桂北不同林龄桉树人工林土壤碳库管理指数和碳组分的变化特征

采用时空互代法,以广西北部低山丘陵地区不同林龄(1、2、3、4、5和8 a)桉树人工林为研究对象,探讨林龄对桉树人工林地土壤碳库管理指数的影响及其规律。结果表明:(1)随着林龄的增加,土壤有机碳总体表现为增加的趋势,1～8 a桉树土壤有机碳范围在5.79～15.57 g· kg^-1之间,随着土层的加深而降低; 0～40 cm土层土壤有机碳平均含量表现为8 a>5 a>3 a>4 a>2 a>1 a。(2)土壤非活性有机碳、碳储量随林龄和土层的变化规律与土壤有机碳基本一致。土壤活性有机碳含量大小依次表现为8 a>5 a>4 a>3 a>2 a>1 a,占土壤有机碳的比例随林龄变化无明显规律,8 a和其他林龄间均具有显著差异。(3)碳库管理指数随林龄增加整体呈上升趋势,8 a桉树人工林土壤碳组分含量及碳库管理指数均高于10 a对照马尾松林。碳库管理指数与土壤有机碳、非活性有机碳、活性有机碳、碳储量、碳库活度、全氮、容重呈极显著或显著的相关性,不同林龄和土层间碳库管理指数有差异性。适当延长桉树人工林的轮伐周期,减少人为对林地凋落物和林下植被的干扰,将有利于提高土壤的有机碳含量,进而改善土壤质量。

Characteristics of soil carbon pool management index and carbon components of Eucalyptus plantations with different ages at North Guangxi

Using the space-time intergenerational method, the plantation of different ages of Eucalyptus plantations in low hilly areas at Northern Guangxi were taken as the research object. The effects of forest age on characteristics of soil organic carbon(SOC), total nitrogen(TN), soil labile organic carbon(LOC)and soil carbon management index(CPMI)were measured in this study. The results were as follows:(1)SOC indicated a trend of increasing with the increase of Eucalyptus forest age, and decreased with the increasing of soil depth. The content of soil organic carbon of 1-8 years old Eucalyptus varied from 5.79 to 15.57 g·kg^-1 in the whole soil layer(0-40 cm), the order of SOC contents was 8 a>5 a>3 a>4 a>2 a>1 a.(2)The variation tendencies of soil not labile organic carbon and carbon storage were consistent with the content of SOC. The order of soil labile organic matter contents was 8 a>5 a>4 a>3 a>2 a>1 a, respectively. There were no obvious change characteristics for the proportion of soil labile organic carbon to soil organic carbon with the increase of forest age. There was significant difference between 8 year old forest age and other forest ages.(3)The carbon pool management index increased with the increase of forest age. The soil carbon pool management index and soil carbon component contents of 8 ywars old Eucalyptus had been higher compared with 10 years old Pinus massoniana forest. Moreover, correlation analysis showed that existing extremely significant or significant correlation to soil organic carbon, soil not labile organiccarbon, labile oragnic carbon, carbon storage, carbon pool activity, total nitrogen, bulk density and soil carbon pool management index. There were also differences of carbon pool management index between different forest ages and soil layers. It was concluded that under the condition of local soil fertility, 8 years old Eucalyptus could both increase SOC contents and improve CPMI, favor soil quality amelioration and soil fertility improvement. Therefore, extending Eucalyptus plantations forest harvesting time and decreasing the disturbance to forest litter and understory vegetation would improve soil quality, and it is also important for promoting sustainable development of Eucalyptus plantations.