Scatena F.N.

Instream-Flow Analysis for the Luquillo Experimental Forest, Puerto Rico: Methods and Analysis

Scatena, F.N.; Johnson, S.L. 2001. Instream-Flow Analysis for the Luquillo Experimental Forest, Puerto Rico: Methods and Analysis. Gen. Tech. Rep. IITF-GTR-11. Rio Piedras, PR: U.S. Department of Agriculture, Forest Service, International Institute of Tropical Forestry. 30 p.

This study develops two habitat-based approaches for evaluating instream-flow requirements within the Luquillo Experimental Forest in northeastern Puerto Rico. The analysis is restricted to instream-flow requirements in upland streams dominated by the common communities of freshwater decapods. In headwater streams, pool volume was the most consistent factor in predicting the abundance of common freshwater shrimp. In second- and third-order tributaries, both water depth and velocity can be used to define their habitats. The most common species of shrimp are reclusive during the day; at night they prefer areas of low velocity (<0.09 m/s) and areas shallower than 0.4 m. In headwater streams, total usable shrimp habitat declines rapidly when water depth in the deepest pools is less than 0.5 m. In second-and third-order tributaries, the amount of habitat declines rapidly when discharge is within one standard deviation of the average annual 7-day minimum flow. These dis-charges are typically exceeded between 95 and 99 percent of the time. Analysis of habitat loss associated with different instream-flow constraints showed that habitat loss increases greatly when water extraction is equal to or greater than Q98. Among-reach differences in the amount of usable habitat resulting from differences in channel morphology can be as high as 35 percent. Therefore, site-specific studies should be conducted when using habitat-preference relations in a particular area.

Controls on soil organic matter content within a northern hardwood forest

Johnson, K.D.; Scatena, F.N.; Johnson, A.H.; Pan, Y. 2009. Controls on soil organic matter content within a northern hardwood forest. Geoderma. 148(3-4): 346-356.

Forest soils can act as both sinks and sources for atmospheric CO2 and therefore have an important role in the global carbon cycle. Yet the controls on forest soil organic matter content (SOM) distribution at the scale of operational land management scales within forest types are rarely quantified in detail. To identify factors that influence the spatial distribution and accumulation of SOM in forests, soils and stand composition data from 42 even-aged northern hardwood forest plots were analyzed using multiple linear regression and non-parametric statistical approaches. The analysis included three layers of SOM pools (forest floor, 0–20 cm mineral soil, and 20+ cm mineral soil) over three spatial scales (point, plot and regional). The largest amounts of total SOM (mean = 289, std dev = 70 Mg ha− 1) occurred in deep and well drained soils located on gently grading slopes. When soil layers were analyzed separately, the following relationships were observed: 1) highest forest floor SOM occurred under mixed species composition as opposed to stands dominated by sugar maple, 2) highest 0–20 cm mineral SOM occurred at high elevations (greater than 450 m) in moderately well drained soils, and 3) highest 20+ cm mineral SOM also occurred at high elevations and when soils were deeper. Further analysis of 0–20 cm mineral layer revealed that lower rock volume and finer soil texture resulted in higher SOM at a single point. When SOM that was predicted from models based on plot-specific attributes (soils series, slope and aspect) were compared to soil survey SOM estimates, the mean SOM values for both approaches were similar (253 and 269 Mg ha− 1 respectively). Easily identifiable characteristics such as mixed stand composition, the presence of forest floor and E horizon thickness may be used as field indicators of SOM storage. The variety of controls identified in this study should be considered when assessing soil carbon response to management options and future changes in climate.

Natural disturbances and the hydrology of humid tropical forests

Scatena FN, Planos-Gutiérrez EO, Schellekens J. 2004. Natural disturbances
and the hydrology of humid tropical forests. In Forests,
Water, and People in the Humid Tropics, Bonell M, Bruijnzeel LA
(eds). Cambridge University Press: Cambridge; 5–28.

