Growth responses of the Everglades wet prairie species Eleocharis cellulosa and Rhynchospora tracyi to water level and phosphate availability

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• 作者：Busch ; Joachim ; Mendelssohn ; Irving A. ; Lorenzen ; Bent ; Brix ; Hans ; Miao ; ShiLi
• 关键词：Growth responses ; Wet prairie species ; Phosphate ; Water level ; Eleocharis ; Rynchospora ; Everglades ; Rhizotron
• 刊名：Aquatic Botany
• 出版年：2004
• 期刊代码：17_03043770
• 类别：abs
• 出版时间：January, 2004
• 卷：78
• 期：1
• 页码：37-54
• 文件大小：280 K

摘要

Root and shoot growth response of Eleocharis cellulosa and Rhynchospora tracyi, two wet prairie species from the Everglades, to water level and phosphate availability were examined in rhizotrons facilitating root growth analysis. Plants were cultivated in Everglades peat subjected to ambient (10μg Pl⁻¹) and high phosphorus (500μg Pl⁻¹) availability and three water levels (+45, +10 and −30cm). Flooded conditions resulted in large increases in canopy height (from 60 to 80cm), maximum shoot length (from 75 to 100cm), and aboveground (from 8.5 to 11g), root (from 2.6 to 3.8g), rhizome (from 1.1 to 1.6g), and total (from 15 to 20g) biomass in E. cellulosa. Flooding also increased relative growth rate (RGR) in E. cellulosa from 0.012 to 0.016gg⁻¹ per day and root densities at −10cm, had no effect on shoot/root ratio, and root density at the 30 and 40cm soil depths, but decreased relative biomass allocation to shoots from 0.77 to 0.73. In R. tracyi, flooded conditions resulted in an increase in shoot/root ratios from 5.1 to 6.7, and relative biomass allocation to shoots (from 0.75 to 0.81) as well as in canopy height (from 59 to 67cm), had no effect on maximum shoot length, root porosity, aboveground biomass, rhizome and total biomass, but decreased root biomass (from 1.5 to 0.8g), RGR of total biomass (from 0.017 to 0.014gg⁻¹ per day), root density (from 22 to 6 at −10cm) and relative biomass allocation to roots (from 0.06 to 0.04). High P-availability increased aboveground (+24%) and total biomass (+22%) and root density in both species (+60%in E. cellulosa and +80%in R. tracyi at −10cm), but had no effect on canopy height, maximum shoot length, and root and rhizome biomass. In E. cellulosa, high P-availability increased RGR of total biomass from 0.012 to 0.016gg⁻¹ per day, but did not influence shoot/root ratio and relative biomass allocation. High P-availability did not influence RGR of total biomass in R. tracyi, but increased shoot/root ratio from 4.3 to 6.6 and increased relative biomass allocation to shoots from 0.76 to 0.80. In E. cellulosa, flooding increased root porosity from 52 to 69%, but had no effect on shoot porosity. In R. tracyi, the opposite was the case (increase of shoot porosity from 19 to 29%). Neither root porosity nor shoot porosity was affected by high P-availability. The results indicate E. cellulosa is better adapted to higher water levels than R. tracyi. Consistently, E. cellulosa performed best under flooded conditions, while R. tracyi growth was better under drained conditions. Thus, the relative success of E. cellulosa and R. tracyi in the field may change with alterations in site hydrology and P-availability.