Nutrient loading of a forest soil

Summary During July 1988 rooted and non-rooted experimental chambers were established in a Norway spruce (Picea abies. Karst) stand in south Devon U.K. Replicates were supplemented with ammonium and nitrate. The leachates were analysed to monitor the release of mineral-N species and cations over the 17-week experimental period. Ammonium treatments leached 300% more calcium and magnesium than controls. The onset of nitrification resulted in a decrease in sodium losses from ammonium treatments reflecting a decrease in the exchanging capacity of the soil solution. These results are discussed in relation to mineral ion leaching in soils subjected to increesed N-loading, and the ability of soils to buffer these perturbations.     

Changes in forest cover in China during the Holocene

Pollen map data at 2000-year intervals are used to reconstruct changes in Holocene forest cover in China north of the Yangtze River. In almost all regions, the early Holocene from 10 ka b.p. to 6 ka b.p. is characterised by an increase in forest cover although there was a reversal to lower forest cover at 8 ka b.p. in the eastern monsoon regions. A maximum of forest cover was reached at 6 ka b.p. in all regions except for Northeast China where forest cover peaked in the late Holocene. All regions except for Northeast China experienced a marked decline in forest cover after 6 ka b.p. Since 6 ka b.p., forest cover has decreased by about 92% in the middle and lower reaches of the Yellow River, 64% in the easternmost part of the Qinghai-Tibet Plateau and 37% between the Yangtze River and the Huaihe River. In contrast, forest cover in Northeast China increased significantly from 6 ka b.p., but has declined between 2 ka b.p. and the present. Changes in forest cover prior to 6 ka b.p. were probably caused by climate, but the evident drop in forest cover since that time in most regions may have been induced predominantly by human activities.     

Assessment of soil aluminium pools along three mountainous elevation gradients

Anthropogenic soil acidification in mountain forests and consequent Al release still present a significant problem in many regions. The effect of deposition may differ according to stand conditions, including altitude. This contribution is focused on three elevation transects, two in the Jizera Mountains strongly influenced by acid deposition, one in the less affected Novohradske Mountains. Quantification of pools of different Al forms and related soil characteristics (organic carbon, exchangeable hydrogen cations, sorption characteristics, etc.) is evaluated. In the Novohradske Mountains, the pool of both organically bound and water-soluble Al increases with increasing altitudes. In the Jizera Mountains, the distribution is more complicated; it is strongly affected by different forest type (beech vs. spruce), deforestation, and other local differences. Higher amounts of Al are bound in the mineral horizons compared to the surface organic horizons, even in the case of organically bound Al pools. Further differences between different altitudes and between soil horizons in Al distribution were revealed by detailed Al speciation using HPLC/IC method.     

Degradation of humic acid of a forest soil by some fungal isolates

Summary In a laboratory incubation study the humic acid isolated from a forest soil of Palamau (Bihar) was subjected to biodegradation for a period of six weeks by using nine cultures of fungi. These fungi were tested earlier for their cellulose decomposing ability. The humic acid was used as sole source of carbon, nitrogen and carbon plus nitrogen in Czapek-Dox broth. Of the nine culturesAspergillus awamori (IARI),Penicillium sp. (Ranchi),Humicola insolense (Hissar) were found to be very effective in decomposing humic acid. The humic acid used as sole source of carbon was most efficiently degraded followed by that used as carbon+nitrogen source. When it was used as sole source of nitrogen, it could not be degraded so efficiently. This may be due to unavailability of its nitrogen to these microorganisms.     

The physical and chemical responses of a degraded sandy clay loam soil to cover crops in southern Nigeria

The physical and chemical responses of a degraded sandy clay loam Ultisol to two leguminous and four grass cover crops in southern Nigeria were studied after five years to assess the rejuvenative effects of the covers. There were relative increases of 26% and 112% in soil organic carbon and phosphorus levels and also appreciable improvements in the CEC and Ca levels under vegetative covers compared with the initial conditions. The improvements were more pronounced with legume covers than with grass covers. Furthermore, the vegetative covers improved mean organic carbon level by 28% and appreciably improved mean CEC, Ca, and Mg levels over the values for the bare soils. The percentage of water-stable aggregates >1.0 mm was significantly reduced under bare fallow ( = 27.7%) compared with soils under vegetative cover = 79.3%). The correlation between water-stable aggregates > 1.0 mm and exchangeable aluminum was negative and significant (r = −0.705°) at p = 0.05. There were highly significant treatment effects (P = 0.01) for penetrometer resistance, pore size distribution, water infiltration, water retention and saturated hydraulic conductivity. Grass and legume fallows which protect the soil and guarantee regular additions of organic materials are ecologically sound and socially acceptable components of sustainable agricultural production. Indications, however, are that this degraded tropical Ultisol would require a period exceeding five years under vegetative covers for restoration of its fertility to acceptable productive status. This revised version was published online in June 2006 with corrections to the Cover Date.     

