降雨氮沉降以及枯落物添加对典型草原羊草化学计量特征的影响
时间:2018-08-26 21:11 来源:毕业论文 作者:毕业论文 点击:次
| 摘要：生态化学计量学在探究生态系统以及化学平衡关系中起到了重要的作用。全球气候变暖和人类活动将导致降水增多、氮沉降和枯落物的增加，这会影响到土壤和叶片的化学计量特征的变化。因此我们通过三年外源输入氮、水分和枯落物的实验，探究这三个因素对内蒙古草地上的优势种——羊草叶片中的元素含量以及碳氮磷（C:N:P）比例的影响。实验发现，增加降水、氮和凋落物，鲜叶中的N、P和Mn浓度将会升高进而使得碳氮比（C:N）和碳磷比（C:P）比值降低，然而对于其他化学计量特征的影响并不大。相比之下，这三个因素对枯叶有更强的影响作用，使枯叶中N、K、Mn、Cu、Zn的浓度升高进而使得氮磷比（N:P）显著增加，降低了碳氮比（C:N）。另外，降水的增加对鲜叶影响与枯落物和氮增加产生的影响相比效果并不显著，但对枯叶来说，降水增加不但使枯叶的化学计量特征有显著差异，并能减缓枯落物和氮输入对枯叶产生的影响。造成鲜叶和枯叶的化学计量特征变化不同可能的原因是因为在不同时期对于养分吸收方式不同，在植株生长旺盛期，可通过自身的平衡机制来减弱环境变化带来的影响，而枯叶通过营养吸收以及自身的调节机制改变化学计量特征从而影响土壤的养分归还。27456 毕业论文关键词：降雨；氮沉降；枯落物；化学计量特征 The response of the stochimetry to the increase of precipitation,nitrogen and litter input in the Leymus chinensis of typical grassland Abstract：Ecological stoichiometry plays an important role in the ecosystem and the chemical balance. Increasing precipitation and nitrogen (N) and litter inputs arising from anthropogenic activities and the global climate changes may cause changes in foliage and soil stoichiometry .Using a 3-year water,N,and litter addition experiment,we investigated the effects of these factors,both inpidually and in combination,on elemental concentrations and carbon-nitrogen-phosphorus (C:N:P) ratios in foliage of Leymus chinensis,a dominant species on the grasslands of Inner Mongolia.We found that increased precipitation,N and litter inputs had little effects on green leaf stoichiometry except enhanced N, P and manganese (Mn) concentrations, and reduced C:N and C:P ratios.By contrast,there were strong treatment effects on senesced leaf stoichiometry, with significant increases of N, potassium, Mn, copper, zinc concentrations and N:P ratio, and decreases of C and C:N ratio. Compared with the influence of litter and N inputs, water addition have weak effects on stoichiometry of green leaves,but for senesced leaf stoichiometry,water treatment effects were stronger, and also moderated the effects of litter and nitrogen inputs.The different response of green and senesced leaf stoichiometry was caused by the treatment effects on nutrient resorption.Our results demonstrate that increased precipitation, N and litter inputs have greater influences on stoichiometry of senesced leaves than that of green leaves via keeping the balance of the elements by the internal adjustment in the green leaves and changing nutrient resorption in the senesced leaf,and consequently, may influence the return of nutrients to soil. Key words: precipitation；nitrogen; litter inputs；ecological stoichiometry 目 录 摘要1 关键词1 Abstract…1 Key words1 引言…1 1 材料与方法…3 1.1 实验地点 2 1.2 实验方案 3 1.2.1 实验设计3 1.2.2 样品采集 …3 1.2.3 样品化学分析3 1.2.4 数据分析4 1.3 技术路线…4 2 结果分析 …4 2.1 不同处理对土壤养分状况的影响4 2.2 不同处理对鲜叶养分状况及碳氮磷比的影响5 2.3 不同处理对枯叶养分状况及碳氮磷比的影响7 3 讨论… 8 (责任编辑：qin) |