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1.
Summary The abilities of 15 coniferous barks for removing toxic heavy metal ions were investigated. The barks considerably varied in the adsorption ability to each metal ion. Of the barks tested, high adsorption ability for heavy metal ions was found inPicea abies (Norway spruce). Equilibrium experiments usingP. jezoensis (Yezo spruce) bark showed that the adsorption of Cd2+ was greatly affected by the pH of solution and the initial Cd2+ concentration in solution. The adsorption of Cd2+ byP. jezoensis bark followed Freundlich isotherm in the concentration range 10–330 mg Cd2+/L. The continuous column experiments usingP. jezoensis bark indicated that the packing had retained 10.1–14.2 mg Cd2+/g adsorbent until the column broke through.  相似文献   

2.
The concentrations and protonation constants of the functional groups like carboxyl and phenolic hydroxyl groups in spruce bark were determined by a potentiometric acid–base titration method. The non-cellulosic carbohydrates in spruce bark were also characterized by acid methanolysis and GC, including determination of the uronic acid units, which are the key units involved in metal sorption. Sorption of metal ions to bark takes place by ion exchange, mainly by complexation to these functional groups. The sorption equilibrium time, studied by using a batch method, was approximately 5 min. The metal sorption capacity of spruce bark and the affinity order of metal ions were studied with four different metal ion mixtures using a column chromatographic method. Because a method of competition was used, concentration of metal ions adsorbed to bark depends on the metal ions present in the mixtures studied. In the sorption experiments with same metal ion mixtures, inner bark of spruce exhibited higher sorption capacity than outer bark. By combination of the results from several experiments, the following affinity order was obtained Fe3+ ? Pb2+ ? Cu2+ ? Cd2+ > Zn2+ > Ni2+ > Ba2+ > Ca2+ > Sr2+ > Mn2+ > Mg2+ ? K+ ~ Na+ ~ Li+. Bark has a great potential as an effective and inexpensive sorbent for removal of metal ions from, e.g., waste water.  相似文献   

3.
广州市酸雨对不同森林冠层淋溶规律的研究   总被引：20，自引：2，他引：20       下载免费PDF全文
１９９８年４月至１９９９年３月对广州市白云山马尾松林和常绿阔叶林、广州市龙眼洞马尾松林两试验点进行了酸雨的监测,并测定和分析了林内穿透雨物理量及化学量,旨在探讨酸雨对不同森林冠层养分淋溶规律的影响。结果表明：（１）广州市酸雨占次数的７９．７％或占降雨量的９５．１％。（２）酸雨通过林冠层后,ｐＨ值明显增加。（３）在马尾松林和常绿阔叶林中,某些单次降雨出现ＳＯ４＾２－、ＮＯ３＾－、ＮＨ４＾＋Ａｌ＾３＋、Ｎａ＾＋的负淋溶现象,说明森林对这些离子（特别是ＮＯ３＾－、Ａａ＾３＋）具有吸收作用;阔叶林全年的ＮＯ３＾－和Ａｌ＾３＋净淋溶为负值,说明阔叶林比马尾松林对这两种离子具有更强的吸收能力。（４）雨水酸度增加（即ｐＨ值减小）,明显提高阳离子Ｃａ＾２＋、Ｍｇ＾２＋、Ｋ＾＋和Ｎａ＾＋冠层淋溶面分率。（５）ＮＨ４＾＋、ＳＯ４＾  相似文献   

