Carex Lasiocarpa Research Articles

Effects of reclamation of natural wetlands to a rice paddy on dissolved carbon dynamics in the Sanjiang Plain, Northeastern China

Natural wetlands play an important role in the global carbon cycle, and loss of dissolved carbon through water has been indicated as one of the most important carbon sources for riverine ecosystems. During the last century, a large natural wetland area was reported to be converted to other land use types such as rice paddy land around the world. In this study, we explored the dynamics of dissolved organic carbon (DOC) and dissolved inorganic carbon (DIC) in two natural freshwater wetlands and a rice paddy field, which was reclaimed from the natural wetlands in the Sanjiang Plain, Northeastern China, during the growing season (May–October) of 2009. The DOC and DIC concentrations in the two ecosystems were significantly different ( P < 0.05). The mean DOC concentrations during the growing season in the surface water of the Deyeuxia angustifolia and Carex lasiocarpa wetlands were 49.88 ± 5.44 and 27.97 ± 1.69 mg/L, respectively, while it was only 8.63 ± 2.54 mg/L in the rice paddy field. Specific ultra-violet light absorption at 254 nm (SUVA 254) of DOC increased by an average of 19.54% in the surface water from the natural wetlands to rice paddy, suggesting that DOC mobilized in the natural wetlands was more aromatic than that in the rice paddy field. The mean DIC concentration in surface water of the rice paddy was 5.25 and 5.04 times higher than that in the natural D. angustifolia and C. lasiocarpa wetlands, respectively. The average ratio of DIC to dissolved total carbon (DTC) for the water sampled from the artificial drainage ditch in the rice paddy field was 61.82%, while it was 14.75% from the nearby channel of natural wetlands. The significant differences in dissolved carbon concentration in surface water and channels originating from different land use types suggested that reclamation of natural wetlands to rice paddy field would reduce DOC runoff and increase the DIC concentration to adjacent watersheds. Our study results for the changed pattern in dissolved carbon after the natural wetland was transformed to paddy field could have important implications for studying the impacts of the large-scale land use change to carbon cycle and management.

Simulation study on purification efficiency for nitrogen in different types of wetlands in Sanjiang Plain, China

The purification law of nitrogen in Deyeuxia angustifolia, Carex lasiocarpa and Deyeuxia angustifolia-Carex lasiocarpa combined wetland systems in the Sanjiang Plain, China was studied by field simulation experiment. The results indicate that the removal rates of TN, NH4+-N and NO3−-N in above three types of wetlands present an obvious logarithm growth trend along with the time. There are evident removal effects for NH4+-N and NO3−-N in water bodies of wetlands after the 30th day of experiment, with the removal rates over 80.0%, but the removal rate of TN is slightly low, being 63.1%–74.3%. NO3−-N is most quickly removed by the combined wetland, and NH4+-N by Deyeuxia angustifolia wetland. The removal speeds of TN by the three wetland systems are comparatively slow, of which the Deyeuxia angustifolia wetland is the fastest. In consideration of plant growth season, Deyeuxia angustifolia wetland has much more practical application value in purifying nitrogen. These results can provide references for the study on the purification function of wetlands and the control of non-point source pollution in Northeast China.

Competition and Facilitation in Three Marsh Plants in Response to a Water-Level Gradient

Biomass accumulation and neighbor effects (measured with a relative neighbor effect index, NEI) were investigated in three marsh plant species (Carex lasiocarpa, Glyceria spiculosa, and Deyeuxia angustifolia) grown at three water levels (0, 20, and 40 cm relative to the soil surface). The three species occur naturally along a water-level gradient in the Sanjiang Plain, the largest freshwater marsh in China. Both intraspecific and interspecific competition were measured using a target-neighbor design, which subjected the three species to different intensities of inter- and intra-specific competition. Biomass accumulation and NEI differences among water levels and competition treatments suggested that intra- and inter-specific competition was strongest at 0 cm inundation. In contrast, neighboring plants stimulated the growth of C. lasiocarpa and D. angustifolia at the 40 cm water level. These results indicate that the strength of intra- and inter-specific competition decreases and the strength of facilitation increases with increasing water levels. Our results support the prediction of the stress-gradient hypothesis (SGH) that plant-plant interactions should switch from competition to facilitation along an increasing water-level stress gradient.

