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1.
Ingeborg Callesen Lars Ola Nilsson Inger Kappel Schmidt Lars Vesterdal Per Ambus Jesper Riis Christiansen Peter Högberg Per Gundersen 《Plant and Soil》2013,368(1-2):375-392
Aims
We investigated the influence of tree species on the natural 15N abundance in forest stands under elevated ambient N deposition.Methods
We analysed δ15N in litter, the forest floor and three mineral soil horizons along with ecosystem N status variables at six sites planted three decades ago with five European broadleaved tree species and Norway spruce.Results
Litter δ15N and 15N enrichment factor (δ15Nlitter–δ15Nsoil) were positively correlated with N status based on soil and litter N pools, nitrification, subsoil nitrate concentration and forest growth. Tree species differences were also significant for these N variables and for the litter δ15N and enrichment factor. Litter from ash and sycamore maple with high N status and low fungal mycelia activity was enriched in 15N (+0.9 delta units) relative to other tree species (European beech, pedunculate oak, lime and Norway spruce) even though the latter species leached more nitrate.Conclusions
The δ15N pattern reflected tree species related traits affecting the N cycling as well as site fertility and former land use, and possibly differences in N leaching. The tree species δ15N patterns reflected fractionation caused by uptake of N through mycorrhiza rather than due to nitrate leaching or other N transformation processes. 相似文献2.
G. Tomlinson N. Buchmann R. Siegwolf P. Weber A. Thimonier E. Graf Pannatier M. Schmitt M. Schaub P. Waldner 《Trees - Structure and Function》2016,30(3):627-638
Key message
For long-term environmental investigations, tree-ring δ 15 N values are inappropriate proxies for foliar δ 15 N for both Fagus sylvatica and Picea abies under moderate N loads.Abstract
Currently it is unclear whether stable nitrogen isotope signals of tree-rings are related to those in foliage, and whether they can be used to infer tree responses to environmental changes. We studied foliar and tree-ring nitrogen (δ15N) and carbon (δ13C) isotope ratios in European beech (Fagus sylvatica L.) and Norway spruce (Picea abies L.) from six long-term forest monitoring sites in Switzerland together with data on N deposition and soil N availability, as well as a drought response index over the last two decades. For both species, tree-ring δ15N and δ13C values were less negative compared to foliar δ15N and δ13C values, most likely due to recycling and reallocation of N within the tree and fractionation processes associated with the transport of sucrose and the formation of tree-rings, respectively. Temporal trends recorded in foliar δ15N were not reflected in tree-ring δ15N, with much higher variations in tree-rings compared to foliage. Soil N availability and N deposition were partially able to explain changes in foliar δ13C, while there were no significant correlations between environmental variables and either tree-ring or foliar δ15N. Our results suggest an uncoupling between the N isotopic composition of tree-rings and foliage. Consequently, tree-ring δ15N values are inappropriate proxies of foliar δ15N values under low-to-moderate N deposition loads. Furthermore, at such low levels of deposition, tree-ring δ15N values are not recommended as archives of tree responses to soil C/N or bulk N deposition.3.
Aims
Coexistence of trees and grasses in nutrient-poor arid savannas may result in competition for soil N. While grasses may be more effective than woody plants in acquiring N from the soil, some leguminous woody species rely on N2 fixation. We assessed the role of N2 fixation in the N-budget of Acacia mellifera seedlings by varying N supply and grass competition.Methods
The contribution of N2 fixation to the N-budget of Acacia mellifera seedlings with varying N supply and grass competition was determined by measuring growth, nutrient concentrations, and 15N values.Results
Tree seedlings were 4-fold taller and had 20-fold more biomass in the absence of grass. Tree foliar δ15N was lower with (?0.25?±?0.2‰, n?=?9) than without grasses (5.2?±?0.1‰, n?=?64). The contribution of N2-fixation to the N budget decreased with increasing N supply. Greater reliance on N2-fixation by trees in the presence of grasses did not result in greater biomass accumulation or tissue [N] relative to tree seedlings grown without grass competition. Tree seedlings competing with grass had significantly more negative δ13C (?29.5?±?0.6‰) than seedlings without grass competition (?28.8‰?±?0.5‰).Conclusions
Induction of N2-fixation by grass may have resulted from competition for nutrients. N2-fixation enables tree seedlings to compensate for limited soil N and survive grass competition at a critical and vulnerable developmental stage of germination and establishment. 相似文献4.
