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1.
We report on soil leaching of dissolved inorganic nitrogen (DIN) along transects across exposed edges of four coniferous and
four deciduous forest stands. In a 64-m edge zone, DIN leaching below the main rooting zone was enhanced relative to the interior
(at 128 m from the edge) by 21 and 14 kg N ha −1 y −1 in the coniferous and deciduous forest stands, respectively. However, the patterns of DIN leaching did not univocally reflect
those of DIN throughfall deposition. DIN leaching in the first 20 m of the edges was lower than at 32–64 m from the edge (17
vs. 36 kg N ha −1 y −1 and 15 vs. 24 kg N ha −1 y −1 in the coniferous and deciduous forests, respectively). Nitrogen stocks in the mineral topsoil (0–30 cm) were, on average,
943 kg N ha −1 higher at the outer edges than in the interior, indicating that N retention in the soil is probably one of the processes
involved in the relatively low DIN leaching in the outer edges. We suggest that a complex of edge effects on biogeochemical
processes occurs at the forest edges as a result of the interaction between microclimate, tree dynamics (growth and litterfall),
and atmospheric deposition of N and base cations. 相似文献
2.
Nitrogen (N) inputs from atmospheric deposition can increase soil organic carbon (SOC) storage in temperate and boreal forests, thereby mitigating the adverse effects of anthropogenic CO2 emissions on global climate. However, direct evidence of N-induced SOC sequestration from low-dose, long-term N addition experiments (that is, addition of < 50 kg N ha−1 y−1 for > 10 years) is scarce worldwide and virtually absent for European temperate forests. Here, we examine how tree growth, fine roots, physicochemical soil properties as well as pools of SOC and soil total N responded to 20 years of regular, low-dose N addition in two European coniferous forests in Switzerland and Denmark. At the Swiss site, the addition of 22 kg N ha−1 y−1 (or 1.3 times throughfall deposition) stimulated tree growth, but decreased soil pH and exchangeable calcium. At the Danish site, the addition of 35 kg N ha−1 y−1 (1.5 times throughfall deposition) impaired tree growth, increased fine root biomass and led to an accumulation of N in several belowground pools. At both sites, elevated N inputs increased SOC pools in the moderately decomposed organic horizons, but decreased them in the mineral topsoil. Hence, long-term N addition led to a vertical redistribution of SOC pools, whereas overall SOC storage within 30 cm depth was unaffected. Our results imply that an N-induced shift of SOC from older, mineral-associated pools to younger, unprotected pools might foster the vulnerability of SOC in temperate coniferous forest soils. 相似文献
3.
Ecosystem restoration by rewetting of degraded fens led to the new formation of large-scale shallow lakes in the catchment
of the River Peene in NE Germany. We analyzed the biomass and the nutrient stock of the submersed ( Ceratophyllum demersum) and the floating macrophytes ( Lemna minor and Spirodela polyrhiza) in order to assess their influence on temporal nutrient storage in water bodies compared to other freshwater systems. Ceratophyllum demersum displayed a significantly higher biomass production (0.86–1.19 t DM = dry matter ha −1) than the Lemnaceae (0.64–0.71 t DM ha −1). The nutrient stock of submersed macrophytes ranged between 28–44 kg N ha −1 and 8–12 kg P ha −1 and that of floating macrophytes between 14–19 kg N ha −1 and 4–5 kg P ha −1 which is in the range of waste water treatment plants. We found the N and P stock in the biomass of aquatic macrophytes being
20–900 times and up to eight times higher compared to the nutrient amount of the open water body in the shallow lakes of rewetted
fens (average depth: 0.5 m). Thereafter, submersed and floating macrophytes accumulate substantial amounts of dissolved nutrients
released from highly decomposed surface peat layers, moderating the nutrient load of the shallow lakes during the growing
season from April to October. In addition, the risk of nutrient loss to adjacent surface waters becomes reduced during this
period. The removal of submersed macrophytes in rewetted fens to accelerate the restoration of the low nutrient status is
discussed. 相似文献
4.
