Forest age, wood and nutrient dynamics in headwater streams of the Hubbard Brook Experimental Forest, NH
Forest age, wood and nutrient dynamics in headwater streams of the Hubbard Brook Experimental Forest, NH
复制标题
新罕布什尔州哈伯德溪实验森林源头溪流的森林年龄、木材和养分动态
DOI：
--
复制
发表时间：
2007
期刊：
影响因子：
--
通讯作者：
G. Likens
中科院分区：
文献类型：
--
作者：
D. Warren;E. Bernhardt;R. Hall;G. Likens
河流内加工可能会极大地改变森林流域的养分输出。本研究测试了新罕布什尔州哈伯德布鲁克实验森林 (HBEF) 内五个流域形成的 66 年时间序列中大型木材和碎片坝积累的连续差异如何影响河流内 N 和 P 的吸收。利用 1998 年夏季的养分富集释放来测量 HBEF 内 5 条溪流对磷酸盐、硝酸盐和铵的吸收速度，结果表明 PO43− 的吸收与森林年龄密切相关。 2004 年，我们量化了每条溪流中大型木材的体积和丰度，以测试大型木材丰度是否与硝酸盐和磷酸盐的吸收有关。河流内木材的体积随着森林年龄的增加而增加，对于这些早期到中期演替的森林，其明显的增长率为每年 0·03 m3 (100 m)−1 (r2 = 0.95)；然而，泥石坝频率却没有。相反，当控制河流大小时，碎片坝频率呈 U 形分布，在非常年轻的森林中坝频率高，在 20-30 年左右的森林中频率低，随着森林成熟，坝频率再次增加。磷酸盐吸收速度随着森林年龄和木材体积的增加而强烈增加（r2 = 0·99；在两种情况下p < 0·001）；然而，硝酸盐和铵的吸收与这两个因素均无关。我们将磷酸盐吸收速度与森林年龄/大木材体积之间的正相关关系归因于木材保留的无机沉积物对磷酸盐的非生物吸附增加。这些河流中的氮吸收主要是生物驱动的，并且不会随着通道的这些结构特征而发生可预测的变化。我们预计，随着森林的成熟，HBEF 溪流中的木材丰度会增加，随后溪流的磷酸盐吸收能力也会增加。版权所有 © 2007 约翰·威利父子有限公司
Instream processing may substantially alter nutrient export from forested watersheds. This study tested how instream uptake of N and P were affected by successional differences in the accumulation of large wood and debris dams in a 66‐year chronosequence formed by five watersheds within the Hubbard Brook Experimental Forest (HBEF), NH. Nutrient enrichment releases in summer 1998 were used to measure the uptake velocities of phosphate, nitrate and ammonium for five streams within HBEF, and results indicated that uptake of PO43− was closely associated with forest age. In 2004, we quantified volume and abundance of large wood in each stream to test whether large wood abundance could be linked to nitrate uptake as well as phosphate. The volume of instream wood increased with forest age, at an apparent rate of 0·03 m3 (100 m)−1 per year for these early to mid‐successional forests (r2 = 0.95); however, debris dam frequency did not. Instead, debris dam frequency, when controlled for stream size, followed a U‐shaped distribution, with high dam frequency in very young forests, low frequency in forests around 20–30 years of age and increasing dam frequency again as forests matured. Phosphate uptake velocity increased strongly with both forest age and large wood volume (r2 = 0·99; p < 0·001 in both cases); however, nitrate and ammonium uptake were not related to either factor. We attribute the positive relationship between phosphate uptake velocity and forest age/large wood volume to increased abiotic adsorption of phosphate by the inorganic sediments retained by wood. Nitrogen uptake in these streams is primarily biologically driven and did not vary predictably with these structural features of channels. We expect wood abundance to increase in HBEF streams as the forest matures, with a subsequent increase in stream phosphate uptake capacity. Copyright © 2007 John Wiley & Sons, Ltd.