敦化林业局灌木林地调查研究

以敦化林业局灌木林资源为对象进行调查与分析,结果表明:全局灌木林地面积为322.17 hm~2,其中,国家特别规定灌木林地面积113.56 hm~2,其他灌木林地面积208.61 hm~2;水土保持林比例最大,占64.18%,其次为水源涵养林,食用原料林最少。国家特别规定灌木林地覆盖度在30%~49%的为92.53 hm~2,50%~69%的为10.82 hm~2,70%以上的为10.21 hm~2;其他灌木林地覆盖度在30%~49%的为54.04 hm~2,50%~69%的为143.39 hm~2,70%以上的为11.18 hm~2。     

东祁连山杜鹃属植物形态特征及其生态适应性

对东祁连山杜鹃灌丛草地杜鹃属植物的形态特征及其生态适应性研究表明:百里香杜鹃和头花杜鹃个体相对低矮,叶片近革质、密被鳞片、有芳香但不强烈;烈香杜鹃个体较前者略高,叶片软革质、上无鳞片但背面有稀疏鳞片、有强烈芳香;陇蜀杜鹃个体最高,叶片坚革质、无鳞片、无芳香。花的数目陇蜀杜鹃和烈香杜鹃较多,为12～17朵;头花杜鹃3～8朵;而百里香杜鹃则为单一、偶成双。其叶片显示出不同的生态适应特点,即百里香杜鹃为小叶密鳞半落叶、头花杜鹃为小叶密鳞强反卷、烈香杜鹃为中叶疏鳞角质反卷、陇蜀杜鹃为大叶厚角质反卷。     

人工栽培灌丛对牧草生长及水土保持效果的研究

对湟水河源头荒山荒坡上人工栽培的沙棘、柠条等灌丛带的牧草地上部与地下部产量进行测定分析,结果表明：在该地区的荒山荒坡上人工栽培沙棘、柠条等灌丛,牧草地上产草量平均提高23.7%,地下根量平均提高18.2%,水土流失减少1 300 t/hm2。     

Black carbon in wildfire‐affected shrubland Mediterranean soils

Because Mediterranean ecosystems are prone to fire, their soils are expected to contain relevant amounts of black carbon (BC); nevertheless, quantitative information is scarce. Herein, we provide data on the abundance of BC in the surface soil (uppermost 5 cm) of shrubland plots on old agricultural fields diversely affected by fires (0, 1, or 2 wildfires in the last 25 y) and with contrasted land‐use histories (either never cropped, early abandoned, or recently abandoned). Black C and black nitrogen (BN) were quantified in the surface horizon (0–5 cm) as the residue of low‐temperature dichromate oxidation, after previous destruction of mineral matter with HF. The obtained amounts of BC ranged from 0.73 to 10.32 g (kg dw)^–1 (mean: 3.07, which corresponds to an average of 8.62% of the total organic C), while the amounts of BN ranged from 21.5 to 373.0 mg (kg dw)^–1 (mean: 97.1, or an average of 4.30% of the total N of the samples). Repeated fires did not consistently increase either the BC or the BN amounts. Black‐C and (especially) BN accumulation seems related to fine silt, whereas the effect of clay is unclear. Even though the amounts of BC obtained in this study are slightly higher than those from other ecosystems, including Mediterranean broad‐leaved forests, overall they are far from the very high values reported in the literature for chernozems from Germany or Canada. Thus, on the whole, in Mediterranean shrublands affected by wildfires, BC does not seem to be a dominant fraction in the soil organic C.     

Does Fusarium‐caused seed mortality contribute to Bromus tectorum stand failure in the Great Basin?

Bromus tectorum (cheatgrass, downy brome) is an important invader in western North America, dominating millions of hectares of former semi‐arid shrubland. Stand failure or ‘die‐off’ is relatively common in monocultures of this annual grass. The study reported here investigated whether soil‐borne pathogens could be causal agents in die‐offs. Soils from two die‐off areas and adjacent B. tectorum stands were used in a glasshouse experiment with sterilised and non‐sterilised treatments. Soil sterilisation did not increase emergence, which averaged 80% in both die‐off and non‐die‐off soils. Seedling biomass was higher in die‐off soils, probably due to increased nitrogen availability. Fusarium was isolated from 80% of killed seeds in non‐sterilised soil treatments. In pathogenicity tests with 16 Fusarium isolates, host seeds incubated under water stress (?1.5MPa for 1 week prior to transfer to free water) suffered over twice the mortality of seeds incubated directly in free water (25–83% with water stress vs. 5–43% without water stress). These results suggest that soil‐borne Fusarium could play a role in B. tectorum stand failure in the field, but that low water stress conditions in the glasshouse experiment were not conducive to high levels of disease. Pathogenic Fusarium isolates were obtained from seeds planted in both die‐off and non‐die‐off soils, suggesting that microenvironmental factors that affect levels of water stress might be as important as relative abundance of soil‐borne pathogens in mediating spatial patterns of disease incidence in the field.     

