八达岭山地次生林土壤养分与磷酸酶活性研究

 为探讨北京八达岭山地土壤肥力状况,以黑桦、糠椴、核桃楸3种次生林为对象,对其土壤养分和磷酸酶活性进行研究。结果表明:土壤养分有明显的表聚效应;土壤全磷含量仅为0.39～0.66g.kg-1之间,有可能出现缺磷现象;土壤磷酸酶的活性以酸性磷酸酶为主,呈垂直递减分布规律;各种土壤养分和磷酸酶活性均有明显的根际效应,根系/本土比值在1.02～5.25之间。用SPSS软件进行分析表明,土壤磷酸酶活性与土壤pH、有机质、全氮、有效氮、有效磷和速效钾显著正相关,可以作为土壤肥力评价的一个指标。     

Profile carbon and nutrient levels and management effect on soil quality indicators in the Mardi watershed of Nepal

Abstract

Soil organic carbon (SOC) and nutrient stocks in the soil profile (0–80 cm) in four dominant land uses [forest, upland maize and millet (Bari), irrigated rice (Khet), and grazed systems)] and 0–15 cm depth along elevation gradient 1000 to 3000 m, and aspects in the Mardi watershed were measured. Soil properties at 0–15 cm depth were also measured in undisturbed forest, forest with free grazed system, managed forest, and grassland to compare the soil quality index (SQI) of topsoils. The SOC and nutrient concentration decreased with increasing profile depth. The SOC and N contents in the 0–15 cm depth of forest soils were significantly greater than the corresponding depth in upland maize and millet, irrigated rice, and grazed systems. On the other hand, available P and K concentrations at the same depth were significantly greater in upland maize and millet compared to irrigated rice, grazed system, and forest land uses. The SOC and N stocks (0–15 cm) increased from agricultural land at the valley bottom at about 1000 m above mean sea level (a.s.l.) (24 and 3 Mg ha^?1) compared to undisturbed forest (74 and 5.9 Mg ha^?1) at 2600 m a.s.l, demonstrating the effects of cover and elevation. Both SOC and N stocks decreased sharply in grassland (54 and 4.5 Mg ha^?1) at elevations of 2600 to 2800 m a.s.l. compared with undisturbed forest. Above 2800 m a.s.l. the cover type changed from grass to coniferous forest, and the SOC and N stocks steadily increased at the summit level (3200 m a.s.l.) to 65 and 6.9 Mg ha^?1, respectively. Slope and aspect significantly affected SOC with the northwest aspect having significantly higher concentrations (46 g kg^?1) than other aspects. Similarly, SOC concentration at the lowest slope position (39 g kg^?1) was significantly higher than the middle or upper positions (25 and 13 g kg^?1). Integrated soil quality index (SQI) values varied from 0.17 to 0.69 for different land uses, being highest for undisturbed forest and lowest for irrigated rice. The SQI demonstrated the degradation status of land uses in the following ascending order: irrigated rice?>?grazed system?>?forest with free grazing?>?upland maize and millet?>?managed forest?>?grass land?>?undisturbed forest. The irrigated rice, grazed system, upland maize and millet, and freely grazed forestlands need immediate attention to minimize further deterioration of soil quality in these land uses.     

Impact of a ski basin on a mountain watershed

The input of heavy metals by automobile exhaust pollution associated with the ski basin activities is the primary concern of this paper. Stream, snowpack and lichen samples were collected and analyzed for Pb, Zn, and Cu. Some lichen samples were also analyzed for Ca, Mg, Na, K, Fe, and Mn, as well as Pb, Zn, and Cu. Snowpack samples from roadside areas demonstrated increased levels of Pb and Cu in comparison to areas up to 180 m from the road, but heavy metal levels at more remote areas were comparable to roadside levels. In all snow samples the heavy metals associated with the particulate matter was the major form of all inputs. Heavy metals in streams were also highly correlated with the particulate matter content. Heavy metal inputs to the watershed were greater than stream export, indicating an accumulation of heavy metals by the system. The forest canopy appears to be the major factor in the accumulation of heavy metals, probably due to better interception and impaction of the particulate matter by the canopy.     

