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1.
Conversion of secondary broadleaved forest into Chinese fir plantation alters litter production and potential nutrient returns 总被引:2,自引:0,他引:2
Litter production, litter standing crop, and potential nutrient return via litterfall to soil were studied during a 4-year
period (January 2004–December 2007) in a Chinese fir (Cunninghamia lanceolata (Lamb.) Hook) plantation and a secondary broadleaved forest in Hunan Province in subtropical China. Mean annual litterfall
in the sampling sites varied from 358 g m−2 in the pure plantation to 669 g m−2 in the secondary broadleaved forest. Total litterfall followed a bimodal distribution pattern for both forests. Amount of
litterfall was also related to the air temperature in both forests. During the period under this study, annual variation in
the total litterfall in the pure plantation was significantly higher than that in the secondary broadleaved forest. Litterfall
was markedly seasonal in the both forests. Leaf proportions of litterfall in the pure plantation and secondary broadleaved
forest were 58.1 and 61.7%, respectively. Total potential nutrient returns to the soil through litterfall in the pure plantation
were only 46.2% of those in the secondary broadleaved forest. Total litter standing crop was 913 and 807 g m−2 in the pure plantation and secondary broadleaved forest, respectively. Our results confirm that conversion from a secondary
broadleaved forest into a pure coniferous plantation changes the functioning of the litter system. 相似文献
2.
Root Growth and Recovery in Temperate Broad-Leaved Forest Stands Differing in Tree Species Diversity
In contrast to studies on aboveground processes, the effect of species diversity on belowground productivity and fine-root
regrowth after disturbance is still poorly studied in forests. In 12 old-growth broad-leaved forest stands, we tested the
hypotheses that (i) the productivity and recovery rate (regrowth per standing biomass) of the fine-root system (root diameter < 2 mm)
increase with increasing tree species diversity, and that (ii) the seasonality of fine-root biomass and necromass is more
pronounced in pure than in tree species-rich stands as a consequence of non-synchronous root biomass peaks of the different
species. We investigated stands with 1, 3, and 5 dominant tree species growing under similar soil and climate conditions for
changes in fine-root biomass and necromass during a 12-month period and estimated fine-root productivity with two independent
approaches (ingrowth cores, sequential coring). According to the analysis of 360 ingrowth cores, fine-root growth into the
root-free soil increased with tree species diversity from 72 g m−2 y−1 in the monospecific plots to 166 g m−2 y−1 in the 5-species plots, indicating an enhanced recovery rate of the root system after soil disturbance with increasing species
diversity (0.26, 0.34, and 0.51 y−1 in 1-, 3-, and 5-species plots, respectively). Fine-root productivity as approximated by the sequential coring data also
indicated a roughly threefold increase from the monospecific to the 5-species stand. We found no indication of a more pronounced
seasonality of fine-root mass in species-poor as compared to species-rich stands. We conclude that species identification
on the fine root level, as conducted here, may open new perspectives on tree species effects on root system dynamics. Our
study produced first evidence in support of the hypothesis that the fine-root systems of more diverse forest stands are more
productive and recover more rapidly after soil disturbance than that of species-poor forests. 相似文献
3.
Xuli Tang Ying-Ping Wang Guoyi Zhou Deqiang Zhang Shen Liu Shizhong Liu Qianmei Zhang Juxiu Liu Junhua Yan 《Plant Ecology》2011,212(8):1385-1395
Using long-term (22 years) measurements from a young and an old-growth subtropical forest in southern China, we found that
both forests accumulated carbon from 1982 to 2004, with the mean carbon accumulation rate at 227 ± 59 g C m−2 year−1 for young forest and 115 ± 89 g C m−2 year−1 for the old-growth forest. Allocation of the accumulated carbon was quite different between these two forests: the young
forest accumulated a significant amount of carbon in plant live biomass, whereas the old-growth forest accumulated a significant
amount of carbon in the soil. From 1982 to 2004, net primary productivity (NPP) increased for the young forest, and did not
change significantly for the old-growth forest. The increase in NPP of the young forest resulted from recruitment of some
dominant tree species characteristic of the subtropical mature forest in the region and an increase in tree density; decline
of NPP of the old-growth forest was caused by increased mortality of the dominant trees. 相似文献
4.
