土壤碳固持量随森林演替显著提高, 对减缓全球变暖具有重要意义; 但是, 演替过程中土壤有机碳库与植被碳归还的关系尚无定论。该研究以浙江天童常绿阔叶林次生演替系列为对象, 通过测定前中后3个演替阶段土壤总有机碳(TOC)、可矿化碳(MC)、可溶性有机碳(DOC)和微生物量碳(MBC) 3种活性有机碳的含量与储量, 植被凋落物年凋落量、地表枯落物现存量和细根年归还量及其碳储量, 利用相关分析和多元逐步回归拟合, 分析土壤碳库与植被碳输入的关系。结果表明: (1)土壤TOC、MC、DOC和MBC含量随演替进行均显著增加(p < 0.05); (2)随演替进行, 土壤TOC储量显著增加(p < 0.05), 而MC、DOC和MBC储量并没有出现一致的变化趋势, 其排序为: 中期>后期>前期; (3)凋落物年凋落量及其碳储量随演替显著增加(p < 0.05), 细根年归还量及其碳储量随演替先增后降(p < 0.05), 而地表枯落物现存量与碳储量显著降低; (4) 3种活性有机碳中, MC储量对土壤总有机碳储量解释的贡献率为34.01% (R2 = 0.388, p < 0.05); (5) TOC和活性碳库(MC、DOC、MBC)受到不同碳归还方式的影响, 但细根的影响最大(分别为28.2%、50.0%、73.4%和68.8%)。总之, 随天童常绿阔叶林演替发生, 土壤总有机碳和3种活性有机碳储量显著增加, 细根生物量和可矿化碳库储量增加是引起土壤碳固持量增加的主要原因。
Aims Increasing sequestration of soil organic carbon with forest succession plays a significant role in reducing global warming. However, the relationship between structure of soil carbon pools and vegetation carbon inputs is still uncertain. Our objective was to examine how structure of the soil carbon pool changes with vegetation carbon return through litterfall, forest floor and fine roots during secondary succession in evergreen broad-leaved forests. Methods The study site is located in Tiantong National Forest Park (29°52′ N, 121°39′ E), Zhejiang Province, in Eastern China. Three successional stages (i.e., early, middle and late stages) were selected to examine contents and stocks for carbon pools for each of total soil organic carbon (TOC), mineralization carbon (MC), dissolved organic carbon (DOC) and microbial biomass carbon (MBC). The amounts of vegetation carbon return through each of the litterfall, forest floor and fine roots were determined. Then relationships between carbon pool stocks and amount of vegetation carbon return were determined by using both Pearson correlation and stepwise regression approaches. Important findings Along the forest successional series, contents of TOC, MC, DOC and MBC increased significantly (p < 0.05). Stocks of TOC also increased through forest succession (p < 0.05), but the other three active organic carbon stocks were highest in middle-, intermediate in late- and lowest in early-successional stages. The amounts of annual biomass and carbon stocks increased for litterfall, but decreased for forest floor, and fine roots annual returned mass and carbon stocks were highest in middle-, intermediate in late- and lowest in early-successional stages (p < 0.05). Among three active organic carbon pools, MC explained 34.01% variation in TOC (R2 = 0.388, p < 0.05). With respect to vegetation carbon return, returned biomass of fine roots explained 28.2%, 50.0%, 73.4% and 68.8% of total variation for TOC, MC, DOC and MBC, respectively. In conclusion, stocks of TOC and three active organic carbon pools elevate gradually with secondary forest succession in the study area. During this process, the accumulation of fine roots and the enhancement of mineralization carbon pool are mainly responsible for soil carbon sequestration.
全 文 :植物生态学报 2013, 37 (9): 803–810 doi: 10.3724/SP.J.1258.2013.00084
Chinese Journal of Plant Ecology http://www.plant-ecology.com
——————————————————
收稿日期Received: 2013-04-15 接受日期Accepted: 2013-07-19
* 通讯作者Author for correspondence (E-mail: eryan@des.ecnu.edu.cn)
浙江天童常绿阔叶林演替过程中土壤碳库与植被
碳归还的关系
孙宝伟1,2 杨晓东1,2 张志浩 马文济1,2 Ali ARSHAD1,2 黄海侠1,2 阎恩荣1,2*
1华东师范大学环境科学系, 上海 200241; 2浙江天童森林生态系统国家野外科学观测研究站, 浙江宁波 315114
摘 要 土壤碳固持量随森林演替显著提高, 对减缓全球变暖具有重要意义; 但是, 演替过程中土壤有机碳库与植被碳归还
的关系尚无定论。该研究以浙江天童常绿阔叶林次生演替系列为对象, 通过测定前中后3个演替阶段土壤总有机碳(TOC)、可
矿化碳(MC)、可溶性有机碳(DOC)和微生物量碳(MBC) 3种活性有机碳的含量与储量, 植被凋落物年凋落量、地表枯落物现
存量和细根年归还量及其碳储量, 利用相关分析和多元逐步回归拟合, 分析土壤碳库与植被碳输入的关系。结果表明: (1)土
壤TOC、MC、DOC和MBC含量随演替进行均显著增加(p < 0.05); (2)随演替进行, 土壤TOC储量显著增加(p < 0.05), 而MC、
DOC和MBC储量并没有出现一致的变化趋势, 其排序为: 中期>后期>前期; (3)凋落物年凋落量及其碳储量随演替显著增加(p
< 0.05), 细根年归还量及其碳储量随演替先增后降(p < 0.05), 而地表枯落物现存量与碳储量显著降低; (4) 3种活性有机碳中,
MC储量对土壤总有机碳储量解释的贡献率为34.01% (R2 = 0.388, p < 0.05); (5) TOC和活性碳库(MC、DOC、MBC)受到不同
碳归还方式的影响, 但细根的影响最大(分别为28.2%、50.0%、73.4%和68.8%)。总之, 随天童常绿阔叶林演替发生, 土壤总
有机碳和3种活性有机碳储量显著增加, 细根生物量和可矿化碳库储量增加是引起土壤碳固持量增加的主要原因。
关键词 活性有机碳, 细根, 地表枯落物, 凋落物, 次生演替, 总有机碳
Relationships between soil carbon pool and vegetation carbon return through succession of
evergreen broad-leaved forests in Tiantong region, Zhejiang Province, Eastern China
SUN Bao-Wei1,2, YANG Xiao-Dong1,2, ZHANG Zhi-Hao1,2, MA Wen-Ji1,2, Ali ARSHAD1,2, HUANG Hai-Xia1,2, and YAN
En-Rong1,2*
1Department of Environment Science, East China Normal University, Shanghai 200241, China; and 2Tiantong National Forest Ecosystem Observation and
Research Station, Ningbo, Zhejiang 315114, China
Abstract
Aims Increasing sequestration of soil organic carbon with forest succession plays a significant role in reducing
global warming. However, the relationship between structure of soil carbon pools and vegetation carbon inputs is
still uncertain. Our objective was to examine how structure of the soil carbon pool changes with vegetation carbon
return through litterfall, forest floor and fine roots during secondary succession in evergreen broad-leaved forests.
