scholarly journals Linking songbird nest predation to seedling density: Sugar maple masting as a resource pulse in a forest food web

2017 ◽  
Vol 7 (24) ◽  
pp. 10733-10742 ◽  
Author(s):  
Marie-Line Fiola ◽  
Alizée Vernouillet ◽  
Marc-André Villard
2003 ◽  
Vol 20 (2) ◽  
pp. 85-91 ◽  
Author(s):  
John M. Lhotka ◽  
James J. Zaczek

Abstract This study investigated whether soil scarification during the presence of abundant white oak (Quercus alba L.) acorns and other mast could be used to increase the density of oak reproduction and reduce competitive midstory species in a mid-successional mixed-oak upland forest. The study was conducted in a 7.3 ha forest with a mature oak overstory and a well-developed midstory of sugar maple (Acer saccharum Marsh.) and pawpaw (Asmina triloba Dunal.) in southern Illinois. The soil scarification was conducted in the autumn after acorn dissemination using a crawler tractor with a six-tooth brush rake. One growing season after treatment, significantly higher numbers of oak seedlings, primarily white oak, were present in the scarified plots (5,164 ha-1) compared to the control plots (1,273 ha-1). Seedling density of all other species classes did not differ between treatments. Scarification affected 61% of midstory trees and thus reduced their density and competitive position. Of these trees, 21% of stems were completely removed by the scarification treatment. Results suggest that, in the presence of abundant acorns, scarification may increase the number of new oak germinants in stands lacking advanced oak reproduction. Finally, because scarification increased the density of oak seedlings and reduced competing midstory trees, it can play a role in promoting the establishment of advanced oak reproduction. North. J. Appl. For. 20(2):85–91.


1991 ◽  
Vol 8 (3) ◽  
pp. 99-104 ◽  
Author(s):  
Peter R. Hannah

Abstract Study plots (1/4 ac) were located in four northern hardwood stands in Vermont, and shelterwood canopy covers of 40, 60, 80, and 100%, and a control (no cutting) were established. Regeneration on small plots within the treated areas was sampled over a 3-year period and the composition of saplings determined after 6 years. While there were substantial increases in amount of regeneration under most canopy covers, there was no significant differences due to treatment. Some important trends, however, were evident. Sugar maple showed some increase in seedling density under most canopy densities with up to 68,000 new sugar maple seedlings per acre under 60% canopy cover. Yellow birch did best under 40 to 80% canopy cover and with good soil scarification. White ash increased under most densities but was best at about 80% canopy cover. Competitors, beech, striped maple, and hobblebush, increased under most densities. At about 60% canopy cover and less, raspberries and blackberries, pin cherry, and other shade-intolerant species increase in abundance. Among regeneration less than 3 ft all after 3 years, preferred species outnumbered less preferred species by 5 to 1. Among regeneration over 3 ft tall when examined 6 years after treatment, the less preferred species, on average, outnumber preferred species by 2 to 1 (sugar maple 0-3430/ac, yellow birch 0-1920/ac, beech 200-2220/ac and striped maple 0-3130/ac). Most beech regeneration seemed to arise as root suckers. Small striped maple grew rapidly and assumed dominance among the regeneration when released. Northern hardwoods have diverse composition in the overstory, and much of the regeneration tallied after 3 years was already in place when the shelterwood cuts were made. Advanced regeneration as well as new regeneration is the key to success, or failure, if it is predominantly undesirable species. In implementing a shelterwood in northern hardwoods, 60 to 80% canopy cover seems good for most species. All trees below the main canopy should be cut to create a high canopy shade. Undesirable species should be controlled by cutting or possibly herbicides before or when the stand is cut, with additional treatment as necessary to maintain desired composition. North. J. Appl. For. 8(3):99-104.


Ecography ◽  
2001 ◽  
Vol 24 (6) ◽  
pp. 742-750 ◽  
Author(s):  
Lena M. Eriksson ◽  
Lars Edenius ◽  
Veronika Areskoug ◽  
Dennis A. Meritt Jr

2019 ◽  
Author(s):  
Gretchen F. Wagner ◽  
Emeline Mourocq ◽  
Michael Griesser

Predation of offspring is the main cause of reproductive failure in many species, and the mere fear of offspring predation shapes reproductive strategies. Yet, natural predation risk is ubiquitously variable and can be unpredictable. Consequently, the perceived prospect of predation early in a reproductive cycle may not reflect the actual risk to ensuing offspring. An increased variance in investment across offspring has been linked to breeding in unpredictable environments in several taxa, but has so far been overlooked as a maternal response to temporal variation in predation risk. Here, we experimentally increased the perceived risk of nest predation prior to egg-laying in seven bird species. Species with prolonged parent-offspring associations increased their intra-brood variation in egg, and subsequently offspring, size. High risk to offspring early in a reproductive cycle can favour a risk-spreading strategy particularly in species with the greatest opportunity to even out offspring quality after fledging.


