What did he say about the trees?
Rashi: He said what is the cure of each, and which are good for building, and planting in a particular land.
Rashi, citing Bamidbar Rabah 19:3: He explained why Taharas Metzora requires the tallest tree (cedar) and the lowest (hyssop). Radak - it explains there, he received Tzara'as because he made himself high (haughty) like a cedar. Once he lowers himself like hyssop, he is purified and healed.
Radak citing Targum Yonasan: He had Nevu'ah about the kings that will come from Beis David.
Malbim: He composed many Seforim about the nature of all kinds of vegetation, living animals, birds, fish and Remes, which includes amphibious beings and small [vermin].
What did he say about the animals?
Rashi: He said what is the cure of each, and its primary habitat, and its food.
Rashi, citing Bamidbar Rabah 19:3: He explained why one must cut one of the two Simanim (windpipe and foodpipe) in a bird [for Shechitah], and both in an animal, and nothing is needed for fish and locusts. Radak - it explains there, it suffices to gather fish, for it says "Degei ha'Yam Ye'asef" (Bamidbar 11:22).
Refer to 5:13:1:4.
What did he say about the birds?
Radak, citing Bamidbar Rabah 19:3: He resolved the verse that says that they were created from the dry land "va'Yitzer? Min ha'Adamah? Kol Of" with the verse that says that they were created from water "Yishretzu ha'Mayim? v'Of" (Bereishis 2:7, 1:20) - they were created from the mud.
What did he say about the Remes?
Radak, citing Bamidbar Rabah 19:3: He explained why one who [on Shabbos, traps or] wounds one of the eight Sheratzim listed in the Torah (Vayikra 11:29-30) is liable, but he is exempt for other Sheratzim (Shabbos 14:1). It is because the eight have skin [distinct from their flesh, so it is considered that the blood was displaced].
Refer to 5:13:1:4.
