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1.
Nature and nurture in the dynamics of C, N and P during litter decomposition in Canadian forests 总被引:3,自引:0,他引:3
We measured changes in carbon (C), nitrogen (N) and phosphorus (P) concentrations and mass of 10 foliar litters decomposing over 12 years at 21 sites across Canada, ranging from subarctic to temperate, to evaluate the influence of litter quality (nature) and forest floor (nurture) on N and P dynamics. Most litters lost P faster than N, relative to C, except in one litter which had a high initial C:P quotient (2,122). Net N loss occurred at mass C:N quotients of between 33 and 68, positively correlated with the C:N quotient in the original litter, and net P loss likely occurred at C:P quotients between 800 and 1,200. Forest floor properties also influenced N and P dynamics: the higher the C:N or C:P quotient in the surface soil organic matter, the smaller the proportion of initial N or P left in the decomposing litter, relative to C. There was a convergence of C:N and C:P quotients as the litters decomposed, with an overall mass ratio of 427:17:1 when the litters reached 20% original C remaining. These results, covering a wide range of sites and litters and thus decomposition rates, showed that the C:N:P quotients followed similar trajectories and converged as the litters decomposed. The relative loss of N and P was affected by both the initial litter nutrient concentration and the chemistry of the site forest floor, with the former being more important than the latter, resulting in spatial variations in nutrient content of the forest floor. 相似文献
2.
We used sugar maple litter double-labeled with 13C and 15N to quantify fluxes of carbon (C) and nitrogen (N) between litter and soil in a northern hardwood forest and the retention
of litter C and N in soil. Two cohorts of litter were compared, one in which the label was preferentially incorporated into
non-structural tissue and the other structural tissue. Loss of 13C from this litter generally followed dry mass and total C loss whereas loss of 15N (20–30% in 1 year) was accompanied by large increases of total N content of this decaying litter (26–32%). Enrichment of
13C and 15N was detected in soil down to 10–15 cm depth. After 6 months of decay (November–May) 36–43% of the 13C released from the litter was recovered in the soil, with no differences between the structural and non-structural labeled
litter. By October the percentage recovery of litter 13C in soil was much lower (16%). The C released from litter and remaining in soil organic matter (SOM) after 1 year represented
over 30 g C m−2 y−1 of SOM accumulation. Recovery of litter 15N in soil was much higher than for C (over 90%) and in May 15N was mostly in organic horizons whereas by October it was mostly in 0–10 cm mineral soil. A small proportion of this N was
recovered as inorganic N (2–6%). Recovery of 15N in microbial biomass was higher in May (13–15%) than in October (about 5%). The C:N ratio of the SOM and microbial biomass
derived from the labeled litter was much higher for the structural than the non-structural litter and for the forest floor
than mineral SOM, illustrating the interactive role of substrates and microbial activity in regulating the C:N stoichiometry
of forest SOM formation. These results for a forest ecosystem long exposed to chronically high atmospheric N deposition (ca.
10 kg N ha−1 y−1) suggest possible mechanisms of N retention in soil: increased organic N leaching from fresh litter and reduced fungal transport
of N from soil to decaying litter may promote N stabilization in mineral SOM even at a relatively low C:N ratio. 相似文献
3.
The carbon (C) and nitrogen (N) status in forest ecosystems can change upon establishment of plantations because different
tree species have different nutrient cycling mechanisms. This study was carried out to evaluate C and N status of litterfall,
litter decomposition and soil in three adjacent plantations consisting of one deciduous (larch: Larix leptolepis) and two evergreen (red pine: Pinus densiflora; rigitaeda pine: P. rigida × P. taeda) species planted in the same year (1963). Both the pine plantations showed comparatively higher C input from needle litter
but significantly lower N concentration and input than the larch plantation (P < 0.05). During the decomposition process, the deciduous larch needle litter showed low C concentration and C remaining in
soil, but high N concentration and N remaining in soil compared to the two evergreen pine needle litters. However, the soil
C and N concentration and their content at a soil depth of 0–10 cm were not affected significantly (P > 0.05) by the plantation type. These results demonstrate the existence of considerable variation in C and N status resulting
from needle litter input and litter decomposition in these three plantations grown at sites with similar environmental conditions. 相似文献
4.
