四翅滨藜叶片C、N、P生态化学计量特征对N添加的响应

以宁夏平罗西大滩四翅滨藜人工林为研究对象,通过设置N添加的野外实验,研究四翅滨藜叶片C、N、P化学计量比的季节动态及其对N添加的响应特征。结果显示:(1)四翅滨藜叶片C、N、P化学计量比在生长季初期和末期较高,在生长季旺期(8～9月)较低。(2)N添加提高了绿叶N浓度和N∶P比,降低了绿叶C∶N、N回收度(NRP)和P回收度(PRP),对其他指标的影响无明显的规律性。(3)N回收效率(NRE)和NRP均与枯叶C∶N比显著正相关;P回收效率(PRE)与绿叶P浓度显著正相关,与枯叶P浓度显著负相关;PRP分别与绿叶P浓度和枯叶C、N、P化学计量比显著正相关,与枯叶C浓度显著负相关。研究表明,N添加促进了四翅滨藜绿叶N摄取,降低了叶片从枯叶中回收N和P的能力,改善了枯叶N分解质量;未来大气N沉降增加会改变干旱半干旱区植物N吸收、分配和回收等策略,促进枯叶中N的释放速率,直接影响N循环,进而间接影响到植被-土壤系统C和P的循环过程。     

扁刺栲不同根序细根形态和化学特征及其对短期氮添加的响应

研究川西亚热带次生常绿阔叶林优势树种扁刺栲1～5级细根形态和化学特征,及其对氮添加的响应.结果表明: 随根序等级的增加,扁刺栲根直径、根组织密度、K含量增加,而比根长、比表面积及N、P、Mg含量降低.氮添加显著增加了扁刺栲细根N含量,降低了Mg含量和C/N,使细根Ca含量呈下降趋势,对根序C、P、K、Na、Al、Mn、Fe含量无显著影响.氮添加未显著影响扁刺栲细根直径、比根长、比表面积和根组织密度.在所有处理中,细根P含量均与各形态特征呈显著线性回归关系.氮添加处理下,细根Mg含量与形态特征之间的线性关系由不显著变为显著,而细根N含量与形态特征之间的线性关系由显著变为不显著.氮添加会影响根系营养元素含量,并增强植物对P和Mg的需求.     

不同降水条件下荒漠草原植物的养分含量及回收对增温和氮素添加的响应

为了探讨荒漠草原植物养分回收特征对长期增温和氮素添加的响应以及自然降水变异对其的调控作用,该研究依托实施12年的模拟增温和氮素添加实验平台,在相对多雨的2016年(超过长期均值52%)和相对少雨的2017年(低于长期均值16%),以常见C_3植物银灰旋花(Convolvulus ammannii)和C_4植物木地肤(Kochia prostrata)为研究对象,测定分析绿叶和枯叶的氮磷含量及回收效率。结果表明:(1)在相对多雨年(2016年),增温使2种植物的绿叶氮、枯叶氮、绿叶磷、枯叶磷含量分别增加了14.32%、25.45%、17.97%和46.47%,氮、磷回收效率分别显著减小了9.41%和16.99%(P0.05);氮素添加使2种植物的绿叶氮、枯叶氮、绿叶磷、枯叶磷含量分别提高了17.32%、25.62%、20.21%和51.41%,而氮、磷回收效率显著降低了9.33%和18.89%(P0.05);增温+氮素添加共同处理显著增加了植物氮磷含量、降低了氮磷回收效率。(2)在相对少雨年(2017年),增温、氮素添加、增温+氮素添加处理对植物叶片氮磷含量、回收效率均无显著影响。(3)叶片氮磷含量在物种间差异极显著(P0.000 1),而氮磷回收效率在物种间无显著差异。(4)回归分析表明,植物叶片氮磷含量随着土壤无机氮、有效磷及含水量的增加而增加,植物氮磷回收效率则随着土壤养分和水分的可利用性的增加而降低。研究认为,荒漠草原植物养分回收对全球变化的响应受自然降水变异的调控。     

