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凋落物是森林生态系统中连接植物和土壤养分的“纽带”,凋落物的凋落和分解是森林生态系统物质循环的基本过程之一[1]。凋落叶是凋落物的主要组成部分,其C、N、P含量及其比值在很大程度上反映了凋落物的分解速率、养分回归效率以及植物对土壤养分的利用策略[2-3],从而间接对一系列生态系统过程产生影响。凋落叶的C、N、P化学计量特征是目前研究森林生态系统物质循环的热点领域之一[4]。
森林生态系统的物种组成具有明显的区域特征,其凋落物的量、组成和凋落特征各不相同,从而影响生态系统过程和速率[5]。基于同一地区不同封育年限的研究表明,次生常绿阔叶林的物种组成变迁导致凋落物量和凋落节律有所差异,常绿阔叶树种在生长初期的集中落叶产生了第一个凋落物高峰,而针叶树种在生长季末的大量落叶对第二个凋落高峰的贡献更大[6]。基于鼎湖山的长期监测表明,常绿阔叶林凋落物量年际之间差异显著,且与群落的组成变化有关[7]。之前大量关于常绿阔叶林凋落物的研究主要集中于常绿阔叶树种的凋落节律,对于群落中其他生活型树种的凋落动态关注较少[8]。对同一群落中不同生活型树种凋落量及凋落节律进行研究有助于加深对常绿阔叶林物质循环过程的理解。
植物叶片C、N、P化学计量特征既反映了不同物种对土壤养分元素的利用能力及其差异化的生长适应对策,又是森林凋落物的主要组成部分,影响分解过程和元素周转效率[9]。
大量的研究表明,物候节律影响植物养分吸收策略,从而改变叶片及凋落叶中的C、N、P等元素的含量[10-12]。对北亚热带常绿阔叶林的研究表明,3个优势常绿阔叶树种叶片N、P含量在一个生长季内的模式各不相同[13]。在同样的气候条件下,人工林中常绿阔叶树种格氏栲(Castanopsis kawakamii Hayata)和常绿针叶树种杉木(Cunninghamia lanceolata (Lamb.) Hook.)叶片C、N、P含量及化学计量特征表现出明显的差异[14]。目前针对常绿阔叶林优势种(常绿阔叶树种)凋落物化学计量特征研究较多,而对同一群落中的不同生活型树种凋落叶的C、N、P化学计量特征的研究较少。
本研究在重庆市缙云山国家级自然保护区常绿阔叶林永久监测样地内对6个不同生活型树种的凋落叶进行了监测,分析不同物种叶凋落量及其凋落模式;探究凋落叶的C、N、P化学计量特征及其季节变化规律;探讨不同物种化学计量特征与其年均凋落叶产量的关系。
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缙云山国家级自然保护区位于重庆市北碚区境内,属于亚热带季风湿润性气候。年均气温14.8 ℃,年均降水量约1 610 mm。缙云山国家级自然保护区主要以保护中亚热带湿润常绿阔叶林地带性植被为主,栲(Castanopsis fargesii Franch.)、润楠(Machilus nanmu (Oliver) Hemsley)、四川大头茶(Polyspora speciosa (Kochs) B. M. Bartholomew & T. L. Ming)和光亮山矾(Symplocos lucida (Thunberg) Siebold & Zuccarini)为该区主要优势种[5]。保护区内植物种类丰富,有维管植物约1700种,是典型的亚热带常绿阔叶林物种基因库。
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采用典型的网格分布法将缙云山面积为1 hm2的常绿阔叶林永久监测样地均匀划分为100个10 m × 10 m的样方,在每个样方的中心点及4个顶点分别布设收集框,其有效收集面积为0.5 m2,共172个。每月末将收集框内的凋落物带回实验室,将凋落叶分离后鉴定至种后分别装入信封,于80 ℃的电热恒温鼓风干燥箱中烘干至恒质量,使用电子天平(分辨率0.0001 g)称量并记录数据。
研究对象包括栲和润楠2个常绿阔叶树种,马尾松(Pinus massoniana Lamb.)和杉木(Cunninghamia lanceolata(Lamb.)Hook.)2个常绿针叶树种以及赤杨叶(Alniphyllum fortunei (Hemsl.) Makino)和枫香树(Liquidambar formosana Hance)2个落叶阔叶树种,这6个树种相对胸高断面积之和达到68.14%,其2018年叶凋落量之和占样地凋落叶总量的63.3%(表1)。
表 1 缙云山6个树种凋落叶量和相对胸高断面积
Table 1. Litter fall and relative basal area of six tree species in Jinyun Mountain
树种 Species 生活型 Life form 叶年凋落量 Litter fall/(kg·hm−2) 相对胸高断面积 RBA/% 百分比 Ratio/% 栲 Castanopsis fargesii 常绿阔叶 1473.54 40.61 33.74 润楠 Machilus nanmu 常绿阔叶 584.30 12.09 13.51 马尾松 Pinus massoniana 常绿针叶 119.04 2.31 2.70 杉木 Cunninghamia lanceolata 常绿针叶 198.36 7.12 4.54 赤杨叶 Alniphyllum fortune 落叶阔叶 203.06 2.47 4.60 枫香树 Liquidambar formosana 落叶阔叶 186.59 3.54 4.22 -
