准噶尔盆地东南缘绿洲-荒漠交错带土壤甲螨群落结构

为了查明准噶尔盆地东南缘绿洲-荒漠交错带土壤甲螨群落特征,2011年4月、7月、9月、11月中旬对该交错带的自然林、灌木林、防护林、荒草原、耕地、菜瓜地和荒漠等7种不同生境进行调查。结果表明:该区域共捕获土壤甲螨成体3767头,28科36属43种,其中覆盖头甲螨、萨勒盖头甲螨、新疆尖棱甲螨和普通尖棱甲螨为优势种,截合若甲螨、长单翼甲螨属、白上罗甲螨大洋亚种为亚优势种,优势种和亚优势种占总数的72.45%。7种不同生境土壤甲螨群落组成和数量分布均有明显的差异(P<0.05),在自然林种类(30种)和个体数(1001头)最多,而在菜瓜地种类(9种)最少,荒漠个体数(118头)最少。不同生境土壤甲螨的个体数具有明显季节变化差异(P<0.05),秋季数量最高、冬季次之、夏季其次、春季最低。MGP分析结果表明,该交错区土壤甲螨群落均属于O型,但G群的种类明显高于M群和P群。甲螨的群落异质性高,各生境间的多样性指数(H)有一定的差异,其中防护林最高,而菜瓜地最低。生境间相似性分析表明,自然林、灌木林、防护林生境之间是中等相似(0.50～0.70),荒漠和荒草原与其他生境间为中等不相似(0.25～0.50)或极不相似(0.00～0.25)。研究表明气候、植被和土壤差异是影响土壤甲螨群落的主要因素。     

策勒绿洲-荒漠过渡带风沙前沿近地面不同方向的输沙特征

利用策勒绿洲-荒漠过渡带风沙前沿输沙资料及风速风向资料,分析这一区域近地面输沙的方向分布特征。结果表明：① 风沙前沿起沙风风向以W、WNW为主,风向变化比较单一;② 观测点输沙量集中于NW、WNW、W、SW、WSW 5个方位,合计占总输沙量的68.3%;0～40 cm高度年输沙量为96.0 kg,年合成输沙量为45.9 kg,合成输沙方向为102.5°;③ 观测点年输沙势为43.2 VU,年合成输沙势为31.04 VU,输沙势的方向分布与实测输沙量存在较大差异。     

干旱区绿洲荒漠交错带土地退化及生态重建

由于经济的发展，土地资源受到越来越大的压力。当这种压力超过了土地资源的承载能力，就导致了土地退化的发生。作为陆地生态系统的基础，土地资源的退化表现为：土壤肥力降低，生物多样性降低，以及伴随的经济发展的落后。当前世界范围内对土地退化的治理，基本方法仍是基于生态学理论的生物方法。但对土地退化的恢复与生态系统的重建的研究，需要经过谨慎设计的长期实验。绿洲荒漠交错带的重要性，不仅表现为是绿洲的保护屏障，而且在绿洲经济的发展中也起到巨大的作用。通过对国内外大量研究的回顾，讨论了在不同地区进行的长期实验所采用的方法。有人为因素参与的退化土地恢复与生态重建，可以在短期内取得明显效果。产生土地退化的原因，不仅仅是土地资源特点与自然环境这样一些自然因素，还包括一些社会与经济因素。因此退化土地的恢复与生态重建的成功，需要一种考虑自然、社会和经济因素的综合的方法。     

农牧交错带地区发展保护性耕作的意义与前景

在系统总结保护性耕作技术的内涵、技术内容和类型的基础上,阐述了保护性耕作保土、保水、提高土地生产力、增加农业效益的重要作用,并根据北方农牧交错带的实际情况,从气候、土壤、农作物和社会因素四个方面对技术的可行性进行了科学的分析,认为保护性耕作技术在农牧交错带地区应用前景广阔,但社会经济因素将是制约保护性耕作技术应用的重要因子。加强配套技术的研究、增加资金的投入以及加快农民观念的转变是农牧交错带地区深入开展保护性耕作技术推广与应用需要重点解决的问题。     