林地覆盖经营对雷竹鞭根主要养分内循环的影响

为了给林地覆盖经营雷竹(Phyllostachys violascens)林可持续经营提供理论参考,探讨了休养式覆盖经营(覆盖3a后休养3a)、长期覆盖经营(覆盖6a)和不覆盖雷竹林(CK)2年生壮龄竹鞭及其1级、2级根N、P、K、Mg、Ca、Fe浓度和养分迁移、内循环率的差异。结果表明:不同覆盖经营年限雷竹林N、P、K、Mg、Ca和Fe浓度总体上1级根显著高于2级根。1级根和2级根中均存在N、P、K、Mg的养分内循环,且1级根养分内循环率大于2级根,Fe、Ca内循环不明显。N、P、K、Mg养分浓度与养分迁移速率随时间的推延,1级根为持续降低,2级根为先升高后降低。与不覆盖雷竹林相比,休养式林地覆盖经营总体上提高了1级、2级根的N、P、K、Ca的浓度和P、K、Mg的迁移速率、N、P、K的迁移量、P、K的养分内循环率以及1级根Mg的浓度和迁移量、2级根N的迁移速率和Mg的内循环率;长期林地覆盖经营虽提高了雷竹1级根N、K的浓度和N的迁移量及2级根N的浓度和内循环率,但总体上降低了1级根P、K、Mg和2级根N、P、Mg的迁移量与1级、2级根P、Mg的迁移速率及P、K、Mg的养分内循环率。研究表明:雷竹林鞭根中存在明显的养分内循环,且1级根对养分内循环的贡献较大。休养式林地覆盖经营利于雷竹林对养分的循环利用,而长期覆盖经营阻碍了根系对养分的平衡吸收,减弱了根系养分的内循环,不利于雷竹林的生长更新。     

增温和氮素添加降低荒漠草原多年生植物氮素回收效率

植物营养器官在枯萎过程中将部分氮素转移到储藏组织之中,是植物适应生境的重要策略。以位于内蒙古荒漠草原的增温和添加氮素的交互试验为平台,对建群种短花针茅(Stipa breviflora)以及优势种无芒隐子草(Cleistogenes songorica)、银灰旋花(Convolvulus ammannii)、冷蒿(Artemisia frigida)和木地肤(Kochia prostrata)等5种多年生植物绿叶期和枯叶期氮浓度,以及氮素回收效率进行了研究。结果表明:增温处理下,植物绿叶期和枯叶期的平均氮素浓度提高了5.5%和11.3%,氮素回收效率显著降低了7.0%。氮素添加使绿叶期植物氮浓度显著提高了5.2%,使植物氮素回收效率降低2.9%。增温和氮素添加对植物枯叶期、绿叶期氮浓度和氮素回收效率有显著的交互作用。氮浓度和氮素回收效率对增温和氮素添加的响应在5个物种间都有显著差异,即这种响应具有物种特异性。研究表明独立的增温和氮素添加以及两者的交互作用都降低该荒漠草原生态系统中植物氮素回收效率,这些结果将为气候变化条件下荒漠生态系统氮素回收效率变化趋势的预测提供数据支持和实验证据。     

