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Special Issue "Nitrogen and Phosphorus Nutrition of Trees and Forests"

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A special issue of Forests (ISSN 1999-4907).

Deadline for manuscript submissions: closed (30 June 2015)

Special Issue Editors

Guest Editor
Prof. Dr. Heinz Rennenberg (Website)

Institute of Forest Sciences, University of Freiburg, 79085 Freiburg, Germany
Guest Editor
Prof. Dr. Mark A. Adams (Website)

Faculty of Agriculture and Environment, University of Sydney, 1 Central Avenue, Eveleigh, 2015 NSW, Australia

Special Issue Information

Dear Colleagues,

Nitrogen (N) and phosphorus (P) nutrition of trees has been studied for many decades, but has largely been focused on inorganic nutrient uptake and leaf level nutrient contents. In recent years it became obvious that N and P cycling at the ecosystem level is of vital importance for tree nutrition and that organic N uptake by trees is an essential part of ecosystem N cycling; in particular on N and/or P poor soils, and in cooler climates. The significance of organic P uptake by trees is still a matter of debate, especially under field conditions. The overlay of climate change on ecosystem N and P cycling has become an important issue of forest research. This overlay raises questions around competition for N and P among structural elements (overstorey vs. undestorey), as well as among dominant species. Many nutritionally related aspects of changing climates, such as effects on rhizosphere and phyllosphere, remain seriously under-studied. The central aim of this Special Issue is to provide new insights into some of these topics at the tree, and the ecosystem level.

Prof. Dr. Heinz Rennenberg
Prof. Dr. Mark A. Adams
Guest Editor

Submission

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Keywords

  • N uptake
  • P uptake
  • inorganic N
  • organic N
  • inorganic P
  • organic P
  • ecosystem N cycling
  • ecosystem P cycling
  • plant–microbial interactions
  • biosphere–atmosphere–hydrosphere exchange

Published Papers (14 papers)

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Research

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Open AccessCommunication Increased Biomass of Nursery-Grown Douglas-Fir Seedlings upon Inoculation with Diazotrophic Endophytic Consortia
Forests 2015, 6(10), 3582-3593; doi:10.3390/f6103582
Received: 8 July 2015 / Revised: 28 September 2015 / Accepted: 6 October 2015 / Published: 12 October 2015
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Abstract
Douglas-fir (Pseudotsuga menziesii) seedlings are periodically challenged by biotic and abiotic stresses. The ability of endophytes to colonize the interior of plants could confer benefits to host plants that may play an important role in plant adaptation to environmental changes. [...] Read more.
Douglas-fir (Pseudotsuga menziesii) seedlings are periodically challenged by biotic and abiotic stresses. The ability of endophytes to colonize the interior of plants could confer benefits to host plants that may play an important role in plant adaptation to environmental changes. In this greenhouse study, nursery-grown Douglas-fir seedlings were inoculated with diazotrophic endophytes previously isolated from poplar and willow trees and grown for fifteen months in nutrient-poor conditions. Inoculated seedlings had significant increases in biomass (48%), root length (13%) and shoot height (16%) compared to the control seedlings. Characterization of these endophytes for symbiotic traits in addition to nitrogen fixation revealed that they can also solubilize phosphate and produce siderophores. Colonization was observed through fluorescent microscopy in seedlings inoculated with gfp- and mkate-tagged strains. Inoculation with beneficial endophytes could prove to be valuable for increasing the production of planting stocks in forest nurseries. Full article
Figures

