Winning and Losing Tree Species of Reassembly in Minnesota’s Mixed and Broadleaf Forests

We examined reassembly of winning and losing tree species, species traits including shade and fire tolerance, and associated disturbance filters and forest ecosystem types due to rapid forest change in the Great Lakes region since 1850. We identified winning and losing species by changes in composition, distribution, and site factors between historical and current surveys in Minnesota’s mixed and broadleaf forests. In the Laurentian Mixed Forest, shade-intolerant aspen replaced shade-intolerant tamarack as the most dominant tree species. Fire-tolerant white pine and jack pine decreased, whereas shade-tolerant ashes, maples, and white cedar increased. In the Eastern Broadleaf Forest, fire-tolerant white oaks and red oaks decreased, while shade-tolerant ashes, American basswood, and maples increased. Tamarack, pines, and oaks have become restricted to sites with either wetter or sandier and drier soils due to increases in aspen and shade-tolerant, fire-sensitive species on mesic sites. The proportion of shade-tolerant species increased in both regions, but selective harvest reduced the applicability of functional groups alone to specify winners and losers. Harvest and existing forestry practices supported aspen dominance in mixed forests, although without aspen forestry and with fire suppression, mixed forests will transition to a greater composition of shade-tolerant species, converging to forests similar to broadleaf forests. A functional group framework provided a perspective of winning and losing species and traits, selective filters, and forest ecosystems that can be generalized to other regions, regardless of species identity.     

Does tree species composition affect soil CO<Subscript>2</Subscript> emission and soil organic carbon storage in plantations?

Key message

Mixed tree plantations are potential silvicultural systems to increase soil carbon storage through altering litter and root inputs and soil physiochemical properties.

Abstract

Afforestation and reforestation are major strategies for global climate change mitigation. Different tree species composition can induce diverse changes in soil CO₂ emission and soil carbon sequestration in tree plantation. This study employed three plantations of monoculture and mixed Pinus yunnanensis and Eucalyptus globulus to estimate the effect of tree species composition on soil CO₂ emission and soil organic carbon storage in subtropical China. We found that tree species composition had a significant effect on the soil CO₂ emission and soil organic carbon storage. Soil CO₂ emission was lower in the mixed plantation than in the P. yunnanensis plantation, whereas it was higher than in the E. globulus plantation. Differences in soil CO₂ emission among the three plantations were determined by leaf litterfall mass, fine root biomass, soil available nitrogen, pH, soil bulk density, and soil C:N ratio. Soil organic carbon storage was 34.5 and 23.2 % higher in the mixed plantation than in the P. yunnanensis and E. globulus plantations, respectively. Higher soil organic carbon stock in the mixed plantation was attributed to lower C/N ratio of leaf litter and soil, greater fine root biomass and soil organic carbon content, and lower soil CO₂ emission. We conclude that mixed tree plantation can enhance soil carbon sequestration, but can decrease or increase soil CO₂ emission through altering litter and root inputs and soil physiochemical properties.

     

Maltotriose transport and utilization in Baker’s and Brewer’s yeast

Maltotriose is metabolized by baker’s and brewer’s yeast only oxidatively, with a respiratory quotient of 1.0, the being, depending on the strain used, 0–11, as compared with of 6–42μL CO₂ per h per mg dry substance. The transport appeared to proceed by facilitated diffusion (no effects of NaF, iodoacetamide and 3-chlorophenylhydrazonomalononitrile) with a K_T of more than 50mm and was inhibited by maltose > maltotriose > methyl-α-D-glucoside > maltotetraose >D-fruetose >D-glucose. The transport was present constitutively in bothSaccharomyces cerevisiae (baker’s yeast) and inS. uvarum (brewer’s yeast) and it was not significantly stimulated by preincubation with glucose or maltose. The pH optimum was 4.5–5.5, the temperature dependence yielded an activation energy of 26 kJ/mol.     

