CO2浓度、氮和水分对春小麦光合、蒸散及水分利用效率的影响

研究了不同土壤氮和土壤水分条件下,大气CO₂浓度升高对春小麦光合作用、气孔导度、蒸散和水分利用效率的影响.结果表明,CO₂浓度升高,干旱处理的春小麦(Triticum aestivum L.)叶片光合作用速率幅度增加大于湿润处理,随着氮肥用量增加光合速率相应增加,而不施氮肥增加有限;干旱处理气孔导度幅度减少大于湿润处理,不施氮肥的大于氮肥充足的.CO₂浓度升高,干旱处理的蒸散量减少比湿润处理多,不施氮肥的蒸散量减少较为明显;但干旱处理单叶WUE增加大于湿润处理;随着氮肥用量增加,冠层WUE提高,而不施氮肥的冠层WUE最低.因而CO₂浓度升高、光合速率增加和蒸散量减少会减缓干旱的不利影响,增强作物对干旱胁迫的抵御能力.     

干旱、CO2和温度升高对春小麦光合、蒸发蒸腾及水分利用效率的影响

研究了干旱、CO₂浓度和温度升高对春小麦生育期、光合速率(P_n)、蒸发蒸腾(ET)及水分利用效率(WUE)的影响.结果表明,大气CO₂浓度升高(550、700μmol·mol^-1)虽可延长抽穗成熟期,但高温(日平均温度高于正常日平均温度约4.8℃)对生育期的影响远大于高CO₂影响,使得高CO₂、高温下抽穗成熟期缩短,且种子提前萌发;CO₂浓度升高和高温共同作用使各水分处理的小麦光合增强、气孔阻力增加、叶片水平的水分利用效率(WUEl)和群体水平的水分利用效率(WUE)增大,但对蒸腾速率影响不显著.对蒸发蒸腾的影响因不同的土壤水分而不同,在高(田间持水量的75%～85%)、中(田间持水量的55%～65%)水分条件下,高温和高CO₂使蒸发蒸腾增加,而在低水分条件(田间持水量的35%～45%)下,高温和高CO₂使蒸发蒸腾减少.     

CO2 effects on the water budget of grassland microcosm communities

Experimental grassland ecosystems, in microcosms 0.2 m in diameter and with a 0.95 m soil column, varied in their responses to elevated partial pressure of CO₂ (pCO₂) and altered moisture inputs. Ecosystems on moderately fertile sandstone soil and with a typical mix of moderately fast-growing sandstone species, responded to elevated pCO₂ with decreases in mid-season evapotranspiration of nearly 50%. This pattern reversed at the end of the growing season, and sandstone ecosystems under elevated pCO₂ continued active transpiration farther into the summer drought. The sandstone ecosystems appeared to convert mid-season water conservation into increased late-season growth. Effects of increased pCO₂ on ecosystem evapotranspiration were much smaller in ecosystems with very infertile serpentine soil and a diverse mixture of slow-growing serpentine species.     

Temperature and moisture sensitivities of CO2 efflux from lowland and alpine meadow soils

Aims This study was conducted to (i) determine if soil CO₂ efflux is more sensitive to temperature changes in alpine areas than in lowland grasslands, (ii) examine the effects of temperature and moisture on soil respiration, and (iii) evaluate the potential for change in soil carbon storage in response to global warming in different grasslands in East Asia.Methods We collected soil samples from two different temperate grasslands, an alpine meadow on the Qinghai-Tibetan plateau, China, and a lowland grassland in Tsukuba, Japan. The CO₂ emission rate was then measured for these soil samples after they were incubated at 25°C and 60% of the water holding capacity for 7 days.Important findings (i)?The soil respiration rate was more sensitive to temperature change in the alpine soil than in the lowland soil. The average Q 10 was 7.6 for the alpine meadow soil but only 5.9 for the lowland soil. The increased sensitivity appears to be due, at least in part, to the soil organic carbon content and/or soil carbon to nitrogen ratio, especially in the surface layer. (ii) The relationship between the CO₂ emission rate and the soil moisture content revealed that the alpine meadow had a more clear response than the lowland soil. (iii) This study suggests that changes in soil moisture and soil temperature may have larger impacts on soil CO₂ efflux in the alpine meadow than in the lowland grassland evaluated here.     

