放牧制度对短花针茅草原主要植物种群繁殖特征的影响

本文对短花针茅荒漠草原划区轮牧与自由放牧条件下主要植物种群的繁殖特性进了比较分析。结果表明 ,划区轮牧与自由放牧相比有利于短花针茅生殖枝的形成 ,且能够产生较多的种子 ;划区轮牧有利于主要植物种群实生苗的存活 ,但禁牧条件下对实生苗的生长更有利 ;短花针茅草原主要植物种群以无性繁殖为主 ,有性繁殖机会较少 ,且受降雨量的影响较大     

伊犁绢蒿(Seriphidium transiliense)个体功能性状对短期禁牧的可塑性响应

为了探讨禁牧对植物个体功能性状的影响,在新疆呼图壁县、玛纳斯县及昌吉市阿什里乡对短期禁牧下蒿类荒漠草地建群种伊犁绢蒿(Seriphidium transiliense)的个体表型特征、构件生物量及其分配比进行了测定。结果表明:伊犁绢蒿个体功能性状对短期禁牧的响应因禁牧地点的差异而有所不同,呼图壁和玛纳斯样地的大多性状如株高、地上生物量、叶片数、叶生物量均呈显著增加(P 0. 05),而昌吉样地多数功能性状虽为增加,但均不显著。总体分析可知,短期禁牧后伊犁绢蒿的株高、地上生物量、叶片数、茎生物量、叶生物量依次显著增加21. 32%、48. 97%、104. 50%、50. 18%、100. 00%(P 0. 05),根颈直径、一级及三级分枝数出现显著下降,而二级分枝数、生殖生物量、各构件生物量分配比变化不显著。伊犁绢蒿个体表型性状与其构件生物量及分配比间均具有显著的联动效应,且短期禁牧可引起其部分个体功能性状间的相关关系发生显著改变。研究表明,短期禁牧促进伊犁绢蒿个体功能性状的恢复,利于退化蒿类荒漠草地的恢复。     

Effect of herbicides and doses on short- and long-term control of Eleusine tristachya

In Argentina, Eleusine tristachya has been recently reported as a problematic weed that can occur at high densities in spring and summer in fallows and in maize and soyabean. The reason for the increase in E. tristachya populations is that once the weed is established, it is difficult to eliminate because it produces a high number of seeds and plant regrowth occurs after herbicide treatments. The aim of this study was to determine the effect of post-emergence application of herbicides (glyphosate, haloxyfop-methyl and clethodim) at the seedling, vegetative and reproductive stages on the short-term (biomass 30 days after treatment—30 DAT) and long-term (tiller number and height and seed production—regrowth at 330 DAT) control of E. tristachya selected biotypes in outdoor pot experiments. Data fitted to a log-logistic model. For all the herbicides considered, at the seedling and vegetative stages, short-term control was achieved with low ED₅₀ and ED₉₀ values, whereas at the reproductive stage, ED₉₀ values were three- to sixfold (glyphosate), six- to 52-fold (haloxyfop-methyl) and five- to 13-fold (clethodim) higher. Long-term control at the recommended dose or lower was not possible at the reproductive stage as tiller regrowth and seed production occurred with all herbicides. It is advisable to control Eleusine tristachya when plants are small at the beginning of the growing season using the recommended herbicide dose. A delayed application will produce tiller regeneration the following year, and consequently, control would only be achieved applying an overdose, which can cause risks to health and the environment. We concluded that a management programme based on the combination of glyphosate with post-emergence graminicides applied at early stages will be effective to control future infestations.     

