Jorge Luis Frangi

Hurricane damage to a flood plain forest in the Luquillo Mountains of Puerto Rico

Hurricane Hugo caused low to moderate damage to a flood plain forest that was partially protected by its topographic position. Treefalls and the location of damage suggested N to NW wind direction during the storm. Thirty percent of the trees, or 693 trees/ha, had some damage and 84 percent of the damage was to the canopy. Most of the damage to trees was caused by direct wind impact (83%) as opposed to secondary effects (16%). Over 80 percent of the snapped, leaning, and uprooted trees were dicotyledonous. Tree mortality was only 1 percent, and most of the damage to the sierra palm Prestoea montana (R. Grah.) Nichols was loss of leaves. Rapid refoliation, epicormic branching, adventitious root production, resprouting, and regeneration from seed in open areas were observed nine months after the event. Ten percent of the aboveground biomass and 12-16 percent of the nutrient stocks (N, P, K, Ca, Mg) were transferred to the forest floor, mostly in the form of woody biomass and nutrient-rich leaves. Palm leaves were the dominant leaf component of necromass. Instantaneous in situ fine and coarse necromass production was 10 and 9.2 Mg/ha, respectively. Net changes in aboveground mass, N, P, K, Ca, and Mg (in percent of prehurricane value) were 8, 3, 0, 3, 12, and 1, respectively, in spite of a high rate of loss by export. The source of additional mass and nutrients were boles from upland forests that fell into and remained inside the flood plain.

Structural and functional changes in Nothofagus pumilio forests along an altitudinal gradient in Tierra del Fuego, Argentina

. Structural (density, height, basal area, above-ground tree biomass, leaf area index) and functional (leaf phenology, growth rate, fine litter fall, leaf decomposition) traits were quantified in four mature forests of Nothofagus pumilio (lenga) along an altitudinal sequence in Tierra del Fuego, Argentina. Three erect forest stands at 220, 440 and 540m and a krummholz stand at 640 m a.s.l. were selected. Along the altitudinal sequence, stem density increased while DBH, height, biomass, leaf-size and growth period, mean growth rate and decay rate decreased. Dead stems increased and basal area and fine-litter fall decreased with an increase in elevation among erect forests, but these trends inverted at krummholz. We suggest that krummholz is not only a morphological response to the adverse climate but is also a life form with functional advantages.

Fruit Fall in the Luquillo Experimental Forest, Puerto Rico1

Fruit fall in the Luquillo Experimental Forest (LEF) varied with forest type but averaged 600 kg/ha/yr for the 11,000 ha forest. Within a given forest type, fruit fall varied spatially and seasonally. A palm (Prestoea montana) flood plain forest averaged 560 kg/ ha/yr and individual palm fruit mass changed from season to season. Lower montane wet, or tabonuco (Dacryodes excelsa ), forest had a low rate of fruit fall (332 kg/ha/yr) and strong seasonal pulses in both space and time. Fruit fall was higher in secondary forests (820 kg/ha/yr) and plantations (1418 kg/ ha/yr) than in mature tabonuco forests that normally occur in those sites. Fruit fall in the upper montane, or palo colorado (Cyrilla racemiflora), forest averaged 263 kg/ha/yr. Somewhere in the LEF there always appears to be a stand at peak rate of fruit production. Fruit fall data are used to reduce a previous estimate of forest carrying capacity for the endangered Puerto Rican parrot, Amazona vittata, from 51,000 to 2000-38,000 birds.