Methods The study site is located in Tiantong National Forest Park (29°52′ N, 121°39′ E), Zhejiang Province, in
Eastern China. Three successional stages (i.e., early, middle and late stages) were selected to examine contents
and stocks for carbon pools for each of total soil organic carbon (TOC), mineralization carbon (MC), dissolved
organic carbon (DOC) and microbial biomass carbon (MBC). The amounts of vegetation carbon return through
each of the litterfall, forest floor and fine roots were determined. Then relationships between carbon pool stocks
and amount of vegetation carbon return were determined by using both Pearson correlation and stepwise
regression approaches.
Important findings Along the forest successional series, contents of TOC, MC, DOC and MBC increased sig-
nificantly (p < 0.05). Stocks of TOC also increased through forest succession (p < 0.05), but the other three active
organic carbon stocks were highest in middle-, intermediate in late- and lowest in early-successional stages. The
amounts of annual biomass and carbon stocks increased for litterfall, but decreased for forest floor, and fine roots
annual returned mass and carbon stocks were highest in middle-, intermediate in late- and lowest in
early-successional stages (p < 0.05). Among three active organic carbon pools, MC explained 34.01% variation in
TOC (R2 = 0.388, p < 0.05). With respect to vegetation carbon return, returned biomass of fine roots explained
28.2%, 50.0%, 73.4% and 68.8% of total variation for TOC, MC, DOC and MBC, respectively. In conclusion,
804 植物生态学报 Chinese Journal of Plant Ecology 2013, 37 (9): 803–810
www.plant-ecology.com
stocks of TOC and three active organic carbon pools elevate gradually with secondary forest succession in the
study area. During this process, the accumulation of fine roots and the enhancement of mineralization carbon pool
are mainly responsible for soil carbon sequestration.
Key words active organic carbon, fine root, forest floor, litterfall, secondary succession, total organic carbon
土壤有机碳库是全球陆地生态系统最大的碳
库, 其碳储量为陆地植被碳库的2–3倍(Dixon et al.,
1994)。土壤有机碳库作为潜在碳汇, 可通过植被将
空气中的CO2固定, 进而转移到土壤中储存, 减缓
全球变暖进程。
森林演替过程中, 群落的种类组成和数量发生
变化, 植被凋落物归还量增大, 土壤有机碳含量升
高。土壤活性碳是总有机碳的一部分, 虽然占总有
机碳库的比例很小, 但其作为微生物分解的主要能
量来源, 直接参与土壤的生物化学过程, 对土壤碳
库形态的转化、转移以及土壤碳固持具有十分重要
的作用(Uselman, 2007; Kalbitz & Kaiser, 2008)。
一般认为, 土壤总有机碳含量的变化主要取决
于植被归还和土壤有机碳分解两个过程(Davidson
& Janssens, 2006; Busse et al., 2009)。凋落物和土壤
细根生物量的归还是引起植被归还量变化的主要
原因(Guo et al., 2005), 而地表枯落物现存量又紧密
联系着凋落物的凋落量和分解量间的动态平衡(周
玉荣等, 2000; 杨玉盛等, 2004)。研究表明, 植被归
还量(地上和地下部分)增大, 分解速率减缓会造成
土壤有机碳的累积, 凋落物输入量的增加与土壤有
机碳组分的变化趋势相同(Sauer et al., 2007; Busse
et al., 2009)。植物细根作为植物将光合产物直接输
入到地下的唯一途径, 直接通过分泌和归还作用将
有机碳归还于土壤。细根虽然在森林生态系统中占
根系总生物量不足30%, 但其净生产力却占森林总
生产力的30%–80% (McClaugherty et al., 1982), 每
年通过细根周转进入土壤中的有机质和归还到土
壤中的碳甚至会超过地上凋落物(Vogt et al., 1986;
Raich & Nadelhoffer, 1989)。
本研究选择了浙江天童常绿阔叶林3个不同次
