Vegetation pattern related tc grazing pressure in alpine meadows of Nanda Devi Biosphere Reserve

The present study aims to analyze the interaction of prevailing biotic pressure on plant species diversity in Nanda Devi Biosphere Reserve (NDBR) which lies in northern part of Uttaranchal hills between 79 degrees 40'E to 80 degrees 05'E longitude and 30 degrees 17' N to 30 degrees 41'N latitude and covers an area of 2236.7 km2. A total of 75 species has been found which included the herbaceous plants viz., grasses, sedges and forbs. Generally, the plants have a short life span of 3-4 months. However, few species persist throughout the growth period i.e. May-October. Phytosociological study performed in plots of varying slope and grazing pressure intensity revealed that the dominant grasses were Danthonia cachemyriana and Poa annua and dominant forbs were Trachydium roylei and Geum elatum in all the plots. Grasses were abundant on west facing slopes while forbs preferred the even topography of east facing meadows. The grasses and sedges together had optimum density during July and August. In general, short lived species exhibited more diversity for one or two months whilst the long lived species exhibited optimum diversity althrough the snow free period. The species diversity is maximum (100%) in moderately grazed bughiyals i.e. Pacchu and minimum in intensively grazed bughiyals i.e. Martoli. The species distribution among the plots was 60-90% contagious and 11.2-38.0% randomirrespective of grazing pressure, thus highlighting the significance of grazing pressure in management of alpine meadows.     

不同放牧梯度下草甸草原土壤微生物和酶活性研究

通过小区控制放牧实验,研究呼伦贝尔草甸草原不同放牧强度下草地土壤微生物和酶活性的变化。结果表明：不同处理土壤微生物数量表现为细菌〉放线菌〉真菌。不同土层土壤微生物总数不放牧处理大于放牧处理,0～30 cm土层土壤微生物生物量碳、氮含量在轻牧区较高,在中牧区较低。土壤脲酶和过氧化氢酶活性轻度放牧和中度放牧高于不放牧和重度放牧。土壤微生物数量、生物量、土壤蛋白酶和过氧化氢酶活性均随土壤深度的增加呈递减趋势。相关分析表明,土壤微生物数量、微生物生物量以及土壤酶活性相互之间密切相关,土壤微生物量N与细菌达到极显著正相关（P〈0.01）,与真菌和放线菌呈显著相关（P〈0.05）。土壤微生物量C与真菌达到极显著负相关（P〈0.01）,与放线菌呈显著负相关（P〈0.05）。土壤微生物数量、土壤微生物量N与转化酶、蛋白酶、过氧化氢酶活性呈显著或极显著正相关。土壤微生物量C与转化酶、蛋白酶、过氧化氢酶呈显著负相关（P〈0.05）。     

子午岭植被演替过程中土壤生物学特性的动态

土壤生物学特性在土壤有机质的形成和降解、营养循环等方面起重要作用。植被的恢复演替显著影响土壤生物学特性,尤其影响土壤酶活性。植被演替过程中土壤酶活性的研究结果表明,随着植被恢复年限的延长,土壤脲酶和转化酶的活性逐渐提高,17 a达到最大值,随后有所降低。土壤酶活性和土壤化学特性和微生物量的相关性分析表明,土壤转化酶和脲酶不仅互相之间具有显著的相关性,而且它们与土壤有机碳、全氮、微生物碳氮之间都具有显著的正相关性,说明土壤酶活性与土壤有机质紧密相关,与微生物的大小紧密相关,所以土壤酶活性可以表征土壤生物学肥力。     

