阔叶林和针叶林土壤有机碳氮组分对氮添加的响应(3)
来源:未知 作者:chunt
发布于:2016-10-31 共14116字
土壤微生物降解过程也是影响土壤活性有机氮含量的重要因子之一,SMBLP代表单位活性有机碳氮组分向微生物生物量碳氮的转化量,可表征微生物的养分利用效率,同时可以指示微生物可利用的基质含量[4].该 研 究 中,氮 添 加 对 土 壤SMB-CLP-C和SMB-NLP-N有显着影响( 见表2) ,说明氮添加可以改变土壤微生物对底物的利用情况,当土壤氮素受限制时,不利于微生物利用底物,氮添加条件下,微生物解除氮的限制,有利于其利用底物[27].其中,除了杉木人工林土壤SMB-NLPⅠ-N随着氮添加水平的增加而降低土壤微生物对底物的利用外,浙江桂天然林和罗浮栲天然林均不同程度地提高了土壤碳氮组分的利用率。可见,输入土壤有机物性质的差异,确实可以通过微生物的利用情况来改变土壤碳氮组分的分配和转化,而氮添加对凋落物分解的作用有所差异[28]. Craine等[29]研究也表明,当土壤中活性有机碳氮组分含量减少时,微生物从惰性有机碳氮库中获取基质的能力提高,从而提高了养分利用效率。这可能是氮添加能发挥调节土壤碳氮组分变化的机理之一,在微生物参与下,不同氮添加水平和土壤原有环境下凋落物归还数量和质量的变化最终调节土壤碳氮组分间的相互转化,影响碳氮循环,重新达到另一种状态,而该模式正期待更多的试验证明。
3. 2不同林分对土壤有机碳氮的影响
不同植被类型通过输入凋落物质量的差异,在氮添加影响土壤碳循环中发挥重要作用[19]. WANG等[30]研究表明,亚热带不同植被类型( 次生阔叶林、杉木林、杉木与桤木混交林、杉木与刺楸混交林) 对土壤活性有机质( 微生物量碳氮、水溶性有机碳氮、轻组有机质) 有显着影响。该研究区内阔叶林凋落物现存量比针叶林多( 见表1) ,从凋落物中淋滤出的可溶性有机质就多[31],结果显示,不同林型下土壤活性和惰性有机碳氮组分含量存在一定差异,但差异不显着,可能与该研究采用酸浸提有机碳氮组分有关,而WANG等[30]只针对土壤活性有机质组分开展研究。凋落物作为外源有机物质,由易分解成分( 如糖类、淀粉、脂肪等) 和难分解成分( 如木质素、多酚等) 组成[32],这些成分与其分解速率密切相关,影响可溶性有机碳的释放。该研究所在区域内阔叶树种---浙江桂天然林和罗浮栲天然林土壤活性有机质中可溶性糖比杉木人工林高,而土壤多酚含量在杉木人工林中最高[33],说明阔叶林土壤活性有机质含量比针叶林高( 见图1、2)。另外,还有研究表明,杉木人工林凋落物养分含量较低、质量较差,不易被微生物分解利用[34],因 而 导 致 杉 木 人 工 林 土 壤w(RP-C) 在w(TC) 中所占比例高于w(LP-C) ,并且w(RP-C) 也高于阔叶林土壤中相应值( 见图1) ; 而这部分惰性有机质中有相当一部分碳主要是以未分解的木质素结构存在于土壤中[35].已有研究[36]表明,针叶树种凋落物中含有较多难分解的、疏水性芳香族化合物,而阔叶树种凋落物中含有较多易变的、亲水性低分子量化合物,这些性质差异的物质在释放和分解过程中也会造成土壤碳氮组分的不同。通常认为,凋落物中较低的CN更有利于凋落物分解释放活性有机质[37],而该研究中,杉木人工林土壤活性有机库中CN最低( 见表1) ,w(RP-C) 却为最高( 见图1) ,这可能是因为针叶林凋落物中木质素含量较高的缘故,木质素会在凋落物的全纤维素类复合物周围形成阻碍分解的屏障[38],从而影响其分解。该研究还发现,土壤w(LPⅠ-C) 与w(SMB-C)、w(LPⅡ-N) 与w(SMB-N)均呈显着正相关(P < 0. 