Nitrogen Oxide Fluxes and Nitrogen Cycling during Postagricultural Succession and Forest Fertilization in the Humid Tropics 总被引:2,自引:0,他引:2
The effects of changes in tropical land use on soil emissions of nitrous oxide (N2O) and nitric oxide (NO) are not well understood. We examined emissions of N2O and NO and their relationships to land use and forest composition, litterfall, soil nitrogen (N) pools and turnover, soil
moisture, and patterns of carbon (C) cycling in a lower montane, subtropical wet region of Puerto Rico. Fluxes of N2O and NO were measured monthly for over 1 year in old (more than 60 years old) pastures, early- and mid-successional forests
previously in pasture, and late-successional forests not known to have been in pasture within the tabonuco (Dacryodes excelsa) forest zone. Additional, though less frequent, measures were also made in an experimentally fertilized tabonuco forest.
N2O fluxes exceeded NO fluxes at all sites, reflecting the consistently wet environment. The fertilized forest had the highest
N oxide emissions (22.0 kg N · ha−1· y−1). Among the unfertilized sites, the expected pattern of increasing emissions with stand age did not occur in all cases. The
mid-successional forest most dominated by leguminous trees had the highest emissions (9.0 kg N · ha−1· y−1), whereas the mid-successional forest lacking legumes had the lowest emissions (0.09 kg N · ha−1· y−1). N oxide fluxes from late-successional forests were higher than fluxes from pastures. Annual N oxide fluxes correlated positively
to leaf litter N, net nitrification, potential nitrification, soil nitrate, and net N mineralization and negatively to leaf
litter C:N ratio. Soil ammonium was not related to N oxide emissions. Forests with lower fluxes of N oxides had higher rates
of C mineralization than sites with higher N oxide emissions. We conclude that (a) N oxide fluxes were substantial where the
availability of inorganic N exceeded the requirements of competing biota; (b) species composition resulting from historical
land use or varying successional dynamics played an important role in determining N availability; and (c) the established
ecosystem models that predict N oxide loss from positive relationships with soil ammonium may need to be modified.
Received 22 February 2000; accepted 6 September 2000. 相似文献
5.
Large Loss of Dissolved Organic Nitrogen from Nitrogen-Saturated Forests in Subtropical China 总被引:5,自引:0,他引:5
Yunting Fang Weixing Zhu Per Gundersen Jiangming Mo Guoyi Zhou Muneoki Yoh 《Ecosystems》2009,12(1):33-45
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 (NO3−) 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 NO3− leaching in all three forests. We hypothesize that abiotic incorporation of excess NO3− (through chemically reactive NO2−) 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
6.
