不同密度红桦幼苗苗冠结构与竞争对CO2浓度升高的响应

研究了两个种植密度下,红桦 (Betula albosinensis)苗冠结构特征对CO₂浓度的响应,在此基础上探讨了CO₂浓度升高对植物竞争压力的影响。结果表明,冠幅、冠高、苗冠表面积和苗冠体积均受CO₂浓度升高的影响而增加,但是受密度增加的影响而降低。CO₂浓度升高对苗冠的促进效应在低密度条件下大于高密度处理,高密度条件下苗冠基本特征部分地受到CO₂浓度升高的促进作用;升高种植密度的效应则在高CO₂浓度条件下大于现行CO₂浓度处理。高CO₂浓度和高密度条件下,LDcpa（单位苗冠投影面积叶片数）、LDcv（单位苗冠体积叶片数） 和苗冠底部枝条的枝角均低于相应的现行CO₂浓度处理和低密度处理,这主要是由于冠幅和冠高的快速生长所造成的。升高CO₂浓度对枝条长度的影响与枝条在主茎上所处位置有关。总之,升高CO₂浓度有利于降低增加种植密度对苗冠所带来的负效应,而增加种植密度降低了升高CO₂浓度的正效应。LDcpa和LDcv的降低表明,红桦在升高CO₂浓度和种植密度的条件下,会作出积极的响应,从而缓解由于生长的增加所带来的竞争压力的增加。     

CO2浓度升高对两个种植密度下红桦生长和养分含量的影响

采用控制环境生长室,研究了CO2浓度升高对2个种植密度下红桦幼苗生长和氮(N)、磷(P)含量的影响。试验设置CO2浓度为350和700μmol.mol-12个水平,每个CO2浓度水平下又设密度28和84株.m-22个水平。结果表明:CO2浓度升高,红桦株高和叶面积指数(LAI)均增加,净同化率(NAR)值增加,叶质比(LMR)和比叶面积(SLA)均下降,但相对生长率(RGR)提高。CO2浓度增加,红桦幼苗茎枝、叶、根和总生物量提高,氮(N)、磷(P)含量降低,但单株N、P总吸收量均增加。CO2浓度升高,氮磷利用效率(NUE和PUE)提高,氮磷累积速率(NAcR和PAcR)显著增加。CO2浓度升高,红桦幼苗体内N、P浓度下降是由于生物量迅速增加引起的稀释效应造成的,而NUE和PUE的提高可以有效缓解CO2浓度升高后,亚高山和高山地区森林土壤中养分元素不足对森林生产力的限制。CO2浓度升高导致的植物生长的增加量会随植株密度的增加而降低,不同器官养分吸收量的增加量在低密度条件下比高密度条件下大得多,主要是因为高种植密度显著降低了植株各部位的干质量。     

CO2浓度和温度升高对红桦根际微生物的影响

应用自控、封闭、独立的生长室系统,研究升高的大气CO2浓度(环境CO2浓度 350(±25)μmol.mol-1,EC)和温度(环境温度 2.0(±0.5)℃,ET)及其交互作用(ECT)对不同栽植密度条件下红桦根际土壤可培养微生物数量的影响。结果表明:(1)EC显著增加了高密度条件下根际细菌数量;在整个生长季中,最大的根际细菌数量增加出现在7月份;而EC对低密度处理的根际细菌数量影响不显著。除了5月和6月份,ET在其余月份均显著增加了根际细菌数量,但是与密度处理没有有意义的相关;ECT对高低密度处理的根际细菌数量均未产生有统计意义的影响。(2)EC对低密度条件下的根际放线菌数量有显著增加,而对高密度条件下的根际放线菌数量无显著影响;ET和ECT对高低密度条件下的根际放线菌数量均未产生有统计意义的影响。(3)EC和ET对高低密度条件下的根际真菌数量无显著增加,而ECT显著增加了根际真菌数量。     