4.
The bark ofPteroceltis tatarinowii is a raw material for manufacturing Xuan Paper. The effects of Ca2+ concentrations on the accumulation of mineral elements in the bark, leaf and root ofPteroceltis tatarinowii were studied under controlled conditions. The types of Hoagland nutrient solution with three Ca2+ concentrations levels (200, 400 and 600 μg·g−1) and a control (without Ca2+ were designed to culturePteroceltis tatarinowii. After 6 months, contents of seven mineral elements including Ca, K, Mg, Mn, Zn, Cu and Na in the root, leaf and bark were analyzed. The results indicated that Ca accumulations content in the root, leaf and bark had positively relation with Ca2+ concentrations (200, 400, 600 μg·g−1), and the order of the Ca content in the three components was root>leaf>bark. Ca content in the root treated with 600 μg·g−1 Ca2+ concentrations was 5.5 times as high as that of the control, and about 1.4 times as high as that of the root treated in 200 and 400 μg/g Ca2+ concentrations respectively. On the contrary, K and Mg contents in the root, leaf and bark were negatively related to Ca2+ concentrations, especially in the bark, and their accumulation trend followed the order of leaf>root>bark. K content in the bark treated with 600 μg·g−1 Ca2+ concentrations was 39.3% of that of the control, and was 79.0% and 91.8% of that of the bark treated with 200μg·g−1 and 400μg·g−1 Ca2+ concentrations respectively; Mg content in the bark treated with 600μg·g−1 Ca2+ concentrations was 23.4% of that of the control, and was 27.1% and 35.4% of that of the bark treated with 200 and 400 μg·g−1 Ca2+ concentrations respectively. Compared with the control, the general tendency of Mn, Zn and Cu content decreased with increasing of Ca2+ concentrations and their contents were in the order: root>leaf>bark. Based on the results of this study, the experiment has been useful for providing academic bases in improving the bark quality ofPteroceltis tatarinowii on non-limestone soil. Foundation item: This paper is supported by National Natural Science Foundation of China (No. 39970608). Biography: Fang Shengzun (1963), male, Professor in Stiiviculture, Nanjing Forestry University, Nanjing 210027, P.R. China. Responsible editor: Zhu Hong  相似文献   

5.
Leaching of major ions from acid precipitation in a subtropical forest was examined based on an experiment in four sample sites in Shaoshan City, Hunan Province, China, from January 2001 to June 2002. Results clearly show that when rain passed through the canopy, pH increased and the evidence of ion uptake was presented for SO4 2−, NO3 −, Mg2+ and NH4 + ions, especially of NH4 + and NO3 −. The percentages of dissolved SO4 2−, Ca2+ and Mg2+ show a decreasing trend with increasing rainfall. Percentages of leaching Ca2+, K+ and Cl− ions show an increasing trend as a function of increased pH values. The forest canopy in Shaoshan City has a strong effect on the uptake of SO4 2− and NO3 − ions under acid rain conditions. The decreasing order of ions leaching in the forest canopy is as follows: K+ > Ca2+ > Cl− > Mg2+ > SO4 2− > NO3 − > NH4 + > Na+. __________ Translated from Scientia Silvae Sinicae, 2007, 43(7): 1–4 [译自: 林业科学]  相似文献   

6.
This study explores the economic feasibility of several long-rotation afforestation scenarios for southern Ontario, Canada. Three species, red pine (Pinus resinosa Ait.), Norway spruce (Picea abies L.) and black walnut (Juglans nigra L.) are examined. We integrate growth and yield models, site suitability maps, and several management scenarios to investigate the investment attractiveness of these species inclusive and exclusive of carbon sequestration values. We report net present values (NPV), internal rates of return (IRR) and two break-even price metrics. For wood value only scenarios the IRRs range from 4.3 to 4.6% for red pine and 3.4–3.6% for Norway spruce (for the most attractive 10,000 ha, in a single rotation scenario). Black walnut had rates of return 3.5–3.7% for the most attractive 10,000 ha area. Adding carbon valued at Cdn $3.4 per metric ton CO2 − e (roughly 2005 prices in the Chicago Climate Exchange) increases rates of return by about 0.6% for red pine and Norway spruce and 0.4% for black walnut scenarios. Perhaps surprisingly these returns are comparable and better than 20-year rotation hybrid poplar plantations. To achieve a 6% real rate of return break-even carbon prices were $10.7/t CO2 − e for red pine, $12.6/t CO2 − e for Norway spruce and $17.2/t CO2 − e for black walnut (again for the “best” 10,000 ha). Although somewhat unremarkable, the results suggest that these longer-rotation species may be a better investment than perhaps previously expected if landowners have the appropriate site conditions.  相似文献   

