Improving radiation use efficiency （RUE） of the canopy is necessary to increase wheat （Triticum aesfivum） production. Tridimensional uniform sowing （U） technology has previously been used to construct a uniforml...Improving radiation use efficiency （RUE） of the canopy is necessary to increase wheat （Triticum aesfivum） production. Tridimensional uniform sowing （U） technology has previously been used to construct a uniformly distributed population structure that increases RUE. In this study, we used tridimensional uniform sowing to create a wheat canopy within which light was spread evenly to increase RUE. This study was done during 2014-2016 in the Shunyi District, Beijing, China. The soil type was sandy loam. Wheat was grown in two sowing patterns： （1） tridimensional uniform sowing （U）; （2） conventional drilling （D）. Four planting densities were used： 1.8, 2.7, 3.6, and 4.5 million plants ha-1. Several indices were measured to compare the wheat canopies： photosynthetic active radiation intercepted by the canopy （IPAR）, leaf area index （LAI）, leaf mass per unit area （LMA）, canopy extinction coefficient （K）, and RUE. In two sowing patterns, the K values decreased with increasing planting density, but the K values of U were lower than that of D. LMA and IPAR were higher for U than for D, whereas LAI was nearly the same for both sowing patterns. IPAR and LAI increased with increasing density under the same sowing pattern. However, the difference in IPAR and LAI between the 3.6 and 4.5 million plants ha-1 treatments was not significant for both sowing patterns. Therefore, LAI within the same planting density was not affected by sowing pattern. RUE was the largest for the U mode with a planting density of 3.6 million plants ha-1 treatment. For the D sowing pattern, the lowest planting density （1.8 million plants ha-1） resulted in the highest yield. Light radiation interception was minimal for the D mode with a planting density of 1.8 million plants ha-1 treatment, but the highest RUE and highest yield were observed under this condition. For the U sowing pattern, IPAR increased with increasing planting density, but yield and RUE were the highest with a planting density of 3.6 million plants ha-1. These results indicated that the optimal planting density for improving the canopy light environment differed between the sowing patterns. The effect of sowing patternxplanting density interaction on grain yield, yield components, RUE, IPAR, and LMA was significant （P〈0.05）. Correlation analysis indicated that there is a positive significant correlation between grain yield and RUE （t=0.880, P〈0.01）, LMA （r=0.613, P〈0.05）, andspike number （t=0.624, P〈0.05）. These results demonstrated that the tridimensional uniform sowing technique, particularly at a planting density of 3.6 million plants ha-0, can effectively increase light interception and utilization and unit leaf area. This leads to the production of more photosynthetic products that in turn lead to significantly increased spike number （P〈0.05）, kernel number, grain weight, and an overall increase in yield.展开更多
Aims With a close association with plant water availability,foliar δ^(13)C had been investigated extensively in alpine regions;however,foliar δ^(15)N has rarely been concurrently used as an indicator of plant nitrog...Aims With a close association with plant water availability,foliar δ^(13)C had been investigated extensively in alpine regions;however,foliar δ^(15)N has rarely been concurrently used as an indicator of plant nitrogen availability.Due to the positive correlations between leaf nitrogen con-tent and foliar δ^(13)C andδ15N found in previous studies,we expected that they should show consistent patterns along an altitudinal gradient.Methods To test our hypothesis,we measured foliar δ^(13)C andδ15N in conjunc-tion with multiple key leaf functional traits of Quercus aquifolioides,a dominant species of alpine forest on the eastern slopes of the sygera mountains,southeastern Tibetan Plateau from 2500 to 3800 m.Important findings(i)Contrary to our hypothesis,foliar δ^(13)C exhibited a significant pos-itive linear relationship with altitude;in contrast,foliarδ15N initially increased and subsequently decreased with altitude,the change in trend occurring around 3300 m.(ii)our analyses indicated that leaf internal resistance and stomatal conductance,rather than photosynthetic capacity indicated by leaf N concentration,appar-ently explained the altitudinal variation in foliar δ^(13)C,while differ-ences in foliar δ^(15)N were likely the result of soil N availability.(iii)Principal component analysis revealed a clear association between δ^(13)C and a tradeoff between water loss and carbon gain,indicated by traits related to gas exchange such as leaf thickness,density,sto-matal properties.In contrast,the second axis was associated withδ15N and nitrogen acquisition strategy in Q.aquifolioides across its altitudinal distribution,represented by traits related to nitrogen concentration and stomata per gram of leaf nitrogen.展开更多
