Plant Conservation by Timothy Walker

Author:Timothy Walker
Language: eng
Format: epub
Publisher: Timber Press
Published: 2013-04-04T04:00:00+00:00

What’s the Damage? The Cost of Leaving Home

The first and most obvious damage is the reduction in biological diversity as a result of swamping and outcompeting native plants for light. This can not only kill the original vegetation but also prevent the growth of any seedings. The knock-on effect of the reduction in biological diversity can be an increase in the instability of the plant community and thus an increase in the possibility of a complete breakdown of the ecosystem services provided by the vegetation. Furthermore, an alteration in the plants in a community will have an effect on the species of animals in the area. The plant invasion might not result in a monospecific stand of the non-native, but the balance of the natives might be changed and some of the less common species will be swamped and killed. Conversely some minor members of the community might become more common at the expense of other native species. Examples of the cost of invasions include changing soil conditions for all the existing plants, alterations in a beneficial fire regime, changes in the water table in a region, and increases in the need for public spending from these ecological events.

When Myrica faya (faya-tree or fire-tree) was brought from Tenerife to Hawaii, it felt so much at home that it spread, pushing out Metrosideros polymorpha among others. In addition to elbowing out some native vegetation, Myrica faya fixes nitrogen, releasing much of this into the soil and thereby altering the ecosystem further. In addition the fruits of Myrica are eaten by and therefore support the non-native birds that have colonized Hawaii. Biology is all about interactions, and the effects of non-native invasive species are no exception.

It is sometimes difficult for gardeners to see fire as anything but bad (or a way to dispose of diseased material) and yet in many parts of the world, fire regimes are a regular part of the ecology. Fire can vary from place to place; its intensity depends on how much flammable material has built up since the last fire but also on the calorific value of the plant material being burned. The more material there is, then the slower the fire moves across the land, giving it more time to burn right up into the canopy of the trees which otherwise would be heated but not incinerated. The plants have evolved to survive the normal fire but can suffer badly if they get caught up in the wrong sort of fire. This is the situation in South Africa where the Port Jackson willow (Acacia saligna) from Western Australia forms thickets that burn too hot for the natives.

If the disruption of the fire regime was not enough, the Port Jackson willow also has a severe impact on the water table. Its roots can grow deeper than the native vegetation and it can “steal” water from greater depths. This not only reduces the amount of water available to the other plants and the animals, it also seriously reduces the volume of fresh water available to the human population.

Download

Copyright Disclaimer:
This site does not store any files on its server. We only index and link to content provided by other sites. Please contact the content providers to delete copyright contents if any and email us, we'll remove relevant links or contents immediately.