Limits...
Seasonal dynamics of mobile carbon supply in Quercus aquifolioides at the upper elevational limit.

Zhu WZ, Cao M, Wang SG, Xiao WF, Li MH - PLoS ONE (2012)

Bottom Line: During the growing season, plants grown at the elevational limit did not show lower NSC concentrations compared to plants at lower elevations, but during the winter season, storage tissues, especially roots, had significantly lower NSC concentrations in plants at the elevational limit compared to lower elevations.The present results suggest the significance of winter reserve in storage tissues, which may determine the winter survival and early-spring re-growth of Q. aquifolioides shrubs at high elevation, leading to the formation of the uppermost distribution limit.This result is consistent with a recent hypothesis for the alpine treeline formation.

View Article: PubMed Central - PubMed

Affiliation: Alpine Ecosystem Observation and Experiment Station of Gongga Mountain, Institute of Mountain Hazard and Environment, Chinese Academy of Sciences, Chengdu, China. wzzhu@imde.ac.cn

ABSTRACT
Many studies have tried to explain the physiological mechanisms of the alpine treeline phenomenon, but the debate on the alpine treeline formation remains controversial due to opposite results from different studies. The present study explored the carbon-physiology of an alpine shrub species (Quercus aquifolioides) grown at its upper elevational limit compared to lower elevations, to test whether the elevational limit of alpine shrubs (<3 m in height) are determined by carbon limitation or growth limitation. We studied the seasonal variations in non-structural carbohydrate (NSC) and its pool size in Q. aquifolioides grown at 3000 m, 3500 m, and at its elevational limit of 3950 m above sea level (a.s.l.) on Zheduo Mt., SW China. The tissue NSC concentrations along the elevational gradient varied significantly with season, reflecting the season-dependent carbon balance. The NSC levels in tissues were lowest at the beginning of the growing season, indicating that plants used the winter reserve storage for re-growth in the early spring. During the growing season, plants grown at the elevational limit did not show lower NSC concentrations compared to plants at lower elevations, but during the winter season, storage tissues, especially roots, had significantly lower NSC concentrations in plants at the elevational limit compared to lower elevations. The present results suggest the significance of winter reserve in storage tissues, which may determine the winter survival and early-spring re-growth of Q. aquifolioides shrubs at high elevation, leading to the formation of the uppermost distribution limit. This result is consistent with a recent hypothesis for the alpine treeline formation.

Show MeSH
Mean concentrations of soluble sugars (dark gray), starch (white), and non-structural carbohydrates (NSC = soluble sugars+starch) in tissues of Quercus aquifolioides grown at 3000 m, 3500 m, and 3950 m a.s.l. during the growing season (May–September) and the dormant season (October–April), calculated using data measured across an one-year cycle from May 2008 to April 2009.Statistical differences in means among elevations within each tissue category and season were tested by t-paired comparison. Different letters indicate statistically significant differences (p<0.05) in NSC among elevations. Standard error bars (+1SE) are given for NSC only.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC3316670&req=5

pone-0034213-g002: Mean concentrations of soluble sugars (dark gray), starch (white), and non-structural carbohydrates (NSC = soluble sugars+starch) in tissues of Quercus aquifolioides grown at 3000 m, 3500 m, and 3950 m a.s.l. during the growing season (May–September) and the dormant season (October–April), calculated using data measured across an one-year cycle from May 2008 to April 2009.Statistical differences in means among elevations within each tissue category and season were tested by t-paired comparison. Different letters indicate statistically significant differences (p<0.05) in NSC among elevations. Standard error bars (+1SE) are given for NSC only.

Mentions: Within each tissue type and elevation where plants grown, concentrations of NSC and soluble sugars in tissues tended to be higher during the dormant season than those during the growing season (Figs. 1 and 2), but tissue starch concentrations showed lower levels during the dormant season than during the growing season (Figs. 1 and 2). Concentrations of sugars peaked during winter (January), and remained at a higher level up to bud flush, and then decreased to reach a minimum level in summer (June–August), whereas starch concentrations increased after winter dormancy, and peaked during the mid-growing season (July–August), then gradually declined to reach a minimum level in deep winter and early spring (Fig. 1). Pooled data across tissue types and elevations showed, for example, that the mean concentrations of NSC and sugars were 10.63% and 5.98% during the growing season (May–September), and 12.15% and 8.69% during the winter dormancy (October–April), respectively (P<0.001 for both NSC and sugars), whereas the mean starch content was 4.65% during the growing season and 3.46% during the dormant season (P<0.001) (data not shown).


