You can use the .blend scene for importing ready to be used, textured models. 

In general I recommend to use APPEND option insted of LINK because in that way you will have full control over textures (which you may want to swap between winter/summer version, or choose a darker or lighter trunk and bark textures.)

To do that, go to  file-> append:

Choose fir_family.blend file and hit Append:

Navigate to Objects folder:

And now simply choose whatever model (or buch of then) you want. If you want to put into your scene winter trees, then don't forget to append coresponting SnowBall model as well:

Simple as that:

... That's it!