The Effect of Phosphorus Availability on Decomposition Dynamics in a Seasonal Lowland Amazonian Forest 总被引:5,自引:0,他引:5
Once the weathering of parent material ceases to supply significant inputs of phosphorus (P), vegetation depends largely on the decomposition of litter and soil organic matter and the associated mineralization of organic P forms to provide an adequate supply of this essential nutrient. At the same time, the decomposition of litter is often characterized by the immobilization of nutrients, suggesting that nutrient availability is a limiting factor for this process. Immobilization temporally decouples nutrient mineralization from decomposition and may play an important role in nutrient retention in low-nutrient ecosystems. In this study, we used a common substrate to study the effects of native soil P availability as well as artificially elevated P availability on litter decomposition rates in a lowland Amazonian rain forest on highly weathered soils. Although both available and total soil P pools varied almost three fold across treatments, there was no significant difference in decomposition rates among treatments. Decomposition was rapid in all treatments, with approximately 50% of the mass lost over the 11-month study period. Carbon (C) and nitrogen (N) remaining and C:N ratios were the most effective predictors of amount of mass remaining at each time point in all treatments. Fertilized treatments showed significant amounts of P immobilization (P < 0.001). By the final collection point, the remaining litter contained a quantity equivalent to two-thirds of the initial P and N, even though only half of the original mass remained. In these soils, immobilization of nutrients in the microbial biomass, late in the decomposition process, effectively prevents the loss of essential nutrients through leaching or occlusion in the mineral soil. 相似文献
5.
The large accumulation of organic matter in peatlands has been partially attributed to litter decomposition rates, which are slowed by a high water table. To test this, we examined whether there were significant differences in the decomposition and N and P dynamics of ten foliar litters and wood blocks at three pairs of upland forest and peatland sites in the transitional grassland, high boreal and low subarctic regions of central Canada, using litterbags collected over a 12-year period. At two of the three pairs, the decomposition rate, as determined by proportion of the original mass remaining after 12 years and by the exponential decay coefficient (k), was faster overall at the upland than at the peatland. In the third pair, there was no significant difference, despite the water table being close to the peat surface; warmer soil temperatures in the peatland than the upland may be the cause. In general, there were small losses or gains of N in the litters after 12 years, compared to the original litter, though there were some differences among litter types and sites, net gains in N likely reflecting the higher exogenous N availability. P was lost from most litters at the two northern pairs of sites, but at the transitional grassland pair, there were large net gains in P and greater variation among litters. The N:P ratio in the original litters ranged from 5 to 26 and after 12 years the ratio narrowed, with the site average of the ten litters ranging from 13 to 22, varying with the soil ratio. Decomposition rates and N and P dynamics after 12 years are different between upland and peatland sites: although the water table is a primary control on these differences, other factors such as temperature and soil nutrient status are also important. 相似文献
6.
Pierre‐Joseph Hatton Cristina Castanha Margaret S. Torn Jeffrey A. Bird 《Global Change Biology》2015,21(3):1358-1367
While plant litters are the main source of soil organic matter (SOM) in forests, the controllers and pathways to stable SOM formation remain unclear. Here, we address how litter type (13C/15N‐labeled needles vs. fine roots) and placement‐depth (O vs. A horizon) affect in situ C and N dynamics in a temperate forest soil after 5 years. Litter type rather than placement‐depth controlled soil C and N retention after 5 years in situ, with belowground fine root inputs greatly enhancing soil C (x1.4) and N (x1.2) retention compared with aboveground needles. While the proportions of added needle and fine root‐derived C and N recovered into stable SOM fractions were similar, they followed different transformation pathways into stable SOM fractions: fine root transfer was slower than for needles, but proportionally more of the remaining needle‐derived C and N was transferred into stable SOM fractions. The stoichiometry of litter‐derived C vs. N within individual SOM fractions revealed the presence at least two pools of different turnover times (per SOM fraction) and emphasized the role of N‐rich compounds for long‐term persistence. Finally, a regression approach suggested that models may underestimate soil C retention from litter with fast decomposition rates. 相似文献
7.
Slowing or even cessation of litter decomposition with time is well-known, but there is insufficient understanding of the
chemical changes that contribute to increasing recalcitrance. Samples from the Canadian Intersite Decomposition Experiment
(CIDET) were used to determine 6-year chemical changes for all 11 litters from a site with rapid initial decomposition (Morgan
Arboretum, MAR) and for three litters at three colder sites. Six-year mass remaining was 17–37% at MAR, with higher values
at the colder sites. Atomic C/N ratios declined and phenolics and condensed tannins generally decreased to minimal values.
