伊金霍洛旗不同土地利用方式下的土壤养分特征

为分析内蒙古鄂尔多斯市伊金霍洛旗在4类土地利用方式(灌木林地、采矿用地、天然牧草地和农地)下,土壤养分质量分数的差异性,运用野外采样和室内化验、分析相结合的方法,测定4种土地类型在0～30 cm土层的土壤有机质和全量氮磷钾质量分数及pH值.结果表明:1)4类土地在0～ 30 cm土层的土壤有机质和全氮质量分数存在显著差异,土壤全磷量和全钾量差异不显著(P＜0.05),土壤有机质质量分数依次为农地＞天然牧草地＞灌木林地＞采矿用地,土壤全量氮磷钾最大值分别为天然牧草地、天然牧草地和灌木林地,最小值分别为采矿用地、灌木林地和天然牧草地;2)在垂直剖面上,采矿用地和天然牧草地的有机质质量分数随着土层深度的增加逐渐减小,农地和灌木林地的有机质质量分数最大值出现在20～30 cm深度的土层,4类土地的土壤全氮量和全磷量均有随土层深度的增加而下降的趋势,全钾量随土层深度的变化不明显.4类土地的土壤全氮和全钾质量分数整体而言较为理想,全磷和有机质质量分数欠缺.农地全磷质量分数基本能满足主要作物的生长需求,有机质和全氮质量分数不能满足主要作物的生长需求.本研究可为内蒙古中部工矿开采区土地合理利用以及退化的生态环境恢复等提供科学依据.     

Changes in soil properties related to different land uses in part of the Nigerian semi-arid Savannah

Abstract. Changes in soil physical and chemical properties associated with different land uses including natural savannah were compared in Nigeria. The study was conducted on large unreplicated sites. There was a significant coarsening of texture, depletion of organic matter and nutrients and increase in bulk density under Eucalyptus camaldulensis and Mangifera indica (mango) plantations, and also under arable and fallow conditions compared with under natural vegetation. The soil conditions were slightly better under Mangifera than under Eucalyptus , and in the fallow land than the arable land and tree plantations, but the differences were mostly non-significant. The land uses studied were less efficient than the natural savannah in protecting the soil from loss of organic matter and nutrients by offtake or surface washing. The options open to Nigerian smallholder fanners are discussed in relation to sustaining soil fertility and productivity.     

Landscape and land use effects on soil resources in a Himalayan watershed

Sustainable land management decisions at all scales require solid, science-based information. Soil quality assessment can provide this regarding soil physical, chemical, and biological characteristics and the ability to provide ecosystem and societal services. Our objective was to make a regional assessment of soils in the Garhwal Himalayas to determine their ability to perform various functions and respond to external influences. Five functional categories were assessed using 13 soil parameters focused on ecological sustainability. Human land use effects on soils were referenced to natural woodlands at each landscape position. Within upper-slope regions, flora and fauna habitat, moisture retention, organic matter and nutrient cycling, air and water infiltration and resistance to erosion were decreased 35, 27, 24, 24, and 9%, respectively. At mid-slope positions the order and magnitude of decrease were organic matter and nutrient cycling, flora and fauna habitat, and moisture retention (26, 22, and 16%, respectively). Changes within the valley were lowest, averaging − 3% for flora and fauna habitat and − 13% for organic matter and nutrient cycling. We conclude that the minimum data set (MDS) used provided a representative assessment of soil quality and could serve as a basis for assessment in similar tropical watersheds.     

