Recovery Patterns of Understory Herbs and Their Use as Indicators of Deciduous Forest Regeneration

Abstract: Habitat fragmentation has reduced the richness of native species of forests in northeastern North America. Despite recent large-scale increases in forest cover, studies indicate that understory herbaceous plant communities may take many decades to recover. We studied recovery patterns of vegetation following up to 35 years of forest regeneration in restored former cottage and road sites at Point Pelée National Park, Ontario, Canada, to assess the vulnerability of the understory herbaceous species. Overall, there were no significant differences in the diversity of native species between restored and relatively undisturbed reference sites. There was, however, significant among-site variation in the composition of the native species component of these plant communities. When only restored sites were examined, variation in native species composition was associated with time since site restoration, soil moisture, canopy cover, and distance to continuous forest. Native species were assigned vulnerability rankings according to their relative occurrence in reference and restored sites. Spring-flowering herbs, with ant- or gravity-dispersed seeds, were absent from restored sites and were defined as highly vulnerable. In contrast, summer- and fall-flowering herbs, with vertebrate- and wind-dispersed seeds, dominated restored sites and were less vulnerable. Species of low and intermediate vulnerability had colonized restored sites successfully, and the latter should function as indicators of recovery. In contrast, species with high vulnerability rankings had not recovered at all and, because of their limited dispersal ranges, may recolonize restored sites only if they are actively reintroduced.     

千年桐与毛竹凋落叶混合分解对土壤酶活性的影响

在16年生千年桐人工林中按5种分解模式(模式A:千年桐叶100%;模式B:毛竹叶100%;模式C:千年桐叶50%+毛竹叶50%;模式D:千年桐叶75%+毛竹叶25%;模式E:千年桐叶80%+毛竹叶20%)进行千年桐、毛竹凋落叶及其混合分解的野外模拟试验,分析千年桐与毛竹凋落叶混合分解对土壤酶活性的影响及其与凋落物主要营养元素全氮(TN)、全磷(TP)、全钾(TK),微量元素钠(Na)、钙(Ca)、锰(Mn)、镁(Mg)、锌(Zn)及有机碳(OC)的释放量之间的关系.结果表明:5种模式叶凋落物分解1年后TN、TP、TK、OC和Na、Ca、Mn、Mg、Zn的释放量大小并不一致,不同元素释放量在5种分解模式之间均存在显著差异;5种混合分解模式下,蔗糖酶和过氧化氢酶的最强活性区均出现在5～10 cm土层,其中蔗糖酶活性比较为模式E>C>A>CK>D>B,过氧化氢酶活性比较为模式E>CK>B>D>A>C.80%千年桐叶+20%毛竹叶的配比对土壤蔗糖酶和过氧化氢酶活性的增强作用比较明显,在实际的人工林栽培中,可考虑以千年桐和毛竹4:1的比例进行毛阔混交林的营造,以最大程度地增强土壤肥力,提高土壤质量,促进两种树种的共同生长.图2表2参37     

耕地土壤中交换态钙镁铁锰铜锌相关关系研究

应用主成份分析、聚类分析和相关性分析对沈阳市郊区1994个耕地土壤样本(0-20cm)的交换态钙、镁、铁、锰、铜、锌含量进行研究，结果表明，影响钙与镁、铁与锰、铜与锌分布的主因子分别在相同的主成份组中，钙与镁、铁与锰、铜与锌之间的相关系数较大，铁、锰、铜、锌之间均为极显著正相关关系，钙与铁、锰、铜、锌均为负相关关系，说明元素的生物地球化学属性对其地理分布有较大的影响。     

Assessment of metals in soil extracts and their uptake and movement within Tamarix nilotica at Lake Nasser banks, Egypt