生演替阶段群落, 通过对土壤总有机碳库、活性碳
库(包括可矿化碳(mineralizable carbon, MC)、可溶
性有机碳(dissolved organic carbon, DOC)和微生物
量碳(microbial biomass carbon, MBC))和不同植被
碳归还方式关系的研究, 旨在验证以下两个科学假
说: (1)随着演替进行, 土壤有机碳库和活性碳库储
量呈增加趋势; (2)土壤有机碳库储量主要受到土壤
细根归还量的影响。
1 研究方法
1.1 研究区概况和样地设置
研究地位于浙江省宁波市天童国家森林公园
(29°52′ N,121°39′ E), 属于温暖湿润的亚热带季风
气候, 全年无霜期237.8天, 年平均气温16.2 , ℃ 平
均年降水量1 374.7 mm, 土壤主要为黄红壤, 土层
厚度不一 , 一般在1 m以下 (宋永昌和王祥荣 ,
1995)。由于该区域植被在不同历史阶段受到的干扰
强度和保护年限不同, 在较小范围存在着处于不同
演替阶段的次生常绿阔叶林类型(阎恩荣等, 2010)。
本研究选择常绿阔叶林演替前期的次生针叶
林马尾松(Pinus massoniana)群落, 中期的次生常绿
阔叶幼年林木荷(Schima superba)群落, 以及演替后
期的成熟常绿阔叶林栲(Castanopsis fargesii)群落为
对象。每个演替阶段各重复设置4块20 m × 20 m的
样地, 样地间距25 m以上。为避免地形等其他因素
造成的影响, 样地设置时, 保证在坡向、海拔、土
壤母质和土壤类型等方面基本一致。样地简介及基
本理化性质见表1。
1.2 样品采集
在每个演替样地内均匀设置5个面积为0.5 m2
的凋落物收集筐(每个群落类型共20个收集筐), 实
验时间1年, 于每月月底收集一次凋落物, 共12次。
地表枯落物通过在样地内随机设置20个20 cm × 20
cm的采样框收集(每个群落类型共80个采样框), 按
季度共收集4次。另外, 每季度收集地表枯落物时,
在每个样地内用内径为7.6 cm的土钻, 分上、中、
下3个坡位, 各自选择5个取样点采集0–20 cm土壤
样品, 带回实验室后, 用自来水浸泡、冲洗并过筛
挑拣细根(≤2 mm), 根据根系的外形、颜色和弹性
区分活、死根(McClaugherty et al., 1982)。每次收集
的凋落物、地表枯落物和细根通过称重、烘干折算
生物量, 并留一部分备用保存, 以测定有机碳含
量。细根生物量通过以下公式换算: 细根现存量
孙宝伟等: 浙江天童常绿阔叶林演替过程中土壤碳库与植被碳归还的关系 805
doi: 10.3724/SP.J.1258.2013.00084
表1 浙江天童常绿阔叶林次生演替不同阶段的样地特征
Table 1 Characteristics of selected plots in a secondary successional series of evergreen broad-leaved forests in Tiantong, Zhejiang
Province
演替阶段
Success-
ional
stage
植被类型
Vegetation type
群落类型
Community
type
年龄
Age
(a)
海拔
Altitude
(m)
坡度
Slope
(°)
主要优势种
Dominant species
高度
层数
Number
of vertical
layer
高度
Top
height
(m)
土壤
容重
Soil bulk
density
(g·cm-3)
土壤
pH
Soil
pH
土壤
总氮
Soil
total N
(kg·hm–2)
土壤
总磷
Soil
total P
(kg·hm–2)
I 次生针叶林
Secondary
coniferous forest
马尾松群落
Pinus
massoniana
community
30 115 15 马尾松
Pinus massoniana
枫香
Liquidambar
formosana
2 12 1.34 4.18 5.98 0.39
II 常绿阔叶幼年林
Young evergreen
broad-leaved
forest
木荷群落
Schima
superba
community
60 163 20 木荷
Schima superba
柯
Lithocarpus glaber
3 20 1.30
4.18 25.07 1.04
III 成熟常绿阔叶林
Mature evergreen
broad-leaved
forest
栲群落
Castanopsis
fargesii
community
120 196 26 栲
Castanopsis fargesii
木荷
Schima superba
3 25 1.07 3.81 40.62 2.12
(t·hm–2) = (平均每根土芯细根干重(g) × 10–6)/[π(7.6/
2)2 × 10–8]]。
采用五点取样法, 用内径7.5 cm、长20 cm的
PVC管砸入土壤, 获取生长旺季的0–20 cm土壤样
品。5个样点的样品混合后分两部分, 一部分迅速过
2 mm筛后于4 ℃保存, 用于可矿化碳、可溶性有机
碳和微生物量碳测定, 另一部分风干磨细, 用于测
定土壤总有机碳。在采样时, 每个样地同时随机采3
个样品, 用于土壤容重的分析。
1.3 室内分析
土壤总有机碳、凋落物、地表枯落物和土壤细
根碳含量采用传统重铬酸钾外加热法测定(中国科
学院南京土壤研究所, 1978); 可矿化碳用33天的室
内矿化滴定实验测定 (Núñez et al., 2001), 得到
CO2-C (g C·kg–1)的累积释放量; 可溶性有机碳用蒸
馏水在25 ℃条件下浸提(水土比5:1), 过0.45 μm滤
膜后, 用TOC-VCPH仪(Shimadzu, Kyoto, Japan)测定
(吕国红等, 2006); 微生物量碳用氯仿熏蒸法(Vance
et al., 1987), 熏蒸后用0.5 mol·L–1的K2SO4溶液浸
提, 过滤并用重铬酸钾外加热法测定, 换算系数为
2.64 (林启美等, 1999)。
1.4 数据处理及统计分析
凋落物年凋落量为12个月内收集凋落物量的
总和; 地表枯落物现存量为4个季度的平均值; 细
根年归还量用细根的年死亡量来表示, 换算见公式
(1)。土壤0–20 cm各类型碳储量用公式(2)计算。
M = Xmax– Xmin + D (1)
S = C × B × 0.2 × 10 (2)
式中: M为细根年死亡量(t·hm–2), Xmax和Xmin分别为
死细根生物量最大值和最小值, D为年分解量; S为
碳储量(t·hm–2), C为碳含量(g·kg–1), B为土壤容重
