Water circulation, groundwater outflow and nutrient dynamics in Mida creek, Kenya

The relationship between physical hydrodynamic processes and nutrients dynamics was investigated in Mida creek, a groundwater influenced mangrovefringed creek in Kenya between March 1996 and May 1997. The research involved spot and timeseries measurement of nitrate–nitrite, ammonia, silicates, phosphates, salinity, temperature, sealevel as well as tidal currents at seven stations located in the front, middle and backwater zones of the creek. Groundwater level as well as total dissolved solids' concentration, salinity, temperature and nutrients' concentration were also measured once every month in shallow wells (watertable<5m) located in the upper region of the creek. Results of the study show that nutrient concentrations vary with the tide and that, though there is no river drainage, they are of the same magnitude as in mangrove creeks with substantial river runoff. The peak concentrations of NH ₄ ⁺ –N (5.45M), NO ₂ –NO ₃ (5.63M), PO ₄ ^3– –P (0.58M) and SiO ₃ ^2– –Si (81.36M) in the creek occurred during flood tide, 2–3h before high waters. The (NO ₂ ^– + NO ₃ ^– )–N concentrations declined rapidly during ebb tide, reaching the minimum levels during low water. Contribution of groundwater seepage to the net nutrients flux (particularly on nitrite–nitrates) is largest in dry seasons. The study shows that groundwater outflow sustains the mangroves during periods of severe salinity stress and nutrients deficiency in dry seasons. This is essentially by limiting salinity increase and by boosting nutrient supply in dry seasons.     

Evaporation over a tropical tidal salt flat

Measurements of temperature, wind speed and humidity within 6 mof the surface of a mangrove-fringed tidal tropical salt flatwere performed. Using the aerodynamic method, this data was usedto infer evaporation rates from the salt flat. For a few daysafter tidal inundation or rain, the salt flats were wet andevaporation rates of about 5×10^-3 m day^-1 prevailed. By 8 daysafter tidal inundation and with no rain, evaporation rates haddropped to less than 2×10^-3 m day^-1. The monthly evaporation ratewas about 7×10^-2 m. This generates high salinity which, togetherwith surface temperatures exceeding 50°C, prevents colonisationof these areas by mangroves.     

Transfer of salt and nutrients in Bruguiera gymnorrhiza leaves during development and senescence

The life span of leaves in Bruguiera gymnorrhiza, non-secretor of salt, can be divided into a leaf developing stage, a leaf functioning stage and a leaf senescing stage. The concentrations (mg/g) and the contents (mg/leaf) of Na and Cl increased at the leaf developing stage and remained almost constant at the leaf functioning stage. At the leaf senescing stage, the concentrations of Na and Cl increased markedly by 45 and 31% respectively, while their contents only increased by 16 and 4% respectively. The K/Na ratio remained constant at the leaf functioning stage, and decreased at the leaf senescing stage. During leaf senescence, there was a marked decline in leaf mass (20%) and in leaf area (15%). During senescence, 60% of its N, 48% of its P and 46% of its K was transferred out of the senescing leaf.     

Response of water and nutrient fluxes to improvement fellings in a tropical montane forest in Ecuador

Management of natural forests might be one option to reduce the high deforestation rate in Ecuador. We therefore evaluated the response of water and nutrient cycles in a natural tropical montane forest to improvement fellings with the aim of favoring economically valuable target trees which will later be harvested with additional ecosystem impacts not considered here.     

水培变叶木、发财树和金钱树的养分配此研究

以海南典型的热带花卉变叶木Codiaeumvariegatum,发财树（瓜栗）pachiramacrocarpa和金钱树Zamioculcaszamiifolia为研究对象,通过一系列的水培试验,并利用有关的统计软件分析,以期达到各品种最佳的养分配比。结果表明,在海南的热带气候条件下,变叶木水培的氮磷钾最适浓度配比为7：1：4,发财树的最适配比为2：3：11,金钱树的最适配比为3：2：8。     

Biogeochemical cycling and chemical fluxes in a managed northern forested wetland, Michigan, USA