Litterfall dynamics in carbonate and deltaic mangrove ecosystems in the Gulf of Mexico 总被引:1,自引:0,他引:1
Carlos Coronado-Molina H. Alvarez-Guillen J. W. DayJr. E. Reyes B. C. Perez F. Vera-Herrera R. Twilley 《Wetlands Ecology and Management》2012,20(2):123-136
From 1996 to 2002, we measured litterfall, standing litter crop, and litter turnover rates in scrub, basin, fringe and riverine
forests in two contrasting mangrove ecosystems: a carbonate-dominated system in the Southeastern Everglades and a terrigenous-dominated
system in Laguna de Terminos (LT), Mexico. We hypothesized that litter dynamics is driven by latitude, geomorphology, hydrology,
soil fertility and soil salinity stress. There were significant temporal patterns in LT with litterfall rates higher during
the rainy season (2.4 g m−2 day−1) than during the dry season (1.8 g m−2 day−1). Total annual litterfall was significantly higher in the riverine forest (12.8 Mg ha−2 year−1) than in the fringe and basin forests (9.7 and 5.2 Mg ha−2 year−1, respectively). In Southeastern Everglades, total annual litterfall was also significantly higher during the rainy season
than during the dry season. Spatially, the scrub forest had the lowest annual litterfall (2.5 Mg ha−2 year−1), while the fringe and basin had the highest (9.1 and 6.5 Mg ha−2 year−1, respectively). In LT, annual standing litter crop was 3.3 Mg ha−1 in the fringe and 2.2 Mg ha−1 in the basin. Litter turnover rates were significantly higher in the fringe mangrove forest (4.1 year−1) relative to the basin forests (2.2 year−1). At Southeastern Everglades there were significant differences in annual standing litter crop: 1.9, 3.3 and 4.5 Mg ha−1 at scrub, basin and fringe mangrove sites, respectively. Furthermore, turnover rates were similar at both basin and fringe
mangrove types (2.1 and 2.0 year−1, respectively) but significantly higher than scrub mangrove forest (1.3 year−1). These findings suggest that litter export is important in regulating litter turnover rates in frequently flooded riverine
and fringe forests, while in infrequently flooded basin forests, in situ litter decomposition controls litter turnover rates. 相似文献
7.
Soil Inorganic N Leaching in Edges of Different Forest Types Subject to High N Deposition Loads 总被引:2,自引:0,他引:2
Karen Wuyts An De Schrijver Jeroen Staelens Lotte Van Nevel Sandy Adriaenssens Kris Verheyen 《Ecosystems》2011,14(5):818-834
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
8.
Woody debris stocks in different secondary and primary forests in the subtropical Ailao Mountains, southwest China 总被引:3,自引:0,他引:3
Woody debris (WD), including coarse woody debris (CWD) and fine woody debris (FWD), is an essential structural and functional
component of many ecosystems, particularly in montane forests. CWD is considered to be the major part in forest WD and it
is primarily composed of logs, snags, stumps and large branches, while FWD mainly consists of small twigs. Attributes of dead
woody material may change in accordance with trends in stand dynamics. The primary forest (primary montane moist evergreen
broad-leaved forest) in Ailao Mountain National Nature Reserve (NNR) preserves the largest tract of natural vegetation in
China. The Alnus nepalensis (D. Don) association, Populus bonatii (Levl.) association and secondary Lithocarpus association represent the secondary and chronological types following human disturbance by fires and logging under different
intensity. The mass and composition of coarse woody debris (CWD, ≥10 cm in diameter) and fine woody debris (FWD, 2.5–10 cm
in diameter) were inventoried in a primary forest and its three secondary counterparts. Estimates of total mass of woody debris
across secondary types to primary forest ranged from 2.4 to 74.9 Mg ha−1. The lowest value was found in the A. nepalensis association and the highest values were in the primary forest of which logs are the considerable differences. The ratios
of CWD to FWD were low in the secondary types (about 1–4) but high in the primary forest (above 15). Our results suggested
that for the recovery of woody debris in the secondary forest, it might last longer than the age of the oldest successional
stage studied.
Yang Lipan and Ma Wenzhang contributed equally to this work. 相似文献
9.