浓度升高对两个种植密度下红桦生长和养分含量的影响

采用控制环境生长室,研究了CO₂浓度升高对2个种植密度下红桦幼苗生长和氮(N)、磷(P)含量的影响。试验设置CO₂浓度为350和700 μmol·mol^-12个水平,每个CO₂浓度水平下又设密度28和84株·m^-22个水平。结果表明：CO₂浓度升高,红桦株高和叶面积指数(LAI)均增加,净同化率(NAR)值增加,叶质比(LMR)和比叶面积(SLA)均下降,但相对生长率(RGR)提高。CO₂浓度增加,红桦幼苗茎枝、叶、根和总生物量提高,氮(N)、磷(P)含量降低,但单株N、P总吸收量均增加。CO₂浓度升高,氮磷利用效率(NUE和PUE)提高,氮磷累积速率(NAcR和PAcR)显著增加。CO₂浓度升高,红桦幼苗体内N、P浓度下降是由于生物量迅速增加引起的稀释效应造成的,而NUE和PUE的提高可以有效缓解CO₂浓度升高后,亚高山和高山地区森林土壤中养分元素不足对森林生产力的限制。CO₂浓度升高导致的植物生长的增加量会随植株密度的增加而降低,不同器官养分吸收量的增加量在低密度条件下比高密度条件下大得多,主要是因为高种植密度显著降低了植株各部位的干质量。     

CO２浓度和温度升高对红桦根际微生物的影响

应用自控、封闭、独立的生长室系统,研究升高的大气CO_２浓度（环境CO_２浓度+350（±25）μmol•mol-1,EC）和温度（环境温度+2.0（±0.5）℃,ET）及其交互作用（ECT）对不同栽植密度条件下红桦根际土壤可培养微生物数量的影响。结果表明：（1）EC显著增加了高密度条件下根际细菌数量;在整个生长季中,最大的根际细菌数量增加出现在7月份;而EC对低密度处理的根际细菌数量影响不显著。除了5月和6月份,ET在其余月份均显著增加了根际细菌数量,但是与密度处理没有有意义的相关;ECT对高低密度处理的根际细菌数量均未产生有统计意义的影响。（2）EC对低密度条件下的根际放线菌数量有显著增加,而对高密度条件下的根际放线菌数量无显著影响;ET和ECT对高低密度条件下的根际放线菌数量均未产生有统计意义的影响。（3）EC和ET对高低密度条件下的根际真菌数量无显著增加,而ECT显著增加了根际真菌数量。     

大气CO2浓度升高对红桦幼苗根系的影响

应用封闭式生长室系统,研究了CO2浓度升高对红桦(Betula albosinensis)幼苗的根/冠、粗根和细根的干质量、非结构性碳水化合物类含量、碳含量和碳/氮、氮和磷的含量及氮磷吸收量的影响。结果表明:CO2浓度升高使红桦幼苗粗根和细根的干质量增加,同时根/冠值显著升高,表明CO2浓度升高使红桦幼苗生物量向根系的分配增加;与对照相比,粗根的还原糖、蔗糖和总可溶性糖含量显著增加,而在细根中没有显著变化;粗根、细根的淀粉和总的非结构性碳水化合物含量显著增加;CO2浓度升高下粗根和细根的碳含量有升高的趋势但未达到显著水平,同时氮含量降低,碳/氮值升高;氮的吸收量在粗根和细根中均无显著变化。上述结果表明,CO2浓度升高下红桦幼苗根系氮含量下降是由非结构性碳水化合物(主要是淀粉)含量升高和(或)根系生物量增加产生的稀释效应引起的。     

大气二氧化碳浓度与温度升高对红桦幼苗养分积累和分配的影响

利用封闭式生长室,研究了CO2浓度升高(环境CO2 350 μmol·mol-1,EC)、温度升高(环境温度 2 ℃,ET)以及二者同时升高(ECT)对川西亚高山红桦幼苗养分积累和分配的影响.结果表明:经过一个生长季, EC处理下红桦幼苗单株N、P、K积累比对照分别增加44%、45%和11%(P《0.05),ET处理下分别增加37%、76%和9%(P《0.05),ECT处理下分别增加24%、88%和20% (P《0.05).EC处理使N向红桦幼苗叶中分配的比例降低11.68%(P《0.05),向枝、茎、根中分配的比例分别增加2.95%、3.39%和5.34%(P》0.05);ET处理使N向叶中分配的比例增加11.09%(P《0.05),向枝、茎、根中分配的比例分别降低0.69%、10.35%和0.05%(P》0.05).ECT处理下N的分配格局与EC处理相似.3种处理下P和K在红桦幼苗中的分配变化差异较大,CO2浓度和温度升高可能促进植物养分的积累,改变养分在植物各器官间的分配.     