对于同一物种,将烘干后的叶片混匀,从中随机挑选3份作为重复,共216个样本,进行元素测定。首先将叶片用球磨机粉碎成粉末,取出0.02~0.03 g放入岛津TOC-TN分析仪的固体进样舟对总碳含量进行直接测定(LY/T 1237—1999);总氮和总磷含量测定前,称取0.1 g左右粉末用98%的H2SO4和30%的H2O2在石墨炉中充分消解,然后用岛津TOC-TN分析仪测定总氮含量(LY/T 1269—1999),用钼锑钪分光光度法测定总磷含量(LY/T 1270—1999)。
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采用多重比较对不同物种、不同生活型和不同季节的凋落叶的C、N、P含量及相应N∶P化学计量比进行差异显著性检验(P = 0.05)。所有的分析和作图在R软件中进行(R Core Team, 2015)。
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缙云山常绿阔叶林凋落叶整体呈现双峰型模式。栲凋落叶月动态为双峰型,在5月达到峰值,并且在10月有一个小高峰;润楠凋落叶表现为单峰型,峰值出现在4月;赤杨叶凋落叶为双峰型,峰值出现在8月;枫香树凋落叶为单峰型,峰值出现在11月。马尾松凋落叶表现为不规则型;杉木凋落叶表现为双峰型,峰值出现在3月(图1、图2)。
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缙云山6个树种凋落叶的C含量在481.35~542.23 g·kg−1之间,不同物种之间差异显著。N含量在5.64~11.85 g·kg−1之间,赤杨叶最高,马尾松最低。P含量在0.39~0.72 g·kg−1之间,马尾松最低,赤杨叶最高;C∶N、C∶P范围分别为45.18~97.12、825.74~1 488.15,均为赤杨叶最低,马尾松最高,N∶P范围为13.05~19.15,杉木最低,栲最高(表2)。
表 2 缙云山6个常见种凋落叶的C、N、P含量及化学计量比(平均值 ± 标准差)
Table 2. Litter fall C, N, P contents and stoichiometry of the six common tree species(mean ± SD)
物种 Species C/(g·kg−1) N/(g·kg−1) P/(g·kg−1) C∶N C∶P N∶P 栲 Castanopsis fargesii 501.58 ± 28.40 b 9.47 ± 2.66 c 0.51 ± 0.14 ab 56.79 ± 14.54 b 1036.86 ± 242.31 ab 19.15 ± 5.65 d 润楠 Machilus nanmu 531.27 ± 7.50 c 7.23 ± 1.41 b 0.56 ± 0.17 b 75.92 ± 13.17 c 1045.94 ± 326.30 ab 13.58 ± 2.54 ab 马尾松 Pinus massoniana 529.56 ± 10.94 c 5.64 ± 1.11 a 0.39 ± 0.12 a 97.12 ± 17.91 d 1488.15 ± 474.18 c 15.15 ± 3.20 ab 杉木 Cunninghamia lanceolata 542.23 ± 12.21 d 6.25 ± 1.41 ab 0.49 ± 0.12 ab 90.84 ± 19.32 d 1180.07 ± 353.91 b 13.05 ± 2.62 a 赤杨叶 Alniphyllum fortunei 522.38 ± 10.13 c 11.85 ± 2.00 d 0.72 ± 0.35 c 45.18 ± 6.90 a 825.74 ± 221.93 a 18.20 ± 4.38 cd 枫香树 Liquidambar formosana 481.35 ± 14.32 a 9.53 ± 2.32 c 0.62 ± 0.21 bc 53.02 ± 10.94 ab 856.63 ± 272.19 a 16.19 ± 3.99 bc 注:同列不同字母表示差异极显著(P < 0.05)
Note: Different lowercase letters within the same column indicate significant differences (P < 0.05) -
栲、枫香树和杉木凋落叶C含量月份间波动较大,润楠、赤杨叶和马尾松凋落叶C含量月份间比较稳定(图3a);6个树种凋落叶N含量月份间的波动都较大(图3b);6个树种凋落叶P含量月份间相对比较稳定,但赤杨叶和枫香树在5月份出现一个较高的峰值(图3c);6个树种N∶P值在8—11月份明显高于其他月份(图3d)。
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马尾松凋落叶C含量与凋落叶产量呈显著正相关关系,其他5个物种凋落叶C含量与凋落叶产量无显著相关关系(图4a);赤杨叶凋落叶N含量与凋落叶产量呈显著正相关关系(图4b);栲、马尾松凋落叶P含量与凋落叶产量呈显著负相关关系(图4c);马尾松凋落叶N∶P与凋落叶产量呈显著正相关关系(图4d)。
缙云山常绿阔叶林6个树种凋落叶量及其C、N、P化学计量学季节动态研究
Seasonal Dynamics of Litterfall and C, N, and P Stoichiometric Characteristics of Six Tree Species in An Evergreen Broad-Leaved Forest on Jinyun Mountains
