In the laboratory, water and sediment from sample sites and in experimental tanks and pots were analyzed for nutrient concentrations using flow injection analyzer (NO3−, NH4+, PO43−, TN and TP). Water pH was measured in the laboratory and alkalinity was determined by end point titration using 0.02 N HCl. Sediment samples were analyzed for organic matter content by drying samples at 104 ◦C and combusting at 400 ◦C for ash free dry weight (AFDW). Total nitrogen (TN) in sediment was measured by catalytic combustion at 900 ◦C on C/N analyzer (CE Instruments). Total recoverable
phosphorus (TRP) in sediment was measured by HNO3/HCl digest at ICP-MS. All data for water and sediment characteristics on the sampling sites are given in Table 1. In the experimental tanks alkalinity was 0.6 mequiv. L−1
(±0.01 SD) and pH was 7.49 (±0.02 SD). Total N was 0.239 mg L−1 with 0.109 mg NO3-N L−1 and 0.002 mg NH4-N L−1. Total P was 0.006 mg L−1 with 0.004 mg PO4 3−-P L−1. Water chemistry was held constant during the experiment. Sediment in the pots had organic matter content of 15.6% DW, total N content of 3.9 g kg−1 (±0.7 SD)
and total P content of 0.73 g kg−1 (±0.01 SD). Plant shoots from five populations of each species were planted
in small pots (9 cm diameter and 7 cm deep) containing 2/3 of mixed garden soil and 1/3 of fine sand. Most obligate aquatic plants are able to establish vegetatively from apical shoots and often this is the most important mechanism of dispersal and establishment in new habitats (Riis, 2008; Nilsson et al., 2010). For each species six shoots were taken from each of the five populations. In each pot a 17 cm shoot was planted with 5 cm embedded in the sediment and 12 cm above the sediment. No branches were present on the shoots. Six replicates of each population were planted with a total of 90 pots (3 species × 5 populations×6 replicates) in each treatment. The plants grew in the tanks for seven weeks during the austral summer (20 January to 9 March 2009).
In the laboratory, water and sediment from sample sites and in experimental tanks and pots were analyzed for nutrient concentrations using flow injection analyzer (NO3−, NH4+, PO43−, TN and TP). Water pH was measured in the laboratory and alkalinity was determined by end point titration using 0.02 N HCl. Sediment samples were analyzed for organic matter content by drying samples at 104 ◦C and combusting at 400 ◦C for ash free dry weight (AFDW). Total nitrogen (TN) in sediment was measured by catalytic combustion at 900 ◦C on C/N analyzer (CE Instruments). Total recoverablephosphorus (TRP) in sediment was measured by HNO3/HCl digest at ICP-MS. All data for water and sediment characteristics on the sampling sites are given in Table 1. In the experimental tanks alkalinity was 0.6 mequiv. L−1(±0.01 SD) and pH was 7.49 (±0.02 SD). Total N was 0.239 mg L−1 with 0.109 mg NO3-N L−1 and 0.002 mg NH4-N L−1. Total P was 0.006 mg L−1 with 0.004 mg PO4 3−-P L−1. Water chemistry was held constant during the experiment. Sediment in the pots had organic matter content of 15.6% DW, total N content of 3.9 g kg−1 (±0.7 SD)and total P content of 0.73 g kg−1 (±0.01 SD). Plant shoots from five populations of each species were plantedในขนาดเล็กกระถาง (เส้นผ่าศูนย์กลาง 9 ซม.และ 7 ซม.ลึก) 2/3 ของดินสวนผสมและ 1/3 ของทรายที่มีการ สุด obligate สาหร่ายจะสร้าง vegetatively จากปลายยอดอ่อน และมักจะเป็นกลไกสำคัญของ dispersal และก่อตั้งในการอยู่อาศัยใหม่ (Riis, 2008 Nilsson et al., 2010) สำหรับแต่ละชนิด หกถ่ายภาพที่ถ่ายจากประชากร 5 ในแต่ละหม้อ ยิง 17 ซม.ถูกปลูก ด้วย 5 เซนติเมตรฝังอยู่ในตะกอนและ 12 ซม.เหนือตะกอน สาขาไม่ได้อยู่ในการถ่ายภาพ เหมือนกับ 6 ของประชากรแต่ละถูกปลูก มีทั้งหมด 90 หม้อ (3 สปีชีส์ใน 5 ประชากร× 6 เหมือนกับ) ในแต่ละทรีทเม้นต์ พืชเติบโตในถังเจ็ดสัปดาห์ในช่วงฤดูร้อนทองเหลือง austral (20 มกราคมถึง 9 2552 มีนาคม)
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