Accumulator, Transporter, Substrate, and Reactor: Multidimensional Perspectives and Approaches to the Study of Bark

Abstract

Woody ecosystems have a relatively thin but aerially extensive and dynamic layer of bark that, like leaves, regulates material exchange at the interface of air, water, and biota. Through interception, retention, and leaching of materials and interactions with epiphytic communities, bark alters the chemistry and composition of water draining over its surface during precipitation. This mini-review explores different perspectives and approaches to the study of bark and what they reveal about the myriad ways bark surfaces influence the quality of sub-canopy precipitation. Observational studies conducted over the past five decades in the fields of environmental science, ecohydrology, epiphyte ecology, and microbiology demonstrate that bark is an accumulator, transporter, substrate, and reactor. Bark passively accumulates materials from the atmosphere, water, and canopies, and also serves as an active transport surface, exchanging materials laterally and longitudinally. In addition, bark substrates influence epiphyte diversity, composition, and distribution, which, in turn, affect material cycling. Bark surfaces are dynamic over time, changing in response to disturbances (e.g., insect outbreaks, aging, and tree death)—how such changes influence the chemical and elemental composition of throughfall and stemflow merits further study. Moving forward, integration of diverse perspectives and approaches is needed to elucidate the influence of bark surfaces on solute and particulate transport and cycling within woody ecosystems.

Wetland tree barks are dynamic hotspots for microbial trace gas cycling

“…Unlike many leaves, bark is present year-round and contains diverse materials with a range of textures, thicknesses, and structures. Moreover, bark can accumulate organic molecules, water, gases, and other nutrients that may promote microbial colonization and survival [4][5][6] . The bark microbiome is likely to be an important, yet vastly understudied, interface along the soil-tree-atmosphere continuum [7][8][9] .…”

Mapping bark bacteria: initial insights of stemflow-induced changes in bark surface phyla

“…The bark surface of every individual tree provides a unique microenvironment in which the air turbulence, temperature, moisture, and pH will be altered from its macroenvironment due to bark texture, aspect, and position within the stand. Trees serve as a source of nutrient enrichment in forested watersheds through rainfall partitioning ( 23 , 24 ). Usually, less than ten percent, but more commonly less than five percent, of intercepted precipitation per projected canopy area gets funneled onto the bark surface and down stems and branches as stemflow.…”