CURRENT UNDERSTANDING OF WHITE AND RED PINE PHYSIOLOGY

For significant and predictable improvements in productivity of red and white pine forests, an increased understanding of the physiological processes in these species is essential. Relatively little physiological research has focused on these two species over the last two decades. However, with renewed interest in these species now for their high social, environmental and economic value this situation is changing. This paper describes past efforts at understanding red and white pine physiology, as well as discussing recent achievements. In addition, new results obtained by the authors through the use of Biotronic growth units are described in more detail to emphasize the high adaptability of white pine seedlings in response to nutrient stress through changes in carbon distribution. nutrient uptake and utilization. The ultimate practical output of much forestry research is often models predicting tree and forest growth. However, models which are based solely on empirical growth measurement data will not provide the understanding that is necessary for sustainable management; thus. increased research on physiological processes will continue to be required in future. Long-term detailed field studies that consider environmental and silvicultural influences at the organ and whole tree level are required to ensure that future models have high explanatory value.