Impact of rapid urbanization on the floral diversity and agriculture land of district Dir,Pakistan

In the World urbanization is a serious problem especially in developing countries which creates serious environmental problems like climatic and ecological changes in the ecosystem. The present paper aims to explain urbanization that causes loss of agriculture lands, biodiversity, soil erosions and grazing in District Dir. Urbanization decreased species richness such as Salix alba and Populus alba in the last few years in the local area. Soil of local area was divided into three different zones and was tested for soil texture and mineral percentage. Zone I soil showed sandy loamy texture with a pH of 8.3, Nitrogen 0.012%, Phosphorus 5.0% and organic matter was 0.74 (ppm). Zone II soil was loamy sand in texture with pH 8.1, Nitrogen 0.011%, Phosphorus 6.2%, and organic matter was 0.24 (ppm) while Zone III soil texture was silty clay loam with a pH of 8.1, Nitrogen 0.032%, Phosphorus 11.3%, and organic matter was 0.60 (ppm). The current work concludes that urbanizations affect natural biodiversity and agriculture lands, and that soil erosion and watering-points trampled by livestock is one of the significant problems in district Dir, and that the main degrading factor is the overexploitation of vegetation for fuel-wood and livestock grazing.     

Study on the effects of different levels of grazing and exclosure on vegetation and soil properties in semi-arid rangelands of Iran

Livestock grazing is one of the main factors of vegetation and soil degradation in arid and semi-arid rangelands of Iran and causes changes in diversity, vegetation, litter and soil characteristics. Therefore, this study has been conducted aimed to examine the effects of exclosure and livestock grazing on vegetation and soil. For this purpose, two grazing areas of medium and high grazing intensity and two exclosure areas (Non-grazing livestock) with duration of 8 and 11 years were selected for sampling. Then, we identified plant species, percentage of coverage of each species, measurement of diversity indices, species similarity and soil chemical properties including electrical conductivity (mho), acidity, organic matter(%), organic carbon (%), nitrogen (%), phosphorus (mg/L) and bulk density (gr/cm³) in each area and they were compared using variance analysis. The results showed that exclosure significantly at 5% level reduced organic matter percentage, electrical conductivity and organic carbon percentage, but it caused a significant increase in soil bulk density at 1% level. Similarity of plant species due to the reduction of livestock grazing intensity and increasing exclosure duration. The results also indicate Livestock grazing increased Coverage of plant family such as Poaceae, Zygophyllacea in the area due to the increase of plant species such as Peganum harmala and Poa bulbosa (non-pleasant species of class III). Based on the results, despite increasing the diversity of plant species in the area over time, increasing diversity does not increase dominant species of the area, as well as companion species increased in the composition of vegetation. It concluded that exclusion has a significant effect on vegetation improvement, vegetation cover percentage, diversity, palatability and litter percentage in the region.     

Factors affecting the occurrence and distribution of entomopathogenic fungi in natural and cultivated soils

Factors affecting the occurrence and distribution of entomopathogenic fungi in 244 soil samples collected from natural and cultivated areas in Spain were studied using an integrated approach based on univariate and multivariate analyses. Entomopathogenic fungi were isolated from 175 of the 244 (71.7 %) soil samples, with only two species found, Beauveria bassiana and Metarhizium anisopliae. Of the 244 soil samples, 104 yielded B. bassiana (42.6 %), 18 yielded M. anisopliae (7.3 %), and 53 soil samples (21.7 %) harboured both fungi. Log-linear models indicated no significant effect of habitat on the occurrence of B. bassiana, but a strong association between M. anisopliae and soils from cultivated habitats, particularly field crops. Also, irrespective of habitat type, B. bassiana predominated over M. anisopliae in soils with a higher clay content, higher pH, and lower organic matter content. Logistic regression analyses showed that pH and clay content were predictive variables for the occurrence of B. bassiana, whereas organic matter content was the predictive variable for M. anisopliae. Also, latitude and longitude predicted the occurrence of these same species, but in opposite directions. Altitude was found to be predictive for the occurrence of B. bassiana. Using principal component analysis, four factors (1 to 4) accounted for 86 % of the total variance; 32.8, 22.9, 19.6 and 10.4 % of the cumulative variance explained, respectively. Factor 1 was associated with high positive weights for soil clay and silt content and high negative weights for soil sand content. Factor 2 was associated with high positive weights for soil organic matter content and high negative weights for soil pH. Factor 3 was associated with high positive weights for latitude and longitude of the sampled localities and factor 4, had high positive weights only for the altitude. Bi-plot displays representing soil samples were developed for different factor combinations and indicated that, irrespective of geographical location, absence of both fungal species was determined by alkaline sandy soils with low organic matter content, whereas heaviness of soil texture, acidity and increasing organic matter content led to progressively higher percentages of samples harbouring entomopathogenic fungi. These results could aid decision-making as to whether or not a particular cultivated or natural soil is suitable for using entomopathogenic fungi as a pest control measure and for selecting the fungal species best suited to a particular soil.     