However, for the three species compared across four sites, phenolics and tannins showed small increases for species with the
lowest initial values and also tended to increase with increasing mass loss. For the foliar litters at MAR, there was an average
increase in proportion of acid-unhydrolyzable residue (AUR) and decreases in proportions of acid-hydrolyzable (ACID) and extractable
fractions, with final AUR/(ACID + AUR) ratios within 0.55–0.66. Principal component analysis showed that foliar litters (and
to a lesser extent wood) became more alike after 6 years, decomposition being associated with increase of Fe, Al, N, and AUR
concentrations and decrease of K, Mg, tannins, phenolics, and non-polar and water-soluble fractions. However, litters were
also affected by site soil chemistry, with some high 6-year accumulations of Ca, Mg, Fe, Al, Mn, and Mg at two sites. Increasing
recalcitrance likely arises from increasing dominance of complex, less-soluble organic structures, collectively represented
by AUR, together with increases in heavy elements such as Al and Fe, which also specifically bind and stabilize organic matter. 相似文献
8.
土壤养分影响植物生长, 进而影响凋落物质量和产量; 凋落物质量和产量影响凋落物分解过程。基于一个生长实验和一个相同环境分解实验, 研究了冬小麦(Triticum aestivum)生境中养分可利用性对凋落物碳(C)和氮(N)释放的影响。结果显示: (1)冬小麦凋落物产量、叶/根C:N比、C释放量和N释放量随土壤养分梯度呈单调变化; (2)土壤养分影响叶凋落物丢失率而不影响根凋落物丢失率; (3)初始叶/根C:N比与其C、N释放量之间存在负相关关系; (4)分解过程降低叶C:N比和根C:N比。结果表明: 生境中土壤养分的提高可加速凋落物C、N归还, 这反过来可能促进冬小麦生长, 因此这种效应是正反馈; 初始C:N比可预测凋落物C、N释放量。 相似文献
9.
为探讨季节性降水增加对荒漠生态系统凋落物分解的影响, 在古尔班通古特沙漠南缘, 选择粗柄独尾草(Eremurus inderiensis)叶、尖喙牻牛儿苗(Erodium oxyrrhynchum)叶、尖喙牻牛儿苗茎、沙漠绢蒿(Seriphidium santolinum)茎4种凋落物样品, 在2009-2011年研究了模拟季节降水增加(冬春增雪、夏季增水)和自然降水处理下凋落物的分解。持续2年的分解实验表明: (1)各组分凋落物的质量损失过程可以用负指数衰减方程较好地拟合(R2> 0.90); 经过637天的分解, 各组分凋落物质量残留率在自然降水、冬春增雪、夏季增水处理下均无显著性差异(p > 0.05)。粗柄独尾草叶、尖喙牻牛儿苗叶、尖喙牻牛儿苗茎、沙漠绢蒿茎在自然降水处理下的质量残留率分别为40.59%、35.50%、36.00%和63.96%; (2)各组分凋落物的质量残留率与N残留率显著正相关, 凋落物N的损失快于其质量损失, 且初始N含量与分解速率显著正相关(r = 0.60, p = 0.038), C/N解释了71%的地面凋落物分解速率。研究表明, 季节性的短暂降水增加对荒漠区地表凋落物分解没有显著影响, 凋落物初始化学组成是预测荒漠区地表凋落物分解的重要因素。 相似文献
10.
沈阳城市和城郊油松凋落叶的分解动态 总被引:1,自引:0,他引:1
为了检测分解地点和凋落物类型对分解的影响,采用交互分解实验分析了油松凋落叶在城市林分和城郊林分中分解时不同立地条件(城市和城郊)以及不同油松凋落叶类型(城市油松凋落物和城郊油松凋落物)对凋落物的分解速率以及N、P残留率的相对作用。结果表明:不同的立地条件对油松凋落叶分解速率有显著影响(P<0.05):城郊林分中的油松凋落叶比城市林分中分解快,说明外在环境条件对分解的影响显著;在同一林分里,凋落物类型对凋落叶分解速率也有显著影响(P<0.05):城市凋落物分解快于城郊凋落物,说明凋落物内在特性对分解的影响显著。分解地点对于N、P残留率没有显著的影响,然而凋落物类型对N、P残留率有显著影响:城郊凋落物由于具有较高的C/N以及C/P初始值,比城市凋落物更容易富集N、P。 相似文献
11.
