Wayt Thomas

Uncertainty in the biomass of Amazonian forests: An example from Rondônia, Brazil

Abstract A critical factor in estimating the contribution of tropical deforestation to nutrient mobilization and to CO2 build-up in the atmosphere is the amount of biomass available to burn. The biomass data for Brazil, a major site for deforestation, are few and of uncertain accuracy. Recent international agreements, however, require national inventories of sources and sinks for atmospheric greenhouse gases; such inventories will need better estimates of biomass and their uncertainties. To provide additional information on biomass uncertainty and on forest structure in southwestern Amazonia, a region of active deforestation, we measured in 1988 the diameter, bole and canopy heights of 474 trees covering a total of 1 ha (10 000 m2) in the Ecological Station of the Samuel Hydroelectric Reservoir in Rondonia (845′S, 63°23′W). Using allometric equations based on destructively sampled trees, we estimated the largest biomass component, standing alive aboveground biomass (SAAB), as 285 Mg (dry weight) ha−1. Fallen trunks and litter were 30 Mg and 10 Mg ha−1, respectively. The sum of these components, 325 Mg ha−1, is an underestimate of the total biomass because the biomass of roots, vines, shrubs, and small trees was not measured. Measurement error of SAAB is ± 20%, ± 57 Mg ha−1 about the mean (95% confidence interval), as derived by a Monte Carlo simulation. The SAAB distribution among trees is highly skewed: 3% of the trees contain 50% of the SAAB. For forests of similar distributions, sampling units typically used for biomass estimates (less than 2000 m2) will usually produce biomass estimates significantly different from those of larger units. Based on subsamples of our data, sampling units of 1000 m2 or smaller had at least a 75% chance of being outside the confidence interval of the global mean (228–342 Mg ha−1) derived from Monte Carlo simulation. To improve estimates of SAAB in similar forests a sampling program should focus on emergent and large canopy trees, the dominant contributors to biomass.

Stable carbon isotope ratio of tree leaves, boles and fine litter in a tropical forest in Rondônia, Brazil

Abstract Leaves of 208 trees were collected for isotopic analysis together with wood from 36 tree boles and 18 samples of fine litter from a terra-firme forest located at Samuel Ecological Reserve, Rondônia State, in the southwestern Amazon region. The range of δ13C values in leaves was from −28 to −36‰, with an average (±1 SD) of −32.1u2009±u20091.5‰, which was more negative than the δ13C values of bole samples (−28.4u2009±u20092.0‰) and fine litter (−28.7u2009±u20092.0‰). These values are within the range found for tropical and subtropical forests. Pooling the δ13C values for leaf samples from trees of the same height gave averages which were positively correlated with plant height at a highly significant level, with a slope of 0.06 and an intercept of −33.3‰ and a correlation coefficient r2=0.70 (P<0.001).

Conservation and monographic research on the flora of Tropical America

Monographs provide fundamental data critical to making informed conservation decisions. Do modern monographs, however, contribute to our knowledge of the diversity of the Neotropical flora or has most of the enumeration of species already been accomplished in older monographs, floristic treatments, and other research? How well monographed is the Neotropical flora and what is the approximate number of Neotropical plant species new to science that await description? Authors of 76 recent monographs of the Neotropical flora recognized a total of 8711 species, of which 2487 (29%) were new species described by the author of the monograph during the course of the research. The number of species of flowering plants new to science remaining to be described is estimated to be ca. 22000, or about 25 percent of the total flora. These estimates show the critical importance of the contributions of monographers to an accurate and complete inventory of Neotropical plant diversity.

