Soil organic carbon dynamics following afforestation of degraded pastures with eucalyptus in southeastern Brazil
Soil organic carbon dynamics following afforestation of degraded pastures with eucalyptus in southeastern Brazil
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DOI：
10.1016/j.foreco.2006.08.331
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发表时间：
2006-11-01
影响因子：
3.7
通讯作者：
Leite, Fernando P.
中科院分区：
文献类型：
--
作者：
Lima, Augusto M. N.;Silva, Ivo R.;Leite, Fernando P.
退化草场的造林可能会增加碳固存，但桉树人工林对土壤有机质组分的影响尚不清楚。我们使用密度和颗粒大小的SOM分值来评估在巴西东南部两个不同地区退化牧场上建立的桉树人工林的SOM变化。草地土壤碳含量（C4光合途径）下降，桉树土壤碳含量（C3光合途径）增加，土壤碳自然丰度为13c。两个研究区位于米纳斯吉拉斯州多塞河谷，分别为：1、贝洛奥连特（Belo Oriente， BO，海拔较低，年平均气温较高，森林生产力较低，以粘土型haplustos为主）；2、Virginopolis （VG，一个海拔较高、森林生产力较高的地区，主要是粘土Rhodic ustos）。BO区桉树种植年限分别为0、4.2、13.2、22.2、32.0和34.2年，VG区桉树种植年限分别为0、8.2、19.2、29.2和33.2年。累积栽培时间约为5轮。在这两个地区，最初的土壤条件都是由一个仍在牧场下的地点来代表的。分析了0 ~ 10 cm和10 ~ 20 cm深度土壤样品的总有机碳（TOC）含量；腐殖质（FAF）、腐殖质（HAF）和腐殖质（HF）中的C；游离（FLF）和闭塞（OLF）部分的C；C与重组分有关，即砂（SF）、粉砂加粘土（S + CF）和粘土（CF）组分；微生物量（MB）中的C。几乎所有有机质组分的碳储量在VG区都是BO区的两倍。BO地区的桉树栽培增加了所有SOM组分的C储量，除了MB组分没有变化，SF组分随着桉树栽培时间的推移而下降。在VG区TOC、FAF和HF有机C组分增加。在整个栽培期内，0-10 cm土层的年平均积累量几乎没有差异，BO区平均为0.22 Mg C ha（-1）年（-1），VG区平均为0.23 Mg C ha（-1）年（-1）。而BO区TOC累积在第3轮和VG区TOC累积在第2轮结束时达到峰值，分别对应于0.35和0.57 Mg C ha（-1）年（-1）。没有明确的证据表明，更不稳定的、快速循环的SOM组分是BO地区桉树种植影响的更敏感指标，而在VG地区，FLF和OLF比TOC对土地利用变化更敏感。(c) 2006 Elsevier B.V.版权所有
Afforestation of degraded pastures can potentially enhance carbon sequestration, but little is known about the effects of eucalyptus plantations on soil organic matter (SOM) fractions. We used density and particle size SOM fractionations to evaluate changes in SOM for a chronosequence of eucalyptus plantations established on degraded pastures in two contrasting regions in southeastern Brazil. Declines in the content of soil C derived from the pasture (C4 photosynthetic pathway) and the accumulation of that derived from the eucalyptus (C3 photosynthetic pathway) were followed through 13 C natural abundance of the SOM. The two study areas were in the Rio Doce River Valley, Minas Gerais State, namely: 1, Belo Oriente (BO, a region with lower elevation, higher mean annual temperature, lower forest productivities and dominated by clayey Typic Haplustoxs); 2, Virginopolis (VG, a region of higher elevation, higher forest productivities and dominated by clayey Rhodic Ustoxs). In the BO region the chronosequence included 0, 4.2, 13.2, 22.2, 32.0 and 34.2 years of eucalyptus cultivation and in the VG region soils were cultivated with eucalyptus for 0, 8.2, 19.2, 29.2 and 33.2 years. The accumulated cultivation time corresponds to about five rotations. In both regions the initial soil condition was represented by a site that was still under pasture. Soil samples collected at 0-10 and 10-20 cm depths were analyzed for: total organic carbon (TOC); C in the fulvic (FAF), humic (HAF) and humin (HF) fractions; C in the free (FLF) and occluded (OLF) light fractions; C associated with the heavy fractions, namely, the sand (SF), silt plus clay (S + CF) and clay (CF) fractions; and C in the microbial biomass (MB). Carbon stocks of virtually all SOM fractions were about twice as high in the VG region than in the BO region. Eucalyptus cultivation in the BO region increased C stocks in all SOM fractions, except for the MB fraction that was not altered and the SF fraction that declined with time of eucalyptus cultivation. Increases in TOC, FAF and HF organic C fractions were observed in the VG region. Mean annual accumulations across the entire cultivation period in the 0-10 cm soil layer showed virtually no difference averaging 0.22 Mg C ha(-1) year(-1) for the BO region and 0.23 Mg C ha(-1) year(-1) for the VG region. However, gains of TOC peaked by the end of the third rotation in the BO region and the second rotation in the VG region, so the TOC accumulation rate during the respective aggrading periods would correspond to 0.35 and 0.57 Mg C ha(-1) year(-1). There was no clear evidence that the more labile, fast cycling SOM fractions were more sensitive indicators of the impact of eucalyptus cultivation in the BO region, whereas in the VG region the FLF and OLF were more sensitive to the land use change than TOC. (c) 2006 Elsevier B.V. All rights reserved.