Five heavy metals in propagules of ten mangrove species of China

Five heavy metals in the propagules of 10 mangrove species in China have been investigated. The results revealed that the levels of five heavy metals in most of the propagules were lower than the background levels of the soil. The levels of copper, manganese, zinc, cadmium, and lead in the propagules varied at about 2.1–7.8 g/g, 3.9–28.0 g/g, 5.7–60.0 g/g, 0.014–0.057 g/g, and 0.018–0.038 g/g, respectively. On average, the levels of five heavy metals were in the order Zn > Mn > Cu > Cd > Pb. The biological absorption coefficients were 0.02–1.30 for copper, manganese, zinc, and cadmium and about 0.0007–0.0020 for lead in propagules, showing the following order: Zn > Cd > Cu > Mn > Pb. The above results indicate that the five heavy metals have low accumulation in most of the propagules of 10 mangrove species and are at safe levels for the effective utilization of mangrove resources.     

百山祖冷杉枝叶主要营养元素特征分析

应用原子吸收光谱法测定了百山祖冷杉枝和针叶中K、Na、Cu、Ca、Zn、Fe、Mg、Mn 8种营养元素的含量,结果表明,百山祖冷杉枝和针叶中均含有所测的K、Cu、Ca、Zn、Fe、Mg、Mn等元素,但未检出Na元素;其含量为CaKMgZnFeMnCuNa。与大多数植物体正常生长发育的元素含量范围值相比较,百山祖冷杉枝和针叶中K含量分别为2 967.68~5 585.95、4 036.13~5 194.30 mg/kg,均低于临界值,针叶中Cu含量2.58~4.70 mg/kg,略低于一般植物水平,枝部Zn、Mn含量及针叶Mn含量则均处于较高水平。     

Dynamics of some mineral nutrients and heavy metals in decomposing forest litter

The dynamics of three major mineral nutrients (K, Ca, Mg) and six heavy metals (Fe, Mn, Zn, Cu, Pb and Cd) were studied in decomposing natural, unpolluted litter in two forest types: Scots pine needle litter in a pure Scots pine forest and oak‐hornbeam leaf litter in a mixed oak‐hornbeam stand. Of the mineral nutrients, only K in the oak‐hornbeam system showed a significant decrease in concentration during the course of litter decomposition. For Ca and Mg in both systems and for K in the Scots pine system no clear relation between concentration and accumulated litter‐mass loss was observed. On the other hand, for Fe, Zn, Pb and Cd at both sites, as well as for Mn in the oak‐hornbeam stand and Cu in the Scots pine stand highly significant positive relations were found between heavy metal concentrations and accumulated mass loss. A decrease in concentration was noted only in the case of Mn in the Scots pine system. No clear pattern was found for Cu in the oak‐hornbeam stand. Concentrations of heavy metals in the decomposing litter reached levels at or above those reported to retard decomposition in other studies. At the oak‐hornbeam stand increased also the absolute amounts of Fe, Zn, Pb and Cd.     

Carbon and nitrogen dynamics in early stages of forest litter decomposition as affected by nitrogen addition

The effects of nitrogen(N) availability and tree species on the dynamics of carbon and nitrogen at early stage of decomposition of forest litter were studied in a 13-week laboratory incubation experiment.Fresh litter samples including needle litter(Pinus koraiensis) and two types of broadleaf litters(Quercus mongolica and Tilia amurensis) were collected from a broadleaf-korean pine mixed forest in the northern slope of Changbai Mountain(China).Different doses of N(equal to 0, 30 and 50 kg·ha-1yr-1, respecti...     

