植物生态学报  2015 , 39 (7): 674-681 https://doi.org/10.17521/cjpe.2015.0064

研究论文

不同来源可溶性有机物对亚热带森林土壤CO2排放的影响

万菁娟, 郭剑芬*, 纪淑蓉, 任卫岭, 司友涛, 杨玉盛

福建师范大学地理科学学院, 湿润亚热带山地生态国家重点实验室培育基地, 福州 350007

Effects of different sources of dissolved organic matter on soil CO2 emission in subtropical forests

WAN Jing-Juan, GUO Jian-Fen*, JI Shu-Rong, REN Wei-Ling, SI You-Tao, YANG Yu-Sheng

State Key Laboratory Breeding Base of Humid Subtropical Mountain Ecology, College of Geographical Sciences, Fujian Normal University, Fuzhou, 350007, China

通讯作者:  * 通讯作者 Author for correspondence (E-mail: jfguo@fjnu.edu.cn)

责任编辑:  WAN Jing-JuanGUO Jian-FenJI Shu-RongREN Wei-LingSI You-TaoYANG Yu-Sheng

版权声明:  2015 植物生态学报编辑部 本文是遵循CCAL协议的开放存取期刊,引用请务必标明出处。

基金资助:  国家自然科学基金(31370615、31130013和31470501)、国家重大科学研究计划课题(2014CB954003)和福建省教育厅重点项目(JA13065)

展开

摘要

采用室内培养法, 比较分析了亚热带地区杉木(Cunninghamia lanceolata)和米槠(Castanopsis carlesii)鲜叶及凋落叶浸提得到的可溶性有机物(dissolved organic matter, DOM)组成和化学性质差异对土壤CO2排放的影响。结果表明: 添加不同来源的DOM后, 土壤CO2瞬时排放速率在培养第1天内均显著高于对照(添加去离子水) (p < 0.05), 分别比对照增加了91.5% (添加杉木鲜叶DOM)、12.8% (添加米槠鲜叶DOM)、61.0% (添加杉木凋落叶DOM)和113.3% (添加米槠凋落叶DOM), 但培养5天后, 分别下降到对照的24.1%、8.3%、14.6%和13.2%, 随后逐渐趋于平稳。单次添加外源DOM到土壤中, 引起土壤CO2排放速率增加的强度较大, 但持续时间短暂。培养31天时, 添加不同来源的DOM均对土壤CO2累积排放量具有显著影响(p < 0.05), 而在培养59天时, 添加杉木鲜叶和凋落叶DOM的土壤CO2累积排放量均显著高于添加米槠鲜叶和凋落叶DOM的土壤CO2累积排放量, 但添加相同树种鲜叶与凋落叶DOM的土壤CO2累积排放量之间差异不显著。培养结束后, 添加杉木鲜叶DOM和杉木凋落叶DOM后增加的土壤碳排放量, 分别是外源添加可溶性有机碳量的1.76倍和2.56倍, 而添加米槠鲜叶DOM和米槠凋落叶DOM后增加的土壤碳排放量只占外源添加可溶性有机碳量的22.5%和50.0%, 表明单次添加不同来源的DOM对土壤总有机碳库的影响是不一致的。

关键词: 碳矿化 ; 米槠 ; 杉木 ; 可溶性有机物 ; 鲜叶 ; 凋落叶

Abstract

Aims Dissolved organic matter (DOM) is an important carbon and nutrient pool, but the effects of different sources of DOM on soil carbon cycling are less well understood. Our objective in this study was to investigate how differences in the quantity and quality of DOM from fresh leaves and leaf litter of Cunninghamia lanceolata and Castanopsis carlesii affected soil CO2 fluxes in a laboratory incubation experiment. Methods Mineral soils (0-10 cm) from an 11-year-old Cunninghamia lanceolata plantation in Sanming of Fujian Province, China, were incubated for 59 days after adding the DOM from fresh leaves and leaf litter of Cunninghamia lanceolata and Castanopsis carlesii. Carbon (C) mineralization during incubation was determined using CO2 respiration method. Important findings Compared to the controls, the rates of C mineralization significantly increased by 91.5%, 12.8%, 61.0% and 113.3% on day 1, following additions of DOM from fresh leaves and leaf litter of Cunninghamia lanceolata and Castanopsis carlesii, respectively; the magnitudes of the increases declined to 24.1%, 8.3%, 14.6% and 13.2% by day 5, indicating that addition of DOM had significant but short-term influences on soil CO2 emission. DOM from different sources had significant effects on the cumulative CO2 production following addition of DOM by day 31 (p < 0.05). After 59 days of incubation, the cumulative quantity of mineralized C following addition of DOM from fresh leaves and leaf litter of Cunninghamia lanceolata was significantly greater than that from those of Castanopsis carlesii, while there was no significant difference in the cumulative CO2 production between DOM from fresh leaves and leaf litter of the same tree species, suggesting that difference in tree species had a greater influence on C mineralization than difference in the degree of leaf decay. Addition of DOM originated from fresh leaves and leaf litter of Castanopsis carlesii resulted in increased C mineralization by 22.5% and 50.0% of C added over the course of 59 day incubation, whereas increases by additions of DOM from fresh leaves and leaf litter of Cunninghamia lanceolata were 1.76 times and 2.56 times, respectively. Thus, a single addition of different sources of DOM may lead to diverse effects on total soil carbon stocks.

