River runoff and chemistry
River drainage networks occur in a radial fashion around the central
peaks of the Luquillo Mountains, El Yunque and East Peak (Fig. 1) and
drain into both the Caribbean Sea and the North Atlantic. Streams and
rivers are very flashy in the Luquillo Mountains (Jones et al. 2012).
Instantaneous discharge is collected by the USGS at multiple sites, with
the longest record (since 1945) at Río Icacos (50075000); other past or
current USGS gauges include Quebrada Guaba (50074950) in the
Icacos/Blanco drainage; Río Mameyes at Puente Roto (50065500), Río
Espiritu Santo at El Verde (50063800), Quebrada Sonadora (50063440) and
Quebrada Toronja at El Verde (50063500), and Río Sabana at Luquillo
(50067000). The University of Puerto Rico and the US Forest Service
International Institute of Tropical Forestry also maintain discharge
records for Quebrada Prieta (El Verde) and the Bisley Experimental
Watersheds (Sabana), respectively. Smaller headwater tributaries are
nested within mainstem rivers (Figure 1; Wymore et al. 2017). Critical
zone structure drives flow duration, with long periods of sustained
baseflow in the granitoid Icacos basin when compared to the Sonadora and
Toronja basins, which are on largely volcaniclastic parent material
(McDowell and Asbury 1994).
Multiple streams are sampled weekly in the Luquillo Mountains, with
periodic storm sampling (e.g. Clark et al. 2017, Wymore et al. 2017).
Analysis of major cations and anions, nutrients and dissolved organic
matter has occurred since 1983 (Figure 3), with a focus on understanding
the response of forested catchments to the frequent hurricane
disturbances in the LEF (McDowell et al. 2013) and describing the role
of watershed (McDowell and Liptzin 2014) versus in-channel controls on
stream N dynamics (Merriam et al. 2002; Rodriguez-Cardona et al. in
press). Recent deployment of high-frequency water quality sensors that
measure NO3-, conductivity,
temperature, dissolved oxygen, fluorescent dissolved organic matter and
turbidity provides new insights into controls on stream chemistry (e.g.
Wymore et al. 2019).
Stream chemistry in the Luquillo Mountains is typically circumneutral,
has relatively high concentrations of sea salts due to large inputs of
marine aerosols, and high concentrations of various weathering products
(e.g. SiO2 and bicarbonate) due to the warm and wet
environment that promotes rapid weathering in both volcaniclastic and
granitoid lithologies (McDowell and Asbury 1994; Shanley et al. 2011;
Murphy and Stallard 2012). Nitrogen concentrations are relatively high,
with inorganic N dominated by nitrate, as is typical of many tropical
forests (Lewis et al. 1999). Phosphorus concentrations are moderate, and
dissolved organic matter concentrations (dissolved organic carbon and
nitrogen) are low to moderate as found in many well-drained forested
catchments (McDowell and Asbury 1994). Concentrations of many solutes
are highly responsive to flow, with strong dilution observed for
weathering products and strong flushing of dissolved organic carbon
(McDowell and Asbury 1994; Shanley et al. 2011). Hurricanes result in
increased concentrations and fluxes of
NO3- and K+, but
little change in other solutes (McDowell et al. 2013; Schaefer et al.
2000; Fig. 3). Differences in structure of the critical zone drive
differences among watersheds in concentration-discharge relationships,
which are particularly evident for dissolved phosphorus (Wymore et al.
2017). Weathering at the bedrock-regolith interface almost 10 m below
the soil surface is a significant source of Mg2+ at
low flows (Chapela Lara et al. 2017), showing that weathering products
may be transported to streams along deep flow paths with little
opportunity for uptake by upland vegetation (McDowell 1998). Biota can
affect stream chemistry, as the assemblage of shrimp species has been
shown experimentally to affect both nitrate and dissolved organic carbon
concentrations (Crowl et al. 2000).
3.0 Data availability statement
Data are freely available at the LTER network EDI data portal,
https://portal.edirepository.org, and the NWIS for stream gauging
by USGS, https://waterdata.usgs.gov/pr/nwis/rt.
