Effects of silvopastoral systems on soil nutrient properties in the low hilly area of western Henan province, China

Silvopastoral systems are widely used for ecological vegetation restoration in fragile areas. As the main landform of western Henan, the low hilly areas are experiencing water and soil loss because of human activities. However, the effect of silvopastoral systems on soil nutrients in low hilly areas has not been well studied. To address this issue, we established a silvopastoral experiment in the low hilly area of western Henan province in 2011, where four plots of pure forest of poplar (Populus simonii, PS), oriental thuja (Platycladus orientalis, PO), Chinese cork oak (Quercus variabilis, QV) and false acacia (Robinia pseudoacacia, RP) was planted on a natural wasteland; perennial alfalfa (Medicago sativa, MS) was intercropped with these pure forest plots as silvopastoral treatments, i.e., PS-MS, PO-MS, QV-MS and RP-MS; one plot of natural wasteland as CK. In 2018, 2019 and 2020, we examined the soil total carbon (TC) and total nitrogen (TN) of different vegetation restorations. Results showed that the silvopastoral treatments (PO-MS, QV-MS and RP-MS) generally increased the TC and TN (by ~ 53% and ~ 51% in 2018, ~ 66% and ~ 49% in 2019, and ~ 66% and ~ 67% in 2020, respectively) compared to the pure forest treatments, and were also higher than the M and PS-MS. The change in relative TC and TN between downslope and upslope positions is higher in PS and PO, lower in RP compared to the PS-MS and PO-MS, RP-MS respectively, and non-different between QV and QV-MS. In summary, soil nutrient properties are generally higher but vary among the slope positions in the silvopastoral treatments compared to pure forest treatments in the low hilly area.