The remarkable biodiversity of the Brazilian Amazon is poorly documented and threatened by deforestation. When undocumented areas become deforested, in addition to losing the fauna and flora, we lose ...the opportunity to know which unique species had occupied a habitat. Here we quantify such knowledge loss by calculating how much of the Brazilian Amazon has been deforested and will likely be deforested until 2050 without having its tree flora sufficiently documented. To this end, we analysed 399 147 digital specimens of nearly 6000 tree species in relation to official deforestation statistics and future deforestation scenarios. We find that by 2017, 30% of all the localities where tree specimens had been collected were mostly deforested. Some 300 000 km2 (12%; 485 25 × 25 km grid cells) of the Brazilian Amazon had been deforested by 2017, without having a single tree specimen recorded. An additional 250 000–900 000 km2 of severely under‐collected rainforest will likely become deforested by 2050. If future tree sampling is to cover this area, sampling effort has to increase two‐ to six‐fold. Nearly 255 000 km2 or 7% of rainforest in the Brazilian Amazon is easily accessible but does yet but remain under‐collected. Our study highlights how progressing deforestation increases the risk of losing undocumented species of a hyper‐diverse tree flora.
The combination of the UV flash equipment, which generates UV flashes in short intervals with a high and homogenous energy density, with UV curing systems for automotive refinish leads to a perfectly ...suitable procedure especially for spot- and micro-repair applications. The UV curing refinish primer technology is well introduced in the market and the repair process time can be reduced by up to 50% compared to conventional systems. The visualization of the reaction grade and speed of the UV-induced radical polymerization is important for development. The skillful combination of the UV flash equipment with a FTIR instrument enables real-time measurements under application oriented UV curing conditions. The influence of applied UV intensity, oxygen inhibition and effectiveness of the polymerization reaction is investigated.
AIM: Tropical forests store 25% of global carbon and harbour 96% of the world's tree species, but it is not clear whether this high biodiversity matters for carbon storage. Few studies have teased ...apart the relative importance of forest attributes and environmental drivers for ecosystem functioning, and no such study exists for the tropics. LOCATION: Neotropics. METHODS: We relate aboveground biomass (AGB) to forest attributes (diversity and structure) and environmental drivers (annual rainfall and soil fertility) using data from 144,000 trees, 2050 forest plots and 59 forest sites. The sites span the complete latitudinal and climatic gradients in the lowland Neotropics, with rainfall ranging from 750 to 4350 mm year⁻¹. Relationships were analysed within forest sites at scales of 0.1 and 1 ha and across forest sites along large‐scale environmental gradients. We used a structural equation model to test the hypothesis that species richness, forest structural attributes and environmental drivers have independent, positive effects on AGB. RESULTS: Across sites, AGB was most strongly driven by rainfall, followed by average tree stem diameter and rarefied species richness, which all had positive effects on AGB. Our indicator of soil fertility (cation exchange capacity) had a negligible effect on AGB, perhaps because we used a global soil database. Taxonomic forest attributes (i.e. species richness, rarefied richness and Shannon diversity) had the strongest relationships with AGB at small spatial scales, where an additional species can still make a difference in terms of niche complementarity, while structural forest attributes (i.e. tree density and tree size) had strong relationships with AGB at all spatial scales. MAIN CONCLUSIONS: Biodiversity has an independent, positive effect on AGB and ecosystem functioning, not only in relatively simple temperate systems but also in structurally complex hyperdiverse tropical forests. Biodiversity conservation should therefore be a key component of the UN Reducing Emissions from Deforestation and Degradation strategy.
Amazon forest response to repeated droughts Feldpausch, T. R.; Phillips, O. L.; Brienen, R. J. W. ...