Soil Properties and their Spatial Pattern in a Degraded Sandy Grassland under Post-grazing Restoration, Inner Mongolia, Northern China

In this study, we use classical and geostatistical methods to identify characteristics of some selected soil properties including soil particle size distribution, soil organic carbon, total nitrogen, pH and electrical conductivity and their spatial variation in a 5-year recovery degraded sandy grassland after two different grazing intensity disturbance: post-heavy-grazing restoration grassland (HGR) and post-moderately grazing restoration grassland (MGR), respectively, in Horqin steppe, Inner Mongolia, northern China. The objective was to examine effect of grazing intensity on spatial heterogeneity of soil properties. One hundred soil samples were taken from the soil layer 0–15 cm in depth of a grid of 10 m×10 m under each treatment. The results showed that soil fine fractions (very fine sand, 0.1–0.05 mm and silt + clay, <0.05 mm), soil organic carbon and total nitrogen concentrations were significant lower and their coefficients of variation significant higher under the HGR than under the MGR. Geostatistical analysis of soil heterogeneity revealed that soil particle size fractions, organic carbon and total nitrogen showed different degree of spatial dependence with exponential or spherical semivariograms on the scale measured under HGR and MGR. The spatial structured variance account for a large proportion of the sample variance in HGR plot ranging from 88% to 97% for soil particle fractions, organic C and total N, however, except for organic C (88.8%), the structured variance only account for 50% of the sample variance for soil particle fractions and total N in the MGR plot. The ranges of spatial autocorrelation for coarse-fine sand, very fine sand, silt + clay, organic C and total N were 13.7 m, 15.8 m, 15.2 m, 22.2 m and 21.9 m in HGR plot, respectively, and was smaller than in MGR plot with the corresponding distance of 350 m, 144.6 m, 45.7 m, 27.3 m and 30.3 m, respectively. This suggested that overgrazing resulted in an increase in soil heterogeneity. Soil organic C and total N were associated closely with soil particle fractions, and the kriging-interpolated maps showed that the spatial distribution of soil organic C and total N corresponded to the distribution patterns of soil particle fractions, indicating that high degree of spatial heterogeneity in soil properties was linked to the distribution of vegetative and bare sand patches. The results suggested that the degree of soil heterogeneity at field scale can be used as an index for indicating the extent of grassland desertification. Also, the changes in soil heterogeneity may in turn influence vegetative succession and restoration process of degraded sandy grassland ecosystem.     

Effect of burning on selected soil parameters in a grass fallow shifting cultivation system in Bhutan

Grass fallow shifting cultivation is an important land use practice in the highlands of Bhutan. Part of the nutrient pool contained in soil organic matter is made available for the traditional buckwheat (Fagopyrum tataricum) crop through a highly labor intensive system exposing 250–500 MT soil ha⁻¹ to temperatures of 500°C and above. Dry topsoil is collected in mounds and burned using plant biomass or manure and soil organic matter as fuel. Labor input ranged from 150–401 days ha⁻¹ with land preparation accounting for 65–85% of the total requirement. The burning increased soil pH from 6.0 to 6.9 and available K from 34 to 69 mg kg⁻¹. Soil organic C and total N were reduced from 3.3 and 0.17% to 0.8 and 0.08%, respectively. Release of P from soil organic matter and plant material and reduction in C/N ratio resulting in increased N availability are considered the most essential effects required for good crop yields. Through the burning about 16 MT of C and 470 kg N ha⁻¹ are released into the atmosphere. Fallow periods of 15–20 years are required for the system to be sustainable. The research was supported by the Department of Agriculture. Royal Government of Bhuttan and the Swiss Association for Technical Assistance The research was supported by the Department of Agriculture. Royal Government of Bhuttan and the Swiss Association for Technical Assistance     

