Changes in soil properties related to conversion of savannah woodland into pine and eucalyptus plantations,Northern Nigeria

Soil properties associated with six age-grade plantations of Pinus oocarpa Schiede and Eucalyptus camaldulensis Dehnh., respectively, including nearby natural vegetation, were compared in the savannah zone of Nigeria. The soil organic matter, total nitrogen and exchangeable nutrients first show declining values with the increasing age of the plantation, then an increase and finally steady or declining values in the 0–15 cm soil depth. Usually the differences between the two youngest plantations and the oldest plantations, and the natural vegetation, were significant. In the 20–30 cm soil depth the properties showed a decrease or steady values over time, with the three oldest plantations showing significant differences from the natural vegetation. The soil pH showed an increased acidity over time. There was little difference in the soil properties between the two tree species. The implications of the results are discussed in relation to sustaining productivity and soil fertility. © 1998 John Wiley & Sons, Ltd.     

桉树-牧草复合经营模式下水土流失和土壤肥力的综合评价

本文通过连续5年监测桉树-牧草和桉树纯林地表径流量和土壤侵蚀量,以及种植前后土壤肥力指标,综合分析间种牧草对桉树林地水土流失和土壤肥力的影响,为桉树人工林科学经营提供理论依据。结果表明:桉树纯林地表径流量和土壤侵蚀量分别在27.4~6612 m~3 hm~(-2) a~(-1)和0~14.9 t hm~(-2) a~(-1)之间,表现出随着种植时间呈逐年减少的变化规律,且水土流失主要集中在前2年;桉树-牧草复合经营模式下林地地表径流量和土壤侵蚀量与桉树纯林随种植时间的变化规律一致,但均低于桉树纯林,降低幅度为20.84%~82.85%;与种植前比,桉树-牧草和桉树纯林土壤pH值分别提高了0.03~0.05和0.14~0.18,有机质、全氮、全磷、全钾、碱解氮、有效磷和速效钾均得到提高(土壤交换性钙和镁除外),增幅分别为0.13~3.00倍和0.39~2.11倍;土壤肥力的关联度从大到小的排列顺序为:桉树-牧草桉树纯林种植前;桉树-牧草和桉树纯林0~20 cm土层土壤肥力指标增幅和关联度均大于20~40 cm土层。可见,与桉树纯林比,间种牧草更有利于改善桉树林地土壤肥力,促进桉树林地可持续性经营,是一种较好的桉树林地复合经营模式。     

Influence of land use on soil properties in a forest region of Southern Nigeria

Abstract. To assess the effect of different land uses on soil properties, five land use types (fallow, Gmelina , arable, secondary forest and cocoa plots) on a sandy loam Alfisol (Typic Kandiudalf) were compared in terms of surface (0–15 cm) soil pH, exchangeable acidity, K, Ca and Mg, extractable P, total N, organic matter, gravimetric moisture, temperature and bulk density. There were significant differences ( P ≤ 0.05- P ≤ 0.001) between the land use types for all the properties except exchangeable acidity and moisture. All the land use types differed significantly from each other in at least four properties. Fallow and secondary forest differed in nine properties, fallow and cocoa in seven and fallow and Gmelina in six. In terms of the number of properties with high variability (CV ≥ 35%), the order was arable, secondary forest and cocoa (4) > Gmelina (3) > fallow (1).     

桉树取代马尾松对土壤养分和酶活性的影响

桉树取代马尾松造林是我国南方典型土地利用变化类型之一,为了探讨该土地利用变化对土壤质量的影响,采用成对设计方法,研究了我国广西桉树取代马尾松造林对土壤养分、微生物生物量和酶活性的影响。结果表明:桉树取代马尾松造林后,土壤全碳、易分解碳库、中等易分解碳库、难分解碳库、全氮和碱解氮含量显著降低,但速效磷显著增加,这可能是由于桉树林施肥和磷素在土壤中移动性弱导致;土壤微生物生物量碳、氮、酚氧化酶、过氧化物酶、蛋白酶、脲酶和酸性磷酸酶活性显著降低。树种变化、桉树林轮伐期短、林下植被差、炼山、翻耕等可能是土壤养分、微生物和酶活性降低的驱动因子;施肥有助于缓解土壤养分降低。在林地转变和经营时,适当保持林下植被和凋落物、减少土壤扰动和合理施肥将有助于改善土壤质量,实现桉树林的可持续经营。     