Global biogeochemical cycles,
July 2016, Letnik:
30, Številka:
7
Journal Article
Recenzirano
Odprti dostop
The Amazon Basin has experienced more variable climate over the last decade, with a severe and widespread drought in 2005 causing large basin‐wide losses of biomass. A drought of similar ...climatological magnitude occurred again in 2010; however, there has been no basin‐wide ground‐based evaluation of effects on vegetation. We examine to what extent the 2010 drought affected forest dynamics using ground‐based observations of mortality and growth from an extensive forest plot network. We find that during the 2010 drought interval, forests did not gain biomass (net change: −0.43 Mg ha−1, confidence interval (CI): −1.11, 0.19, n = 97), regardless of whether forests experienced precipitation deficit anomalies. This contrasted with a long‐term biomass sink during the baseline pre‐2010 drought period (1998 to pre‐2010) of 1.33 Mg ha−1 yr−1 (CI: 0.90, 1.74, p < 0.01). The resulting net impact of the 2010 drought (i.e., reversal of the baseline net sink) was −1.95 Mg ha−1 yr−1 (CI:−2.77, −1.18; p < 0.001). This net biomass impact was driven by an increase in biomass mortality (1.45 Mg ha−1 yr−1 CI: 0.66, 2.25, p < 0.001) and a decline in biomass productivity (−0.50 Mg ha−1 yr−1, CI:−0.78, −0.31; p < 0.001). Surprisingly, the magnitude of the losses through tree mortality was unrelated to estimated local precipitation anomalies and was independent of estimated local pre‐2010 drought history. Thus, there was no evidence that pre‐2010 droughts compounded the effects of the 2010 drought. We detected a systematic basin‐wide impact of the 2010 drought on tree growth rates across Amazonia, which was related to the strength of the moisture deficit. This impact differed from the drought event in 2005 which did not affect productivity. Based on these ground data, live biomass in trees and corresponding estimates of live biomass in lianas and roots, we estimate that intact forests in Amazonia were carbon neutral in 2010 (−0.07 Pg C yr−1 CI:−0.42, 0.23), consistent with results from an independent analysis of airborne estimates of land‐atmospheric fluxes during 2010. Relative to the long‐term mean, the 2010 drought resulted in a reduction in biomass carbon uptake of 1.1 Pg C, compared to 1.6 Pg C for the 2005 event.
Key Points
During the 2010 drought interval, Amazon forests did not gain biomass, regardless of whether forests experienced precipitation deficit anomalies
Biomass losses were partially driven by a decline in productivity related to precipitation anomalies
Pre‐2010 droughts did not compound the effects of the 2010 drought
Aboveground tropical tree biomass and carbon storage estimates commonly ignore tree height (H). We estimate the effect of incorporating H on tropics-wide forest biomass estimates in 327 plots across ...four continents using 42 656 H and diameter measurements and harvested trees from 20 sites to answer the following questions: 1. What is the best H-model form and geographic unit to include in biomass models to minimise site-level uncertainty in estimates of destructive biomass? 2. To what extent does including H estimates derived in (1) reduce uncertainty in biomass estimates across all 327 plots? 3. What effect does accounting for H have on plot- and continental-scale forest biomass estimates? The mean relative error in biomass estimates of destructively harvested trees when including H (mean 0.06), was half that when excluding H (mean 0.13). Power- and Weibull-H models provided the greatest reduction in uncertainty, with regional Weibull-H models preferred because they reduce uncertainty in smaller-diameter classes (≤40 cm D) that store about one-third of biomass per hectare in most forests. Propagating the relationships from destructively harvested tree biomass to each of the 327 plots from across the tropics shows that including H reduces errors from 41.8 Mg ha−1 (range 6.6 to 112.4) to 8.0 Mg ha−1 (−2.5 to 23.0). For all plots, aboveground live biomass was −52.2 Mg ha−1 (−82.0 to −20.3 bootstrapped 95% CI), or 13%, lower when including H estimates, with the greatest relative reductions in estimated biomass in forests of the Brazilian Shield, east Africa, and Australia, and relatively little change in the Guiana Shield, central Africa and southeast Asia. Appreciably different stand structure was observed among regions across the tropical continents, with some storing significantly more biomass in small diameter stems, which affects selection of the best height models to reduce uncertainty and biomass reductions due to H. After accounting for variation in H, total biomass per hectare is greatest in Australia, the Guiana Shield, Asia, central and east Africa, and lowest in east-central Amazonia, W. Africa, W. Amazonia, and the Brazilian Shield (descending order). Thus, if tropical forests span 1668 million km2 and store 285 Pg C (estimate including H), then applying our regional relationships implies that carbon storage is overestimated by 35 Pg C (31–39 bootstrapped 95% CI) if H is ignored, assuming that the sampled plots are an unbiased statistical representation of all tropical forest in terms of biomass and height factors. Our results show that tree H is an important allometric factor that needs to be included in future forest biomass estimates to reduce error in estimates of tropical carbon stocks and emissions due to deforestation.
S. J. Gunst, J. Q. Stropp and J. Service
Division of Thoracic Diseases and Internal Medicine, Mayo Clinic and Foundation, Rochester, Minnesota 55905.
