氮磷配比对水曲柳光合作用的影响

以水曲柳2年生苗木作为试验材料,在人工气候室中用霍格兰水培营养液修改配方(四种氮、磷的不同配比,清水作为对照)进行水培试验,测定了叶片的光合作用、叶绿素荧光以及叶绿素含量等,以期从光合作用角度探讨不同配比的氮、磷对水曲柳幼苗生产力的影响。结果表明:不同氮、磷配比对水曲柳的多个光合指标差异影响显著。在一定范围内随着施磷量的逐渐增加净光合速率(Pn)升高;施磷肥对提高水曲柳叶片光合作用能力有积极作用;磷胁迫使叶绿素含量降低且对水曲柳叶片的碳同化和光能利用产生负影响。     

不同氮水平条件下油茶苗养分积累及化学计量特征

【目的】研究氮添加对油茶幼苗养分积累和主要大量营养元素含量、比值等计量特征的影响,为探究氮对油茶苗生长的影响机理及其与碳、磷等互作关系提供科学参考,同时可为油茶苗氮素养分管理提供理论依据。【方法】以油茶2年生实生苗为试验材料,设置0 mmol·L^-1(N0,CK)、5 mmol·L^-1(N1)、10 mmol·L^-1(N2)、15 mmol·L^-1(N3)、20 mmol·L^-1(N4)共5个氮浓度处理,开展盆栽试验。测定油茶苗各器官生物量和碳氮磷钾元素含量,计算养分累积量、养分利用效率和元素化学计量比。【结果】氮添加显著提升油茶体内N素含量,各器官N含量均在N3水平下达到峰值。随着氮水平的升高,根系C、P含量和叶片P含量呈下降趋势,叶片C和茎部C、P、K含量保持不变。中高浓度氮素(N3、N4)能促进油茶苗干物质和养分的积累,N4处理促进作用最大。氮浓度处理改变了养分的分配格局,随着氮水平的升高,根系养分占比下降,叶片养分比例升高。氮添加降低了N素利用效率,对P、K利用效率影响...     

氮沉降对木荷马尾松林叶片元素计量比的影响

为研究氮沉降对不同林龄木荷—马尾松混交林养分的影响,在室外分别设置了N0(0 kg·hm-2·a-1)、N1(50 kg·hm-2·a-1)、N2(100 kg·hm-2·a-1)和N3(150 kg·hm-2·a-1)4个处理的浓度,进行1 a的氮沉降模拟试验。结果表明,N1、N2和N3处理在试验后期均使30、50年生林木叶片中碳、氮、磷含量较试验前期有所增加,40年生林木叶片碳、氮含量增长明显,而磷含量在N2、N3处理较试验前期有所下降。30、50年生林木叶片氮磷比值主要在14-16之间,说明30、50年生林木同时受到氮、磷的限制,而40年生林木叶片氮磷比值均大于16,说明40年生林木主要受到磷的限制,但不同林龄叶片碳氮比值在试验后期均低于试验前期,下降明显。因此,氮沉降对不同林龄木荷—马尾松混交林叶片的碳、氮、磷含量及其计量比有着不同的影响。     

大岭山森林公园不同海拔土壤碳氮磷化学计量特征研究

森林土壤碳氮磷化学计量特征是土壤养分的供应能力、评估土壤质量以及预测生态系统响应的重要指标。研究以大岭山森林公园为研究对象,在5个海拔梯度设置26个调查样点进行不同海拔土壤碳氮磷化学计量特征分析,结果表明:土壤有机碳及氮含量均随海拔上升逐渐增加,土壤磷含量则为先增大后减小的变化趋势;土壤氮磷比、碳磷比均为随海拔上升呈增大趋势;碳氮比整体差异不大,反映为全区域碳限制;海拔与土壤氮含量、有机碳含量、土壤碳氮比呈显著的相关关系,显示碳、氮同为影响森林公园森林生态系统的关键因子。     

