Automorphisms of nil-triangular subrings of chevalley algebras of type $G_2$ over the field of characteristic $2$

Let $N\Phi(K)$ be a niltriangular subalgebra of the Chevalley algebra of an associative-commutative ring $K$ with identity, associated with the root system $\Phi$ (the basis $N\Phi(K)$ consists of all elements $e_r\in\Phi^+$ of the Chevalley basis). We describe automorphisms of a niltriangular Lie ring of type $G_2$ over a field $K$ under the constraint $2K=0$. To study automorphisms, the upper and lower central series described in this paper are essentially used.