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1.
Bernd Zeller Claude Bréchet Jean-Paul Maurice François Le Tacon 《Annals of Forest Science》2008,65(6):607-607
2.
外生菌根真菌能与某些树木形成稳定的菌植共生体——外生菌根。外生菌根能吸收土壤中植物难以吸收的无机或有机形式营养物质,并传递至宿主植物为其所利用。由于这种养分传递的生态重要性,外生菌根真菌介导的“菌植”N传递关系受到研究人员的广泛关注。文中综述了外生菌根真菌的可利用N形式及其促进宿主植物N营养吸收的机理,主要归纳为:1）菌根增加了养分吸收面积,促进N吸收;2）外生菌根真菌编码利用N源所必需的一套酶和转运体,协助宿主对难吸收的硝酸盐和有机N的利用。在全球N沉降日益加剧的背景下,本综述将有助于了解外生菌根在当前和未来气候情景下的生态作用。 相似文献
3.
The relative diversity and abundance of different functional groups of macrofungi were investigated in the northern jarrah forest, a mediterranean climate sclerophyllous forest dominated by eucalyptus trees in Western Australia. We sampled paired sites that were either severely affected by dieback, a disease caused by Phytophthora cinnamomi which causes selective plant mortality, or unaffected by this type of forest decline. Macrofungi were sampled 3 times during the growing season along six 100 m × 2 m transects in these sites. Dieback-unaffected sites were found to have significantly different macrofungal floras than unaffected sites. Macrofungal abundance and diversity were approximately 1.5 times and 1.8 times greater respectively in dieback-unaffected sites than in severely affected sites. Dieback-affected sites had a similar diversity of saprotrophic and ectomycorrhizal fungi, whereas more fungal taxa on dieback-unaffected sites were mycorrhizal (>60%). Dung fungi were the most common saprophytes, especially in dieback-affected sites, but abundance data greatly overestimated the importance of these relatively small fungi. We concluded that vegetation changes linked to dieback had a negative effect on fungal community structure and biodiversity in the northern jarrah forest, in a similar manner to other forms of severe disturbance. Conversely, high tree mortality increased the abundance of wood decay fungi, at least in the short term. We expect that reductions in macrofungal species richness were indirectly linked to impacts on mycorrhizal host plants and saprotrophic substrates. Our data show that changes in vegetation composition had the greatest effect on ectomycorrhizal fungi, presumably due to their obligate symbiotic associations. 相似文献
4.
Mireia Llorente Bruno Glaser María-Belén Turrión 《European Journal of Forest Research》2010,129(6):1143-1153
In the last century, many calcareous soils in Castilla León (northwestern Spain) have been transformed from natural Quercus ilex forest to cropped land. Reforestation with Pinus halepensis has been taking place during the past 40 years. In order to obtain a better understanding of how these disturbances affect
ecosystem functioning, we studied the quantity and quality of soil organic matter (SOM) in natural forest ecosystems, cropland
and Pinus plantations. Density fractionation combined with ultrasonic dispersion enables separation and study of SOM fractions:
free organic matter (OM), OM occluded into aggregates and OM stabilized in organo-mineral complexes, considered on the basis
of the type of physical protection provided. We separated SOM density fractions and determined the concentrations of C and
N, C/N ratios and the natural isotopic abundance (δ13C and δ15N values). Transformation of Quercus forest to cropland resulted in major losses of SOC and N, as expected. However, subsequent
reforestation with Pinus resulted in good recovery of the original SOC and soil N pools. This indicates the potential for
enhanced C storage in agricultural soils by their reversion to a forested state. Study of the density fractions and their
13C and 15N signatures enabled better understanding of the high stability of OM in calcareous soils, and analysis of δ13C variations throughout the profile also enabled identification of past C3/C4 vegetation change. Despite the different OC
contents of soils under different land use, OM stabilization mechanisms were not significantly different. In calcareous soils,
accumulation of SOC and N is mainly due to organo-mineral associations, resulting in physicochemical stabilization against
further decomposition. 相似文献
5.