The modification of large areas of tropical forest to agricultural uses has consequences for the movement of inorganic nitrogen
(N) from land to water. Various biogeochemical pathways in soils and riparian zones can influence the movement and retention
of N within watersheds and affect the quantity exported in streams. We used the concentrations of NO 3
− and NH 4
+ in different hydrological flowpaths leading from upland soils to streams to investigate inorganic N transformations in adjacent
watersheds containing tropical forest and established cattle pasture in the southwestern Brazilian Amazon Basin. High NO 3
− concentrations in forest soil solution relative to groundwater indicated a large removal of N mostly as NO 3
− in flowpaths leading from soil to groundwater. Forest groundwater NO 3
− concentrations were lower than in other Amazon sites where riparian zones have been implicated as important N sinks. Based
on water budgets for these watersheds, we estimated that 7.3–10.3 kg N ha −1 y −1 was removed from flowpaths between 20 and 100 cm, and 7.1–10.2 kg N ha −1 y −1 was removed below 100 cm and the top of the groundwater. N removal from vertical flowpaths in forest exceeded previously
measured N 2O emissions of 3.0 kg N ha −1 y −1 and estimated emissions of NO of 1.4 kg N ha −1 y −1. Potential fates for this large amount of nitrate removal in forest soils include plant uptake, denitrification, and abiotic
N retention. Conversion to pasture shifted the system from dominance by processes producing and consuming NO 3
− to one dominated by NH 4
+, presumably the product of lower rates of net N mineralization and net nitrification in pasture compared with forest. In
pasture, no hydrological flowpaths contained substantial amounts of NO 3
− and estimated N removal from soil vertical flowpaths was 0.2 kg N ha −1 y −1 below the depth of 100 cm. This contrasts with the extent to which agricultural sources dominate N inputs to groundwater
and stream water in many temperate regions. This could change, however, if pasture agriculture in the tropics shifts toward
intensive crop cultivation. 相似文献
5.
The objective of this study was to evaluate the effect of N fertilization and the presence of N 2 fixing leguminous trees on soil fluxes of greenhouse gases. For a one year period, we measured soil fluxes of nitrous oxide
(N 2O), carbon dioxide (CO 2) and methane (CH 4), related soil parameters (temperature, water-filled pore space, mineral nitrogen content, N mineralization potential) and
litterfall in two highly fertilized (250 kg N ha −1 year −1) coffee cultivation: a monoculture (CM) and a culture shaded by the N 2 fixing legume species Inga densiflora (CIn). Nitrogen fertilizer addition significantly influenced N 2O emissions with 84% of the annual N 2O emitted during the post fertilization periods, and temporarily increased soil respiration and decreased CH 4 uptakes. The higher annual N 2O emissions from the shaded plantation (5.8 ± 0.3 kg N ha −1 year −1) when compared to that from the monoculture (4.3 ± 0.1 kg N ha −1 year −1) was related to the higher N input through litterfall (246 ± 16 kg N ha −1 year −1) and higher potential soil N mineralization rate (3.7 ± 0.2 mg N kg −1 d.w. d −1) in the shaded cultivation when compared to the monoculture (153 ± 6.8 kg N ha −1 year −1 and 2.2 ± 0.2 mg N kg −1 d.w. d −1). This confirms that the presence of N 2 fixing shade trees can increase N 2O emissions. Annual CO 2 and CH 4 fluxes of both systems were similar (8.4 ± 2.6 and 7.5 ± 2.3 t C-CO 2 ha −1 year −1, −1.1 ± 1.5 and 3.3 ± 1.1 kg C-CH 4 ha −1 year −1, respectively in the CIn and CM plantations) but, unexpectedly increased during the dry season. 相似文献
6.