Forest recovery after swidden cultivation across a 40-year chronosequence in the Atlantic forest of southern Bahia, Brazil

Tree species composition and structure of a 40-year chronosequence of secondary forests was compared with old-growth forests in southern Bahia, Brazil. Twelve stands were randomly selected that represented three age classes: 10, 25, and 40xa0year old with four replications in each class. All stands selected had been established after abandonment from swidden cultivation and were surrounded by old-growth forests. In every stand, ten 0.01-ha transects were established and all stems (≥5xa0cm diameter at breast height) were measured and identified. Results were compared with the dataset of two neighboring old-growth sites. Mean diameter, total height, and stand basal area increased with age. Number of trees/ha peaked in 40xa0year old stands. The results showed that secondary forests in this region take much more than 40xa0years to recover the structure of old-growth forests. In contrast, species richness recovery was rapid with a continuous accumulation of species with age in secondary forests. Species richness and diversity increased with age as did similarity between secondary stands and old-growth stands. More than half of the species found in the 40xa0year old stands were shared with the neighboring old-growth forests. However, species richness and diversity were higher in old growth sites.

Diversity of Cyperaceae in Brazil

Diversity of Cyperaceae in Brazil) The purpose of this catalogue was to combine the available data from publications, theses, databases, and herbarium specimens from around 120 Herbaria, and colections sampled in Brazilian vegetation during the last 15 years to produce the most complete list, as possible as, of Cyperaceae species for Brazil. We catalogued ca. 1,700 names for 678 species in 42 genera occurring in Brazil. These values represent ca. 15 percent of the species and 40 percent of the genera found in the world. Both subfamilies of Cyperaceae are found in Brazil with Cyperoideae being the most diverse at both generic and specific levels. Although lower species were recorded for the tribes Cryptangieae, Sclerieae, and Trilepideae, these tribes represent a much higher percentage of the worlds totals for genera and species. The most diverse genera are Rhynchospora (157 spp.), Cypents (101 spp.), Scleria (82 spp.) and Eleocharis (69 spp.). Fifteen genera have one species in Brazil, although five of them are monospecific. The most species-rich regions in Brazil are the North and Southeast. There are no genera endemic to Brazil. There are, however, around 200 endemic species, of which 40 are in the genus Rhynchospora. Taxonomic and nomenclatural problems found are pointed under the species. For each catalogued species, the principal synonyms, bibliographic references, distribution within Brazils five regions, vegetation type, and citation of selected material examined are provided.

Variation in Nutrient Distribution and Potential Nutrient Losses by Selective Logging in a Humid Tropical Forest of Rondonia, Brazil1

Abstract Despite having one of the worlds highest deforestation rates, the tropical forest of Rondônia state in the southwest Amazon is virtually unknown in terms of nutrient dynamics. To fill this knowledge gap, the distribution of nutrients in a humid tropical forest located in the Ecological Reserve of Samuel, Rondônia state, was addressed. A total of 474 trees with diameter at breast height (DBH) >10 cm were mapped at the Ecological Reserve of Samuel, a 20,000-ha area bordering the Samuel Hydroelectric Reservoir, which is located 50 km south of Porto Velho, Rondônia state, Amazon region, Brazil. These individuals belonged to ca 220 species distributed in 41 families. From this total, leaves of 354 trees were collected for chemical compositional analysis; boles of 96 trees and fine branches of 75 trees also were collected. Soil samples were gathered for fertility analysis at two soil depth intervals: 0–50 and 50–100 cm. In general, soils were acidic and very poor in terms of elemental contents. For plants, the highest concentrations of P, K, and Mg were found in leaves and fine branches, and the highest concentration of Ca was in the litter. The lowest nutrient concentration was observed in boles. The nutrient concentrations of leaves collected at Samuel were similar to that found in other terra firme forests of the Amazon region and other tropical forests growing on poor soils. Comparisons of nutrient concentrations among families, genera, and species revealed that only N concentrations were distinct among botanical taxa; the variability found in concentrations of other nutrients were larger and did not reveal any significant differences. Like aboveground biomass, the total nutrient stocks of trees was concentrated in a few large individuals. This fact reveals important implications about the impacts caused by selective logging. Although few trees are cut per hectare in this activity, the effects on the ecosystem structure, due to the loss of nutrients, may be underestimated.

