Mixed Scots Pine Research Articles

Total, organic and extractable-P in humus and soil beneath Sitka spruce planted in pure stands and in mixture with Scots pine

Total, organic and extractable P were measured in the humus and underlying soil to 10 cm depth beneath Sitka spruce (SS) and mixed Sitka spruce and Scots pine (SS+SP) stands planted on upland heath. The humus beneath SS+SP contained significantly (p<0.01) greater amounts of total and organic-P than that in SS and the mixed stands had more effectively retained approximately 87 per cent of previously applied fertilizer-P, totalling 100 kg P ha−1, compared with 70 per cent in SS. Despite the larger amounts of total-P in the mixed plots 0.01 M CaCl2 extractable molybdate reactive phosphorus (MRP) was significantly (p<0.05) greater in SS+SP humus only during March and April. Greater concentrations of MRP were released from the humus and soil during July and August at a mean rate of 58 g P ha−1 day−1. This coincided with drying of the soil during the summer and the rate of release, attributed to death of fine roots and microorganisms, was 4 to 30 times greater than reported values for rates of net mineralization of P from forest soils.

Ethylene formation in some coniferous forest soils

SEthylene formation in different litter components and soil layers from a Scots pine forest (site 1) and a mixed Scots pine and Norway spruce forest (site 2) is reported. The effects of temperature. moisture, length of incubation and anaerobic incubation on C 2H 4 formation in humus are also reported. The highest concentrations of C 2H 4 that accumulated in 24 h under ambient conditions in the laboratory were 3 and 17 parts/10 6 in humus from sites 1 and 2 respectively and 153 parts/10 6 in pine-needle litter. The most frequent microfungi from site I were tested for C 2H 4 formation on different media. A Mucor silvaticus isolate was found to form C 2H 4in the presence of methionine. The origin and significance of the C 2H 4 formed is discussed.