This study aims to determine heavy-metal levels in soil from the banks of Lake Nasser, the ability of Tamarix nilotica to accumulate such metals from soil and hence its potential for phytoextraction. Soil and Tamarix samples were collected from the banks of four bights around Lake Nasser and analysed for Fe, Mn, Ca, Mg, Cr, Cu, Ni, Zn, Cd and Pb by atomic absorption spectrometry, whereas Na and K were measured by atomic emission spectrophotometry. Three different methods of extraction were used for the soil samples. Lead, copper and zinc were equally distributed between the exchangeable phase and Fe/Mn oxide-bound form, while other measured metals were mainly present in the Fe/Mn oxide fraction. With the exception of iron, all metals studied showed total concentrations within the geochemical background values. T. nilotica exhibited elevated concentrations of Na (36.2-48.5 mg g^-1) and K (2.74-4.33 mg g^-1) in stems, and relatively high concentrations of Pb, Cd and Co (0.39-1.03 µg g^-1, 0.24-1.3 µg g^-1 and 1.94-5.3 µg g^-1, respectively) are found in plant leaves. Bioaccumulation factors of Na and K (9.3 and 12.63, respectively) were high in T. nilotica stems. While the bioaccumulation of Pb, Cd, Co and Ni (2870.1, 2035.4, 10.5 and 5313.2, respectively) was high in plant leaves, Fe, Mn, Ca and Mg were accumulated relatively equally in plant stems and leaves. T. nilotica was found to secrete high amounts of Na, Ca and K, in addition to small amounts of all accumulated metals except Cd and Cu. These secreted metals appeared as salt crystals (67.5% Na; 25.8% Ca; 5% Mg; 1.5% K and 0.16% trace and minor elements) on the plant surface. The concentrations of all the metals studied in T. nilotica were higher than in the salt crystals. Statistical analysis of the database suggests bioaccumulation of these metals from soil to T. nilotica. This reflects the importance of using T. nilotica as a model in the phytoremediation process as an established environmental clean-up technology.     

排水对三江平原沼泽湿地土壤中化学元素的影响

以三江平原沼泽湿地生态试验站为研究基地 ,选择典型采样点 ,对排水沟土壤、沼泽土壤、沼泽化草甸土壤 (共有 6个采样点 ,2 8个样品 )进行测试 ,分析土样中主要离子 (HCO3- 、Cl- 、NO3- 、SO4 2 - 、Ca2 +、Mg2 +、K+、Na+)含量、重金属 (铁、锰、锌、铜 )含量、营养元素含量、有机质含量以及土壤pH值 ,研究沼泽排水对沼泽土壤中的化学元素含量的影响。研究结果表明 ,排水使沼泽土壤丧失大量的化学元素     

Effect of acid rain on the fractionation of heavy metals and major elements in contaminated soils

Acid rain is a serious environmental problem worldwide. In the present study, we investigated the effect of acid rain (1:1 equivalent basis H₂SO₄:HNO₃) at pH values of 2.0, 4.0 and 7.0 on the fractionation of heavy metals (Cd, Cu, Fe, Mn, Ni, Pb and Zn) and major elements (K, Na, Ca, and Mg) in contaminated calcareous soils over a 2084 h period. Heavy metals and major elements in soil samples were fractionated before and after 2084 h kinetic release using a sequential extraction procedure. Before kinetic studies the predominant fractions of K, Na, Ca, Mg, Cd and Ni were mainly associated with carbonate fraction (CARB), whereas Fe, Mn and Zn were associated with the Fe–Mn oxide fraction (Fe–Mn oxide). The highest percentage of Pb and Cu were found in the exchangeable (EXC) and organic matter (OM) fractions, respectively. After kinetic study using different simulated acid rain solutions, the major fractions of heavy metals (expect of Cu) and Na was the same as before release. Upon the application of different acid rain solutions, K and Mg were found dominantly in Fe–Mn oxide fraction, whereas Ca was in the EXC fraction. The results provide valuable information regarding metal mobility and indicated that speciation of metals (Cu and Zn) and major elements in contaminated calcareous soils can be affected by acid rain.     

Mobilization of different metals between Tamarix parts and their crystal salts – soil system at the banks of river Nile,Aswan, Egypt