7.
ABSTRACT

Soil erosion is a major socioeconomic and environmental problem in Turkey. Almost 86% of the land in Turkey has suffered various degrees of soil erosion. The objective of this study was to determine whether differences in tree species affect soil characteristics and microbial activity in degraded soils. Results from this study showed that organic C (Corg) was highest in the black locust soil at 0–20 cm depth and lowest in the bare land. Microbial biomass C (Cmic) increased in the order black locust > Scotch pine > bare land at two soil depths. One-way ANOVA demonstrated that afforested soils contain significantly higher microbial biomass C than those in the bare land soils. Microbial quotient (Cmic/Corg) of soils are positively influenced by afforestation as the bare land soils exhibited lower microbial quotient than the associated Scotch pine and black locust soils. Microbial communities in black locust soils were energetically more efficient—had a lower metabolic quotient (qCO2)—with a higher Cmic/Corg compared to those in Scotch pine soils. However, the microbial quotient in our study was still below range and cannot reach equilibrium again 15 yr after afforestation. Restoration of degraded lands could be a long-term process from microbial activity in the observed regions.  相似文献   

8.
The insecticidal activity of an entomopathogenic fungus, Isaria farinosa on pine bark-weevil (Pissodes punctatus) at different life stages underwent laboratory testing. Larvae, pupae and adults of Pissodes punctatus were exposed to a range of concentrations of fungal conidia in suspension for 5 s; mean mortality and LC50 values were calculated. The results showed I. farinosa can effectively infect larvae, pupae and adult pine bark-weevils, and the highest mean mortalities at each life stage can exceed 88%. The mean mortalities increased with higher concentrations of I. farinosa. Larvae were most susceptible with LC50 1.2 × 106 conidia ml−1 (15 days), pupae (30 days) exhibited the second largest effects, and adults (15 days) with LC50 1.72 × 106 and 1.99 × 106 conidia ml−1, respectively, at end of the experiments. This suggests that I. farinosa could be a potential bio-control agent against the pine bark-weevil.  相似文献   

9.
 Kraft lignins modified by radical sulfonation or alkaline oxygen treatment were rich in acidic groups, such as sulfonic acid, carboxylic acid, and phenolic hydroxyl groups, and were effective as soil-conditioning agents, especially because of their ability to trap aluminum ions eluted from soil under acidic conditions. Formation of complexes between aluminum ions and modified lignins was examined using potentiometric titration and 27Al nuclear magnetic resonance (NMR) spectroscopy. Changes in the titration curve of a modified lignin by the addition of aluminum ions suggest the release of protons after the formation of complexes between them. Disappearance of 27Al-NMR signals assigned to various aluminum ions by the addition of kraft lignin treated with alkaline oxygen was also attributed to the formation of complexes. The relative ease of proton release because of complex formation between a modified lignin and metal ions was as follows: Fe3+ > Al3+ > Cu2+ > Pb2+ > Mn2+ > Ca2+. This indicates that aluminum complexes are quite stable, and the aluminum ion is not exchanged with cations other than Fe3+. Received: October 24, 2001 / Accepted: January 16, 2002 Present address: Asian Natural Environmental Science Center, The University of Tokyo, Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan Tel. +81-3-5841-7506; Fax +81-3-5841-5230 e-mail: ukyoko@mail.ecc.u-tokyo.ac.jp Part of this study was presented at the 11th International Symposium on Wood and Pulping Chemistry, Nice, June 2001 Correspondence to:K.S. Katsumata  相似文献   

