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1.
Response of Litter Decomposition to Simulated N Deposition in Disturbed, Rehabilitated and Mature Forests in Subtropical China 总被引:16,自引:1,他引:15
The response of decomposition of litter for the dominant tree species in disturbed (pine), rehabilitated (pine and broadleaf
mixed) and mature (monsoon evergreen broadleaf) forests in subtropical China to simulated N deposition was studied to address
the following hypothesis: (1) litter decomposition is faster in mature forest (high soil N availability) than in rehabilitated/disturbed
forests (low soil N availability); (2) litter decomposition is stimulated by N addition in rehabilitated and disturbed forests
due to their low soil N availability; (3) N addition has little effect on litter decomposition in mature forest due to its
high soil N availability. The litterbag method (a total of 2880 litterbags) and N treatments: Control-no N addition, Low-N:
−5 g N m−2 y−1, Medium-N: −10 g N m−2 y−1, and High-N: −15 g N m−2 y−1, were employed to evaluate decomposition. Results indicated that mature forest, which has likely been N saturated due to both long-term high N deposition in the region
and the age of the ecosystem, had the highest litter decomposition rate, and exhibited no significant positive and even some
negative response to nitrogen additions. However, both disturbed and rehabilitated forests, which are still N limited due
to previous land use history, exhibited slower litter decomposition rates with significant positive effects from nitrogen
additions. These results suggest that litter decomposition and its responses to N addition in subtropical forests of China
vary depending on the nitrogen status of the ecosystem. 相似文献
2.
Response of soil respiration to simulated N deposition in a disturbed and a rehabilitated tropical forest in southern China 总被引:3,自引:1,他引:2
Jiangming Mo Wei Zhang Weixing Zhu Yunting Fang Dejun Li Ping Zhao 《Plant and Soil》2007,296(1-2):125-135
Responses of soil respiration (CO2 emission) to simulated N deposition were studied in a disturbed (reforested forest with previous understory and litter harvesting)
and a rehabilitated (reforested forest with no understory and litter harvesting) tropical forest in southern China from October
2005 to September 2006. The objectives of the study were to test the following hypotheses: (1) soil respiration is higher
in rehabilitated forest than in disturbed forest; (2) soil respiration in both rehabilitated and disturbed tropical forests
is stimulated by N additions; and (3) soil respiration is more sensitive to N addition in disturbed forest than in rehabilitated
forest due to relatively low soil nutrient status in the former, resulting from different previous human disturbance. Static
chamber and gas chromatography techniques were employed to quantify the soil respiration, following different N treatments
(Control, no N addition; Low-N, 5 g N m−2 year−1; Medium-N, 10 g N m−2 year−1), which had been applied continuously for 26 months before the respiration measurement. Results showed that soil respiration
exhibited a strong seasonal pattern, with the highest rates observed in the hot and wet growing season (April–September) and
the lowest rates in winter (December–February) in both rehabilitated and disturbed forests. Soil respiration rates exhibited
significant positive exponential relationship with soil temperature and significant positive linear relationship with soil
moisture. Soil respiration was also significantly higher in the rehabilitated forest than in the disturbed forest. Annual
mean soil respiration rate in the rehabilitated forest was 20% lower in low-N plots (71 ± 4 mg CO2-C m−2 h−1) and 10% lower in medium-N plots (80 ± 4 mg CO2-C m−2 h−1) than in the control plots (89 ± 5 mg CO2-C m−2 h−1), and the differences between the control and low-N or medium-N treatments were statistically significant. In disturbed forest,
annual mean soil respiration rate was 5% lower in low-N plots (63 ± 3 mg CO2-C m−2 h−1) and 8% lower in medium-N plots (61 ± 3 mg CO2-C m−2 h−1) than in the control plots (66 ± 4 mg CO2-C m−2 h−1), but the differences among treatments were not significant. The depressed effects of experimental N deposition occurred
mostly in the hot and wet growing season. Our results suggest that response of soil respiration to elevated N deposition in
the reforested tropical forests may vary depending on the status of human disturbance.
Responsible Editor: Hans Lambers. 相似文献
3.