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摘要:
目的 研究6个树种凋落叶C、N、P化学计量学特征及季节动态,分析其与凋落叶量之间的关系。 方法 利用网格法在样地内均匀布设172个凋落叶收集框,每月末定期将收集框内的凋落叶带回实验室,进行分类称量,粉碎后测量其C、N、P元素含量。 结果 (1)缙云山6个树种的凋落节律各不相同。常绿阔叶树种栲(Castanopsis fargesii)和润楠(Machilus nanmu)、常绿针叶树种杉木(Cunninghamia lanceolata)的凋落高峰出现在春季;落叶树种赤杨叶(Alniphyllum fortune)凋落高峰出现在夏季;落叶树种枫香树(Liquidambar formosana)凋落高峰出现在冬季;常绿针叶树种马尾松(Pinus massoniana)全年无明显的凋落高峰。(2)6个树种凋落叶的C、N、P含量分别在481.35~542.23、5.64~11.85、0.39~0.72 g·kg−1之间,N∶P范围为13.05~19.15。(3)6个树种C、N、P含量季节动态明显。马尾松凋落叶C含量与凋落叶产量呈显著正相关关系(P < 0.05),赤杨叶凋落叶N含量与凋落叶产量呈显著正相关关系(P < 0.05),栲和马尾松凋落叶P含量与凋落叶产量呈显著负相关关系(P < 0.05),马尾松凋落叶N∶P与凋落叶产量呈显著正相关关(P < 0.05)。 结论 缙云山常绿阔叶林6个树种凋落叶季节动态各不相同;6个物种呈现出低N和低P的格局,总体表现为受N、P共同限制,且N限制作用要强于P限制;在一个生长季内,6个树种C、N、P化学计量学特征月份间的差异较大,凋落叶量与凋落叶C、N、P含量之间的关系与物种特性有关;凋落叶量与凋落物化学计量特征关系不明显。 Abstract:Objective Taking 6 tree species in an evergreen broad-leaved forest in Jinyun Mountain National Nature Reserve as object to study the stoichiometric characteristics and seasons of litter C, N and P and analyze the relationship between them and the amount of litter. Method The grid method was used to evenly arrange 172 litter leaf collection frames in the plot. At the end of each month, the leaf litter in the collection frame were regularly collected for classification and weighing in laboratory. After crushing, the contents of C, N, P element were measured. Result (1) The seasonal variation of leaf litter of the six tree species were different. The litter peaks of the evergreen broad-leaved tree species Castanopsis fargesii and Machilus nanmu, and evergreen coniferous species Cunninghamia lanceolata appeared in spring; the litter peak of deciduous tree species Alniphyllum fortune appeared in summer; the wither peak of deciduous tree species Liquidambar formosana appeared in winter; while the evergreen coniferous tree species Pinus massoniana had no obvious wither peaks throughout the year. (2) The C, N and P contents of the litter of the six tree species were 481.35~542.23, 5.64~11.85, and 0. 39~0.72 g·kg −1, the N: P range was 13.05~19.15. The deciduous broad-leaved tree species had higher N and P contents, and the evergreen coniferous species had lower N and P contents. (3) The seasonal dynamics of C, N and P contents of the six tree species were obvious. There was a significant positive correlation between the C content of Pinus massoniana and the yield of litter (P < 0.05), the N content