刈割大花咸豐草的再生性在土壤管理之應用

Abstract

大花咸豐草(Bidens pilosa L. var. radiata Sch. Bip.)是目前平地常見雜草，其多年生、四季均可開花和可進行營養繁殖等優勢，使其已被列入危害力最高的20種入侵植物之一。本研究探討刈割對大花咸豐草根、莖、葉生長的影響，來考量刈割下來的地上部回歸土壤對土壤肥力的貢獻。探討刈割對其不同深度根系生長和死亡的影響，來考量不同深度根系成為供應該深度土壤有機質的機會。探討野外大花咸豐草生長與土壤有機質的關係，來考量大花咸豐草生長對土壤有機質的供獻。 實驗分三個部分，第一部分透過盆栽實驗，用非成對t-test比較刈割組和控制組在根、莖、葉的生物量和有機質含量、葉面積、地上部的氮、磷、鉀濃度的差異，來分析刈割對大花咸豐草生長的影響。第二部分透過根系觀察箱，在刈割前後進行根系觀察，將根系分成活的根、死的根的總長在0~30cm、30~60cm、60~90cm土壤深度中，用Duncan’s test比較刈割前後和不同深度間的根系的差異。第三部分透過野外調查，用非成對t-test比較在海邊大花咸豐草和馬鞍藤(Ipomoea pes-caprae)生長區域的土壤特性-有機質含量、酸鹼值、導電度、現地體積含水量、假比重。並使用線性複迴歸分析大花咸豐草的株數和土壤參數，以探討各項土壤參數與大花咸豐草的關係。 研究結果發現，刈割組和控制組相比，莖比例極顯著降低、葉比例顯著增加、葉面積沒有顯著差異、莖有機質含量顯著降低，推論刈割後大花咸豐草的再生傾向於葉部生長，大量累積葉面積，以獲取更多光源。刈割後大花咸豐草再生的莖和葉擁有較高氮、磷、鉀濃度，表示刈割後再生的地上部營養含量較高。由根系觀察箱發現，刈割後到刈割後第14天，在3個土壤深度中的根系仍持續生長，表示能繼續成為供應這3個土壤深度中有機質的來源。刈割後0~30cm和30~60cm土壤深度中的死亡根長顯著增加，表示刈割後死亡的根系，即可成為該深度土壤有機質的來源，增加該深度土壤有機質。刈割前後大花咸豐草在表層(0~30cm)均擁有最多根長。野外調查發現，大花咸豐草生長區域和馬鞍藤生長區域相比，有極顯著較高的土壤有機質含量，推測大花咸豐草在增加土壤有機質含量上和馬鞍藤相比，有較佳的表現。由線性複迴歸分析發現，土壤有機質含量和大花咸豐草的株數，有顯著正相關。藉此推測，大花咸豐草生長的株數增加，對於土壤有機質的增加，有顯著相關。

Bidens pilosa L. var. radiata Sch. Bip. is a common weed in the low altitude area in Taiwan. Its advantages on perennial life cycle, flowering in all seasons and vegetative reproductivity make it is listed as one of the most twenty noxious invasive plants in Taiwan. This study works on the influence of clipping on its growth of vegetative organs to consider the the contribution to soil fertility of by the return of clipped shoot to the soil. We study on the influence of clipping on the root growth and death in different depth to consider the possibility of providing soil organic matters through the management of clipping B. pilosa var. radiata. And we also study on the relationship between wild B. pilosa var. radiata growth and the soil organic matters to estimate its contribution to soil organic matters. There are three experiments. The first experiment is a pot-culture experiment. To analyze the influence to B. pilosa var. radiata, we compare the biomass in leaves, roots and stems and the difference in organic matters, leaf area and Nitrogen, Phosphates, Potassium concentrations between the control and the clipping treatment with unpaired t-test. In the second experiment, we plant the B. pilosa var. radiata in the rhizotrons and observe the root length. We recorded the full root length, dead and alive separately, in the depth of 0-30 cm, 30-60 cm and 60-90 cm, and compare the difference between the lengths before and after clipping with Duncan’s test. The third experiment, through the field research, compares the soil quality, organic matters, pH value, conductivity, on-site volune wetness and bulk density, of living regions between the B. pilosa var. radiata and Ipomoea pes-caprae. The multiple regression analysis of the numbers of B. pilosa var. radiata and the soil parameters were also done to study on the relationship between soil parameters and B. pilosa var. radiata. The results show that, compared to control, the cliping treated plants have a very significant decrease in the porpotion of stem and a significantly higher leaf porpotion but having no differences in leaf area. This may resulted from its tendency to increasing leaf area by leaf growth in order to harvest more light energy. The clipped stem and leaf of B.pilosa var. radita have a higher Nitrogen , Phosphate and Potassium concentration, indicates that the clipped B. pilosa var. radiata has a higher shoot nutrient. From observing the rhizotron we noticed that, in the 14 days after clipping, the root systems in three depths remained growing, it means that it can continues to provide organic matters in the three soil depth. The dead root length in 0-30 cm and 30-60 cm increased significantly, it means that the dead root systems can be the source of the soil depth, increasing its soil organic matters. In both before and after clipping, B. pilosa var. radiata have most of the root length in 0-30 cm. Through the field research, compared to the living region of Ipomoea pes-caprae, the living region of the B. pilosa var. radiata has a very significantly higher soil organic matters. We can conclude that B. pilosa var. radiata has a better performance on increasing soil organic matters than Ipomoea pes-caprae. The multiple regression analysis shows a significant positive correlation between the number of B. pilosa var. radiata and the soil organic matters. It can be concluded that the more B. pilosa var. radiata plants growing has a significant correlation with higher increase of soil organic matters.