Effects of Different Slope Aspects on Leaf Non-Structural Carbohydrate Characteristics and Leaf–Soil Stoichiometry of Sapindus mukorossi

Slope aspect and slope position have an important influence on plant growth by changing the microclimate and soil conditions such as light, temperature, moisture, and nutrients. In this study, 15-year-old <i>Sapindus mukorossi</i> forests with different slope aspects and positions were selected and the differences in tree height and diameter at breast height (DBH), leaf non-structural carbohydrate (NSC) characteristics, and leaf-soil nitrogen (N), phosphorus (P), and potassium (K) stoichiometric characteristics between sunny and shady slopes, and upper, middle, and down slope positions were compared and analyzed. The results show that the tree height and DBH of <i>S. mukorossi</i> were better in the same slope aspect and lower slope position, while in the same slope position, the tree height and diameter at DBH were better on the shady slopes. In the upper slope position, the starch content on the shady slope was significantly higher than that on the sunny slope, and the NSC content was significantly higher than that on the sunny slope. On shady and sunny slopes, <i>S. mukorossi</i> is mainly limited by N. The leaf and soil P content of <i>S. mukorossi</i> on the sunny slope was the highest and significantly higher than that on the upper slope. The coefficient of variation of each index of <i>S. mukorossi</i> on the shady slope and the sunny slope was medium and below. Soil N/P, soil N, soil N/K, soluble sugar/starch, leaf P, leaf K, leaf N, and soil K had strong plasticity under different slope aspects. Therefore, it indicated that the shady slope and down slope were more suitable for <i>S. mukorossi</i>.