破碎化生境中粗柄独尾草种群大小对繁殖特性的影响

景观破碎化是目前存在的一种普遍现象,导致物种生存的原有生境总面积减小,产生许多大小不一的斑块种群。不同斑块生境中植物种群的大小直接反映植物对环境的响应特征和适应对策,与植物繁殖有关的开花结实特性、种子形态及萌发特性的研究将有助于深入了解植物在不同生境中的生存策略。以粗柄独尾草(Eremurus inderiensis)为研究对象,以野外调查为基础,对比研究不同斑块粗柄独尾草种群的种群大小和生殖成功,揭示不同生境中粗柄独尾草的生态适应性。结果表明:(1)不同斑块生境中,种群大小差异较大,且较小的种群幼苗比例也较小,种群大小与种群幼苗比例呈显著相关;(2)较小的种群自然座果率、结籽率较低,种群间差异显著;(3)随着生境破碎化程度增加,种子千粒重,种子长、宽等形态特征呈减小趋势,但种翅占比增大;(4)在粗柄独尾草最适萌发温度下,随着生境破碎化程度增加,种子萌发率有下降趋势。针对人类干扰程度强的衰退型粗柄独尾草种群,亟需减少人为干扰,依据不同生境中的干扰因素及种群生存现状,制定科学与切实可行的保护和恢复策略。     

独叶草种群年龄结构及动态分析

对太白山不同生境条件下的独叶草种群年龄结构、生命表及存活曲线进行了研究,结果表明,不同生境的独叶草种群在3～6年生阶段个体数量最多。幼年个体和老年个体数量较少,生命表中。幼龄级的dx、qx、Kx等为负数,可以反映种群幼龄个体缺乏程度．以无性繁殖独叶草不同与以有性生殖为主的植物,它可产生不同龄级的无性系分株,幼龄个体少的年龄结构并不代表种群必然衰退．随海拔升高,种群密度增加,个体寿命延长,反映了种群在适应性方面的调整．独叶草种群根状茎生存于腐殖质层中,仅有叶片露出地面;种群所在的牛皮桦、巴山冷杉和太白红杉群落人为干扰较少。生境相对稳定,种群可以长期维持．对种群保护应注重所处的环境及森林群落保护。     

生境破碎对古尔班通古特沙漠南缘骆驼刺种群生物学特性的影响

在破碎化生境中,植物种群的生物学特性直接反映植物对环境的响应特征和适应对策,探讨不同破碎化程度生境中植株的大小、密度、结实率、种子大小、种子质量以及萌发特性等,对深入了解植物在不同生境中的生存和繁殖状况有重要的指导意义。对古尔班通古特沙漠南缘9个斑块化骆驼刺种群的形态特征和繁殖生物学参数进行了连续2年的调查研究,研究结果表明：随着生境破碎化程度的加剧,骆驼刺的株高、冠幅、密度、结实率、种子大小、种子质量以及萌发率等均显著下降（P < 0.05）。生境破碎不仅强烈抑制了骆驼刺植株的营养生长,使其生长矮小,个体分布稀疏,而且严重阻碍了骆驼刺的繁殖成功和种群更新,增加了种群衰退甚至灭绝的风险。     

准噶尔盆地东南缘梭梭种群结构与动态研究

通过样地调查和数据统计分析,对准噶尔盆地东南缘梭梭种群现状绘制径级结构图,编制生命表、分析存活曲线、死亡率曲线和寿命期望等参数,并运用时间序列模型预测种群数量动态.结果表明:种群整体结构属于增长型,但梭梭种群幼苗个体少,Ⅰ、Ⅱ龄级个体数目少于Ⅲ龄级的个体数目.存活曲线基本接近DeeveyⅢ型,种群偏离典型存活曲线的程度与幼苗缺乏有关;环境因素和人为干扰的影响,梭梭在Ⅲ～V龄级死亡率较高,种群在第Ⅳ级出现死亡高峰,且只有少量幼年个体能进入成年阶段,个体平均生存能力的期望在第Ⅳ级最大;时间序列分析表明,在未来第Ⅱ、Ⅳ、Ⅵ、Ⅷ龄级的个体会呈现老龄个体增加的趋势,种群稳定性长期维持困难.适当的人工辅助恢复和现有植株及生境的保护是保持梭梭种群自然更新和种群恢复的关键.     