Background and aims
The aim of weed control and fertilization in forest plantations was to increase tree growth by reducing competition for available nutrients and water. However, treatments that influence weed biomass can also have significant impacts on soil carbon (C) and nitrogen (N) cycling which can in turn lead to changes in the dynamics of stable C (δ13C) and N (δ15N) isotope compositions in soils and tree foliage.Methods
We examined the key C and N cycling processes influenced by routine and luxury weed control and fertilization treatments as reflected by soil and foliar δ13C and δ15N and long-term tree growth in an 8-year old F1 hybrid pine (Pinus elliottii x P. caribaea) plantation in southeast Queensland, Australia. Weed control treatments varied by treatment frequency and intensity while fertilization treatments varied by the application of N, phosphorus (P), potassium (K) and micronutrients. Different soil and canopy sampling positions were assessed to determine if sampling position enhanced the relationships among soil N transformations and tree N use, water use efficiency and carbon gain under the early establishment silviculture.Results
Routine weed control was associated with increased weed biomass returned to the soil, compared with luxury weed control. Soil δ13C increased at the 0–5 cm soil sampling depth in both the inter-planting (IPR) and planting row (PR) as a result of the routine weed control treatments. In addition, soil δ13C was significantly higher as a result of fertilisation treatment in the 0–5 cm soil sampling depth in the PR. Soil δ13C was negatively correlated to soil δ15N at the 0–5 cm soil sampling depth in the IPR. Soil δ15N increased in the 0–5 and 5–10 cm soil sampling depths in the IPR, as a result of more frequent (luxury) weed control. Foliar δ15N and tree water use efficiency (WUE) (as indicated by foliar δ13C) were positively correlated with tree growth at age 8 years. While relationships between δ13C and δ15N in the soil and foliage varied depending on soil sampling depth and position, and with canopy sampling position where there were consistent relationships between soil δ13C (or δ15N) and foliar δ15N.Conclusions
This study demonstrates how early establishment silviculture has important implications for soil C and N cycling and how soil δ13C and δ15N were consistent with changes in soil C cycling and N transformations as a result of weed control treatments, while foliar δ15N was linked to more rapid N cycling as reflected in the soil δ15N, which increased tree growth and tree WUE (as reflected by foliar δ13C).5.
Stephen D. LeDuc David E. Rothstein Zhanna Yermakov Susan E. Spaulding 《Plant and Soil》2013,373(1-2):955-965
Background and aims
Natural abundance of the stable nitrogen (N) isotope 15N can elucidate shifts in plant N acquisition and ecosystem N cycling following disturbance events. This study examined the potential relationship between foliar δ15N and depth of plant N acquisition (surface organic vs. mineral soil) and nitrification as conifer stands develop following stand-replacing wildfire.Methods
We measured foliar δ15N along an 18-site chronosequence of jack pine (Pinus banksiana) stands, 1 to 72 years in age post-wildfire. Foliar δ15N was compared to total δ15N of the organic (Oe + Oa) and mineral (0–15 cm) soil horizons, and organic horizon N mineralization and nitrification as functions of total mineralization.Results
Foliar δ15N declined with stand age, yet wildfire effects were heterogeneous. Jack pine seedlings on burned, mineral soil patches in the youngest stand were significantly more enriched than those on unburned, organic patches (P?=?0.007). High foliar values in the youngest stands relative to mineral-horizon δ15N indicate that nitrification also likely contributed to seedling enrichment.Conclusions
Our results suggest jack pine seedlings on burned patches obtain N from the mineral soil with potentially high nitrification rates, whereas seedlings on unburned patches and increasingly N-limited, mature jack pine acquire relatively more N from organic horizons. 相似文献6.
