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Altor, Anne

Anderson, Chris J.

Hernandez, Maria E.

Mitsch, William J.

Zhang, Li

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Macrophyte Production ♦  57Net primary productivity of macrophyte communities in the experimental marshes after eleven growing seasonsWilliam J. Mitsch, Chris J. Anderson, Maria E. Hernandez, Anne Altor, and Li ZhangSchool of Environment and Natural Resources and Environmental Science Graduate Program, The Ohio State UniversityFigure 1.  Potential sampling stations for macrophyte harvesting.  Fifteen stations were sampled in Wetland 1 and 10 in Wetland 2 in 2004.IntroductionDirect measurements of macrophyte net primary productivity (NPP) were ﬁrst made at the experimental wetland basins of the Olentangy River Wetland Research Park (ORWRP) in 1997.  This study in 2004 represents the eighth set of such measurements. Prior to 1997 (the fourth growing season), macrophyte harvesting for estimation of biomass was not considered a good option as vegetation was just getting established in the basins.MethodsAboveground net primary productivity (NPP) was estimated by harvesting peak biomass at the end of the growing season on August 9, 2004 at selected stations in the two experimental wetland basins at the ORWRP (Figure 1).  The biomass harvesting stations that are used each year were established in 1997 along the permanent boardwalk system (Mitsch and Bouchard, 1998).  To avoid harvesting plants from the exact same spots from one year to the next, 1-m2 PVC sampling frames are tossed randomly from the boardwalks into the vegetation.  These 1-m2 frames are used to delineate quadrats in which vegetation is harvested. While there are potentially 22 stations in each wetland,  a maximum of 16 sites are harvested annually in each basin, and stations lacking emergent vegetation are skipped.  Fifteen quadrats were sampled in Wetland 1 and 10 quadrats were sampled in Wetland 2.  Eight out of a possible eight plots were sampled in the northern half (inﬂow area) of Wetland 2, but only two out of a possible eight plots in the southern half of Wetland 2 were sampled.  Vegetation in the outﬂow of Wetland 2 remains sparse since extensive herbivory occurred during 2002.In each quadrat, plants were clipped at ground level (the water was lowered in the wetlands to facilitate sampling). Samples were segregated both by quadrat and by species, placed in plastic bags and weighed in the ﬁeld with a hanging balance (accuracy ± 40 g).  Sub-samples were taken to the laboratory where both wet weight and dry weight (dried at 105°F for 48 hours) were determined to estimate dry/wet ratios.  Average ratios for each species were multiplied by the total wet weight of that species in each quadrat to estimate total dry weight production.  The sum of all species in a quadrat was the estimated peak biomass, and hence annual aboveground net primary productivity (NPP).Results and DiscussionComparison of Basins and LocationIn 2004, macrophyte aboveground NPP was 408 ± 37 g m-2 yr-1  for the 15 sites in Wetland 1, and 586 ± 91 g m-2 yr-1 for the 10 sites in Wetland 2.  Although productivity was similar at the inﬂow and outﬂow sites in the two wetlands (Figure 2), outﬂow results from Wetland 2 were based on only two sampling sites.  Aside from the two areas in which biomass was harvested in the outﬂow of Wetland 2, this region had little emergent vegetation (see vegetation cover chapter).Dry/Wet RatiosAs discussed in previous annual reports, dry/wet ratios of individual plant species that are necessary for estimating NPP are provided (Table 2). 58  ♦  The Olentangy River Wetland Research Park 2004Table 1.  Estimated net above-ground primary productivity (NPP) of macrophyte communities in the experimental wetlands based on peak biomass harvest, 1999 - 2004. Numbers are avg ± std error [# samples].