Wei Li Kai-wen Pan Ning Wu Jin-chuang Wang Chun-mei Han Xiao-lan Liang 《Ecological Research》2009,24(4):761-769
This study was carried out to compare the ecological function of exotic pine (Pinus radiata—Pr) and native pine (Pinus tabulaeformis—Pt) in terms of litter decomposition and its related N dynamics and to evaluate if the presence of broad-leaved tree species
(Cercidiphyllum japonicum—Cj) or shrub species (Ostryopsis davidiana—Od) litter would promote the decomposition of pine needles and N cycling. Mass remaining, N release of the four single-species
litters and mixed-species (Pt + Cj; Pr + Cj; Pt + Od; Pr + Od) litters and soil N dynamics were measured at microcosm scale
during an 84-day incubation period. The Pt and Pr litter, with poorer substrate quality, indicated slower decomposition rates
than did the Cj and Od litter. Due to their high C/N ratios, the N mass of Pt and Pr litter continuously increased during
the early stage of decomposition, which showed that Pt and Pr litter immobilized exogenous N by microbes. No significant differences
of soil inorganic, dissolved organic and microbial biomass N were found between the Pt and Pr microcosm at each sampling.
The results showed that the exotic Pr performed similar ecological function to the native Pt in terms of litter decomposition
and N dynamics during the early stage. The presence of Cj or Od litter increased the decomposition rates of pine needle litter
and also dramatically increased soil N availability. So it is feasible for plantation managers to consider the use of Cj as
an ameliorative species or to retain Od in pine plantations to promote the decomposition of pine litter and increase nutrient
circulation. The results also suggested that different species litters induced different soil dissolved organic nitrogen (DON).
As a major soluble N pool in soil, DON developed a different changing tendency over time compared with inorganic N, and should
be included into soil N dynamic under the condition of our study. 相似文献
12.
Litter N:P ratios indicate whether N or P limits
the decomposability of graminoid leaf litter 总被引:2,自引:0,他引:2
The N:P ratio of leaf litter may determine if decomposability is N-limited (litter with low N:P ratio) or P-limited (litter with high N:P ratio). To test this hypothesis and to determine the threshold between N and P limitation, we studied relationships between litter N and P concentrations, litter mass loss and effects of fertilisation on litter mass loss in laboratory experiments. Leaf litter of 11 graminoid species was collected in Swiss and Dutch wetlands, yielding 84 litter samples with a broad range of N and P concentrations (3.2–15.1 mg N g−1, 0.04–1.93 mg P g−1) and with N:P mass ratios ranging from 5 to 100. On nutrient-free sand, dry mass loss after five or ten weeks (5.5–53% of initial mass) correlated positively with the N and P concentrations of the litter. Within species, mass loss correlated mainly with N for litter with low N:P ratio, and with P for litter with high N:P ratio, in agreement with our hypothesis. Among species, however, these relationships did not exist, and decomposition rather correlated with the specific leaf area. When the litter was incubated on fertilised sand, 35 out of 50 litter samples decomposed faster than on nutrient-free sand. Decomposition was generally accelerated by P fertilisation (i.e. P-limited) when the N:P ratio of the litter was above 25 and the P concentration below 0.22 mg g−1, supporting our hypothesis. N-limited decomposition was not significantly related to the litter N:P ratio but occurred rarely for litter with N:P ratio greater than 25, and only for litter with N concentration below 11.3 mg g−1. We conclude that the N:P ratio of leaf litter indicates whether its decomposability is more likely to be N- or P-limited. The critical N:P ratio (threshold between N and P limitation) appeared to be 25 for graminoid leaf litter. 相似文献
13.
