春天时给玫瑰丛覆盖一层木屑可以保持土壤湿润。

In spring, ___mulching the rose bushes with wood chips helps retain soil moisture.

我们在花园里铺了一层木屑覆盖物来保持土壤水分。

We spread a layer of wood chip ___mulching in the garden to retain soil moisture.