Scatena F.N.


Controls of Primary Productivity: Lessons from the Luquillo Mountains in Puerto Rico
Robert B. Waide, Jess K. Zimmerman and F. N. Scatena
Vol. 79, No. 1 (Jan., 1998), pp. 31-37

The Luquillo Mountains of eastern Puerto Rico are used as a case study to evaluate possible single- or multiple-factor controls of productivity in montane forests. A review of published studies from the Luquillo Mountains revealed that canopy height, productivity, and species richness decline while stem density increases with elevation, as is typical of other montane forests. A mid-elevation floodplain palm stand with high levels of productivity provides a notable exception to this pattern. Previous basic and applied studies of productivity in the Luquillo Mountains have consistently considered the overall gradient in productivity to be important in understanding forest structure and function. Recent observational and experimental studies have determined that disturbance of all types is an important factor mediating productivity in both low- and high-elevation (cloud) forests. For example, low-elevation forest recovers more quickly from hurricane disturbance and is more responsive to nutrient additions than is cloud forest. All of the factors proposed for limiting productivity are supported in one way or another by research in the Luquillo Mountains. What is critically lacking is both an appreciation for the way that these factors interact and experiments appropriate to evaluate multiple controls acting simultaneously.

Relationship Between Aboveground Biomass and Multiple Measures of Biodiversity in Subtropical Forest of Puerto Rico

Vance-Chalcraft, Heather D.; Willig, Michael R.; Cox, Stephen B.; Lugo, Ariel E.; Scatena, Frederick N. 2010. Relationship between aboveground biomass and multiple measures of biodiversity in subtropical forest of Puerto Rico. Biotropica. 42(3):290-299.

Anthropogenic activities have accelerated the rate of global loss of biodiversity, making it more important than ever to understand the structure of biodiversity hotspots. One current focus is the relationship between species richness and aboveground biomass (AGB) in a variety of ecosystems. Nonetheless, species diversity, evenness, rarity, or dominance represent other critical attributes of biodiversity and may have associations with AGB that are markedly different than that of species richness. Using data from large trees in four environmentally similar sites in the Luquillo Experimental Forest of Puerto Rico, we determined the shape and strength of relationships between each of five measures of biodiversity (i.e., species richness, Simpson’s diversity, Simpson’s evenness, rarity, and dominance) and AGB. We quantified these measures of biodiversity using either proportional biomass or proportional abundance as weighting factors. Three of the four sites had a unimodal relationship between species richness and AGB, with only the most mature site evincing a positive, linear relationship. The differences between the mature site and the other sites, as well as the differences between our richness–AGB relationships and those found at other forest sites, highlight the crucial role that prior land use and severe storms have on this forest community. Although the shape and strength of relationships differed greatly among measures of biodiversity and among sites, the strongest relationships within each site were always those involving richness or evenness.


This paper compares aboveground forest structure and macronutrient stoichiometry over 5 15 years of hurricane induced secondary succession by species, life history groups, community 6 species composition, and geomorphic setting. Stem density continually increased after the 7 impact of the Category 4 hurricane Hugo and 15 years later, it was greater than pre-hurricane. 8 There were significant spatial and temporal differences in the number of species, the diversity 9 index per plot, forest structure, and biomass. The greatest compositional differences occurred 10 between the post-Hugo and the 15-year census. Prior to hurricane Hugo most plots had very 11 similar species composition and abundances, and thus occupied a small area in non-metric 12 multidimensional species space. Following the hurricane new species combinations occurred 13 and the location of plots was spread in multidimensional space. Diversity indices were 14 significantly different among geomorphic settings before and immediately after hurricane Hugo. 15 However, these differences were not observed again until the 15-year census where they returned 16 to pre-hurricane levels. Plant associations based on abundance, life history traits, and landscape 17 position had measurable differences in their structure, composition, aboveground nutrient 18 storage, and stoichiometry. However, these differences were reflected in a variety of ways at 19 different spatial scales. At the species level differences in macronutrient tissue concentrations 20 were apparent when comparing co-existing primary forests dominants, early successional 21 dominants, high-light and low-light species, and species whose stem densities are negatively 22 correlated. Community level differences were greater for forest structure and total nutrient 23 storage compared to the mass weighted concentrations of macronutrients. The largest differences observed were in Mg and can be attributed to the succession of pioneer species 2 following the hurricane. Over the entire 15-year period, the watershed average aboveground 3 stoichiometry was relatively consistent and this is linked to the biomass dominance of a few 4 species. The successional history recorded here also suggests that community level differences 5 in species composition, structure, and stoichiometry were well established after 10 to 15 years of 6 secondary succession.

Evaporation from a tropical rain forest, Luquillo Experimental Forest, eastern Puerto Rico

Schellekens, J., L. A. Bruijnzeel, F. N. Scatena, N. J. Bink, and F. Holwerda (2000), Evaporation from a tropical rain forest, Luquillo Experimental Forest, eastern Puerto Rico, Water Resour. Res., 36(8), 2183–2196, doi:10.1029/2000WR900074.