In normal humans and dogs, the airways do not ...constrict to closure even
when maximally stimulated. However, airway closure can be produced in
isolated canine lobes and bronchial segments that are stimulated with
maximal concentrations of bronchoconstrictors. These observations suggest
that under normal conditions, physiological mechanisms to limit
bronchoconstriction exist in vivo. In this investigation, we evaluated how
mechanical factors that influence airway smooth muscle contractility
contribute to the modulation of the pressure-volume characteristics of
contracted canine intraparenchymal airways in vitro. Our results
demonstrated that maximal and even submaximal contractile stimuli can
produce airway closure in bronchi that are allowed to contract under
isobaric conditions. However, the effectiveness of bronchoconstrictors is
significantly reduced when the airways are subjected to tidal volume
oscillations during contraction. In addition, airways contracted
isovolumetrically at low volumes exhibit a markedly reduced sensitivity to
submaximal concentrations of acetylcholine. This may limit
bronchoconstriction at low lung volumes and transpulmonary pressures where
the effectiveness of parenchymal stress in keeping the airways open is
reduced. Together these factors could provide a mechanism by which
bronchoconstriction is limited to low levels of airway resistance under
normal conditions in vivo.
S. J. Gunst and J. Q. Stropp
Department of Physiology and Biophysics, Mayo Clinic and Mayo Foundation, Rochester, Minnesota 55905.
Intraparenchymal canine airway segments with branches tied off were ...mounted
between two fluid-filled cannulas in an organ chamber. Airways were
inflated to successive volumes ranging from 4 to 100% of the segment volume
at 25 cmH2O. At each volume, pressure was monitored during isovolumetric
contractions elicited by 10(-3) M acetylcholine. Small bronchi developed
pressures greater than 30 cmH2O in response to acetylcholine at all volumes
and were able to constrict to closure. Large bronchi developed pressures
greater than 30 cmH2O only near maximal volumes and were able to constrict
to only 30% of maximal volume. Maximal active pressures occurred at low
volumes in small bronchi and at high volumes in large bronchi. However,
maximal active circumferential tension and stress occurred at near-maximal
volumes in both large and small bronchi. Circumferential length
active-stress curves and maximal active-stress development for bronchi and
trachealis muscle strips were similar. Similar length active-stress
properties in different bronchi may produce significant differences in
volume-pressure characteristics.
1. Comparative analyses of diversity variation among and between regions allow testing of alternative explanatory models and ideas. Here, we explore the relationships between the tree x-diversity of ...small rain forest plots in Africa and in Amazonia and climatic variables, to test the explanatory power of climate and the consistency of relationships between the two continents. 2. Our analysis included 1003 African plots and 512 Amazonian plots. All are located in old-growth primary non-flooded forest under 900 m altitude. Tree a-diversity is estimated using Fisher's alpha calculated for trees with diameter at breast height ≥ 10 cm. Mean diversity values are lower in Africa by a factor of two. 3. Climate-diversity analyses are based on data aggregated for grid cells of 2.5 x 2.5 km. The highest Fisher's alpha values are found in Amazonian forests with no climatic analogue in our African data set. When the analysis is restricted to pixels of directly comparable climate, the mean diversity of African forests is still much lower than that in Amazonia. Only in regions of low mean annual rainfall and temperature is mean diversity in African forests comparable with, or superior to, the diversity in Amazonia. 4. The climatic variables best correlated with the tree α-diversity are largely different in the African and Amazonian data, or correlate with African and Amazonian diversity in opposite directions. 5. These differences in the relationship between local/landscape-scale a-diversity and climate variables between the two continents point to the possible significance of an array of factors including: macro-scale climate differences between the two regions, overall size of the respective species pools, past climate variation, other forms of long-term and short-term environmental variation, and edaphics. We speculate that the lower a-diversity of African lowland rain forests reported here may be in part a function of the smaller regional species pool of tree species adapted to warm, wet conditions. 6. Our results point to the importance of controlling for variation in plot size and for gross differences in regional climates when undertaking comparative analyses between regions of how local diversity of forest varies in relation to other putative controlling factors.
Positive aboveground biomass trends have been reported from old-growth forests across the Amazon basin and hypothesized to reflect a large-scale response to exterior forcing. The result could, ...however, be an artefact due to a sampling bias induced by the nature of forest growth dynamics. Here, we characterize statistically the disturbance process in Amazon old-growth forests as recorded in 135 forest plots of the RAINFOR network up to 2006, and other independent research programmes, and explore the consequences of sampling artefacts using a data-based stochastic simulator. Over the observed range of annual aboveground biomass losses, standard statistical tests show that the distribution of biomass losses through mortality follow an exponential or near-identical Weibull probability distribution and not a power law as assumed by others. The simulator was parameterized using both an exponential disturbance probability distribution as well as a mixed exponential-power law distribution to account for potential large-scale blowdown events. In both cases, sampling biases turn out to be too small to explain the gains detected by the extended RAINFOR plot network. This result lends further support to the notion that currently observed biomass gains for intact forests across the Amazon are actually occurring over large scales at the current time, presumably as a response to climate change.
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