Open AccessArticle Native and Alien Plant Species Richness Response to Soil Nitrogen and Phosphorus in Temperate Floodplain and Swamp Forests
Forests 2015, 6(10), 3501-3513; doi:10.3390/f6103501
Received: 30 June 2015 / Revised: 21 September 2015 / Accepted: 22 September 2015 / Published: 7 October 2015
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Abstract
Soil nitrogen and phosphorus are commonly limiting elements affecting plant species richness in temperate zones. Our species richness-ecological study was performed in alder-dominated forests representing temperate floodplains (streamside alder forests of Alnion incanae alliance) and swamp forests (alder carrs of Alnion glutinosae [...] Read more.
Soil nitrogen and phosphorus are commonly limiting elements affecting plant species richness in temperate zones. Our species richness-ecological study was performed in alder-dominated forests representing temperate floodplains (streamside alder forests of Alnion incanae alliance) and swamp forests (alder carrs of Alnion glutinosae alliance) in the Western Carpathians. Species richness (i.e., the number of vascular plants in a vegetation plot) was analyzed separately for native and alien vascular plants in 240 vegetation plots across the study area covering Slovakia, northern Hungary and southern Poland. The relationship between the species richness of each plant group and total soil nitrogen content, plant-available phosphorus and carbon to nitrogen (C/N) ratio was analyzed by generalized linear mixed models (GLMM) with Poisson error distribution and log-link function. The number of recorded native and alien species was 17–84 (average 45.4) and 0–9 (average 1.5) species per plot, respectively. The GLMMs were statistically significant (p ˂ 0.001) for both plant groups, but the total explained variation was higher for native (14%) than alien plants (9%). The richness of native species was negatively affected by the total soil nitrogen content and plant-available phosphorus, whereas the C/N ratio showed a positive impact. The alien richness was predicted only by the total soil nitrogen content showing a negative effect. Full article
Open AccessArticle Soil Nitrogen Transformations and Availability in Upland Pine and Bottomland Alder Forests
Forests 2015, 6(9), 2941-2958; doi:10.3390/f6092941
Received: 28 June 2015 / Revised: 23 August 2015 / Accepted: 24 August 2015 / Published: 27 August 2015
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Abstract
Soil nitrogen (N) processes and inorganic N availability are closely coupled with ecosystem productivity and various ecological processes. Spatio-temporal variations and environmental effects on net N transformation rates and inorganic N concentrations in bulk soil and ion exchange resin were examined in [...] Read more.
Soil nitrogen (N) processes and inorganic N availability are closely coupled with ecosystem productivity and various ecological processes. Spatio-temporal variations and environmental effects on net N transformation rates and inorganic N concentrations in bulk soil and ion exchange resin were examined in an upland pine forest (UPF) and a bottomland alder forest (BAF), which were expected to have distinguishing N properties. The annual net N mineralization rate and nitrification rate (kg N·ha−1·year−1) were within the ranges of 66.05–84.01 and 56.26–77.61 in the UPF and −17.22–72.24 and 23.98–98.74 in the BAF, respectively. In the BAF, which were assumed as N-rich conditions, the net N mineralization rate was suppressed under NH4+ accumulated soils and was independent from soil temperature. On the other hand, in the UPF, which represent moderately fertile N conditions, net N transformation rates and N availability were dependent to the generally known regulation by soil temperature and soil water content. Stand density might indirectly affect the N transformations, N availability, and ecosystem productivity through different soil moisture conditions. The differing patterns of different inorganic N indices provide useful insight into the N availability in each forest and potential applicability of ion exchange resin assay. Full article
Open AccessArticle Juvenile Southern Pine Response to Fertilization Is Influenced by Soil Drainage and Texture
Forests 2015, 6(8), 2799-2819; doi:10.3390/f6082799
Received: 1 July 2015 / Revised: 6 August 2015 / Accepted: 13 August 2015 / Published: 14 August 2015
Cited by 2 | PDF Full-text (1134 KB) | HTML Full-text | XML Full-text
Abstract
We examined three hypotheses in a nutrient dose and application frequency study installed in juvenile (aged 2–6 years old) Pinus stands at 22 sites in the southeastern United States. At each site, eight or nine treatments were installed where nitrogen was applied [...] Read more.