Forest fragmentation in tropical ecosystems can alter nutrient cycling in diverse ways. We have analysed the effects of the
forest-pasture edge on nutrient soil dynamics in a tropical deciduous forest (TDF) in Mexico. In two remnant forest fragments,
both larger than 10 ha, litterfall, litter and soil samples associated to the tree Caesalpinia eriostachys were collected at five distances from the pasture edge into the inner forest (10 m in the pasture and 0–10, 30–40, 70–80
and 100–110 m towards the forest interior). We measured the concentrations of carbon (C), nitrogen (N) and phosphorus (P)
in litterfall, surface litter and soil, and soil microbial C (Cmic) and microbial N (Nmic). Soil nutrient concentrations and Cmic and Nmic were lower in the pasture soils than in the forest soil samples. Total C and N pools, and Cmic and Nmic in the pasture were lower than in the forest. In contrast, net N immobilization and the increase in Nmic from rain to dry season increased from the edge to the inner forest. Soil P concentration was lower in the pasture and at
the first distance class in the forest margin (0–10 m) than in the sites located further into the forest, while litter P concentration
had the inverse pattern. Litterfall P was also reduced near the edge and increased towards the forest interior. As a consequence,
litterfall C:P and N:P ratios decreased from the edge to the inner forest. These results suggest that the forest–pasture edge
disrupts P dynamics within the first 10 m in the forest. Thus, plants' use of nutrients and productivity could be altered
in the edge of fragmented forests. 相似文献
14.
Alison H. Magill John D. Aber Glenn M. Berntson William H. McDowell Knute J. Nadelhoffer Jerry M. Melillo Paul Steudler 《Ecosystems》2000,3(3):238-253
This article reports responses of two different forest ecosystems to 9 years (1988–96) of chronic nitrogen (N) additions
at the Harvard Forest, Petersham, Massachusetts. Ammonium nitrate (NH4NO3) was applied to a pine plantation and a native deciduous broad-leaved (hardwood) forest in six equal monthly doses (May–September)
at four rates: control (no fertilizer addition), low N (5 g N m-2 y-1), high N (15 g N m-2
y-1), and low N + sulfur (5 g N m-2 y-1 plus 7.4 g S m-2 y-1). Measurements were made of net N mineralization, net nitrification, N retention, wood production, foliar N content and litter
production, soil C and N content, and concentrations of dissolved organic carbon (DOC) and nitrogen (DON) in soil water. In
the pine stand, nitrate losses were measured after the first year of additions (1989) in the high N plot and increased again
in 1995 and 1996. The hardwood stand showed no significant increases in nitrate leaching until 1995 (high N only), with further
increases in 1996. Overall N retention efficiency (percentage of added N retained) over the 9-year period was 97–100% in the
control and low N plots of both stands, 96% in the hardwood high N plot, and 85% in the pine high N plot. Storage in aboveground
biomass, fine roots, and soil extractable pools accounted for only 16–32% of the added N retained in the amended plots, suggesting
that the one major unmeasured pool, soil organic matter, contains the remaining 68–84%. Short-term redistribution of 15N tracer at natural abundance levels showed similar division between plant and soil pools. Direct measurements of changes
in total soil C and N pools were inconclusive due to high variation in both stands. Woody biomass production increased in
the hardwood high N plot but was significantly reduced in the pine high N plot, relative to controls. A drought-induced increase
in foliar litterfall in the pine stand in 1995 is one possible factor leading to a measured increase in N mineralization,
nitrification, and nitrate loss in the pine high N plot in 1996.
Received 2 April 1999; Accepted 29 October 1999. 相似文献
15.
Effects of Single Chinese Fir and Mixed Leaf Litters on Soil Chemical, Microbial Properties and Soil Enzyme Activities 总被引:3,自引:0,他引:3
The quality of leaf litter can control decomposition processes and affect the nutrient availability for plant uptake. In this
study, we investigated the effect of single leaf litter (Chinese fir – Cunninghamia lamcealata (Lamb.) Hook) and mixed leaf litters (C. lamcealata, Liquidamba formosana Hance and Alnus cremastogyne Burk) on soil chemical properties, soil microbial properties and soil enzyme activities during 2 years decomposition. The
results showed that soil microbial biomass C, the ratio of soil microbial biomass C to total soil organic C (soil microbial
quotient, Cmic/Corg) and soil enzymes (urease, invertase, dehydrogenase) activities increased significantly in mixed leaf
litters treatments whereas soil chemical properties remained unchanged. However, soil microbial metabolic quotient (qCO2) values and soil polyphenol oxidase activity were higher in the single Chinese fir leaf litter treatment that had a higher
C:N (carbon:nitrogen) ratio (79.53) compared with the mixed leaf litter (C:N ratios of 76.32, 56.90, 61.20, respectively).