Pastures store over 90% of their carbon and nitrogen below-ground as soil organic matter. In contrast, temperate conifer forests
often store large amounts of organic matter above-ground in woody plant tissue and fibrous litter. Silvopastures, which combine
managed pastures with forest trees, should accrete more carbon and nitrogen than pastures or timber plantations because they
may produce more total annual biomass and have both forest and grassland nutrient cycling patterns active. This hypothesis
was investigated by conducting carbon and nitrogen inventories on three replications of 11 year-old Douglas-fir (Pseudotsuga menziesii)/perennial ryegrass (Lolium perenne)/subclover (Trifolium subterraneum) agroforests, ryegrasss/subclover pastures, and Douglas-fir timber plantations near Corvallis, Oregon in August 2000. Over
the 11 years since planting, agroforests accumulated approximately 740 kg ha–1 year –1 more C than forests and 520 kg ha–1 year–1 more C than pastures. Agroforests stored approximately 12% of C and 2% of N aboveground compared to 9% of C and 1% of N above
ground in plantations and less than 1% of N and C aboveground in pastures. Total N content of agroforests and pastures, both
of which included a nitrogen-fixing legume, were approximately 530 and 1200 kg ha–1 greater than plantations, respectively. These results support the proposition that agroforests, such as silvopastures, may
be more efficient at accreting C than plantations or pasture monocultures. However, pastures may accrete more N than agroforests
or plantations. This apparent separation of response in obviously interrelated agroecosystem processes, points out the difficulty
in using forest plantation or pasture research results to predict outcomes for mixed systems such as agroforests.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
6.
Darta Klavina Audrius Menkis Talis Gaitnieks Sannakajsa Velmala Andis Lazdins Tiina Rajala 《Scandinavian Journal of Forest Research》2016,31(2):156-165
In 2010, dieback of Norway spruce (Picea abies) was observed in Latvia. As mostly stands on seasonally or permanently water-saturated soils were damaged, we hypothesized that the recorded foliar damage might be associated with belowground factors. We established 48 sample plots in stands with damage symptoms for soil parameter evaluation and fine root sampling to determine the number of fine roots in different growth stages and to describe the associated fungal community. Among sample plots on organic soils, there were fewer viable older fine roots and greater number of dead fine roots in more damaged sites than in less damaged. These root parameters were significantly correlated with higher groundwater level and soil pH. The fungal community was dominated by ectomycorrhizal (ECM) species (the most common was Tylospora asterophora), the endophyte Oidiodendron maius and saprotrophic species Cryptococcus magnus. Saprotrophic species had higher abundance in more damaged sites, suggesting a shift in fungal communities from ECM fungi. In conclusion, the results of this work suggest Norway spruce root system response to short-term climatic stress, which should be considered when planning spruce forest management, especially on organic soils with a high groundwater level. 相似文献
7.
