旅游干扰对历山亚高山草甸植物多样性的影响

历山是国家级自然保护区,也是山西省自然保护区中面积最大、物种资源最丰富的自然保护区.运用丰富度指数、物种多样性指数和均匀度指数,结合方差分析研究了旅游干扰对历山舜王坪亚高山草甸植物多样性的影响及其变化规律.结果表明:(1)随着距游径距离的增加,不同样带主要科、属、种的数量均有所上升,毛茛科所含种数增加幅度较大,菊科、蔷薇科、禾本科所含种数变化幅度较小.(2)不同样带植物主要优势种的相对盖度、相对密度、相对高度均发生了不同程度的变化(p〉0.05),距离游径越远,主要优势种的相对盖度、相对密度、相对高度越大;伴人植物则表现出相反的变化趋势,即距离游径越远,伴人植物的相对盖度、相对密度、相对高度越小,个别物种甚至消失(如扁蓄).(3)生活型功能群中,多年生草本植物的种数最多,占总种数的79.24%,1年生植物和灌木合占总种数的20.76%.随着旅游干扰强度的增加,1年生植物的比例略有增加,多年生草本植物的比例略有下降,灌木所占比例较为稳定.(4)随着远离游径,物种丰富度和物种多样性指数略有增加,而物种均匀度指数表现为先升后降的趋势,增减幅度经方差分析未达到显著水平(P〉O.05).鉴于目前旅游活动对历山舜王坪草甸植物多样性的干扰程度,建议保护区应在开展旅游的同时,加强资源的保护和可持续利用. 高度越小,个别物种甚至消失(如扁蓄).(3)生活型功能群中,多年生草本植物的种数最多,占总种数的79.24%,1年生植物和灌木合占总种数的20.76%.随着旅游干扰强度的增加,1年生植物的比例略有增加,多年生草本植物的比例略有下降,灌木所占比例较为稳定.(4)随着远离游径,物种丰富度和物种多样性指数略有增加,而物种均匀度指数表现为先升后降的趋势,增减幅度经方差分析未达到显著水平(P》O.05).鉴于目前旅游活动对历山舜王坪草甸 物多样性的干扰程度,建议保护区应在开展旅游的同时,加强资源的保护和可持续利用. 高度越小,个别物种甚至消失(如扁蓄).(3)生活型功能群中,多年生草本植物的种数最多,占总种数的79.24%,1年生植物和灌木合占总种数的20.76%.随着旅游干扰强度的增加,1年生植物的比例略有增加,多年生草本植物的比例略有下降,灌木所占比例较为稳定.(4)随着远离游径,物种丰富度和物种多样性指数略有增加,而物种均匀度指数表现为先升后降的趋势,增减幅度经方差分析未达到显著水平(P》O.05).鉴于目前旅游活动对历山舜王坪草甸 物多样性的干     

河水漫溢对塔里木河下游荒漠河岸林地表植被与土壤种子库的影响

采用种子萌发法,研究了河水漫溢对塔里木河下游荒漠河岸林地表植被与土壤种子库的影响.结果表明：塔里木河下游漫溢区地表植被分属8科13属14种,非漫溢区为10科21属26种植物;与非漫溢区相比,漫溢区地表植被中出现了一些浅根系和喜湿的草本植物;漫溢区单位面积物种数、植被盖度、植株密度、物种多样性指数和丰富度指数均比非漫溢区有明显增加.漫溢区土壤种子库中有物种19种,比非漫溢区增加了5种;漫溢区土壤种子库总密度比非漫溢区增加了3.94倍;与非漫溢区相比,漫溢区1年生草本植物种子的比例增加了23.07%,而灌木植物种子比例减少了20.99%;多年生草本的变化则不明显;河水漫溢提高了土壤种子库的生物多样性.漫溢区和非漫溢区土壤种子库与地表植被的共有物种分别为18和9种,土壤种子库与地表植被的相似性系数分别为0.842和 0.667.     

