雷州半岛桉树人工林凋落物量和养分循环研究

为了解雷州半岛地区桉树人工林凋落物量和养分归还特征,对不同林龄人工林凋落物量和养分动态连续12个月进行监测。结果表明,桉树人工林的凋落物总量为5 a9 a7 a,5 a生桉树人工林的凋落物总量显著高于7和9 a生林分,且7和9 a生林分间没有显著差异。不同林龄桉树人工林凋落物总量具有明显的季节变化,均呈双峰型,峰值出现在雨季初期和末期。林分结构因子同凋落物量相关性不显著,但气候因子中的月均温与凋落物量存在显著正相关关系。不同林龄桉树人工林的养分年循环量由凋落物量和凋落物养分含量共同决定,氮、磷、钾元素的养分年归还总量为9 a7 a5 a,且彼此间达到显著差异。凋落物养分元素归还高峰期集中在雨季前后,以冬季养分归还量较低。因此,为增加桉树人工林产量且利于人工林地力恢复,桉树人工林应适当增加种植年限,且采伐季节选择在冬季。

Litterfall and Nutrient Cycling of Eucalyptus Plantation with Different Ages on Leizhou Peninsula

In order to understand the changes in litterfall and nutrient cycling of Eucalyptus urophylla×E. grandis plantations with different ages on Leizhou Peninsula, the litterfall amount and nutrient return of Eucalyptus plantations with different ages were surveyed continued for 12 months. The results showed that the annual contents of litterfall of Eucalyptus plantations were in the order of 5 a > 9 a > 7 a, the total litterfall of 5 a plantation was significantly higher than that of 7 a and 9 a plantations, but there was no significant difference between later plantations. The litterfall contents of Eucalyptus plantations with different ages showed obvious seasonal changes with bimodal pattern, and the peak values appeared in the early or late rainy season. There was no significant correlation between forest structure factors and amount of litterfall, but there was a significant positive correlation between the monthly average temperature and litterfall amount. The annual nutrient flux of different forest ages was dominated by amount of litterfall and nutrient content. The annual nutrient flux of nitrogen, phosphorus and potassium in Eucalyptus plantations was in the order of 9 a > 7 a > 5 a, and there were significant differences among them. The peak period of nutrient restitution was concentrated around the rainy season, while the amount of nutrient restitution in winter was low. Therefore, in order to increase the yield of Eucalyptus plantation and facilitate the recovery of plantation soil fertility, the planting years of Eucalyptus plantation should be increased and the cutting season should be in winter.