The extent to which historical dispersal, environmental features and geographical barriers shape the phylogenetic structure and turnover of tree communities in northwestern Amazonia at multiple ...spatial scales remains poorly understood.
We used 85 floristically standardized 0.1‐ha plots (DBH ≥ 2.5 cm) distributed in three subregions of northwestern (NW) Amazonia across three main habitat types (floodplain, swamp and terra firme forests) to hypothesize that (a) historical dispersal overcome geographical barriers, which meant low local phylogenetic relatedness and low phylogenetic turnover. (b) Geographical barriers triggered dispersal limitation, causing high local and subregional phylogenetic clustering and high regional phylogenetic turnover. (c) Edaphic properties and flooding were negatively associated with stem size and determined the tree phylogenetic structure and turnover at local and regional scales in Amazon forests.
We found that the extent to which environmental or evolutionary features shaped the phylogenetic structure and phylogenetic similarity of tree communities in NW Amazonia was scale dependent. Specifically, we show that the relative importance of environmental factors increases as spatial scale and species pool decreases. Furthermore, we find that these results are generally robust for both adult and juvenile trees.
Synthesis. Our analysis at the regional (NW Amazon) scale lends support to the idea of Amazonian forests as a large meta‐community primarily structured by historical dispersal at large spatial scales with an increasing importance of environmental factors at finer spatial scales. The convergence of ancestral lineages across habitat types may have been due to the relatively recent formation of geographical barriers that promoted local isolation and allopatric speciation.
a
En este estudio evaluamos el grado en que la dispersión histórica, la variación ambiental y las barreras geográficas afectan la estructura y recambio filogenético de comunidades de árboles en la Amazonía noroccidental a multiples escalas espaciales.
Usamos 85 parcelas de 0.1 ha (DAP > 2.5 cm) florísticamente estandarizadas que fueron distribuidas en tres subregiones de la Amazonía noroccidental en tres diferentes hábitats (planos inundables, pantanos y tierra firme). Las hipótesis planteadas fueron: (i) la dispersión histórica es más importante que las barreras geográficas, por lo que se espera una baja diferenciación filogenética entre parcelas y una sobredispersión filogenética local. (ii) Las barreras geográficas promueven la limitación en dispersión, por lo que se espera un alto agrupamiento filogenético local y alta diferenciación filogenética entre parcelas. (iii) Las características del suelo e inundación estas asociadas negatívamente con el tamaño de los árboles y determinan la estructura y recambio filogenético a escala local y regional en los bosques amazónicos.
Encontramos que el grado en que las características ambientales y los procesos biogegráficos afectan la estructura y el recambio filogenético en las comunidades de árboles amazónicos es dependiente de la escala. Especificamente, mostramos que la importancia relativa de las características ambientales incrementa cuando la escala espacial y el acervo de especies se reduce. Estos resultados fueron robustos para árboles adultos y juveniles.
Nuestro análisis a escala regional (Amazonia noroccidental) agrega soporte a la idea de los bosques amazónicos son una gran metacomunidad estructurada principalmente por dispersión de los linajes a lo largo de la historia evolutiva y que los factores ambientales son más importantes a escalas finas (a nivel de paisaje o local). La convergencia de linajes en lo más profundo de la filogenia a lo largo de diferentes habitats, puede ser debido a la reciente formación de las barreras, las cuales promueve el aislamiento local y potencialmente la especiación alopátrica.
Our analysis at the regional (NW Amazon) scale lends support to the idea of Amazonian forests as a large meta‐community primarily structured by historical dispersal at large spatial scales with an increasing importance of environmental factors at finer spatial scales. The convergence of ancestral lineages across habitat types may have been due to the relatively recent formation of geographical barriers that promoted local isolation and allopatric speciation.