《Forest Ecology and Management》2004,196(1):29-41
Increased atmospheric deposition of N to forests is an issue of global concern, with largely undocumented long-term effects on soil solution chemistry. In contrast to bulk soil properties, which are typically slow to respond to a chronic stress, soil solution chemistry may provide an early indication of the long-term changes in soils associated with a chronic stress. At the Harvard Forest, soil solution was collected beneath the forest floor in zero tension lysimeters for 10 years (1993–2002) as part of an N saturation experiment. The experiment was begun in 1988 with 5 or 15 g N m−2 per year added to hardwood and pine forest plots, and our samples thus characterize the long-term response to N fertilization. Samples were routinely analyzed for inorganic nitrogen, dissolved organic nitrogen (DON), and dissolved organic carbon (DOC); selected samples were also analyzed to determine qualitative changes in the composition of dissolved organic matter. Fluxes of DOC, DON, and inorganic N were calculated based on modeled water loss from the forest floor and observed concentrations in lysimeter samples. The concentration and flux of inorganic N lost from the forest floor in percolating soil solution are strongly affected by N fertilization and have not shown any consistent trends over time. On average, inorganic N fluxes have reached or exceeded the level of fertilizer application in most plots. Concentrations of DOC were unchanged by N fertilization in both the hardwood and pine stands, with long-term seasonal averages ranging from 31–57 mg l−1 (hardwood) and 36–93 mg l−1 (pine). Annual fluxes of DOC ranged from 30–50 g m−2 per year. DON concentrations more than doubled, resulting in a shift toward N-rich organic matter in soil solution percolating from the plots, and DON fluxes of 1–3 g m−2 per year. The DOC:DON ratio of soil solution under high N application (10–20) was about half that of controls. The organic chemistry of soil solution undergoes large qualitative changes in response to N addition. With N saturation, there is proportionally more hydrophilic material in the total DON pool, and a lower C:N ratio in the hydrophobic fraction of the total DOM pool. Overall, our data show that fundamental changes in the chemistry of forest floor solution have occurred in response to N fertilization prior to initiation of our sampling. During the decade of this study (years 5–14 of N application) both inorganic N and dissolved organic matter concentrations have changed little despite the significant biotic changes that have accompanied N saturation. 相似文献
8.
丛枝菌根（AM）真菌和外生菌根（EM）真菌与约80%的维管植物可形成共生体,其共生体除了促进植物生长发育外,还具有调节凋落物和土壤有机质分解的重要生态功能。在AM和EM真菌主导的生态系统中,凋落物分解速率在不同的基质类型（AM树种凋落物、EM树种凋落物）、不同的分解阶段（早期阶段、后期阶段）和不同的环境条件（水分、温度等）下均存在显著差异。虽然部分菌根真菌缺乏腐生生物的直接作用于凋落物的能力,但它们通过其他方式影响分解。普遍认为,AM和EM真菌与腐生微生物的相互作用是影响分解速率的主要原因,二者互作机制主要表现为激发效应（向腐生微生物提供能量）和养分竞争效应（与腐生微生物竞争养分）。文中阐述AM和EM真菌对凋落物分解的影响及相关因素,剖析AM和EM真菌与腐生微生物分解凋落物的作用机制,旨在为全面分析AM和EM真菌在森林生态系统中的生态学功能提供参考。 相似文献
9.
Rosa M. Cuevas Claudia Hidalgo Fidel Payán Jorge D. Etchevers Julio Campo 《European Journal of Forest Research》2013,132(5-6):667-677
In a transect study involving 15 mature seasonally dry tropical forests growing on uniform geological substrate in the Yucatan Peninsula, Mexico, we analyzed the influence of a large reduction in mean annual precipitation (1,036–537 mm year?1) on carbon (C) and nitrogen (N) pools in soils. We investigated the C content in organic soil and in active fraction pools (organic matter and microbial biomass) and analyzed the dependence of these pools on precipitation. Carbon (total, inorganic and organic, and in microbial biomass) and N (total) concentrations in bulk soil decreased as rainfall increased from <600 mm year?1 >1,000 mm year?1. Additionally, in all organic matter fractions, C and N concentrations generally decreased with greater precipitation. Soil average C mineralization decreased by 61 % from the wettest to the driest region. Reduced precipitation during the dry season increased microbial biomass C and water-extractable C concentrations and decreased the C concentration in organic matter fractions. No other significant changes were observed between seasons in C concentrations, N concentrations or C mineralization. Overall, we conclude that physical (macroclimate) and biological processes are more active in soils in the wettest region, resulting in a faster turnover of organic matter. 相似文献
10.
