The Element Contents of Platycladus orientalis plantation in Beijing

Carbon is the most abundant element in the organs of the edificator-31 years old Platy- cladus orientalis. High content of Ca occurred in the edificator, there are plenty of N. K. Mg as well with relatively low content of P and high content of Fe. The concentration of elements is greater in leaves than int woody tissues of tree and shrub. The element accumulation in the aboveground part was higher than those in the under ground part of the tree layer, 51 percent of C was accumulated in trunks. The largest percentage of other elements was accumulated by leaves. On the contrary, in tile tree layer the element accumulation in the under ground part was larger than those in the aboveground part of the shrub layer except N accumulation. The element accumulation in the plantation reached 17,000 kg/ha for C, 400 kg/ha for Ca, 104 kg/ha for N, 87 kg/ha for K, 30 kg/ha for Mg, 11–16 kg/ha for Al, P and Fe, 2.5 kg/ha for Na, 1 kg/ha for Mn, Cu and Zn. The retention of C in the plantation was the highest among the elements. The retention in the Tree layer decreased from Ca to N. K. The retention of N in shrub layer is greater than that of Ca. The element retentions in the plantation were 2700 kg/ha, a for C, 70 kg/ ha.a for Ca. 15–20 kg/ha.a for N, K, 2-5 kg/ha, for P, Fe, Al, and Mg, 1 kg/ha.a for the others. The nutrient pool in soil showed C>Ca>N>Fe>Mg>K>P>Na >Al, Mn>Cu>Zn in order. In the same soil condition, the element enrichment factors by various plants were quite different. Usually the enrichment factors of the shrub were greater than those of the tree. The following sequence of the requirment of nutrients by plantation was shown: C> Ca>N >K>Mg >Fe>P>AI>Na>Mn >Cu> Zn.     

北京人工刺槐林化学元素含量特征

 31年生人工刺槐(Robinia pseudoacacia)林内各种植物的化学元素含量以C素最高,尤以刺槐树干中C含量多。N和Ca在刺槐叶片中含量大。丛生隐子草(Cleistogenes caespitosa)地上部分含K量高于林内其他植物。Fe在荆条(Vitex negundo var．heterophylla)叶片中含量较多。Al和Na在植物细根中含量为大。酸枣(Zizyphus jujuba var．spinosa) 叶中含有较高的Mg和Mn。 刺槐林的乔木、灌木、草本层化学元素积累量以C>Ca>N> K>Mg>P>Fe>Al>Na>Mn>Cu>Zn为序。灌木层化学元素积累量除C和Ca以外,均高于乔木层。对比地表枯枝落叶层化学元素总量与人工林元素的积累量,以Na的比值最高,Ca、Mn、Fe、Zn比值次之,元素归还量都较大。P比值较低,归还量较少。刺槐林土壤化学元素贮存量是以Ca>N>Mg>Fe>K>P>Na>Mn>Al>Zn>Cu为序。植物对土壤中化学元素的富集系数以K、Al和P较高。人工林元素积累量与土壤元素贮存量之比,亦以K、P、Al比值较高。可见土壤中的K、P和Al相对是不足的。     

兴安落叶松人工林营养元素的分析

落叶松人工林能否保持无机动态平衡、稳定生长,主要取决于每年还原于土壤中凋落物营养元素成分和数量。本研究目的在于揭示凋落物变化的各种规律,以及营养元素的潜在还原量。为改善林地条件,建立最佳结构模式的林分提供科学依据。为此我们对黑龙江省东部尚志县帽儿山兴安落叶松人工林四年凋落物营养元素进行了分析研究。结果表明: 1.落叶松树种的凋落物数量,包括叶、枝、皮等,四年平均每公顷干重量为3099.5kg,林内天然阔叶树为237.4kg,总计为3336.9kg。 2.不同种类凋落物营养元素的含量差异显著,叶含量最多,枝次之,皮中含量最小。 3.平均每年每公顷还原于林地的营养元素总量(N、P、K、Ca、Mg、Cu、Zn、Mn)为98.8697kg,其中落叶松叶为85.5998kg,阔叶树叶为8.385kg,落叶松落枝为2.0335kg,林内落叶松落皮为9.13kg,阔叶树枝为9.27kg。     