干旱和CO2浓度升高对干旱区春小麦气孔密度及分布的影响

 通过对不同土壤水分状况、不同CO2浓度条件下春小麦叶片气孔的观测结果表明：干旱和CO2浓度升高不仅影响叶片气孔密度,而且也影响其分布。随干旱程度的加剧,气孔密度有明显的上升趋势,气孔在叶片上的分布趋向均匀;随CO2浓度的升高,气孔密度有明显的下降趋势,其分布也趋向均匀。水分状况和CO2浓度相同时,气孔密度及分布受不同温度的影响。     

干旱和CO_2浓度升高对干旱区春小麦气孔密度及分布的影响

通过对不同土壤水分状况、不同 CO2 浓度条件下春小麦叶片气孔的观测结果表明 :干旱和 CO2 浓度升高不仅影响叶片气孔密度 ,而且也影响其分布。随干旱程度的加剧 ,气孔密度有明显的上升趋势 ,气孔在叶片上的分布趋向均匀 ;随 CO2 浓度的升高 ,气孔密度有明显的下降趋势 ,其分布也趋向均匀。水分状况和 CO2 浓度相同时 ,气孔密度及分布受不同温度的影响     

大气CO2浓度升高对不同施氮土壤酶活性的影响

利用中国唯一的无锡FACE（Free-air CO2 enrichment,开放式空气CO2浓度升高）平台,研究了大气CO2浓度升高对土壤β-葡糖苷酶、转化酶、脲酶、酸性磷酸酶、-氨基葡糖苷酶的影响。研究发现,不同氮肥处理下大气CO2浓度升高对某些土壤酶活性的影响不同。在低氮施肥处理中,大气CO2浓度升高显著降低-葡糖苷酶活性,但是在高氮施肥处理下,大气CO2浓度升高显著增加β-葡糖苷酶活性。在低氮和常氮施肥处理中大气CO2浓度升高显著增加了土壤脲酶活性,但在高氮水平下影响不显著。在低氮、常氮施肥处理中,大气CO2浓度升高对土壤酸性磷酸酶活性没有影响,而在高氮施肥处理中显著增强了土壤中磷酸酶活性。大气CO2浓度升高对土壤转化酶活性和-氨基葡糖苷酶的活性有增加趋势,但影响不显著。研究还发现,在不同的CO2浓度下,土壤酶活性对不同氮肥处理的响应也不同。在正常CO2浓度下,土壤中β-葡糖苷酶活性随着氮肥施用量的增加而降低,而在大气CO2浓度升高条件下,却随着氮肥施用量的增加而增加。在大气CO2浓度升高条件下,高氮施肥显著增加了转化酶和酸性磷酸酶活性,而在正常CO2浓度下,影响不显著。在大气CO2浓度升高条件下,氮肥处理对脲酶活性的影响不大,但在正常CO2浓度下,脲酶活性随着氮肥施用量的增加而增加。氮肥对β-氨基葡糖苷酶活性的影响不明显。     

Determination of the site of CO₂ sensing in poplar: is the area-based N content and anatomy of new leaves determined by their immediate CO₂ environment or by the CO₂ environment of mature leaves?