Chasing genes in Alzheimer’s and Parkinson’s disease

Alzheimers disease (AD), the most common type of dementia, and Parkinsons disease (PD), the most common movement disorder, are both neurodegenerative adult-onset diseases characterized by the progressive loss of specific neuronal populations and the accumulation of intraneuronal inclusions. The search for genetic and environmental factors that determine the fate of neurons during the ageing process has been a widespread approach in the battle against neurodegenerative disorders. Genetic studies of AD and PD initially focused on the search for genes involved in the aetiological mechanisms of monogenic forms of these diseases. They later expanded to study hundreds of patients, affected relative-pairs and population-based studies, sometimes performed on special isolated populations. A growing number of genes (and pathogenic mutations) is being identified that cause or increase susceptibility to AD and PD. This review discusses the way in which strategies of gene hunting have evolved during the last few years and the significance of finding genes such as the presenilins, -synuclein, parkin and DJ-1. In addition, we discuss possible links between these two neurodegenerative disorders. The clinical, pathological and genetic presentation of AD and PD suggests the involvement of a few overlapping interrelated pathways. Their imbricate features point to a spectrum of neurodegeneration (tauopathies, synucleinopathies, amyloidopathies) that need further intense investigation to find the missing links.     

Assortative pairing and divergent evolution in Darwin’s Small Tree Finch, Camarhynchus parvulus

Size assortative mating has received increasing attention due to its potential to drive divergence and perhaps speciation. In this study, we examined assortative pairing at 17 nests of Darwin’s Small Tree Finches, Camarhynchus parvulus. We found positive assortative pairing for two traits: bill length and tarsus length, and these traits showed a significant positive correlation to each other. Assortative pairing could be driven by female choice for similar phenotypes because male–male competition has rarely been observed in the Small Tree Finch, nor have males been observed to reject potential mates. Given the high heritability of bill morphology in Darwin’s finches, it is possible that female preference for male bill length, a trait that is known to be important for foraging, will influence offspring bill size to maximise efficient exploitation of resources. The finding of size assortative pairing on the basis of tarsus length requires more research, but suggests different trait utilities for different foraging niches. Interestingly, the highland distribution of tarsus length across the population showed a unimodal distribution, but a bimodal distribution after pairing. While not significant, we found comparatively large differences across study plots in tarsus length, which suggests the possibility of phenotype–habitat matching at a small spatial scale in this species. Our findings are significant in the context of the adaptive radiation of Darwin’s finches as they are consistent with the allopatric model of speciation but also show potential for adaptive divergence in sympatry in Darwin’s tree finches.     

Factors influencing soil enzyme activity in China’s forest ecosystems

Enzyme activity (EA) mediates soil organic matter (SOM) degradation, transformation, and mineralization, thereby maintaining the biogeochemical cycles and energy flow of ecosystems. To determine the main factors explaining EA variations in China’s forest ecosystems, we created a database of soil EAs and relevant variables using data from the literature and analysed relationships between EAs and both climatic and edaphic variables. Catalase, phenol oxidase, acid (alkaline) phosphatase, and protease activities differed significantly among different types of forests. Catalase and urease activities were generally higher in primosols, cambisols, and argosols than in ferrosols. EA largely decreased with soil depth and increased with SOM. Phenol oxidase and urease activities were negatively correlated with mean annual temperature (MAT); in contrast, catalase, invertase, and protease activities first decreased (< 2.5 °C), increased (2.5–17.5 °C), and then decreased (> 17.5 °C) with increasing MAT. Although protease activity was slightly positively correlated with mean annual precipitation (MAP), catalase, phenol oxidase, and urease activities were all negatively related to MAP. Catalase, invertase, acid (alkaline) phosphatase, urease, and protease activities first increased (< 2000 m.a.s.l.) and then decreased (2000–4100 m.a.s.l.) with increasing elevation. Principal component analysis revealed most EAs to be correlated with climate conditions and soil pH. These findings suggest that climatic and edaphic variables directly and indirectly correlate with forest type and greatly impact soil EA.     

Tree diversity and conservation value of Ngovayang’s lowland forests,Cameroon

The Ngovayang Massif of southern Cameroon is a range of small hills near the Atlantic coast, in the Lower Guinea floristic region. This region is known to harbor forests with high levels of biodiversity and endemism, but this Massif is botanically poorly known. We assessed tree species diversity, floristic composition and level of endemism of the Ngovayang forest, comparing it with other sites in Central Africa. Five 1-ha permanent plots within old-growth lowland forests of the Ngovayang Massif were censused. A total of 2,658 individuals with dbh ≥ 10 cm were recorded, belonging to 293 species, 170 genera and 60 families. The mean number of stems was 532 ± 75 stems ha⁻¹. Taking into account other data available, the list of vascular plants known in the Massif reaches a total of 450 species. We found 47 species of high conservation value, including Cameroon endemics and other rare and threatened species. Species richness and endemism are comparable to those of the richest known sites in Central African forests. The forests of Ngovayang were found to be particularly rich in Fabaceae-Caesalpinioideae. Topographic heterogeneity, high precipitation and atmospheric humidity owing to the proximity of the ocean, and permanence of a forest cover during past geological times probably all contribute to explaining the Massif’s high tree diversity and endemism. This study highlights the botanical importance of the poorly studied Ngovayang forest within the Lower Guinea region, justifying efforts for improved assessment of this value and for the development of suitable national conservation strategies.     