Evaluation of effects of sustained decadal precipitation manipulations on soil carbon stocks

Throughout a 13 year period, the Throughfall Displacement Experiment sustained both increased (+33; wet) and decreased (−33%; dry) throughfall into an upland oak forest in Tennessee. Organic (O) horizon carbon (C) stocks were measured at several occasions before, during and after the experiment and mineral soil C stocks before and after the experiment. In the O horizon, higher C stocks were observed in the dry treatment compared to the ambient and wet, attributable to a combination of enhanced litter inputs and reduced decomposition. No precipitation treatment effects on mineral soil C stocks were found to a depth of 60 cm. Conversely, long-term reductions in surface mineral soil C stocks were surprisingly high for all treatments (3.5–2.7% C in the 0–15 cm layer and from 0.6 to 0.5% in the 15–30 cm layer) over the duration of the experiment. A clear explanation for this temporal trend in C storage was not readily apparent.     

Influence of vegetation cover on evapotranspiration patterns in mountainous areas

The study presents results of calculation of potential evapotranspiration based on vegetation cover and actual solar energy income modeling obtained in the Jalovecky creek experimental hydrological basin in the Western Tatra mountains. Vegetation cover in the basin is represented by Bare rock, Grass, Natural grassland, Coniferous forest and Dwarf pine. Spatial evapotranspiration patterns for vegetation cover were calculated with three different methods build in the SOLEI model. They are Simple regression model, Radiation model by FAO and Penman-Monteith model. Vegetation cover is represented in all mentioned methods by albedo maps derived from the land use grid map. Together with Digital elevation model (DEM) it is the main input value to the SOLEI model. Albedo coefficients influence mainly solar energy income to the slopes. Because the Simple regression model and Radiation model by FAO are mainly based on solar energy income, the shapes of calculated spatial evapotranspiration patterns are similar to solar energy spatial maps. Results obtained from PenmanMonteith model are more closed to vegetation maps.     

Effect of reclamation of sandy soil on some chemical and microbiological properties

The physico-chemical properties of the soil were gradually improved; a progressive increase in silt and clay, moisture equivalent, organic matter, total nitrogen, C : N ratio and cation exchange capacity was observed during reclamation. Microbiological analysis showed that bacteria, actinomycetes and fungi had increased progressively as a result of cultivation. The increase in the microbial counts showed a positive relation with the increase in the organic matter content of the soil. This indicates that one of the limiting factors for microbial proliferation is organic matter. It was also found that the aerobic cellulose-decomposers, nitrifiers, Azotobacter and Clostridia had increased gradually with the cultivation of these soils. The increase of Clostridia was more remarkable than that of Azotobacter.     

The effect of some soil amendments on chemical and microbiological properties of an alkali soil

Summary A representative alkali soil sample from Tal-El-Kebir was treated in pots with different rates of gypsum or sulphur. These amounts were calculated according to the exchangeable sodium present in the soil. Chemical and microbiological properties were studied during reclamation process.Addition of gypsum in appropriate amounts to replace exchangeable sodium on the clay complex is much faster and more superior to the addition of the corresponding amounts of sulphur.Counts of total microbial flora, Azotobacter, nitrifiers, and aerobic cellulose-decomposers increased as the reclamation proceeded, on the other hand, counts of spores of aerobic sporeformers, streptomyces, and clostridia decreased.Cultivation of such reclaimed soils exerted beneficial effect on its microbial flora. Plant vigor which was taken as a resultant of the improvement of the physico-chemical and biological properties of the soil due to reclamation was found to be superior in case of addition of an amount of gypsum equivalent to the amount of adsorbed sodium.     