Changes of soil labile organic carbon in different land uses in Sanjiang Plain, Heilongjiang Province

In the Sanjiang Plain, Northeast China, the natural wetland is undergoing a rapid conversion into agricultural land, which has resulted in drastic ecological changes in the region. To investigate the effects of different land uses on soil labile organic carbon, soils of Calamagrostis angustifolia wetland, Carex lasiocarpa wetland, dry farmland, paddy field, forest land and abandoned cultivated land were collected for measuring the contents of soil microbial biomass carbon (MBC), dissolved organic carbon (DOC), readily oxidizable carbon (ROC) and carbohydrate carbon (CHC). The results show that soil organic carbon contents follow the order: Carex lasiocarpa wetland>Calamagrostis angustifolia wetland>forest land>paddy field>dry farmland. The contents of MBC and DOC in Calamagrostis angustifolia and Carex lasiocarpa wetlands are significantly higher than those in other land use types. The contents of CHC and ROC are the highest in Calamagrostis angustifolia wetland and the lowest in dry farmland. The contents of all the labile organic carbon increase along with the years of abandonment of cultivated land. The ratios of MBC, DOC and ROC to SOC also follow the order: Carex lasiocarpa wetland>Calamagrostis angustifolia wetland>forest land>paddy field>dry farmland, while the ratio of CHC to SOC is paddy field>forest field>Carex lasiocarpa wetland>Carex lasiocarpa wetland>dry farmland. When natural wetlands were cultivated, the activity of soil organic carbon tends to reduce in some extent due to the disappearance of heterotrophic environment and the reduction of vegetation residue. Thus, the abandonment of cultivated land is an effective way for restoring soil organic carbon.

Response of regeneration diversity of Carex Lasiocarpa community to different water levels in Sanjiang Plain, China

The species diversity at the regeneration stage, inflenced by different water levels, is important for community composition in the later growing season. Regeneration diversity of Carex lasiocarpa community under different water levels was studied at two stages, recruitment and adult, in the Sanjiang Plain, Heilongjiang Province, China. The results showed that, at the two growing stages, important value of C. lasiocarpa population and species richness of the community decreased with the increasing water level, while the Simpson and Shannon-Wiener diversity indexes and Pielou evenness index increased. Under different water levels, community diversities were higher at the recruitment stage, while population important values of C. lasiocarpa were higher at the adult stage. Indexes in vegetation evaluation must be chosen prudentially for successful restoration and effective management of wetlands, and especially for wetland restoration, the optimal time should be selected according to the restoration objectives and costs.

Method Exploring on Dew Condensation Monitoring in Wetland Ecosystem

Dew is a crucial factor of water cycle in wetland ecosystem. This study aims to set up a series of parameters about dew characterization, to build the system of monitoring dewfall and make a model of predicting dew in mire wetland ecosystem. The experiment was in situ carried out during the growing season from mid-May through mid-October in a mire wetland where Carex lasiocarpa is the dominant plant. Dew was measured by using four different kinds of collectors which were glass, poplar woodstick, sunflower stick and filter paper, respectively. Statistical analysis showed that, compared to other collectors, poplar woodstick was the optimal collector for dew measurement considering the ideal surface idiosyncrasy and its convenience for material and operation. Dew began to condense from one and a half hour after sunset and Dew Intensity reached the peak at about half an hour before sunrise. The factual Dewfall in unit field area was calculated by the factors of leaf area index, Dew Days, Dew Intensity, etc. Based on the synchronous meteorological factors, a stepwise linearmulti-variation regression model was established to predict Dew Intensity. Furthermore, the model successfully interpreted the relationship between simulated and measured Dew Intensity. This method which used poplar woodstick, as well as the formula for calculating Dewfall offered a reliable way to analyze dewfall datas in wetland ecosystem, and most importantly, the parameters of dew, which were defined for the first time, provide a more precise way to describe and study dew.

