RealChop plugin has this options:

DetectBlockBreak

Tree will fall (after physics check), when player break this type of blocks:
default: all
Possible values:

• log - only LOG blocks (tree parts)
  
• leaves - LOG and LEAVES blocks
  
• all - any blocks

BlockProcessingLimit

Setting limit of blocks for physics calculation.
High value can produce heavy server load, when process massive structures, builded from LOG blocks.
default: 150
Possible values:

• number from 5 to 1000

FallingLeaves true | false

Process LEAVES blocks, or just LOG blocks.
default: false
Possible values:

• true
  
• false