Assessment of soil organic matter mineralization under various management practices

ABSTRACT

Mineralization is the main organic matter conversion process, which leads not only to preservation of organic matter in the soil but also to its sequestration. Soil organic matter has equal value as mineral part if we want to improve soil quality or increase the yield. Because of intensive farming, irresponsible use of mineral fertilizers and natural factors, soil organic matter is decreasing. To counteract this process, different soil-friendly management practices and techniques, such as shallow tillage, no-tillage or direct drilling and application of additional organic matter are used. The objective of the present study was to assess the changes in the intensity of soil organic matter mineralization as influenced by primary soil tillage of different intensity in combination with organic matter incorporation. Long-term studies showed that land management practices differentiated the soil into two layers: upper (0–10?cm) layer containing more moisture and nutrients and lower (10–20?cm) layer comprising less moisture and nutrients. The conditions of aeration in the arable soil layer did not change under the effect of ploughing. In this soil, the rate of mineralization was lower than that in the ploughless tillage treatment. The most active mineralization of soil organic matter in the ploughless tillage treatment occurred in the autumn period, when high level of rainfall promoted the loss of nutrients from the topsoil layer.     

宣城市岗坡地土壤养分特征及其与颗粒组成关系

对宣城市岗坡地土壤养分特征及其与颗粒组成关系进行了分析,结果表明:⑴不同土地利用类型中,林地土壤有机质和全氮含量显著高于其它3种土地利用类型;耕地和新耕地土壤全磷、速效养分含量都高于林地和灌丛;土壤有机质、速效氮和速效磷含量与土地利用类型有显著的相关性。⑵土壤有机质、全氮含量中、上坡位都显著高于下坡位,全磷和速效养分的含量随坡位下降呈显著增加趋势;有机质、全磷和速效磷与坡位有显著的相关性。⑶土壤有机质与粘粒(<0.002 mm)和粉粒(0.002~0.02 mm)的含量均呈显著的正相关,与砂粒(0.02~2 mm)含量呈显著负相关,全氮与粉粒含量呈现显著正相关,全磷与粉粒、砂粒含量显著正相关。     

Evidence that stable C is as vulnerable to priming effect as is more labile C in soil

A significant fraction of soil organic carbon, named stable organic carbon (C) pool, has residence times longer than centuries and its vulnerability to land use or climatic changes is virtually unknown. Long-term bare fallows offer a unique opportunity to isolate the stable organic pool of soils and study its properties. We investigated the vulnerability of the stable organic C pool to fresh organic matter inputs by comparing the mineralization in a long-term bare fallow soil with that of an adjacent arable soil, containing stable C as well as more labile C. For this, we amended or not the soil samples with two different ¹³C-labelled fresh organic matter (straw or cellulose). In all cases we found a positive priming effect (i.e. an increased mineralization of soil organic carbon) when fresh organic matter was added. By comparing the results obtained on both soils, we estimated that half of the “primed” C in the arable soil due to straw addition as fresh organic matter, originated from the stable C pool. Our results suggest that under such conditions, which frequently occur, the stable pool of soil organic matter may largely contribute to soil extra-CO₂ emissions due to priming effect. Consequently, the C storage potential of this pool may be modified by changes in land use and/or biomass production that might change the priming of the mineralization of the stable pool of soil organic carbon.     