F. C. Zaia A. C. Gama-Rodrigues E. F. Gama-Rodrigues M. K. S. Mo?o A. G. Fontes R. C. R. Machado V. C. Baligar 《Agroforestry Systems》2012,86(2):197-212
Large amounts of plant litter deposited in cacao agroforestry systems play a key role in nutrient cycling. Organic matter, nitrogen and phosphorus cycling and microbial biomass were investigated in cacao agroforestry systems on Latosols and Cambisols in Bahia, Brazil. The objective of this study was to characterize the microbial C and N, mineralizable N and organic P in two soil orders under three types of cacao agroforestry systems and an adjacent natural forest in Bahia, Brazil and also to evaluate the relationship between P fractions, microbial biomass and mineralized N with other soil attributes. Overall, the average stocks of organic C, total N and total organic P across all systems for 0?C50?cm soil depth were 89,072, 8,838 and 790?kg?ha?1, respectively. At this soil depth the average stock of labile organic P was 55.5?kg?ha?1. For 0?C10?cm soil depth, there were large amounts of microbial biomass C (mean of 286?kg?ha?1), microbial biomass N (mean of 168?kg?ha?1) and mineralizable N (mean of 79?kg?ha?1). Organic P (total and labile) was negatively related to organic C, reflecting that the dynamics of organic P in these cacao agroforestry systems are not directly associated with organic C dynamics in soils, in contrast to the dynamics of N. Furthermore, the amounts of soil microbial biomass, mineralizable N, and organic P could be relevant for cacao nutrition, considering the low amount of N and P exported in cacao seeds. 相似文献
11.
Continuous increases in anthropogenic nitrogen (N) deposition are likely to change soil microbial properties, and ultimately to affect soil carbon (C) storage. Temperate plantation forests play key roles in C sequestration, yet mechanisms underlying the influences of N deposition on soil organic matter accumulation are poorly understood. This study assessed the effect of N addition on soil microbial properties and soil organic matter distribution in a larch (Larix gmelinii) plantation. In a 9-year experiment in the plantation, N was applied at 100 kg N ha?1 a?1 to study the effects on soil C and N mineralization, microbial biomass, enzyme activity, and C and N in soil organic matter density fractions, and organic matter chemistry. The results showed that N addition had no influence on C and N contents in whole soil. However, soil C in different fractions responded to N addition differently. Soil C in light fractions did not change with N addition, while soil C in heavy fractions increased significantly. These results suggested that more soil C in heavy fractions was stabilized in the N-treated soils. However, microbial biomass C and N and phenol oxidase activity decreased in the N-treated soils and thus soil C increased in heavy fractions. Although N addition reduced microbial biomass and phenol oxidase activity, it had little effect on soil C mineralization, hydrolytic enzyme activities, δ13C value in soil and C–H stretch, carboxylates and amides, and C–O stretch in soil organic matter chemistry measured by Fourier transform infrared spectra. We conclude that N addition (1) altered microbial biomass and activity without affecting soil C in light fractions and (2) resulted in an increase in soil C in heavy fractions and that this increase was controlled by phenol oxidase activity and soil N availability. 相似文献
12.
Felipe García-Oliva Juan F. Gallardo Lancho Noé Manuel Montaño Pilar Islas 《Agroforestry Systems》2006,66(2):93-100
Gains and losses of soil carbon (C), have been reported when tropical forests are converted to pastures. Regional studies
are crucial for setting regional baselines and explaining each particular trend, in order to solve this controversy. Tropical
deciduous forest (TDF) is under high deforestation pressure, mainly for conversion to pastures. The present study compared
soil organic C (SOC) and nitrogen (SON) in the surface layer (0–5 cm) of forest and pasture soils in a TDF of western Mexico.
SOC and SON concentrations were 18 and 60% lower in pasture soils than in forest soils, and C:N ratio increased in pasture
soils. Furthermore, pasture soils had lower labile C and available inorganic nitrogen (N) than forest soils. These results
can be explained as a reduction in C inputs to pasture soils and management-induced disruption of soil aggregates. In forest
soils, macroaggregates (> 250 μm) were predominant (85%), whereas in pasture soils they were reduced to 35% of dry sand-free soil mass. The estimated SOC
and SON losses from the top 5 cm of soil were 3 Mg C ha−1 and 0.9 Mg N ha−1, respectively. 相似文献
13.