间伐对杉木人工林凋落物-土壤碳氮磷含量及储量的影响

森林经营管理影响植物-土壤系统碳氮磷元素转化及其计量关系。在浙江开化县林场开展了不同间伐强度下凋落物和土壤碳氮磷储量及其生态化学计量关系研究。结果表明,间伐7年后,凋落物生物量及碳氮磷储量在不同间伐处理之间没有显著差异,土壤总有机碳、易氧化有机碳、总磷和有效磷储量在不同间伐处理之间的差异也不显著,但中度间伐处理土壤总氮和水解氮储量比未间伐处理分别增加了40.7%和32.3%,轻度间伐处理与未间伐处理之间土壤总氮和水解氮储量差异不显著。凋落物和土壤碳氮磷生态化学计量比在不同间伐处理之间差异不显著,但土壤易氧化有机碳/水解氮随间伐强度增大逐渐降低(50.1～35.9),水解氮/有效磷随间伐强度增大逐渐增加(60.0～81.6)。因此,间伐有利于土壤氮素的积累,这可能与间伐后凋落物生物量的增加有关。     

几种常见果树缺硼症状及其防治措施

硼是植物生长发育的必需营养元素之一 ,对碳水化合物的运转以及生殖器官的发育都有重要作用。硼主要分布在生命活动旺盛的组织和器官中 ,对果树花粉形成和受精有促进作用 ,能提高坐果率 ,增加果实中维生素Ａ、Ｃ和糖的含量 ,提高果实品质。硼还能加强土壤中的硝化作用 ,增加根际微生物活动 ,改变某些微生物的组成和增加土壤中可溶性磷的含量 ,改善果树营养。硼有助于叶绿素的形成 ,提高光合作用 ,促进碳水化合物的转化、运输。而且硼与细胞分裂、细胞内果胶形成及分生组织和传导组织的正常发育也有密切关系。缺硼时 ,树体内碳水化合物发生紊…     

深圳市坝光湿地园银叶树群落优势树种与土壤生态化学计量特征分析

以深圳坝光湿地园银叶树（Heritiera littoralis）群落为研究对象,分析了深圳坝光湿地园银叶树群落 8 种优势树种叶片碳、氮、磷含量及其化学计量关系,以及 3 种生境（沼泽、山地、临海）土壤和不同土壤深度（0~10 cm、10~20 cm、20~40 cm）有机质、全氮、碱解氮、全磷、有效磷含量及其化学计量关系。结果表明：不同优势树种叶片的碳、氮、磷含量及其计量特征具有显著差异,显示出明显的种间差异性;不同生境（临海、山地、沼泽）之间的土壤差异主要表现为氮及碳氮比,其他如有机质、磷等差异不明显;不同土层则表现为有机质和氮差异明显,浅层土壤元素含量最高,其他指标在各土层中差异不显著。研究表明,除银叶树生长可能受到氮限制外,其他优势树种元素限制现象不明显。     

森林冠层叶片氮浓度高光谱遥感反演研究进展

氮素是植物生命活动所需的重要营养元素,在森林植被的光合作用和生态系统固碳方面起着关键作用。因此,理解森林叶片氮浓度在叶片和冠层（遥感像元）尺度上的高光谱特征,是开展森林冠层叶片氮浓度（CNC）遥感反演、优化森林碳循环模拟、应对气候变化的重要基础工作。当前,森林CNC的光谱特征提取受到冠层结构因素的影响,其高光谱遥感反演的理论亦不明确。文中通过梳理国内外大量植被叶氮高光谱反演的代表性研究成果,以时间为轴线从叶片和冠层2个尺度上进行文献综述,详细阐述当前国内外森林叶氮浓度高光谱遥感反演的主要方法、研究热点和面临的问题,并对近年来学界关于森林冠层结构在冠层叶片氮浓度遥感反演中的影响进行综述,并展望森林冠层叶氮浓度高光谱遥感反演的发展方向。     