10.
Abstract

Soil water and nutrient regimes of naturally established old-growth conifer stands and those of intensively managed Norway spruce [Picea abies (L.) Karst.] sites were assessed over a range of lithological provinces in Finnish Lapland. Soil dielectric permittivity (ε), as a measure of soil water content (θ v) and soil electrical conductivity (σ a), as a measure of soil solute content, were species specific, such that high soil θ v>0.27 cm3cm?3 (ε>15) constitutes an edaphic constraint for Scots pine (Pinus sylvestris L.) and low soil solute content (σ a<0.5 mS m?1) is constraining for Norway spruce. The spatial pattern of the soil θ v was temporally stabile, such that intraseasonal and interseasonal soil θ v was significantly higher in silty tills of spruce stands compared to sandy tills of pine stands. Scots pine was the only conifer on tills derived from felsic rocks of Hetta granite (HG) and Lapland granulite (LG). Norway spruce dominated on tills derived from the mafic rocks of Lapland greenstone belt (LGB), but tills of LG and HG constitute a dispersal barrier for spruce. Mechanical site preparation (MSP) with ploughing (Marttiini) was not able to amend soil θ v to meet site requirements of Scots pine at former spruce sites. MSP resulted in significant reduction in soil nutrient content such that untreated control σ a>tilt/shoulder σ a>trench σ a. The results imply that MSP treatments through which cross-contour tracks are created pose a risk to the sustainability of soil quality in Lapland.  相似文献   

11.
Black stain root disease (BSRD) caused by Leptographium wageneri var. ponderosum (Verticicladiella wageneri) is a destructive disease in many Jeffrey pine (Pinus jeffreyi) and ponderosa pine (P. ponderosa) forests of the western United States. Overcrowding is a pervasive problem in these forests, unless alleviated by thinning. In an overcrowded BSRD‐infested second‐growth Jeffrey/ponderosa pine forest in northern California, a large study (16.2 hr; 40 acres) was designed to determine the impact of thinning to four levels—6.9 m2/ha (30 ft2/acre), 13.8 m2/ha (60 ft2/acre), and 20.7 m2/ha (90 ft2/acre) of basal area and a control with no thinning—on the incidence of BSRD‐caused mortality. Ten years after this experiment was initiated, results indicate that thinning to any of these levels lowered the incidence of BSRD‐caused mortality as compared with BSRD‐caused mortality in unthinned control plots.  相似文献   

12.
The phenolic composition of pine bark from a variety of Pinus species was estimated by measuring Klason lignin, acid-soluble lignin, and a 1% NaOH extract. Polyphenol contents of hot water extracts from pine bark were determined by the Folin-Ciocalteu assay and the vanillin-H2SO4 assay. Among the pine bark varieties investigated, Pinus radiata bark showed the highest polyphenol content and potent antioxidant activity. Pinus rigida bark was also a usable polyphenol-rich source, whereas Pinus densiflora bark had a low yield (5.1%) of hot water extract, although it showed potent antioxidant activity. Correlations between proanthocyanidin content in pine bark and antioxidant activity were observed. The results suggested that proanthocyanidin was the crucial contributor to potent antioxidant activity in pine bark. The publication of this article was made possible by an Emachu Research Fund. The authors are grateful for the fund.  相似文献   

13.
Agroforestry (AgB) and grass buffers (GB) are often adopted as alternative resource management tools in agroecosystems for environmental and economic benefits. The objective of this study was to compare the influence of AgB and GB systems under rotationally stocked (RP) and continuously stocked (CP) pasture systems on water infiltration measured using ponded infiltration and tension infiltration methods. Buffers were surrounded by a fence that prevented cattle from grazing within these areas. Soils at the site are Menfro silt loam (fine-silty, mixed, superactive, mesic Typic Hapludalf). Infiltration rates were measured using ponded ring infiltration units during 2 years for the four (AgB, GB, RP and CP) treatments with three replicates from two subareas within each treatment. Infiltration rate as a function of tension (at 50, 100, and 150 mm) was also measured using a tension infiltrometer. Water infiltration parameters were estimated using Green-Ampt and Parlange infiltration equations. Quasi-steady state infiltration rates (q s ) and field-saturated hydraulic conductivity (K fs ) for buffers were about 31 and 46 times higher as compared to pasture treatments, respectively. Green-Ampt and Parlange models appeared to fit measured data with r 2 values ranging from 0.91 to 0.98. The q s (measured with ponded method) in the first year for the GB treatment was the highest (221 mm h−1) and for the CP treatment was the lowest (3.7 mm h−1). For both years, estimated sorptivity (S) and saturated hydraulic conductivity (K s ) parameters were higher for buffer areas compared to the stocked pasture areas. Grazing reduced the infiltration rate for the pasture (RP and CP) treatments. Results show that the buffer areas have higher infiltration rates which imply lower runoff compared to pasture areas.  相似文献   

