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- Acer platanoides (2)
- Acer pseudoplatanus (2)
- Climate change (2)
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In this study, we analyzed the influence of soil mineral characteristics (e. g., clay concentration and mineralogical composition, iron and aluminum oxide concentration and crystallinity, specific surface area, and exchangeable cation concentration) on (i) organic carbon (OC) content (kg m(-2)) and (ii) the concentration (g kg(-1)), composition, and stability of the mineral-associated organic matter (OM) of arable and forest topsoils. We selected seven soil types with different mineral characteristics for this study. For each soil type, samples were taken from topsoils of a deciduous forest and an adjacent arable site. The arable and forest sites have been used continuously for more than 100 years. Na-pyrophosphate soluble OM fractions (OM(PY)), representing mineral-associated OM, were extracted, analyzed for OC and C-14 concentrations, and characterized by FTIR spectroscopy. For the forest and arable topsoils, a linear relationship was found between the OC content and exchangeable Ca. For the arable topsoils (pH 6.7-7.5), correlation analyses indicated that the OCPY concentration increased with an increase in oxalate soluble Fe and Al, exchangeable Ca, and Na-pyrophosphate soluble Mg and Fe concentrations. The stability of OM(PY) determined by the C-14 measurements of the near-neutral arable topsoils was shown to increase with the specific surface area and the concentration of exchangeable Ca. For the acidic forest topsoils (pH < 5), the stability of OM(PY) was found to increase as the pH, and the concentration of C=O groups and Na-pyrophosphate soluble Mg increase.
Ecological niches of organisms vary across geographical space, but niche shift patterns between regions and the underlying mechanisms remain largely unexplored. We studied shifts in the pH niche of 42 temperate forest plant species across a latitudinal gradient from northern France to boreo-nemoral Sweden. We asked 1) whether species restrict their niches with increasing latitude as they reach their northern range margin (environmental constraints); 2) whether species expand their niches with increasing latitude as regional plant species richness decreases (competitive release); and 3) whether species shift their niche position toward more acidic sites with increasing latitude as the relative proportion of acidic soils increases (local adaptation). Based on 1458 vegetation plots and corresponding soil pH values, we modelled species response curves using Huisman-Olff-Fresco models. Four niche measures (width, position, left and right border) were compared among regions by randomization tests. We found that with increasing latitude, neutrophilic species tended to retreat from acidic sites, indicating that these species retreat to more favorable sites when approaching their range margin. Alternatively, these species might benefit from enhanced nitrogen deposition on formerly nutrient-poor, acidic sites in southern regions or lag behind in post-glacial recolonization of potential habitats in northern regions. Most acidophilic species extended their niche toward more base-rich sites with increasing latitude, indicating competitive release from neutrophilic species. Alternatively, acidophilic species might benefit from optimal climatic conditions in the north where some have their core distribution area. Shifts in the niche position suggested that local adaptation is of minor importance. We conclude that shifts in the pH niche of temperate forest plants are the rule, but the directions of the niche shifts and possible explanations vary. Our study demonstrates that differentiating between acidophilic and neutrophilic species is crucial to identify general patterns and underlying mechanisms.
Recent global warming is acting across marine, freshwater, and terrestrial ecosystems to favor species adapted to warmer conditions and/or reduce the abundance of cold-adapted organisms (i.e., "thermophilization" of communities). Lack of community responses to increased temperature, however, has also been reported for several taxa and regions, suggesting that "climatic lags" may be frequent. Here we show that microclimatic effects brought about by forest canopy closure can buffer biotic responses to macroclimate warming, thus explaining an apparent climatic lag. Using data from 1,409 vegetation plots in European and North American temperate forests, each surveyed at least twice over an interval of 12-67 y, we document significant thermophilization of ground-layer plant communities. These changes reflect concurrent declines in species adapted to cooler conditions and increases in species adapted to warmer conditions. However, thermophilization, particularly the increase of warm-adapted species, is attenuated in forests whose canopies have become denser, probably reflecting cooler growing-season ground temperatures via increased shading. As standing stocks of trees have increased in many temperate forests in recent decades, local microclimatic effects may commonly be moderating the impacts of macroclimate warming on forest understories. Conversely, increases in harvesting woody biomass-e.g., for bioenergy-may open forest canopies and accelerate thermophilization of temperate forest biodiversity.
Permafrost-related processes drive regional landscape dynamics in the Arctic terrestrial system. A better understanding of past periods indicative of permafrost degradation and aggradation is important for predicting the future response of Arctic landscapes to climate change. Here, we used a multi-proxy approach to analyse a4m long sediment core from a drained thermokarst lake basin on the northern Seward Peninsula in western Arctic Alaska (USA). Sedimentological, biogeochemical, geochronological, micropalaeontological (ostracoda, testate amoebae) and tephra analyses were used to determine the long-term environmental Early-Wisconsin to Holocene history preserved in our core for central Beringia. Yedoma accumulation dominated throughout the Early to Late-Wisconsin but was interrupted by wetland formation from 44.5 to 41.5ka BP. The latter was terminated by the deposition of 1m of volcanic tephra, most likely originating from the South Killeak Maar eruption at about 42ka BP. Yedoma deposition continued until 22.5ka BP and was followed by a depositional hiatus in the sediment core between 22.5 and 0.23ka BP. We interpret this hiatus as due to intense thermokarst activity in the areas surrounding the site, which served as a sediment source during the Late-Wisconsin to Holocene climate transition. The lake forming the modern basin on the upland initiated around 0.23ka BP and drained catastrophically in spring 2005. The present study emphasises that Arctic lake systems and periglacial landscapes are highly dynamic and that permafrost formation as well as degradation in central Beringia was controlled by regional to global climate patterns as well as by local disturbances. Copyright (c) 2015 John Wiley & Sons, Ltd.