Nitrogen Addition Shapes Soil Phosphorus Availability in Two Reforested Tropical Forests in Southern China 总被引:3,自引:0,他引:3
Xiankai Lu Jiangming Mo Frank S. Gilliam Hua Fang Feifei Zhu Yunting Fang Wei Zhang Juan Huang 《Biotropica》2012,44(3):302-311
Scant information is available on how soil phosphorus (P) availability responds to atmospheric nitrogen (N) deposition, especially in the tropical zones. This study examined the effect of N addition on soil P availability, and compared this effect between forest sites of contrasting land‐use history. Effects of N addition on soil properties, litterfall production, P release from decomposing litter, and soil P availability were studied in a disturbed (reforested pine forest with previous understory vegetation and litter harvesting) and a rehabilitated (reforested mixed pine/broadleaf forest with no understory vegetation and litter harvesting) tropical forest in southern China. Experimental N‐treatments (above ambient) were the following: Control (no N addition), N50 (50 kg N ha?1 yr?1), and N100 (100 kg N ha?1 yr?1). Results indicated that N addition significantly decreased soil P availability in the disturbed forest. In the rehabilitated forest, however, soil P availability was significantly increased by N addition. Decreases in soil P availability may be correlated with decreases in rates of P release from decomposing litter in the N‐treated plots, whereas the increase in soil P availability was correlated with an increase in litterfall production. Our results suggest that response of soil P availability to N deposition in the reforested tropical forests in southern China may vary greatly with temporal changes in tree species composition and soil nutrient status, caused by different land‐use practices. 相似文献
4.
Emissions of nitrous oxide from three tropical forests in Southern China in response to simulated nitrogen deposition 总被引:2,自引:0,他引:2
Wei Zhang Jiangming Mo Guirui Yu Yunting Fang Dejun Li Xiankai Lu Hui Wang 《Plant and Soil》2008,306(1-2):221-236
Emissions of nitrous oxide (N2O) from the soil following simulated nitrogen (N) deposition in a disturbed (pine), a rehabilitated (pine and broadleaf mixed)
and a mature (monsoon evergreen broadleaf) tropical forest in southern China were studied. The following hypotheses were tested:
(1) addition of N will increase soil N2O emission in tropical forests; and (2) any observed increase will be more pronounced in the mature forest than in the disturbed
or rehabilitated forest due to the relatively high initial soil N concentration in the mature forest. The experiment was designed
with four N treatment levels (three replicates; 0, 50, 100, 150 kg N ha−1 year−1 for C (Control), LN (Low-N), MN (Medium-N), and HN (High-N) treatment, respectively) in the mature forest, but only three
levels in the disturbed and rehabilitated forests (C, LN and MN). Between October 2005 to September 2006, soil N2O flux was measured using static chamber and gas chromatography methodology. Nitrogen had been applied previously to the plots
since July 2003 and continued during soil N2O flux measurement period. The annual mean rates of soil N2O emission in the C plots were 24.1 ± 1.5, 26.2 ± 1.4, and 29.3 ± 1.6 μg N2O–N m−2 h−1 in the disturbed, rehabilitated and mature forest, respectively. There was a significant increase in soil N2O emission following N additions in the mature forest (38%, 41%, and 58% when compared to the C plots for the LN, MN, and
HN plots, respectively). In the disturbed forest a significant increase (35%) was observed in the MN plots, but not in the
LN plots. The rehabilitated forest showed no significant response to N additions. Increases in soil N2O emission occurred primarily in the cool-dry season (November, December and January). Our results suggest that the response
of soil N2O emission to N deposition in tropical forests in southern China may vary depending on the soil N status and land-use history
of the forest. 相似文献
5.
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
6.
The influence of stand age (5, 10, 15, 20, 30 and 40 years) on the decomposition of litter fractions, nutrient and energy
release of mixtures of N2-fixing alder (Alnus
nepalensis) and non-N2-fixing large cardamom (Amomum subulatum) systems was compared. Seasonal decomposition rates were distinct with the highest rate in the first 6 months followed by
subsequent seasons. The decomposition rate was substantially high in younger stands (10- to 15-years) and declined in the
older stands. Heat sink from the stand floor litter increased from 171 × 106 kJ year−1 in 5 years to 299 × 106 kJ year−1 at 15 years and then considerably decreased with advancing age. However, energy and nutrient releases were slow at a high
initial lignin-to-initial N ratio and C-to-N ratio, and there was an inverse relationship between the k-value of ash-free-mass and N expressed as a function of the C-to-N ratio. Quantities of nutrient release and energy loss
per unit area in 24 months of decomposition were highest in 15 years and subsequently they lowered with advancing age. Nutrient
loss indicated approximately uniform absolute and relative rates. Absolute energy consistently decreased by 81–88% in 24 months.