In a combined field and laboratory study in the southwest of Burkina Faso, we quantified soil-atmosphere N 2O and NO exchange. N 2O emissions were measured during two field campaigns throughout the growing seasons 2005 and 2006 at five different experimental
sites, that is, a natural savanna site and four agricultural sites planted with sorghum ( n = 2), cotton and peanut. The agricultural fields were not irrigated and not fertilized. Although N 2O exchange mostly fluctuated between −2 and 8 μg N 2O–N m −2 h −1, peak N 2O emissions of 10–35 μg N 2O–N m −2 h −1 during the second half of June 2005, and up to 150 μg N 2O–N m −2 h −1 at the onset of the rainy season 2006, were observed at the native savanna site, whereas the effect of the first rain event
on N 2O emissions at the crop sites was low or even not detectable. Additionally, a fertilizer experiment was conducted at a sorghum
field that was divided into three plots receiving different amounts of N fertilizer (plot A: 140 kg N ha −1; plot B: 52.5 kg N ha −1; plot C: control). During the first 3 weeks after fertilization, only a minor increase in N 2O emissions at the two fertilized plots was detected. After 24 days, however, N 2O emission rates increased exponentially at plot A up to a mean of 80 μg N 2O–N m −2 h −1, whereas daily mean values at plot B reached only 19 μg N 2O–N m −2 h −1, whereas N 2O flux rates at plot C remained unchanged. The calculated annual N 2O emission of the nature reserve site amounted to 0.52 kg N 2O–N ha −1 a −1 in 2005 and to 0.67 kg N 2O–N ha −1 a −1 in 2006, whereas the calculated average annual N 2O release of the crop sites was only 0.19 kg N 2O–N ha −1 a −1 and 0.20 kg N 2O–N ha −1 a −1 in 2005 and 2006, respectively. In a laboratory study, potential N 2O and NO formation under different soil moisture regimes were determined. Single wetting of dry soil to medium soil water
content with subsequent drying caused the highest increase in N 2O and NO emissions with maximum fluxes occurring 1 day after wetting. The stimulating effect lasted for 3–4 days. A weaker
stimulation of N 2O and NO fluxes was detected during daily wetting of soil to medium water content, whereas no significant stimulating effect
of single or daily wetting to high soil water content (>67% WHC max) was observed. This study demonstrates that the impact of land-use change in West African savanna on N trace gas emissions
is smaller—with the caveat that there could have been potentially higher N 2O and NO emissions during the initial conversion—than the effect of timing and distribution of rainfall and of the likely
increase in nitrogen fertilization in the future. 相似文献
7.
The present study was undertaken in seven major forest types of temperate zone (1500 m a.s.l. to 3100 m a.s.l.) of Garhwal
Himalaya to understand the effect of slope aspects on carbon (C) density and make recommendations for forest management based
on priorities for C conservation/sequestration. We assessed soil organic carbon (SOC) density, tree density, biomass and soil
organic carbon (SOC) on four aspects, viz. north-east (NE), north-west (NW), south-east (SE) and south-west (SW), in forest
stands dominated by Abies pindrow, Cedrus deodara, Pinus roxburghii, Cupressus torulosa, Quercus floribunda, Quercus semecarpifolia and Quercus leucotrichophora. TCD ranged between 77.3 CMg ha −1 on SE aspect ( Quercus leucotrichophora forest) and 291.6 CMg ha −1 on NE aspect (moist Cedrus deodara forest). SOC varied between 40.3 CMg ha −1 on SW aspect (Himalayan Pinus roxburghii forest) and 177.5 CMg ha −1 on NE aspect (moist Cedrus deodara forest). Total C density (SOC + TCD) ranged between 118.1 CMg ha −1 on SW aspect (Himalayan Pinus roxburghii forest) and 469.1 CMg ha −1 on NE aspect (moist Cedrus deodara forest). SOC and TCD were significantly higher on northern aspects as compared with southern aspects. It is recommended that
for C sequestration, the plantation silviculture be exercised on northern aspects, and for C conservation purposes, mature
forest stands growing on northern aspects be given priority. 相似文献
8.
