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Biological Responses in Context
Published in Arthur T. Johnson, Biology for Engineers, 2019
Once a new area is left undisturbed, a set of pioneer species of plants, animals, and, presumably, microbes, colonize the area. Because the area is not suitable for all local species, only a certain few characteristically colonize the area. Once the pioneer species become established, they modify the environment to make it more suitable for later species. For instance, the first plant species to invade a newly undisturbed area may be a local grass or weed, such as dandelion (Molles, 1999). As they grow and die, these plants leave behind organic matter that encourages insects and additional plant species to colonize the area. Later, tree seedlings may become established, and, as they grow, small animals invade, and birds begin to nest. Eventually, other species characteristic of the area become established. The diversity of plant and animal species increases rapidly at first (Figures 6.21.3 and 6.21.4), but begins to level off after a time interval that may vary from 1.5 months to 1500 years, depending on climatic conditions (Molles, 1999).
Water Erosion Control
Published in R.P.C. Morgan, R.J. Rickson, Slope Stabilization and Erosion Control, 2003
Vegetation species are normally chosen to replicate the type of colonization and ecological succession that would occur naturally (Chapter 3), but at the same time to try and speed up the process. Under natural conditions, a few pioneer species, well-adapted to the local, often adverse, environment colonize an area, stabilize it and, over time, modify the environment so that other vegetation species are able to invade and displace the pioneers. In practice, the need to establish a ground cover rapidly means that grasses generally form the major component of the colonizing species. In order to allow for the risk of failure of individual species, particularly on soils of low fertility, mixtures are often used, containing some six to ten species including a 10–50% content of legumes or herbaceous plants. The mixture may be adapted to include both quick- and slow-growing species with the intention of providing a plant succession of ‘nurse’ species to give immediate protection followed by other species to give a more diversified ecology. Also, once established, leguminous species generally have a better survival rate and a lower management requirement than grasses. Although there are some cultivars of grasses that grow slowly to only a short height and, therefore, require little mowing or cutting, they usually produce very limited root growth and so are unsuitable for an engineering role (Coppin and Richards, 1990).
Urban forest restoration ecology: a review from Hamilton, New Zealand
Published in Journal of the Royal Society of New Zealand, 2019
Kiri Joy Wallace, Bruce D. Clarkson
Restoration of the urban forest is a new and important initiative in many cities in New Zealand and beyond. Here we have reviewed ecological restoration research from Hamilton, New Zealand and summarised key findings to help inform successful restoration of urban forest ecosystems. By understanding the importance of species traits, filters and thresholds, restoration plantings can be designed using appropriate pioneer species, with the goal of crossing ecological thresholds like canopy closure. We have emphasised why increased native species richness of plantings is important for resilience, and that awareness about the indigenous cover on the surrounding landscape can be helpful. When choosing a reference ecosystem, urban forest remnants are useful targets for restoration as they indicate what species will tolerate urban conditions. In reviewing tree regeneration, seed banks and seed rain, and seed predation, we highlight why it is important to understand barriers to what late-successional species can and will regenerate spontaneously. When desirable late-successional species do not regenerate spontaneously, we encourage enrichment planting under the right environmental conditions. Finally, we encourage practitioners to remember to restore for both forest structure and ecological function.
Ecological restoration of eroded karst utilizing pioneer moss and vascular plant species with selection based on vegetation diversity and underlying soil chemistry
Published in International Journal of Phytoremediation, 2018
J. C. Shen, Z. H. Zhang, R. Liu, Z. H. Wang
This study suggests the use of a succession of species to form a stable ecological environment on eroded karst. Selection of pioneer species which are gradually replaced by secondary and finally, climax species, will be more effective in the management and control of soil erosion. The choice of pioneer species should not only take into consideration the adaptability of the species to the extreme environment on eroded areas of karst but also consider the effect of the selected taxa on soil quality. In this study, using pRDA of survival factors and soil chemical properties of dominant species, the plants suitable for the restoration of soil erosion on karst landforms were found to be the mosses E. leptothallum, Cyrto-hypnum pygmaeum and B. perminusculum, the herbs V. arvensis and Y. japonica and the tree P. salicina. These taxa are best adapted to the high temperatures and extreme aridity of eroded karst and are most effective at optimizing soil nutrients, and are the most suitable species to introduce as pioneer plants for restoration. Mosses and vascular plants are very different from each other in terms of environmental adaptability and effects on soil quality. Mosses have the potential to colonize bare rocks and initiate soil formation process; vascular plants have the potential to improve soil quality, so it would appear that the combination of both mosses and vascular plants would be beneficial for the repair of soil erosion. When environmental adaptability and effect on soil quality is considered, the use of recommended pioneer mosses to colonize rock, and pioneer herbs, shrubs and trees to rejuvenate soil, appears to be the optimum combination for the recovery of karst soil erosion. A trial recovery plan using the recommended species would provide valuable data that could be used in further recovery and restoration of severely affected areas of karst.