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  • Key wordsBetula  (2)
  • Pot size  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Regenerating temperate forest mesocosms in elevated CO2: belowground growth and nitrogen cycling (1997)
    Springer
    Oecologia 113 (1997), S. 115-125 
    Details
    ISSN: 1432-1939
    Keywords: Key wordsBetula ; CO2 ; Mycorrhizal fungi ; Nitrogen ; Pool dilution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The response of temperate forest ecosystems to elevated atmospheric CO2 concentrations is important because these ecosystems represent a significant component of the global carbon cycle. Two important but not well understood processes which elevated CO2 may substantially alter in these systems are regeneration and nitrogen cycling. If elevated CO2 leads to changes in species composition in regenerating forest communities then the structure and function of these ecosystems may be affected. In most temperate forests, nitrogen appears to be a limiting nutrient. If elevated CO2 leads to reductions in nitrogen cycling through increased sequestration of nitrogen in plant biomass or reductions in mineralization rates, long-term forest productivity may be constrained. To study these processes, we established mesocosms of regenerating forest communities in controlled environments maintained at either ambient (375 ppm) or elevated (700 ppm) CO2 concentrations. Mesocosms were constructed from intact monoliths of organic forest soil. We maintained these mesocosms for 2 years without any external inputs of nitrogen and allowed the plants naturally present as seeds and rhizomes to regenerate. We used 15N pool dilution techniques to quantify nitrogen fluxes within the mesocosms at the end of the 2 years. Elevated atmospheric CO2 concentration significantly affected a number of plant and soil processes in the experimental regenerating forest mesocosms. These changes included increases in total plant biomass production, plant C/N ratios, ectomycorrhizal colonization of tree fine roots, changes in tree fine root architecture, and decreases in plant NH4 + uptake rates, gross NH4 + mineralization rates, and gross NH4 + consumption rates. In addition, there was a shift in the relative biomass contribution of the two dominant regenerating tree species; the proportion of total biomass contributed by white birch (Betula papyrifera) decreased and the proportion of total biomass contributed by yellow birch (B. alleghaniensis) increased. However, elevated CO2 had no significant effect on the total amount of nitrogen in plant and soil microbial biomass. In this study we observed a suite of effects due to elevated CO2, some of which could lead to increases in potential long term growth responses to elevated CO2, other to decreases. The reduced plant NH4 + uptake rates we observed are consistent with reduced NH4 + availability due to reduced gross mineralization rates. Reduced NH4 + mineralization rates are consistent with the increases in C/N ratios we observed for leaf and fine root material. Together, these data suggest the positive increases in plant root architectural parameters and mycorrhizal colonization may not be as important as the potential negative effects of reduced nitrogen availability through decreased decomposition rates in a future atmosphere with elevated CO2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004420050359
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  • 2
    Electronic Resource
    Electronic Resource
    Elevated CO2 ameliorates birch response to high temperature and frost stress: implications for modeling climate-induced geographic range shifts (1998)
    Springer
    Oecologia 114 (1998), S. 335-342 
    Details
    ISSN: 1432-1939
    Keywords: Key wordsBetula ; Carbon dioxide ; Climate change ; heat stress ; Freezing stress
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Despite predictions that both atmospheric CO2 concentrations and air temperature will rise together, very limited data are currently available to assess the possible interactive effects of these two global change factors on temperate forest tree species. Using yellow birch (Betula alleghaniensis) as a model species, we studied how elevated CO2 (800 vs. 400 μl l−1) influences seedling growth and physiological responses to a 5°C increase in summer air temperatures (31/26 vs. 26/21°C day/night), and how both elevated CO2 and air temperature during the growing season influence seedling ability to survive freezing stress during the winter dormant season. Our results show that while increased temperature decreases seedling growth, temperature-induced growth reductions are significantly lower at elevated CO2 concentrations (43% vs. 73%). The amelioration of high-temperature stress was related to CO2-induced reductions in both whole-shoot dark respiration and transpiration. Our results also show that increased summer air temperature, and to a lesser degree CO2 concentration, make dormant winter buds less susceptible to freezing stress. We show the relevance of these results to models used to predict how climate change will influence future forest species distribution and productivity, without considering the direct or interactive effects of CO2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004420050455