准噶尔盆地东南缘绿洲-荒漠交错带土壤螨类群落特征初步研究

为了查明准噶尔盆地东南缘绿洲-荒漠交错带土壤螨类群落特征及其季节动态变化,2010年4月、7月、9月和11月中旬对该区的自然林、人工林、耕地、菜地、荒草原、灌木林及荒漠等7种不同生境进行采样调查研究。结果表明,共获得土壤螨类5200只,隶属于4目41科61属,其中菌甲螨属(Scheloribates)和若合甲螨属(Zygoribatula)为该区的优势类群,分别占总数量的18.21%和12.52%,而懒甲螨属(Nothrus)、扇珠足甲螨属(Licnodamaeus)、盖头甲螨属(Tectocepheus)、尖棱甲螨属(Ceratozetes)大翼甲螨属(Galumna)等15类群为常见类群,占总数量的53.6%。其余的44类群为稀有类群,占总量的15.67%。研究区七种不同生境土壤螨类个体数和类群数均有差异,个体数分别为自然林>菜地>荒草原>人工林>灌木林>耕地>荒漠;类群数分别为自然林>人工林>灌木林>荒草原>菜地>耕地>荒漠。不同季节所获得的土壤螨类总个体数量的大小顺序为9月>11月>7月>4月。垂直分布结果表明土壤螨类主要集中分布于表层土壤,即0～5cm土层最多,其次为5～10cm土层,在10cm以下的土层中土壤螨类数量急剧减少,不同土层间的个体数差异极显著(P<0.01)。     

Effects of tidal inundation and predation on Avicennia germinans seedling establishment and survival in a sub-tropical mangal/salt marsh community

The black mangrove, Avicennia germinans, occurs sympatric withSpartina alterniflora in coastal Louisiana. Zonation exists alongan elevational gradient with A. germinans dominant at higherelevation creekbanks and S. alterniflora at interior, lowerelevation sites with greater depth and duration of flooding.Establishment of A. germinans seedlings was examined in cagesthat excluded predators and limited horizontal, but not vertical,movement of propagules by the tides and showed that blackmangrove could readily establish in the Spartina zone. Survivalof A. germinans seedlings after one year in cages was notsignificantly different between the two zones, and seedlings weresignificantly taller in the Spartina zone. Thus, neitherinundation per se nor other abiotic factors alone could accountfor the absence of A. germinans in the interior marsh. Althoughpropagules were dispersed into both zones, a net removal ofuncaged propagules from plots in the Spartina zone (–1.3 ± 0.6m^-2 d^-1) compared to a net addition to plots in the Avicennia zone (+0.5 ± 0.4 m^-2d^-1) indicated that retention of propagulesdiffered between zones. Causes of mortality were decay (Spartina> Avicennia zone), desiccation (Avicennia > Spartina zone), andpredation (Spartina > Avicennia zone). Although few propaguleswere completely consumed by predators (snails and crabs), damageto the cotyledons promoted decay. The results suggest that tidalaction limits retention and settlement of A. germinans propagulesin the Spartina zone, and a combination of predator damage andfrequent flooding leads to rapid decay of propagules that strandthere.     

Plant species diversity of wetland ecosystem in an arid and semi-arid region in northwest China

In order to study the changes of plant species diversity along the biotope gradient and its influencing factors in a wetland-arid grassland ecosystem in the arid and semi-arid regions of northwest China, four transect lines were set along the biotope gradient in four directions: east, northeast, west and northwest, and altogether 123 sample plots were investigated on species composition, density, foliage cover, height and biomass (calculated in fresh weight). The whole study area was divided into the wetland zone, the ecotone and the arid grassland zone in terms of habitat characteristics and vegetation types. In this paper, we analyzed and compared the species diversity in the ecotone of a wetland-dry grassland ecosystem in Yanchi County, Ningxia Hui Autonomous Region, with the help of biodiversity software BioDiversity Pro and statistical software Microcal Origin, as well as the combined measurement of species diversity indices. The results revealed distinct differences between those three vegetation zones along each transect line. The ecotone had the highest richness indices (R) and comprehensive diversity indices (Y), reflecting the edge effect. The greatest evenness indices (E) were found in the arid grassland zones. This result agreed with the phenomenon of desertification reversion, vegetation restoration and dominant communities’ formation. As for the four transect lines, the east and the northeast scored higher in each diversity index than the others due to less human disturbance, gentler topography uplift and more intercepted materials and energies. The highest Simpson index value was found in the northeast transect line, which was 39.9% higher than the lowest in the Northwest. Translated from Journal of Beijing Forestry University, 2006, 28(5): 12–17 [译自: 北京林业大学学报]     