Our results demonstrated that the mixed leaf litter can improve forest soil quality, and that soil microbial properties and
soil enzyme activities are more sensitive in response to litter quality change than soil chemical properties. 相似文献
16.
This study was designed to examine saprophytic fungi diversity under different tree species situated in the same ecological
context. Further, the link between the diversity and decomposition rate of two broadleaved, two coniferous and two mixed broadleaved-coniferous
litter types was targeted. Litter material was decomposed in litter bags for 4 and 24 months to target both early and late
stages of the decomposition. Fungal diversity of L and F layers were also investigated as a parallel to the litter bag method.
Temperature gradient gel electrophoresis fingerprinting was used to assess fungal diversity in the samples. Mass loss values
and organic and nutrient composition of the litter were also measured. The results showed that the species richness was not
strongly affected by the change of the tree species. Nevertheless, the community compositions differed within tree species
and decomposition stages. The most important shift was found in the mixed litters from the litter bag treatment for both variables.
Both mixed litters displayed the highest species richness (13.3 species both) and the most different community composition
as compared to pure litters (6.3–10.7 species) after 24 months. The mass loss after 24 months was similar or greater in the
mixed litter (70.5% beech–spruce, 76.2% oak–Douglas-fir litter) than in both original pure litter types. This was probably
due to higher niche variability and to the synergistic effect of nutrient transfer between litter types. Concerning pure litter,
mass loss values were the highest in oak and beech litter (72.8% and 69.8%) compared to spruce and D. fir (59.4% and 66.5%,
respectively). That was probably caused by a more favourable microclimate and litter composition in broadleaved than in coniferous
plantations. These variables also seemed to be more important to pure litter decomposition rates than were fungal species
richness or community structure. 相似文献
17.
The decomposition and the fate of 15N- labelled beech litter was monitored in a beech forest (Vosges mountains, France) over 3 years. Circular plots around beech
trees were isolated from neighbouring tree roots by soil trenching. After removal of the litter layer, 15N-labelled litter was distributed on the soil. Samples [labelled litter, soil (0–15 cm depths], fine roots, mycorrhizal root
tips, leaves) were collected during the subsequent vegetation periods and analysed for total N and 15N concentration. Mass loss of the 15N-labelled litter was estimated using mass loss data from a litterbag experiment set up at the field site. An initial and
rapid release of soluble N from the decomposing litter was balanced by the incorporation of exogenous N into the litter. Fungal
N accounted for approximately 35% of the N incorporation. Over 2 years, litter N was continuously released and rates of N
and mass loss were equivalent, while litter N was preferentially lost during the 3rd year. Released 15N accumulated essentially at the soil surface. 15N from the decomposing litter was rapidly (i.e. in 6 months) detected in roots and beech leaves and its level increased regularly
and linearly over the course of the labelling experiment. After 3 years, about 2% of the original litter N had accumulated
in the trees. 15N budgets indicated that soluble N was the main source for soil microbial biomass. Nitrogen accumulated in storage compounds
was the main source of leaf N, while soil organic N was the main source of mycorrhizal N. Use of 15N-labelled beech litter as decomposing substrate allowed assessment of the fate of litter N in the soil and tree N pools in
a beech forest on different time scales.
Received: 3 May 1999 / Accepted: 3 January 2000 相似文献
18.
Cumulative effects of nitrogen additions on litter decomposition in three tropical forests in southern China 总被引:3,自引:1,他引:2
A field-scale experiment with nitrogen (N) addition treatments was performed in three forest types – a pine (Pinus massoniana Lamb.) forest, a pine-broadleaf mixed forest (mixed) and a mature monsoon evergreen broadleaf forest (mature) – in tropical
China. Two kinds of leaf litter, Schima superba Chardn. & Champ. and Castanopsis chinensis Hance, were studied using the litterbag technique after more than 2 years of continuous N additions. The objective of this
study was to understand the cumulative effect of N addition on litter decomposition in the tropical forests and to determine
if the initial effects of N addition changes over time. Results indicated that leaf litter decomposition was significantly
faster in the mature forest than in the mixed or pine forests. The mean fraction of mass remaining after 12-months of decomposition
was: mature (0.22) < mixed (0.50) < pine (0.51) for the two litters. Nitrogen addition significantly depressed litter decomposition
in the pine forest and the mature forest, but had no significant effect in the mixed forest. These results suggest that N
deposition has significant cumulative effect on litter decomposition. 相似文献
19.