Dynamics of dissolved iron under pedohydrological regime caused by pulsed rainfall events in wetland soils

The effect of pedohydrological regime caused by pulsed rainfall events (PRE) on the dynamics of dissolved iron in wetland soil solutions was examined through in-situ sampling of three typical wetlands (perennial Carex lasiocarpa humus marsh, seasonal submerged Calamgrostis angustifolia meadow marsh, and seasonal dry paddy field) in the Sanjiang Plain, Northeast China. The results showed that the dissolved iron of the upper soil layers (10 cm) of the three wetland soils corresponded to the pedohydrological regime to some extent, while the effect on the deeper layers (20–60 cm) was insignificant. The Eh and pH response of the meadow marsh soil to PRE was much greater than the other two soils. Dissolved iron in the humus marsh soil showed more regularity than the other two soils. The negative significant correlations between Fe(II) and redox potential (Eh), Fe(III) and Eh, and Fe(III)/Fe(II) and pH were only observed in the humus marsh soil. As a redox indicator, Fe(III)/Fe(II) had a significantly positive correlation with Eh. Fe (II) was less correlated with Fe(III) than other chemical parameters during PRE. The total dissolved iron (Fe(II) + Fe(III)) had significantly positive correlation with total nitrogen (TN) in the humus marsh soil, while that of the meadow marsh soil had significantly positive correlation with TN, total phosphorus (TP), and total carbon (TC). These findings will be useful to better understand the environmental behavior of iron and their influencing factors, and provides an improved scientific basis for understanding the environmental fate of iron in wetland soils.

Growth and morphological responses to water level and nutrient supply in three emergent macrophyte species

Sanjiang Plain is the largest freshwater marsh in China, where plant zonation along water-level gradients is a common phenomenon. The aim of this experiment was to identify the role of water level and nutrient availability on plant zonation in the plain. Growth and root morphology of three perennial emergent macrophyte species were investigated by growing in two water levels (0.1 and 10.0 cm, relative to soil surface) and in two levels of nutrient supply (0 and 0.5 g slow-release fertilizer per container). In the plain, Carex lasiocarpa typically occurs at low elevations, Glyceria spiculosa at medial elevations, and Deyeuxia angustifolia at high elevations. The relative growth rate was the highest in C. lasiocarpa and the lowest in D. angustifolia in the 10.0-cm water level. Among the three species, only total biomass of D. angustifolia was affected by water level, and decreased with increasing water level. High nutrient supply led to increased total biomass in C. lasiocarpa and G. spiculosa. High water level led to an increased root diameter in G. spiculosa and a decreased root length in C. lasiocarpa. In the 10.0-cm water level, low nutrient supply led to thinner roots in D. angustifolia, but resulted in an increased specific root length (SRL) in C. lasiocarpa and root diameter in G. spiculosa. Water-level effect on root porosity was only observed in G. spiculosa, and nutrient amendment did not influence root porosity in all the species. These data indicate that both nutrient and water level are important factors regulating plant distribution pattern in the Sanjiang Plain, because both C. lasiocarpa and G. spiculosa are relatively sensitive to nutrient supply whereas D. angustifolia is sensitive to water level.

Gradients controlling vegetation in Alnus japonica forests in Kushiro mire, Hokkaido, Japan

This study examined factors controlling the vegetation in Kushiro mire, northern Japan, especially in the alder and reed communities. The alder community was classified into four types that were arranged by canonical correspondence analysis (CCA) as follows: Carex lasiocarpa type, Carex augustinowiczii type, Persicaria type, and Spiraea type. The four types exhibited differences in size (tree height) and in the ratio of sprouting stems. Although plants growing on the forest floor primarily determined the species composition of the community, shading by alder crowns had no marked effect on the community gradient. Therefore, hydrochemical variables could control the growth and occurrence of both the floor plants and alder tree size. The differences between reed community and the alder community sites were characterized as heavily eutrophic by the Kruskal–Wallis test. Overall, the chemical variables pH and P2O5 and the hydrochemical variables maximum and range of water level were positively correlated with the CCA axis, and effectively explained the community gradient in relation to alder growth. These variables could be controlled by the inflow of neutral and turbid water from river floods or run-off, which would increase pH by replacing the acidic mire water, ash content, and P2O5 by conveying suspended inorganic particles that adsorb phosphorus.

