Thermal Acclimation of Foliar Carbon Metabolism in Pinus taiwanensis Along an Elevational Gradient

Climate change could negatively alter plant ecosystems if rising temperatures exceed optimal conditions for obtaining carbon. The acclimation of plants to higher temperatures could mitigate this effect, but the potential of subtropical forests to acclimate still requires elucidation. We used space-for-time substitution to determine the photosynthetic and respiratory-temperature response curves, optimal temperature of photosynthesis (Topt), photosynthetic rate at Topt, temperature sensitivity (Q10), and the rate of respiration at a standard temperature of 25°C (R25) for Pinus taiwanensis at five elevations (1200, 1400, 1600, 1800, and 2000 m) in two seasons (summer and winter) in the Wuyi Mountains in China. The response of photosynthesis in P. taiwanensis leaves to temperature at the five elevations followed parabolic curves, and the response of respiration to temperature increased with temperature. Topt was higher in summer than winter at each elevation and decreased significantly with increasing elevation. Q10 decreased significantly with increasing elevation in summer but not winter. These results showed a strong thermal acclimation of foliar photosynthesis and respiration to current temperatures across elevations and seasons, and that R25 increased significantly with elevation and were higher in winter than summer at each elevation indicating that the global warming can decrease R25. These results strongly suggest that this thermal acclimation will likely occur in the coming decades under climate change, so the increase in respiration rates of P. taiwanensis in response to climatic warming may be smaller than predicted and thus may not increase atmospheric CO2 concentrations.

Convergency and Stability Responses of Bacterial Communities to Salinization in Arid and Semiarid Areas: Implications for Global Climate Change in Lake Ecosystems

Climate change has given rise to salinization and nutrient enrichment in lake ecosystems of arid and semiarid areas, which have posed the bacterial communities not only into an ecotone in lake ecosystems but also into an assemblage of its own unique biomes. However, responses of bacterial communities to climate-related salinization and nutrient enrichment remain unclear. In September 2019, this study scrutinized the turnover of bacterial communities along gradients of increasing salinity and nutrient by a space-for-time substitution in Xinjiang Uyghur Autonomous Region, China. We find that salinization rather than nutrient enrichment primarily alters bacterial communities. The homogenous selection of salinization leads to convergent response of bacterial communities, which is revealed by the combination of a decreasing β-nearest taxon index (βNTI) and a pronounced negative correlation between niche breadth and salinity. Furthermore, interspecific interactions within bacterial communities significantly differed among distinct salinity levels. Specifically, mutualistic interactions showed an increase along the salinization. In contrast, topological parameters show hump-shaped curves (average degree and density) and sunken curves (modularity, density, and average path distance), the extremums of which all appear in the high-brackish environment, hinting that bacterial communities are comparatively stable at freshwater and brine environments but are unstable in moderately high-brackish lake.

Does transition to retirement increase frequence of volunteering: Findings from the Survey of Health, Ageing and Retirement in Europe

Objectives Several studies have shown that retired older adults volunteer more than their working counterparts. However, there is a lack of research detecting whether the transition to retirement increases the frequency of volunteering over time and the extent to which this potential effect of retirement varies between sociodemographic groups.Methods We used seven waves of data from the longitudinal Survey of Health, Ageing and Retirement in Europe, collected between 2011 and 2018 from 19 countries. Within-person (or panel fixed-effect) regression models, which considered individual variations and person-specific changes over time, were conducted.Results Transition to retirement over time was associated with an increased frequency of volunteering among older Europeans. In addition, transition to retirement was more strongly associated with volunteering in countries with higher overall rates of volunteering, among more highly educated individuals, and among more religious people.Discussion Our findings supported the impact of time substitution and the centrality of social norms in shaping individual behavior. However, we were unable to find support for an influence of social tie replacement. Overall, transition to retirement tends to open up new ways to organize everyday life and increases the time spent volunteering among older Europeans.

