Pristine Clouds Research Articles

A needle in a haystack? Catching Population III stars in the epoch of reionization: I. Population III star-forming environments

ABSTRACT Despite extensive search efforts, direct observations of the first [Population III (Pop III)] stars have not yet succeeded. Theoretical studies have suggested that late Pop III star formation is still possible in pristine clouds of high-mass galaxies, co-existing with Pop II stars, down to the epoch of reionization. Here, we re-assess this finding by exploring Pop III star formation in six 50 h−1 cMpc simulations performed with the hydrodynamical code dustyGadget. We find that Pop III star formation (∼10−3.4–10−3.2 M⊙ yr−1 cMpc−3) is still occurring down to z ∼ 6–8, i.e. well within the reach of deep JWST surveys. At these epochs, $\gtrsim\!{10}~{{\ \rm per\ cent}}$ of the rare massive galaxies with M⋆ ≳ 3 × 109 M⊙ are found to host Pop III stars, although with a Pop III/Pop II mass fraction $\lesssim\!0.1~{{\ \rm per\ cent}}$ . Regardless of their mass, Pop III-hosting galaxies are mainly found on the main sequence, at high star-formation rates, probably induced by accretion of pristine gas. This scenario is also supported by their increasing star-formation histories and their preferential location in high-density regions of the cosmic web. Pop III stars are found both in the outskirts of metal-enriched regions and in isolated, pristine clouds. In the latter case, their signal may be less contaminated by Pop IIs, although its detectability will strongly depend on the specific line of sight to the source, due to the complex morphology of the host galaxy and its highly inhomogeneous dust distribution.

Global evidence of aerosol-induced invigoration in marine cumulus clouds

Abstract. Aerosol–cloud–precipitation interactions can lead to a myriad of responses within shallow cumulus clouds, including an invigoration response, whereby aerosol loading results in a higher rain rate, more turbulence, and deepening of the cloud layer. However few global studies have found direct evidence that invigoration occurs. The few satellite-based studies that report evidence for such effects generally focus on only the deepening response. Here, we show evidence of invigoration beyond a deepening response by investigating the effects of aerosol loading on the latent heating and vertical motion profiles of warm rain. Using latent heating and vertical motion profiles derived from CloudSat radar observations, we show precipitating cumulus clouds in unstable, polluted environments exhibit a marked increase in precipitation formation rates and cloud top entrainment rates. However, invigoration is only discernible when the stability of the boundary layer is explicitly accounted for in the analysis. Without this environmental constraint, the mean polluted and pristine cloud responses are indiscernible from each other due to offsetting cloud responses in stable and unstable environments. Invigoration, or suppression depending on the environment, may induce possible feedbacks in both stable and unstable conditions that could subdue or enhance these effects, respectively. The strength of the invigoration response is found to additionally depend on cloud organization defined here by the size of the warm rain system. These results suggest that warm cloud parameterizations must account for not only the possibility of aerosol-induced cloud invigoration, but also the dependence of this invigorated state on the environment and the organization of the rain system.

The relevance of cloud forest fragments and their transition zones for butterfly conservation in Taita Hills, Kenya

A main driver of biodiversity loss is the transformation of pristine habitats into agricultural land, plantations of exotic trees, and settlements. The cloud forest of the Taita Hills in southern Kenya has suffered under such transformation processes. In consequence, remaining forests are small and isolated and often provide degraded forest habitats. We studied butterfly communities in four habitat types, cloud forest, cloud forest margin, exotic tree plantations, and agricultural land. We counted butterflies along transects during the rainy and the dry season. We assessed species traits for each butterfly species found. The four habitat types harbour distinct butterfly communities with only slight overlap among each other. Community compositions differed between the dry and rainy season. Forest specialist butterflies mainly occurred in the interior of the cloud forest, but were also observable along the forest edge. Species richness was highest at the transition between pristine cloud forest and agricultural land. The butterfly community of open agricultural landscapes was dominated by common and widespread East African savannah species, equipped with more elongated wings compared with those found inside the cloud forest. Exotic tree plantations showed a mixed butterfly species composition, consisting of many common and widespread savannah species, but also forest species with comparatively low specialization. In conclusion, typical cloud forest butterflies are on the need for intact cloud forest patches and cannot be compensated by surrogate habitats, such as exotic tree plantations.