Responses of soil bacterial and fungal communities to reciprocal transfers of soil between adjacent coniferous forest and meadow vegetation in the Cascade Mountains of Oregon

Little information exists on the responses of soil fungal and bacterial communities in high elevation coniferous forest/open meadow ecosystems of the northwest United States of America to treatments that impact vegetation and soil conditions. An experiment was conducted in which soil cores were reciprocally transplanted between immediately adjacent forests and meadows at two high elevation (∼1,600 m) sites (Carpenter and Lookout) in the H.J. Andrews Experimental Forest located in the Cascade Mountains of Oregon. Half of the cores were placed in PVC pipe (closed) to prevent new root colonization, whereas the other cores were placed in mesh bags (open) to allow recolonization by fine roots. A duplicate set of open and closed soil cores was not transferred between sites and was incubated in place. After 2 year, soil cores were removed and changes in fungal and bacterial biomasses determined using light microscopy, and changes in microbial community composition determined by PLFA analysis, and by length heterogeneity PCR of the internal transcribed spacer region of fungal ribosomal DNA. At both sites soil microbial community structures had responded to treatments after 2 year of incubation. At Carpenter, both fungal and bacterial community structures of forest soil changed significantly in response to transfer from forest to meadow, with the shift in fungal community structure being accompanied by a significant decrease in the PLFA biomarker of fungal biomass,18:2ω6,9. At Lookout, both fungal and bacterial community structures of forest soil changed significantly in response to open versus closed core treatments, with the shift in the fungal community being accompanied by a significant decrease in the 18:2ω6,9 content of closed cores, and the shift in the bacterial community structure being accompanied by a significant increase in bacterial biomass of closed cores. At both sites, fungal community structures of meadow soils changed differently between open and closed cores in response to transfer to forest, and were accompanied by increases in the18:2ω6,9 content of open cores. Although there were no significant treatment effects on the bacterial community structure of meadow soil at either site, bacterial biomass was significantly higher in closed versus open cores regardless of transfer.     

Controls on leaching from coniferous forest floor microcosms

Summary Studies were conducted with coniferous forest floor microcosms to examine the potential influence of acid precipitation, temperature changes, and plant uptake upon the chemistry of soil leachate solutions. The experimental design included two temperatures and three different simulated throughfall chemistry treatments. When the acidity of throughfall inputs to the microscosms increased, the forest floors exhibited increased leaching losses of calcium, magensium, potassium, and ammonium. The fact that aluminum losses did not incrase correspondingly suggested that there may be a kinetic lag in the mobilization and leaching of aluminum. When microcosms were exposed to warmer temperatures, percolates showed increased leaching losses of calcium, potassium, ammonium, sulfate, nitrate, and organic anions. Forest floor microcosms exposed to simulated average field conditions behaved very much like field plots under the same environmental conditions; however, there were predictable differences in leaching losses between laboratory and field systems for those ions which are strongly controlled by plant uptake. In general, the exclusion of plant uptake from microcosms resulted in increased leaching of potassium, nitrate, ammonium. and sulfate relative to field plots.     

Effectiveness of natural protected areas to prevent land use and land cover change in Mexico

This study evaluated the extent to which natural protected areas (NPAs) in Mexico have been effective for preventing land use/land cover change, considered as a major cause of other degradation processes. We developed an effectiveness index including NPA percentage of transformed areas (agriculture, induced vegetation, forestry plantations, and human settlements) in 2002, the rate and absolute extent of change in these areas (1993–2002), the comparison between rates of change observed inside the NPA and in an equivalent surrounding area, and between the NPA and the state(s) in which it is located. We chose 69 terrestrial federal NPAs, decreed before 1997, that were larger than 1,000 ha, not urban/reforested with non-native vegetation, not islands and not coastal strips, and estimated the extent of transformed areas using 1993 and 2002 land use/land cover maps. Over 54% of NPAs were effective, and were heterogeneously distributed by management categories: 65% of Biosphere Reserves, 53% of Flora and Fauna Protection Areas, and 45% of National Parks. 23% of NPAs were regarded as weakly effective, and the remaining 23% as non-effective. We recognize the importance of NPAs as a relevant conservation instrument, as half of NPAs analyzed (particularly biosphere reserves) prevented natural vegetation loss compared with their geographic context. Our results suggest that conservation based on NPAs in Mexico still faces significant challenges. Our approach can be expanded for evaluating the effectiveness of NPA in other regions, as land use/land cover maps are now available almost worldwide.     