宁夏引黄灌区农田土壤酶活性及其空间变异

采集了同一地点不同土地利用方式,及不同地点不同典型土地利用类型下银川平原的灌淤土样品,在分析了土壤基本理化性质的基础上,用奈氏比色法、苯磷酸二钠比色法和高锰酸钾滴定法,分别测定了宁夏引黄灌区农田不同利用方式下土壤的磷酸酶、脲酶、过氧化氢酶的活性状况,并对土壤酶活性与土壤的基本理化性质的相关性进行了相关分析。结果表明,土地利用方式对三种酶活性有很大的影响。12年果园磷酸酶活性最高,常年旱田脲酶和过氧化氢酶活性最高,而盐化旱田及常年淹水的稻田,三种酶活性都很低。脲酶活性与土壤全氮之间显著正相关,全磷与三种酶活性都极显著相关,三种酶之间达到显著或极显著正相关关系。表明磷酸酶、脲酶和过氧化氢酶活性的大小可以敏感地表征宁夏引黄灌区土壤肥力和生产力的高低。     

不同载畜率对短花针茅荒漠草原土壤呼吸的影响

草地是我国最大的陆地生态系统,土壤呼吸是草地碳循环研究的重要内容,是土壤碳库输出的主要方式,影响大气中CO2浓度变化。放牧是草地主要利用方式之一,通过动物采食和践踏,改变植被冠层结构,对土壤理化性质、土壤有机质和土壤微生物产生影响,进而改变土壤呼吸速率。为探究不同载畜率对短花针茅（Stipa breviflora）荒漠草原土壤呼吸速率的影响,2011—2012年用Li-8100开路式碳通量测定系统,对生长季内（6—10月）4个不同载畜率处理下的土壤呼吸进行测定,测定周期为2周1次。辅助测定地下10 cm的土壤温度及土壤湿度,并分析土壤呼吸与土壤温、湿度的关系。结果表明：1）2011年不同载畜率对土壤呼吸速率无显著影响,表现为对照〉中度放牧〉轻度放牧〉重度放牧的变化趋势。2012年与对照（1.6μmol·m-2·s-1）相比,重度放牧（1.07μmol·m-2·s-1）显著降低土壤呼吸速率。总体而言,2011年土壤呼吸速率低于2012年,但差异不显著。2011年土壤温度（20.73℃）显著高于2012年（14.38℃）,不同处理间无显著差异,重度放牧区偏高。2012年土壤湿度（7.24%）显著高于2011年（4.11%）,对2年数据整体分析发现,轻度放牧区土壤湿度显著低于对照和中度放牧。2011年土壤湿度变化趋势为中度放牧〉对照〉重度放牧〉轻度放牧。2012年,轻度放牧土壤湿度最小,各处理间差异不显著。2）2011年,土壤呼吸与土壤温度月动态无明显规律,与土壤湿度呈现相反的变化趋势。2012年土壤呼吸的月动态与土壤温、湿度变化趋势相似。3）2011年,土壤呼吸速率随温度升高出现波动,与土壤湿度呈负相关。2012年,土壤呼吸速率随土壤温、湿度升高而增大。在干旱年份,降水减少会掩盖放牧对土壤呼吸的影响;在降雨较多的年份,重度放牧显著降低土壤呼吸速率。     

Short-term and long-term facilitation of goose grazing by livestock in the Dutch Wadden Sea area

We studied the impact of livestock grazing on the distribution ofBranta bernicla bernicla (Dark-bellied Brent goose) in the Dutch Wadden Sea during spring. It was hypothesized that livestock facilitate short-term (within-season) grazing for geese as well as long-term (over years). Therefore we measured grazing pressure by geese in salt marsh and polder areas that were either grazed (spring-grazed) or ungrazed during spring (summer-grazed). Additionally, we carried out a preference experiment with captive geese to test the preference between spring-grazed and summer-grazed polder swards. We furthermore compared patterns of use by geese between long-term ungrazed and grazed salt marshes. In May, there is a difference in grazing pressure by geese between polder pastures that are grazed or ungrazed during spring. In this month, the ungrazed polder pastures are abandoned and the geese shift to either the grazed polder pastures or to the salt marsh. Vegetation in the polder that had been spring-grazed had a lower canopy height and a higher tiller density than summer-grazed vegetation. The captive geese in the preference experiment showed a clear preference for vegetation that had been spring-grazed by sheep over ungrazed vegetation. Goose grazing pressure was negatively correlated to canopy height, both on the polder and on the salt marsh. Within the plant communities dominated byFestuca rubra andPuccinellia maritima, marshes that were intensively grazed by livestock generally had higher grazing pressure by geese than long-term ungrazed or lightly grazed salt marshes.     