Cloud Data Storage using Attribute based Encryption with Verifiable Outsourcing Auditor Security Schemes

Cloud storage services turned out to be continuously elegant. Owing to the implication of security, a few cloud storage secret composing schemes are anticipated to monitor data from those that don't approach. Every single such plan accepted that cloud storage providers region unit safe and can't be hacked; at the same time, in pursue, a few experts may drive cloud storage providers to uncover client insider facts or confidential data on the cloud, hence by and large going around storage mystery composing schemes. Amid this paper, we tend to bless our style for a pristine cloud storage mystery composing subject that permits cloud storage providers to make persuading false client privileged insights to protect client security. Since coercers can't reveal whenever acquired insider facts zone unit genuine or not, the cloud storage providers ensure that client security keeps on being immovably secured. The vast majority of the anticipated schemes expect cloud storage service providers or dependable outsiders taking care of key administration square measure solid and can't be hacked; nonetheless, in pursue, a few substances would conceivably capture interchanges among clients and cloud storage providers at that point urge storage providers to unfasten client privileged insights by misuse government control or diverse proposes that. All through this case, scrambled information square measure thought to be known and storage provider's square measure asked for to unfasten client insider facts

A representation of the collisional ice break-up process in the two-moment microphysics LIMA v1.0 scheme of Meso-NH

Abstract. The paper describes a switchable parameterization of collisional ice break-up (CIBU), an ice multiplication process that fits in with the two-moment microphysical Liquid Ice Multiple Aerosols (LIMA) scheme. The LIMA scheme with three ice types (pristine cloud ice crystals, snow aggregates, and graupel hail) was developed in the cloud-resolving mesoscale model (Meso-NH). Here, the CIBU parameterization assumes that collisional break-up is mostly efficient for the small and fragile snow aggregate class of particles when they are hit by large, dense graupel particles. The increase of cloud ice number concentration depends on a prescribed number (or a random number) of fragments being produced per collision. This point is discussed and analytical expressions of the newly contributing CIBU terms in LIMA are given. The scheme is run in the cloud-resolving mesoscale model (Meso-NH) to simulate a first case of a three-dimensional deep convective event with heavy production of graupel. The consequence of dramatically changing the number of fragments produced per collision is investigated by examining the rainfall rates and the changes in small ice concentrations and mass mixing ratios. Many budgets of the ice phase are shown and the sensitivity of CIBU to the initial concentration of freezing nuclei is explored. The scheme is then tested for another deep convective case where, additionally, the convective available potential energy (CAPE) is varied. The results confirm the strong impact of CIBU with up to a 1000-fold increase in small ice concentrations, a reduction of the rainfall or precipitating area, and an invigoration of the convection with higher cloud tops. Finally, it is concluded that the efficiency of the ice crystal fragmentation needs to be tuned carefully. The proposed parameterization of CIBU is easy to implement in any two-moment microphysics scheme. It could be used in this form to simulate deep tropical cloud systems where anomalously high concentrations of small ice crystals are suspected.

The implications of dust ice nuclei effect on cloud top temperature in a complex mesoscale convective system

Mineral dust is the most important natural source of atmospheric ice nuclei (IN) which may significantly mediate the properties of ice cloud through heterogeneous nucleation and lead to crucial impacts on hydrological and energy cycle. The potential dust IN effect on cloud top temperature (CTT) in a well-developed mesoscale convective system (MCS) was studied using both satellite observations and cloud resolving model (CRM) simulations. We combined satellite observations from passive spectrometer, active cloud radar, lidar, and wind field simulations from CRM to identify the place where ice cloud mixed with dust particles. For given ice water path, the CTT of dust-mixed cloud is warmer than that in relatively pristine cloud. The probability distribution function (PDF) of CTT for dust-mixed clouds shifted to the warmer end and showed two peaks at about −45 °C and −25 °C. The PDF for relatively pristine cloud only show one peak at −55 °C. Cloud simulations with different microphysical schemes agreed well with each other and showed better agreement with satellite observations in pristine clouds, but they showed large discrepancies in dust-mixed clouds. Some microphysical schemes failed to predict the warm peak of CTT related to heterogeneous ice formation.

