共查询到20条相似文献,搜索用时 31 毫秒
1.
The distribution of fine (<2 mm diameter) and small roots (2–20 mm diameter) was investigated in a chronosequence consisting
of 9-year-old, 26-year-old, 82-year-old and 146-year-old European beech (Fagus sylvatica) stands. A combination of trench wall observations and destructive root sampling was used to establish whether root distribution
and total biomass of fine and small roots varied with stand age. Root density decreased with soil depth in all stands, and
variability appeared to be highest in subsoil horizons, especially where compacted soil layers occurred. Roots clustered in
patches in the top 0–50 cm of the soil or were present as root channels at greater depths. Cluster number, cluster size and
number of root channels were comparable in all stands, and high values of soil exploitation occurred throughout the entire
chronosequence. Overall fine root biomass at depths of 0–120 cm ranged from 7.4 Mg ha−1 to 9.8 Mg ha−1, being highest in the two youngest stands. Small root biomass ranged from 3.6 Mg ha−1 to 13.3 Mg ha−1. Use of trench wall observations combined with destructive root samples reduced the variability of these estimates. These
records showed that variability in fine root distribution depended more on soil depth and edaphic conditions than on stand
age, and suggest that trench wall studies provide a useful tool to improve estimates of fine root biomass. 相似文献
2.
Variability of fine root (diameter < 2 mm) distribution was investigated in four 55 to 56-year-old Maritime pine (Pinus pinaster) stands using a combination of trench wall observations and destructive sampling. Our objectives were to assess patterns
of fine root distribution, to estimate tree fine root biomass and to explore interactions with understorey vegetation in a
gradient of relevant site conditions. Results showed that root density decreased with soil depth in all stands, and variability
appeared to be highest in litter and subsoil layers especially where compacted soil layers occurred. Roots were clustered
in patches in the top 0–50 cm of the soil or were present as root channels at greater depths. Cluster number, cluster size
and number of root channels were comparable in all four stands. Overall fine root biomass at depths of 0–120 cm ranged from
2.7 to 7.2 Mg ha−1 and was highest for the two driest stands. The use of trench wall records made it possible to reduce the variability of these
estimates. Understorey species represented as much as 90% of the total number of fine roots in the upper layers, and the understorey
formed a considerable proportion of the total ecosystem biomass, suggesting that understorey species are likely competitors
for nutrients in this ecosystem. Further studies should focus on the interaction of the understorey and pine roots and the
ecological significance of clustered roots and nutrient distributions. 相似文献
3.
Pavel Šamonil Martin Valtera Stanislav Bek Barbora Šebková Tomáš Vrška Jakub Houška 《European Journal of Forest Research》2011,130(6):1075-1091
Soil variability was assessed in a 74.2-ha area within the Žofínsky prales natural forest. Parameters evaluated for 1765 soil
profiles inside 353 graticule plots were as follows: (1) thickness of organic horizons, (2) thickness and form of mineral
horizons, (3) humus form (HF), (4) soil taxonomic unit (STU) and (5) anomalies. In addition, soil reaction (pHKCl) and oxidizable carbon content (Cox) were measured in the laboratory for 734 samples from the upper mineral (A) and lower mineral (B) horizons. The most frequently
occurring humus form was mor followed by moder, hydromor and peaty T-horizon. Entic Podzols, Dystric Cambisols, Haplic Cambisols,
Albic Podzols, Histic (or Haplic) Gleysols, Endogleyic Stagnosols, Fibric or Hemic or Sapric Histosols and Stagnic Gleysols
were all present at the site despite its homogeneous geological bedrock. Overall coefficient of variance (CV) was lower in
terrestrial soils compared with (semi-)hydromorphic soils. Overall variance decreased in both soil groups with increasing
depth, as did CV differences between the fine (up to 10 m) and the locality scales. The lowest CV values occurred for Cox and pHKCl. The CV values differed between STUs as well. Compared to lower horizons, variograms of upper horizons showed greater autocorrelation
at the intermediate spatial scale (10–320 m)—ranging from 50 to 150 m. Semivariance values, however, reached 70–80% of sill
already at a distance of 10 m. The most significant factor of variability at all studied spatial scales is presumably the
soil disturbance regime, followed by terrain micro-topography and the effect of tree species. 相似文献
4.
