*Article* **Relationship between Vegetation and Environment in an Arid-Hot Valley in Southwestern China**

#### **Jun Pei, Wei Yang \*, Yangpeng Cai, Yujun Yi and Xiaoxiao Li**

State Key Laboratory of Water Environment Simulation, School of Environment, Beijing Normal University, Beijing 100875, China; 201621180020@mail.bnu.edu.cn (J.P.); yanpeng.cai@bnu.edu.cn (Y.C.); yiyujun@bnu.edu.cn (Y.Y.); xxli@mail.bnu.edu.cn (X.L.)

**\*** Correspondence: yangwei@bnu.edu.cn; Tel.: +86-159-1118-1787

Received: 25 November 2018; Accepted: 11 December 2018; Published: 14 December 2018

**Abstract:** The sparse and fragile vegetation in the arid-hot valley is an important indicator of ecosystem health. Understanding the correlation between this vegetation and its environment is vital to the plant restoration. We investigated the differences of soil moisture and fertility in typical vegetation (*Dodonaea viscosa* and *Pinus yunnanensis*) under a range of elevations, slopes, and aspects in an arid-hot valley of China's Jinsha River through field monitoring and multivariate statistical analysis. The soil moisture differed significantly between the dry and rainy seasons, and it was higher at high elevation (>1640 m) and on shade slopes at the end of the dry season. Soil fertility showed little or no variation among the elevations, but was highest at 1380 m. *Dodonaea viscosa* biomass increased, then decreased, with increasing elevation on the shade slopes, but decreased with increasing elevation on the sunny slopes. On the shade slopes, *Pinus yunnanensis* biomass was higher at low elevations (1640 m) than it was on sunny slopes, but lower at high elevation (1940 m) on the sunny slopes. We found both elevation and soil moisture were significantly positively correlated with *P. yunnanensis* biomass and negatively correlated with *D. viscosa* biomass. Thus, changes in soil moisture as a function of elevation control vegetation restoration in the arid-hot valley. Both species are adaptable indigenous plants with good social and ecological benefits, so these results will allow managers to restore the vegetation more effectively.

**Keywords:** arid-hot valley; vegetation; environmental factors; reservoir region