长白山北坡森林群落交错区优势树种动态

基于28个20mx90m样地的调查数据,利用Lotka-Volterra模型,本文分析了长白山北坡阔叶红松(Pinuskoraiensis)林和云冷杉林(也叫暗针叶林)群落交错区优势树种之间的竞争及动态。结果显示:在自然条件下,群落将向两个方向分化,一是以云杉(PiceajezoensisandP.koraiensis)和冷杉(Abiesnephrolepis)为优势的群落,并在达到平衡时冷杉占绝对优势(相对优势度的77.1%):另一种是以红松或云冷杉和阔叶树占绝对优势的针阔混交林,并在达到平衡时,阔叶树在阔叶红松林中占相对优势度的50%,在云冷杉一阔叶林类型中占66%。同时,本研究说明:(1)阔叶红松林和云冷杉林都是长白山气候顶极群落:(2)交错区具有过渡性质:(3)森林群落的分化结果说明演替的方向受局部生境的影响。图1表3参24。     

Changes in soil carbon stocks and related soil properties along a 50-year grassland-to-cropland conversion chronosequence in an agro-pastoral ecotone of Inner Mongolia, China

Land use change significantly influences soil properties.There is little information available on the long-term effects of post-reclamation from grassland to cropland on soil properties.We compared soil carbon(C) and nitrogen(N) storage and related soil properties in a 50-year cultivation chronosequence of grassland in the agro-pastoral ecotone of Inner Mongolia.Field surveys on land use changes during the period of 1955-2002 were conducted to build a chronosequence of cropland of different ages since the conversion from grassland.The results showed that soil C and N storage,soil texture,and soil nutrient contents varied with land use types and cropland ages(P<0.01).In the 0-30 cm soil layer,the soil organic carbon(SOC) density was significantly lower in the croplands(3.28 kg C/m2 for C50 soil) than in the grasslands(6.32 kg C/m2).After 5,10,15,20,35,and 50 years of crop planting(years since the onset of cultivation),the SOC losses were 17%,12%,19%,47%,46%,and 48%,respectively,compared with the grasslands.The soil total nitrogen(TN) density of the grasslands was 65 g N/m2,and TN density of the cropland soil was 35 g N/m2 after 50 years of crop planting.Both the SOC and TN densities could be quantitatively determined by a negative exponential function of cropland age(P<0.0001,R2=0.8528;P<0.0001,R2=0.9637).The dissolved organic carbon(DOC) content,soil available potassium(AK) content,clay content,and pH value were decreased;and the soil bulk density and sand content were increased since the conversion of grassland into cropland during the 50-year period.Our results show soil nutrients were higher in grassland than in cropland.The conversion of grasslands to croplands induced a loss of soil C storage and changes of related soil properties.The reclamation time of cultivated soil(cropland age) had significant effects on soil properties in the study area.     

北方农牧交错区草地生态系统服务间接价值的初步评估——以太仆寺旗和沽源县境内为例

以草地地上生物量为基础,运用经济学的市场价值法、物质量法、水量平衡法等方法对太仆寺旗和沽源县境内的农牧交错区草地的固定CO2、释放O2、土壤侵蚀控制、涵养水源、营养物质循环5项生态系统服务功能进行初步的评估。结果表明：由这5项功能构成的生态系统服务的间接价值在农区为16 668元/（hm2·a）,在草原区为17 223元/（hm2·a）。尽管草原区的间接价值比农区的高3.33%,但研究所选的农牧交错区由于农业活动的干扰,并没有导致草地生态系统服务功能间接价值的显著下降。这说明维持现阶段的农业活动或退耕还草可能促进草地生态系统生态经济价值的可持续性发展;但若继续开垦和破坏草地,草地生态系统的服务功能可能会显著下降,草地所具有的生态屏障作用也会减弱甚至消失。