definitions/feature_rules/savanna_surface_trees_feature.json

{
  "format_version": "1.13.0",
  "minecraft:feature_rules": {
    "description": {
      "identifier": "minecraft:savanna_surface_trees_feature",
      "places_feature": "minecraft:legacy:savanna_tree_feature"
    },
    "conditions": {
      "placement_pass": "surface_pass",
      "minecraft:biome_filter": [
        {
          "test": "has_biome_tag",
          "operator": "==",
          "value": "savanna"
        },
        {
          "test": "has_biome_tag",
          "operator": "!=",
          "value": "mutated"
        }
      ]
    },
    "distribution": {
      "iterations": 1,
      "x": 0,
      "y": 0,
      "z": 0
    }
  }
}