Rice-based ( Oryza sativa L.) rainfed lowlands are the major cropping system in northeast Thailand. Average yields are low, which is generally explained by frequent drought events, low soil fertility, and poor fertilizer response. However, neither the relative importance of these factors nor their interaction is well understood. Therefore, we analyzed an existing database on fertilizer trials conducted between 1995 and 1997 at eight different sites in northeast Thailand with the objective to determine indigenous nutrient supplies, internal efficiencies, and recovery efficiencies of applied nutrients in rainfed lowland rice. Of particular interest was the effect of variety type (traditional) and water supply on these components. Comparison of N, P, and K concentrations in grain and straw (average N–P–K grain concentration of 11.0–2.7–3.4 g kg −1; average N–P–K straw concentration of 5.2–0.9–16.4 g kg −1) in the traditional-type varieties used at all trial sites with literature values showed no differences for these parameters between traditional and modern-type varieties or between irrigated and rainfed environments. In contrast, internal efficiencies of N, P, and K (average IEN: 46 kg grain per kg N uptake; IEP: 218 kg grain per kg P uptake; IEK: 25 kg grain per kg K uptake) were much lower than reported for irrigated systems, and the difference was greatest for K, which is mainly accumulated in the straw. Indigenous nutrient supply (average INS: 38 kg ha −1; IPS: 10 kg ha −1; IKS: 89 kg ha −1) and recovery efficiency (average REN: 0.28 kg kg −1; REP: 0.13 kg kg −1; REK: 0.49 kg kg −1) were low but comparable to the lower values reported from irrigated systems. Average seasonal field water resources seemed to reduce the indigenous nutrient supply but had no or little effect on internal efficiency and recovery efficiency. We concluded that the main reason for the low system productivity without and with fertilizer in northeast Thailand is the dominant use of traditional-type varieties with low harvest indices, which was the dominant cause for the observed low internal nutrient efficiency. Therefore, intensification of rainfed systems through substantially increased nutrient inputs can be recommended only where varieties with an average harvest index of close to 0.4 or higher are available. 相似文献
9.
There is growing evidence from different sources that prolonged high N deposition causes a shift from nitrogen (N) limitation
to nitrogen and phosphorus (P) co-limitation or even P limitation in many terrestrial ecosystems. However, the number of ecosystems
where the type of limitation has been directly tested by longer-term full-factorial field experiments is very limited. We
conducted a 5-year fertilization experiment with N and P in the Lüneburger Heide (NW Germany) to test the hypothesis that,
following decades of elevated atmospheric N inputs, plant growth in dry lowland heaths may have shifted from N to N–P co-limitation
or P limitation. We also tested whether the plant tissue N:P ratio reflects the type of nutrient limitation in a continental
lowland heathland. Experimental plots dominated by Calluna vulgaris received regular additions of N (50 kg N ha −1 y −1), P (20 kg P ha −1 y −1), a combination of both, or water only (control) from 2004 to 2008. Over the whole study period, a highly significant positive
N effect on shoot length was found, thus indicating N limitation. We conclude that a clear shift from N limitation to N–P
co-limitation or P limitation has not yet occurred. Tissue N:P ratios showed a high temporal variability and no relationship
between tissue N:P ratio and the shoot length response of Calluna to nutrient addition was found. The N:P tool is thus of limited use at the local scale and within the range of N:P ratio
observed in this study, and should only be used as a rough indicator for the prediction of the type of nutrient limitation
in lowland heathland on a larger geographical scale with a broader interval of N:P ratio. 相似文献
10.
Nitrous oxide (N 2O) emissions from grazed grasslands are estimated to be approximately 28% of global anthropogenic N 2O emissions. Estimating the N 2O flux from grassland soils is difficult because of its episodic nature. This study aimed to quantify the N 2O emissions, the annual N 2O flux and the emission factor (EF), and also to investigate the influence of environmental and soil variables controlling
N 2O emissions from grazed grassland. Nitrous oxide emissions were measured using static chambers at eight different grasslands
in the South of Ireland from September 2007 to August 2009. The instantaneous N 2O flux values ranged from -186 to 885.6 μg N 2O-N m −2 h −1 and the annual sum ranged from 2 ± 3.51 to 12.55 ± 2.83 kg N 2O-N ha −1 y −1 for managed sites. The emission factor ranged from 1.3 to 3.4%. The overall EF of 1.81% is about 69% higher than the Intergovernmental
Panel on Climate Change (IPCC) default EF value of 1.25% which is currently used by the Irish Environmental Protection Agency
(EPA) to estimate N 2O emission in Ireland. At an N applied of approximately 300 kg ha −1 y −1, the N 2O emissions are approximately 5.0 kg N 2O-N ha −1 y −1, whereas the N 2O emissions double to approximately 10 kg N ha −1 for an N applied of 400 kg N ha −1 y −1. The sites with higher fluxes were associated with intensive N-input and frequent cattle grazing. The N 2O flux at 17°C was five times greater than that at 5°C. Similarly, the N 2O emissions increased with increasing water filled pore space (WFPS) with maximum N 2O emissions occurring at 60–80% WFPS. We conclude that N application below 300 kg ha −1 y −1 and restricted grazing on seasonally wet soils will reduce N 2O emissions. 相似文献
11.
