Mineral nutrient content variations between heartwood and sapwood of sandal (Santalum album L.) located in Jianfeng Mountain of Hainan

Objective  To investigate the rules of mineral nutrient concentrations in heartwood and sapwood of sandal (Santalum album L.) plantation, and provide references for further study of heartwood formation process.

Method  Variations of mineral nutrient contents of nitrogen (N), phosphorus (P), potassium (K), calcium (Ca) and magnesium (Mg) at different positions (pith, middle heartwood, outer heartwood, sapwood) and directions (east, south, west, north) in 21-year old sandal plantation in Jianfeng Mountain, Hainan Island were investigated.

Result  The distribution patterns of mineral nutrients between heartwood and sapwood in 21-year old sandal plantation in Jianfeng Mountain were element-specific. The contents of P, K and Ca decreased in turn from outside to the central pith, the P contents in sapwood, outer heartwood, middle heartwood and pith were 0.153, 0.032, 0.020 and 0.020 g·kg⁻¹ respectively, the K contents were 1.883, 0.529, 0.190 and 0.182 g·kg⁻¹ respectively, and the Ca contents were 2.414, 1.417, 1.321 and 1.281 g·kg⁻¹ respectively. The contents of P, K and Ca in sapwood were statistically higher than those in heartwood (P<0.01), while N content got a complete opposite distribution pattern, meaning that N content in heartwood was statistically higher than that in sapwood (P<0.01). However, there was no significant difference of Mg content across radius (P=0.132). No significant difference of all above mineral nutrient contents between heartwood and sapwood was observed among four azimuths including east, south, west and north (P>0.05).

Conclusion  P, K and Ca are recycled from heartwood to sapwood during heartwood formation in sandal, which can improve nutrient use efficiency. N keeps a higher content in heartwood than that in sapwood, indicating that sandal can acquire enough N from its hosts or soil.