Ash-free mass of decomposing litter remaining at different retrieval dates was associated with a narrowing of the C-to-N ratio.
The relative loss rate of ash-free mass, nutrients and energy content was strongly related to the C-to-N ratio, litter temperature
and litter moisture. The influence of Alnus in the younger stands on nutrient and energy releases were rapid, indicating accelerated nutrient cycling and energy dynamics.
The intensity of the processes was highly phenomenal and considerably high in younger stands up to 20 years. Thus, an appropriate
management cycle of the Alnus-cardamom system for sustainability is 15–20 years. 相似文献
7.
Response of litter decomposition and related soil enzyme activities to different forms of nitrogen fertilization in a subtropical forest 总被引:1,自引:0,他引:1
Congyan Wang Guomin Han Yong Jia Xiaoguang Feng Peng Guo Xingjun Tian 《Ecological Research》2011,26(3):505-513
With the continuing increase in the impact of human activities on ecosystems, ecologists are increasingly becoming interested
in understanding the effects of nitrogen deposition on litter decomposition. At present, numerous studies have investigated
the effects of single form of nitrogen fertilization on litter decomposition in forest ecosystems. However, forms of N deposition
vary, and changes in the relative importance of different forms of N deposition are expected in the future. Thus, identifying
the effects of different forms of N deposition on litter decomposition in forest ecosystems is a pressing task. In this study,
two dominant litter types were chosen from Zijin Mountain in China: Quercus acutissima leaves from a late succession broad-leaved forest and Pinus massoniana needles from an early succession coniferous forest. The litter samples were incubated in microcosms with original forest
soil and treated with four different forms of nitrogen fertilization [NH4
+, NO3
−, CO(NH2)2, and a mix of all three]. During a 5-month incubation period, litter mass losses, soil pH values, and soil enzyme activities
were determined. Results show that all four forms of nitrogen fertilization significantly accelerate litter decomposition
rates in the broadleaf forest, while only two forms of nitrogen fertilization [i.e., mixed nitrogen and CO(NH2)2] significantly accelerate litter decomposition rates in the coniferous forest. Litter decomposition rates with the mixed
nitrogen fertilization were higher than those in any single form of nitrogen fertilization. All forms of nitrogen fertilization
enhanced soil enzyme activities (i.e., catalase, cellulase, invertase, polyphenol oxidase, nitrate reductase, urease, and
acid phosphatase) during the litter decomposition process for the two forest types. Soil enzyme activities under the mixed
nitrogen fertilization were higher than those under any single form of nitrogen fertilization. These results suggest that
the type and activity of the major degradative enzymes involved in litter decomposition vary in different forest types under
different forms of nitrogen fertilization. They also indicate that a long-term consequence of N deposition-induced acceleration
of litter decomposition rates in subtropical forests may be the release of carbon stored belowground to the atmosphere. 相似文献
8.
Estimates of biomass and primary productivity in a high-altitude maple forest of the west central Himalayas 总被引:4,自引:0,他引:4
S. C. Garkoti 《Ecological Research》2008,23(1):41-49
The paper describes the biomass and productivity of maple (Acer cappadocicum) forest occurring at an altitude of 2,750 m in the west central Himalayas. Total vegetation biomass was 308.3 t ha−1, of which the tree layer contributed the most, followed by herbs and shrubs. The seasonal forest-floor litter mass varied
between 5.4 t ha−1 (in rainy season) and 6.6 t ha−1 (in winter season). The annual litter fall was 6.2 t ha−1, of which leaf litter contributed the largest part (59% of the total litter fall). Net primary productivity of total vegetation
was 19.5 t ha−1 year−1. The production efficiency of leaves (net primary productivity/leaf mass) was markedly higher (2.9 g g−1 foliage mass year−1) than those of the low-altitude forests of the region. 相似文献
9.
