Modifying effect of ant colonization on soil heterogeneity along a chronosequence of tropical forest restoration on slash-burn lands

Abstract

Ants act as ecosystem engineers in regulating soil heterogeneities. Little is known about the degree and direction of these modifications on soils across a restoration chronosequence of tropical forests. Our objectives aimed to explore the effect of belowground-nesting ants on soil characteristics across four forest restoration stages (i.e., 12-, 28-, 42- and 53-yr olds) on slash-burn lands in the tropical Xishuangbanna, southwestern China. We confirmed the hypotheses about a positive effect of ant colonization on soil physical characteristics, and on the enrichment of microbial carbon and mineral nutrients in nest soils across the four restoration stages. Ant nests had the highest enrichment of soil organic matter (103%), readily oxidizable carbon (78%), total nitrogen (114%), available nitrogen (126%), NH4+ (133%) and NO3– (140%) at the 12-yr old stage compared with the surrounding soils. In contrast, the highest enrichment of microbial carbon (110%) in nest soils was showed at the 53-yr old stage. The enrichment of microbial carbon in nest soils increased with restoration age, but that of soil mineral nutrients would not follow the forest restorations. A higher enrichment of mineral nutrients in nest soils at the early restoration stage can improve soil fertility, which might promote the spontaneous forest restorations. A higher abundance and area of ant nests at the older restoration stage may create a higher bare space for plant development. Therefore, our results suggest that ant colonization can regulate forest restorations, possibly through creating and maintaining higher soil nutrient heterogeneity at earlier stage, and greatly stirring microbial growth and opening up space for plant development at older stage on slash-burn tropical lands.