北美地区温带针阔叶混交林5个常绿树种叶片呼吸特性

【目的】探讨不同树种叶片的呼吸作用特性及其影响因素,通过呼吸作用的差异量化叶片碳通量估计的影响,以期揭示不同树种叶片呼吸作用的差异以及光对暗呼吸产生的抑制作用。【方法】选取北美地区温带针阔混交林中的尖叶扁柏、刚松、脂松、乔松和铁杉5个常绿树种叶片为试验材料,测量叶片的光响应CO_2响应和呼吸温度响应曲线及叶片结构和生化指标;采用线性回归分析叶片呼吸特性同结构、生化及生理指标间的关系,并运用气孔-光合作用耦合模型和测量得到的参数模拟试验期间叶片碳同化速率。【结果】1)不同树种间叶片比叶面积(SLA)和单位面积氮含量(N_(area))呈显著差异,但单位质量氮含量(N_(mass))差异不显著。叶片单位面积呼吸速率(R_(area))呈现明显种间差异,但同样受到叶片结构性状的调控;2)叶片呼吸同叶片氮含量、净碳同化速率(A)以及SLA间存在显著正相关关系;3)光对5个树种叶片暗呼吸作用均表现出一定的抑制作用,光下线粒体呼吸速率(R_L)同暗呼吸速率(R_n)的比值在0.39~0.90之间。R_L/R_n同Rubisco酶的最大氧化速率(v_(o1500))和最大羧化速率(v_(c1500))均呈显著正相关。此外R_L还和R_n之间具有较强的相关性;4)物种间呼吸作用的Q_(10)为1.44~2.24,不同树种间呼吸作用的总活化能(E_0)虽有差异,但变化幅度较小;5)使用固定的Q_(10)(2.0)并假定R_L=R_n对5个树种叶片碳同化量的模拟均造成一定影响,但影响的方向和大小在物种间各不相同。而此种简化对叶片碳同化量之和造成的影响较小。【结论】不同树种的呼吸生理特性存在种间差异。呼吸速率的种间差异不仅和叶片氮含量有关,同时还和叶片结构形状关系密切。光对暗呼吸的抑制作用受到Rubisco酶羧化和氧化的调控,反映出叶片光合生理和呼吸生理的内在联系。忽视叶片呼吸特性的种间差异及光对暗呼吸的抑制作用将可能导致错误的估计叶片的碳通量,此类误差将会在冠层、生态系统及全球尺度上增大。     

土壤肥力与苗木生长

在苗木的生长过程中,需要大量的养分,需要多种化学元素作为营养,通过光合作用来制造碳水化合物,供其生长需要。苗木的生长过程中对氮、磷、钾3种元素需要量较多,而这3种元素尤其是氮、磷在土壤中含量较少,常感不足。长期以来,通过生产实践,人们把氮、磷、钾称为肥料3元素,它们是植物生长缺一不可的主要营养元素。     

Ontogenetic changes in stomatal and biochemical limitations to photosynthesis of two co-occurring Mediterranean oaks differing in leaf life span

A quantitative analysis was applied to the stomatal and biochemical limitations to light-saturated net photosynthesis under optimal field conditions in mature trees and seedlings of the co-occurring evergreen oak, Quercus ilex L., and the deciduous oak, Q. faginea Lam. Stomatal limitation to photosynthesis, maximal Rubisco activity and electron transport rate were determined from assimilation versus intercellular leaf carbon dioxide concentration response curves of leaves that were subsequently analyzed for nitrogen (N) concentration, mass per unit area, thickness and percent internal air space. In both species, seedlings had a lower leaf mass per unit area, thickness and leaf N concentration than mature trees. The root system of seedlings during their third year after planting was dominated by a taproot. A lower leaf N concentration of seedlings was associated with lower maximal Rubisco activity and electron transport rate and with assimilation rates similar to or lower than those of mature trees, despite the higher stomatal conductances and potential photosynthetic nitrogen-use efficiencies of seedlings. Consequently, stomatal limitation to photosynthesis increased with tree age in both species. In both seedlings and mature trees, a lower assimilation rate in Q. ilex than in Q. faginea was associated with lower stomatal conductance, N allocation to photosynthetic functions, maximal Rubisco activity and electron transport rate, and potential photosynthetic nitrogen-use efficiency but greater leaf thickness and leaf mass per unit area. Tree-age-related changes differed quantitatively between species, and the characteristics of the two species were more similar in seedlings than in mature trees. Despite higher stomatal conductances, seedlings are more N limited than adult trees, which contributes to lower biochemical efficiency.     

