Let G be a graph such that the color of its vertices is white or black. A dynamic vertex coloring for G is defined as follows. One starts with a certain set of black vertices. Then, at each time step, a black vertex with exactly one white neighbor forces its white neighbor to become black. The initial set of black vertices is called a zero forcing set if by iterating this process, all of the vertices of G become black. The zero forcing number of G (denoted by Z(G)) is the minimum cardinality of a zero forcing set in G. In this paper, we study the zero forcing number of trees. Let T be a tree with at least two vertices. We show that \(\Delta (T)-1\le Z(T)\le r(T)-1\), where \(\Delta (T)\) and r(T) are the maximum degree and the number of pendant vertices of T, respectively. As a consequence, we obtain that \(Z(L(T))\ge Z(T)\), where L(T) is the line graph of T. We characterize all trees T such that \(Z(T)=\Delta (T)-1\). Finally, we study trees T with \(Z(T)= r(T)-1\).

令G为图，使其顶点的颜色为白色或黑色。G的动态顶点着色定义如下。一个从一组特定的黑色顶点开始。然后，在每个时间步长上，只有一个白色邻居的黑色顶点会迫使其白色邻居变成黑色。如果通过迭代此过程，G的所有顶点都变为黑色，则初始的黑色顶点集称为零强制集。G的零强迫数（用Z（G）表示）是G中设置的零强迫的最小基数。在本文中，我们研究了零强迫树。让T是至少有两个顶点的树。我们证明\（\ Delta（T）-1 \ le Z（T）\ le r（T）-1 \），其中\（\ Delta（T）\）和r（T）是最大度数，T的悬垂顶点数目。结果，我们获得\（Z（L（T））\ GE Z（T）\） ，其中大号（Ť）是折线图Ť。我们描述了所有的树木牛逼，使得\（Z（T）= \三角洲（T）-1 \） 。最后，我们研究了树牛逼用\（Z（T）= R（T）-1 \） 。