Effects of eucalypt residue management on nutrient leaching and soil properties

Effects of harvest residues on nutrient leaching and soil chemical properties were studied in a lysimeter experiment. Treatments were: (A) forest floor litter and harvest residues, other than branches, incorporated into the soil, (B) as A, but with branches cut in 20 cm long bits and placed on the soil surface, (C) as B, but with bits incorporated into the soil, (D) as B, but with branches chopped into chips, (E) as C, but with branches chopped into chips, (F) forest floor litter and harvest residues on the soil surface, with branches cut in 20 cm long bits, (G) as F, but with branches chopped into chips, and (H) absence of harvest residues (control). Treatments were applied in zero-tension lysimeters containing 25 kg of soil. Leachates were collected for a 6-year period. At the end of the experiment, lysimeters were dismantled and soil was divided in four layers. Residues, other than branches, increased N leaching, as compared with the control. Branches on the soil surface reduced N leaching when cut in chips. Branches incorporated into the soil reduced leaching independently of their size. Organic residues on the soil surface showed similar effect to those incorporated into the soil. However, harvest residues on the soil surface increased leachate volume, and reduced Ca and P losses. Such a placement of residues led to high contents of Ca and P in the 0–5 cm top soil layer. Contents of organic C, total N and base cations were not affected by the treatments.     

Long-term prescribed burning increases nutrient uptake and growth of loblolly pine seedlings

Loblolly pine (Pinus taeda L.) seedlings were grown from seed in a greenhouse on A1 horizon soil collected from field plots that have been burned each winter or maintained in an unburned condition for 33 years. Soils from burned and unburned plots were treated with phosphorus (P), P and calcium (Ca), or left untreated. After 32 weeks, height, biomass, and nitrogen (N) and P uptake were greater on soil from burned versus unburned plots, although application of P masked these effects. Addition of P increased plant biomass, seedling height, and uptake of N and P, but depressed levels of soil NH₄N. These results suggest that long-term prescribed burning may have a positive effect on nutrient availability that will benefit seedlings of the next stand.     

混合接菌对马尾松苗木生长的影响

许多研究证明,菌根菌混合接种对宿主植物生长具有正效应。本试验中发现,504、EG、HX和Pt2四种菌根菌混合接种能显著促进幼苗生长,与单一接种相比有显著性提高。在促进幼苗生物量的积累上,四种菌根菌混合接种分别比504、EG、HX和Pt2单一接种增加了379.68%、184.84%、126.21%和38.21%,比对照增加了467.79%。     

测土配方施肥对湿地松生长与养分含量及其土壤肥力的影响

选择4年生湿地松优良家系试验林,通过测土配方施肥,研究其对湿地松生长与叶片、枝条养分含量及其土壤肥力的影响。结果表明:施肥后第2年,土壤全P含量与湿地松树高及胸径生长呈现极显著正相关,其数学模型分别为:y=-5.944 4 x+1.318 9、y=-7.500 0 x+2.700 0;施肥后土壤中速效K含量与叶片中全K含量呈现极显著正相关,其数学模型为:y=0.010 8 x-0.163 3;速效K含量与湿地松树高及胸径生长,其数学模型分别为:y=-0.032 8 x+1.513 3、y=-0.047 4 x+3.002 9;土壤中全N增长与湿地松叶片全N含量增长均呈现显著正相关,其数学模型为:y=7.016 1 x+0.162 1。湿地松平均树高与胸径相较于未施肥的对照组增幅分别达11%与13%以上,其差异达到了极显著水平。     

Effects of liming on chemical properties of soil, needle nutrients and growth of Scots pine transplants