Optimal farm management responses to emerging soil salinisation in a dryland catchment in eastern Australia

Secondary salinisation of soil and water resources is an acute management issue over large parts of Australia. This paper focusses on the situation in the Liverpool Plains, where secondary soil salinity is on the increase due to rising saline groundwater tables. The Liverpool Plains are famous for the vast alluvial floodplains where self-mulching black clays provide the production basis for an extensive dryland cropping industry. The farmers there are asking how best to manage their resources under the present hydrological conditions, and are concerned whether their businesses will remain viable in the future. A multi-period programming model is applied to a model farm situation. The objective function reflects the economic paradigm of farming. The model includes a simulation sub-routine which links land use, rainfall and lateral groundwater flow into a point water balance and estimates the salt-affected area. A feedback relationship applies between soil salinity and land productivity. The results of the model suggest that the prevailing cropping practices that rely on long fallowing for soil moisture retention are sub-optimal. Increased cropping frequency increases farm income and reduces on-farm recharge to groundwater. Diversification into lucerne is favourable for the same reasons. Unless trees have commercial value, tree planting is not a favoured option except on salt-affected land. The farm achieves complete on-farm recharge control. However, assuming that the groundwater table rises at a rate of 10 cm per year independent of on-farm recharge, salinisation continues despite these land management changes. The subsequent land productivity losses render the model farm financially unviable in the medium term. Sustaining the productivity of the Liverpool Plains is an issue of reducing recharge to the groundwater system by changing land-use practices throughout the entire catchment. © 1997 John Wiley & Sons, Ltd.     

密云水库上游地区不同土地利用方式面源污染试验

为了更合理地利用土地、减少面源污染,利用密云水库上游石匣坡地径流场不同土地利用试验小区的5年观测数据,分析不同土地利用方式对面源污染的影响。研究表明:不同土地利用方式多年平均次径流系数差异明显,依次为清耕休闲地>坡耕地玉米>荒草坡>鱼鳞坑刺槐>水平条山楂,多年平均土壤侵蚀量与径流中TP、TN和CODMn流失量随径流系数的增大而增加,流失量与径流系数呈显著的正相关关系;径流中养分含量与径流系数之间没有显著相关关系。因此,通过增加植被覆盖或改变土地利用方式可大大减轻水土流失及其造成的面源污染。     

Carbon,nitrogen, phosphorus and enzymatic activity under different land uses in a tropical,dry ecosystem

We compared total C, N and P, available forms of N and P and dehydrogenase, urease and acid phosphatase activities in soils from primary forests, 26‐year‐old pastures and 26‐year‐old secondary forests in the tropical dry forest region of Chamela, Jalisco, Mexico. We hypothesized that, because of their natural regeneration and greater plant diversity, secondary forest soils would have higher fertility and enzyme activities than pasture soils and would be more similar to primary forest soils. We predicted also that enzymes would be better indicators of land‐use effects on soil fertility than nutrients. Only one nutrient, available phosphorus, and one enzyme, acid phosphatase, were significantly and consistently affected by land use. As expected, these parameters were greater in primary and secondary forests than in pastures. Principal components analysis using all variables placed secondary forests intermediate between primary forests and pastures, as predicted, and total C, N and P, available P, ammonium, phosphatase, urease and the C:P ratio were the variables associated with this spatial arrangement of land uses. We conclude that secondary forest soils showed improved fertility and were overall closer to primary forests than to pastures in most variables measured.     

小流域土地利用变化对土壤养分的影响

运用统计学方法,研究重庆市长寿区代家沟小流域土地利用变化对土壤养分的影响.结果表明:经过三年的小流域综合治理,坡耕地向其它土地利用类型转变,其土壤养分平均含量变化表现为有机质全氮、全磷、全钾、碱解氮、有效磷和速效钾分别增咖了9.2%、12.9%、0.7%、5.2%、42.8%、12.8%和9.9%退耕还林还草、坡改梯等治理措施,不仅改变了土地覆盖、微地形,防治了水土流失和土地退化,而且还在一定程度上提高了土壤养分.特别是有机质的增加很明显,改变了土壤的结构,更有效的控制了水土流失的发生,提高了土壤的质量.     