(g·cm–3), 0.2为土壤深度(m), 10为换算系数。而对于
细根年分解量, 其由分解速率和死细根现存量换算
得到; 细根分解速率引用施家月(2005)的研究结果;
凋落物、细根的碳归还量和地表枯落物的碳储量分
别为各自碳含量与其单位面积归还量的乘积。
用单因素方差分析(one-way ANOVA)判断随演
替进行土壤总有机碳库及活性碳库含量和储量, 凋
落物凋落量、地表枯落物现存量和土壤细根年归还
量及其碳储量的变化。数据进行多重比较前, 首先
进行方差齐性检验, 满足方差齐性的采用最小显著
差别(least significant difference, LSD)方法比较, 不
满足则采用Dunnett法。另外, 为揭示土壤活性有机
碳库和土壤总有机碳库的关系, 以及凋落物年凋落
量、地表枯落物现存量和细根年归还量与土壤不同
类型碳库间的关系, 本文采用了Pearson相关分析和
多元逐步回归的处理方法。数据分析和作图分别在
SPSS 19.0和Origin 8.1软件中完成。
2 结果
2.1 土壤不同类型碳库动态
随着常绿阔叶林次生演替的进行, 0–20 cm土
层总有机碳(TOC)和3种活性有机碳(MC、DOC、
MBC)含量显著增加(p < 0.05)。即: 次生针叶林<次
806 植物生态学报 Chinese Journal of Plant Ecology 2013, 37 (9): 803–810
www.plant-ecology.com
生常绿阔叶幼年林<成熟常绿阔叶林(表2)。进一步
两两比较后发现, 相邻演替阶段土壤TOC、DOC和
MBC含量均存在显著差异(p < 0.05), 而MC含量在
常绿阔叶幼年林与成熟林之间差异不显著(表2)。
土壤有机碳储量与碳含量变化趋势有所不同,
表现为随着森林演替进行, TOC储量显著增加(p <
0.05), MC、DOC和MBC储量先升后降。活性有机
碳库中, MC和DOC储量在演替前期和后期存在显
著性差异(p < 0.05), 而MBC差异不显著, 三者在演
替中期土壤中储量最高(表2)。
2.2 凋落物年凋落量、地表枯落物现存量和细根年
归还量及其碳储量特征
随着演替的进行, 常绿阔叶林凋落物年凋落量
(F = 1 109.99, p < 0.001)及其碳储量(F = 5.14, p <
0.05)均显著增加, 而地表枯落物的现存量(F = 4.92,
p < 0.05)及其碳储量(F = 7.54, p < 0.05)均随演替显
著减小(图1)。细根年归还量(F = 292.77, p < 0.001)
及其碳储量(F = 238.10, p < 0.001)均随演替显著地
先增后减, 在中期最大。
2.3 土壤不同类型碳库的相关性及其与植被碳归
还的关系
2.3.1 不同类型碳库的相关性
根据Pearson相关分析(表3), 土壤TOC储量与
MC及DOC储量显著正相关(p < 0.05), 与MBC储量
不显著相关。而DOC储量与MC和MBC储量显著相
关(p < 0.01), MC储量与MBC储量不显著相关。另
外, 根据逐步回归, 3种活性有机碳中, MC储量对土
壤总有机碳储量的解释贡献为34.01% (R2 = 0.388,
表2 浙江天童常绿阔叶林次生演替阶段不同土壤碳库的含量及储量(平均值±标准误差)
Table 2 Contents and stocks of different soil carbon pools among secondary successional stages in evergreen broad-leaved forests
in Tiantong, Zhejiang (mean ± SE)
含量 Content 储量 Stock 演替阶段
Successional
stage
TOC
(g·kg–1)
MC
(g·kg–1)
DOC
(mg·kg–1)
MBC
(mg·kg–1)
TOC
(t·hm–2)
MC
(t·hm–2)
DOC
(t·hm–2)
MBC
(t·hm–2)
I 34.20 ± 1.63a 1.21 ± 0.04a 27.24 ± 0.14a 220.47 ± 5.28a 91.53 ± 3.49a 3.24 ± 0.13a 0.073 ± 8.55×10–4a 0.59 ± 0.019a
II 44.60 ± 2.74b 1.87 ± 0.06b 34.03 ± 0.53b 271.93 ± 6.87b 116.25 ± 7.53b 4.87 ± 0.16b 0.089 ± 9.10×10–4c 0.71 ± 0.020b
III 55.58 ± 3.54c 2.15 ± 0.19b 38.15 ± 0.64c 295.71 ± 8.36c 118.90 ± 6.73b 4.59 ± 0.36b 0.082 ± 2.04×10–3b 0.63 ± 0.026a
DOC, 可溶性有机碳; MBC, 微生物量碳; MC, 可矿化碳; TOC, 土壤总有机碳。I、II、III同表1。同一列不同小写字母表示差异显著(p < 0.05)。
DOC, dissolved organic carbon; MBC, microbial biomass carbon; MC, mineralization carbon; TOC, total soil organic carbon. I, II, III, see Table 1.
Different letters on the same column indicate significant differences (p < 0.05).
图1 浙江天童常绿阔叶林演替过程中凋落物年凋落量、地表枯落物现存量和细根年归还量(A)及碳储量(B) (平均值±标准误
差)。I、II、III同表1。同一组不同小写字母表示差异显著(p < 0.05)。
Fig. 1 Annual amounts of litterfall, forest floor biomass and annual return mass of fine roots (A), as well as carbon stocks among
litterfall, forest floor and fine roots (B) along a successional series in evergreen broad-leaved forest in Tiantong, Zhengjiang (mean ±
SE). I, II, III, see Table 1. Different letters on the same column group indicate significant difference (p < 0.05).