05) ( 见表3) ,说明凋落物进入土壤后,其活性有机质为微生物提供了碳源,同时也增加了土壤微生物数量[31]. ZHOU等[39]研究发现,土壤微生物生物量的增加会加快土壤活性有机库的分解速率,从而有可能推动惰性有机库的分解。正如有研究指出,尽管林分、林分与氮添加的交互影响不显着,但不同条件下,氮添加对土壤碳含量的影响存在差异,应当考虑林分对氮添加影响土壤碳保存的不同响应[40],而且对于微生物分解和利用惰性碳氮来说,在土壤养分供给、满足植物需求方面,活性碳氮组分存在积极作用; 同时在维持与促进土壤碳氮组分稳定、保护生态环境方面活性碳氮组分表现出消极作用,因此,应当在一个系统内综合考虑它们之间复杂的利弊关系,才能客观认识其内在规律、做出前瞻性的预判。
结果显示,w(LP-N) 与w(Ⅱ-DIN)、w(LPⅠ-C)与w(Ⅱ-DIN) 均呈正相关,而w(LP-N) 与w(RIN)、w(LPⅡ-C) 与w(RIC) 均呈负相关( 见表3) ,说明凋落物中易分解物质( 如单糖、淀粉和简单的氨基酸、蛋白质等) 进入土壤后很容易优先被微生物利用、矿化,而凋落物中剩余的较难分解的木质素、纤维素和单宁等在合适条件下才缓慢被微生物利用[41].而无论采用 哪 种 方 法 研 究 土 壤 有 机 质 的 功 能 和 稳 定性[42],不但需要了解不同碳氮组分的状态,更需要研究各组分之间相互转化的机理,而后者对于揭示碳氮组分响应环境变化、回答一些生态问题而言,可能显得更为重要。该研究还发现,土壤w(TC) 与w(DIN)呈显着正相关( 见表3) ,而土壤活性有机质中,3个样地内土壤C/N为11. 40 ~ 11. 74,相对较低,说明土壤有机质腐殖程度很高、有机氮很容易矿化[43].其中,罗浮栲林土壤中活性有机质库Ⅰ的C/N最高,说明其活性有机氮库Ⅰ的矿化程度较高; 另外,浙江桂天然林土壤中活性有机质库Ⅰ的C/N比活性有机质库Ⅱ低,而罗浮栲天然林土壤中活性有机质库Ⅰ的C/N高于活性有机质库Ⅱ,杉木人工林土壤活性有机质库Ⅰ和活性有机质库Ⅱ的C/N差异不显着。虽然浙江桂天然林土壤中w(RP-N) 较低,但在惰性有机质库中C/N最高,说明在一定程度上活性有机质保持较高的稳定性,并且浙江桂天然林土壤的碳氮循环必然在某些方面与同是阔叶林的罗浮栲之间存在差异,说明不同林分土壤活性有机氮库矿化与有机质腐殖程度、凋落物数量、质量和C/N具有差异性外,还可能与针叶林和阔叶林下土壤微生物群落组成有显着差异有关[44],但对于特定微生物功能组是如何影响土壤活性有机库Ⅰ和活性有机库Ⅱ的形成及转化,尚需要进一步研究。
4 结论
a) 在氮添加影响下,不同林分土壤活性有机碳氮组分之间存在差异,其中,氮添加增加了针叶林土壤中的w(LPⅠ-C) 和w(LP-N) ,同时也增加了浙江桂天然林土壤中的w(LPⅡ-C) ,而迅速降低罗浮栲天然林土壤中的w(LP-N) ; 另外,同是阔叶林树种,其土壤有机质也存在差异,说明该试验区土壤有机碳氮组分不仅受外源氮的影响,还受到凋落物数量和质量的影响。
b) 高氮处理可促进微生物对罗浮栲天然林、杉木人工林土壤活性有机碳的利用,但对浙江桂天然林土壤影响不显着,是因为高氮处理条件下浙江桂天然林土壤中惰性有机质库中C/N最高,而且高氮处理对罗浮栲天然林和杉木人工林土壤活性和惰性碳氮组分的影响有所差异,表明不同树种对氮添加的响应不同。
c) 研究显示,仅用酸水解方法获得土壤活性和惰性碳氮组分,并研究土壤碳氮转化及其对氮添加的响应,会忽略一些细微、快速变化的组分特征,而采用更加全面、系统的分级开展研究可能更为有效。
参考文献(References) :
[1]GRUBER N,GALLOWAY J N. An earth-system perspective of theglobal nitrogen cycle[J]. Nature,2008,451(7176) :293-296.