We examined three hypotheses in a nutrient dose and application frequency study installed in juvenile (aged 2–6 years old) Pinus stands at 22 sites in the southeastern United States. At each site, eight or nine treatments were installed where nitrogen was applied at different rates (0, 67, 134, 268 kg ha−1) and frequencies (0, 1, 2, 4 and 6 years) in two or four replications. Phosphorus was applied at 0.1 times the nitrogen rate and other elements were added as needed based on foliar nutrient analysis to insure that nutrient imbalances were not induced with treatment. Eight years after treatment initiation, the site responses were grouped based on texture and drainage characteristics: soil group 1 consisted of poorly drained soils with a clayey subsoil, group 2 consisted of poorly to excessively drained spodic soils or soils without a clay subsoil, and group 3 consisted of well-drained soils with a clayey subsoil. We accepted the first hypothesis that site would be a significant factor explaining growth responses. Soil group was also a significant factor explaining growth response. We accepted our second hypothesis that the volume growth-cumulative dose response function was not linear. Volume growth reached an asymptote in soil groups 1 and 3 between cumulative nitrogen doses of 300–400 kg ha−1. Volume growth responses continued to increase up to 800 kg ha−1 of cumulatively applied nitrogen for soil group 2. We accepted our third hypothesis that application rate and frequency did not influence the growth response when the cumulative nitrogen dose was equivalent. There was no difference in the growth response for comparisons where a cumulative nitrogen dose of 568 kg ha−1 was applied as 134 kg ha−1 every two years or as 269 kg ha−1 every four years, or where 269 kg ha−1 of nitrogen was applied as four applications of 67 kg ha−1 every two years or as two applications of 134 kg ha−1 every four years. Clearly, the sites examined here were limited by nitrogen and phosphorus, and applications of these elements to young stands effectively ameliorated these limitations. However, there were differences in the response magnitude that were related to soil texture and drainage. Juvenile fertilizer applications resulted in high stocking levels early in the rotation; this condition should be considered when undertaking juvenile fertilization programs. Full article
Open AccessArticle Importance of Arboreal Cyanolichen Abundance to Nitrogen Cycling in Sub-Boreal Spruce and Fir Forests of Central British Columbia, Canada
Forests 2015, 6(8), 2588-2607; doi:10.3390/f6082588
Received: 30 June 2015 / Revised: 19 July 2015 / Accepted: 20 July 2015 / Published: 31 July 2015
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Abstract
The importance of N2-fixing arboreal cyanolichens to the nitrogen (N)-balance of sub-boreal interior hybrid spruce (Picea glauca × engelmannii) and subalpine fir (Abies lasiocarpa) forests was examined at field sites in central BC, Canada. Host trees [...] Read more.
The importance of N2-fixing arboreal cyanolichens to the nitrogen (N)-balance of sub-boreal interior hybrid spruce (Picea glauca × engelmannii) and subalpine fir (Abies lasiocarpa) forests was examined at field sites in central BC, Canada. Host trees were accessed by a single-rope climbing technique and foliage as well as arboreal macrolichen functional groups were sampled by branch height in eight random sample trees from each of two high (High Cyano) and two low (Low Cyano) cyanolichen abundance sites for a total of 32 sample trees. Natural abundances of stable isotopes of N (15N, 14N) and carbon (13C, 12C) were determined for aggregate host tree and epiphytic lichen samples, as well as representative samples of upper organic and soil horizons (Ae and Bf) from beneath host trees. As expected, N2-fixing cyanolichens had 2–6-fold greater N-contents than chlorolichens and a δ15N close to atmospheric N2, while foliage and chlorolichens were more depleted in 15N. By contrast, soils at all trees and sites were 15N-enriched (positive δ15N), with declining (not significant) δ15N with increased tree-level cyanolichen abundance. Lichen functional groups and tree foliage fell into three distinct groups with respect to δ13C; the tripartite cyanolichen Lobaria pulmonaria (lightest), host-tree needles (intermediate), and bipartite cyanolichens, hair (Alectoria and Bryoria spp.) and chlorolichens (heaviest). Branch height of host trees was an effective predictor of needle δ13C. Our results showed a modest positive correlation between host tree foliage N and cyanolichen abundance, supporting our initial hypothesis that higher cyanolichen abundances would elevate host tree foliar N. Further study is required to determine if high cyanolichen abundance enhances host tree and/or stand-level productivity in sub-boreal forests of central BC, Canada. Full article
Open AccessArticle Growth and Nutrient Status of Foliage as Affected by Tree Species and Fertilization in a Fire-Disturbed Urban Forest
Forests 2015, 6(6), 2199-2213; doi:10.3390/f6062199
Received: 11 May 2015 / Revised: 14 June 2015 / Accepted: 15 June 2015 / Published: 19 June 2015
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Abstract
The aim of the present study was to evaluate the growth and macronutrient (C, N, P, K) status in the foliage of four tree species (LT: Liriodendron tulipifera L.; PY: Prunus yedoensis Matsumura; QA: Quercus acutissima Carruth; PT: Pinus thunbergii Parl.) in [...] Read more.
