氮添加对人工油松林叶凋落物分解的影响
发布时间：2019-01-17 10:44
【摘要】：凋落物分解是森林生态系统物质循环和能量流动的重要环节。目前持续增加的氮(N)沉降正在显著影响着森林生态系统的物质循环和能量流动过程。然而对于N沉降对凋落物分解的过程和机制还不是十分清楚。对此,本研究于2014年至2016年,在宜川铁龙湾林场对人工油松林进行N添加实验,共设置4个N添加处理(0,3,6,9gNm-2a-1),通过埋袋法研究N添加条件下油松叶凋落物分解动态过程变化规律,所得结果如下:(1)叶凋落物分解具有明显的阶段性:分解初期(0-60天)凋落叶分解速率较高,中期(60-180天)分解较慢,在后期(180-300天)分解速率有所增高,分解300天后凋落物质量残留率分别为72.66%(CK)、72.40%(N3)、69.08%(N6)、70.11%(N9)。利用Olson指数衰减模型求得各处理的分解系数,各处理分解系数k值为0.368(CK)、0.341(N3)、0.424(N6)、0.388(N9)。(2)N添加增加了叶凋落物初始N含量,P含量和NSC含量,对初始C含量和木质素含量影响较小。N添加处理对凋落物元素和化学组成含量以及化学计量比有不同的作用:N添加促进了 C元素的释放;N3处理凋落物N含量显著高于CK和N6处理,而初始N含量越高,N释放速率越快;N添加对分解过程中P元素的影响较小;N添加对凋落物NSC降解有促进作用;N3处理对木质素降解影响较小,N6和N9处理显著促进了木质素降解;分解过程中施N处理的C/N、C/P、木质素/N低于CK处理。(3)短期N添加对表层土壤水稳性团聚体含量无显著影响;随着N添加水平增加,大、微团聚体有机碳含量,大、微团聚体中活性和高活性有机碳含量呈先升高后降低的变化规律,并在N6处理(6 gNm-2 a-1)下上述各指标达到最大。短期N添加主要通过影响表层大、微团聚体中的中活性有机碳进而影响土壤表层有机碳含量。主成分分析表明,N添加改变了土壤理化性质,进而导致根系生物量增加和凋落物分解,是表层土壤团聚体活性有机碳变化的主要原因。(4)通径分析表明,不同处理下影响凋落物分解的因素不尽相同,木质素含量是影响凋落物分解的主要因素。N添加对木质素降解的影响大小与N添加量以及受之影响的凋落物基质质量和分解环境有关。CK和N3处理会因为叶凋落物N含量的影响使木质素降解受到抑制。总之,低N(3 gN·m-2·a-1)添加对人工油松林叶凋落物分解无影响,中N(6gN·m-2·a-1)和高N(9gN·m-2·a-1)添加加快了叶凋落物分解。利用凋落物初始N含量、C/N、C/P、木质素/N并不能够准确预测凋落物的分解过程,而木质素含量能很好地预测凋落物分解。
[Abstract]:Litter decomposition is an important link of material circulation and energy flow in forest ecosystem. At present, the increasing nitrogen (N) deposition is significantly affecting the material cycle and energy flow process of forest ecosystem. However, the process and mechanism of N deposition for litter decomposition are not well understood. From 2014 to 2016, the experiment was carried out on artificial Pinus tabulaeformis forest in Tielongwan Forest Farm, Yichuan. The dynamic process of litter decomposition of Pinus tabulaeformis was studied by burying bag method. The results were as follows: (1) the decomposition rate of leaf litter in the early stage (0-60 days) was higher than that in the early stage (0-60 days). The decomposition rate increased in the late stage (180-300 days), and the residual rate of litter weight was 72.66% (CK), (N3) and 69.08% (N6), respectively, in the middle period (60-180 days). 70.11% (N9). The decomposition coefficients of each treatment were obtained by using Olson exponent attenuation model. The decomposition coefficients of each treatment were 0.368 (CK), 0.341 (N3), 0.424 (N6), 0.388 (N9). (2) N, and the initial N content of leaf litter was increased. P content and NSC content had little effect on initial C content and lignin content. N addition had different effects on litter element and chemical composition content and stoichiometric ratio. The N content of litter in N _ 3 treatment was significantly higher than that in CK and N _ 6 treatments, but the higher the initial N content was, the faster the N release rate was, the smaller the effect of N addition on the decomposition of P element, and the effect of N addition on the degradation of NSC in litter. N3 treatment had little effect on lignin degradation, while N6 and N9 treatments significantly promoted lignin degradation. The lignin / N ratio of C / N / P in N treatment was lower than that in CK treatment. (3) Short-term N addition had no significant effect on the content of water-stable aggregates in surface soil. With the increase of N addition level, the content of organic carbon in microaggregates and microaggregates increased first and then decreased, while the content of active and highly active organic carbon in microaggregates increased first and then decreased. Under N6 treatment (6 gNm-2 a-1), the above indexes reached the maximum. Short-term N addition mainly affected the content of soil surface organic carbon by influencing the content of medium active organic carbon in microaggregates. Principal component analysis (PCA) showed that N addition changed soil physical and chemical properties, which led to the increase of root biomass and decomposition of litter, which was the main reason for the change of active organic carbon in surface soil aggregates. (4) path analysis showed that: 1. The factors affecting litter decomposition were different under different treatments. Lignin content is the main factor affecting litter decomposition. The effect of N addition on lignin degradation is related to N addition and the quality of litter substrate affected by N addition and decomposition environment. CK and N3 treatment will cause leaf withering. The degradation of lignin was inhibited by the effect of N content. In conclusion, low N (3 gN m-2 a-1) addition had no effect on leaf litter decomposition in artificial Pinus tabulaeformis forest, but medium N (6gN m-2 a-1) and high N (9gN m-2 a-1) increased leaf litter decomposition. Using the initial N content of litter, C / N / P, lignin / N could not accurately predict the decomposition process of litter, but lignin content could predict litter decomposition very well.