Donald Midoko Iponga Rykielle Grace J. Mpikou Joël Loumeto Nicolas Picard 《African Journal of Ecology》2020,58(2):281-290
Tropical rain forests worldwide are affected by anthropogenic disturbances, and secondary forests that develop afterwards are often dominated by pioneer tree species, but the consequences of different anthropogenic disturbances on nutrient cycling are poorly understood. Because most nutrient cycling in tropical rain forests occurs through litterfall and in the soil organic layer, we measured litterfall of a widespread and dominant pioneer tree, okoume (Aucoumea klaineana, Burseraceae) in Gabon, in one forest previously disturbed by logging and in another by agriculture. Litterfall of okoume trees, measured over 14 months, was 18.2 Mg ha−1 year−1 in the formerly logged forest, which was 72.6% greater than in the forest more recently disturbed by agriculture (10.6 Mg ha−1 year−1). Litter decomposition rates were more rapid in the formerly logged forest, and this may explain why litter thickness was 32% lower in the formerly logged forest, despite the greater litterfall within it. Our results highlight that two widespread anthropogenic disturbances in Gabonese rain forests have significantly different consequences on litterfall of a dominant tree and therefore are likely to have different effects on nutrient cycling and forest ecosystem function. 相似文献
10.
Decomposition of fine roots is a fundamental ecosystem process that relates to carbon (C) and nutrient cycling in terrestrial ecosystems. However, this important ecosystem process has been hardly studied in Patagonian ecosystems. The aim of this work was to study root decomposition and nutrient release from fine roots of grasses and trees (Nothofagus antarctica) across a range of Patagonian ecosystems that included steppe, primary forest and silvopastoral forests. After 2.2 years of decomposition in the field all roots retained 70–90% of their original mass, and decomposition rates were 0.09 and 0.15 year?1 for grass roots in steppe and primary forest, respectively. For N. antarctica roots, no significant differences were found in rates of decay between primary and silvopastoral forests (k = 0.07 year?1). Possibly low temperatures of these southern sites restricted decomposition by microorganisms. Nutrient release differed between sites and root types. Across all ecosystem categories, nitrogen (N) retention in decomposing biomass followed the order: tree roots > roots of forest grasses > roots of steppe grasses. Phosphorus (P) was retained in grass roots in forest plots but was released during decomposition of tree and steppe grass roots. Calcium (Ca) dynamics also was different between root types, since trees showed retention during the initial phase, whereas grass roots showed a slow and consistent Ca release during decomposition. Potassium (K) was the only nutrient that was rapidly released from both grass and tree roots in both grasslands and woodlands. We found that silvopastoral use of N. antarctica forests does not affect grass or tree root decomposition and/or nutrient release, since no significant differences were found for any nutrient according to ecosystem type. Information about tree and grass root decomposition found in this work could be useful to understand C and nutrient cycling in these southern ecosystems, which are characterized by extreme climatic conditions. 相似文献
11.
Litter Decomposition and Nutrient Dynamics in a Phosphorus Enriched Everglades Marsh 总被引:3,自引:0,他引:3
A field study was conducted in a nutrient-impacted marsh in Water Conservation Area 2A (WCA-2A) of the Everglades in southern
Florida, USA, to evaluate early stages of plant litter (detritus) decomposition along a well-documented trophic gradient,
and to determine the relative importance of environmental factors and substrate composition in governing decomposition rate.
Vertically stratified decomposition chambers containing native plant litter (cattail and sawgrass leaves) were placed in the
soil and water column along a 10-km transect coinciding with a gradient of soil phosphorus (P) enrichment. Decomposition rate
varied significantly along the vertical water–soil profile, with rates typically higher in the water column and litter layer
than below the soil surface, presumably in response to vertical gradients of such environmental factors as O2 and nutrient availability. An overall decrease in decomposition rate occurred along the soil P gradient (from high- to low-impact).
