The After-effect of Wind on the Photosynthesis and Transpiration of Festuca arundinacea

The after-effect of wind on photosynthesis and transpiration of Festuca arundinacea Schreb, was determined. Following a period of exposure In a controlled environment wind tunnel the wind-treated plants showed reduced rates of photosynthesis when compared with the controls under standard conditions. Evaporation from paper model tillers was measured and the boundary layer resistance was shown to be low in all but very low wind speeds. Analysis of CO₂ and H₂O diffusion pathways indicated that mesophyll resistance in wind-treated plants was higher whilst leaf surface resistance was lower than in the controls. The high mesophyll resistance in the wind-treated plants was attributed to reduced water content.     

After-effect of Water Stress on Stomatal Opening Potential: II. POSSIBLE CAUSES

Experiments were carried out to elucidate the temporary after-effectof a period of water stress on the opening potential of stomataof tobacco (Nicotiana tabaccum) and beans (Vicia faba). Stomatalaperture was measured on floating leaf discs or epidermal stripsafter a period of time in light under controlled conditions;direct effects of leaf-water deficit were thus avoided. Theresponses of the two species were not qualitatively different. Only a minor part of the post-stress damage was located in themesophyll in beans, the major part (approximately two-thirds)being located in the guard cells themselves. The CO¹ compensationpoint for tobacco leaves showed no after-effect of stress. However,the response of stomata to normal and CO¹-free air in both speciessuggested that a minor part of the after-effect on stomatalopening, presumably that part arising in the mesophyll, maybe explained by elevated CO¹ concentrations in the stomatalcavity. The nature of that part of the after-effect arising within theguard cells themselves was not clarified. Guard-cell starchcontent was apparently unaffected by stress in both species;in tobacco, epidermal-cell starch content was reduced in thestress and post-stress condition. Stomatal responses to theshort-term addition of energy-supplying metabolites (ATP, glycolate,and glucose-1-phosphate) showed no interaction with the post-stresscondition. Similarly responses to the addition of stomatal inhibitors(sodium azide, dodecenylsuccinic acid, atrazine, and phenylmercuricacetate) did not indicate the exact nature of the after-effect,although there was a marked increase in the sensitivity to atrazinein post-stress leaf discs. In tobacco leaf discs an examination of the process of eliminationof this after-effect, as distinct from studies directly on itsnature, suggested that complete recovery involved at least twosteps, together lasting 2 to 3 days. One step required timeand was independent of light; the other required light of atleast 1 klx for a day or more and did not occur in CO²-freeair. Stomata recovered almost completely in 2 days without lightwhen discs were floated on 005 M glucose-1-phosphate.     

After-effect of Water Stress on Stomatal Opening Potential: I. TECHNIQUES AND MAGNITUDES

The after-effect of a period of water stress upon the light-openingability of stomata was studied in tobacco (Nicotiana tabaccum)and broad bean (Vicia faba). Stomatal opening was always measuredafter floating leaf discs on water under favourable conditionsof light and temperature to obtain maximal opening at full leafturgor. Thus possible interference due to persistence of leaf-waterdeficits in the post-stress leaves was eliminated. Stomatalaperture was accurately estimated using a resistance porometer;values so obtained were substantiated by the direct measurementof aperture. Two to 4 days of wilting of tobacco, producing leaf-water deficitsof 30 to 40 per cent, had a marked after-effect on tobacco stomata.The ability to open in light was depressed and complete recoveryfrom this depression required 2 to 5 days after rewatering.In some cases over-recovery was observed; this was probablyrelated to a physiologically younger condition of leaves ofstressed plants following turgor recovery. In beans similarstresses caused after-effects smaller in magnitude but qualitativelysimilar to those in tobacco. In both tobacco and beans the magnitudeof the after-effect was approximately proportional to the leaf-waterdeficit attained immediately prior to rewatering.     