喀斯特峰丛洼地不同类型森林养分循环特征

以中国西南喀斯特峰丛洼地为研究区域用标准木法和收获法对人工林、次生林、原生林3个不同类型森林的6个代表性群落的生物量、营养元素生物循环量及循环特征进行了研究。结果表明:(1)不同类型森林群落乔木各器官的养分含量大小顺序为:叶枝根干,林下植被层和凋落物层的养分含量比较高,其含量普遍高于乔木层各组分,仅次于乔木叶片;各组分中营养元素以K、Ca最高,P、Mg最低;(2)3种类型森林间乔木层的养分积累量总规律表现为原生林(4540.30 kg/hm~2)次生林(2107.09 kg/hm~2)人工林(719.51 kg/hm~2),分别占林分养分积累量的88.30%、79.57%和62.60%;(3)3种类型森林生态系统养分总贮量相差不大,均主要集中在土壤层在各层分配格局有所差异;营养元素的年吸收量和年归还量均为次生林原生林人工林,年吸收量分别为:418.80、271.17和148.79 kg hm~(-2)a~(-1);年归还量分别为:182.98、111.43和43.37 kg hm_(-2)a~(-1);(4)不同类型森林养分利用系数总规律为人工林(0.35)次生林(0.20)原生林(0.10);循环系数则相反,为原生林(0.48)次生林(0.46)人工林(0.30);而周转时间为原生林(37.32)人工林(18.63)次生林(13.93)。喀斯特峰丛洼地土层薄,养分贮存能力差,森林养分循环能力相对较弱,沿着强、中、弱干扰递减梯度,3种类型森林养分利用效率和循环能力呈增长趋势。     

Litter production and forest floor nutrient dynamics in pine and hardwood stands of New Brunswick, Canada

Biomass and nutrient transfer (N, P, K, Ca, Mg) of overstory (branches and leaves) and understory litter fall were examined over a two year period in four jack pine stands aged 16, 29, 49 and 57 years and four mixed hardwood stands aged 7, 17, 20 and 29 years. Relative amounts of the five nutrients in litter fall for both series of stands were N > K ≷ Ca > P = Mg. Return of mineral elements to the forest floor was generally twice as high on the hardwood stands as for similarly aged pine stands. Overall return of nutrients plotted versus stand age generally exhibited a plateau relationship, with relatively little difference among stands; however, some exceptions occurred. Understory contribution to litter fall was very important on these stands, since in most cases the nutrient mass in understory litter was usually similar to or higher than that from the tree layer. Data on forest floor biomass, nutrient distribution and turnover rates of these stands were also presented; mobility of nutrients in the forest floor was in the order K > Mg ≥ P ≥ Ca ≥ N.     

红松人工林凋落物营养元素的分析

红松(Pinus koraiensis)人工林凋落物是生态系统中物质循环和能量转化的一个组成部分,是近于封闭式养分循环的重要环节。因此进行调落物营养元素的分析不仅能揭示营养循环的变化规律,而且对生物自肥,增加地力潜在生产力,予测红松人工林生长的前景有其重要意义。     