Positive association between soil arsenic concentration and mortality from alzheimer’s disease in mainland China

ObjectivesThe current study was designed to investigate the relationship between the soil arsenic (As) concentration and the mortality from Alzheimer’s disease (AD) in mainland China.Study designEcological study.MethodsTwenty-two provinces and 3 municipal districts in mainland China were included in this study. The As concentrations in soil in 1990 was obtained from the China State Environmental Protection Bureau; the data on annual mortality of AD from 1991 to 2000 were obtained from the National Death Cause Surveillance Database of China. Using these data, we calculated the spearman correlation coefficient between soil As concentration and AD mortality, and the relative risk (RR) between soil As levels and AD mortality by quartile-dividing study groups.ResultsThe spearman correlation coefficient between As concentration and AD mortality was 0.552 (p = 0.004), 0.616 (p = 0.001) and 0.622 (p = 0.001) in the A soil As (eluvial horizon), the C soil As (parent material horizon), and the Total soil As (A soil As + C soil As), respectively. When the A soil As concentration was over 9.05 mg/kg, 10.40 mg/kg and 13.10 mg/kg, the relative risk was 0.835 (95 % CI: 0.832, 0.838), 1.969 (95 %CI: 1.955, 1.982), and 2.939 (95 % CI: 2.920, 2.958), respectively; when the C soil As reached 9.45 mg/kg, 11.10 mg/kg and 13.55 mg/kg, the relative risk was 4.349 (95 % CI: 4.303, 4.396), 6.108 (95 % CI: 6.044, 6.172), and 9.125 (95 %CI: 9.033, 9.219), respectively. No correlation was found between lead, cadmium, and mercury concentration in the soil and AD mortality.ConclusionThere was an apparent soil As concentration dependent increase in AD mortality. Results of this study may provide evidence for a possible causal linkage between arsenic exposure and the death risk from AD.     

Intraspecific variation in allelochemistry determines an invasive species’ impact on soil microbial communities

Invasive species can benefit from altered species interactions in their new range, and by interfering with species interactions among native competitors. Since exotic invasions are generally studied at the species level, relatively little is known about intraspecific variation in the traits that determine an invader’s effect on native species. Alliaria petiolata is a widespread and aggressive invader of forest understories that succeeds in part by interfering with mutualistic interactions between native plants and soil fungi. Here, I show that the impact of A. petiolata on soil microbial communities varied among individuals due to variation in their allelochemical concentrations. The differential impacts translated into varied effects on native tree growth, partly because A. petiolata’s allelochemicals preferentially affected the most mutualistic fungal taxa. These results highlight the importance of considering the spatial and temporal variation in an invasive species’ impacts for understanding and managing the invasion process.     

Does invasion by an alien plant species affect the soil seed bank?

Questions: How does invasion affect old‐field seed bank species richness, composition and density? How consistent are these effects across sites? Does the soil seed bank match vegetation structure in old‐fields? Location: Menorca, Balearic Islands, Spain, western Mediterranean basin. Methods: We monitored seed germination in soils from old‐fields that were both uninvaded and invaded (legacy effect) by the annual geophyte Oxalis pes‐caprae. We also added O. pes‐caprae bulbs to uninvaded soils to test O. pes‐caprae interference with seedling emergence (competitive effect). We compared species composition in the seed bank with that of the vegetation. Results: Species richness in the seed bank and in the vegetation was not significantly different between invaded and uninvaded areas. Uninvaded areas did not have larger seed banks than invaded areas. More seedlings, especially of geophytes, emerged when O. pes‐caprae bulbs were added to the soil. Species similarity between invaded and uninvaded areas was higher in the seed bank (74%) than in the vegetation (49%). Differences in species composition were as important as differences among sites. The degree of species similarity between the seed bank and the vegetation was very low (17%). Conclusions: Despite invasion by O. pes‐caprae not affecting species richness, the variation in the seed bank species composition in invaded and uninvaded areas, and the differences between the seed bank and the mature vegetation, highlights that even if the invader could be eradicated the vegetation could not be restored back to the exact composition as found in uninvaded areas.     

