1,721,009 research outputs found
Broadleaf seedling responses to warmer temperatures “chilled” by late frost that favors conifers
No full textClimate change includes not only shifts in mean conditions but also changes in the frequency and timing of extreme weather events. Tree seedlings, as the potential future overstory, are responding to the selective pressures of both mean and extreme conditions. We investigated how increases in mean temperature and the occurrence of late spring frosts affect emergence, development, growth, and survival of 13 native and non-native broadleaf and conifer tree species common in central Europe. Three temperature levels (ambient, +3, and +6 °C) and three spring frost treatments (control, late, and very late) were applied. Development responses of first-year seedlings to warmer temperatures were similar in direction and magnitude for broadleaf and conifer species. Stem size also increased with rising mean temperature for most species, though broadleaf species had maximal height advantage over conifer species in the warmest treatment. Sensitivity to frost differed sharply between the broadleaf and conifer groups. Broadleaf survival and stem length exhibited strong reductions due to frost events while conifer species only showed minor decreases in survival. Importantly, more rapid development and earlier leaf-out in response to warmer temperatures were associated with increased mortality from frost for broadleaf species but decreased mortality for conifer species. This research suggests that compositional shifts in the direction of species favored by increasing mean temperatures may be slowed by extreme events, and thus, the occurrence and impacts of such weather events must be acknowledged and incorporated into research and forest planning
Wildlife warning reflectors do not alter the behavior of ungulates to reduce the risk of wildlife-vehicle collisions
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Long-term effects of canopy opening and liming on leaf litter production, and on leaf litter and fine-root decomposition in a European beech (Fagus sylvatica L.) forest
No full textThe long-term (>20 yr) effects of canopy opening and liming on leaf litter production over 2 periods (1990-1997; 2000-2010), and fine root and litter decomposition over 3 periods (1992-1993; 1996-1997; 2012-2013) were examined in a mature European beech (Fagus sylvatica L.) stand on a nutrient-poor site. The results did partially support the hypothesis that the combined or single effects of liming and/or canopy removal on the litter production and decomposition lasted for more than 20 years. The main results were: (1) Along with beech regeneration, the annual leaf litter input in all study plots was higher for the period 2000-2010 (2.9 Mg ha(-1) yr(-1)) than for 1990-1997 (2.5 Mg ha(-1) yr(-1)), and the differences among the treatments were getting smaller; (2) The mass of beech leaf litter fall was higher in the stands than in the gaps; (3) Liming accelerated the fine root and OF layer litter decomposition in the period April 1992 to July 1993, and fine root and leaf litter from June 1996 to September 1997, but this effect was not observed in the period March 2012 to July 2013; (4) The gap effect alone did not accelerate the litter decomposition rate in the first period, but in the second and third periods; (5) 23 years after liming and canopy opening, the quality of the leaf litter was different, and the canopy opening continued to accelerate both leaf litter and fine-root decomposition. (C) 2014 Elsevier B.V. All rights reserved.China Scholarship Council; German BMB
Microbial-mediated feedbacks of leaf litter on invasive plant growth and interspecific competition
No full textFeedbacks between plants and soil microbes can play an important role in competition between potential invaders and the resident community. However, the role of saprophytic soil microbes is poorly understood because research largely focuses on the role of specific soil-borne pathogens. Our aim was to examine the role of plant-saprophyte feedbacks in soil processes (decomposition and enzyme activities) and plant competition. We preconditioned a common soil in microcosms by decomposing litter of four species; two exotic invasive species (Microstegium vimineum and Berberis thunbergii) and two native species (Viburnum acerifolium and Vaccinium corymbosum). We then replaced the litter with either the same species' litter or a different species' litter on the preconditioned soil. We measured the effect of preconditioning on subsequent litter decomposition, microbial community structure (phospholipid fatty acids) and function (soil enzyme activities and decomposition). We then grew Berberis and Viburnum seedlings in preconditioned soils under intraspecific and interspecific competition to determine whether litter preconditioning had a feedback effect on competition. Changes in microbial community structure during preconditioning persisted through time and altered subsequent soil enzyme activities and litter decomposition. These changes also affected the growth rate of two shrub species, but because both shrubs grew best in soil that previously contained Berberis litter, competition between these species was not directly affected. Plant litter creates a legacy that influences the future structure of the microbial community even after that litter is gone. This legacy effect has functional consequences on decomposition and plant growth, and could be an important but under-appreciated factor in soil and plant community ecology. Further study is needed to determine how these consequences affect plant community composition and invasibility.National Science Foundation [DEB-0309047