Aims Both dominance distribution of species and the composition of the dominant species determine the distribution of traits within community.Leaf carbon(C)and nitrogen(N)isotopic composition are important leaf traits...Aims Both dominance distribution of species and the composition of the dominant species determine the distribution of traits within community.Leaf carbon(C)and nitrogen(N)isotopic composition are important leaf traits,and such traits of dominant species are associated with ecosystem C,water and N cycling.Very little is known how dominant species with distinct traits(e.g.N-fixing leguminous and non-leguminous trees)mediate resource utilization of the ecosystems in stressful environment.Methods Leaves of 81 dominant leguminous and non-leguminous trees were collected in forest(moist semi-deciduous and dry semi-deciduous ecosystems)and savanna(costal savanna,Guinean savanna and west Sudanian savanna ecosystems)areas and the transitional zone(between the forest and the savanna)along the transect from the south to the north of Ghana.We measured leaf traits,i.e.leafδ13C,leafδ15N,leaf water content,leaf mass per area(LMA)and C and N concentration.Correlation analyses were used to examine trait–trait relationships,and relationships of leaf traits with temperature and precipitation.We used analysis of covariance to test the differences in slopes of the linear regressions between legumes and non-legumes.Important Findings Leafδ13C,δ15N,leaf water content and LMA did not differ between leguminous and non-leguminous trees.Leaf N concentration and C:N ratio differed between the two groups.Moreover,leaf traits varied significantly among the six ecosystems.δ13C values were negatively correlated with annual precipitation and positively correlated with mean annual temperature.In contrast,leafδ15N of non-leguminous trees were positively correlated with annual precipitation and negatively correlated with mean annual temperature.For leguminous trees,such correlations were not significant.We also found significant coordination between leaf traits.However,the slopes of the linear relationships were significantly different between leguminous and non-leguminous trees.Our results indicate that shifts in dominant trees with distinct water-use efficiency were corresponded to the rainfall gradient.Moreover,leguminous trees,those characterized with relative high water-use efficiency in the low rainfall ecosystems,were also corresponded to the relative high N use efficiency.The high proportion of leguminous trees in the savannas is crucial to mitigate nutrient stress.展开更多
基金supported by the National Key Research and Development Program of China (2016YFD0300407)the earmarked fund for China Agriculture Research System (CARS-03)
文摘Improving radiation use efficiency （RUE） of the canopy is necessary to increase wheat （Triticum aesfivum） production. Tridimensional uniform sowing （U） technology has previously been used to construct a uniformly distributed population structure that increases RUE. In this study, we used tridimensional uniform sowing to create a wheat canopy within which light was spread evenly to increase RUE. This study was done during 2014-2016 in the Shunyi District, Beijing, China. The soil type was sandy loam. Wheat was grown in two sowing patterns： （1） tridimensional uniform sowing （U）; （2） conventional drilling （D）. Four planting densities were used： 1.8, 2.7, 3.6, and 4.5 million plants ha-1. Several indices were measured to compare the wheat canopies： photosynthetic active radiation intercepted by the canopy （IPAR）, leaf area index （LAI）, leaf mass per unit area （LMA）, canopy extinction coefficient （K）, and RUE. In two sowing patterns, the K values decreased with increasing planting density, but the K values of U were lower than that of D. LMA and IPAR were higher for U than for D, whereas LAI was nearly the same for both sowing patterns. IPAR and LAI increased with increasing density under the same sowing pattern. However, the difference in IPAR and LAI between the 3.6 and 4.5 million plants ha-1 treatments was not significant for both sowing patterns. Therefore, LAI within the same planting density was not affected by sowing pattern. RUE was the largest for the U mode with a planting density of 3.6 million plants ha-1 treatment. For the D sowing pattern, the lowest planting density （1.8 million plants ha-1） resulted in the highest yield. Light radiation interception was minimal for the D mode with a planting density of 1.8 million plants ha-1 treatment, but the highest RUE and highest yield were observed under this condition. For the U sowing pattern, IPAR increased with increasing planting density, but yield and RUE were the highest with a planting density of 3.6 million plants ha-1. These results indicated that the optimal planting density for improving the canopy light environment differed between the sowing patterns. The effect of sowing patternxplanting density interaction on grain yield, yield components, RUE, IPAR, and LMA was significant （P〈0.05）. Correlation analysis indicated that there is a positive significant correlation between grain yield and RUE （t=0.880, P〈0.01）, LMA （r=0.613, P〈0.05）, andspike number （t=0.624, P〈0.05）. These results demonstrated that the tridimensional uniform sowing technique, particularly at a planting density of 3.6 million plants ha-0, can effectively increase light interception and utilization and unit leaf area. This leads to the production of more photosynthetic products that in turn lead to significantly increased spike number （P〈0.05）, kernel number, grain weight, and an overall increase in yield.