不同竹龄雷竹中硅及其他营养元素吸收和积累特征

在浙江省临安市的雷竹主产区,分别采集不同竹龄(1～4 a)和不同器官(叶、枝、秆)的雷竹样品,分析了Si和其他营养元素含量、吸收和积累特征,以及Si和其他营养元素之间的相互关系.结果表明： 雷竹各器官中C含量的大小顺序为竹秆>竹枝>竹叶,Si、N、P、K、Ca、Mg、Al、Fe和Mn含量的大小顺序为竹叶>竹枝>竹秆.除Mn主要积累在竹叶中外,其他9种营养元素主要积累在1年生雷竹的秆中.3～4年生雷竹竹叶的Si平均含量为13.66 g · kg^-1. 雷竹属于Si积累植物.随竹龄的增加,雷竹叶中的N、P、K和Mg含量减少,C、Al和Mn含量增加.雷竹对Si的吸收主要集中在第2年(57.1%),对N和K的吸收主要集中在前两年(67.7%～93.7%),此后N和K从植株体内流出,其流失量分别占总积累量的19.1%～39.1%.雷竹中Si与Ca、Al、Mn呈显著正相关,与N、P、K、Mg呈显著负相关.     

陕西红富士苹果矿质营养DRIS标准研究

通过对60个红富士苹果园叶片中N、P、K、Ca、Mg、Fe等6种元素含量的测定和统计分析表明,苹果产量和品质是叶片N、P、K、Ca、Mg、Fe等元素含量综合作用的结果;通过主因素分析,各因素对产量的影响顺序为产量(Y1)x3(K)>x2(P)>x1(N)>x4(Mg)>x5(Ca)>x6(Fe);对可溶性固形物浓度(Y2)的影响顺序为x4(Mg)>x3(K)>x6(Fe)>x1(N)>x5(Ca)>x2(P);对硬度(Y3)的影响顺序为x1(N)>x6(Fe)>x3(K)>x4(Mg)>x2(P)>x5(Ca);对>80%果面红色果占有率(Y4)的影响顺序为x3(K)>x2(P)>x1(N)>x4(Mg)>x5(Ca)>x6(Fe);对低产组(产量<22 500 kg/hm2)大量元素需肥强度影响最大的为K,占该组的53.4%,对中量元素需肥强度影响最大的为Ca和Mg,均占该组的40%;对高产组(产量≥22 500 kg/hm2)DRIS重要参数的表达式为N/K、P/N、K/P,Ca/Mg、Fe/Ca、Fe/Mg,N/K、Ca/K、Ca/N,K/P、Fe/P、Fe/K,Ca/K、Mg/K、Ca/Mg,根据试验结果制定出红富士苹果园N、P、K、Ca、Mg、Fe的DRIS适宜指数范围分别为-8.355～23.011、-13.784～22.078、-12.772～9.544、-2.114～11.532、-2.503～8.902、-4.617～5.291;各园的需肥顺序用图示法和指数法判断,其结果一致.     

元谋干热河谷燥红土和变性土上植物叶片的元素含量及其重吸收效率

采用盆栽试验,研究元谋干热河谷燥红土和变性土上生长的植物叶片以及凋落叶营养元素含量,并分析养分重吸收效率对土壤类型与物种互作的响应.结果表明: 土壤类型对叶片N、P、Ca、Mg、Cu、Zn、Fe、N∶P以及凋落叶N、P、Mn、N∶P均有显著影响;燥红土植物叶片与凋落叶N、Mn含量和N∶P显著高于变性土,而燥红土植物叶片P、Ca、Mg、Fe、Cu、Zn和凋落叶P含量显著低于变性土.燥红土植物叶片N含量较变性土高34.8%,而P含量低40.0%;在叶片凋落时,N、P、K表现为重吸收,而其他元素呈富集状态.燥红土凋落叶Ca、Mg、Mn富集系数显著高于变性土.物种仅对叶片N含量有显著影响,物种与土壤交互作用对植物叶片和凋落叶元素含量影响不显著,表明各土壤类型对不同物种元素含量的影响方式较为一致.土壤类型对植物元素含量的影响可进一步作用于干热河谷植物凋落物分解、植物-土壤的养分反馈以及生物地球化学循环.     