Grazing every month minimizes size but boosts photosynthesis in Stipa grandis in the steppe of Inner Mongolia,China

In order to explore the effects of grazing frequency on functional traits and to test whether Stipa gandis has compensatory photosynthesis during the frequent grazing period, we investigated morphological traits, biomass allocation, photosynthetic traits, and chlorophyll fluorescence parameters of the species in Inner Mongolia, China. The grazing frequency treatments included fencing(T_0), grazing in May and July(T_1, i.e., two months per year) and grazing from May to September(T_2, i.e., continuous five months per year). Results indicate that T_1 and T_2 treatments did not affect individual biomass, but T_2 treatment negatively affected individual size, i.e., plant height, stem length, and leaf length. Physiological traits of S. grandis were significantly affected by grazing, year, and their interaction. In July 2014(i.e., dry environment and low relative humidity), the photosynthetic rate, transpiration rate and water use efficiency were highest under T_2 treatment, which was caused by the increase in stomatal conductance. However, in July 2015(i.e., wet environment and high relative humidity), the photosynthetic rate and water use efficiency were higher under T_1 and T_2 treatments, which were caused by the increase in actual quantum efficiency and stomatal conductance. Our results implied that under frequent grazing treatment, S. grandis had small height and efficient compensatory photosynthesis, which promoted its resistance to severe grazing.     

放牧对短花针茅草原土壤微生物和土壤养分的影响及其季节动态

研究了短花针茅草原不同季节、不同放牧梯度内土壤微生物数量、土壤养分的变化及土壤微生物与土壤养分之间的相关性,结果表明:轻度放牧区(LG)和重度放牧区(HG)内土壤微生物数量春季最高,土壤微生物数量(0-10 cm)在三个放牧区内随着季节的变化均呈下降趋势。而在10-20 cm,对照区内土壤微生物数量的高峰期出现在夏季然后开始下降,轻度放牧区和重度放牧区土壤微生物随着季节的变化而下降。土壤微生物数量到了秋季在三个放牧梯度内均呈现显著性的差异,土壤养分也是在秋季出现了显著性差异(P<0.05)。土壤微生物总数在不同放牧梯度内的变化规律是对照和轻度放牧区均大于重度放牧区。土壤微生物与土壤有机质和土壤全氮呈较强的正相关。     

乌拉特荒漠草原群落物种多样性和生物量关系对放牧强度的响应

以内蒙古乌拉特荒漠草原灌丛和草本植物群落为对象,研究这2种植物群落的物种组成、物种多样性及其与地上生物量关系对不同放牧处理(对照、中牧、重牧)的响应。结果表明:①随着放牧强度的增加,灌丛群落中红砂(Reaumuria songarica)和碱韭(Allium polyrhizum)的优势度增大,沙生针茅(Stipa glareosa)的优势度减小;重牧降低草本群落中沙生针茅的优势度,增加了蒙古韭(Allium mongolicum)和碱韭的优势度。②不同放牧处理显著降低了灌丛和草本群落的盖度、高度以及灌丛群落的密度,消除了灌丛和草本群落之间盖度的差异(P> 0. 05)。中牧降低灌丛群落的Pielou均匀度指数,重牧降低灌丛群落的物种丰富度,灌丛和草本群落的其他多样性指数在放牧处理之间无显著差异(P> 0. 05)。除物种丰富度外,其他多样性指数在灌丛和草本群落之间差异显著(P <0. 05)。③不同放牧处理降低了灌丛和草本群落的地上生物量和凋落物量,导致灌丛和草本群落之间地上生物量的显著差异(P <0. 05)。④地上生物量与Simpson优势度指数负相关,与Shannon-Wienner多样性指数和Pielou均匀度指数正相关;放牧处理下地上生物量与密度、物种丰富度正相关。放牧处理改变了荒漠草原植物群落组成、结构和功能,进而改变了群落结构和功能的重要关系。     