Variation in gene expression patterns across a conifer hybrid zone highlights the architecture of adaptive evolution under novel selective pressures

Variation in gene expression among natural populations are key contributors to adaptive evolution. Understanding the architecture underlying adaptive trait evolution provides insights into the adaptive potential of populations exposed to novel selective pressures. We investigated patterns and processes driving trait differentiation under novel climatic conditions by combining common garden experiments with transcriptome-wide datasets obtained from Pinus strobiformis - Pinus flexilis hybrid zone populations. We found strong signals of genotype-environment interactions at the individual transcript and the co-expression module level, a marked influence of drought related variables on adaptive evolution and an environment dependent influence of P. flexilis ancestry on survival. Using co-expression network connectivity as a proxy for pleiotropy we highlight that adaptive transcripts were pleiotropic across both gardens and modules with strong population differentiation exhibited lower preservation across gardens. Our work highlights the utility of integrating transcriptomics with space-for-time substitution studies to evaluate the adaptive potential of long-lived species. We conclude by suggesting that the combination of pleiotropic trait architectures and substantial genetic variation may enable long-lived forest tree species to respond to rapid shift in climatic conditions.

Response of Northern Populations of Black Spruce and Jack Pine to Southward Seed Transfers: Implications for Climate Change

A variety of responses to climate change have been reported for northern tree populations, primarily from tree-ring and satellite-based studies. Here we employ provenance data to examine growth and survival responses of northern populations (defined here as those occurring north of 52° N) of black spruce (Picea mariana) and jack pine (Pinus banksiana) to southward seed transfers. This space for time substitution affords insights into potential climate change responses by these important northern tree species. Based on previous work, we anticipated relatively flat response curves that peak at much warmer temperatures than those found at seed source origin. These expectations were generally met for growth-related responses, with peak growth associated with seed transfers to environments with mean annual temperatures 2.2 and 3.6 °C warmer than seed source origin for black spruce and jack pine, respectively. These findings imply that northern tree populations harbor a significant amount of resilience to climate warming. However, survival responses told a different story, with both species exhibiting reduced survival rates when moved to warmer and drier environments. Together with the growth-based results, these findings suggest that the warmer and drier conditions expected across much of northern Canada under climate change may reduce survival, but surviving trees may grow at a faster rate up until a certain magnitude of climate warming has been reached. We note that all relationships had high levels of unexplained variation, underlining the many factors that may influence provenance study outcomes and the challenges in predicting tree responses to climate change. Despite certain limitations, we feel that the provenance data employed here provide valuable insights into potential climate change outcomes for northern tree populations.

Isotope Analysis Reveals Differential Impacts of Artificial and Natural Afforestation On Soil Organic Carbon Dynamics in Abandoned Farmland

Backgrounds A multitude of studies have applied different methods to study the dynamics of soil organic carbon (SOC), but the differential impact of artificial and natural afforestation on SOC dynamic are still poorly understood. Methods and aims We investigated the SOC dynamics following artificial and natural afforestation in Loess Plateau of China, characterizing soil structure and stoichiometry using stable isotope carbon and radiocarbon models. We aim to compare SOC dynamics, clarify SOC source under different afforestation, examine comparability of the study areas and find how soil aggregate size classes control SOC dynamics, finally to evaluate effect of reforestation project.Results The 0-10cm and 10-20 cm SOC stocks were significant higher than other two land-use system. At other depths, there is no significant difference among the three land-use system. Total top soil SOC stocks, C:N and C:P of differently sized soil aggregates significantly increased following afforestation. 13C results and Radiocarbon models indicated that the SOC decomposition rate and new SOC input rate were lower under natural afforestation than artificial afforestation. Conclusions Afforestation can accumulate SOC in top soils mainly resulting from in topsoil changing. SOC resource is mainly from macroaggregate formation provided by fresh plant residues. SOC loss from soil respiration was derived from microaggregates during afforestation. The“space-for-time substitution” method is suitable for comparability of the study areas.