氮、磷和水分供给对羊草枯叶分解质量的影响

研究不同氮(N)、磷(P)和水分梯度上植物枯叶的N和P浓度及C : N和C : P的响应格局, 对于预测N沉降增加和降水格局改变对枯叶分解乃至养分循环的潜在影响具有一定的实践意义。该研究通过3个盆栽控制试验(N、P添加试验: 0、0.5、1.0、2.0、4.0、8.0、16.0、32.0、64.0和128.0 g N(P)∙m^-210个水平; 控水试验: 3 600、3 900、4 500、5 100、6 000、7 200、9 000、12 000、 18 000和36 000 mL∙pot^-110个水平), 探讨了这些环境因子改变对羊草(Leymus chinensis)枯叶分解质量的影响。结果表明, 在一定范围内, N添加提高了羊草枯叶的N浓度, 降低了C : N, 对P浓度和C : P没有明显的影响; P添加提高了枯叶的N和P浓度, 降低了C : N和C : P; 供水量增加显著降低了枯叶的N和P浓度, 提高了C : N和C : P。这表明, N、P和水分因子的改变影响了植物枯叶的性状, 且不同梯度的影响程度不同。因此, 全球气候变化可能影响植物枯叶的分解质量, 进而可能改变植被-土壤系统的养分循环。     

硼在梨树苗不同部位的分布及与其他元素分配的关系

以‘翠冠'梨树苗为试验材料,采用微波消解提取灰分结合等离子发射光谱仪测定法,研究硼(B)添加对梨不同部位B分布及对P、K、Ca、Mg、Fe、Zn、Mn和Cu 8种元素吸收分配的影响.结果表明:‘翠冠'梨不同器官B浓度大小为叶片>根系>茎,随营养液B浓度增加,‘翠冠'梨根、茎、叶B浓度呈增加的趋势,营养液B浓度越高根系B浓度增加幅度越大,不同处理间差异显著.高B处理明显影响‘翠冠'梨苗8种矿质元素在根、茎、叶中的分配.根中P、K、Mg、Zn、Mn和cu浓度随营养液B浓度增加而提高,Ca和Fe浓度随营养液B浓度增加而降低,而转运系数均随B浓度增加而增大;茎中P、Ca、Mg、Zn、Mn和Cu浓度随营养液B浓度增加而提高,K和Fe随营养液B浓度增加而降低,P和K转运系数随B浓度增加而增大,Fe无明显变化,其他元素的转运系数随营养液B浓度增加而降低;叶中P、K、Mn和Cu浓度随营养液B浓度增加而提高,Fe和Zn则相反,而Ca和Mg则先升高后降低,除Zn与Mn外,其他元素的转运系数随营养液B浓度增加而增大.     

Concentrations and resorption patterns of 13 nutrients in different plant functional types in the karst region of south-western China

Background and Aims

Elucidating the stoichiometry and resorption patterns of multiple nutrients is an essential requirement for a holistic understanding of plant nutrition and biogeochemical cycling. However, most studies have focused on nitrogen (N) and phosphorus (P), and largely ignored other nutrients. The current study aimed to determine relationships between resorption patterns and leaf nutrient status for 13 nutrient elements in a karst vegetation region.

Methods

Plant and soil samples were collected from four vegetation types in the karst region of south-western China and divided into eight plant functional types. Samples of newly expanded and recently senesced leaves were analysed to determine concentrations of boron (B), calcium (Ca), copper (Cu), iron (Fe), potassium (K), magnesium (Mg), manganese (Mn), molybdenum (Mo), N, sodium (Na), P, sulphur (S) and zinc (Zn).

