臺灣35種闊葉樹種的葉部耐旱性及全株耐旱性

極端氣候造成乾旱發生的頻度及嚴重性增加，林木遭遇缺水逆境的機會及受害程度也會提高。為因應乾旱對林木的危害，需要知道造林或生態復育作業選用樹種的耐旱能力。本研究目的為量化臺灣常見35種闊葉樹種的生理耐旱性，提供未來造林時樹種選擇的依據。本研究以兩項試驗進行，第一項為藉壓力-體積曲線求得各樹種膨壓喪失點葉部水勢(πtlp)，由此量化其葉部耐旱性。第二項為藉長期斷水處理測得各樹種盆栽樹苗光合作用停止時的黎明前葉部水勢(ΨA0M)，當作樹種全株耐旱性的量化指標。葉部耐旱性的測定結果發現，供試樹種πtlp範圍在-2.79 ~ -2.29 MPa，其中πtlp低於-2.60 MPa的有13種，以恆春哥納香及無患子葉部耐旱性最高。πtlp介於-2.59 ~ -2.40 MPa的樹種有20種；πtlp大於-2.40 MPa的樹種只有蟲屎及白匏仔，葉部耐旱性最低。經歷長期斷水處理後，供試樹種ΨA0M範圍在-6.32 ~ -3.41 MPa，其中有9樹種的ΨA0M小於-6.0 MPa，包括銳葉高山櫟、光蠟樹、交力坪鐵色等，全株耐旱性極高。ΨA0M介於-6.0 ~ -5.0 MPa的樹種有6種，介於-5.0 ~ -4.0 MPa的樹種有14種，ΨA0M大於-4.0 MPa的只有樟樹、茄苳、白匏仔、蘭嶼肉桂、牛樟及蟲屎等6種，全株耐旱性最低。供試35樹種的πtlp及ΨA0M此兩參數間具極顯著正相關，顯示葉部耐旱性較高的樹種，全株耐旱性也會較高。本研究所有樹種達膨壓喪失點葉部水勢時，其光合作用及氣孔導度均尚未完全停止，平均分別仍可維持飽水狀態時的20及17%，有7樹種該兩性狀均能維持20%以上。本研究供試35樹種中，ΨA0M小於-6.0 MPa，且πtlp小於-2.60 MPa的樹種有銳葉高山櫟、交力坪鐵色、無患子、大葉桃花心木、恆春哥納香、圓果青剛櫟及土樟等7種，生理耐旱性最高。未來若要在有缺水逆境之生育地造林時，可選用上述生理耐旱性較高的樹種供栽植，可增加造林成功的機會。

關鍵字

葉部耐旱性；長期斷水處理；光合作用停止時的水勢；膨壓喪失點水勢；全株耐旱性

並列摘要

Extreme climate has caused more frequent and much severe drought events, thus increased the chances of water stress and the damages suffered by forest trees. To be responsive to the drought stress due to extreme climate, it is necessary to verify the drought tolerant ability of tree species chosen for forestations or eco-restorations. For future forest practices, this research quantified the physiological drought-tolerance of 35 broadleaf tree species of Taiwan. Two experiments were conducted in this study. First, water potential at turgor loss point (πtlp) of each tree species was calculated by pressure-volume curves to quantify the leaf drought-tolerance. Second, water potential at photosynthesis cease (ΨA0M) of each species was retrieved by long-term water withholding treatments as a quantified index for whole-plant drought-tolerance. The leaf drought-tolerance measurements showed that the range of πtlp of all tested species was -2.79 ~ -2.29 MPa. There were 13 species showed πtlp < -2.60 MPa with Goniothalamus amuyon and Sapindus mukorossii having the highest leaf drought-tolerance; 20 species showed the range of πtlp in -2.59 ~ -2.40 MPa; only Melanolepis multiglandulosa and Mallotus paniculatus showed πtlp > -2.40 MPa, indicating these 2 species had the least leaf drought tolerant ability. After the long-term water withholding treatments, the range of ΨA0M of all tested species was -6.32 ~ -3.41 MPa. There were 9 species had ΨA0M < -6.0 MPa, including Quercus tarokoensis, Fraxinus griffithii, and Drypetes karapinensis, indicating these species had high whole-plant drought-tolerance; 6 species showed ΨA0M in the range of -6.0 ~ -5.0 MPa; 14 species in the range of -5.0 ~ -4.0 MPa; only 6 species showed ΨA0M > -4.0 MPa, including Cinnamomum camphora, Bischofia javanica, Mal. paniculatus, C. kotoense, C. kanehirae, and Mel. multiglandulosa, indicating these species had the least whole-plant drought-tolerance. The πtlp and ΨA0M of the 35 tested species showed significant positive relationship, meaning that those species having high leaf drought-tolerance would have high whole-plant drought-tolerance as well. In this research, when all the species had reached the water potential at turgor loss point, their photosynthesis and stomatal conductance had not completely ceased and maintained at 20 and 17%, respectively, of the traits when under well watered condition, with 7 of them even maintained above 20% in both traits. Among the 35 species, there were 7 species showed ΨA0M < -6.0 MPa and πtlp < -2.60 MPa, including Q. tarokoensis, D. karapinensis, Sap. mukorossii, Swietenia macropnylla, G. amuyon, Q. globosa and C. reticulatum, indicating these species had the highest physiological drought tolerant ability. In the future, if the sites of forest practices will encounter severe water-stressed conditions, these high physiological drought-tolerant species could be chosen to assure the success of forestations.