First-order rate constant (k) values for decomposition ranged from 1.0 to 9.2 × 10−3 day−1 (mean = 2.8 ×10−3 day−1) for cattails, and from 6.7 × 10−4 to 3.0 × 10−3 day−1 (mean = 1.7 × 10−3 day−1) for sawgrass. Substantial N and P immobilization occurred within the litter layer, being most pronounced at nutrient-impacted
sites. Nutrient content of the decomposing plant tissue was more strongly correlated to decomposition rate than was the nutrient
content of the surrounding soil and water. Our experimental results suggest that, although decomposition rate was significantly
affected by initial substrate composition, the external supply or availability of nutrients probably played a greater role
in controlling decomposition rate. It was also evident that nutrient availability for litter decomposition was not accurately
reflected by ambient nutrient concentration, e.g., water and soil porewater nutrient concentration. 相似文献
12.
De Schrijver A Geudens G Augusto L Staelens J Mertens J Wuyts K Gielis L Verheyen K 《Oecologia》2007,153(3):663-674
Converting deciduous forests to coniferous plantations and vice versa causes environmental changes, but till now insight into
the overall effect is lacking. This review, based on 38 case studies, aims to find out how coniferous and deciduous forests
differ in terms of throughfall (+stemflow) deposition and seepage flux to groundwater. From the comparison of coniferous and
deciduous stands at comparable sites, it can be inferred that deciduous forests receive less N and S via throughfall (+stemflow)
deposition on the forest floor. In regions with relatively low open field deposition of atmospheric N (<10 kg N ha−1 year−1), lower NH4+ mean throughfall (+stemflow) deposition was, however, reported under conifers compared to deciduous forest, while in regions
with high atmospheric N pollution (>10 kg N ha−1 year−1), the opposite could be concluded. The higher the open field deposition of NH4+, the bigger the difference between the coniferous and deciduous throughfall (+stemflow) deposition. Furthermore, it can be
concluded that canopy exchange of K+, Ca2+ and Mg2+ is on average higher in deciduous stands. The significantly higher stand deposition flux of N and S in coniferous forests
is reflected in a higher soil seepage flux of NO3−, SO42−, K+, Ca2+, Mg2+ and Al(III). Considering a subset of papers for which all necessary data were available, a close relationship between throughfall
(+stemflow) deposition and seepage was found for N, irrespective of the forest type, while this was not the case for S. This
review shows that the higher input flux of N and S in coniferous forests clearly involves a higher seepage of NO3− and SO42− and accompanying cations K+, Ca2+, Mg2+ and Al(III) into the groundwater, making this forest type more vulnerable to acidification and eutrophication compared to
the deciduous forest type. 相似文献
13.
模拟氮沉降对华西雨屏区天然常绿阔叶林凋落叶分解过程中基质质量的影响 总被引:2,自引:0,他引:2
为理解氮沉降对华西雨屏区天然常绿阔叶林凋落物分解过程的影响,采用立地控制实验和凋落物分解袋法,研究了低氮沉降(L,50 kg N hm~(-2)a~(-1))、中氮沉降(M,150 kg N hm~(-2)a~(-1))和高氮沉降(H,300 kg N hm~(-2)a~(-1))对华西雨屏区天然常绿阔叶林凋落叶分解过程中基质质量的影响。结果表明:N沉降抑制了凋落叶的分解,并随着N沉降量的增加,抑制作用增强。N沉降遏制了凋落叶的C、N释放和纤维素降解,促进了P释放。N沉降提高了凋落叶的C/P比,中氮和高氮处理提高了凋落叶C/N比。N沉降显著增加了凋落叶N、木质素和纤维素的含量,分解1年后,各N沉降处理的木质素/N和纤维素/N均显著高于对照。N沉降提高了质量残留率与C/N、木质素/N和纤维素/N的相关性,降低了与C/P的相关性。可见,模拟N沉降显著影响了华西雨屏区天然常绿阔叶林凋落叶分解过程中的基质质量,进而影响了凋落叶的分解过程。 相似文献
14.
Lars Ola Nilsson Håkan Wallander Erland Bååth Ursula Falkengren-Grerup 《Biogeochemistry》2006,80(1):43-55
Anthropogenic N deposition may change soil conditions in forest ecosystems as demonstrated in many studies of coniferous forests,
whereas results from deciduous forests are relatively scarce. Therefore the influence of N deposition on several variables
was studied in situ in 45 oak-dominated deciduous forests along a N deposition gradient in southern Sweden, where the deposition ranged from
10 to 20 kg N ha−1 year−1. Locally estimated NO
−
3
deposition, as measured with ion-exchange resins (IER) on the soil surface, and grass N concentration (%) were positively
correlated with earlier modelled regional N deposition. Furthermore, the δ15N values of grass and uppermost soil layers were negatively correlated with earlier modelled N deposition. The data on soil
NO
−
3
, measured with IER in the soil, and grass N concentration suggest increased soil N availability as a result of N deposition.