Dissolved organic nitrogen (DON) has recently been recognized as an important component of terrestrial N cycling, especially
under N-limited conditions; however, the effect of increased atmospheric N deposition on DON production and loss from forest
soils remains controversial. Here we report DON and dissolved organic carbon (DOC) losses from forest soils receiving very
high long-term ambient atmospheric N deposition with or without additional experimental N inputs, to investigate DON biogeochemistry
under N-saturated conditions. We studied an old-growth forest, a young pine forest, and a young mixed pine/broadleaf forest
in subtropical southern China. All three forests have previously been shown to have high nitrate (NO 3−) leaching losses, with the highest loss found in the old-growth forest. We hypothesized that DON leaching loss would be forest
specific and that the strongest response to experimental N input would be in the N-saturated old-growth forest. Our results
showed that under ambient deposition (35–50 kg N ha −1 y −1 as throughfall input), DON leaching below the major rooting zone in all three forests was high (6.5–16.9 kg N ha −1 y −1). DON leaching increased 35–162% following 2.5 years of experimental input of 50–150 kg N ha −1 y −1. The fertilizer-driven increase of DON leaching comprised 4–17% of the added N. A concurrent increase in DOC loss was observed
only in the pine forest, even though DOC:DON ratios declined in all three forests. Our data showed that DON accounted for
23–38% of total dissolved N in leaching, highlighting that DON could be a significant pathway of N loss from forests moving
toward N saturation. The most pronounced N treatment effect on DON fluxes was not found in the old-growth forest that had
the highest DON loss under ambient conditions. DON leaching was highly correlated with NO 3− leaching in all three forests. We hypothesize that abiotic incorporation of excess NO 3− (through chemically reactive NO 2−) into soil organic matter and the consequent production of N-enriched dissolved organic matter is a major mechanism for the
consistent and large DON loss in the N-saturated subtropical forests of southern China.
Dr. YT Fang performed research, analyzed data, and wrote the paper; Prof. WX Zhu participated in the initial experimental
design, analyzed data, and took part in writing the paper; Prof. P Gundersen conceived the study and took part in writing;
Prof. JM Mo and Prof. GY Zhou conceived study; Prof. M Yoh analyzed part of the data and contributed to the development of
DON model. 相似文献
12.
This study was conducted to examine the influences of soil-moisture conditions on soil nitrogen (N) dynamics, including in
situ soil N mineralization, N availability, and denitrification in a pure Alnus japonica forest located in Seoul, central Korea. The soil N mineralization, N availability, and denitrification were determined using
the buried bag incubation method, ion exchange resin bag method, and acetylene block method, respectively. The annual net
N mineralization rate (kg N ha −1 year −1) and annual N availability (mg N bag −1) were 40.26 and 80.65 in the relatively dry site, −5.43 and 45.39 in the moist site, and 7.09 and 39.17 in the wet site,
respectively. The annual net N mineralization rate and annual N availability in the dry site were significantly higher than
those in the moist and wet sites, whereas there was no significant difference between the moist and wet sites. The annual
mean denitrification rate (kg N ha −1 year −1) in the dry, moist, and wet sites was 2.37, 2.76, and 1.59, respectively. However, there was no significant difference among
sites due to the high spatial and temporal variations. Our results indicate that soil-moisture condition influenced the in
situ N mineralization and resin bag N availability in an A. japonica forest, and treatments of proper drainage for poorly drained sites would increase soil N mineralization and N availability
and consequently be useful to conserve and manage the A. japonica forest. 相似文献
13.