Effects of herbicide chlorsulfuron on growth and nutrient uptake parameters of wheat genotypes differing in Zn-efficiency

Prunings of Calliandra calothyrsus, Grevillea robusta, Leucaena diversifolia and farm yard manure were applied each cropping season at 3 and 6 t dry matter ha⁻¹ to an Oxisol in Burundi. The field plots also received basal applications of nitrogen (N), phosphorus (P) and potassium (K). Application of the tree prunings or farm yard manure decreased the concentration of monomeric inorganic aluminium (Al) in soil solution from 2.92 mg Al dm⁻³ in the control plots to 0.75 mg Al dm⁻³ in the plots receiving 6 t ha⁻¹ Calliandra prunings. The other organic materials also decreased the concentration of monomeric inorganic aluminium in the soil solution. The lowered Al concentration led to a corresponding decrease in the percentage Al saturation of the 0–10 cm soil layer from 80% to 68%. Grain yields of maize and beans were strongly inversely related to the percentage Al saturation of the soil. This confirms that soil acidity was the main constraint to maize and beans production. The yield improvement was mainly attributed to the ameliorating effects of the organic matter application on Al toxicity. The nutrient content had less effect presumably because of fertilizer use. In the best treatments, the yield of maize increased from 0.9 to 2.2 t ha⁻¹ and the corresponding beans yield increased from 0.2 to 1.2 t ha⁻¹. A C Borstlap Section editor     

Spatial Variability of Soil Properties in the Shortgrass Steppe: The Relative Importance of Topography, Grazing, Microsite, and Plant Species in Controlling Spatial Patterns

We conducted a study to evaluate the relative importance of topography, grazing, the location of individual plants (microsite), and plant species in controlling the spatial variability of soil organic matter in shortgrass steppe ecosystems. We found that the largest spatial variation occurs in concert with topography and with microsite-scale heterogeneity, with relatively little spatial variability due to grazing or to plant species. Total soil C and N, coarse and fine particulate organic matter C and N, and potentially mineralizable C were significantly affected by topography, with higher levels in toeslope positions than in midslopes or summits. Soils beneath individual plants (Bouteloua gracilis and Opuntia polyacantha) were elevated by 2–3 cm relative to surrounding soils. All pools of soil organic matter were significantly higher in the raised hummocks directly beneath plants than in the soil surface of interspaces or this layer under plants. High levels of mineral material in the hummocks suggest that erosion is an important process in their formation, perhaps in addition to biotic accumulation of litter beneath individual plants. Over 50 y of heavy grazing by cattle did not have a significant effect on most of the soil organic matter pools we studied. This result was consistent with our hypothesis that this system, with its strong dominance of belowground organic matter, is minimally influenced by aboveground herbivory. In addition, soils beneath two of the important plant species of the shortgrass steppe, B. gracilis and O. polyacantha, differed little from one another. The processes that create spatial variability in shortgrass steppe ecosystems do not affect all soil organic matter pools equally. Topographic variability, developing over pedogenic time scales (centuries to thousands of years), has the largest effect on the most stable pools of soil organic matter. The influence of microsite is most evident in the pools of organic matter that turn over at time scales that approximate the life span of individual plants (years to decades and centuries).     

Transformation of zinc in soils under submerged condition and its relation with zinc nutrition of rice

Laboratory and greenhouse experiments were conducted with two soilsviz., laterite and alluvial to study the transformation of applied Zn in soil fractions under submerged condition in the presence and absence of added organic matter and its relationship with Zn nutrition of rice plants. The results showed that application of organic matter caused a decrease in the concentration of Zn in shoot and root of rice plants and helped in translocating the element from root to shoot. The per cent utilization of applied Zn by plants was also found to increase by the application of organic matter. The transformation of applied Zn in different fractions in soils showed that a major portion (53.6–72.6%) of it found its way to mineral fractions leaving only 1.0–3.3, 6.6–18.9, 11.0–21.6 and 2.3–8.8% of the applied amounts in water soluble plus exchangeable, organic complexed, amorphous sesquioxides and crystalline sesquioxides bound fractions respectively. Application of organic matter favoured such transformation of applied Zn into these fractions except the mineral and crystalline sesquioxides bound ones. Simple correlation and multiple regression analyses between applied Zn in different soil fractions and fertilizer Zn content in plants showed that organic matter application increased the predictability of fertilizer Zn content in plants which has been attributed to the higher per cent recovery of applied Zn in plant available fractions in soils in presence of added organic matter.     