In order to study the relation of the mobility and distribution of metals between Tamarix parts and their crystal salts – soil system, different experiments were conducted with plant-rich and plant-free soils at the banks of river Nile, Aswan, Egypt. For these purposes, Tamarix top and subsoil samples near and far from the plant were collected from six different locations at the banks of river Nile. Elemental analysis of Fe, Mn, Ca, Mg, Cr, Cu, Ni, Zn, Cd and Pb in soil, and in different parts of Tamarix and their crystal salt samples was carried out by atomic absorption spectrometry, whereas Na and K were measured by atomic emission spectrophotometry. The bioavailability of metals in the soil samples was evaluated by determining their contents using sequential extraction single-step, providing higher metal concentrations in occluded Fe/Mn oxide fraction. The ratio of heavy metal concentrations in topsoil to that in subsoil enhancement (RTE) ranged from 0.67 to 4.4 and 0.22 to 4.61 for soil Tamarix and soil free from plant, respectively for all measured total element concentrations. Data indicate that the mobility expressed as transfer factor (TF) was obtained as Fe?>?Mg?>?Cr?>?Mn?>?Ca?>?K?>?Na, for Tamarix leaves. The major part of accumulated Na in Tamarix is retained in the plant leaves, while roots accumulated high concentration of Co.     

南京市中心城区道路绿地土壤中重金属含量及污染评价

为了解不同绿化时间段道路绿地土壤中重金属的含量特征,采集了南京市中心城区不同绿化时间段道路绿地土壤0～5cm、5—20cm土样共50个。土壤经微波消解后,用原子吸收分光光度计分别测定土壤中cu、zn、Pb、cd和cr的全量。结果表明,南京城市土壤中cu、zn、Ph、cd和cr的全量分别为38．8±14．3、113．4±25．5、53．1±27．7、0．114±0．06、51．8±8．9mg／kg,最高值约为最低值的2．4～18．5倍。从变异系数来看,除zn、cr元素的变异系数在20％左右,其它重金属元素均在35％～55％之间。2000年前绿化的道路绿地土壤中重金属含量显著高于2000年后的绿地土壤（P〈0．05）。Pb、Cu和Zn存在不同程度的污染,Pb和cu在2000年前绿化的道路绿地土壤中达到中度污染水平,Cr处于警戒限水平,cd处于清洁水平。由于受交通和人为活动的影响,绿地表层土壤中重金属出现积累。     

Mineral status of soils and forage in the Mole National Park,Ghana and implications for wildlife nutrition

Geochemical mapping of soils and selected plant species has been carried out in the Mole National Park, Ghana. The distribution of the essential nutrients: cobalt, copper and manganese is largely controlled by bedrock geology, while the geochemical dispersion of Ca, I, Fe, Mg, Mo, P, K, Se, Na and Zn has been modified by soil and hydromorphic processes. From selective extraction experiments, Fe, Mn and Co are found to be largely fixed in the soil mineral fraction. Larger proportions of Cu, I, Mo, Se and Zn are EDTA extractable and have a high chelation potential.Cobalt, Cu and Mn were preferentially concentrated in grass species while molybdenum and selenium are concentrated in browse plants. Copper uptake is antagonistic to Fe, Mo and Zn accumulation in all plant and grass samples. Similarly, Se and Mn appear antagonistic and Fe uptake is antagonistic to Co, Cu, Mn, Mo and Zn.The low concentration of P points to a potential dietary deficiency of this element throughout the park. Cobalt deficiency may also occur due to a love extractability of these elements in the soils and low concentration in plants. However, the lack of data on the elemental requirements of wildlife allows only tentative conclusions to be drawn.     

Forest floor depth mediates understory vigor in xeric Pinus palustris ecosystems.

Longleaf pine (Pinus palustris) woodlands and savannas are among the most frequently burned ecosystems in the world with fire return intervals of 1-10 years. This fire regime has maintained high levels of biodiversity in terms of both species richness and endemism. Land use changes have reduced the area of this ecosystem by >95%, and inadequate fire frequencies threaten many of the remnants today. In the absence of frequent fire, rapid colonization of hardwoods and shrubs occurs, and a broad-leaved midstory develops. This midstory encroachment has been the focus of much research and management concern, largely based on the assumption that the midstory reduces understory plant diversity through direction competition via light interception. The general application of this mechanism of degradation is questionable, however, because midstory density, leaf area, and hardwood species composition vary substantially along a soil moisture gradient from mesic to extremely xeric sites. Reanalysis of recently reported data from xeric longleaf pine communities suggests that the development of the forest floor, a less conspicuous change in forest structure, might cause a decline in plant biodiversity when forests remain unburned. We report here a test of the interactions among fire, litter accumulation, forest floor development, and midstory canopy density on understory plant diversity. Structural equation modeling showed that within xeric sites, forest floor development was the primary factor explaining decreased biodiversity. The only effects of midstory development on biodiversity were those mediated through forest floor development. Boundary line analysis of functional guilds of understory plants showed sensitivity to even minor development of the forest floor in the absence of fire. These results challenge the prevailing management paradigm and suggest that within xeric longleaf pine communities, the primary focus of managed fire regime should be directed toward the restoration of forest floor characteristics rather than the introduction of high-intensity fires used to regulate midstory structure.     