施用竹叶生物质炭对板栗林土壤CO2通量和活性有机碳库的影响

于2012年7月—2013年7月,在浙江省临安市典型板栗林样地采用静态箱-气相色谱法测定了施用竹叶生物质炭后板栗林土壤CO₂排放速率及土壤温度、含水量、水溶性有机碳(WSOC)和微生物生物量碳(MBC)含量变化.结果表明： 板栗林土壤CO₂排放通量呈现显著的季节性变化特征.在试验的第1个月中,生物质炭处理土壤CO₂排放通量显著高于对照(无生物质炭),但之后无显著差异;生物质炭处理的土壤CO₂通量年均值和年累积排放量与对照相比无显著差异.生物质炭处理土壤MBC含量年均值(362 mg·kg^-1)显著高于对照(322 mg·kg^-1),而土壤WSOC年均值无显著差异.土壤CO₂排放通量与不同土层土壤温度之间均具有显著相关性;生物质炭处理的土壤呼吸温度敏感系数Q₁₀值显著高于对照;土壤CO₂排放通量与WSOC含量之间具有显著相关性,而与土壤含水量和MBC含量均无显著相关性.综上所述,施用竹叶生物质炭对板栗林土壤CO₂年累积排放量无显著影响,但增加了土壤Q₁₀值;土壤温度和WSOC含量是影响板栗林土壤CO₂排放的主要因素.     

Effects of elevated carbon dioxide concentration and soil temperature on the growth and biomass responses of mountain maple (Acer spicatum) seedlings to light availability

Aims Some shade-tolerant understory tree species such as mountain maple (Acer spicatum L.) exhibit light-foraging growth habits. Changes in environmental conditions, such as the rise of carbon dioxide concentration ([CO₂]) in the atmosphere and soil warming, may affect the performance of these species under different light environments. We investigated how elevated [CO₂] and soil warming influence the growth and biomass responses of mountain maple seedlings to light availability.Methods The treatments were two levels of light (100% and 30% of the ambient light in the greenhouse), two [CO₂] (392 μmol mol^-1 (ambient) and 784 μmol mol^-1 (elevated)) and two soil temperatures (T soil) (17 and 22°C). After one growing season, we measured seedling height, root collar diameter, leaf biomass, stem biomass and root biomass.Important findings We found that under the ambient [CO₂], the high-light level increased seedlings height by 70% and 56% at the low T soil and high T soil, respectively. Under the elevated [CO₂], however, the high-light level increased seedling height by 52% and 13% at the low T soil and high T soil, respectively. The responses of biomasses to light generally followed the response patterns of height growth under both [CO₂] and T soil and the magnitude of biomass response to light was the lowest under the elevated [CO₂] and warmer T soil. The results suggest that the elevated [CO₂] and warmer T soil under the projected future climate may have negative impact on the colonization of open sites and forest canopy gaps by mountain maple.     

CO2加富下水氮耦合对黄瓜叶片光合作用和超微结构的影响

以‘津优35号’黄瓜为试材,采用裂区-再裂区设计,研究了CO₂加富下水氮耦合对黄瓜叶片光合作用和超微结构的影响.主区设大气CO₂浓度(400 μmol·mol^-1,A)和加富CO₂浓度(800±20 μmol·mol^-1,E)2个CO₂浓度处理,裂区设无干旱胁迫(田间持水量的95%,W)和干旱胁迫(田间持水量的75%,D)2个水分处理,再裂区设施氮量450 kg·hm^-2(低氮,N₁)和900 kg·hm^-2(高氮,N₂)2个氮素处理.结果表明: 在干旱和高氮条件下,CO₂加富提高了黄瓜的株高,且使高氮下的叶面积显著增加.正常灌溉条件下,高氮处理的光合速率、气孔导度和蒸腾速率高于低氮处理,而干旱条件下则相反;CO₂加富提高了黄瓜叶片的水分利用效率,并且随着施氮量的增加,其水分利用效率提高.干旱胁迫下,黄瓜近轴面气孔密度增加,而CO₂加富和高氮却显著降低了气孔密度.高氮处理增加了黄瓜叶片叶绿体数量而减少了淀粉粒数量,干旱胁迫使叶绿体数量减少,但使淀粉粒数量呈上升趋势.干旱胁迫增加了叶绿体长度和宽度,显著增加了淀粉粒的大小,而高氮降低了叶绿体和淀粉粒的长度和宽度.CO₂加富和高氮均使基粒厚度和片层数增加(ADN₂除外),并且EDN₂处理的片层数显著高于ADN₂.综上所述,CO₂加富和适宜的水、氮条件能促进黄瓜叶片叶绿体类囊体膜系的发育,显著增加基粒厚度和基粒片层数,有效改善黄瓜的叶绿体结构,增强光合性能,提高黄瓜植株对CO₂和水、氮的吸收利用能力.     

