Clonal integration under heterogeneous water environment increases plant biomass and nitrogen uptake in a temperate steppe

Background and aims Clonal integration between ramets under heterogeneous environment has crucial implications for the clonal plants, is widely distribute in the arid ecosystems because it helps to transfer water and nutrients from the habitats with high moisture or fertility to lower ones. How the clonal integration affects the plant productivity and nutrient uptake under heterogeneous environment still remains unclear. Methods Leymus chinensis and the neighbouring Stipa grandis grew at two soil moisture environments (homogeneous water content: 8% in both the donor and recipient compartments; or heterogeneous water content: 16% in the donor and 8% in the recipient compartments) and two root connections (connected or severed L. chinensis ). After 4 weeks of growth, the plants of donor L. chinensis were labelled with either 15 NH 4 + or 15 NO 3 − . Results The biomass of recipient L. chinensis and S. grandis and N uptake rate by S. grandis were larger under heterogeneous water water content with connected roots than that with severed roots. The NO 3 − uptake rate was 40 times faster than that of NH 4 + by all the plants irrespective of soil moisture condition and root connection. Consequently, clonal integration increased N translocation from donor to recipient ramets and subsequent N utilization by neighbouring S. grandis . Unexpectedly, NH 4 + uptake by recipient L. chinensis with severed roots was 1.5 times faster than that with connected roots under homogeneous environment, this largely ascribed to that the translocation of NH 4 + from donor to recipient L. chinensis through common mycorrhizal networks (CMNs). Conclusions Clonal integration increases plant biomass and N uptake in heterogeneous environment and weakens them in homogeneous environment. Plants prefer direct NO 3 − uptake, whereas arbuscular mycorrhizal fungi preferentially translocate NH 4 + to recipient clonal ramets. These findings indicate that clonal plants rely on the clonal integration of clonal roots and CMNs to acquire N from soil.