Annie Jiang: Rock of Life

As I stand still in the forest, life rustles around me restlessly. The gentle breeze shakes the leaves of the plants, challenging its ground. Bees rush from flower to flower, thirsty for nectar and pollen. White aster plants loudly bare their flowers in clusters, collectively calling the bees. Moss creates a fuzzy blanket of green over the soil, keeping it warm with activity. All of this life I witness surrounds one single entity. A large rock. Its rough surface, spotted with discoloration, indicates signs of wear. Tiny holes and cracks allow little organisms to crawl in and out of. The slanted side of the rock creates a roof of shade for a portion of land under from where a patch of moss grows comfortably. From under the rock, a small plant peeks out from hiding, with its luscious, green leaves reaching for the sun, ready to grow. A rock, a seemingly lifeless object surrounded by a plethora of blooming activity, might not be so lifeless after all.

Through various forms of weathering, rocks release nutrients that are consumed by plants and organisms and are essential for their survival and growth. Moss and lichen can grow and colonize on rocks, releasing acids that cause chemical weathering of the rocks (3). Acid rain due to sulfur and nitrogen oxide emissions can cause rapid and enhanced weathering of rocks, washing away its nutrients (2). The nutrients released from the rocks make their way into the soil where they enter the free market and are available for plants and organisms to consume. To take in the nutrients from the soil, plants depend on their root system. One method of direct nutrient uptake from soil is via water intake, which transports nutrients from the soil through the roots into the stem of the plant and ultimately to its leaves.

One major nutrient that plants need but cannot directly consume from the soil and use is nitrogen. To help solve this issue, plants release flavonoids, a chemical messenger, into the soil to invite a special guest. These messengers attract nitrogen fixing bacteria Rhizobia who become enveloped by the plant root hairs where they stay to convert nitrogen into a usable form for the plants (1). In return, the bacteria receive carbohydrates from the plant for energy. In this way, rocks bring together plants and bacteria, benefitting both species.

Although the rocks serve an important function of providing nutrients to plants, rock weathering is influenced by many factors and may occur at varying rates leading to fluctuations in the abundance and diversity of nutrients made available in the soil. To account for this unpredictability, plants have mechanisms that allow for them to maintain nutrient homeostasis primarily through root growth. In conditions of limited nutrient availability, plants may increase root growth in elongation of root systems and increase in root surface area (1). This allows them to be able to access more nutrients to satisfy their needs. In exchange for using their limited resources towards root growth, plants sacrifice resources used for above ground plant growth. Conversely, in conditions of excess nutrient availability, plants may reduce nutrient intake to prevent cellular damage.

Over time, as the flowers wilt and leaf litter increases in volume, covering up the moss the rock remains in place just as it is. If one day, the trees are removed and the plants plucked, the rocks above and below will still be there, remaining a dependable life source for the life around it, through all seasons and generations to come.

Sources

1. Morgan, J. B. & Connolly, E. L. (2013) Plant-Soil Interactions: Nutrient Uptake. Nature Education Knowledge 4(8):2

2. Ribeiro, I. D. A., et. al. (2020). Use of Mineral Weathering Bacteria to Enhance Nutrient Availability in Crops: A Review. Frontiers in Plant Science.

3. Papadopoulou, S. (2016). Weathering of rocks by mosses may explain climate change during the Late Ordovician. Department of Environmental Science Stockholm University. https://www.aces.su.se/news/weathering-of-rocks-by-mosses-may-explain-climate-change-during-the-late-ordovician/