C_3、C_4植物叶片净CO_2同化速率的模拟及其对环境因子的响应(英文)

本文首先模拟建立了叶片光合作用机制模型，然后，考虑环境因子对叶光合作用的影响，进 行了三种敏感性试验，包括C3、C4植物叶片净CO2同化速率对胞间CO2浓度、叶片温度和光合 有效辐射（PAR）的影响。结果表明数值模拟的叶光合作用机制模型可以指示C3、C4植物的 光合作用的主要特征，进一步可以作为陆面过程模式的一部分耦合到区域气候模型中，更好 地研究植被和大气的相互作用关系。     

Simulating leaf net CO2 assimilation rate of C3 & C4 plants and its response to environmental factors

Basic structure and algorithm of leaf mechanism photosynthesis model were described in first part of this study based on former researcher results. Then, considering some environmental factors influencing on leaf photosynthesis, three numerical sensitivity experiments were carried out. We simulated the single leaf net CO₂ assimilation, which acts as a function of different light, carbon dioxide and temperature conditions. The relationships between leaf net photosynthetic rate of C₃ and C₄ plant with CO₂ concentration intercellular, leaf temperature, and photosynthetic active radiation (PAR) were presented, respectively. The results show the numerical experiment may indicate the main characteristic of plant photosynthesis in C₃ and C₄ plant, and further can be used to integrate with the regional climate model and act as land surface process scheme, and better understand the interaction between vegetation and atmosphere. Foundation Item: This paper was supported by Natural Science Foundation of China (Grant No. 39900084) Biography: ZHANG Jia-hua (1966-), male, Ph. Doctor, Associate professor in START, Institute of Atmospheric Physics. Chinese Academy of SciencesBeijing, 100029, P. R. China Responsible editor: Chai Ruihai     

Effects of elevated carbon dioxide concentration on growth and nitrogen fixation in Alnus glutinosa in a long-term field experiment

Nitrogen-fixing plant species may respond more positively to elevated atmospheric carbon dioxide concentrations ([CO2]) than other species because of their ability to maintain a high internal nutrient supply. A key factor in the growth response of trees to elevated [CO2] is the availability of nitrogen, although how elevated [CO2] influences the rate of N2-fixation of nodulated trees growing under field conditions is unclear. To elucidate this relationship, we measured total biomass, relative growth rate, net assimilation rate (NAR), leaf area and net photosynthetic rate of N2-fixing Alnus glutinosa (L.) Gaertn. (common alder) trees grown for 3 years in open-top chambers in the presence of either ambient or elevated atmospheric [CO2] and two soil N regimes: full nutrient solution or no fertilizer. Nitrogen fixation by Frankia spp. in the root nodules of unfertilized trees was assessed by the acetylene reduction method. We hypothesized that unfertilized trees would show similar positive growth and physiological responses to elevated [CO2] as the fertilized trees. Growth in elevated [CO2] stimulated (relative) net photosynthesis and (absolute) total biomass accumulation. Relative total biomass increased, and leaf nitrogen remained stable, only during the first year of the experiment. Toward the end of the experiment, signs of photosynthetic acclimation occurred, i.e., down-regulation of the photosynthetic apparatus. Relative growth rate was not significantly affected by elevated [CO2] because although NAR was increased, the effect on relative growth rate was negated by a reduction in leaf area ratio. Neither leaf area nor leaf P concentration was affected by growth in elevated [CO2]. Nodule mass increased on roots of unfertilized trees exposed to elevated [CO2] compared with fertilized trees exposed to ambient [CO2]. There was also a biologically significant, although not statistically significant, stimulation of nitrogenase activity in nodules exposed to elevated [CO2]. Root nodules of trees exposed to elevated [CO2] were smaller and more evenly spaced than root nodules of trees exposed to ambient [CO2]. The lack of an interaction between nutrient and [CO2] effects on growth, biomass and photosynthesis indicates that the unfertilized trees maintained similar CO2-induced growth and photosynthetic enhancements as the fertilized trees. This implies that alder trees growing in natural conditions, which are often limited by soil N availability, should nevertheless benefit from increasing atmospheric [CO2].     

