Juice Stephanie M, Fahey Timothy J, Siccama Thomas G, Driscoll Charles T, Denny Ellen G, Eagar Christopher, Cleavitt Natalie L, Minocha Rakesh, Richardson Andrew D
Department of Natural Resources, Cornell University, Ithaca, New York 14853, USA.
Ecology. 2006 May;87(5):1267-80. doi: 10.1890/0012-9658(2006)87[1267:rosmtc]2.0.co;2.
Watershed budget studies at the Hubbard Brook Experimental Forest (HBEF), New Hampshire, USA, have demonstrated high calcium depletion of soil during the 20th century due, in part, to acid deposition. Over the past 25 years, tree growth (especially for sugar maple) has declined on the experimental watersheds at the HBEF. In October 1999, 0.85 Mg Ca/ha was added to Watershed 1 (W1) at the HBEF in the form of wollastonite (CaSiO3), a treatment that, by summer 2002, had raised the pH in the Oie horizon from 3.8 to 5.0 and, in the Oa horizon, from 3.9 to 4.2. We measured the response of sugar maple to the calcium fertilization treatment on W1. Foliar calcium concentration of canopy sugar maples in W1 increased markedly beginning the second year after treatment, and foliar manganese declined in years four and five. By 2005, the crown condition of sugar maple was much healthier in the treated watershed as compared with the untreated reference watershed (W6). Following high seed production in 2000 and 2002, the density of sugar maple seedlings increased significantly on W1 in comparison with W6 in 2001 and 2003. Survivorship of the 2003 cohort through July 2005 was much higher on W1 (36.6%) than W6 (10.2%). In 2003, sugar maple germinants on W1 were approximately 50% larger than those in reference plots, and foliar chlorophyll concentrations were significantly greater (0.27 g/m2 vs. 0.23 g/m2 leaf area). Foliage and fine-root calcium concentrations were roughly twice as high, and manganese concentrations twice as low in the treated than the reference seedlings in 2003 and 2004. Mycorrhizal colonization of seedlings was also much greater in the treated (22.4% of root length) than the reference sites (4.4%). A similar, though less dramatic, difference was observed for mycorrhizal colonization of mature sugar maples (56% vs. 35%). These results reinforce and extend other regional observations that sugar maple decline in the northeastern United States and southern Canada is caused in part by anthropogenic effects on soil calcium status, but the causal interactions among inorganic nutrition, physiological stress, mycorrhizal colonization, and seedling growth and health remain to be established.
美国新罕布什尔州哈伯德布鲁克实验森林（HBEF）的流域预算研究表明，20世纪土壤中的钙大量流失，部分原因是酸沉降。在过去25年里，HBEF实验流域的树木生长（尤其是糖枫）有所下降。1999年10月，以硅灰石（CaSiO3）的形式向HBEF的1号流域（W1）添加了0.85 Mg Ca/ha，到2002年夏天，该处理使Oi层的pH值从3.8提高到5.0，Oa层的pH值从3.9提高到4.2。我们测量了糖枫对W1上钙施肥处理的反应。处理后第二年开始，W1中树冠糖枫的叶片钙浓度显著增加，第四年和第五年叶片锰含量下降。到2005年，与未处理的对照流域（W6）相比，处理过的流域中糖枫的树冠状况要健康得多。在2000年和2002年种子高产之后，2001年和2003年W1上糖枫幼苗的密度与W6相比显著增加。2003年的幼苗群体到2005年7月在W1上的存活率（36.6%）远高于W6（10.2%）。2003年，W1上的糖枫幼苗比对照地块的大约大50%，叶片叶绿素浓度也显著更高（0.27 g/m2对0.23 g/m2叶面积）。2003年和2004年，处理过的幼苗的叶片和细根钙浓度大约是对照幼苗的两倍，锰浓度则是对照幼苗的一半。处理过的幼苗（根长的22.4%）的菌根定殖也比对照地块（4.4%）多得多。在成熟糖枫的菌根定殖方面也观察到了类似但不太显著的差异（56%对35%）。这些结果强化并扩展了其他区域观察结果，即美国东北部和加拿大南部糖枫数量的减少部分是由人为对土壤钙状况的影响导致的，但无机营养、生理胁迫、菌根定殖以及幼苗生长和健康之间的因果相互作用仍有待确定。