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  • 3
    Electronic Resource
    Electronic Resource
    Elevated CO2 alters deployment of roots in “small” growth containers (1993)
    Springer
    Oecologia 94 (1993), S. 558-564 
    Details
    ISSN: 1432-1939
    Keywords: CO2 ; Nutrients ; Pot size ; Root deployment ; Root restriction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Previously we examined how limited rooting space and nutrient supply influenced plant growth under elevated atmospheric CO2 concentrations (McConnaughay et al. 1993). We demonstrated that plant growth enhancement under elevated CO2 was influenced more by the concentration of nutrients added to growth containers than to either the total nutrient content per pot or amount or the dimensions of available rooting space. To gain insight into how elevated CO2 atmospheres affect how plants utilize available belowground space when rooting space and nutrient supply are limited we measured the deployment of roots within pots through time. Contrary to aboveground responses, patterns of belowground deployment were most strongly influenced by elevated CO2 in pots of different volume and shape. Further, elevated CO2 conditions interacted differently with limited belowground space for the two species we studied,Abutilon theophrasti, a C3 dicot with a deep taproot, andSetaria faberii, a C4 monocot with a shallow fibrous root system. ForSetaria, elevated CO2 increased the size of the largest region of low root density at the pot surface in larger rooting volumes independent of nutrient content, thereby decreasing their efficiency of deployment. ForAbutilon, plants responded to elevated CO2 concentrations by equalizing the pattern of deployment in all the pots. Nutrient concentration, and not pot size or shape, greatly influenced the density of root growth. Root densities forAbutilon andSetaria were similar to those observed in field conditions, for annual dicots and monocots respectively, suggesting that studies using pots may successfully mimic natural conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00566972
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  • 4
    Electronic Resource
    Electronic Resource
    Limitations to CO2-induced growth enhancement in pot studies (1993)
    Springer
    Oecologia 94 (1993), S. 550-557 
    Details
    ISSN: 1432-1939
    Keywords: Elevated CO2 ; Growth enhancement ; Nutrients ; Pot size ; Root restriction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Recently, it has been suggested that small pots may reduce or eliminate plant responses to enriched CO2 atmospheres due to root restriction. While smaller pot volumes provide less physical space available for root growth, they also provide less nutrients. Reduced nutrient availability alone may reduce growth enhancement under elevated CO2. To investigate the relative importance of limited physical rooting space separate from and in conjunction with soil nutrients, we grew plants at ambient and double-ambient CO2 levels in growth containers of varied volume, shape, nutrient concentration, and total nutrient content. Two species (Abutilon theophrasti, a C3 dicot with a deep tap root andSetaria faberii, a C4 monocot with a shallow diffuse root system) were selected for their contrasting physiology and root architecture. Shoot demography was determined weekly and biomass was determined after eight and ten weeks of growth. Increasing total nutrients, either by increasing nutrient concentration or by increasing pot size, increased plant growth. Further, increasing pot size while maintaining equal total nutrients per pot resulted in increased total biomass for both species. CO2-induced growth and reproductive yield enhancements were greatest in pots with high nutrient concentrations, regardless of total nutrient content or pot size, and were also mediated by the shape of the pot. CO2-induced growth and reproductive yield enhancements were unaffected by pot size (growth) or were greater in small pots (reproductive yield), regardless of total nutrient content, contrary to predictions based on earlier studies. These results suggest that several aspects of growth conditions within pots may influence the CO2 responses of plants; pot size, pot shape, the concentration and total amount of nutrient additions to pots may lead to over-or underestimates of the CO2 responses of real-world plants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00566971
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