塔里木河下游不同退化区地表植被和土壤种子库特征

对塔里木河下游不同退化程度的4个典型断面进行了植被和土壤种子库的取样调查,采用种子萌发试验研究了不同退化区植被和土壤种子库的特征,结果表明:(1)塔里木河下游地表植被表现为严重的逆行演替,具体体现为胡杨林都为过熟林,几乎没有胸径在10cm以下的幼林;植被盖度、密度和多样性指数均维持在一个较低的水平上;随退化程度不断加重,地表植被中草本植物的相对密度、相对盖度和相对频度逐渐降低,而灌木和乔木的相对密度、相对盖度和相对频度逐渐增加;(2)研究区土壤种子库的基本特征是:土壤种子库种类贫乏、密度低、多样性指数和相似性系数不高;(3) 随退化程度的加重,土壤种子库物种数不断减少、密度明显下降、优势种组成趋于单一、表层种子库比例升高、1年生草本植物占优势逐渐向多年生草本植物和灌木植物转变及土壤种子库物种组成与地上植被物种组成上差异显著.     

石羊河中游沙漠化逆转过程土壤种子库的动态变化

在石羊河中游,应用空间代替时间的方法,选择流动沙丘以及封育恢复5a、15a和25a的沙漠化逆转过程序列,研究了沙漠化逆转过程土壤种子库的变化特征。结果表明:石羊河中游沙漠化土地土壤种子库由4科12种植物组成,种子库主要分布于表层0-5cm。在沙漠化逆转过程中,土壤种子库物种数趋于增加,物种组成以1年生草本植物占优势逐渐向多年生草本植物和半灌木植物转变;种子库密度、表层土壤种子比例、物种多样性指数、与地上植被的相似性呈现先增大后降低趋势;沙漠化土地生态恢复间隔的时间越长,土壤种子库间的相似性程度越低;沙漠化土地与地带性植被区种子库的相似性逐渐增大,但是恢复25a沙漠化土地也仅达到0.36。研究认为,沙漠化逆转过程也是沙漠化土地土壤种子库向地带性植被土壤种子库演变的过程,而且是一个十分缓慢的过程,该研究有助于丰富干旱区土壤种子库的理论和指导干旱内陆河流域沙漠化土地的生态恢复实践。     

新疆准噶尔盆地荒漠草地水源圈植物群落退化格局

游牧民定居放牧是目前主要的放牧方式,导致水源圈在中国北方干旱半干旱区草场上普遍存在。2014年5月底至6月初,在新疆北部荒漠草地上,以一个典型的牧场水源点为中心,在8个方向上设置50、100、200、400、800和1200 m共6个采样距离进行植物群落调查取样。通过分析植物群落的组成、物种重要值、丰富度以及群落的盖度、高度和地上生物量的变化特征,期望为荒漠草地退化生态系统的恢复和可持续管理提供科学依据。结果表明:随着与水源点距离的减少、放牧强度的增加,荒漠草地植物群落特征呈现明显梯度变化,建群植物博洛塔绢蒿优势度逐渐降低,1年生植物优势度逐渐增加;植物群落、多年生草本植物和1年生草本植物的物种丰富度逐渐增加;群落总盖度逐渐降低,与建群植物博洛塔绢蒿的盖度显著正相关。1年生植物和有毒植物骆驼蓬在水源点附近优势度增加,说明放牧导致水源点附近地上植物群落趋于退化。因此,在这一地区开展游牧民定居导致水源圈大量出现,可能加剧荒漠草地的退化。     

科尔沁沙地植被恢复演替进程中群落土壤种子库研究

研究了科尔沁沙地植被恢复演替进程中各群落土壤种子库种类组成、密度以及物种多样性等特征。主要结论是:①科尔沁沙地植被退化后的恢复演替是一种次生的中途恢复演替。演替各阶段土壤种子库密度为流动沙丘<半流动沙丘<固定沙丘,从流动到半流动沙丘阶段,土壤种子库密度平均增加了709%;从半流动到固定沙丘阶段,土壤种子库密度平均增加了393%。从流动到半流动沙丘阶段是土壤种子库密度的快速增长期。②植被恢复演替过程中,土壤种子库组成均以1年生草本植物为主(优势度为60.40%~91.83%),到演替中后期阶段,多年生草本植物的种类有所增加,但其所占比例仍很小。③演替各阶段群落种子库物种多样性指数分别为0.6616、0.7736、0.7281、1.0939、1.0648和0.9682,可见种子库物种多样性最高的群落并非是演替历史最大的群落。④恢复演替系列各阶段土壤种子库间的相似性系数都较大,在0.368~1.000范围之内,任一群落总是与其下一阶段最邻近的群落具有最高的相似性系数。     

