Knowledge Resource Center for Ecological Environment in Arid Area
| 氮添加和林下植被去除对沙地樟子松养分回收的影响 | |
| 其他题名 | Effects of nitrogen addition and understory removal on nutrient resorption of Pinus sylvestris var. mongolica |
| 郑琳琳 | |
| 出版年 | 2017 |
| 学位类型 | 硕士 |
| 导师 | 赵琼 |
| 学位授予单位 | 中国科学院大学 |
| 中文摘要 | 叶片的养分回收是植物重要的养分保存机制。然而，由于叶片养分回收与土壤养分有效性之间的关系存在很大的不确定性，对于叶片养分回收是植物固有特性还是适应性对策仍存在很大争议。樟子松是我国北方干旱和半干旱区主要的造林树种。大部分造林区土壤养分贫瘠，人为干扰严重，养分是这些地区樟子松生长的重要限制因素。因此，通过研究环境变化和人为干扰下土壤性质的变化如何影响樟子松叶片的养分回收，不仅能促进养分回收理论的完善，还是更好的了解樟子松的养分利用特性，对樟子松人工林的管理具有指导意义。本文以科尔沁沙地12年生樟子松人工林为研究对象，通过野外氮(N)添加(对照和10g N·m-2·a-1)与林下植被管理(去除和对照)控制试验，分析樟子松叶片养分回收和土壤生物化学性质对实验处理的响应，主要结论如下：(1)氮添加和林下植被去除都显著降低了土壤有效磷(P)含量和微生物量碳。氮添加显著降低了土壤pH值，增加了土壤无机氮含量。这说明氮添加不仅通过土壤酸化使更多的有效磷被固定，还抑制了土壤微生物的活性，降低了有机磷的矿化。林下植被对维持樟子松人工林土壤微生物量及微生物主导的土壤养分转化过程起重要作用。(2)氮添加和林下植被去除均显著提高了叶片磷回收效率，降低了氮回收效率，对氮和磷回收能力没有显著影响。磷回收效率与土壤有效磷含量间呈显著负相关；氮回收效率(NRE)与土壤无机氮显著负相关；叶片氮回收能力与土壤无机氮显著正相关，而磷的回收能力(PRP)与土壤指标间的相关性不显著。可见，养分回收效率对土壤养分有效性的敏感度要强于养分回收能力。(3)氮添加显著降低了叶片磷含量(19%)和比叶面积(8%)，提高了叶片氮含量(31%)、叶干物质含量(10%)和单叶干重(14%)；林下植被去除对所有叶片性状都没有显著影响。叶龄较大的叶片对氮添加和林下植被去除的响应要强于当年生叶片，尤其是比叶面积和叶片氮含量。比叶面积和叶干物质含量与土壤有效磷之间的相关性要强于与土壤无机氮间的相关性，而且叶干物质含量与土壤有效磷之间的相关性强于比叶面积与土壤有效磷间的相关性。可见，氮添加通过降低土壤磷的有效性，限制了樟子松叶片的光合能力。此外，往年生叶较当年生叶、叶干物质含量较比叶面积能更好地指示土壤养分的变化。(4)本研究发现季节变化与叶龄对樟子松针叶养分含量有显著的交互作用，实验处理对针叶磷含量的季节变化有显著的影响。氮添加及林下植被去除处理显著影响樟子松当年生针叶磷含量的季节变化。在对照样地，当年生针叶磷含量在8月份值最高，而在氮添加、林下植被去除及二者共同处理样地均为6月份值最高。当年生针叶氮含量季节变化在各处理下差异不显著。樟子松一、二、三年生针叶的氮和磷含量的季节变化在不同处理下趋势相近，氮含量在整个生长期呈现为先降低(4-6月)后急剧增加(6-8月)再降低(8-10月)的趋势；磷含量的季节变化呈现为先下降后升高再趋于稳定，相比氮含量的变化趋势更为平缓。 |
| 英文摘要 | Nutrient resorption during leaf senescence is an important way by which plants could conserve nutrients. However, there are controversy opinions whether nutrient resorption is an intrinsic nature of plants or an adaptive strategy to variation in nutrient supply, as the relationship between nutrient resorption efficiency and soil nutrient availability are largely uncertain. Mongolian pine (Pinus sylvestris var.mongolica) is the most important afforestation tree species in arid and semi-arid regions of northern China. Most of the Mongolian pine plantations were established on poor soils and under intensive human disturbances. Nutrient deficiency is the important factors that limiting Mongolian pine growth. Therefore, researches on how nutrient resorption of Mongolian pine responds to variation in soil properties resulting from environment change and human disturbances, can increase our understanding the nutrient use strategies of Mongolian pine, and have important implications for guiding the management of Mongolian pine plantations.In the present study, we set a randomized block experiment with 4 replicates and 4 treatments including Control (the control without any disturbance), N+ (Addition of 10 g N m-2 year-1), U- (Removal of all understory vegetation), and N+U- (Combination of N+ and U-) in a 12 year-old Pinus sylvestris var. mongolica plantation in Keerqin Sandy Land. We established four blocks with each block consists of four 20 m × 30 m plots, and the four treatments were randomly arranged in the four plots of each block. Leaf nutrient resorption, seasonal dynamics of nutrients and morphological traits of different-aged needles, as well as soil biochemical properties were measured. The results are as followings:(1) N addition and understory removal both significantly reduced soil Olsen-P concentration and microbial biomass C. N addition significantly reduced soil pH and increased soil inorganic nitrogen concentration. This indicated that N addition can not only acidify the soil and hence made more phosphate was adsorbed, but also inhibit soil microbial activity and reduce the mineralization of organic P. Understory vegetation play an important role in improving microbial biomass and microbial mediated nutrient transformation processes.