青海森林生态系统中灌木层和土壤生态化学计量特征

灌木层作为森林生态系统的重要组成部分, 了解其生态化学计量特征将有助于揭示森林生态系统物质周转和养分循环等生态功能。该研究选取青海省7种主要优势林分——白桦(Betula platyphylla)林、毛白杨(Populus tomentosa)林、红桦(Betula albosinensis)林、青扦(Picea wilsonii)林、山杨(Populus davidiana)林、圆柏(Sabina chinensis)林、云杉(Picea asperata)林为研究对象, 采用野外取样和室内实验分析相结合的方法, 研究了不同林分林下灌木层不同器官(叶、枝干、根)及其表层(0-10 cm)土壤的碳(C)、氮(N)、磷(P)含量及其相关性。结果表明: 7种林分间灌木(叶、枝干、根) P含量、C:P均没有明显差异性; 山杨林、圆柏林、云杉林的林下灌木(叶、枝干、根) N含量、N:P高于白桦林、毛白杨林、红桦林和青扦林, C:N则相反。圆柏林的林下灌木生长受P限制, 其余6种林分的林下灌木生长受N限制。7种林分间土壤有机碳(SOC)和总氮(TN)含量呈现出明显差异性, 而总磷(TP)含量则差异不明显。相关性分析表明, 林下灌木(叶、枝干、根) N含量、C:N、N:P与土壤TN含量、C:N、N:P呈极显著相关性, 而P含量、C:P与土壤TP含量呈显著相关性。冗余分析表明, 林下灌木层植被C、N、P含量及生态化学计量特征受到土壤化学计量特征及各环境因子的共同影响, 其中土壤C:N、海拔、年平均气温、年降水量为主要影响因子。     

陕西省森林群落乔灌草叶片和凋落物C、N、P生态化学计量特征

研究陕西省121个森林群落中乔叶、灌叶、草叶和凋落物4个层次的C、N、P化学计量学特征及其变异性,分析了各层次间及其与地理因子间的关系.结果表明： 乔叶C、N含量最高,草叶P含量最高,凋落物C、N、P含量均最低.乔叶、灌叶、草叶和凋落物的C∶N∶P分别为439.4∶14.2∶1、599.2∶13.5∶1、416.5∶13.3∶1、504.8∶15.5∶1,乔叶、灌叶、草叶N∶P值差异不显著,但均与凋落物N∶P值差异显著,表明不同生活型活体植物叶片的N∶P值具有一定的稳定性.与N含量相比,C和P含量在各层次间表现出更好的相关性;C、N、P含量及其比值在草叶与乔叶之间较在灌叶与乔叶之间表现出更好的相关性;凋落物与乔叶和草叶之间C、N、P含量均表现出显著正相关,与灌叶只在P含量之间存在显著正相关.灌叶N、P含量随纬度增加而增加,草叶N、P含量随经度增加而降低,海拔对叶片和凋落物C、N、P含量及其比值的影响较小,只有乔叶N∶P与海拔之间存在显著负相关.各地理因子对草叶的影响大小表现为经度>纬度>海拔,对乔叶、灌叶和凋落物的影响大小表现为纬度>经度>海拔.     

Spatial variability of soil nutrients and microbiological properties after the establishment of leguminous shrub Caragana microphylla Lam. plantation on sand dune in the Horqin Sandy Land of Northeast China

The objective of this study is to determine the spatial variability of nutrients, microbial biomass, and enzyme activities of soil due to the establishment of shrub plantation on moving sandy dunes, as part of an effort to understand the microenvironmental factors that control the soil microbiological properties. Caragana microphylla Lam., an indigenous leguminous shrub, is the dominant plant species used to control desertification in the semi-arid Horqin Sandy Land of Northeast China. In a 26-year-old C. microphylla plantation, soil samples were collected from three soil depths (0-5 cm, 5-10 cm, and 10-20 cm), three slope positions (windward slope, top slope, and leeward slope), and two microsites (under shrubs and between shrubs). The results showed significant differences in soil EC, nutrient content (except for total K), microbial biomass C and N, and the activities of dehydrogenase, urease, and protease at different slopes, soil depths, and microsites. Significant differences in pH at different microsites and slopes, soil moisture and polyphenol oxidase activity at different soil depths and slopes, and activities of phosphomonoesterase and nitrate reductase at different soil depths were also observed. The soil nutrient contents and microbiological activities were greater in the surface soil layer and decreased with the increase of soil depth. Soil organic C, total N, total P, available P and K, microbial biomass C and N, and the activities of enzymes tested (except for protease) under shrubs were higher than those in between shrubs. Furthermore, significant correlations among soil organic C, microbial biomass C and N, the activities of phosphomonoesterase, dehydrogenase, urease, protease, and nitrate reductase were observed, and correlations were also found among EC, total N, total P, available P and K, enzyme (except for polyphenol oxidase) activities, and microbial biomass C and N contents. These results suggest that microenvironmental factors (slope, soil depth and microsite) have significant influences on the spatial distribution of soil nutrients and microbiological properties when the C. microphylla sand-fixing plantation is established in the moving sand dunes in the Horqin Sandy Land.     

