ESTUDIO PRELIMINAR DE LA MACROFAUNA DEL SUELO EN ÁREAS DE VARILLALES Y CHAMIZALES DE LA AMAZONÍA PERUANA

La densidad (individuos/m2) y biomasa (g de peso fresco/m2) de la macrofauna del suelo, fueron estudiadas en las áreas de varillales y chamizales de una parte de la Amazonía peruana. El estudio fue desarrollado en el Centro de Investigaciones de Jenaro Herrera (CIJH), 200 km sur oeste de la ciudad de Iquitos, en la margen derecha del río Ucayali, y en la Zona Reservada Allpahuayo-Mishana, situada en el km 29 de la carretera Iquitos-Nauta.El método de muestreo utilizado fue recomendado por el Programa «Tropical oilBiology and Fertility» (TSBF), y se realizó en los meses de marzo (época lluviosa) y setiembre (época de menos lluvias) del 2001. En cada sistema se colectaron 3 muestras, a un intervalo de 5 metros a lo largo de una línea recta cuyo origen y dirección fue escogido al azar, y la macrofauna fue separada en forma manual en monolitos de 25 cm x 25 cm x 30 cm.En los varillales del CIJH se encontró una densidad poblacional de 1 611 a 2 781individuos/m2 y una biomasa de 30.3 a 42.7 g peso fresco/m2 en la época luviosa y menos lluviosa, respectivamente. En la Zona Reservada de Allpahuayo-Mishana, la densidad fue de 10 209 individuos/m2 en la época lluviosa, y 768 individuos/m2 en la época menos lluviosa. La biomasa tuvo un rango de 236.9 a 96.2 g de peso fresco/m2 en las dos épocas de muestreo.La densidad poblacional en los chamizales de Allpahuayo-Mishana fueron de 670a 1 179 individuos/m2 y una biomasa de 31.5 a 100.0 g de peso fresco/m2 en la época lluviosa y menos lluviosa, respectivamente. En el CIJH se encontró una densidad de 1 728 a 4 205 individuos/m2 y la biomasa estuvo en un rango de 31.3 a 42.0 g de peso fresco/m2, en las mismas épocas de muestreo

Imaging spectroscopy predicts variable distance decay across contrasting Amazonian tree communities

1. The forests of Amazonia are among the most biodiverse on Earth, yet accurately quantifying how species composition varies through space (i.e., beta‐diversity) remains a significant challenge. Here, we use high‐fidelity airborne imaging spectroscopy from the Carnegie Airborne Observatory to quantify a key component of beta‐diversity, the distance decay in species similarity through space, across three landscapes in Northern Peru. We then compared our derived distance decay relationships to theoretical expectations obtained from a Poisson Cluster Process, known to match well with empirical distance decay relationships at local scales. 2. We used an unsupervised machine learning approach to estimate spatial turnover in species composition from the imaging spectroscopy data. We first validated this approach across two landscapes using an independent dataset of forest composition in 49 forest census plots (0.1–1.5 ha). We then applied our approach to three landscapes, which together represented terra firme clay forest, seasonally flooded forest and white‐sand forest. We finally used our approach to quantify landscape‐scale distance decay relationships and compared these with theoretical distance decay relationships derived from a Poisson Cluster Process. 3. We found a significant correlation of similarity metrics between spectral data and forest plot data, suggesting that beta‐diversity within and among forest types can be accurately estimated from airborne spectroscopic data using our unsupervised approach. We also found that estimated distance decay in species similarity varied among forest types, with seasonally flooded forests showing stronger distance decay than white‐sand and terra firme forests. Finally, we demonstrated that distance decay relationships derived from the theoretical Poisson Cluster Process compare poorly with our empirical relationships. 4. Synthesis. Our results demonstrate the efficacy of using high‐fidelity imaging spectroscopy to estimate beta‐diversity and continuous distance decay in lowland tropical forests. Furthermore, our findings suggest that distance decay relationships vary substantially among forest types, which has important implications for conserving these valuable ecosystems. Finally, we demonstrate that a theoretical Poisson Cluster Process poorly predicts distance decay in species similarity as conspecific aggregation occurs across a range of nested scales within larger landscapes

Understanding different dominance patterns in western Amazonian forests

Dominance of neotropical tree communities by a few species is widely documented, but dominant trees show a variety of distributional patterns still poorly understood. Here, we used 503 forest inventory plots (93,719 individuals ≥2.5 cm diameter, 2609 species) to explore the relationships between local abundance, regional frequency and spatial aggregation of dominant species in four main habitat types in western Amazonia. Although the abundance-occupancy relationship is positive for the full dataset, we found that among dominant Amazonian tree species, there is a strong negative relationship between local abundance and regional frequency and/or spatial aggregation across habitat types. Our findings suggest an ecological trade-off whereby dominant species can be locally abundant (local dominants) or regionally widespread (widespread dominants), but rarely both (oligarchs). Given the importance of dominant species as drivers of diversity and ecosystem functioning, unravelling different dominance patterns is a research priority to direct conservation efforts in Amazonian forests.Publisher PDFPeer reviewe