Key Results

Nutrient concentrations of the karst plants were lower than those normally found in other regions of China and the rest of the world, and plant growth was mainly limited by P. Overall, four nutrients revealed resorption [N (resorption efficiency 34·6 %), P (48·4 %), K (63·2 %) and Mg (13·2 %)], seven nutrients [B (–16·1 %), Ca (–44·0 %), Cu (–14·5 %), Fe (–205·5 %), Mn (–72·5 %), Mo (–35·6 %) and Zn (–184·3 %)] showed accumulation in senesced leaves and two nutrients (Na and S) showed no resorption or accumulation. Resorption efficiencies of K and Mg and accumulation of B, Ca, Fe and Mn differed among plant functional types, and this strongly affected litter quality. Resorption efficiencies of N, P and K and accumulation of Ca and Zn increased with decreasing concentrations of these nutrients in green leaves. The N:P, N:K and N:Mg ratios in green leaves predicted resorption proficiency for N, K and Mg, respectively.

Conclusions

The results emphasize the fact that nutrient resorption patterns strongly depend on element and plant functional type, which provides new insights into plant nutrient use strategies and nutrient cycling in karst ecosystems.     

滨海沙地主要造林树种叶片功能性状及养分重吸收特征

为探讨不同树种对滨海沙地干旱贫瘠环境的适应策略,以滨海沙地主要造林树种木麻黄、湿地松、厚荚相思和尾巨桉为对象,研究了不同树种叶片功能性状及养分重吸收特征.结果表明:阔叶树种(厚荚相思和尾巨桉)的叶面积、比叶面积显著高于针叶树种(木麻黄和湿地松),而针叶树叶干物质含量、叶厚度最高.成熟叶和凋落叶的N、P含量表现为阔叶树高于针叶树,成熟叶高于凋落叶,但凋落叶N∶P较高.针叶树种的N、P养分重吸收效率大于阔叶树种,P重吸收效率明显高于N,木麻黄、湿地松、厚荚相思和尾巨桉的N、P吸收效率分别为64.2%、63.1%、47.0%、16.8%和92.5%、81.6%、80.3%、18.0%.比叶面积与叶片N、P含量呈显著正相关,与叶干物质含量,叶厚度以及N、P养分重吸收效率呈显著负相关;叶干物质含量与叶厚度及N、P养分重吸收效率呈显著正相关.就叶片功能的权衡关系而言,木麻黄和湿地松属于缓慢投资-收益型物种,具有较高的养分重吸收效率,而厚荚相思和尾巨桉属于快速投资-收益型物种,养分的重吸收效率较低.不同滨海沙地造林树种通过叶片功能性状及养分重吸收之间的相互协调实现对滨海沙地特殊生境的适应性.     

Characteristics of foliar chemistry in a commerical spruce-fir stand of northern New England,USA

Monthly foliage samples were evaluated for elemental composition from red spruce and balsam fir trees in a commercial, low elevation spruce-fir stand at Howland, Maine during the 1987 growing season. Balsam fir showed consistently higher concentrations in A1 and to a lesser extent N, Ca, Mg, and Fe when compared to red spruce. Red spruce exhibited consistently higher Mn and K concentrations. Both species showed a marked seasonal trend in the foliar concentrations of N, P, K, and Ca in current year foliage. For N, P, and K current year foliar concentrations declined rapidly during the early part of the growing season. Calcium concentrations steadily increased during the growing season for both species and age class of needles. Foliar concentrations of N and P in both species suggests that the availability of these nutrients is limited for this site.     