Effects of forest liming on the nutrient status of podzolic soils in Finland

The results of 40 long-term liming experiments in Scots pine and Norway spruce stands on mineral soil sites of varying fertility are reviewed in this paper. Limestone was broadcast at a dose of 2 t ha^–1 at the end of the 1950s and sampling was carried out at the end of the 1970s. Liming resulted in considerable accumulation (10 to 50% increase) of organic matter in the humus layer, but no changes in the mineral soil. The C/N ratio of the humus increased on the most productive sites. Liming brought about a long-term decrease in acidity of the humus layer on all site types, as well as a decrease in the mineral soil (0 to 10 cm) of the least productive ones. There was also a corresponding increase in base saturation. There was considerable accumulation of B and Mn in the humus layer. Sulphur was found to have been immobilized to a considerable extent in the humus layer, presumably as Al sulfate. Liming at fairly low doses (e.g. 2 t ha^–1) thus seems to be sufficient to counteract any future increases in soil acidification without bringing about any adverse effects (apart from perhaps B levels) on the nutrient status of the soil.     

Effects of forest liming on the nutrient status of podzolic soils in Finland

The results of 40 long-term liming experiments in Scots pine and Norway spruce stands on mineral soil sites of varying fertility are reviewed in this paper. Limestone was broadcast at a dose of 2 t ha^?1 at the end of the 1950s and sampling was carried out at the end of the 1970s. Liming resulted in considerable accumulation (10 to 50% increase) of organic matter in the humus layer, but no changes in the mineral soil. The C/N ratio of the humus increased on the most productive sites. Liming brought about a long-term decrease in acidity of the humus layer on all site types, as well as a decrease in the mineral soil (0 to 10 cm) of the least productive ones. There was also a corresponding increase in base saturation. There was considerable accumulation of B and Mn in the humus layer. Sulphur was found to have been immobilized to a considerable extent in the humus layer, presumably as Al sulfate. Liming at fairly low doses (e.g. 2 t ha^?1) thus seems to be sufficient to counteract any future increases in soil acidification without bringing about any adverse effects (apart from perhaps B levels) on the nutrient status of the soil.     

Factors determining soil nutrient distribution in a small-scaled watershed in the purple soil region of Sichuan Province, China

Determining soil nutrient distribution is critical to identify sites which are at risk of N and P loading. Equally important are determining factors that influence such distribution (e.g. land use, land management, topography, etc.). In this research, soil nutrient distribution and its influencing factors were studied in a small-scaled watershed in the purple soil region of Sichuan Province, China. The watershed is 1.3 km² with a complex land management system including agriculture and forestry. Surface soil samples (0–20 cm) from 48 sites within the watershed were collected in the spring of 1999 and analysed for chemical properties. When spatial distribution patterns of soil organic matter and soil nutrients were considered, several patterns were evident. Soil organic matter and total nitrogen coincided with high soil nutrients in the center of the watershed. Total phosphorus was linked to low soil nutrient contents on hilltops, while total potassium was characterized by low variability and high soil nutrient content throughout the watershed. Water-soluble nutrients in soils were highly variable throughout the watershed. Results of this study indicate that land use, topography and other variables play important roles in controlling the spatial distribution of most soil nutrients. However, the relative roles of these indices were nutrient specific. The relationship was therefore complex. Land use, silt, and sand content contributed to a high level of heterogeneity for soil organic matter and total nitrogen with the former being the dominant factor. Land use, particle size distribution (silt and sand) and topographic factors (slope and elevation) contributed to the variability of total phosphorus. However, particle size distribution and topographic factors were the dominant factors affecting total phosphorus. Elevation influenced the concentration of total potassium and land use controlled the concentration of dissolved phosphorous. No significant relationship was found between the studied characteristics and nitrate nitrogen.     

A systems analysis of soil and forest degradation in a mid‐hill watershed of Nepal using a bio‐economic model

Forest degradation, manifested through decline in forest cover, and the resulting soil erosion and organic carbon losses, is a serious problem caused by a complex coupling of bio‐physical, socio‐economic and technological factors in the Himalayan watersheds. Greater understanding of the linkages between these factors requires a systems approach. We have proposed such an approach using a bio‐economic model to explore the system behaviour of forest degradation, soil erosion, and soil C losses in the forest areas. The outcome of the model simulation over a 20‐year period indicates that soil erosion and C loss rates may increase more than four‐fold by the year 2020 under the existing socio‐economic and biophysical regime (the base scenario). Reductions in the population growth rate, introduction of improved agricultural technology and increase in the prices of major agricultural crops can help slow down the rates of forest decline, soil erosion and C loss or even stabilize or reverse them. The results suggest that economic incentives may be highly effective in the reduction of soil loss, as well as C release to the atmosphere. Copyright © 2005 John Wiley & Sons, Ltd.     