Effects of long-term management practices on grassland plant assemblages in Mediterranean cork oak silvo-pastoral systems

The assessment of the effects of long-term management practices is relevant in understanding the current patterns of plant assemblages in semi-natural ecosystems. We hypothesized that the variety of management practices across different farming systems under the same ecological conditions directly and indirectly shapes these patterns via the long-term changes induced in soil features. The aims of this paper were to evaluate the influence of two sets of variables describing long-term management practices and soil features on plant assemblages and their importance in the context of Mediterranean silvo-pastoral systems. The analysis of variance revealed that richness and grazing value were not affected at all by grazing livestock species and soil tillage frequency and that they both showed relatively high absolute values for the specific context under study. Trifolium subterraneum was a key species in contributing to grassland grazing value and habitat biodiversity. The Canonical Correspondence Analysis highlighted the influence of management practices and soil features on plant assemblage composition, which was significantly affected by grazing livestock species and stocking rate and by soil pH and K content. The Redundancy Analysis showed that soil pH and related features were in turn affected by stocking rate, supporting our hypothesis that management practices influenced plant assemblage composition directly and indirectly via their long-term effects on soil features. The results also highlighted that a systemic analytical perspective applied at a grazing system scale can be effective in addressing sustainable grassland management issues in Mediterranean silvo-pastoral systems.     

Ecology of the rampant weed Nymphaea lotus L. Willdenow in natural and ricefield habitats of the Nile delta, Egypt

In a field study conducted around Lake Manzala (Egypt) during 1995–1996, the distribution of the floating-leafed lotus (Nymphaea lotus L.) in irrigation canals and ricefields was analyzed by classification and ordination methods. Environmental factors associated with its abundance and distribution were evaluated. A data set of 30 stands of lotus and nine environmental variables was analyzed by Canonical Correspondence Analysis (CCA) ordination relating environmental factors to the occurrence of the weed. Ordination analysis detected a strong association between soil organic matter and fine sediment (silt + clay) in the distribution of lotus. Water variables were less important. The density of lotus averaged 3.3±0.49 plants m−2 in the irrigation canals and 6.6±1.4 plants m−2 in the ricefields. The phytomass of lotus ranged from 877 g m−2 in the pure stands to 226 g m−2 in ricefield habitats. The highest proportion of lotus phytomass was allocated to leaf blade, with values reaching 40% of total phytomass in the infested ricefields. Allocation proportions to other plant organs varied between natural and ricefield habitats. Lotus plants allocated more dry matter to vegetative reproduction than to sexual reproduction. The ratio of vegetative to sexual reproduction ranged from 3.48 in the pure stands to 9.63 in infested ricefields. Populations of lotus showed wider variation in leaf area classes in pure stands than in rice stands. Presence of lotus as a weed in ricefields significantly reduced the growth and grain yield of the crop, indicating the risk of its spreading as an invasive weed. This revised version was published online in July 2006 with corrections to the Cover Date.     

Multi-scale responses of vegetation to removal of horse grazing from Great Basin (USA) mountain ranges

Although free-roaming equids occur on all of the world’s continents except Antarctica, very few studies (and none in the Great Basin, USA) have either investigated their grazing effects on vegetation at more than one spatial scale or compared characteristics of areas from which grazing has been removed to those of currently grazed areas. We compared characteristics of vegetation at 19 sites in nine mountain ranges of the western Great Basin; sites were either grazed by feral horses (Equus caballus) or had had horses removed for the last 10–14 years. We selected horse-occupied and horse-removed sites with similar aspect, slope, fire history, grazing pressure by cattle (minimal to none), and dominant vegetation (Artemisia tridentata). During 1997 and 1998, line-intercept transects randomly located within sites revealed that horse-removed sites exhibited 1.1−1.9 times greater shrub cover, 1.2–1.5 times greater total plant cover, 2–12 species greater plant species richness, and 1.9–2.9 times greater cover and 1.1–2.4 times greater frequency of native grasses than did horse-occupied sites. In contrast, sites with horses tended to have more grazing-resistant forbs and exotic plants. Direction and magnitude of landscape-scale results were corroborated by smaller-scale comparisons within horse-occupied sites of horse-trail transects and (randomly located) transects that characterized overall site conditions. Information-theoretic analyses that incorporated various subsets of abiotic variables suggested that presence of horses was generally a strong determinant of those vegetation-related variables that differed significantly between treatments, especially frequency and cover of grasses, but also species richness and shrub cover and frequency. In contrast, abiotic variables such as precipitation, site elevation, and soil erodibility best predicted characteristics such as forb cover, shrub frequency, and continuity of the shrub canopy. We found species richness of plants monotonically decreased across sites as grazing disturbance increased, suggesting that either the bell-shaped diversity-disturbance curve of the intermediate-disturbance hypothesis does not apply in this system or that most sites are already all on the greater-disturbance slope of the curve. In our study, numerous vegetation properties of less-grazed areas and sites differed notably from horse-grazed sites at local and landscape scales during a wetter and an average-precipitation year. Electronic Supplementary Material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

