氮磷添加对内蒙古温带典型草原净氮矿化的影响

doi:10.17521/cjpe.2015.0374

摘要/Abstract

摘要：

氮素矿化是决定土壤供氮能力的重要生态过程, 也是目前国内外土壤氮循环研究的重点。养分添加在调节土壤的氮转化方面起着重要的作用。该文以内蒙古锡林河流域温带典型草原为研究对象, 通过不同水平的氮(N)和磷(P)养分添加实验, 利用树脂芯原位培养法分析研究不同水平施氮、施磷对生长季草地土壤氮矿化的影响。结果表明: 高氮处理对草地土壤硝态氮(NO₃^--N)、铵态氮(NH₄⁺-N)及无机氮都有明显的影响, 其中25 g N·m^?2·a^?1和10 g N·m^?2·a^?1高氮处理显著提高了无机氮含量, 25 g N·m^?2·a^?1高氮处理显著增加土壤的NO₃^--N及NH₄⁺-N含量。与施氮相比, 施磷处理对土壤NO₃^--N、NH₄⁺-N及无机氮的影响较为有限, 只有12.5 g P₂O₅·m^-2·a^-1的磷处理显著促进了NO₃^--N及无机氮含量。高氮处理对草地土壤氮素转化有明显影响, 其中25 g N·m^?2·a^?1高氮处理对净硝化速率、氨化速率及矿化速率都有显著的促进作用, 说明高梯度的施氮处理有利于提高土壤的供氮能力。氮是内蒙古锡林河流域草原生态系统有机氮矿化的限制因子。与施氮相比, 施磷处理对草地土壤氮转化的作用较为有限, 仅有12.5 g P₂O₅·m^-2·a^-1+ 2 g N·m^?2·a^?1处理显著促进生长季中期的净氨化速率。说明施磷对土壤氮转化的影响弱于施氮的影响。养分添加显著提高了草地的地上生物量。养分添加情景下, 土壤湿度与净矿化速率极显著相关, 表明湿度是影响该区域温带草原土壤氮矿化的主效因素。环境因子(如有机碳含量、土壤全氮及土壤C/N)与不同氮处理下的净矿化速率之间显著相关, 而土壤微生物碳、氮含量与土壤氮矿化均没有显著相关性。

关键词: 温带草原, 氮磷添加, 氮矿化, 无机氮, 影响因子

Abstract: <i>Aims</i>

Nitrogen (N) mineralization is an important ecological process which determines soil N supplying ability, and it is a key research domain of soil N cycling worldwide at present. Nutrient addition can play a key role in regulating soil N transformations. The objective of the study was to evaluate the effects of different levels of N and P additions on in situ N mineralization during growing seasons in the temperate grasslands.

<i>Methods</i>

We conducted an field N and P fertilization addition experiment in the temperate grassland in Nei Mongol in June 2014. Five levels of N (0-25 g N·m^?2·a^?1), five levels of P (0-12.5 g P₂O₅·m^-2·a^-1) addition treatments, and a control were set up. We measured the in situ net mineralization rate, ammonification rate, and nitrification rate using the resin core incubation technique once a month from July to October 2014. Aboveground biomass and some selected soil chemical and microbial properties were also measured in the study.

Important findings

High nitrogen addition did significantly affect the contents of inorganic N. High N addition levels (25 g N·m^?2·a^?1+ 1 g P₂O₅·m^-2·a^-1 and 10 g N·m^?2·a^?1+ 1 g P₂O₅·m^-2·a^-1) significantly increased soil inorganic N content, and the 25 g N·m^?2·a^?1+ 1 g P₂O₅·m^-2·a^-1 treatment markedly increased soil nitrate- (NO₃^--N) and ammonium-N (NH₄⁺-N). Compared to N addition, P addition had limited effects on soil inorganic N, NO₃^--N and NH₄⁺-N. Only the 12.5 g P₂O₅·m^-2·a^-1 + 2 g N·m^?2·a^?1treatment significantly increased soil ammonium-N and inorganic N. N addition did significantly affect microbial N transformation rates. The 25 g N·m^?2·a^?1+ 1 g P₂O₅·m^-2·a^-1 treatment significantly stimulated soil net N nitrification rate, mineralization rate and ammonification rate, suggesting that high N addition can effectively improve soil available N supply. N was a limiting factor to soil organic N mineralization in the study area. P addition had negligible effects on soil net N mineralization and nitrification rates, and only the 12.5 g P₂O₅·m^-2·a^-1+ 2 g N·m^?2·a^?1treatment significantly enhanced ammonification rate in the middle of growing season. The results also indicated that impacts of P addition on soil N mineralization were weaker than impacts of N. Moreover, N and P addition significantly increased aboveground biomass. Under the N and P addition, soil moisture was significantly correlated with net mineralization and nitrification rate, which suggested that it was one of the dominant factors affecting N. Net N mineralization and nitrification rate under N fertilization was significantly correlated with environmental factors (soil organic C, soil C/N and soil total N). Soil N mineralization was not positively correlated with the soil microbial biomass N or C.