Foliar status and factors affecting foliar and soil chemistry in a natural aleppo pine forest

The foliar status and the factors affecting the foliar chemistry in a natural Aleppo pine forest grown on calcareous soils in Greece were examined. It was found that the Aleppo pine needles had significantly higher calcium (Ca) concentrations, but significantly lower concentrations of magnesium (Mg), potassium (K), phosphorus (P), iron (Fe) and manganese (Mn) than the respective average concentrations of natural Aleppo pine forests in Spain. It was also found that only foliar Ca and Mn had a significant correlation with the exchangeable Ca and available Mn in soils, respectively. Principal component analysis showed that the nature of the calcareous parent material, (colluvial rocks and hard limestones) were the main factors affecting both foliar and soil chemistry. This finding is important as colluvial soils always coexist with other soil types in hilly and mountainous regions containing calcareous material.     

Factors affecting snowmelt streamwater chemistry in the black forest (West Germany)

Site conditions such as parent material, soils, but also vegetation cover and elevation explain the varying snowmelt streamwater chemistry in the Black Forest. The results are derived from multiple statistical analysis of a regional survey of 104 small mountain streams in the first phase of snowmelt in spring 1984. Cluster analysis classifies the snowmelt streams into three groups which are clearly linked to bedrock geology. Factor analysis finds podsolization, weathering and mineralization processes in the soils of the catchments to have most impact even under snowmelt conditions. There is no evidence that acidic atmospheric deposition directly affects the acidity of the investigated streams. However, the deposition rates are low compared to certain other regions in Central Europe. In areas with podsolic soils the organic soil layer plays a key role in the acidity and mobilization of Al and heavy metals. This is shown in the high correlations between pH, DOC, UV-extinction, color and metal concentrations. Because the concentrations of DOC are low (<10 mg.L^?1) and an anion deficit cannot be found, it is assumed that water acidity is not caused by dissolved humic acids, but by cations exchanged in the organic layer of acidic soils. Streamwater chemistry in areas with brown earth soil types is mainly affected by leaching of basic cations in the mineral soil horizons and mineral weathering.     

Change in the acid-base status of an appalachian mountain catchment following forest defoliation by the gypsy moth

Infestation by the gypsy moth (Lymantria dispar) can alter biogeochemical conditions in affected catchments. Stream-water concentration data obtained over the period of 1980–1993 for White Oak Run, a stream in Shenandoah National Park, Va., indicate that change in catchment acid-base status is associated with forest defoliation by the moth larva. Stream-water concentration changes following defoliation included increasing concentrations of strong-acid anions, base-cations, and hydrogen ion, as well as decreasing concentrations of acid-neutralization capacity (ANC) and sulfate. The largest change was in the concentration of nitrate; annual discharge-weighted mean concentrations increased from predefoliation levels consistently less than 5 μeq L^?1 to postdefoliation levels greater than 50 μeq L^?1. An intensification of acidification was indicated by record-high hydrogen ion concentrations and record-low ANC concentrations. The long-term biogeochemical implications of the infestation are uncertain due to the nonlinearity of the observed responses and unknown patterns of recovery and recurrence.     

Fluxes of methane and carbon dioxide from soil under forest, grazing land, irrigated rice and rainfed field crops in a watershed of Nepal

Field evolution of CH₄ and CO₂ from soils under four dominant land uses in the Mardi watershed, western Nepal, were monitored at 15-day intervals for 1 year using closed chamber techniques. The CH₄ oxidation rate (mean±SE, g CH₄ m^–2 h^–1) in the forest (22.8±6) was significantly higher than under grazing land (14±2) and an upland rainfed maize and millet system (Bari) (2.6±0.9). Irrigated rice fields (Khet) showed an oxidation rate of 6±0.8 g CH₄ m^–2 h^–1 in the dry season (December–May) but emitted a mean rate of 131 g CH₄ m^–2 h^–1 in the rainy season and autumn (June–October). The evolution of CO₂ ranged from 10 mg CO₂ m^–2 h^–1 in the Bari in January to 1,610 mg CO₂ m^–2 h^–1 in the forest in July. Higher evolution of CO₂ (mean±SE, mg CO₂ m^–2 h^–1) was observed in the Bari (399±39) and forest (357±36) compared to Khet (246±25) and grazing (206±20) lands. The annual emission of CO₂ evolution varied from 86.6 to 1,836 g CO₂ m^–2 year^–1. The activation energy for CH₄ and CO₂ varied between 16–283 and 80–117 kJ mol^–1, respectively. The estimated temperature coefficient for CO₂ emission varied from 2.5 to 5.0. Temperature explained 46–51% of the variation in CO₂ evolution, whereas it explained only 4–36% of the variation in CH₄ evolution.     

