To use your models

1.Open your project, then click file--append or press Shift+f1.

2.Find the PineTrees.blend file, select object folder and choose the trees you want to append.

3.Click "Append from library"

Polygon count:

1: 336,477  faces   2: 311,505  faces    3: 311,514  faces    4: 318,951  faces

To get a brighter tree, please set Render--LightPath--Transparency to around 20.

If you have any questions, feel free to ask me.