The δ15N values of grass and uppermost soil layers indicate increased nitrification rates in high N deposition sites, but no large
downward movements of NO
−
3
in these soils. Only a few sites had NO
−
3
concentrations exceeding 1 mg N l−1 in soil solution at 50 cm depth, which showed that N deposition to these acid oak-dominated forests has not yet resulted
in extensive leaching of N. The δ15N enrichment factor was the variable best correlated with NO
−
3
concentrations at 50 cm and is thus a variable that potentially may be used to predict leaching of NO
−
3
from forest soils. 相似文献
15.
Rae-Hyun Kim Yowhan Son Jong Hwan Lim Im Kyun Lee Kyung Won Seo Jin Woo Koo Nam Jin Noh Soung-Ryoul Ryu Sun Kee Hong Byung Sun Ihm 《Ecological Research》2006,21(6):819-827
Coarse woody debris (CWD) is an essential component of forests. However, quantification of both the mass and nutrient content
of CWD within a given environment tends to be a fairly labor-intensive proposition that requires long-term studies to be conducted
for viable data to be obtained. As a result, various aspects of CWD in forest ecosystems remain somewhat poorly understood.
In this review, we have compiled all available estimates of CWD mass and nutrients from both coniferous and deciduous forests
in Korea. The CWD mass data varied substantially by forest type, age, location, and sampling time, ranging from 1.5 to 24.5 Mg ha−1, and for the amount (kg ha−1) of nutrients in the CWD, ranging from 3.5 to 23.6 for nitrogen (N), 0.8 to 4.7 for phosphorus (P), 3.9 to 13.3 for potassium
(K), 25.9 to 30.9 for calcium (Ca), 1.4 to 4.2 for magnesium (Mg), and 0.1 to 0.6 for sodium (Na). The mass of CWD transferred
from live trees to the forest floor ranged between 0.1 and 4.9 Mg ha−1 year−1, and these values were roughly equivalent to 26–42% of the annual litterfall inputs (2.5–10.8 Mg ha−1 year−1) for mixed Quercus spp. forests within the relevant region. Annual nutrients inputs (kg ha−1 year−1) through CWD decomposition were 0.7–1.6 for N, 0.04–0.3 for P, 0.3–1.0 for K, 1.7–3.1 for Ca, and 0.1–0.3 for Mg. Consequently,
these results revealed that the ecological value of CWD for C and nutrient cycling was relatively insignificant. However,
only a limited number of studies have been conducted on CWD in different coniferous or mixed deciduous forests in the region.
As a direct result of this paucity of data, further long-term studies on CWD mass and nutrients in a variety of forest types
are required in order to be able to evaluate accurately the ecological value of CWD on biodiversity and physical properties
in Korean forest ecosystems. 相似文献
16.
Mark S. Castro Keith N. Eshleman Louis F. Pitelka Geoff Frech Molly Ramsey William S. Currie Karen Kuers Jeffrey A. Simmons Bob R. Pohlad Carolyn L. Thomas David M. Johnson 《Biogeochemistry》2007,84(3):333-348
The objective of this study was to evaluate the nitrogen (N) biogeochemistry of an 18–22 year old forested watershed in western
Maryland. We hypothesized that this watershed should not exhibit symptoms of N saturation. This watershed was a strong source
of nitrate (NO3
−) to the stream in all years, with a mean annual export of 9.5 kg N ha−1 year−1 and a range of 4.4–18.4 kg N ha−1 year−1. During the 2001 and 2002 water years, wet deposition of inorganic N was 9.0 kg N ha−1 year−1 and 6.3 kg N ha−1 year−1, respectively. Watershed N export rates in 2001 and 2002 water years were 4.2 kg N ha−1 year−1 and 5.3 kg N ha−1 year−1, respectively. During the wetter water years of 2003 and 2004, the watershed exported 15.0 kg N ha−1 year−1 and 18.4 kg N ha−1 year−1, rates that exceeded annual wet deposition of N by a factor of two (7.5 kg N ha−1 year−1 in 2003) and three (5.5 kg N ha−1 year−1 in 2004). Consistent with the high rates of N export, were high concentrations (2.1–3.3%) of N in foliage, wood (0.3%) and
fine roots, low C:N ratios in the forest floor (17–24) and mineral soil (14), high percentages (83–96%) of the amount of mineralized
N that was nitrified and elevated N concentrations (up to 3 mg N l−1) in soil solution. Although this watershed contained a young aggrading forest, it exhibited several symptoms of N saturation
commonly observed in more mature forests. 相似文献
17.
