Wetlands are valuable ecosystems because they harbor a huge biodiversity and provide key services to societies. When natural or human factors degrade wetlands, ecological restoration is often carried ...out to recover biodiversity and ecosystem services (ES). Although such restorations are routinely performed, we lack systematic, evidence-based assessments of their effectiveness on the recovery of biodiversity and ES. Here we performed a meta-analysis of 70 experimental studies in order to assess the effectiveness of ecological restoration and identify what factors affect it. We compared selected ecosystem performance variables between degraded and restored wetlands and between restored and natural wetlands using response ratios and random-effects categorical modeling. We assessed how context factors such as ecosystem type, main agent of degradation, restoration action, experimental design, and restoration age influenced post-restoration biodiversity and ES. Biodiversity showed excellent recovery, though the precise recovery depended strongly on the type of organisms involved. Restored wetlands showed 36% higher levels of provisioning, regulating and supporting ES than did degraded wetlands. In fact, wetlands showed levels of provisioning and cultural ES similar to those of natural wetlands; however, their levels of supporting and regulating ES were, respectively, 16% and 22% lower than in natural wetlands. Recovery of biodiversity and of ES were positively correlated, indicating a win-win restoration outcome. The extent to which restoration increased biodiversity and ES in degraded wetlands depended primarily on the main agent of degradation, restoration actions, experimental design, and ecosystem type. In contrast, the choice of specific restoration actions alone explained most differences between restored and natural wetlands. These results highlight the importance of comprehensive, multi-factorial assessment to determine the ecological status of degraded, restored and natural wetlands and thereby evaluate the effectiveness of ecological restorations. Future research on wetland restoration should also seek to identify which restoration actions work best for specific habitats.
Over half of the world's forests are disturbed, and the rate at which ecosystem processes recover after disturbance is important for the services these forests can provide. We analyze the drivers' ...underlying changes in rates of key ecosystem processes (biomass productivity, litter productivity, actual litter decomposition, and potential litter decomposition) during secondary succession after shifting cultivation in wet tropical forest of Mexico.
We test the importance of three alternative drivers of ecosystem processes: vegetation biomass (vegetation quantity hypothesis), community-weighted trait mean (mass ratio hypothesis), and functional diversity (niche complementarity hypothesis) using structural equation modeling. This allows us to infer the relative importance of different mechanisms underlying ecosystem process recovery.
Ecosystem process rates changed during succession, and the strongest driver was aboveground biomass for each of the processes. Productivity of aboveground stem biomass and leaf litter as well as actual litter decomposition increased with initial standing vegetation biomass, whereas potential litter decomposition decreased with standing biomass. Additionally, biomass productivity was positively affected by community-weighted mean of specific leaf area, and potential decomposition was positively affected by functional divergence, and negatively by community-weighted mean of leaf dry matter content.
Our empirical results show that functional diversity and community-weighted means are of secondary importance for explaining changes in ecosystem process rates during tropical forest succession. Instead, simply, the amount of vegetation in a site is the major driver of changes, perhaps because there is a steep biomass buildup during succession that overrides more subtle effects of community functional properties on ecosystem processes. We recommend future studies in the field of biodiversity and ecosystem functioning to separate the effects of vegetation quality (community-weighted mean trait values and functional diversity) from those of vegetation quantity (biomass) on ecosystem processes and services.
ABSTRACT
Old‐growth tropical forests are being extensively deforested and fragmented worldwide. Yet forest recovery through succession has led to an expansion of secondary forests in human‐modified ...tropical landscapes (HMTLs). Secondary forests thus emerge as a potential repository for tropical biodiversity, and also as a source of essential ecosystem functions and services in HMTLs. Such critical roles are controversial, however, as they depend on successional, landscape and socio‐economic dynamics, which can vary widely within and across landscapes and regions. Understanding the main drivers of successional pathways of disturbed tropical forests is critically needed for improving management, conservation, and restoration strategies. Here, we combine emerging knowledge from tropical forest succession, forest fragmentation and landscape ecology research to identify the main driving forces shaping successional pathways at different spatial scales. We also explore causal connections between land‐use dynamics and the level of predictability of successional pathways, and examine potential implications of such connections to determine the importance of secondary forests for biodiversity conservation in HMTLs. We show that secondary succession (SS) in tropical landscapes is a multifactorial phenomenon affected by a myriad of forces operating at multiple spatio‐temporal scales. SS is relatively fast and more predictable in recently modified landscapes and where well‐preserved biodiversity‐rich native forests are still present in the landscape. Yet the increasing variation in landscape spatial configuration and matrix heterogeneity in landscapes with intermediate levels of disturbance increases the uncertainty of successional pathways. In landscapes that have suffered extensive and intensive human disturbances, however, succession can be slow or arrested, with impoverished assemblages and reduced potential to deliver ecosystem functions and services. We conclude that: (i) succession must be examined using more comprehensive explanatory models, providing information about the forces affecting not only the presence but also the persistence of species and ecological groups, particularly of those taxa expected to be extirpated from HMTLs; (ii) SS research should integrate new aspects from forest fragmentation and landscape ecology research to address accurately the potential of secondary forests to serve as biodiversity repositories; and (iii) secondary forest stands, as a dynamic component of HMTLs, must be incorporated as key elements of conservation planning; i.e. secondary forest stands must be actively managed (e.g. using assisted forest restoration) according to conservation goals at broad spatial scales.