Partititioning concurrent influences of nitrogen and phosphorus supply on photosynthetic model parameters of Pinus radiata

Responses of photosynthesis (A) to intercellular CO(2) concentration (C(i)) were measured in a fast- and a slow-growing clone of Pinus radiata D. Don cultivated in a greenhouse with a factorial combination of nitrogen and phosphorus supply. Stomatal limitations scaled with nitrogen and phosphorus supply as a fixed proportion of the light-saturated photosynthetic rate (18.5%) independent of clone. Photosynthetic rates at ambient CO(2) concentration were mainly in the V(cmax)-limited portion of the CO(2) response curve at low-nitrogen supply and at the transition between V(cmax) and J(max) at high-nitrogen supply. Nutrient limitations to photosynthesis were partitioned based on the ratio of foliage nitrogen to phosphorus expressed on a leaf area basis (N(a)/P(a)), by minimizing the mean square error of segmented linear models relating photosynthetic parameters (V(cmax), J(max), T(p)) to foliar nitrogen and phosphorus concentrations. A value of N(a)/P(a) equal to 23 (mole basis) was identified as the threshold separating nitrogen (N(a)/P(a) < or = 23) from phosphorus (N(a)/P(a) > 23) limitations independent of clones. On an area basis, there were significant positive linear relationships between the parameters, V(cmax), J(max), T(p) and N(a) and P(a), but only the relationships between T(p) and N(a) and P(a) differed significantly between clones. These findings suggest that, in genotypes with contrasting growth, the responses of V(cmax) and J(max) to nutrient limitation are equivalent. The relationships between the parameters V(cmax), J(max), T(p) and foliage nutrient concentration on a mass basis were unaffected by clone, because the slow-growing clone had a significantly greater leaf area to mass ratio than the fast-growing clone. These results may be useful in discriminating nitrogen-limited photosynthesis from phosphorus-limited photosynthesis.     

Seasonal changes in photosynthesis and growth of Zizyphus attopensis seedlings in three contrasting microhabitats in a tropical seasonal rain forest

We hypothesized that photosynthesis and growth of tropical vegetation at its most northern distribution in Asia (Xishuangbanna, SW China) is adversely affected by seasonal drought and chilling temperatures. To test this hypothesis, we measured photosynthetic and growth characteristics of Zizyphus attopensis Pierre seedlings grown in three contrasting forest microhabitats: the understory, a small gap and a large gap. Photosynthetic capacity (light-saturated photosynthetic rate (A(max)), maximum rate of carboxylation and electron transport rate) and partitioning of leaf nitrogen (N) into carboxylation and electron transport differed significantly among seasons and microhabitats. Specific leaf area (SLA) did not change seasonally, but differed significantly among microhabitats and showed a negative linear relationship with daily integrated photon flux (PPF(i)). In contrast, leaf N concentration per unit area (N(a)) changed seasonally but did not differ among microhabitats. Measurements of maximum PSII photochemical efficiency (F(v)/F(m)) indicated that chronic photoinhibition did not occur in seedlings in any of the microhabitats during the study. Photosynthetic capacity was greatest in the wet season and lowest in the cool season. During the cool and dry seasons, the reduction in A(max) was greater in seedlings grown in the large gap than in in the understory and the small gap. Close logarithmic relationships were detected between PPF(i), leaf N(a) and photosynthetic capacity. Stem mass ratio decreased, and root mass ratio increased, in the dry season. We conclude that seasonal acclimation in growth and photosynthesis of the seedlings was associated with changes in biochemical features (particularly N(a) and partitioning of total leaf N between the different photosynthetic pools) and biomass allocation, rather than with changes in leaf morphological features (such as SLA). Local irradiance is the main factor driving seasonal variations in growth and photosynthesis in the study area, where the presence of heavy fog during the cool and dry seasons limits irradiance, but supplies water to the soil surface layers.     