The present study was undertaken to assess the benefit and compare the functioning of AM fungi on wheat grown conventionally
and on beds. Ten treatment combinations were used, treatments 1 and 2: no fertilizers with and without arbuscular mycorrhizal
(AM) fungi (In vitro produced Glomus intraradices); 3:100% of recommended NPK: (120 kg ha −1 N; 60 kg ha −1 P; 50 kg ha −1 K), and 4 and 5: 75% of recommended NPK dose with and without AM inoculation in a 5 × 2 split-plot design on wheat using
conventional/flat system and elevated/raised bed system. The maximum grain yield (3.84 t ha −1) was obtained in AM fungi inoculated plots of raised bed system applied with 75% NPK and was found higher (although non-
significant) than the conventional (3.73 t ha −1) system. The AM inoculation at 75% fertilizer application can save 8.47, 5.38 kg P and 16.95, 10.75 kg N ha −1, respectively, in bed and conventional system. While comparing the yield response with 100% fertilizer application alone,
AM inoculation was found to save 20.30, 15.79 kg P and 40.60, 31.59 kg N ha −1, respectively, in beds and conventional system. Mycorrhizal inoculation at 75% NPK application particularly in raised bed
system seems to be more efficient in saving fertilizer inputs and utilizing P for producing higher yield and growth unlike
non-mycorrhizal plants of 100% P. Besides the yield, mycorrhizal plants grown on beds had higher AM root colonization, soil
dehydrogenases activity, and P-uptake. The present study indicates that the inoculation of AM fungi to wheat under raised
beds is better response (although non-significantly higher) to conventional system and could be adopted for achieving higher
yield of wheat at reduced fertilizer inputs after field validation. 相似文献
14.
Biomass and aboveground net primary production (ANPP) in a monospecific pioneer stand of a mangrove Kandelia obovata (S., L.) Yong were quantified. The estimated biomasses in leaves, branches, stems, roots, aboveground and total were 5.61
(3.68%), 28.8 (18.9%), 46.1 (30.2%), 71.8 (47.2%), 80.5 (52.8%) and 152 Mg ha −1 (100%), respectively. Stem phytomass increment per tree was estimated using allometric relationships and stem analysis. Stem
volume without bark of harvested trees showed a strong allometric relationship with D
0.12
H ( D
0.1, diameter at a height of one-tenth of tree height H) ( R
2 = 0.924). Annual stem volume increment per tree showed a strong allometric relationship with D
0.12
H ( R
2 = 0.860). Litterfall rate ranges from 3.87 to 56.1 kg ha −1 day −1 for leaves and 0.177 to 46.2 kg ha −1 day −1 for branches. Seasonal changes of litterfall rate were observed, which showed a peak during wet season (August–September).
Total annual litterfall was estimated as 10.6 Mg ha −1 year −1, in which 68.2% was contributed by the leaves. The ANPP in the K. obovata stand was 29.9–32.1 Mg ha −1 year −1, which is ca. 2.8–3.0 times of annual litterfall. The growth efficiency (aboveground biomass increment/LAI) was 5.35–5.98 Mg ha −1 year −1. The low leaf longevity (9.3 months) and high growth efficiency of K. obovata makes it a highly productive mangrove species. 相似文献
15.
This study evaluated the sources, sinks, and factors controlling net export of nitrogen (N) from watersheds on the west coast
of the US. We calculated input of new N to 22 watersheds for 1992 and 2002. 1992 inputs ranged from 541 to 11,644 kg N km −2 year −1, with an overall area-weighted average of 1,870 kg N km −2 year −1. In 2002, the range of inputs was 490–10,875 kg N km −2 year −1, averaging 2,158 kg N km −2 year −1. Fertilizer was the most important source of new N, averaging 956 (1992) and 1,073 kg N km −2 year −1 (2002). Atmospheric deposition was the next most important input, averaging 833 (1992) and 717 kg N km −2 year −1 (2002), followed by biological N fixation in agricultural lands. Riverine N export, calculated based on measurements taken
at the furthest downstream USGS water quality monitoring station, averaged 165 (1992) and 196 kg N km −2 year −1 (2002), although data were available for only 7 watersheds at the latter time point. Downstream riverine N export was correlated
with variations in streamflow (export = 0.94 × streamflow − 5.65, R
2 = 0.66), with N inputs explaining an additional 16% of the variance (export = 1.06 × streamflow + 0.06 × input − 227.78,
R
2 = 0.82). The percentage of N input that is exported averaged 12%. Percent export was also related to streamflow (%export = 0.05 × streamflow − 2.61,
R
2 = 0.60). The correlations with streamflow are likely a result of its large dynamic range in these systems. However, the processes
that control watershed N export are not yet completely understood. 相似文献
16.