放牧对祁连山高寒金露梅灌丛草甸土壤微生物的影响

以祁连山北支冷龙岭东段南麓的甘柴滩夏季牧场集体长期混合(藏系绵羊、牦牛)放牧的高寒金露梅(Potentilla fruticosa)灌丛草地为对象,采用平板涂抹分离法和氯仿熏蒸法对不同放牧压力梯度下土壤微生物(细菌、真菌和放线菌)和土壤微生物碳、微生物氮量进行研究,结果表明:不同放牧压力梯度下,金露梅灌丛和丛间草地土壤微生物以细菌占绝对优势,放线菌和真菌较少,垂直分布明显;随着放牧压力梯度的增加,金露梅灌丛和丛间草地,0～25 cm土层中的细菌、放线菌、真菌及微生物碳和微生物氮数量呈降低趋势,其降低程度与放牧压力梯度呈直线正相关.与无放牧金露梅灌丛相比0～25 cm土层的细菌、真菌、放线菌最大降幅分别为49.64%、37.76%和46.64%;金露梅灌丛土壤微生物碳量占土壤有机碳的比例变化为0.85%～0.43%,微生物氮占土壤全氮的0.90%～1.11%,微生物量对土壤营养库的贡献率较低;土壤微生物量和土壤有机质呈显著线形正相关;土壤细菌数量和土壤水分呈显著线形正相关.     

Interactive effects of rabbit grazing and environmental factors on plant species-richness on dunes of Norderney

On the German island Norderney rabbit grazing effects on vegetation, soil and microclimate were investigated with exclosures in different dune vegetation. Differences in species composition between grazed and ungrazed plots increased with grazing activity. A decline in growth height resulted in higher light availability and temperature on the grazed sites. One of the most visible effects was the decline in flowering plants. Most grazing effects varied between habitat types. Grey dunes were distinctly affected by rabbit grazing. In relation to the habitat type, life forms were differently affected: in closed vegetation, rabbit activities further open patches, resulting in more therophytes. In contrast, in open vegetation rabbit activities were too strong and following sand dynamics too high for many therophytes. In general, grazing diversified habitats, slightly supported the total species-richness, and enhanced the heterogeneity of species composition. Highest species-richness in total and of herbs was reached at intermediate levels of grazing pressure. The study is in line that highest species-diversity will be found at intermediate levels of disturbance and environmental stress and that grazing effects vary with the habitat type.     

坡位对马尾松林下土壤理化性质、酶活性及微生物特性影响

以我国南方花岗岩区退化马尾松林地土壤为研究对象,通过典型样地调查方法研究不同坡位（坡上、坡中,坡底）马尾松对土壤理化性质、酶活性和微生物学性质的影响。结果表明,0～20和20～40 cm土层土壤w（有机质）、w（全氮）、w（碱解氮）和w（速效钾）坡位间差异均显著（p〈0.05）,其中w（有机质）和w（全氮）均表现为坡底〉坡中〉坡上;而w（全磷）和w（全钾）位间差异不显著;3坡位中坡底土壤w（粘粒）较高容重较小。土壤酶活性坡位间差异不显著,可能受林分密度影响较大。两土层微生物生物量碳氮与土壤呼吸强度均为坡底最大,且与有机质和全氮相关性分别达显著（p〈0.05）和极显著（p〈0.01）正相关,但在微生物对碳利用效率、有机碳氮累积程度等方面坡位间差异不显著。所以,对养分瘠薄且易受侵蚀的花岗岩红壤区域,马尾松作为恢复植被须谨慎选择。     

