【作者】 孙玥；

【导师】 王政权；

【作者基本信息】 东北林业大学 ， 森林培育， 2010， 博士

【摘要】 细根周转向土壤中释放的碳(C)和养分被认为是陆地C和营养循环的重要组成部分。植食性土壤动物通过直接取食根系,加速细根的死亡和周转。因此,研究土壤动物对细根生理生态过程的影响对于认识森林生态系统C和养分循环具有重要意义。但是已往树木根系研究中忽视了土壤动物的影响。本研究以相同立地条件下水曲柳(Fraxinus mandshurica)和落叶松(Larix gmelinii)人工林为研究对象,通过施氮(N)肥和施杀虫剂处理以及不同土层、不同季节的取样,研究土壤动物数量的改变对水曲柳和落叶松细根生物量、形态、生产、周转以及菌根侵染率的影响。主要研究结果如下：(1)施N肥处理使水曲柳和落叶松林分四个季节、两个土层中土壤动物数量均呈现先增加后降低的趋势。施肥处理使腐食性土壤动物数量显著降低,植食性土壤动物数量显著增加,而捕食性土壤动物数量未发生明显变化。施杀虫剂以及施肥+施杀虫剂处理使两林分四个季节,两个土层中腐食性、植食性和捕食性土壤动物数量均显著降低。两林分土壤动物数量秋季>春季>夏季,土壤表层>亚表层。此外,土壤动物数量与土壤温度、pH值、土壤有机质、土壤有效N和土壤有效磷(P)显著相关。(2)土钻法研究得到,施肥处理使两林分四个季节、两个土层中1-5级根生物量显著降低。施杀虫剂处理导致两林分四个季节、两个土层中细根生物量显著增加,但是,两树种仅前两级根的生物量显著增加。植食性土壤动物与两树种的前两级根的生物量显著负相关,而与3-5级根的生物量相关性不显著。腐食性和捕食性土壤动物与两树种前两级根以及3-5级根的生物量均不相关。(3)施肥、施杀虫剂以及施肥+施杀虫剂处理使两林分各取样季节细根直径和长度显著增加,比根长(SRL)和分枝数显著降低。在所有的土壤理化指标中,土壤有效N对细根形态影响最为显著,随着土壤N有效性增加,直径和根长增加,SRL降低。另外,菌根真菌侵染率影响细根形态,施肥和施杀虫剂处理导致两林分不同土层1级根菌根侵染率显著降低。(4)内生长法研究得到,施杀虫剂处理使水曲柳前三级根和落叶松前两级根生产量显著增加,进一步证明植食性土壤动物主要取食低级根(前两级根)。如果不考虑土壤动物的取食,两林分细根生产量至少被低估20%,周转至少被低估10%。更多还原

【Abstract】 Fine root turnover is an important component of carbon (C) allocation and nutrient cycles in terrestrial ecosystems. Root herbivores accelerate root death and turnover via consuming root tissues. Therefore research on the effects of soil fauna on fine root eco-physiological processes is important in understanding C and nutrient cycling in forest ecosystems. However, the effects of soil fauna on fine roots have been overlooked in most previous studies. In this study, manchurican ash(Fraxinus mandshurica) and dahurian larch (Larix gmelinii), two important planting species in the Northeast China, were used as experimental stands. This study focuses on the effects of soil fauna on root biomass, morphology, production and turnover rate as well as mycorrhizal colonization under nitrogen (N) and insecticide treatments in both plantations.The results showed that the total density of soil fauna in both plantations was increased at initial period and decreased at later during four sampling seasons in two soil depths under N fertilized treatments, In generally, N fertilization reduced the density of soil detritivores, increased the density of root herbivores, but unchanged the density of soil predators. However, insecticide and N+insecticide treatments significant reduced all soil faunal densities across four sampling seasons and two soil depths. Soil fauna was the highest in autumn, and the lowest in summer, which have close relations with soil temperature, pH, organic matter, available N and P.N fertilization in both plantations significant decreased the biomass of the first five order roots by the method of soil cores in four sampling seasons and two soil depths. Insecticide treatment increased fine root biomass, however, significant increase was only observed in the first two order roots. There was a strong negative correlation between the density of root herbivores and the biomass of the first two order roots, but uncorrelated with higher order roots, and so does in other soil fauna.Fine root diameter and length in both plantations were significant increased under N fertilization, insecticide, and N+insecticide treatments, but specific root length (SRL) and branching roots significant decreased in four sampling seasons. In soil factors, available N was the most important factor in affecting root morphology, root diameter and length increased and SRL decreased with increasing soil N. In addition, mycorrhizal colonization affect fine root morphology, N fertilization and insecticide treatment significant decreased the mycorrhizal colonization in root tips across two soil depths in the two plantations.Fine root biomass production estimated by ingrowth cores were significant increased in the first three order roots for ash and the first two order roots for larch under insecticide treatments, suggesting that root herbivores only graze low order roots in both plantations. Overlooking the effects of root herbivores on fine root growth and mortality, fine root production and turnover rate would be underestimated by about 20% and 10%, respectively, in both plantations.更多还原