大气CO2浓度升高对绿豆叶片光合作用及叶绿素荧光参数的影响

利用FACE系统在大田条件下通过盆栽试验研究了大气CO₂浓度升高\[CO₂浓度平均为（550±60) μmol·mol^-1\]对绿豆叶片光合生理和叶绿素荧光参数的影响.结果表明： 与对照\[CO₂浓度平均为（389±40）μmol·mol^-1左右\]相比,大气CO₂浓度升高使花荚期绿豆叶片净光合速率(P_n)和胞间CO₂浓度(C_i)分别升高11.7%和9.8%,气孔导度(G_s)和蒸腾速率(T_r)分别下降32.0%和24.6%, 水分利用效率(WUE)提高83.5%;在蕾期,CO₂浓度升高对绿豆叶片叶绿素初始荧光(F_o)、最大荧光（F_m）、可变荧光（F_v）、F_v/F_m和F_v/F_o没有显著影响;在鼓粒期,CO₂浓度升高使绿豆叶片F_o增加19.1%,F_m和F_v分别下降9.0%和14.3%,F_v/F_o和F_v/F_m分别下降25.8%和6.2%.表明大气CO₂浓度升高可能使绿豆生长后期光系统Ⅱ反应中心结构受到破坏,叶片的光合能力下降.     

CO2加富下水氮耦合对黄瓜叶片光合作用和超微结构的影响

以‘津优35号’黄瓜为试材,采用裂区-再裂区设计,研究了CO₂加富下水氮耦合对黄瓜叶片光合作用和超微结构的影响.主区设大气CO₂浓度(400 μmol·mol^-1,A)和加富CO₂浓度(800±20 μmol·mol^-1,E)2个CO₂浓度处理,裂区设无干旱胁迫(田间持水量的95%,W)和干旱胁迫(田间持水量的75%,D)2个水分处理,再裂区设施氮量450 kg·hm^-2(低氮,N₁)和900 kg·hm^-2(高氮,N₂)2个氮素处理.结果表明: 在干旱和高氮条件下,CO₂加富提高了黄瓜的株高,且使高氮下的叶面积显著增加.正常灌溉条件下,高氮处理的光合速率、气孔导度和蒸腾速率高于低氮处理,而干旱条件下则相反;CO₂加富提高了黄瓜叶片的水分利用效率,并且随着施氮量的增加,其水分利用效率提高.干旱胁迫下,黄瓜近轴面气孔密度增加,而CO₂加富和高氮却显著降低了气孔密度.高氮处理增加了黄瓜叶片叶绿体数量而减少了淀粉粒数量,干旱胁迫使叶绿体数量减少,但使淀粉粒数量呈上升趋势.干旱胁迫增加了叶绿体长度和宽度,显著增加了淀粉粒的大小,而高氮降低了叶绿体和淀粉粒的长度和宽度.CO₂加富和高氮均使基粒厚度和片层数增加(ADN₂除外),并且EDN₂处理的片层数显著高于ADN₂.综上所述,CO₂加富和适宜的水、氮条件能促进黄瓜叶片叶绿体类囊体膜系的发育,显著增加基粒厚度和基粒片层数,有效改善黄瓜的叶绿体结构,增强光合性能,提高黄瓜植株对CO₂和水、氮的吸收利用能力.     

施用竹叶生物质炭对板栗林土壤CO2通量和活性有机碳库的影响

于2012年7月—2013年7月,在浙江省临安市典型板栗林样地采用静态箱-气相色谱法测定了施用竹叶生物质炭后板栗林土壤CO₂排放速率及土壤温度、含水量、水溶性有机碳(WSOC)和微生物生物量碳(MBC)含量变化.结果表明： 板栗林土壤CO₂排放通量呈现显著的季节性变化特征.在试验的第1个月中,生物质炭处理土壤CO₂排放通量显著高于对照(无生物质炭),但之后无显著差异;生物质炭处理的土壤CO₂通量年均值和年累积排放量与对照相比无显著差异.生物质炭处理土壤MBC含量年均值(362 mg·kg^-1)显著高于对照(322 mg·kg^-1),而土壤WSOC年均值无显著差异.土壤CO₂排放通量与不同土层土壤温度之间均具有显著相关性;生物质炭处理的土壤呼吸温度敏感系数Q₁₀值显著高于对照;土壤CO₂排放通量与WSOC含量之间具有显著相关性,而与土壤含水量和MBC含量均无显著相关性.综上所述,施用竹叶生物质炭对板栗林土壤CO₂年累积排放量无显著影响,但增加了土壤Q₁₀值;土壤温度和WSOC含量是影响板栗林土壤CO₂排放的主要因素.     