Long-term effects of gap creation and lime application on element input and output in a European beech (Fagus sylvatica L.) forest
No full textFour gaps of 30m diameter were cut in a mature European beech (Fagus sylvatica L.) forest in 1989. In two of the gaps and their surrounding areas, dolomite lime (3t ha(-1)) was applied. The study was designed to examine the long-term effects of lime application and canopy removal on element input via throughfall and output in seepage water at 80cm depth in this European beech forest. Throughfall and seepage water were collected in the unlimed gap center, the limed gap center and the undisturbed beech stand in 1991, 1992, 1993, 1996 and 2012. The canopy opening increased the seepage water acidity from 1991 to 1996. The pH values of the seepage water were higher in the limed gaps than in the unlimed gaps during the five study periods. The amount of annual throughfall and of seepage water were higher in the gaps during the study period; in 2012, the annual amounts of seepage water were significantly higher in the gaps than in the closed stand, whereas the input of most elements decreased from 1991 to 2012. The seepage water in the unlimed gaps had higher nitrate nitrogen (NO3-N) concentrations, but lower sulfate sulfur (SO4-S) concentrations than in the limed gaps in 1991, 1992, 1993 and 1996. The amount of leaching NO3-N and SO4-S in 2012 was, however, significantly higher in the limed gaps than in the unlimed gaps, while the input of nitrogen (N) and SO4-S was significantly lower in the limed gaps than in the closed stand. In general, the annual amounts of element input via throughfall were higher in the closed stand than in the gaps. However, the element output through leaching was much higher in the gap centers than in the closed stand. The net losses of aluminum (Al), calcium (Ca), magnesium (Mg) and manganese (Mn) were higher in the unlimed gaps than in the limed gaps and the closed stand in 1991. In 2012, 23years after liming and canopy opening, the effects of gaps and liming, and the interaction of gap and liming on element leaching, were still significant compared to the untreated stand. Overall, canopy opening reduced N, sulfate, Al, and base cation deposition in the long run. Canopy opening in combination with liming affected the seepage water acidity and the leaching losses of base cations up to 23years after canopy removal and liming in this European beech forest
Long-term Effects of Canopy Opening and Liming on Soil Nutrient Dynamics in a European Beech (Fagus sylvatica L.) Forest
No full textForest management has a considerable influence on the soil nutrient dynamics of forest ecosystems. This study was designed to examine the long-term effects of lime application and canopy removal on soil nutrient budgets in a mature European beech (Fagus sylvatica L.) forest. In 1989, trees were felled to create four 30-m wide circular gaps in this beech forest, and two of these gaps and the surrounding area were limed with 3 t ha(-1) of fine dolomite, whereas the remaining two gaps and most parts of the stand were not limed. Main nutrient concentrations in the forest floor and in the mineral soil were determined in 1989, 1997, and 2011. In addition, we examined the influence of liming and gaps on the forest floor organic matter. The significant effects of liming and gap creation on the forest floor dry mass in 1997 were no longer obvious in 2011, unlike their influence on the C and N pools, which was still significant in 2011. In the long-term, the forest floor C and N pools increased less in the limed and opened plots compared with the untreated stand, and the N pool only decreased in the mineral soil of the limed gaps. Soil acidity was reduced significantly 8 years after liming at any depth in the limed plots (limed stand, limed gaps) and in the deeper layers (5-40 cm) of the unlimed plots, indicating a general soil recovery from acid depositions in earlier decades. After 22 years, the pH values were still higher at 5 to 10 cm mineral soil depth in the limed plots, which partly reflected the higher base saturation in the mineral soil of the limed gaps. However, the pH values were surprisingly dropping from 1997 to 2011 in the upper soil layers of all plots. Overall, some effects of canopy opening and liming on soil nutrients lasted for more than two decades in this European beech forest.China Scholarship Council; German BMB
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