An official website of the United States government
Stream bryophytes (mosses and liverworts) are widely recognized as important macroinvertebrate habitats, but their overall role in the stream ecosystem, particularly in nutrient cycling, remains understudied. Hubbard Brook Experimental Forest contains some of the most extensively researched streams in the world, yet few studies mention their bryophytes. Perhaps this is because early estimates place stream bryophyte coverage at an insignificant 2%. However, data from 2019 show that contemporary coverage ranges from 4%–40% among streams. To investigate how stream bryophyte cover may be changing over time and influencing stream nutrient stocks, we conducted field surveys, measured organic and inorganic mass contents of bryophytes, and quantified nutrient uptake with bottle incubations of bryophyte mats. This study marks a novel attempt to map stream bryophyte coverage with estimates of carbon, phosphorus, and nitrogen stocks and fluxes. From our 2022 field surveys, we found that median bryophyte coverage can vary greatly across streams in the same catchment (0%–41.4%) and can also shift from just three years prior. We estimate that these bryophyte mats store between 14–414 g of organic matter per m2 of stream in the form of live biomass and captured particulates. Out of 36 bryophyte clump samples, 35 sorbed peak historical water column concentrations of PO43- measured within the Hubbard Brook stream chemistry record within 12 hours of light incubation. In Bear Brook, our scaled estimate of bryophyte mat nitrate uptake (2.3 g N y-1) constitutes a substantial portion of previously estimated whole-stream nitrate uptake (12 g N y-1). Cumulatively, our data demonstrates that bryophytes and their associated mineral substrates and biota—known as the bryosphere—are crucial in facilitating headwater stream nutrient cycling. These bryospheres may contribute significantly to interannual variability in stream nutrient concentrations within nutrient-poor streams, especially in climate-sensitive regions. These data were gathered as part of the Hubbard Brook Ecosystem Study (HBES). The HBES is a collaborative effort at the Hubbard Brook Experimental Forest, which is operated and maintained by the USDA Forest Service, Northern Research Station.
more »
« less
Bryospheres in oligotrophic headwater streams provide nutrient-dense habitats and dominate stream nutrient cycling
Stream bryophytes (mosses and liverworts) are widely recognized as important macroinvertebrate habitats, but their overall role in the stream ecosystem, particularly in nutrient cycling, remains understudied. Hubbard Brook Experimental Forest in New Hampshire, USA, contains some of the most extensively researched streams in the world, yet few studies mention their bryophytes. Perhaps this is because early estimates place bryophyte coverage in these streams at an insignificant 2%. However, data from 2019 show that contemporary coverage ranges from 4 to 40% among streams. To investigate how stream bryophyte cover may be changing over time and influencing stream nutrient stocks, we conducted field surveys, measured the mass of organic and inorganic bryophyte contents, and quantified nutrient uptake with bottle incubations of bryophyte mats. This study marks a novel attempt to map stream bryophyte coverage with estimates of C, P, and N stocks and fluxes. From our 2022 field surveys, we found that median bryophyte coverage varied across streams in the same catchment (0–41.4%) and shifted from just 3 y prior. We estimate that these bryophyte mats stored between 14 and 414 g of organic matter per m2 of stream in the form of live biomass and captured particulates. Within 12 h of light incubation, 35 out of 36 bryophyte clump samples sorbed peak historical water-column concentrations of PO43– as measured in the Hubbard Brook stream chemistry record. In Bear Brook, our scaled estimate of bryophyte mat NO3– uptake (2.3 g N/y) constitutes a substantial portion of previously estimated whole-stream NO3– uptake (12 g N/y). Cumulatively, our data demonstrate that bryophytes and their associated mineral substrates and biota—known as the bryosphere—are crucial in facilitating headwater stream nutrient cycling. These bryospheres may contribute significantly to interannual variability in stream nutrient concentrations within nutrient-poor streams, especially in climate-sensitive regions.
