biomass

Carbon Sequestration and Plan Community Dynamics Following Reforestation of Tropical Pasture

Silver W.L., Kuppers L.M., Lugo A.E. et al. Carbon Sequestration and Plan Community Dynamics Following Reforestation of Tropical Pasture. Ecological Applications, Vol 14(4), 2004 pp 1115-1127.

Abstract: 
Conversion of abandoned cattle pastures to secondary forests and plantations in the tropics has been proposed as a means to increase rates of carbon (C) sequestration from the atmosphere and enhance local biodiversity. We used a long-term tropical reforestation project (55–61 yr) to estimate rates of above- and belowground C sequestration and to investigate the impact of planted species on overall plant community structure. Thirteen tree species (nine native and four nonnative species) were planted as part of the reforestation effort in the mid to late 1930s. In 1992, there were 75 tree species (.9.1 cm dbh) in the forest. Overall, planted species accounted for 40% of the importance value of the forest; planted nonnative species contributed only 5% of the importance value. In the reforested ecosystem, the total soil C pool (0–60 cm depth) was larger than the aboveground C pool, and there was more soil C in the forest (102 6 10 Mg/ha [mean 6 1 SE]) than in an adjacent pasture of similar age (69 6 16 Mg/ha). Forest soil C (C3-C) increased at a rate of ;0.9 Mg·ha21·yr21, but residual pasture C (C4-C) was lost at a rate of 0.4 Mg·ha21·yr21, yielding a net gain of 33 Mg/ha as a result of 61 years of forest regrowth. Aboveground C accumulated at a rate of 1.4 6 0.05 Mg·ha21·yr21, to a total of 80 6 3 Mg/ha. A survey of 426 merchantable trees in 1959 and 1992 showed that they grew faster in the second 33 years of forest development than in the first 22 years, indicating that later stages of forest development can play an important role in C sequestration. Few indices of C cycling were correlated with plant community composition or structure. Our results indicate that significant soil C can accumulate with reforestation and that there are strong legacies of pasture use and reforestation in plant community structure and rates of plant C sequestration.

LONG-TERM PATTERNS IN TROPICAL REFORESTATION: PLANT COMMUNITY COMPOSITION AND ABOVEGROUND BIOMASS ACCUMULATION

MARIN-SPIOTTA, E. ; OSTERTAG, R.; SILVER W. L. 2007. Long-term, patterns in tropical reforestation: plant community composition and aboveground biomass accumulation.. Ecological Applications, 17(3), :828-839.

Abstract: 
Primary tropical forests are renowned for their high biodiversity and carbon storage, and considerable research has documented both species and carbon losses with deforestation and agricultural land uses. Economic drivers are now leading to the abandonment of agricultural lands, and the area in secondary forests is increasing. We know little about how long it takes for these ecosystems to achieve the structural and compositional characteristics of primary forests. In this study, we examine changes in plant species composition and aboveground biomass during eight decades of tropical secondary succession in Puerto Rico, and compare these patterns with primary forests. Using a well-replicated chronosequence approach, we sampled primary forests and secondary forests established 10, 20, 30, 60, and 80 years ago on abandoned pastures. Tree species composition in all secondary forests was different from that of primary forests and could be divided into early (10-, 20-, and 30-year) vs. late (60- and 80-year) successional phases. The highest rates of aboveground biomass accumulation occurred in the first 20 years, with rates of C sequestration peaking at 6.7 6 0.5 Mg Cha1yr1. Reforestation of pastures resulted in an accumulation of 125 Mg C/ha in aboveground standing live biomass over 80 years. The 80 year-old secondary forests had greater biomass than the primary forests, due to the replacement of woody species by palms in the primary forests. Our results show that these new ecosystems have different species composition, but similar species richness, and significant potential for carbon sequestration, compared to remnant primary forests.

Separating the effects of forest type and elevation on the diversity of litter invertebrate communities in a humid tropical forest in Puerto Rico

RICHARDSON, BARBARA A.; RICHARDSON, MICHAEL J.; SOTO-ADAMES, FELIPE N. 2005. Separating the effects of forest type and elevation on the diversity of litter invertebrate communities in a humid tropical forest in Puerto Rico.. Journal of Animal Ecology 74, :926-936.

