氮沉降下滇中华山松林土壤特性变化对土壤呼吸的影响

研究氮(N)沉降背景下湿、干季土壤理化性质、微生物特征及酶活性变化对土壤呼吸影响,阐明N沉降下土壤呼吸的季节变化特征以及土壤呼吸与土壤特性之间的动态响应,为滇中亚高山森林生态系统C循环研究提供科学依据。选择云南玉溪磨盘山华山松人工林为研究对象,研究模拟N沉降下(对照-CK,0 g·m^(-2)·a^(-1)、低N-LN,10 g·m^(-2)·a^(-1)、中N-MN,20 g·m^(-2)·a^(-1)、高N-HN,25 g·m^(-2)·a^(-1))湿(7月)、干(1月)季土壤理化性质、酶活性、土壤微生物数量、微生物量C(MBC)、微生物量N(MBN)以及土壤呼吸变化特征,阐明N沉降下土壤呼吸与土壤特性的动态变化特征。结果表明,1)湿季时,与CK相比,各N沉降处理下土壤TP、TK、NH_(4)^(+)-N、NO_(3)^(-)-N、AN均显著增加(13.1%~95.5%);干季时,TN、TP、NH_(4)^(+)-N、AN显著增加(26.9%~69.6%)。2)在湿干两季过氧化氢酶活性均在各N处理下显著降低(14.8%~61.8%),多酚氧化酶活性则在湿季各N处理下降低(15.0%~52.2%),蔗糖酶及脲酶活性在不同季节分别在LN、HN处理以及HN处理下显著降低(7.1%~48.9%和10.5%~16.7%);在湿干季时,HN处理降低了土壤微生物数量、MBC、MBN(10.3%~49.8%)。3)N沉降抑制了华山松林土壤呼吸,且随着施N浓度的增加,土壤呼吸抑制作用越明显;土壤呼吸与湿干季土壤温度呈正显著相关;各N处理均降低了土壤温度敏感性Q_(10)(2.93%~36.86%)。综上,N沉降抑制了华山松林的土壤呼吸,且并未改变华山松林土壤呼吸的季节变化规律与日变化规律。

贡嘎山东坡亚高山不同林地土壤水分特性与生态环境效应

森林土壤水分特性,包括水分的渗透与蒸发、保持与贮存等对森林生态环境都有重要意义。本文研究了长江上游贡嘎山亚高山不同森林类型土壤的水分特征及其生态环境作用,结果表明:成熟林、过熟林土壤在储水、渗透、容水、蒸发和持水特性等多数方面利于保持和改善生态环境,次生或林分单一森林类型次之,林木皆伐后最差。研究区以成熟林和过熟林为主,生态环境保护较好。尽管该区与长江上游其它地区一样同具自然地理条件差、生态环境脆弱的特征,但由于该区森林植被和环境得到了有效保护,土壤水分特性好,促进了森林生态系统的良性循环,生态环境问题得到进一步改善。

Soil Physical and Chemical Properties of Five Subtropical Forests in Lingao of Hainan

With 5 types of typical forests as research object, the physical and chemical properties of different types of forests were analyzed by sample plot investigation method. The results showed that： the soil total porosity was the highest in the Casuarina equisetifolia forest （46.168%）, but the lowest in the Encalyptus robusta forest （39.46%）. The soil capillary porosity was the highest in the Acacia mangium forest （22.57%）, but the lowest in the secondary forest （18.95%）. The soil water content was the highest in the C. equisetifolia forest, with a mean value of 27.85%, but the lowest in the secondary forest, with a mean value of 4.34%. The soil pH values were in the range of 4.81-6.59, the soils in the A. mangium forest, C. equisetifolia forest and E. robusta forest were strongly acidic （pH 4.5-5.5）, and the soils in the secondary forest and C. nucifera forest were weakly acidic. The soils had organic matter contents in the range of 0.34-28.68 g/kg, and showed an order of A. mangium forest〉C. equisetifolia forest〉E. robusta forest〉secondary forest〉C. nucifera forest, with a decreasing trend with the soil depth increasing. The soil total N contents were in the range of 0.10-1.63 g/kg, the A. mangium forest showed the highest soil total N contents, while the C. nucifera forest exhibited the lowest soil total N contents; the soil total P contents were in the range of 0.21-1.74 g/kg, and the E. robusta forest had the highest soil total P contents; and the soil total K contents were in the range of 0.16-2.15 g/kg, and the A. mangium forest exhibited the highest soil total K contents. The soil available P contents were in the range of 0.98-132.46 mg/kg; and the secondary forests had the highest soil available P contents; and the soil rapidly available K contents were in the range of 3.03-27.35 mg/kg, and the C. nucifera forest exhibited the highest soil rapidly available K contents. The soil ammonium N contents were in the range of 1.38-5.15 mg/kg, and the nitrate N contents were in the range were in the range of 0.56 -3.51 mg/kg. The A. mangium forest showed the highest soil nitrate N contents （with a mean value of 2.29 mg/kg） and ammonium N contents （with a mean value of 3.93 mg/kg）. For the same forest type, with the increase of soil depth, the nitrate nitrogen and ammonium nitrogen content also showed a decreasing trend.