The effects of limestone (2.0 and 4.0 Mg ha⁻¹) on chemical properties of soil, nutrient concentrations of needles and growth of Scots pine (Pinus sylvestris L.) transplants were investigated on three reforestation areas on infertile acidic sites in southern Finland. The limestone was applied either on the soil surface (unploughed plots) or was mixed into the topsoil (ploughed plots). All the treatments were replicated four times. Surface broadcast of lime elevated the pH in the organic layer and in the 0-10 cm layer of mineral soil. The increase in the pH of the organic layer after 21 years was, on average, 0.7 and 1.1 pH units, with a dose of lime 2 and 4 Mg ha⁻¹, respectively. On the ploughed plots, the pH in the uppermost 0-10 cm soil layer was 0.4-0.5 units higher than on the corresponding unlimed plots. Both doses of lime significantly increased the amount of exchangeable Ca and the base saturation (BS) in the topsoil on the ploughed plots, and the amount of exchangeable Ca and Mg, as well as the base saturation (BS) in the organic layer + the 0-10 cm layer of mineral soil on the unploughed plots. Regardless of the techniques used for application of lime, after 21 growing seasons the Ca and Mg concentrations in needles were significantly higher on the limed plots than on the controls. In needles, the Ca/Mn ratio was the best indicator for measuring the response to liming. Only on the unploughed plots did liming increase stand volume and dominant diameter of pines. Intensive disc ploughing produced significantly more stems and increased both stand volume and the dominant height of pines compared to unploughed plots.     

Effects of soil temperature on shoot and root growth and nutrient uptake of 5-year-old Norway spruce seedlings

Soil temperature is a main factor limiting root growth in the boreal forest. To simulate the possible soil-warming effect of future climate change, 5-year-old Norway spruce (Picea abies (L.) Karst.) seedlings were subjected to three simulated growing seasons in controlled environment rooms. The seedlings were acclimated to a soil temperature of 16 degrees C during the first (GS I) and third growing seasons (GS III), but were assigned to random soil-temperature treatments of 9, 13, 18 and 21 degrees C during the second growing season (GS II). In GS II, shoot diameter growth was lowest in the 21 degrees C treatment and root growth was lowest in the 9 degrees C treatment. In GS III, shoot height and root length growth improved in seedlings that had been kept at 9 degrees C during GS II, indicating compensatory growth in response to increased soil temperature. The temporary decrease in soil temperature had no long-lasting significant effect on seedling biomass or total nutrient uptake. At the end of GS III, fine roots of seedlings exposed to a soil temperature of 21 degrees C in GS II were distributed more evenly between the organic and mineral soil layers than roots of seedlings in the other treatments. During GS II and GS III, root growth started earlier than shoot growth, decreased during the rapid shoot elongation phase and increased again as shoot growth decreased.     

大量元素缺乏对樟树幼苗生长的影响

为探讨不同营养元素缺乏对樟树幼苗生长的影响,以樟树当年生幼苗为材料,设置全素、缺N、缺P、缺K、缺Mg 5个处理,观测其营养缺乏症状及生长状况.结果表明:樟树幼苗缺N时症状出现较早,表现最为明显,其叶片偏小、变黄绿色,整株矮小,长势较弱,其次为缺Mg,而缺P和缺K幼苗症状出现缓慢,表现相对不明显.不同缺素处理的樟树幼苗的苗高、地径、各组织生物量、主根长、侧根数量和叶面积均显著低于全素处理(P<0.05),其中缺N影响最大,其次为缺Mg处理.缺素处理增加了幼苗叶生物量比,降低了根生物量比和根冠比,其中缺Mg对根系生长影响最大.因此,N和Mg是限制樟树幼苗生长的主要影响因子,在樟树苗期营养管理中,应及时施用N肥,并保证Mg、P和K肥的供应.     

Effect of removal of logging residue on nutrient leaching and nutrient pools in the soil after clearcutting in a Norway spruce stand

Following clearcutting applying the conventional stem-only harvesting method in a Norway spruce (Picea abies (L.) Karst.) stand and different levels of removal of logging residue, the nutrient fluxes from the heaps of logging residue and from the O horizon were monitored over four growing seasons and the soil nutrient pools were determined. Three levels of removal of logging residue were carried out using (i) conventional stem-only harvesting (no residues removed); (ii) residues removed; and (iii) removal of branches (foliage left on site). The heaps of logging residue were a minor source of inorganic N entering the soil in the water percolating through the heaps, but they were a significant source of organic N, P, Ca, Mg, and especially K. Nutrient fluxes from the O horizon were in general greater under the heaps of logging residue as compared to soils without overlying logging residue. The leaching of inorganic N from the O horizon under the heaps of logging residue resulted in a net loss of these compounds, while the O horizon without overlying logging residue gained N. The removal of logging residue significantly decreased the extractable K pools in the soil while it or conversely, the presence of residue heaps had no significant effect on the pools of organic matter and the pools of N, P, Ca, and Mg in the O horizon and in the 0–10 cm soil layer. The results show that the short-term effects of logging residue on nutrient dynamics in the soil can be complex and difficult to interpret in terms of site productivity as there are changes in the nutrient fluxes, which imply the opposite effects on site productivity. However, the results do indicate that, in the short-term, the removal of logging residue does not impair pools of N in the soil nor site productivity on sites where the availability of N limits productivity.     

