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Succession is concerned with community development over time. Find out more in our general section on succession.


Salt Marsh

Succession in a Salt Marsh

Competition

What do you need if you're a plant?

Water, light, carbon dioxide, oxygen, nutrients and space, that's what.

If a whole lot of other species (or a whole lot of your own species) want these things in the same place and at the same time as you and there isn't enough of any or all of them to go around you get competition.

Imagine (if you need to) you are a male pop-star. (this isn't sexism, you have to be a chap for the purposes of this example). Not for you the modern, healthy, muesli, yoga and caffeine-free soya milk approach. You are a pop-star in the great 1960s tradition of drink, drugs, night-clubs, sex, more sex, even more sex, a quick drink, more sex, a few more drugs and just a bit more sex.............then you die aged 19 (of a heart attack while having sex).

What have you achieved? Not a lot in musical terms (you were always drunk or drugged or having sex). You have however spread your seed far and wide (pre-aids, just pre-oral contraceptives and you never had time to get to the shops for condoms). You have however left a lot of offspring behind. In short you have lived fast and died young. Not something most people would recommend once they get near to the death age.

Let's imagine an alternative: You are still a male pop-star but you adopt a different approach. You do the concerts and retire straight to bed (alone) with a cup of low-fat, sugar-free, caffeine reduced cocoa. You save all your money and have a hit every year for decades. Eventually you get around to reproducing which you do just a couple of times. You live to 122 and leave vast wealth to your 2 offspring and their children.

In general terms we can think of the competition stage on our marsh as the "live fast die young species" (opportunistic species) being replaced by the "nice cup of cocoa, big pension and live to 122 species" (equilibrium species).

Opportunistic species put most of their energy into fast growth rapid maturation and production of vast numbers of offspring. These offspring are spread far and wide. The offspring don't have much in the way of food reserves. They depend entirely on finding by chance a suitable habitat. Most of them will die or be eaten but because of their vast numbers some will survive and within a short time produce offspring of their own. This approach can be very successful (think of a dandelion for instance).

Equilibrium species invest more of their energy in long lasting structures. It may be years before they reach maturity and produce offspring of their own. They will not make so many offspring and they may not be so widely dispersed. Each one however will have protection (say a tough coat or nasty chemicals) and be provided with a food reserve to ensure a good start in life. This strategy can also work very well (think of an oak tree).

Pioneers tend towards the opportunistic end of things and equilibrium species tend towards the long term approach. During the competition stage of succession our pioneer species will tend to be out-competed and replaced by equilibrium species.

It's not easy to demonstrate this directly in the field but we can see species like Spartina and Salicornia replaced by species like Halimione portulacoides (sea purslane) and Armeria maritima (thrift or sea pink).

The number of species continues to increase as abiotic factors become more favourable. Competitive exclusion would suggest that where different species are in strong competition one will prevail at the expense of the other. Leading to our next stage of community development. You can find out about this by clicking the link.

<< Succession: Establishment
Succession: Stabilisation >>


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