Abstract: 
1. The primary effects of climatic conditions on invertebrate litter communities, and the secondary effects of different forest types, were distinguished by using the sierra palm as a control in a natural experiment along an elevational gradient in the Luquillo Mountains. These mountains have three well-defined forest types along the gradient, with the palm occurring as stands within each forest. 2. Palm litter samples were richer in nutrients, particularly phosphorus, than nonpalm litter, significantly so at higher elevations where leaching would have been expected. In nonpalm litter, mineral concentrations were significantly lower at higher elevations. 3. Animal abundance mirrored the pattern of mineral amounts and declined significantly in mid- and high-altitude forests, but did not decline with increasing elevation in palm stands. A pulse of post-hurricane litterfall was reflected in the high abundance of Coleoptera and Isoptera the following year. 4. The species richness of communities (Margalef’s index) declined with increasing elevation in nonpalm forest litter, but was remarkably similar in palm litter at all elevations. 5. Palm litter communities were more similar to each other (Sørensen’s index) than nonpalm communities, which became less similar with increasing elevation. 6. The differences observed from the lower slopes to the summits, in animal abundance, species richness and the uniformity of communities, are better explained by the contribution of forest composition to the chemical and physical nature of litter and forest heterogeneity, rather than to direct effects of temperature and rainfall differences.

Lack of Ecotypic Differentiation: Plant Response to Elevation, Population Origin, and Wind in the Luquillo Mountains, Puerto Rico

Fetcher, Ned; Cordero, Roberto A.; Voltzow, Janice 2000. Lack of Ecotypic Differentiation: Plant Response to Elevation, Population Origin, and Wind in the Luquillo Mountains, Puerto Rico. BIOTROPICA 32(2) :225-234 .

Abstract: 
How important is ecotypic differentiation along elevational gradients in the tropics? Reciprocal transplants of two shrubs, Clibadium erosum (Asteraceae) and Psychotria berteriana (Rubiaceae), and a palm, Prestoea acuminata var. montana (Palmaceae), were used to test for the effect of environment and population origin on growth and physiology in the Luquillo Experimental Forest of Puerto Rico. Two sites were used, one at Pico del Este (1000 m in cloud forest) and one at El Verde (350 m in lower montane rain forest). At the cloud forest site, plastic barriers were erected around a subset of the plants to examine if protection from wind affected survival or biomass accumulation. Survival of C. erosum and P. berteriana was not affected by site, population origin, or the presence of barriers. For P. acuminata var. montana, survival was higher for plants with barriers, but not affected by site and population origin. Plants of C. erosum and P. berteriana at El Verde grew larger than at Pico del Este, but there was no effect of population origin or barrier treatment on biomass accumulation for these species. For P. acuminata var. montana, there was no effect of environment, population origin, or barrier treatment on biomass accumulation. Light-saturated photosynthetic rate (Amax) of C. erosum, P. berteriana, and P. acuminata var. montana, as well as leaf anatomical characteristics of C. erosum, were unaffected by environment, population origin, and barrier treatment. On balance, there seems to be little evidence of ecotypic differentiation in these species along the gradient.

Effects of nutrient availability and other elevational changes on bromeliad populations and their invertebrate communities in a humid tropical forest in Puerto Rico

RICHARDSON, BARBARA A.; RICHARDSON,M. J.; SCATENA, F. N.; MCDOWELL, W. H. 2000. Effects of nutrient availability and other elevational changes on romeliad populations and their invertebrate communities in a humid tropical forest in Puerto Rico. Journal of Tropical Ecology 16:167±188.

Abstract: 
Nutrient inputs into tank bromeliads were studied in relation to growth and productivity, and the abundance, diversity and biomass of their animal inhabitants, in three forest types along an elevational gradient. Concentrations of phosphorus, potassium and calcium in canopy-derived debris, and nitrogen and phosphorus in phytotelm water, declined with increasing elevation. Dwarf forest bromeliads contained the smallest amounts of debris/plant and lowest concentrations of nutrients in plant tissue. Their leaf turnover rate and productivity were highest and, because of high plant density, they comprised 12.8% of forest net primary productivity (0.47 t ha-1 y-1), and contained 3.3 t ha-1 of water. Annual nutrient budgets indicated that these microcosms were nutrient-abundant and accumulated < 5% of most nutrients passing through them. Exceptions were K and P in the dwarf forest, where accumulation was c. 25% of inputs. Animal and bromeliad biomass/plant peaked in the intermediate elevation forest, and were positively correlated with the debris content/bromeliad across all forest types. Animal species richness showed a signi®cant mid-elevational peak, whereas abundance was independent of species richness and debris quantities, and declined with elevation as forest net primary productivity declined. The unimodal pattern of species richness was not correlated with nutrient concentrations, and relationships among faunal abundance, species richness, nutrient inputs and environment are too complex to warrant simple generalizations about nutrient resources and diversity, even in apparently simple microhabitats.