Recent Advances in Nano‐ and Micromotors Fernández‐Medina, Marina; Ramos‐Docampo, Miguel A.; Hovorka, Ondrej ...
Advanced functional materials,
03/2020, Volume:
30, Issue:
12
Journal Article
Peer reviewed
Nano‐ and micromotors are fascinating objects that can navigate in complex fluidic environments. Their active motion can be triggered by external power sources or they can exhibit self‐propulsion ...using fuel extracted from their surroundings. The research field is rapidly evolving and has produced nano/micromotors of different geometrical designs, exploiting a variety of mechanisms of locomotion, being capable of achieving remarkable speeds in diverse environments ranging from simple aqueous solutions to complex media including cell cultures or animal tissue. This review aims to provide an overview of the recent developments with focus on predominantly experimental demonstrations of the various motor designs developed in the past 24 months. First, externally driven motors are discussed followed by considering fuel‐driven approaches. Finally, a short future perspective is provided.
This review outlines the recent developments in nano‐ and micromotors, focusing on examples from the past 24 months. These motors employ external power sources such as magnetic fields, ultrasound, and light. Alternatively, they can self‐propel using catalytic surfaces and environmental fuel or self‐disintegration. In both cases, fast locomotion in complex environments is illustrated.
We tested whether and how functional composition changes with succession in dry deciduous and wet evergreen forests of Mexico. We hypothesized that compositional changes during succession in dry ...forest were mainly determined by increasing water availability leading to community functional changes from conservative to acquisitive strategies, and in wet forest by decreasing light availability leading to changes from acquisitive to conservative strategies. Research was carried out in 15 dry secondary forest plots (5-63 years after abandonment) and 17 wet secondary forest plots (<1-25 years after abandonment). Community-level functional traits were represented by community-weighted means based on 11 functional traits measured on 132 species. Successional changes in functional composition are more marked in dry forest than in wet forest and largely characterized by different traits. During dry forest succession, conservative traits related to drought tolerance and drought avoidance decreased, as predicted. Unexpectedly acquisitive leaf traits also decreased, whereas seed size and dependence on biotic dispersal increased. In wet forest succession, functional composition changed from acquisitive to conservative leaf traits, suggesting light availability as the main driver of changes. Distinct suites of traits shape functional composition changes in dry and wet forest succession, responding to different environmental filters.
Light is a key resource for tree performance and hence, tree species partition spatial and temporal gradients in light availability. Although light distribution drives tree performance and species ...replacement during secondary forest succession, we yet lack understanding how light distribution changes with tropical forest development.
This study aims to evaluate how changes in forest structure lead to changes in vertical and horizontal light heterogeneity during tropical forest succession.
We described successional patterns in light using a chronosequence approach in which we compared 14 Mexican secondary forest stands that differ in age (8–32 years) since agricultural abandonment. For each stand, we measured vertical light profiles in 16 grid cells, and structural parameters (diameter at breast height, height and crown dimensions) for each tree.
During succession, we found a rapid increase in stand size (basal area, crown area and length) and stand differentiation (i.e. a gradual leaf distribution along the forest profile), which leads to fast changes in light conditions and more light heterogeneity. The inflection points of the vertical light gradient (i.e. the absolute height at which 50% relative light intensity is attained) rapidly moved towards higher heights in the first 20 years, indicating that larger amounts of light are intercepted by canopy trees. Light attenuation rate (i.e. the rate of light extinction) decreased during succession due to slower accumulation of the crown area with height. Understorey light intensity and heterogeneity slightly decreased during succession because of an increase in crown size and a decrease in lateral gap frequency. Understorey relative light intensity was 1.56% at 32 years after abandonment.
Synthesis. During succession, light conditions changed linearly, which should lead to a continuous and constant replacement of species. Especially in later successional stages, stronger vertical light gradients can limit the regeneration of light‐demanding pioneer species and increase the proportion of shade‐tolerant late‐successional species under the canopy. These changes in light conditions were largely driven by the successional changes in forest structure, as basal area strongly determined the height where most light is absorbed, whereas crown area, and to a lesser extent crown length, determined light distribution.
Secondary forest succession is driven by changes in forest structure and light environment, but few studies have quantified both factors. During succession in a Mexican tropical rainforest, light in the understory became more homogeneously distributed, whereas vertical light heterogeneity increased. Stand basal area determined the height where most light is absorbed, whereas crown architecture determined horizontal and vertical light distribution.
Esterases catalyze the hydrolysis of esters to form a carboxylic acid and alcohol. These enzymes play a key role in both the detoxification of xenobiotic compounds and the metabolism of drugs and ...prodrugs. Numerous fluorogenic probes have been developed to monitor esterase activity. Most are based on an aromatic alcohol, and the others are based on an aromatic acid. These restrictions leave unexplored the specificity of esterases for aliphatic esters. Here, we report on the use of esters of thiopheneacetic acid coupled with the luminescence of terbium(III) as the basis for a continuous assay of esterase activity. This probe allows for a wide variation of the alcohol moiety and the detection of its hydrolysis at submicromolar concentrations. The assay verifies steady-state kinetic parameters for catalysis by pig liver esterase from either initial rates or the integration of progress curves, and its utility is evident with unpurified esterases in bacterial and human cell lysates.