Forests play a major role in global carbon (C) cycle, and the carbon density (CD) could reflect its ecological function of
C sequestration. Study on the CD of different forest types on a community scale is crucial to characterize in depth the capacity
of forest C sequestration. In this study, based on the forest inventory data of 168 field plots in the study area (E 111°30′–113°50′,
N 37°30′–39°40′), the forest vegetation was classified by using quantitative method (TWINSPAN); the living biomass of trees
was estimated using the volume-derived method; the CD of different forest types was estimated from the biomass of their tree
species; and the effects of biotic and abiotic factors on CD were studied using a multiple linear regression analysis. The
results show that the forest vegetation in this region could be classified into 9 forest formations. The average CD of the
9 forest formations was 32.09 Mg ha −1 in 2000 and 33.86 Mg ha −1 in 2005. Form. Picea
meyeri had the highest CD (56.48 Mg ha −1), and Form. Quercus liaotungensis + Acer mono had the lowest CD (16.14 Mg ha −1). Pre-mature forests and mature forests were very important stages in C sequestration among four age classes in these formations.
Forest densities, average age of forest stand, and elevation had positive relationships with forest CD, while slope location
had negative correlation with forest CD. 相似文献
17.
The over use of synthetic nitrogen (N) fertilizers is the major anthropogenic cause of low N-use efficiency and environmental damage in wetland rice production. Biochar (B) addition to soil is suggested as a climate change mitigation tool that supports carbon sequestration and reduces N losses and greenhouse gas emissions from the soil. Therefore, this study assessed the effect of four levels of B (0, 10, 20 and 30 t ha?1) combined with two levels of N (135 and 180 kg ha?1) on soil health, roots dynamics, physiological attributes, and yield components of rice. The addition of B at 30 t ha?1 combined with 135 N kg ha?1 increased chlorophyll content, net photosynthetic rate, biomass, and grain yield by 104%, 64%, 12%, and 30%, respectively, over control. Further, root traits such as total root length (TRL), total root volume (TRV), total root surface area (TRSA), and total average root diameter (TARD) were improved under 30 t ha?1 combined with 135 N kg ha?1 by 20%, 13%, 13%, and 25%, respectively, than non-biochar treatment under lower N application. Improvements in these traits resulted from higher N uptake due to improved soil physiochemical properties and soil microbial biomass combined with biochar. Interestingly, enhanced N metabolizing enzyme activities, including nitrate reductase (NR), glutamine synthetase (GS), and glutamine oxoglutarate aminotransferase (GOGAT) in biochar-treated plots, further supported the increases in these traits. Our results revealed that the integration of 30 t B ha?1 with 135 kg N ha?1 is a favorable option for enhancing soil health and rice grain yield. 相似文献
18.