黄土区露天煤矿排土场土壤与地形因子对植被恢复的影响

在脆弱的生态环境改善和恢复过程中,植被恢复与重建扮演着重要的角色。黄土露天煤矿区生态环境极其脆弱,认识矿区损毁土地植被恢复与地形、土壤因子之间的作用规律对矿区土地复垦与生态恢复改善至关重要。为此,选择山西平朔安太堡露天煤矿南排土场对2条样带27个复垦样地的土壤、地形、植被参数进行了采集与测定,并应用单因素方差分析与CANOCO4.5软件的降趋势对应分析和冗余分析研究了地形与土壤因子对植被恢复的影响。结果表明:植被与土壤变量之间呈显著相关,与地形变量之间相关性不明显;坡度主要影响草本覆盖度,坡向与有机质和速效磷之间具有线性相关性;速效钾对植被的变化起着重要的作用;土壤容重与砾石含量对土壤养分含量具有明显的指示作用;有机质与全氮呈显著正相关,各土壤养分指标之间存在明显的相关关系。为了改善和恢复黄土区露天煤矿排土场脆弱的生态系统,应该考虑植被和土壤的联合演替。在当地的生态环境状况下土地复垦与生态恢复的关键是改善土壤状况和增加人工植被,同时加强对排土场人工和自然植被的保护。     

不同麋鹿干扰强度对栖息地土壤理化特性的影响

动物对草地的采食和践踏直接影响着土壤的理化特性。以大丰麋鹿保护区半散养麋鹿为研究对象,分析了不同麋鹿干扰强度下土壤含水率、容重、全盐量、有机质、全氮、全磷和全钾的差异,探讨麋鹿放养对土壤理化性质的影响。结果表明:(1)随着麋鹿干扰强度的增加,土壤含水量和有机质呈现下降的趋势;土壤盐分、容重和氮、磷、钾全量呈现上升的趋势。(2)麋鹿放养对土壤理化指标的影响显著,重度干扰样地与对照样地之间差异性达到极显著水平(P0.01)。(3)土壤氮、磷、钾全量,在重度干扰区域达到最大值,分别为1.56 g/kg、0.95 g/kg和13.43 g/kg,全氮量的增长幅度最大。(4)在麋鹿活动最为频繁的重度干扰区域,土壤盐分含量达到9.26 g/kg,土壤盐碱化,这是导致栖息地退化的主要原因。麋鹿干扰强度增加最终导致土壤盐渍化加重,栖息地生境明显退化,严重区域向光裸地的演化。     

Assessing nitrogen fluxes from roots to soil associated to rhizodeposition by apple (<Emphasis Type="Italic">Malus domestica</Emphasis>) trees

The mass transfer from root to soil by means of rhizodeposition has been studied in grasses and forest trees, but its role in fruit trees is still unknown. In this study, N fluxes from roots to soil were estimated by applying a ¹⁵N mass balance technique to the soil–tree system. Apple (Malus domestica) trees were pre-labelled with ¹⁵N and then grown outdoors in 40 L pots for one vegetative season in (1) a coarse-textured, low organic matter soil, (2) a coarse-textured, high organic matter soil, and (3) a fine-textured, high organic matter soil. At tree harvest the ¹⁵N abundance of the soils was higher than at transplanting, but the total amount of ¹⁵N present in the tree–soil system was similar at transplanting and tree harvest. The soils had a strong effect on N fluxes from and to the soil. In the fine-textured soil, 11% of the total plant-derived nitrogen was transferred to the soil, compared with 2–5% in the two coarse-textured soils. Rhizodeposition was higher in the fine soil (18% of the primary production) than in the coarse-textured soils, whereas higher soil organic matter depressed rhizodeposition. Nitrogen uptake was almost double in the coarse-textured, high organic matter soil versus the other soils. Our results indicate that belowground primary productivity is significantly underestimated if based on root production data only. Rhizodeposition represents a major process, whose role should not be underestimated in carbon and nitrogen cycles in orchard ecosystems.     

