天然枫桦红松林凋落量动态及养分归还量

三年定位研究表明小兴安岭天然枫桦红松林年均凋落量有5.8t／ha(干重)。凋落量的季节变化格局是随着气候变冷有一明显秋季凋落高峰期(9—10月)。凋落物每年养分的归还量：Ca、N、K、Mg、P，相应为67.0、56.9、14.8、9.5、和6.6kg／ha，总计155.0kg／ha。据测定阔叶树落叶养分含量明显高于所有针叶的含量。尽管阔叶树的年凋落量仅占该混交林的年总凋落量的三分之一，阔叶树落叶仍有相当高的养分比例(43.4%)归还土壤。因此，红松林分的经营管理中，保留适当比重的阔叶树有利于土壤改良和促进林分生长。

LITTER DYNAMICS AND ITS RETURN OF NUTRIENTS IN NATURAL BIRCH-KOREAN PINE FORESTS

The mean annual litter in Birch-Korean Pine forests is 5.8 t/ha (dryweight) over a 3-year study period in the Lesser Xing anling mountains.The seasonal pattern of litter exhibits a distinct autumal peak as the we-ather grows cold (September to October). Return of the nutrients; Ca, N,K, Mg and P elements in the litterfall per year are 67.0, 56.9, 14.8, 9.5and 6.6 kg/ha respectively, totaling 155.0kg/ha. Nutrient content in thedeciduous leaf litter is obviously greater than that determined for allother coniferous leaf litters. In spite of the fact that the annual litter ofdeciduous trees only amounts to about 1/3 of the total in the mixed fo-rest, the litter leaves of deciduous trees, however still have a fairly largepercentage (43.4) of nutrients returned to the soil. Therefore, retainingsome deciduous trees in forest management with Korean Pine stands wouldbe useful for improving soil fertility and promoting stand growth.