Effects of water gradients on soil enzyme activity and active organic carbon composition under Carex lasiocarpa marsh

The responses of soil enzyme activity of freshwater marsh, microbial biomass carbon (MBC), dissolved organic carbon (DOC) and aboveground biomass to water gradients were studied with Carex lasiocarpa pot culture experiment. The relationships between soil enzyme activity and MBC, DOC and aboveground biomass were discussed. The water gradients were W1, 15 cm; W2, −5 cm; W3, −5–5 cm; W4, submerged. The results indicated that acid phosphatase, invertase and urease activities were decreased with the increase of water level, while catalase activity was increased with moisture content increasing. Drying-wetting alternation (W3) increased soil enzyme activities if compared with W1. MBC content followed the order of W3 > W1 > W2 > W4, and the activities of invertase, urease and catalase were significantly positively correlated with MBC ( p < 0.05). DOC content presented the order of W4 > W1 > W3 > W2, and the activities of urease and acid phosphatase were most significantly negatively correlated with DOC ( p < 0.01). In addition, drying-wetting alternation promoted the growth of Carex lasiocarpa. When water submerged plants, the growth of Carex lasiocarpa was significantly inhibited. The aboveground biomass was positively related to soil enzyme activities. There were close relationships between the activities of invertase, urease and catalase and the growth situation of Carex lasiocarpa.

A study of the vegetation and floristic diversity of two peatland complexes of post-settlement origin in Lake Umbagog National Wildlife Refuge, Coos County, New Hampshire

The floristic diversity and vegetation communities of Leonard Marsh and Harpers Meadow, two peatland complexes of recent origin within the Lake Umbagog National Wildlife Refuge in Coos County, New Hampshire, were investigated. The combined vascular floras of Leonard Marsh and Harpers Meadow consisted of 178 species, 111 of which occurred in both peatlands. The flora included two state-listed species, Eriophorum angustifolium subsp. angustifolium (endangered) and Listera cordata (threatened). Abundance and frequency data from 617 quadrats along 35 transects were analyzed by two-way indicator species analysis (TWINSPAN) and resulted in the recognition of nine vegetation cover types (CT): Thuja occidentalis–Alnus incana CT, the Picea mariana–Nemopanthus mucronatus CT, the Nemopanthus mucronatus–Alnus incana CT, the Rhododendron canadense–Nemopanthus mucronatus CT, the Rhododendron canadense–Chamaedaphne calyculata CT, the Chamaedaphne calyculata–Carex oligosperma CT, the Scheuchzeria palustris–Carex oligosperma CT, the Carex lasiocarpa–Chamaedaphne calyculata CT, and the Dulichium arundinaceum–Potentilla palustris CT. A tenth cover type consisting of aquatic vegetation, the Brasenia schreberi–Potamogeton spp. CT, was recognized based on qualitative field observations. Despite the recent formation of these peatland complexes following the construction of the Errol Dam in 1853, the vegetation composition of Leonard Marsh and Harpers Meadow shares broad similarities with peatlands in New England, the northcentral United States, and adjacent Canada. Leonard Marsh and Harpers Meadow are best classified as oligotrophic to weakly minerotrophic level peatland complexes occupying broad and shallow outwash plains. Historical records, botanical evidence, and patterns in basin topography suggest that terrestrialization and paludification have been critical processes in the post-settlement development of these two large peatland complexes.

Trade-off between tolerance to drought and tolerance to flooding in three wetland plants

ABSTRACT We tested whether a trade-off exists between tolerance to flooding and tolerance to drought in wetland plants by assessing biomass accumulation, relative growth rate (RGR), survival rate, and physiological response of three wetland plants growing in drought or flooded environments. In wetlands of China's Sanjiang Plain, Carex lasiocarpa typically occurs at low elevations (10–50 cm water depths), Carex limosa at medial elevation (10–30 cm depths), and Deyeuxia angustifolia at high elevation (0–10 cm depths). Plants of three species were subjected to flooding and drought treatments (25 days) in a greenhouse experiment. In the flooding treatments, biomass accumulation (range 0.007–0.031 g per plant) and survival rate (11%) were lowest in D. angustifolia. Relative growth rate (RGR) was highest in C. lasiocarpa (−0.006 d−1), intermediate in C. limosa (−0.051 d−1), and lowest in D. angustifolia (−0.118 d−1) at the end of the flooding experiment. Alcohol dehydrogenase (ADH) activity in C. lasiocarpa and...