14.
In this paper we analyzed the dry matter yields (DM) produced in an agroforestry trial consisting of pine trees grown over (1) Control (bare ground), (2) ryegrass/clovers (Lolium perene/Trifolium spp.), (3) ryegrass only, and (4) lucerne (Medicago sativa) during the third growing season between 1992 and 1993. In addition these pastures were grown alone in separate plots in the open. The results show that:
1.  Pasture yields during the one-year period in the agroforestry plots were little affected by the presence of trees although there were seasonal trends: yields were generally unaffected or increased in summer, but reduced in spring as a result of tree shade. Total pasture yield during the one-year period was in the following order: lucerne > ryegrass/clovers > ryegrass. This trend was the exact opposite of that shown by the above-ground tree weight which was reduced in the pasture ground covers by between 16 and 52%. The reduction in tree weights was associated with reduced soil moisture availability arising from competition with the pasture species. Thus the relationship between the yields of trees and pasture species in the agroforestry plots was reciprocal.
2.  The combined DM for both the trees and pastures in the agroforestry plots during the one-year period was in the following order: lucerne (20 t ha–1) > ryegrass/clovers (16 t) > ryegrass (11 t) > control (6 t) which was consistent with the total water used and photosynthetically active radiation (PAR) intercepted. The trees accounted for 55, 44, 34 and 24% of water used respectively in control, ryegrass, ryegras/cclovers and lucerne ground covers. The balance was largely accounted for by pasture transpiration, except in the control where soil evaporation was significant. The fraction of intercepted PAR accounted for by the trees followed a similar trend to that of the water used.
3.  The crop coefficient for water use efficiency (k) (Pa) was 2.3 for radiata pine, 3.6 for ryegrass/clovers, 2.8 for ryegrass and 4.8 for lucerne. The DM produced per unit of water used (kg mm–1 ha–1) during the one-year period was 24.5 for radiata pine, 41.1 for lucerne, 30.0 for ryegrass/clovers and 23.1 for ryegrass. Radiation use efficiency (g DM MJ–1 m–2) was 1.33 for pine, 1.83 for ryegrass/clovers, 1.49 for ryegrass and 2.34 for lucerne.
4.  The land equivalent ratio (LER), i.e. the sum of ratios of DM produced by the plant species in the agroforestry plots to those produced in the sole plots, was 1.95 for ryegrass, 1.71 for ryegrass/clovers and 1.45 for lucerne ground covers.
5.  These results indicate the susceptibility of pasture species to shading and interception of rainfall by the tree crowns (aboveground interactions), and the trees to competition for soil moisture (underground interaction).
  相似文献   

15.
《Southern Forests》2013,75(2):101-108
Harvesters estimate bark thickness primarily from diameter over bark (DOB) and use it to estimate log volume and value. Harvester bark thickness estimation errors can reduce returns through poor bucking optimisation and out-of-specification logs. Radiata pine bark thickness data from harvested logs and permanent sample plots (PSP) were analysed to determine best-fit coefficients for current and potential future harvester bark thickness models. The most suitable current harvester bark thickness model for radiata pine is: double bark thickness = b 0 + b 1*DOB (the ‘DOB model’). This describes a straight line, whereas radiata pine bark relative to DOB is thicker near the stem base and consistent over the remainder. PSP data set coefficients for this model overestimated upper stem bark thickness and underestimated lower stem values. The harvester model for Scots pine bark fitted better than the DOB model for diameters <400 mm but performed poorly for larger logs, as it is restricted to trees with a diameter at breast height <590 mm. Two better models were identified: (1) a model using relative height to account for bark thickness changes with height, and (2) implementing separate DOB models for the bottom 10% and top 90% of the stem split by relative height. These approaches require approval by the StanForD committee to be implemented. Prior to approval, the upper 90% model coefficients could be applied to the entire stem to improve upper 90% stem volume and value predictions at the expense of the lower 10%. Further research will determine if this approach produces acceptable results when optimising bucking. Increasing variability of bark thickness estimates with increasing DOB in the PSP data set may reflect manual measurement errors with thicker bark or may show that additional explanatory variables are needed. Efforts to identify new variables would need to be weighed against additional returns and probable reductions in numbers of larger trees by as the clearfell age is reduced.  相似文献   