Impacts of disturbance initiated by road construction in a subtropical cloud forest in the Luquillo Experimental Forest, Puerto Rico

Olander, Lydia P.; Scatena, F.N; Silver, Whendee L. 1998. Impacts of disturbance initiated by road construction in a subtropical cloud forest in the Luquillo Experimental Forest, Puerto Rico. Forest Ecology and Management 109 ;33-49.

Abstract: 
The impacts of road construction and the spread of exotic vegetation, which are common threats to upper elevation tropical forests, were evaluated in the subtropical cloud forests of Puerto Rico. The vegetation, soil and microclimate of 6-month-old road®lls, 35-year-old road®lls and mature forest with and without grass understories were compared. Recent road®lls had higher light levels, soil temperatures, bulk densities, larger pools of exchangeable soil nutrients and higher soil oxygen concentrations; but lower soil moisture, soil organic matter and total soil N than the mature forest. On the 35-year-old road®lls, bulk density, soil pH and P pools were statistically similar to the mature forest while soil moisture, total N and base cations were different. The total aboveground biomass of 6-month-old road®lls was about 2 Mg/ha and dominated by a variety of monocot and herbaceous species. The 35-year-old road®ll areas had a biomass of 10.5 Mg/ha, 77% of which was nonwoody. Seedling density, tree density and total woody biomass were 12, 28 and 2% of mature forest sites, respectively. In these areas, where soils were disturbed during construction, accumulation of biomass is the slowest known for the LEF. It may take 200-300 years for biomass to attain mature forest levels. In areas that were not directly disturbed during construction, the road has had little effect on the vegetative composition beyond a 5±10 m zone immediately adjacent to the pavement. Although non-native monocots, one of which had been planted along the road 35 years earlier, were copious along the disturbed roadside, they were generally absent from the mature forest and only abundant in habitats of anthropogenic origin.

Export of Carbon, Nitrogen, and Major Ions from Three Tropical Montane Watersheds

Export of Carbon, Nitrogen, and Major Ions from Three Tropical Montane Watersheds
William H. McDowell and Clyde E. Asbury
Limnology and Oceanography
Vol. 39, No. 1 (Jan., 1994), pp. 111-125

Abstract: 
Annual exports of suspended sediment, dissolved and particulate C and N, dissolved N and P, and major cations and anions were measured in three montane tropical rain forest watersheds in Puerto Rico during 1983-1986. Organic C was primarily exported in the form of DOC, and DOC export (33-94 kg ha-1 yr-1) was similar to values in larger tropical watersheds with similar runoff. Particulate and dissolved organic N accounted for 60-70% of the 4-9 kg ha-1 yr-1 of total N exported. Export of base cations and rates of weathering varied with bedrock geology in the three watersheds. Concentrations of suspended sediment, particulate C and N, and DOC increased as a function of discharge in all three streams. NH4+, NO3-, SO42-, and K+ concentrations showed little or no response to variations in discharge; Na-, Ca2+, Mg2+, Cl-, HCO3-, and SiO2 all decreased at high flows. After removing the effects of discharge, residual NO, concentrations in each stream were inversely related to estimated rates of leaf fall. On a watershed basis, export and accumulation of N in biomass were greater than precipitation inputs, suggesting that unmeasured inputs (8-16 kg ha-1 yr-1) were large.

THE EARTHWORMS OF BANO DE ORO, LUQUILLO EXPERIMENTAL FOREST, PUERTO RICO

Borges, S. and M. Alfaro. 1997. The earthworms of
Baño de Oro, Luquillo Experimental Forest, Puerto
Rico. Soil Biol. Biochem. 29:231-234.