基金This research was supported by the Program for New Century Excellent Talents in University(NCET-08-0257)the National Natural Science Foundation of China(30972337,30930072 and 31170571)Fundamental Research Funds for the Central Universities(lzujbky-2010-47 and lzujbky-2012-k20)。
文摘Aims With a close association with plant water availability,foliar δ^(13)C had been investigated extensively in alpine regions;however,foliar δ^(15)N has rarely been concurrently used as an indicator of plant nitrogen availability.Due to the positive correlations between leaf nitrogen con-tent and foliar δ^(13)C andδ15N found in previous studies,we expected that they should show consistent patterns along an altitudinal gradient.Methods To test our hypothesis,we measured foliar δ^(13)C andδ15N in conjunc-tion with multiple key leaf functional traits of Quercus aquifolioides,a dominant species of alpine forest on the eastern slopes of the sygera mountains,southeastern Tibetan Plateau from 2500 to 3800 m.Important findings(i)Contrary to our hypothesis,foliar δ^(13)C exhibited a significant pos-itive linear relationship with altitude;in contrast,foliarδ15N initially increased and subsequently decreased with altitude,the change in trend occurring around 3300 m.(ii)our analyses indicated that leaf internal resistance and stomatal conductance,rather than photosynthetic capacity indicated by leaf N concentration,appar-ently explained the altitudinal variation in foliar δ^(13)C,while differ-ences in foliar δ^(15)N were likely the result of soil N availability.(iii)Principal component analysis revealed a clear association between δ^(13)C and a tradeoff between water loss and carbon gain,indicated by traits related to gas exchange such as leaf thickness,density,sto-matal properties.In contrast,the second axis was associated withδ15N and nitrogen acquisition strategy in Q.aquifolioides across its altitudinal distribution,represented by traits related to nitrogen concentration and stomata per gram of leaf nitrogen.
基金National Natural Science Foundation of China(41271118)One-Three-Five Strategic Planning Project of Science and Technology,Chinese Academy of Sciences.
文摘Aims Both dominance distribution of species and the composition of the dominant species determine the distribution of traits within community.Leaf carbon(C)and nitrogen(N)isotopic composition are important leaf traits,and such traits of dominant species are associated with ecosystem C,water and N cycling.Very little is known how dominant species with distinct traits(e.g.N-fixing leguminous and non-leguminous trees)mediate resource utilization of the ecosystems in stressful environment.Methods Leaves of 81 dominant leguminous and non-leguminous trees were collected in forest(moist semi-deciduous and dry semi-deciduous ecosystems)and savanna(costal savanna,Guinean savanna and west Sudanian savanna ecosystems)areas and the transitional zone(between the forest and the savanna)along the transect from the south to the north of Ghana.We measured leaf traits,i.e.leafδ13C,leafδ15N,leaf water content,leaf mass per area(LMA)and C and N concentration.Correlation analyses were used to examine trait–trait relationships,and relationships of leaf traits with temperature and precipitation.We used analysis of covariance to test the differences in slopes of the linear regressions between legumes and non-legumes.Important Findings Leafδ13C,δ15N,leaf water content and LMA did not differ between leguminous and non-leguminous trees.Leaf N concentration and C:N ratio differed between the two groups.Moreover,leaf traits varied significantly among the six ecosystems.δ13C values were negatively correlated with annual precipitation and positively correlated with mean annual temperature.In contrast,leafδ15N of non-leguminous trees were positively correlated with annual precipitation and negatively correlated with mean annual temperature.For leguminous trees,such correlations were not significant.We also found significant coordination between leaf traits.However,the slopes of the linear relationships were significantly different between leguminous and non-leguminous trees.Our results indicate that shifts in dominant trees with distinct water-use efficiency were corresponded to the rainfall gradient.Moreover,leguminous trees,those characterized with relative high water-use efficiency in the low rainfall ecosystems,were also corresponded to the relative high N use efficiency.The high proportion of leguminous trees in the savannas is crucial to mitigate nutrient stress.