The influence of elevation on soil properties and forest litter in the Siliceous Moncayo Massif,SW Europe

Understanding the effects of elevation and related factors(climate,vegetation) on the physical and chemical soil properties can help to predict changes in response to future climate or afforestation forcings.This work aims to contribute to the knowledge of soil evolution and the classification of forest soils in relation to elevation in the montane stage,with special attention to podzolization and humus forms.The northern flank of the Moncayo Massif(Iberian Range,SW Europe) provides a unique opportunity to study a forest soils catena within a consistent quartzitic parent material over a relatively steep elevation gradient.With increasing elevation,pH,base saturation,exchangeable potassium,and fine silt-sized particles decrease significantly,while organic matter,the C/N ratio,soil aggregate stability,water repellency and coarse sand-sized particles increase significantly.The soil profiles shared a set of properties in all horizons:loamy-skeletal particle-size,extreme acidity(pH-H_2O<5.6) and low base saturation(<50%).The most prevalent soil forming processes in the catena include topsoil organic matter accumulation and even podzolization,which increases with elevation.From the upper to lower landscape positions of wooded montane stage of the Moncayo Massif,mull-moder-mor humus and an UmbrisolCambisol-Podzol soil unit sequences were found.

Vegetation Geo-climatic Zonation in the Rocky Mountains, Northern Utah, USA

We developed a vegetation geo-climatic zonation incorporating the zonal concept, gradient and discriminant analysis in Wasatch Range, northern Utah, USA. Mountainous forest ecosystems were sampled and described by vegetation, physiographic features and soil properties. The Snowpack Telemetry and National Weather Service Cooperative Observer Program weather station networks were used to approximate the climate of sample plots. We analysed vegetation and environmental data using clustering, ordination, classification, and ANOVA techniques to reveal environmental gradients affecting a broad vegetation pattern and discriminate these gradients. The specific objective was to assess and classify the response of the complex vegetation to those environmental factors operating at a coarse-scale climatic level. Ordination revealed the dominant role of regional, altitude-based climate in the area. Based on vegetation physiognomy, represented by five tree species, climatic data and taxonomic classification of zonal soils, we identified two vegetation geo-climatic zones:(1) a montane zone, with Rocky Mountain juniper and Douglas-fir; and(2) a subalpine zone, with Engelmann spruce and subalpine fir as climatic climax species. Aspen was excluded from the zonation due to its great ecological amplitude. We found significant differences between the zones in regional climate and landformgeomorphology/soils. Regional climate was represented by elevation, precipitation, and air and soil temperatures; and geomorphology by soil types. This coarse-scale vegetation geo-climatic zonation provides a framework for a comprehensive ecosystem survey, which is missing in the central Rocky Mountains of the United States. The vegetation-geoclimatic zonation represents a conceptual improvement on earlier classifications. This framework explicitly accounts for the influence of the physical environment on the distribution of vegetation within a complex landscape typical of the central Rocky Mountains and in mountain ranges elsewhere.

Shifting cultivation effects on soil fungi and bacterial population in Chittagong Hill Tracts, Bangladesh

A study was conducted at two pair sites of Chittagong Hill Tracts in Bangladesh to find out the effects of shifting cultivation on soil fungi and bacterial population. The first pair of sites with shifting culti-vation and village common forest-managed by indigenous community was at Madhya Para in Rangamati district and the second pair of sites with the shifting cultivated land and village common forest at Ampu Para in Bandarban district of Chittagong Hill Tracts. At both the locations with two different land uses, soil textures in surface （0？10 cm） and sub-surface （10？20 cm） soils varied from sandy loam to sandy clay loam. Soil pH and moisture content were lower in shifting cultivated land com-pared to village common forest. The results also showed that both fungal and bacterial population in surface and subsurface soils was significantly （p ≤ 0.05） lower, in most cases, in shifting cultivated land compared to village common forest at both Madhya Para and Ampu Para. At Ranga-mati and Bandarban in shifting cultivated lands, Colletrotrichum and Fusarium fungi were absent and all the bacterial genus viz. Coccus, Bacillus and Streptococcus common in two different locations with dif-ferent land uses. Common identified fungi at both the land uses and locations were Aspergillus, Rhizopus, Trichoderma and Penicillium. Further study can be done on the other soil biota to understand the extent of environmental deterioration due to shifting cultivation.

Adsorption and Desorption of Mercury(Ⅱ) in Three Forest Soils in Shandong Province,China

As one of the most toxic heavy metals with persistence, bioaccumulation, and toxicity in environment, mercury and its envi- ronmental problems have caused a global concern. To fully understand the behavior and fate of mercury （Hg）（II） in forest soils, a series of batch experiments were conducted to determine the adsorption and desorption characteristics of Hg（II） by three dark brown forest soils from Mount Taishan, Laoshan Mountain, and Fanggan Village in Shandong Province, China. The adsorption solution was prepared using 0.1 mol L-1 NaNO3 as background electrolyte, with Hg（II） at rising concentration gradients of 0.0, 2.0, 4.0, 6.0, 8.0, and 10.0 mg L-1. Fourier transform infrared （FTIR） spectroscopy was adopted to characterize the soil samples and soil-Hg complexes. It was found that Hg（II） adsorption isotherms could be well fitted with both Langmuir and Freundlich equations. The soil from Mount Taishan had the largest potential Hg（II） adsorption capacity, though with less adsorptive intensity. The percentages of Hg（II） desorbed from all soil samples were less than 0.6~, which suggested that all the soils studied had a high binding strength for Hg（II）. The soil from Mount Taishan had a higher Hg（II） desorption capacity than the other soils, which indicated that the Hg（II） deposited on the topsoil of Mount Taishan from atmosphere may easily discharge to surface water through runoff. Results of the FTIR spectroscopy showed that the three soils contained the same functional groups. The relative absorbencies of soil-Hg complexes changed significantly compared with those of the soil samples and the adsorption of Hg（II） mainly acted on the O-H, C-O, and C=O groups of the soils.