Plant Requirements Govern Recovery

purple and white foxglove flowers shaped like bells grow in front of a woodland background

Biological Strategy

Plants

AskNature Team

Image: Steve Slater / Flickr / Some rights reserved

Physically Assemble Structure

Living systems use physical materials to create structures to serve as protection, insulation, and other purposes. These structures can be internal (within or attached to the system itself), such as cell membranes, shells, and fur. They can also be external (detached), such as nests, burrows, cocoons, or webs. Because physical materials are limited and the energy required to gather and create new structures is costly, living systems must use both conservatively. Therefore, they optimize the structures’ size, weight, and density. For example, weaver birds use two types of vegetation to create their nests: strong, a few stiff fibers and numerous thin fibers. Combined, they make a strong, yet flexible, nest. An example of an internal structure is a bird’s bone. The bone is comprised of a mineral matrix assembled to create strong cross-supports and a tubular outer surface filled with air to minimize weight.

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Cooperate Within an Ecosystem

An ecosystem is a community of organisms (plants, animals, and microbes) interacting with one another and the nonliving components of their environment (such as air, water, and mineral soil). This interaction can be passive or active, and can cooperatively enhance the functioning of the ecosystem as a whole. For cooperation to contribute to maintaining communities within an ecosystem, it must be beneficial to at least some members of the community. Cooperation consists of symbiotic relationships, such as mutualism (in which two or more species in an ecosystem benefit) and commensalism (in which one species benefits and the effect on others is neutral). An example of a commensal relationship is that between bromeliad plants and trees: bromeliads live on trees without harming them. Bromeliads have mutualistic relationships with other species, including insects, frogs, and worms. The plants capture water in their base, forming a pond that these organisms join. The nutrients that these organisms excrete in their droppings nourish the bromeliad.

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Manage Disturbance in a Community

When environmental conditions change, they can disrupt an ecosystem’s equilibrium. Excessive rain can cause flooding and drought can cause forest fires. An ecosystem must be resilient to such disturbances. Disturbances are unpredictable in location, size, and intensity, so ecosystems must be able to regrow and must have a variety of duplicate forms, processes, or systems that are dispersed in location. For example, a forest ecosystem can recover from fire because diverse organisms play different roles in different ways and in different locations. Many organisms can resprout or grow from seeds triggered by fire, and their dispersed distribution ensures that an entire population isn’t decimated. Though the recovered ecosystem may look totally different from the pre-fire one, the ecosystem as a whole remains healthy.

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Plants

Phylum Plantae (“plants”): Angiosperms, gymnosperms, green algae, and more

Plants have evolved by using special structures within their cells to harness energy directly from sunlight. There are currently over 350,000 known species of plants which include angiosperms (flowering trees and plants), gymnosperms (conifers, Gingkos, and others), ferns, hornworts, liverworts, mosses, and green algae. While most get energy through the process of photosynthesis, some are partially carnivores, feeding on the bodies of insects, and others are plant parasites, feeding entirely off of other plants. Plants reproduce through fruits, seeds, spores, and even asexually. They evolved around 500 million years ago and can now be found on every continent worldwide.

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Woodland ecosystems recover from disturbances via succession, depending on plants' various requirements for nutrients and light.

In October 1987 a hurricane struck southern England and over 15 million trees were destroyed. A few months later, foxgloves, which need good light to grow, sprang up quickly in the nutrient-rich woodland soil. During the first year of growth, the foxgloves store surplus food in their roots. During the second year, they flower and disperse about a quarter of a million seeds each. Many of the foxgloves then die, and their offspring may have to wait decades before having an opportunity to sprout. Nettles, which also require nutrient-rich soil, begin to compete with the foxgloves–they start more slowly, but spread more rapidly, developing mats of horizontal stems that other seedlings have a hard time penetrating. After several years, the nettles have extracted so many nutrients from the soil that it no longer meets their needs. They begin to falter, and the seeds of other plants with larger food stores, such as birch, begin to emerge. The birch seeds require lots of light to sprout, and once sprouted remain as seedlings for several years until conditions are most favorable. The birch gradually form a thicket, shading out other plants. Acorns also sprout and very slowly begin to grow. As the birch begin to fail, the oaks gradually reclaim the territory they held decades ago. The oaks, in turn, provide food and shelter for hundreds of woodland creatures. (Summarized from Attenborough 1995:149-158)