2014 ◽  
Vol 26 (3-4) ◽  
pp. 42-61
Author(s):  
O. G. Lucyshyn ◽  
I. K. Teslenko

The recent ecological situation of Kyiv megalopolis has a special specific of environment technogenic pollution as a chemical features and content of polluting phytotoxicants. During 2007–2012, our observation revealed what the most dangerous factors which have harm impact on the street woody plants are the huge concentration of phytotoxic elements (Na+, Cl-, Pb2+, Cd2+). Nowadays, the technogenic impact on the megalopolyisis surrounding comes to the dangerous, even, catastrophic level. The main reason of total and chloral necrose of leaves, the summer defoliation of crown and major tree's death is the over pollution of the soil and plant's phytomass by phytotoxic elements, the concentration of which by standards evaluation and by trees reactions are critical and exists at the level of adaptation possibility and survival. The main sources of Pb2+ and Cd2+ ions are transport outcomes (> 90 % of total technogenic pollution). The increasing of Pb2+ and Cd2+ in the soil is depended from intensivity of transport outcomes, using of ethylated petrol, and location of trees along roads as well as from the trees species. Continuously increasing of number of cars at the city streets is accompanying with similar increasing of ions concentration. Thus, in the soil around root system of street woody plants, depending from their location along roads, the concentration of Pb2+ (moving form) is between 41,7 (I. Kudri str.) and 102,6 mg\kg of soil (Nauki avenue). It exceeds the maximum permissible concentration (MPC), which is 20,8–51,3 mg\kg of soil. Next, for Norway maple (Acer platanoides) the concentration of Pb2+ in the soil varies from 41,7 to 80,5 mg / kg of soil in the area of the root system and it is around 20,8–40,2 MPC. In the leaves of this tree it is 7,83–13,5 mg / kg of dry mass (MPC is 15,8–27,0). For the horse chestnut (Aedculus hippocastanum) at the Nauka avenue, the concentration of plumbum in the root is 13,4 mg / kg (MPC is 26,8), in the cortex – 17,7 mg / kg (MPC is 35,4), in leaves – 8,21 mg / kg (MPC is 16,4), which by the normative evaluation are the critical concentrations. The source of Na+ and Cl-, which is a new factor for Kyiv megalopolis, is irregular load of high concentrations of industrial salt NaCl into the environment, as a way against black ice in winter time, where the Na+ ions ( mobile form) is in the high concentrations in leaves (0,76 % for Norway maple (Acer platanoides) on the I. Kudri str., 1,28 % – small-leaved linden (Tilia cordata) at the 40-richya Zhovtnya ave, 2,0 % – horse chestnut (Aedculus hippocastanum) at the Nauki ave), those are exceeded the concentration of the element comparing to the control test object, respectively, in 10,6, 12,8 and 5,0 times. Na+ ions are an aggressive phytotoxins and the main factor of leaves necrose of tree crown (within 70–100 % necrosis leaves in the crown). Degradation and total reduction of the specific weight of plants in the megalopolis environment are decrease the cleaning role of the street tree plants, which are the main alive filters for soil and air cleaning, as well as the main bioaccumulators and detoxicants of harm substances of anthropogenic pollution. Species adaptive specificity is revealed at the bioaccumulation level and the selective locality of phytotoxic elements (Na+, Cl-, Pb2+, Cd2+, agile form) in technourbanhabitats-pic conditions, there dominated bioaccumulation and localization of Na+ ions by trees assimilative system is caused the adaptive orientation of endogenic and intraspecific variability of phytoindicative morphophysiologic features of plants functional condition under the stressing factors. This also is defined the sensitivity of small-leaved linden (Tilia cordata Mill.), norway maple (Acer platanoides L.) and horse chestnut (Aesculus hippocastanum L.) to the big concentration of potassium as the most danger one for the plant survival. The biggest accumulation of Na+ ions at the roots of Lombardy poplar (Populus pyramidalis Roz.), Bolle's poplar (Populus bolleana Lauche) and sugar maple (Acer saccharinum L.) is lead to a higher resistance of their assimilation system. At the technourbohabitate-pic conditions, the level of realization of ontogenetic and phylogenetic adaptive capacity of the sensitive species of trees is harmfully low (21,3–44,3 %). It is at the level of survival/death of plants. The street Lombardy poplar, Bolle's poplar and sugar maple, despite of more higher level of their adaptation (68,4–87,7 %), still also can't fully adapt to the critical levels of technogenic pollution of megalopolis environment. 


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