Carbon uptake in Eurasian boreal forests dominates the high-latitude net ecosystem carbon budget

Arctic-boreal landscapes are experiencing profound warming, along with changes in ecosystem moisture status and disturbance from fire. This region is of global importance in terms of carbon feedbacks to climate, yet the sign (sink or source) and magnitude of the Arctic-boreal carbon budget within recent years remains highly uncertain. Here, we provide new estimates of recent (2003–2015) vegetation gross primary productivity (GPP), ecosystem respiration (R_eco), net ecosystem CO₂ exchange (NEE; R_eco − GPP), and terrestrial methane (CH₄) emissions for the Arctic-boreal zone using a satellite data-driven process-model for northern ecosystems (TCFM-Arctic), calibrated and evaluated using measurements from >60 tower eddy covariance (EC) sites. We used TCFM-Arctic to obtain daily 1-km² flux estimates and annual carbon budgets for the pan-Arctic-boreal region. Across the domain, the model indicated an overall average NEE sink of −850 Tg CO₂-C year⁻¹. Eurasian boreal zones, especially those in Siberia, contributed to a majority of the net sink. In contrast, the tundra biome was relatively carbon neutral (ranging from small sink to source). Regional CH₄ emissions from tundra and boreal wetlands (not accounting for aquatic CH₄) were estimated at 35 Tg CH₄-C year⁻¹. Accounting for additional emissions from open water aquatic bodies and from fire, using available estimates from the literature, reduced the total regional NEE sink by 21% and shifted many far northern tundra landscapes, and some boreal forests, to a net carbon source. This assessment, based on in situ observations and models, improves our understanding of the high-latitude carbon status and also indicates a continued need for integrated site-to-regional assessments to monitor the vulnerability of these ecosystems to climate change.     

Tropical rain forest types and soil factors in a watershed area in Guyana

Abstract. An inventory was made of the vegetation and soils of a watershed area of 480 ha in the tropical rain forest of Guyana. 252 plots of 0.05 ha were sampled. In total 111 tree species > 20 cm were recorded. A TWINSPAN analysis resulted in seven groupings. Correspondence Analysis revealed that the major environmental differentiation underlying the floristic variation is according to soil type. Finally, five main forest communities were described. Most sites in the watershed area are characterized by the dominance of one or a few species. Species distribution patterns are strongly determined by soil type and drainage class.     

Environmental,geographical and time-related impacts on avian malaria infections in native and introduced populations of house sparrows (Passer domesticus), a globally invasive species

Aim

The increasing spread of vector-borne diseases has resulted in severe health concerns for humans, domestic animals and wildlife, with changes in land use and the introduction of invasive species being among the main possible causes for this increase. We explored several ecological drivers potentially affecting the local prevalence and richness of avian malaria parasite lineages in native and introduced house sparrows (Passer domesticus) populations.

Location

Global.

Time period

2002–2019.

Major taxa studied

Avian Plasmodium parasites in house sparrows.

Methods

We analysed data from 2,220 samples from 69 localities across all continents, except Antarctica. The influence of environment (urbanization index and human density), geography (altitude, latitude, hemisphere) and time (bird breeding season and years since introduction) were analysed using generalized additive mixed models (GAMMs) and random forests.

Results

Overall, 670 sparrows (30.2%) were infected with 22 Plasmodium lineages. In native populations, parasite prevalence was positively related to urbanization index, with the highest prevalence values in areas with intermediate urbanization levels. Likewise, in introduced populations, prevalence was positively associated with urbanization index; however, higher infection occurred in areas with either extreme high or low levels of urbanization. In introduced populations, the number of parasite lineages increased with altitude and with the years elapsed since the establishment of sparrows in a new locality. Here, after a decline in the number of parasite lineages in the first 30 years, an increase from 40 years onwards was detected.

Main conclusions

Urbanization was related to parasite prevalence in both native and introduced bird populations. In invaded areas, altitude and time since bird introduction were related to the number of Plasmodium lineages found to be infecting sparrows.     

HomeRange: A global database of mammalian home ranges

Motivation

Home range is a common measure of use of space by animals because it provides ecological information that is useful for conservation applications. In macroecological studies, values are typically aggregated to species means to examine general patterns of use of space by animals. However, this ignores the environmental context in which the home range was estimated and does not account for intraspecific variation in home range size. In addition, the focus of macroecological studies on home ranges has historically been biased towards terrestrial mammals. The use of aggregated numbers and the terrestrial focus limit our ability to examine home-range patterns across different environments, their variation in time and variation between different levels of organization. Here, we introduce HomeRange, a global database with 75,611 home-range values across 960 different species of mammals, including terrestrial, aquatic and aerial species.