Hui Wang Jiangming Mo Xiankai Lu Jinghua Xue Jiong Li Yunting Fang 《Frontiers of Forestry in China》2009,4(1):21-27
2003
Wallenstein M D.McNulty S.Fernandez I J.Boggs J Schlesinger W H
Nitrogen fertilization decreases forest soil fungal and bacterial biomass in three long-term experiments [其它论文]
2006
Wang X F.Li S Y.Bai K J.Kuang T Y
Influence of doubled CO2 on plant growth and soil microbial biomass C and N
1998(12)
Xue J H.Mo J M.Li J.Li D J
The short-term response of soil microorganism number to simulated nitrogen deposition
2007(02)
Yao W H.Yu Z Y
The nutrient content of throughfall inside the artificial forests on downland
1995
Yi Z G.Yi W M.Zhou L X.Wang X M
Soil microbial biomass of the main forests in Dinghushan Biosphere Reserve
2005(05)
Zhou G Y.Yan J H
The influence of region atmospheric precipitation characteristics and its element inputs on the existence and development of Dinghushan forest ecosystems [其它论文]
-Acta Ecologica Sinica2001
14.
Stable isotopes of nitrogen are potentially a valuable tool for regional assessments of nitrogen saturation because they provide an integrated measure of the past nitrogen cycling history of a site. We measured δ15N of soil and litter, as well as net nitrification potential, at three sites across a nitrate-loss gradient in the White Mountains, New Hampshire to test the hypotheses: (1) that δ15N in soil and litter increase across a spatial gradient of nitrate loss; and (2) that δ15N in soil and litter is elevated when nitrification is elevated. δ15N was found not to vary significantly among the three sites. Patterns of leaf litter and forest floor δ15N, however, were strongly influenced by species composition in individual plots. Beech litter had significantly higher δ15N than yellow birch, sugar maple, and red maple. The conifer-dominated plots had significantly lower δ15N in both the organic soil horizons and in litter than did the hardwood-dominated plots. When we adjusted for spatial heterogeneity in mineral soil δ15N values by using an enrichment factor, δ15Nfoliar − δ15NBs, in place of absolute soil δ15N values, a positive relationship was found with net nitrification for hardwoods. δ15N may also be a useful tool for evaluating species differences in nitrogen cycling and nitrogen uptake. The distinct pattern we observed of decreasing δ15N across the continuum from hardwood-dominated to conifer-dominated sites may suggest that local drivers (for example, nitrification rate) regulate the absolute value of foliar δ15N, while species-driven factors (e.g., timing and type of uptake) control the foliar δ15N value of one species relative to another in the same plot. 相似文献
15.
外生菌根菌对巨桉人工林土壤理化性质的影响 总被引：1，自引：0，他引：1
该文调查了四川乐山沙湾、眉山丹棱巨桉人工林下外生菌根菌土,测定了土壤养分情况。结果表明：两地所采集的菌根土的理化指标与对照相比有明显变化,样地Ⅰ菌根土pH值显著高于对照土,有机质含量与对照相比并不显著,样地ⅡpH值显著低于对照,而有机质含量明显高于对照;两样地菌根土的全N、水解N、全P和有效P含量均显著高于对照;大孢硬皮马勃的菌根土全K含量与对照相比并不显著,彩色豆马勃和马勃状硬皮马勃的菌根土全K含量均显著低于对照（P〈0.05）;样地Ⅰ菌根土速效K含量与对照差异不显著,样地Ⅱ菌根土速效K含量显著低于对照。由此可见,巨桉外生菌根真菌对提高巨桉人工林的土壤肥力,维护人工林地力具有一定作用。 相似文献
16.
