What do we call the second four plants?

Answer 1

If you mean that the 'first' 4 planets (Mercury, venus, earth and mars) are a group then this group is called the ROCKY planets.

Using the same grouping the next 4 planets (jupiter, saturn, uranus and neptune) are called the GAS GIANT planets.

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Answer 2

The second four plants are called secondary succession plants. These plants typically appear after the pioneer species have established themselves and helped create soil conditions that are more favorable for other plant species to grow.