Humid tropical forests are highly dynamic ecosystems that are affected by a wide array of environmental processes and disturbances (Figure 19.1). Quantifying the magnitude, frequency, and impacts of natural disturbances is essential for designing hydraulic structures, developing water management strategies, and distinguishing between natural variation and man-made influences. A disturbance can be defined as any discrete event that transfers mass and energy from one part of a system to another in a manner that disrupts ecosystem, community, or population structure and changes resource availability or the physical environment (see White and Pickett 1985 for a detailed discussion). Natural disturbances can be driven by both external factors – hurricanes, meteor impacts, etc. – and the biological properties of the system such as senescence, pathogens, etc. The natural disturbances specified by the United Nations in the International Decade of Natural Disaster Reduction were earthquakes, windstorms, tsunamis, floods, landslides, volcanic eruptions, wildfires, grasshopper and locust infestations, drought, and desertification (Board on Natural Disasters, 1999). Additional natural disturbances known to affect the hydrology of humid tropical forests are tree falls, pathogens, exotic invasions and meteor impacts. Quantifying the effects of disturbances on landform morphology and ecosystem development have been major themes in geomorphology and ecology (Wolman and Miller, 1960, Connell, 1978). This approach has led to the paradigm that landscapes are structured by the processes acting upon them (O’Neill et al., 1986, Urban et al., 1987, Scatena, 1995). It is now generally recognised that the ability of a disturbance to affect the morphology of a landscape or the structure of an ecosystem depends on: (1) the type of disturbance (e.g., flood, fire, landslide, biologic, anthropogenic etc.); (2) the force exerted (e.g. wind velocity and duration, rainfall magnitude and intensity, earthquake magnitude etc.); (3) the ecosystem component that is impacted directly (e.g. soil, biomass, leaf area etc.); (4) the area affected and the spatial distribution of impacts; (5) the return period or frequency of the event; (6) the condition of the system at the time of the disturbance (e.g. structure, regeneration phase, time since last disturbance); and (7) the magnitude of the constructive or restorative processes that occur between disturbances.

Emergy Evaluation of Reforestation Alternative in Puerto Rico

Odum, H.T., Doherty, S.J., Scatena, F.N., Kharecha, P.A., 2000. Emergy
evaluation of reforestation alternatives in Puerto Rico. Forest Science
46 (4), 521–530.

Six alternative ways of reforesting degraded lands in Puerto Rico were evaluated using emergy (spelled with an “m”). Emergy and its economic equivalent, emdollars, put the contributions of environmental work and human services on a comparable basis. This article shows the emergy method for evaluating forest contributions to public benefit and its use to select alternatives for reforestation. Emdollar values were compared for six scenarios for reforestation of degraded land in Puerto Rico: (1) the natural succession within or adjacent to mature forest; (2) reforestation from the spread of the exotic tree siris (Albizia lebbek); (3) reforestation with plantations of siris and mahogany for harvest; (4) reforestation by leaving plantations unharvested; (5) direct planting of seedlings of many species; and (6) starting patches of forest by massive transfer of topsoil, seed bank, and roots. After energy systems diagrams were made for each reforestation alternative, data were assembled and evaluation tables prepared that estimated the emergy required for: (1) canopy closure and (2) developing species complexity if left unharvested. To explain the method, detailed calculations were included for one of the alternatives, exotic Albizia lebbek plantation on 11 yr harvest cycle. All alternatives generated net public benefit (emdollar yield ratios 4.2 to 24.3). The emdollar value of a closed canopy developed in 10 to 20 yr ranged from 20,000 to 48,000 em$ /ha, whereas the economic costs were $1200 to $9700. For complex forest development in 25 to 60 yr, values ranged from 63,000 to 118,000 em$ /ha, much higher than economic costs of $4000 to $12,000/ha. Highest public benefit per dollar cost came from succession (24.7 em$/$) and exotic colonization (19.1 em$/$). Highest potential monetary returns were from exotic spread (15.1 $/$) and plantations (17.9 and 14.5 $/$). Stand quality after 60 yr, as measured by the transformity (emergy/energy), was largest in mahogany plantation (6.4 × 10 4 sej/J) and succession forest (3.9 × 104 sej/J).

