Immobilization of avian excreta-derived nutrients and reduced lignin decomposition in needle and twig litter in a temperate coniferous forest
Immobilization of avian excreta-derived nutrients and reduced lignin decomposition in needle and twig litter in a temperate coniferous forest
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DOI：
10.1016/j.soilbio.2005.05.022
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发表时间：
2006-03
影响因子：
9.7
通讯作者：
T. Osono;S. Hobara;K. Koba;K. Kameda;H. Takeda
中科院分区：
文献类型：
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作者：
T. Osono;S. Hobara;K. Koba;K. Kameda;H. Takeda
在日本中部碧和湖附近的温带常绿针叶林中，研究了大鸬鹚（Great Cormorant Phalacrocorax）排泄物对养分（N、P、Ca、K、Mg）和有机化学成分（木质素、总碳水化合物）分解过程和动态的可能影响。在未被鸬鹚定居的对照点（C点）和已被鸬鹚定居的点（2点），研究了长叶蝉针叶2年的分解过程。针叶的质量损失比树枝快。这些凋落物类型在站点C的质量损失比站点2快，这是由于站点2的酸不溶性“木质素”的质量损失率降低。站点2的针叶和细枝发生了氮、磷和钙的净固定；而在C点，这些元素的质量在分解过程中没有固定而减少。这些营养物质在站点2的固定期在针叶中估计为1.6 ~ 2.5年，在树枝中估计为19.6 ~ 23.5年。对于氮和钙，针叶和细枝的固定电位（每克初始材料中外源养分的最大固定化量）相似，但对于磷，细枝比针叶高10倍左右，针叶的δ13C在第一年相对稳定，第二年增加，而细枝的δ13C在分解过程中是可变的。与全针叶（1.6 ~ 2.1‰）和细枝（2.0 ~ 2.5‰）相比，酸不溶性组分在13c中的含量较低。针叶和细枝及其酸不溶组分的δ15N在2点分解过程中接近排泄物的δ15N。这一结果表明，由于酸不溶性木质素样物质与排泄物来源的N络合形成，排泄物来源的N固定在凋落物中，而K和Mg在分解过程中没有固定，它们的质量在两个地点都有所下降。在此基础上，结合2站点凋落物和排泄物的数据，初步计算了凋落物在林分水平的固定潜力及其对排泄物氮磷总量的贡献。因此，被固定在凋落物（针叶和细枝）中的潜在最大量估计占总排泄物来源的N和P的5-7%。
The possible effects of excreta of the Great Cormorant Phalacrocorax carbo on decomposition processes and dynamics of nutrients (N, P, Ca, K, Mg) and organic chemical components (lignin, total carbohydrates) were investigated in a temperate evergreen coniferous forest near Lake Biwa in central Japan. Two-year decomposition processes of needles and twigs of Chamaecyparis obtusa were examined at two sites, control site never colonized by the cormorants (site C) and colonizing site (site 2). Mass loss was faster in needles than in twigs. Mass loss of these litter types was faster at site C than at site 2, which was ascribed to the decreased mass loss rate of acid-insoluble ‘lignin’ at site 2. Net immobilization of N, P, and Ca occurred in needles and twigs at site 2; whereas at site C, mass of these elements decreased without immobilization during decomposition. Duration of immobilization phase of these nutrients at site 2 was estimated to be 1.6 to 2.5 years in needles and 19.6 to 23.5 years in twigs. Immobilization potential (maximum amount of exogenous nutrient immobilized per gram initial material) was similar between needles and twigs for N and Ca but was about 10 times higher in twigs than in needles for P. δ13C in needles was relatively constant during the first year and then increased during the second year, whereas δ13C in twigs was variable during decomposition. Acid-insoluble fraction was depleted in13C compared to whole needles (1.6–2.1‰) and twigs (2.0–2.5‰). δ15N of needles and twigs and their acid-insoluble fractions approached to δ15N of excreta during decomposition at site 2. This result demonstrated the immobilization of excreta-derived N into litter due to the formation of acid-insoluble lignin-like substances complexed with excreta-derived N. No immobilization occurred in K and Mg and their mass decreased during decomposition at both sites. Based on these results of nutrient immobilization during decomposition and on the data of litter fall and excreta amount at site 2, we tentatively calculated stand-level immobilization potential of litter fall and its contribution to total amount of N and P deposited as excreta. Thus, the potential maximum amount immobilized into litter fall (needles and twigs) was estimated to account for 5–7% of total excreta-derived N and P.