Jeffrey M. Klopatek 《Plant and Soil》2007,294(1-2):157-167
Litterfall and fine root production were measured for three years as part of a carbon balance study of three forest stands
in the Pacific Northwest of the United States. A young second-growth Douglas-fir [Pseudotsuga menziesii (Mirb.) Franco] stand, a second-growth Douglas-fir with red alder (Alnus rubra Bong.) stand, and an old-growth (∼550 years) Douglas-fir stand were monitored for inputs of carbon and nitrogen into the
soil from litterfall and fine root production, as well as changes in soil C and N. Fine root production and soil nutrient
changes were measured through the use of soil ingrowth bags containing homogenized soil from the respective stands. Litterfall
biomass was greatest in the Douglas-fir-alder stand (527 g m−2 yr−1) that annually returned nearly three times the amount of N as the other stands. Mean residence time for forest floor material
was also shortest at this site averaging 4.6 years and 5.5 years for C an N, respectively. Fine root production in the upper
20 cm ranged from 584 g m−2 in the N rich Douglas-fir-alder stand to 836 g m−2 in the old-growth stand. Fine root production (down to one meter) was always greater than litterfall with a below:above ratio
ranging from 3.73 for the young Douglas-fir stand to 1.62 for the Douglas-fir-alder stand. The below:above N ratios for all
three stands closely approximate those for biomass. Soil changes in both C and N differed by site, but the soil C changes
in the old-growth stand mirrored those obtained in an ongoing CO2 flux study. Results from the soil ingrowth bags strongly suggest that this method provides a simple, but sufficient device
for measuring potential fine root biomass production as well as soil chemical changes. 相似文献
10.
Detritus Production and Soil N Transformations in Old-Growth Eastern Hemlock and Sugar Maple Stands 总被引:2,自引:0,他引:2
To examine the linkage between forest cover type, litter inputs, and patterns of net N mineralization versus the turnover
of N among soil microbes, we measured both the net and gross rates of N mineralization in replicated, adjacent old-growth
eastern hemlock [Tsuga canadensis(L.) Carr.] or sugar maple (Acer saccharum Marsh.) stands in upper Michigan. Mean aboveground net primary production and annual litterfall mass were significantly higher
(P < 0.01) in the maple forests (870 g·m-2·y-1 and 439 g·m-2·y-1, respectively) than in the hemlock forests (480 g·m-2·y-1 and 344 g·m-2·y-1, respectively). Forest floor and coarse woody debris mass, however, were significantly lower (P < 0.05) in the maple forests (2.2 and 0.1 kg·m-2, respectively) than in the hemlock forests (2.9 and 0.2 kg·m-2, respectively). Litterfall N concentration was not significantly different (P > 0.10) between the two forest types. In situ gross rates of N mineralization were higher (P < 0.06) in the maple forests than in the hemlock forests (7.5 and 6.1 mg N·kg soil-1·d-1 respectively), but in situ net N mineralization varied independently of forest type and stand-level litterfall N concentration. Cover type–dependent
differences in detritus production and detritus C quality appear to result in different N turnover rates, but the balance
between gross mineralization and immobilization of N is very sensitive to within stand variability and varies at a scale smaller
than cover type alone can predict.
Received 3 Feburary 1999; accepted 27 August 1999. 相似文献
11.
In forested streams, surrounding riparian forests provide essential supplies of organic matter to aquatic ecosystems. We focused
on two pathways of particulate organic matter inputs: direct input from upper riparian forests and indirect lateral input
from bank slopes, for which there are limited quantitative data. We investigated the inputs of coarse particulate organic
matter (CPOM) and carbon and nitrogen in the CPOM into the uppermost reaches of a headwater stream with steep bank slopes
in Hokkaido, Japan. CPOM collected by litter traps was divided into categories (e.g., leaves, twigs) and weighed. Monthly
nitrogen and carbon inputs were also estimated. The annual direct input of CPOM (ash-free dry mass) was 472 g m−2, a common value for temperate riparian forests. The annual lateral CPOM input was 353 g m−1 and 941 g m−2 when they were converted to area base. This value surpassed the direct input. Organic matter that we could not separate from
inorganic sediments contributed to the total lateral input from the bank slopes (124 g m−1); this organic matter contained relatively high amounts of nitrogen and carbon. At uppermost stream reaches, the bank slope
would be a key factor to understanding the carbon and nitrogen pathways from the surrounding terrestrial ecosystem to the
aquatic ecosystem. 相似文献
12.