Shi-xing Zhou Cong-de Huang Bo-han Han Yong-xiang Xiao Jian-dong Tang Yuan-bin Xiang Chao Luo 《Plant and Soil》2017,420(1-2):135-145
Background and aims
Litter, an essential component of forest ecosystems, plays an important role in maintaining soil fertility, sequestering carbon (C) and improving soil biodiversity. However, litter decomposition is affected by increased nitrogen (N) deposition. Numerous reports have presented N deposition experiments in different forest ecosystems to investigate the effects of N deposition on litter decomposition, but the effects remain unclear, especially in ecosystems receiving increasingly higher levels of ambient N deposition. To address this gap, we performed a litterbag experiment to understand the effects of increasing N deposition on the litter decomposition process in natural evergreen broad-leaved forest in the Rainy Area of Western China.Methods
A 2-year field litter decomposition experiment was conducted using the litterbag method. Four levels of N deposition were established: control (CK; 0 kg·N·ha?1·year?1), low N deposition (LN; 50 kg·N·ha?1·year?1), medium N deposition (MN; 150 kg·N·ha?1·year?1), and high N deposition (HN; 300 kg·N·ha?1·year?1). The simulated N depositions ranged from 50% to 320% of the ambient rate of wet N deposition.Results
Simulated N deposition significantly increased the remaining mass, C, N, lignin and cellulose of the litter. The LN treatment decreased the remaining phosphorus (P); conversely, the HN treatment increased it. In the late stage of the study period, the mass remaining was positively closely correlated to the lignin and cellulose remaining during the decomposition process.Conclusions
Simulated N deposition significantly suppressed the litter decomposition in the natural evergreen broad-leaved forest, despite the high rate of ambient N deposition, and the inhibitory effects increased with the N deposition levels. The suppressive effect of N deposition on litter decomposition may be primarily explained by the inhibition of lignin and cellulose degradation by the exogenous inorganic N. With ongoing N deposition in future, N deposition may have a potentially significant impact on C and N cycles in such forest ecosystems.18.
This study compared litter production, litter decomposition and nutrient return in pure and mixed species plantations. Dry
weight and N, P, K, Ca, Mg quantities in the litterfall were measured in one pure Cunninghamia lanceolata plantation (PC) and two mixed-species plantations of C. lanceolata with Alnus cremastogyne (MCA) and Kalopanax septemlobus (MCK) in subtropical China. Covering 6 years of observations, mean annual litter production of MCA (4.97 Mg·ha−1) and MCK (3.97 Mg·ha−1) was significantly higher than that of PC (3.46 Mg·ha−1). Broadleaved trees contributed 42% of the total litter production in MCA and 31% in MCK. Introduction of broadleaved tree
species had no significant effect on litterfall pattern. Total litterfall was greatest in the dry season from November to
March. Nutrient returns to the forest floor through leaf litter were significantly higher in both MCA and MCK than in PC (P < 0.05). The amounts of N, K, and Mg returned to the forest floor through leaf litter were highest in the MCA, and P and
Ca returns were highest in the MCK. Percent contribution of broadleaf litter to total nutrient returns ranged from 41.7% to
86.9% in MCA and from 49.3% to 74.8% in MCK. The decomposition rate of individual leaf litter increased in the order: C. lanceolata < K. septemlobus < A. cremastogyne. Litter mixing had a positive effect on decomposition rate of the more recalcitrant litter and promoted nutrient return.