4.0 Acknowledgements
Primary support for this project comes from the US National Science
Foundation, particularly the Luquillo LTER (NSF DEB 1831592). Additional
support came from many specific projects such as the Luquillo CZO (NSF
EAR 1331841) and the USGS WEBB program. In addition to the authors of
this data note, contributors to the data sets described are authors on
the papers referencing the findings. Major support is provided by the
University of Puerto Rico and USDA Forest Service International
Institute of Tropical Forestry. Partial funding was provided by the New
Hampshire Agricultural Experiment Station. This is Scientific
Contribution Number 2876. This work was supported by the USDA National
Institute of Food and Agriculture McIntire-Stennis Project 1006760.
5.0 References cited
Barone, J. A., Thomlinson, J., Cordero, P. A., & Zimmerman, J. K.
(2008). Metacommunity structure of tropical forest along an elevation
gradient in Puerto Rico. Journal of Tropical Ecology, 24 ,
525-534. doi:10.1017/s0266467408005208
Boccheciamp, R. A. (1977). Soil survey of Humacao area of eastern
Puerto Rico : U.S.D.A Soil Conservation Service.
Brocard, G. Y., Willenbring, J. K., Miller, T. E., & Scatena, F. N.
(2016). Relict landscape resistance to dissection by upstream migrating
knickpoints. Journal of Geophysical Research: Earth Surface,
121 (6), 1182-1203. doi:10.1002/2015jf003678
Buss, H. L., Chapela Lara, M., Moore, O. W., Kurtz, A. C., Schulz, M.
S., & White, A. F. (2017). Lithological influences on contemporary and
long-term regolith weathering at the Luquillo Critical Zone Observatory.Geochimica et Cosmochimica Acta, 196 , 224-251.
doi:https://doi.org/10.1016/j.gca.2016.09.038
Chapela Lara, M., Buss, H. L., Pogge von Strandmann, P. A. E.,
Schuessler, J. A., & Moore, O. W. (2017). The influence of critical
zone processes on the Mg isotope budget in a tropical, highly weathered
andesitic catchment. Geochimica et Cosmochimica Acta, 202 ,
77-100. doi:https://doi.org/10.1016/j.gca.2016.12.032
Clark, K. E., Shanley, J. B., Scholl, M. A., Perdrial, N., Perdrial, J.
N., Plante, A. F., & McDowell, W. H. (2017). Tropical river suspended
sediment and solute dynamics in storms during an extreme drought.Water Resources Research, 53 (5), 3695-3712.
doi:10.1002/2016wr019737
Crook, Kelly E.; Scatena, Fred N.; Pringle, Catherine M. 2007. Water
Withdrawn From the Luquillo Experimental Forest, 2004. U.S. Department
of Agriculture, Forest Service, International Institute of Tropical
Forestry. Gen. Tech. Rep. IITF-GTR-36.
Crowl, T. A., McDowell, W. H., Covich, A. P., & Johnson, S. L. (2001).
Freshwater shrimp effects on detrital processing and nutrients in a
tropical headwater stream. Ecology, 82 (3), 775-783.
doi:10.1890/0012-9658(2001)082[0775:fseodp]2.0.co;2
Cusack, D. F., Silver, W. L., Torn, M. S., & McDowell, W. H. (2011).
Effects of nitrogen additions on above- and belowground carbon dynamics
in two tropical forests. Biogeochemistry, 104 (1-3), 203-225.
doi:10.1007/s10533-010-9496-4
Eugster, Werner ; Burkard, Reto; Holwerda, Friso; Scatena, Frederick N.;
Bruijnzeel, L.A.(Sampurno) 2006. Characteristics of fog and fogwater
fluxes in a Puerto Rican elfin cloud forest. Agricultural and Forest
Meteorology 139 :288–306
González, G. 2017: Luquillo Mountains meteorological and ceilometer
data, Fort Collins, CO: Forest Service Research Data Archive,
https://doi.org/10.2737/RDS-2017-0023, 2017.