山区小流域生态恢复研究进展

 山区小流域恢复是一项复杂的系统工程,山区流域生态恢复的对象是山区流域生态经济系统,目前国内已开展山区小流域生态恢复的理论和实践研究。从生态恢复的理论基础、实践过程、生态恢复的条件和目标,以及生态恢复的生态效应方面进行讨论,以期对目前的研究有所帮助。     

Decomposition and nutrient content of litter in a fertilized eucalypt forest

The decomposition and nutrient content of litter was studied for 2 years in regrowth Eucalyptus diversicolor forest to which N (0, 200 kg ha^-1 year^-1) and P (0, 30, 200 kg ha^-1) had been applied. The P addition increased, and the N addition decreased, the rate of dry weight loss of decomposing litter. Analysis of the coefficients of a double exponential decay model with components describing the release of labile and resistant fractions indicated that decomposition of the resistant component of litter was most affected by the fertilizer additions. Treatment with N reduced the rate of loss of this component and increased its half-life by approximately 30%, whereas P treatment increased its rate of decay and decreased its half-life by approximately 30%. P accumulated in litter during decomposition. P uptake and retention was greater in P-treated than untreated plots. The application of N reduced P accumulation in litter. An accumulation of N also occurred during decomposition, the amount of N imported into litter being greater on plots treated with N fertilizer. Treatment with N affected the amount of S in decomposing litter. Litter on N-treated plots either accumulated more S or released it more slowly than litter on plots not treated with N. The application of N as NH₄NO₃ decreased forest-floor litter pH, increased litter layer mass (by 15%), and increased the amount of N (by 34%) and S (by 32%) stored in the forest floor. Treatment with P reduced the amount of N (by 22%) stored in the litter layer. The application of 200 kg P ha^-1 in the absence of N increased the store of P in the litter layer by 80%, but when N and P were applied together the amount of P in the litter was not significantly different between P treatments.     

贡嘎山天然林和盐亭人工林土壤侵蚀研究

 为了解长江上游代表性林区土壤侵蚀及相关土壤性质对土壤侵蚀的影响,通过取样分析、计算土壤侵蚀间接指标及其与有机质含量、土壤团聚体稳定性、土壤渗透性能等因素的定量关系。结果表明:长江上游区域贡嘎山亚高山天然林区表层土壤侵蚀率较小,盐亭紫色土丘陵区人工林区表层土壤侵蚀率较大。相关系数和回归分析表明土壤有机质含量、土壤团聚体稳定性、土壤渗透性能等因素对土壤侵蚀率具有较大影响,均达到了0.01极显著性置信水平。     

Factors affecting the formation of dark, thick epipedons beneath forest vegetation, Michigan, USA

Extremely gravelly, coarse-textured soils (frigid Udorthents and Rendolls) with different thicknesses of Oa+A horizon sequences were studied to identify factors that have influenced their genesis. These well-drained, forested soils occur on geomorphic surfaces that range in age from 3200 to 6000 years BP. The soils all have more than 500 g kg^?1 coarse fragments by mass; most contain less than 300 g kg^?1 fine earth. In the lower solum of most pedons, content of cobbles increases and amount of fine earth decreases. Most coarse fragments are dolomite and chert. Thick, gravelly Oa and A horizons are weakly correlated with parent material characteristics such as high pH and carbonate contents. Organic matter concentrations in, and thicknesses of, upper horizons are enhanced by an abundance of coarse clasts, as soils with the most gravel exhibited the thickest and darkest epipedons. Relatively high amounts of crystalline clasts in the fine gravel fraction, as well as feldspathic minerals in the fine sands, also appear to promote the development of mollic epipedons.     