山西芦芽山林线附近土壤水分空间分布特征及其影响因素

于2008年植被生长季,在芦芽山荷叶坪亚高山草甸及森林-草甸过渡带内布设观测样带,应用FDR土壤剖面水分测量仪测量10～40 cm深度土壤含水量,并分析其空间分布特征和影响因素。结果表明:(1)根据所处位置及地上植被状况可将样带分为林地样带和草甸样带,林地样带土壤含水量随深度增加呈先升高后降低的变化趋势,草甸样带则恰好相反。(2)10和40 cm深度为土壤含水量稳定层,20和30 cm深度为活跃层,且林地样带10 cm深度土壤含水量小于草甸样带,20、30和40 cm深度土壤含水量则大于草甸样带。(3)降雨发生后,阴坡上部树岛样带土壤含水量增幅最大,阳坡上、中、下部草甸样带土壤含水量增幅也较大;不同土层深度比较而言,10cm深度土壤含水量增幅最大,20、30和40 cm深度土壤含水量增幅较为接近,土壤含水量对降雨的响应存在1～2d的时滞。(4)10、20和30 cm土壤含水量变化值与坡度呈显著正相关,30、40 cm土壤含水量变化值与初始土壤含水量呈显著负相关,20、30 cm土壤含水量变化值与地形湿度指数呈显著负相关。研究区内土壤含水量空间分布格局及其动态变化受植被和降雨影响显著,初始土壤含水量、坡度以及地形湿度指数对其也有一定影响。     

不同年龄小叶锦鸡儿固沙群落土壤酶活性及微生物生物量的变化

小叶锦鸡儿(Caragana microphylla)是科尔沁沙地广为采用的豆科固沙植物。为探讨采用小叶锦鸡儿固定流沙后,土壤生物活性的变化特点和发展趋势,选取5、10、22年生小叶锦鸡儿人工固沙群落为对象,以半流动沙丘和天然群落为对照,研究了人工固沙群落发育过程中土壤磷酸单酯酶、蔗糖酶、蛋白酶、脲酶、脱氢酶的活性和微生物生物量C、N、P质量分数的变化特征。土壤按5层取样:0~10,10~20,20~30,30~40,40~50cm。结果表明,随着小叶锦鸡儿固沙群落发育时间的增长,群落内土壤生物活性逐渐改善,沙土中5种酶的活性和土壤微生物生物量C、N和P质量分数均大幅度提高,其中0~10cm土层增幅最大。土壤酶中蔗糖酶的活性增加最为迅速,5、10和22年生群落0~10cm土层中蔗糖酶的活性分别是半流动沙丘的76.80,167.27和261.63倍。22年生群落的土壤生物活性已接近于天然群落,处于相对稳定的状态。小叶锦鸡儿群落中土壤酶和微生物生物量之间存在极显著的正相关关系。以上表明,小叶锦鸡儿不仅具有较好的防风固沙性能,而且表现出强大的改善土壤生物活性的能力,可作为优良的固沙植物材料在本地区大面积推广应用。     

Soil Quality: A Review of the Science and Experiences in the USA

An increasing human population is placing greater demand on soil resources, and as a result degradation is taking place in many regions of the world. This is critical because soils perform a number of essential processes including supporting food and fiber production, influencing air quality through interaction with the atmosphere, and serving as a medium for storage and purification of water. The soil quality concept was introduced to complement soil science research by making our understanding of soils more complete and helping guide the use and allocation of labor, energy, fiscal, and other inputs as agriculture intensifies and expands to meet increasing world demands. Soil quality thus provides a unifying concept for educating professionals, producers, and the public about the important processes that soils perform. It also provides an assessment tool for evaluating current management practices and comparing alternative management practices. Soil attributes comprising a minimum data set have been identified, and both laboratory and field methods have been developed for measuring them. A soil quality index is being developed to normalize measured soil quality indicator data and generate a numeric value that can be used to compare various management practices or to assess management-induced changes over time. Using previously published data, we evaluated the soil quality index as a tool to assess a wide range of management practices in the Northern Great Plains. The index ranked the treatments: grazed fertilized tame pasture > moderately grazed > ungrazed> heavily grazed > annual cropping with no-tillage > conventionally tilled crop-fallow which agrees with the way they were subjectively ranked in the publications. The soil quality index shows potential for use as a management assessment tool.     