Cluster analysis of inorganic elements in particulate matter in the air environment of an equatorial urban coastal location

Concentrations of nine inorganic elements (Na, Zn, Ca, Fe, Ni, Mn, Cu, Cd and Al) in particulate matter (PM₁₀) in the air of an equatorial urban coastal location during 2009 were studied during summer and winter monsoon seasons using high-volume sampling techniques. Atomic absorption spectrophotometry was used to analyse the samples. The concentrations of most inorganic elements were higher during summer than winter, except for Cu and Zn. The main inorganic elements in PM₁₀ are Na, Zn and Ca. High concentrations of Na and Ca are due to marine aerosols. Analysis of enrichment factors showed that inorganic elements are from non-crustal sources. Cluster analysis identified five clusters in the summer and six in the winter: (1) PM₁₀–Ni, (2) Zn–Na, (3) Fe–Cu–Ca–Cd, (4) Mn and (5) Al for summer; and (1) PM₁₀, (2) Zn, (3) Fe–Ni, (4) Cu–Ca–Na–Cd, (5) Mn and (6) Al for winter. Combining both correlation and cluster analysis, it was found that Fe–Cu–Cd was from industry/vehicle emissions, Zn was from resuspended soil, Mn was from metallurgical processes, Ni was from a nearby power plant and Al was from crustal sources. Inorganic element concentrations could be a good indicator of local sources of PM₁₀.     

Assessment of metals in soil extracts and their uptake and movement within Tamarix nilotica at Lake Nasser banks,Egypt

This study aims to determine heavy-metal levels in soil from the banks of Lake Nasser, the ability of Tamarix nilotica to accumulate such metals from soil and hence its potential for phytoextraction. Soil and Tamarix samples were collected from the banks of four bights around Lake Nasser and analysed for Fe, Mn, Ca, Mg, Cr, Cu, Ni, Zn, Cd and Pb by atomic absorption spectrometry, whereas Na and K were measured by atomic emission spectrophotometry. Three different methods of extraction were used for the soil samples. Lead, copper and zinc were equally distributed between the exchangeable phase and Fe/Mn oxide-bound form, while other measured metals were mainly present in the Fe/Mn oxide fraction. With the exception of iron, all metals studied showed total concentrations within the geochemical background values. T. nilotica exhibited elevated concentrations of Na (36.2–48.5?mg?g^?1) and K (2.74–4.33?mg?g^?1) in stems, and relatively high concentrations of Pb, Cd and Co (0.39–1.03?µg?g^?1, 0.24–1.3?µg?g^?1 and 1.94–5.3?µg?g^?1, respectively) are found in plant leaves. Bioaccumulation factors of Na and K (9.3 and 12.63, respectively) were high in T. nilotica stems. While the bioaccumulation of Pb, Cd, Co and Ni (2870.1, 2035.4, 10.5 and 5313.2, respectively) was high in plant leaves, Fe, Mn, Ca and Mg were accumulated relatively equally in plant stems and leaves. T. nilotica was found to secrete high amounts of Na, Ca and K, in addition to small amounts of all accumulated metals except Cd and Cu. These secreted metals appeared as salt crystals (67.5% Na; 25.8% Ca; 5% Mg; 1.5% K and 0.16% trace and minor elements) on the plant surface. The concentrations of all the metals studied in T. nilotica were higher than in the salt crystals. Statistical analysis of the database suggests bioaccumulation of these metals from soil to T. nilotica. This reflects the importance of using T. nilotica as a model in the phytoremediation process as an established environmental clean-up technology.     

