Cullings Kenneth W, New Michael H, Makhija Shilpa, Parker V Thomas
NASA-Ames Research Center, Moffett Field, Mountain View, CA 94035-1000, USA.
Appl Environ Microbiol. 2003 Jul;69(7):3772-6. doi: 10.1128/AEM.69.7.3772-3776.2003.
Increasing soil nutrients through litter manipulation, pollution, or fertilization can adversely affect ectomycorrhizal (EM) communities by inhibiting fungal growth. In this study, we used molecular genetic methods to determine the effects of litter addition on the EM community of a Pinus contorta stand in Yellowstone National Park that regenerated after a stand-replacing fire. Two controls were used; in unmodified control plots nothing was added to the soil, and in perlite plots perlite, a chemically neutral substance, was added to maintain soil moisture and temperature at levels similar to those under litter. We found that (i) species richness did not change significantly following perlite addition (2.6 +/- 0.3 species/core in control plots, compared with 2.3 +/- 0.3 species/core in perlite plots) but decreased significantly (P < 0.05) following litter addition (1.8 +/- 0.3 species/core); (ii) EM infection was not affected by the addition of perlite but increased significantly (P < 0.001) in response to litter addition, and the increase occurred only in the upper soil layer, directly adjacent to the added litter; and (iii) Suillus granulatus, Wilcoxina mikolae, and agaricoid DD were the dominant organisms in controls, but the levels of W. mikolae and agaricoid DD decreased significantly in response to both perlite and litter addition. The relative levels of S. granulatus and a fourth fungus, Cortinariaceae species 2, increased significantly (P < 0.01 and P < 0.05, respectively) following litter addition. Thus, litter addition resulted in some negative effects that may be attributable to moisture-temperature relationships rather than to the increased nutrients associated with litter. Some species respond positively to litter addition, indicating that there are differences in their physiologies. Hence, changes in the EM community induced by litter accumulation also may affect ecosystem function.
通过凋落物处理、污染或施肥增加土壤养分，可能会抑制真菌生长，从而对外生菌根（EM）群落产生不利影响。在本研究中，我们使用分子遗传学方法，来确定添加凋落物对黄石国家公园一片在皆伐火烧后重新生长的扭叶松林中EM群落的影响。我们设置了两个对照组；在未改良的对照样地中，土壤未添加任何物质，而在珍珠岩样地中添加了珍珠岩（一种化学中性物质），以将土壤湿度和温度维持在与凋落物覆盖下相似的水平。我们发现：（i）添加珍珠岩后物种丰富度没有显著变化（对照样地中为2.6±0.3种/核心，珍珠岩样地中为2.3±0.3种/核心），但添加凋落物后显著降低（P<0.05）（1.8±0.3种/核心）；（ii）添加珍珠岩对外生菌根感染没有影响，但添加凋落物后显著增加（P<0.001），且这种增加仅发生在紧邻添加凋落物的上层土壤中；（iii）颗粒牛肝菌、米氏威尔考克逊菌和伞菌状DD在对照组中是优势生物，但添加珍珠岩和凋落物后，米氏威尔考克逊菌和伞菌状DD的水平均显著下降。添加凋落物后，颗粒牛肝菌和另一种真菌——丝膜菌科物种2的相对水平显著增加（分别为P<0.01和P<0.05）。因此，添加凋落物产生了一些负面影响，这可能归因于湿度-温度关系，而非与凋落物相关的养分增加。一些物种对添加凋落物有积极反应，表明它们的生理机能存在差异。因此，凋落物积累引起的外生菌根群落变化也可能影响生态系统功能。