Persistent soil seed banks in old-growth Hyrcanian Box tree (Buxus hyrcana) stands in northern Iran 总被引:1,自引:0,他引:1
Hamed Asadi Seyed Mohsen Hosseini Omid Esmailzadeh Carol C. Baskin 《Ecological Research》2012,27(1):23-33
Little is known about the soil seed bank and the influence of plant communities on the interaction between the seed bank and
aboveground vegetation in the Hyrcanian temperate deciduous forest. We surveyed species composition and diversity of the persistent
soil seed bank and the aboveground vegetation in six community types in old-growth Hyrcanian Box tree (Buxus
hyrcana) stands in northern Iran. Fifty-two species with an average of 3,808 seeds/spores m−2 germinated; forbs accounted for 64% of the seed bank flora. Thirty-four species in the aboveground vegetation were not presented
in the seed bank, 32 species in the seed bank were not found in the vegetation, and 20 species were in both. The dominant
tree species were Diospyros lotus and Alnus subcordata with an average of 17 and 4.6 seeds m−2, respectively. Our results suggest that (1) vernal geophytes and shade-tolerant perennials are not incorporated in the seed
bank, (2) early successional species are well represented in the seed bank, (3) plant community type has significant impacts
on seed bank densities, and seed bank richness and diversity were significantly related to presence/absence of Box tree in
the aboveground vegetation. The persistent seed bank contained species that potentially have a negative impact on the regeneration
of forests, thus forest managers should retain old-growth Hyrcanian Box tree stands to conserve disturbance-sensitive indicator
forest species. 相似文献
13.
We re-visited a seven-stand boreal chronosequence west of Thompson, Manitoba, Canada, in which coarse woody debris (CWD) and
its instantaneous decomposition were measured in 2000. New CWD measurements were performed in 2007, and tree inventories updated
to provide mortality and snag failure data. These data were used to model CWD changes, compare methods of estimating decomposition,
and infer possible fragmentation rates. Measured CWD was between 9.7 (in both the 77- and 43-year-old stands) and 80.4 (in
the 18-year-old stand) Mg ha−1 in 2007. Spatial variability was high; at most stands CWD levels had not changed significantly from 2000 to 2007. Tree mortality
was a significant flux only in older stands, whereas snag fall rate varied by an order of magnitude, from 2.9% y−1 (0.2 Mg ha−1 y−1) in the 9-year-old stand to 9.8% y−1 (2.3 Mg ha−1 y−1) in the 12-year-old stand. A one-pool model based on these inputs underestimated actual 2000–2007 CWD decomposition in the
younger stands, suggesting that fragmentation could be an important part of the carbon flux exiting the CWD pool. We compared
three independent measures of annual decomposition (k): direct measurements of CWD respiration, rates based on the 7-year re-sampling effort described here, and rates inferred
from the chronosequence design itself. Mean k values arrived at via these techniques were 0.06 ± 0.03, 0.05 ± 0.04, and 0.05 ± 0.05 y−1, respectively. The four-pool model suggested that the transition rate between decay classes was 0.14–0.19 y−1; the model was most sensitive to initial CWD values. Although the computed k values implied a problem with chronosequence site selection for at least one site, the overall CWD trend was consistent with
a larger number of sites surveyed in the region. 相似文献
14.