Changes in the chemical composition of water percolating through the soil profile in a moderately polluted catchment

Throughfall (TF), stemflow (SF), soil solution below the organic layer (SS_org) and at 50 cm depth (SS₅₀), and output with stream water (SW) were measured and analyzed for four years in a moderately polluted forest catchment in southern Poland. The input of water with stemflow was ca. 6% of input with TF. However, due to higher concentrations of most ions in SF, the input of most elements with SF was from 8% to 9%. Sulphate (SO₄ ^2–), chloride (Cl^–) and magnesium (Mg²⁺) were the only ions steadily increasing in concentrations in water percolating through the soil profile. Nitrogen reached the forest floor mainly as ammonium (NH₄ ⁺). In the soil organic layer the NH₄ ⁺ concentration decreased, while concentrations of nitrate (NO₃ ^–) and hydrogen (H⁺) increased, probably due to nitrification. For NO₃ ^–, sodium (Na⁺) and calcium (Ca²⁺), the highest concentrations were found in SS_org and SW. This indicates both efficient cycling in the biotic pool of the ecosystem and intensive weathering processes in the mineral soil below the plant rooting zone. The latter was especially pronounced for Mg and Ca. Concentrations of zinc (Zn), lead (Pb) and cadmium (Cd) were the highest in SS_org and SS₅₀. As this was accompanied by a low pH and constant input of H⁺, NH₄ ⁺ and heavy metal ions to the catchment area, it may pose a serious threat to forest health.     

Effects of different land use types on infiltration capacity in a catchment in the highlands of Ethiopia

Infiltration capacity is an important variable for understanding and predicting a range of soil processes. This study investigated for different slope positions the effects of forest conversion to cultivation and grazing on soil infiltration capacity. Infiltration capacity was measured in the field in each land use type using a double‐ring infiltrometer. A total of 108 soil samples (3 slope positions × 3 land use types × 4 soil profiles × 3 soil depths) were collected to determine the variables that affect infiltration capacity viz. particle size distribution, organic carbon content, dry bulk density and soil moisture content. The results showed that in the cultivated and grazed land compared with forest, infiltration capacity and soil moisture content were 70 and 45% smaller respectively, and dry bulk density was 13–20% larger. Changes in soil structure caused by surface soil compaction because of tillage and animal trampling coupled with a smaller soil organic carbon content, are likely to be the principal factors causing the decline in infiltration capacity and soil moisture content after conversion of forest to cultivation and grazing.     

Association of soil organic carbon with physically separated soil fractions in different land uses of Costa Rica

Abstract

Yams (Dioscorea spp.) are known to be very demanding in terms of soil fertility. The influence of deleterious soil fertility on the growth of yams, however, has not yet been studied. A field study was carried out in Côte d'Ivoire, in a fertile forest site and in a low fertility savanna site, submitted to identical climatic conditions, to determine how soil fertility affects Leaf Area Index, Leaf Area Ratio, Crop Growth Rate, Tuber Bulking Rate, Radiation Interception, Radiation Use Efficiency and final tuber yields in D. alata and D. rotundata, grown in the presence of adequate fertilizers. While germination and establishment of both species were not affected by the site, growth parameters of D. alata were superior to those of D. rotundata. This resulted in higher yields of D. alata, when compared to D. rotundata. Only the radiation use efficiency was higher in D. rotundata than in D. alata. Both species reached higher Crop growth rate and Tuber bulking rate and produced higher fresh tuber yields at the forest site than at the savanna site, reflecting the known demand of yams for high fertility soil. Correlation analyses showed significant relationships between the mean Leaf Area Index measured over the entire growth period, Tuber Growth Rate calculated between tuber initiation and harvest, and fresh tuber yields, suggesting that the development of leaf area is determining the growth rate of the tuber which itself determines the fresh tuber yield. The decrease in D. alata tuber yields at the savanna site was explained by a decrease in Leaf Area Index, while the decrease in D. rotundata tuber yields at this site was explained by a decrease in Radiation Use Efficiency. Both effects might have been the consequence of a suboptimal nitrogen and potassium nutrition at the savanna site.     

