to sigh a new lease and it says we willbe responcible for trimming and removing trees on our lot, how can they do that , we dont own the land trees???

A lease is an agreement, a contract, and parties can pretty much make any agreement they want between themselves.  If you don't want to be responsible for trimming and removing the trees, see if you can get the landlord to remove that clause from the lease before you sign it.  If the landlord insists, don't sign the lease, but you will have to live elsewhere.