H. González-Rodríguez T. G. Domínguez-Gómez I. Cantú-Silva M. V. Gómez-Meza R. G. Ramírez-Lozano M. Pando-Moreno C. J. Fernández 《Plant Ecology》2011,212(10):1747-1757
The aim of this study was to determine the litterfall production and macronutrient (Ca, K, Mg, N, and P) deposition through
leaf litter in four sites with different types of vegetation. Site one (Bosque Escuela) was located at 1600 m a.s.l. in a
pine forest mixed with deciduous trees, second site (Crucitas at 550 m a.s.l.) in the ecotone of a Quercus spp. forest and the Tamaulipan thornscrub and third and fourth sites (Campus at 350 m a.s.l. and Cascajoso at 300 m a.s.l.,
respectively) were in the Tamaulipan thornscrub. Litter constituents (leaves, reproductive structures, twigs, and miscellaneous
residues) were collected at 15-day intervals from December 21, 2006, throughout December 20, 2007. Collections were carried
out in ten litter traps (1.0 × 1.0 m) randomly situated at each site of approximately 2,500 m2. Total annual litterfall deposition was 4407, 7397, 6304, and 6527 kg ha−1 y−1 for Bosque Escuela, Crucitas, Campus and Cascajoso, respectively. Of total annual litter production, leaves were higher varying
from 74 (Bosque Escuela) to 86% (Cascajoso) followed by twigs from 4 (Cascajoso) to 14% (Crucitas), reproductive structures
from 6 (Bosque Escuela) to 10% (Crucitas), and miscellaneous litterfall from <1 (Campus) to 12% (Bosque Escuela). The Ca annual
deposition was significantly higher in Cascajoso (232.7 kg ha−1 y−1), followed by Campus (182.3), Crucitas (130.5) and Bosque Escuela (30.3). The K (37.5, 32.5, 24.8, 7.2, respectively), Mg
(22.6, 17.7, 13.7, 4.5, respectively) followed the same pattern as Ca. However, N was higher in Campus (85.8) followed by
Crucitas (85.1), Cascajoso (68.3), and Bosque Escuela (18.3). The P was higher in Campus and Crucitas (4.0) followed by Cascajoso
(3.4) and Bosque Escuela (1.4). On an annual basis for all sites, the order of nutrient deposition through leaf litter was
Ca > N> K > Mg > P, whereas on site basis of total nutrient deposition (Ca + N + K + Mg + P), the order was Cascajoso > Campus > Crucitas > Bosque
Escuela. Ca, K, Mg, N, and P nutrient use efficiency values in leaf litter were higher in Bosque Escuela, while lower figures
were acquired in Cascajoso and Crucitas sites. It seems that the highest litterfall deposition was found in the ecotone of
a Quercus spp. forest and the Tamaulipan thornscrub; however, the Tamaulipan thornscrub vegetation alone had better leaf litter nutrient
return. 相似文献
15.
Pools and fluxes of carbon in three Norway spruce ecosystems along a climatic gradient in Sweden 总被引:1,自引:0,他引:1
Dan Berggren Kleja Magnus Svensson Hooshang Majdi Per-Erik Jansson Ola Langvall Bo Bergkvist Maj-Britt Johansson Per Weslien Laimi Truus Anders Lindroth Göran I. Ågren 《Biogeochemistry》2008,89(1):7-25
This paper presents an integrated analysis of organic carbon (C) pools in soils and vegetation, within-ecosystem fluxes and
net ecosystem exchange (NEE) in three 40-year old Norway spruce stands along a north-south climatic gradient in Sweden, measured
2001–2004. A process-orientated ecosystem model (CoupModel), previously parameterised on a regional dataset, was used for
the analysis. Pools of soil organic carbon (SOC) and tree growth rates were highest at the southernmost site (1.6 and 2.0-fold,
respectively). Tree litter production (litterfall and root litter) was also highest in the south, with about half coming from
fine roots (<1 mm) at all sites. However, when the litter input from the forest floor vegetation was included, the difference
in total litter input rate between the sites almost disappeared (190–233 g C m−2 year−1). We propose that a higher N deposition and N availability in the south result in a slower turnover of soil organic matter
than in the north. This effect seems to overshadow the effect of temperature. At the southern site, 19% of the total litter
input to the O horizon was leached to the mineral soil as dissolved organic carbon, while at the two northern sites the corresponding
figure was approx. 9%. The CoupModel accurately described general C cycling behaviour in these ecosystems, reproducing the
differences between north and south. The simulated changes in SOC pools during the measurement period were small, ranging
from −8 g C m−2 year−1 in the north to +9 g C m−2 year−1 in the south. In contrast, NEE and tree growth measurements at the northernmost site suggest that the soil lost about 90 g C m−2 year−1.