Urban Geochemistry: Investigations in the Berlin Metropolitan Area

The distribution of 41 trace and 11 major elements in 4000 samples of topsoils (0–20cm) from the Berlin Megacity is interpreted. The detailed comparative analysis of the element distributions and the results of factor analysis showed that the distributions of the elements Al, K, Na, Rb, Zr, Nb and Ti are mainly natural origin, i.e. related to the composition of the parent material. Industrial and commercial areas often display considerably elevated values for Mo, Ni, As, Ag, Cr, Sb, Fe, Mn, Mg, P, TOC and especially Pb, Hg and electrical conductivity relative to the geogenic background of the area surrounding Berlin. Industrial areas tend to be characterised by contamination of the subsoil with Cu, Cd, Zn, Hg, Pb and Sn. In the area around Berlin, extensive, strong anamalies of Cd, Zn, Pb, Cu and Hg occur near iron and steel industries and construction materials industries, as well as in the vicinity of sewage farms.     

Effects of Roads on Movements by Understory Birds in Mixed-Species Flocks in Central Amazonian Brazil

Abstract: Roads through tropical forest create linear disturbances that have unknown consequences for forest birds. We studied how a narrow, rarely used road through otherwise undisturbed Amazonian forest affected the movements and area requirements of understory birds that form mixed-species flocks. Differences in road maintenance led to two distinct treatments along the same road. Trees along the "closed" road formed a partial canopy connecting the two sides of the road, although the roadway itself was kept open. The "open" road was regularly maintained, making a complete opening 10–30 m wide.We followed 15 flocks, 5 each in interior forest, along the open road, and along the closed road. These flocks were led by Thamnomanes antshrikes, and each flock had a discreet, permanent territory. Flock territory size (mean = 8.5 ha) did not differ among the three locations. The open road formed the territorial boundary for all five flocks, although birds moved within a few meters of the edge of the road. The closed road was less of a barrier: 2 of 5 flocks used both sides of the closed road. Playback experiments showed that flocks readily crossed the closed road to approach agonistic vocalizations. Along the open road, even though birds responded to playback by becoming agitated and moving to the extreme edge of the roadside vegetation, they were less likely to cross the road and did so only after a longer duration of playback. Our results suggest that flocks respond to a road as they would to a long linear gap. They use the vegetation along the edges of the road, but because they are unwilling to cross the open area, it becomes a flock territory boundary. Similarly, as in forest gaps, successional change along the closed road produced suitable habitat for flocks. Although this suggests that roads are a trivial problem, we caution that this result applies only to narrow roads that are not accompanied by deforestation or other disturbance.     

Detection of elements and radioactivity in pellets from long-eared owls (Asio otus) inhabiting the city of Belgrade (Serbia)

In this study, we analysed pellets from long-eared owls (Asio otus) collected from four localities in Belgrade (Serbia). The pellets contained the remains of prey, namely voles (Arvicola terrestris) and field mice (Apodemus agrarius). The concentrations of 14 elements (Ca, P, Mg, Na, K, Fe, Zn, Sr, Ba, Mn, Ti, Cu, Si, B) were evaluated in whole pellets and in samples containing only bone tissue, which were dissected from the whole pellet. The increased levels of certain elements, including Mn, Zn, Ba, Cu and radioactive ⁴⁰K, indicate contamination of the soil by various sources, such as industrial plants and agricultural practices. From the results presented in this article, we suggest that the analysis of owl pellets may indicate the quality of the local environment.     

Long-term aboveground and belowground consequences of red wood ant exclusion in boreal forest

Despite their ubiquity, the role of ants in driving ecosystem processes both aboveground and belowground has been seldom explored, except within the nest. During 1995 we established 16 ant exclusion plots of approximately 1.1 x 1.1 m, together with paired control plots, in the understory layer of a boreal forest ecosystem in northern Sweden that supports high densities of the mound-forming ant Formica aquilonia, a red wood ant species of the Formica rufa group. Aboveground and belowground measurements were then made on destructively sampled subplots in 2001 and 2008, i.e., 6 and 13 years after set-up. While ant exclusion had no effect on total understory plant biomass, it did greatly increase the relative contribution of herbaceous species, most likely through preventing ants from removing their seeds. This in turn led to higher quality resources entering the belowground subsystem, which in turn stimulated soil microbial biomass and activity and the rates of loss of mass and carbon (C) and nitrogen (N) from litter in litterbags placed in the plots. This was accompanied by losses of approximately 15% of N and C stored in the humus on a per area basis. Ant exclusion also had some effects on foliar stable isotope ratios for both C and N, most probably as a consequence of greater soil fertility. Further, exclusion of ants had multitrophic effects on a microbe-nematode soil food web with three consumer trophic levels and after six years promoted the bacterial-based relative to the fungal-based energy channel in this food web. Our results point to a major role of red wood ants in determining forest floor vegetation and thereby exerting wide-ranging effects on belowground properties and processes. Given that the boreal forest occupies 11% of the Earth's terrestrial surface and stores more C than any other forest biome, our results suggest that this role of ants could potentially be of widespread significance for biogeochemical nutrient cycling, soil nutrient capital, and sequestration of belowground carbon.     

