data-driven models (Hůnová et al 2011(Hůnová et al , 2016, in which it substantially enhances total atmospheric deposition of environmentally relevant substances, particularly in mountain forested areas (Igawa et al 2002;Lange et al 2003). Stable hydrogen and oxygen isotope composition of rain has been used in the CR to study the role of rain in the hydrological balance in small water catchments (Šanda et al 2011, 2019), whereas that of fog has not been measured.…”