The aim of the present study was to evaluate the growth and macronutrient (C, N, P, K) status in the foliage of four tree species (LT: Liriodendron tulipifera L.; PY: Prunus yedoensis Matsumura; QA: Quercus acutissima Carruth; PT: Pinus thunbergii Parl.) in response to fertilization with different nutrient ratios in a fire-disturbed urban forest located in BongDaesan (Mt.), Korea. Two fertilizers (N3P8K1 = 113:300:37 kg·ha−1·year−1; N6P4K1 = 226:150:37 ha−1·year−1) in four planting sites were applied in April 2013 and March 2014. The growth and nutrient responses of the foliage were monitored six times for two years. Foliar growth and nutrient concentrations were not significantly different (p > 0.05) in response to different doses of N or P fertilizer, but the foliage showed increased N and P concentrations and content after fertilization compared with the control (N0P0K0). Foliar C and K concentrations were little affected by fertilization. Foliar nutrient concentrations and contents were significantly higher in PY and LT than in PT. The results suggest that the foliar N and P concentration could be used as a parameter to assess the nutrient environments of tree species restored in a fire-disturbed urban forest. Full article
Open AccessArticle Impact of Nitrogen Fertilization on Forest Carbon Sequestration and Water Loss in a Chronosequence of Three Douglas-Fir Stands in the Pacific Northwest
Forests 2015, 6(6), 1897-1921; doi:10.3390/f6061897
Received: 20 April 2015 / Revised: 25 May 2015 / Accepted: 26 May 2015 / Published: 29 May 2015
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Abstract
To examine the effect of nitrogen (N) fertilization on forest carbon (C) sequestration and water loss, we used an artificial neural network model to estimate C fluxes and evapotranspiration (ET) in response to N fertilization during four post-fertilization years in a Pacific [...] Read more.
To examine the effect of nitrogen (N) fertilization on forest carbon (C) sequestration and water loss, we used an artificial neural network model to estimate C fluxes and evapotranspiration (ET) in response to N fertilization during four post-fertilization years in a Pacific Northwest chronosequence of three Douglas-fir stands aged 61, 22 and 10 years old in 2010 (DF49, HDF88 and HDF00, respectively). Results showed that N fertilization increased gross primary productivity (GPP) for all three sites in all four years with the largest absolute increase at HDF00 followed by HDF88. Ecosystem respiration increased in all four years at HDF00, but decreased over the last three years at HDF88 and over all four years at DF49. As a result, fertilization increased the net ecosystem productivity of all three stands with the largest increase at HDF88, followed by DF49. Fertilization had no discernible effect on ET in any of the stands. Consequently, fertilization increased water use efficiency (WUE) in all four post-fertilization years at all three sites and also increased light use efficiency (LUE) of all the stands, especially HDF00. Our results suggest that the effects of fertilization on forest C sequestration and water loss may be associated with stand age and fertilization; the two younger stands appeared to be more efficient than the older stand with respect to GPP, WUE and LUE. Full article
Open AccessArticle Nitrogen Transfer to Forage Crops from a Caragana Shelterbelt
Forests 2015, 6(6), 1922-1932; doi:10.3390/f6061922
Received: 7 April 2015 / Revised: 13 May 2015 / Accepted: 20 May 2015 / Published: 29 May 2015
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Abstract
Caragana shelterbelts are a common feature of farms in the Northern Great Plains of North America. We investigated if nitrogen (N) from this leguminous shrub contributed to the N nutrition of triticale and oat forage crops growing adjacent to the shelterbelt row. [...] Read more.
Caragana shelterbelts are a common feature of farms in the Northern Great Plains of North America. We investigated if nitrogen (N) from this leguminous shrub contributed to the N nutrition of triticale and oat forage crops growing adjacent to the shelterbelt row. Nitrogen transfer was measured using 15N isotope dilution at distances of 2 m, 4 m, 6 m, 15 m and 20 m from the shelterbelt. At 2 m caragana negatively impacted the growth of triticale and oat. At 4 m from the shelterbelt productivity was maximum for both forage crops and corresponded to the highest amount of N originating from caragana. The amount of N transferred from caragana decreased linearly with distance away from the shelterbelt, but even at 20 m from the shelterbelt row measureable amounts of N originating from caragana were detectable in the forage biomass. At 4 m from the shelterbelt approximately 40% of the N in both oat and triticale was from caragana, and at 20 m from the shelterbelt approximately 20% of the N in oat and 8% of the N in triticale was from caragana. Full article
Open AccessArticle Biomass, Carbon and Nutrient Storage in a 30-Year-Old Chinese Cork Oak (Quercus Variabilis) Forest on the South Slope of the Qinling Mountains, China
Forests 2015, 6(4), 1239-1255; doi:10.3390/f6041239