Soil quality: a review of the science and experiences in the USA

An increasing human population is placing greater demand on soil resources, and as a result degradation is taking place in many regions of the world. This is critical because soils perform a number of essential processes including supporting food and fiber production, influencing air quality through interaction with the atmosphere, and serving as a medium for storage and purification of water. The soil quality concept was introduced to complement soil science research by making our understanding of soils more complete and helping guide the use and allocation of labor, energy, fiscal, and other inputs as agriculture intensifies and expands to meet increasing world demands. Soil quality thus provides a unifying concept for educating professionals, producers, and the public about the important processes that soils perform. It also provides an assessment tool for evaluating current management practices and comparing alternative management practices. Soil attributes comprising a minimum data set have been identified, and both laboratory and field methods have been developed for measuring them. A soil quality index is being developed to normalize measured soil quality indicator data and generate a numeric value that can be used to compare various management practices or to assess management-induced changes over time. Using previously published data, we evaluated the soil quality index as a tool to assess a wide range of management practices in the Northern Great Plains. The index ranked the treatments: grazed fertilized tame pasture > moderately grazed > ungrazed > heavily grazed > annual cropping with no-tillage > conventionally tilled crop-fallow which agrees with the way they were subjectively ranked in the publications. The soil quality index shows potential for use as a management assessment tool.     

秸秆还田配施化肥及微生物菌剂对水田土壤酶活性和微生物数量的影响

土壤微生物学特性是表征土壤质量的重要生物学指标。通过田间试验研究了秸秆还田配施不同配比化肥及微生物菌剂对水田土壤酶活性和微生物数量的影响。结果表明,与单施秸秆相比,秸秆还田配施N、P、K及微生物菌剂后,土壤过氧化氢酶、转化酶和尿酶活性分别提高了37.5%~68.8%、32.3%~61.5%和48.8%~102%,细菌和真菌数量分别提高了95.3%~174%、286%~351%,放线菌数量减少了34.5%~39.4%,差异显著。统计分析显示,土壤过氧化氢酶与尿酶活性之间及其酶活性与微生物数量之间关系密切。氨化细菌和硝化细菌数量主要控制土壤过氧化氢酶活性,真菌数量是转化酶活性的主要影响因素,而尿酶活性主要受细菌数量影响。秸秆还田配施微生物菌剂及平衡施肥可以促进酶活性的增强,使土壤微生物群落物种个体数增加更多,分布更为均匀。过量施用氮肥会抑制土壤酶活性和微生物的生长和繁殖。     

Cattle Grazing Impacts on Annual Forbs and Vegetation Composition of Mesic Grasslands in California

Abstract:   Livestock grazing represents a major human alteration of natural disturbance regimes in grasslands throughout the world, and its impacts on plant communities have been highly debated. We investigated the impact of cattle grazing on the California coastal prairie plant community with a focus on native annual forbs, a number of which are of conservation concern. In spring 2000 and 2001, we surveyed the vegetation community composition, vegetation structure, and soil chemical parameters at 25 paired grazed and ungrazed sites over a 670-km range of the ecosystem. Native annual forb species richness and cover were higher in grazed sites, and this effect was concomitant with decreased vegetation height and litter depth. Soil properties explained less of the variation. Exotic annual grass and forb cover were higher in grazed sites. Native grass cover and species richness did not differ in grazed and ungrazed sites, but cover and species richness of native perennial forbs were higher in ungrazed sites. Our results suggest that cattle grazing may be a valuable management tool with which to conserve native annual forbs in the ecosystem we studied but that grazing differentially affects the various life-history guilds. Therefore, land managers must focus on creating a matrix of disturbance regimes to maintain the suite of species native to these mesic grasslands. The results of this and other studies highlight the importance of considering the adaptation of vegetation communities to disturbance in making recommendations for grazing management.     