鲁中山区小流域不同土地利用类型的土壤分形及水分入渗特征

为探讨坡耕地土壤入渗性能退化特征与分形机制,对鲁中山区选择典型小流域,运用土壤分形和水文学原理与方法,通过测定坡耕地、弃耕地、生态林地和经济林地4种土地利用类型的土壤分形特征与入渗性能,探讨土壤人渗速率与土壤颗粒分维及孔隙分维的定量关系。结果表明：1）不同土地利用类型土壤稳渗速率表现为坡耕地〉弃耕地〉生态林地〉经济林地,土壤颗粒分维数与孔隙分维数表现为生态林地〉经济林地〉弃耕地〉坡耕地;2）研究区土壤颗粒分维与孔隙分维数之间显著正相关,二者与土壤黏粒及粉粒体积分数显著正相关、与土壤入渗速率显著负相关;3）霍顿入渗模型和幂函数模型比较适用于拟合研究区土壤入渗过程与入渗速率,而菲利浦模型的适用性较差。因此,研究区土壤具有粗骨性砂土的物理特性,坡耕地耕作会加剧土壤中粉粒和黏粒等细粒物质流失,降低土壤颗粒分布与孔隙分布的均匀性及其分维数,导致土壤入渗性能增强但水肥保蓄性能降低。     

Role of soil organic matter in stabilization of water-stable aggregates in Soils under different types of land use

Three Andosols (used as grassland, upland field, and paddy field) and two Gray Lowland soils (used as upland field and paddy field) were examined to study the role of organic matter in the stabilization of soil aggregates. It was found that prolonged use of Andosols as grassland or as upland field enabled to maintain a higher level of soil organic carbon than use as paddy field. However, paddy soil exhibited a greater aggregate stability (determined by wet-sieving procedure) than soil under upland field or grassland management. Comparison between two Gray Lowland soils also showed that aggregates in the paddy soil were more stable than in the upland field soil. Among organic constituents examined (such as sodium pyrophosphate (SPP)-extractable organic matter and carbohydrates), only the contents of hot water (HW)-extractable carbohydrates of the soils were significantly correlated with aggregate stability. Paddy soils which showed a greater aggregate stability contained a larger amount of HW -extractable carbohydrates in the soils, and a larger amount of HW -extractable carbohydrates regardless of the size of their aggregates compared with other soils. These findings suggest that HW -extractable carbohydrates which represents easily decomposable organic materials may be of special importance for the stabilization of aggregates in the soils.     

Temporal change in land use and its relationship to slope degree and soil type in a small catchment on the Loess Plateau of China

We sought to detect the temporal change (1958–1999) in land use patterns and its relationship to physical landscape parameters in a small catchment in the semi-arid hilly area of the Chinese Loess Plateau. Degree of slope and soil type were selected as stable discriminating parameters that might constrain land use. With the help of GIS and canonical correspondence analysis, the relationship between rural land use distribution or transformation and the selected physical parameters was examined. The land use had undergone a general shift from farmland to woodland or grassland. Canonical correspondence analyses (CCA) indicated that a relationship between land use and the selected physical parameters was evident, farmland coincided with favorable conditions of fertile soil and gentle slope, while grassland and woodland were associated with conditions of poorer soil and steep slope. In the more favorable conditions the main land use change process was the intensification of farming, while in the less favourable conditions it was the abandonment of farmland. A thorough understanding of the relationship between land use temporal or spatial patterns and landscape physical parameters in the Loess Plateau of China, like degree of slope and soil type, will enhance our capability to predict landscape dynamics and lead to more sound and effective land use management strategies.     