Forest harvesting and subsequent regeneration treatments may cause changes in soil and solution chemistry that adversely affect forest productivity and environmental quality. The objective of this study was to assess soil carbon (C), nitrogen (N), and base cation pools and fluxes, and to construct a hydrogen ion (H⁺) mass balance to identify major processes controlling acidity production and consumption 14 years following whole-tree harvesting and regeneration in a northern forested wetland with underlying mineral soils derived from calcareous glacial drift. Results for soil elemental and nutrient pools in the harvested/regenerated stand were compared to an adjacent non-harvested stand and a riparian zone. The riparian zone had the highest soil total C, total N, and exchangeable calcium (Ca) and magnesium (Mg) pools; however, no difference in exchangeable potassium (K) was evident among stand types. Moreover, no differences between the harvested/regenerated and uncut stands were evident in any of the soil chemical pools.Net export of base cations was minimal and the H⁺ mass balance indicated that net cation exchange was not a significant process in H⁺ production or consumption in either the uncut or harvested/regenerated stands. The most striking differences in the H⁺ mass balance were (1) eight times the H⁺ consumption from sulfate (SO₄²⁻) reduction in the harvested/regenerated stand compared to that in the uncut condition and (2) nearly twice the H⁺ production due to N immobilization in the harvested/regenerated stand. However, both stand types were net H⁺ sinks and increases in H⁺ export due to whole-tree harvesting were not evident.The riparian zone was a net exporter of base cations. This finding was attributed to a combination of base cation exchange and carbonate mineral weathering; data suggested the importance of the latter. More research, however, is required to isolate the contributions of cation exchange and carbonate weathering on base cation export from the riparian zone. Stream chemistry was consistent with that of the riparian zone, indicating a strong linkage between the riparian zone stream chemistry, and whole-tree harvesting had no intermediate term (i.e., 14 years) effects on stream acidification in this managed northern wetland ecosystem.     

PHYSIOLOGY OF WOODY PLANT UNDER SALT CONDITION

INTRODUCTIoNBccauscofthetvidespreadofsalinityinthct`or1d-plantsareincreasinglybeingsub-Jcctedtothcadverseconditions.Theimpactofcxccssivcsalinit)'onxvOodyplantSistvide-sprcadandcost-ald1ougl1rePOrtsontheseis-sucsarcnotasnumerousasthoseofagricuI-taralcrops(Alle11ctaI.l994).Sincclbrcstsarcanin1portantcomPoncntofthccontincntalccoIogY.-Fhc}pla}anil11portantrolci11stabi-Il,lllgdcgradatIol1i11so111ct'uInerablearcas.Solncsalttolcra11ttrccscangrot`ttclIinarcasx`llcrcagriculturaicropscalll1ot…     

桉树人工林与天然林土壤养分的对比研究

在野外调查取样和室内实验分析的基础上,对人工林与天然林的土壤养分进行比较分析,结果表明人工林土壤表层的有机质、全氮、全磷、全钾含量都明显低于天然林,反映了人工林对养分的旺盛需求和消耗,并且人工林还会造成土壤阳离子交换量的降低和土壤容重的增大。提出变炼山全垦为块状整地、轮栽并适当休闲养地、提高人工林生物多样性、建立复杂的人工林群落等措施,以实现桉树人工林土壤养分平衡与生态系统的良性循环。     

耐盐碱乔木在盐碱地环境中的应用概况

时滨城区盐碱土绿化乔木的应用状况进行了调查。结果表明：该地区有盐碱土绿化乔木17科,37种;现已广泛栽培应用21种,其中有24．32％能耐中度盐碱,部分种类只耐轻度盐碱,有1种为特耐盐植物;有野生及乡土耐盐碱乔木种类7种,其中2种为很有价值的盐碱土绿化乔木。     

中国亚热带地区不同发育阶段杉木林生物量、凋落物及养分流

杉木生长快、产量高、材质好,是中国亚热带地区最重要的造林树种之一,在中国南方人工林经营中占有重要地位。对8、14和24年生杉木人工林生物量、凋落物及其养分流进行的研究结果表明:杉木人工林具有很高的生物生产力和50%-70%的树干生物量积累比例。杉木是低养分归还的针叶树种,凋落量少,而且针叶凋落前养分发生一定程度的转移,凋落物养分含量低,短轮伐期连栽收获制度造成的养分损失是导致杉木人工林地力衰退的原因之一。图1表7参22。     

不同施钾水平对油茶树体生长和林地养分含量的影响

为了确定油茶幼林钾肥最适施用量,从而为油茶的科学施肥提供理论依据,以‘赣无’系列的5年生油茶林分为试验对象,设置了5个钾素水平处理(K0、K1、K2、K3、K4),1个施用复合肥的对照处理(CKFHF)和1个不施肥的处理对照(CK0),就不同施肥处理对油茶树体生长、叶片养分积累和土壤养分含量的影响情况进行了试验、测定与分析。结果表明:施肥均能显著提高油茶树体各生长指标的增幅和叶片及土壤中各种养分的含量;随着施钾水平的提高,油茶树体各生长指标的增幅和叶片中各种养分的含量均随之增加,K3处理的达到最大值,复合肥处理的肥效小于K2处理;随着施钾水平的提高,油茶林地土壤中速效钾和有机质的含量均显著性增加,而土壤中碱解氮和有效磷的含量则随着施钾水平的提高均先减小后增加,K4处理的降到最小值;对油茶叶片中的钾含量、土壤中的速效钾含量与施钾量进行拟合,得出其响应曲线,并确定了对油茶幼树施用钾肥的最适用量范围为317.72~322.25 g/株。     