The impact of seasonalities on direct radiative effects and radiative heating rates of absorbing aerosols above clouds

The impact of seasonalities on direct radiative effects (DREs) and radiative heating rates (RHRs) of absorbing aerosols above clouds in the southeast Atlantic is examined using radiative transfer calculations. For an aerosol optical thickness of 0.6 located between 0 and 4 km, a cloud optical thickness of 9.0 and a cloud effective radius of 12.8 µm at 0.55 µm located between 1 and 2 km, the diurnally averaged RHR at noon in the aerosol layer increases from ∼6.6 K day−1 in June to ∼8.9 K day−1 in October. In June (October), the RHR in the cloud layer at noon is 1.3 (1.7) K day−1 higher than the case of pristine clouds. However, an elevated aerosol layer (2–4 km) reduces the RHR by ∼0.2 K day−1 in the cloud layer relative to a pristine cloudy case. The DRE at top‐of‐atmosphere (TOA) reaches its peak when the solar zenith angle (SZA) is 54°. The DRE increases (decreases) with SZA for SZA less (greater) than 54°. The primary peak DRE is ∼29.5 W m−2 at 5.0°S 5.0°E, occurring at 0800 UTC. At noon, the DRE at TOA is ∼18.9, ∼20.5 and ∼23.1 W m−2 at 5.0°S, 15.0°S and 25.0°S along 5.0°E, respectively. This study provides data and theoretical understanding to help positioning science flights that target measurements of above‐cloud aerosol radiative effects.

MUSE searches for galaxies near very metal-poor gas clouds atz∼ 3: new constraints for cold accretion models

We report on the search for galaxies in the proximity of two very metal-poor gas clouds at z~3 towards the quasar Q0956+122. With a 5-hour MUSE integration in a ~500x500 kpc^2 region centred at the quasar position, we achieve a >80% complete spectroscopic survey of continuum-detected galaxies with m<25 mag and Ly{\alpha} emitters with luminosity L>3e41 erg/s. We do not identify galaxies at the redshift of a z~3.2 Lyman limit system (LLS) with log Z/Zsun = -3.35 +/- 0.05, placing this gas cloud in the intergalactic medium or circumgalactic medium of a galaxy below our sensitivity limits. Conversely, we detect five Ly{\alpha} emitters at the redshift of a pristine z~3.1 LLS with log Z/Zsun < -3.8, while ~0.4 sources were expected given the z~3 Ly{\alpha} luminosity function. Both this high detection rate and the fact that at least three emitters appear aligned in projection with the LLS suggest that this pristine cloud is tracing a gas filament that is feeding one or multiple galaxies. Our observations uncover two different environments for metal-poor LLSs, implying a complex link between these absorbers and galaxy halos, which ongoing MUSE surveys will soon explore in detail. Moreover, in agreement with recent MUSE observations, we detected a ~90 kpc Ly{\alpha} nebula at the quasar redshift and three Ly{\alpha} emitters reminiscent of a "dark galaxy" population.

Radiative effect of dust aerosols on cloud microphysics and meso-scale dynamics during monsoon breaks over Arabian sea

During monsoon breaks (large scale rainfall below the long term normal), dry air laddened with dust aerosols intrude over central India through Arabian sea (AS) from West Asian desert regions. To understand the effect of these dust aerosols on marine clouds over AS during monsoon breaks, Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) and Cloud and the Earth's Radiant Energy System (CERES) data have been analyzed for the period 2007 to 2013. The vertical profile of dust backscatter coefficient (DBS) showed an elevated layer between 2 and 5 km and the maximum heating rate observed is 9 K/Day which is higher by 3 K/day as compared to the heating observed in June to September (JJAS) mean. Semi-direct effect due to the interaction of the long range transported dust with pristine cloud environment is observed in both warm and cold clouds. Significant differences in shortwave and longwave fluxes at the top of the atmosphere (TOA), cloud micro and macrophysical parameters are observed between the clouds with and without dust. Also, the percentage differences are more in cold clouds as compared to warm clouds. Dust induced semi-direct effect is found to be more pronounced in cold clouds, while indirect effect in warm clouds. Zonal anomalies of dynamical parameters due to dust induced heating, affect the circulation patterns in the immediate meso-scale environment, which strengthen/extend the monsoon break situation.