An erratum to this article can be found at 相似文献
16.
Differences in Englemann Spruce Forest Biogeochemistry East and West of the Continental Divide in Colorado, USA 总被引:5,自引:2,他引:3
We compared Englemann spruce biogeochemical processes in forest stands east and west of the Continental Divide in the Colorado
Front Range. The divide forms a natural barrier for air pollutants such that nitrogen (N) emissions from the agricultural
and urban areas of the South Platte River Basin are transported via upslope winds to high elevations on the east side but
rarely cross over to the west side. Because there are far fewer emissions sources to the west, atmospheric N deposition is
1–2 kg N ha−1 y−1 on the west side, as compared with 3–5 kg N ha−1 y−1 on the east side. Species composition, elevation, aspect, parent material, site history, and climate were matched as closely
as possible across six east and six west side old-growth forest stands. Higher N deposition sites had significantly lower
organic horizon C:N and lignin:N ratios, lower foliar C:N ratios, as well as greater %N, higher N:Ca, N:Mg, and N:P ratios,
and higher potential net mineralization rates. When C:N ratios dropped below 29, as they did in east-side organic horizon
soils, mineralization rates increased linearly. Our results are comparable to those from studies of the northeastern United
States and Europe that have found changes in forest biogeochemistry in response to N deposition inputs between 3 and 60 kg
ha−1 y−1. Though they are low by comparison with more densely populated and agricultural regions, current levels of N deposition,
have caused measurable changes in Englemann spruce forest biogeochemistry east of the Continental Divide in Colorado.
Received 22 January 2001; accepted 11 June 2001. 相似文献
17.
Toshiyuki Ohtsuka Wenhong Mo Takami Satomura Motoko Inatomi Hiroshi Koizumi 《Ecosystems》2007,10(2):324-334
Biometric based carbon flux measurements were conducted over 5 years (1999–2003) in a temperate deciduous broad-leaved forest
of the AsiaFlux network to estimate net ecosystem production (NEP). Biometric based NEP, as measured by the balance between
net primary production (including NPP of canopy trees and of forest floor dwarf bamboo) and heterotrophic respiration (RH),
clarified the contribution of various biological processes to the ecosystem carbon budget, and also showed where and how the
forest is storing C. The mean NPP of the trees was 5.4 ± 1.07 t C ha−1 y−1, including biomass increment (0.3 ± 0.82 t C ha−1 y−1), tree mortality (1.0 ± 0.61 t C ha−1 y−1), aboveground detritus production (2.3 ± 0.39 t C ha−1 y−1) and belowground fine root production (1.8 ± 0.31 t C ha−1 y−1). Annual biomass increment was rather small because of high tree mortality during the 5 years. Total NPP at the site was
6.5 ± 1.07 t C ha−1 y−1, including the NPP of the forest floor community (1.1 ± 0.06 t C ha−1 y−1). The soil surface CO2 efflux (RS) was averaged across the 5 years of record using open-flow chambers. The mean estimated annual RS amounted to
7.1 ± 0.44 t C ha−1, and the decomposition of soil organic matter (SOM) was estimated at 3.9 ± 0.24 t C ha−1. RH was estimated at 4.4 ± 0.32 t C ha−1 y−1, which included decomposition of coarse woody debris. Biometric NEP in the forest was estimated at 2.1 ± 1.15 t C ha−1 y−1, which agreed well with the eddy-covariance based net ecosystem exchange (NEE). The contribution of woody increment (Δbiomass + mortality)
of the canopy trees to NEP was rather small, and thus the SOM pool played an important role in carbon storage in the temperate
forest. These results suggested that the dense forest floor of dwarf bamboo might have a critical role in soil carbon sequestration
in temperate East Asian deciduous forests. 相似文献
18.
Biomass and net production were measured in aPhyllostachys bambusoides stand in Kyoto Prefecture, central Japan, which had carried out gregarious flowering in 1969 and has been recovering vegetatively.