Hung Dinh Viet Jin-Hyeob Kwak Kwang-Seung Lee Sang-Sun Lim Miwa Matsushima Scott X. Chang Kye-Han Lee Woo-Jung Choi 《Plant and Soil》2013,363(1-2):101-112
Background and aims
Soil acidification is known to be one of the constraints of tree growth; however, it is unclear how it affects tree growth at photosynthesis level (i.e., through affecting stomatal conductance vs. carboxylation rate) during the growth of trees. This paper studied the effects of soil acidification on Pinus densiflora foliar chemistry and tree ring C isotope ratio (13C/12C, expressed as δ13C) and their relationship with tree growth.Methods
Tree growth (diameter, annual growth ring area, and root biomass), soil chemistry (pH, mineral N, and exchangeable Ca and Al), foliage chemistry (N, Ca/Al, and δ13C), and tree ring δ13C in P. densiflora stands along a soil pH gradient (from 4.38 to 4.83, n?=?9) in southern Korea were investigated.Results
Overall, trees with relatively poor growth under more acidic soil conditions (low pH and Ca/Al) had lower values of foliar N concentration and δ13C and tree ring δ13C, suggesting that restricted N uptake under more acidic soil conditions caused N limitation for photosynthesis, leading to poor tree growth. In addition, relationships between mean annual area increment and carbon isotope discrimination of tree rings at five-yr intervals from 1968 to 2007 revealed that the impact of soil acidification on tree growth became severer during the last 15 yrs as negative correlations between them became significant after 1993.Conclusions
Reduced N uptake under acidic soil conditions resulted in lower radial growth of P. densiflora via non-stomatal limitation of photosynthesis. 相似文献7.
Variations in nitrogen-15 natural abundance of plant and soil systems in four remote tropical rainforests, southern China 总被引:1,自引:0,他引:1
Ang Wang Yun-Ting Fang De-Xiang Chen Keisuke Koba Akiko Makabe Yi-De Li Tu-Shou Luo Muneoki Yoh 《Oecologia》2014,174(2):567-580
The foliar stable N isotope ratio (δ15N) can provide integrated information on ecosystem N cycling. Here we present the δ15N of plant and soil in four remote typical tropical rainforests (one primary and three secondary) of southern China. We aimed to examine if (1) foliar δ15N in the study forests is negative, as observed in other tropical and subtropical sites in eastern Asia; (2) variation in δ15N among different species is smaller compared to that in many N-limited temperate and boreal ecosystems; and (3) the primary forest is more N rich than the younger secondary forests and therefore is more 15N enriched. Our results show that foliar δ15N ranged from ?5.1 to 1.3 ‰ for 39 collected plant species with different growth strategies and mycorrhizal types, and that for 35 species it was negative. Soil NO3 ? had low δ15N (?11.4 to ?3.2 ‰) and plant NO3 ? uptake could not explain the negative foliar δ15N values (NH4 + was dominant in the soil inorganic-N fraction). We suggest that negative values might be caused by isotope fractionation during soil NH4 + uptake and mycorrhizal N transfer, and by direct uptake of atmospheric NH3/NH4 +. The variation in foliar δ15N among species (by about 6 ‰) was smaller than in many N-limited ecosystems, which is typically about or over 10 ‰. The primary forest had a larger N capital in plants than the secondary forests. Foliar δ15N and the enrichment factor (foliar δ15N minus soil δ15N) were higher in the primary forest than in the secondary forests, albeit differences were small, while there was no consistent pattern in soil δ15N between primary and secondary forests. 相似文献
8.
Background and aims
Detailed analyses of root chemistry by branching order may provide insights into root function, root lifespan and the abundance of root-associated mycorrhizal fungi in forest ecosystems.Methods
We examined the nitrogen and carbon stable isotopes (δ15N and δ13C) and concentration (%N and %C) in the fine roots of an arbuscular mycorrhizal tree, Fraxinus mandshurica, and an ectomycorrhizal tree, Larix gmelinii, over depth, time, and across five root branching orders.Results and conclusions
Larix δ15N increased by 2.3?‰ from 4th order to 1st order roots, reflecting the increased presence of 15N-enriched ECM fungi on the lower root orders. In contrast, arbuscular mycorrhizal Fraxinus only increased by 0.7?‰ from 4th order to 1st order roots, reflecting the smaller 15N enrichment and lower fungal mass on arbuscular mycorrhizal fine roots. Isotopic and anatomical mass balance calculations indicate that first, second, and third order roots in ectomycorrhizal Larix averaged 36 %, 23 %, and 8 % fungal tissue by mass, respectively. Using literature values of root production by root branching order, we estimate that about 25 % of fine root production in ECM species like Larix is actually of fungal sheaths. In contrast to %N, %C, and δ15N, δ13C changed minimally across depth, time, and branching order. The homogeneity of δ13C suggests root tissues are constructed from a large well-mixed reservoir of carbon, although compound specific δ13C data is needed to fully interpret these patterns. The measurements developed here are an important step towards explicitly including mycorrhizal production in forest ecosystem carbon budgets. 相似文献9.
