We study the expressivity and complexity of two modal logics interpreted on finite forests and equipped with standard modalities to reason on submodels. The logic extends the modal logic K with the composition operator from ambient logic whereas features the separating conjunction from separation logic. Both operators are second-order in nature. We show that is as expressive as the graded modal logic (on trees) whereas is strictly less expressive than . Moreover, we establish that the satisfiability problem is Tower-complete for , whereas it is (only) AExpPol-complete for , a result that is surprising given their relative expressivity. As by-products, we solve open problems related to sister logics such as static ambient logic and modal separation logic.