Keywords: C mineralization ; Castanopsis carlesii ; Cunninghamia lanceolata ; dissolved organic matter ; fresh leaves ; leaf litter

0

PDF (367KB) 元数据 多维度评价 相关文章 收藏文章

本文引用格式 导出 EndNote Ris Bibtex

万菁娟, 郭剑芬, 纪淑蓉, 任卫岭, 司友涛, 杨玉盛. 不同来源可溶性有机物对亚热带森林土壤CO2排放的影响[J]. 植物生态学报, 2015, 39(7): 674-681 https://doi.org/10.17521/cjpe.2015.0064

WAN Jing-Juan, GUO Jian-Fen, JI Shu-Rong, REN Wei-Ling, SI You-Tao, YANG Yu-Sheng. Effects of different sources of dissolved organic matter on soil CO2 emission in subtropical forests[J]. Chinese Journal of Plant Ecology, 2015, 39(7): 674-681 https://doi.org/10.17521/cjpe.2015.0064

土壤有机碳库是陆地生态系统最大碳储存库, 储量高达1500 Pg (Eswaran et al., 1993), 是大气碳库的2倍、植物碳库的3倍多, 因此土壤碳库的动态变化对全球碳循环起着重要作用。土壤有机碳库变化受到凋落物输入与土壤有机碳(SOC)矿化的共同影响(Vesterdal et al., 2012)。而土壤有机碳矿化不仅受到温度、水等环境因素的调控, 也受外源有机物(包括有机物的质量和数量)的影响(Kirschbaum, 2004; Fierer et al., 2005; Hartley & Ineson, 2008)。如输入活性碳到土壤中后, 会增加土壤有机碳矿化(Kuzyakov et al., 2000; Blagodatskaya & Kuzyakov, 2008; Kuzyakov, 2010; Cheng et al., 2014)。在森林生态系统中, 降雨淋溶、凋落物淋溶的可溶性有机物(DOM)是土壤有机物(SOM)中活性碳库的重要来源(Gauthier et al., 2010), 亦是土壤微生物分解作用的主要底物来源(Marschner & Kalbit, 2003; Li et al., 2010), 因此, 研究不同来源的DOM对土壤碳库的影响具有重要意义。

已有研究发现不同来源的DOM化学组成和性质差异较大(Inamdar et al., 2012; Kothawala et al., 2012)。如阔叶树凋落叶可溶性有机碳(DOC)含量高于针叶树(Wieder et al., 2008), 相同树种的凋落叶DOC含量高于鲜叶(Cleveland et al., 2004), 鲜叶淋溶的DOM中含有更多低分子量、易分解的有机物, 而凋落叶DOM中含有更多的芳香性化合物和腐殖化程度更高的有机物(Kalbitz et al., 2007; Inamdar et al., 2012)。因此, 分析不同树种鲜叶与凋落叶DOM的差异对土壤CO2排放的影响是生态系统碳循环的重要环节。已有的野外研究表明不同树种DOM对土壤CO2累积排放量具有显著影响(Kiikkilä et al., 2012)。室内试验也证明添加不同树种凋落叶DOM后, 会影响土壤CO2排放而影响土壤碳库(Wieder et al., 2008)。

中亚热带常绿阔叶林是全球同纬度带上的“绿洲” (全球同纬度地带多为荒漠、稀树草原), 亦是全球重要的森林碳汇区, 其中米槠(Castanopsis carlesii)是常绿阔叶林的重要群系之一(章浩白, 1993)。而杉木(Cunninghamia lanceolata)作为我国南方特有的经济树种, 种植面积已经达到12 × 106 hm2, 占世界总人工林面积的6.5% (Chen et al., 2013)。本研究选择米槠和杉木的鲜叶及凋落叶DOM作为研究对象, 探讨添加不同来源的DOM对土壤CO2排放差异及其土壤碳库的影响, 为该区森林土壤碳循环研究提供一个新思路。

1 材料和方法

1.1 试验地概况

试验地在福建省三明市格氏栲自然保护区(26.17º N, 117.47º E)。该保护区气候属于中亚热带季风气候, 试验地附近的三明市年平均气温20.1 ℃, 年降水量1670 mm, 降水多集中于3-8月份(吴君君等, 2014)。杉木人工林为2003年米槠次生林皆伐后 营造人工纯林形成, 树龄11年。

1.2 样品采集

2014年3月, 于杉木人工林的上、中、下坡, 随机布设3块20 m × 20 m的标准样地, 在每个标准样地内按照S型布设5个点, 分别用土钻取表层土壤(0-10 cm), 混合, 迅速冷藏并带回实验室。一部分用于风干测定其理化性质(表1), 另一部分在4 ℃冷藏保存, 用于后续的培养实验。同时在杉木人工林和临近的米槠天然林试验样地内, 布设上、中、下坡3条平行于等高线的样线, 每条样线上随机设10个25 cm × 25 cm的小样方, 收集未分解的凋落叶样品, 并用高枝剪从东、西、南、北四个方向采摘树冠中上部的鲜叶, 带回实验室。一部分烘干测定含水量, 另一部分保存在低温环境中, 用于后续的浸提实验。

