Christenson Lynn M, Lovett Gary M, Mitchell Myron J, Groffman Peter M
Institute of Ecosystem Studies, Millbrook, NY, 12545, USA.
SUNY College of Environmental and Science Forestry, Syracuse, NY, 13210, USA.
Oecologia. 2002 May;131(3):444-452. doi: 10.1007/s00442-002-0887-7. Epub 2002 May 1.
Forest defoliation by insects can lead to severe disruptions of the nitrogen (N) cycle resulting in elevated NO levels in stream water. To trace the movement of insect-mobilized N in a forest soil, N-labeled gypsy moth frass or N-labeled oak leaf litter was added to trenched plots in an oak forest over 29 months. Nitrogen movement from the frass or litter was measured in the available, mineralizable, microbial and total soil pools. Uptake of N by oak seedlings and inorganic N leaching losses were also measured. No significant differences were found between the frass or leaf treatments for total N in any of the pools. Significant differences were found among the treatments in the distribution of the N tracer. Forty percent of the N added as frass became incorporated in the soils, with less than 1% found in oak seedlings. Almost 80% of N added as leaves remained in the undecomposed leaf material after 2 years. Less than 0.001% of the added N was leached in both treatments. Our data indicate that N in frass is mobilized more quickly than N in leaf litter. However, this frass N may be largely unavailable to plants and microorganisms as little of it was found in the extractable, microbial, or readily mineralizable pools.
昆虫造成的森林落叶会导致氮（N）循环严重紊乱，致使溪水中的一氧化氮（NO）水平升高。为追踪森林土壤中昆虫活动所调动的氮的移动情况，在29个月的时间里，将氮标记的舞毒蛾粪便或氮标记的橡树叶凋落物添加到橡树林中的沟渠样地中。测定了从粪便或凋落物中转移到有效、可矿化、微生物和总土壤库中的氮。还测定了橡树幼苗对氮的吸收以及无机氮的淋失损失。在任何一个库中，粪便或树叶处理之间的总氮没有显著差异。在氮示踪剂的分布上，各处理之间存在显著差异。作为粪便添加的氮有40%被土壤吸收，在橡树幼苗中发现的不到1%。作为树叶添加的氮在两年后，几乎80%仍留在未分解的树叶材料中。在两种处理中，添加的氮淋失量均不到0.001%。我们的数据表明，粪便中的氮比落叶中的氮移动得更快。然而，这种粪便氮对植物和微生物来说可能大多无法利用，因为在可提取、微生物或易矿化库中很少发现。