Deposition of litter and nutrients in leaves and twigs in different plant communities of northeastern Mexico

Studies on litterfall and decomposition provide estimations of decomposition rates of different ecosystems.This is key information to understanding ecosystem dynamics and changes in a scenario of global warming.The objective of this research was to assess litterfall production,the potential deposition of macro and micronutrients through leaf and twig fall as well as macronutrient—use efficiency in three forest ecosystems at different altitudes: a pine forest mixed with deciduous species(S1); a Quercus spp.forest(S2); and,a Tamaulipan thornscrub forest(S3).Total annual litterfall deposition was 594,742 and 533 g m~(-2) for S1,S2 and S3.Leaf litter was higher (68%) than twigs(18%),reproductive structures(8%) or miscellaneous material(6%).Micronutrient leaf deposition was higher for Fe followed by Mn,Zn and Cu.Macronutrient leaf deposition was higher for Ca followed by K,Mg and P.Even though P deposition in leaves and twigs was lower than other macronutrients,its nutrient use efficiency was higher than Ca,Mg or K.Altitude and species composition determine litter and nutrient deposition,with higher values at mid-altitudes(550 m).Altitude is an important factor to consider when analyzing litter production as well as nutrient deposition as shown in this study.Litter production and nutrient deposition are expected to change in a scenario of global warming.     

灰木莲人工林营养元素分配及其积累特征

对南宁市46年生灰木莲人工林的9种营养元素(N、P、K、Ca、Mg、Fe、Mn、Zn和Cu)的含量、积累量、年净积累量及其分配特征进行了研究。结果表明:灰木莲不同组分的营养元素含量大致为树叶>树皮>树根>树枝>干材。大量元素N、K在树根中的含量最高,P、Mg在树叶中的含量最高,而Ca则在树皮中含量最高;微量元素在各组分中的含量则以Mn最高,Fe、Zn次之,Cu最低。灰木莲人工林营养元素积累总量为1 948.78 kg/hm2,其中乔木层的营养元素积累量为1 715.22 kg/hm2,占林分营养元素积累总量的88.02%;草本层为74.33 kg/hm2,占总积累量的3.81%;灌木层为83.19 kg/hm2,占总积累量的4.26%;凋落物层为76.04 kg/hm2,占总积累量的3.90%。灰木莲人工林营养元素年净积累量为37.32 kg/(hm2·a),各组分营养元素年净积累量排列顺序为干材>树根>树皮>树叶>树枝。     

Local basal area affects needle litterfall,nutrient concentration,and nutrient release during decomposition in <Emphasis Type="Italic">Pinus halepensis</Emphasis> Mill. plantations in Spain

Key message

Stand density has a positive effect on C, K and Mg concentration in needle litterfall and a negative one on C, N, Ca, K, Mg, P, S, Zn, and Cu release from needle litter. Consequently, forest management practices such as thinning decrease nutrient concentration in needle litterfall and accelerate nutrient release from decomposing needles in Pinus halepensis plantations in Spain.

Context

Silvicultural practices usually include stand density reduction resulting in changes in litterfall and litter decomposition rates. Little is known about the effect on nutrient concentrations in litterfall and nutrient release during decomposition even when this is the main path of nutrient return to soils.

Aims

The aims of the study are to evaluate the seasonal pattern of nutrient concentration in litterfall, to study how nutrients are released from needle litterfall during decomposition, and to assess whether local basal area of the stand affects nutrient concentration of litterfall and nutrient release during litter decomposition.

Methods

Eight plots were established on each of four stands covering the widest range in local basal area. A littertrap and 15 litterbags were placed on each plot. Periodically, needle litterfall and litter contained in the litterbags were analyzed for C, N, Ca, K, Mg, P, S, Fe, Cu, Mn, and Zn.

Results

Local basal area had a positive effect on C, K, and Mg concentration in needle litterfall and a negative effect on the release of all the nutrients studied but Fe and Mn during the first 2 years of litter decomposition.

Conclusion

Density management of stands has an impact on nutrient cycling, reducing nutrient concentration in needle litterfall, and accelerating nutrient release during decomposition.

     

Ozone fumigation of Quercus ilex L. slows down leaf litter decomposition with no detectable change in leaf composition

Context

The evaluation of changes in litter decomposition rate due to increasing trend in tropospheric ozone is an emerging field of investigation, providing relevant information on long-term forest ecosystem sustainability.

Aims

This research aims to clarify the effects of ozone exposure on Quercus ilex leaf chemical composition and decomposition slow down.

Methods

Young plants were fumigated in growth chambers at a cumulative dose of 17.15 ppm h. To assess the fumigation effectiveness, stomatal conductance and net photosynthesis were monitored. Leaves were analysed for C, N, S, Ca, Mg, K, Fe, Zn, Mn, total soluble sugars, starch, acid-detergent fibre (ADF), lignin and cellulose prior to the incubation in litter bags in mesocosms, and during decomposition along 395 days.