Effects of serpentine soil factors on Virginia pine (Pinus virginiana) seedlings

Effects of simulated serpentine soil conditions (elevated Mg:Ca ratio and Ni concentration) on seedlings from populations of Virginia pine (Pinus virginiana Mill.) from serpentine and non-serpentine sites were evaluated in sand culture. We determined (1) how seedlings are affected by elevated Mg:Ca ratio and Ni concentrations, (2) if there are interactive effects between Mg:Ca ratio and Ni concentrations on seedling growth, needle pigment concentrations, and nutrition, and (3) if Virginia pine populations from serpentine areas are edaphic ecotypes. A Mg:Ca ratio of 5 and 50 microM Ni both reduced seedling growth compared with control seedlings grown in the presence of the standard Mg:Ca ratio of 0.5 and no Ni. Interactive effects between Mg:Ca ratio and Ni concentrations were highly significant for growth, foliar pigments, and needle and root elemental concentrations. Nickel-mediated reductions in growth and foliar pigment concentrations were less at the serpentine Mg:Ca ratio of 5 than at the standard (non-serpentine) Mg:Ca ratio of 0.5. Foliar N was reduced by Ni concentrations as low as 10 microM, and foliar and root K, Ca and P concentrations were significantly reduced by Ni concentrations above 25 microM, with greater reductions at a Mg:Ca ratio of 0.5 than at a Mg:Ca ratio of 5. There were no population x serpentine soil factor interactions for seedling growth, foliar pigment concentrations, or nutrition, suggesting that seedlings from trees growing on serpentine soils are not edaphic ecotypes. We conclude that serpentine conditions present at the site of seed collection have not resulted in the selection of edaphic ecotypes of Virginia pine with respect to Mg:Ca ratio and Ni concentration.     

Loblolly pine growth and soil nutrient stocks eight years after forest slash incorporation

Incorporation of forest slash during stand establishment is proposed as a means of increasing soil carbon and nutrient stocks. If effective, the increased soil carbon and nutrient status may result in increased aboveground tree growth. Eight years after study installation, the impact of forest slash incorporation into the soil on soil carbon and nutrient stocks, foliar nutrients and loblolly pine growth are examined on mineral and organic sites on the North Carolina Lower Coastal Plain. Treatments include leaving forest slash on the surface and flat planting (control); V-shear and bedding (conventional), mulch forest slash followed by bedding (strip mulch) and mulch forest slash and till into the soil followed by bedding (strip mulch till). After eight years, mulching and/or tillage did not have a significant impact (p > 0.05) on soil bulk density or soil chemical properties (pH, cation exchange capacity, soil nutrients). Additionally, neither tree foliar nutrients nor stand volume were significantly impacted. However, significant effects were observed for soil phosphorus contents and stand volume between the control plots and the other treatment plots. For example, the mean stand volumes on the mineral site were 24.49 ± 1.28, 38.16 ± 2.90, 44.59 ± 3.07 and 46.96 ± 2.74 m³ ha⁻¹ for the control, conventional, strip mulch and strip mulch till plots. These observations are more likely due to the effect of bedding rather than mulching or tillage of the forest slash. These results are consistent for the mineral and the organic sites. Considering the greater expense to install the mulch and tillage treatments, the lack of a treatment effect on soil carbon and nutrient stocks and tree growth does not justify these treatments on these sites.     