Biomass structure and dry matter dynamics of subtropical alluvial and exotic Ligustrum forests at the Río de la Plata, Argentina

Biomass, litterfall, litter standing crop, and decomposition was studied in a native subtropical alluvial forest locally known as Selva Marginal (SM) and an exotic Ligustrum lucidum forest (LF) at the Reserva Integral de Punta Lara, Buenos Aires Province, 34°47′S and 58°1′W. The alluvial forest site was at the southern limit of distribution of subtropical forests in South America. The Ligustrum forest was invading disturbed areas. Total biomass was 147.7 Mg/ha (86% aboveground and 14% belowground) in the SM, and 71.4 Mg/ha (93% and 7%, respectively) in the LF. Litterfall was 10.3 Mg/ha·yr and 13.8 Mg/ha·yr respectively. Annual leaf decomposition rate was greater for Ligustrum (k=4.07) than for SM species (k=1.48). The mean residence time of aboveground biomass was 12 yr for the SM and 5 yr for the LF. The k1 values (litterfall/standing crop) were 1.9 and 2.0 for SM and LF respectively. The influence of coastal road and wall in the hydroperiod, native forested wetland ecosystem survival and exotic forest invasion is discussed.

Decomposition and nutrient release from leaf litter in Eucalyptus grandis plantations on three different soils in Entre Ríos, Argentina

La descomposicion de la materia organica que ingresa al suelo a traves de la caida a la hojarasca es una fuente importante de nutrientes para la vegetacion. Se estimaron la tasa de descomposicion de la materia organica, la liberacion/inmovilizacion de nitrogeno, fosforo, potasio, calcio, magnesio, manganeso, hierro y aluminio de hojas recien caidas de Eucalyptus grandis utilizando bolsas de descomposicion en parcelas de ensayo situadas en tres tipos de suelos: Oxic Quartzipsamment (arenoso), Fluventic Haplumbrept (mestizo) y Argiudolic Pelludert (arcilloso). La tasa anual de descomposicion de la materia seca (k) fue mas rapida en el suelo arcilloso (0,44) que en los suelos arenoso y mestizo (0,30). El patron temporal de cambios de las concentraciones de nutrientes en la hojarasca fue similar entre los suelos arenoso y mestizo, comparados con el arcilloso. La concentracion de nitrogeno y fosforo aumento con el tiempo en los tres sitios, pero su inmovilizacion fue mayor en el sitio arcilloso. Las concentraciones de calcio, magnesio y manganeso fluctuaron de forma diferente en cada tipo de suelo. En cada sitio, las concentraciones de hierro y aluminio aumentaron de manera similar. Una mayor tasa de perdida de masa seca, junto con un aumento de inmovilizacion de nitrogeno y fosforo se observo en el suelo arcilloso, relativamente mas rico en nutrientes.

Biomass and nutrient accumulation in ten year old bryophyte communities inside a flood plain in the Luquillo Experimental Forest, Puerto Rico

Ten year old bryophyte communities growing on wooden stakes along a microtopographic gradient in a flood plain forest at 750 m elevation accumulated between 210 and 1400 kg/ha of ash-free biomass and an average of 14.5, 0,8, 5.3, 2.7, 2.7, 18.5, and 22.0 kg/ha of N, P, K, Ca, Mg, Mn, Fe, and Al, respectively. This biomass and nutrient accumulation was in the same order of magnitude as the accumulation of biomass and nutrients in fine litter. Both biomass and nutrient accumulation were greater in communities on stream bank slopes or slopes of tree mounds (...)

Fertilization in a Fourth Rotation Eucalyptus grandis Plantation with Minimal Management

ABSTRACT Successive rotation and wood harvest of fast growing trees, like Eucalyptus grandis, can deplete soil nutrient pools. In these intensively used soils, productivity can decrease, and fertilization can be necessary to recover soil fertility. The aim of this work is to evaluate if fertilization with N and P increases tree growth and foliar nutrients in an Eucalyptus grandis plantation growing over a soil used for three rotations of this species. In the same experiment, both fertilization on seedlings and coppiced trees were evaluated. One and two years after planting, any fertilization treatment increased tree growth, even though coppiced trees had higher total height and DBH than replanted trees. Coppiced trees had lower specific leaf area, as well as lower N and P leaf concentration. The lack of promotion in growth due to fertilization can be explained by the inputs of nutrients from the harvest residues of the previous rotation. As residues were never burned in this site, its decomposition released a high part of nutrients necessary to sustain growth during the first two years. We conclude that in sites where residues were left on site and were not burned, nutrient availability is enough and so fertilization at establishment is not necessary. It remains to be determined if fertilization is necessary at mid or end rotation, in order to balance nutrients export with harvest wood.