Hydrometeorology of tropical montane cloud forests: emerging patterns

Bruijnzeel LA, Mulligan M, Scatena FN. 2010. Hydrometeorology of
tropical montane cloud forests: emerging patterns. Hydrological
Processes. DOI: 10.1002/hyp.7974.

altitudinal limits between which TMCF generally occur (800–3500 m.a.s.l. depending on mountain size and distance to coast) their current areal extent is estimated at ¾215 000 km2 or 6Ð6% of all montane tropical forests. Alternatively, on the basis of remotely sensed frequencies of cloud occurrence, fog-affected forest may occupy as much as 2Ð21 Mkm2. Four hydrologically distinct montane forest types may be distinguished, viz. lower montane rain forest below the cloud belt (LMRF), tall lower montane cloud forest (LMCF), upper montane cloud forest (UMCF) of intermediate stature and a group that combines stunted sub-alpine cloud forest (SACF) and ‘elfin’ cloud forest (ECF). Average throughfall to precipitation ratios increase from 0Ð72 š 0Ð07 in LMRF (n D 15) to 0Ð81 š 0Ð11 in LMCF (n D 23), to 1Ð0 š 0Ð27 (n D 18) and 1Ð04 š 0Ð25 (n D 8) in UMCF and SACF–ECF, respectively. Average stemflow fractions increase from LMRF to UMCF and ECF, whereas leaf area index (LAI) and annual evapotranspiration (ET) decrease along the same sequence. Although the data sets for UMCF (n D 3) and ECF (n D 2) are very limited, the ET from UMCF (783 š 112 mm) and ECF (547 š 25 mm) is distinctly lower than that from LMCF (1188 š 239 mm, n D 9) and LMRF (1280 š 72 mm; n D 7). Field-measured annual ‘cloud-water’ interception (CWI) totals determined with the wet-canopy water budget method (WCWB) vary widely between locations and range between 22 and 1990 mm (n D 15). Field measured values also tend to be much larger than modelled amounts of fog interception, particularly at exposed sites. This is thought to reflect a combination of potential model limitations, a mismatch between the scale at which the model was applied (1 ð 1 km) and the scale of the measurements (small plots), as well as the inclusion of near-horizontal wind-driven precipitation in the WCWB-based estimate of CWI. Regional maps of modelled amounts of fog interception across the tropics are presented, showing major spatial variability. Modelled contributions by CWI make up less than 5% of total precipitation in wet areas to more than 75% in low-rainfall areas. Catchment water yields typically increase from LMRF to UMCF and SACF–ECF reflecting concurrent increases in incident precipitation and decreases in evaporative losses. The conversion of LMCF (or LMRF) to pasture likely results in substantial increases in water yield. Changes in water yield after UMCF conversion are probably modest due to trade-offs between concurrent changes in ET and CWI. General circulation model (GCM)-projected rates of climatic drying under SRES greenhouse gas scenarios to the year 2050 are considered to have a profound effect on TMCF hydrological functioning and ecology, although different GCMs produce different and sometimes opposing results. Whilst there have been substantial increases in our understanding of the hydrological processes operating in TMCF, additional research is needed to improve the quantification of occult precipitation inputs (CWI and wind-driven precipitation), and to better understand the hydrological impacts of climate- and land-use change. Copyright  2010 John Wiley & Sons, Ltd.

Helping HELP with limited resources: the Luquillo experience

Scatena, F.N.; Ortiz-Zayas, JR; Blanco-Libreros, J.F. 2008. Helping HELP with limited resources: the Luquillo experience. Water SA. 34(4 special HELP edition): 497-508.