孙宝伟等: 浙江天童常绿阔叶林演替过程中土壤碳库与植被碳归还的关系 807
doi: 10.3724/SP.J.1258.2013.00084
表3 浙江天童常绿阔叶林不同演替阶段土壤不同类型碳储
量间的Pearson相关系数
Table 3 Pearson correlation coefficients of carbon stocks
among different soil carbon pools across successional stages in
evergreen broad-leaved forests in Tiantong, Zhejiang
TOC
(t·hm–2)
MC
(t·hm–2)
DOC
(t·hm–2)
MBC
(t·hm–2)
TOC (t·hm–2) 1.000
MC (t·hm–2) 0.632* 1.000
DOC (t·hm–2) 0.528* 0.701** 1.000
MBC (t·hm–2) 0.439 0.442 0.865** 1.000
DOC, 可溶性有机碳; MBC, 微生物量碳; MC, 可矿化碳; TOC, 土
壤总有机碳。*, p < 0.05; **, p < 0.01。
DOC, dissolved organic carbon; MBC, microbial biomass carbon; MC,
mineralization carbon; TOC, total soil organic carbon. *, p < 0.05; **, p
< 0.01.
p = 0.031), 回归方程为: TOC储量= 56.6 + 12.347 ×
MC储量, 可见, 演替过程中, MC储量增加是引起
土壤总有机碳储量增加的主要原因。
2.3.2 植被碳归还与土壤不同类型碳库间的关系
凋落物年凋落量、地表枯落物现存量和土壤细
根年归还量与土壤不同类型碳库的相关分析表明:
细根年归还量与TOC、MC、DOC和MBC储量间显
著正相关(p < 0.05)。凋落物年凋落量与TOC、MC
储量显著正相关, 与DOC、MBC储量不显著相关,
而地表枯落物现存量与TOC、MC、DOC和MBC储
量均不显著相关(表4)。
将凋落物年凋落量、地表枯落物现存量和土壤
细根年归还量作为自变量对各土壤不同类型碳库
逐步回归后, 发现细根年归还量对TOC、MC和DOC
和MBC储量的解释贡献最大(分别为28.2%、50.0%、
73.4%和68.8%), 是引起上述碳库随演替变化的主
要因素(表5)。此外, MBC储量还受到地表枯落物现
存量的影响。
3 讨论
3.1 土壤各形态碳库的演替规律
随着天童常绿阔叶林次生演替的进行, 土壤
TOC和3种活性有机碳(MC、DOC和MBC)含量均显
著增加(p < 0.05)。土壤总有机碳的含量是植被碳归
还量与分解速率平衡的结果, 归还量大而分解速率
缓慢时土壤有机碳积累(Sauer et al., 2007)。随着常
绿阔叶林演替的进行, 植被凋落物(包括地上和地
下部分)的种类和数量增加(张庆费等, 1999), 引起
土壤微生物群落结构发生变化(王清奎, 2011), 使微
表4 浙江天童常绿阔叶林不同演替阶段土壤不同类型碳库
与凋落物年凋落量、地表枯落物现存量及细根年归还量的
Pearson相关系数
Table 4 Pearson correlation coefficients between different
types of soil carbon and annual amounts of litterfall, forest
floor biomass and annual fine roots mass across successional
stages in evergreen broad-leaved forests in Tiantong, Zhejiang
TOC
(t·hm–2)
MC
(t·hm–2)
DOC
(t·hm–2)
MBC
(t·hm–2)
凋落物年凋落量
Annual amounts of
litterfall (t·hm–2)
0.632* 0.609* 0.445 0.213
地表枯落现存量
Forest floor biomass
(t·hm–2)
–0.411 –0.483 –0.209 0.134
细根年归还量
Annual fine roots
mass (t·hm–2)
0.714** 0.853** 0.901** 0.700*
DOC, 可溶性有机碳; MBC, 微生物量碳; MC, 可矿化碳; TOC, 土
壤总有机碳。
DOC, dissolved organic carbon; MBC, microbial biomass carbon; MC,
mineralization carbon; TOC, total soil organic carbon. *, p < 0.05; **, p
< 0.01.
表5 浙江天童常绿阔叶林不同演替过程中不同类型碳库储
量与凋落物年凋落量、地表枯落物现存量及细根年归还量的
逐步回归结果
Table 5 Results of stepwise regression between carbon stocks
in each of four soil pools and annual amounts of litterfall, forest
floor biomass and annual fine roots mass across successional
stages in evergreen broad-leaved forests in Tiantong, Zhejiang
Y 方程 Equation R2 p value
TOC Y = 65.844 + 39.009 X1 0.510 0.009
MC Y = 1.640 + 2.351 X1 0.728 <0.001
DOC Y = 0.058 + 0.021 X1 0.812 <0.001
MBC Y = 0.485 + 0.145 X1 0.490 0.011
DOC, 可溶性有机碳; MBC, 微生物量碳; MC, 可矿化碳; TOC, 土
壤总有机碳。X1, 细根年归还量。
DOC, dissolved organic carbon; MBC, microbial biomass carbon; MC,
mineralization carbon; TOC, total soil organic carbon. X1, annual fine
roots mass.