Ayumi Tanaka-Oda Tanaka Kenzo Yuta Inoue Midori Yano Keisuke Koba Tomoaki Ichie 《Trees - Structure and Function》2016,30(2):509-522
Key message
Large variations in leaf δ 15 N in Bornean tropical rainforest trees may indicate that various tropical species have species-specific strategy for nitrogen uptake under low soil nutrient conditions, including root symbiotic microorganisms such as ectomycorrhiza.Abstract
Lowland tropical rainforests in Southeast Asia are characterized by high species diversity despite limited soil nutrient conditions. The plant nitrogen isotope ratio (δ15N) reflects plant uptake of soil nitrogen. We analyzed δ15N values and nitrogen content (N %) in leaves and roots of 108 woody species with different types of symbiotic microorganisms, of different life forms (emergent, canopy, sub-canopy, understory, and canopy gap species), and from different families in a Bornean lowland dipterocarp forest to gain more insight into the diversity of nitrogen uptake strategy in the rhizosphere. Leaf δ15N values in the species studied varied largely from ?7.2 to 5.0 ‰, which is comparable to the values of known Asian trees including temperate, sub-tropical, and tropical mountain forests. Leaf δ15N also varied significantly among both life forms and families, though the phylogenetically independent contrast (PIC) relationships were not statistically significant among life form, family, and symbiotic types. Some families showed specific leaf δ15N values; Dipterocarpaceae, the dominant family in the canopy layer with symbiotic ectomycorrhiza in Southeast Asia, had small intraspecific variation and higher leaf δ15N values (0.03 ‰) compared with species exhibiting arbuscular mycorrhiza, whereas several families such as Burseraceae, Euphorbiaceae, and Myrtaceae showed large interspecific variation in leaf δ15N (e.g., from ?7.2 to 5.0 ‰ in Euphorbiaceae). These variations suggest that tropical species may have family- or species-specific strategy, such as root symbiotic microorganisms, for nitrogen uptake under low-nutrient conditions in tropical rainforests in Southeast Asia.10.
Yelin Zeng Wenhua Xiang Xiangwen Deng Xi Fang Cong Liu Changhui Peng 《Plant and Soil》2014,384(1-2):231-242
Background and aims
Knowledge related to extent of differing soil N forms and N transformation rates in subtropical southern China is severely limited. Accordingly, the purpose of this study was to investigate if and how tree species of different foliage types (coniferous, deciduous, and evergreen broadleaved) influence N forms and microbial biomass carbon (MBC) and microbial biomass nitrogen (MBN) content as well as gross N transformation rates in the organic and mineral soils of three distinct subtropical forests in China.Methods
Chloroform fumigation extraction was used to determine MBC and MBN content while 15N-isotope dilution techniques were used to measure gross N transformation rates. Canonical correspondence analysis (CCA) was used to quantify relationships between soil chemical characteristics and changes in soil N transformation rates.Results
Soil N forms, MBC and MBN content, and N transformation rates were found to be significantly different between tree species. Deciduous forest soil exhibited the highest N transformation rates. Soil N transformation rates were closely associated with total soil C and N and MBC and MBN content.Conclusions
Soil substrate quantity and soil microbial activity play a more important role in soil N transformation processes than does soil quality in China’s subtropical forests. Tree species type should therefore be taken into account when trying to determine ecosystem N cycling. 相似文献11.