By definition the HELP approach involves the active participation of individuals from a wide range of disciplines and backgrounds, including representatives of industry, academics, natural resource managers, and local officials and community leaders. While there is considerable enthusiasm and support for the integrated HELP approach, a central problem for all HELP basins is how to effectively engage individuals and groups with few, if any financial resources. In the Luquillo HELP project we have managed this issue by focusing our efforts on holding small, public meetings and workshops with technocrats and managers who are engaged in local water resource management. To date several forums have been organised, including: technical meetings with the directors of natural resource agencies; presentations and panel discussions at the meetings of local professional societies, including the societies of Civil Engineers and Architects, the Commonwealth Association of Tourism, the Association of Builders and Developers, and the Puerto Rican Association of Lawyers. During these forums HELP specialists gave presentations and led discussions on how integrated watershed management can help resolve local problems. Because the audience are directly involved with these issues, they are quite responsive to these discussions and have often provided unique solutions to common problems. Technical workshops are co-sponsored by local municipalities – these day-long workshops are hosted by a municipality and include managers from other municipalities, the local water authority, and local community leaders. Additional activities include: technical advice on water infrastructure projects is given; there are educational exchanges between local and international students, scientists, natural resource managers, and community leaders; and synthesis publications relevant to integrated water resource management are produced. Other activities have included compiling oral environmental histories and organising watershed restoration activities. This paper describes these activities and discusses the benefits and costs of each approach.

Twelve testable hypotheses on the geobiology of weathering

Critical Zone (CZ) research investigates the chemical, physical, and biological processes that modulate the Earth's surface. Here, we advance 12 hypotheses that must be tested to improve our understanding of the CZ: (1) Solar-to-chemical conversion of energy by plants regulates flows of carbon, water, and nutrients through plant-microbe soil networks, thereby controlling the location and extent of biological weathering. (2) Biological stoichiometry drives changes in mineral stoichiometry and distribution through weathering. (3) On landscapes experiencing little erosion, biology drives weathering during initial succession, whereas weathering drives biology over the long term. (4) In eroding landscapes, weathering-front advance at depth is coupled to surface denudation via biotic processes. (5) Biology shapes the topography of the Critical Zone. (6) The impact of climate forcing on denudation rates in natural systems can be predicted from models incorporating biogeochemical reaction rates and geomorphological transport laws. (7) Rising global temperatures will increase carbon losses from the Critical Zone. (8) Rising atmospheric P(CO2) will increase rates and extents of mineral weathering in soils. (9) Riverine solute fluxes will respond to changes in climate primarily due to changes in water fluxes and secondarily through changes in biologically mediated weathering. (10) Land use change will impact Critical Zone processes and exports more than climate change. (11) In many severely altered settings, restoration of hydrological processes is possible in decades or less, whereas restoration of biodiversity and biogeochemical processes requires longer timescales. (12) Biogeochemical properties impart thresholds or tipping points beyond which rapid and irreversible losses of ecosystem health, function, and services can occur.

Comparison of passive fog gages for determining fog duration and fog interception by a Puerto Rican elfin cloud forest

Holwerda, F.; Bruijnzeel, L.A.; Scatena, F.N. 2010. Comparison of passive fog gages for determining fog duration and fog interception by a Puerto Rican elfin cloud forest. Bruijnzeel, L.A.; Scatena, F.N.; Hamilton, L.S., eds. Tropical Montane Cloud Forests: Science for Conservation and Management. Cambridge, UK: Cambridge University Press. p. 275-281.