黄河三角洲滨海湿地地下水位变化对土壤种子库特征的影响

地下水位是影响湿地生态系统结构和功能的重要环境因子之一,然而其如何影响滨海湿地土壤种子库特征尚不清楚。通过地下水位控制试验,研究黄河三角洲滨海非潮汐湿地地下水位梯度（-20、-60、-100 cm）下,土壤种子库密度、物种多样性等特征,并通过土壤化学指标与对应的土壤种子库特征之间的通径分析,探讨地下水位深度变化对土壤种子库特征的影响机理。研究发现,在该区域秋季采样的土壤种子库中,碱蓬和盐地碱蓬的种子数量最多;地下水位变化对土壤种子库密度无显著影响,但对土壤种子库的物种组成影响较大,随着地下水位深度增加,多年生草本植物种类呈增加趋势。整体上,随着地下水位深度增加,土壤种子库的Margalef丰富度指数和Shannon-Wiener多样性指数随之增大。主成分分析表明,土壤盐是影响黄河三角洲滨海湿地土壤种子库组成特征的主导因素,贡献率为69.482%,土壤养分为次要影响因素,贡献率为23.710%,进一步通径分析表明,土壤水溶性盐总量对种子库物种多样性起到限制作用,同时,有效磷浓度通过水溶性盐总量对Margalef指数和Shannon-Wiener指数表现为间接负作用,总磷浓度对种子库与地上植被相似性起到促进作用。研究表明,黄河三角洲滨海湿地地下水位深度变化,主要通过影响土壤水溶性盐总量,进而影响土壤种子库物种多样性。     

腾格里沙漠东南缘公路对路域植被物种组成的影响

沿腾格里沙漠东南缘省道201线沙坡头-景泰段2侧设置48条垂直于公路的样线,调查距路缘不同距离处植被的物种分布特征,研究干旱荒漠区公路建设和运营对植被物种组成的影响.结果表明:随着距路缘距离的增加,草本植物的种数、盖度、生物量和α多样性均逐渐减小,5 m后与对照差异不显著,高度在0～6 m处较大,密度变化不显著.0～2 m处草本植物的物种周转速率较低,2～5 m处最高,10 m后物种组成与对照相似.路缘处的草本植物群落以禾本科植物占优势,抗干扰能力较强的白草、虎尾草和冰草占草本植物总个体数的68.6%.其中,虎尾草在距路缘1 m后,白草和冰草在距路缘2 m后数量和频度迅速减小,而菊科植物茵陈蒿和冷蒿急剧增加,距路缘2 m后占草本植物总个体数的70%.路缘处灌木植物的盖度和密度显著小于对照,物种组成与对照没有显著差异.     