表1   试验地表层土壤(0-10 cm)性质(平均值±标准误差)

Table 1   Surface soil (0-10 cm ) properties of the study sites (mean ± SE)

试验地
Study site
有机碳
Organic carbon
(g·kg-1)
全氮
Total N (g·kg-1)
C:N可溶性有机碳
Dissolved organic
carbon (mg·kg-1)
可溶性有机氮
Dissolved organic
nitrogen (mg·kg-1)
微生物生物量碳
Microbial biomass
carbon (mg·kg-1)
杉木人工林
Cunninghamia lanceolata
plantation
17.55 ± 1.701.31 ± 0.13313.37 ± 0.5573.27 ± 8.158.79 ± 0.79423.52 ± 5.93

新窗口打开

1.3 试验设计

DOM浸提采用样品与水的比例为1:2, 即各取100 g杉木鲜叶(相当于66.56 g干质量)、米槠鲜叶(相当于76.51 g干质量)、杉木凋落叶(相当于89.67 g干质量)和米槠凋落叶(相当于87.98 g干质量), 加入200 mL去离子水, 浸泡24 h后, 上清液用0.45 μm玻璃纤维过滤器减压过滤, 滤液在4 ℃保存, 并及时测定DOM的性质(表2)。

表2   不同来源可溶性有机物的性质(平均值±标准误差)

Table 2   Properties of different sources of dissolved organic matter (mean ± SE)

可溶性有机碳
Dissolved organic
carbon (g·kg-1)
可溶性有机氮
Dissolved organic
nitrogen (g·kg-1)
紫外吸收值
Special ultraviolet visible absorption (UV)
腐殖化指标
Humification
index (HIX)
分子量大小
Molecular size
pH
杉木鲜叶
Fresh leaves of Cunninghamia lanceolata
2.60 ± 0.51a0.005 ± 0.001a0.24 ± 0.01a0.26 ± 0.01a5.24 ± 0.98a5.98 ± 0.12a
米槠鲜叶
Fresh leaves of Castanopsis carlesii
0.80 ± 0.11b0.024 ± 0.002b0.76 ± 0.08b1.75 ± 0.11b3.75 ± 0.10b5.91 ± 0.05b
杉木凋落叶
Leaf litter of Cunninghamia lanceolata
0.99 ± 0.03c0.014 ± 0.001c1.61 ± 0.02c1.91 ± 0.03c6.90 ± 0.07c5.76 ± 0.05c
米槠凋落叶
Leaf litter of Castanopsis carlesii
1.59 ± 0.02d0.020 ± 0.001d1.64 ± 0.04c1.90 ± 0.02c4.80 ± 0.30d4.28 ± 0.01d

Different lowercase letters indicate significant differences among different sources of dissolved organic matter.不同小写字母表示不同来源可溶性有机物之间有显著差异。

新窗口打开

取相当于50 g风干土重的鲜土样品到500 mL的特质瓶中, 调节土壤含水量为饱和含水量(43.7%)的40%, 放置在25 ℃生化培养箱中进行15天预培养, 使土壤内部环境趋于稳定。预培养结束后, 分别加入按照上面方法浸提得到的杉木鲜叶DOM (DOC:MBC是1:9, MBC是微生物生物量碳)、米槠鲜叶DOM (DOC:MBC是1:26)、杉木凋落叶DOM (DOC:MBC是1:12)和米槠凋落叶DOM (DOC:MBC是1:8)各4 mL, 等量去离子水作为对照, 调节土壤含水量达到饱和含水量的60%, 每个处理3个重复。在添加不同来源DOM后的第1、2、3、5、7、10、17、24、31、38、45、52、59天抽气取样, 取样前2 h将瓶盖拧紧, 取样结束后调节土壤含水量, 然后将气体注入气相色谱仪(GC-2010, Shimadzu, Kyoto, Japan)进行分析, 计算土壤CO2排放速率和CO2累积排放量。

浸提得到的DOC及用氯仿-熏蒸浸提法得到的MBC, 用总有机碳分析仪(TOC-VCPH, Shimadzu, Kyoto, Japan)测定; DON用流动注射分析仪(San++, Skalar, Breda, Netherlands)测定; 土壤C、N元素含量采用碳氮元素分析仪(vario MAX, Elementar Analysensysteme GmbH, Hanau, Germany)测定。

为了测定结果的可比性, 用于紫外和荧光光谱测定样品的DOC浓度用去离子水稀释至10 mg·L-1, pH值用稀HCl调为2。用紫外可见分光光度计(UV- 2450, Shimadzu, Kyoto, Japan)测定紫外可见吸光值, 待测液在254 nm处的紫外吸光值(UV)可用于计算芳香性指数(AI); 用250 nm和365 nm的紫外吸光度比值计算分子量大小E2:E3; 荧光发射光谱通过日立F7000仪器(Hitachi, Tokyo, Japan)获得, 激发波长λex = 254 nm, 狭缝宽10 nm, 发射波长λem是300-480 nm, 狭缝宽10 nm, 扫描速度2400 nm·min-1, 腐殖化指标HIX通过计算发射光谱中Σ435-480 nm区域与Σ300-345 nm区域峰面积比值获得(熊丽等, 2014)。