Rates and amounts of fog interception by vegetation depend on wind speed, fog liquid water 4 content (LWC) and duration, as well as surface area and geometry of the vegetation 5 (Schemenauer, 1986). Information on the timing and duration of fog can be obtained with 6 passive fog gages, provided these are protected from rainfall and equipped with a recording 7 device (Bruijnzeel et al., 2005). Fog LWC may also be evaluated from collections by passive 8 gages when information on their collection efficiency and prevailing wind speeds is available 9 (e.g. Schemenauer and Joe, 1989). A variety of passive gages is available, and there has been 10 some discussion as to what is the most suitable type of gage to characterize local fog 11 conditions (Juvik and Nullet, 1995a; Schemenauer and Cereceda, 1995; cf. Delay and 12 Giambelluca, in press; Frumau et al., this issue). For example, a cylindrical gage is considered 13 superior to a flat screen, because it has uniform exposure to all wind directions (Juvik and 14 Nullet, 1995a; cf. García Santos and Bruijnzeel, this issue; Giambelluca et al., this issue). On 15 the other hand, a flat screen generally has a much larger collection area than a cylindrical 16 gage, and may thus measure fog when LWC or wind speeds are low (Schemenauer and 17 Cereceda, 1995).

Characteristics of fog and fogwater fluxes in a Puerto Rican elfin cloud forest

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.

The Luquillo Mountains of northeastern Puerto Rico harbours important fractions of tropical montane cloud forests. Although it is well known that the frequent occurrence of dense fog is a common climatic characteristic of cloud forests around the world, it is poorly understood how fog processes shape and influence these ecosystems. Our study focuses on the physical characteristics of fog and quantifies the fogwater input to elfin cloud forest using direct eddy covariance net flux measurements during a 43-day period in 2002.We used an ultrasonic anemometer–thermometer in combination with a size-resolving cloud droplet spectrometer capable of providing number counts in 40 droplet size classes at a rate of 12.5 times per second. Fog occurred during 85% of the time, and dense fog with a visibility <200 m persisted during 74% of the period. Fog droplet size depended linearly on liquid water content(r2 ¼ 0:89) with a volume-weighted mean diameter of 13.8 mm. Due to the high frequency of occurrence of fog the total fogwater deposition measured with the eddy covariance method and corrected for condensation and advection effects in the persistent upslope air flow, averaged 4.36 mm day1, rainfall during the same period was 28 mm day1. Thus, our estimates of the contribution of fogwater to the hydrological budget of elfin cloud forests is considerable and higher than in any other location for which comparable data exist but still not a very large component in the hydrological budget. For estimating fogwater fluxes for locations without detailed information about fog droplet distributions we provide simple empirical relationships using visibility data.

An EMERGY Evaluation of Puerto Rico and the Luquillo Experimental Forest

Scatena, F.N.; Doherty, S.J.; Odum, H.T.; Kharecha, P. 2002. An EMERGY
evaluation of Puerto Rico and the Luquillo Experimental Forest. Gen. Tech. Rep.
IITF-GTR-9. Río Piedras, PR: U.S. Department of Agriculture, Forest Service,
International Institute of Tropical Forestry. 79 p.

The many functions of Puerto Rico and the Luquillo Experimental Forest (the Forest) were evaluated in units of solar EMERGY, an energy-based measure of resource contribution and influence, defined as the energy of one type required to produce a flow or storage of another type. Rainfall and tectonic uplift are the largest environmental inputs into the Forest. The interaction of these inputs results in an erosional landscape where the EMERGY of biological processes is less than the EMERGY associated with the physical and chemical sculpturing of the landscape. The environmental work that built the natural capital of these forests is 9 to 50 times their current dollar market values. Of the investments evaluated in this study, the effects associated with water extraction are the largest. Tectonic inputs and the hydrologic cycle also provide most of the environmental EMERGY flows in the island of Puerto Rico. The ratio of societal inputs to environmental inputs, however, is 45 for Puerto Rico and 3.5 for the Forest. Per capita EMERGY- use is typical of moderately developed economies, but the island has one of the most investment-intensive, least self-sufficient economies known and an EMERGY signature that resembles a city-state.
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