The reconstruction of vegetation change in the last 55 years on a mire of Bereg plain (Hungary)

The study area is the peaty bed of Navad-patak mire situated in the North-Eastern Alföld, on the Bereg plain, which is slightly investigated area. The purpose of our research was to reconstruct the recent vegetation dynamic processes of the mire from 1950 till 2005. Beside the aerial photos we used the ERDAS Imagination remote sensing program, and made digital photo interpretation. We divided the vegetation history into three parts. In the first period, the nutrient load of the mire was increased, peat decaying and foresting processes started, the open peat-moss dominated associations ( Eriophoro vaginati-Sphagnetum, Carici lasiocarpae-Sphagnetum ) were disappeared. In the second period the expansion of the forest vegetation continued, the species composition transformed, and the characteristic species of the mentioned associations ( Eriophorum vaginatum, E. angustifolium, Carex lasiocarpa, Drosera rotundifolia, Sphagnum magellanicum ) were all disappeared. The third period starts with the artificial flooding in 1994. In the beginning the peat-mosses were all extinct, floating mires appeared immediately and their quick succession started and still runs. The fourth period would be start with the appearance of peat-mosses.

Evapotranspiration from a freshwater marsh in the Sanjiang Plain, Northeast China

Water loss by evapotranspiration (ET) is a principle component of the hydrological cycle in wetlands. Using eddy covariance method, we measured ET from a Carex lasiocarpa dominated marsh in the Sanjiang Plain, northeast China, during the growing season (May to September) of 2005. The seasonal variation of daily ET rates and the main environmental factors influencing ET were analyzed. Penman, Penman–Monteith (PM) and Priestley–Taylor (PT) models were then used for simulating daily ET and a comparison between the estimates of the three models and the measured ET was done. The results showed that daily ET rates ranged from 0.58–4.80 mm d −1 with an average of 2.31 mm d −1 during the measurement period. The values of decoupling factor ( Ω ) were generally larger than 0.5 during the growing season with an average of 0.82, demonstrating that net radiation was the main factor affecting ET while the influence of vapor pressure deficit (VPD) and surface resistance on marsh ET were relatively small. ET corresponded to leaf area index (LAI) in a linear manner when LAI was less than 1. The Penman model overpredicted the mean measured ET for the growing season by 35% while the PM model underestimated the mean measured ET by 18%. The agreement between estimated ET and measured ET was best for the PT model with α = 1.01, among the three models used in this research. Given its simplicity and accuracy, the PT method was most applicable to model daily ET during the growing season at the study site. Additionally, relation between estimates by PT method and measured ET can provide prediction of ET in other, environmentally similar, freshwater marsh for which meteorological data can be obtained or estimated.

Influence of environment and substrate quality on the decomposition of wetland plant root in the Sanjiang Plain, Northeast China

The litterbag method was used to study the decomposition of wetland plant root in three wetlands along a water level gradient in the Sanjiang Plain, Northeast China. These wetlands are Calamagrostis angustifolia (C.aa), Carex meyeriana (C.ma) and Carex lasiocarpa (C.la). The objective of our study is to evaluate the influence of environment and substrate quality on decomposition rates in the three wetlands. Calico material was used as a standard substrate to evaluate environmental influences. Roots native to each wetland were used to evaluate decomposition dynamics and substrate quality influences. Calico mass loss was statistically different among the three wetlands in the upper soil profile (0-10 cm) and in the lower depth range (10-20 cm). Hydrology, temperature and pH all influence calico decomposition rates in different ways at different depths of the soil profiles. The decomposition rates of native roots declined differentially with the increase of depth in the soil profiles. The mass loss of native roots showed a statistical decrease among the three wetlands in the upper soil profile (0-10 cm) and in the lower depth range (10-20 cm) as C.ma wetland > C.aa wetland > C.la wetland. Both the C:P ratio and N:P ratio were positively interrelated with decomposition rates. Decomposition rates were negatively related to initial P concentration in all three wetlands, indicating that P concentration seems to be an important factor controlling the litter loss.

