Effects of Polygonatum cyrtonema and Sarcandra glabra planted under Cunninghamia lanceolata forest on soil physical and chemical properties

The effects of cultivating Polygonatum cyrtonema and Sarcandra glabra planted under Cunninghamia lanceolata forests on soil physicochemical properties is not yet clear. Based on this, an under-canopy cultivation experiment was conducted in the Cunninghamia lanceolata plantation of Luoguopu State-owned Forest Farm in Linshui County, Guang'an City, Sichuan Province. A randomized block design was used, setting up cultivation areas for Polygonatum cyrtonema and Sarcandra glabra, as well as a control area of pure Cunninghamia lanceolata forest. Soil samples from the 0-20 cm layer were collected to determine the soil moisture content, pH, organic carbon (SOC), total nitrogen (TN), ammonium nitrogen (NH₄⁺-N), nitrate nitrogen (NO₃⁻-N), total phosphorus (TP), available phosphorus (AP), total potassium (TK), and available potassium (AK) content. The results showed that the cultivation of Polygonatum cyrtonema and Sarcandra glabra under Cunninghamia lanceolata significantly increased the SOC and TN contents by 29.94%, 22.63%, 51.16%, 36.7% respectively, and the promotion effect of Polygonatum cyrtonema on SOC and TN was more significant. The cultivation of Polygonatum cyrtonema and Sarcandra glabra under Cunninghamia lanceolata also significantly increased the soil NH₄⁺-N and NO₃⁻-N contents by 38.87%, 51.25%, 29.50%, 16.14%, respectively. Additionally, the cultivation of Polygonatum cyrtonema and Sarcandra glabra under Cunninghamia lanceolata increased the soil TK and AK contents by 7.56%, 9.45% and 36.12%, 21.50% respectively. However, there was a tendency for the cultivation of Polygonatum cyrtonema and Sarcandra glabra under Cunninghamia lanceolata to reduce soil moisture content, TP, and AP content. To sum up, planting Polygonatum cyrtonema and Sarcandra glabra under Cunninghamia lanceolata forest improved soil fertility on the whole.