Secondary succession
Imperata grasslands are caused by human activities such as logging, forest clearing for shifting cultivation, agriculture and grazing, and also by frequent fires.
[3] However, when not maintained by frequent fires and human disturbances, they regenerate naturally and speedily to secondary young forest.
The effects of secondary succession on soil are strongest in the A-horizon (0–10 cm (0.0–3.9 in)), where an increase in carbon stock, N, and C/N ratio, and a decrease in bulk density and pH are observed.
Before the fire, the vegetation was dominated by tall trees with access to the major plant energy resource: sunlight.
Due to, at least in part, changes in the environment brought on by the growth of the grasses and other species, over many years, shrubs will emerge along with small pine, oak, and hickory trees.
Eventually, over 150 years, the forest will reach its equilibrium point where species composition is no longer changing and resembles the community before the fire.
[5] Generation of carbonates from burnt plant material following fire disturbance causes an initial increase in soil pH that can affect the rate of secondary succession, as well as what types of organisms will be able to thrive.
Soil composition prior to fire disturbance also influences secondary succession, both in rate and type of dominant species growth.
For example, certain fungal species such as Trichoderma polysporum and Penicillium janthinellum have a significantly decreased success rate in spore germination within fire-affected areas, reducing their ability to recolonize.
- A stable deciduous forest community.
- A disturbance, such as a fire, starts.
- The fire destroys the vegetation.
- The fire leaves behind empty, but not destroyed soil.
- Grasses and other herbaceous plants grow back first.
- Small bushes and trees begin to colonize the public area.
- Fast-growing evergreen trees and bamboo trees develop to their fullest, while shade-tolerant trees develop in the understory.
- The short-lived and shade-intolerant evergreen trees die as the larger deciduous trees overtop them. The ecosystem is now back to a similar state to where it began.