Assessing scale effects on modelled soil organic carbon contents as a result of land use change in Belgium

This paper explores the influence of spatial scale on modelled projections of soil organic carbon (SOC) content. The effect of land use change (LUC) on future SOC stocks was estimated using the Rothamsted Carbon model for a small area of southern Belgium. The study assumed no management change and used a single climate change scenario. Three model experiments were used to identify how data scale affects predicted SOC stocks: (i) using European LUC datasets at a resolution of 10′ and assuming equal distribution of change within the study area, (ii) using more accurate regional data aggregated to the 10’ resolution, and (iii) using the regional data at a spatial resolution of 250 m. The results show that using coarse resolution (10′) data is inappropriate when modelling SOC changes in the study area as only the methods using precise data predict a change in SOC stocks similar to those reported in the literature. This is largely because of differences in model parameterisation. However, precisely locating LUC does not significantly affect the results. The model, using either pan‐European or region‐specific precise data predicts an average SOC increase of 1 t C ha^?1 (1990–2050), mainly resulting from afforestation of 13% of agricultural land.     

The response of a high-yielding canola hybrid to sulfur fertilization in three contrasting Saskatchewan soils

Abstract

Canola (Brassica napus) is the primary oilseed crop in western Canada; however, it is often grown on sulfur (S)-deficient soils. Moreover, canola has a high S demand compared to cereals and, therefore, is particularly sensitive to S deficiency. This study examined the growth and nutrient uptake responses of a high-yielding canola hybrid cultivar to S fertilization when grown on three contrasting soils differing in S fertility, with and without the addition of fertilizer S. The soils were collected from three soil-climatic zones within Saskatchewan (Brown, Black, and Gray) and three different fertilizer S forms were used: ammonium sulfate (AS); ammonium thiosulfate (ATS); and a composite fertilizer containing nitrogen (N), phosphorus (P), and S (NPS; 50-50 blend of sulfate (SO₄) salt and elemental S). Sulfur fertilization increased the canola biomass, along with plant uptake of N, P, and S on all three soils. Fertilizer S use efficiency (i.e. recovery) ranged from 11-75%. For all three soils, the general trend among fertilizer S forms for biomass, nutrient uptake, and fertilizer use efficiency was AS?>?ATS?>?NPS. The greatest differences were observed with the Gray soil, which had the poorest S fertility. Residual soil SO₄ after harvest was greater for ATS and NPS; reflecting continued oxidation of thiosulfate and elemental S to SO₄. Principal component analysis demonstrated the importance of tissue N:S ratio as a key diagnostic measurement related to canola growth and nutrient uptake in S-deficient soils.     

Conversion of cropland into grassland: Implications for soil organic‐carbon stocks in two soils with different texture

Soil organic‐carbon (SOC) stocks are expected to increase after conversion of cropland into grassland. Two adjacent cropland and grassland sites—one with a Vertisol with 23 y after conversion and one with an Arenosol 29 y after conversion—were sampled down to 60 cm depth. Concentrations of SOC and total nitrogen (N_tot) were measured before and after density fractionation in two light fractions and a mineral‐associated fraction with C adsorbed on mineral surfaces. For the soil profiles, SOC stocks and radiocarbon (¹⁴C) concentrations of mineral associated C were determined. Carbon stocks and mineral‐associated SOC concentrations were increased in the upper 10 cm of the grassland soil compared to the cropland. This corresponded to the root‐biomass distribution, with 59% and 86% of the total root biomass at 0–5 cm soil depth of the grasslands. However, at the Arenosol site, at 10–20 cm depth, C in the mineral‐associated fraction was lost 29 y after the conversion into grassland. Over all, SOC stocks were not significantly different between grassland and cropland at both sites when the whole profile was taken into account. At the Arenosol site, the impact of land‐use conversion on SOC accumulation was limited by low total clay surface area available for C stabilization. Subsoil C (30–50 cm) at cropland of the Vertisol site comprised 32% of the total SOC stocks with high ¹⁴C concentrations below the plowing horizon. We concluded that fresh C was effectively translocated into the subsoil. Thus, subsoil C has to be taken into account when land‐use change effects on SOC are assessed.     