Mass and nutrient loss of fresh plant biomass in a small black-water tributary of Caura river, Venezuelan Guayana

Decomposition rates and nutrient dynamic (N, P, K, Ca and Mg) were determined for green leaves and fine branches immersed in the water of a small tributary of Caura river (SE-Venezuela). 16% of the original dry weight of leaves and 11% of branches were lost at the end of the first sampling period: first month for leaves and second month for branches. This dry weight reduction was probably due to leaching of soluble material. After a 9-month period, the mass loss was 60% for leaves and 20% for fine branches. The pattern of dry weight and nutrient losses are in general agreement with previous studies of decomposition of leaf litter in both terrestrial and aquatic ecosystems. Potassium and magnesium are the elements most rapidly lost, showing the dominance of leaching processes; at the end of the first month 7% of the initial amount of K and 18% of the initial amount of Mg remained in leaves. The loss of calcium and phosphorus was much slower: 61% of Ca and 47% of P remained in the leaf material after the first sampling period. In contrast to K, Mg, Ca and P, the initial amount of nitrogen in leaves remained relatively unchanged during the first month of decomposition; in the subsequent sampling period, the amount of N decreased. The elements K and Mg in branches behaved similar to leaves: 4% of K and 22% of Mg were left at the end of the first sampling period. The initial amount of Ca and P in branches decreased slightly: 88% of Ca and 83% of P remained in branches at the end of this first sampling. Nitrogen behaved differently in branches than that in leaves. In branches the amount of N remained relatively unchanged during the first 5 months of decomposition; afterwards, N showed gradual increases, probably due to immobilization. At the end of the experiment the amount of N in branches was 16% higher than the initial amount.     

北京西山（卧佛寺附近）人工油松林群落学特性及生物量的研究

28年生人工油松林标准地设置在西山海拔300一350米的南坡与北坡山地。试用了多种数学模型预测人工林乔木层的生物量,应用w(树干)=2.372(D2H)0.664, w(枝条)=1.317(D2H)0.992,w(叶子)=1.417(D2H)0.833和w(根系)=1.593(D2H)0.757幂函数方程,分别获得树干、枝条、叶子和根系的生物量。南、北坡油松林乔木层生物量分别为29.13吨／公顷和42.46吨／公顷。用直接收获法测得不同坡向油松林的灌木层和草本层生物量的季节动态,以8月份生物量计,南、北坡灌木层生物量为8.05吨／公顷和5.78吨／公顷,草本层为0.74吨／公顷和0.77吨／公顷。南,北坡油松林的总生物量为38.08吨／公顷和48.68吨／公顷。     

鼎湖山南亚热带常绿阔叶林植物营养元素含量分配格局研究

在鼎湖山南亚热带常绿阔叶林中,植物叶片营养元素含量为Ｎ ０．９４６％－２．５３５％,Ｐ ０．０３０－０．１２７％,Ｋ ０．６１４％－１．８３３％,Ｃａ ０．４４２％－１．９９５％,Ｍｇ ０．０２４％－０．１８８％。叶片各营养养元素间相关性较差,仅Ｐ与Ｍｇ及Ｍｇ与Ｋ之间存在显著的线性相关。叶片Ｎ元素平均含量在各层中的序列为：乔木Ⅲ〉乔木Ⅱ〉乔木Ⅰ〉灌木〉藤本〉草本;其它营养元素浓度随层次分配的规律性     