Results

Ozone-exposed leaves showed a significant reduction in net photosynthesis and stomatal conductance but did not differ from control leaves in all the chemical parameters analysed. Nevertheless, leaf decomposition rate was lower in treated leaves. The main differences between the models describing the mass loss in exposed and control leaves were played by ADF for exposed leaves and by lignin for control leaves, as well as by N, that showed a greater contribution in the model for the exposed leaves.

Conclusion

Ozone fumigation of Q. ilex results in leaf litter decomposition slowing down, mainly due to ADF joint dynamics with the other variables describing mass decay, even if no detectable changes in initial leaf composition occur.     

Lateral fluxes of organic carbon in a mangrove forest partly contaminated with sewage wastes

Lateral fluxes of macrodetritus, particulate matter and dissolved organic carbon were determined. Samples were collected monthly at the mangrove forest–inshore water boundary and within the forest. Floating macrodetritus (mainly mangrove leaves) was collected by a net (2mm mesh size). Dissolved and particulate matter were separated by filtration (0.45m filter) and centrifugation. Dissolved and particulate carbon were determined by a total organic carbon analyser (SHIMADZU model TOC5000). There was a significant export of mangrove litter to the adjacent marine environment during spring tides. Rates of import and export of particulate matter in the forest were not statistically different. Translocation of material within the forest was clearly demonstrated. A relatively high export of macrodetritus was recorded at the marine fringe (mainly colonised by Sonneratia alba). There was low export of litter in the terrestrial fringe zone, a monospecific stand occupied by Avicennia marina (Forsk) Vierh. Net organic carbon export from the entire forest was 79×10⁶g C y^–1, dissolved organic carbon accounted for about 78% of the total export.     

The effect of Spartina alterniflora Loisel on trace metals accumulation in inter-tidal sediments

We present the distribution of Cd and Zn in sediment cores taken under Spartina alterniflora Loisel. marsh and compare with adjacent mud flats without plant cover. Vertical distribution of Cd and Zn in the mud flat and S. alterniflora cores were different. From 0 to 5 cm of depth Zn and Cd concentrations did not change with depth in the two cores but were higher in the mud flat. From 5 to 15 cm, corresponding to maximum root biomass under S. alterniflora, Zn and Cd concentrations remained constant in the mud flat cores, but increased by a factor of nearly 4 under S. alterniflora. Below this depth concentrations dropped in both cores. Manganese distribution in S. alterniflora cores suggests that oxides are precipitated at the depth of maximum root biomass. More oxic environment under S. alterniflora (average Eh = +5 mV) with low sulfide concentration (0.58 mg l^-1) relative to the mud flat cores (average Eh = –204 mV; sulfide 47.1 mg l^-1), may favor Fe and Mn oxi-hydroxides precipitation, causing an accumulation of Cd and Zn at the root zone. In the mud flat cores, Zn and Cd highest concentrations were at the sediment water interface, where oxic waters favor their precipitation with Fe and Mn oxi-hydroxides. The results discourages the indiscriminate use of salt marsh sediments in environmental monitoring of trace metals, since the possibility of post-deposition mobilization of trace metals due to root metabolism, will make correlation with trace metal loading rates impossible.     

文冠人工种群叶片成分分析

为了探析不同植株类型和不同染病程度的文冠果叶片成分差异,于2012年8月采集其叶片测定了12种成分（干物质、粗蛋白、粗脂肪、碳水化合物、维生素C、有机酸和6种微量元素）。结果表明,文冠果叶片干物质含量38.80%,干物质中粗蛋白和粗脂肪含量较高,分别为17.56%和9.81%;6种微量元素中钙含量最高（达2.218%）,其次为镁（0.507%）,其它4种含量均小于0.04%。不同植株类型（毛枝型和光枝型）上的叶片间成分无显著差异。不同病虫害危害程度除对叶片铁含量有显著影响以外,对其他成分含量并无显著影响。叶片12种成分在文冠果群体中变异程度不一且差异较大,其中钙变异最大,其次是维生素C,次之是铁和有机酸,锌变异最小最稳定。     