三峡库区消落带水淹初期地上植被与土壤种子库的关系

采用种子萌发法,研究了三峡库区消落带水淹初期所形成的已淹区段、未淹区段以及留存原有植被的对照样带地表植被与土壤种子库之间的关系。结果表明:三峡库区消落带已淹区段地表植被分属47科71属100种,未淹区段84科163属223种,优势科主要为菊科、豆科、禾本科、蔷薇科、莎草科。地上植被的物种生活型,已淹区段以生长周期短、适应性较强的1年生草本为主,灌木和乔木共占19%;未淹区段中1年生草本占20.45%,多年生草本占36.36%,灌木或藤本占28.18%,乔木占15%;对照样带中1年生草本占23.24%,多年生草本占41.32%,灌木及藤本占32.02%,乔木占17.05%。与对照样带相比,已淹区段地表植被物种多样性指数和丰富度指数都明显降低,未淹区段地表植被却表现出明显增加的趋势,只有Pielou均匀度指数都降低;已淹区段、未淹区段土壤种子库分别具有物种79种和108种,分别比对照样带增加了9种和38种;已淹区段种子库密度为(12667±2225.25)粒/m2、未淹区段为(38013±9796.04)粒/m2、对照样带为(18715±8234.77)粒/m2,与对照样带土壤种子库总密度相比,已淹区段降低了32.32%,未淹区段增加了103.12%,都以草本植物占绝大多数比例,且1年生草本所占比例大于多年生草本所占比例。土壤种子库的生物多样性指数、丰富度指数和均匀度指数与地表植被变化相一致,但变化幅度较小。消落带已淹区段、未淹区段、对照样带地表植被和土壤种子库共同出现的物种数分别为9,40和15种,土壤种子库和地表植被间Sorensen相似性系数分别为0.328,0.241,0.186,表明三峡库区消落带水淹初期区域整体相似系数较低,这与消落带形成时间短有很大的关系。     

贺兰山低山区土壤种子库空间分布特征北大核心CSCD

土壤种子库作为地上植被更新的潜在种源,在植被自然恢复和演替过程以及生态系统建设中起着重要作用。该研究对贺兰山低山区不同海拔高度植物群落土壤理化性质变化与其土壤种子库特征之间的关系进行分析,以揭示贺兰山低山区植物群落的土壤种子库空间分布特征和自然恢复潜力。研究结果表明:(1)海拔1200 m处种子主要来源于一年生草本,海拔1600 m土壤种子库主要来源于多年生草本,海拔2000 m土壤种子库主要来源于灌木和小灌木;随着海拔升高,隶属于禾本科的物种数呈下降趋势,菊科和藜科呈增加趋势,蒺藜科、大戟科、豆科和玄参科消失。(2)5个海拔高度土壤种子库物种数均显著低于地上植被;在物种生活型组成上,土壤种子库中物种数占比最大为一年生草本,地上植被为多年生草本。(3)土壤理化性质对种子库物种多样性影响中,土壤pH、电导率最为显著。贺兰山低山区5个海拔高度土壤种子库种子密度和物种多样性均较低,无法满足植被自然恢复需求,可通过飞播等生态恢复措施来弥补表层土壤种子的不足,从而满足地上植被恢复所需种源量。     

FINE STRUCTURE OF THE SNOW ALGA (CHLAMYDOMONAS NIVALIS) AND ASSOCIATED BACTERIA1

Chlamydomonas nivalis (Bau.) Wille is present in red snow as large spherical resting cells. Fine structural studies reveal an abundance of clear granules in the cytoplasm and occasional starch grains in the chloroplast. Individual cells display a thick cell wall with a smooth outer surface. Cells may be surrounded by a loose fibrous network in which encapsulated bacteria are seen. The bacteria have a characteristic Gram-negative cell wall and constrictive mode of division. The algal-bacterial association appears to be characteristic of red snow populations.     

Energy feedbacks of northern high-latitude ecosystems to the climate system due to reduced snow cover during 20th century warming

The warming associated with changes in snow cover in northern high-latitude terrestrial regions represents an important energy feedback to the climate system. Here, we simulate snow cover-climate feedbacks (i.e. changes in snow cover on atmospheric heating) across the Pan-arctic over two distinct warming periods during the 20th century, 1910–1940 and 1970–2000. We offer evidence that increases in snow cover–climate feedbacks during 1970–2000 were nearly three times larger than during 1910–1940 because the recent snow-cover change occurred in spring, when radiation load is highest, rather than in autumn. Based on linear regression analysis, we also detected a greater sensitivity of snow cover–climate feedbacks to temperature trends during the more recent time period. Pan-arctic vegetation types differed substantially in snow cover–climate feedbacks. Those with a high seasonal contrast in albedo, such as tundra, showed much larger changes in atmospheric heating than did those with a low seasonal contrast in albedo, such as forests, even if the changes in snow-cover duration were similar across the vegetation types. These changes in energy exchange warrant careful consideration in studies of climate change, particularly with respect to associated shifts in vegetation between forests, grasslands, and tundra.     

