Biomass allocation and multiple resource limitation in tree seedlings

1996 ◽  
Vol 26 (9) ◽  
pp. 1521-1530 ◽  
Author(s):  
C.D. Canham ◽  
A.R. Berkowitz ◽  
V.R. Kelly ◽  
G.M. Lovett ◽  
S.V. Ollinger ◽  
...  

We conducted a greenhouse experiment to determine how differences among tree species in allocation of biomass to roots versus shoots affected their responses to different combinations of light, water, and soil nutrients. Across a full range of light levels, we were specifically interested in examining the sensitivity of tree seedlings to additional reductions in aboveground growth due to soil resource limitation, and the relative sensitivity of seedlings to water versus nutrient stress under different light regimes. The four tree species used in our experiment included two species that are the most common initial tree invaders of abandoned agricultural lands (old fields) in the Hudson Valley (red maple (Acerrubrum L.) and white pine (Pinusstrobus L.)) and two species that are less frequently found in old fields, but that are dominant forest species, and are noted for their tolerance of either light stress or water stress (sugar maple (Acersaccharum Marsh.) and red oak (Quercusrubra L.), respectively). At the lowest light levels (2% of full sun), there was no effect of variation in soil resource availability on shoot growth of any of the four species. At the 9% full sun light level, red maple seedlings showed clear evidence of simultaneous limitation by light, water, and nitrogen. At higher light levels (20–100% of full sun), all four species responded to variation in at least one of the two soil resources. The four species showed two contrasting patterns of allocation of biomass to roots. Red maple and white pine responded to an increase in soil resource availability by reducing relative allocation to roots and increasing aboveground growth. Sugar maple and red oak had much more conservative root allocation patterns: root allocation was high (58–75% of added biomass allocated to roots) and did not vary in response to soil resource availability. Allocation to roots was affected more strongly by variation in soil nitrogen availability than it was by soil moisture availability.

Author(s):  
Raeya Jackiw

In response to ecological disturbances, sedge species like Carex pensylvanica form dense monocultures on the forest floor. These “sedge mats” have been shown to severely inhibit plant growth, and limit understory species diversity. In recent years, concern has grown that they may also be restricting the regeneration of economically valuable tree species like sugar maple through belowground competition. To determine if and how Carex pensylvanica may be impacting tree seedling growth through belowground competition I located and exclosed 44 tree seedlings in areas of representatively dense sedge at two forest sites at the Queen’s University Biological Station. I removed sedge from half the plots, and measured soil resource availability and seedling growth response at all plots throughout the growing season. I predicted that sedge would negatively impact the growth of tree seedlings by decreasing the availability of soil resources. I found that the presence of sedge did not affect seedling growth over one growing season, but that it did impact soil resource availability by increasing the availability of surface soil moisture and decreasing the availability of soil nitrate, changes which may have implications for seedling growth beyond the single growing season studied. My results were also site specific, indicating that location is important when managing sedge impact on tree regeneration. Understanding the impact of sedge on tree seedling regeneration is important for predicting changes in the trajectory of forest communities and for informing the management of economically valuable species like sugar maple.


1990 ◽  
Vol 20 (9) ◽  
pp. 1479-1484 ◽  
Author(s):  
F. A. Bazzaz ◽  
J. S. Coleman ◽  
S. R. Morse

We examined how elevated CO2 affected the growth of seven co-occurring tree species: American beech (Fagusgrandifolia Ehrh.), paper birch (Betulapapyrifera Marsh.), black cherry (Prunusserotina Ehrh.), white pine (Pinusstrobus L.), red maple (Acerrubrum L.), sugar maple (Acersaccharum Marsh.), and eastern hemlock (Tsugacanadensis (L.) Carr). We also tested whether the degree of shade tolerance of species and the age of seedlings affected plant responses to enhanced CO2 levels. Seedlings that were at least 1 year old, for all species except beech, were removed while dormant from Harvard Forest, Petersham, Massachusetts. Seeds of red maple and paper birch were obtained from parent trees at Harvard Forest, and seeds of American beech were obtained from a population of beeches in Nova Scotia. Seedlings and transplants were grown in one of four plant growth chambers for 60 d (beech, paper birch, red maple, black cherry) or 100 d (white pine, hemlock, sugar maple) under CO2 levels of 400 or 700 μL•L−1. Plants were then harvested for biomass and growth determinations. The results showed that the biomass of beech, paper birch, black cherry, sugar maple, and hemlock significantly increased in elevated CO2, but the biomass of red maple and white pine only marginally increased in these conditions. Furthermore, there were large differences in the magnitude of growth enhancement by increased levels of CO2 between species, so it seems reasonable to predict that one consequence of rising levels of CO2 may be to increase the competitive ability of some species relative to others. Additionally, the three species exhibiting the largest increase in growth with increased CO2 concentrations were the shade-tolerant species (i.e., beech, sugar maple, and hemlock). Thus, elevated CO2 levels may enhance the growth of relatively shade-tolerant forest trees to a greater extent than growth of shade-intolerant trees, at least under the light and nutrient conditions of this experiment. We found no evidence to suggest that the age of tree seedlings greatly affected their response to elevated CO2 concentrations.


1995 ◽  
Vol 12 (3) ◽  
pp. 115-120 ◽  
Author(s):  
David B. Kittredge ◽  
P. Mark S. Ashton

Abstract Browsing preferences by white-tailed deer were evaluated for 6 tree species in northeastern Connecticut. Deer density averaged 23/mile². Deer exhibited no species-specific preferences for seedlings greater than 19 in. For seedlings less than 19 in., hemlock and black birch were preferred. Red maple, sugar maple, and white pine seedlings were avoided. Red oak seedlings were neither preferred nor avoided. A much higher proportion of seedlings greater than 19.7 in. in height was browsed, regardless of species. Browsing preferences for species in the smaller seedling class, combined with a lack of preference for species in the larger class may result in future stands with less diverse tree species composition. Deer densities in excess of 23/mile² may be incompatible with regeneration of diverse forests in southern New England. North. J. Appl. For. 12(3):115-120.


Plant Ecology ◽  
2010 ◽  
Vol 209 (2) ◽  
pp. 375-382 ◽  
Author(s):  
Fu-Sheng Chen ◽  
De-Hui Zeng ◽  
Timothy J. Fahey ◽  
Cheng-Yi Yao ◽  
Zhan-Yuan Yu

2010 ◽  
pp. 195-202
Author(s):  
Fu-Sheng Chen ◽  
De-Hui Zeng ◽  
Timothy J. Fahey ◽  
Cheng-Yi Yao ◽  
Zhan-Yuan Yu

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