1.4 计算方法及数据处理

CO2产生速率计算方法:

F = k × v/m × Δc/Δt × 273/(273 + T)

式中, F表示气体排放的速率(mg·kg-1·h-1); k是常数, 取值为1.964 kg·m-3; Δc/Δt表示在观测时间内气体浓度随时间变化的直线斜率(mg·h-1); v为培养容器的体积(m-3); m为土壤质量(kg); T为培养温度(℃)。CO2累积排放量采用相邻两次产生CO2速率的平均值乘以间隔的时间而获得。

E2:E3可以反映DOC的平均分子量大小(Peuravuori & Pihlaja, 1997), E2:E3值越高, 说明DOC的平均分子量越小, 其计算公式如下:

E2:E3 = UV250:UV365

式中UV250为250 nm的紫外吸光度值, UV365为365 nm的紫外吸光度值。

所有数据的处理主要在Excel和SPSS 17.0的软件下完成, 相关图表在Origin 8.0 软件下完成。采用单因素方差分析(one-way ANOVA)检验添加不同来源的DOM对土壤CO2排放的影响和多因素方差分析(multiple comparisons ANOVA)检验杉木和米槠的鲜叶及凋落叶DOM组成和化学性质差异的显著性。

2 结果和分析

2.1 DOM含量和光谱特征

通过多因素方差分析发现, 不同树种、相同树种鲜叶和凋落叶、不同树种的鲜叶和凋落叶的交互作用均对DOC浓度具有极显著影响(p < 0.01)。如米槠凋落叶DOC浓度最大(698.8 mg·L-1), 而米槠鲜叶DOC浓度最小(203.7 mg·L-1), 其相互之间差异多于3倍(表2)。相同树种鲜叶的可溶性有机氮(DON)浓度显著低于凋落叶DON浓度(p < 0.05), 说明鲜叶中N元素更难释放, 即凋落叶DOM中含有更多的含氮营养物质。腐殖化指标(HIX)、紫外吸收值(UV)和分子量大小(E2:E3)是用来表示DOM化学性质的指标, 本研究发现杉木鲜叶DOM的HIXUV均显著低于米槠鲜叶DOM的(p < 0.05), E2:E3则相反, 表明阔叶树种鲜叶DOM比针叶树种鲜叶DOM中含有更多高分子量的、腐殖化程度较高的有机物。这与相对荧光光谱图的趋势一致(图1), 由针叶树种到阔叶树种最大荧光强度所对应波长向更长的波长转移, 表明DOM中共轭体系在增大, 分子复杂结构更多。另外, 相同树种鲜叶DOM的HIXUV显著低于凋落叶DOM的(p < 0.05), E2:E3值则相反, 表明鲜叶浸提得到的DOM中含有更多低分子量、易分解的有机物, 而凋落叶DOM中以高分子量的腐殖质为主。

图1   不同来源可溶性有机物的荧光发射光谱。

Fig. 1   Fluorescence emission spectra of different sources of dissolved organic matter.

2.2 添加不同来源DOM后土壤CO2排放速率特征

本研究发现添加杉木鲜叶DOM、米槠鲜叶DOM、杉木凋落叶DOM和米槠凋落叶DOM到土壤中后, 培养第1天土壤CO2瞬时排放速率均显著高于对照(p < 0.05), 分别比对照增加了91.5%、12.8%、61.0%和113.3%, 但培养5天后, 分别下降到对照的24.1%、8.3%、14.6%和13.2%, 随后逐渐趋于平稳(图2), 表明单次添加外源DOM到土壤中后, 引起土壤CO2排放速率增加的强度较大, 但持续时间短暂。添加不同来源DOM后土壤CO2瞬时排放速率均在培养第1天达到最大值, 其中添加杉木鲜叶DOM后土壤CO2瞬时排放速率显著高于添加杉木凋落叶DOM的18.9%, 添加米槠凋落叶DOM后土壤CO2瞬时排放速率显著高于添加米槠鲜叶DOM的89%, 但随着培养时间延长, 添加不同来源的DOM对土壤CO2排放速率影响不显著。

图2   添加不同来源可溶性有机物后土壤CO2排放速率的变化(平均值 ± 标准误差)。

Fig. 2   Changes in the rate of CO2 emission following addition of different sources of dissolved organic matter (mean ± SE).