杉木人工林冰雪灾害受灾和萌生情况调查

以九龙山国家级自然保护区的主要公益林杉木人工林作为研究对象,选择具有代表性的受灾区域,自海拔700 m至900 m设置样地,共10块样地,总面积4 000 m2。分析其受2008年初严重冰雪灾害破坏及灾后萌生情况与胸径、树高、尖削度、海拔之间的关系。结果表明：1）杉木人工林损害严重,其中断冠、断干植株比例较高,而掘根和冻死植株相对较少;杉木具有极强的萌生能力,以断冠杉木的萌生能力最强。2）不同胸径、树高、尖削度的杉木对于冰雪灾害的抵御能力及萌生能力存在一定差异,小径级矮小的个体受灾较重,易被冻死和掘根,大径级的较高个体受灾相对较轻,主要表现为断冠和断干危害,且不同径级下的受灾杉木上部萌生均占较大比例。3）杉木的抵御能力和萌生能力与海拔存在一定的关系,高海拔地区杉木受灾较重,而中海拔地区的杉木萌生能力相对较强。     

青藏高原1979-2007年间的积雪变化

利用雪深被动微波遥感数据产品,对青藏高原1979—2007年积雪深度、积雪日数的分布变化及其趋势进行了分析。结果表明:青藏高原积雪日数、积雪深度和海拔三者之间在空间上具有显著正相关;青藏高原积雪在1988年发生突变,该年前后积雪分布有显著不同,这与20世纪80年代中后期青藏高原由暖干时期进入暖湿时期有关;将青藏高原按夏季水汽来源不同将其分为南北两部分,发现29年来北部积雪日数变化与全国积雪变化相反呈极显著增加趋势(R2=0.39,P0.01),以1.40 d/a的趋势增加,主要原因是西北部地区冬季积雪日数增加;南部积雪深度与全国积雪变化一致呈极显著减少趋势(R2=0.24,P0.01),以-0.04 cm/a的趋势减少,主要原因是东南部春、夏、秋三季积雪深度减少。     

Impact of spruce forest on rainfall interception and seasonal snow cover evolution in the Western Tatra Mountains,Slovakia

The paper analyzes the impacts of the spruce forest on precipitation interception and evolution of snow cover in the mountain catchment of the Jalovecky creek, the Western Tatra Mountains, Slovakia. Both processes were monitored at the elevation of 1420 m a.s.l.. Interception was measured from the end of August 2006 until November 2008 by a network of 13 raingauges. Mean interception over the studied period in forest window was 23%. Mean values for the dripping zone under tree branches, near stems of the trees and under the young trees were 28%, 65% and 44%, respectively. With exception of forest window, the interception at the same characteristic positions was highly variable. Calculated daily precipitation thresholds needed to fulfill the storage capacity of the canopy were about 0.8–0.9 mm. Differences in snow accumulation and melt in the open area (elevation 1500 m a.s.l.) and in the forest were measured in winters 2003–2008. Snow depths (SD) and water equivalents (SWE) were typically smaller in the forest, although the differences were getting smaller towards the end of snow season. SD and SWE in the forest were higher than in the open area for a short time before the end of season in winters 2003 and 2005. The correlations between SD and SWE in the open area and in the forest explained about 90% of variability. The energy balance snow model UEB satisfactorily simulated the evolution of snow cover in the forest and in the open area.     

Nitrate concentrations in snow from remote areas: implication for the global NO x flux

Increased emissions of nitrogen compounds to the atmosphere by human activities have been well documented. However, in order to better quantify these anthropogenic emissions, better knowledge of natural emissions rates must be known. In addition, variation in natural emissions through time should be documented. In this note we present data collected and/or analyzed by us for NO₃ ^– in recent snow from remote regions of the world. We also summarize existing data sets from other remote regions. This is done to establish a better understanding of NO₃ ^– deposition rates in these regions as well as to add more information to our global understanding of NO₃ ^– deposition.     