低温、干旱和盐胁迫下沙冬青幼苗脯氨酸含量的变化

沙冬青(Ammopiptanthus mongolicus.(Maxim)Cheng.f)为我国西北荒漠区唯一的常绿灌木,具有极强的抗性。本文对低温、干旱和盐胁迫下沙冬青幼苗中脯氨酸积累的变化进行研究,以期探讨不同胁迫下脯氨酸累积的共性和特异性,为进一步探讨逆境下脯氨酸积累的生理意义提供参考。     

Eucalyptus urophylla root growth, stem sprouting and nutrient supply from the roots and soil

Lack of information concerning root growth of trees limits our knowledge of plant development and fertilizer response. The objective of this work was to study root growth dynamics of an E. urophylla forest after harvesting and the supply of nutrients from the roots and the soil to the new sprouts originating from the stumps. About 7-year-old eucalypt trees were felled and the sprouts and roots were sampled at 0, 60, 120, 180, 240, 330 days after harvesting. The roots were separated into fine roots (<1 mm), medium roots (1–3 mm), coarse roots (>3 mm), and taproot. Nutrient supply to sprouts from the old roots and the soil was calculated based on the change in nutrient content of the roots with time and accumulation of nutrients in the sprouts. Fine, medium and coarse root biomass increased with time after harvesting. However, the increase was more pronounced with fine roots. Between harvesting and day 60 of the new growth, all nutrients allocated to the sprouts, excluding potassium, were supplied by the soil. K was the nutrient most dependent on root reserves for the initial growth of sprouts. The contribution of the old roots to N, P, Ca, and Mg accumulation in the sprouts increased between day 60 and 120. At 330 days after harvesting, about 9.2, 23.9, and 12.6% of the N, K, and Mg, respectively, that had accumulated in the sprouts were supplied by the roots, while all P and Ca were supplied by the soil.     

三倍体毛白杨品种和种植密度对其叶片营养元素含量的影响

在田间试验条件下,采用裂区设计,以三倍体毛白杨无性系S1、S6、S8、S11为试验材料,以二倍体毛白杨S10为对照,采用7种种植密度A1(2 m×2 m)、A2(2 m×3 m)、A3(2 m×3.5 m)、A4(3 m×4 m)、A5(2 m×4 m)、A6(2 m×5 m)、A7(3 m×3 m),研究了不同品种和种植密度对三倍体毛白杨叶片营养元素含量的影响。结果表明:不同的无性系对三倍体毛白杨叶片中N、P、K、Ca、Mg的含量均有极显著的影响。叶片中N含量最高的是S6(27.41 g/kg),P含量最高的是S1(1.88 g/kg),K含量最高的是S8(3.59 g/kg),Ca、Mg含量最高的分别是S10(10.48 g/kg)、S11(4.61 g/kg)。不同种植密度对叶片中N元素的含量有显著的影响,其中叶片含N量最多的是A6,达26.97 g/kg。而不同种植密度的无性系叶片中P、K、Ca、Mg的含量无显著差异。相关性分析表明,各元素之间存在一定的相关性,Mg与Ca之间呈显著正相关,与K之间呈显著负相关。     

Spatial pattern of soil carbon and nutrient storage at the alpine tundra ecosystem of Changbai Mountain,China

气候变化对土壤碳和养分的影响越来越受到生态学家的关注,尤其是对高山冻原生态系统的影响。本研究目的是长白山高山冻原系统土壤碳和养分的空间异质性。结果表明:不同土层深度的土壤碳在Meadow alpine tundra vegetation (MA)中显著地高于其他植被类型(p<0.05);在每一植被类型中,表层(010 cm)碳含量显著地高于1020 cm的土层;土壤氮的分布格局是氮素在表层和1020 cm土层变化规律相似;不同土层深度的土壤磷在Lithic alpine tundra vegetation (LA) 中显著地低于其他植被类型(p<0.05);土壤钾浓度在Felsenmeer alpine tundra vegetation (FA) 和LA中显著地高于其他植被类型,但在每一植被类型中土壤钾浓度随土壤深度没有明显的变化;不同深度土壤硫在MA中显著地高度其他植被类型;对每一植被类型而言,C: N, C: P, C: K 和C: S随土壤深度增加而降低。除了在SA的表层外,表层的土壤C: N高于1020 cm的土层。在长白山高山冻原系统中,随植被类型的变化,土壤碳和养分储量有着显著的空间异质性。参29表3图1。     

The role of groundwater flow in controlling the spatial distribution of soil salinity and rooted macrophytes in a southeastern salt marsh, USA

Groundwater flow is an important factor in governing botanical zonation in the salt marsh at North Inlet, SC. Areas of the marsh adjacent to upland forest are characterized by upward flow of fresh groundwater. This inhibits the infiltration and evapoconcentration of saline tidal water and the development of a habitat for hypersaline-tolerant fugitive species such as Salicornia europaea. Areas of high marsh that are not adjacent to extensive upland forest are characterized by downward gradients in hydraulic head. This allows the infiltration and evapoconcentration of tidal water and the development of hypersaline conditions that are suitable for salt-tolerant fugitives.     