Conditions for HD cooling in the first galaxies revisited: interplay between far-ultraviolet and cosmic ray feedback in Population III star formation

HD dominates the cooling of primordial clouds with enhanced ionization, e.g. shock-heated clouds in structure formation or supernova remnants, relic HII regions of Pop III stars, and clouds with cosmic-ray (CR) irradiation. There, the temperature decreases to several 10 K and the characteristic stellar mass decreases to $\sim 10\ {\rm M}_{\odot}$, in contrast with first stars formed from undisturbed pristine clouds ($\sim 100\ {\rm M}_{\odot}$). However, without CR irradiation, even weak far ultra-violet (FUV) irradiation suppresses HD formation/cooling. Here, we examine conditions for HD cooling in primordial clouds including both FUV and CR feedback. At the beginning of collapse, the shock-compressed gas cools with its density increasing, while the relic HII region gas cools at a constant density. Moreover, shocks tend to occur in denser environments than HII regions. Owing to the higher column density and the more effective shielding, the critical FUV intensity for HD cooling in a shock-compressed gas becomes $\sim 10$ times higher than in relic HII regions. Consequently, in the shock-compressed gas, the critical FUV intensity exceeds the background level for most of the redshift we consider ($6 \lesssim z \lesssim 15$), while in relic HII regions, HD cooling becomes effective after the CR intensity increases enough at $z \lesssim 10$. Our result suggests that less massive ($\sim 10\ {\rm M}_{\odot}$) Pop III stars may be more common than previously considered and could be the dominant population of Pop III stars.

Impact of aerosol on post-frontal convective clouds over Germany

We carried out simulations with predefined and simulated aerosol distributions in order to investigate the improvement in the forecasting capabilities of an operational weather forecast model by the use of an improved aerosol representation. This study focuses on convective cumulus clouds developing after the passage of a cold front on 25 April 2008 over Germany. The northerly flow after the cold front leads to increased sea salt aerosol concentrations compared to prefrontal conditions. High aerosol number concentrations are simulated in the interactive scenario representing typically polluted conditions. Nevertheless, due to the presence of sea salt particles, effective radii of cloud droplets reach values typical of pristine clouds (between 7 µm and 13 µm) at the same time. Compared to the predefined continental and maritime aerosol scenarios, the simulated aerosol distribution leads to a significant change in cloud properties such as cloud droplet radii and number concentrations. Averaged over the domain covered by the convective cumuli clouds, we found a systematic decrease in precipitation with increasing aerosol number concentrations. Differences in cloud cover, short wave radiation and cloud top heights are buffered by systematic differences in precipitation and the related diabatic effects. Comparisons with measured precipitation show good agreement for the interactive aerosol scenario as well as for the extreme maritime aerosol scenario.

A new model for the origin of very metal poor stars and their chemical composition

The genesis and chemical patterns of the metal-poor stars in the galactic halo remain an open question. Current models do not seem to give a satisfactory explanation for the observed abundances of lithium in the galactic metal-poor stars and the existence of carbon-enhanced metal-poor (CEMP) and nitrogen-enhanced metal-poor (NEMP) stars. In order to deal with some of these theoretical issues, we suggest an alternative explanation, where some of the Pop III supernovae (SNe) are followed by the detonation of their neutron stars [quark-novae (QNe)]. In QNe occurring a few days to a few weeks following the preceding SN explosion, the neutron-rich relativistic QN ejecta leads to spallation of 56Ni processed in the ejecta of the preceding SN explosion and thus to ‘iron/metal impoverishment’ of the primordial gas swept by the combined SN+QN ejecta. We show that the generation of stars formed from fragmentation of pristine clouds swept up by the combined SN+QN ejecta acquires a metallicity with −7.5 < [Fe/H] < −1.5 for dual explosions with 2 < tdelay (d) < 30. Spallation leads to the depletion of 56Ni and formation of sub-Ni elements such as Ti, V, Cr and Mn providing a reasonable account of the trends observed in galactic halo metal-poor stars. CEMP stars form in dual explosions with short delays (tdelay < 5 d). These lead to important destruction of 56Ni (and thus to a drastic reduction of the amount of Fe in the swept-up cloud) while preserving the carbon processed in the outer layers of the SN ejecta. Lithium is produced from the interaction of the neutron-rich QN ejecta with the outer (oxygen-rich) layers of the SN ejecta. A lithium plateau with 2 < A(Li) < 2.4 can be produced in our model as well as a corresponding 6Li plateau with 6Li/7Li < 0.3.

