Why didn't Xixia Mausoleum plant grass and raise birds?

At the foot of Helan Mountain, about 30 kilometers west of Yinchuan, the capital of Ningxia Hui Autonomous Region, the resting place of the Nine Emperors of Xixia Mausoleum is located here. Holding my breath, I want to find a machine that travels through time and space, retrograde to the time and space called Xixia Dynasty 900 years ago, to explore the legendary glory of Xixia Empire. Moreover, Helan Mountain can block the invasion of some northwest winds, which is exactly the same as the meaning of "being in harmony with the right time and the right place" often mentioned in China culture. But the most surprising tombs and ancillary buildings are under the barrier of Helan Mountain. Why don't they stand silently in the wind and rain without the support of the annex building? How many mysterious traces of Xixia dynasty are hidden behind this mysterious ancient tomb, and what does the persistence of Xixia dynasty show? These have left one suspense after another for future generations.

Why doesn't grass grow on the grave? There is a line in the drama "Zhao Li Ranfei" in the Yuan Dynasty: "Hutou Village, Qiuyishan, an outlaw, has to do it." So, the story of becoming an outlaw is like this. Comparing grass with grass shows that grass seeds can take root when they land, and they can survive with tenacious vitality no matter how bad the environment is. The Tangut people who live at the foot of Helan Mountain mainly live a nomadic life of primitive tribes. There are many good places for herders to graze cattle and sheep around the tomb of Xixia, but why is this tomb alone barren? Some people say that the mausoleum is built of rammed earth, and there is no gap for grass seeds to stay and take root. On its hard and smooth surface, there is no condition for grass seeds to survive, but can the soil be harder than stone? As we all know, there is a tiny crack in the stone. When grass seeds fall, grass can grow. The rammed earth of the mausoleum can't be without cracks. This is obviously a far-fetched statement. Some archaeologists have also put forward an argument that it is possible that when the mausoleum was built, the nutrients grown by grass seeds were fumigated and removed, so it is not impossible to grow grass.