阔叶红松林不同演替阶段灌木器官的N、P分配特征

氮（N）、磷（P）是植物生长发育重要的限制元素,N、P以及N、P间的关系是化学计量学研究的重要内容。植物不同器官对N、P的需求存在差异,因此N、P的分配与权衡对植物的生长发育起到重要的调节作用。为了探究阔叶红松（Pinus koraiensis）林不同演替阶段主要灌木器官的N、P化学计量特征及其分配格局,了解灌木的养分限制因子及其分配策略,在黑龙江凉水国家级自然保护区的阔叶红松林四个演替阶段——白桦（Betula platyphylla）次生林、阔叶混交林、针阔混交林和阔叶红松林内,选取主要灌木种,分析了叶片、枝条、茎干和根的N、P化学计量特征以及异速生长关系。结果发现：灌木不同器官之间的N、P含量差异显著,其中叶的N、P含量均为最高,茎干的N、P含量均为最低。所有器官中,叶的N ： P最高,为7.59;根的N ： P最低,为5.47。灌木叶、茎干、根之间的N ： P存在显著差异,而茎干、根与枝条之间的N ： P没有显著差异。阔叶红松林不同演替阶段对灌木同一器官N、P化学计量的影响不同,灌木叶片的N含量在不同演替中具有显著差异,其他器官的差异不显著;不同演替阶段灌木器官的P含量均无显著差异。在不同演替阶段中各器官的N ： P均小于14,说明N元素是阔叶红松林各演替阶段灌木生长的限制因子,而P对灌木的生长没有起到限制作用。研究表明在不同演替阶段中,N、P的异速生长关系普遍存在于灌木器官中,呈现显著的正相关关系;整体上各器官之间的斜率没有显著差异,说明灌木采取保守分配策略,以此来适应环境和满足自身生长发育的需要。     

Foliar decomposition in a broadleaf-mixed Korean pine (Pinus koraiensis Sieb. Et Zucc) plantation forest: the impact of initial litter quality and the decomposition of three kinds of organic matter fraction on mass loss and nutrient release rates

Foliar litter decomposition of nine species in broadleaf-mixed Korean pine plantation forests, northeast China was assessed over a 34-month field experiment using litterbag method. Litter mass loss generally followed a sequential decomposition of water-soluble fraction (WSF), acid-soluble fraction (ASF), and acid-insoluble fraction (AIF). WSF decomposition contributed most of litter mass loss in the first 6 months, while ASF accounted for most of litter mass loss thereafter. There existed significant autocorrelations among the initial litter quality indices. Initial N, K, Ca, AIF, AIF/N, ASF/N, and WSF/N were significantly related to the percent remaining of litter mass, N, P, Ca, and Mg in both month 12 and month 34. No litter quality can significantly predict the percent remaining of AIF and K. N and P were immobilized by all litters, but Ca, Mg, and K exhibited minor or no immobilization phase. N was the most limiting element in this forest based on the results of correlation analysis and nutrient elements release dynamics. The relationships between WSF, ASF, and AIF loss and N or P release rate fitted the polynomial regression. The decomposition of WSF and ASF were faster than N and P were mineralized during the study. AIF loss rate relative to N and P loss varied greatly among species, with high-N litter showing slower AIF decomposition rates than N and P. The loss rates of WSF and ASF were in proportion to that of K, Ca, and Mg, while AIF decomposed slower than K, Ca, and Mg. This suggested that the decomposition of WSF and ASF caused the net release of K, Ca, and Mg. Responsible Editor: David E. Crowley.     