生物对凋落物的分解能力增强, 增加了土壤可利用
的碳源, 造成土壤有机碳的积累(黄靖宇等, 2008)。
随演替进行, 土壤通气性能和持水能力增强
(Li & Shao, 2006), 土壤孔隙度提高, 土壤容重显著
降低(表1, p < 0.05)。而土壤有机碳储量是其含量和
容重的综合, 反映了有机碳在土壤中的分布。本研
究中 , TOC储量随演替进行显著增加(p < 0.05);
MC、DOC和MBC储量也有增加趋势, 但在中期达
到最高(p < 0.05)。是由于演替中期到后期土壤容重
的降低程度远大于从前期到中期的降低程度(表1),
虽然导致了土壤有机碳含量随演替增加, 但活性碳
储量在演替中期却最大。这种现象说明土壤物理结
808 植物生态学报 Chinese Journal of Plant Ecology 2013, 37 (9): 803–810
www.plant-ecology.com
构影响土壤有机碳储量的估算。
土壤活性碳作为土壤总有机碳的组成部分, 其
含量在很大程度上取决于土壤总有机碳含量
(Anderson & Domsch, 1989)。在本研究中, 土壤TOC
与MC和DOC储量显著正相关(p < 0.05) (表3), 且可
矿化碳对土壤总有机碳储量的解释贡献率为
34.01%。因此, 演替过程中土壤活性碳组分的变化
影响土壤总有机碳储量的变化。因为随演替进展,
森林土壤接收的凋落物量增加(演替前、中和后期阶
段地上和地下凋落物年归还总量分别为8.61、11.53
和14.45 t·hm–2) (阎恩荣等, 2008), 使土壤总有机碳
增加。这一方面增加了MC的来源和淋溶到土壤中
DOC的量, 另一方面为土壤微生物提供了更加丰富
的物质能量来源以及适宜生存环境(如土壤年平均
温度、年平均土壤含水量随演替升高等(张庆费等,
1997)), 引起MC、DOC和MBC的含量随演替显著升
高(表2)。
3种土壤活性有机碳是较高活性的土壤碳素的
不同表征形式, 它们之间可通过矿化过程、微生物
代谢等过程进行关联。如土壤可矿化碳表示在一定
时间内能够被土壤微生物矿化的有机碳, 其矿化量
受初始可溶性有机碳和微生物的影响。而微生物裂
解死亡后其残体成为土壤可溶性有机碳和矿化碳
的来源(王清奎等, 2007)。本文中, MC和DOC显著相
关(p < 0.01), DOC和MBC显著相关(p < 0.01), 而
MC和MBC相关不显著(p > 0.05) (表3), 说明活性有
机碳在一定程度上可以相互转化。
3.2 凋落物年凋落量、地表枯落物现存量和土壤细
根归还量及其碳储量的演替规律
凋落物是植物有机碳向土壤归还的主要方式
之一, 凋落物年凋落量的变化与植物群落的种类组
成和数量有关。在演替前期, 群落结构简单, 高度
较低, 物种组成单一, 地上、地下植被的总生物量
较小, 归还量有限。而发育至成熟群落, 物种组成
多样, 群落水平和垂直结构趋于复杂, 优势物种获
得资源的能力增强, 拥有极大的凋落物来源, 归还
量也随之增加。因而, 在亚热带常绿阔叶林演替过
程中, 后期凋落物年凋落量和碳储量高于中前期
(图1)。
植物细根主要分布在近地表0–20 cm内, 其作
为植物有机碳向土壤归还的另外一种方式, 是地下
碳循环的重要组成部分。随着常绿阔叶林的演替,
细根总生物量显著升高(分别为0.72、2.74和3.21
t·hm–2) (p < 0.05)。这是因为森林随着演替过程, 群
落的水热条件、土壤养分、质地等改善(张小全,
2001), 更有利于植物生长, 使群落内生产力提高,
细根生物量增加, 进而影响死细根的年归还量。而
本研究中, 细根年归还量在中期最大(图1A), 这是
细根寿命、分解速率和周转率(施家月, 2005)共同作
用的结果。
地表枯落物层作为凋落物归还到土壤的中转
站, 是联系地上植物碳库和地下土壤碳库的桥梁,
其现存量是凋落物归还与地表枯落物分解动态平
衡的结果(Xu & Hirata, 2002), 主要受到群落结构、
物种组成和数量、凋落物分解特性等因素的影响。
在凋落量不变的条件下, 分解速率小可造成地表枯
落物积累, 相反, 若分解速率大, 则地表枯落物量
随演替减小。根据张庆费等(1999)的研究结果, 凋落
物分解速率随演替显著增加, 导致地表枯落物现存
量和碳储量在天童地区随演替显著降低(图1A)。
3.3 土壤碳库变化的影响因素
凋落物和细根归还是土壤有机碳的主要来源,
它们归还量的增加必然引起土壤总有机碳的增加。
本研究中, 凋落物凋落量显著增加, 细根归还量随
演替先增后减(p < 0.05) (图1A), 且两者均与TOC储
量显著正相关。在多元逐步回归的结果中, 细根年
归还量和凋落物年凋落量对TOC随演替增加的解
释贡献率分别为28.2%和6.7%, 说明细根年归还量
是引起TOC储量在演替上变化的主要原因。地表枯
落物作为凋落物分解的中间形态, 在本文的回归结
果中, 相对于凋落物和细根输入, 其与TOC储量随
演替变化的相关性不大。
土壤活性碳组分是土壤有机碳中最为活跃的
部分, 与土壤总有机碳相比, 活性有机碳组分对环
境变化的响应更加敏感、迅速(Haynes, 1999; Ahn et
al., 2009)。本研究中, 土壤MC、DOC、MBC碳库
储量均与土壤细根年归还量显著正相关(表4), 且在
多元回归结果中, 细根归还量对3种活性碳库的解
释贡献率分别为50.0%、73.4%和68.8%, 说明细根
年归还量也是引起土壤活性碳储量在演替上变化
的主要原因。而对于凋落物年凋落量, 其仅与活性
碳库中的MC储量显著相关, 与DOC和MBC均没有
显著关系(表4)。这是由于凋落物落到地表, 还需要
进一步进行分解、淋溶后才能够归还到土壤中, 而
孙宝伟等: 浙江天童常绿阔叶林演替过程中土壤碳库与植被碳归还的关系 809
doi: 10.3724/SP.J.1258.2013.00084
细根可以直接以死细根生物量或者活细根分泌有
机物的方式归还到土壤中。
最后, 对天童地区主要演替阶段土壤不同深度
碳储量的研究表明, 土壤0–20 cm碳储量约为20–40
cm碳储量的2倍(周武等, 2009), 而本研究只探讨了
植物碳归还对表层0–20 cm土壤有机碳库的影响,
因此, 对演替中土壤有机碳库与植被碳归还全面关
系的研究还有待深入。
基金项目 国家自然科学基金海外及港澳学者合
作研究基金(31228004)。
参考文献
Ahn MY, Zimmerman AR, Comerford NB, Sickman JO,
Grunwald S (2009). Carbon mineralization and labile
organic carbon pools in the sandy soils of a North Florida
watershed. Ecosystems, 12, 672–685.