若尔盖沙化草地恢复过程中土壤特性及水源涵养功能

1995年以来,政府大力开展对若尔盖沙化草地生态系统的恢复重建工作,其生态恢复效益受到广泛关注。而水源涵养功能作为衡量草地生态系统恢复程度的重要生态指标,其变化对水分循环及全球气候变化有一定的影响和响应。以若尔盖县不同治理年限的沙化草地治理区为研究对象(包括1995年、2007年、2009年、2010年、2011年的治理区,2012年的正常放牧区和2012年的无治理区),采用野外采样和室内分析相结合的方法,将土壤含水量作为研究指标,结合土壤的理化性质,分析沙化草地在恢复重建过程中水源涵养功能的变化及其影响因素,结果表明:若尔盖草地在恢复重建过程中,(1)土壤质地发生变化,由紧砂土逐渐恢复成砂壤土,保水能力及保肥性都得到显著提高;土壤容重随着治理时间的增加而降低,由无治理区的1.7 g/cm~3下降到正常放牧区的1.3 g/cm~3;(2)土壤p H值随着治理时间的增加而逐渐降低,由7.6逐渐下降到6.7,土壤总体上为中性土,适宜植被生长;土壤有机质的变化相对不明显,但治理区的有机质远低于正常放牧区的土壤有机质,总体呈缓慢上升趋势;(3)土壤含水量呈"V"型变化趋势,在治理初期,土壤含水量先减小,2009年治理区的含水量最低,仅为6.8%,但到了治理后期,土壤的含水量开始增加,1995年的沙化治理区含水量达到了12.1%,说明水源涵养能力得到相应的提升;(4)经过相关分析,土壤含水量和有机质、土壤质地、土壤p H值、生物量以及土壤碳含量呈显著相关关系,其中,含水量与有机质、土壤质地以及土壤碳含量呈极显著正相关,而与p H值呈显著负相关;(5)随着治理时间的增加,土壤退化指数逐渐减小,土壤状况得到不断的改善。     

Influence of livestock grazing on vegetation in a saline area in Northeast Thailand

The influence of grazing by water buffalo (Bubalas bufalis) and cattle (Bos taurus) was estimated for vegetation inside and outside cages in a saline area at Khon Kaen, Northeast Thailand. The home range of water buffalo and cattle shifted in response to the period of rice cultivation: during the rice-growing season these animals grazed on roadsides and abandoned places such as the study area; after rice harvest they grazed mainly rice stubble on the paddy. The vegetation in the study area was divided into three types: 1) dominated by the annual grassesChloris barbata andIschaemum rugosum; vegetational cover and plant height in the cage increase due to the increase of these grasses; 2) thorny shrub patch ofMaytenus mekongensis; other species in this patch almost died a year after experimental elimination of this shrub; this salt-tolerant shrub not only protected the co-existing species from grazing, but also suppressed salt accumulation; 3) almost pure stand ofPanicum repens; livestock preferred this perennial grass over others. Electrical conductivity (EC) of surface soil did not increase under the vegetation protected from grazing. Litter and other organic matter in the soil suppressed the upward movement of brine. Grazing led to an increase of bare ground where NaCl accumulated, and modified the heterogeneity of vegetation, which was reflected in the degree of salt accumulation.     

Grazing intensity significantly affects belowground carbon and nitrogen cycling in grassland ecosystems: a meta‐analysis