Science Podcast

The show includes pristine gas clouds, the indirect effects of aerosols, moving research forward with a tighter budget, and more.

An integrated modeling study on the effects of mineral dust and sea salt particles on clouds and precipitation

Abstract. This report addresses the effects of pollution on the development of precipitation in clean ("pristine") and polluted ("hazy") environments in the Eastern Mediterranean by using the Integrated Community Limited Area Modeling System (ICLAMS) (an extended version of the Regional Atmospheric Modeling System, RAMS). The use of this model allows one to investigate the interactions of the aerosols with cloud development. The simulations show that the onset of precipitation in hazy clouds is delayed compared to pristine conditions. Adding small concentrations of GCCN to polluted clouds promotes early-stage rain. The addition of GCCN to pristine clouds has no effect on precipitation amounts. Topography was found to be more important for the distribution of precipitation than aerosol properties. Increasing by 15% the concentration of hygroscopic dust particles for a case study over the Eastern Mediterranean resulted in more vigorous convection and more intense updrafts. The clouds that were formed extended about three kilometers higher, delaying the initiation of precipitation by one hour. Prognostic treatment of the aerosol concentrations in the explicit cloud droplet nucleation scheme of the model, improved the model performance for the twenty-four hour accumulated precipitation. The spatial distribution and the amounts of precipitation were found to vary greatly between the different aerosol scenarios. These results indicate the large uncertainty that remains and the need for more accurate description of aerosol feedbacks in atmospheric models and climate change predictions.

Aerosol nucleation and its role for clouds and Earth's radiative forcing in the aerosol-climate model ECHAM5-HAM

Abstract. Nucleation from the gas phase is an important source of aerosol particles in the Earth's atmosphere, contributing to the number of cloud condensation nuclei, which form cloud droplets. We have implemented in the aerosol-climate model ECHAM5-HAM a new scheme for neutral and charged nucleation of sulfuric acid and water based on laboratory data, and nucleation of an organic compound and sulfuric acid using a parametrization of cluster activation based on field measurements. We give details of the implementation, compare results with observations, and investigate the role of the individual aerosol nucleation mechanisms for clouds and the Earth's radiative forcing. The results of our simulations are most consistent with observations when neutral and charged nucleation of sulfuric acid proceed throughout the troposphere and nucleation due to cluster activation is limited to the forested boundary layer. The globally averaged annual mean contributions of the individual nucleation processes to total absorbed solar short-wave radiation via the direct, semi-direct, indirect cloud-albedo and cloud-lifetime effects in our simulations are −1.15 W/m2 for charged H2SO4/H2O nucleation, −0.235 W/m2 for cluster activation, and −0.05 W/m2 for neutral H2SO4/H2O nucleation. The overall effect of nucleation is −2.55 W/m2, which exceeds the sum of the individual terms due to feedbacks and interactions in the model. Aerosol nucleation contributes over the oceans with −2.18 W/m2 to total absorbed solar short-wave radiation, compared to −0.37 W/m2 over land. We explain the higher effect of aerosol nucleation on Earth's radiative forcing over the oceans with the larger area covered by ocean clouds, due to the larger contrast in albedo between clouds and the ocean surface compared to continents, and the larger susceptibility of pristine clouds owing to the saturation of effects. The large effect of charged nucleation in our simulations is not in contradiction with small effects seen in local measurements: over southern Finland, where cluster activation proceeds efficiently, we find that charged nucleation of sulfuric acid and water contributes on average less than 10% to ultrafine aerosol concentrations, in good agreement with observations.