Greater organic matter inputs in agroforestry systems contribute to the long-term storage of carbon (C) in the soil, and the
use of simulation models provides an opportunity to evaluate the dynamics of the long-term trends of soil organic carbon (SOC)
stocks in these systems. The objective of this study was to apply the Century model to evaluate the long-term effect of agroforestry
alley crop and sole crop land management practices on SOC stocks and soil C fractions. This study also evaluated the accuracy
between measured field data obtained from a 19-year old tropical (TROP) and 13-year old temperate (TMPRT) alley crop and their
respective sole cropping systems and simulated values of SOC. Results showed that upon initiation of the TROP and TMPRT alley
cropping systems, levels of SOC increased steadily over a ~100 year period. However, the sole cropping systems in both tropical
and temperate biomes showed a decline in SOC. The active and passive C fractions increased in the TROP agroforestry system,
however, in the TMPRT agroforestry system the active and slow fractions increased. The input of organic matter in the TROP
and TMPRT agroforestry systems were 83 and 34% greater, respectively, compared to the sole crops, which likely contributed
to the increased SOC stock and the C fractions in the alley crops over the 100 year period. Century accurately evaluated levels
of SOC in the TROP (r
2 = 0.94; RMSE = 226 g m−2) and TMPRT (r
2 = 0.94; RMSE = 261 g m−2) alley crops, and in the TROP (r
2 = 0.82; RMSE = 101 g m−2) and TMPRT (r
2 = 0.83; RMSE = 64 g m−2) sole crops. Century underestimated simulated values in the alley cropping systems compared to measured values due to the
inability of the model to account for changes in soil bulk density with increasing organic matter inputs with tree age from
prunings or litterfall. 相似文献
5.
在孟加拉吉大港丘陵地区,调查了热带季风气候条件下的3种人工林(7年生大叶相思(Acacia auriculiformis)林、15年生大叶相思林和18年生混交林)和1种天然林的森林凋落物及其对土壤性质的作用.结果表明,总的有机质积累随人工林树龄增加而增加,但是年积累量随之降低.在同一植被类型内,不同坡位新鲜或部分分解的凋落物有机质累计量变化较大,坡底部有机质积累量最高,沿着山坡向上逐渐减少.在15年生大叶相思人工林内,土壤整合有机物积累量变化趋势与新鲜或部分分解有机质积累量变化趋势相反.在7年生和15年生的大叶相思林以及18年龄的阔叶混交人工林内,新鲜、部分分解和完全分解(含土壤整合有机质)有机质总生产速率分别是2554.31、705.79和1028.01kg.ha-1·a-1,新鲜凋落物有机质在3种林分中的生产速率分别是38.23,19.40和30.48 kg·ha-1·a-1.3种人工林和自然林内,平均新鲜凋落物的有机质积累占有机质产出总量的32.45%,部分分解凋落物占13.50%,而全分解整合土壤有机质占54.56%.森林土壤酸度随凋落物分解阶段的深入而增加. 相似文献
6.
In this study, a weeding-duration model for Larix kaempferi plantations was developed that employs a generalized linear model. The number of years that weeding is necessary is the response
variable, and elevation, slope, maximum snow depth, annual precipitation, geological type, soil type, site index, slope aspect,
and vegetation type are explanatory variables. Among the explanatory variables, geological type, soil type, slope aspect,
and vegetation type are categorical data. We assumed a Poisson distribution for the response variable. The link function was
log. Among the models that could be developed from these variables, we chose the model with the smallest Akaike’s information
criterion (AIC). The weeding-duration model can be written as follows: years that weeding is necessary = Exp (−0.0172833 × site
index + 0.0014053 × maximum snow depth (cm) + 1.7417731). The results of this study imply that weeding of Larix kaempferi plantations is needed for more years as the maximum snow depth increases and fewer years as the site index increases. This
model is useful for cost–benefit analyses of afforestation or reforestation with Larix kaempferi. 相似文献
7.