Macromolecular condensation resulting from biologically regulated liquid–liquid phase separation is emerging as a mechanism to organize intracellular space in eukaryotes, with broad implications for ...cell physiology and pathology. Despite their small size, bacterial cells are also organized by proteins such as FtsZ, a tubulin homolog that assembles into a ring structure precisely at the cell midpoint and is required for cytokinesis. Here, we demonstrate that FtsZ can form crowding‐induced condensates, reminiscent of those observed for eukaryotic proteins. Formation of these FtsZ‐rich droplets occurs when FtsZ is bound to SlmA, a spatial regulator of FtsZ that antagonizes polymerization, while also binding to specific sites on chromosomal DNA. The resulting condensates are dynamic, allowing FtsZ to undergo GTP‐driven assembly to form protein fibers. They are sensitive to compartmentalization and to the presence of a membrane boundary in cell mimetic systems. This is a novel example of a bacterial nucleoprotein complex exhibiting condensation into liquid droplets, suggesting that phase separation may also play a functional role in the spatiotemporal organization of essential bacterial processes.
Synopsis
Elements of the bacterial cell division machinery assemble into condensates by liquid‐liquid phase separation in cell‐like crowded conditions. This suggests that phase‐separated condensation may also help to organize intracellular space in bacteria.
The essential bacterial cell division protein FtsZ forms phase‐separated condensates in the presence of nucleoprotein complexes organized by the FtsZ spatial regulator SlmA.
The condensates are dynamic and disband upon GTP‐dependent reversible formation of FtsZ fibers whose lifetimes are significantly shortened by SlmA.
Condensates are observed in cell‐like crowding conditions in solution and inside phase‐separated systems encircled by a lipid membrane.
Phase‐separated FtsZ condensates may constitute a novel element of spatiotemporal organization of essential bacterial cell cycle processes.
Elements of the bacterial cell division machinery assemble into condensates by liquid‐liquid phase separation in cell‐like crowded conditions. This suggests that phase‐separated condensation may also help to organize intracellular space in bacteria.
Gene expression in eukaryotes is controlled by DNA sequences at promoter and enhancer regions, whose accessibility for binding by regulatory proteins dictates their specific patterns of activity. ...Here, we identify the protein Zbtb7a as a factor required for inducible changes in accessibility driven by transcription factors (TFs). We show that Zbtb7a binds to a significant fraction of genomic promoters and enhancers, encompassing many target genes of nuclear factor kappa B (NFκB) p65 and a variety of other TFs. While Zbtb7a binding is not alone sufficient to directly activate promoters, it is required to enable TF-dependent control of accessibility and normal gene expression. Using p65 as a model TF, we show that Zbtb7a associates with promoters independently of client TF binding. Moreover, the presence of prebound Zbtb7a can specify promoters that are amenable to TF-induced changes in accessibility. Therefore, Zbtb7a represents a widely used promoter factor that transduces signals from other TFs to enable control of accessibility and regulation of gene expression.
In closed‐canopy systems globally, plants exhibit intense competition for light, prioritizing vertical growth to attain elevated positions within the canopy. Light competition is especially intense ...in tropical rainforests because of their dense shaded stands, and during forest succession because of concomitant changes in vertical light profiles. We evaluated how the height growth of individual tree differs among forest light strata (canopy, sub‐canopy and understorey) and successional guilds (early, mid‐ and late successional species) during secondary succession in a Mexican rainforest. Fourteen secondary forest stands differing in time since agricultural abandonment (1–25 years) were monitored for seven consecutive years. For each stand and census year we estimated relative light intensity (RLI) for each height and categorized trees into forest light strata: understorey (RLI ≦ 33.3%), sub‐canopy (33.3% ≦ RLI ≦ 66.6%) and canopy (RLI ≧ 66.6%), and into successional guilds based on the literature. We estimated two measures of height growth: absolute height growth (HGabs, cm year−1) calculated as the difference in tree height between two consecutive censuses, and biomass partitioning to height growth (HGbp, in kg kg−1 × 100) calculated as the percentage of total aboveground biomass growth partitioned to height growth. Earlier in succession, trees for all strata had greater HGabs and HGbp, resulting in rapid vertical forest development. HGabs was fastest for canopy trees, followed by sub‐canopy and understorey trees. These differences in HGabs among strata, combined with their inter‐specific variation and continuous recruitment of small individuals, lead to a rapid differentiation in tree sizes and increase stand structural heterogeneity. HGbp was greater for understorey and sub‐canopy trees than for canopy trees, reflecting ontogenetic changes in the light competition strategy from growth to persistence. With succession, both HGabs and HGbp decreased, most strongly for canopy trees, probably because of an increased exposure to drought stress. These successional changes stabilize stand size structure and reduce the rate of development.
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