Relative to mass loss of A. cremastogyne decomposing alone, higher mass loss of the mixture of C. lanceolata and A. cremastogyne was observed after 330 days of decomposition. These results indicate that mixed plantations of different tree species have
advantages over monospecific plantations with regards to nutrient fluxes and these advantages have relevance to restoration
of degraded sites.
Responsible Editor: Alfonso Escudero. 相似文献
19.
Li-hua Tu Gang Chen Yong Peng Hong-ling Hu Ting-xing Hu Jian Zhang Xian-wei Li Li Liu Yi Tang 《PloS one》2014,9(7)
Many vital ecosystem processes take place in the soils and are greatly affected by the increasing active nitrogen (N) deposition observed globally. Nitrogen deposition generally affects ecosystem processes through the changes in soil biochemical properties such as soil nutrient availability, microbial properties and enzyme activities. In order to evaluate the soil biochemical responses to elevated atmospheric N deposition in bamboo forest ecosystems, a two-year field N addition experiment in a hybrid bamboo (Bambusa pervariabilis × Dendrocalamopsis daii) plantation was conducted. Four levels of N treatment were applied: (1) control (CK, without N added), (2) low-nitrogen (LN, 50 kg N ha−1 year−1), (3) medium-nitrogen (MN, 150 kg N ha−1 year−1), and (4) high-nitrogen (HN, 300 kg N ha−1 year−1). Results indicated that N addition significantly increased the concentrations of NH4
+, NO3
−, microbial biomass carbon, microbial biomass N, the rates of nitrification and denitrification; significantly decreased soil pH and the concentration of available phosphorus, and had no effect on the total organic carbon and total N concentration in the 0–20 cm soil depth. Nitrogen addition significantly stimulated activities of hydrolytic enzyme that acquiring N (urease) and phosphorus (acid phosphatase) and depressed the oxidative enzymes (phenol oxidase, peroxidase and catalase) activities. Results suggest that (1) this bamboo forest ecosystem is moving towards being limited by P or co-limited by P under elevated N deposition, (2) the expected progressive increases in N deposition may have a potential important effect on forest litter decomposition due to the interaction of inorganic N and oxidative enzyme activities, in such bamboo forests under high levels of ambient N deposition. 相似文献
20.
Anthropogenic release of biologically available N has increased atmospheric N deposition in forest ecosystems, which may slow
decomposition by reducing the lignolytic activity of white-rot fungi. We investigated the potential for atmospheric N deposition
to reduce the abundance and alter the composition of lignolytic basidiomycetes in a regional network of four northern hardwood
forest stands receiving experimental NO3
− deposition (30 kg NO3
−−N ha−1 year−1) for a decade. To estimate the abundance of basidiomycetes with lignolytic potential, we used PCR primers targeting laccase
(polyphenol oxidase) and quantitative fluorescence PCR to estimate gene copy number. Natural variation in laccase gene size
permitted use of length heterogeneity PCR to profile basidiomycete community composition across two sampling dates in forest
floor and mineral soil. Although past work has identified significant and consistent negative effects of NO3
− deposition on lignolytic enzyme activity, microbial biomass, soil respiration, and decomposition rate, we found no consistent
effect of NO3
− deposition on basidiomycete laccase gene abundance or community profile. Rather, laccase abundance under NO3
− deposition was lower (−52%), higher (+223%), or unchanged, depending on stand. Only a single stand exhibited a significant
change in basidiomycete laccase gene profile. Basidiomycete laccase genes occurring in mineral soil were a subset of the genes
observed in the forest floor. Moreover, significant effects on laccase abundance were confined to the forest floor, suggesting
that species composition plays some role in determining how lignolytic basidiomycetes are affected by N deposition. Community
profiles differed between July and October sampling dates, and basidiomycete communities sampled in October had lower laccase
gene abundance in the forest floor, but higher laccase abundance in mineral soil. Although experimental N deposition significantly
suppresses lignolytic activity in these forests, this change is not related to the abundance or community composition of basidiomycete
fungi with laccase genes. Understanding the expression of laccases and other lignolytic enzymes by basidiomycete fungi and
other lignin-decaying organisms appears to hold promise for explaining the consistent decline in lignolytic activity elicited
by experimental N deposition.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献