In this study, the supply and input–output balances of phosphorus (P) were investigated for a 10-year-period at 85 long-term
monitoring sites in German forest ecosystems under the European Level II programme. These sites encompass 23 European beech
(Fagus sylvatica L.) stands, 9 oak stands comprised of common oak (Quercus robur L.) and/or sessile oak (Quercus petraea Liebl.), 20 Scots pine (Pinus sylvestris L.) and 33 Norway spruce (Picea abies H.Karst.) stands. We quantified P concentrations in needles and leaves, P inputs from the atmosphere, P outputs through leaching
and harvesting, and total P in the soil and humus layers. The P concentrations in European beech leaves from two sites (>1 mg P g−1 dry weight), and in Norway spruce needles from four sites (>1.2 mg P g−1 dry weight), were deficient over several years. In contrast, the oak and Scots pine sites were well supplied with P. When
P removal through harvesting was disregarded, P balances were positive or stable (median 0.21 kg P ha−1 a−1). With harvesting, balances were mostly negative (median −0.35 kg P ha−1 a−1), with long-term P removal from the forest ecosystems. 相似文献
8.
Anne Thimonier Elisabeth Graf Pannatier Maria Schmitt Peter Waldner Lorenz Walthert Patrick Schleppi Matthias Dobbertin Norbert Kräuchi 《European Journal of Forest Research》2010,129(3):443-461
Nitrogen (N) deposition exceeds the critical loads for this element in most parts of Switzerland apart from the Alps. At 17
sites (8 broadleaved stands, 8 coniferous stands, and 1 mixed stand) of the Swiss Long-term Forest Ecosystem Research network,
we are investigating whether N deposition is associated with the N status of the forest ecosystems. N deposition, assessed
from throughfall measurements, was related to the following indicators: (1) nitrate leaching below the rooting zone (measured
on a subset of 9 sites); (2) the N nutrition of the forest stand based on foliar analyses (16 sites); and (3) crown defoliation,
a non specific indicator of tree vitality (all 17 sites). Nitrate leaching ranging from about 2 to 16 kg N ha−1 a−1 was observed at sites subjected to moderate to high total N deposition (>10 kg ha−1 a−1). The C/N ratio of the soil organic layer, or, when it was not present, of the upper 5 cm of the mineral soil, together with
the pool of organic carbon in the soil, played a critical role, as previous studies have also found. In addition, the humus
type may need to be considered as well. For instance, little nitrate leaching (<2 kg N ha−1 a−1) was recorded at the Novaggio site, which is subjected to high total N deposition (>30 kg ha−1 a−1) but characterized by a C/N ratio of 24, large organic C stocks, and a moder humus type. Foliar N concentrations correlated
with N deposition in both broadleaved and coniferous stands. In half of the coniferous stands, foliar N concentrations were
in the deficiency range. Crown defoliation tended to be negatively correlated with N concentrations in the needles. In the
majority of the broadleaved stands, foliar N concentrations were in the optimum nutritional range or, on one beech plot with
high total N deposition (>25 kg ha−1 a−1), above the optimum values. There was no correlation between the crown defoliation of broadleaved trees and foliar concentrations. 相似文献
9.
The two-spotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae), and the onion thrips, Thrips tabaci Lind. (Thysanoptera: Thripidae), are significant field pests of potato in the Ardabil region of Iran. Orius niger (Wolf.) and O. minutus (L.) (Hemiptera: Anthocoridae) are locally the predominant natural enemies of these pests. This study compared the functional
responses of O. niger and O. minutus to female mites and second instar thrips larvae across a range of prey densities (5, 10, 20, and 40 prey/arena) under controlled
conditions of 24 ± 1°C, 50 ± 5% RH and 16:8 h (L:D). The resulting data were appropriately fit to Type II functional response
models in four predator–prey interactions, including: (1) O. niger to second instar thrips larvae (a = 0.009 h−1; and T
h = 1.62 h); (2) O. niger to females mites (a = 0.006 h−1 and T
h = 1.28 h); (3) O. minutus to second instar thrips larvae (a = 0.008 h−1 and T
h = 1.93 h) and (4) O. minutus to females mites (a = 0.01 h−1 and T
h = 1.1 h). The number of second instar thrips larvae attacked by O. niger was greater than that by O. minutus (P ≤ 0.01); conversely, the number of females mites attacked by O. minutus was greater than that by O. niger (P ≤ 0.01). These results confirm the potential for both O. niger and O. minutus to make valuable contributions to a biological control program against onion thrips and the two-spotted spider mites infesting
potato fields in this region. 相似文献
10.