Exposure to an elevated CO(2) concentration ([CO(2)]) generally decreases leaf N content per unit area (N(area)) and stomatal density, and increases leaf thickness. Mature leaves can 'sense' elevated [CO(2)] and this regulates stomatal development of expanding leaves (systemic regulation). It is unclear if systemic regulation is involved in determination of leaf thickness and N(area)-traits that are significantly correlated with photosynthetic capacity. A cuvette system was used whereby [CO(2)] around mature leaves was controlled separately from that around expanding leaves. Expanding leaves of poplar (Populus trichocarpa×P. deltoides) seedlings were exposed to elevated [CO(2)] (720 μmol mol(-1)) while the remaining mature leaves inside the cuvette were under ambient [CO(2)] of 360 μmol mol(-1). Reverse treatments were performed. Exposure of newly developing leaves to elevated [CO(2)] increased their thickness, but when mature leaves were exposed to elevated [CO(2)] the increase in thickness of new leaves was less pronounced. The largest response to [CO(2)] was reflected in the palisade tissue thickness (as opposed to the spongy tissue) of new leaves. The N(area) of new leaves was unaffected by the local [CO(2)] where the new leaves developed, but decreased following the exposure of mature leaves to elevated [CO(2)]. The volume fraction of mesophyll cells compared with total leaf and the mesophyll cell density changed in a manner similar to the response of N(area). These results suggest that N(area) is controlled independently of the leaf thickness, and suggest that N(area) is under systemic regulation by [CO(2)] signals from mature leaves that control mesophyll cell division.     

Growth and Wood/Bark Properties of Abies faxoniana Seedlings as Affected by Elevated CO2

Growth and wood and bark properties of Abies faxoniana seedlings after one year's exposure to elevated CO2 concentration (ambient 350 (=1= 25) μmol/mol) under two planting densities (28 or 84 plants/mz) were investigated in closed-top chambers. Tree height, stem diameter and cross-sectional area, and total biomass were enhanced under elevated CO2 concentration, and reduced under high planting density. Most traits of stem bark were improved under elevated CO2 concentration and reduced under high planting density. Stem wood production was significantly increased in volume under elevated CO2 concentration under both densities, and the stem wood density decreased under elevated CO2 concentration and increased under high planting density. These results suggest that the response of stem wood and bark to elevated CO2 concentration is density dependent. This may be of great importance in a future CO2 enriched world in natural forests where plant density varies considerably. The results also show that the bark/wood ratio in diameter, stem cross-sectional area and dry weight are not proportionally affected by elevated CO2 concentration under the two contrasting planting densities. This indicates that the response magnitude of stem bark and stem wood to elevated CO2 concentration are different but their response directions are the same.     

Photosynthetic acclimation to elevated CO2 in a sunflower canopy

Sunflower canopies were grown in mesocosom gas exchange chambers at ambient and elevated CO2 concentrations (360 and 700 ppm) and leaf photosynthetic capacities measured at several depths within each canopy. Elevated [CO2] had little effect on whole-canopy photosynthetic capacity and total leaf area, but had marked effects on the distribution of photosynthetic capacity and leaf area within the canopy. Elevated [CO2] did not significantly reduce the photosynthetic capacities per unit leaf area of young leaves at the top of the canopy, but it did reduce the photosynthetic capacities of older leaves by as much as 40%. This effect was not dependent on the canopy light environment since elevated [CO2] also reduced the photosynthetic capacities of older leaves exposed to full sun on the south edge of the canopy. In addition to the effects on leaf photosynthetic capacity, elevated [CO2] shifted the distribution of leaf area within the canopy so that more leaf area was concentrated near the top of the canopy. This change resulted in as much as a 50% reduction in photon flux density in the upper portions of the elevated [CO2] canopy relative to the ambient [CO2] canopy, even though there was no significant difference in the total canopy leaf area. This reduction in PFD appeared to account for leaf carbohydrate contents that were actually lower for many of the shaded leaves in the elevated as opposed to the ambient [CO2] canopy. Photosynthetic capacities were not significantly correlated with any of the individual leaf carbohydrate contents. However, there was a strong negative correlation between photosynthetic capacity and the ratio of hexose sugars to sucrose, consistent with the hypothesis that sucrose cycling is a component of the biochemical signalling pathway controlling photosynthetic acclimation to elevated [CO2].     