The "liana dominance hypothesis" posits that lianas are increasing in abundance in tropical forests, thereby potentially reducing tree biomass due to competitive interactions between trees and ...lianas. This scenario has implications not only for forest ecosystem function and species composition, but also climate change given the mass of carbon stored in tropical trees. In 2003 and 2013, all Myristicaceae trees in the 50-ha Yasuní Forest Dynamics Plot, Ecuador, were surveyed for liana presence and load in their crowns. We tested the hypothesis that the proportion of trees with lianas increased between 2003 and 2013 in line with the liana dominance hypothesis. Contrary to expectations, the total proportion of trees with lianas decreased from 35% to 32%, and when only trees ≥10 cm diameter at breast height were considered liana incidence increased 44–48%. Liana load was dynamic with a large proportion of trees losing or gaining lianas over the 10-yr period; large trees with intermediate liana loads increased in proportion at the expense of those with low and high loads. Lianas also impacted performance: trees with 26–75% crown cover by lianas in 2003 had reduced growth rates of 80% compared to of liana-free trees, and trees with >75% crown cover had 33% the growth rate and a log odds of mortality eight times that of liana-free trees. We suggest that the lack of strong support found for the liana dominance hypothesis is likely due to the aseasonal climate of Yasuní, which limits the competitive advantage lianas maintain over trees during dry seasons due to their efficient capture and use of water. We propose further research of long-term liana dynamics from aseasonal forests is required to determine the generality of the increasing liana dominance hypothesis in Neotropical forests.
1. The relationship between species richness and ecosystem function, as measured by productivity or biomass, is of long-standing theoretical and practical interest in ecology. This is especially true ...for forests, which represent a majority of global biomass, productivity and biodiversity. 2. Here, we conduct an analysis of relationships between tree species richness, biomass and productivity in 25 forest plots of area 8-50 ha from across the world. The data were collected using standardized protocols, obviating the need to correct for methodological differences that plague many studies on this topic. 3. We found that at very small spatial grains (0.04 ha) species richness was generally positively related to productivity and biomass within plots, with a doubling of species richness corresponding to an average 48% increase in productivity and 53% increase in biomass. At larger spatial grains (0.25 ha, 1 ha), results were mixed, with negative relationships becoming more common. The results were qualitatively similar but much weaker when we controlled for stem density: at the 0.04 ha spatial grain, a doubling of species richness corresponded to a 5% increase in productivity and 7% increase in biomass. Productivity and biomass were themselves almost always positively related at all spatial grains. 4. Synthesis. This is the first cross-site study of the effect of tree species richness on forest biomass and productivity that systematically varies spatial grain within a controlled methodology. The scale-dependent results are consistent with theoretical models in which sampling effects and niche complementarity dominate at small scales, while environmental gradients drive patterns at large scales. Our study shows that the relationship of tree species richness with biomass and productivity changes qualitatively when moving from scales typical of forest surveys (0.04 ha) to slightly larger scales (0.25 and 1 ha). This needs to be recognized in forest conservation policy and management.
The conservation of tropical forest carbon stocks offers the opportunity to curb climate change by reducing greenhouse gas emissions from deforestation and simultaneously conserve biodiversity. ...However, there has been considerable debate about the extent to which carbon stock conservation will provide benefits to biodiversity in part because whether forests that contain high carbon density in their aboveground biomass also contain high animal diversity is unknown. Here, we empirically examined medium to large bodied ground-dwelling mammal and bird (hereafter "wildlife") diversity and carbon stock levels within the tropics using camera trap and vegetation data from a pantropical network of sites. Specifically, we tested whether tropical forests that stored more carbon contained higher wildlife species richness, taxonomic diversity, and trait diversity. We found that carbon stocks were not a significant predictor for any of these three measures of diversity, which suggests that benefits for wildlife diversity will not be maximized unless wildlife diversity is explicitly taken into account; prioritizing carbon stocks alone will not necessarily meet biodiversity conservation goals. We recommend conservation planning that considers both objectives because there is the potential for more wildlife diversity and carbon stock conservation to be achieved for the same total budget if both objectives are pursued in tandem rather than independently. Tropical forests with low elevation variability and low tree density supported significantly higher wildlife diversity. These tropical forest characteristics may provide more affordable proxies of wildlife diversity for future multi-objective conservation planning when fine scale data on wildlife are lacking.