21种迁地保护植物微量元素与土壤养分状况分析

在“生态相似性”的迁地保护理论的指导下．研究了武汉植物园迁地保护植物樟科和木兰科21种珍稀植物的营养状况,及其所生长土壤的营养条件．结果表明:酸性土壤中Fe、Mn、Cu、Zn、B、Mo6种微量元素的有效态含量顺序为Fe>Mo>Cu>Zn>B >Mo,其平均值大小与全国平均值相差不大;植物叶片中微量元素含量大小顺序为Fe>Mn(或Mn>Fe)>B>Zn(或Zn>B)>Cu> Mo;与正常含量范围相比,所有植物Mn含量偏高,部分植物Fe含量较大．Cu、Zn、B含量较为正常,Mo含量偏低;生物吸收系数大小顺序为Zn>Fe>Mn>B>Cu．     

川西退耕还林地苦竹林碳密度、碳贮量及其空间分布

利用标准样方法研究了退耕还林地苦竹林碳素密度和碳贮量及其空间分布。结果表明:苦竹不同器官碳素密度波动在0.348 498~0.518 63gC0/g,按碳素密度高低排列依次为竹秆>竹蔸>竹鞭>竹枝>竹根>竹叶;枯落物碳素含量为0.341 655 gC0/g,土壤碳素密度由上至下呈下降趋势。碳贮量在苦竹不同器官中的分配以竹秆所占比例最大,为53.06%,其次为竹叶,占13.83%,占比例最小的是竹根,仅占3.14%;苦竹林生态系统中碳总贮量为135.808 110 t/hm2,其中乔木层为46.032 420 t/hm2,占33.9%,林下及其枯落物层为2.60 068 t/hm2,占1.91%。土壤层0~60 cm总计为87.175 0 t/hm2,占64.19%;退耕还林地苦竹林乔木层年固碳量约为8.142 t/(hm2.a)。     

秦岭北麓大熊猫主食竹矿物元素含量分析

采用原子吸收分光光度计法,测定和分析了生长于秦岭北麓陕西省楼观台实验林场的淡竹、毛环水竹、金竹、早园竹、唐竹、茶秆竹、巴山木竹、横枝竹、斑苦竹、阔叶箬竹等10种大熊猫主食竹的Ca、Na、Fe、Cu、K、Mg、Mn、Zn等8种矿物元素含量,结果显示10种竹子矿物质元素含量Ca元素介于733.00±24.58～3406.19±119.21 ug·g-1之间,早园竹最高,毛环水竹最低,差异显著（P＜0.05）;Na含量148.53±17.27～1687.60±122.32 ug·g-1,阔叶箬竹最高,茶秆竹最低,差异显著（P＜0.05）;Fe含量935.28±43.83～345.33±46.25 ug·g-1,阔叶箬竹最高,茶秆竹最低,差异显著（P＜0.05）;Cu含量56.23±10.96～346.50±13.04 ug·g-1,淡竹最高,斑苦竹最低,差异显著（P＜0.05）;K含量2410.32±90.28～7305.74±320.62 ug·g-1,唐竹最高,横枝竹最低,差异显著（P＜0.05）;Mg含量1830.42±86.57～5829.91±179.99ug·g-1,阔叶箬竹最高,斑苦竹最低,差异显著（P＜0.05）;Mn含量216.02±18.21～666.13±12.14 ug·g-1,阔叶箬竹最高,斑苦竹最低,差异显著（P＜0.05）;Zn含量115.06±15.24～515.97±56.28 ug·g-1,阔叶箬竹最高,横枝竹最低,差异显著（P＜0.05）;8种元素之间存在着复杂的相关关系.     