Aluminum accumulation in nineteen Melastomataceae species from three contrasting plant formations in acid soils

This study describes the aluminum (Al) accumulation in relation to macronutrient and micronutrient elements in 19 Melastomataceae species in the Guayana Region in Venezuela. The purpose was to investigate the Al accumulation in four tribes and different life forms. Aluminum accumulation was predicted in the basal tribes Miconieae and Merianieae in contrast to the derived tribes and herbs from any tribe, which generally do not accumulate Al. The survey was done in a vegetation continuum, which includes a savanna shrubland, a palm‐swamp community, and an evergreen forest in the Guayana region in southeastern Venezuela. The highest value of soil Al concentration was found in the savanna shrubland, where ten lignified Miconiae and one Merianeae Al accumulators were present. At the forest, the site with highest soil acidity, four Al‐accumulator tree species from Miconiae were found. Miconia lepidota showed similar Al foliar concentrations in the savanna shrubland and forest, but foliar Ca was lower in the forest, even though it was the site with highest Ca in the soil. At the palm‐swamp community, the Melastomeae shrub Macairea pachyphylla was found with an Al concentration of 0.59 g kg^–1 in leaves and 0.16 g kg^–1 in bark. At the same site, Al accumulation occurred in one Microlicieae species, one Miconieae species, and in the Melastomeae herbs Pterogastra divaricata (13.25 g [kg dry mass]^–1) and Pterolepis trichotoma (17.83 g kg^–1). The report of Al hyperaccumulation in P. trichotoma is new for the genus, and Al accumulation in herbs is considered exceptional. The foliar Al concentration was positively correlated (p < 0.005) with Fe (r = 0.64, n = 20) and Zn (r = 0.63). The analysis of the relationships between soil Al, Fe, or Zn and the concentrations of these elements in leaves revealed they were not significantly correlated. The results indicate Al hyperaccumulation in two herbaceous Melastoamataceae species and suggest Al accumulation in this life form deserves future research. However, they also confirm the highest number of Al accumulators in lignified species of the ancient tribe Miconiae (14 out of 19 species studied).     

开垦利用对东祁连山高寒灌丛草地土壤养分含量的影响

对同一海拔高度的东祁连山金露梅、山生柳高寒灌丛草地以及灌丛草地开垦后种植燕麦的土地,进行了土壤养分含量的研究.结果表明:金露梅灌丛草地和山生柳灌丛草地的土壤养分含量除全钾外,其他元素都是随土层加深而下降,且各土层差异显著(P<0.05).燕麦地除了全钾、速效钾、速效锰外,都是随土层加深而下降,且各土层差异显著(P<0.05).山生柳灌丛草地与金露梅灌丛草地土壤养分差异不显著(P>0.05).但灌丛草地与开垦地土壤养分差异显著(P<0.05),并且开垦后种植燕麦的土壤养分含量明显受到人为的控制和干扰,其土壤有机质、全氮、速效氮、速效磷和速效锌含量均比灌丛草地高,而全磷、速效钾、速效铁、速效铜和速效锰含量比灌丛草地低,速效钾含量并不随土层加深而变化,速效铁和速效锰含量则随土层加深而上升.     

Perspective article: Simulation models for semi‐arid rangelands of southern Africa

Abstract

In semi‐arid regions, the effects of grazing or sparing management on natural communities of long‐lived plants generally take decades to become evident. Event‐driven dynamic behaviour, unpredictable and low rainfall, and complicated interactions between species make it difficult to gather sufficient understanding of vegetation dynamics to be able to develop guidelines for sustainable management. Simulation models that consider the essential processes that determine vegetation dynamics offer scope for quantitatively exploring long‐term vegetation dynamics of arid and semi‐arid rangelands. In this paper we review three models that were aimed to provide an understanding of the vegetation dynamics and management of different typical vegetation types in South Africa, including the Karoo shrubland, the shrub‐grassland of the southern Kalahari, and pure semi‐arid grasslands.     

黄土丘陵区柠条林地土壤水分垂直变化

为了解水资源紧缺地区多年生林地的土壤水分状况,采用中子仪测定法,于2002-2006年对宁夏自治区固原市上黄生态试验站人工柠条林地(生长季4-10月)的土壤水分进行了监测。并应用隔室分析法建立了土壤水分垂直变化模型,对柠条林地土壤水分实测数据进行了拟合。分析结果表明,在参数取值特定的条件下,模型可表达试区内不同降雨条件下柠条人工林下的土壤水分垂直变化,拟合优度R2符合统计学要求,模型具有较好的应用价值。     

Water repellency and moisture content spatial variations under Rosmarinus officinalis and Quercus coccifera in a Mediterranean burned soil

Variations in the distribution pattern of soil water repellency (SWR) and soil moisture are of major importance for the hydrological and geomorphological processes in Mediterranean burned areas, and also for their ecological implications concerning to re-establishment of the vegetation cover. This paper studies the influence of Rosmarinus officinalis L. and Quercus coccifera L. vegetated patches on SWR and their relationships with soil moisture content (SMC) and soil organic matter (SOM) in burned and unburned calcareous soils of a Mediterranean shrubland ecosystem, considering the first rainfall event occurred after the wildfire in Les Useres (Castellón, eastern Spain).