González, G.; Lodge, D.J.; Richardson, B.A.; Richardson, M.J. 2014. A
canopy trimming experiment in Puerto Rico: The response of litter
decomposition and nutrient release to canopy opening and debris
deposition in a subtropical wet forest. Forest Ecology and Management.
332:32-46.
González, G.; Waide, R.B.; Willig, M.R. 2013. Advancements in the
understanding of spatiotemporal gradients in tropical landscapes: a
Luquillo focus and global perspective. Ecological Bulletins 54:245-250.
Harris, N. L. L., A.E.; Brown, S.; and Heartsill Scalley, T. (2012).Luquillo Experimental Forest: Research history and opportunities .
Washington, DC: U.S. Department of Agriculture.
Heartsill-Scalley, T., Scatena, F. N., Estrada, C., McDowell, W. H., &
Lugo, A. E. (2007). Disturbance and long-term patterns of rainfall and
throughfall nutrient fluxes in a subtropical wet forest in Puerto Rico.Journal of Hydrology, 333 (2-4), 472-485.
Jones, J. A., Creed, I. F., Hatcher, K. L., Warren, R. J., Adams, M. B.,
Benson, M. H., . . . Williams, M. W. (2012). Ecosystem Processes and
Human Influences Regulate Streamflow Response to Climate Change at
Long-Term Ecological Research Sites. Bioscience, 62 (4), 390-404.
doi:10.1525/bio.2012.62.4.10
Larsen, M. C., Liu, Z., & Zou, X. (2012). Effects of Earthworms on
Slopewash, Surface Runoff, and Fine-Litter Transport on a Humid-Tropical
Forested Hillslope in Eastern Puerto Rico. Chapter G. In S. F. Murphy &
R. F. Stallard (Eds.), Water quality and landscape processes of
four watersheds in eastern Puerto Rico . Reston, VA: USGS Professional
Paper 1789–G.
Lewis, J. W. M., Melack, J. M., McDowell, W. H., McClain, M., & Richey,
J. E. (1999). Nitrogen yields from undisturbed watersheds in the
Americas. Biogeochemistry, 46 , 149-162.
López-Marrero, T., Heartsill-Scalley, T., Rivera-López, C. F.,
Escalera-García, I. A., & Echevarría-Ramos, M. (2019). Broadening our
understanding of hurricanes and forests on the Caribbean island of
Puerto Rico: Where and what should we study now? Forests, 10 (9).
doi:10.3390/f10090710
Lugo, A. E., Waide, R. B., Willig, M. R., Crowl, T. A., Scatena, F. N.,
Thompson, J., . . . Brokaw, N. (2012). Ecological Paradigms for the
Tropics: Old Questions and Continuing Challenges. In N. Brokaw, T. A.
Crowl, A. E. Lugo, W. H. McDowell, R. B. Waide, & M. R. Willig (Eds.),A Caribbean Forest Tapestry: The Multidimensional Nature of
Disturbance and Response (pp. 3-41). New York: Oxford University Press.
McClintock, M. A., McDowell, W. H., González, G., Schulz, M., &
Pett-Ridge, J. C. (2019). African dust deposition in Puerto Rico:
Analysis of a 20-year rainfall chemistry record and comparison with
models. Atmospheric Environment, 216 .
doi:10.1016/j.atmosenv.2019.116907
McDowell, W. H. (1998). Internal nutrient fluxes in a tropical rain
forest. Journal of Tropical Ecology, 14 , 521-536.
McDowell, W. 2017a. Chemistry of rainfall and throughfall from El Verde
and Bisley ver 2110851. Environmental Data Initiative.
https://doi.org/10.6073/pasta/8a6c85713bf55573c457d92076385bee (Accessed
2020-09-29).
McDowell, W. 2017b. Chemistry of stream water from the Luquillo
Mountains ver 4923051. Environmental Data Initiative.
https://doi.org/10.6073/pasta/f9df56348f510da0113b1e6012fa2967 (Accessed
2020-09-29).