[2]GALOWAY J N,COWLING E B. Relative nitrogen and the world:200 years of change[J]. AMBIO:A Journal of the HumanEnvironment,2002,31(2) :64-71.
[3]MELILLO J M,COWLING E B. Reactive nitrogen and publicpolicies for environmental protection[J]. AMBIO:A Journal of theHuman Environment,2002,31(2) :150-158.
[4]BELAY-TEDLA A,ZHOU Xuhui,SU Bo,et al. Labile,recalcitrant,and microbial carbon and nitrogen pools of a tallgrassprairie soil in the US Great Plains subjected to experimentalwarming and clipping[J]. Soil Biology and Biochemistry,2009,41(1) :110-116.
[5]DAVIDSON E A,JANSSENS I A. Temperature sensitivity of soilcarbon decomposition and feedbacks to climate change[J]. Nature,2006,440(7081) :165-173.
[6]MCLAUCHLAN K K,HOBBIE S E. Comparison of labile soilorganic matter fractionation techniques[J]. Soil Science Society ofAmerica Journal,2004,68(5) :1616-1625.
[7]ROVIRA P,VALLEJO V R. Labile,recalcitrant,and inert organicmatter in Mediterranean forest soils[J]. Soil Biology andBiochemistry,2007,39(1) :202-215.
[8] 王蓓,孙庚,罗鹏,等。模拟升温和放牧对高寒草甸土壤有机碳氮组分和微生物生物量的影响[J].生态学报,2011,31(6) :1506-1514.WANG Bei,SUN Geng,LUO Peng,et al. Labile and recalcitrantcarbon and nitrogen pools of an alpine meadow soil from the easternQinghai-Tibetan Plateau subjected to experimental warming andgrazing[J]. Acta Ecologica Sinica,2011,31(6) :1506-1514.
[9]MO Jiangming,XUE Jinghua,FANG Yunting. Litter decompositionand its responses to simulated N deposition for the major plants ofDinshushan forests in subtropical China[J]. Acta Ecologica Sinica,2004,24(7) :1413-1420.
[10] 程淑兰,方华军,马艳。氮输入对森林土壤有机碳截存与损耗过程的影响[J].水土保持学报,2007,21(5) :82-85.CHENG Shulan,FANG Huajun,MA Yan. Effects of nitrogen inputon sequestration and depletion of organic carbon of forest soils[J].Journal of Soil and Water Conservation,2007,21(5) :82-85.
[11]FANG Yunting,YOH M,KOBA K,et al. Nitrogen deposition andforest nitrogen cycling along an urban-rural transect in southernChina[J]. Global Change Biology,2011,17(2) :872-885.
[12]YANG Yusheng,GUO Jianfen,Chen Guangshui,et al. Litterproduction,seasonal pattern and nutrient return in seven naturalforests compared with a plantation in southern China[J]. Forestry,2005,78(4) :403-415.
[13] 李君剑,赵溪,潘恬豪,等。不同土地利用方式对土壤活性有机质的影响[J].水土保持学报,2011,25(1) :147-151.LI Junjian J,ZHAO Xi,PAN Tianhao,et al. Effects of differentland-use type on soil labile organic matter[J]. Journal of Soil andWater Conservation,2011,25(1) :147-151.
[14]JOERGENSEN R G. The fumigation-extraction method to estimatesoil microbial biomass:calibration of the kECvalue[J]. Soil Biologyand Biochemistry,1996,28(1) :25-31.