Effects of different N sources on growth, nutrient uptake and ionic balance ofLarlix gmelini seedlings

The effect of different sources and levels of N on dry matter production, nutrient uptake and ionic balance ofLarlix gmelini was studied. The results showed that the growth of the plants fertilized with ammonium was not as good as the control treatment. The growth of the plants fertilized with ammonium nitrate did not differ significantly from that in control or nitrate treatment, but was better than that in the ammonium treatment. Total cation concentrations in shoots varied little with N level in the ammonium and ammonium nitrate treatments, while those in the shoot increased with N level in the nitrate treatment. The treatments had little effect on the anion concentrations in the shoot. In the roots, the concentrations of both cations and anions changed little except for SO₄ ²⁻ and Ca²⁺. There existed a higher carboxylate production in the plants fertilized with nitrate. The ratio between the production of carboxylate and the production of organic N Δ(C-A)/ΔN_org was constant with N supply in the plants receiving nitrate, but obviously declined with N supply for ammonium-fed plants. Δ (C-A)/ΔN_org values were intermediate between those of the nitrate and the ammonium-fed plants as for the mixed N source. Foundation item: This paper was supported by “Hundred Scientists” Project of Chinese Academy of Sciences. Biography: CHEN Yong-liang (1969-), male, Ph. Doctor, lecture of Northeast Forestry University, Harbin 150040, Post-doctor in Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110016, P.R. China. Responsible editor: Song Fuman     

铝对马尾松菌根苗生长及营养元素吸收的影响

以接种褐环乳牛肝菌和未接种的马尾松幼苗为试验材料,采用水培法研究不同浓度铝(Al^3+)处理(0、0.2、0.4、0.8和1.2 mmol·L^-1)对菌根化和非菌根化马尾松幼苗生长、营养元素吸收的影响,揭示菌根化马尾松苗木对Al^3+的适应机制,为减轻马尾松苗木铝毒害现象提供理论和技术依据。结果表明,在相同浓度Al^3+胁迫下,接种褐环乳牛肝菌的马尾松幼苗苗高、生物量、根系形态以及对氮(N)、磷(P)、钾(K)的吸收能力均优于不接种的马尾松苗。马尾松幼苗苗高、干物质量积累以及根系生长随着Al^3+浓度的增大均呈现先升后降再升的趋势,随着Al^3+浓度的逐渐增大,马尾松幼苗根、茎、叶中的N、P、K含量呈现出低促高抑的趋势,根、茎、叶中Al^3+含量的分配为根>茎>叶。Al^3+胁迫下,接种褐环乳牛肝菌的马尾松幼苗,通过改变马尾松幼苗根系结构,促进了幼苗的生长,特别是根系的生长,以及对N、P、K等营养元素的吸收,抑制了根系吸收Al^3+,提高了马尾松幼苗的耐铝能力。     

不同N源对兴安落叶松苗木生长,养分吸收及离子平衡的影响(英文)

本文研究了不同N源对落叶松苗木干物重、养分吸收及离子平衡的影响。结果表明:施铵态N的苗木干物重小于对照处理;施硝铵态N的苗木生长与对照和施硝态N的苗木差别不大,但较施铵态N的苗木生长要好。铵态N与硝铵态N处理苗木地上部的阳离子总浓度受N水平的影响很小,而硝态N处理时则阳离子浓度增加;各处理对地上部阴离子浓度的影响均不大。在根部除硫酸根与钙离子外,阳离子与阴离子浓度均变化不大。硝态N处理的苗木具有较高的C-A值;△(C-A)/△Norg值在硝态N处理的苗木中随N供应量的增加而略有变化,但铵态N处理则明显下降;硝铵态N处理苗木的△(C-A)/△Norg值界于铵态N处理与硝态N处理之间。     

Effect of burning and brush treatments on nutrient and soil physical properties in young longleaf pine stands

Over a period of 16 years, unburned longleaf pine (Pinus palustris Mill.) pole stands grew an average of 27% more volume than similar stands regularly burned. Treatments included biennial burns in winter, spring, and summer plus an unburned check, each of which was combined with three supplemental treatments, namely, initial herbicide injection of all hardwoods, repeated handclearing of all woody stems, and no treatment. All unburned and winter-burned plots were paired to study this growth reduction relative to treatments. The status of nitrogen, phosphorus, available moisture holding capacity, bulk density, and macropore space was determined in both surface and subsurface soils. Foliage from pines on sampled plots was analyzed for N, P, K, Ca, Mg, Mn, Cu, Fe, and Zn. Burning did not significantly affect either soil N and P or foliar nutrients. However, burning reduced available moisture holding capacity and macropore space and increased the bulk density of surface soils, and also reduced the moisture-holding capacity of subsurface soils. The results from this and other studies suggest that growth losses are due, at least in part, to increased moisture stress associated with changes in soil physical properties.     