Architectural and growth traits differ in effects on performance of clonal plants: an analysis using a field-parameterized simulation model

Individual traits are often assumed to be linked in a straightforward manner to plant performance and processes such as population growth, competition and community dynamics. However, because no trait functions in isolation in an organism, the effect of any one trait is likely to be at least somewhat contingent on other trait values. Thus, to the extent that the suite of trait values differs among species, the magnitude and even direction of correlation between values of any particular trait and performance is likely to differ among species. Working with a group of clonal plant species, we assessed the degree of this contingency and therefore the extent to which the assumption of simple and general linkages between traits and performance is valid. To do this, we parameterized a highly calibrated, spatially explicit, individual-based model of clonal plant population dynamics and then manipulated one trait at a time in the context of realistic values of other traits for each species. The model includes traits describing growth, resource allocation, response to competition, as well as architectural traits that determine spatial spread. The model was parameterized from a short-term (3 month) experiment and then validated with a separate, longer term (two year) experiment for six clonal wetland sedges, Carex lasiocarpa, Carex sterilis, Carex stricta, Cladium mariscoides, Scirpus acutus and Scirpus americanus. These plants all co-occur in fens in southeastern Michigan and represent a spectrum of clonal growth forms from strong clumpers to runners with long rhizomes. Varying growth, allocation and competition traits produced the largest and most uniform responses in population growth among species, while variation in architectural traits produced responses that were smaller and more variable among species. This is likely due to the fact that growth and competition traits directly affect mean ramet size and number of ramets, which are direct components of population biomass. In contrast, architectural and allocation traits determine spatial distribution of biomass; in the long run, this also affects population size, but its net effect is more likely to be mediated by other traits. Such differences in how traits affect plant performance are likely to have implications for interspecific interactions and community structure, as well as on the interpretation and usefulness of single trait optimality models.

Architectural and growth traits differ in effects on performance of clonal plants: an analysis using a field‐parameterized simulation model

Individual traits are often assumed to be linked in a straightforward manner to plant performance and processes such as population growth, competition and community dynamics. However, because no trait functions in isolation in an organism, the effect of any one trait is likely to be at least somewhat contingent on other trait values. Thus, to the extent that the suite of trait values differs among species, the magnitude and even direction of correlation between values of any particular trait and performance is likely to differ among species. Working with a group of clonal plant species, we assessed the degree of this contingency and therefore the extent to which the assumption of simple and general linkages between traits and performance is valid. To do this, we parameterized a highly calibrated, spatially explicit, individual‐based model of clonal plant population dynamics and then manipulated one trait at a time in the context of realistic values of other traits for each species. The model includes traits describing growth, resource allocation, response to competition, as well as architectural traits that determine spatial spread. The model was parameterized from a short‐term (3 month) experiment and then validated with a separate, longer term (two year) experiment for six clonal wetland sedges, Carex lasiocarpa, Carex sterilis, Carex stricta, Cladium mariscoides, Scirpus acutus and Scirpus americanus. These plants all co‐occur in fens in southeastern Michigan and represent a spectrum of clonal growth forms from strong clumpers to runners with long rhizomes.Varying growth, allocation and competition traits produced the largest and most uniform responses in population growth among species, while variation in architectural traits produced responses that were smaller and more variable among species. This is likely due to the fact that growth and competition traits directly affect mean ramet size and number of ramets, which are direct components of population biomass. In contrast, architectural and allocation traits determine spatial distribution of biomass; in the long run, this also affects population size, but its net effect is more likely to be mediated by other traits. Such differences in how traits affect plant performance are likely to have implications for interspecific interactions and community structure, as well as on the interpretation and usefulness of single trait optimality models.

