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为了诊断沙地樟子松人工林的衰退原因,我们比较分析了沙地樟子松天然林和人工林中的叶片养分含量。结果表明,天然林中的樟子松叶片内氮、磷含量均比人工林中低,而钾含量比人工林高。樟子松人工林叶片中 N:P, P: K 和N: K在45年前随年龄增加而增加,从植物养分含量的角度来看,这一结果表明氮或磷可能不是沙地樟子松生长的绝对限制因子。然而,天然林和人工林叶片中的钾含量比以前报道过的松属植物中的含量都要低。天然林叶片中的N: P比值在正常的范围内,但人工林的则在该范围以外。这些结果表明天然林具有比人工林更好的养分平衡状况。如果只从樟子松的生长地来考虑,我们可以认为樟子松人工林的衰退现象可能是因其它的矿物元素或者氮和磷的有效性,而不是氮和磷的绝对含量不足造成的。养分的不平衡状况和人工林内针叶快速分解可能也是衰退的重要因素。图3表3参42。
In order to diagnose the recession reason of Pinus sylvestris var. Mongolica plantations, we compared leaf nutrient contents of natural and artificial forests of Pinus sylvestris var. Mongolica on sandy land. The results showed that the content of nitrogen and phosphorus in Pinus sylvestris var. Mongolica in natural forest was lower than that in plantation, while the content of potassium was higher than that in plantation. The N: P, P: K and N: K in leaves of Pinus sylvestris var. Mongolica increased with age 45 years ago. From the point of view of plant nutrient content, this result indicated that nitrogen or phosphorus may not be the dominant species of Pinus sylvestris The absolute limit of growth of pine. However, potassium levels in natural and plantation leaves are lower than those previously reported for Pinus. Natural forest leaves in the N: P ratio within the normal range, but the plantation is outside the range. These results show that natural forests have better nutrient balance than plantations. If we consider only the growth of Pinus sylvestris var. Mongolica, we can think that the recession of Pinus sylvestris plantation may be due to the availability of other mineral elements or nitrogen and phosphorus, not the absolute content of nitrogen and phosphorus. The imbalance of nutrients and the rapid decomposition of needles in plantations may also be important factors in the recession. Figure 3 Table 3 Reference 42.