PHOTOSYNTHESIS IN THE SNOW: THE ALGA CHLAMYDOMONAS NIVALIS (CHLOROPHYCEAE)1

Red blooms of snow algae consisting almost exclusively of large spherical red cells of Chlamydomonas nivalis (Bauer) Wille are widespread during the summer in the Beartooth Mountains in Montana and Wyoming. Field studies designed to examine the effects of temperature, light, and water potential on algal activity were performed with natural populations using photosynthetic ¹⁴C-HCO₃- or ¹⁴CO₂ incorporation as a measure of activity. The algae photo-synthesized optimally at 5.4 × 10⁴ lx, but were not inhibited by increased light intensity up to 8.6 × 10⁴ lx, the maximum observed in the field. Photosynthesis was sensitive to a reduction in water potential, and since low water potentials develop in snow at temperatures below 0 C, it is unlikely that significant algal activity occurs at the sub-0 temperatures which occur throughout winter. Photosynthesis was much lower following melting of the snow, but this was probably due to decreased diffusion of CO₂. The optimal temperatures varied considerably among the different algal populations. Most samples photo-synthesized optimally at 10 or 20 C but retained substantial activity at temperatures as low as 0 or -3 C. Exceptional samples photosynthesized optimally at 0 or -3 C. It is proposed that the varied temperature responses reflect the presence of different temperature strains. Taken together, the data suggest that development of the snow algae can occur only during the summer months.     

Spectral distribution of light under a subarctic winter lake cover

This study examines the spectral distribution of light penetrating the snow and ice cover of a lake in subarctic Labrador. Using a large sample under a range of cover conditions, the role of distinct layers, (snow, white or snow ice, black or clear ice) commonly found in subartic and temperate lake winter covers, was investigated. Measurement and analysis were restricted to wavelengths between 450 nm and 720 nm. Snow and white ice light transmittance was greatest at 450 and 470 to 500 nm respectively. Absorption was greatest in the red portion of the measured spectrum; white ice showing greater red absorption than snow. Black ice light transmittance showed only a slight wavelength dependence. The differential spectral absorption of light by snow and white ice layers produced a marked spectral distribution of the light that reaches the lake water surface. The importance of a spectral, rather than polychromatic, approach to the study of light, in winter biological limnology studies, is stressed.     

The consequences of multiple resource shifts on the productivity and composition of alpine tundra communities: inferences from a long-term snow and nutrient manipulation experiment

Background: Gradients in the amounts and duration of snowpack and resulting soil moisture gradients have been associated with different plant communities across alpine landscapes.

Aims: The extent to which snow additions could alter plant community structure, both alone and in combination with nitrogen (N) and phosphorus (P) additions, provided an empirical assessment of the strength of these variables on structuring the plant communities of the alpine tundra at Niwot Ridge, Colorado Front Range.

Methods: A long-term snow fence was used to study vegetation changes in responses to snowpack, both alone and in conjunction with nutrient amendments, in plots established in dry and moist meadow communities in the alpine belt. Species richness, diversity, evenness and dissimilarity were evaluated after 20 years of treatments.

Results: Snow additions, alone, reduced species richness and altered species composition in dry meadow plots, but not in moist meadow; more plant species were found in the snow-impacted areas than in nearby controls. Changes in plant community structure to N and N + P additions were influenced by snow additions. Above-ground plant productivity in plots not naturally affected by snow accumulation was not increased, and the positive responses of plant species to nutrient additions were reduced by snow addition. Plant species showed individualistic responses to changes in snow and nutrients, and indirect evidence suggested that competitive interactions mediated responses. A Permanova analysis demonstrated that community dissimilarity was affected by snow, N, and P additions, but with these responses differing by community type for snow and N. Snow influenced community patterns generated by N, and finally, the communities impacted by N + P were significantly different than those affected by the individual nutrients.

Conclusions: These results show that changes in snow cover over a 20-year interval produce measureable changes in community composition that concurrently influence and are influenced by soil nutrient availability. Dry meadow communities exhibit more sensitivity to increases in snow cover whereas moist meadow communities appear more sensitive to N enrichment. This study shows that the dynamics of multiple limiting resources influence both the productivity and composition of alpine plant communities, with, species, life form, and functional traits mediating these responses.