Tree species richness and composition 15 years after strip clear-cutting in the Peruvian Amazon

Although strip clear-cutting has a long history of use in the temperate zone, it was only recently introduced for timber extraction in tropical rain forests, where it is known as the Palcazú Forest Management System. In this system heterogeneous tropical forests are managed for native gap-dependent timber species by simulating gap dynamics through clear-cutting long, narrow strips every 40 years. As part of an assessment of the sustainability of this system, we evaluated the recovery of tree basal area, species richness, and composition after 15 years of regeneration on two strips (30 × 150 m) clear-cut in 1989 in Jenaro Herrera, Peru. Timber stocking and the effects of silvicultural thinning were assessed in both strips. The strips recovered 58–73% of their original basal area and 45–68% of their original tree species richness. Although both strips recovered more than 50% of their original composition, commercial species had lower basal areas and lower densities than in the forest before the clearing. Pioneer species with high basal areas remained dominant 15 years after the cutting. Silvicultural thinning in 1996 reduced the abundance of pioneer species in both strips, and increased the abundance of commercial species in one of the strips. Half of one strip was harvested by deferment-cut (only commercial trees >30 cm dbh and “other” species >5 cm dbh were cut); regeneration here had greater abundance of commercial species and lower abundance of pioneer species. The low stocking of commercial trees challenges the sustainability claims for this forest management system.     

Catecholamine metabolism in children with Asperger’s and Kanner’s syndromes

In a stable state children with Asperger’s and Kanner’s syndromes demonstrate a similar decrease in plasma norepinephrine. In the aggravated state, these changes become more expressed and are characterized by a decrease in plasma tyrosine, norepinephrine, normetanephrine, and by an increase in dopamine and homovanillic acid and a decrease in excretion of norepinephrine and an increase in excretion of homovanillic acid, epinephrine and 3-methoxy-4-hydroxyphenylglycol (MHPG). In the aggravated state children with Kanner’s syndrome were characterized by increased plasma MHPG, decreased excretion of tyrosine and increased expression of normetanephrine. The observed imbalance in dopamine and epinephrine/norepinephrine systems suggests importance of combined analysis of changes in catecholamines and their metabolites as the most informative approach in the study of the effect of autistic disorders.     

What Explains Differences in Men’s and Women’s Production?

Researchers commonly use long-term average production inequalities to characterize cross-cultural patterns in foraging divisions of labor, but little is known about how the strategies of individuals shape such inequalities. Here, we explore the factors that lead to daily variation in how much men produce relative to women among Martu, contemporary foragers of the Western Desert of Australia. We analyze variation in foraging decisions on temporary foraging camps and find that the percentage of total camp production provided by each gender varies primarily as a function of men’s average bout successes with large, mobile prey. When men target large prey, either their success leads to a large proportional contribution to the daily harvest, or their failure results in no contribution. When both men and women target small reliable prey, production inequalities by gender are minimized. These results suggest that production inequalities among Martu emerge from stochastic variation in men’s foraging success on large prey measured against the backdrop of women’s consistent production of small, low-variance resources.

Metalloproteinase’s Activity and Oxidative Stress in Mild Cognitive Impairment and Alzheimer’s Disease

Matrix metalloproteinases (MMPs) and oxidative stress have been implicated in neurological diseases such as Alzheimer’s disease (AD). Plasma MMP-2 and MMP-9 activities were assessed in Mild Cognitive Impairment (MCI) and AD subjects compared with aged-matched controls, and subsequently analysed in relation to oxidative stress markers. Both MMP-2 and MMP-9 showed no significant changes versus control subjects. Plasma glutathione peroxidase Se-dependent (GPx-Se) activity and malondialdehyde (MDA) levels were higher in AD than in controls (P < 0.05), suggesting a role for GPx-Se in controlling oxidative stress in AD. Negative correlations were observed between MMPs and MDA in AD and MCI patients (P < 0.05). In conclusion, oxidative stress events did not include activation of MMPs and this similar pattern in AD and MCI suggests that both are biochemically equivalent.     

Can temporal covariation and autocorrelation in demographic rates affect population dynamics in a raptor species?