2.3 添加不同来源DOM后土壤CO2累积排放量的差异

在培养31天时, 添加杉木和米槠DOM、鲜叶和凋落叶DOM均对土壤CO2累积排放量具有显著影响(p < 0.05), 而在培养59天时, 添加相同树种鲜叶与凋落叶DOM的土壤CO2累积排放量之间差异不显著, 表明随着培养时间的延长, 添加不同树种DOM后土壤CO2排放之间的差异比添加相同树种鲜叶与凋落叶DOM后土壤CO2排放之间的差异更大。培养前31天, 添加杉木鲜叶DOM的土壤CO2累积排放量显著高于添加米槠鲜叶DOM的(p < 0.05), 而添加杉木凋落叶DOM与添加米槠凋落叶DOM的土壤CO2累积排放量之间没有显著差异。培养59天时, 添加杉木鲜叶和凋落叶DOM的土壤CO2累积排放量均显著高于添加米槠鲜叶和凋落叶DOM的(p < 0.05) (图3)。

图3   添加不同来源可溶性有机物后土壤CO2累积排放量(平均值 ± 标准误差)。

Fig. 3   Cumulative emission CO2 following addition of different sources of dissolved organic matter (mean ± SE).

在培养59天时, 添加不同来源的DOM增加的土壤碳排放量分别是外源添加DOC的176% (添加杉木鲜叶DOC量是46.9 mg·kg-1)、22.5% (添加米槠鲜叶DOC量是16.3 mg·kg-1)、256% (添加杉木凋落叶DOC量是35.7mg·kg-1)和50.0% (添加米槠凋落叶DOC量是55.9 mg·kg-1), 即外源添加米槠鲜叶和凋落叶DOM后, 增加了土壤总有机碳库, 而添加杉木鲜叶和凋落叶DOM后降低了土壤总有机碳库。

3 讨论

3.1 不同来源的DOM的差异

本研究发现杉木鲜叶DOC浓度(586.1 mg·L-1) 显著高于米槠鲜叶DOC浓度(203.7 mg·L-1), 而米槠凋落叶DOC浓度(698.8 mg·L-1)显著高于杉木凋落叶DOC浓度(446.1 mg·L-1), 这与不同树种的叶片质量和结构差异有关。杉木鲜叶和凋落叶DOM的pH值均显著高于米槠鲜叶和凋落叶DOM的, 这与Kiikkilä等(2011)的研究结果不一致, 可能是由亚热带地区和温带地区的立地条件差异引起。HIXUVE2:E3均是衡量DOM化学性质差异性的指标, 其中HIX能反映芳香类化合物的含量, 且比UV更加灵敏, 区分度更高(康根丽等, 2014)。本研究中相同树种鲜叶DOM的HIXUV均显著低于凋落叶DOM的, 相对荧光强度值也验证了这个结果, 凋落叶到鲜叶所对应的波长由长波向短波转移表明DOM中共轭体系在减少(Haken & Wolf, 1995; Bu et al., 2011), 凋落叶淋溶的DOM化学性质更复杂(Inamdar et al., 2012)。同时, 本研究结果显示杉木和米槠凋落叶DOM的HIXUV差异不显著, 这与前期研究的结果不一致, 其原因可能在于浸提比例不一样。

3.2 添加不同来源的DOM后土壤CO2排放的差异

已有研究表明, 添加外源DOM后会显著影响土壤CO2排放(Wieder et al., 2008; Leff et al., 2012), 本研究也发现, 添加不同来源的DOM后土壤CO2累积排放量均高于对照。在培养31天时, 添加米槠凋落叶DOM的土壤CO2累积排放量高于添加杉木凋落叶DOM的(p = 0.351), 但培养结束时, 添加米槠凋落叶DOM的土壤CO2累积排放量比添加杉木凋落叶DOM的低11%, 这除了与培养时间有关, 可能也与不同树种DOM的差异有关(Kiikkilä et al., 2014)。培养31天时, 添加米槠鲜叶DOM的土壤CO2累积排放量显著低于添加米槠凋落叶DOM的, 这可能是因为外源添加DOC:DON大于25, 使外源N成了土壤微生物生长和繁殖的限制性因素, 因而, 含氮量高的DOM进入土壤后微生物迅速繁殖促进了土壤CO2排放(Nourbakhsh & Dick, 2005; Sun et al., 2009)。而在培养59天时, 添加米槠鲜叶DOM的土壤CO2累积排放量与添加米槠凋落叶DOM的差异不显著, 表明随着培养时间延长, 添加米槠鲜叶DOM与米槠凋落叶DOM的土壤CO2累积排放量之间的差异在逐渐减小。同时, 添加杉木鲜叶和凋落叶DOM的土壤CO2累积量均显著高于添加米槠鲜叶和凋落叶DOM的, 表明单次添加外源可溶性有机物到土壤中, 添加杉木树种DOM对土壤CO2排放的影响更大。

培养59天时, 添加米槠鲜叶和凋落叶DOM后增加了土壤总有机碳库, 这与许多外源添加有机物对土壤碳库的影响是一致的(Qiao et al., 2014; Xiao et al., 2014)。但添加杉木鲜叶和凋落叶DOM后降低了土壤总有机碳库, Fontaine等(2004)、Hoosbeek和Scarascia-Mugnozza (2009)也得到类似的研究结果, 这与外源添加DOM的差异有关。如Wieder等(2008)的研究表明, 添加不同树种凋落叶DOM到土壤中后, 对土壤总有机碳库的影响是不一致的, 这主要是由外源添加的DOM的化学性质差异引起。在培养前31天时, 添加米槠凋落叶DOM的土壤CO2累积排放量比对照高15.4%, 但培养59天时下降到4.3%, 说明在培养后期添加米槠凋落叶DOM的土壤CO2累积排放量与对照逐渐趋于一致, 这与其他3种处理的结果相反, 其原因除了与培养时间有关外, 还可能由于添加外源DOM的质量对土壤微生物活动的影响(Gauthier et al., 2010), 如本研究发现外源添加的米槠凋落叶DOM中含有更多大分子量、难分解的化合物。

