Disturbances Help Maintain Diversity

Biological Strategy

Sitka spruce

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Maintain Biodiversity

The greater the amount of genetic and species variation in an ecosystem, the more resilient that ecosystem is to disturbances. Variation in ecosystems across the Earth also contributes to the Earth’s resilience to unpredictable changes. This variation is called biodiversity. Because living systems compete with each other for scarce resources, maintaining biodiversity involves creating conditions for a large variety of species to successfully co-occur and reproduce. For example, within a wetland, there are different vegetation types. This diversity results in a complex mosaic of microenvironments as the vegetation types alter air flows, light regimes, and water temperatures and chemistry. Because organisms vary in their ideal environmental conditions, these micro-environments increase the diversity of plants in the wetland. In turn, having a wetland in an otherwise dry area increases biodiversity at an even larger scale.

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Conifers and Others (Pines, Spruce, Gingko)

Clade Gymnosperms (“naked seeds“): Conifers, cycads, Gingko, gnetophytes

There are approximately 1,000 known species of Gymnosperms. These include well known needle-bearing plants like pines, firs, and spruce, as well as some with broad leaves like the Gingko and the gnetophytes. Instead of flowers, gymnosperms produce unenclosed (“naked”)seeds exposed on the surface of cone scales. Economically, conifers make up 45 percent of the world’s lumber production. The first gymnosperms evolved over 390 million years ago in the Paleozoic Era and dominated landscapes for a quarter of a billion years before the evolution and diversification of flowering plants.

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Western hemlock-Sitka spruce forests maintain diversity partly thanks to wind disturbance patterns.

“The dynamics of British planted forests are compared with disturbance dynamics of analogous natural forests with particular reference to disturbance by strong winds. Western hemlock-Sitka spruce (Tsuga heterophylla-Picea sitchensis) forests in the Pacific North-west of North America and particularly South-east Alaska provide the most promising comparison. There are few reports on disturbance in these forests, but the regime includes both gap-phase and stand replacement dynamics due to wind. However, the landscape proportion and pattern of resulting structural types are not well defined…Two stand types have been identified in the hemlock-spruce forest types in the Pacific North-west: (1) even-aged stands following catastrophic blowdown; and (2) multi-aged stands resulting from gradual but non-catastrophic attrition (Deal et al., 1991). Sitka spruce can maintain a presence in forest communities in both situations (Taylor, 1990). It is not known what the proportion of the two stand types (fine grain and even-aged) is for any one region.” (Quine et al. 1999:337, 347)

Last Updated August 18, 2016

References

Journal article

Should the wind disturbance patterns observed in natural forests be mimicked in planted forests in the British uplands?

Forestry | 11/11/2004 | C. Quine

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