of Alniphyllum fortune and the yield of litter was significantly positively correlated (P < 0.05), the P content of Castanopsis fargesii and Pinus massoniana litter leaves showed a significantly negative correlation with the yield of litter leaves (P < 0.05), and the N: P of litter leaves of Pinus massoniana showed a positive correlation with the yield of litter (P < 0. 05). Conclusion The seasonal dynamics of the litter of six tree species in the evergreen broad-leaved forest of Jinyun Mountain are different. These six species show a pattern of low N and low P. The overall performance is limited by N and P together, and the N limiting effect is stronger than the P limiting. Within a growing season, the C, N, and P stoichiometric characteristics of the six species vary greatly from month to month, and the relationship between the amount of litter and the C, N, and P contents of the litter is related to the species characteristics. The relationship between quantity of litter and its stoichiometry is not obvious. -
Key words:
- evergreen broad-leaved forest
- / litter
- / stoichiometric characteristics
- / life form
- / seasonal dynamics
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表 1 缙云山6个树种凋落叶量和相对胸高断面积
Table 1. Litter fall and relative basal area of six tree species in Jinyun Mountain
树种 Species 生活型 Life form 叶年凋落量 Litter fall/(kg·hm−2) 相对胸高断面积 RBA/% 百分比 Ratio/% 栲 Castanopsis fargesii 常绿阔叶 1473.54 40.61 33.74 润楠 Machilus nanmu 常绿阔叶 584.30 12.09 13.51 马尾松 Pinus massoniana 常绿针叶 119.04 2.31 2.70 杉木 Cunninghamia lanceolata 常绿针叶 198.36 7.12 4.54 赤杨叶 Alniphyllum fortune 落叶阔叶 203.06 2.47 4.60 枫香树 Liquidambar formosana 落叶阔叶 186.59 3.54 4.22 表 2 缙云山6个常见种凋落叶的C、N、P含量及化学计量比(平均值 ± 标准差)
Table 2. Litter fall C, N, P contents and stoichiometry of the six common tree species(mean ± SD)
物种 Species C/(g·kg−1) N/(g·kg−1) P/(g·kg−1) C∶N C∶P N∶P 栲 Castanopsis fargesii 501.58 ± 28.40 b 9.47 ± 2.66 c 0.51 ± 0.14 ab 56.79 ± 14.54 b 1036.86 ± 242.31 ab 19.15 ± 5.65 d 润楠 Machilus nanmu 531.27 ± 7.50 c 7.23 ± 1.41 b 0.56 ± 0.17 b 75.92 ± 13.17 c 1045.94 ± 326.30 ab 13.58 ± 2.54 ab 马尾松 Pinus massoniana 529.56 ± 10.94 c 5.64 ± 1.11 a 0.39 ± 0.12 a 97.12 ± 17.91 d 1488.15 ± 474.18 c 15.15 ± 3.20 ab 杉木 Cunninghamia lanceolata 542.23 ± 12.21 d 6.25 ± 1.41 ab 0.49 ± 0.12 ab 90.84 ± 19.32 d 1180.07 ± 353.91 b 13.05 ± 2.62 a 赤杨叶 Alniphyllum fortunei 522.38 ± 10.13 c 11.85 ± 2.00 d 0.72 ± 0.35 c 45.18 ± 6.90 a 825.74 ± 221.93 a 18.20 ± 4.38 cd 枫香树 Liquidambar formosana 481.35 ± 14.32 a 9.53 ± 2.32 c 0.62 ± 0.21 bc 53.02 ± 10.94 ab 856.63 ± 272.19 a 16.19 ± 3.99 bc 注:同列不同字母表示差异极显著(P < 0.05)