Key words: temperate grassland, N and P additions, nitrogen mineralization, soil inorganic N, affecting factor

罗亲普, 龚吉蕊, 徐沙, 宝音陶格涛, 王忆慧, 翟占伟, 潘琰, 刘敏, 杨丽丽. 氮磷添加对内蒙古温带典型草原净氮矿化的影响. 植物生态学报, 2016, 40(5): 480-492. DOI: 10.17521/cjpe.2015.0374

Qin-Pu LUO, Ji-Rui GONG, Sha XU, Taogetao BAOYIN, Yi-Hui WANG, Zhan-Wei ZHAI, Yan PAN, Min LIU, Li-Li YANG. Effects of N and P additions on net nitrogen mineralization in temperate typical grasslands in Nei Mongol, China. Chinese Journal of Plant Ecology, 2016, 40(5): 480-492. DOI: 10.17521/cjpe.2015.0374

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链接本文: https://www.plant-ecology.com/CN/10.17521/cjpe.2015.0374

https://www.plant-ecology.com/CN/Y2016/V40/I5/480

图/表 7

图1 不同氮处理下的土壤NO3--N (A)、NH4+-N (B)及无机氮含量(C)的时间变化(平均值±标准偏差, n = 3)。竖线表示不同氮处理间的差异显著性(p < 0.05)。CK, 对照, 未添加氮素和磷素。N1、N2、N3、N4、N5分别添加氮素0、2、5、10、25 g N·m?2·a?1, 添加磷素1 g P2O5·m?2·a?1。

Fig. 1 Temporal variations of soil NO3--N (A), NH4+-N (B) and soil inorganic N concentration (C) under different N treatments (mean ± SD, n = 3). The vertical line denotes the least significant difference among different N treatments (p < 0.05). CK, control, without nitrogen and phosphorus. N1, N2, N3, N4, N5 add nitrogen 0, 2, 5, 10, 25 g N·m?2·a?1, respectively. Other than in the control, 1 g P2O5·m?2·a?1 is added to each treatment.

图2 不同磷处理下的土壤NO3- -N (A)、NH4+ -N (B)及无机氮含量(C)的时间变化(平均值±标准偏差, n = 3)。竖线表示不同磷处理间的差异显著性(p < 0.05)。CK, 对照, 未添加氮素和磷素。P1、P2、P3、P4、P5分别添加磷素0、1、2.5、5、12.5 g P2O5·m?2·a?1, 添加氮素2 g N·m?2·a?1。

Fig. 2 Temporal variations of soil NO3--N (A), NH4+-N (B) and soil inorganic N concentration (C) under different P treatments (mean ± SD, n = 3). The vertical line denotes the least significant difference among different P treatments (p < 0.05). CK, control, without nitrogen and phosphorus. P1, P2, P3, P4, P5 add phosphorus 0, 1, 2.5, 5, 12.5 g P2O5·m?2·a?1, respectively. Other than in the control, 2 g N·m?2·a?1 is added to each treatment.

图3 不同氮处理下, 不同时间段的净硝化速率(A)、氨化速率(B)及矿化速率(C) (平均值±标准偏差, n = 3)。不同字母代表差异显著(p < 0.05)。n.s.表示处理间差异不显著。处理同图1。

Fig. 3 Soil net N nitrification (A), ammonification rates (B) and mineralization rates (C) in different periods under different N treatments (mean ± SD, n = 3). Different lowercase letters represent significant differences at p < 0.05. Non-significant differences are indicated by n.s. Treatment see Fig. 1.