Effects of soil moisture and temperature on CO2 and CH4 soil-atmosphere exchange of various land use/cover types in a semi-arid grassland in Inner Mongolia, China

The aim of this study was to investigate the combined effects of soil moisture and temperature as well as drying/re-wetting and freezing/thawing on soil-atmosphere exchange of CO₂ and CH₄ of the four dominant land use/cover types (typical steppe, TS; sand dune, SD; mountain meadow, MM; marshland, ML) in the Xilin River catchment, China. For this purpose, intact soil cores were incubated in the laboratory under varying soil moisture and temperature levels according to field conditions in the Xilin River catchment. CO₂ and CH₄ fluxes were determined approximately daily, while soil CH₄ gas profile measurements at four soil depths (5 cm, 10 cm, 20 cm and 30 cm) were measured at least twice per week. Land use/cover generally had a substantial influence on CO₂ and CH₄ fluxes, with the order of CH₄ uptake and CO₂ emission rates of the different land use/cover types being TS ≥ MM ≥ SD > ML and MM > TS ≥ SD > ML, respectively. Significant negative soil moisture and positive temperature effects on CH₄ uptake were found for most soils, except for ML soils. As for CO₂ flux, both significant positive soil moisture and temperature effects were observed for all the soils. The combination of soil moisture and temperature could explain a large part of the variation in CO₂ (up to 87%) and CH₄ (up to 68%) fluxes for most soils. Drying/re-wetting showed a pronounced stimulation of CO₂ emissions for all the soils —with maximum fluxes of 28.4 ± 2.6, 50.0 ± 5.7, 81.9 ± 2.7 and 10.6 ± 1.2 mg C m⁻² h⁻¹ for TS, SD, MM and ML soils, respectively—but had a negligible effect on CH₄ fluxes (TS: −3.6 ± 0.2; SD: 1.0 ± 0.9; MM: −4.1 ± 1.3; ML: −5.6 ± 0.8; all fluxes in μg C m⁻² h⁻¹). Enhanced CO₂ emission and CH₄ oxidation were observed for all soils during thawing periods. In addition, a very distinct vertical gradient of soil air CH₄ concentrations was observed for all land use/cover types, with gradually decreasing CH₄ concentrations down to 30 cm soil depth. The changes in soil air CH₄ concentration gradients were in accordance with the changes of CH₄ fluxes during the entire incubation experiment for all soils.     

Abundance and community structure of sulfate reducing prokaryotes in a paddy soil of southern China under different fertilization regimes

Flooded rice paddy soils represent a typical anaerobic freshwater habitat of microorganisms. The abundance and community structure of sulfate reducing prokaryotes (SRP) were investigated in order to understand their response to different fertilization practices in rice paddy, including control without fertilizers (CT) and arrangements of different chemical fertilizers of nitrogen (N), phosphorus (P) and potassium (K): N, NP, NK and NPK. The abundance of total bacteria and sulfate reducing prokaryotes of the rice paddy in summer and in winter were quantified by real-time PCR assays based on the 16S rRNA gene and the dissimilatory (bi)sulfite reductase gene (dsrAB) β-subunit. No significant differences in the bacterial and SRP abundance were observed among different fertilization treatments in both winter and summer. The mean copy numbers of bacteria was 7.26 × 10⁹ copies g⁻¹ dry soil in winter and 1.27 × 10¹⁰ copies g⁻¹ dry soil in summer. The average dsrAB gene copy numbers of the SRP was 5.08 × 10⁸ copies g⁻¹ dry soil in winter and 5.92 × 10⁸ copies g⁻¹ dry soil in summer. The dsrAB gene clone libraries of the five fertilization treatments were constructed and their RFLP analysis yielded 22-25 restriction patterns, suggesting a high degree of dsrAB sequence diversity in different fertilization treatments. There was no significant change in the soil SRP community structure among the different fertilization regimes. More than half of the sequences were affiliated with novel branching clusters which were uncultured SRP. Clostridia and Deltaproteobacteria were also found with a high proportion in the clone libraries, while Desulfovibrionaceae was absent. High proportion of novel uncultured SRP implies that they may play important roles in paddy soils and deserve further studies.