Long-term impacts of harvest residue management on nutrition, growth and productivity of an exotic pine plantation of sub-tropical Australia

Residue retention is an important issue in evaluating the sustainability of production forestry. However, its long-term impacts have not been studied extensively, especially in sub-tropical environments. This study investigated the long-term impact of harvest residue retention on tree nutrition, growth and productivity of a F1 hybrid (Pinus elliottii var. elliottii × Pinus caribaea var. hondurensis) exotic pine plantation in sub-tropical Australia, under three harvest residue management regimes: (1) residue removal, RR₀; (2) single residue retention, RR₁; and (3) double residue retention, RR₂. The experiment, established in 1996, is a randomised complete block design with 4 replicates. Tree growth measurements in this study were carried out at ages 2, 4, 6, 8 and 10 years, while foliar nutrient analyses were carried out at ages 2, 4, 6 and 10 years. Litter production and litter nitrogen (N) and phosphorus (P) measurements were carried out quarterly over a 15-month period between ages 9 and 10 years. Results showed that total tree growth was still greater in residue-retained treatments compared to the RR₀ treatment. However, mean annual increments of diameter at breast height (MAID) and basal area (MAIB) declined significantly after age 4 years to about 68–78% at age 10 years. Declining foliar N and P concentrations accounted for 62% (p < 0.05) of the variation of growth rates after age 4 years, and foliar N and P concentrations were either marginal or below critical concentrations. In addition, litter production, and litter N and P contents were not significantly different among the treatments. This study suggests that the impact of residue retention on tree nutrition and growth rates might be limited over a longer period, and that the integration of alternative forest management practices is necessary to sustain the benefits of harvest residues until the end of the rotation.     

Effects of aluminum on growth and nutrient status of Douglas-fir seedlings grown in culture solution

Effects of Al on growth, nutrient uptake and proton efflux were studied in Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) seedlings grown for about nine months in culture solutions with a pH between 3.4 and 3.6 and with both calcium and magnesium (Ca + Mg) at a concentration of 0.1, 0.5 or 2.5 mM. In the absence of Al, plant dry matter production and root development increased with increasing concentrations of (Ca + Mg) in the culture solution. At the low and intermediate (Ca + Mg) concentrations, optimal root and shoot development were observed at an Al concentration of 4 mg l(-1). At the highest (Ca + Mg) concentration, Al up to 4 mg l(-1) did not affect growth, but at higher concentrations, it significantly reduced both shoot and root growth. As the concentration of (Ca + Mg) in the nutrient solution increased, the concentrations of Ca and Mg increased in shoots and roots also. The concentrations of Ca and Mg in the roots were unaffected by the presence of Al, whereas in the shoots they were either unaffected, or increased, by Al. Concentrations of Al in, or on, roots, or in shoots, did not change in response to changing concentrations of Ca + Mg in the nutrient medium. In general, concentrations of P and K in shoots and roots were higher in seedlings grown in nutrient solutions containing Al. Stimulation of growth by moderate concentrations of Al, which was observed at suboptimal (Ca + Mg) concentrations, was associated with a low NH(4) preference and a low root proton efflux. The Al-induced increase in internal K concentration and reduction in NH(4) preference may be explained by a lower efflux of K and NO(3), respectively.     

Effects of overstorey canopy, plant-plant interactions and soil properties on Mediterranean maritime pine seedling dynamics

Seedling emergence, survival and early growth of the Mediterranean conifer P. pinaster were studied under closed canopy and open canopy (gaps) cover conditions in a Mediterranean forest of central Spain during two consecutive years (March 2008 to January 2010). Our main objective was to understand how overstorey structure, shrubs and soil properties influence recruitment in this species. Natural emergence and seedling survival were significantly better under closed canopy cover than under open canopy during the two consecutive years of the study; survival increased as radiation decreased. Proximity to shrubs under closed canopy cover was associated with lower mortality rates as well as a positive and apparently transitive effect on early growth. Amelioration of microclimatic conditions is hypothesized as the primary facilitation agent of those observed. Younger seedlings established during the spring of 2008 experienced higher mortality rates than older seedlings established before 2008, and soil properties affected seedling survival significantly. Water stress during summer appeared to be the main cause of seedling mortality in both years. Our study suggests that seedlings of shade-intolerant species may require overstorey cover to establish successfully, and that positive plant-plant interactions in forest communities may be more important than expected in the milder conditions provided by overstorey canopy cover.     

