Primary vs secondary succession, hydrarch vs xerarch, and is "climax" permanent? Making a table
Tanvi Deshmukh12th Sample
4 Sept 2026 Β· 1 min read
Ecological succession is my favourite thing to make a flowchart for!! πΏ But I want to make sure my chart is right before I laminate it (yes I will laminate it).
What I have:
Primary succession: starts where no life existed before: bare rock, new lava flow, a newly cooled lava, a newly created pond. Very slow, may take hundreds to thousands of years because soil must be formed first. Secondary succession: starts in areas that lost the community but soil remains, e.g. abandoned farmland, burned or flooded forest. Faster.
Xerarch (dry area): crustose lichens β foliose lichens β mosses β herbs β shrubs β trees Hydrarch (water): phytoplankton β submerged plants β floating plants β reed swamp β marsh meadow β scrub β trees
Questions:
- Is the order right? I'm unsure about where mosses and herbs sit.
- What are "pioneer species" and "seral stages"? Are they the same?
- What decides the climax community? And once it's reached, does it stay forever?
- In both xerarch and hydrarch, the end result is a mesic condition. How is that possible if one starts dry and the other wet?
Also I read that succession on a new volcanic island is primary. Right?
7 answers & replies
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[+][β]Zoya Khan12thSampleΒ· 1mo ago
Your two flowcharts are right in outline, and Q4 is the best insight in the chapter. In xerarch succession, the early species change the substrate: lichens secrete acids that weather rock and form a little soil, mosses add more organic matter and hold it, so herbs and later shrubs and trees can grow. The habitat gets wetter/richer as it proceeds. In hydrarch succession, the water body gets filled with silt and organic matter and becomes shallower, then land, so the habitat gets drier. Both move towards a medium (mesic) condition, neither too wet nor too dry. That's why they end in similar mesic communities.
[+][β]Tanvi Deshmukh12thSampleΒ· 1mo agoAuthor
YES. The "both go towards mesic" line is exactly what I couldn't phrase. Laminating tomorrow! π
[+][β]Kavya NaikDropperSampleΒ· 1mo ago
Pioneer species = the first species to colonise a bare area (lichens on a rock, phytoplankton in a pond). Seral stages (or sere) = the whole series of communities that come one after another. So "pioneer" is just the first sere, and "seral stages" are all of them. Not the same word, but related. And the final stable community is the climax community.
[+][β]Ishita GoyalDropperSampleΒ· 1mo ago
Climax: determined mainly by the climate of the region. In the same climate, different starting points tend to converge to similar climax communities. It's relatively stable and in equilibrium with the environment, but "stable" doesn't mean frozen. A change in climate or a big disturbance (fire, flood, felling) can set the community back and succession begins again. Good exam word: "a community that's in near equilibrium with the environment".
[+][β]Rahul DubeyDropperSampleΒ· 1mo ago
Secondary succession starts on bare rock after a volcanic eruption, doesn't it? Since the lava is a new surface?
[+][β]Nisha Verma12thSampleΒ· 1mo ago
Rahul, no, that's primary. Fresh lava rock has no soil, no seed bank, nothing, so it's primary. Secondary succession needs soil (and often seeds/roots) to survive, like abandoned farmland or a burnt forest. Quick test: is there soil? Yes β secondary, faster. No β primary, slow.
[+][β]Rahul DubeyDropperSampleΒ· 1mo ago
Ah ok, "is there soil" is a good test, thanks. I should not answer biology after a long day π