Note: Different lowercase letters within the same column indicate significant differences (P < 0.05) -
[1] Hobbie S E. Plant species effects on nutrient cycling: revisiting litter feedbacks.[J]. Trends in Ecology & Evolution, 2015, 30(6): 357-363. [2] Berg B, McClaugherty C. Plant Litter, Decomposition, Humus Formation, Carbon Sequestration[M]. Berlin: Springer, 2014. [3] Riikka R, Anders M, Sven J. Effects of litter addition and warming on soil carbon, nutrient pools and microbial communities in a subarctic heath ecosystem[J]. Applied Soil Ecology, 2008, 39(3): 271-281. doi: 10.1016/j.apsoil.2007.12.014 [4] Tessier J T, Raynal D J. Use of nitrogen to phosphorus ratios in plant tissue as an indicator of nutrient limitation and nitrogen saturation[J]. Journal of Applied Ecology, 2003, 40(3): 523-534. doi: 10.1046/j.1365-2664.2003.00820.x [5] 杨 超, 黄 力, 高祥阳, 等. 缙云山常绿阔叶林凋落动态及组成[J]. 林业科学研究, 2016, 29(1):1-9. doi: 10.3969/j.issn.1001-1498.2016.01.001 [6] 兰长春. 肖坑亚热带常绿阔叶林凋落物量及养分动态[D]. 合肥: 安徽农业大学, 2008. [7] 官丽莉, 周国逸, 张德强, 等. 鼎湖山南亚热带常绿阔叶林凋落物量20年动态研究[J]. 植物生态学报, 2004, 28(4):449-456. doi: 10.3321/j.issn:1005-264X.2004.04.002 [8] 阎恩荣, 王希华, 郭 明, 等. 浙江天童常绿阔叶林、常绿针叶林与落叶阔叶林的C: N: P化学计量特征[J]. 植物生态学报, 2010, 34(1):48-57. doi: 10.3773/j.issn.1005-264x.2010.01.008 [9] Aerts R, Chapin F S. The mineral nutrition of wild plants revisited: A re-evaluation of processes and patterns[J]. Advances in Ecological Research, 1999, 30: 1-67. doi: 10.1016/S0065-2504(08)60016-1 [10] Yang Y H, Luo Y Q. Carbon: nitrogen stoichiometry in forest ecosystems during stand development[J]. Global Ecology and Biogeography, 2011, 20(2): 354-361. doi: 10.1111/j.1466-8238.2010.00602.x [11] Zhang H C, Yuan W P, Dong W J, et al. Seasonal patterns of litterfall in forest ecosystem worldwide[J]. Ecological Complexity, 2014, 20(12): 240-247. [12] Darren S B, Gavin N R, Alison M M, et al. The short-term effects of salinization on anaerobic nutrient cycling and microbial community structure in sediment from a freshwater wetland[J]. Wetlands, 2006, 26(2): 455-464. doi: 10.1672/0277-5212(2006)26[455:TSEOSO]2.0.CO;2 [13] 柯 立, 杨 佳, 余 鑫, 等. 北亚热带常绿阔叶林三优势树种叶水平碳氮磷化学计量及季节变化特征[J]. 土壤通报, 2014, 45(5):1170-1174. [14] 孟庆权, 葛露露, 林 宇, 等. 格氏栲天然林及人工林和杉木人工林生活叶-凋落叶-土壤生态化学计量特征[J]. 