The spatial distributions of the effective nitrogen and phosphorus possess great heterogeneity in forest soil, which results in unbalance supply of introgen and phosphorus for the rhizosphere of forest trees. In this resent paper,unbalance supply of nitrogen and phosphorus was applied to Fraxinus mandshurica seedlings, and we studied the uptake of nitrogen and phosphorus,growth response,and the ability to integrate nitrogen and phosphorus resources of these seedlings.Our results showed that total amount of nitrogen and phosphorus in an individual seedling supplied with balanced nitrogen and phosphorus was significantly higher than that in an individual seedling supplied with unbalanced nitrogen and phosphorus.Nitrogen concentration in leaves of nitrogen-deficient seedlings was significantly lower than that in leaves of nitrogen-enough seedlings.Nitrogen deficiency increased specific leaf area.Unbalance supply of nitrogen and phosphorus reduced biomass partitioning to leaves and increased biomass partitioning to roots.Total biomass of seedlings supplied with balanced nitrogen and phosphorus was significantly higher than that of seedlings supplied with unbalanced nitrogen and phosphorus,suggesting that F. mandshurica seedlings don’t have ability to integrate nitrogen and phosphorus resources.
The spatial distribution of standing fine roots in tree rows of different species in a 12-year-old mixed stand of ash (Fraxinus mandshurica Rupr.) and larch (Larix olgensis Henry) was studied by soil core sampling in early spring, 2001. It is found that ash and larch differ greatly in their belowground biomass distribution. Ash has much higher fine root biomass density in the soil than larch at stand level (with the max value of 4442.3 vs. 2234.9 gm-3). Both tree species deployed more fine roots in their neighboring zone, suggesting a less intensive competition between roots of the two species. Both fine root biomass density and root length density of ash in the zone between larch tree rows are greater than that of larch in zone between ash tree rows, indicating that ash is more powerful than larch in belowground competition. The spatial distribution feature of roots favors the growth of ash in the mixed stand.
