Termites (Isoptera) are often considered major ecosystem engineers that alter soil properties. In the mound structures of fungus-growing termite species, the quantity and quality of soil organic matter (SOM) are variable depending on the initial soil properties and on the specific species. However, the mechanisms of termite mound turnover and the effects of such turnover on temporal and spatial patterns of nutrients in surrounding soils have rarely been studied.
Prof. LIU Wenjie and his team of Xishuangbanna Tropical Botanical Garden (XTBG) conducted a study to investigate the relationship between the stabilization and redistribution of soil nutrient properties and the chronological development of termite mounds (primary, secondary-occupied and abandoned mounds).
The experiment was conducted in an artificial rubber plantation catchment in XTBG (21°55′39″ N, 101°15′55″ E). Samples were collected along a transect at regular intervals proportional to the size of the biogenic structure.
The researchers assessed the concentrations of nutrients and water content in the biogenic structures produced by two fungus-growing termites (M. annandalei and O. yunnanensis) in different mound stages.
They found that termites promoted NH4+, but decreased organic carbon and total nitrogen (N) contents. The concentration of NO3− was in the following sequence: active mound, abandoned mound, and the surrounding soils. The concentrations of organic carbon and total N in the active mounds were significantly lower than those in the surrounding top soils, although a weak difference was observed with subsoils.
They further found that termites play an important role in nutrients redistribution in the tropics. The mean concentrations of nutrients were significantly different between fresh parts and old parts of the secondary-occupied mounds. The nutrients in the fresh parts of the mound approached the values in the primary mound; whereas the nutrients in the old part of the mound approached the values in the abandoned mound. Nutrients change through the chronological development of termite mounds.
The study indicated that hot spots of nutrients occur that affect the dynamic equilibrium of nutrients at specific spatial and temporal scales through the fixation and redistribution of the nutrients.