福建东山短枝木麻黄小枝氮磷含量及其再吸收率季节动态

对福建东山赤山林场短枝木麻黄纯林小枝中的N和P含量、N ∶ P比、养分再吸收率的季节动态进行研究.结果表明,随着小枝的成熟和衰老,各季节N和P的含量依次降低,其中衰老小枝中N和P含量分别为(3.97±0.21)～(8.64±0.58) mg · g~(-1)和(0.04±0.03)～(0.10±0.03) mg · g~(-1),基本上表现为N和P的完全再吸收.成熟小枝N ∶ P比的季节动态介于(18.67±3.24)～(37.98±1.32)之间,均高于16,表明木麻黄的生长受到不同程度的P限制.N、P再吸收率的季节变化分别为(51.02±4.66)%～(63.00±8.61)%和(81.24 ±5.08)%～(91.78±5.84)%,P再吸收率显著高于N.N和P的再吸收率之间以及成熟叶中N、P含量与二者再吸收率之间没有显著相关性,但在衰老叶中存在显著负相关,表明养分再吸收程度越高,其再吸收率就越高.因此,木麻黄通过小枝衰老过程中的养分再吸收,减少养分的损失,从而适应贫瘠的立地条件.

Seasonal dynamics of nitrogen and phosphorus concentrations, and nutrient resorption efficiencies of Casuarina equisetifolia branchlets in Dongshan County, Fujian

Seasonal dynamics of nitrogen and phosphorus concentrations, N ∶ P ratios and nutrient resorption efficiency of Casuarina equisetifolia branchlets was studied at Chishan Forestry Center of Dongshan County, Fujian Province, China. The results showed that N and P concentrations were highest in young branchlets and decreased with maturity and senescence. N and P concentrations of senescent branchlets ranged from (3.97±0.21) to (8.64±0.58) mg g~(-1) and (0.04±0.03) to (0.10±0.03) mg g~(-1), respectively. N ∶ P ratios of mature branchlets ((18.67±3.24)～(37.98±1.32)) were all above 16 through the year, showing P was more limiting than N. Nitrogen resorption efficiency (RE_N) and phosphorus resorption efficiency (RE_P) were from (51.02±4.66)% to (63.00±8.61)% and from (81.24±5.08)% to (91.78±5.84)% through the year, respectively, and RE_P was significantly higher than REN. There is no significant correlation between RE_N and RE_P. RE_N is not correlated with either N concentration or N:P ratios in mature branchlets, no correlation was also found between RE_P and either P concentration or N ∶ P ratios in mature branchlets. While the significant negative correlation was observed in senescent branchlets.