Effects of mechanized pine straw raking on population densities of longleaf pine seedlings

Longleaf pine communities occupy a small fraction of their original extent in the southeastern United States and are in great need of restoration and conservation management. Recent anthropogenic disturbances, such as pine straw raking, may interfere with seedling survival and, hence, restoration efforts. We examined the effects of mechanized straw raking on longleaf pine (Pinus palustris Mill.) seedlings (pre-grass stage, or <3-yr-old) in natural, fire-maintained plant communities in Croatan National Forest, North Carolina, by testing the effects of number of rakings (0–4 times during a 2-yr period (1992–1994)) and community type (pine-turkey oak, dry savanna, and mesic savanna) on seedling densities in 1-m² quadrats. Despite initial differences in densities of seedlings among communities, analyses of variance did not detect significant differences among communities as averaged over time and raking treatment. Both raked and unraked quadrats exhibited declines in seedling density during the study, but the declines were greater for raked quadrats. After 2 yr, initial densities were, on average, reduced by 34% in unraked quadrats and by 47%, 63%, 78%, and 77% in quadrats raked one, two, three, and four times, respectively. In quadrats raked four times, censuses performed after each raking indicated significant declines in densities in response to all but the first raking. Raking either injures pine seedlings directly and/or modifies microsite conditions in ways unfavorable for seedling survival. Having established a link between raking and mortality, we now recommend additional work to reveal the causal mechanisms. Land management decisions should accommodate the potential adverse effects of mechanized raking on pine regeneration.     

Effects of nickel and copper on growth and mycorrhiza of Scots pine seedlings inoculated with Gremmeniella abietina

Scots pine (Pinus sylvestris) seedlings were planted in soil originating from two localities with different background levels of nickel and copper. In addition, some of the seedlings were exposed to additional nickel (20.5 mg Ni/l of soil) or copper (63.5 mg Cu/l of soil), or a combination of both Ni and Cu, via soil without direct shoot exposure during their second growing period. The seedlings were either irrigated with spring water (pH 6) or got only natural rain during the whole field experiment. All seedlings were inoculated with conidia of a shoot‐pathogen Gremmeniella abietina during their third growing season, and harvested the following spring. Lengths of shoots of different year‐classes were used as growth estimates. In roots, the proportion of fungal (assumedly mycorrhizal) biomass was estimated by measuring ergosterol concentration. Guajacol peroxidase activity was measured. Short roots were classified into two groups according to their condition and the composition of the mycorrhizal community was expressed as a proportion of morphotypes in the roots. The seedlings exposed to additional Ni had higher shoot growth than the seedlings in the other treatments. The mean Ni concentration in the roots of seedlings exposed to additional Ni was 79 p.p.m. and in other seedlings 16 p.p.m. Additional Ni also decreased the frequency of clearly senescent short roots and the proportion of the mycorrhizal morphotype with the thinnest mantle. These results indicate that the Ni exposure levels used in this experiment had some positive effects on the seedlings. The relative fungal biomass was about 6% lower (p = 0.0981) in the fine roots of seedlings treated with additional Cu. The mean Cu concentration in the roots of seedlings exposed to additional Cu was 256 p.p.m. and in other seedlings 29 p.p.m. Peroxidase activity, which was used as a general stress indicator in this study, was not affected by any of the treatments. The shoot growth and the relative biomass of fungi in the fine roots were positively correlated in all seedlings, and this correlation was stronger in seedlings exposed to additional Ni that were not irrigated compared with seedlings not exposed to additional Ni that were irrigated. The frequency of asymptomatic infections of G. abietina was positively correlated with the proportion of senescent short roots in the irrigated seedlings but not in not‐irrigated seedlings. The general condition of seedlings may be an important factor for infection by G. abietina when moisture is high enough for the fungi to infect seedlings by conidia.