Simulated climate change decreases nutrient resorption from senescing leaves

Nutrient resorption is the process whereby plants recover nutrients from senescing leaves and reallocate them to storage structures or newer tissues. Elemental resorption of foliar N and P has been shown to respond to temperature and precipitation, but we know remarkably little about the influence of warming and drought on the resorption of these and other essential plant macro‐ and micronutrients, which could alter the ability of species to recycle their nutrients. We conducted a 5 year manipulative field study to simulate predicted climate change conditions and studied the effects of warming (W), rainfall reduction (RR), and their combination (W+RR) on nutrient resorption efficiency in five coexisting shrub species in a semiarid shrubland. Both mature and senesced leaves showed significant reductions in their nutrient contents and an altered stoichiometry in response to climate change conditions. Warming (W, W+RR) reduced mature leaf N, K, Ca, S, Fe, and Zn and senesced leaf N, Ca, Mg, S, Fe, and Zn contents relative to ambient temperature conditions. Warming increased mature leaf C/N ratios and decreased N/P and C/P ratios and increased senesced leaf C/N and C/P ratios. Furthermore, W and W+RR reduced nutrient resorption efficiencies for N (6.3%), K (19.8%), S (70.9%) and increased Ca and Fe accumulation in senesced leaves (440% and 35.7%, respectively) relative to the control treatment. Rainfall reduction decreased the resorption efficiencies of N (6.7%), S (51%), and Zn (46%). Reductions in nutrient resorption efficiencies with warming and/or rainfall reduction were rather uniform and consistent across species. The negative impacts of warming and rainfall reduction on foliar nutrient resorption efficiency will likely cause an impairment of plant nutrient budgets and fitness across coexisting native shrubs in this nutrient‐poor habitat, with probable implications for key ecosystem functions such as reductions in nutrient retention in vegetation, litter decomposition, and nutrient cycling rates.     

Nutrient resorption in tropical savanna forests and woodlands of central Brazil

Nutrient limitation in Brazilian savanna (known as cerrado) presumably causes trees to maximize nutrient resorption from senesced leaves to reduce their dependence on nutrient availability. To assess patterns between nutrient resorption and soil fertility, we measured community-level nitrogen (N), phosphorus (P), and potassium (K) concentrations in mature and senesced leaves and soil fertility in the upper 50 cm soil layer in structurally diverse cerrado ecosystems in the Cuiaba Basin (CB) and Pantanal (PAN) of Mato Grosso, Brazil. Foliar nutrient concentration data were used to estimate resorption efficiency and proficiency, and correlation was used to determine whether resorption efficiency and proficiency varied across soil fertility gradients. We found that N and P resorption proficiency (NRP and PRP, respectively) and P resorption efficiency (PRE) increased significantly as total soil N (NRP) and extractable P (PRP and PRE) declined. In contrast, K resorption efficiency (KRE) declined as soil sand content and bulk density increased, which was likely due to a reduction in soil water-holding capacity. Leaf N/P ratios indicate potential N limitation and/or N + P co-limitation for ecosystems in the PAN and P limitation and/or N + P co-limitation for ecosystems in the CB, while trends in leaf N/K ratios indicate possible K or K + P co-limitation for the CB only. Our results illustrate that cerrado forests and woodlands have highly variable nutrient resorption capacities that vary predictably across soil fertility or textural gradients and indicate that cerrado communities have flexible nutrient resorption that can reduce their dependence on soil nutrient availability.     

Nutrient resorption patterns of plant functional groups in a tropical savanna: variation and functional significance

Green and senesced leaf nitrogen (N) and phosphorus (P) concentrations of different plant functional groups in savanna communities of Kruger National Park, South Africa were analyzed to determine if nutrient resorption was regulated by plant nutritional status and foliar N:P ratios. The N and P concentrations in green leaves and the N concentrations in senesced leaves differed significantly between the dominant plant functional groups in these savannas: fine-leaved trees, broad-leaved trees and grasses. However, all three functional groups reduced P to comparable and very low levels in senesced leaves, suggesting that P was tightly conserved in this tropical semi-arid savanna ecosystem. Across all functional groups, there was evidence for nutritional control of resorption in this system, with both N and P resorption efficiencies decreasing as green leaf nutrient concentrations increased. However, specific patterns of resorption and the functional relationships between nutrient concentrations in green and senesced leaves varied by nutrient and plant functional group. Functional relationships between N concentrations in green and senesced leaves were indistinguishable between the dominant groups, suggesting that variation in N resorption efficiency was largely the result of inter-life form differences in green leaf N concentrations. In contrast, observed differences in P resorption efficiencies between life forms appear to be the result of both differences in green leaf P concentrations as well as inherent differences between life forms in the fraction of green leaf P resorbed from senescing leaves. Our results indicate that foliar N:P ratios are poor predictors of resorption efficiency in this ecosystem, in contrast to N and P resorption proficiencies, which are more responsive to foliar N:P ratios.     