Extinction rates in the Anthropocene are three orders of magnitude higher than background and disproportionately occur in the tropics, home of half the world's species. Despite global efforts to ...combat tropical species extinctions, lack of high-quality, objective information on tropical biodiversity has hampered quantitative evaluation of conservation strategies. In particular, the scarcity of population-level monitoring in tropical forests has stymied assessment of biodiversity outcomes, such as the status and trends of animal populations in protected areas. Here, we evaluate occupancy trends for 511 populations of terrestrial mammals and birds, representing 244 species from 15 tropical forest protected areas on three continents. For the first time to our knowledge, we use annual surveys from tropical forests worldwide that employ a standardized camera trapping protocol, and we compute data analytics that correct for imperfect detection. We found that occupancy declined in 22%, increased in 17%, and exhibited no change in 22% of populations during the last 3-8 years, while 39% of populations were detected too infrequently to assess occupancy changes. Despite extensive variability in occupancy trends, these 15 tropical protected areas have not exhibited systematic declines in biodiversity (i.e., occupancy, richness, or evenness) at the community level. Our results differ from reports of widespread biodiversity declines based on aggregated secondary data and expert opinion and suggest less extreme deterioration in tropical forest protected areas. We simultaneously fill an important conservation data gap and demonstrate the value of large-scale monitoring infrastructure and powerful analytics, which can be scaled to incorporate additional sites, ecosystems, and monitoring methods. In an era of catastrophic biodiversity loss, robust indicators produced from standardized monitoring infrastructure are critical to accurately assess population outcomes and identify conservation strategies that can avert biodiversity collapse.
We test the hypotheses proposed by Gentry and Schnitzer that liana density and basal area in tropical forests vary negatively with mean annual precipitation (MAP) and positively with seasonality. ...Previous studies correlating liana abundance with these climatic variables have produced conflicting results, warranting a new analysis of drivers of liana abundance based on a different dataset. We compiled a pan-tropical dataset containing 28,953 lianas (> 2.5 cm diam.) from studies conducted at 13 Neotropical and 11 Paleotropical dry to wet lowland tropical forests. The ranges in MAP and dry season length (DSL) (number of months with mean rainfall < 100 mm) represented by these datasets were 860-7250 mm/yr and 0-7 mo, respectively. Pan-tropically, liana density and basal area decreased significantly with increasing annual rainfall and increased with increasing DSL, supporting the hypotheses of Gentry and Schnitzer. Our results suggest that much of the variation in liana density and basal area in the tropics can be accounted for by the relatively simple metrics of MAP and DSL.
Deuterium-labeled water was used to study the effect of the Tapajós Throughfall Exclusion Experiment (TTEE) on soil moisture movement and on depth of water uptake by trees of Coussarea racemosa, ...Sclerolobium chrysophyllum, and Eschweilera pedicellata. The TTEE simulates an extended dry season in an eastern Amazonian rainforest, a plausible scenario if the El Niño phenomenon changes with climate change. The TTEE excludes 60% of the wet season throughfall from a 1-ha plot (treatment), while the control 1-ha plot receives precipitation year-round. Mean percolation rate of the label peak in the control plot was greater than in the treatment plot during the wet season (0.75 vs. 0.07 m/mo). The rate was similar for both plots during the dry season (ca. 0.15 m/mo), indicative that both plots have similar topsoil structure. Interestingly, the label peak in the control plot during the dry season migrated upward an average distance of 64 cm. We show that water probably moved upward through soil pores--i.e., it did not involve roots (hydraulic lift)--most likely because of a favorable gradient of total (matric + gravitational) potential coupled with sufficient unsaturated hydraulic conductivity. Water probably also moved upward in the treatment plot, but was not detectable; the label in this plot did not percolate below 1 m or beyond the depth of plant water uptake. During the dry season, trees in the rainfall exclusion plot, regardless of species, consistently absorbed water significantly deeper, but never below 1.5-2 m, than trees in the control plot, and therefore may represent expected root function of this understory/subcanopy tree community during extended dry periods.
