台灣地區木麻黃及相思樹下層植物之碳庫存及多樣性現況解析

本研究分別於海拔500m以下永安漁港(北部)、台中港(中部)、四湖(南部)、台東太麻里(東部)之木麻黃林暨苗栗通霄、恆春半島之相思樹造林地林進行調查，估算不同森林下層植被每公頃之生物量及碳庫存量，同時瞭解低海拔地區相思樹、木麻黃林分下層植群之組成。木麻黃（Casuarina equisetifolia）林分之下層植物生物量，以東部太麻里樣區蓄積最高，平均達3.1Mg
ha-1；中部四湖樣區最少僅0.95 Mg ha-1；相思樹（Acacia confusa）林分之下層植物生物量，以通宵樣區最高，為5.02 Mg ha-1，此數據亦遠大於木麻黃每公頃生物量之最高值。木麻黃林下主要生物量由馬纓丹（Lantana camara）、巴拉草（Brachiaria mutica）、大花咸豐草（Bidens pilosa）、瓊麻（Agave sisalana）及雙面刺（Zanthoxylum nitidum）等組成，含碳百分比依序為馬纓丹44.92%、瓊麻40.15%、大花咸豐草40%、雙面刺43.81%。相思樹林林下主要下層生物量由大黍(Panicum maximum)、馬纓丹、扛香藤（Mallotus repandus）等組成，含碳百分比依序為大黍36.14%、馬纓丹45.12%、扛香藤43.43%。
以從生物多樣性觀點論之，木麻黃林下植物種類以太麻里的歧異度最高，植物種類達40種。相思樹林下植物之物種歧異度以恆春半島最高，植物種類達36種。

This study conducted field surveys in low-elevation (*<500 m a.s.l.*) *Casuarina equisetifolia* forests at Yong’an Fishing Harbor (northern Taiwan), Taichung Harbor (central Taiwan), Sihu (southern Taiwan), and Taimali, Taitung (eastern Taiwan), as well as in *Acacia confusa* afforestation stands in Tongxiao, Miaoli and the Hengchun Peninsula. We estimated the understory vegetation biomass and carbon stock per hectare across different forest types, and characterized the understory vegetation community composition of these low-elevation *Casuarina equisetifolia* and *Acacia confusa* stands.
For understory plant biomass of *Casuarina equisetifolia* stands, the Taimali (eastern Taiwan) sample plot exhibited the highest accumulation, with an average of 3.1 Mg ha⁻¹, while the Sihu sample plot in central Taiwan had the lowest value, at only 0.95 Mg ha⁻¹. For understory plant biomass of *Acacia confusa* stands, the Tongxiao sample plot had the highest value of 5.02 Mg ha⁻¹, which was considerably higher than the maximum per-hectare understory biomass of *Casuarina equisetifolia* stands.
The dominant understory biomass contributors in *Casuarina equisetifolia* stands were *Lantana camara*, *Brachiaria mutica*, *Bidens pilosa*, *Agave sisalana*, and *Zanthoxylum nitidum*. Their carbon content percentages, in order, were 44.92% for *Lantana camara*, 40.15% for *Agave sisalana*, 40% for *Bidens pilosa*, and 43.81% for *Zanthoxylum nitidum*.
The dominant understory biomass contributors in *Acacia confusa* stands were *Panicum maximum*, *Lantana camara*, and *Mallotus repandus*. Their carbon content percentages, in order, were 36.14% for *Panicum maximum*, 45.12% for *Lantana camara*, and 43.43% for *Mallotus repandus*.
From a biodiversity perspective, the Taimali sample plot had the highest plant species diversity among *Casuarina equisetifolia* stands, with a total of 40 plant species recorded. The Hengchun Peninsula sample plot had the highest plant species diversity among *Acacia confusa* stands, with a total of 36 plant species recorded.