what is "community dynamics"?
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发布时间：2022-06-27 09:47
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热心网友
时间：2024-11-17 14:25
community dynamics
by Peter Donovan
Soil scientist Michael Crofoot has said, "Ecological processes are not only more complex than we think, they are more complex than we can ever think." An understanding and appreciation of the ecosystem as process or processes--water cycle, energy flow, mineral cycle, and community dynamics or succession--allows us to work with, rather than against, the complexity of the ecosystem (Allan Savory, Holistic Management: A New Framework for Decision Making).
The concept of ecological succession was developed by plant ecologists who observed a series of stages, or vegetation communities, over time. For example, the development of algae and moss, lichens, is then followed where possible by grass, and perhaps trees or shrubs.
On surfaces such as bare rock, extremes of temperature and lack of moisture-holding capacity severely limit the life forms that can establish themselves. Succession is one word for the ways that living organisms build soil and habitat on bare rock. As succession advances (or declines), communities of organisms change. In order to be successful, an organism must adapt to the successional community of organisms in which it lives and helps create.
Ecological succession is also a force, a coiled spring. In most areas we can maintain a monoculture (wheat for example) only with continued high inputs, and even then we will have to change what we do to fight successive pathogens and weeds. Diversity of species, both above and below ground, is intrinsically more stable and cheaper to maintain. But succession is not a linear force. Organisms such as yellowstar thistle or knapweed may form virtual monocultures for years, with secretions or mycorrhizal associations that may inhibit successional advance to a more complex community.
Many people view the natural world as pretty much a question of competition. They see plants competing for water, sunlight, and nutrients. The even spacing of bunchgrasses on a south-facing hillside, or of trees in a forest, is clear evidence of competition. Resources are scarce, organisms compete for them, and survival goes to the strong. Our role as managers is to help the good species win over the bad.
But this isn't fact. It is a belief, often strongly held. If you have this belief, it is easy to assemble "facts" to back up the belief at every point.
But other beliefs are possible. The even spacing of bunchgrasses on a south hillside, or trees in the forest, can be just as much evidence of synergy and community--the plants are helping each other create the conditions in which the community can flourish. Trees shelter each other from destructive winds and moisture loss. They contribute to a biological community--a whole forest--in which the indivial tree can succeed. Likewise each bunchgrass plant helps its neighbors by holding soil and moisture, contributing organic matter, and contributing in countless and perhaps "unthinkable" ways to a biological community to which the indivial bunchgrass plant is well adapted.
One belief is not intrinsically better or truer than the other, nor are they mutually exclusive, but they do have different consequences, different results.
The perspective of community dynamics or ecological succession enables us to manage whole communities rather than indivial species or even habitats. It becomes possible to see, monitor, and manage for relationships and interdependencies that enhance pleasure and profit.
As with the water cycle, mineral cycle, and energy flow, the condition of the soil surface is critical. In brittle environments, where moisture is seasonal and intermittent, succession may not advance from bare ground or algae and mosses to grasses without soil disturbance and the creation of microenvironments where grass seedlings can become established--such as can be provided by grazing animals.
But as with the other ecosystem processes, the perspective of community dynamics enables us to go beyond the question of whether there are or aren't hoofprints, whether this piece of land is grazed or ungrazed, logged or unlogged, with "native" organisms or exotic ones. Instead we ask, how can we create, manage for, or adapt to the kind of community that will sustain us?
This kind of whole-ecosystem management cannot be mandated or legislated. It is a different kind of result than what rules, prescriptions, and regional plans proce.
Shared goals or visions are more likely to be developed where strong community bonds exist--on a small scale, as in a family farm, ranch, or partnership. Where community trust, shared visions, or the ability to maintain these are not well-developed, or where people do not have experience of trust and shared vision, community-building skills such as the consensus approach are essential.
热心网友
时间：2024-11-17 14:25
热心网友
时间：2024-11-17 14:26
给你一个地址参考一下吧
http://maine.washcoll.e/lecture9.htm
热心网友
时间：2024-11-17 14:26