三江源区不同建植年代人工草地群落演替与土壤养分变化

研究了了三源区不同建植期人工修复草地在不同演替阶段毒杂草[主要是甘肃马先蒿(Pedicularis kansuensis)]的入侵规律、数量特征,植物群落物种组成、生物苗和草地质最以及土壤养分、微生物活性的变化规律.结果表明,不同建植期人工修复草地植物群落的种类组成、植物功能群组成和群落数量特征存在显著差异.随着演替时间的推移,人工草地群落盖度、高度、物种数、生物最和多样性指数均表现出"V"字型变化规律,杂类草--甘肃马先蒿的数量特征变化尤为明显,在4 a的人工草地群落中开始局部入侵,在5～6 a的人工草地群落中大面积入侵,其入侵速度、入侵面积达到高峰期.土壤的含水量、容重、土壤中有机质、氮素和磷素在演替过程(7 a、9 a草地)中逐渐降低,到一定时期又逐步增加;随着演替的进行,不同建植期人工草地的土壤微牛物生物量碳和酶活性均呈"V"字型,变化.对于退化生态系统的恢复首先是植被恢复,其次是土壤肥力的恢复.土壤有机质等养分的积累、微生物活性的改善不仅能使土壤-植物复合系统的功能得以恢复,同时也能促进物种多样性的形成,有利于人工草地群落稳定性的提高.在试验区尽管植被恢复演替进行得比较缓慢,但从土壤发展的角度看,仍属进展演替.所以,在退化高寒草甸的恢复过程中,若降低和有效控制外界的干扰(如围栏封育),可为退化草地恢复提供繁殖体与土壤环境,实现人工草地逐步向恢复(正向)演替进行.图3表6参34     

三江源国家公园不同草地土壤微生物功能基因的差异性分析

土壤微生物在陆地生物地球化学循环过程中起着非常重要的作用。为了探索青藏高原高寒草地类型地上植被特性和地下土壤环境与土壤微生物功能基因之间关系,以三江源国家公园高寒草原、高寒沼泽化草甸及高寒草甸3种典型草地类型为研究对象,利用基因芯片(GeoChip 5.0)技术测定其微生物功能基因丰度,并分析它们之间的差异及影响因素。结果表明:(1)3种草地类型地上群落结构和地下土壤环境存在差异性,其中高寒草原物种多样性指数、pH值较高,沼泽化草甸中土壤含水量、微生物量碳、地上生物量、土壤速效氮含量较高,高寒草甸中则是土壤微生物量氮含量较高;(2)3种高寒草地类型的碳循环、氮循环、磷循环、有机修复的土壤微生物功能基因丰度存在显著差异,其中这些功能基因的丰度在高寒沼泽化草甸最高,高寒草甸、高寒草原次之;(3)地上植物物种多样性虽对功能基因丰度变化的解释率(r2)在57.1%-61.2%之间,但统计学上不显著(P>0.05),而微生物基因丰度随地上生物量的增加而增加,且解释率(r2)为77.5%-80.0%(P<0.05)。在pH、土壤含水量、土壤微生物量等地下土壤环境因子中,pH对功能基因丰度存在显著影响(P<0.01)解释率在83.4%-87.5%间,且土壤微生物功能基因丰度随土壤pH的增加而降低;土壤含水量、土壤微生物量对土壤微生物功能基因丰度的解释率分别为81.9%-83.1%(P<0.05)和76.8%-86.2%(P<0.05),微生物功能基因丰度随这两者含量的增加呈上升趋势。进一步运用RDA分析发现,pH、土壤微生物量、地上生物量是影响微生物功能基因丰度的主要因子,其中土壤微生物量是土壤有机质的重要组成部分,土壤有机质又是通过地上植被凋落物沉积所得到的。因此,地上植被特性的自上而下控制因子影响了土壤环境中自下而上的控制因子,间接的影响了微生物功能基因丰度。由此得出,地上植被特性和地下土壤环境因子共同作用控制了微生物功能基因丰度使其出现差异性。     