16.
A field-based study was carried out to broaden our knowledge of fully mechanized cut-to-length harvesting productivity in naturally grown forests in the northern European part of Russia (NEPR). The recorded data comprised 38 midsized single-grip harvesters (JD 1270D) in clear-cutting operations in the Karelia, Komi, Vologda, Leningrad, Tver, and Kirov regions in NEPR, 4.3 million felled trees, and 1.4 million m3 u.b. (under bark) of processed timber. Harvesting operations were conducted in forest stands composed of spruce (48% on average), pine (19%), birch (22%), and aspen (11%), with an average stem volume 0.31 m3 u.b. The cut-to-length harvesters produced from 4.3 to 14.9 m3 u.b./productive machine hour (PMH) and 16.0–49.5 m3 u.b./stem processing machine hour (S proc MH). A machine evaluation analysis and a regression analysis were used to formulate models for predicting cutting productivity of modern single-grip harvester. The regression models were developed to estimate the productivity of the harvesters in the regions taking into account two significant factors influencing the productivity: the stem volume and tree species of the felled trees. Productivity/cubic meter u.b. of processed timber/PMH was calculated according to stem volume and tree species distributions in most forest-covered NEPR regions. Further research is suggested to improve the developed productivity models and to allow prediction of system performance over a broad range of stand and site conditions.  相似文献   

17.
Nitrogen inputs from biological nitrogen fixation contribute to productivity and sustainability of agroforestry systems but they need to be able to offset export of N when trees are harvested. This study assessed magnitudes of biological nitrogen fixation (natural 15N abundance) and N balance of Acacia mangium woodlots grown in farmer’s fields, and determined if N2 fixation capacity was affected by tree age. Tree biomass, standing litter, understory vegetation and soil samplings were conducted in 15 farmer’s fields growing A. mangium as a form of sequential agroforestry in Claveria, Misamis Oriental, Philippines. The trees corresponded to ages of 4, 6, 8, 10 and 12 years, and were replicated three times. Samples from different plant parts and soils (0–100 cm) were collected and analyzed for δ15N and nutrients. The B-value, needed as a reference of isotopic discrimination when fully reliant on atmospheric N, was generated by growing A. mangium in an N2-free sand culture in the glasshouse. Isotopic discrimination occurring during N2 fixation and metabolic processes indicated variation of δ15N values in the order of nodules > old leaves > young leaves > stems > litterfall and roots of the trees grown in the field, with values ranging from −0.8 to 3.5‰ except nodules which were enriched and significantly different from other plant parts (P < 0.0001). Isotopic discrimination was not affected by tree age (P > 0.05). Plants grown in N free sand culture exhibited the same pattern of isotopic discrimination as plants grown in the field. The estimated B-value for the whole plant of A. mangium was −0.86‰. Mature tree stands of 12 years accumulated up to 1994 kg N ha−1 in aboveground biomass. Average proportion of N derived from N2 fixation of A. mangium was 54% (±22) and was not affected by age (P > 0.05). Average yearly quantities of N2 fixed were 128 kg N ha−1 in above-ground biomass amounting to 1208 kg N fixed ha−1 over 12 years. Harvest of 12-year old trees removed approximately 91% of standing aboveground biomass from the site as timber and fuel wood. The resulting net N balance was +151 kg N ha−1 derived from remaining leaves, twigs, standing litter, and +562 kg N ha−1 when tree roots were included in the calculation. The fast growing A. mangium appears to be a viable fallow option for managing N in these systems. However, other nutrients have to be replaced by using part of the timber and fuel wood sales to compensate for large amounts of nutrient removed in order for the system to be sustainable.  相似文献   