重寄生真菌盾壳霉胞外蛋白酶产生条件及酶活影响因子

重寄生真菌盾壳霉Coniothyrium minitans是核盘菌Sclerotinia sclerotiorum的重要生防菌。为了探讨盾壳霉胞外蛋白酶在寄生核盘菌过程中的作用,采用明胶平板法对盾壳霉寄生核盘菌菌核产生的蛋白酶活性进行了检测,并进一步采用福林酚法定量测定蛋白酶活性,研究盾壳霉产生胞外蛋白酶的培养条件及影响蛋白酶活性的因子。试验结果表明,在被盾壳霉寄生的核盘菌菌核中检测到蛋白酶活性,表明蛋白酶可能参与盾壳霉重寄生作用。发现核盘菌菌核浸出液培养基适合盾壳霉产生胞外蛋白酶,摇培(20℃、200r/min)5d时蛋白酶活性最高,达到0.22U/mL。盾壳霉胞外蛋白酶酶促反应的最适温度为60℃,最适pH7.0。当温度不高于40℃时,蛋白酶酶活较稳定。5mmol/L的金属离子Mg²⁺、Zn²⁺、Ca²⁺、Cu²⁺、Mn²⁺、Li⁺和K⁺等对蛋白酶酶活没有显著影响(P>0.05),而Fe²⁺(5mmol/L)显著(P<0.05)提高了蛋白酶活性。盾壳霉蛋白酶对苯甲基磺酰氟(PMSF)敏感,说明盾壳霉产生的胞外蛋白酶可能主要是丝氨酸蛋白酶。这些结果为盾壳霉胞外蛋白酶的分离纯化和功能研究奠定了基础。     

不同放牧制度对荒漠草原短花针茅空间异质性的影响

在不同放牧制度下,以荒漠草原短花针茅植物种群为研究对象,采用GS＋软件和地统计学分析方法对其空间异质性分布进行了研究。结果显示：对照区和划区轮牧区或自由放牧区都表现出很强的空间自相关性,且结构是导致短花针茅空间变异的主要因素。对照区、划区轮牧区和自由放牧区,短花针茅空间格局的分形维数相近,都接近于2。不同放牧制度下短花...     

Effects of grassland management on the community structure,aboveground biomass and stability of a temperate steppe in Inner Mongolia,China

Plant community structure responds strongly to anthropogenic disturbances, which greatly influence community stability. The changes in community structure, aboveground biomass(AGB), biodiversity and community stability associated with different management practices were studied with a three-year field investigation in a temperate steppe of Inner Mongolia, China. The species richness, Shannon-Wiener index, evenness, plant functional type abundance, AGB, temporal community stability, summed covariance, scaling coefficient and dominant species stability were compared among areas subjected to long-term reservation(R), long-term grazing(G), mowing since enclosure in 2008(M) and grazing enclosure since 2008(E). Site R had higher perennial grass abundance and lower species richness than sites G, M and E, although the AGB was not significantly different among the four sites. The species structure varied from a single dominant species at site R to multiple dominant species at sites G, M and E. The long-term reservation grassland had lower biodiversity but higher stability, whereas the enclosed grassland with/without mowing had higher biodiversity but lower stability. Different stability mechanisms, such as the compensatory dynamics, mean-variance scaling and dominant species stability were examined. Results showed that community stability was most closely related to the relative stability of the dominant species, which supports the biomass ratio hypothesis proposed by Grime.     

围栏与不同放牧强度对东祁连山高寒草甸植被和土壤的影响

在东祁连山高寒草地,对围栏7年和不同放牧强度的草地进行了物种数、地上生物量、地下生物量、土壤理化性质等研究。结果表明,围栏7年的高寒草地鲜草产量为425.8 g·m-2,显著高于夏季中牧159.3 g·m-2和夏季重牧91.0 g·m-2,但与冬季轻牧、夏季轻牧差异不显著。围栏条件下的物种数为26.3种·16 m-2,显著低于其他放牧条件下的物种数,但显著高于夏季重牧条件下的物种数23.0种·16 m-2;轻度或重度放牧都会使物种数减少,夏季中牧下的物种数最高(33.5种·16 m-2)。在0~10 cm的表层土壤中,围栏7年的草地根系生物量显著高于其他放牧强度。随着放牧强度的增加,根系生物量在0~10 cm土壤中呈下降趋势,在30~40 cm土壤中则表现为升高趋势。围栏7年的土壤容重低于其他放牧强度下的土壤容重,但差异不显著;夏季重牧的土壤容重显著高于围栏7年和其他放牧强度的土壤容重。随着放牧强度的增加,0~10 cm土壤碱解氮增加,围栏7年草地最低。围栏封育可有效改善和恢复草地植被,但不能长时间禁牧不进行放牧利用。合理的放牧能够维护高寒草甸草地生态系统功能、促进物种丰富度和土壤营养的均衡。     