Anderson TH, Domsch KH (1989). Ratios of microbial
biomass carbon to total organic carbon in arable soils. Soil
Biology & Biochemistry, 21, 471–479.
Busse MD, Sanchez FG, Ratcliff AW, Butnor JR, Carter EA,
Powers RF (2009). Soil carbon sequestration and changes
in fungal and bacterial biomass following incorporation of
forest residues. Soil Biology & Biochemistry, 41, 220–227.
Davidson EA, Janssens IA (2006). Temperature sensitivity of
soil carbon decomposition and feedbacks to climate
change. Nature, 440, 165–173.
Dixon RK, Solomon AM, Brown S, Houghton RA, Trexier
MC, Wisniewski J (1994). Carbon pools and flux of global
forest ecosystems. Science, 263, 185–190.
Guo LB, Halliday MJ, Siakmotu SJM, Gifford RM (2005).
Fine root production and litter input: its effects on soil
carbon. Plant and Soil, 272, 1–10.
Haynes RJ (1999). Labile organic matter as an indicator of
organic matter quality in arable and pastoral soils in New
Zealand. Soil Biology & Biochemistry, 32, 211–219.
Huang JY, Song CC, Zhang JB, Guo YD, Liao YJ (2008).
Influence of litter importation on basal respiration and
labile carbon in restored farmland in Sanjiang Plain. Acta
Ecologica Sinica, 28, 3417–3424. (in Chinese with
English abstract) [黄靖宇, 宋长春, 张金波, 郭跃东, 廖
玉静 (2008). 凋落物输入对三江平原弃耕农田土壤基
础呼吸和活性碳组分的影响 . 生态学报 , 28,
3417–3424.]
Institute of Soil Science, Chinese Academy of Sciences (1978).
Soil Physical and Chemical Analysis. Shanghai Scientific
and Technical Publishers, Shanghai. 132–136. (in
Chinese) [中国科学院南京土壤研究所 (1978). 土壤理
化分析. 上海科学技术出版社, 上海. 132–136.]
Kalbitz K, Kaiser K (2008). Contribution of dissolved organic
matter to carbon storage in forest mineral soils. Journal of
Plant Nutrition and Soil Science, 171, 52–60.
Li YY, Shao MA (2006). Change of soil physical under
long-term natural vegetation restoration in the Loess
Plateau of China. Journal of Arid Environments, 64,
77–96.
Lin QM, Wu YG, Liu HL (1999). Modification of fumigation
extraction method for measuring soil microbial biomass
carbon. Chinese Journal of Ecology, 18(2), 63–66. (in
Chinese with English abstract) [林启美, 吴玉光, 刘焕龙
(1999). 熏蒸法测定土壤微生物量碳的改进. 生态学杂
志, 18(2), 63–66.]
Lü GH, Zhou GS, Zhou L, Jia QY (2006). Methods of soil
dissolved organic carbon measurement and their
applications. Journal of Meteorology and Environment,
22(2), 51–55. (in Chinese with English abstract) [吕国红,
周广胜, 周莉, 贾庆宇 (2006). 土壤溶解性有机碳测定
方法与应用. 气象与环境学报, 22(2), 51–55.]
McClaugherty CA, Aber JD, Melillo JM (1982). The role of
fine roots in the organic matter and nitrogen budgets of
two forested ecosystems. Ecology, 63, 1481–1490.
Núñez S, Martínez-Yrízar A, Búrquez A, García-Oliva F
(2001). Carbon mineralization in the southern Sonoran
desert. Acta Oecologica, 22, 269–276.
Raich JW, Nadelhoffer KJ (1989). Belowground carbon
allocation in forest ecosystems: global trends. Ecology, 70,
1346–1354.
Sauer TJ, Cambardella CA, Brandle JR (2007). Soil carbon and
tree litter dynamics in a red cedar-scotch pine shelterbelt.
Agroforestry Systems, 71, 163–174.
Shi JY (2005). Fine Root Turnover and Nutrient Dynamics in
the Secondary Succession of Evergreen Broad-Leaved
Forest in Tiantong. Master degree dissertation, East China
Normal University, Shanghai. (in Chinese with English
abstract) [施家月 (2005). 天童常绿阔叶林次生演替过
程中细根的周转和养分动态. 硕士学位论文, 华东师范
大学, 上海.]
Song YC, Wang XR (1995). Vegetation and Flora of Tiantong
National Forest Park, Zhejiang Province, China.