[15]BROOKES P C,LANDMAN A,PRUDEN G,et al. Chloroformfumigation and the release of soil nitrogen:a rapid direct extractionmethod to measure microbial biomass nitrogen in soil[J]. SoilBiology and Biochemistry,1985,17(6) :837-842.
[16]SJBERG G,BERGKVIST B,BERGGREN D,et al. Long-term Naddition effects on the C mineralization and DOC production in morhumus under spruce[J]. Soil Biology and Biochemistry,2003,35(10) :1305-1315.
[17]DEFOREST J L,ZAK D R,PREGITZER K S,et al. Atmosphericnitrate deposition and the microbial degradation of cellobiose andvanillin in a northern hardwood forest[J]. Soil Biology andBiochemistry,2004,36(6) :965-971.
[18]LOVETT G M,ARTHUR M A,WEATHERS K C,et al. Nitrogenaddition increases carbon storage in soils,but not in trees,in aneastern U. S. deciduous forest[J]. Ecosystems,2013,16(6) :980-1001.
[19]HE Yixi,SUN Geng,LIU Lin,et al. Impact of yak dung on soilnutrient in northwest grassland of Sichuan[J]. Chinese Journal ofApplied and Environmental Biology,2009,15(5) :666-671.
[20]POLYAKOVA O,BILLOR N. Impact of deciduous tree species onlitterfall quality,decomposition rates and nutrient circulation inpine stands[J]. Forest Ecology and Management,2007,253(1) :11-18.
[21] 董妍玲,潘学武。植物次生代谢产物简介[J].生物学通报,2002,37(11) :17-19.DONG Yanling,PAN Xuewu. Brief introduction for plant secondarymetabolites[J]. Bulletin of Biology,2002,37(11) :17-19.
[22]GILLESPIE A W,DIOCHON A,MA B L,et al. Nitrogen inputquality changes the biochemical composition of soil organic matterstabilized in the fine fraction:a long-term study[J].Biogeochemistry,2014,117(2 3) :337-350.
[23]LUCE M S,WHALEN J K,NOURA Z,et al. Labile organicnitrogen transformations in clay and sandy-loam soils amended with15N-labelled faba bean and wheat residues[J]. Soil Biology andBiochemistry,2014,68:208-218.
[24]GUNDERSEN P,EMMETT B A,KJONAAS O J,et al. Impacts ofnitrogen deposition on nitrogen cycling in forests:a synthesis ofNITREX data[J]. Forest Ecology and Management,1998,101(1) :37-55.
[25] 马红亮,闫聪微,高人,等。林下凋落物去除与施氮对针叶林和阔叶林土壤氮的影响[J].环境科学研究,2013,26(12) :1316-1324.MA Hongliang,YAN Congwei,GAO Ren,et al. Effects of litterremoval and nitrogen addition on nitrogen dynamics in Chinese firand broad-leaved forest soil[J]. Research of EnvironmentalSciences,2013,26(12) :1316-1324.
[26]BERG B,MATZNER E. Effect of N deposition on decomposition ofplant litter and soil organic matter in forest systems[J].Environmental Reviews,1997,5(1) :1-25.
[27]MADRITCH M D,HUNTER M D. Intraspecific litter diversity andnitrogen deposition affect nutrient dynamics and soil respiration[J]. Oecologia,2003,136(1) :124-128.
[28]LIU Xuejun,DUAN Lei,MO Jiangming,et al. Nitrogen depositionand its ecological impact in China:an overview[J]. EnvironmentalPollution,2011,159(10) :2251-2264.
[29]CRAINE J M,MORROW C,FIEREI N. Microbial nitrogenlimitation increases decomposition[J]. Ecology,2007,88(8) :2105-2113.
[30]WANG Qingkui,WANG Silong. Response of labile soil organicmatter to changes in forest vegetation in subtropical regions[J].Applied Soil Ecology,2011,47(3) :210-216.
[31]KUITERS A T,MULDER W. Water-soluble organic matter in forestsoils[J]. Plant and Soil,1993,152(2) :225-235.
