Although climax communities are assumed to be the endpoint of ecological succession, some believe that there is no such thing... that a community never actually reaches a climax. I will be holding a debate with my botany/ecology students on this issue.
I am looking for a paper to provide to them which gives good background for such a debate. Does anyone know of a good article or paper? Good readability and relatively simple language would be preferred.
It is essential to recognize that this is a classic question in community ecology that has been the subject of informed debate for decades.
Some older papers do an excellent job of covering the history of the "climax" concept and ensuing conceptual developments and disagreements. Reading some of this older literature is rather essential to ensure that the discipline of ecology actually does conceptually advance. In particular I would recommend:
Connell, J. H., & Slatyer, R. O. (1977). Mechanisms of succession in natural communities and their role in community stability and organization. American Naturalist, 111:1119-1144.
Whittaker, R. H. (1953). A consideration of climax theory: the climax as a population and pattern. Ecological Monographs, 23:41-78.
Your question made me think. And I did the following thought experiment. Do I know a vegetation patch/zone/belt anywhere that was the same 100, 1000 or 10 000 years ago and may be the same at that time scale in the future? From my profile you may deduct I have worked in most major biomes. My answer may be YES at the 100 years time scale, but NO at the 10 000 year scale. The millennium scale would show a more complex pattern. Next we need to agree on an operational definition of "community". If monospecific beech forest is considered a (floristic) plant community, it may qualify as climax on the millennium time scale and the meso and macro spatial scale (landscape; mountain chain). However, the structure of the canopy will have changed both historically and will do in the future. The animal assemblage in the forest will also have changed in both directions.
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Hein, you got it right.
In ecology, everything depends on scale. Every definition of climax has to depend on the time scale considered, and the spatial scale where possible changes occur. So the climax concept itself is nothing fixed, but dependent on scale.
We all know about glaciation and so on. A useful climax concept only makes sense in the context of stable climatic conditions (time scale), which vary for different regions of the earth (spatial scale).
When a community reaches at climax it does not mean that growth completely stops at time. Growth retards and slow growth that can not visualizes easily continues.
Climax communities such as North American tolerant hardwood forests and ruminant grazer- prairie grasslands display long-term stability -- however invasive species (such as humans) and natural cyclic climate change (such as regular 100,000 year repeating glaciation) alter or destroy long-term climax communities.
Time scale and spatial resolution have popped up in more than a single answer. However, "community" appears to have been taken as a given. It should be defined upfront, more so in a class discussion. Most of us probably have an implicit concept of "community" that should be made explicit. Community has at least a component of spatial extent, geo-location and dominant (biomass, space, process?) species as is obvious in the answers: tree (Apennine beech and North American hardwood forest) and grass plus grazier defined terrestrial communities. That raises already a fundamental issues. Plant, animal or species community?
I think the answer is yes, with some qualifiers.
The discussion over the existence and generality of climax communities goes back nearly a century to the foundational papers of Clements, Gleason, and explansions by Whittaker, Connell and Slatyer, etc. I am of the mind that they are not very common, but can be observed on decadal timescales and over dozens to thousands of hectares. In my fieldwork I have noticed a large range in the "climaxness" of various vegetation types, which seems to depend upon the dominance hierarchy among the species present (Keddy and Shipley 1989, Keddy and MacLellan 1990).
As examples where competitive hierarchies are prominent, coniferous forests of the Pacific Northwest and wetlands in North America show pretty clear hierarchies in relative growth rates, shade tolerance, and resistance to fire that can result in highly stable communities in specific biophysical settings (e.g., redwood (Sequoia sempervirens) forests in north coastal California, cat-tail (Typha spp.) or Phragmites, or Cladium communities in eutrophic wetlands). The communities assemble because the dominant species exhibit strong competitive primacy over co-occurring species, coupled with longevity and strong regenerating capabilities, such a stump sprouting, clonal growth. If conditions change markedly, such hierarchies inevitably break down, but they can nonetheless be important on ecological times scales, and can yield highly predictable succession outcomes.
Keddy P A, MacLellan P. 1990. Centrifugal organization in forests. Oikos 59:75-84.
Keddy P A, Shipley B. 1989. Competitive hierarchies in herbaceous plant Communities. Oikos 54:234-241.
I suggest, if humans had a lifespan of a 100,000 years or more a 'climax' concept never had come up since everybody would have been able to experience change everywhere during his/her lifetime. Supposedly, a concept of climax communities never had come up in its present form and name then, or at least would have been much more related to certain relevant spatial and temporal scales.
Yes. While there is no universal formula to form a climax community, this stage in particular is relative to the immediate environment. For example, the area surrounding Glacier Bay in Alaska has assumed climax status. Within this area, different abiotic factors come into play such that they result in their own corresponding climax communities, such as how a hemlock forest is the climax community of a well-drained, steep slope or muskeg is the climax community of poorly drained soil on the shallow slopes of Glacier Bay. Climax status can be determined by community stability. The dominant species are not necessarily the most tolerant to disturbances, and resources are allocated as fully among the dominant species, among other factors that determine stability. Additionally, community stability may be a result of a lack of disturbance or the community's resistance to change.
http://sky.scnu.edu.cn/life/class/ecology/chapter/Chapter20.htm
This s very interesting up-to-date question.
Most forests, before being slashed and burned in tropical regions, are in a climax state. Considering soil development, these soils have reached a level of maturity that supports a wide range of microorganisms, and geochemical processes are ongoing to ensure their fertility. The only factor causing unstably is human action to develop his agriculture.
Lara Barbara(2023). Resilience and the shift of paradigm in ecology: a new name for an old concept or a different explanatory tool?
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