Effects of plant allocation patterns on soil nutrients and their stoichiometry in red soil slope

Background  Intensive human activities and specific natural conditions cause soil and water losses in Shenzhen frequently occur. Plantation is the main measure to prevent soil erosion and restore ecological environment. Soil nutrient stoichiometry contains abundant information such as the interaction between vegetation and soil, and soil nutrient limitation on vegetation growth. Studying the soil nutrients and their stoichiometric characteristics after plantation is conducive to understanding the effect of vegetation improvement on soil quality, which is instructive to the soil erosion control and ecological restoration in this area.

Methods  In order to explore the effects of plant allocation patterns on soil nutrients and their stoichiometry in red soil slope after a long time of vegetation reconstruction, this paper selected plots in Shenzhen Soil and Water Conservation Demonstration Garden as an example, on which vegetation reconstruction has been implemented for 10 years. Soils in depths of 0-10, 10-20 and 40-50 cm were taken from the plots of three different plant allocation patterns (grass land, wood land, wood & shrub land), as well as bare land for comparison, and the soil organic carbon (SOC), total nitrogen (TN), total phosphorus (TP), alkaline nitrogen (AN), available phosphorus (AP), and their stoichiometry were determined.

Results  1) The main contributing layer of plants on soil nutrients was 0-10 cm surface layer. The improvement of surface soil SOC, TNand ANwas the most significant in wood & shrub land, while the improvement of surface soil TP and AP was the most significant in wood land. 2) Surface soil C∶Nsignificantly increased after vegetation reconstruction, but had no significant difference between the three plant allocation patterns (P>0.05). The surface soil C∶P and N∶P of wood & shrub land were both significantly higher than those of grass land and wood land (P < 0.05). 3) The stoichiometric ratios of C, N, P were controlled by the amount of soil Cand N. The coupling relationship between Cand Nwas stable. Soil C∶P and N∶P had extremely significant positive correlations with Cand N(P < 0.01).

Conclusions  Soil nutrients and their stoichiometric characteristics are both influenced by soil depth and plant allocation patterns. Vegetation reconstruction demonstrate obvious effects on the improvement of soil quality. The improvement of soil C, Nby wood & shrub with high C∶P and N∶P meanwhile is more significant than the independent performance of woods and grasses. Nis the main limiting element of vegetation growth in the study area as it is more easily lost by soil erosion. The results of this study can provide references for the optimal allocation and performance evaluation of vegetation reconstruction in the soil erosion area of Shenzhen.