腾格里沙漠沙坡头地区荒漠地衣与生物地毯工程

文章论述了荒漠地衣与“沙漠生物地毯工程”。在沙坡头结皮微型生物中发现了23种地衣,其中两个新种已发表,一属6种为中国新记录。对于在腾格里沙漠东南角沙坡头地区人工植被固沙防护体系建成后的生态演替进行了分析。由于人工植被为形成结皮的微型生物提供了适宜的生长环境而导致微型生物结皮的形成和发育。在水分平衡规律的作用下漫长生态演替过程中,具有抽水机效应的人工植被使沙土深层水分消耗殆尽,从而导致人工植被自身逐年衰退。然而,与此相反的是无抽水机效应而具有固沙、固碳和抗旱功能的结皮微型生物却逐年形成并发育。这一结果为借助于结皮微型生物的接种技术在干旱沙漠构建“沙漠生物地毯工程”的可行性提供了科学依据。为了优化“沙漠生物地毯工程”利用荒漠地衣耐旱基因以构建转基因草地植物的研究也正在进行中。该研究是“沙漠生物地毯工程”基础研究的组成部分。     

大漠骄子

全世界有骆驼约1900万峰,双峰驼仅占10％以下。我国有骆驼约30万峰,都是双峰驼。主要品种有阿拉善双峰驼、新疆双峰驼,苏尼特双峰驼,另外甘肃,青海也有一定数量的双峰驼。     

民勤沙区几种荒漠植物群落的现实生态位研究

民勤沙区属于典型的干旱荒漠气候,植被以灌木荒漠为主,盖度一般只有5%~15%.植物群落内生态位宽度悬殊,植物种之间的生态位相似比例很小.生态位宽度和生态位相似比例小是受制于干旱荒漠生境条件的结果,是干旱荒漠生态环境中稀疏荒漠植物的主要特征之一.植物的现实生态位宽度与年际降水量关系密切,在地貌、土壤颗粒、土壤水分、土壤养分等影响因子中,土壤水分是主导因子.当地地下水位深20 m左右,植物无法利用,植物种之间对资源的竞争主要表现为对水分资源的竞争,降水资源是植物种之间竞争的关键资源.同一种植物在不同群落中的生态位宽度变幅较大,不同群落内部植物种竞争关系的差异是由物种的生态位和由相对稳定的地貌、土壤条件以及随年际变动的降水条件共同作用的结果.群落中的优势种植物的生态位最宽,当优势种生态位减小时,一年生短命植物往往会进入群落中.荒漠植物的冠层单一,以冠幅占样方面积比作为植物的特征值计算其生态位特征值比较准确可靠.     

荒漠与荒漠化

在讨论“荒漠”与“沙漠”概念之基础上,通过熟悉联合国《防治荒漠化公约》对“荒漠化(desertification)”的定义．了解我国专家强调“沙漠化”的缘由,认识荒漠化是当今世界最关注的环境-社会经济问题之一。我国是《防治荒漠化公约》的签约国,实施“西部大开发”战略,必须重视生态环境建设中荒漠化的防治问题,尤其是沙漠化和沙尘暴的防治工作。     

浑善达克沙地小毛足鼠的生物学习性

小毛足鼠 (Ｐｈｏｄｏｐｕｓｒｏｂｏｒｏｖｓｋｉｉ)为内蒙古沙地生境中主要鼠种之一 ,在固定沙丘、半固定沙丘、流动沙丘上均有分布[2～ 4 ] 。小毛足鼠主要取食植物种子和昆虫 ,对沙丘植被的恢复与更新起重要作用 ,是沙地生态系统重要组成成员[1] 。近年来 ,位于内蒙古自治区锡林郭勒境内的浑善达克沙地已成为京津地区沙尘暴灾害的重要沙源地之一 ,各级政府及诸多研究人员日渐重视该地区的生态恢复与重建研究 ,有关浑善达克沙地植被重建与恢复过程中的鼠害防治问题开始引起人们的普遍关注。由于研究该地区小毛足鼠的生物学特性 ,对于进一…     