Shanghai Scientific and Technological Literature
Publishing House, Shanghai. 11–12. (in Chinese) [宋永昌,
王祥荣 (1995). 浙江天童国家森林公园的植被和区系.
上海科学技术文献出版社, 上海. 11–12.]
Uselman SM, Qualls RG, Lilienfein J (2007). Contribution of
roots vs. leaf litter to dissolved organic carbon leaching
through soil. Soil Science Society of America Journal, 71,
1555–1563.
Vance ED, Brookes PC, Jenkinson DC (1987). An extraction
method for measuring soil microbial biomass C. Soil
Biology and Biochemistry, 19, 703–707.
Vogt KA, Grier CC, Vogt DJ (1986). Production, turnover, and
810 植物生态学报 Chinese Journal of Plant Ecology 2013, 37 (9): 803–810
www.plant-ecology.com
nutrient dynamics of above- and belowground detritus of
world forests. Advances in Ecological Research, 15,
303–337.
Wang QK (2011). Responses of forest soil carbon pool and
carbon cycles to the changes of carbon input. Chinese
Journal of Applied Ecology, 22, 1075–1081. (in Chinese
with English abstract) [王清奎 (2011). 碳输入方式对森
林土壤碳库和碳循环的影响研究进展. 应用生态学报,
22, 1075–1081.]
Wang QK, Wang SL, Yu XJ, Zhang J, Liu YX (2007). Soil
carbon mineralization potential and its effect on soil active
organic carbon in evergreen broadleaved forest and
Chinese fir plantation. Chinese Journal of Ecology, 26,
1918–1923. (in Chinese with English abstract) [王清奎,
汪思龙, 于小军, 张剑, 刘燕新 (2007). 常绿阔叶林与
杉木林的土壤碳矿化潜力及其对土壤活性有机碳的影
响. 生态学杂志, 26, 1918–1923.]
Xu XN, Hirata E (2002). Forest floor mass and litterfall in
Pinus luchuensis plantations with and without
broad-leaved trees. Forest Ecology and Management, 157,
165–173.
Yan ER, Wang XH, Guo M, Zhong Q, Zhou W (2010). C: N: P
stoichiometry across evergreen broad-leaved forests,
evergreen coniferous forests and deciduous broad-leaved
forests in the Tiantong region, Zhejiang Province, eastern
China. Chinese Journal of Plant Ecology, 34, 48–57. (in
Chinese with English abstract) [阎恩荣, 王希华, 郭明,
仲强, 周武 (2010). 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. 植物生态学报,
34, 48–57.]
Yan ER, Wang XH, Zhou W (2008). Characteristics of litterfall
in relation to soil nutrients in mature and degraded
evergreen broad-leaved forests of Tiantong, East China.
Chinese Journal of Plant Ecology, 32, 1–12. (in Chinese
with English abstract) [阎恩荣, 王希华, 周武 (2008).
天童常绿阔叶林不同退化群落的凋落物特征及其与土
壤养分动态的关系. 植物生态学报, 32, 1–12.]
Yang YS, Guo JF, Lin P, He ZM, Xie JS, Chen GS (2004).
Carbon and nutrient pools of forest floor in native forest
and monoculture plantations in subtropical China. Acta
Ecologica Sinica, 24, 359–367. (in Chinese with English
abstract) [杨玉盛, 郭剑芬, 林鹏, 何宗明, 谢锦升, 陈
光水 (2004). 格氏栲天然林与人工林枯枝落叶层碳库
及养分库. 生态学报, 24, 359–367.]
Zhang QF, Song YC, Wu HQ, You WH (1999). Dynamics of
litter amount and it’s decomposition in different succes-
sional stages of evergreen broad-leaved forest in Tiantong,
Zhejiang Province. Acta Phytoecologica Sinica, 23,
250–255. (in Chinese with English abstract) [张庆费, 宋
永昌, 吴化前, 由文辉 (1999). 浙江天童常绿阔叶林演
替过程凋落物数量及分解动态 . 植物生态学报 , 23,
250–255.]
Zhang QF, You WH, Song YC (1997). Influence of plant
community succession on soil physical properties in
Tiantong Forest Park, Zhejiang Province. Journal of Plant
Resources and Environment, 6(2), 36–40. (in Chinese with
English abstract) [张庆费, 由文辉, 宋永昌 (1997). 浙
江天童森林公园植物群落演替对土壤物理性质的影响.
植物资源与环境, 6(2), 36–40.]
Zhang XQ (2001). Fine-root biomass, production and turnover
of trees in relations to environmental conditions. Forest
Research, 14, 566–573. (in Chinese with English abstract)
[张小全 (2001). 环境因子对树木细根生物量、生产与
周转的影响. 林业科学研究, 14, 566–573.]
Zhou W, Guo M, Zhong Q, Wang XH, Yan ER (2009).
Characteristics of soil profile and organic carbon density
among succession stages in the evergreen broad-leaved
forests of Tiantong region, Zhejiang Province. Journal of
East China Normal University (Natural Science), (2),
11–20. (in Chinese with English abstract) [周武, 郭明,
仲强, 王希华, 阎恩荣 (2009). 天童常绿阔叶林主要演
替阶段的土壤剖面及碳密度特征. 华东师范大学学报
(自然科学版), (2), 11–20.]
Zhou YR, Yu ZL, Zhao SD (2000). Carbon storage and budget
of major Chinese forest types. Acta Phytoecologica Sinica,
24, 518–522. (in Chinese with English abstract) [周玉荣,
于振良, 赵士洞 (2000). 我国主要森林生态系统碳储
量和碳平衡. 植物生态学报, 24, 518–522.]
责任编委: 马克平 责任编辑: 李 敏