Special Feature: Diversity of Insect-Plant Interactions in the Eastern Andes of Ecuador

Special Feature: Diversity of Insect-Plant Interactions in the Eastern Andes of Ecuador

Effects of land use change on biodiversity and ecosystem services in tropical montane cloud forests of Mexico

Tropical montane cloud forests deliver important goods and services to society, such as timber, the supply and purification of fresh water, and carbon sequestration. In spite of their relevance, current deforestation rates are very high, at the expense of affecting the provision of ecosystem services. We explore the impact of land use change in terms of provision of ecosystem services by following two approaches, one very detailed (focused on hydrological services – water quality) and another one with a broader perspective (at a large scale and considering the ecosystem service value (ESV) of several ecosystems and their ecosystem services at the same time). In the highlands of the State of Veracruz, previously forested lands were converted into coffee plantations and cattle ranches. To evaluate the role of species composition and community structure on water quality, we studied nine small watersheds (<15 ha) covered by pristine cloud forest, coffee plantations and cultivated grassland (three each). Species richness of the three land use types was similar, although species composition was as different as 90%. Overall species diversity as well as that of woody species, and growth form diversities decreased in the transformed land uses. Water quality of streams flowing through these watersheds declined: nutrients (nitrate), conductivity, cations, chloride and suspended solids were lowest in the forest streams and highest in streams from coffee watersheds, whereas grasslands were intermediate. We also calculated ecosystem service values (using the transfer value method) and estimated economic market–non-market gains and losses owing to land transformation. Loss of natural ecosystems may imply a significant economic loss to society in terms of ecosystem services, although market gains may still lead land owners to land conversion because revenues are higher. Adequate Payment for Ecosystem Services may be a good option to prevent deforestation, but the compensation should be at least equal to the opportunity cost of the promoted land use. Our estimates are indicative of the urgent need to go beyond water quantity as the most relevant ecosystem service considered in PES schemes.

Aerosol Impacts on the Diurnal Cycle of Marine Stratocumulus

Abstract Recent large-eddy simulation (LES) studies of the impact of aerosol on the dynamics of nocturnal marine stratocumulus revealed that, depending on the large-scale forcings, an aerosol-induced increase of the droplet concentration can lead to either an increase or a decrease of the liquid water path, hence contrasting with the cloud thickening that is expected from a reduction of the precipitation efficiency. In this study, the aerosol impacts on cloud microphysics are examined in the context of the boundary-layer diurnal cycle using 36-h LES simulations of pristine and polluted clouds. These simulations corroborate previous findings that during nighttime aerosol-induced liquid water path changes are sensitive to the large-scale forcings via enhancement of cloud-top entrainment such that, ultimately, the liquid water path may be reduced when the free-tropospheric-entrained air is drier. During the day, however, enhanced entrainment, inhibition of drizzle evaporation below cloud base, and reduced sensible heat flux from the surface lead to a more pronounced decoupling of the boundary layer, which significantly amplifies the liquid water path reduction of the polluted clouds. At night the sign of the liquid water path difference between pristine and polluted clouds depends upon large-scale forcings, while during the day the liquid water path of polluted clouds is always smaller than the one of the pristine clouds. Suggestions are made on how observational studies could be designed for validation of these simulations.

Luis A. Vivanco: Green Encounters: Shaping and Contesting Environmentalism in Rural Costa Rica