Impact of spruce forest and grass vegetation cover on soil micromorphology and hydraulic properties of organic matter horizon

Two organic matter horizons developed under a spruce forest and grass vegetation were chosen to demonstrate the impact of a different vegetation cover on the micromorphology, porous system and hydraulic properties of surface soils. Micromorphological studies showed that the decomposed organic material in the organic matter horizon under the grass vegetation was more compact compared to the decomposed organic material in the organic matter horizon under the spruce forest. The detected soil porous system in the organic matter horizon under the spruce forest consisted of two clusters of pores with different diameters that were highly connected within and between both clusters. The soil porous system in the organic matter horizon under the grass vegetation consisted of one cluster of pores with the larger diameters and isolated pores with the smaller diameter. The retention ability of the organic matter horizon under the grass vegetation was higher than the retention ability of the organic matter horizon under the spruce forest. Presented at the International Conference on Bioclimatology and Natural Hazards, Poľana nad Detvou, Slovakia, 17–20 September 2007.     

Influence of tree species and ground vegetation on nitrification in an acid forest soil

Soil N transformations were studied at Ironhill, near Liphook, UK as part of a forest fumigation experiment. Nitrification potential was measured in a humoferric podzol soil, of pH 3 (in 0.01 M CaCl₂). An initial experiment into nitrogen mineralisation potential indicated that nitrification was linked strongly to the species of coniferous tree growing in the soil. Transfer of soil solution between soils had no influence on mineralisation potential and allelopathic effects of the trees were not demonstrated. The initial finding was attributed subsequently to the type of ground vegetation and its management. Attempts to reproduce soil conditions, which promoted nitrification, were partially successful.Soil, from the Ironhill site, was incubated with various nitrogenous substrates and other nutrients and sources of carbon to test whether heterotrophs were responsible for nitrification. Organic N (which was ammonified) promoted nitrification, but the addition of ammonium was inhibitory unless supplied with a readily available carbon source such as acetate. Nitrification potential was unaffected when soils were incubated with an inhibitor of autotrophic nitrification. The results of these experiments supported strongly the hypothesis that heterotrophic organisms were responsible for nitrification in this soil.     

Developing a disturbance index for five East African forests using GIS to analyse historical forest use as an important driver of current land use/cover

A means of deriving a disturbance index reflecting forest use history is demonstrated here to establish a disturbance gradient and enable comparison of different forest areas within and across individual forests. Detailed reference is made to Kakamega Forest in western Kenya for which a long‐term time series has been established, although the study is spread to four further forests in Kenya and Uganda. A wide variety of sources are drawn upon for spatially resolved data that are integrated in a geographic information system. Three indices are derived: for commercial disturbance, local disturbance, and forest cover change. Results show a wide range of disturbance values (from low to heavy) for the research sites within Kakamega Forest, while results for Budongo and Mabira Forest sites show low and moderate levels, respectively. Correlations of low disturbance levels with nature or national reserves appear to be marked, while a correlation of disturbance with differing management authority is also suggested with Kenya Wildlife Service achieving the lowest disturbance levels. Results from the index are reviewed against other means of estimating disturbance with the conclusion that disturbance evaluations should be both spatially resolved and long‐term in nature.     

Effect of soil salinity on the electro-chemical and chemical kinetics of some plant nutrients in submerged soils

Summary The electro-chemical and chemical kinetics of six California rice soils were significantly influenced by the presence of salts up to an EC of 9 mmhos/cm in saturation extract (EC_e). Subsamples of each soil salinity treatment were incubated for periods up to 10 weeks after flooding. Most of the changes in Eh and pH values took place in the first 3–4 weeks after submergence. Salinity decreased pH values, but slightly increased the redox-potential. Both ammonification and nitrate reduction were significantly decreased, by increasing soil salinity. Salinity up to 9 mmhos/cm did not affect levels of Bray and Kurtz extractable P, but increased the water extractable Ca, Mg, K and Mn. In DTPA extract, salinity in incubated soils had no effect on Zn in 4 soils, but it decreased Fe in acid and neutral soils. Possible explanations for the electro-chemical and chemical kinetic changes due to flooding and salinity are discussed.     