Changes in leaf nutrient traits and photosynthesis of four tree species: effects of elevated [CO2], N fertilization and canopy positions

Aims Leaf traits of trees exposed to elevated [CO₂] in association with other environmental factors are poorly understood in tropical and subtropical regions. Our goal was to investigate the impacts of elevated [CO₂] and N fertilization on leaf traits in southern China.Methods Four tree species, Schima superba Gardn. et Champ. (S. superba), Ormosia pinnata (Lour.) Merr (O. pinnata), Castanopsis hystrix AC. DC. (C. hystrix) and Acmena acuminatissima (Blume) Merr. et Perry (A. acuminatissima) were studied in a factorial combination of atmospheric [CO₂] (ambient at ~390 μmol mol ? 1 and elevated [CO₂] at ~700 μmol mol^-1) and N fertilization (ambient and ambient + 100 kg N ha^-1 yr^-1) in open-top chambers in southern China for 5 years. Leaf mass per unit leaf area (LMA), leaf nutrient concentration and photosynthesis (A sat) were measured.Important findings Results indicated that leaf traits and photosynthesis were affected differently by elevated [CO₂] and N fertilization among species. Elevated [CO₂] decreased LMA in all species, while N fertilization did not affect LMA. Leaf mass-based N concentration (N M) was significantly greater in O. pinnata and C. hystrix grown in elevated [CO₂] but was lower in S. superba. Leaf mass-based P concentration (P M) was significantly greater in C. hystrix and A. acuminatissima exposed to elevated [CO₂] but was lower in S. superba. N fertilization significantly increased P M in O. pinnata but decreased P M in S. superba. Photosynthetic stimulation in O. pinnata, C. hystrix and A. acuminatissima was sustained after 5 years of CO₂ fumigation. N fertilization did not modify the effects of elevated [CO₂] on photosynthesis. Leaf traits (N M, N A, P M, P A) and light-saturated photosynthesis were decreased from the upper to lower canopy. Canopy position did not alter the responses of leaf traits and photosynthesis to elevated [CO₂]. Results suggest that photosynthetic stimulation by elevated [CO₂] in native species in subtropical regions may be sustained in the long term.     

Effects of CO2 enrichment on soluble amino acids and organic acids in barley primary leaves as a function of age, photoperiod and chlorosis

Responses of soluble amino acids and organic acids to either ambient (36 Pa) or elevated (100 Pa) CO₂ treatments were determined using barley primary leaves (Hordeum vulgare L. cv. Brant). Total soluble amino acids were increased 33% by CO₂ enrichment 9 days after sowing (DAS), but a decrease relative to the ambient CO₂ treatment was observed with increasing leaf age. Marked declines of glutamine and asparagine were observed under CO₂ enrichment, both diurnally and with advancing leaf age. Consequently, total soluble amino acids were 59% lower in the elevated compared to the ambient CO₂ treatment 17 DAS. It was likely that chlorosis in response to CO₂ enrichment negatively impacted soluble amino acid levels in older barley primary leaves. In contrast to the ambient CO₂ treatment, glutamine and most other soluble amino acids decreased as much as 60% during the latter half of a 12 h photoperiod in primary leaves of 13-day-old seedlings grown under enhanced CO₂. Malate was decreased about 9 percent by CO₂ enrichment and citrate and succinate were increased by similar amounts when measured 9 and 13 DAS. Malate accumulation was also decreased about 20% by CO₂ enrichment on a diurnal basis. The onset of CO₂-dependent leaf yellowing had much less of an effect on organic acids than on soluble amino acids. This above results emphasized the sensitivity of N metabolism to CO₂ enrichment in barley. Increased levels of citrate and succinate in response to CO₂ enrichment suggested that the tricarboxylic acid cycle was upregulated in barley by CO₂ enrichment. In summary, organic and amino acid levels in barley primary leaves were dynamic and were altered by age, diurnally and in response to CO₂ enrichment.     