Mats Fröberg Karna HanssonDan Berggren Kleja Ghasem Alavi 《Forest Ecology and Management》2011,262(9):1742-1747
The effects of three common tree species - Scots pine, Norway spruce and silver birch - on leaching of dissolved organic carbon and dissolved nitrogen were studied in an experimental forest with podzolised soils in southern Sweden. We analyzed soil water collected with lysimeters and modeled water fluxes to estimate dissolved C and N fluxes. Specific UV absorbance (SUVA) was analyzed to get information about the quality of dissolved organic matter leached from the different stands. Under the O horizon, DOC concentrations and fluxes in the birch stands were lower than in the spruce and pine stands; annual fluxes were 21 g m−2 y−1 for birch and 38 g m−2 y−1 and 37 g C m−2 y−1 for spruce and pine, respectively. Under the B horizon, annual fluxes for all tree species ranged between 3 and 5 g C m−2 y−1, implying greater loss of DOC in the mineral soil in the coniferous stands than in the birch stands. We did not find any effect of tree species on the quality of the dissolved organic matter, as measured by SUVA, indicating that the chemical composition of the organic matter was similar in leachates from all three tree species. Substantial amounts of nitrogen was leached out of the soil profile at the bottom of the B horizon from the pine and birch stands, whereas the spruce stands seemed to retain most of the nitrogen in the soil. These differences in N leaching have implications for soil N budgets. 相似文献
17.
Chemical characteristics of forest soils subjected to long-term deposition of alkaline and acid air pollutants were analysed in spruce (Picea abies (L.) Karst.) stands in eastern Germany. Three forest sites along an emission gradient of 3, 6, and 15 km downwind of a coal-fired power plant were selected, representing high, intermediate, and low fly-ash input rates. Past emissions caused an accumulation of mineral fly-ash constituents in the organic layer, resulting in an atypically high mass of organic horizons of forest soils, especially in the F and H horizons. Total mass of organic layers at the site with heavy deposition loads was as high as 128 t ha–1, compared to 58 t ha–1 at the low input site. Fly-ash deposition significantly increased the pH values in the L, F and H horizons and mineral topsoil (0–10 cm). Significantly higher concentrations of NH4Cl-extractable cations (i.e. effective cation exchange capacities) and base saturations of >66% were found in the humic horizons at sites where the pH was increased due to the direct and indirect (i.e. higher proportions of deciduous trees) effects of fly-ash emissions. Stocks of basic cations were dominated by Ca2+ and decreased significantly along the fly-ash deposition gradient from 33.6 to 5.3 kmolc ha–1. Proportions of water-soluble basic cations out of the total potentially exchangeable (i.e. NH4Cl-extractable) basic cations generally increased in the forest soil with decreasing deposition loads following the cation exchange capacity and base saturation along the fly-ash gradient. Higher proportions of monovalent cations, such as K+ and Na+, were observed in the water extracts from fly-ash-affected forest soils, while the NH4Cl-extracts were dominated by bivalent cations, such as Ca2+ and Mg2+. These results suggest a greater leaching tendency for monovalent cations in these soils. Stocks of organic C and total N in the humus layer decreased from sites with high fly-ash deposition levels to sites with low levels, from 57.4 to 46.4 t C ha–1 and from 2.43 to 1.99 t N ha–1. The C/N ratios of the organic horizons varied from 22 to 25, revealing no distinct pattern along the fly-ash gradient. Measurements of hot-water-extractable and water-soluble organic C suggested a reduced availability or a faster decomposition of soil organic matter in soils with historically high fly-ash loads. 相似文献
18.
