If there's anyone more obsessed with experiencing the wonders of nature than Emily, it just might be St. Aubert. He's the kind of dad who takes you camping all the time, even in the dead of winter. But you can't blame him: he's just super-nostalgic for a childhood spent playing in the wilderness. And years of hanging out in the forest have really done wonders for his patience. He can listen "with thrilling delight to the mystic murmurings of the woods" for, like, a really, really, long time (1.1.50).
St. Aubert really likes playing the dad card. He's had a lot of life experiences, remember? Mostly, he just wants Em to keep her emotions under control. And he practices what he preaches after his wife dies:
Having indulged his tears awhile, he would dry them and return to his chamber with a countenance composed by an endeavor which did but increase his grief. (1.1.61)
Since we already know he's a pretty emotional guy, maybe he just wants to set a good example for his little girl.
Em thinks she knows her dad pretty well, but what's with all the secretive stuff in his study? She catches a glimpse of him gazing "earnestly and tenderly" on a portrait of a beautiful woman who is most definitely not her mom (1.2.32). Plus, he makes Em promise to burn all those papers without sneaking a peek. Maybe his secrets aren't quite as bad as Em thinks they are, but he's still engaging in some shady behavior. Could it be that, like his daughter, St. Aubert has a flair for the dramatic?