Soil enzyme activities and their indication for fertility of urban forest soil

To reveal the biological characteristics of urban forest soil and the effects of soil enzyme on soil fertility as well as the correlation between physicochemical properties and enzyme activities, 44 urban forest soil profiles in Nanjing were investigated. Basic soil physicochemical properties and enzyme activities were analyzed in the laboratory. Hydrogen peroxidase, dehydrogenase, alkaline phosphatase, and cellulase were determined by potassium permanganate titration, TTC (C₁₉H₁₅N₄·Cl) colorimetry, phenyl phosphate dinatrium colorimetry, and anthrone colorimetry, respectively. The result showed that soil pH, organic carbon (C), and total nitrogen (N) had great effects on hydrogen peroxidase, dehydrogenase, and alkaline phosphatase activities in 0–20 cm thick soil. However, pH only had great effect on hydrogen peroxidase, dehydrogenase, and alkaline phosphatase activities in 20–40 cm thick soil. Hydrogen peroxidase, dehydrogenase, and alkaline phosphatase were important biological indicators for the fertility of urban forest soil. Both in 0–20 cmand 20–40 cmsoil, soil enzyme system (hydrogen peroxidase, dehydrogenase, alkaline phosphatase, and cellulase) had a close relationship with a combination of physicochemical indicators (pH, organic C, total N, available K, available P, cation exchange capacity (CEC), and microbial biomass carbon (C_mic)). The more soil enzyme activities there were, the higher the fertility of urban forest soil.     

不同母岩区马尾松人工林土壤酶活性及微生物学性质研究

红壤丘陵区马尾松人工林对土壤性质有重要影响。研究马尾松长期种植对该区主要母岩（花岗岩、第四纪红黏土和红砂岩）发育土壤酶活性及微生物学性质的影响。微生物性质结果显示,土壤微生物生物量碳氮在花岗岩区较高,但有机碳在第四纪红黏土区矿化相对强烈;0～20 cm土层,花岗岩区和红砂岩区土壤有机碳相对趋向累积,而20～40 cm土层,第四纪红黏土区土壤有机碳相对累积;花岗岩区林地土壤微生物群落相对稳定,且0～20 cm层土壤微生物群落真菌较多。转化酶活性和脲酶活性在花岗岩和第四纪红黏土区较高;酸性磷酸酶活性在第四纪红黏土区显著较高;各母岩区土壤多酚氧化酶活性无显著性差异;过氧化氢酶活性在花岗岩区显著较高;因此,在马尾松与土壤长期作用下,花岗岩区土壤微生物群落稳定性,生化强度较高,相对适宜马尾松林种植。     

Vegetation roles on changes of soil properties and microbial activities in a coastal sand dune. A case study

The vegetation effects on changes of soil physicochemical properties and microbial activities in the costal sand dune were investigated to understand the roles of vegetation on sand dune ecosystem. Eight sites from six vegetation zones and two bare zones in the dune front, dune crest, and dune back regions were selected. Soil microbial enzyme activities of β-glucosidase, acid phosphatase, arylsulfatase, and dehydrogenase, and soil physicochemical properties of each site were evaluated. The results showed that all the enzyme activities were higher in the mixed vegetation sites with native sand dune plants and naturalized plants and in Pinus thunbergii community site both located in the dune back regions where the accumulation of organic matter and nitrogen were more prominent. The results demonstrated that soil organic matter and nutrients are the primary determinants of the microbial activity in sand dune where are exposed to a gradient of physicochemical stress such as high salinity, moisture and salt spray. Therefore, the conservation of vegetation that generates more soil organic matter and nutrients is important factor in controlling the soil microbial activities and biogeochemical cycles in the coastal sand dune systems.