Received: 5 December 2014 / Revised: 2 March 2015 / Accepted: 13 April 2015 / Published: 21 April 2015
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Abstract
Chinese cork oak (Quercus variabilis) forests are protected on a large-scale under the Natural Forest Protection (NFP) program in China to improve the ecological environment. However, information about carbon (C) storage to increase C sequestration and sustainable management is lacking. [...] Read more.
Chinese cork oak (Quercus variabilis) forests are protected on a large-scale under the Natural Forest Protection (NFP) program in China to improve the ecological environment. However, information about carbon (C) storage to increase C sequestration and sustainable management is lacking. Biomass, C, nitrogen (N) and phosphorus (P) storage of trees, shrubs, herb, litter and soil (0–100 cm) were determined from destructive tree sampling and plot level investigation in approximately 30-year old Chinese cork oak forests on the south slope of the Qinling Mountains. There was no significant difference in tree components’ biomass estimation, with the exception of roots, among the available allometric equations developed from this study site and other previous study sites. Leaves had the highest C, N and P concentrations among tree components and stems were the major compartments for tree biomass, C, N and P storage. In contrast to finding no difference in N concentrations along the whole soil profile, higher C and P concentrations were observed in the upper 0–10 cm of soil than in the deeper soil layers. The ecosystem C, N, and P storage was 163.76, 18.54 and 2.50 t ha−1, respectively. Soil (0–100 cm) contained the largest amount of C, N and P storage, accounting for 61.76%, 92.78% and 99.72% of the total ecosystem, followed by 36.14%, 6.03% and 0.23% for trees, and 2.10%, 1.19% and 0.03% for shrubs, herbs and litter, respectively. The equations accurately estimate ecosystem biomass, and the knowledge of the distribution of C, N and P storage will contribute to increased C sequestration and sustainable management of Chinese cork oak forests under the NFP program. Full article
Open AccessArticle Residual Long-Term Effects of Forest Fertilization on Tree Growth and Nitrogen Turnover in Boreal Forest
Forests 2015, 6(4), 1145-1156; doi:10.3390/f6041145
Received: 13 March 2015 / Revised: 1 April 2015 / Accepted: 2 April 2015 / Published: 10 April 2015
Cited by 1 | PDF Full-text (279 KB) | HTML Full-text | XML Full-text
Abstract
The growth enhancing effects of forest fertilizer is considered to level off within 10 years of the application, and be restricted to one forest stand rotation. However, fertilizer induced changes in plant community composition has been shown to occur in the following [...] Read more.
The growth enhancing effects of forest fertilizer is considered to level off within 10 years of the application, and be restricted to one forest stand rotation. However, fertilizer induced changes in plant community composition has been shown to occur in the following stand rotation. To clarify whether effects of forest fertilization have residual long-term effects, extending into the next rotation, we compared tree growth, needle N concentrations and the availability of mobile soil N in young (10 years) Pinus sylvestris L. and Picea abies (L.) H. Karst. stands. The sites were fertilized with 150 kg·N·ha−1 once or twice during the previous stand rotation, or unfertilized. Two fertilization events increased tree height by 24% compared to the controls. Needle N concentrations of the trees on previously fertilized sites were 15% higher than those of the controls. Soil N mineralization rates and the amounts of mobile soil NH4-N and NO3-N were higher on sites that were fertilized twice than on control sites. Our study demonstrates that operational forest fertilization can cause residual long-term effects on stand N dynamics, with subsequent effects on tree growth that may be more long-lasting than previously believed, i.e., extending beyond one stand rotation. Full article
Open AccessArticle Mid-Rotation Silviculture Timing Influences Nitrogen Mineralization of Loblolly Pine Plantations in the Mid-South USA
Forests 2015, 6(4), 1061-1082; doi:10.3390/f6041061
Received: 3 February 2015 / Revised: 15 March 2015 / Accepted: 30 March 2015 / Published: 8 April 2015
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Abstract
Intensively managed loblolly pine (Pinus taeda L.) plantations often develop nutrient deficiencies near mid-rotation. Common silvicultural treatments for improving stand nutrition at this stage include thinning, fertilization, and vegetation control. It is important to better understand the influence of timing fertilization [...] Read more.