不同土地利用和施肥方式对土壤酶活性及相关肥力因子的影响

以中国科学院海伦农业生态实验站长期定位试验为平台,研究了不同土地利用和施肥方式对土壤酶活性和相关肥力因子的影响,结果表明,种植苜蓿和土地休闲两种方式与裸地相比脲酶、转化酶、磷酸酶、过氧化氢酶活性、土壤全碳、全氮含量和碱解氮、速效磷、速效钾含量均显著增加。其中,脲酶活性增加了24.5%和25.0%,转化酶活性增加了18.4%和18.9%,磷酸酶活性增加了54.6%和50.4%,过氧化氢酶活性增加了8.52%和59.3%,土壤全碳、全氮含量分别增加了13.8%、13.0%和36.8%、33.7%,但苜蓿和休闲两种方式间无显著差异。不同施肥方式相比,土壤酶活性、土壤全碳、全氮含量及土壤养分含量相差显著,其高低顺序为:NPKOM （氮磷钾肥＋有机肥）＞NPKST （氮磷钾肥＋秸秆）＞NPK（氮磷钾肥）＞CK （无肥）;施肥,特别是有机肥,显著提高了土壤酶活性,使土壤全碳、全氮、有效养分含量显著增加。表明黑土经自然恢复和人工恢复及施肥后土壤肥力提高,土壤质量得到改善。     

Effects of organic versus conventional arable farming on soil structure and organic matter dynamics in a marine loam in the Netherlands

Abstract. We compared the effects of conventional and organic arable farming on soil organic matter (SOM) content, soil structure, aggregate stability and C and N mineralization, which are considered important factors in defining sustainable land management. Within one soil series, three different farming systems were selected, including a conventional and an organic arable system and permanent pasture without tillage. The old pasture represents optimal conditions in terms of soil structure and organic matter inputs and is characterized by high earthworm activity. More than 70 years of different management has caused significant differences in soil properties. SOM content, mineralization, earthworm activity and water-stable aggregation decreased as a result of tillage and arable cropping when compared with pasture, but were significantly greater under organic farming than under conventional farming. Total SOM contents between 0 and 20 cm depth amounted to 15, 24 and 46 g kg⁻¹ for the conventional arable, organic arable and permanent pasture fields, respectively. Although less sensitive to slaking than the conventionally managed field, the soil under organic farming was susceptible to compaction when high pressures were exerted on the soil under wet conditions. The beneficial effects of organic farming are generally associated with soil biochemical properties, but soil physical aspects should also be considered. Depending on soil type and climate, organic farmers need to be careful not to destroy the soil structure, so that they can enjoy maximum advantage from their organic farming systems.     

Soil organic carbon,nitrogen, and phosphorus distribution in stable aggregates of an Ultisol under contrasting land use and management history

Different land‐use affects the organization of mineral soil particles and soil organic components into aggregates and the consequent arrangement of the aggregates will influence essential ecosystem functions. We investigated a continuous rubber plantation (forested), land fallowed for 10 y (fallow), 10‐y continuous arable cropping land and cropped land with top soil removed (TSR) for concentrations of C, N, and P in bulk soil and dry aggregates. Results showed that a high level of soil disturbance decreased the proportion of surface (0–15 cm) soil aggregate stability (low mean weight diameter) in TSR by 149% and arable cropping by 125% compared with the forested. Aggregate associated SOC was higher in aggregate‐size fractions of forested land‐use when compared with that in 10‐y fallow, continuous arable cropping, and TSR. For aggregate associated N, fallow and forested land‐use types concentrated higher proportion across aggregate sizes than the arable cropping and TSR. Macro aggregate fractions generally contained higher concentrations of C, N, and P compared with the micro‐aggregates. Water transmission indicators like total porosity and saturated hydraulic conductivity recorded higher values with forested and fallow land‐use than the others. We can thus conclude that long‐term soil disturbance due to cultivation and removal of top soil reduces the accumulation of soil C, N, and P in bulk soil and decreases water transmission properties. On the other hand, aggregate‐associated C, N and P accumulations are dependent on the level of soil surface disturbance and aggregate sizes.     

Effects of different land-use types on soil quality in the hilly area of Rawalakot Azad Jammu and Kashmir