(2) N addition and understory removal both significantly increased leaf P resorption efficiency (PRE), reduced leaf N resorption efficiency (NRE), and had no significant effect on resorption proficiency of N(NRP) and P(PRP). PRE, was negatively correlated with soil Olsen-P concentration,. NRE was negatively correlated with soil inorganic N. NRP was positively correlated with soil inorganic N concentration, while the correlation between PRP and soil nutrient concentration was not significant. The results showed that the nutrient resorpton efficiency was more sensitive to the soil nutrient availability than nutrient resorpton proficiency.(3) N addition significantly reduced foliar P concentration (by 19%) and specific leaf area (SLA, by 8%), and elevated N concentration (by 31%), leaf dry matter content (LDMC, by 10%) and individual leaf dry weight (by 14%); understory removal had no significant effects on all leaf traits. Older needles responded more strongly to N addition and understory removal than current-year needles, particularly for SLA and N concentration. SLA and LDMC correlated more strongly with soil Olsen-P than with soil inorganic N, and LDMC correlated more closely with soil Olsen-P than SLA did. These results indicate that aggravated P limitation resulting from N addition and understory removal could constrain Mongolian pine growth through their effects on leaf traits. In addition, older needles and LDMC are better than current-year needles and SLA to indicate the variation in nutrient availability.(4) There are significant interactions of season and on needle nutrient concentrations, and treatments had significant effects on the needle P concentration. N addition and understory removal significantly altered the seasonal dynamics of P concentration in current-year needles of Mongolian pine. For current-year needles, P concentration was the highest in August in CK plots, but highest in June in N+, U-, N+U- plots; there was no significant difference in seasonal variation of needle N concentration under different treatments. For 1-, 2-,3-year-old needles ,The seasonal variation of N and P concentrations were similar under different treatments. N concentration reduced from April to June, then increased sharply from June to August, and then decreased again from August to October. The seasonal variation of needle P concentration decreased first and then increased, which was more stable than needle N concentration. |
| 中文关键词 | 养分回收 ; 季节动态 ; 氮添加 ; 林下植被去除 ; 有效磷 |
| 英文关键词 | Nutrient resorption Seasonal dynamics Nitrogen addition understory removal Soil available phosphorus |
| 语种 | 中文 |
| 国家 | 中国 |
| 来源学科分类 | 生态学 |
| 来源机构 | 中国科学院沈阳应用生态研究所 |
| 资源类型 | 学位论文 |
| 条目标识符 | http://119.78.100.177/qdio/handle/2XILL650/287906 |
| 推荐引用方式 GB/T 7714 | 郑琳琳. 氮添加和林下植被去除对沙地樟子松养分回收的影响[D]. 中国科学院大学,2017. |
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