Gonzalo Caballé María Elena Fernández Javier Gyenge Alejandro Aparicio Tomás Schlichter 《Agroforestry Systems》2011,83(1):13-24
The integrated relationship in a simple mechanistic model between the critical environmental factors controlling leaf photosynthesis
of understory species would be a useful tool to optimize the management of the silvopastoral systems. Individual effect of
leaf temperature, water stress and light environment over net maximum photosynthetic rate (Pmax) was evaluated on Festuca pallescens leaves grown in a silvopastoral system of two Pinus ponderosa canopy covers (350 and 500 trees ha−1) and natural grassland. The aim was to integrate individual functions for Pmax against these environmental factors into a multiplicative model. We measured pre-dawn water potential (ψ
pd), leaf temperature and net photosynthetic rate (Pn), stomatal conductance (gs) and intercellular CO2 concentration (Ci) as a function of photosynthetic photon flux density (PPFD). The highest Pmax under non-limiting conditions was 20.4 μmol CO2 m−2 s−1 and was defined as standardized dimensionless Pmax
s
= 1 for comparison of environmental factors. The leaf temperature function showed an optimum range between 20.2 and 21.8°C
where Pmax
s
= 1. Then, Pmax
s
declined by an average 1 μmol CO2 m−2 s−1 C−1 from the optimum to 4.7 and 38.5°C. Pmax
s
decreased at a rate of 9.49 μmol CO2 m−2 s−1 MPa−1 as water potential reaches −1.9 MPa and showed a lower slope as water potential decreased down to −4.3 MPa. The light environment
was estimated from hemispherical photograph analysis. Pmax
s
was 20% higher in leaves of open control plants than under the maximum tree canopy cover. The simple multiplicative model
accounted for 0.82 of the variation in Pmax. Such a simple mechanistic model is the first step towards a more effective decision support tool. 相似文献
11.
Kevin Lombard Mick O’Neill John Mexal April Ulery Blake Onken Greg Bettmann Robert Heyduck 《Agroforestry Systems》2010,78(1):1-11
Iron chlorosis caused by an elevated soil pH remains an important selection criteria in evaluating hybrid Populus trials in northwest New Mexico. Compared to expensive extraction methods or visual ranking scales, the soil plant analysis
development (SPAD) chlorophyll meter is a handheld tool that objectively indicates leaf color. SPAD calibration curves pertaining
to Fe status in Populus leaves were developed for two clones: NM-6 (Populus nigra × Populus maximowiczii) and OP-367 (Populus deltoides × Populus nigra). Hybrids were grown in the greenhouse in a sandy loam soil of pH > 8 and the same soil amended with composted biosolids
enriched with 420 mg kg−1 Fe. SPAD measurements related to foliar Fe as follows: r
2 = 0.72 for NM-6 and r
2 = 0.58 for OP-367. SPAD measurements correlated with total chlorophyll as follows: r
2 = 0.66 for NM-6 and r
2 = 0.85 for OP-367. Based on the total chlorophyll content (supported with foliar element data), Fe sufficiency threshold
values from SPAD measurements were estimated in these two clones. 相似文献
12.
《Forest Ecology and Management》2006,221(1-3):291-298
Wood ash is recommended as a compensatory fertiliser to counteract the effects of acidic deposition on forest ecosystems. Spatial distribution of biomass, necromass and morphology parameters of the fine roots (diameter classes <1, 1–2, <2 mm) of Norway spruce (Picea abies (L.) Karst.) were analysed in response to fertilisation with granulated wood ash (GWA) in a long-term field experiment in SW Sweden. GWA was applied as a single dose of 3200 kg ha−1 and the fine roots were sampled 9 years later by soil coring. Soil cores were divided into 1-cm strata within the top 0–2.5 cm humus limits, the lower humus below 2.5 cm (with varying thickness) and the mineral soil to 50 cm depth (from ground surface). Total fine-root biomass in the control (C) and GWA treatment, 256 ± 20 and 258 ± 25 g m−2, respectively, and length 2072 ± 182 and 1800 ± 198 m m−2, respectively, did not differ statistically from each other. Total fine-root necromass in the 1–2 mm fraction was significantly higher in C than in the GWA treatment, 130 ± 12 and 80 ± 10 g m−2, respectively. Fine-root biomass in the <1 mm fraction was significantly greater in the lower humus in the GWA treatment, but this did not affect the total biomass in the <1 mm fraction in the whole soil profile. The biomass-to-necromass ratio (1–2 mm) was significantly higher in the GWA treatment in the 0–30 cm soil layer than in the corresponding layer of the control. Specific root length (SRL) was lower in the GWA treatment than in the control in the 0–5 cm soil layer. The lower necromass and SRL were more clearly related to the GWA treatment, whereas the difference in the vertical distribution of biomass may have been related to the thicker humus layer in the GWA plots. 相似文献
13.