Floristic composition and structure of the arboreal component of a transitional area of Atlantic forest in southern Bahia, Brazil

The purpose of this study was to attempt to detect a floristic transition in forest along an altitudinal gradient on a mountain side in southern Bahia, Brazil. The study site is located at the east-west transition from tropical moist to semideciduous forests. A belt transect of one hectare (10 × 1000 m) was established running up the slope (from ca. 350 m to 750 m elevation). All included trees and lianas > 5 cm in diameter at breast height were numbered, collected, and measured. Density, dominance, frequency, and importance values (IV) were calculated for each species. We encountered 1400 individuals and 264 species of woody plants in 56 families. Cariniana legalis (Mart.) Kuntze had the highest IV, based on the dominance of a small number of trees. Discocarpus pedicellatus Fiaschi & Cordeiro and Ampelocera glabra Kuhlm. were the most frequent trees, with 90 and 86 individuals respectively. Ninety-six species were represented by a single individual. The Fabaceae and Myrtaceae were the most diverse families with 37 and 31 species respectively. Cluster analysis and correspondence analysis (DCA) revealed that the composition of the forest along the uppermost 30 percent of the transect was distinct from the rest. The lower and upper forests can be considered respectively as semideciduous and moist forests. Although there are some well-marked floristic differences between these forests, both clearly belong to the southern Bahian sector of the Atlantic coastal forests.

Large-scale monographs and floras: the sum of local floristic research

Large-scale systematic efforts, both floristic and taxonomic, are the result of the unification of information found in smaller-scale projects or even collections. Three examples, all from tropical America, are presented to illustrate how these data and ideas are pooled. The effort to monograph the genus Leiothrix (Eriocaulaceae) is the successful work of a single researcher over time. The project to monograph the tribe Miconieae (Melastomataceae) demonstrates how joint effort by a collaborating group can monograph a group too large for any single person to attempt. The ‘List of Species of the Flora of Brazil’ project, with over 40,000 species listed, shows how over 400 systematists successfully contributed their knowledge to create a large-scale floristic reference.

Nothotalisia, a new genus of Picramniaceae from tropical America

A new genus of Picramniaceae from tropical America, Nothotalisia, is described. Of the three species in the genus, N. piranii and N. cancellata, are new to science. The third, N. peruviana, was originally described as Talisia peruviana in the Sapindaceae. The genus and all three species are described, illustrated, and distinguished by means of a key.ResumenEl nuevo género Neotropical Nothotalisia de la familia Picramniaceae es descrito. De las tres especies en el género, N. piranii y N. cancellata son nuevas para ciencia. La tercera especie, N. peruviana, fue describida originalmente como Talisia peruviana en la familia Sapindaceae. Las tres especies dentro de este género nuevo son descritas, ilustradas y distinguidas mediante una clave.

New synonymy and new distributional records in Bulbostylis (Cyperaceae) from South America

Studies of type material from Argentina, Brazil, Paraguay, and Uruguay together with observations of achenes using scanning electron microscopy permit us to synonymizeBulbostylis aphylla withB. brevifolia, B. closii andB. scabra fm.evolutior withB. major, andB. spectabilis withB. amambayensis. For the first time,B. major is recorded for Bolivia andB. brevifolia for Uruguay. The known distributions ofB. amambayensis, B. brevifolia, andB. major are expanded.ResumenEl análisis morfológico de ejemplares tipo, abundante material de Argentina, Brasil, Paraguay y Uruguay, así como observaciones de los frutos con microscopio electrónico de barrido, nos permitió sinonimizarBulbostylis aphylla conB. brevifolia, B. closii yB. scabra f.evolutior conB. major yB. spectabilis conB. amambayensis. Por otra parte se cita por primera vez aB. major para la flora de Bolivia y aB. brevifolia para Uruguay. Se amplia el área de distribución deB. amambayensis, B. brevifolia yB. major.