Changes in stable nitrogen and carbon isotope ratios of plants and soil across a boreal forest fire chronosequence 总被引:1,自引:0,他引:1
Fujio Hyodo Soichiro Kusaka David A. Wardle Marie-Charlotte Nilsson 《Plant and Soil》2013,364(1-2):315-323
Background and Aim
Nitrogen (N) and carbon (C) isotopic signatures (δ15N and δ13C) serve as powerful tools for understanding temporal changes in ecosystem processes, but how these signatures change across boreal forest chronosequences is poorly understood.Methods
The δ15N, δ13C, and C/N ratio of foliage of eight dominant plant species, including trees, understory shrubs, and a moss, as well as humus, were examined across a 361 years fire-driven chronosequence in boreal forest in northern Sweden.Results
The δ13C and C/N ratio of plants and humus increased along the chronosequence, suggesting increasing plant stress through N limitation. Despite increasing biological N fixation by cyanobacteria associated with feather mosses, δ15N showed an overall decline, and δ15N of the feather moss and associated vascular plants diverged over time from that of atmospheric N2.Conclusions
Across this chronosequence the N fixed by cyanobacteria is unlikely to be used by mosses and vascular plants without first undergoing mineralization and mycorrhizal transport, which would cause a change in δ15N signature due to isotopic fractionation. The decreasing trend of δ15N suggests that as the chronosequence proceeds, the plants may become more dependent on N transferred from mycorrhizal fungi or from N deposition. 相似文献12.
Forest ecosystem nitrogen (N) response to disturbance has often been examined by space-for-time substitution, but there are few objective tests of the possible variation in disturbance type and intensity across chronosequence sites. We hypothesized that tree ring δ15N, as a record of ecosystem N status, could validate chronosequence assumptions and provide isotopic evidence to corroborate N trends. To test this we measured soil N availability, soil δ15N, and foliar N attributes of overstory Douglas-fir (Pseudotsuga menziesii) and understory western hemlock (Tsuga heterophylla) across three old-growth stands and nine second-growth plantations on southeast Vancouver Island, British Columbia (Canada). Increment cores for wood δ15N were retrieved from three co-dominant Douglas-fir per plot. Bulk soil δ15N was well aligned with both foliar and recent wood δ15N, demonstrating the utility of wood δ15N in monitoring ecosystem N status. Strongly contrasting trends in tree ring δ15N were evident among second-growth stands, with most trees from plantations older than 50 years exhibiting steep declines (3–4‰) in δ15N but with no temporal trends detected for younger plantations. The discrepancy in tree ring δ15N suggests disturbance history varied considerably among second-growth sites, likely because of greater slash loads and hotter broadcast burns on older cutblocks. As a consequence, the pattern of increased soil N availability and foliar N concentration with time since disturbance derived from the chronosequence could not be validated. Tree ring δ15N may provide insights into disturbance intensity, especially fire, and correlations with foliar N concentration could inform the extent of changes in stand nutrition. 相似文献
13.
Background and aims
Below-ground grass competition limits woody establishment in savannas. N2-fixing legumes may, however, have a nutritional advantage over broad-leaved species. We hypothesised that broad-leaved non-legume savanna thicket species would be more severely constrained by grass competition for N and consequently respond more to N-fertilization than the legume, Acacia karroo.Methods
A. karroo and five non-legume thicket species (Maytenus senegalensis, M. heterophylla, Euclea divinorum, Ziziphus mucronata, Schotia brachypetala) were grown together in an irrigated competition experiment with clipped-, unclipped-grass and without grass with/without N-fertilizer. The biomass, foliar nutrient, δ13C and δ15N of grasses and woody species were determined.Results
Growth of both A. karroo and the non-legume species was equally sensitive (c. 90 % reduction) to both clipped- and unclipped-grass competition, regardless of N-fertilization. With grass competition, however, foliar [N] increased and δ15N decreased in response to N-fertilization. Grass biomass accumulation was also unchanged by fertilisation, despite increases in foliar [N] and decreases in δ15N.Conclusions
The N2-fixation capacity of A. karroo provided no growth advantage over non-legumes. The lack of responsiveness of biomass accumulation by both the woody species and the grasses to N-fertilization, despite evidence that plants accessed the N-fertilizer, indicates limitation by other nutrients. 相似文献14.
J. A. Ramírez J. D. León-Peláez D. Craven D. A. Herrera C. M. Zapata M. I. González-Hernández J. Gallardo-Lancho W. Osorio 《Plant and Soil》2014,378(1-2):215-226
Background and aims
Exotic coniferous species have been used widely in restoration efforts in tropical montane forests due to their tolerance to adverse conditions and rapid growth, with little consideration given to the potential ecological benefits provided by native tree species. The aim of this study was to elucidate differences in litterfall and nutrient flow between a montane oak forest (Quercus humboldtii Bonpl.) and exotic coniferous plantations of pine (Pinus patula Schltdl. & Cham.) and cypress (Cupressus lusitanica Mill.) in the Colombian Andes.Methods
Litter production, litter decomposition rate, and element composition of leaf litter were monitored during 3 years.Results
Litter production in the oak forest and pine plantation was similar, but considerably lower in the cypress plantation . Similar patterns were observed for nutrient concentrations in litterfall, with the exception of Ca which was three times higher in the cypress plantation. The annual decay rate of litter was faster in the montane oak forest than in either of the exotic coniferous plantations. The potential and net return of nutrients to the forest floor were significantly higher in oak forest than in the exotic coniferous plantations.Conclusions
Future restoration programs should consider new species that can emulate the nutrient flow of native broadleaf species instead of exotic species that tend to impoverish soil nutrient stocks in tropical montane forests. 相似文献15.