Evaporation losses from a watertight 6.34 ha rain forest catchment under wet maritime tropical conditions in the Luquillo Experimental Forest, Puerto Rico, were determined using complementary hydrological and micrometeorological techniques during 1996 and 1997. At 6.6 mm d−1 for 1996 and 6.0 mm d−1 for 1997, the average evapotranspiration (ET) of the forest is exceptionally high. Rainfall interception (Ei), as evaluated from weekly throughfall measurements and an average stemflow fraction of 2.3%, accounted for much (62–74%) of the ET at 4.9 mm d−1 in 1996 and 3.7 mm d−1 in 1997. Average transpiration rates (Et) according to a combination of the temperature fluctuation method and the Penman-Monteith equation were modest at 2.2 mm d−1 and 2.4 mm d−1 in 1996 and 1997, respectively. Both estimates compared reasonably well with the water-budget-based estimates (ET − Ei) of 1.7 mm d−1 and 2.2 mm d−1. Inferred rates of wet canopy evaporation were roughly 4 to 5 times those predicted by the Penman-Monteith equation, with nighttime rates very similar to daytime rates, suggesting radiant energy is not the dominant controlling factor. A combination of advected energy from the nearby Atlantic Ocean, low aerodynamic resistance, plus frequent low-intensity rain is thought to be the most likely explanation of the observed discrepancy between measured and estimated Ei.

Relative scales of time and effectiveness of watershed processes in a tropical montane rain forest of puerto rico

Scatena FN. 1995. Relative scales of time and effectiveness of watershed
processes in a tropical montane rain forest of Puerto Rico. Pages 103–111
in Costa JE, Miller AJ, Potter KW, Wilcock PR, eds. Natural and Anthropogenic
Influences in Fluvial Geomorphology.Washington (DC):
American Geophysical Union. Geophysical Monograph 89.

Streams of the Montane Humid Tropics

Tropical montane streams produce a disproportionately large amount of the sediment and carbon that reaches coastal regions and have often been considered to be distinct fluvial systems. They typically drain orogenic terrains that have not been recently glaciated, but have undergone climatic changes throughout the Pleistocene and currently receive 2000–3000 mm or more of precipitation each year. Steep gradient reaches with numerous boulders, rapids, and waterfalls that alternate with lower gradient reaches flowing over weathered rock or a thin veneer of coarse alluvium characterize these streams. Although their morphology and hydrology have distinctive characteristics, they do not appear to have diagnostic landforms that can be solely attributed to their low-latitude locations. While they are relatively understudied, an emerging view is that their distinctiveness results from a combination of high rates of chemical and physical weathering and a high frequency of significant geomorphic events rather than the absolute magnitudes of individual floods or other geomorphic processes. Their bedrock reaches and abundance of large and relatively immobile boulders combined with their ability to transport finer-grained sediment also suggest that the restorative processes in these systems may be less responsive than in other fluvial systems.


Multivariate analysis of water quality and physical
characteristics of selected watersheds in Puerto Rico.
Journal of the American Water Resources Association 39:

Multivariate analyses were used to develop equations that could predict certain water quality (WQ) conditions for unmonitored watersheds in Puerto Rico based on their physical characteristics. Long term WQ data were used to represent the WQ of 15 watersheds in Puerto Rico. A factor analysis (FA) was performed to reduce the number of chemical constituents. Cluster analysis (CA) was used to group watersheds with similar WQ characteristics. Finally, a discriminant analysis (DA) was performed to relate the WQ clusters to different physical parameters and generate predicting equations. The FA identified six factors (77 percent of variation explained): nutrients, dissolved ions, sodium and chloride, silicacious geology, redox conditions, and discharge. From the FA, specific conductance, sodium, phosphorous, silica, and dissolved oxygen were selected to represent the WQ characteristics in the CA. The CA determined five groups of watersheds (forested, urban polluted, mixed urban/rural, forested plutonic, and limestone) with similar WQ properties. From the five WQ clusters, two categories can be observed: forested and urban watersheds. The DA found that changes in forest cover, percent of limestone, mean annual rainfall, and watershed shape factor were the most important physical features affecting the WQ of watersheds in Puerto Rico.

Cropping and fallowing sequences of small farms in the "terra firme" landscape of the Brazilian Amazon: a case study from Santarem, Para

Scatena, F. N.; Walker, R. T.; Homma, A. K. O.; de Conto, A. J.; Palheta Ferreira, C. A.; Carvalho, R. A.; Neves da Rocha, A. C. P.; Moreira dos Santos, A. I., and Mourao de Oliveira, P. 1996. Cropping and fallowing sequences of small farms in the "terra firme" landscape of the Brazilian Amazon: a case study from Santarem, Para.. Ecological Economics . 18(1) :29-40.