Seasonal dynamics of mobile carbon supply in Quercus aquifolioides at the upper elevational limit.

Zhu WZ, Cao M, Wang SG, Xiao WF, Li MH - PLoS ONE (2012)

Mean concentrations of soluble sugars (dark gray), starch (white), and non-structural carbohydrates (NSC = soluble sugars+starch) in tissues of Quercus aquifolioides grown at 3000 m, 3500 m, and 3950 m a.s.l. during the growing season (May–September) and the dormant season (October–April), calculated using data measured across an one-year cycle from May 2008 to April 2009.Statistical differences in means among elevations within each tissue category and season were tested by t-paired comparison. Different letters indicate statistically significant differences (p<0.05) in NSC among elevations. Standard error bars (+1SE) are given for NSC only.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3316670&req=5

pone-0034213-g002: Mean concentrations of soluble sugars (dark gray), starch (white), and non-structural carbohydrates (NSC = soluble sugars+starch) in tissues of Quercus aquifolioides grown at 3000 m, 3500 m, and 3950 m a.s.l. during the growing season (May–September) and the dormant season (October–April), calculated using data measured across an one-year cycle from May 2008 to April 2009.Statistical differences in means among elevations within each tissue category and season were tested by t-paired comparison. Different letters indicate statistically significant differences (p<0.05) in NSC among elevations. Standard error bars (+1SE) are given for NSC only.
Mentions: Within each tissue type and elevation where plants grown, concentrations of NSC and soluble sugars in tissues tended to be higher during the dormant season than those during the growing season (Figs. 1 and 2), but tissue starch concentrations showed lower levels during the dormant season than during the growing season (Figs. 1 and 2). Concentrations of sugars peaked during winter (January), and remained at a higher level up to bud flush, and then decreased to reach a minimum level in summer (June–August), whereas starch concentrations increased after winter dormancy, and peaked during the mid-growing season (July–August), then gradually declined to reach a minimum level in deep winter and early spring (Fig. 1). Pooled data across tissue types and elevations showed, for example, that the mean concentrations of NSC and sugars were 10.63% and 5.98% during the growing season (May–September), and 12.15% and 8.69% during the winter dormancy (October–April), respectively (P<0.001 for both NSC and sugars), whereas the mean starch content was 4.65% during the growing season and 3.46% during the dormant season (P<0.001) (data not shown).

Bottom Line: During the growing season, plants grown at the elevational limit did not show lower NSC concentrations compared to plants at lower elevations, but during the winter season, storage tissues, especially roots, had significantly lower NSC concentrations in plants at the elevational limit compared to lower elevations.The present results suggest the significance of winter reserve in storage tissues, which may determine the winter survival and early-spring re-growth of Q. aquifolioides shrubs at high elevation, leading to the formation of the uppermost distribution limit.This result is consistent with a recent hypothesis for the alpine treeline formation.

View Article: PubMed Central - PubMed

Affiliation: Alpine Ecosystem Observation and Experiment Station of Gongga Mountain, Institute of Mountain Hazard and Environment, Chinese Academy of Sciences, Chengdu, China. wzzhu@imde.ac.cn

ABSTRACT
Many studies have tried to explain the physiological mechanisms of the alpine treeline phenomenon, but the debate on the alpine treeline formation remains controversial due to opposite results from different studies. The present study explored the carbon-physiology of an alpine shrub species (Quercus aquifolioides) grown at its upper elevational limit compared to lower elevations, to test whether the elevational limit of alpine shrubs (<3 m in height) are determined by carbon limitation or growth limitation. We studied the seasonal variations in non-structural carbohydrate (NSC) and its pool size in Q. aquifolioides grown at 3000 m, 3500 m, and at its elevational limit of 3950 m above sea level (a.s.l.) on Zheduo Mt., SW China. The tissue NSC concentrations along the elevational gradient varied significantly with season, reflecting the season-dependent carbon balance. The NSC levels in tissues were lowest at the beginning of the growing season, indicating that plants used the winter reserve storage for re-growth in the early spring. During the growing season, plants grown at the elevational limit did not show lower NSC concentrations compared to plants at lower elevations, but during the winter season, storage tissues, especially roots, had significantly lower NSC concentrations in plants at the elevational limit compared to lower elevations. The present results suggest the significance of winter reserve in storage tissues, which may determine the winter survival and early-spring re-growth of Q. aquifolioides shrubs at high elevation, leading to the formation of the uppermost distribution limit. This result is consistent with a recent hypothesis for the alpine treeline formation.

Show MeSH