大气CO2浓度升高对干旱条件下冬小麦叶片光合适应的影响

大气CO₂浓度升高是全球气候变化的主要特征,但大气CO₂浓度长期升高条件下冬小麦叶片发生光合适应的机制尚不十分清楚。本研究以盆栽冬小麦‘郑麦9023’为试验材料,在人工气候控制室内设置2个CO₂浓度(400和600 μmol·mol^-1)、2个水分条件(田间持水量的80%±5%和55%±5%),测定拔节期和抽穗期的光合特征曲线、叶绿素荧光动力学参数、叶氮含量和收获后的籽粒产量等指标,探讨干旱条件下库源关系改变对叶片光合适应的影响。结果表明: 在小麦拔节期,干旱条件下CO₂浓度升高处理的小麦PSⅡ实际光化学效率没有显著增加,但通过提升最大电子传递速率和电子向光化学方向的传递比例,增强了Rubisco的羧化速率,从而提高了最大净光合速率;在抽穗期,功能叶最大电子传递速率和电子向光化学方向的传递比例虽然较高,但PSⅡ实际光化学转换效率降低,Rubisco羧化速率和丙糖磷酸利用效率下降,以致最大净光合速率降低。干旱条件下,CO₂浓度升高增加了小麦单茎生物量、单穗粒数和穗粒重,降低了不孕小穗数,提高了籽粒产量。土壤干旱条件下,CO₂浓度升高对收获期小麦单茎籽粒产量的促进作用可能主要来自于生长前期的光合产物积累。生长后期光合适应发生的主要原因是功能叶PSⅡ实际光化学转换效率和丙糖磷酸利用效率的降低,而不是最大电子传递速率、光化学方向的电子传递比例和新叶库强的变化。     

控墒补灌对新疆春玉米产量和穗叶光合特性的影响

为探讨北疆绿洲区滴灌春玉米的高产栽培水分管理模式,以‘郑单958’(ZD958)和‘垦玉2号’(KY02)为试验材料,研究了控墒补灌对滴灌春玉米大喇叭口期(V12)至蜡熟期(R5)叶片SPAD值以及灌浆期(R3)穗叶色素、光合和荧光等参数的影响.结果表明: 土壤墒度过低或过高均会显著(P<0.05)降低V12-R3期叶片SPAD值,R5期宜保持在田间持水量的65%以上.灌浆期土壤墒度<75%时玉米叶绿素a、b及叶绿素总含量、类胡萝卜素、叶绿素a/b显著下降,但土壤墒度>85%时差异并不显著;土壤墒度<75%时玉米净光合速率(P_n)、蒸腾速率(T_r)及气孔导度(g_s)显著下降,胞间CO₂浓度(C_i)显著上升,但土壤墒度>85%时并未观察到g_s的降低.土壤墒度过高或过低均可显著降低最大光化学效率(F_v/F_m)、潜在活性(F_v/F_o)、PSⅡ实际光化学效率(Φ_PSⅡ)、光化学淬灭(q_P)和光合电子传递速率(rETR)等荧光参数,热耗散量子比率(F_o/F_m)、非光化学淬灭(NPQ)显著升高;通径分析发现,P_n降低主要由F_v/F_o和rETR的下降导致,最终表现为产量的降低.这表明各生育时期土壤墒度保持在V6>60%、V12 >70%、R1 >75%、R3 >80%、R5 >65%是本地区滴灌春玉米获得高产的最佳水分管理模式.     

Empirical relationship between specific leaf area and thermal dissipation of Phragmites australis in salt marshes of Qinwangchuan