Abstract

Vegetative cover plays an important role for the quality of soil especially in hilly and mountainous areas such as Azad Jammu and Kashmir where erosion is a major threat to the ecosystem and productivity. The study focuses on the impact of land-use types on soil quality by measuring the differences in chemical and physical properties at three sites in adjacently located natural forest land (forest), fallow grassland (grass) and arable land (arable). Soil samples from 0-15 and 15-30 cm depth were collected and examined for particle distribution, dry bulk density, organic matter (OM), pH, macro- and micro-nutrients. Land-use types had a significant effect on primary soil particle distribution. Highest clay content was found in forest and highest sand content in arable. Forest had relatively the highest levels of OM, macro- and micro-nutrients and arable the lowest. Most of the properties of the 0-15 cm surface level of grass were similar to those observed in the 15-30 cm level in forest. Arable exhibited lowest nutrient status and poorest physical conditions, indicating a degrading effect of arable cultivation practices on soil. Grass and arable showed, compared to forest, a 30–60% average increase in bulk density and 26–66% average decrease in OM. Regression analysis showed a significant correlation of OM with available phosphorus and potassium while it had negative correlation with dry bulk density and pH. Natural vegetation appeared to be a main contributor of soil quality as it maintained the organic carbon stock, and increased the nutrient status of soil and is therefore important for sustainable development of Azad Jammu and Kashmir and other similar areas. Furthermore, OM was shown to be an important indicator of soil quality.     

The influence of different types of urban land use on soil microbial biomass and functional diversity in Beijing,China

Soil microbes in urban ecosystems are affected by a variety of abiotic and biotic factors resulting from changes in land use. However, the influence of different types of land use on soil microbial properties and soil quality in urban areas remains largely unknown. Here, by comparing five types of land use: natural forest, park, agriculture, street green and roadside trees, we examined the effects of different land uses on soil microbial biomass and microbial functional diversity in Beijing, China. We found that soil properties varied with land uses in urban environments. Compared to natural forest, soil nutrients under the other four types of urban land use were markedly depleted, and accumulation of Cu, Zn, Pb and Cd was apparent. Importantly, under these four types of land use, there was less microbial biomass, but it had greater functional diversity, particularly in the roadside‐tree soils. Furthermore, there were significant correlations between the microbial characteristics and physicochemical properties, such as organic matter, total nitrogen and total phosphorus (P < 0.05), suggesting that lack of nutrients was the major reason for the decrease in microbial biomass. In addition, the larger C/N ratio, Ni concentration and pool of organic matter together with a higher pH contributed to the increase in microbial functional diversity in urban soils. We concluded that different land uses have indirect effects on soil microbial biomass and microbial community functional diversity through their influence on soil physicochemical properties, especially nutrient availability and heavy metal content.     

沙地整治下榆林土地利用及土壤有机质时空分异特征

毛乌素沙地是典型的生态脆弱区,近年来针对其在榆林境内的沙地整治利用取得显著成效,也对土壤环境产生了深刻影响。为了探究沙地不同整治利用方式对土壤有机质的影响,该研究选取榆林市显性沙地,利用多光谱遥感影像及相关光谱指数,结合沙地土地利用变化特征,通过XGBoost机器学习方法,反演1990-2020年土壤有机质含量;分析不同土地类型下土壤有机质含量变化,通过半变异函数揭示了其空间变异性,厘清人为因素和自然环境的影响程度。结果表明,30 a间榆林5 460 km2沙地中超过半数得到整治和利用,沙地-草地是最主要的地类转变方式,建设用地面积增长最迅速;沙区土壤有机质含量上升,但整体呈现先增加后降低的趋势,有机质均值由0.34%增长至0.79%,近10年降低至0.51%;榆林沙区土壤有机质具有较强的空间自相关性。起初,人为利用对其有积极作用,但随着沙地的利用强度增大,对土壤有机质产生负向作用,进而致使其含量下降,面临土地退化危机。建议加强退化林草的修复改良,放缓建设用地开发力度,研究以期为沙地整治提供理论和实践借鉴意义,保护榆林沙地土壤环境安全。     

雷州半岛桉树人工林土壤肥力特征及其成因

对雷州林业局桉树人工林地进行了土壤普查,结果表明,桉树人工林土壤肥力很低;其现状肥力特征的形成与桉树人工林生态系统水土流失严重,人为因素对土壤养分生物积累过程的干扰,桉树全树利用方式,耕垦和采后剩余物处理不适当有关。因此,增加桉树人工林生物多样性、回归林地凋落物于土壤,应用适当地采伐利用方式和采伐剩余物的处理方式,是改善桉树人工林土壤肥力必须采取的措施。     

A comparison of soil and water properties in organic and conventional farming systems in England