Abstract: 
The earthworm fauna of the four forest types at the Batio de Oro region of the Luquillo Experimental Forest was sampled over 6 months. Eight species were found: two Glossoscolecidae, one Ocnerodrilidae, four Megascolecidae, and one Eudrilidae. The total species density and biomass showed no significant correlation to forest type or soil depth, but some species did show different distribution patterns according to certain soil properties. Exotic species were more abundant, but native species accounted for most of the biomass. Species number and density were low when compared with similar studies in other neotropical forests. This could be due to the high moisture content of the soils and its effects on other soil properties.

The First five years in the reorganization of aboveground biomass and nutrient use following hurricane Hugo in the bisley Experimental Watersheds, luquillo Experimental Fortest, Puerto Rico

Scatena, F. N. ; Moya, S.; Estrada, C; Chinea, J.D. 1996. The First five years in the reorganization of aboveground biomass and nutrient use following hurricane Hugo in the bisley Experimental Watersheds, luquillo Experimental Fortest, Puerto Rico. Biotropica 28(4) : 424-440.

Abstract: 
Five years after Hurricane Hugo reduced the aboveground biomass by 50 percent in two forested watersheds in the Luquillo Experimental Forest of Puerto Rico, regeneration and growth of survivors had increased the aboveground biomass to 86 percent of the pre-hurricane value. Over the 5 yr, the net aboveground productivity averaged 21.6 Mg·ha-1·yr-1 and was faster than most plantations and secondary forests in the area. Woodfall and associated nutrient fluxes never attained pre-storm values but by the fifth yr, mean daily total litterfall, and N, P, K, Ca, and Mg fluxes in litterfall were 83, 74, 62, 98, 75, and 81 percent of their pre-disturbance values, respectively. Aboveground nutrient pools of these nutrients ranged from 102 to 161 percent of their pre-disturbance values and were larger after 5 yr because of higher nutrient concentrations in the regeneration compared to the older wood that it replaced. The following sequence of ecosystem reorganization during this first 5 yr period is suggested. An initial period of foliage production and crown development occurred as hurricane survivors re-leafed and herbaceous vegetation and woody regeneration became established. During this period, 75 to 92 percent of the nutrient uptake was retained in the aboveground vegetation and there was a relatively low rate of aboveground carbon accumulation per mole of nutrient cycled. This initial period of canopy development was followed by a peak in aboveground productivity that occurred as early successional species entered the sapling and pole stages. This period was followed by the establishment of the litterfall nutrient cycle and an increase in the net productivity per mole of nutrient cycled. During this 5 yr period, the Bisley forest had some of the lowest withinstand nutrient-use-efficiencies and some of the highest levels of aboveground productivity ever observed in the LEF. The study demonstrates that high levels of productivity and rapid rates of aboveground reorganization can be achieved with rapid within-system cycling and inefficient within-stand nutrient use.

Biomass and Nutrient Content of the Bisley Experimental Watersheds, Luquillo Experimental Forest, Puerto Rico, Before and After Hurricane Hugo

Biomass and Nutrient Content of the Bisley Experimental Watersheds, Luquillo Experimental Forest, Puerto Rico, Before and After Hurricane Hugo, 1989
F. N. Scatena, W. Silver, T. Siccama, A. Johnson and M. J. Sanchez
Biotropica
Vol. 25, No. 1 (Mar., 1993), pp. 15-27

Abstract: 
The biomass and nutrient content of two steepland watersheds were estimated using allometric equations and nutrient concentrations derived from a subsample of the vegetation. Prior to the passage of Hurricane Hugo in September 1989, the watersheds had a total vegetative biomass of 301 tons/ha, 75 percent of which was aboveground. The total nutrient content of this vegetation was 907, 49, 644, 653, and 192 kg/ha for N, P, K, Ca, and Mg, respectively and varied with topographic setting. Concentrations per unit dry weight of P (0.16), K (2.49), Ca (2.13), and Mg (0.62) in aboveground vegetation were similar to other steepland tropical forests, while the concentration of N (2.9) was greater. Following the passage of Hurricane Hugo, the standing aboveground biomass was reduced to 113 t/ha and the aboveground nutrient content of the forest was reduced 45 to 48 percent.
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