Response of Ulmus americana seedlings to varying nitrogen and water status. 1 Photosynthesis and growth

Well-watered American elm (Ulmus americana L.) seedlings responded to increased nitrate availability with increased leaf nitrogen (N) concentration and photosynthetic rate, larger and more numerous leaves, greater total growth and greater proportional allocation of carbon to shoot than root. Plasticity of growth and carbon allocation were greater than plasticity of N concentration and photosynthetic capacity. For a given N availability, allocation of N per unit leaf area was positively correlated with dry mass per unit leaf area (specific leaf mass), but these relationships differed with N availability. Rates of net photosynthesis and leaf conductance declined logarithmically with decreasing predawn water status. Increased water stress resulted in a greater relative decline in net photosynthesis and leaf conductance for high-N than low-N plants.     

Leaf phosphorus and nitrogen concentrations and net photosynthesis in Eucalyptus seedlings

Seedlings of Eucalyptus grandis Hill ex Maiden, E. pilularis Smith and E. gummifera (Sol. ex Gaertner) Hochr. were grown in solution culture with 100 micromol phosphorus (P). After eight weeks, half of the seedlings were transferred to solution cultures containing 1 micromol P. After a further four weeks, growth, net photosynthesis and foliar P and nitrogen (N) concentrations were measured. The seeds of E. grandis came from a relatively fertile site and those of the other two species from phosphorus-deficient sites. Growth and net photosynthesis did not change in E. pilularis subjected to the low-P treatment, whereas in E. grandis, and to a limited extent in E. gummifera, the low-P treatment resulted in an increase in net photosynthesis that was associated with higher foliar N concentrations (especially protein-N), possibly as a result of nitrogen being retranslocated from the roots. In response to the low-P treatment, leaf phosphorus concentration was reduced by 50-60% in E. grandis and E. pilularis and by 20-30% in E. gummifera. Of the chemical fractions examined, the greatest decrease occurred in the inorganic-P pool. The data suggest that photosynthesis is not limited by leaf phosphorus concentrations typical of those found in Eucalyptus seedlings growing on phosphorus-deficient sites.     

Vertical profiles reveal impact of ozone and temperature on carbon assimilation of Betula pendula and Populus tremula

Rising temperature and tropospheric ozone (O(3)) concentrations are likely to affect carbon assimilation processes and thus the carbon sink strength of trees. In this study, we investigated the joint action of elevated ozone and temperature on silver birch (Betula pendula) and European aspen (Populus tremula) saplings in field conditions by combining free-air ozone exposure (1.2?×?ambient) and infrared heaters (ambient +1.2 °C). At leaf level measurements, elevated ozone decreased leaf net photosynthesis (P(n)), while the response to elevated temperature was dependent on leaf position within the foliage. This indicates that leaf position has to be taken into account when leaf level data are collected and applied. The ozone effect on P(n) was partly compensated for at elevated temperature, showing an interactive effect of the treatments. In addition, the ratio of photosynthesis to stomatal conductance (P(n)/g(s) ratio) was decreased by ozone, which suggests decreasing water use efficiency. At the plant level, the increasing leaf area at elevated temperature resulted in a considerable increase in photosynthesis and growth in both species.