When you increase the ATK of a monster with "Wild Nature's Release", then apply another modifier, the new modifier is applied to the current ATK points.
If "Ojama Yellow" is equipped with "Axe of Despair" (1000 ATK, 1000 DEF), if "Wild Nature's Release" is activated then it increases "Ojama Yellow" to 2000 ATK, 1000 DEF. If "Axe of Despair" is then destroyed, "Ojama Yellow" remains 2000 ATK, 1000 DEF.
If a monster is affected by "Wild Nature's Release", and its Type is then changed with "DNA Surgery", the effect of "Wild Nature's Release" is not negated and the monster is still destroyed during the End Phase.
If you activate multiple "Wild Nature's Releases", the effects are cumulative.