西北林学院学报, 2019, 34(6):8-15. doi: 10.3969/j.issn.1001-7461.2019.06.02 [15] 袁 方. 缙云山常绿阔叶林凋落物组成、动态及其影响因素研究[D]. 重庆: 重庆大学, 2018. [16] 吴擢溪. 人促常绿阔叶次生林凋落物数量、组成及动态[J]. 山地学报, 2006, 24(2):215-221. doi: 10.3969/j.issn.1008-2786.2006.02.015 [17] 徐定兰. 官山森林大样地凋落物产量、储量及分解动态[D]. 南昌: 江西农业大学, 2019. [18] Kikuzawa K. Phenological and morphological adaptations to the light environment in two woody and two herbaceous plant species[J]. Functional Ecology, 2003, 17(1): 29-38. doi: 10.1046/j.1365-2435.2003.00707.x [19] 龚 滨. 浙江天童8种常绿乔木树种的叶片生活史研究[D]. 南京: 南京师范大学, 2014. [20] 夏洋洁. 浙江天童国家森林公园常绿阔叶植物二次抽枝进程研究[D]. 南京: 南京师范大学, 2013. [21] 杨智杰, 陈光水, 谢锦升, 等. 杉木、木荷纯林及其混交林凋落物量和碳归还量[J]. 应用生态学报, 2010, 21(9):2235-2240. [22] 宁晓波, 项文化, 王光军, 等. 湖南会同连作杉木林凋落物量20年动态特征[J]. 生态学报, 2009, 29(9):5122-5129. doi: 10.3321/j.issn:1000-0933.2009.09.063 [23] 徐旺明, 闫文德, 李洁冰, 等 亚热带4种森林凋落物量及其动态特征[J]. 生态学报, 2013, 33(23): 7570-7575. [24] 樊后保, 苏兵强, 刘春华, 等. 林下套种阔叶树的马尾松林凋落物生态学研究Ⅱ. 凋落物养分归还动态[J]. 福建林学院学报, 2003, 23(2):97-101. doi: 10.3969/j.issn.1001-389X.2003.02.001 [25] 卢立华, 贾宏炎, 何日明, 等 南亚热带6种人工林凋落物的初步研究[J]. 林业科学研究, 2008, 21(3): 346-352. [26] 贺金生, 韩兴国. 生态化学计量学: 探索从个体到生态系统的统一化理论[J]. 植物生态学报, 2010, 34(1):2-6. doi: 10.3773/j.issn.1005-264x.2010.01.002 [27] 杨会侠, 汪思龙, 范 冰, 等 不同林龄马尾松人工林年凋落量与养分归还动态[J]. 生态学杂志, 2010, 29(12): 2334-2340. [28] 张首和. 天童常绿阔叶林凋落叶养分的时空分布特征及其影响因素[D]. 上海: 华东师范大学, 2019. [29] Elser J J, Fagan W F, Denno R F, et al. Nutritional constraints in terrestrial and freshwater food webs[J]. Nature, 2000, 408(6812): 578-580. doi: 10.1038/35046058 [30] Han W X, Fang J Y, Guo D L, et al. Leaf nitrogen and phosphorus stoichiometry across 753 terrestrial plant species in China[J]. New Phytologist, 2005, 168(2): 377-385. doi: 10.1111/j.1469-8137.2005.01530.x [31] 曾昭霞, 王克林, 刘孝利, 等. 桂西北喀斯特森林植物-凋落物-土壤生态化学计量特征[J]. 植物生态学报, 2015, 39(7):682-693. doi: 10.17521/cjpe.2015.0065 [32] Liu C, Berg B, Kutsch W, et al. Leaf litter nitrogen concentration as related to climatic factors in Eurasian forests[J]. Global Ecology and Biogeography, 2006, 15(5): 438-444. doi: 10.1111/j.1466-822X.2006.00251.x [33] Kang H Z, Xin Z J, Berg B, et al. Global pattern of leaf litter nitrogen and phosphorus in woody plants[J]. Annals of Forest Science, 2010, 67(8): 811p1-811p8. [34] 邢雪荣, 韩兴国, 陈灵芝. 植物养分利用效率研究综述[J]. 应用生态学报, 2000, 11(5): 785-790.. [35] Yuan Z Y, Chen H Y H. Global trends in senesced-leaf nitrogen and phosphorus[J]. Global Ecology & Biogeography, 2010, 18(5): 532-542.