This paper analyzes field survey results and develops a conceptual model of the factors that influence cropping and fallowing practices on small farms in the terra firme landscape near Santarem, Brazil. A multi-fallow cultivation system that used rice, corn and bitter manioc in various relay-intercropping combinations was the most common cultivation practice observed. Five different types of fallow vegetation were identified and used by the farmers: (1) mature forest vegetation greater than 20 years old; (2) secondary forest vegetation 8 to 12 years old; (3) young secondary forest vegetation 3 to 6 years old; (4) brushy vegetation 2 to 4 years old; and (5) weed vegetation less than 2 years old. Distinct relay-intercropping sequences were associated with each of these fallows. We suggest that the selection of fallow length and cropping sequence is subject to the following general constraints: (1) the productivity of the landscape as determined by soil, water and climate; (2) ecological requirements and risks associated with particular crops; (3) land availability and the costs of site preparation, and cultural treatments; (4) the availability of hired labor; (5) the age structure of the families, their subsistence requirements and preferences for particular crops, leisure and non-farm-related production activities; and (6) local economic conditions including land values, access to credit and non-farm-related employment, and the conditions of commodity markets. To maximize agricultural production and general household utility given these constraints, the farmers have several options, including: (1) varying the length of fallows; (2) varying the types and sequences of crops that are planted following a given fallow; (3) modifying the clearing and cultivation practices; (4) improving subsequent yields by managing regeneration within a fallow; (5) developing diversified land use systems that contain combinations of pasture, perennials, semi-permanent annuals, areas of extractive reserves and true shifting cultivation; and (6) increasing production through the use of external inputs like fertilizer, irrigation and farm machinery. Most farmers in the study area have chosen to modify cropping sequences and vary the lengths of natural fallows rather than using expensive external inputs. Our data suggest that a major factor in selecting a fallow length is the cost of land clearance and preparation. Moreover, since clearing costs are dramatically reduced for young secondary vegetation, the reduction in site preparation costs over several short rotations compensates for the lost production caused by using short fallows instead of long fallows.

Asynchronous fluctuation of soil microbial biomass and plant litterfall in a tropical wet forest

Ruan, H.H., Zou, X.M., Scatena, F.N., Zimmerman, J.K., 2004.
Asynchronous fluctuation of soil microbial biomass and plant litterfall
in a tropical wet forest. Plant and Soil 260, 147–154.

Carbon availability often controls soil microbial growth and there is evidence that at regional scales soil microbial biomass is positively correlated with aboveground forest litter input. We examined the influence of plant litterfall on annual variation of soil microbial biomass in control and litter-excluded plots in a tropical wet forest of Puerto Rico. We also measured soil moisture, soil temperature, and plant litterfall in these treatment plots. Aboveground plant litter input had no effect on soil microbial biomass or on its pattern of fluctuation. Monthly changes in soil microbial biomass were not synchronized with aboveground litter inputs, but rather preceeded litterfall by one month. Soil microbial biomass did not correlate with soil temperature, moisture, or rainfall. Our results suggest that changes in soil microbial biomass are not directly regulated by soil temperature, moisture, or aboveground litter input at local scales within a tropical wet forest, and there were asynchronous fluctuation between soil microbial biomass and plant litterfall. Potential mechanisms for this asynchronous fluctuation include soil microbial biomass regulation by competition for soil nutrients between microorganisms and plants, and regulation by below-ground carbon inputs associated with the annual solar and drying-rewetting cycles in tropical wet forests.

Global and local variations in tropical montane cloud forest soils

Roman L, Scatena FN, Bruijnzeel LA. 2010. In Tropical Montane Cloud Forests: Science for Conservation and Management, Bruijnzeel LA, Scatena FN, Hamilton LS (eds).

Although soil resources are widely considered as a major factor that reduces the productivity, stature, and diversity of tropical montane cloud forests (TMCF), systematic comparisons of soil resources within and between TMCF are lacking. This study combines published reports on TMCF soils with new data on the soils and forest structure of the Luquillo Mountains in Puerto Rico to assess the current state of knowledge regarding global and local-scale variation in TMCF soils. At the global scale, soils from 33 TMCF sites and over 150 pedons are reviewed. Compared to soils in humid lowland tropical forests, TMCF soils are relatively acidic, have higher organic matter content, and are relatively high in total nitrogen and extractable phosphorus. Across all sites, significant correlations also exist between mean annual precipitation and soil pH and base saturation, but not between any soil chemical factor and canopy height, site elevation, or air temperature. Although comparisons between TMCF are limited by inconsistent sampling protocols, analysis of available data does indicates that lower montane cloud forests (LMCF) have taller canopies, higher soil pH, lower soil nitrogen, and higher C/N ratios than upper montane cloud forests (UMCF). Within an UMCF in NE Puerto Rico, the abundance of soil nitrogen, carbon, and potassium accounted for 25% to 54% of the variation in canopy height. However, as much as 68% of the variation in stand height could be accounted for when site exposure, slope gradient, and the percent coverage of surface roots were also included in the analysis.
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