六盘山四种森林生态系统的碳氮储量、组成及分布特征

碳和氮是森林生态系统的重要组成元素,其含量有很大时空差异,并和立地及森林特征关系很大,需做大量的积累性调查才能得到其变化规律,尤其是加强在过去较少研究的西北地区的调查。在宁夏六盘山区选择华北落叶松(Larix principisrupprechtii)人工林、华山松(Pinus armandii)次生林、桦木(Betula platyphylla)次生林和野李子(Prunus salicina)灌丛4种典型森林,测定了乔木层(分不同器官)、灌木层、草本层、枯落物层、根系层(0—100 cm土壤)的碳、氮含量,分析了生态系统的碳、氮储量及成分组成和层次分布特征。结果表明,碳含量在不同乔木树种及其不同器官之间的差异不明显;但氮含量存在显著的树种差别和器官差异,以树叶的最高、树干的最低。灌木层和草本层的碳氮含量均表现为地上部分地下部分。各森林样地的乔木层、灌木层、草本层的碳含量依次降低,但氮含量依次增高;枯落物层的碳含量低于各植被层,但氮含量高于各植被层;根系层土壤的碳、氮含量则随土层增深而递减。包括活植被层、枯落物层和根系层土壤在内的华北落叶松人工林、华山松次生林、桦木次生林、野李子灌丛的生态系统碳储量依次为364.56、450.98、640.02、196.55 t/hm2,氮储量依次为27.86、36.19、47.02、15.99 t/hm2。所有4种森林生态系统的根系层土壤的碳氮储量均占整个生态系统总储量的绝大部分,其比例对碳储量为84.69%—93.92%,氮储量为98.09%—98.64%。从乔木层、灌木层、草本层、枯落物层到根系层(土壤),呈现出C/N比依次减小的趋势;根系层土壤和整个生态系统的C/N比分别为华北落叶松林的11.84和13.12、华山松林的10.76和12.56、桦木林的12.48和13.52、野李子灌丛的11.70和12.29。     

沙漠绿洲过渡带柽柳灌丛沙堆-丘间地系统土壤养分空间异质性

以塔克拉玛干沙漠南缘策勒沙漠绿洲过渡带为研究区,选取植被盖度依次为30%、15%—20%、10%和5%的4个典型样地,对各样地的柽柳灌丛沙堆-丘间地系统典型部位0—10 cm和10—20 cm土壤进行系统采样,分析土壤枯落物、有机质、全效N、P、K和速效N、P、K含量,从风沙地貌的角度研究过渡带沙漠化进程中土壤养分分布特征。结果表明:(1)随着植被总盖度的降低,灌丛沙堆表层0—10 cm土壤的枯落物、有机质、全N、全K、速效K含量呈降低趋势,平均降幅为69.3%、37.0%、35.3%、8.3%和24.5%。全P含量没有明显的变化,速效N和速效P含量呈先减小后增大的趋势;(2)从灌丛下→沙堆边缘→丘间地→风影区,土壤枯落物、有机质、全N、全P、速效N、速效P、速效K含量表现出先减小后增大的趋势,最大值位于灌丛下部位,最小值位于丘间地,但在植被盖度5%的样地,沙堆-丘间地系统各部位之间养分含量无显著性差异;(3)与0—10 cm土层相比,10—20 cm土层的枯落物、有机质、全N、全P和速效P含量显著降低,平均降幅为40.0%、27.0%、25.0%、4.5%和2.0%,全K、速效N和速效K含量明显增加,平均增幅为4.8%、103.3%和12.1%。随着植被盖度的降低,10—20 cm土层的养分含量具有与0—10 cm土层相对一致的变化趋势;(4)灌丛的生物反馈作用使得灌丛下部位具有明显的养分富集效应,但随着植被总盖度的降低和风沙活动不断加剧,非生物因素逐渐占据主导,灌丛的养分富集效应趋于减弱和消失。     

