Ecosystem response to 15 years of chronic nitrogen additions at the Harvard Forest LTER, Massachusetts, USA
Ecosystem response to 15 years of chronic nitrogen additions at the Harvard Forest LTER, Massachusetts, USA
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DOI：
10.1016/j.foreco.2004.03.033
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发表时间：
2004-07-12
影响因子：
3.7
通讯作者：
Steudler, P
中科院分区：
文献类型：
--
作者：
Magill, AH;Aber, JD;Steudler, P
人类改变氮的全球和区域循环比任何其他元素都要多。森林中氮循环模式和过程的改变是全世界加速氮沉降的一个潜在的负面结果。为了评估氮沉降对温带森林的潜在影响，在两种不同的森林类型（红松种植园和阔叶混交林）中设计了一系列长期氮添加，作为哈佛森林（HF）长期生态研究（LTER）项目的核心试验。本文详细描述了慢性氮实验研究地点，并介绍了1988年开始处理时建立的长期基线测量结果。本文报道的结果继续或加速了以前文献中提出的趋势。无机氮的损失仍然很高，在高N地块（高于松树比硬木）和低N地块的松树林也有可测量的DIN损失。叶片和细根N浓度显著升高。到2002年，在松树高氮区，红松死亡率达到56%，生物量积累也停止了。高氮阔叶林表现出增加的ANPP，但过量的氮供应和严重的干旱在1995年促成了72%的红枫树死亡率到2002年。1995年后，物种的重要性和凋落物格局发生了变化，在几个地块。根，叶和木材减少了净汇增加的N，重新强调土壤中的作用，氮的保留。在1998年的一篇综述论文中提出了两种增加氮的大净保持机制。其中，越来越多的论文支持非生物固定化，而真菌的同化和再分泌则建议增加DON浓度。(C)2004 Elsevier B.V.保留所有权利。
Humans have altered the global and regional cycles of nitrogen more than any other element. Alteration of N cycling patterns 14 and processes in forests is one potentially negative outcome of accelerated N deposition worldwide. To assess potential impacts of N deposition on temperate forests, a series of chronic nitrogen additions in two contrasting forest types (red pine plantation and mixed hardwood stand) were designed as a core experiment of the Harvard Forest (HF) Long-term Ecological Research (LTER) pro-ram. This paper describes the chronic N experimental study site in detail and presents the long-term baseline measurements established at the beginning of treatments in 1988.Results reported here continue or accelerate trends presented in previous papers. Losses of inorganic N remain high in the high N plots (higher in pines than hardwoods) and low N plots in the pine stand also have measurable DIN losses. Foliar and fine root N concentrations are elevated significantly. Mortality of red pine reached 56% by 2002 in the Pine high N plot, and biomass accumulation has stopped alto.gether. The high N hardwood stand shows increased ANPP, but excess N availability and a severe drouaht in 1995 contributed to mortality of 72% of red maple trees by 2002. Species importance and litterfall patterns were altered in several plots after 1995. Roots, foliage and wood have diminished as net sinks for added N, re-emphasizing the role of soils in N retention. Two mechanisms for large net retention of added N were suggested in a review paper in 1998. Of these, abiotic immobilization is supported by a growing set of papers, while assimilation and re-exudation by mycorrhizae is suggested by increased DON concentrations. (C) 2004 Elsevier B.V. All rights reserved.