溫度對雪山地區玉山杜鵑開花物候之影響

Abstract

高山生態系在全球氣候變遷下是面臨威脅最嚴重的生態系之一，而植物物候變化反應了氣候變化的綜合結果，也是植物適應氣候變化的過程，是最容易觀測和理想的重要感應器；因此，透過植物物候長期觀察可以監測氣候的變化。本研究主要針對雪山地區3,000 m以上蟲媒花之高山植物進行物候調查，建立高山植物物候學基礎資料，進行之環境因子與物候現象之分析，並探討全球氣候變遷下對高山植物物候與繁殖之影響。研究結果顯示，雪山主東峰線植物開花物候約在2月底開始，11月中旬結束，5-8月為蟲媒花植物開花物候之高峰期；同種植物愈往高海拔有愈晚開花的趨勢，而較高海拔之植物亦有較晚開花的趨勢。因海拔是間接因子，其反映在溫度的變化，推測較高海拔溫度較低且熱量不足，致使該區之開花物候較晚。其中，玉山櫻草等對溫度變化敏感之植物，可作為氣候變遷指標植物之一。玉山杜鵑是臺灣分布海拔最高的木本植物之一，花大而豔麗，是非常適宜作為長期物候觀測比較的植物。2010及2011年玉山杜鵑的物候與生育地各項因子分析結果顯示，海拔是影響最大的環境因子，海拔、光環境與坡向等3個環境因子間交互作用不顯著，而3因子皆與溫度有關，反映出溫度對玉山杜鵑的物候影響很大。隨海拔上升，展葉期、始花期和終花期明顯隨著遞延，花前累積時數、花前累積熱量、每花序花朵數(2010年)和每枝條新葉數顯著減少。在森林、林緣、草生灌叢等3種不同光環境下，玉山杜鵑之每花序花朵數、每枝條新葉數、始花期和終花期等均呈現顯著差異。玉山杜鵑的物候反應在不同方向坡向雖然差異不顯著，但生長在西北方向的植株通常較晚開花。玉山杜鵑地徑與各項物候現象無顯著相關。比較玉山杜鵑不同年度的開花物候發現，2010年的始花期較2011年早約4-33天，且2年度間的差異隨著海拔升高有縮小之趨勢；此可能反映出2010年1-5月平均溫度較2011年高，致使熱量累積較高所致。再者，雪山地區2010年玉山杜鵑在無論是單株或族群的開花皆較2011年來得茂盛，並且在2012年再度繁盛，可能反映出玉山杜鵑開花物候的豐欠年。研究結果推測，未來若持續暖化，玉山杜鵑在高海拔者較能適應，而較低海拔者則漸漸退縮。

Alpine ecosystems are one of the most severely threatened ecosystems under global climate change. Changes in plant phenology reflect the cumulative effects of climate change, show the subsequent process of plant adaptation, and are an important and ideal indicator that is easy to observe. Therefore, longitudinal observations of plant phenology can monitor climate changes. This study primarily conducted phenological surveys on alpine plants above 3,000 m with entomophilous flowers in the Mt. Xue. These surveys established basic alpine plant phenological data to conduct analyses on the relationship between phenological phenomena and environmental factors. The effects of global climate change on the phenology and reproduction of alpine plants was also studied. Study results indicated that the flowering phenology of plants along the East Xue Trail on Mt. Xue begins approximately at end of February and concludes in mid-November. The peak period of the flowering phenology for entomophilous flower plants was from May to August. The same species of plants tended to flower later as they take root in higher altitudes. In addition, plants in higher altitudes generally showed a trend of later flowering. Because altitude is an indirect factor that is reflected in temperature change, it is inferred that the temperature at higher altitudes was reduced and insufficient, which led to the later flowering phenology in the area. Plant species that are sensitive to temperature changes, such as Yushan Cowsli (Primula miyabeana), can be used as indicator species for climate change. The Yushan Azalea (Rhododendron pseudochrysanthus) is one of the highest altitude growing woody plants in Taiwan. It has large and colorful flowers, and is well-suited for long term phenological observations and comparisons. The results from an analysis on the factors in phenology and sites of reproduction of the Yushan Azalea in from the years 2010 and 2011 showed that altitude is the most influential environmental factor. The interaction among the three factors of altitude, lighting environment, and slope direction were insignificant. All three factors are related to temperature, reflecting the strong influence of temperature on the phenology of the Yushan Azalea. Along with increases in altitude, the leaf expansion period, first flowering date, and last flowering date were significantly delayed. The cumulative hours before flowering, cumulative heat-value before flowering, number of flowers per inflorescence (2010), and number of leaves per branch all decreased significantly. Under the three differing lighting environments of the interior, edge, and shrubbery regions of a forest, the number of flowers per inflorescence, number of new leaves per branch, first flowering date, and last flowering date all demonstrated significant differences. Although the phenological reaction of the Yushan Azalea to different slope directions was not significant, plants that grew facing northwest typically flowered later. The trunk base diameter of the Yushan Azalea and the various phenological phenomena were not significantly correlated. Comparing the flowering phenology of the Yushan Azalea for different years showed that the first flowering date in 2010 was between four and thirty-three days earlier than in 2011. The difference between the two years decreased with when the altitude increased. This may reflect the higher average temperature from January to May in 2010 than in 2011, which led to more accumulated heat. In addition, regardless of whether there was a single plant or a cluster of plants, the Yushan Azalea in the Mt. Xue area flowered more extensively in 2010 than in 2011, and again flowered abundantly in 2012. This may reflect the abundant and lean years in terms of the flowering phenology of the Yushan Azalea. The results of the study indicated that if global warming continues in the future, it would be easier for Yushan Azalea plants in higher altitudes to adapt to these changes, whereas the range of the plants in lower altitudes would gradually shrink.