Wetland buffers may play an important role in the retention of nitrogen (N) and phosphorus (P) that can be released in large quantities from forestry operations. In this study, we investigated the retention capacity of N and P of wetland vegetation comparing the control area with two experimental areas within one site before and after N and P pulse (45 kg N and 15 kg P) lasting one growing season (ca. 150 d). N and P pulse caused a significant increase in the plant biomass and N and P content in the upper experimental area, which received most of the added nutrients. Added N and P was mainly retained in the above and below ground parts of E. vaginatum, especially in storage organs and roots which form a long-term sink for nutrients. Total N retention in the plant biomass during the first year after N and P treatment ranged from 25.3 kg (equals to 126.7 kg N ha –1) in the upper experimental area to 6.1 kg (20.4 kg N ha –1) in the lower experimental area and 4.7 kg (15.7 kg N ha –1) in the control area. P retention ranged from 2.6 kg (13.1 kg P ha –1) in the upper experimental area to 1.0 kg (3.4 kg P ha –1) in the lower experimental area and 0.5 kg (1.8 kg P ha –1) in the control area. The retained proportions of N and P in the plant biomass in the two experimental areas were approximately 70% of the added N (45 kg N y –1) and approximately 25% of the added P (15 kg P y –1) during the first year after N and P addition in 1999. Our study shows that vigorously colonising and growing vegetation is the main factor in the retention of N, a significant factor in the retention of P in a constructed wetland buffer, and thus an important contributor to the prevention of detrimental effects of N and P leaching on watercourses. 相似文献
19.
A number of studies have investigated regional and continental scale patterns of carbon (C) stocks in forest ecosystems; however,
the altitudinal changes in C storage in different components (vegetation, detritus, and soil) of forest ecosystems remain
poorly understood. In this study, we measured C stocks of vegetation, detritus, and soil of 22 forest plots along an altitudinal
gradient of 700–2,000 m to quantify altitudinal changes in carbon storage of major forest ecosystems ( Pinus koraiensis and broadleaf mixed forest, 700–1,100 m; Picea and Abies forest, 1,100–1,800 m; and Betula ermanii forest, 1,800–2,000 m) on Mt Changbai, Northeast China. Total ecosystem C density (carbon stock per hectare) averaged 237 t C ha −1 (ranging from 112 to 338 t C ha −1) across all the forest stands, of which 153 t C ha −1 (52–245 t C ha −1) was stored in vegetation biomass, 14 t C ha −1 (2.2–48 t C ha −1) in forest detritus (including standing dead trees, fallen trees, and floor material), and 70 t C ha −1 (35–113 t C ha −1) in soil organic matter (1-m depth). Among all the forest types, the lowest vegetation and total C density but the highest
soil organic carbon (SOC) density occurred in Betula ermanii forest, whereas the highest detritus C density was observed in Picea and Abies forest. The C density of the three ecosystem components showed distinct altitudinal patterns: with increasing altitude, vegetation
C density decreased significantly, detritus C density first increased and then decreased, and SOC density exhibited increasing
but insignificant trends. The allocation of total ecosystem C to each component exhibited similar but more significant trends
along the altitudinal gradient. Our results suggest that carbon storage and partitioning among different components in temperate
forests on Mt Changbai vary greatly with forest type and altitude. 相似文献
20.
Soil soluble organic N (SON) plays an important role in N biogeochemical cycling. In this study, 22 surface forest soils (0–10 cm)
were collected from southeast Queensland, Australia, to investigate the size of SON pools extracted by water and salt solutions.
Approximately 5–45 mg SON kg −1, 2–42 mg SON kg −1 and 1–24 SON mg kg −1 were extracted by 2 M KCl, 0.5 M K 2SO 4 and water, on average, corresponding to about 21.1, 13.5 and 7.0 kg SON ha −1 at the 0–10 cm forest soils, respectively. These SON pools, on average, accounted for 39% (KCl extracts), 42% (K 2SO 4 extracts) and 43% (water extracts) of total soluble N (TSN), and 2.3% (KCl extracts), 1.3% (K 2SO 4 extracts) and 0.7% (water extracts) of soil total N, respectively. Large variation in SON pools observed across the sites
in the present study may be attributed to a combination of factors including soil types, tree species, management practices
and environmental conditions. Significant relationships were observed among the SON pools extracted by water, KCl and K 2SO 4 and microbial biomass N (MBN). In general, KCl and K 2SO 4 extracted more SON than water from the forest soils, while KCl extracted more SON than K 2SO 4. The SON and soluble organic C (SOC) in KCl, K 2SO 4 and water extracts were all positively related to soil organic C, total N and clay contents. This indicates that clay and
soil organic matter play a key role in the retention of SON in soil. 相似文献
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