A long-term (20 months) bulk litter decomposition experiment was conducted in a subtropical plantation in southern China in
order to test the hypothesis that stable isotope discrimination occurs during litter decomposition and that litter decomposition
increases concentrations of nutrients and organic matter in soil. This was achieved by a litter bag technique. Carbon (C),
nitrogen (N) and phosphorus (P) concentrations in the remaining litter as well as δ13C and δ15N during the experimental period were measured. Meanwhile, organic C, alkali-soluble N and available P concentrations were
determined in the soils beneath litter bags and in the soils at the control plots. The dry mass remaining (as % of the initial
mass) during litter decomposition exponentially declined (y = 0.9362 e−0.0365x
, R
2 = 0.93, P < 0.0001), but total C in the remaining litter did not decrease significantly with decomposition process during a 20-month
period. By comparison, total N in the remaining litter significantly increased from 5.8 ± 1.7 g kg−1 dw litter in the first month to 10.1 ± 1.4 g kg−1 dw litter in the 20th month. During the decomposition, δ13C values of the remaining litter showed an insignificant enrichment, while δ15N signatures exhibited a different pattern. It significantly depleted 15N (y = −0.66x + 0.82, R
2 = 0.57, P < 0.0001) during the initial 7 months while showing 15N enrichments in the remaining 13 months (y = 0.10x − 4.23, R
2 = 0.32, P < 0.0001). Statistically, litter decomposition has little impact on concentrations of soil organic C and alkali-soluble N
and available P in the top soil. This indicates that nutrient return to the topsoil through litter decomposition is limited
and that C cycling decoupled from N cycling during decomposition in this subtropical plantation in southern China. 相似文献
14.
G.I. Nyadzi B.H. Janssen R.M. Otsyina H.W.G. Booltink C.K. Ong O. Oenema 《Agroforestry Systems》2003,59(3):215-229
The objective of this study was to compare the effects of woodlots of five tree species, continuous maize (Zea mays L.) and natural fallow on soil water and nitrogen dynamics in western Tanzania. The tree species evaluated were Acacia crassicarpa (A. Cunn. ex Benth.), Acacia julifera (Berth.), Acacia leptocarpa (A. Cunn. ex Benth), Leucaena pallida (Britton and Rose), and Senna siamea (Lamarck) Irwin & Barneby). The field experiment was established in November 1996 in a completely randomized block design
replicated three times. Maize was intercropped between the trees during the first three years after planting and thereafter
the trees were allowed to grow as pure woodlots for another two years. Transpiration by the trees was monitored when they
were 3 years old using sap flow gauges. Soil water content was measured using the neutron probe approach between November
1999 and March 2001. Soil inorganic N profiles were measured when the trees were four years old in all treatments. The results
indicated that the trees transpired more water than natural fallow vegetation during the dry season. The difference was apparent
at a depth of 35 cm soil, but was more pronounced in deeper horizons. The water content in the entire soil profile under woodlots
and natural fallow during the dry period was 0.01 to 0.06 cm3 cm−3 lower than in the annual cropped plots. This pattern was reversed after rainfall, when woodlots of A. crassicarpa, A. leptocarpa, A. julifera, S. siamea and L. pallida contained greater quantity of stored water than natural fallow or continuous maize by as much as 0.00 to 0.02, 0.01 to 0.04,
0.01 to 0.04, 0.01 to 0.03 and 0.00 to 0.02 cm3 cm−3, respectively. Natural fallow plots contained the lowest quantity of stored water within the entire profile during this period.
Transpiration was greatest in A. crassicarpa and lowest in L. pallida. All tree species examined were `scavengers' of N and retrieved inorganic N from soil horizons up to 2-m depth and increased
its concentration close to their trunks. This study has provided evidence in semi-arid environments that woodlots can effectively
retrieve subsoil N and store more soil water after rains than natural fallow and bare soil.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
15.