Amazon tree dominance across forest strata

The forests of Amazonia are among the most biodiverse plant communities on Earth. Given the immediate threats posed by climate and land-use change, an improved understanding of how this extraordinary biodiversity is spatially organized is urgently required to develop effective conservation strategies. Most Amazonian tree species are extremely rare but a few are common across the region. Indeed, just 227 ‘hyperdominant’ species account for >50% of all individuals >10 cm diameter at 1.3 m in height. Yet, the degree to which the phenomenon of hyperdominance is sensitive to tree size, the extent to which the composition of dominant species changes with size class and how evolutionary history constrains tree hyperdominance, all remain unknown. Here, we use a large floristic dataset to show that, while hyperdominance is a universal phenomenon across forest strata, different species dominate the forest understory, midstory and canopy. We further find that, although species belonging to a range of phylogenetically dispersed lineages have become hyperdominant in small size classes, hyperdominants in large size classes are restricted to a few lineages. Our results demonstrate that it is essential to consider all forest strata to understand regional patterns of dominance and composition in Amazonia. More generally, through the lens of 654 hyperdominant species, we outline a tractable pathway for understanding the functioning of half of Amazonian forests across vertical strata and geographical locations

COMUNIDADE DE MACRO-INVERTEBRADOS DO SOLO EM PLANTÍOS FLORESTAIS E SISTEMAS NATURAIS NA AMAZÔNIA PERUANA

Avaliou-se a comunidade dos macro-invertebrados do solo e as propriedades químicas do solo em plantios florestais de Cedrelinga catenaeformis e Simarouba amara comparando-as com uma floresta primária e uma floresta secundária em Jenaro Herrera, na Amazônia peruana. Os macro-invertebrados foram coletados pelo método recomendado pelo Programa de Biologia e Fertilidade de Solos Tropicais (TSBF) e o solo com um trado metálico durante o período de maiores precipitações em 2001. Os valores da densidade (expressados em indivíduos/m-2) dos macro-invertebrados foram maiores nos plantios florestais de Simarouba amara (3702 ind.m-2) e de Cedrelinga catenaeformis (2176 ind.m-2) do que na floresta primaria e floresta secundaria respectivamente. Assim, destaca-se que os plantios florestais mesmo em forma de monocultivo, no qual a ciclagem de nutrientes ficou restrito aos compostos da própria espécie, apresentaram um efeito favorável na composição dos macro-invertebrados e nas propriedades químicas do solo, mostrando um efeito positivo na recuperação do sol