The culm density fluctuated around an average value of 12 040 ha−1 during the research period (1985–91). Annual recruirment and mortality rates of culms were 1340 and 1133 ha−1, respectively. The mean diameter at breast height increased from 7.28 cm in 1985 to 8.68 cm in 1991, and the biomass of culms
increased from 71.3 to 111.6t ha−1 over the same time period. Branch and leaf biomasses were almost constant, 10.0 and 9.4t ha−1 on average, respectively. The leaf area index of the stand was 11.6 ha ha−1, which is one of the largest values found in Japanese forests. The belowground biomass of 32.6t ha−1 for rhizomes and 14.8t ha−1 for fine roots resulted in the smaller ratio of aboveground parts to the root system (2.38) than those determined for forest
stands. The amount of litterfall, excluding culms and large branches, was large (9.13t ha−1 year−1), corresponding to those measured in equatorial stands. The aboveground net production was 24.6t ha−1 year−1, larger than the average value reported for forest stands under similar weather conditions. 相似文献
19.
The Imprint of Land-use History: Patterns of Carbon and Nitrogen in Downed Woody Debris at the Harvard Forest 总被引:9,自引:1,他引:8
Few data sets have characterized carbon (C) and nitrogen (N) pools in woody debris at sites where other aspects of C and N
cycling are studied and histories of land use and disturbance are well documented. We quantified pools of mass, C, and N in
fine and coarse woody debris (CWD) in two contrasting stands: a 73-year-old red pine plantation on abandoned agricultural
land and a naturally regenerated deciduous forest that has experienced several disturbances in the past 150 years. Masses
of downed woody debris amounted to 40.0 Mg ha−1 in the coniferous stand and 26.9 Mg ha−1 in the deciduous forest (20.4 and 13.8 Mg C ha−1, respectively). Concentrations of N were higher and C:N ratios were lower in the deciduous forest compared to the coniferous.
Pools of N amounted to 146 kg N ha−1 in the coniferous stand and 155 kg N ha−1 in the deciduous forest; both are larger than previously published pools of N in woody debris of temperate forests. Woody
detritus buried in O horizons was minimal in these forests, contrary to previous findings in forests of New England. Differences
in the patterns of mass, C, and N in size and decay classes of woody debris were related to stand histories. In the naturally
regenerated deciduous forest, detritus was distributed across all size categories, and most CWD mass and N was present in
the most advanced decay stages. In the coniferous plantation, nearly all of the CWD mass was present in the smallest size
class (less than 25 cm diameter), and a recognizable cohort of decayed stems was evident from the stem-exclusion phase of
this even-aged stand. These results indicate that heterogeneities in site histories should be explicitly included when biogeochemical
process models are used to scale C and N stocks in woody debris to landscapes and regions.
Received 27 April 2001; accepted 4 January 2002. 相似文献
20.
In a declining sugar maple (SM) stand, we tested the hypothesis that an increasing relative abundance of American beech (AB)
and yellow birch (YB) would improve litter quality by providing a higher proportion of litterfall richer in base cations and
lower in acidity. From 1989 to 2006, SM leaf fall diminished from 59% (1,718 kg ha−1 year−1) to 36% (915 kg ha−1 year−1) of the total leaf fall biomass. Overall, the increase in AB and YB litterfall compensated for the SM decrease, resulting
in constant annual leaf litterfall fluxes (2,803 kg ha−1 year−1) over the period studied. However, because the leaf litter for AB and YB had Ca and Mg concentrations 2–3 times higher than
did SM, Ca and Mg concentrations and fluxes in leaf litterfall significantly increased between 1989 and 2006. Leaf litterfall
of AB and YB also has a higher base/acid ratio than SM. Consequently, changes in forest composition following SM decline led
to a clear improvement in litterfall quality in terms of base cations content and fluxes and acid–base properties. 相似文献