E. D. Schulze D. Nicolle A. Boerner M. Lauerer G. Aas I. Schulze 《Trees - Structure and Function》2014,28(4):1125-1135
Key message
Eucalyptus and Acacia species were surprisingly similar with respect to variations in δ 13 C, δ 15 N. Both genera respond with speciation and associated changes in leaf structure to drought.Abstract
Stable carbon and nitrogen isotope ratios (δ13C and δ15N) in leaves of eucalypts (Corymbia and Eucalyptus) and Acacia (and some additional Fabaceae) species were investigated together with specific leaf area (SLA), leaf nitrogen (N) and leaf phosphorous (P) concentration along a north–south transect through Western Australia covering winter- and summer-dominated rainfall between 100 and 1,200 mm annually. We investigated 62 eucalypts and 78 woody Fabaceae species, mainly of the genus Acacia. Leaf δ13C values of Eucalyptus and Acacia species generally increased linearly with latitude from ?29.5 ± 1.3 ‰ in the summer-dominated rainfall zone (15°S–18°S) to about ?25.7 ± 1.1 ‰ in the winter-dominated rainfall zone (29°S–31°S). δ15N increased initially with southern latitudes (0.5 ± 1.6 ‰ at 15°S; 5.8 ± 3.3 ‰ at 24–29°S) but decreased again further South (4.6 ± 3.5 ‰ at 31°S). The variation in δ13C and δ15N was probably due to speciation of Eucalyptus and Acacia into very local populations. There were no species that were distributed over the whole sampling area. The variation in leaf traits was larger between species than within species. Average nitrogen concentrations were 11.9 ± 1.05 mg g?1 in Eucalyptus, and were 18.7 ± 4.1 mg g?1 in Acacia. Even though the average nitrogen concentration was higher in Acacia than Eucalyptus, δ15N gave no clear indication for N2 fixation in Acacia. In a multiple regression, latitude (as a surrogate for rainfall seasonality), mean rainfall, leaf nitrogen concentration, specific leaf area and nitrogen fixation were significant and explained 69 % of the variation of δ13C, but only 36 % of the variation of δ15N. Higher nitrogen and phosphorus concentration could give Acacia an advantage over Eucalyptus in arid regions of undefined rainfall seasonality. 相似文献16.
Wenjuan Huang Juxiu Liu Ying Ping Wang Guoyi Zhou Tianfeng Han Yin Li 《Plant and Soil》2013,364(1-2):181-191
Background and Aims
Phosphorus (P) is commonly one of most limiting nutrients in tropical and subtropical forests, but whether P limitation would be exacerbated during forest succession remains unclear.Methods
Soil phosphatase activity is often used as an indicator of P limitation. Here we examined soil acid phosphatase activity (APA) underneath tree species in pine forest (PF), mixed pine and broadleaf forest (MF) and monsoon evergreen broadleaf forest (MEBF) which represented the early, middle and late successional stages of subtropical forests in China, respectively. We also analyzed other indicators of P status (soil available P and N and P stoichiometry of the tree species).Results
APA or APA per unit soil organic carbon under tree species was relatively low in the early successional forest. Different from PF and MF, soil available P beneath the tree species was lower than in the bulk soils in MEBF. Soil APA was closely related to N:P ratios of tree species across all three forests.Conclusions
Our results imply that P limitation increases during forest succession at our site. The dominant tree species with low soil APAs in MEBF are likely more P-limited than other tree species. 相似文献17.