Main types of variables contained

The dataset contains estimates of home ranges of mammals, species names, methodological information on data collection, method of home-range estimation, period of data collection, study coordinates and name of location, in addition to species traits derived from the studies, such as body mass, life stage, reproductive status and locomotor habit.

Spatial location and grain

The collected data are distributed globally. Across studies, the spatial accuracy varies, with the coarsest resolution being 1°.

Time period and grain

The data represent information published between 1939 and 2022. Across studies, the temporal accuracy varies; some studies report start and end dates specific to the day, whereas for other studies only the month or year is reported.

Major taxa and level of measurement

Mammalian species from 24 of the 27 different taxonomic orders. Home-range estimates range from individual-level values to population-level averages.

Software format

Data are supplied as a comma-delimited text file (.csv) and can be loaded directly into R using the “HomeRange” R package ( https://github.com/SHoeks/HomeRange ).     

Mercury translocation in and evaporation from soil. III. quantification of evaporation of mercury from podzolized soil profiles treated with Hg Cl

Mercury evaporation from undisturbed iron‐humus podzol lysimeters was measured over 3 months after treatment with HgCl₂ spiked with radioactive ²⁰³Hg. The relative evaporation rate from HgCl₂ treated soils followed the sum of two exponential functions. Because evaporation asymptotically approaches zero with time, the integral of the fit curve represents the evaporative loss in percent of atmospheric deposition. For the soil investigated, about 5% of atmospheric Hg deposition was reemitted into the atmosphere. It is hypothesized that mercury evaporation can decrease the leaching of mercury in and from soil significantly; this effect is probably increasing with decreasing rain acidity or soil acidity. Mercury deposited as soluble salt remains susceptible to reemission to air for 300 d after incorporation into the soil matrix. Indications are found that Hg evaporation from soils in geological background areas predominantly derives from recent atmospheric Hg deposition and not from geological sources.     

The IleL229 → Met mutation impairs the quinone binding to the QB-pocket in reaction centers of Rhodobacter sphaeroides

A spontaneous mutant (R/89) of photosynthetic purple bacterium Rhodobacter sphaeroides R-26 was selected for resistance to 200 M atrazin. It showed increased resistance to interquinone electron transfer inhibitors of o-phenanthroline (resistance factor, RF=20) in UQ_o reconstituted isolated reaction centers and terbutryne in reaction centers (RF=55) and in chromatophores (RF=85). The amino acid sequence of the Q_B binding protein of the photosynthetic reaction center (the L subunit) was determined by sequencing the corresponding pufL gene and a single mutation was found (Ile^L229 Met). The changed amino acid of the mutant strain is in van der Waals contact with the secondary quinone Q_B. The binding and redox properties of Q_B in the mutant were characterized by kinetic (charge recombination) and multiple turnover (cytochrome oxidation and semiquinone oscillation) assays of the reaction center. The free energy for stabilization of Q_AQ_B ^– with respect to Q_A ^–Q_B was G_AB=–60 meV and 0 meV in reaction centers and G_AB=–85 meV and –46 meV in chromatophores of R-26 and R/89 strains at pH 8, respectively. The dissociation constants of the quinone UQ_o and semiquinone UQ_o ^– in reaction centers from R-26 and R/89 showed significant and different pH dependence. The observed changes in binding and redox properties of quinones are interpreted in terms of differential effects (electrostatics and mesomerism) of mutation on the oxidized and reduced states of Q_B.Abbreviations BChl bacteriochlorophyll - Ile isoleucine - Met methionin - P primary donor - Q_A primary quinone acceptor - Q_B secondary quinone acceptor - RC reaction center protein - UQ_o 2,3-dimethoxy-5-methyl benzoquinone - UQ₁₀ ubiquinone 50 This work is dedicated to the memory of Randall Ross Stein (1954–1994) and is, in a small way, a testament to the impact which Randy's ideas have had on the development of the field of competitive herbicide binding.     

Purification and characterization of a novel extracellular Streptomyces lividans 66 enzyme inactivating fusidic acid.

The wild-type strain Streptomyces lividans 66 is resistant against the steroid-like antibiotic fusidic acid. Comparative studies of the wild-type strain and a fusidic acid-sensitive mutant allowed the identification of an extracellular enzyme which inactivates fusidic acid. With the help of a combination of ultrafiltration and chromatographies with Phenyl-Sepharose and an anion exchanger, the enzyme was highly purified. Its apparent molecular mass is 48 kDa, its optimal activity ranges between 45 and 55 degrees C, and its optimal pH is 6.0 to 9.0. It is stimulated by neither monovalent nor divalent ions. The enzyme acts as a specific esterase which removes the acetyl group at C-16 from fusidic acid. The resulting intermediate is unstable, and spontaneous lactonization between C-21 and C-16 occurs rapidly.