According to you. Even if Gaara can sense Hashirama, he still has to hit him to end the gen jutsu. Its not like Hashirama Hashirama is just going to stand there and say "hit me Gaara-sama".His sensing wont help detect an attack which has no chakra like say a kunai or explosive tag.
Secondly, you know trees hold the soil together right. Gaara wont be able to manipulate sand which is held together
by roots of trees as easily as he does to loose soil. And no a desert isnt bigger than a forest. The forest Madara created for instance is way larger than anything Gaara has ever created.
gaara found muu who had no chakra signature,and warned onoki that he was abt to attack him,he senses anything that his sansor sand reaches,he has no problem attacking hashirama from BOD as long as he can sense him,which he can easily,kunais and explosive tags?,LOL gaara blocked those as a 6 yr old,he dosent need to see to block an attack as proven with the susanoo incident,not to mention he can use a third eye out of the range of hashi's genjutsu,it wont be affected,and all this is if hashi can get close enough and if gaara isnt flying which is unlikely.
Gaara makes sand out of rocks and minerals in the ground easily,he wont have any problem with soil held by trees,and he can simply make more from the ground anyway.
A forest bigger than a dessert?:sy:,gaara created a sand wave big enough to make 5 kages look like dots,just to test their response,he made a sand wave that basically turned a forest to a sand box at 13,besides he is flying above the wood,and the sand isnt going anywhere even if hashi makes a forest,infact he could easily raise it up and attack hashi easily,or surprise him from below.