Effects of Spatial Expansion Between Phragmites Australis And Cyperus Malaccensis On Temporal Variations And Bioaccumulation of Vanadium In Coastal Marshes of The Min River Estuary, Southeast China

Vanadium (V) plays important roles in physio-ecological processes of marsh plants. To investigate the effects of spatial expansion between native invasive species (Phragmites australis, PA) and common native species (Cyperus malaccensis, CM) on temporal variations and bioaccumulation of V in coastal marshes of the Min River estuary, in situ filed sampling was conducted in PA marsh (PAM, before expansion), CM marsh (CMM, before expansion) and ecotonal marsh (EM, during expansion, marsh plants were denoted by PA' and CM') at different seasons by space-for-time substitution method. Results showed that, over all sampling seasons, the mean V contents in marsh soils ranged from 99.71 to 108.41 mg·kg-1 which exceeded its background value in soils of Fujian province (78.3 mg·kg-1). The V levels in soils differed among seasons or marshes. Higher V contents in soils of PAM, EM and CMM generally occurred in spring and winter. Over all sampling seasons, the V levels in profiles of EM were much higher than those of PAM and CMM. The temporal variation of V levels in soils of EM might rest with the alterations of soil pH, SOM and plant ecological traits during the spatial expansion. Although the V contents in PA, PA', CM' and CM differed among tissues, both the roots/stems (R/S) and roots/leaves (R/L) ratios were larger than 1 while the stems/leaves (S/L) ratios were less than 1, implying that the values in roots were much higher than those in other tissues. The V levels in tissues differed among species or seasons, which could be interpreted by the differences in ecological traits among plants and the competitive absorption for V by plants during the spatial expansion. Allocations of V in organs differed among seasons or species and roots were the main V stock of plant subsystems. This paper found that the V in soils of the Min River estuary existed enrichment process and the spatial expansion between PA and CM promoted its enrichment in soils and its bioaccumulation by plants.

Tree cover change proves stability and instability in tropical ecosystems

Terrestrial tropical ecosystems’ resilience is determined predominantly based on space-for-time substitution, which assumes that the current ‘static’ frequency distribution of ecosystems’ tree cover structure across space also holds across time. However, dynamic and temporal aspects are increasingly important to explicitly account for under ongoing rapid climate change. Here, we empirically study ecosystem stability and instability using remote sensing-derived tree cover change (ΔTC) over the last two decades. We find that considerable ΔTC predominantly takes place in intermediate tree cover ecosystems (i.e., areas with 30-60% tree cover), whereas high (>75%) and low (<10%) tree cover ecosystems only experience limited ΔTC. Our results further suggest that root zone storage capacity, which defines the adaptive capacity of the ecosystem to absorb water stress perturbations, does mediate the relationship between ecosystems’ stability and ΔTC by instigating investment in ecosystems subsoil structure. Based on these analyses, we propose a modified forest resilience metric using both precipitation and root zone storage capacity, which reveals that the Congo rainforests are more resilient than if only precipitation is considered. This study emphasises the importance of temporal dynamics and adaptation of ecosystems in inferring and assessing the risk of forest-savannah transitions under change.

Landscape Configuration Influences Species Occupancy Over Multiple Spatial Scales: A Case Study On Tawny Owl

ABSTRACT Landscape configuration can influence the distribution of species across multiple spatial scales. The primary factors related to this process are connectivity, the size and position of habitat patches, and edge effects. These factors together determine the overall fragmentation of a landscape, which in turn influences species occurrence. Although some species show a negative response to fragmentation, others benefit from it. Potential effects may act over multiple spatial scales, possibly with contrasting effects on species occurrence. We chose the Tawny Owl (Strix aluco), a ubiquitous and generalist species, to study the influence of fragmentation on species occurrence and to identify relevant landscape metrics, using multi-scale hierarchical modelling. Between 2016 and 2018, we recorded Tawny Owls on 64 sampling sites located in a forested landscape. We used a space-for-time substitution in the framework of occupancy modelling to assess Tawny Owl responses to landscape fragmentation. We found that the Tawny Owl is widespread in the study area. Its distribution across the landscape (larger spatial scale) was related to a heterogeneous configuration of forest patches, while high connectivity of coniferous forest influenced its occurrence at a smaller spatial scale (sites). Overall, the Tawny Owl prefers landscapes with well-connected forest patches and an uneven patch distribution in the surrounding area.