百山祖冷杉枝叶营养元素含量与适生立地土壤养分关系分析

研究了百山祖冷杉(Abies beshanzuensis)分布区适生立地表层土壤养分及其与百山祖冷杉枝叶营养元素含量的相关性.结果表明,土壤pH5.11～6.42,土壤有机质含量、全氮含量、速效磷含量、速效钾含量分别为119.075 0g/kg、2.196 2g/kg、15.016 3mg/kg、136.215 2mg/kg;百山祖冷杉对土壤N、P、K富集能力均较高,而对微量元素富集能力较弱,且枝部和针叶均未检出Na元素;较高的土壤N含量,可相应显著提高百山祖冷杉叶N、K含量水平,较高的土壤P含量,则显著抑制百山祖冷杉叶对K和枝对N的积累水平,较高的土壤Cu含量显著降低了Cu元素在叶器官中的积累,而显著增加了枝条中Cu和Zn的积累水平,较高的土壤Fe含量则显著促进了针叶中Fe元素和枝中Fe、Mn元素的积累水平.     

A comparison of decomposition dynamics among green tree leaves,partially decomposed tree leaf litter and their mixture in a warm temperate forest ecosystem

Decomposition dynamics were compared among green tree leaves, partially decomposed tree leaf litter (i.e., decayed tree leaf litter on forest floor) and a mixture of the two in a warm temperate forest ecosystem in central China to test the influence of litter chemical quality on the degree of decomposition. The study was conducted in situ at two contrasting forest sites, an oak forest dominated by Quercus aliena var. acuteserrata Maxim., and a mixed pine and oak forest dominated by Pinus armandii Franch. and Q. aliena var. acuteserrata. We found marked differences in the rate of decomposition among litter types at both forest sites; the litter decomposition constant, k, was about 39 % greater at the oak forest site and more than 70 % greater at the pine-oak forest site, for green leaves than for partially decomposed leaf litter. The decomposition dynamics and temporal changes in litter chemistry of the three litter types also greatly differed between the two forest sites. At both forest sites, the higher rate of decomposition for the green leaves was associated with a higher nitrogen (N) content and lower carbon to N ratio (C/N) and acid-unhydrolyzable residue to N ratio (AUR/N). We did not find any non-additive effects when mixing green leaves and partially decomposed leaf litter. Our findings support the contention that litter chemical quality is one of the most important determinants of litter decomposition in forest ecosystems at the local or regional scale, but the effect of litter chemical quality on decomposition differs between the contrasting forest types and may vary with the stage of decomposition.     

Growth and nutrition of Betula pendula at different relative supply rates of zinc

Small birch plants (Betula pendula Roth) were cultivated in a hydroponic spray solution where the relative growth rate (R(G); day(-1)) was controlled by the relative supply rate of zinc (R(Zn); day(-1)). After an adjustment phase to steady-state growth, R(G) equaled R(Zn). The R(Zn) treatments were 0.05, 0.125 and 0.20 day(-1) with free access to all other nutrients. In an additional treatment, there was free access to all nutrients, including zinc (FA treatment). The pH of the nutrient solution was approximately 4.5 and conductivity was 100 &mgr;S cm(-1). The duration of each treatment depended on R(Zn) and ranged from 4 (FA treatment) to 10 weeks (at R(Zn) = 0.05 day(-1)). The plants showed persistent and typical zinc-deficiency symptoms at steady-state growth when R(G) was 0.05 and 0.125 day(-1), whereas there were few symptoms when R(G) was 0.2 day(-1). The Zn concentration of the plants ranged from 8 (at R(Zn) = 0.05 day(-1)) to 21 &mgr;g g(DM) (-1) (DM = dry mass) (at R(Zn) = 0.2 day(-1)) and was approximately 42 &mgr;g g(DM) (-1) in the FA treatment. Uptake rates of Zn, calculated per root growth rate (&mgr;mol g(DM, root) (-1)), were about 2.8 times higher at R(Zn) = 0.20 day(-1) than at R(Zn)= 0.05 day(-1). The root and stem biomass fractions were approximately constant at all supply rates of Zn, whereas the leaf biomass fraction tended to increase with increasing supply rate of Zn. Net assimilation rate was constant from FA to an R(Zn) of 0.125 day(-1) but decreased by a factor of about 2 at R(Zn) = 0.05 day(-1). Leaf area ratio and specific leaf area were smaller at low supply rates of zinc than at high supply rates.     