more »
« less
- PAR ID:
- 10572528
- Publisher / Repository:
- University of Chicago Press for the Society for Freshwater Science
- Date Published:
- Journal Name:
- Freshwater Science
- Volume:
- 43
- Issue:
- 4
- ISSN:
- 2161-9549
- Page Range / eLocation ID:
- 439 to 452
- Subject(s) / Keyword(s):
- bryophyte aquatic moss Hubbard Brook biomass disturbance anchor ice nitrate phosphate detritus
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
This is the data and code associated with "Stream bryophytes promote 'cryptic' productivity in highly oligotrophic headwaters. Recent observations document increased abundance of algae in the headwater streams of Hubbard Brook Experimental Forest (HBEF). It is possible that this 'greening up' of HBEF streams may be due to climate change with rising temperatures, altered terrestrial phenology, and shifting hydrologic regimes. Alternatively, stream 'greening' could be due to the slow recovery of stream chemistry from decades of acid rain, which have led to rising stream water pH, declining concentrations of toxic Al3+, and extremely low solute concentrations. Three years of weekly algal measurements on contrasting substrates, 6 nutrient enrichment experiments reveal important new insights about the interactions between these two groups of autotrophs. We predicted that light availability, hydrologic disturbance and nutrient limitation were all important determinants of algal biomass in streams. To evaluate the relative strength and hierarchy of these limiting factors, we used nutrient diffusing substrates to investigate the role of nutrients for algae and compared algal accrual rate on artificial rock vs. moss substrates in stream channels vs. weir ponds to assess the role of hydrologic disturbance and scour. Our surveys and experiments spanned across seasons and local light regimes. Algal biomass was substantially higher in protected weir ponds than in stream channels, and in both habitats, algal biomass was substantially higher on artificial moss substrates than on tiles. Taken together, these results suggest that moss can provide physical protection from flood scour. Algal biomass instream on both substrate types was higher in high light seasons (pre-leaf out) and well-lit habitats indicating strong light limitation. Results from a series of 6 nutrient diffusing substrate experiments over the course of 2 years provided little evidence of nutrient limitation instream. The most striking finding of our investigation is the previously unsuspected role of stream bryophytes in providing critical refugia for algae in these steep, heavily shaded and oligotrophic headwaters. Shifts in stream productivity over time are likely to be closely tied to changes in bryophyte cover. These data were gathered as part of the Hubbard Brook Ecosystem Study (HBES). The HBES is a collaborative effort at the Hubbard Brook Experimental Forest, which is operated and maintained by the USDA Forest Service, Northern Research Station.more » « less
-
{"Abstract":["Detailed surveys of stream nitrate concentrations in the\n calcium-enriched (W1), hydrologic reference (W3), and biogeochemical\n reference (W6) watersheds were performed in the summer of 2015 with\n the goal of identifying "hotspots" of NO3- inflows into\n streams.\n\n \n Additional details on methods and analysis can be found at:\n\n \n Marinos, R. E., Campbell, J. L., Driscoll, C. T., Likens, G. E.,\n McDowell, W. H., Rosi, E. J., Rustad, L. E., & Bernhardt, E. S.\n (2018). Give and Take: A Watershed Acid Rain Mitigation Experiment\n Increases Baseflow Nitrogen Retention but Increases Stormflow Nitrogen\n Export. Environmental Science & Technology, 52(22), 13155\u201313165.\n https://doi.org/10.1021/acs.est.8b03553\n\n \n These data were gathered as part of the Hubbard Brook Ecosystem Study\n (HBES). The HBES is a collaborative effort at the Hubbard Brook\n Experimental Forest, which is operated and maintained by the US Forest\n Service, Northern Research Station."]}more » « less
-
Sponseller, Ryan (Ed.)Recent observations document increased abundance of algae in the headwater streams of Hubbard Brook Experimental Forest (HBEF). It is possible that this “greening up” of HBEF streams may be due to climate change, with rising temperatures, altering terrestrial phenology, and shifting hydrologic regimes. Alternatively, stream “greening” could be from the slow recovery of stream chemistry after decades of acid rain, which has led to rising pH, declining concentrations of toxic Al3+, and low solute concentrations. Four years of weekly algal measurements on artificial moss and ceramic tiles, along with six nutrient enrichment experiments, revealed new insights about the interactions between these two autotrophs. We found that in protected weir ponds and in stream channels, algal biomass was higher on artificial moss substrates than on tiles—with this effect amplified in the stream channels. These results suggest that bryophytes can provide physical protection from flood scour or may trap nutrients to support algal growth. In stream channels, algal biomass was higher in well‐lit habitats and time periods indicating strong light limitation. We only measured nitrogen and phosphorus limitation of algal biomass in nutrient enrichment experiments conducted within weir ponds, with higher light availability and lower flow. By comparison, results from the remaining four instream experiments provided little evidence for nutrient limitation, with only one trial showing increased algal growth in response to nutrient addition. The most striking implication of our study is the role of bryophytes in providing refugia, and potentially nutrients, to algae in shaded and oligotrophic headwater streams.more » « less
-
Conceptual models of nutrient retention in ecosystems suggest that mature forests receiving chronically elevated atmospheric nitrogen (N) deposition should experience increased nitrate (NO3-) losses to streams. However, at the Hubbard Brook Experimental Forest (New Hampshire, USA), recent stream NO3- concentrations have been unexpectedly low in mature watersheds. Poorly understood retention of NO3 matter (SOM) may explain this discrepancy. The relative availability of C and N in SOM influences NO3--N retention and may vary during succession due to processes of N mining and reaccumulation. To evaluate the strength of the SOM sink for NO3--N, we applied a 15NO3- tracer to the mineral soil in eight stands spanning a forest chronosequence from about 20 years to old growth ( 200 years). We tracked 15N recovery in SOM fractions in the upper 10 cm of B horizon over 5 weeks. Overall, forest age did not directly control the 5-week recovery of 15N, but it had an indirect effect via its influence on SOM properties such as C/N. Old-growth forest soils had the lowest C/N, implying closer proximity to effective N saturation. Across sites, both the particulate- and mineral-associated SOM fractions rapidly incorporated 15N, but recovery in each fraction generally declined with time, reflecting the dynamic nature of SOM. These results indicate that mineral horizons can provide an important N sink through the short term in forests of all ages, but that SOM-N remains subject to active cycling and potential loss from the soil pool over the longer term.more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1086/733067