不同生境下濒危植物裸果木种群结构及动态特征

裸果木(Gymnocarpos przewalskii)为古地中海旱生植物区系孑遗种, 是砾质荒漠的主要建群种之一。通过对安西极旱荒漠国家级自然保护区内3种生境(水冲滩地、山间冲沟、平缓戈壁)条件下裸果木种群的样地调查, 编制不同生境裸果木种群的静态生命表, 绘制其存活曲线和生存分析函数的曲线, 并采用时间序列模型对种群的数量动态进行预测, 以揭示不同生境下裸果木的种群结构和动态特征。结果表明: 3种生境下裸果木种群均属增长型, 数量变化动态指数(V’ pi) > 0, 但对外界干扰比较敏感, 存活曲线趋于Deevey-II型, 表明种群各龄级的死亡率基本接近; 不同生境裸果木种群大小依次为水冲滩地>山间冲沟>平缓戈壁, 结合对种群年龄结构的分析, 进一步表明水分条件较好的水冲滩地和山间冲沟生境更加适宜裸果木生存; 生存分析和时间序列预测表明幼龄个体的缺乏是未来裸果木种群发生衰退的主要原因, 且平缓戈壁生境下的裸果木种群将先于另外两种生境下的种群发生更加快速的衰退。     

海南吊罗山濒危植物山铜材种群结构与动态特征

为探究海南吊罗山山铜材（Chunia bucklandioides）种群结构与动态特征，以当地山铜材野生种群为研究对象，将种群集中分布区域设为典型样地并开展样地调查，以空间代替时间构建种群年龄结构，采用动态量化分析、绘制存活曲线、计算生存函数等方法分析现有种群结构特点和动态特征，并通过时间序列预测模型推测种群未来发展趋势。结果表明：（1）吊罗山山铜材种群年龄结构接近不规则金字塔型，动态量化分析显示该种群为增长型种群，但第Ⅰ～Ⅲ龄级间存在衰退现象，种群增长性弱，稳定性差，受外界干扰敏感度高，有向稳定型种群转变的趋势。（2）随龄级增加，山铜材标准化存活个体数量减少，生命期望降低，死亡率和消失率总体呈上升趋势，存活曲线趋近于Deevey-Ⅱ型。（3）生存分析显示吊罗山山铜材种群具有前期增长、中期稳定、后期衰退的特点。（4）经过未来2、4、6龄级时间后，Ⅰ～Ⅲ龄级个体数量将逐渐减少，Ⅳ～Ⅶ龄级个体数量少量增加，幼龄苗木自我更新能力不足，种群存在规模收缩和衰退的风险。研究表明，生境碎片化、分布范围小、植株结实量少和幼龄个体不足是导致吊罗山山铜材濒危的主要因素，建议通过设立自然保护小区、辅助种子入...     

类短命植物异翅独尾草的传粉特性

该文对生长于新疆古尔班通古特沙漠的类短命植物异翅独尾草(Eremurus anisopterus)的传粉习性做了观察研究,结果如下:异翅独尾草的花期从4月下旬至5月中旬,单花花期一般为1 d,而当遭遇最高温度不足20 ℃的阴雨天气时,单花花期可延长至2 d。单花的开花时间一般为每天10∶30~15∶00,大约4~5 h,单个花药的散粉时间约为40 min,但其6枚花药的开裂与散粉具有明显的不同步性,显著地延长了单花的散粉时间,这是对干热多风的沙漠生境中传粉者不确定性高度适应的结果。异翅独尾草花粉借风传播的距离可达70 m,但其中约60%花粉的散布距离集中在20 m以内;昆虫是异翅独尾草的重要传粉媒介,蜜蜂、食蚜蝇、麻蝇、切叶蜂、隧蜂等是主要的传粉者。蜜蜂和食蚜蝇访花时,都是先飞落到花基部黄绿色斑点处,然后沿着花被片的紫色脉纹进入到花内,黄绿色斑点是对花蜜的拟态,是异翅独尾草对高温多风沙环境高度适应的结果。昆虫的访花行为最活跃的时间在10∶30~13∶30之间。一天当中单花的开放时间与沙漠中风速的日变化及访花昆虫的活动习性之间呈现出显著的相关性。异翅独尾草的花粉与胚珠比(P/O)等于6 164,为适合于异花传粉的类型。人工套袋试验结果表明自交是可育的,这可能是对占据了不稳定的、先锋生境的异翅独尾草缺乏远交机会的有效补偿。不存在无融合生殖现象。     

安徽皇藏峪自然保护区青檀种群数量动态

根据野外调查资料编制皇藏峪自然保护区不同生境青檀种群的静态生命表,绘制存活曲线、死亡率曲线、消失率曲线以及4个生存函数曲线,分析种群数量特征。同时,结合种群动态量化方法和时间序列预测模型,分析种群数量动态变化。结果表明:1)不同生境青檀种群径级结构大体呈金字塔型,中、幼龄阶段个体数量丰富,老龄阶段个体数量相对较少,种群在发育过程中存在一定波动性,但种群数量变化动态指数Vpi和Vpi’(考虑外部干扰时)均大于零。种群属稳定增长型。2)不同生境青檀种群在幼龄阶段死亡率较高,随着龄级的增加,死亡率逐渐降低。进入生理衰老阶段时,阳坡、阴坡种群死亡率再次上升,而坡谷种群由于老龄个体受到较好保护,死亡率略有下降。3)不同生境存活曲线存在差异,阳坡、阴坡种群趋于Deevey-Ⅱ型,坡谷种群趋于Deevey-Ⅲ型。4)生存分析表明,阳坡、阴坡种群具有前期锐减、中期稳定、后期衰退的特点;坡谷种群表现为前期锐减、中后期稳定的特点。5)在未来2年、5年中,不同生境青檀种群呈增长趋势。     

新疆独尾草属植物的核型分析

对新疆独尾草属（Eremurus）植物的核型进行了研究。核型公式如下：阿尔泰独尾草[E.altaicus（Pall.）Stev.]2n=2x=14=4m＋8sm＋2st;异翅独尾草[E.anisopterus（Kar.et Kit）Regel]2n=4x=28=4m＋4sm＋20st;粗柄独尾草[E.inderiensis （M.Bieb）Regel]2n=2x=14=10sm＋4st,首次发现古尔班通古特沙漠南缘所产的异翅独尾草2n=4x=28,与前人报道其为二倍体2n=2x=14的结果不一致。     

濒危植物太白红杉种群年龄结构及其时间序列预测分析

为了阐明太白红杉(Larix potaninii var.chinensis)种群的年龄结构和未来发展趋势,合理保护现有资源,在太白山地区调查了 29个样地(10 m×10m),对处于不同生境的 5个种群的年龄结构、静态生命表和时间序列预测进行了分析。种群年龄结构分析表明,各种群个体数量主要集中于Ⅲ、Ⅳ、Ⅴ、Ⅵ、Ⅶ龄级(个体数量比重占68.64％),幼、老龄个体数量较少。受所处生境条件影响,不同种群年龄结构特点不同:海拔较低的种群(B)由于水热条件适宜,林内有林窗出现,幼龄级个体数相对丰富;而其他种群由于幼龄个体严重缺乏,衰退趋势明显。太白红杉不同种群生命表和存活曲线的分析表明,尽管所处的生境差异较大,但存活曲线基本属于Deevey Ⅲ型,种群偏离典型存活曲线的程度与幼苗缺乏程度有关,一般V-Ⅸ龄级死亡率较高。时间序列分析表明,在未来20、60、100和200年中,各太白红杉种群均会呈现老龄级株数先增加后减少的趋势,种群稳定性维持困难。太白红杉种群年龄结构和动态趋势与银杉(Cathaya argyrophylla)等其他濒危植物比较,导致种群衰退的原因相似:在郁闭的林下种子萌芽和幼苗生长困难。应该利用太白红杉喜光、耐旱和中老年个体产种量丰富的特性,对现有太白红杉林分实行就地保护,合理抚育管理。低海拔地区,应适当间伐非目的树种     

Pollination characteristics of the ephemeroid plant Eremurus anisopterus

This study was conducted to examine the pollination characteristics of Eremurus anisopterus, an ephemeroid plant in the Gurbantunggut Desert in Xinjiang, China. An integrative approach combining field studies with lab analysis was adopted. Pollen traps were used to measure air-borne pollen loads and artificial isolation experiments were applied to test the potentiality of cross-pollination or apomixes. Results show that the duration of the flowering of Eremurus anisopterus varied from late April to mid-May. Anthesis of a single flower often lasted for 1 d. However, if the daily maximum air temperature was under 20°C, the anthesis of a single flower could be prolonged up to 2 d. The pollen dispersion period of the single flower could last for 4 to 5 h, from 10:30 to 15:00 local time, with the duration of pollen dispersion for a single anther lasting approximately 40 min. The heterotypical maturation of the stigma could significantly prolong the pollen dispersion period of the single flower suggesting an adaptation to the habitat of E. anisopterus in the desert where the pollinators were not reliable. The timing of the blossoms of the ephemeroid plant show close correlations with the wind velocity and the habit and characteristics of the pollinators in the desert. Plant pollens may be spread to over 70 m by wind with approximately 60% of the pollens falling within 20 m away from the plant. Insects, especially bees, hover flies, flesh flies, mason bees and Halictus sp. were very important pollinators. Bees and hover flies usually landed on the yellowish green spot on the tepal and then entered the flower along the purple vein on the pink tepals. The yellowish green spot might be a mimetic structure of nectar that could attract insects to visit. This was also an adaptation of the plant to the sandy desert environment. A higher visiting frequency was reached between 10:30 and 13:30. The pollen-ovule ratio (P/O) of E. anisopterus (6164) suggested that the species was from cross-pollination according to Cruden’s criterion. However, the artificial isolation experiment shows that E. anisopterus is self-compatible which might act as a compensation mechanism for the inadequate opportunities for breeding in the desert environment. Since there was no seed set in the bagged emasculated flowers, apomixes did not occur. In conclusion, E. anisopterus might adapt to the unreliable pollinator habits by self-pollination and by lengthening the pollen dispersion period of a single flower. __________ Translated from Journal of Plant Ecology (formerly Acta Phytoecologica Sinica), 2006, 30(6): 1012–1017 [译自: 植物生态学报]     

Remnants fragments preserve genetic diversity of the old forest lichen <Emphasis Type="Italic">Lobaria pulmonaria</Emphasis> in a fragmented Mediterranean mountain forest

Fragmentation represents a serious threat to biodiversity worldwide, however its effects on epiphytic organisms is still poorly understood. We study the effect of habitat fragmentation on the genetic population structure and diversity of the red-listed epiphytic lichen, Lobaria pulmonaria, in a Mediterranean forest landscape. We tested the relative importance of forest patch quality, matrix surrounding fragments and connectivity on the genetic variation within populations and the differentiation among them. A total of 855 thalli were sampled in 44 plots (400 m²) of 31 suitable forest fragments (beeches and oaks), in the Sierra de Ayllón in central Spain. Variables related to landscape attributes of the remnant forest patches such as size and connectivity and also the nature of the matrix or tree species had no significant effects on the genetic diversity of L. pulmonaria. Values of genetic diversity (Nei’s) were only affected by habitat quality estimated as the age patches. Most of the variation (76%) in all populations was observed at the smallest sampled unit (plots). Using multiple regression analysis, we found that habitat quality is more important in explaining the genetic structure of the L. pulmonaria populations than spatial distance. The relatively high level of genetic diversity of the species in old forest patches regardless of patch size indicates that habitat quality in a highly structured forest stand determines the population size and distribution pattern of this species and its associated lichen community. Thus, conservation programmes of Mediterranean mountain forests have to prioritize area and habitat quality of old forest patches.     

Demographic variation in cycad populations inhabiting contrasting forest fragments

Reduced habitat quality after fragmentation can significantly affect population viability, but the effects of differing quality of the remaining habitat on population fitness are rarely evaluated. Here, I compared fragmented populations of the cycad Zamia melanorrhachis from habitats with different history and subject to contrasting levels of disturbance to explore potential demographic differences in populations across habitat patches that could differ in habitat quality. Secondary-forest fragments had a lower canopy cover and soil moisture than remnant-forest fragments, which may represent a harsh environment for this cycad. A smaller average plant size and lower population density in the secondary-forest fragments support the hypothesis that these fragments may be of lower quality, e.g., if plants have reduced survival and/or fecundity in these habitats. However, variation in the stage-structure of populations (i.e., the relative proportions of non-reproductive and reproductive plants) was associated with the area of the forest fragments rather than the type of habitat (remnant versus secondary forest). These results suggest that different demographic parameters may respond differently to habitat fragmentation, which may be explained if processes like adult survival and recruitment depend on different characteristics of the habitat, e.g., average light/water availability versus suitable area for plant establishment. This study shows that forest fragments may differ drastically in environmental conditions and can sustain populations that can vary in their demography. Understanding how forest fragments may represent different habitat types is relevant for evaluating population viability in a heterogeneous landscape and for designing conservation programs that account for this heterogeneity.     

From horticultural plantings into wild populations: movement of pollen and genes in <Emphasis Type="Italic">Lobelia cardinalis</Emphasis>

The Southern Grassland biome in Brazil has long been neglected by the government and by the scientific community as well. Lack of studies about the effects of disturbance (mostly fire and grazing) on plant community and populations are the main hindrances for the future management plans, which complicates the conservation of this rich and unique biome. In this study, the population biology of a rosette species, Eryngium horridum (Apiaceae), has been investigated, in order to compare the effects of fire, grazing and abandonment. E. horridum is a very common species and many farmers consider it a nuisance. Two different areas were chosen for the study purposes: Morro Santana and the Research Center Pró-Mata. Areas under different types (fire and grazing) and disturbance histories were compared. Populations were analysed in plots of 25 m², divided in age-state classes (seedlings, young, adult and reproductive individuals). Both morphological and phenological traits have been investigated. Fire influenced populations in a direct way, whilst grazing showed an indirect effect. Seedlings were found only in areas excluded from disturbance for 3 years on Morro Santana. Due to this, seedling establishment might be more related to environmental conditions than to disturbance regimes. Young individuals were mainly found in recently burned areas, while adult individuals were dominant in areas excluded from disturbance. Additionally, individuals from E. horridum showed a great capacity of resprouting after plant damage. Reproductive individuals also showed the capacity of producing new rosettes after the death of the inflorescence axis. This strategy is probably of great importance for the survival of populations in areas excluded from disturbance. Therefore, vegetative reproduction seemed to be the most important strategy for the maintenance and survival of its populations, allowing longer population persistence over time, even in the absence of disturbance.     

Structure and composition of grassland habitats used by wintering Smith's Longspurs: the importance of native grasses

ABSTRACT Smith's Longspurs (Calcarius pictus) are a species of concern in North America because of their limited range and apparent low population size. To better understand winter habitat needs and guide management of this species, we examined habitat associations of Smith's Longspurs in eastern Arkansas by comparing grassland patches where Smith's Longspurs flushed to randomly located patches in the same area. Smith's Longspurs were found in sparse grassland patches of relatively low height adjacent to airport runways where the native grass prairie three‐awn (Aristida oligantha) dominated ground cover and vertical structure. Smith's Longspurs were not found in vegetation plots dominated by non‐native Bermuda grass (Cynodon dactylon). Prairie three‐awn grass may provide concealment from predators and their seeds may be an important food source. Occurrence of Smith's Longspurs was also correlated with less litter, perhaps because deeper litter could make walking and searching for seeds more difficult. Availability of suitable habitat for Smith's Longspurs along airport runways may be declining due to natural succession of grassland habitat in the absence of disturbance and recent changes in management that favor Bermuda grass. Conversion and degradation of native prairie has resulted in the decline in abundance and distribution of Chestnut‐collared Longspurs (C. ornatus) and McCown's Longspurs (Rhynchophanes mccownii). Our findings suggest that conversion of native grasslands to non‐native grasslands results in loss and degradation of habitat for wintering populations of Smith's Longspurs.     

人为干扰栖息地退化对潮间带中华鲎幼鲎种群数量的影响

栖息地退化是中华鲎（Tachypleus tridentatus）面临的主要威胁因素。然而,人类活动和中华鲎栖息地退化之间的关系研究尚且不足。为了厘清人类活动对中华鲎幼鲎栖息地退化的影响,以北部湾潮间带为研究范围,于2014、2017和2020年对潮间带中华鲎幼鲎丰度进行随机样方法调查,并获取对应年份遥感影像（分辨率30m）作为数据源,借助GIS空间分析、景观格局分析和人为干扰度指数（human disturbance index,HDI）模型,量化评估人为干扰对北部湾潮间带中华鲎幼鲎栖息地景观格局及种群丰度的影响。结果表明：（1）2014-2020年,北部湾潮间带幼鲎栖息地退化严重,无干扰类型景观面积逐渐减少,大部分转化为养殖;（2）北部湾潮间带人为干扰逐渐加强,无干扰等级HDI指数面积不断减少,潮间带大部分面积HDI指数呈增强趋势;（3） HDI指数与幼鲎种群丰度呈显著负相关性,HDI指数高值斑块不适合幼鲎生存。依据HDI指数动态变化及空间分布,可为潮间带中华鲎幼鲎种群栖息地景观格局优化及鲎人工放流增殖选址等保护行动提供理论依据。     

Variable reproductive success in fragmented populations

Marine habitats are naturally patchy and anthropogenic disturbance can further fragment them. Many marine animals are sessile as adults or obligate inhabitants of particular habitats, so populations living in isolated patches of habitat are linked largely by dispersal of planktonic larvae. Theoretically, larvae are more likely to find and settle into large patches of habitat than small patches, thus small habitat patches may experience a more discontinuous supply of recruits resulting in small populations with unusual size- or age-structures or odd sex ratios — conditions where Allee effects on reproductive success are likely. We tested this hypothesis for the Caribbean spotted spiny lobster (Panulirus guttatus), an obligate inhabitant of coral patch reefs whose mating dynamics are size-dependent. We found that P. guttatus were less abundant on small reefs where their size structure and per capita reproductive success were significantly more variable, particularly among large females that are susceptible to sperm limitation that diminishes fertilization rates. These results are indicative of Allee effects and provide a mechanistic understanding of how size-dependent mating dynamics influence reproductive success in ways that alter population dynamics in patchy habitats.     

Estimating disturbance effects from military training using developmental instability and physiological measures of plant stress

We used developmental instability, water potential, and variable fluorescence to determine if populations of winged sumac (Rhus copallinum) were being negatively effected by military training disturbance. We established nine sites that represented a land-use disturbance gradient with three impact levels (low, medium, and high), the effects mostly due to mechanized infantry training maneuvers. Although mean values of developmental instability, water potential, and variable fluorescence differed significantly among sites, the patterns did not consistently differentiate sites relative to the disturbance gradient. At the population level, some measures of developmental instability and variable fluorescence were positively correlated. All nine sites consisted of habitat mosaics, with the abundance of higher quality habitat patches and canopy gaps closely related to habitat impacts. It may be that R. copallinum is selecting similar micro-environments at all sites and therefore minimizing inter-site variation in stress measures, despite large differences in overall habitat condition. Our results call for caution in developing ecological indicators using the response of physiological and morphological measures from a single plant species.