【学位授予单位】：西北农林科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：S714
本文编号：2409981
[Abstract]:Litter decomposition is an important link of material circulation and energy flow in forest ecosystem. At present, the increasing nitrogen (N) deposition is significantly affecting the material cycle and energy flow process of forest ecosystem. However, the process and mechanism of N deposition for litter decomposition are not well understood. From 2014 to 2016, the experiment was carried out on artificial Pinus tabulaeformis forest in Tielongwan Forest Farm, Yichuan. The dynamic process of litter decomposition of Pinus tabulaeformis was studied by burying bag method. The results were as follows: (1) the decomposition rate of leaf litter in the early stage (0-60 days) was higher than that in the early stage (0-60 days). The decomposition rate increased in the late stage (180-300 days), and the residual rate of litter weight was 72.66% (CK), (N3) and 69.08% (N6), respectively, in the middle period (60-180 days). 70.11% (N9). The decomposition coefficients of each treatment were obtained by using Olson exponent attenuation model. The decomposition coefficients of each treatment were 0.368 (CK), 0.341 (N3), 0.424 (N6), 0.388 (N9). (2) N, and the initial N content of leaf litter was increased. P content and NSC content had little effect on initial C content and lignin content. N addition had different effects on litter element and chemical composition content and stoichiometric ratio. The N content of litter in N _ 3 treatment was significantly higher than that in CK and N _ 6 treatments, but the higher the initial N content was, the faster the N release rate was, the smaller the effect of N addition on the decomposition of P element, and the effect of N addition on the degradation of NSC in litter. N3 treatment had little effect on lignin degradation, while N6 and N9 treatments significantly promoted lignin degradation. The lignin / N ratio of C / N / P in N treatment was lower than that in CK treatment. (3) Short-term N addition had no significant effect on the content of water-stable aggregates in surface soil. With the increase of N addition level, the content of organic carbon in microaggregates and microaggregates increased first and then decreased, while the content of active and highly active organic carbon in microaggregates increased first and then decreased. Under N6 treatment (6 gNm-2 a-1), the above indexes reached the maximum. Short-term N addition mainly affected the content of soil surface organic carbon by influencing the content of medium active organic carbon in microaggregates. Principal component analysis (PCA) showed that N addition changed soil physical and chemical properties, which led to the increase of root biomass and decomposition of litter, which was the main reason for the change of active organic carbon in surface soil aggregates. (4) path analysis showed that: 1. The factors affecting litter decomposition were different under different treatments. Lignin content is the main factor affecting litter decomposition. The effect of N addition on lignin degradation is related to N addition and the quality of litter substrate affected by N addition and decomposition environment. CK and N3 treatment will cause leaf withering. The degradation of lignin was inhibited by the effect of N content. In conclusion, low N (3 gN m-2 a-1) addition had no effect on leaf litter decomposition in artificial Pinus tabulaeformis forest, but medium N (6gN m-2 a-1) and high N (9gN m-2 a-1) increased leaf litter decomposition. Using the initial N content of litter, C / N / P, lignin / N could not accurately predict the decomposition process of litter, but lignin content could predict litter decomposition very well.
【学位授予单位】：西北农林科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：S714
【引证文献】
相关硕士学位论文 前1条
1 史君怡;间伐和林下引种对人工刺槐林群落特征的影响[D];西北农林科技大学;2018年
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