Because my first visit to the Monteverde Cloud Forest Reserve (MCFR) in Costa Rica took place before the ecotourist boom of the late 1980s, and because I return frequently, I like to pretend that I am not a Northern elitist bent on importing her vision of nature. I’ve had enough encounters with scorpions not to romanticize the tropics, although I continue to appreciate every sighting of a toucan or quetzal. My familiarity gives me license to lament every “improvement” to the MCFR facilities, including the everexpanding visitor center with its cheap tourist souvenirs and the cement-block tiles over trails that were once deep in foot-sucking mud. Catering to foreign ecotourists does have its comical side. One day, walking in my characteristically reverential mode along a misty trail, I paused to listen to a howler monkey whooping nearby. A minute later, the thundering primate was revealed to be a local (and very human) guide performing an impressive imitation. It was funny but sad, a vulgar encroachment on the pristine tropical cloud forest I felt privileged to have known. My introductory anecdotes would fit perfectly in Luis A. Vivanco’s critical and thought-provoking monograph, Green Encounters. Vivanco examines the paradoxical and contradictory effects of environmental activism, biodiversity conservation, and the movement to “save the rainforest” in a well-known Central American ecotourist community. He is particularly interested in how environmental movements shape people’s lives, identities and relationships in the region he calls “Monte Verde” (the two words referring to the wider zone beyond the region settled by North American expatriates over 50 years ago). In exemplifying the tensions inherent in how environmentalism has unfolded in this now-famous cloud forest, Vivanco argues that there is nothing essential about Costa Rican “nature” (in spite of the tag line for a tourist ad campaign that reads, “No artificial ingredients”). Nor is there anything inevitable about Costa Rican conservationism, he says, despite a publicity campaign that would have ecotourists think otherwise (p. 12). He argues, rather, that environmentalism and conservation are shaped by encounters between people who hold conflicting assumptions and expectations about their relationships to each other and to the environment in which they live. Vivanco might nod knowingly to see how I begin this review, because he is keenly aware of how people invoke “nature,” and their relationship to the MCFR specifically, to position themselves. To his credit, Vivanco conducted much of his ethnographic research among rural Costa Ricans rather than in the English-speaking North American segment of Monte Verde. This allowed him access to stories not often told in triumphalist media accounts of the Costa Rican cloud forest. He focuses on several frictional “encounters” over environmentalism (p. 17), paying special attention to dynamic processes of change and trying (sometimes with difficulty) to avoid making essentialist assumptions about environmentalists, rural farmers, Quakers, biologists, and others. Indeed, Vivanco’s attention to the tension generated when scientists, advocates of tourism and development, and members of rural communities encounter one another might have served as inspiration for Anna Tsing, whose recent book, Frictions, takes a similarly processual approach to analyzing the dynamic co-constitution of environmentalism and development. Green Encounters is organized into three parts, each of which examines a specific feature of environmentalism in the Monte Verde region: formal efforts to protect land Hum Ecol (2008) 36:611–612 DOI 10.1007/s10745-008-9181-6

Successional changes in soil, litter and macroinvertebrate parameters following selective logging in a Mexican Cloud Forest

The environmental and vegetation shifts associated with logging disturbance and secondary succession in Tropical Montane Cloud Forests have been studied in detail, however little is known about the consequences that these changes have for the soil system. The present study was undertaken to determine the impact of selective logging and subsequent secondary succession on soil microenvironmental conditions, leaf litter quality and quantity, soil nutrient concentration and soil and litter macroinvertebrate community composition. The study was carried out in three successional chronosequences, two recently logged sites and two pristine tropical mountain cloud forest sites in Oaxaca, Mexico. Results showed that selective harvesting of Quercus spp. trees caused an increase in soil temperature of ca. 4 °C that is not completely reversed after 100 years of succession. During 100 years of secondary succession litter diversity increased and soil organic matter accumulated (16.4% increase in total C). The availability of cations (Ca, Mg, Na, and K) in the topsoil decreased by more than 50% as a result of logging, and only Mg increased again between 75 and 100 years after disturbance. Pristine cloud forests sustain a diverse litter and soil macroinvertebrate community, but its composition and diversity was negatively affected by logging. The effect of Quercus harvesting activities on the litter community was apparent within 2 months of disturbance (total abundance declined by ca. 65%, higher taxa richness by ca. 10% and diversity by ca. 35%). For the soil community there was a time-lag in the effect of logging. Two months after disturbance there was no significant effect on the soil community but 15 years after abandonment, total macroinvertebrate abundance in the soil was ca. 80% lower and higher taxa richness ca. 30% lower compared to undisturbed sites. Full recovery of the macroinvertebrate community composition appeared to take more than 100 years both in the litter and soil. Reduced abundances of Coleoptera and Enchytraeidae were apparent even after 100 years of succession. The endemic earthworm Ramiellona wilsoni was found almost exclusively in the pristine forests and therefore its abundance could be used as a sensitive indicator of disturbance in these forests.