Contenido de nutrientes en las raíces finas y el mantillo de rodales de Eucalyptus grandis de diferente edad en la Mesopotamia Argentina

La provincia de Entre Rios es un nucleo importante de plantaciones de Eucalyptus spp. en Argentina. Se planteo como hipotesis que con el aumento en la edad de las plantaciones aumenta la biomasa de raices finas y la masa del mantillo. Se muestrearon rodales de cinco, siete y diecisiete anos de edad de Eucalyptus grandis, de primera rotacion. Se estimaron las masas del mantillo y de las raices finas (< 5 mm) en los primeros 30 cm de profundidad. Se analizaron quimicamente: carbono, nitrogeno, fosforo, potasio, calcio y magnesio en raices finas vivas y en el mantillo. Se calcularon sus contenidos minerales. Se empleo ANDEVA para las comparaciones entre rodales. A 30 cm de profundidad las raices finas vivas de los rodales de siete y diecisiete anos presentaron similares biomasas y contenidos de nutrientes, pero mayores que a los cinco anos. A 10 cm de profundidad, el rodal de diecisiete anos presento la mayor biomasa y contenido de nutrientes de raices que aquellos de menor edad. Antes de los siete anos se estabilizaron la biomasa y contenido de nutrientes de raices finas. Con la edad aumento la masa y contenido mineral del mantillo. La redistribucion de raices en el perfil del suelo con la edad de los rodales se relaciono con el incremento del mantillo y su influencia sobre la dinamica del agua y los nutrientes del suelo.

Dissolved organic carbon in water fluxes of Eucalyptus grandis plantations in northeastern Entre Ríos Province, Argentina

Water fluxes in tree plantations and other ecosystems carry dissolved organic carbon (DOC) provided by atmospheric inputs, autotrophic and heterotrophic metabolisms and from the lysis of dead material. These compounds may be colorless or provide a yellow-to-brown color to water and may also absorb visible light due to the presence of chromophores in the chemical structure. Concentration and composition of DOC and DOC annual flux in water pathways of a Eucalyptus grandis plantation were studied in Entre Rios, Argentina. Samples of bulk precipitation, throughfall, stemflow, litter lixiviation, surface runoff and water table were analyzed for DOC concentration and color (optical density). Regression analyses for DOC concentration vs water fluxes intensity and for DOC concentration vs color were done. A DOC circulation model was calculated using available information on water budgets fluxes. Results showed that molecular features, values and range of DOC concentrations varied among fluxes, which may be explained by factors and processes influencing water gains and losses and by composition and availability of organic matter that may be dissolved in water in contact with biomass, necromass, soil and subsoil. Regression parameters from DOC concentration vs optical density were useful for DOC chemical composition analyses and interpretation of DOC changes. Annual circulation of DOC (in kg ha-1 year-1) showed that atmospheric contribution is low (ca. 30), aboveground biomass lixiviation is about 3-4 times the atmospheric input (126.7 to 101.4), and inputs to mineral soil (374.4 to 348.0) came mainly (74 to 78 %) from litter lixiviation.

Effect of Thinning and Harvest Type on Storage and Losses of Phosphorous in Pinus taeda L. Plantations in Subtropical Argentina

The aim of this study was to evaluate the effect of thinning intensity and different harvest types on ecosystem P conservation in 20-year-old Pinus taeda plantation ecosystems at Misiones province, Argentina. The plantation was established in 1985, thinned at three intensities—0, 33, and 66% of basal area of control plots removed by thinning—and harvested in 2005. The nutrient content at harvest was determined for tree, shrub, and herb layers, the forest floor and upper mineral soil. Two harvest types were simulated: stem only and whole tree. Total P content was 56.8, 46.8, and 38.6 kg· ha−1 for 0, 33, and 66% thinning, respectively. Total P exported by harvest was different among treatments, the highest at 0% thinning treatment. Phosphorus stability index values indicated that the P most conservative management option is 66% thinning, harvest of stem only and retention of forest floor, understory, and harvest residues.