Aims
Forest thinning is expected to affect tree water use and carbon assimilation, but the related influence from climate variability is little known. Recent forest thinning in the Wungong catchment coincided with a record dry year following the thinning, which provides a rare opportunity to understand the climate influence on the thinning effect.Methods
A field experiment was conducted to examine changes before and after thinning, especially the rainfall, soil moisture, leaf water status, tissue isotope signature (13?C and 15?N) and N concentration of overstorey and understorey juvenile trees of Eucalyptus marginata (Donn ex Sm.).Results
Despite the post-thinning drought, surface soil was moister and juvenile jarrah plants were less water stressed, attributable to reduced rain interception and transpiration as a result of less canopy cover. The overstorey was under stress but mainly due to drought rather than by thinning. The concentration of N declined in both tree stems and juvenile leaves along with available N in soil, suggesting a soil N limitation. No treatment effects were detected from leaf relative water content and tissue isotope signature (13?C and 15?N).Conclusions
The drought effects were superimposed over the thinning effects on overstorey growth, with stemwood δ13C being a major indicator of water stress. The water relations and carbon assimilation of understorey juveniles were however dependent more on topsoil moisture, and the wetter soil during the year following thinning enhanced growth activity and hence the depletion of 13?C (more negative δ13C) in juvenile leaves. 相似文献18.
Isabel Parraga-Aguado Jose-Ignacio Querejeta María Nazaret González-Alcaraz Francisco J. Jiménez-Cárceles Hector M. Conesa 《Plant and Soil》2014,379(1-2):93-107
Background and aims
Aleppo pine (Pinus halepensis Mill.) is a widely used species for restoring degraded semiarid areas, but its use for the revegetation of metal(loid) polluted soils has not been thoroughly investigated. The main goal of this research was to study the ecophysiological status and elemental composition of spontaneous populations of Pinus halepensis growing on mine tailings to assess their use in phytomanagement of mine spoils in semiarid climates.Methods
Edaphic characteristics and the physiological (by stable isotopes) and nutritional status of pine trees were determined on mine tailings, in the metalloid-polluted surroundings and a non-polluted control area.Results
Low soil phosphorus availability at the tailings was found to be a more important limiting factor for pine physiological performance than high soil metal(lloid)s concentrations. Foliar phosphorus concentrations showed a strong negative correlation with foliar sulphur concentrations along the studied transect. The carbon and oxygen isotopic composition (δ13C and δ18O) of pine needles indicated that trees at the tailings were less water stressed than those in surroundings or control areas. The low foliar δ15N of pines growing at the tailings was due to low soil fertility and/or a heavy reliance on symbiotic ectomycorrhizal fungi for nitrogen uptake.Conclusions
The results of this study indicate that Pinus halepensis is a suitable tree species for the phytostablisation of neutral or slightly-alkaline mining wastes in semiarid environments, thanks to its drought hardiness and good adaptation to low soil fertility and salinity. 相似文献19.
Background and aims
Conversion of natural forests to plantations often results in a considerable loss of plant species and thus likely a reduction in quantity and quality of plant debris entering the soil. Larch plantation is widespread in northeastern China, but its ecological impacts receive little attention. This study aimed to assess soil quality under larch stands against the secondary forest stands using a suite of soil chemical and microbiological properties.Methods
Four pairs of larch plantations and secondary forests were randomly selected from a mountainous area and mineral soils of top 15 cm were collected from each field.Results
Soil carbon (C) and nitrogen (N) concentrations, microbial biomass, C and N mineralization and the activities of hydrolytic enzymes were significantly lower in the larch plantations than those in the secondary forests. However, light fraction C as a proportion of soil C was greater in the larch plantations, suggesting less accumulation and stabilization of soil C to heavy fraction in the larch plantations compared to the secondary forests. We also used δ15N records in light and heavy fractions to derive the relative stability of soil C and found that soil C stability was lower in the larch plantations. This was supported by Fourier transform infrared spectroscopy analysis because carboxylate stretching, which might result from microbial oxidation, was less abundant in the larch plantations.Conclusions
The differences in soil organic matter quality between the larch plantations and the secondary forests were reliably reflected in soil microbial properties and microbially-mediated processes. Our results indicated that the larch plantations reduced soil quality as well as nutrient cycling rate. 相似文献20.
Jiahao Wen Huawei Ji Ningxiao Sun Huimin Tao Baoming Du Dafeng Hui Chunjiang Liu 《Plant and Soil》2018,425(1-2):113-131