Aims The correlation between specific leaf area (SLA) and thermal dissipation reflects not only the accumulation and dissipation of plant photosynthesis, but also plants’ adaptation to their habitats and changing environment. The objective of this study is to examine the correlation between SLA and thermal dissipation of reed (Phragmites australis) under different soil moisture conditions and salt contents.Methods Our study site was located in the National Wetland Park in Qinwangchuan, Gansu Province, China. Our sampling site extends from the edge to the central of a salt marsh where the reed was the single dominant species. The study site was divided into three zones based on the distance from the water. Within each zone, six 2 m × 2 m sampling plots were randomly located to select six reed individuals in each plot (total = 18). Vegetation height, aboveground biomass, soil moisture, and soil electrical conductivity (EC) were measured, with the six reed individuals taken to the laboratory to measure leaf thickness. Leaf net photosynthetic rate (P_n), transpiration rate (T_r), and other parameters of the reeds were also measured in each plot prior to harvesting. Quantitative measures of chlorophyll fluorescence were taken after 30-min dark adaptation. Quadrat survey method was used to model the empirical relationship between the transpiration rate and leaf characteristics.Important findings Vegetation height and aboveground biomass increased with soil moisture content, but EC and photosynthetically active radiation decreased. Leaf area, T_r and P_n increased along the gradient, leaf thickness showed decreasing, but the increasing trend of SLA switched to a decreasing trend, while leaf dry mass presented an opposite trend. From plot I to III, the quantum yield of regulated energy dissipation (Y(NPQ)) and non-photochemical quenching decreased, the actual photochemical efficiency of PSII and photochemical quenching increased, and quantum yield of non-regulated energy dissipation increased before decreasing. There appeared a highly significant negative correlation (p < 0.01) between SLA and Y(NPQ) at plot I and III, and a less significant negative correlation (p < 0.05) at plot II. Along the soil moisture gradient, reed seemed using light effectively by changing leaf thermal dissipation through adjusting their leaf size and SLA—A potential self-protection mechanism in light of adapting the habitat.     

N availability does not modify plant-mediated responses of Trichoplusia ni to elevated CO2

Aims Elevated CO₂ and increased N availability can alter a variety of plant physiological processes leading to changes in the nutritional quality of leaf tissue for herbivores. Numerous experiments have examined the responses of herbivores to environmental change; however the potential effects of simultaneous change in multiple factors on leaf-chewing insect herbivores are less well understood. The plant-mediated effects of elevated CO₂ and high N on the performance of a generalist leaf-chewing insect herbivore, Trichoplusia ni, were investigated.Methods Newly hatched T. ni larvae were introduced to Amaranthus viridis and Polygonum persicaria plants grown under ambient and elevated CO₂ and low and high N conditions. Insect performance was assessed by measuring larvae weight after ten days of feeding. Plant photosynthesis, biomass, leaf area and specific leaf weight were measured to determine the effects of elevated CO₂, N and insect feeding on plant performance.Important findings Elevated CO₂ did not have strong effects on plant or insect performance, only affecting a few responses under low or high N conditions, but not both. Growth under high nitrogen improved almost all measures of plant performance. Trichoplusia ni performed significantly better on Amaranthus viridis (C 4) compared to Polygonum persicaria (C 3), despite similar leaf C:N ratios in both species. The performance of T. ni caterpillars was only improved by the high nitrogen treatment when they were feeding on P. persicaria, the host they performed poorly on. The only interactions between N and CO₂ affecting plant performance were seen for leaf photosynthesis of P. persicaria and leaf area of A. viridis. Contrary to the predictions, there were no significant CO₂ by N interactions affecting T. ni performance.     

不同化学性质叶凋落物添加对土壤有机碳矿化及激发效应的影响

凋落物输入可显著影响土壤有机碳(SOC)矿化速率,但添加不同化学性质叶凋落物对土壤有机碳矿化释放CO₂及激发效应的影响及其机理仍不清楚。本研究将亚热带6种树种¹³C标记的叶凋落物添加至天然次生林0～10 cm原位土柱中,比较不同树种叶凋落物添加对土壤总CO₂、外源凋落物和土壤来源CO₂释放速率和累积量以及激发效应的影响,并量化叶凋落物化学性质与土壤CO₂释放累积量、激发效应的相关关系。结果表明: 添加叶凋落物能够显著提高土壤总CO₂和土壤来源CO₂释放量,存在显著正激发效应,激发效应值为68%～128%。不同树种叶凋落物添加对土壤有机碳矿化和激发效应的影响存在显著差异。Pearson相关分析和逐步多元线性回归分析发现,凋落物来源CO₂释放累积量与叶凋落物C、P和纤维素含量呈显著负相关,而土壤来源CO₂释放量与叶凋落物C:N和木质素:N呈显著正相关。综上,不同化学性质的叶凋落物对土壤有机碳矿化和激发效应的影响存在异质性,在亚热带地区森林类型转变过程中营造具有高质量叶凋落物的人工林将有助于减少森林土壤碳损失。     