Experimental warming effects on the microbial community of a temperate mountain forest soil

Soil microbial communities mediate the decomposition of soil organic matter (SOM). The amount of carbon (C) that is respired leaves the soil as CO₂ (soil respiration) and causes one of the greatest fluxes in the global carbon cycle. How soil microbial communities will respond to global warming, however, is not well understood. To elucidate the effect of warming on the microbial community we analyzed soil from the soil warming experiment Achenkirch, Austria. Soil of a mature spruce forest was warmed by 4 °C during snow-free seasons since 2004. Repeated soil sampling from control and warmed plots took place from 2008 until 2010. We monitored microbial biomass C and nitrogen (N). Microbial community composition was assessed by phospholipid fatty acid analysis (PLFA) and by quantitative real time polymerase chain reaction (qPCR) of ribosomal RNA genes. Microbial metabolic activity was estimated by soil respiration to biomass ratios and RNA to DNA ratios. Soil warming did not affect microbial biomass, nor did warming affect the abundances of most microbial groups. Warming significantly enhanced microbial metabolic activity in terms of soil respiration per amount of microbial biomass C. Microbial stress biomarkers were elevated in warmed plots. In summary, the 4 °C increase in soil temperature during the snow-free season had no influence on microbial community composition and biomass but strongly increased microbial metabolic activity and hence reduced carbon use efficiency.     

重庆石灰岩地区3种林分林下枯落物持水能力比较

通过对重庆石灰岩地区慈竹林、柏木林、女贞林3种林分林下枯落物调查及其风干和持水试验,比较了不同林分林下枯落物吸持降水能力的强弱.结果表明:慈竹林下枯落物厚度最大(5.83cm),而后依次为女贞林(1.77cm)和柏木林(1.60cm);3种林分林下枯落物的储量为慈竹林(13870kg·cm-2)和柏木林(11780kg·hm-2)大于女贞林(5130kg·hm-2);自然含水率为慈竹林(188.3%)和女贞林(194.9%)大于柏木林(150.4%);最大吸水率为女贞林(229.8%)＞慈竹林(195.3%)＞柏木林(155.6%);风干时间以慈竹林最长;最初4d的失水速率为女贞林＞慈竹林＞柏木林;最大吸水速率为慈竹林＞女贞林＞柏木林.从而推断,各林分单位质量枯落物的吸持降水率为竹林(慈竹林)＞阔叶林(女贞)＞针叶林(柏木);单位面积枯落物总的吸持降水量为慈竹林＞柏木林＞女贞林.     

Factors affecting sulfate adsorption,organic sulfur formation,and mobilization in forest and grassland spodosols

Forest and grassland soils that contained varying amounts of Fe and Al were collected from England and Wales. Fractionation of free Fe and Al was accomplished to determine which components affected sulfate adsorption. Organic Fe and Al were the dominant fractions in most soil horizons and high amounts of these organically bound metals and, to some extent, crystalline Fe oxide were associated with high sulfate adsorption potentials. These adsorption potentials reflected naturally occurring amounts of absorbed sulfate and ester sulfate. Overall, the C content exhibited a positive relationship with sulfate adsorption potentials. Soils with a high C content also exhibited high rates of organic S formation. The rate of organic S mobilization was greater in soils with higher amounts of soluble sulfate. Organic S was the largest pool and, typically, sulfonate S was the most abundant constituent of the organic pool.     

Factors limiting denitrification in a Mediterranean riparian forest

In situ denitrification (DNT) and denitrification enzyme activity (DEA) were measured in a Mediterranean riparian forest soil during two periods under contrasting soil moisture conditions in order to investigate the factors that affect denitrification through the year. Results showed that in summer, soil moisture limited denitrification throughout the entire soil profile, whereas in winter, anaerobic conditions in the soil were more favourable for denitrifiers. The potential for denitrification was larger at shallow depths (<30 cm), and neither nitrate nor organic carbon limited denitrification significantly. Some denitrification was measured during winter at depths below 30 cm, suggesting that a reduction of groundwater nitrate could occur in some areas of this riparian forest during the wet period. In summer, low denitrification, together with high mineralization rates, brought about an increase of soil N, which could be leached to the stream channel during rainfall events. This study suggests that Mediterranean riparian soils act as sources or sinks of dissolved nitrogen depending on the period of the year.     

太湖流域农田肥料投入与养分平衡状况分析

通过对太湖流域9个县市的700多份实地作物施肥情况调查,并结合相关统计资料,综合分析了太湖流域目前农田肥料投入以及氮、磷养分的平衡(盈亏)状况,重点进行了大田作物和蔬菜等经济作物氮、磷肥料投入量、养分平衡状况以及有机肥和化肥投入比较。分析结果表明,蔬菜等经济作物的养分投入和盈余状况整体上均高于粮食、油料作物,而大宗粮食、油料作物的周年养分投入支出基本平衡。蔬菜播种面积尽管只占到所统计4类作物总播种面积的30%,但是其施磷量却达总施磷量的50%以上,而磷素是造成我国水体富营养化的关键因素之一,加之目前经济作物的种植面积日益扩大,对水环境的影响不容忽视。