3.3 外源DOM对土壤CO2排放的影响机制

研究表明, 外源添加有机物的数量与质量均会影响土壤CO2排放。如Cleveland等(2010)的研究表明土壤CO2排放量随外源添加DOC的增加而增加。Wang等(2013, 2014)认为外源添加有机物的化学性质差异也会影响土壤CO2排放。因异养微生物能快速利用土壤中活性的(低分子量)、易分解的有机物从而促进土壤CO2排放(Abera et al., 2012; He & Ruan, 2014; Yang & Zhu, 2015)。本研究结果发现, 土壤CO2排放受到外源添加DOM数量与质量的共同影响。如在培养第1天时, 添加不同来源的DOM的土壤CO2瞬时排放速率随外源添加DOC的增加而增加。而在培养59天时, 添加杉木凋落叶DOM的土壤CO2累积排放量显著高于添加米槠凋落叶DOM的土壤CO2累积排放量, 但外源添加杉木凋落叶DOC (35.7 mg·kg-1)显著低于外源添加米槠凋落叶DOC (55.9 mg·kg-1), 这可能与外源添加DOM的化学性质有关, 因为杉木凋落叶DOM的E2:E3值显著高于米槠凋落叶DOM的, 即外源添加的杉木凋落叶DOM中含有更多的小分子有机物, 而周转快的小分子物质能增加土壤CO2的排放(van Hees et al., 2005; Fujii et al., 2010; Rousk et al., 2011)。因此, 为了更好地区分外源添加DOM的数量与质量对土壤CO2排放的影响, 后期研究需要通过控制外源DOM的数量或者质量, 从而更加深入地分析添加不同来源的DOM对土壤CO2排放的影响机制。

4 结论

单次添加外源DOM对培养初期土壤CO2排放的影响较大。在培养59天时, 添加相同树种鲜叶DOM与凋落叶DOM的土壤CO2累积排放量之间差异不显著, 但添加杉木鲜叶和凋落叶DOM的土壤CO2累积排放量均显著高于添加米槠鲜叶和凋落叶DOM的。在培养结束时, 添加米槠鲜叶和凋落叶DOM后增加的土壤碳排放量是外源添加DOC量的22.5%和50.0%, 而添加杉木鲜叶和凋落叶DOM的超过了100%, 说明添加不同来源的DOM对土壤总有机碳库的影响是不一样的。因本研究没有采用同位素标记的技术, 因而不能区分土壤CO2排放来源。今后可结合13C-DOM标记技术, 并从微生物群落结构及酶活性等方面更加深入地研究不同来源的DOM添加对土壤CO2排放的影响机制。

The authors have declared that no competing interests exist.

作者声明没有竞争性利益冲突.


参考文献

[1] Abera G, Wolde-meskel E, Bakken LR (2012).

Carbon and nitrogen mineralization dynamics in different soils of the tropics amended with legume residues and contrasting soil moisture contents.

Biology and Fertility of Soils, 48, 51-66.

[本文引用: 1]     

[2] Blagodatskaya E, Kuzyakov Y (2008).

Mechanisms of real and apparent priming effects and their dependence on soil microbial biomass and community structure: Critical review.

Biology and Fertility of Soils, 45, 115-131.

[本文引用: 1]     

[3] Bu XL, Ding JM, Wang LM, Yu XN, Huang W, Ruan HH (2011).

Biodegradation and chemical characteristics of hot-water extractable organic matter from soils under four different vegetation types in the Wuyi Mountains, southeastern China.

European Journal of Soil Biology, 47, 102-107.

[本文引用: 1]     

[4] Chen GS, Yang ZJ, Gao R, Xie JS, Guo JF, Huang ZQ, Yang YS (2013).

Carbon storage in a chronosequence of Chinese fir plantations in southern China.

Forest Ecology and Management, 300, 68-76.

[本文引用: 1]     

[5] Cheng WX, Parton WJ, Gonzalez-Meler MA, Phillips R, Asao S, McNickle GG, Brzostek E, Jastrow JD (2014).

Synthesis and modeling perspectives of rhizosphere priming.

New Phytologist, 201, 31-44.

[本文引用: 1]     

[6] Cleveland CC, Neff JC, Townsend AR, Hood E (2004).

Composition, dynamics, and fate of leached dissolved organic matter in terrestrial ecosystems: Results from a decomposition experiment.

Ecosystems, 7, 175-285.

[本文引用: 1]     

[7] Cleveland CC, Wieder WR, Reed SC, Townsend AR (2010).