Theoretical studies suggest that temporal covariation among and temporal autocorrelation within demographic rates are important features of population dynamics. Yet, empirical studies have rarely focused on temporal covariation and autocorrelation limiting our understanding of these patterns in natural populations. This lack of knowledge restrains our ability to fully understand population dynamics and to make reliable population forecasts. In order to fill this gap, we used a long‐term monitoring (15 years) of a kestrel Falco tinnunculus population to investigate covariation and autocorrelation in survival and reproduction at the population level and their impact on population dynamics. Using Bayesian joint analyses, we found support for positive covariation between survival and reproduction, but weak autocorrelation through time. This positive covariation was stronger in juveniles compared with adults. As expected for a specialized predator, we found that the reproductive performance was strongly related to an index of vole abundance explaining 86% of the temporal variation. This very strong relationship suggests that the temporally variable prey abundance may drive the positive covariation between survival and reproduction in this kestrel population. Simulations suggested that the observed effect size of covariation could be strong enough to affect population dynamics. More generally, positive covariation and autocorrelation have a destabilizing effect increasing substantially the temporal variability of population size.     

Does an earthworm species acclimatize and/or adapt to soil calcium conditions? The consequences of soil nitrogen mineralization in forest soil

Calcium (Ca)-rich food can increase feeding of Lumbricidae. Earthworms can be genetically differentiated at a small spatial scale and acclimatize to the local environment during growth. Soil feeding and subsequent cast production by earthworms affects soil N mineralization. Here, we hypothesized that soil feeding and subsequent cast production by Lumbricidae species increases with high soil Ca content and that this increase is stronger in worms from high-Ca soil. We also hypothesized that changes in the soil feeding of Lumbricidae species along with the Ca content affects the soil N mineralization via changes in the cast production. Using a geophageous earthworm species (Eisenia japonica) originated from two different Ca environments (calcareous soil and sedimentary soil), we investigated cast production and soil N mineralization in three soils (sedimentary soil, sedimentary soil with Ca addition, and calcareous soil). The soil feeding of E. japonica from both origins did not always increase despite the high soil Ca content. We suggest that both the Ca content and other soil conditions (e.g., soil C:N) might be major factors in increasing soil feeding by E. japonica. Furthermore, the influence of Ca addition on cast production varied according to the earthworm origin. As expected, these differences in cast production are linked to soil N mineralization (especially nitrification). In summary, our study suggests that the acclimatization and/or adaptation of Lumbricidae species to local environmental factors not only soil Ca content explains spatially heterogeneous soil N mineralization in forest soil.     

Antioxidative system’s responses in the leaves of six Caragana species during drought stress and recovery

For investigating the protective roles of antioxidative system in desiccation tolerance of Caragana species as they adapt to arid environments, we monitored a variety of ecophysiological parameters in the leaves of Caragana arborescens (mesophyte), C. microphylla (semiarid species), C. roborovskyi, C. stenophylla, C. acanthophylla, and C. tragacanthoides (xerophyte) grown under a drying-rehydration cycle. Relative leaf water content and chlorophyll content were decreased by 17.4?C39.2?%, and by 14?C40?%, respectively, after exposure to 48?days of drought stress. Malondialdehyde did not increase in xeric Caragana species. Hydrogen peroxide concentrations increased by 13.1?C43.9?% except in C. acanthophylla. The activities of superoxide dismutase (SOD), guaiacol peroxidase (POD), ascorbate peroxidase (APX), glutathione reductase (GR) and reduced glutathione (GSH) in xeric Caragana species were significantly elevated with progressing drought stress. However, catalase in all species decreased markedly before drought stress treatment reached 40?days. The xeric Caragana species showed higher SOD, POD, APX, and GR activities, as well as ascorbate content, and more manganese SOD isoenzymes. C. arborescens and C. microphylla accumulated more free proline. Our data indicate that SOD and POD with the ascorbate?Cglutathione cycle have important protective effects in xeric Caragana species under drought stress. Free proline may be crucial in the resistance of C. arborescens and C. microphylla to drought stress.     

Do method and species lifestyle affect measures of maximum metabolic rate in fishes?

The rate at which active animals can expend energy is limited by their maximum aerobic metabolic rate (MMR). Two methods are commonly used to estimate MMR as oxygen uptake in fishes, namely during prolonged swimming or immediately following brief exhaustive exercise, but it is unclear whether they return different estimates of MMR or whether their effectiveness for estimating MMR varies among species with different lifestyles. A broad comparative analysis of MMR data from 121 fish species revealed little evidence of different results between the two methods, either for fishes in general or for species of benthic, benthopelagic or pelagic lifestyles.