Fungus-growing termites play a prominent role in nutrient cycling in tropical ecosystems through building numerous mounds with differing properties compared to the adjacent soils. However, far less is known about the nutrient variability within the mounds and the nutrient stocks in whole mounds. Here, we investigated the spatial distribution of nutrients and their related nutrient stocks within active mounds (built by Odontotermes yunnanensis), abandoned mounds and adjacent soils in Xishuangbanna, southwestern China. Detailed sampling was conducted in transect of an active mound, an abandoned mound and an adjacent soil; soils were also sampled along the central vertical line from the surface to 1.60 m in four active mounds, four abandoned mounds and four adjacent soils. The nutrient stocks were calculated according to the nutrient concentrations and their related density for each sampling location. We found that, compared to the corresponding values in adjacent soils, the nutrient stocks (except for NH4+ and exchangeable Na) of organic carbon, total N, exchangeable K, hydrolysable N, available P, and NO3- in the active mounds increased, on average, by 47.84%, 25.31%, 31.63%, 42.82%, 49.90%, and 620.80%, respectively. In addition, the nutrient stocks (except for NH4+ and exchangeable Na) of organic carbon, total N, exchangeable K, hydrolysable N, available P, and NO3- in the abandoned mounds increased, on average, by 43.45%, 22.36%, 23.33%, 43.67%, 50.38%, and 47.96%, respectively. High spatial homogeneity and weak or no spatial dependence of nutrient distributions (except for hydrolysable N and exchangeable Na) were found in the active mounds, whereas high heterogeneity and moderate or strong spatial dependence of nutrient distributions were observed in the abandoned mounds and adjacent soils. The results indicated that the accumulation and spatial distribution of the nutrients within termite mounds was not only related to the termite activities but was also affected by environmental factors, such as erosion and leaching, and the invasion of plants. Our study demonstrates that termite mounds are “hot spots” of nutrients and provides evidence supporting conjectures about the homogeneity of physicochemical properties within mound structures.