Response of root traits of Reaumuria soongorica and Salsola passerina to facilitation

C3 plant Reaumuria soongorica and C4 plant Salsola passerina are super xerophytes and coexist in a mixed community in either isolated or associated growth, and interspecific facilitation occurs in associated growth. In the present study, the root traits including root distribution, root length(RL), root surface area(RSA), root weight(RW) and specific root length(SRL) of both species in two growth forms were investigated to clarify their response to facilitation in associated growth. Six isolated plants of each species, as well as six associated plants similar in size and development were selected during the plant growing season, and their roots were excavated at 0–10, 10–20, 20–30, 30–40 and 40–50 cm soil depths at the end of the growing season. All the roots of each plant were separated into the two categories of fine roots(2 mm diameter) and coarse roots(≥2 mm diameter). Root traits such as RL and RSA in the fine and coarse roots were obtained by the root analyzing system WinRHIZO. Most of the coarse roots in R. soongorica and S. passerina were distributed in the top 10 cm of the soil in both growth forms, whereas the fine roots of the two plant species were found mainly in the 10–20 and 20–30 cm soil depths in isolated growth, respectively. However, the fine roots of both species were mostly overlapped in 10–20 cm soil depth in associated growth. The root/canopy ratios of both species reduced, whereas the ratios of their fine roots to coarse roots in RL increased, and both species had an increased SRL in the fine roots in associated growth. In addition, there was the increase in RL of fine roots and content of root N for S. passerina in associated growth. Taken together, the root growth of S. passerina was facilitated for water and nutrient exploration under the interaction of the overlapped roots in both species in associated growth, and higher SRL allowed both species to more effectively adapt to the infertile soil in the desert ecosystem.     

Effects of choke disease in the grass Brachypodium phoenicoides

Using phenotypic and molecular characters, as well as mating compatibility tests, the fungus causing choke disease in Brachypodium phoenicoides was identified as Epichloë typhina . A three year field experiment conducted with infected and uninfected plants of a single clone of B. phoenicoides showed no significant differences in biomass production during their vegetative growth stage, but the content of calcium, magnesium and manganese was significantly greater, and that of sodium was significantly lower in infected plants compared to uninfected plants. Infected plants produced up to twice as many reproductive tillers as healthy plants, but their reproductive tissue biomass was significantly smaller than that of healthy plants, because tiller development was arrested by choke forming stromata.     

两种昆虫病原线虫防治核桃云斑天牛田间效果评价

云斑天牛Batocera lineolata Chevrolat是核桃树的严重蛀干害虫,隐蔽性强,化学、物理防治方法难以奏效,昆虫病原线虫可以主动寻找寄主并在蛀道内建立种群,省工长效。本研究评价了不同剂量（250、500、1000、2000和4000 IJs/mL）的2种昆虫病原线虫（小卷蛾斯氏线虫Steinernema carpocapsae和嗜菌异小杆线虫Heterorhabditis bacteriophora）对核桃云斑天牛卵和幼虫的防治效果。结果表明,2种线虫对天牛卵和幼虫的最终防控效果随施用剂量增大而增强。施用剂量为4000 IJs/mL的小卷蛾斯氏线虫和嗜菌异小杆线虫对该天牛卵的校正防治效率分别达65.0%和39.5%,对幼虫的最终校正防治效率分别达93.8%和82.4%;2种线虫在2000 IJs/mL剂量下对天牛卵的校正防治效率分别达48.8%和32.3%,对幼虫的校正防治效率分别达85.9%和83.4%。从而说明,适宜剂量的昆虫病原线虫对云斑天牛幼虫的田间防控效果好于对卵的效果,可以作为云斑天牛的有效防治技术。     