______________________________________________Wetland/ Total NPP, Inﬂow NPP, Outﬂow NPP,Year g m-2 yr-1 g m-2 yr-1 g m-2 yr-1_______________________________________________________________________________Wetland 11999 657±76 [16] 601±126 [8] 714±90 [8]2000 482±64 [16] 597±87 [8] 368±79 [8]2001 393±87 [9] 454±98 [7] 181±120 [2]2002 689±93 [16] 915±126 [8] 462±79 [8]2003 432±60 [16] 570±90 [8] 295±45 [8]2004 408±37 [15] 441±59 [8] 369±41 [7]Wetland 21999 1023±94 [16] 790±75 [8] 1256±130 [8]2000 1013±105 [16] 882±126 [8] 1144±163 [8]2001 832±85 [9] 746±76 [7] 1134±145 [2]2002 519±64 [15] 699±84 [7] 361±53 [8]2003 192±54 [10] 226±62 [8] 54±19 [2]2004 586±91 [10] 583±92 [8] 596±361 [2]Comparison with Previous YearsAs a whole, macrophyte productivity in Wetland 1 in 2004 was similar to that of 2003, but productivity in Wetland 2 was higher in 2004 compared to 2003 (Figure 3).  When paired sites were compared between the two wetlands in 2003 (16 sites), NPP on a plot-by-plot basis was not statistically different in (planted) Wetland 1 than in (naturally colonized) Wetland 2 (α = 0.05).  NPP, on a plot-by-plot basis, was signiﬁcantly higher in in Wetland 2 compared to Wetland 1 for four years, from 1998 to 2001.Species Dominating NPPMacrophyte species found in sample quadrats in 2002 and 2003 are listed in Table 3.  Data for 2002 are corrected from previously-published data (Mitsch et al., 2003).  As was the case in previous years, the species harvested in the two wetlands indicate certain differences that can still be attributed to the original 1994 planting.  Four of the 12 species planted in Wetland 1 (Schoenoplectus tabernaemontani, Sparganium eurycarpum, Scirpus ﬂuviatalis, and Sagittaria Figure 2.  Aboveground net primary productivity in Wetland 1 and 2 inﬂow and outﬂow areas for 2004..Table 2. Dry/wet ratios (avg ± std error (# samples)) of dominant macrophyte species in the experimental wetlands from 2001-2004.______________________________________________Species/ Wetland 1 Wetland 2______________________________________________Schoenoplectus tabernaemontani   2002 0.15±0.01 (14) 0.16±0.02 (14)   2003 0.16±0.01 (14) 0.05±0.01 (7)   2004 0.19±0.01 (14) Polygonum sp.  2002 0.16±0.01 (13) 0.15±0.01 (7)Scirpus ﬂuviatilis   2001          na        na   2002 0.13±0.03 (3)        na   2004 0.34±0.0 (2)Sagittaria latifolia  2002 0.07±0.01 (3)         na   2004 0.22 (1)Sparganium eurycarpum   2001 0.16±0.03 (7)        na    2002 0.10±0.01 (10)        na   2003 0.15±0.01 (15)        na   2004 0.17±0.01 (16)        naTypha spp.   2001 0.20±0.05 (2) 0.29±0.03 (9)   2002 0.14±0.03 (4) 0.21±0.04 (8)   2003 0.23±0.02 (5) 0.11±0.00 (3)   2004 0.21±0.02 (4)Leersia oryzoides   2002 0.25±0.03 (10) 0.23 ± 0.02 (4)   2003 0.21±0.2 (15) 0.10±0.02 (6)   2004 0.27±0.03 (13)Cyperus sp.    2002 0.15±0.01 (8) 0.21±0.02 (9)Echinochloa sp.   2002 0.13 ±0.03 (5) 0.17±0.04 (2)Lycopus americanus   2002 0.18±0.01 (2)  naLudwigia sp.   2003          na 0.14±0.4 (2)Alisma plantago   2004 0.035 (1)______________________________________________latifolia) were still contributing to macrophyte productivity in both 2003 and 2004.  S. tabernaemontani contributed 34% of the productivity in W1 and Sparganium eurycarpum added 26% of the productivity in 2004 (Table 3). The naturally colonizing species Typha and Leersia contributed 11 and 22% of the productivity  in Wetland 1, respectively, in 2004. S. tabernaemontani, which had reestablished from the seedbank in Wetland 2 during spring drawdown in 2001, accounted for 38% of the productivity of this wetland in 2004, and 37% of its productivity in 2003.  Typha again dominated NPP in Wetland 2 with 57% of the productivity in 2004. By contrast, Typha contributed 41% of the productivity in Wetland 1 and 100% of the productivity in Wetland 2 in 2001, but lost dominance in both wetlands as a result of muskrat herbivory in winter 2001, followed by g m-2 yr-1Macrophyte Production ♦  59Figure 3. Aboveground net primary productivity for 1997-2004 in the experimental wetlands. * indicates signiﬁcant differences between the two wetlands (α=0.05).Table 3. Percent dominance of macrophytes according to aboveground primary productivity in quadrats in 2002 (n = 16 for W1; n = 15 for W2), 2003 (n = 16 for W1; n = 10 for W2) and 2004 (n = 15 for W1; n = 10 for W2), and species richness in quadrats. “nd” indicates not detected in biomass samples; 0.0 indicates species was present but did not contribute signiﬁcantly to productivity.