Intensively managed loblolly pine (Pinus taeda L.) plantations often develop nutrient deficiencies near mid-rotation. Common silvicultural treatments for improving stand nutrition at this stage include thinning, fertilization, and vegetation control. It is important to better understand the influence of timing fertilization and vegetation control in relation to thinning as part of improving the efficiency of these practices. The objective of this study was to determine the effects of fertilization and vegetation control conducted within a year prior to thinning and within a year after thinning on soil N supply in mid-rotation loblolly pine plantations on a gradient of soil textures. Net N mineralization (Nmin) and exchangeable N were measured monthly. Fertilization increased annual Nmin at all sites irrespective of timing relative to thinning, with the increase more pronounced when combined with vegetation control. This finding suggests some management flexibility in the timing of mid-rotation fertilization relative to thinning for increasing soil N supply. However, the site with the highest total soil N and the lowest C:N ratio was more prone to NO3-N increases after fertilization conducted pre- and post-thinning. At all sites, fertilization with vegetation control promoted increases in NO3-N when done after thinning, which may indicate that this practice increased soil N supply to levels that exceeded stand N demand. Full article
Open AccessArticle Influence of Tree Spacing on Soil Nitrogen Mineralization and Availability in Hybrid Poplar Plantations
Forests 2015, 6(3), 636-649; doi:10.3390/f6030636
Received: 26 January 2015 / Revised: 14 February 2015 / Accepted: 25 February 2015 / Published: 4 March 2015
Cited by 1 | PDF Full-text (651 KB) | HTML Full-text | XML Full-text
Abstract
Nitrogen (N) availability and mineralization are key parameters and transformation processes that impact plant growth and forest productivity. We hypothesized that suitable plantation spacing can lead to enhanced soil N mineralization and nitrification, which in turn promote tree growth. Studies were conducted [...] Read more.
Nitrogen (N) availability and mineralization are key parameters and transformation processes that impact plant growth and forest productivity. We hypothesized that suitable plantation spacing can lead to enhanced soil N mineralization and nitrification, which in turn promote tree growth. Studies were conducted to evaluate seasonal patterns of soil inorganic N pools as well as rates of nitrification and N mineralization of three soil layers under four tree spacing treatments. Results showed tree spacing significantly affected annual net N mineralization, whereas inorganic N content in surface soils was significantly affected by tree spacing only during the growing season. The total annual cumulative net N mineralization ranged from 80.3–136.0 mg·kg−1 in the surface soils (0–20 cm), whereas the cumulative net N mineralization of 6 × 6 m and 4.5 × 8 m spacings was 65% and 24% higher than that of the 5 × 5 m, respectively. In general, tree spacing would affect N availability in soil by altering N mineralization rates, while high annual N mineralization was found in soils of low density plantations, with higher rates in square spacing than rectangular spacing. The obtained results suggest that suitable spacing could lead to enhanced N mineralization, but seasonal variation of soil N mineralization may not only be directly related to plantation productivity but also to understory vegetation productivity. Full article
Open AccessArticle Seasonal Pattern of Decomposition and N, P, and C Dynamics in Leaf litter in a Mongolian Oak Forest and a Korean Pine Plantation
Forests 2014, 5(10), 2561-2580; doi:10.3390/f5102561
Received: 22 August 2014 / Revised: 17 October 2014 / Accepted: 17 October 2014 / Published: 23 October 2014
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Abstract
Distinct seasons and diverse tree species characterize temperate deciduous forests in NE Asia, but large areas of deciduous forests have been converted to conifer plantations. This study was conducted to understand the effects of seasons and tree species on leaf litter decomposition [...] Read more.
Distinct seasons and diverse tree species characterize temperate deciduous forests in NE Asia, but large areas of deciduous forests have been converted to conifer plantations. This study was conducted to understand the effects of seasons and tree species on leaf litter decomposition in a temperate forest. Using the litterbag method, the decomposition rate and nitrogen, phosphorous, and carbon dynamics of Mongolian oak (Quercus mongolica), Korean pine (Pinus koraiensis), and their mixed leaf litter were compared for 24 months in a Mongolian oak stand, an adjacent Korean pine plantation, and a Mongolian oak—Korean pine mixed stand. The decomposition rates of all the leaf litter types followed a pattern of distinct seasonal changes: most leaf litter decomposition occurred during the summer. Tree species was less influential on the leaf litter decomposition. The decomposition rates among different leaf litter types within the same stand were not significantly different, indicating no mixed litter effect. The immobilization of leaf litter N and P lasted for 14 months. Mongolian oak leaf litter and Korean pine leaf litter showed different N and P contents and dynamics during the decomposition, and soil P2O5 was highest in the Korean pine plantation, suggesting effects of plantation on soil nutrient budget. Full article