不同林龄第2代杉木林枝叶凋落前的养分转移特征

利用会同杉木林25年的定位测定的基础数据,探讨了不同林龄杉木(Cunninghamia lanceolata(lamb) Hook)枝叶凋落前的养分转移特征,为人工林经营管理提供科学依据。结果表明:杉木枝叶凋落前年均养分转移量为3.22—31.89 kg hm~(-2) a~(-1),其中,叶占71.31%—94.41%,枝占5.59%—28.69%。枝的养分转移量随林龄增加而增加。林分20年生以前,叶的养分转移量呈上升趋势,20年生以后,呈下降趋势。枝的养分转移率为20.97%—22.59%,叶是22.98%—26.06%,枝和叶的养分转移率都随林龄增加而增大。各林龄段的枝的养分转移率差异不显著(P0.05),叶的养分转移率除1—7年生与其他林龄段的差异显著(P0.05),其余各林龄段之间差异不显著(P0.05)。转移的元素量中,N和K占83.75%—84.25%,P、Ca、Mg占15.75%—16.25%。N、P、K、Ca、Mg的转移率分别为24.59%—34.53%,36.36%—46.64%,42.86%—51.27%,3.68%—7.35%,3.67%—9.56%。养分转移率主要受枝叶凋落前、后的养分浓度差值与枝叶凋落前的养分浓度控制,与凋落物量无关。养分的转移量不仅受枝叶凋落前、后的养分浓度差值的影响外,更多地取决于凋落物量,而且与杉木生长发育特征有很大的关联。     

亚热带杉木纯林生态系统中营养元素的积累、分配和循环的研究

本文是1980--1983年本所湖南会同森林生态实验站成年杉木纯林中进行定位研究根据所取得的观测资料,分析和论述了营养元素在林内的积累与分配;以及从降雨中的输入量,计算了营养元素的年吸收量和归还量。研究表明,杉木纯林在21--23年生时,即达到主伐年龄期,营养元素年吸收量仍大于归还量,整个林分还处在养分消耗阶段。     

Variation in Nickel Content in the Nickel-Hyperaccumulating Shrub Psychotria douarrei (Rubiaceae) from New Caledonia1

Plants that hyperaccumulate Ni contain > 1000 ppm (dry wt.) in their tissues. Variation of Ni content within hyperaccumulating plant species is poorly explored. Using the Ni-hyperaccumulating shrub Psychotria douarrei, we documented variation of leaf Ni levels within individual shrubs, and variation with respect to plant size and leaf age. Plant size did not correlate significantly with leaf Ni content, and leaf Ni content did not correlate significantly with soil Ni content. Older leaves contained twice as much Ni as younger leaves. Older leaves also contained greater concentrations of Ca, Fe, and Cr but less K, P, and Cu. Five elements (Zn, Pb, Co, Mn, Mg) showed no significant variation due to leaf age. We also examined the effect of leaf age on epiphyll cover, finding increased epiphyll cover on the upper surface of older leaves. The dominant leafy liverwort epiphyll had a relatively high Ni content (400 ppm), suggesting that epiphylls of Ni hyperaccumulators obtain some Ni from host leaves. Individual shrubs differed in mean leaf Ni content almost two-fold (14,900-27,700 ppm). Variation among branches within individuals also ranged widely; however, this intraplant variability was not strongly correlated with the mean leaf Ni content of an individual shrub. We concluded that Ni contents in leaves of P. douarrei vary considerably due to leaf age, among individual shrubs, and among branches within a shrub.     

Nutrient content and dynamics in north Swedish shrub tundra areas

Forbs and leaves of deciduous shrubs had high concentrations of Ca, Mg, K, P, and N. Deciduous dwarf shrubs had intermediate concentrations but higher than evergreen dwarf shrubs. Monocots, cryptogams, woody and belowground tissues had low concentrations.
Plant nutrient concentrations and nutrient content in soil organic matter increased from dry towards moist tundra areas.
The residence time of nutrients was considerably less than ten years in surface litter, but several decades or centuries in total organic matter. The longest residence time was found in the moist part of the tundra.
N, K, and P in Betula nana leaves were translocated to a great extent prior to leaf fall, whereas Mg and particularly Ca were only slightly translocated. As on other tundra areas shortage of nutrients probably limits plant growth. In that case short supply of N and F seems most probable due to retention in litter and soil organic matter.