Interactions between leaf litter and soil organic matter on carbon and nitrogen mineralization in six forest litter-soil systems 总被引:2,自引:0,他引:2
Background and aims
Leaf litter decomposes on the surface of soil in natural systems and element transfers between litter and soil are commonly found. However, how litter and soil organic matter (SOM) interact to influence decomposition rate and nitrogen (N) release remains unclear.Methods
Leaf litter and mineral soil of top 0–5 cm from six forests were incubated separately, or together with litter on soil surface at 25 °C for 346 days. Litter N remaining and soil respiration rate were repeatedly measured during incubation. Litter carbon (C) and mass losses and mineral N concentrations in litter and soil were measured at the end of incubation.Results
Net N transfer from soil to litter was found in all litters when incubated with soil. Litter incubated with soil lost more C than litter incubated alone after 346 days. For litters with initial C: N ratios lower than 52, net Nmin after 346 days was 100 % higher when incubated with soil than when incubated alone. Litter net Nmin rate was negatively related to initial C: N ratio when incubated with soil but not when incubated alone. Soil respiration rate and net Nmin rate did not differ between soil incubated with litter and soil incubated alone.Conclusions
We conclude that soils may enhance litter decomposition rate by net N transfer from soil to litter. Our results together with studies on litter mixture decomposition suggest that net N transfer between decomposing organic matter with different N status may be common and may significantly influence decomposition and N release. The low net Nmin rate during litter decomposition along with the small size of litter N pool compared to soil N pool suggest that SOM rather than decomposing litter is the major contributor to plant mineral N supply. 相似文献20.
Impact of Ecosystem Management on Microbial Community Level Physiological Profiles of Postmining Forest Rehabilitation 总被引:1,自引:0,他引:1
We investigated the impacts of forest thinning, prescribed fire, and contour ripping on community level physiological profiles
(CLPP) of the soil microbial population in postmining forest rehabilitation. We hypothesized that these management practices
would affect CLPP via an influence on the quality and quantity of soil organic matter. The study site was an area of Jarrah
(Eucalyptus marginata Donn ex Sm.) forest rehabilitation that had been mined for bauxite 12 years previously. Three replicate plots (20 × 20 m) were established
in nontreated forest and in forest thinned from 3,000–8,000 stems ha−1 to 600–800 stems ha−1 in April (autumn) of 2003, followed either by a prescribed fire in September (spring) of 2003 or left nonburned. Soil samples
were collected in August 2004 from two soil depths (0–5 cm and 5–10 cm) and from within mounds and furrows caused by postmining
contour ripping. CLPP were not affected by prescribed fire, although the soil pH and organic carbon (C), total C and total
nitrogen (N) contents were greater in burned compared with nonburned plots, and the coarse and fine litter mass lower. However,
CLPP were affected by forest thinning, as were fine litter mass, soil C/N ratio, and soil pH, which were all higher in thinned
than nonthinned plots. Furrow soil had greater coarse and fine litter mass, and inorganic phosphorous (P), organic P, organic
C, total C, total N, ammonium, microbial biomass C contents, but lower soil pH and soil C/N ratio than mound soil. Soil pH,
inorganic P, organic P, organic C, total C and N, ammonium, and microbial biomass C contents also decreased with depth, whereas
soil C/N ratio increased. Differences in CLPP were largely (94%) associated with the relative utilization of gluconic, malic
(greater in nonthinned than thinned soil and mound than furrow soil), l-tartaric, succinic, and uric acids (greater in thinned than nonthinned, mound than furrow, and 5–10 cm than 0–5 cm soil).
The relative utilization of amino acids also tended to increase with increasing soil total C and organic C contents but decreased
with increasing nitrate content, whereas the opposite was true for carboxylic acids. Only 45% of the variance in CLPP was
explained using a multivariate multiple regression model, but soil C and N pools and litter mass were significant predictors
of CLPP. Differences in soil textural components between treatments were also correlated with CLPP; likely causes of these
differences are discussed. Our results suggest that 1 year after treatment, CLPP from this mined forest ecosystem are resilient
to a spring prescribed fire but not forest thinning. We conclude that differences in CLPP are likely to result from complex
interactions among soil properties that mediate substrate availability, microbial nutrient demand, and microbial community
composition. 相似文献