Experimental drought in a tropical rain forest increases soil carbon dioxide losses to the atmosphere.

Ecology, 91, 2313-2323.

[8] Eswaran H, van Den Berg E, Reich P (1993).

Organic carbon in soils of the world.

Soil Science Society of America Journal, 57, 192-194.

[本文引用: 1]     

[9] Fierer N, Craine JM, McLauchlan K, Schimel JP (2005).

Litter quality and the temperature sensitivity of decomposition.

Ecology, 86, 320-326.

[本文引用: 1]     

[10] Fontaine S, Bardoux G, Abbadie L, Mariotti A (2004).

Carbon input to soil may decrease soil carbon content.

Ecology Letters, 7, 314-320.

[11] Fujii K, Hayakawa C, van Hees PA, Funakawa S, Kosaki T (2010).

Biodegradation of low molecular weight organic compounds and their contribution to heterotrophic soil respiration in three Japanese forest soils.

Plant and Soil, 334, 475-489.

[本文引用: 1]     

[12] Gauthier A, Amiotte-Suchet P, Nelson PN, Lévêque J, Zeller B, Hénault C (2010).

Dynamics of the water extractable organic carbon pool during mineralisation in soils from a Douglas fir plantation and an oak-beech forest―An incubation experiment.

Plant and Soil, 330, 465-479.

[本文引用: 2]     

[13] Haken H, Wolf HC (1995). Molecular Physics and Elements of Quantum Chemistry. Springer-Verlag, Berlin.

[本文引用: 1]     

[14] Hartley IP, Ineson P (2008).

Substrate quality and the temperature sensitivity of soil organic matter decomposition.

Soil Biology & Biochemistry, 40, 1567-1574.

[本文引用: 1]     

[15] He DM, Ruan HH (2014).

Long term effect of land reclamation from Lake on chemical composition of soil organic matter and its mineralization.

PLoS ONE, 9, e99251.

[本文引用: 1]     

[16] Hoosbeek MR, Scarascia-Mugnozza GE (2009).

Increased litter build up and soil organic matter stabilization in a poplar plantation after 6 years of atmospheric CO2 enrichment (FACE): Final results of POP-Euro FACE compared to other forest FACE experiments.

Ecosystems, 12, 220-239.

[17] Inamdar S, Finger N, Singh S, Mitchell M, Levia D, Bais H, Scott D, McHale P (2012).

Dissolved organic matter (DOM) concentration and quality in a forested mid- Atlantic watershed, USA.

Biogeochemistry, 108, 55-76.

[本文引用: 3]     

[18] Kalbitz K, Meyer A, Yang R, Gerstberger P (2007).

Response of dissolved organic matter in the forest floor to long-term manipulation of litter and throughfall inputs.

Biogeochemistry, 86, 301-318.

[本文引用: 1]     

[19] Kang GL, Yang YS, Si YT, Yin YF, Liu Z, Chen GS, Yang ZJ (2014).

Quantities and spectral characteristics of DOM released from leaf and litterfall in Castanopsis carlesii forest and Cunninghamia lanceolata plantation.

Acta Ecologica Sinica, 34, 1946-1955.

[本文引用: 1]     

(in Chinese with English abstract) [康根丽, 杨玉盛, 司友涛, 尹云锋, 刘翥, 陈光水, 杨智杰 (2014).

米槠人促更新林与杉木人工林叶片及凋落物溶解性有机物的数量和光谱学特征

. 生态学报, 34, 1946-1955.]

[本文引用: 1]     

[20] Kiikkilä O, Kitunen V, Smolander A (2011).

Properties of dissolved organic matter derived from silver birch and Norway spruce stands: Degradability combined with chemical characteristics.

Soil Biology & Biochemistry, 43, 421-430.

[21] Kiikkilä O, Kitunen V, Spetz P, Smolander A (2012).

Characterization of dissolved organic matter in decomposing Norway spruce and silver birch litter.

European Journal of Soil Science, 63, 476-486.

[本文引用: 1]     

[22] Kiikkilä O, Kanerva S, Kitunen V, Smolander A (2014).

Soil microbial activity in relation to dissolved organic matter properties under different tree species.

Plant and Soil, 377, 169-177.

[本文引用: 1]     

[23] Kirschbaum MUF (2004).

Soil respiration under prolonged soil warming: Are rate reductions caused by acclimation or substrate loss?

Global Change Biology, 10, 1870-1877.

[本文引用: 1]     

[24] Kothawala DN, Roehm C, Blodau C, Moore TR (2012).

Selective adsorption of dissolved organic matter to mineral soils.

Geoderma, 189-190, 334-342.

[本文引用: 1]     

[25] Kuzyakov Y (2010).

Priming effects: Interactions between living and dead organic matter.

Soil Biology & Biochemistry, 42, 1363-1371.

[本文引用: 1]     

[26] Kuzyakov Y, Friedel JK, Stahr K (2000).

Review of mechanisms and quantification of priming effects.

Soil Biology & Biochemistry, 32, 1485-1498.

[本文引用: 1]     

[27] Leff JW, Nemergut DR, Grandy AS, O’Neill SP, Wickings K, Townsend AR, Cleveland CC (2012).