北京地区侧柏人工林密度效应

密度是影响森林尤其是人工林生长的重要因素,林冠层是森林生态系统与其他系统进行能量和物质交换的重要场所,树木及树冠生长对林分密度的响应关系可以看作是生物对环境变化产生的适应性现象。林分密度效应是生态学和森林培育学的重要研究内容之一。以23块8种不同密度梯度的北京山区侧柏人工幼龄林林分为研究对象分析其树木生长及树冠生长对密度的响应关系,其中树冠指标使用了参照了美国林务局(USDA)的树冠调查指标。研究结果表明:(1)林分平均胸径、平均树高和平均冠幅生长均随密度增大而减小,林分密度大于3000株/hm2时各指标减小的趋势变缓,使用异速生长模型可以很好地拟合这种变化关系;(2)随密度增加,树冠水平方向和垂直方向生长均到显著地抑制作用,树冠外形表现出由饱满冠型向狭长冠型变化的适应性现象;(3)使用树冠二维、三维指标与密度进行相关性分析可知树冠长度、树冠率等指标与林分密度呈负相关关系,树冠圆满度及树冠生产效率与密度表现出极显著正相关关系;(4)采用枝解析的方法研究了树枝长度、材积的平均生长量、连年生长量与密度的关系,结果表明幼龄期各生长量差异不大;(5)在建立冠幅模型时考虑了自变量间的多重共线性问题,所建的胸径单自变量二次方模型能够很好地预测侧柏人工幼龄林冠幅生长过程,模型相关系数R2为0.961。     

Elevated CO22 and Leaf Longevity in the C44 Grassland-Dominant Andropogon gerardii

In central U.S. grasslands, plant and ecosystem responses to elevated CO2 are most pronounced when water availability is limited. In a northeast Kansas grassland, responses to elevated CO2 in leaf area, number, development, and longevity were quantified for the tallgrass prairie dominant, Andropogon gerardii. Plants were grown in open-top chambers (OTCs) modified to limit water availability and to maximize responses to elevated CO2. In OTCs with elevated (x2 ambient) levels of CO2, aboveground biomass production and leaf water potentials were increased significantly compared with those of plants in OTCs with ambient CO2. There were no differences in leaf area or leaf number per tiller in A. gerardii in elevated compared with ambient OTCs. However, leaf area in adjacent unchambered plots with greater water availability was significantly higher than in the OTCs. The time required for developing leaves to achieve maximum leaf area was reduced by 29%, and the period of time until leaves senesced was increased by 20% for plants exposed to elevated compared with ambient CO2. Thus, leaves of this C4 grass species expanded more rapidly (6 d) and remained green longer (9 d) when exposed to elevated CO2. Such CO2-mediated increases in leaf longevity in the dominant species may allow this grassland to respond more opportunistically to temporally variable rainfall patterns in high-CO2 environments. These responses should be included in leaf-based simulation models that attempt to mechanistically link physiological alterations to predicted canopy responses to increased CO2.     

Elevated CO2 induces physiological, biochemical and structural changes in leaves of Arabidopsis thaliana

Leaves of Arabidopsis thaliana grown under elevated or ambient CO2 (700 or 370 micromol mol(-1), respectively) were examined for physiological, biochemical and structural changes. Stomatal characters, carbohydrate and mineral nutrient concentrations, leaf ultrastructure and plant hormone content were investigated using atomic absorption spectrophotometry, transmission electron microscopy and enzyme-linked immunosorbent assay (ELISA). Elevated CO2 reduced the stomatal density and stomatal index of leaves, and also reduced stomatal conductance and transpiration rate. Elevated CO2 increased chloroplast number, width and profile area, and starch grain size and number, but reduced the number of grana thylakoid membranes. Under elevated CO2, the concentrations of carbohydrates and plant hormones, with the exception of abscisic acid, increased whereas mineral nutrient concentrations declined. These results suggest that the changes in chloroplast ultrastructure may primarily be a consequence of increased starch accumulation. Accelerated A. thaliana growth and development in elevated CO2 could in part be attributed to increased foliar concentrations of plant hormones. The reductions in mineral nutrient concentrations may be a result of dilution by increased concentrations of carbohydrates and also of decreases in stomatal conductance and transpiration rate.     

