这可能与棕钙土的长期干旱有关。

This one relate to arid of brown soil.

youdao

黄土是在相对冷干气候条件下发育的成熟的灰黄色古土壤，不同地区黄土所属土壤类型主要为灰钙土、栗钙土、棕钙土、棕漠土和黑垆土。

But compared with reddish paleosols, it was formed in dry and cold conditions, so, loess even could serve as an indicator of dry and cold climate.

youdao

黄土是在相对冷干气候条件下发育的成熟的灰黄色古土壤，不同地区黄土所属土壤类型主要为灰钙土、栗钙土、棕钙土、棕漠土和黑垆土。

But compared with reddish paleosols, it was formed in dry and cold conditions, so, loess even could serve as an indicator of dry and cold climate.

youdao