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標題: | 以物理分餾與穩定同位素分析檢視臺灣平地造林之土壤有機碳動態 Soil Organic Matter Dynamics Analysis in Taiwan Plain Afforestation Areas Using Physical Fractionation and Stable Isotope |
作者: | 魏子穎 Zi-Ying Wei |
指導教授: | 鄭智馨 Chih-Hsin Cheng |
關鍵字: | 造林,土壤團粒,團粒與密度劃分,土壤有機碳,13C自然豐度, Afforestation,Soil Aggregates,Aggregate and density fractions,Soil Organic Carbon,13C Natural Abundance, |
出版年 : | 2024 |
學位: | 碩士 |
摘要: | 土壤有機碳庫的增減,受到土地利用改變的影響。在農地造林之後,除了簡易量測的土壤碳匯變化,這些變化在土壤團粒與團粒間物質之間仍有資訊空缺。本研究樣區位於嘉義太保與彰化溪洲地區,為近18年的蔗田平地造林,並以C4 (甘蔗)與C3 (造林)植群轉換對土壤進行的自然δ13C標記,檢視土壤有機碳動態。樣區包含了嘉義地區持續耕作的甘蔗田區與三種林木 (茄冬、桃花心木與櫸木),以及彰化地區的四種林木 (水黃皮、阿勃勒、苦苓與台灣欒樹)與鄰近甘蔗田區。土壤團粒以濕篩法取得,分成穩定大團粒 (Water Stable Macroaggregate, > 250 µm)與穩定小團粒 (Water Stable Microaggregate, < 250 µm),並進一步以密度劃分取得團粒內的顆粒有機質 (Particle Organic Matter, POM)與礦物有機質 (Mineral associated Organic matter, mSOM),。
結果顯示在18年的平地造林在表層土壤 (0-20 cm) 影響程度較甘蔗樣區大,具有降低的土壤容積密度、增加的土壤碳含量與碳氮比,但下層 (20-30 cm)土壤則與甘蔗樣區相近。在0-30 cm土層中,嘉義與彰化造林樣區的土壤有機碳儲存量分別介於44.1-65.2 Mg ha-1與33.4.2-38.8 Mg ha-1,平均較甘蔗田區增加了21.0 Mg ha-1與12.7 Mg ha-1的有機碳儲存量。嘉義造林樣區中,黏粒與交換性鈣含量高於彰化造林樣區,也反應在嘉義樣區具較高的碳儲存量、團粒平均重量直徑 (Mean weight diameter, MWD)。 甘蔗樣區中的土壤穩定團粒主要由小團粒 (Microaggregate)所組成,嘉義造林活動使穩定團粒分布由小團粒變為大團粒 (Macroaggregate)所主導。經由13C數值計算,林木來源的有機碳量在團粒內的POM與mSOM相當;彰化造林區域中由於較弱的團粒化作用,土壤結構組成仍以小團粒為主,然而林木來源POM主要分布於大團粒,在團粒內大於礦質有機質的碳儲存量。兩地的農地造林的過程顯現一致的特徵,使造林樣區逐漸形成大團粒,並於大團粒中積聚POM。縱使過往研究多顯示造林將主要增加在POM的碳庫上,然而在本研究中,嘉義與彰化樣區中林木累積的mSOM碳庫量仍大於POM的形式,顯示經過18年的造林,不只有增加土壤有機碳庫,這些「新」有機碳已經以較穩定的有機碳形式儲存。 Land use change is often reported to strongly affect the dynamic of soil organic carbon pools. Afforestation of farmland could be a net carbon sink, yet questions persist about its influence on soil aggregates and intra-aggregate substances. This study is aim to get insight into dynamics of soil organic carbon after land use change, especially in size and density aggregates fractions. Our sample area was located at Taibao in Chiayi County and Hsichou in Changhua County, where plain afforestation of sugarcane field has been ongoing for nearly 18 years. The sample plot included continuous sugarcane cultivation fields and three tree species (Swietenia macrophylla, Zelkova serrata and Bischofia javanica) at Chiayi, four tree species (Melia azedarach, Cassia fistula, Millettia pinnata and Koelreuteria henryi) at Changhua. We separate soil into water stable macroaggregate (> 250 µm) and microaggregate (< 250 µm), and further conduct density separation to get intra-aggregate Particulate Organic Matter (POM) and Mineral-associated Organic Matter (mSOM) in each aggregate fraction. The results showed that the impact of afforestation was more significant in the surface soil (0-20 cm), with decreased soil bulk density, increased soil carbon content and CN ratio. However, the physic and chemical property of the subsoil (20-30 cm) remained similar to the sugarcane control area. In the 0-30 cm soil layer, the soil organic carbon storage in the afforested areas of Chiayi and Changhua ranged from 44.1-65.2 Mg ha-1 and 33.4-38.8 Mg ha-1, respectively, and the average increase in organic carbon storage is 21.0 Mg ha-1 and 12.7 Mg ha-1 in Chiayi and Changhua, respectively. In the Chiayi afforested area, the high content of clay and exchangeable calcium appeared to affect the carbon storage and mean weight diameter (MWD) of aggregates. In the sugarcane field, stable soil aggregates were mainly composed of microaggregates, but afforestation in Chiayi led to a shift of aggregate mass distribution from microaggregates to macroaggregates. The amount of afforestation derived organic carbon shortage was comparable between POM and mSOM. In the afforested area of Changhua, the distribution of aggregate mass was still predominantly composed of microaggregates due to weaker aggregation processes. However, the mass proportion of macroaggregates in the afforested area remained higher than that in the sugarcane field. Afforestation derived POM was mainly accumulated in macroaggregates, resulting in higher carbon storage in aggregates. The afforestation process in both areas displayed consistent characteristics. After establishment of afforestation, the aggregate mass distribution gradually shifts toward macroaggregates with the accumulation of intra-aggregate POM. Despite prior studies suggesting that afforestation primarily increases particle organic matter, our study found that the amounts of forest-derived mSOM in Chiayi and Changhua were still greater than those in POM. This suggest that after 18 years of afforestation, the newly accumulated organic carbon could have been stored in a more stable form. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/91794 |
DOI: | 10.6342/NTU202400289 |
全文授權: | 同意授權(全球公開) |
顯示於系所單位: | 森林環境暨資源學系 |
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