Abstract:

Moso bamboo culms have well-developed underground stems which help them expand to adjacent ecosystems by rapid growing and elongating. It is crucial to explore the variability of soil acidity, soil organic matter, soil main nutrients and their content ratios at different expansion stages for understanding the regulatory mechanism. In this study, three 10 m × 50 m transects were set up along the expansion direction from bamboo forest to broadleaved forest, and each transect was divided into 5 subplots. The soil nutrients and content ratios at different expansion stages were analyzed, and the effects of bamboo expansion on soil nutrients were summarized. The results show that (1) the content of soil pH, total phosphorus, available phosphorus, total potassium, and available potassium decreased, while the content of soil organic matter, total nitrogen and hydrolyzed nitrogen increased with the expansion of moso bamboo to broadleaved forest. There was a significant difference (P=0.0000) in these indicators among different expansion stages. Compared with the early stage of expansion, soil pH, total phosphorus, available phosphorus, total potassium, and available potassium of the later expansion stage reduced by 6.59%, 7.61%, 30.15%, 12.89% and 4.00%, respectively, and the content of soil organic matter, total nitrogen, and hydrolyzed nitrogen of the latest expansion stage increased by 8.16%, 4.68% and 10.31%, respectively. (2) w_(C):w_(N), w_(C):w_(P), w_(N):w_(P) and w_(HN):w_(AP) tended to increase with the expansion of moso bamboo into adjacent broadleaved forest. Compared with the early stage of the expansion, w_(C):w_(N), w_(C):w_(P), w_(N):w_(P) and w_(HN):w_(AP) in the later stage of the expansion increased by 7.05%, 12.55%, 7.83% and 231.02%, respectively, with mean values at 17.37, 119.73, 6.81 and 59.57, respectively. (3) Strong correlations among pH, organic matter, total nitrogen, total phosphorus, total potassium, hydrolyzed nitrogen, available phosphorus and available potassium content were observed. The correlations between soil total phosphorus and soil w_(N):w_(P), total potassium and available phosphorus, available phosphorus content and soil w_(C):w_(N), w_(C):w_(P), and w_(N):w_(P) were not significant. There was a strong coupling between the main soil nutrients and their ratios. As moso bamboo expanded to broadleaved forests, soil acidity increased and microbial activity decreased, limiting the decomposition of organic matter. The accumulation of organic matter increased, and soil w_(C):w_(N) and w_(C):w_(P) increased. The soil w_(C):w_(N) and w_(C):w_(P) in the study area were significantly higher than their average values of moso bamboo forests across the country, indicating a lack of nitrogen and phosphorus in the soil. The average value of soil w_(N):w_(P) was 6.81, higher than the national average value of 4.28 for moso bamboo forests. The deficiency of phosphorus was more severe than the deficiency of nitrogen, especially available phosphorus. The addition of N and P to the soil at the junction of moso bamboo and broadleaved forests in the study area could improve the growth efficiency of moso bamboo forests.

Key words: expansion of moso bamboo forest, broadleaved forest, soil nutrient, Stoichiometric characteristics

摘要：

毛竹具有发达的地下茎（竹鞭）,通过竹鞭伸长生长,不断向邻近生态系统扩展。开展毛竹林扩展过程中土壤酸碱性、有机质、主要养分及其计量比值的变化规律研究对毛竹林扩展调控具有支撑作用。以竹-阔扩展界面为研究对象,沿毛竹扩展方向设置3个10 m×50 m调查样带,每一样带平均划分为5个样方,系统调查和分析了不同样方土壤养分以及计量特征,揭示了毛竹扩展对土壤养分的影响规律。结果表明,（1）随着毛竹向阔叶林扩展,土壤pH、全磷、有效磷、全钾、速效钾质量分数呈降低趋势,土壤有机质、全氮、水解氮质量分数呈升高的趋势,不同扩展阶段差异达到极显著水平（P=0.0000）。扩展后期与扩展前期相比,土壤pH、全磷、有效磷、全钾、速效钾质量分数分别降低了6.59%、7.61%、30.15%、12.89%和4.00%,土壤有机质、全氮、水解氮质量分数分别升高了8.16%、4.68%和10.31%。（2）随着毛竹向阔叶林扩展,w_(C):w_(N)、w_(C):w_(P)、w_(N):w_(P)和w_(HN):w_(AP)呈升高的趋势;扩展后期与扩展前期相比分别升高了7.05%、12.55%、7.83%和231.02%,平均值分别为17.37、119.73、6.81和59.57。（3）除土壤全磷质量分数与土壤w_(N):w_(P)、全钾质量分数与有效磷质量分数、有效磷质量分数与土壤w_(C):w_(N)、w_(C):w_(P)、w_(N):w_(P)的相关性未达到显著水平外（P>0.05）,土壤pH、有机质、全氮、全磷、全钾、水解氮、有效磷和速效钾质量分数之间存在着显著或者极显著的相关性,土壤主要养分及其计量比之间存在着很强的耦合性。随着毛竹向阔叶林扩展,土壤酸性增强,有机质累积量增多,土壤w_(C):w_(N)、w_(C):w_(P)升高,且明显高于全国毛竹林土壤w_(C):w_(N)、w_(C):w_(P)的平均值,土壤缺乏氮元素和磷元素;土壤w_(N):w_(P)平均值为6.81,高于全国毛竹林地土壤w_(N):w_(P)平均值4.28,因此,相对于氮元素缺乏,磷元素缺乏更严重,尤其是有效磷。在研究区毛竹林扩展界面土壤中,添加N、P元素可以提升毛竹林的生长效率。

关键词: 毛竹扩展, 阔叶林, 土壤养分质量分数, 计量特征