走进巴丹吉林沙漠——个充满谜团的世界

巴丹吉林沙漠是阿拉善第一、中国第三、世界第四大沙漠,总面积达5．051万平方公里,相当于半个浙江省。沙漠中湖泊多达114个,常年有水的湖泊达74个,其中淡水湖12个。这里有着世界上最高大的沙山系统,超过100米的高大沙山占总面积的近70％,最高沙山相对高度达四百余米,号称沙山“珠峰”。然而,这里也是一个。充满谜团的世界。     

开垦对阿拉善荒漠啮齿动物群落功能多样性的影响

开垦会导致荒漠化的加剧,并对动物群落产生严重的影响。而功能多样性恰恰能体现环境或干扰胁迫导致的群落结构差异。但有关啮齿动物群落功能多样性的研究并不多见,为此,我们在2018至2020年的4月、7月和10月利用铗日法对开垦区和未开垦区的啮齿动物群落进行调查,选择并量化了与其营养、生活史、生理、形态及活动节律等相关的5个功能性状,以探讨开垦对啮齿动物群落组成的影响,以及性状组成和功能多样性变化。研究结果表明：(1)开垦区群落的丰富度指数、多样性指数和均匀度指数均低于未开垦区,开垦改变了啮齿动物群落性状组成;(2)阿拉善荒漠啮齿动物群落组成与蛰眠、繁殖周期和食性等功能性状显著相关;(3)开垦区春、秋季群落功能丰富度和功能均匀度高于未开垦区,各季节群落功能离散度显著高于未开垦区;而未开垦区夏季群落功能丰富度高于开垦区,秋季群落功能均匀度高于开垦区;(4)开垦区和未开垦区群落功能丰富度最高值均出现在夏季,二者在不同季节间差异较大;开垦区群落功能均匀度最高值出现在春季、功能离散度最高值出现在秋季,二者在季节间差异均较小;未开垦群落功能均匀度最高值出现在秋季、功能离散度最高值出现在夏季,二者在季节间差异均较大。上述结果说明,阿拉善荒漠区啮齿动物群落功能多样性变化与土地开垦和季节相关联,开垦会从啮齿动物群落的生态空间利用程度、资源利用、种间竞争及生态位等方面影响群落功能多样性。     

古尔班通古特沙漠中4种荒漠草本植物的生物量与化学计量特征

对于荒漠植物不同生长期生物量分配和化学计量比的研究有助于深入了解荒漠植物的功能结构,更好掌握环境对植物的生存影响。本研究选取古尔班通古特沙漠4种一年生荒漠草本植物沙蓬（Agriophyllum sqarrosum（L.）Moq.）、雾冰藜（Bassssia dasyphylla（Fisch.et Mey.）O.Kuntze）、角果藜（Ceratocarpus arenarius L.）和碱蓬（Suaeda glauca（Bge.）Bge.）对比研究了4种生物量分配与N、P化学计量学随植物生长的变化。结果显示：（1）4种荒漠植物生物量积累配过程中,根冠比随生长季的延长逐渐降低。地上、地上生物量相关生长关系表明,角果藜为等速→异速的变化过程,沙蓬从采样初期至末期的变化过程为异速→等速生长,而沙蓬和碱蓬的相关生长指数相反,分别为异速→等速→异速、等速→异速→等速的变化格局;（2）4种植物N、P含量随生长期的延长逐步降低。在整个生长季节4种植物的N与P含量的变化趋势均为相似。（3）植物N、P含量间达到正相关显著,除沙蓬和雾冰藜的N：P之外其余指标分别与植物的地上、地下生物量及总生物量间呈负相关显著,而根冠比、相关生长指数与化学计量特征间未达到显著水平,表明了二者较弱的相关性。研究表明,4种荒漠草本植物生物量与化学计量特征的相关性不大,说明化学计量比并不是影响植物生物量及生活策略的主要因素,而更多是受植物自身遗传特性的影响。同时也体现了荒漠草本植物在养分匮乏的条件下,形成了自身独特的生理生态特征,且具有相对稳定的适应特性。