淀粉酶产色链霉菌1628中toyF基因的克隆与丰加霉素合成相关性

为考察编码腺苷琥珀酸裂解酶toyF基因对淀粉酶产色链霉菌Streptomyces diastatochromogenes 1628合成丰加霉素的影响,本研究设计简并引物,首次克隆获得了菌株1628的toyF基因,并构建了敲除质粒pKC1132-toyF',通过接合转移转入菌株1628,获得toyF基因缺失株1628-ΔTOYF。结果表明,与原始菌株1628相比,缺失株1628-ΔTOYF中TOYF的酶活和丰加霉素产量分别降低66.7%、87.5%。在缺失株1628-ΔTOYF中回补表达toyF基因构建了重组菌1628-ΔTOYF/toyF。重组菌1628-ΔTOYF/toyF中的TOYF酶活和丰加霉素产量,较缺失株1628-ΔTOYF分别提高了2.7和8.3倍。由此可见,toyF基因是参与菌株1628生物合成丰加霉素的关键酶基因。本文toyF基因的克隆及其功能研究,为克隆完整的丰加霉素生物合成基因簇及其丰加霉素生物合成机制的研究奠定了基础。     

短花针茅荒漠草原土壤种子库对不同放牧强度的响应

在内蒙古短花针茅荒漠草原,采用野外随机定点取样与室内萌发相结合的方法,对不同放牧强度下围封草地土壤种子库的密度、垂直结构、多样性、丰富度、均匀度、以及种子库与地上植被的相似性进行了研究。结果表明,在各试验区土壤种子库主要分布在0～20cm土层,占种子库总密度的87%～96%;随着放牧强度的增加,土壤种子库总密度减少,同时地上植被与土壤种子库的相似物种数减少,种子库组成的相异性增加;轻度放牧对土壤种子库中一二年生草本所占比例影响较小,而中度和重度放牧使土壤种子库中一二年生草本所占比例增加;土壤种子库的物种丰富度、多样性、均匀度均随放牧强度的增加而减小。     

Effects of warming and clipping on plant and soil properties of an alpine meadow in the Qinghai-Tibetan Plateau,China

Climate warming and livestock grazing are known to have great influences on alpine ecosystems like those of the Qinghai-Tibetan Plateau(QTP) in China. However, it is lacking of studies on the effects of warming and grazing on plant and soil properties in these alpine ecosystems. In this study, we reported the related research from manipulative experiment in 2010–2012 in the QTP. The aim of this study was to investigate the individual and combined effects of warming and clipping on plant and soil properties in the alpine meadow ecosystem. Infrared radiators were used to simulate climate warming starting in July 2010, while clipping was performed once in October 2011 to simulate the local livestock grazing. The experiment was designed as a randomized block consisting of five replications and four treatments: control(CK), warming(W), clipping(C) and warming+clipping combination(WC). The plant and soil properties were investigated in the growing season of the alpine meadow in 2012. The results showed that W and WC treatments significantly decreased relative humidity at 20-cm height above ground as well as significantly increases air temperature at the same height, surface temperature, and soil temperature at the depth of 0–30 cm. However, the C treatment did not significantly decrease soil moisture and soil temperature at the depth of 0–60 cm. Relative to CK, vegetation height and species number increased significantly in W and WC treatment, respectively, while vegetation aboveground biomass decreased significantly in C treatment in the early growing season. However, vegetation cover, species diversity, belowground biomass and soil properties at the depth of 0–30 cm did not differ significantly in W, C and WC treatments. Soil moisture increased at the depth of 40–100 cm in W and WC treatments, while belowground biomass, soil activated carbon, organic carbon and total nitrogen increased in the 30–50 cm soil layer in W, C and WC treatments. Although the initial responses of plant and soil properties to experimental warming and clipping were slow and weak, the drought induced by the downward shift of soil moisture in the upper soil layers may induce plant belowground biomass to transfer to the deeper soil layers. This movement would modify the distributions of soil activated carbon, organic carbon and total nitrogen. However, long-term data collection is needed to further explain this interesting phenomenon.     