McDowell, W. H., & Asbury, C. E. (1994). Export of carbon, nitrogen,
and major ions from three tropical montane watersheds. Limnology
and Oceanography, 39 , 111-125.
McDowell, W. H., Brereton, R. L., Scatena, F. N., Shanley, J. B.,
Brokaw, N. V., & Lugo, A. E. (2013). Interactions between lithology and
biology drive the long-term response of stream chemistry to major
hurricanes in a tropical landscape. Biogeochemistry, 116 ,
175–186. doi:10.1007/s10533-013-9916-3
McDowell, W. H., Gines-Sanchez, C., Asbury, C. E., & Ramos-Perez, C. R.
(1990). Influence of seasalt aerosols and long range transport on
precipitation chemistry at El Verde, Puerto Rico. Atmospheric
Environment, 24A , 2813-2821.
McDowell, W. H., & Liptzin, D. (2014). Linking soils and streams:
Response of soil solution chemistry to simulated hurricane disturbance
mirrors stream chemistry following a severe hurricane. Forest
Ecology and Management, 332 , 56-63. doi:10.1016/j.foreco.2014.06.001
McDowell, W. H., Pérez-Rivera, K. X., & Shaw, M. E. (2020). Assessing
the ecological significance of throughfall in forest ecosystems. InForest-Water Interactions (pp. 299-318).
McDowell, W. H., Scatena, F. N., Waide, R. B., Brokaw, N. V., Camilo, G.
R., Covich, A. P., . . . Zimmerman, J. (2012). Geographic and ecological
setting of the Luquillo Mountains. In N. Brokaw, T. A. Crowl, A. E.
Lugo, W. H. McDowell, F. N. Scatena, R. B. Waide, & M. W. Willig
(Eds.), A Caribbean Forest Tapestry: The Multidimensional Nature of
Disturbance and Response (pp. 72-163). New York: Oxford University
Press.
Medina, E.; González, G.; Rivera, M. M. 2013. Spatial and temporal
heterogeneity of rainfall inorganic ion composition in northeastern
Puerto Rico. Ecological Bulletins 54:157-168.
Merriam, J. L., McDowell, W. H., Tank, J. L., Wollheim, W. M., Crenshaw,
C. L., & Johnson, S. L. (2002). Characterizing nitrogen dynamics,
retention and transport in a tropical rainforest stream using anin situ 15N addition. Freshwater Biology,
47 , 143-160.
Murphy, S. F., & Stallard, R. F. (2012). Water quality and
landscape processes of four watersheds in eastern Puerto Rico . Reston,
VA: U.S. Geological Survey Professional Paper 1789.
Murphy, S. F., Stallard, R. F., Scholl, M. A., González, G., &
Torres-Sánchez, A. J. (2017). Reassessing rainfall in the Luquillo
Mountains, Puerto Rico: Local and global ecohydrological implications.PLOS One, 12 (7), e0180987. doi:10.1371/journal.pone.0180987
O’Connell, C. S., Ruan, L., & Silver, W. L. (2018). Drought drives
rapid shifts in tropical rainforest soil biogeochemistry and greenhouse
gas emissions. Nat Commun, 9 (1), 1348.
doi:10.1038/s41467-018-03352-3
Ping, C.-L.; Michaelson, G. J.; Stiles, C. A.; González, G. 2013. Soil
characteristics, carbon stores, and nutrient distribution in eight
forest types along an elevational gradient, eastern Puerto Rico.
Ecological Bulletins 54: 67-86.
Porder, S., Johnson, A. H., Xing, H. X., Brocard, G., Goldsmith, S., &
Pett-Ridge, J. (2015). Linking geomorphology, weathering and cation
availability in the Luquillo Mountains of Puerto Rico. Geoderma,
249-250 , 100-110. doi:10.1016/j.geoderma.2015.03.002
Scatena, Frederick N. 1989. An Introduction to the Physiography and
History of the Bisley Experimental Watersheds in the Luquillo Mountains
of Puerto Rico. Gen. Tech. Rep. SO-72. New Orleans, LA: U.S. Dept of
Agriculture, Forest Service, Southern Forest Experiment Station. 22 p.