In the cold semiarid region of northeastern Mongolia, we used stable isotopes (
18O and D) to determine potential plant water sources during the 2003 growing season (June to September) in two ...habitats: montane forest and an elevation gradient from the forest to Kherlen river bank. The forest is dominated by larch (
Larix sibirica) with patches of cinquefoil shrubs (
Potentilla fruticosa). The latter also grow throughout the elevation gradient, while the larch grows only on the top slope. Poplar (
Populus spp.) and willow (
Salix spp.) trees grow only on the river bank. All plant and soil samples showed isotopic signatures similar to summer precipitation, which is isotopically heavier in summer than winter. In July and August, larch trees in the forest tended to shift their water uptake to shallow depths in response to recent rainfall, but during the remaining months (June and September), depths of water uptake were unclear. Further, both the larch trees and cinquefoil shrubs in the forest used water at similar depths, suggesting potential competition for water. Plants along the elevation gradient showed different patterns of water use: (1) in July, larch used recent rainfall only, but in other months, the pattern was unclear; (2) cinquefoil depended on rainfall from recent weeks (as in August), but sometimes used antecedent rainwater from one month prior; and (3) poplar and willow seemed to use water from the river (as in August) or from precipitation that fell a few weeks prior (as in September), but the factors controlling this unusual shift are unknown. This study contributes to our understanding of plant water use strategies in cold semiarid ecosystems, and provides baseline data for models designed to understand large-scale hydrological effects of global climate change.
•Deforestation, land conversion and natural resources overexploitation endanger “mortiño”.•Mortiño reproductive phenology not shows chronological orderly progression in monitored areas.•Different ...reproductive stages (bud, flower and fruit) were even observed within same individuals.•Extreme climatic conditions of paramo imposed physiological limitations on mortiño phenology.
Vaccinium floribundum Kunth (Ericaceae) is a native Andean species with shrubby habit and edible fruits. It is mostly distributed in the paramos of the Andes, from Venezuela to Bolivia, where it is commonly known as "mortiño". In this study, we describe the reproductive phenological growth stages of V. floribundum in the paramo of the Chimborazo volcano in Ecuador, using an adaptation of the BBCH scale system, and according to semi-monthly observations conducted in three localities from January 2017 to June 2018 (18 months). In addition, a linear regression analysis was performed to detect any potential influence of climatic parameters on the reproductive phenology of “mortiño”. Throughout the monitoring period, different stages of reproductive growth such as bud, flower and fruit were simultaneously found among individuals and, sometimes, even in the same plant. The reproductive phenology of sampled individuals from sites 1 and 2 (Mindala Loma and Polylepis, respectively) were relatively synchronized, whereas individuals from site 3 (Mechahuasca) showed a different phenological pattern. A significant, apparently quick, loss of flowers was evident in all localities during the study period. The patterns observed could reflect physiological constraints imposed by the extreme weather conditions of the paramo.
We analyze forest structure, diversity, and dominance in three large-scale Amazonian forest dynamics plots located in Northwestern (Yasuni and Amacayacu) and central (Manaus) Amazonia, to evaluate ...their consistency with prevailing wisdom regarding geographic variation and the shape of species abundance distributions, and to assess the robustness of among-site patterns to plot area, minimum tree size, and treatment of morphospecies. We utilized data for 441,088 trees (DBH ≥1 cm) in three 25-ha forest dynamics plots. Manaus had significantly higher biomass and mean wood density than Yasuni and Amacayacu. At the 1-ha scale, species richness averaged 649 for trees ≥1 cm DBH, and was lower in Amacayacu than in Manaus or Yasuni; however, at the 25-ha scale the rankings shifted, with Yasuni < Amacayacu < Manaus. Within each site, Fisher’s alpha initially increased with plot area to 1–10 ha, and then showed divergent patterns at larger areas depending on the site and minimum size. Abundance distributions were better fit by lognormal than by logseries distributions. Results were robust to the treatment of morphospecies. Overall, regional patterns in Amazonian tree species diversity vary with the spatial scale of analysis and the minimum tree size. The minimum area to capture local diversity is 2 ha for trees ≥1 cm DBH, or 10 ha for trees ≥10 cm DBH. The underlying species abundance distribution for Amazonian tree communities is lognormal, consistent with the idea that the rarest species have not yet been sampled. Enhanced sampling intensity is needed to fill the still large voids we have in plant diversity in Amazon forests.
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