Organic farming and improvements to agricultural sustainability are often seen as synonymous. However, an extensive European review demonstrated that in practice this is not always true. This study aims to compare the status of soil and water properties between separate fields managed in either an organic or a conventional manner. Soil samples were collected from 16 pairs of farms, throughout England, with both arable and grass fields within each pair on similar soil type. Chemical (nutrients, pesticides, herbicides) and physical (aggregate stability, field capacity, shear strength, soil organic matter, infiltration rates) soil properties were measured in four main soil texture classes in organic and conventional fields. The physical soil properties varied significantly between the different classes of texture and land use. The heavier textured soils have significantly higher soil organic carbon (SOC), aggregate stability and shear strength. The coarse‐textured soils have significantly lower field capacity moisture contents. The grassland has a significantly higher level of SOC, field capacity moisture content, aggregate stability and soil shear strength. However, there were no significant differences between organic and conventional treatments for any of the soil physical properties measured. There were fewer traces of agrochemicals in the soil water from the organic fields compared with the conventionally managed fields. The conventional arable fields had higher levels of total inorganic nitrogen than the other land uses and treatments. There was evidence to show that infiltration rates were significantly higher on organically managed grassland soils (7.6 mm/h) than conventionally managed grassland (2.5 mm/h) with lower stocking rates. The results suggest that improved grassland management, whether organic or conventional, could reduce predicted runoff by 28%.     

不同巨桉林下紫色土壤抗蚀性与土壤因子的耦合关系分析

为揭示耕地退耕成巨桉林后对土壤抗蚀性的影响,在野外调查和室内分析的基础上,以紫色土上栽培的6a生巨桉纯林、巨桉+果树、巨桉+粮食作物及农耕地土壤作为研究对象,利用主成分方法分析了影响巨桉林土壤抗蚀性的主要理化指标,同时结合灰色关联度构建了抗蚀性指数—土壤理化性质指标的耦合模型,对不同巨桉林的抗蚀性进行综合判定。结果表明:影响土壤抗蚀性的主要因子有0.25mm团聚体含量、容重、有机质、平均重量直径、水稳性指数、有效钾、碱解氮,其中0.25mm团聚体含量是决定土壤抗蚀性水平的最关键因素;平均重量直径和水稳性指数与土壤理化性质指标分别属于中等和较强关联,土壤理化性质对土壤抗蚀性的影响依次为0.25mm团聚体含量碱解氮有效磷有机质有效钾容重;土壤抗蚀性与土壤理化性质系统的整体耦合水平属于弱协调,系统耦合协调程度为巨桉纯林(中度协调)耕地(弱协调)林粮(轻度不协调)林果(轻度不协调)。研究结论可为耕地退耕成巨桉林地的土壤抗蚀性评价提供一定的理论依据。     

Changes in soil N status and N supply rates in agricultural land afforested with eucalypts in south-western Australia

In south-western Australia, plantations of Eucalyptus globulus are being established on land that has previously been used for conventional agriculture. Sustaining the productivity of these tree plantations in second and subsequent rotations will depend partly on maintenance of soil fertility, especially soil nitrogen (N) supply rates. We compared soil N status and supply rates between adjacent pasture and 6-11 year old first-rotation eucalypt plantations at 31 paired sites in south-western Australia. Total soil N varied widely among sites (0.07-0.68% in the fraction <2 mm of the 0-10 cm soil layer), but concentrations averaged over all sites did not differ between land-use types. However, measurements of the indices of mineralization (mineral N produced during incubation of intact cores), potentially available N (from short-term anaerobic incubation) and model-predicted mineralization rates during 28-day aerobic incubations were generally lower in afforested soils than in pasture soils. This finding was supported by in situ field estimates of N mineralization over a full year at two contrasting paired pasture-plantation sites. At each site there was a marked reduction (2-3-fold) in net annual mineral N flux rates in soils under eucalypt plantations. Reduced N mineralization associated with tree plantations was due to both changes in soil organic matter quality and the generally lower soil moisture content under trees in comparison with pasture. These results suggest that N supply rates of pasture soils are likely to decline when the land is planted to successive crops of eucalypts. Eucalypt plantation managers will need to take account of this and implement management strategies to maintain adequate N nutrition to sustain tree growth in future rotations.     