Effect of NaCl on growth and ion relations in two salt-tolerant strains of Paxillus involutus

The effect of NaCl on growth, biomass and ion relations of two salt-tolerant isolates of Paxillus involutus, MAJ and NAU were investigated. The two Paxillus strains were exposed to the following concentrations of NaCl： 0, 100, 200 and 500 mmol·L^-1. Growth of MAJ and NAU was enhanced by 100 mmol·L^-1 NaCl but severely inhibited at the concentration of 500 mmol·L^-1. NAU exhibited a greater capacity to exclude Na^＋ and Cl^- under all salinity levels, whereas the salt-includer MAJ had a higher capacity in nutrient uptake under salt stress. The ratios Na^＋/K^＋, Na^＋/Ca^2＋ and Na^＋/Mg^2＋ in NaCl-treated MAJ and NAU did not increase at levels of 100 and 200 mmol·L^-1 NaCl but markedly increased at 500 mmol·L^-1. This suggests that the two strains, especially MAJ, enhanced nutrient uptake corresponding to the increased Na^＋ influx at moderate salinity. We conclude that both MAJ and NAU are able to tolerate 500 mmol·L^-1 NaCl but there are species-specific differences in retaining ionic homeostasis in the two Paxillus strains. NAU is a salt-excluder, MAJ is a salt-includer but retains a high capacity in nutrient selectivity under saline conditions. Their definite mechanisms to enhance salt tolerance of mycorrhizal hosts need further study.     

日本北海道北部寒温带森林流域林冠层凋落物及其养分归还量的景观格局(英文)

Within a forested watershed at the Uryu Experimental Forest of Hokkaido University in northern Hokkaido, overstory litterfall and related nutrient fluxes were measured at different landscape zones over two years. The wetland zone covered with Picea glehnii pure stand. The riparian zone was deciduous broad-leaved stand dominated by Alnus hirsuta and Salix spp., while the mixture of deciduous broadleaf and evergreen conifer dominated by Betula platyphylla, Quercus crispula and Abies sachalinensis distributed on the upland zone. Annual litterfall averaged 1444, 5122, and 4123 kg.hm^-2·a^-1 in the wetland, riparian and upland zones, respectively. Litterfall production peaked in September-October, and foliage litter contributed the greatest amount （73.4%-87.6 %） of the annual total litterfall. Concentrations of nutrients analyzed in foliage litter of the dominant species showed a similar seasonal variation over the year except for N in P glehnii and A. hirsuta. The nutrient fluxes for all elements analyzed were greatest on riparian zone and lowest in wetland zone. Nutrient fluxes via litterfall followed the decreasing sequence： N （11-129 kg.hm-2.aq） 〉 Ca （9-69） 〉 K （5-20） 〉 Mg （3-15） 〉 P （0.4-4.7） for all stands. Significant differences were found in litterfall production and nutrient fluxes among the different landscape components. There existed significant differences in soil chemistry between the different landscape zones. The consistently low soil C：N ratios at the riparian zone might be due to the higher-quality litter inputs （largely N-fixing alder）.     

Temporal variation in nutrient concentrations of Pinus sylvestris needles

Temporal variation in nutrient concentrations of Scots pine (Pinus sylvestris L.) needles was studied during a three‐year period in three stands of differing stages of development. Concentrations of N, P and K varied significantly between years; this variation was related to differences in needle dry weight. Concentrations of all measured nutrients (N, P, K, Ca, Mg, Mn, Cu, Zn, Fe, B) and Al varied between seasons; this variation was related to nutrient mobility and the annual physiological cycle. Concentrations of the mobile nutrients N, P and K decreased in spring and early summer during shoot and needle elongation and increased in late summer and autumn during needle senescence and litterfall. Concentrations of Mg, Cu, Zn and B followed somewhat similar patterns. The poorly mobile nutrients Ca, Mn and Fe accumulated gradually in needles during each growing season. Needle nutrient concentrations were stable during the nonactive period.     

Absence of creeks and pans in temperate Australian salt marshes

The absence of creeks and pans in many temperate Australian salt marshes is not compatible with current models of salt marsh formation and needs to be taken into account in the development of new models.