__________________________________________________________________  2002  2003   2004Species W1 W2 W1 W2  W1 W2__________________________________________________________________Schoenoplectus t.,  72.8 55.9 36.7 37.3  33.8 38.1Polygonum spp. 12.5 21.8 0.0 0.0    0.0   ndTypha spp. 6.9 16.1   16.3 41.9  11.5  57.2Sparganium eury.  0.5 nd 18.0   nd  26.4   ndLeersia oryzoides   5.1 6.3 28.2 25.3  22.5   4.7Cyperus sp.   1.9 5.7   0.0   nd     nd   ndEchinochloa 0.6 0.4 0.0   nd     nd   nd    Panicum sp. nd 0.2 nd   5.6     nd   nd    Lycopus sp. 0.5 0.0 nd   nd      nd   nd    Scirpus ﬂuviatilis 0.5 nd  0.9   nd    5.3   ndSagittaria latifolia 0.4 0.0 0.0   nd    0.5   ndLudwigia palustris 0.0 0.0 nd nd     nd   ndPenthorum sedoides nd nd nd   0.0     nd   ndGratiola virginiana nd nd nd   0.0     nd   ndMimulus ringens nd nd 0.0   nd     nd   ndAlisma plantago nd nd nd nd    0.0   nd ___ ___ ___ ___  ____ ____TOTAL 100.0 100.0 100.0 100.0  100.0 100.0Species richness 11 10 10 7      8    3*****60  ♦  The Olentangy River Wetland Research Park 2004Table 4.  Estimated macrophyte above-ground net primary productivity in each experimental wetland, 1997-2004 (kg dry-wt per wetland basin).______________________________________________Year  Wetland 1 Wetland 2______________________________________________2004  2,434  2,1222003  2,397    6252002  4,478  3,3302001    963  1,2502000  1,960  4,2651999  5,800  6,8001998  3,300  3,5001997  2,525  3,040Total             24,757              24,932seedbank regeneration and subsequent agressive growth by Schoenoplectus in 2002.There were eight macrophyte species found in sampling plots in Wetland 1, and three species in Wetland 2, in 2004.  By comparison, ten and seven species were found in 2003, and 11 and 10 species in 2002 in Wetlands 1 and 2 respectively. Lycopus spp. and Ludwigia palustris were seen in Wetland 1 in 2002, but not in 2003 or 2004, and Mimulus ringens was seen in sampling quadrats for the ﬁrst time in 2003 in Wetland 1, but not in 2004.  Smartweed (Polygonum spp.) continued to be found in both wetlands in 2003, although it did not contribute signiﬁcantly to NPP.  In 2004,  Polygonum spp was found only in Wetland 1. This is a considerable decline from 2002, when it contributed 12 and 22% of the productivity respectively to Wetlands 1 and 2.Basin ProductivityBased on the aboveground productivity estimates reported here, and on estimates of macrophyte cover presented elsewhere in this annual report (Mitsch et al., 2005;  W1 = 5967 m2; W2 = 3622 m2), aboveground productivity of macrophytes was estimated to be 2434 and 2122 kg yr-1 in Wetlands 1 and 2 respectively (Table 4). Overall NPP increased slightly in Wetland 1, and increased three-fold in Wetland 2, from 2003 to 2004.  The year 2004 is the third year in a row in which the planted Wetland 1 had a higher esimated macrophyte carbon sequestration than the naturally colonized Wetland 2.  The cumulative organic matter production by macrophytes over the last eight-years is now almost equal in the two wetlands (~25 Mg basin-1) (Table 4).ReferencesMitsch, W.J. and V. Bouchard. 1998. Net primary productivity of macrophytes in experimental marshes. In: W.J. Mitsch and V. Bouchard (eds.), The Olentangy River Wetland Research Park at the Ohio State University, Annual Report 1997. The Ohio State University, Columbus, OH, pp. 71-75.Mitsch, W.J.,  C.J. Anderson, M.E. Hernandez, and L. Zhang. 2003. Net primary productivity of macrophyte communities after nine growing seasons in experimental planted and unplanted marshes. In: W.J. Mitsch, L. Zhang, and C.J. Anderson (eds.), The Olentangy River Wetland Research Park at the Ohio State University, Annual Report 2002. The Ohio State University, Columbus, OH, pp. 37-40.Mitsch, W.J., L. Zhang, and R. Mauk. 2005. Plant community development after eleven growing seasons in two experimental wetland basins. In: W.J. Mitsch, L. Zhang, and A. Altor (eds.), The Olentangy River Wetland Research Park at the Ohio State University, Annual Report 2004. The Ohio State University, Columbus, OH, pp. 51-56.

Net primary productivity of macrophyte communities in the experimental marshes after eleven growing seasons

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Net primary productivity of macrophyte communities in the experimental marshes after eleven growing seasons

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