18.
Nitrogen (N) limits productivity in many coniferous forests of the western US, but the influence of post-fire structure on N cycling rates in early successional stands is not well understood. We asked if the heterogeneity created by downed wood and regenerating pine saplings affected N mineralization and microbial community composition in 15-yr old lodgepole pine (Pinus contorta var. latifolia) stands established after the 1988 fires in Yellowstone National Park (Wyoming, USA). In three 0.25-ha plots, we measured annual in situ net N mineralization in mineral soil using resin cores (n = 100 per plot) under pine saplings, downed wood (legacy logs that survived the fire, and fire-killed trees that had fallen and were contacting or elevated above the ground), and in bare mineral soil. Annual in situ net N mineralization and net nitrification rates were both greater in bare mineral soil (8.4 ± 0.6 and 3.6 ± 0.3 mg N kgsoil−1 yr−1, respectively) than under pine saplings, contact logs, or elevated logs (ca. 3.9 ± 0.5 and 0.8 ± 0.1 mg N kgsoil−1 yr−1, respectively). Net nitrification was positively related to net N mineralization under all treatments except for elevated logs. In laboratory incubations using 15N pool dilution, NH4+ consumption exceeded gross production by a factor of two in all treatments, but consumption and gross production were similar among treatments. Contrary to our initial hypothesis, microbial community composition also did not vary among treatments. Thus, two- to three-fold differences in in situ net N mineralization rates occurred despite the similarity in microbial communities and laboratory measures of gross production and consumption of NH4+ among treatments. These results suggest the importance of microclimate on in situ annual soil N transformations, and differences among sites suggest that broader scale landscape conditions may also be important.  相似文献   

19.
The effects of the warm and dry weather in the southern upper Rhine plain in the southwest of Germany on the carbon balance of the Scots pine forest at the permanent forest meteorological experimental site Hartheim were analysed over a 14-month period. The investigation of the net ecosystem exchange of carbon dioxide (F NEE) of the Scots pine forest started in the extraordinary hot and dry August 2003. Carbon dioxide fluxes were measured continuously using an eddy covariance system and analysed by use of the EDDYSOFT software package. After determining the temperature dependence of the forest ecosystem respiration and the daytime light dependence of the CO2 exchange, monthly and annual carbon balances of the Scots pine forest were calculated. Mean peak daytime F NEE rates observed in August and September 2003 (−6.5±3.6 μmol m−2 s−1) were drastically lower than in August and September 2004 (−11.8±5.2 μmol m−2 s−1), which did not show pronounced deviations from the mean long-term (1978–2002) climatic conditions. In August 2003, the Hartheim Scots pine forest was a distinct CO2 source (35 g C m−2). The estimates of the annual carbon sink strength of the Scots pine forest ranged between −132 g C m−2 (August 2003–July 2004) and −211 g C m−2 (October 2003–September 2004). The main uncertainty in the determination of the carbon balance of the Hartheim Scots pine forest was introduced by the frequently low turbulence levels, i.e. the friction velocity corrected night-time F NEE fluxes.  相似文献   

20.
Because soil CO2 efflux or soil respiration (RS) is the major component of forest carbon fluxes, the effects of forest management on RS and microbial biomass carbon (C), microbial respiration (RH), microbial activity and fine root biomass were studied over two years in a loblolly pine (Pinus taeda L.) plantation located near Aiken, SC. Stands were six-years-old at the beginning of the study and were subjected to irrigation (no irrigation versus irrigation) and fertilization (no fertilization versus fertilization) treatments since planting. Soil respiration ranged from 2 to 6 μmol m−2 s−1 and was strongly and linearly related to soil temperature. Soil moisture and C inputs to the soil (coarse woody debris and litter mass) which may influence RH were significantly but only weakly related to RS. No interaction effects between irrigation and fertilization were observed for RS and microbial variables. Irrigation increased RS, fine root mass and microbial biomass C. In contrast, fertilization increased RH, microbial biomass C and microbial activity but reduced fine root biomass and had no influence on RS. Predicted annual soil C efflux ranged from 8.8 to 10.7 Mg C ha−1 year−1 and was lower than net primary productivity (NPP) in all stands except the non-fertilized treatment. The influence of forest management on RS was small or insignificant relative to biomass accumulation suggesting that NPP controls the transition between a carbon source and sink in rapidly growing pine systems.  相似文献   

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