R. Chikowo P. Mapfumo P. Nyamugafata G. Nyamadzawo K.E. Giller 《Agroforestry Systems》2003,59(3):187-195
Improved or planted fallows using fast-growing leguminous trees are capable of accumulating large amounts of N through biological
N2-fixation and subsoil N capture. During the fallow phase, the cycling of nutrients is largely efficient. However, there are
few estimates of the fate of added N during the cropping phase, after the 'safety net' of fallow-tree roots is removed. Nitrate-N
at the end of the fallow phase, which is pre-season to the subsequent crop, was monitored in seven land use systems in successive
20-cm soil layers to 120 cm depth at Domboshawa, Zimbabwe in October 2000. Thereafter, nitrate-N dynamics was monitored during
cropping phase until April 2001 at 2-week intervals in plots that had previously 2-year planted fallows of Acacia angustissima and Sesbania sesban, and in a continuous maize control. Pre-season nitrate concentrations below 60 cm soil depth were <3 kg N ha−1 layer−1 for S. sesban,
A. angustissima, Cajanus cajan and natural woodland compared with the maize (Zea mays L.) control, which had >10 kg N ha−1 layer−1. There was a flush of nitrate in the S. sesbania and A. angustissima plots with the first rains. Topsoil nitrate had increased to >29 kg N ha−1 by the time of establishing the maize crop. This increase in nitrate in the topsoil was not sustained as concentrations decreased
rapidly due to leaching. Nitrate then accumulated below 40 cm, early in the season when maize root length density was still
low (<0.1 cm cm−3) and inadequate to effectively intercept the nitrate. It is concluded that under light soil and high rainfall conditions,
there is an inherent problem in managing nitrate originating from mineralization of organic materials as it accumulates at
the beginning of the season, well ahead of peak demand by crops, and is susceptible to leaching before the crop root system
develops.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
16.
Steen Magnussen Lutz Fehrman William J. Platt 《European Journal of Forest Research》2012,131(2):307-320
Density estimators for k-tree distance sampling are sensitive to the amount of extra Poisson variance in distances to the kth tree. To lessen this sensitivity, we propose an adaptive composite estimator (COM). In simulated sampling from 16 test
populations, a three-component composite density estimator (COM)–with weights determined by a multinomial logistic function
of four readily available ancillary variables–was identified as superior in terms of average relative absolute bias. Results
from a different set of nine validation populations–with widely different stem densities and spatial patterns of tree locations—confirmed
that relative root mean squared errors (RRMSE) of COM were, on average, considerably lower than those obtained with the three-component
k-tree density estimators. The RRMSE performance of COM improved with increasing values of k. With k = 6 and sample sizes of 10, 20, and 30, the average relative bias of COM was between −5 and 5% in seven validation populations
but in an open low-density savanna-like population bias reached −12% (1979 data) and 7% (1996 data). For k = 6 and n = 10, the RRMSE of COM was, in six of the nine validation populations, within 3.3 percentage points of the RRMSE for sampling
with fixed-area plots. Jackknife estimates of the precision of COM estimates of density were negatively biased, leading to
under-coverage (7%) of computed 95% confidence intervals. 相似文献
17.
This study presents empirical data on regeneration and growth of understory trees and constructs simple models for predicting
these characteristics at various stand structure and post-thinning standing volume levels. The field experiment was established
on a grass/herb mineral soil site in central Finland. Regeneration and understory tree growth data were collected from 24
Norway spruce (Picea abies L.)-dominated mixed substands. Seedlings with heights from 5 to 130 cm were measured in 1996 and 2007. In addition, the annual
height growth of Norway spruce seedlings was measured in 2007. The spatial pattern of the substands varied from clustered
to regular with a decreasing standing volume. Stand complexity was uniform across the range of standing volume. In the 2007
survey, the amount of Norway spruce regeneration increased from approximately 400 to 5,000 seedlings ha−1 when the post-thinning standing volume level was reduced from 230 to 90 m3 ha−1, respectively. Nearly no seedlings were found when the standing volume was over 300 m3 ha−1. The annual diameter increment in Norway spruce understory (dbh < 5 cm) trees decreased, on the average, from 2.3 to 0.3 mm
with an increase in the standing volume level from 90 to 340 m3 ha−1, respectively; their height growth showed also a decreasing trend when the standing volume increased. The results indicated
that a post-thinning standing volume lower than 150 m3 ha−1 with a regular overstory spatial structure provides a suitable environment for regeneration and growth of Norway spruce understory
trees in the studied forest type. 相似文献
18.