Effects of elevated CO2 on the capacity for photosynthesis of a single leaf and a whole plant, and on growth in a radish

The atmospheric concentration of CO2 will probably rise to about 700 micromol mol(-1) by the end of this century. The effects of elevated growth CO2 on photosynthesis are still not fully understood. Effects of elevated growth CO2 on the capacity for photosynthesis of a single leaf and a whole plant were investigated with the radish cultivar White Cherish. The plants were grown under ambient ( approximately 400 micromol mol(-1)) or elevated CO2 ( approximately 750 micromol mol(-1)). The rates of net photosynthesis per leaf area with a whole plant and a single leaf of plants of various ages (15-26 d after planting) were measured under ambient and elevated CO2. The rates of photosynthesis were increased by 20-28% by elevated CO2. There was no effect of elevated growth CO2 on the rate of photosynthesis, clearly indicating no downward acclimation of photosynthesis to elevated CO2. Elevated CO2 increased dry weight accumulation by >27%. The effect of elevated CO2 on other growth characteristics will also be shown.     

Increase of photosynthesis and starch in potato under elevated CO2 is dependent on leaf age

Potato plants (Solanum tuberosum cv. Bintje) were grown in open top chambers under ambient (400 microL L(-1)) and elevated CO2 (720 microL L(-1)). After 50 days one half of each group was transferred to the other CO2 concentration and the effects were studied in relation to leaf age (old, middle-aged and young leaves) in each of the four groups. Under long-term exposure to elevated CO2, photosynthesis increased between 10% and 40% compared to ambient CO2. A subsequent shift of the same plants to ambient CO2 caused a 20-40% decline in photosynthetic rate, which was most pronounced in young leaves. After shifting from long-term ambient to elevated CO2, photosynthesis also increased most strongly in young leaves (90%); these experiments show that photosynthesis was downregulated in the upper young fully expanded leaves of potato growing long-term under elevated CO2. Soluble sugar content in all leaf classes under long-term exposure was stable irrespective of the CO2 treatment, however under elevated CO2 young leaves showed a strongly increased starch accumulation (up to 400%). In all leaf classes starch levels dropped in response to the shift from 720 to 400 microL L(-1) approaching ambient CO2 levels. After the shift to 720 microL L(-1), sucrose and starch levels increased, principally in young Leaves. There is clear evidence that leaves of different age vary in their responses to changes in atmospheric CO2 concentration.     

Foliage of oaks grown under elevated CO2 reduces performance of Antheraea polyphemus (Lepidoptera: Saturniidae)

To understand how the increase in atmospheric CO2 from human activity may affect leaf damage by forest insects, we examined host plant preference and larval performance of a generalist herbivore, Antheraea polyphemus Cram., that consumed foliage developed under ambient or elevated CO2. Larvae were fed leaves from Quercus alba L. and Quercus velutina Lam. grown under ambient or plus 200 microl/liter CO2 using free air carbon dioxide enrichment (FACE). Lower digestibility of foliage, greater protein precipitation capacity in frass, and lower nitrogen concentration of larvae indicate that growth under elevated CO2 reduced the food quality of oak leaves for caterpillars. Consuming leaves of either oak species grown under elevated CO2 slowed the rate of development of A. polyphemus larvae. When given a choice, A. polyphemus larvae preferred Q. velutina leaves grown under ambient CO2; feeding on foliage of this species grown under elevated CO2 led to reduced consumption, slower growth, and greater mortality. Larvae compensated for the lower digestibility of Q. alba leaves grown under elevated CO2 by increasing the efficiency of conversion of ingested food into larval mass. Despite equivalent consumption rates, larvae grew larger when they consumed Q. alba leaves grown under elevated compared with ambient CO2. Reduced consumption, slower growth rates, and increased mortality of insect larvae may explain lower total leaf damage observed previously in plots in this forest exposed to elevated CO2. By subtly altering aspects of leaf chemistry, the ever-increasing concentration of CO2 in the atmosphere will change the trophic dynamics in forest ecosystems.