图4 不同磷处理下, 不同时间段的净硝化速率(A)、氨化速率(B)及净矿化速率(C) (平均值±标准偏差, n = 3)。同一培养时期比较, 不同字母代表差异显著(p < 0.05)。n.s.表示处理间差异不显著。处理同图2。

Fig. 4 Soil net N nitrification (A), ammonification rates (B) and mineralization rates (C) in different periods under different P treatments (mean ± SD, n = 3). Different lowercase letters represent significant differences at p < 0.05. Non-significant differences are indicated by n.s. Treatment see Fig. 2.

图5 2014年8月份不同氮(A)、磷处理(B)下的地上生物量(平均值±标准偏差, n = 3)。不同字母分别表示处理间差异显著(p < 0.05)。CK, 对照, 未添加氮素和磷素。N1、N2、N3、N4、N5分别添加氮素0、2、5、10、25 g N·m?2·a?1, 添加磷素1 g P2O5·m?2·a?1。 P1、P2、P3、P4、P5分别添加磷素0、1、2.5、5、12.5 g P2O5·m?2·a?1, 添加氮素2 g N·m?2·a?1。

Fig. 5 The aboveground biomass under different N (A) and P addition treatments (B) in August of 2014 (mean ± SD, n = 3). Different lowercase letters represent significant differences at p < 0.05. CK, control, without nitrogen and phosphorus. N1, N2, N3, N4, N5 add nitrogen 0, 2, 5, 10, 25 g N·m?2·a?1, respectively. P1, P2, P3, P4, P5 add phosphorus 0, 1, 2.5, 5, 12.5 g P2O5·m?2·a?1, respectively. Other than in the control, 1 g P2O5·m?2·a?1 is added to each treatment in the N addition experiment, and 2 g N·m?2·a?1 is added to each treatment in the P addition experiment.

表1 不同氮处理下的净矿化、硝化及氨化速率与环境及生物因子之间的相关性

Table 1 Correlation between environmental/biological factors and net N mineralization, nitrification, and ammonification rates under different N addition treatments

环境及生物因子 Environment/biological factor	净矿化速率 Mineralization (mg·kg^-1·d^-1)	净硝化速率 Nitrification (mg·kg^-1·d^-1)	净氨化速率 Ammonification (mg·kg^-1·d^-1)
土壤湿度 Soil moisture (V/V)	0.825^***	0.813^***	0.323
土壤温度 Soil temperature (℃)	0.142	0.114	0.245^*
土壤有机碳 Soil organic C (g·kg^-1)	0.887^*	0.879^*	0.418
土壤全氮 Soil total N (%)	0.848^*	0.830^*	0.612
土壤碳氮比 Soil C:N ratio	0.849^*	0.858^*	0.014
微生物碳 Microbial biomass C (mg·kg^-1)	0.422	0.410	0.396
微生物氮 Microbial biomass N (mg·kg^-1)	0.298	0.266	0.791

表2 不同磷处理下的净矿化、硝化及氨化速率与环境及生物因子之间的相关性

Table 2 Correlation between environmental/biological factors and net N mineralization, nitrification, and ammonification rates under various P addition treatments

环境及生物因子 Environment/biological factor	矿化速率 Mineralization (mg·kg^-1·d^-1)	硝化速率 Nitrification (mg·kg^-1·d^-1)	氨化速率 Ammonification (mg·kg^-1·d^-1)
土壤湿度 Soil moisture (V/V)	0.730^***	0.673^**	0.10
土壤温度 Soil temperature (℃)	0.246	0.326	0.725^**
土壤有机碳 Soil organic C (g·kg^-1)	0.527	0.626	0.601
土壤全氮 Soil total N (%)	0.372	0.544	0.662
土壤碳氮比 Soil C:N ratio	0.573	0.292	0.251
微生物碳 Microbial biomass C (mg·kg^-1)	0.269	0.308	0.280
微生物氮 Microbial biomass N (mg·kg^-1)	0.391	0.511	0.556

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