The effects of soil bacterial community structure on decomposition in a tropical rain forest.

Ecosystems, 15, 284-298.

[本文引用: 1]     

[28] Li ZP, Han CW, Han FX (2010).

Organic C and N mineralization as affected by dissolved organic matter in paddy soils of subtropical China.

Geoderma, 157, 206-213.

[本文引用: 1]     

[29] Marschner B, Kalbitz K (2003).

Controls of bioavailability and biodegradability of dissolved organic matter in soils.

Geoderma, 113, 211-235.

[本文引用: 1]     

[30] Nourbakhsh F, Dick RP (2005).

Net nitrogen mineralization or immobilization potential in a residue―Amended calcareous soil.

Arid Land Research and Management, 19, 299-306.

[本文引用: 1]     

[31] Peuravuori J, Pihlaja K (1997).

Molecular size distribution and spectroscopic properties of aquatic humic substances.

Analytica Chimica Acta, 337, 133-149.

[本文引用: 1]     

[32] Qiao N, Schaefer D, Blagodatskaya E, Zou XM, Xu XL, Kuzyakov Y (2014).

Labile carbon retention compensates for CO2 released by priming in forest soils.

Global Change Biology, 20, 1943-1954.

[本文引用: 1]     

[33] Rousk J, Brookes PC, Glanville HC, Jones DL (2011).

Lack of correlation between turnover of low-molecular-weight dissolved organic carbon and differences in microbial community composition or growth across a soil pH gradient.

Applied and Environmental Microbiology, 77, 2791-2795.

[本文引用: 1]     

[34] Sun G, Luo P, Wu N, Qiu PF, Gao YH, Chen H, Shi FS (2009).

Stellera chamaejasme L. increases soil N availability, turnover rates and microbial biomass in an alpine meadow ecosystem on the eastern Tibetan Plateau of China.

Soil Biology & Biochemistry, 41, 86-91.

[本文引用: 1]     

[35] van Hees PAW, Jones DL, Finlay R, Godbold DL, Lundström US (2005).

The carbon we do not see-the impact of low molecular weight compounds on carbon dynamics and respiration in forest soils: A review.

Soil Biology & Biochemistry, 37, 1-13.

[本文引用: 1]     

[36] Vesterdal L, Elberling B, Christiansen JR, Callesen I, Schmidt IK (2012).

Soil respiration and rates of soil carbon turnover differ among six common European tree species.

Forest Ecology and Management, 264, 185-196.

[本文引用: 1]     

[37] Wang QK, Liu SP, Wang SL (2013).

Debris manipulation alters soil CO2 efflux in a subtropical plantation forest.

Geoderma, 192, 316-322.

[38] Wang QK, Wang SL, He TX, Liu L, Wu JB (2014).

Response of organic carbon mineralization and microbial community to leaf litter and nutrient additions in subtropical forest soils.

Soil Biology & Biochemistry, 71, 13-20.

[39] Wieder WR, Cleveland CC, Townsend AR (2008).

Tropical tree species composition affects the oxidation of dissolved organic matter from litter.

Biogeochemistry, 88, 127-138.

[本文引用: 3]     

[40] Wu JJ, Yang ZJ, Liu XF, Xiong DC, Lin WS, Chen CQ, Wang XH (2014).

Analysis of soil respiration and components in Castanopsis carlesii and Cunninghamia lanceolata planta- tions.

Chinese Journal of Plant Ecology, 38, 45-53.

[本文引用: 1]     

(in Chinese with English abstract) [吴君君, 杨智杰, 刘小飞, 熊德成, 林伟盛, 陈朝琪, 王小红 (2014).

米槠和杉木人工林土壤呼吸及其组分分析

. 植物生态学报, 38, 45-53.]

[本文引用: 1]     

[41] Xiao Y, Zhou GY, Zhang QM, Wang WT, Liu SZ (2014).

Increasing active biomass carbon may lead to a breakdown of mature forest equilibrium.

Scientific Reports, 4, doi:10.1038/srep03681.

[本文引用: 1]     

[42] Xiong L, Yang YS, Wang QZ, Yang ZJ, Huang H, Si YT (2014).

Movement of dissolved organic carbon in natural forest soil of Castanopsis carlesii.

Journal of Subtropical Resources and Environment, 9(1), 46-52.

[本文引用: 1]     

(in Chinese with English abstract) [熊丽, 杨玉盛, 王巧珍, 杨智杰, 黄惠, 司友涛 (2014).

可溶性有机碳在米槠天然林土壤中的淋溶特征

. 亚热带资源与环境学报, 9(1), 46-52.]

[本文引用: 1]     

[43] Yang K, Zhu JJ (2015).

Impact of tree litter decomposition on soil biochemical properties obtained from a temperate secondary forest in Northeast China.

Journal of Soils and Sediments, 15, 13-23.

[本文引用: 1]     

[44] Zhang HB (1993). Forest in Fujian. China Forestry Publishing House, Beijing.

[本文引用: 1]     

(in Chinese) [章浩白 (1993). 福建森林. 中国林业出版社, 北京.]

[本文引用: 1]     

/