Review

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Open AccessReview Nitrogen Nutrition of Trees in Temperate Forests—The Significance of Nitrogen Availability in the Pedosphere and Atmosphere
Forests 2015, 6(8), 2820-2835; doi:10.3390/f6082820
Received: 11 May 2015 / Revised: 12 July 2015 / Accepted: 5 August 2015 / Published: 14 August 2015
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Abstract
Nitrogen (N) is an essential nutrient that is highly abundant as N2 in the atmosphere and also as various mineral and organic forms in soils. However, soil N bioavailability often limits the net primary productivity of unperturbed temperate forests with low [...] Read more.
Nitrogen (N) is an essential nutrient that is highly abundant as N2 in the atmosphere and also as various mineral and organic forms in soils. However, soil N bioavailability often limits the net primary productivity of unperturbed temperate forests with low atmospheric N input. This is because most soil N is part of polymeric organic matter, which requires microbial depolymerization and mineralization to render bioavailable N forms such as monomeric organic or mineral N. Despite this N limitation, many unfertilized forest ecosystems on marginal soil show relatively high productivity and N uptake comparable to agricultural systems. The present review article addresses the question of how this high N demand is met in temperate forest ecosystems. For this purpose, current knowledge on the distribution and fluxes of N in marginal forest soil and the regulation of N acquisition and distribution in trees are summarized. The related processes and fluxes under N limitation are compared with those of forests exposed to high N loads, where chronic atmospheric N deposition has relieved N limitation and caused N saturation. We conclude that soil microbial biomass is of decisive importance for nutrient retention and provision to trees both in high and low N ecosystems. Full article

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