宁夏河东沙地不同放牧方式对物种结构及多样性的影响

以宁夏河东沙地退化草场的不同放牧方式为研究对象,对植物群落结构及多样性的进行研究,结果表明:不同放牧方式一定程度上改变了植物群落优势种的分布,增加了物种数,使植物群落逐渐趋于稳定性,且6区轮牧、4区轮牧、2区轮牧的盖度分别比单轮(自由放牧)提高了28.26%、39.13%、10.87%;从植物群落多样性的平均值来看,以2区轮牧和6区轮牧的最高、自由放牧(单轮)的最低,而且植物的均匀度指数与多样性指数呈相同趋势,生态优势度指数和多样性指数呈相反趋势;封育、6区轮牧、4区轮牧、2区轮牧的草产量分别比自由放牧(单轮)提高133.04%、47.96%、33.99%40.65%,说明在20亩/羊单位下,采用不同放牧方式一定程度上提高了草产量,并且以6区轮牧的效果较好。     

不同保护和利用方式下羊草草原群落生物量及能量功能群构成的比较

基于野外调查数据,结合能量功能群分类方法,对不同围封年限(围封4年,围封9年,围封29年)及不同利用方式(放牧、割草)影响下羊草草原的生物量、根冠比及不同能量功能群优势度进行比较分析,结果表明:围封使得群落地上、地下总生物量增加,并随着围封年限的增加渐趋稳定。相比围封保护,放牧和打草利用均会使群落根冠比变大。5个样地比较,放牧退化对群落的能量功能群构成影响较大,相比其他样地,低能值植物功能群优势度明显增加,而中能值和高能值植物功能群则明显下降。几个围封样地和打草场样地之间则没有显出规律性变化。相比重度放牧而言,围封和打草这两种利用方式都可以使羊草草原得到很好的保护。而对于围封而言,围封3-5年后对羊草草原加以适度的利用对草原保护和经济的发展都是有利的。     

不同强度放牧对贝加尔针茅草原群落和土壤理化性质的影响

在一个生长季内,比较分析了贝加尔针茅草甸草原不同放牧强度地段(非牧段,轻牧段,中牧段和重牧段,以放牛为主)植物群落的总地上现存量、总投影盖度、平均高度和土壤理化性质的变异。结果表明,不同强度放牧条件下各项指标均呈规律性变化,表现为植被的生长状况和土壤状况随着放牧强度的增加而劣化,且群落总地上现存量、总投影盖度、群落高度之间具有显著的相关性。土壤的pH值和电导率与地面凋落物的量之间存在显著负相关。考虑各项指标对放牧反应的敏感性、变化的稳定性和测定的方便性,可以把群落盖度、土壤化学性质的变化作为草地健康评价的关键指标。     

Long-term effects of mowing on plasticity and allometry of Leymus chinensis in a temperate semi-arid grassland,China

Mowing is an important land management practice for natural semi-arid regions.A growing body of empirical evidence shows that different mowing regimes affect the functioning of grassland ecosystems.However,the responses of plant functional traits to long-term mowing and their allometric scaling under long-term mowing are poorly understood.For a better understanding of the effects of mowing on grassland ecosystems,we analyzed the allometric traits of leaves and stems of Leymus chinensis(Trin.) Tzvel.,a dominant grass species in eastern Eurasian temperate grassland,at different mowing intensities(no clipping,clipping once every two years,once a year and twice a year).Experiments were conducted on plots established over a decade ago in a typical steppe of Xilinhot,Inner Mongolia,China.Results showed that most of the functional traits of L.chinensis decreased with the increased mowing intensity.The responses of leaves and stems to long-term mowing were asymmetric,in which leaf traits were more stable than stem traits.Also significant allometric relationships were found among most of the plant functional traits under the four mowing treatments.Sensitive traits of L.chinensis(e.g.leaf length and stem length) were primary indicators associated with aboveground biomass decline under high mowing intensity.In conclusion,the allometric growth of different functional traits of L.chinensis varies with different long-term mowing practices,which is likely to be a strategy used by the plant to adapt to the mowing disturbances.