[32]LI Yiqing,XU Ming,SUM O J,et al. Effects of root and litterexclusion on soil CO2efflux and microbial biomass in wet tropicalforests[J]. Soil Biology and Biochemistry,2004,36(12) :2111-2114.
[33] 高艳,马红亮,高人,等。模拟氮沉降对森林土壤酚类物质和可溶性糖含量的影响[J].土壤,2014,46(1) :41-46.GAO Yan,MA Hongliang,GAO Ren,et al. Effects of simulatednitrogen deposition on phenolics and soluble sugar in forest soils[J]. Soils,2014,46(1) :41-46.
[34] 王清奎,汪思龙,于小军,等。杉木与阔叶树叶凋落物混合分解对土壤活性有机质的影响[J].应用生态学报,2007,18(6) :1203-1207.WANG Qingkui,WANG Silong,YU Xiaojun,et al. Effects ofCunninghamia lanceolata-broadleaved tree species mixed leaflitters on active soil organic matter[J]. Chinese Journal of AppliedEcology,2007,18(6) :1203-1207.
[35]THEVENOT M,DIGNAC M F,RUMPEL C. Fate of lignins insoils:a review[J]. Soil Biology and Biochemistry,2010,42(8) :1200-1211.
[36]KALBITZ K,SCHWESIG D,SCHMERWITZ J,et al. Changes inproperties of soil-derived dissolved organic matter induced bybiodegradation[J]. Soil Biology and Biochemistry,2003,35(8) :1129-1142.
[37] 李雪峰,张岩,牛丽君,等。长白山白桦纯林和白桦山杨混交林凋落物的分解[J].生态学报,2007,27(5) :1782-1790.LI Xuefeng,ZHANG Yan,NIU Lijun,et al. Litter decompositionprocesses in the pure birch(Betula platyphlla)forest and the pureand poplar(Populus Davidiana)mixed forest[J]. Acta EcologicaSinica,2007,27(5) :1782-1790.
[38] 李海涛,于贵瑞,李家永,等。井冈山森林凋落物分解动态及磷、钾释放速率。应用生态学报,2007,18(2) :233-240.LI Haitao,YU Guirui,LI Jiayong,et al. Dynamics of litterdecomposition and phosphorus and potassium release in JinggangMountain region of Jiangxi Province,China[J]. Chinese Journal ofApplied Ecology,2007,18(2) :233-240.
[39]ZHOU Xuhui,WAN Shiqiang,LUO Yiqi. Source components andinterannual variability of soil CO2efflux under experimentalwarming and clipping in a grassland ecosystem[J]. Global ChangeBiology,2007,13(4) :761-775.
[40]RODRIGUEZ A,LOVETT G M,WEATHERS K C,et al. Lability ofC in temperate forest soils:assessing the role of nitrogen additionand tree species composition[J]. Soil Biology and Biochemistry,2014,77:129-140.
[41]AERTS R,CALUWE H D. Nutritional and plant-mediated controlson leaf litter decomposition of Carex species[J]. Ecology,1997,78(1) :244-260.
[42]VON LUTZOW M,KOGEL-KNABNER I,EKSCHMITT K,et al.SOM fractionation methods:relevance to functional pools and tostabilization mechanisms[J]. Soil Biology and Biochemistry,2007,39(9) :2183-2207.
[43] 白军红,邓伟,朱颜明,等。湿地土壤有机质和全氮含量分布特征对比研究: 以向海与科尔沁自然保护区为例[J].地理科学,2002,22(2) :232-237.BAI Junhong,DENG Wei,ZHU Yanming,et al. Comparactive studyon the distribution characteristics of soil organic matter and totalnitrogen in wetlands:a case study of Xianghai and Horqin NatureReserve[J]. Scientia Geographica Sinica,2002,22(2) :232-237.
[44]CHEN Chengrong,XU Zhihong. Analysis and behavior of solubleorganic nitrogen in forest soils[J]. Journal of Soils and Sediments,2008,8(6) :363-378.
作者单位:
相关标签: