巴丹吉林沙漠东缘天然梭梭种群空间分布异质性

梭梭(Haloxylon ammodendron(C.A.Mey.)Bunge)是生长于沙漠地区的一种特有灌木,在维持荒漠生态系统平衡和地区经济发展中发挥着不可替代的作用。为掌握天然梭梭种群空间分布规律,以巴丹吉林沙漠东缘塔木素地区的"野生肉苁蓉及梭梭产籽基地"为试验区,采用样线法测定梭梭株高、冠幅直径,统计梭梭分布密度,分析梭梭种群数量特征空间分布特征及其与生境之间的关系。结果表明:梭梭林密度、株高、冠幅直径均符合正态分布,表现为强度变异;株高、密度、冠幅直径的半方差函数理论模型均为高斯理论模型,其相应的变程为1249、909、1035 m;空间自相关比例均超过70%,受随机因素影响较小,保持着较好的天然分布和生长状态。梭梭种群数量特征的分形维数均大于1.5,空间依赖性强,空间结构性好。长期风蚀作用,小地形海拔高度体现为不同沙层厚度,梭梭株高、冠幅直径和密度在空间上的分布呈西高东低,北高南低的趋势,与海拔高度存在极显著相关;梭梭群落的空间异质性表现出一定的适度沙埋效应。     

巴丹吉林沙漠东缘主要植物种群空间分布关系

梭梭(Haloxylon ammodendron)、红砂(Reaumuria songarica)和白刺(Nitraria tangutorum)是巴丹吉林沙漠防风固沙的主要植物,对改善生态环境具有重要意义.为探讨其空间分布及其相互作用关系,本研究以阿拉善右旗塔木素苏木地区“塔木素野生肉苁蓉及梭梭产籽基地”为试验区,从...     

乌兰布和沙漠天然梭梭种群动态及空间分布

为进一步明晰乌兰布和沙漠天然梭梭(Haloxylon ammodendron)种群动态和空间分布特征,该研究以乌兰布和沙漠天然梭梭林为研究对象,采用静态生命表、存活曲线、生存分析和空间分布格局指数等方法分析种群动态与内在生活史特征和外在干扰之间的互动关系,探讨梭梭种群波动特征及其存续机制,以揭示天然梭梭种群动态及空间分布特征,为梭梭种群的合理保护与种群恢复提供依据。结果表明:(1)乌兰布和沙漠天然梭梭种群龄级结构呈倒“J”形,为增长型,但相邻龄级个体数量波动性较大;种群年龄结构数量变化动态指数V_(pi)=17.43,受随机干扰时种群年龄结构动态指数V_(pi)′=1.02,种群年龄结构对随机干扰的敏感性指数P_(max)=5.88,说明种群对外界干扰较为敏感。(2)研究区天然梭梭种群的存活曲线趋于Deevey-Ⅱ型,各年龄级种群有相近的死亡率;生存函数、累积死亡率、死亡密度在第Ⅰ~Ⅹ龄级(基径<10 cm)变化较大,且在第Ⅰ~Ⅸ龄级危险率较高;生存函数、累计死亡率、死亡密度在第Ⅺ~ⅩⅧ龄级(基径≥10 cm)趋于稳定,危险率在第Ⅹ龄级后逐渐增加,种群动态呈现出低龄级间个体数量波动大,高龄级衰退的特征。(3)研究区天然梭梭种群密度在328.57~942.86株/km^(2)之间,平均为706.34株/km^(2),种群空间分布大多呈聚集分布。研究表明,乌兰布和沙漠在现阶段环境气候条件下,适宜梭梭种群的生长,而且在不受人为干扰的情况下,梭梭种群能够稳定存续,可以抵抗一定的气候风险。建议减轻人为干扰对低龄级种群数量的影响,在局部梭梭林衰退严重区可参考天然梭梭种群密度与空间分布型建植人工梭梭林。     

基于地貌类型的中国东海大陆海岸带景观动态分析

基于东海地貌信息数据和6期景观数据,研究1990—2015年东海大陆海岸带地貌类型与景观动态变化特征,分析各地貌类型下景观格局时空分布规律。结果表明:(1)东海海岸带以丘陵地貌为主,其次是小起伏山地、平原、台地和中起伏山地。景观类型林地占主导,其次为耕地和建设用地。(2)平原、台地和丘陵地貌景观变化以耕地转为建设用地为主,小和中起伏山地则以草地转林地为主。(3)不同地貌单元下的景观变化剧烈程度依次为:平原>台地>丘陵>小起伏山地>中起伏山地,2005—2015年景观变化叠合度小于1990—2005年,景观变化剧烈程度下降。(4)地貌类型对景观分维数和稳定性指数影响差异较大,平原上水域分维数值最大,台地和丘陵耕地分维数最大,小起伏山地未利用地分维数最大,中起伏山地建设用地分维数最大,稳定性指数相反。耕地在海拔较低的地貌类型中趋于稳定,林地和草地多分布在海拔较高丘陵和山地,水域和建设用地在平原地区分维数最大,稳定性更强。     

古尔班通古特沙漠土壤因素对退化梭梭更新局限的影响

古尔班通古特沙漠梭梭退化主要发生在平原和小沙丘(高度5m)区域,而与其邻近的大沙丘(高度10m)生境中梭梭却长势良好。本文对比分析了退化区和正常生长区小尺度范围梭梭种群年龄结构、不同盐分梯度下梭梭种子及其萌发特征、土壤理化性质及其对梭梭种群更新的影响。结果表明:退化区梭梭幼株缺乏,自然更新明显受阻。平原、小沙丘和大沙丘3种生境中梭梭种子的带果翅百粒重、无果翅百粒重和果翅直径差异显著,无盐胁迫条件下梭梭种子萌发率差异不显著,而在有盐胁迫条件下差异显著,且萌发率都随盐分浓度的增加而降低,说明退化区梭梭林更新不良与种子特征关系不大,与土壤盐分关系密切。3种生境土壤理化性质差异显著,平原和小沙丘土壤电导率明显高于大沙丘。梭梭活株密度与各土层土壤电导率、土壤含水量呈极显著负相关,梭梭幼株数(株高40cm)与土壤表层(0～30cm)电导率极显著负相关。综上所述,退化区高的土壤盐分导致梭梭植株密度严重降低、抑制种子萌发和限制梭梭幼苗存活,进而使得梭梭林自然更新不良。     

不同沙障材料对固沙林地面节肢动物群落结构分布的影响

为了明确沙障材料差异性对固沙林地面节肢动物群落结构的影响规律,以腾格里沙漠东南缘2013年布设的麦草、尼龙网两种沙障模式下的固沙林地为研究样地,于2018年春、夏、秋季,研究了沙丘底部和顶部不同沙障模式下的固沙林地地面节肢动物群落组成及多样性分布特征。结果发现:(1)沙丘底部, 2种沙障林地地面节肢动物优势类群除了均包括蠼螋科、步甲科、叶甲科外,麦草方格林地还包括拟步甲科和鞘翅目幼虫2个类群,而尼龙网方格林地还包括鳞翅目幼虫1个类群;但在沙丘顶部, 2种沙障林地地面节肢动物优势类群均为蠼螋科、步甲科、叶甲科和拟步甲科。(2)沙丘底部和顶部,优势类群步甲科、叶甲科个体数在2种沙障林地间均无显著差异;但优势类群拟步甲科个体数表现为麦草方格林地显著高于尼龙网方格。在沙丘底部,蠼螋科个体数表现为2种沙障林地间无显著差异;而在顶部,蠼螋科个体数表现为麦草方格林地显著高于尼龙网方格。(3)沙丘底部和顶部,地面节肢动物个体数、类群数均表现为麦草方格林地显著高于尼龙网方格,但Shannon指数、优势度指数2种沙障林地间均无显著差异。(4)RDA和偏RDA分析结果表明,花棒冠幅与高度、油蒿冠幅是不同微生...     

古尔班通古特沙漠西部梭梭种群退化原因的对比分析

古尔班通古特沙漠植被的建群种梭梭在沙漠的低平地和小沙丘(高度<5 m)区域发生大面积退化死亡,而在大沙丘(高度>10 m)生境中梭梭却长势良好。对此分析了梭梭林枯死植株的空间分布、活株和死株的年龄结构,研究了地下水埋深以及对比低平地、小沙丘和大沙丘3种生境土壤理化性质对梭梭生存的影响。发现梭梭死亡植株在观测的19个样点中的15个呈显著的集群分布,表明梭梭植株死亡并非是种内自疏。梭梭各年龄级植株均在死亡,说明死亡与植株年龄关系不大。退化区地下水埋深过浅或过深均对梭梭生长不利,表明地下水埋深对梭梭生长产生显著影响。低平地和小沙丘区土壤电导率高,土壤水分入渗速率慢,且0-90 cm深度范围梭梭侧根数和成活的梭梭幼苗幼株数较少,与梭梭正常生长的大沙丘区明显不同。综合分析认为梭梭退化主要是由自身的根系分布特性,以及地下水位、土壤盐分、土壤水分入渗变化等综合作用,实质是梭梭水分利用受限和种群更新不良引起的。     

沙丘微地形生境蚁丘分布特征及其对恢复过程的响应

为了阐明沙丘微地形生境蚁丘特征及分布规律对沙丘固定过程的响应规律,以科尔沁沙地为研究区,选择不同固沙阶段沙丘的4个方位（西北、东南、西南、东北）布设调查样地,测定了不同样地的蚁丘密度、直径和高度,分析了不同样地蚁丘特征及空间分布规律。结果表明：（1）流动沙丘背风向（即东南方位）蚁丘密度显著高于其他方位,但从流动沙丘到半流动沙丘,背风向（即东南方位）蚁丘密度显著低于其他方位;从半固定沙丘开始,半固定和固定沙丘微地形对蚁丘密度分布的影响较小。（2）在流动沙丘、半流动沙丘、半固定沙丘,不同微地形生境中蚁丘直径和高度均呈现出相似的分布规律,即东南方位均小于其他方位。在固定沙丘,蚁丘高度表现为东南方位亦较低,但蚁丘直径表现为西南和东北方位显著小于西北方位。（3）在流动沙丘,西北、西南和东南方位上蚁丘空间分布均表现为均匀分布型,而在半流动、半固定和固定沙丘,4个方位上蚁丘空间分布均表现为聚集分布型。（4）相关性分析表明,不同固沙阶段不同微生境下蚁丘密度、高度、直径与植物密度、多样性间的相关性不同。随着固沙阶段演替,不同微生境下蚁丘特征与植物密度、多样性的相关性增强。研究表明,在科尔沁沙地,随着流动沙丘固定和生境逐渐恢复,沙丘不同空间方位上蚁丘密度分布差异缩小,而蚁丘直径和高度仍存在沙丘微地形间显著差异性,并且蚁丘空间方位上均呈现聚集分布状态。     

南京玄武湖菹草石芽空间变异及其原因探讨

为了解玄武湖菹草石芽的空间分布状况,用网格法布设52个石芽采样点,采样点以GPS定位,在每个点采集表层底泥15cm深度以上石芽,每个点采集4个样,然后求和代表该点石芽密度。运用ArcGIS的geostatistics组件分析了玄武湖菹草石芽数量的空间变异特征及其形成原因。结果表明:①石芽数量的半方差函数可拟合为球状模型,石芽在空间呈聚集分布;②石芽在各湖中具有非常明显的空间异质性,东北湖石芽密度最大(均值30.5颗/m2),西南湖密度最小(均值10颗/m2);从石芽密度的分维数来看石芽密度的空间异质性,全方向<椭圆半长轴方向<椭圆半短轴方向上;③割草干扰、种群数量、水深、水流、立地条件的空间异质性造成石芽密度的空间异质性;④石芽数量的空间自相关尺度,远远大于菹草石芽能够自行散落的距离,说明流水的带动起了很重要的扩散作用。       

准噶尔盆地东南缘梭梭种子雨特征

为了研究梭梭种子散布规律,通过布设种子雨收集器结合室内实验分析,对准噶尔盆地东南缘梭梭种子雨特征进行了研究。研究显示:(1)梭梭种子雨的累积密度达到平均189粒/m2,其中有活力种子占约80%;(2)种子散布的高峰集中在11月初到11月15日时间段,其落种量占整个种子雨的65%。其后种子雨密度随时间逐渐减小;(3)整个种子雨过程,不同时期散落的种子雨质量存在差异,表现为不同时期散落种子的萌发率呈现出先增大后减小的趋势;(4)变异函数分析表明,梭梭种子雨在8.12 m的有效变程内,种子雨具有明显的空间格局,其由空间自相关和随机因素引起的空间异质性各占50.0%。准噶尔盆地东南缘梭梭种子雨密度大且质量较高,同时其时空分布异质性较高,这些特征均将影响梭梭种群的分布格局和种群更新。     

Role for dopamine in malonate-induced damage in vivo in striatum and in vitro in mesencephalic cultures

Defects in mitochondrial energy metabolism have been implicated in the pathology of several neurodegenerative disorders. In addition, the reactive metabolites generated from the metabolism and oxidation of the neurotransmitter dopamine (DA) are thought to contribute to the damage to neurons of the basal ganglia. We have previously demonstrated that infusions of the metabolic inhibitor malonate into the striata of mice or rats produce degeneration of DA nerve terminals. In the present studies, we demonstrate that an intrastriatal infusion of malonate induces a substantial increase in DA efflux in awake, behaving mice as measured by in vivo microdialysis. Furthermore, pretreatment of mice with tetrabenazine (TBZ) or the TBZ analogue Ro 4-1284 (Ro-4), compounds that reversibly inhibit the vesicular storage of DA, attenuates the malonate-induced DA efflux as well as the damage to DA nerve terminals. Consistent with these findings, the damage to both DA and GABA neurons in mesencephalic cultures by malonate exposure was attenuated by pretreatment with TBZ or Ro-4. Treatment with these compounds did not affect the formation of free radicals or the inhibition of oxidative phosphorylation resulting from malonate exposure alone. Our data suggest that DA plays an important role in the neurotoxicity produced by malonate. These findings provide direct evidence that inhibition of succinate dehydrogenase causes an increase in extracellular DA levels and indicate that bioenergetic defects may contribute to the pathogenesis of chronic neurodegenerative diseases through a mechanism involving DA.     

Scurvy in capybaras bred in captivity in Argentine

In order to determine if the absence of vitamin C in the diet of capybaras (Hydrochoerus hydrochaeris) causes scurvy, a group of seven young individuals were fed food pellets without ascorbic acid, while another group of eight individuals received the same food with 1 g of ascorbic acid per animal per day. Animals in the first group developed signs of scurvy-like gingivitis, breaking of the incisors and death of one animal. Clinical signs appeared between 25 and 104 days from the beginning of the trial in all individuals. Growth rates of individuals deprived of vitamin C was considerably less than those observed in the control group. Deficiency of ascorbic acid had a severe effect on reproduction of another population of captive capybaras. We found that the decrease in ascorbic acid content in the diet affected pregnancy, especially during the first stages. The results obtained suggest that it is necessary to supply a suitable quantity of vitamin C in the diet of this species in captivity.     

Changes in lactate dehydrogenase activity in chicken tissues in hyperthyreosis in ontogenesis

The lactate dehydrogenase activity in reactions of lactate oxidation and synthesis was studied in subfractions of the chicken brain, heart and liver at the embryonal, early postembryonal and adult stages of development after thyroxine administration. It has been shown that during embryogenesis thyroxine predominantly enhanced the rate of lactate oxidation in the mitochondrial tissues. A marked increase in the lactate synthesis was found in cytoplasm of the adult chicken tissues. Specificity of enzyme activity alterations was detected in the chicken brain during ontogenesis after thyroxine administration.     

SSTR5 ablation in islet results in alterations in glucose homeostasis in mice

Somatostatin (SST) peptide is a potent inhibitor of insulin secretion and its effect is mediated via somatostatin receptor 5 (SSTR5) in the endocrine pancreas. To investigate the consequences of gene ablation of SSTR5 in the mouse pancreas, we have generated a mouse model in which the SSTR5 gene was specifically knocked down in the pancreatic beta cells (betaSSTR5Kd) using the Cre-lox system. Immunohistochemistry analysis showed that SSTR5 gene expression was absent in beta cells at three months of age. At the time of gene ablation, betaSSTR5Kd mice demonstrated glucose intolerance with lack of insulin response and significantly reduced serum insulin levels. Insulin tolerance test demonstrated a significant increase of insulin clearance in vivo at the same age. In vitro studies demonstrated an absence of response to SST-28 stimulation in the betaSSTR5Kd mouse islet, which was associated with a significantly reduced SST expression level in betaSSTR5Kd mice pancreata. In addition, betaSSTR5Kd mice had significantly reduced serum glucose levels and increased serum insulin levels at 12 months of age. Glucose tolerance test at an older age also indicated a persistently higher insulin level in betaSSTR5Kd mice. Further studies of betaSSTR5Kd mice had revealed elevated serum C-peptide levels at both 3 and 12 months of age, suggesting that these mice are capable of producing and releasing insulin to the periphery. These results support the hypothesis that SSTR5 plays a pivotal role in the regulation of insulin secretion in the mouse pancreas.