Soil respiration associated with plant succession at the meadow steppes in Songnen Plain,Northeast China

Aims Soil CO₂ emission from steppes is affected by soil properties and vegetation in different successional stages. Primary and secondary succession of plants frequently occurred at the meadow steppe in Songnen Plain, Northeast China, which indicates the large uncertainty associated with CO₂ emission in this environment. This study aims to investigate the temporal variations of soil respiration (Rs) and the effect of plant succession on cumulative soil CO₂ emission during the growing season.Methods Using a LI-6400 soil CO₂ flux system, Rs of five vegetation types which represented different stages of plant succession in meadow steppes of Songnen Plain, China, was investigated during the growing seasons of 2011 and 2012.Important findings Soil temperature (Ts) was the dominant controlling factor of Rs, which could explain ~64% of the change in CO₂ fluxes. The Q 10 values of Rs were ranged from 2.0 to 6.7, showing a decreasing trend with the plant successional stages. The cumulative CO₂ emission increased with the degree of vegetation succession and it averaged to 316±6g C m ?2 (ranges: 74.8±6.7 to 516.5±11.4g C m ?2) during the growing season. The magnitude of soil CO₂ emission during the growing season was positively correlated with aboveground plant biomass, soil organic carbon content and mean soil water content, while negatively linked to mean Ts, pH, electrical conductivity and exchangeable sodium percentages. The results implied that soil CO₂ emission increased with the development of plant communities toward more advanced stages. Our findings provided valuable information for understanding the variations of CO₂ emission in the process of vegetation succession.     

Correlation between vein density and water use efficiency of Salix matsudana in Zhangye Wetland,China

Aims The correlation between vein density and water use efficiency (WUE) affects the balance between water supply and demand of plant leaves, which is significant for comprehending the ecological adaptation strategies of plants. The objective of this study was to study how Salix matsudana modulated vein density and WUE along a soil moisture gradient in Zhangye Wetland, China. Methods The study was conducted in floodplain wetland near Heihe River in Zhangye City, Gansu Province, China. Three sample plots, at a spatial interval of 70 m, were set up along a soil moisture gradient ordinally from the area near the water body to the wetland edge, plot I (69.23%), spot II (48.38%) and spot III (35.27%). Community traits were investigated by using diagonal method, and all individuals of S. matsudana were used for measurements of height and canopy. At each plot, 5 individuals of S. matsudana at 4 vertices and diagonal intersection were selected for measurements of vein density, WUE, net photosynthetic rate (P_n), transpiration rate (T_r), photosynthetically active radiation (PAR), saturated vapor pressure differences (VPD), specific leaf area, stomatal conductance (G_s) and intercellular CO₂ concentration (C_i). We used mathematical methods of correlation analysis and standardized major axis to investigate relationships between vein density and WUE. Important findings With decreasing soil moisture, the height, canopy, specific leaf area, G_s and C_i of S. matsudana decreased gradually, while the vein density, WUE, P_n, T_r, PAR and VPD increased gradually. The correlation between vein density and WUE was positive in all the three plots, but the relationship varied along the soil moisture plots gradient. There was a highly significant positive correlation (p < 0.01) between the vein density and WUE at plot I and III, whereas the correlation only reached a significant level (p < 0.05) at plot II; The correlation coefficient between vein density and WUE is significantly smaller than 1 at plot I (p < 0.05), while the correlation coefficient is significant greater than 1 at plot II and III (p < 0.05). We can conclude that varied relationships between vein density and WUE of S. matsudana along a soil moisture gradient could reflect plant acclimation.     

根际CO2浓度富集对番茄光合生理的影响

本文采用气雾法栽培方式,研究了60 d根际CO₂浓度富集处理对番茄光合生理的影响.结果表明： 2500 μL·L^–1及以上CO₂浓度处理下,番茄植株叶片叶绿素含量、叶面积显著降低,叶片Mg²⁺ ATPase、Ca²⁺ ATPase和磷酸烯醇式丙酮酸羧化酶(PEPC)活性显著减少,而根系PEPC活性显著增加,叶片净光合速率、气孔导度和胞间CO₂浓度均显著降低.表明根际高CO₂浓度条件下,根系PEPC活性增强、叶片固定CO₂的能力减弱、叶片Mg^2+ ATPase和Ca²⁺ ATPase活性显著降低,根际长期高CO₂浓度处理可能是导致植株光合生理指标下降的原因之一.