Impacts of warming and changes in precipitation frequency on the regeneration of two Acer species
(2015)
Millennial-scale Dansgaard Oeschger (DO) variability at northern high latitudes has influenced climatic and environmental conditions in the Mediterranean during the last glacial period. There is evidence that the hemispheric transmission of the DO variability occurred at the end of DO event 25; however, the exact timing and the trigger that activated the environmental response in the Mediterranean remains incompletely understood. Here, we provide evidence that the clear millennial-scale teleconnection between Greenland and the Mediterranean started at similar to 111.4 ka BP and was initiated by a sub-millennial scale cooling in Greenland (GI-25b). High-resolution sediment proxies and the pollen record of Lago Grande di Monticchio (MON), Italy, reflect climatic instability during the last millennium of the last interglacial, which was characterised by a first and short cooling episode (MON 1) at 111.44 +/- 0.69 ka BP, coinciding with the Greenland cold sub-event GI-25b in duration and timing (within dating uncertainties). MON and Greenland (NorthGRIP ice core) also agree in recording a subsequent warm rebound phase that abruptly culminated in the stadial MON 2/GS-25, marking the transition into the last glacial period. Our results show that the GI-25b triggered an early environmental response at MON to centennial-scale climate change in Greenland as a prelude to the millennial-scale teleconnection that was maintained during the glacial period.
Changes in faecal bacteria and metabolic parameters in foals during the first six weeks of life
(2011)
Many foals develop diarrhoea within the first two weeks of life which has been suggested to coincide with postpartum oestrus in their dams. To analyse the pathogenesis of this diarrhoea we have determined faecal bacteria in foals and their dams (n = 30 each), and serum IGF-1 and gamma-globulins for 6 weeks after birth. In addition, effects of beta-carotene supplementation to mares (group 1: 1000 mg/day, n = 15, group 2: control, n = 15) on diarrhoea in foals were studied. Diarrhoea occurred in 92 and 79% of foals in groups 1 and 2, respectively, but was not correlated with oestrus in mares. Beta-carotene supplementation was without effect on foal diarrhoea. In mares, bacterial flora remained stable. The percentage of foals with cultures positive for E. coli was low at birth but increased within one day, the percentage positive for Enterococcus sp. was low for 10 days and for Streptococcus sp. and Staphylococcus sp. was low for 2-4 weeks. By 4 weeks of age, bacterial flora in foals resembled an adult pattern. Concentration of serum IGF-1 was low at birth (group 1:149 +/- 11, group 2:166 17 ng/ml), increased after day 1 (day 7 group 1:384 +/- 30, group 2: 372 +/- 36) but at no time differed between groups. Serum gamma-globulin concentration in foals was low before colostrum intake and highest on day 1 (p < 0.001 over time). In conclusion, neonatal diarrhoea in foals does not coincide with postpartum oestrus in their dams but with changes in intestinal bacteria and is not influenced by beta-carotene supplementation given to mares.
Climate change will likely affect population dynamics of numerous plant species by modifying several aspects of the life cycle. Because plant regeneration from seeds may be particularly vulnerable, here we assess the possible effects of climate change on seed characteristics and present an integrated analysis of seven seed traits (nutrient concentrations, samara mass, seed mass, wing length, seed viability, germination percentage, and seedling biomass) of Acer platanoides and A. pseudoplatanus seeds collected along a wide latitudinal gradient from Italy to Norway. Seed traits were analyzed in relation to the environmental conditions experienced by the mother trees along the latitudinal gradient. We found that seed traits of A. platanoides were more influenced by the climatic conditions than those of A. pseudoplatanus. Additionally, seed viability, germination percentage, and seedling biomass of A. platanoides were strongly related to the seed mass and nutrient concentration. While A. platanoides seeds were more influenced by the environmental conditions (generally negatively affected by rising temperatures), compared to A. pseudoplatanus, A. platanoides still showed higher germination percentage and seedling biomass than A. pseudoplatanus. Thus, further research on subsequent life-history stages of both species is needed. The variation in seed quality observed along the climatic gradient highlights the importance of studying the possible impact of climate change on seed production and species demography.
Climate change is acting on several aspects of plant life cycles, including the sexual reproductive stage, which is considered amongst the most sensitive life-cycle phases. In temperate forests, it is expected that climate change will lead to a compositional change in community structure due to changes in the dominance of currently more abundant forest tree species. Increasing our understanding of the effects of climate change on currently secondary tree species recruitment is therefore important to better understand and forecast population and community dynamics in forests. Here, we analyse the interactive effects of rising temperatures and soil moisture reduction on germination, seedling survival and early growth of two important secondary European tree species, Acer pseudoplatanus and A.platanoides. Additionally, we analyse the effect of the temperature experienced by the mother tree during seed production by collecting seeds of both species along a 2200-km long latitudinal gradient. For most of the responses, A.platanoides showed higher sensitivity to the treatments applied, and especially to its joint manipulation, which for some variables resulted in additive effects while for others only partial compensation. In both species, germination and survival decreased with rising temperatures and/or soil moisture reduction while early growth decreased with declining soil moisture content. We conclude that although A.platanoides germination and survival were more affected after the applied treatments, its initial higher germination and larger seedlings might allow this species to be relatively more successful than A.pseudoplatanus in the face of climate change.