Generic or default values to account for biomass and carbon accumulation in tropical forest ecosystems are generally recognized
as a major source of errors, making site and species specific data the best way to achieve precise and reliable estimates.
The objective of our study was to determine carbon in various components (leaves, branches, stems, structural roots and soil)
of single-species plantations of Vochysia guatemalensis and Hieronyma alchorneoides from 0 to 16 years of age. Carbon fraction in the biomass, mean (±standard deviation), for the different pools varied between
38.5 and 49.7% (±3 and 3.8). Accumulated carbon in the biomass increased with the plantation age, with mean annual increments
of 7.1 and 5.3 Mg ha−1 year−1 for forest plantations of V. guatemalensis and H. alchorneoides, respectively. At all ages, 66.3% (±10.6) of total biomass was found within the aboveground tree components, while 18.6%
(±20.9) was found in structural roots. The soil (0–30 cm) contained 62.2 (±13) and 71.5% (±17.1) of the total carbon (biomass
plus soil) under V. guatemalensis and H. alchorneoides, respectively. Mean annual increment for carbon in the soil was 1.7 and 1.3 Mg ha−1 year−1 in V. guatemalensis and H. alchorneoides. Allometric equations were constructed to estimate total biomass and carbon in the biomass which had an R
2aj (adjusted R square) greater than 94.5%. Finally, we compare our results to those that could have resulted from the use
of default values, showing how site and species specific data contribute to the overall goal of improving carbon estimates
and providing a more reliable account of the mitigation potential of forestry activities on climate change. 相似文献
19.
Aboveground and belowground biomass of 15-year-old under-planted European beech seedlings (Fagus sylvatica L.) in Norway spruce stand were studied along a light gradient in three plots, in the northern part of Slovenia. Differences
in soil water content, aboveground and fine root biomass distribution were confirmed between studied plots. Light had significant
effect on the total biomass, root-shoot ratio (0.388 ± 0.076 under canopy, 0.549 ± 0.042 in the edge, 0.656 ± 0.047 in the
open), specific root length (SRL) of fine beech roots (561.9 ± 42.2 under canopy, 664.3 ± 51.2 in the edge, 618.2 ± 72.8 in
the open) and specific leaf area in beech, indicating morphological adjustment to shade. However, SRL of beech fine roots
indicated no change between plots. The correlation between total aboveground and root biomass and light below the mature stand
canopy was higher in the case of diffuse light intensity. Most fine roots of spruce were concentrated in the top (0–20 cm)
soil layer. Beech fine roots under canopy and edge conditions were also concentrated in top (0–20 cm) soil layer and exhibited
shift downwards to deeper soil horizons in open plot. Root proportion between beech and spruce changed with light toward beech
with increasing light intensity for both fine and coarse roots. 相似文献
20.
Linda Scattolin Lucio Montecchio Elena Mosca Reinhard Agerer 《European Journal of Forest Research》2008,127(5):347-357
The vertical distribution of the ectomycorrhizal (ECM) community was studied in four old high-mountain Norway spruce (Picea abies [L.] Karst.) stands in northern Italy. The aim was to verify if the variability in the community structure could be explained
by characteristics of the organic and mineral soil horizons. The community structure was evaluated in terms of both fungal
species and their ability to explore soil (exploration types). From the 128 humus profiles sampled over the two study periods,
31 ECM species were recorded. The study demonstrated that the number of both non-vital tips and vital non-mycorrhized tips
decreases with soil depth, from organic to mineral horizons, while the number of ectomycorrhizal tips mainly increases with
soil depth. A preference was found of some ECM species and exploration types for specific organic or mineral soil layers and
their features, especially moisture and available nitrogen. These results can help in understanding how the functional role
of the single consortia and the ecological features determining this “adaptive diversity” in ectomycorrhizal communities could
be of major importance to assess the resilience in forest soil ecosystems. 相似文献