Livestock grazing activities potentially alter ecosystem carbon (C) and nitrogen (N) cycles in grassland ecosystems. Despite the fact that numerous individual studies and a few meta‐analyses had been conducted, how grazing, especially its intensity, affects belowground C and N cycling in grasslands remains unclear. In this study, we performed a comprehensive meta‐analysis of 115 published studies to examine the responses of 19 variables associated with belowground C and N cycling to livestock grazing in global grasslands. Our results showed that, on average, grazing significantly decreased belowground C and N pools in grassland ecosystems, with the largest decreases in microbial biomass C and N (21.62% and 24.40%, respectively). In contrast, belowground fluxes, including soil respiration, soil net N mineralization and soil N nitrification increased by 4.25%, 34.67% and 25.87%, respectively, in grazed grasslands compared to ungrazed ones. More importantly, grazing intensity significantly affected the magnitude (even direction) of changes in the majority of the assessed belowground C and N pools and fluxes, and C : N ratio as well as soil moisture. Specifically,light grazing contributed to soil C and N sequestration whereas moderate and heavy grazing significantly increased C and N losses. In addition, soil depth, livestock type and climatic conditions influenced the responses of selected variables to livestock grazing to some degree. Our findings highlight the importance of the effects of grazing intensity on belowground C and N cycling, which may need to be incorporated into regional and global models for predicting effects of human disturbance on global grasslands and assessing the climate‐biosphere feedbacks.     

Reversibility of Soil Productivity Decline with Organic Matter of Differing Quality Along a Degradation Gradient

In the highlands of Western Kenya, we investigated the reversibility of soil productivity decline with increasing length of continuous maize cultivation over 100 years (corresponding to decreasing soil organic carbon (SOC) and nutrient contents) using organic matter additions of differing quality and stability as a function of soil texture and inorganic nitrogen (N) additions. The ability of additions of labile organic matter (green and animal manure) to improve productivity primarily by enhanced nutrient availability was contrasted with the ability of stable organic matter (biochar and sawdust) to improve productivity by enhancing SOC. Maize productivity declined by 66% during the first 35 years of continuous cropping after forest clearing. Productivity remained at a low level of 3.0 t grain ha^-1 across the chronosequence stretching up to 105 years of continuous cultivation despite full N–phosphorus (P)–potassium (K) fertilization (120–100–100 kg ha⁻¹). Application of organic resources reversed the productivity decline by increasing yields by 57–167%, whereby responses to nutrient-rich green manure were 110% greater than those from nutrient-poor sawdust. Productivity at the most degraded sites (80–105 years since forest clearing) increased in response to green manure to a greater extent than the yields at the least degraded sites (5 years since forest clearing), both with full N–P–K fertilization. Biochar additions at the most degraded sites doubled maize yield (equaling responses to green manure additions in some instances) that were not fully explained by nutrient availability, suggesting improvement of factors other than plant nutrition. There was no detectable influence of texture (soils with either 11–14 or 45–49% clay) when low quality organic matter was applied (sawdust, biochar), whereas productivity was 8, 15, and 39% greater (P < 0.05) on sandier than heavier textured soils with high quality organic matter (green and animal manure) or only inorganic nutrient additions, respectively. Across the entire degradation range, organic matter additions decreased the need for additional inorganic fertilizer N irrespective of the quality of the organic matter. For low quality organic resources (biochar and sawdust), crop yields were increasingly responsive to inorganic N fertilization with increasing soil degradation. On the other hand, fertilizer N additions did not improve soil productivity when high quality organic inputs were applied. Even with the tested full N–P–K fertilization, adding organic matter to soil was required for restoring soil productivity and most effective in the most degraded sites through both nutrient delivery (with green manure) and improvement of SOC (with biochar).     

Comparison of conditions for mycelial growth of <Emphasis Type="Italic">Lepista sordida</Emphasis> causing fairy rings on <Emphasis Type="Italic">Zoysia matrella</Emphasis> turf to those on <Emphasis Type="Italic">Agrostis palustris</Emphasis> turf

Symptoms of fairy rings caused by Lepista sordida have been reported on Zoysiagrass (Zoysia spp.) turf maintained at fairway height (2 cm), but not on bentgrass (Agrostis spp.) maintained at putting green height (0.5 cm). The mycelia of this fungus inhabit primarily the upper 0–2 cm layer of the soil extending into the thatch. To compare conditions for the mycelial growth in Z. matrella turf to those in A. palustris turf, we examined the effects of nutrients, temperature, water potential, and pH in the field as well as in the laboratory. Greater growth of the mycelia was observed in medium that included hot water extracts from soil of the 0–1 cm zone in Z. matrella turf compared to that from A. palustris. The upper soil layer in Z. matrella turf contained more organic matter from clippings than that in A. palustris. The temperature and water potential of the 0–2 cm soil zone in Z. matrella turf were also more favorable for the mycelial growth. The soil pH values of this zone in Z. matrella turf were less favorable compared to A. palustris but within the range for accelerating mycelial growth. Part of this study was presented orally at the 46th meeting of the Mycological Society of Japan in 2002