The contrasting effects of nutrient enrichment on growth,biomass allocation and decomposition of plant tissue in coastal wetlands

Background

Most studies focus on macronutrient of C, N and P and ignore other elements, which restrict our understanding on the strategy of plant nutrient adaption and nutrient cycling.

Methods

We investigated 14 element (C, N, P, S, K, Ca, Mg, Fe, Mn, Zn, Cu, Na, Al, and Ba) concentrations of green and senesced leaves in Quercus variabilis along the altitude in the Baotianman Mountains, China, and assessed their relationships with climate, soil, and plant functional traits.

Results

Leaf N,S and K increased with, C, Ca, Na, Fe, Mn, Cu and Ba decreased with, and P, Mg, Al, Zn and N:P did not change significantly with altitude. NRE and SRE increased with, and CRE decreased with altitude (p < 0.05). Among the 14 elements, nucleic acid-protein elements (N, K, S and P) were resorbed preferentially, compare to structural (Ca, Mn, and B) and enzymatic (C, Cu, Mg and Zn) that were discriminated against, and toxic (Al and Fe) elements that were totally excluded.

Conclusions

Q. variabilis can synergetically regulate green leaf multielement stoichiometry and nutrient resorption in responses to environment change. Deciduous plants may have a trade-off mechanism at the end of growing season to rebalance somatic nutrients.

     

Inter‐specific Variation in Foliar Nutrients and Resorption of Nine Canopy‐tree Species in a Secondary Neotropical Rain Forest

The influence of environmental gradients on the foliar nutrient economy of forests has been well documented; however, we have little understanding of what drives variability among individuals within a single forest stand, especially tropical forests. We evaluated inter‐ and intra‐specific variation in nutrient resorption, foliar nutrient concentrations and physical leaf traits of nine canopy tree species within a 1‐ha secondary tropical rain forest in northeastern Costa Rica. Both nitrogen (N) and phosphorus (P) resorption efficiency (RE) and proficiency of the nine tree species varied significantly among species, but not within. Both N and P RE were significantly negatively related to leaf specific strength. Green leaf N and P concentrations were strongly negatively related to leaf mass per area, and senesced leaf nutrient concentrations were significantly positively related to green leaf nutrient concentrations. This study reveals a strong influence of physical leaf traits on foliar nutrient and resorption traits of co‐occurring species in a secondary wet tropical forest stand.     

Nutrient cycling and foliar status in an urban pine forest in Athens, Greece

The nutrient cycling and foliar status for the elements Ca, Mg, K, N, P, S, Fe, Mn, Zn and Cu were investigated in an urban forest of Aleppo pine (Pinus halepensis) in 2004 in Athens, Greece in order to draw conclusions on the productivity status and health of the ecosystem. The fluxes of bulk and throughfall deposition were characterized by the high amounts of Ca, organic N and sulfate S. The magnitude of the sulfate S fluxes indicated a polluted atmosphere. The nutrient enrichment in throughfall was appreciable for ammonium N, P and Mn. The mineral soil formed the largest pool for all the elements followed by the forest floor, trunk wood and trunk bark. The understory vegetation consisting of annual plants proved important for storing N, P and K. Compared to current year needles of Aleppo pine in remote forests of Spain, the needles of the Aleppo pine trees in Athens had significantly higher concentrations of Ca, N, P and Cu and significantly lower concentrations of Mg and Zn. The soil had a high concentration of calcium carbonate and accordingly high pH values. When all inputs to the forest floor were taken into account, the mean residence time of nutrients in the forest floor followed the order Fe > Mn > Cu > Ca > Mg > P > Zn > N > K > S.