N. Kulakova 《European Journal of Forest Research》2012,131(6):1717-1726
The unique forest ecosystems investigated were created on the place of natural steppe biogeocoenoses 60?years ago. The aim of the study was to elucidate the effect of plant species on the formation of organic C and N stocks in soils and to estimate nitrogen availability for artificial wood plantation. For this purpose, 290 soil samples were taken from four forest monocultures (Quercus robur L., Pinus sylvestris L., Cotinus coggygria Scop., and Acer tataricum L.) and from virgin steppe ecosystem. The amounts and stocks of organic C, total and readily nitrified N, and seasonal dynamics of NO3 ? and NH4 + ions activities were determined. It was shown that the species composition of the stands influenced the stock of organic C and N in soils. The storages of C and total N differed by 74 and 4.4?Mg/ha?1, respectively, in the litter and upper horizons (0–40-cm layer) in the stands studied. The differences in distribution of stocks of these elements in virgin steppe and artificial forest ecosystems were found. Organic C and N stocks increased 1.6–6.6 times in the forest litter compared to the steppe one, while in 5–40-cm layer, the storages of C and N decreased by 20–35% compared to the virgin soil. The impact of litter on total N content in arid climate was limited in 0–5-cm layer. The deficit of mineral N compounds was observed in autumn in soil with low stock of total N. 相似文献
19.
[目的]研究不同林分类型以及林龄对晋西黄土区土壤养分的改良效应,以期为森林可持续经营提供参考、丰富该区域的生态服务评估资料。[方法]采用林分调查、土壤取样和室内分析方法,于2011年和2016年7—8月对3种不同林龄(山杨中龄林、油松幼龄林、侧柏中龄林)林地内的不同土层有机碳、全氮、全磷含量进行分析,并研究林内各土层间的C、N、P化学计量关系。[结果]表明:各林地土壤养分都有极强的表聚性,0~30 cm土层内有机质、全氮、全磷含量占0~100 cm土层的70%以上;经过5年时间,山杨、油松和侧柏林地0~50 cm土层内平均全氮含量分别增长了9.4%、7.4%、7.5%,全磷含量分别增长了11.6%、12.2%、21.4%;0~100 cm土层内碳储量分别增加了21.17、23.74、2.21 t·hm-2。不同林地之间土壤C:N值随土层深度逐渐减小,而N:P、C:P值随土层变化并没有规律;随着林龄的增加,土壤表层(0~10 cm)的N:P和C:P值明显减小,而C:N值变化不明显。[结论]根据全国土壤养分分级标准,试验林地内碳和氮含量较为丰富,而全磷平均含量为0.36~0.46 g·kg-1、为4~5级标准。在试验林地内,对土壤碳储量、全氮、全磷改良效果相对较好的分别为油松林、山杨林和侧柏林。 相似文献
20.
The conversion of forests to agroecosystems or agroforests comes with many changes in biological and chemical processes. Agroforestry,
a tree based agroecosystem, has shown promise with respect to enhanced system nutrient accumulation after land conversion
as compared to sole cropping systems. Previous research on tropical agroforestry systems has revealed increases in soil organic
matter and total organic nitrogen in the short term. However, research is lacking on long-term system level sustainability
of nutrient cycles and storage, specifically in traditional multi-strata agroforestry systems, as data on both the scope and
duration of nutrient instability are inconclusive and often conflicting. This study, conducted in Ghana, West Africa, focused
on carbon and nitrogen dynamics in a twenty-five year chronosequence of cacao (Theobroma cacao Linn.) plantations. Three treatments were selected as on-farm research sites: 2, 15 and 25-year-old plantations. Soil carbon
(C, to a depth of 15 cm) varied between treatments (2 years: 22.6 Mg C ha−1; 15 years: 17.6 Mg C ha−1; 25 years: 18.2 Mg C ha−1) with a significant difference between the 2- and 15- and the 2- and 25-year-old treatments (p < 0.05). Total soil nitrogen in the top 15 cm varied between 1.09 and 1.25 Mg N ha−1 but no significant differences were noted between treatments. Soil nitrification rates and litter fall increased significantly
with treatment age. However, photosynthetically active radiation (PAR) and soil temperature showed a significant decrease
with age. No difference was found between decay rates of litter at each treatment age. By 25 years, system carbon sequestration
rates were 3 Mg C ha−1 y−1, although results suggest that even by 15 years, system-level attributes were progressing towards those of a natural system. 相似文献