Effect of brewery sludge amendments on some chemical properties of acid soil in pot experiments

A laboratory experiment was performed for an incubation period of 120 days in order to evaluate the changes in chemical properties of an acid soil amended with 0, 15, 30, 60 and 120 t ha-' of brewery sludge (BS). Increasing BS rates and incubation time reduced pH of the soil by 0.3-0.5 unit with respect to the control while soluble salts increased from 0.11 to 0.80 dS m(-1). Organic C, exchangeable cations, soluble cations and anions, NH4+-N and NO3--N contents of the amended soil increased as BS rates increased. In addition, BS application caused a slight increase in cation exchange capacity (CEC) and a slight decrease in exchangeable acidity.     

Relations of soil properties to topography and vegetation in a subtropical rain forest in southern Taiwan

Soil chemical properties for a subtropical rain forest in the Nanjenshan Reserve, southern Taiwan, were examined to determine soil-landscape and soil-vegetation relationships. Soil sampling sites were separated into four groups based on landscape features and exposure to the prevailing northeasterly monsoon winds. Corresponding vegetation types were delimited along the first DCA axis. The forest showed a drastic change both in structure and floristic composition along the wind-stress gradient. Redundancy analysis (RDA) showed that both topographic variables and vegetation types were needed to explain the variation in soil data. Soil properties that differed significantly among landforms were pH, available N, CEC, exchangeable Al, K, Ca and Mg. Levels of pH, exchangeable Ca and Mg increased in a downslope direction, and exchangeable Al tended to be higher in the upper slope soils. These trends pointed to the importance of slope processes in redistribution of soil minerals. The main differences in soil properties attributed to the influence of the occupying vegetation were apparently aspect dependent. The contents of available N, exchangeable K, and CEC in the 0–40 cm depth of soils under windward low-stature (mostly sclerophyllous) forest were consistently lower compared to those under the leeward forest. For a given catena, however, soil variability associated with vegetation differences seemed to be confounded by the slope processes.     

牧草覆盖对坡面土壤矿质氮素流失的影响

利用室内模拟降雨试验,探讨了降雨、地表径流以及土壤矿质氮素有效作用深度（effective depth of interaction,EDI）的确定方法,研究了牧草覆盖对土壤矿质氮素EDI和地表流失的影响．结果表明,牧草覆盖增加了地表径流与表层土壤的相互作用,导致水土混合体深度增加,较深土层的土壤矿质氮通过溶解和解吸作用、对流-扩散作用等方式进入到地表径流中,矿质氮EDI增加．覆盖度越大,EDI值越大．与裸地相比,60％、80％和100％覆盖度处理中径流矿质氮平均浓度分别增加了34．52％、32．67％和6．00％,地表径流量分别减少了4．72％、9．84％和12．89％,侵蚀泥沙量分别减少了83．55％、87．11％和89．01％．60％和100％覆盖度处理的矿质氮地表流失总量分别为裸地处理的95．73％和84．05％,而80％覆盖度处理则为裸地处理的109．04％．草地植被对矿质氮素地表流失有“双重效应”：加剧了矿质氮向地表径流中的释放,使径流养分浓度高于裸地浓度;不同程度地减少了地表径流量和泥沙量及其养分含量．两种效应共同决定了土壤矿质氮素的地表流失量．     

The effects of flooding for rice culture on soil chemical properties and subsequent maize growth

Summary The effects of flooding and lowland rice culture on soil chemical properties and subsequent maize growth were investigated in two contrasting rice soils of S.E. Australia. The effects of incorporating rice straw, either during or after flooding were also studied. The experiment was conducted in a glasshouse with the use of large intact soil cores.Previous flooding markedly reduced maize growth, leaf P concentration and P uptake, despite the application of a large quantity of P fertilizer after drainage. Soil analyses showed that previous flooding increased the Langmuir sorption terms for maximum P sorption and bonding energy. The availability of P was more closely related to the bonding energy between soil and P than to the capacity of the soils to sorb P. The increases, in the P sorption parameters, were associated with decreases in the crystallinity of the free iron oxides as determined by their oxalate solubility. It was concluded that depressed P supply to maize sown in previously flooded soils was due to stronger P sorption by the drained soils, rather than to P immobilization during flooding.Rice plants grown during flooding reduced the amount of N available to the subsequent maize crop, but did not significantly affect P availability. Rice straw added during flooding did not affect subsequent maize growth, but when added after flooding caused microbial immobilization of N.Salts, Fe or Mn from previous flooding did not affect maize growth.