Understanding different dominance patterns in western Amazonian forests

<p><span>Dominance of neotropical tree communities by a few species is widely documented, but dominant trees show a variety of distributional patterns still poorly understood. Here, we used 503 forest inventory plots (93,719 individuals ≥ 2.5 cm diameter, 2,609 species) to explore the relationships between local abundance, regional frequency, and spatial aggregation of dominant species in four main habitat types in western Amazonia. Contrary to the widely supported positive abundance-occupancy relationship in ecology, we found that among dominant Amazonian tree species, there is a strong negative relationship between local abundance and regional frequency and/or spatial aggregation across habitat types. Our findings suggest an ecological trade-off whereby dominant species can be locally abundant (local dominants) or regionally widespread (widespread dominants), but rarely both (oligarchs). Given the importance of dominant species as drivers of diversity and ecosystem functioning, unraveling different dominance patterns is a research priority to direct conservation efforts in Amazonian forests.</span></p><p>Funding provided by: Ministry of Economy, Industry and Competitiveness<br>Crossref Funder Registry ID: https://ror.org/034900433<br>Award Number: CGL2016–75414–P</p><p>Funding provided by: Ministerio de Ciencia e Innovación<br>Crossref Funder Registry ID: https://ror.org/05r0vyz12<br>Award Number: PID2019-105064GB-I00</p><p>Funding provided by: Ministry of Economy, Industry and Competitiveness<br>Crossref Funder Registry ID: https://ror.org/034900433<br>Award Number: CGL2015-72431-EXP</p><p><span>We used data from 503 forest inventory plots spread across western Amazonia, from Colombia to Bolivia. A total of 363 plots had an area of 0.1 ha, 134 plots were smaller than 0.1 ha (range from 0.025 to 0.08 ha), and 6 plots were larger (range from 0.128 to 0.213 ha). Plots are included in the RedGentry network</span><span>. </span><span>Across all plots, we measured stems with a diameter at breast height ≥ 2.5 cm within the plot limits. <span>Plots covered the main four habitat types in western Amazonia: 383 in terra firme (76%), 54 in floodplain (11%), 35 in swamp (7%) and 31 in white sand (6%) forests.</span></span></p> <p><span>We excluded all individuals not identified to species level (mean 14% of individuals per plot), since plot data came from different projects and morphospecies were not cross-checked. We also excluded individuals from doubtful identifications, e.g. 'cf.' and 'aff.' (mean 3% of individuals per plot). To the remaining individuals, we checked species names for synonym and spelling mistakes, using the R package 'Taxonstand'</span><span>. Identifications that were difficult to designate to a species were considered morphospecies and were also removed. Finally, we cross-checked our species names list against the most recent checklists of Amazonian species</span><span>. Species not found in these checklists (635 species) were compared with collection records in the Tropicos database, and were excluded because: 572 species of them were growth forms not consistently included in all datasets (epiphytes, lianas, herbs and ferns), 25 were illegitimate Amazonian species with ranges outside of our region and 38 species were considered wrong identifications because they do not have recorded collection since their descriptions. After these filters, </span><span>2,609 </span><span>species and </span><span>93,719 </span><span>individuals remained available for our analyses.</span></p> <p><span>Since plot size varied among datasets, we transformed abundances into relative abundances (i.e., number of individuals per species/total individuals per plot). Then, we defined dominant species as those species that together accounted for 50% of the total relative abundance of all individual trees in each habitat</span><span>. We analyzed separately dominant species by habitat type.</span></p> <p><span>Since our plots are not evenly distributed in space, identifying dominant species considering all plots in each habitat type could favor the selection of spatially clumped species. To explore the effect of this potential bias, we divided our study area into equal 100 x 100 km squares, and we extracted 100 random subsamples from the complete set of plots in each habitat type drawing one plot from each square each time. We identified dominant species in the complete dataset and each subsample.</span></p> <p><span>To test the relationship between local abundance and regional frequency of dominant species by habitat type, we built beta regression models with a logit link function. We used the mean local relative abundance of each dominant species as the dependent variable and both the regional relative frequency and the habitat type as predictors.</span><span> </span>We built species-level rank abundance distribution graphs within each habitat type to explore if local abundance in each plot of each dominant species gave similar information that their mean local abundance. We<span><span> conducted these analyses for: i) the complete dataset, including all plots of each habitat type; and ii) for the 100 subsamples. We further wanted to explore how the tendency changed adding sequentially rarer species. Therefore, we conducted the same analyses for species that account for 60%, 70%, 80%, 85%, 90%, 92.5%, 95%, 97.2% and 100% of the total relative abun</span></span><span><span>dance.</span> </span>To study the relative spatial aggregation of species, we analyzed the co-dominance of each species at each spatial extent and habitat. To do so, we calculated the F index related to each geographical distance between plots to all species and relativized these values to the community-level aggregation curve. </p&gt

Understanding different dominance patterns in western Amazonian forests (all versions - software)

Dominance of neotropical tree communities by a few species is widely documented, yet the different pathways that Amazonian plants follow to achieve dominance remain poorly understood. Here, we used 503 forest inventory plots (93,719 individuals ≥ 2.5 cm diameter, 2,609 species) to explore the relationships between local abundance, regional frequency, and spatial aggregation of dominant species across habitats in western Amazonia. Contrary to the well-supported abundance-occupancy relationship, we found that among dominant Amazonian tree species, there is a strong negative relationship between local abundance and regional frequency/spatial aggregation across habitat types. Our findings suggest an ecological trade-off whereby dominant species can allocate resources to being locally abundant (local dominants) or regionally widespread (widespread dominants), but rarely both (oligarchs). Given the importance of dominant species as drivers of diversity and ecosystem functioning, unraveling different modes of dominance is a research priority to direct conservation efforts in Amazonian forests

Understanding different dominance patterns in western Amazonian forests

Dominance of neotropical tree communities by a few species is widely documented, but dominant trees show a variety of distributional patterns still poorly understood. Here, we used 503 forest inventory plots (93,719 individuals ≥ 2.5 cm diameter, 2,609 species) to explore the relationships between local abundance, regional frequency, and spatial aggregation of dominant species in four main habitat types in western Amazonia. Contrary to the widely supported positive abundance-occupancy relationship in ecology, we found that among dominant Amazonian tree species, there is a strong negative relationship between local abundance and regional frequency and/or spatial aggregation across habitat types. Our findings suggest an ecological trade-off whereby dominant species can be locally abundant (local dominants) or regionally widespread (widespread dominants), but rarely both (oligarchs). Given the importance of dominant species as drivers of diversity and ecosystem functioning, unraveling different dominance patterns is a research priority to direct conservation efforts in Amazonian forests