Comparison of soil properties of native forests,Pinus patula plantations and adjacent pastures in the Andean highlands of southern Ecuador: land use history or recent vegetation effects?

In the high Andes of Ecuador scarcity of farmland has led to accelerated deforestation, in particular over the last 40 years. Soil mis‐management has caused the rapid decline of soil fertility and most farmland has been irreversibly transformed into grassland or tree plantations. The present study assessed whether pastures and particularly pine plantations were associated with less soil nutrients. The soils from six sites each of native forests and Pinus patula plantations, and their adjacent pastures were sampled in a geographically large area in the Paute watershed, south Ecuador. Soil analyses showed statistically significant differences for soil cations and effective cation exchange capacity (ECEC) only. ECEC was highest in soils from native forests and their adjacent pastures (6.4 cmol/kg) compared to pine plantations and their pastures (4.2 cmol/kg). Mean soil organic matter and pH were similar in native forests/pastures (39% SOM; pH 5.4) and in plantations/pastures (40% SOM; pH 5). As pasture soils had ECEC concentrations statistically similar to those of their adjacent forest or plantation, they do not form a single homogeneous land use type based on soil nutrients. Therefore, this study cannot conclude that the presence of pines alone has caused soil degradation, but instead that the soil at the site was already degraded before pines were planted. This study proposes the scenario that pine plantations are established in pastures as a last resort, when the soils are already strongly degraded, and more profitable land uses are not available. Farmers are reluctant to use fertile land for tree plantations, and only the planting of well‐known species, such as pines, is officially encouraged.     

Soil Organic Carbon and Soil Physical Characteristics as Affected by Land Uses under Semiarid Irrigated Conditions

ABSTRACT

Rice-Wheat rotation is the dominant land use in the state of Punjab, resulting in over exploitation of ground water resources. Thus, it is necessary to evaluate other land uses that requires less water and are sustainable. The present investigation was planned with four land uses viz., fallow (FLU), rice-wheat (ALU), grasses (GLU) and pear (PLU) with respect to their effect on soil organic carbon and soil physical characteristics in surface and subsurface depth in district Ludhiana, Punjab. The soil organic carbon (SOC) content was higher by 10, 30.9 and 24.9% under rice-wheat, grasses, and pear than that under fallow. The grasses showed higher soil moisture characteristics curve (SMCC) and lower bulk density (Db) than that under rice-wheat. The larger mean weight diameter (MWD) were observed under pear, grasses and fallow than that under rice-wheat by 0.21, 0.51 and 0.41 mm, respectively. The saturated hydraulic conductivity (K_s) was higher in magnitude by 56.1, 55.4 and 28%, respectively under PLU, GLU and FLU over ALU. Of the evaluated land uses, pear and grasses proved to be more sustainable by retaining more moisture, maintaining better soil physical characteristics and SOC under semiarid irrigated conditions in the state on long term gradual response.     

Restoration of surface soil fertility of an eroded red soil in southern China

To ameliorate degraded red soils and restore their productivity, it is necessary to quantitatively assess the effects of different land uses on soil fertility. In this study, surface soil samples (0–20 cm) under different land uses were collected from an 18-year ameliorative experiment site of a eroded red soil in Lanxi county, Zhejiang province of southern China. The status of surface soil fertility was quantified with a ryegrass growth test in the greenhouse and by numerical analysis of twelve important fertility indexes. The soil fertility indexes were grouped into three major factors using a factor analysis, i.e., organic matter-nitrogen-structure, acidity and phosphate. By means of principal component analysis and cluster analysis of these fertility factors, the fertility of the eroded red soil as a function of land use patterns had the following decreased order: vegetable land>paddy field, cropping arable land and ryegrass land>tea garden>citrus garden>forestland>wasteland. The result suggested that organic matter, total N, available N, and water-stable aggregates were the main characteristics for fertility restoration of the eroded red soil. Soil fertility was most rapidly restored where the soil had been used as vegetable land, and least restored when left as wasteland. The results indicated that land use strongly affected the fertility restoration of eroded red soils because of its effect on the input of nutrients and energy, thus determining the speed and direction of soil fertility evolution.