Dissolved inorganic nitrogen cycling in Banzu intertidal sand-flat,Japan

The sediment-water exchange of nitrogen, nitrification, denitrification and sedimentary oxygen production were simultaneously measured in the Banzu intertidal sand-flat, Tokyo Bay, Japan. The exchange flux across the sediment-water interface showed a sink of dissolved inorganic nitrogen (DIN) in the light. However, in the dark, the intertidal sediment acted as a source. The diffusive flux obtained by the ammonium profile explained only 22% of the source flux directly measured in the dark, suggesting that bioturbation or excretion by macrofauna greatly contributed to the exchange flux. The total microphytobenthic uptake of DIN estimated from O2 productivity and the Redfield ratio was 573.4 ± 64.4 mol N m2 h-1, 31% (175.9 ± 64.4 mol N m-2 h-1) of which was assumed to be derived from the overlying water. The release rate of DIN from the sediment to the water column (1.1 mmol N m-2 day-1) was balanced with the removal rate of DIN from the water column by benthic microalgae on a diurnal basis. This result suggests that DIN was recycled within the sediment, and the microalgae on the sediment surface played a significant role in suppressing the release of mineralized DIN from the sediment. The measured denitrification rate using an acetylene inhibition technique was 99.6 ± 23.5 mol N m-2 h-1. Since the direct supply of nitrate or nitrite from the water column only accounted for 27% of the total denitrification at the highest estimate, nitrogenous oxide in the sediment pool was the major contributor to sedimentary denitrification.     

Biomass,decomposition and nutrient release of Vaccinium myrtillus leaf litter in four forest stands

Biomass and nutrient transfer (N, P, K, Ca, Mg) of bilberry (Vaccinium myrtillus L.) leaf litter fall, as well as decomposition and nutrient release, were studied in four mature forest stands situated in Central and South Sweden. Bilberry leaf litter fall amounted to between 33 and 55 kg ha^‐1 yr^‐1 in the four stands. Only minor differences between sites were noted for litter concentrations of N, P and Ca, whereas K and Mg showed somewhat larger variability. Relative amounts of the five nutrient elements in the litter fall were generally in the order N > Ca > K > Mg > P. The amounts of nutrients returned to the forest floor by the annual leaf litter fall in the stands ranged from 0.4 to 0.8 kg ha^‐1 for N, 0.4 to 0.6 kg ha^‐1 for Ca, 0.2 to 0.7 kg ha^‐1 for K, 0.1 to 0.2 kg ha^‐1 for Mg and 0.04 to 0.08 kg ha^‐1 for P.

The decomposition of the local bilberry leaf litter was followed by means of litterbags during three years. At all sites there was an extremely rapid mass loss from the litter (between 45% and 54%) during the first four to five months of decomposition. After this initial phase, the decomposition rates decreased markedly and after three years the accumulated mass losses of the litters varied between 64% and 78% at the studied sites. After two and three years of decomposition, three of the sites exhibited almost similar litter mass losses whereas at the fourth site the litter was decomposed to a significantly lower degree. The pattern of nutrient release from the decomposing bilberry leaf litter differed somewhat from site to site. Minor differences were, however, noted for P, Ca and Mg while N and K were more strongly retained in the litter at one of the sites.     

红锥人工幼林营养特性研究

对不同月份红锥叶片中营养元素含量的变化及其结构进行研究,结果表明,叶片中N、P、K、Ca、Mg、Mn、Fe、Cu、Zn营养元素含量呈季节性变化,普遍地在生长初期（春季）较高,生长旺期（夏季）最低,而秋冬季生长缓慢时由于积累所致而略有回升;叶片中常量元素含量以N、K、P较高,依次排序为：N〉K〉P〉Mg〉Ca,微量元素含量以Mn、Fe为高,依次排序为：Mn〉Fe〉Zn〉Cu,N、P、K、Ca、Mg、Mn、Fe、Zn、Cu比例为：7.40∶1.00∶5.96∶0.30∶0.51∶1.10∶0.16∶0.05∶0.01;根据研究结果及南方山地的土壤特点,红锥人工幼林的施肥时间宜在春季或春夏之交季节,在肥种及配比上,应在施用大量元素N、P、K、Mg、Ca的基础上配施微肥Zn,配比为N∶P∶K∶Ca∶Mg∶Zn=7.40∶1.00∶5.96∶0.30∶0.51∶0.05.