Scatena, F. N. (1990). Watershed scale rainfall interception on two
forested watersheds in the Luquillo Mountains of Puerto Rico.Journal of Hydrology, 113 , 89-102.
Scatena, F. N., & Larsen, M. C. (1991). Physical aspects of Hurricane
Hugo in Puerto Rico. Biotropica, 23 (4), 317-323.
Schaefer, D.A., McDowell, W.H., Scatena, F.N. and Asbury, C.E. 2000.
Effects of hurricane disturbance on stream water concentrations and
fluxes in eight tropical forest watersheds of the Luquillo Experimental
Forest, Puerto Rico. Journal of Tropical Ecology 16:189-207.
Seiders, V. M. (1971). Geologic map of the El Yunque quadrangle,
Puerto Rico. Miscellaneous Geological Investigation I-658 . Washington,
D.C.: U.S. Department of the Interior, Geological Survey.
Shanley, J. B., McDowell, W. H., & Stallard, R. F. (2011). Long-term
patterns and short-term dynamics of stream solutes and suspended
sediment in a rapidly weathering tropical watershed. Water
Resources Research, 47 (7), W07515. doi:10.1029/2010wr009788
Silver, W. 2018. Canopy Trimming Experiment Litterfall Nutrients Data
ver 7. Environmental Data Initiative.
https://doi.org/10.6073/pasta/bcbe47a10a08bc6ddca69fb2c59959ca (Accessed
2020-09-29).
Silver, W. L., Hall, S. J., & González, G. (2014). Differential effects
of canopy trimming and litter deposition on litterfall and nutrient
dynamics in a wet subtropical forest. Forest Ecology and
Management, 332 , 47-55.
doi:http://dx.doi.org/10.1016/j.foreco.2014.05.018
Staff, S. S. (1995). Order 1 soil survey of the Luquillo long-term
ecological research grid, Puerto Rico : U.S. Department of Agriculture,
Natural Resources Conservation Service, Lincoln, NE.
Uriarte, M., Thompson, J., & Zimmerman, J. K. (2019). Hurricane Maria
tripled stem breaks and doubled tree mortality relative to other major
storms. Nat Commun, 10 (1), 1362. doi:10.1038/s41467-019-09319-2
Van Beusekom, A. E., González, G., & Scholl, M. A. (2017). Analyzing
cloud base at local and regional scales to understand tropical montane
cloud forest vulnerability to climate change. Atmospheric
Chemistry and Physics, 17 (11), 7245-7259. doi:10.5194/acp-17-7245-2017
White, A. F., & Blum, A. E. (1995). Effects of climate on chemical
weathering in watersheds. Geochimica et Cosmochimica Acta, 59 (9),
1729-1747.
Wymore, A. S., Brereton, R. L., Ibarra, D. E., Maher, K., & McDowell,
W. H. (2017). Critical zone structure controls concentration-discharge
relationships and solute generation in forested tropical montane
watersheds. Water Resources Research, 53 (7), 6279-6295.
doi:10.1002/2016wr020016
Wymore, A. S., Leon, M. C., Shanley, J. B., & McDowell, W. H. (2019).
Hysteretic response of solutes and turbidity at the event scale across
forested tropical montane watersheds. Frontiers in Earth Science,
7 . doi:10.3389/feart.2019.00126
Figure 1. Map of the Luquillo Mountains of Puerto Rico and the Luquillo
Experimental Forest. Colors represent major lithology types and the
primary study catchments are outlined. RI: Río Icacos; QG: Quebrada
Guaba; MPR: Mameyes at Puente Roto; Q1-3: Bisley 1,2, and 3; RS: Río
Sabana; RES4: Rio Espiritu Santo; QS: Quebrada Sonadora; QP: Quebrada
Prieta; RG: Río Grande.