NUTRIENT LIMITATION AND WETLAND BOTANICAL DIVERSITY IN NORTHEAST CHINA

The effect of fertilization on species richness was investigated in wetland ecosystems in northeast China. Plant nitrogen-to-phosphorus ratios (N/P) were used to assess nutrient limitation. A freshwater wetland Carex lasiocarpa community was grown at 12 nutrient treatments (4 N treatments, 4 P treat

Comparison of net ecosystem CO 2 exchange in two peatlands in western Canada with contrasting dominant vegetation, Sphagnum and Carex

Net ecosystem carbon dioxide exchange was measured in two contrasting peatlands in northern Alberta, Canada using the eddy covariance technique during the growing season (May–October). Sphagnum spp. made up approximately 66% of the total LAI (1.52 m 2 m −2) at the poor fen and the total N content of Sphagnum capitula was 7.8 mg g −1 at the peak of the growing season. In contrast, the dominant plant species at the extreme-rich fen site, the perennial sedge, Carex lasiocarpa, accounted for approximately 60% of the total LAI (1.09 m 2 m −2), and had leaf total N content of 19.3 mg g −1 at peak biomass. In addition, the peak aboveground biomass was higher at the poor fen (230.9 g m −2) than at the extreme-rich fen (157.1 g m −2). Both sites had maximum daily rates of net CO 2 uptake of approximately 5 μmol m −2 s −1, and typical nighttime rates of CO 2 loss of approximately 2 μmol m −2 s −1 during the peak of the growing season. Calculations of maximum photosynthetic and respiratory capacity were consistently higher at the extreme-rich fen. The poor fen was a net sink for CO 2 during 4 of the 6 months (peaking at 44 g C m −2 in July), while only slight net losses of CO 2 (3 g C m −2) occurred in May and September. In contrast, the extreme-rich fen was calculated to be a significant net sink for CO 2 only during 2 months of the growing season (peaking at 30 g C m −2 in August), while significant net losses of CO 2 occurred in May (8 g C m −2) and in October (13 g C m −2). The plant species at the poor fen site were active earlier and later in the growing season, while it took longer for C. lasiocarpa to develop leaf tissue, and leaf senescence and reduction in photosynthetic activity occurred earlier in the fall at the extreme-rich fen. When integrated over the 6-month growing season, the poor fen was a net sink (90 g C m −2) that was three times larger than the extreme-rich fen (31 g C m −2). The ratio of cumulative total ecosystem respiration to gross primary production was 0.7 at the poor fen and 0.9 at the extreme-rich fen.

Evaluation of geographic, geomorphic and human influences on Great Lakes wetland indicators: A multi-assemblage approach

Developing effective indicators of ecological condition requires calibration to determine the geographic range and ecosystem type appropriate for each indicator. Here, we demonstrate an approach for evaluating the relative influence of geography, geomorphology and human disturbance on patterns of variation in biotic indicators derived from multiple assemblages for ecosystems that span broad spatial scales. To accomplish this, we collected abundance information on six biotic assemblages (birds, fish, amphibians, aquatic macroinvertebrates, wetland vegetation, and diatoms) from over 450 locations along U.S. shorelines throughout each of the Great Lakes during 2002–2004. Sixty-six candidate taxon- and function-based indicators analyzed using hierarchical variance partitioning revealed that geographic (lake) rather than geomorphic factors (wetland type) had the greatest influence on the proportion of variance explained across all indicators, and that a significant portion of the variance was also related to response to human disturbance. Wetland vegetation, fish and bird indicators were the most, and macroinvertebrates the least, responsive to human disturbance. Proportion of rock bass, Carex lasiocarpa, and stephanodiscoid diatoms, as well as the presence of spring peepers and the number of insectivorous birds were among the indicators that responded most strongly to a human disturbance index, suggesting they have good potential as indicators of Great Lakes coastal wetland condition. Ecoprovince, wetland type, and indicator type (taxa vs function based) explained relatively little variance. Variance patterns for macroinvertebrates and birds were least concordant with those of other assemblages, while diatoms and amphibians, and fish and wetland vegetation were the most concordant assemblage pairs. Our results strongly suggest it will not be possible to develop effective indicators of Great Lakes coastal wetland condition without accounting for differences among lakes and their important interactions. This is one of the first attempts to show how ecological indicators of human disturbance vary over a broad spatial scale in wetlands.