李氏禾與鋪地黍在不同季節及水位生長及光合作用的比較

Comparison of Growth and Photosynthesis of Leersia hexandra and Panicum repens in Different Seasons and Water Levels

林藜臻(Li-Jhen Lin)

指導教授 ： 郭耀綸

國立屏東科技大學/農學院/森林系所/碩士(2015年)

https://doi.org/10.6346/NPUST.2015.00134

摘要

本研究目的在於瞭解李氏禾與鋪地黍兩禾本科濕地植物，在南仁湖不同水位微生育地的分布狀況，並探討鋪地黍在南仁湖草澤區陸化環境取代李氏禾的原因。為達成此目的，本研究在南仁湖現地觀察上述兩植物在不同水位微生育地的覆蓋度，另在屏科大苗圃測定兩植物的光合作用性狀，並以人為淹水試驗比較兩植物在不同季節及不同水位下的生長表現。
研究結果發現，在南仁湖草澤區李氏禾或鋪地黍獨佔的群落，各植物的覆蓋度與水位深度呈顯著負相關；但在兩植物混生的群落，李氏禾的覆蓋度與水位呈顯著正相關，而鋪地黍卻是呈顯著負相關，鋪地黍在水位較淺處覆蓋度顯著高於李氏禾。在南仁湖也觀察到鋪地黍進入秋季時會大量枯萎，至春季時再萌發新葉。2014年秋季在屏科大苗圃進行的淹水試驗，發現單植時李氏禾在水位30 cm處生物量顯著較其他水位高，鋪地黍則在不淹水時生物量最高。秋季試驗當兩植物混植時，在不淹水處理兩植物生物量無顯著差異，但在水位30及60 cm時，李氏禾的生物量均顯著較鋪地黍高。另一個在2015年春季進行的淹水試驗，發現單植時兩植物的生物量均以不淹水處理顯著較各淹水處理高；當兩植物混植時，在不淹水處理鋪地黍的生物量顯著高於李氏禾，而在水位15及30 cm時，兩植物的生物量並無顯著差異。上述結果顯示，鋪地黍在春季於不淹水環境之競爭能力會顯著高於李氏禾，但在秋季則無此現象，這可能是因鋪地黍在入秋後植體會衰老，因此在秋季對李氏禾的競爭能力會減弱。本研究在屏科大苗圃測得鋪地黍光合潛力顯著高於李氏禾(29.4 vs. 18.8 µmol CO2 m-2 s-1)。此兩植物在不淹水環境下的淨光合作用率均顯著高於淹水15 cm之環境，然而，此兩植物在上述淹水條件下的淨光合作用率，分別仍可維持在不淹水條件時的75%以上。
本研究結果支持「鋪地黍在不淹水環境有能力競爭排擠李氏禾」的假說。因此在南仁湖草澤區陸化明顯的棲地，鋪地黍較李氏禾佔有優勢，在水位較深的棲地鋪地黍的競爭能力可能不如李氏禾，李氏禾在水位較深之處可佔優勢。
關鍵字：競爭、李氏禾、南仁湖、鋪地黍、光合作用、淹水試驗、水位。

關鍵字

競爭 ； 李氏禾 ； 南仁湖 ； 鋪地黍 ； 光合作用 ； 淹水試驗 ； 水位

並列摘要

The purpose of this study is to understand the distribution of two Gramineae wetland plants Leersia hexandra and Panicum repens in different water level microhabitats of Nanjen Lake, and investigate the reason why L. hexandra was replaced by P. repens in non-flooded areas. To achieve this purpose, we observed the coverage of L. hexandra and P. repens in different water level microhabitats of Nanjen Lake, measured their photosynthetic characteristics in NPUST nursery, as well as compared their growth performances in different seasons and water levels with artificially submerged experiments.
The results showed that, in monopolized community of either L. hexandra or P. repens in the grassy marsh area of Nanjen Lake, the coverage of each species was negatively related to water levels. While in mixed community of both species, the relationship between coverage and water levels was significantly positive for L. hexandra but negative for P. repens. The coverage of P. repens was significantly higher than that of L. hexandra in shallower water levels. In Nanjen Lake, we also observed that P. repens would wither in substantial amount in autumn and re-sprout in spring. An artificially submerged experiment was conducted in autumn, 2014, at nursery of NPUST. Results showed that when each species was mono-planted, the biomass of L. hexandra was significantly higher at 30 cm water level than the biomass at other water levels. On the other hand, the biomass of P. repens was highest in non-flooded treatment. When the two species were mix-planted, biomass of the two species showed no significant difference in non-flooded treatment, while the biomass of L. hexandra was significantly higher than that of P. repens when water level was 30 cm or deeper. Another submerged experiment was conducted in spring, 2015. The results showed that, when mono-planted, biomass of L. hexandra or P. repens was significantly higher in non-flooded treatment than their biomass at any other water levels. Yet when mix-planted, P. repens was advantageous in non-flooded treatment while the two species were equally competitive at 15 and 30 cm water levels. According to the above results, P. repens showed higher competiveness than L. hexandra under non-flooded condition in spring but not in autumn. It might due to the phonological nature of P. repens. This species would become weak and wither in autumn, so that its growth and competiveness against L. hexandra would decline. In addition, the photosynthetic capacity of both species measured in NPUST nursery indicated that P. repens was significantly higher than L. hexandra (29.4 vs. 18.8 µmol CO2 m-2 s-1). The net photosynthesis rates of both species were significantly higher under non-flooded condition than under 15-cm submerged condition. However, both species could still maintain their net photosynthetic rates under flooded conditions at above 75% of net photosynthesis under non-flooded condition.
The above results supported our hypothesis that " P. repens has the ability to competitively exclude L. hexandra under non-flooded condition." Therefore, P. repens is capable of competitively excluding L. hexandra under non-flooded condition in Nanjen Lake, but L. hexandra will dominate at habitat with deeper water levels.
Keywords：Competition, Leersia hexandra, Nanjen Lake, Panicum repens, Photosynthesis, Submerge experiments, Water levels.

並列關鍵字

Competition ； Leersia hexandra ； Nanjen Lake ； Panicum repens ； Photosynthesis ； Submerge experiments ； Water levels

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