不同地区何首乌无机元素含量的比较

采用ICP法测定了不同地区何首乌植物及其生境土壤中的15种元素(Al、B、Ba、Ca、Cu、Fe、K、Mg、Mn、Na、Ni、P、Sr、Ti、Zn),分析比较了各种元素在不同地区何首乌体内和生境土壤中的分布规律及不同地区何首乌对无机元素的吸收富集能力.结果表明,不同地区何首乌和土壤中无机元素含量存在着显著差异,德庆、井冈山、靖西三地何首乌的Mn含量较高;不同地区何首乌对元素的富集系数无显著性差异,而何首乌对不同无机元素的富集系数则有显著差异,主要表现在对Ca、K、Mg、Sr的吸收富集能力较强.表6参14     

Concentrations of various elements and inorganic ions in rice straw and ash

Various elements and inorganic ions in rice straw and ash samples were analyzed by using inductively coupled plasma atomic emission spectrometry (ICP‐AES) and ion chromatography (IC). Five major elements: Mg, Mn, Al, Ca, and Fe and eight minor and trace elements: Cr, Cu, Ti, Zn, La, Sr, Ba, and Hg were detected in these samples, at more than ppm‐level. In ash samples the trace elements such as Y, As, V, Se, and Sc were also identified. The concentrations of SO₄, PO₄, Cl, Na, and K ions in these samples were higher than those of other ions measured. These elements and inorganic ion concentrations were approximately one order of magnitude higher in the ash than in the straw samples. Gas chromatography/mass spectrometry (GC/MS) and library search showed the presence of fatty‐, carboxylic‐ and nicotinic acids, and their derivatives in small quantities in the straw samples.     

The Nutrient Status of Some Graminaceous Species in Britain. 2. Deschampsia Flexuosa (L.) Trin

Above-ground biomass of Deschampsia flexuosa from 40 sites throughout Britain was analysed for concentrations of elements (N, P, K, Ca, Mg, Fe, Mn, Cu, Zn and Na), with matching analyses of nutrient levels in the soils, together with pH and LOI. Seasonal variation in the nutrients was also studied in detail at one of the sites. the grass was found on acid sites ranging between pH 3.1 and 4.7. the soil humus content varied widely, and there were significant correlations between that and elements (N, P, K, Ca, Mg, Zn and Na) in the soil. Concentrations of zinc and manganese in the plant material were the only elements that significantly correlated with extractable levels in the soils. Tissue concentrations of nitrogen, phosphorus, and potassium declined throughout the growing season, whereas the other elements showed a tendency to build up until the end of September. Calcium, magnesium and manganese concentrations then declined as growth ceased. the results are compared with above-ground concentrations of minerals in other plants and the growth strategy of this perennial grass.     

Cycling of metals in desert soils: effects of Tamarix nilotica and inundation by lake water

Concentrations of Ca, Mg, K, Na, Cu, Zn, Al, Fe and Mn were measured in soils and in Tamarix nilotica from Wadi Allaqi on the shore of Lake Nasser in the Eastern Desert of Egypt. All of the elements were concentrated in the leaves of Tamarix relative to the stems and roots. Leaf:soil concentration ratios, used as an indicator of metal accumulation in the plant, showed high enrichment factors for Na (67.5), K (63.0) and Mg (35.0); of the trace elements measured, Zn had the highest enrichment factor (7.64). Comparison with other desert species suggested that Tamarix was exceptional only in the accumulation of sodium. Periodic inundation of the soil by Lake Nasser caused dilution and dispersion of the accumulated salts.