芦芽山华北落叶松(Larix principis-rupprechtii)树轮宽度年表对气候因子的响应

在芦芽山地区采集3个不同海拔的华北落叶松(Larix principis-rupprechtii),在传统去趋势的基础上,采用"signal-free"方法对拟合曲线进行修正,避免了中等频率的气候信息引起的拟合偏差,最终建立3个不同海拔树轮宽度标准年表(STD)。同时以10a为界对上述年表进行滤波处理,得到3个低频年表。年表特征值表明,随着海拔升高,年轮平均轮宽变窄,敏感性和高频信息增强,低频信息减弱,这可能与逐渐恶劣的生境有关。中、低海拔年表的低频信息更一致,中、高海拔的高频信息更接近,而高、低海拔无论是标准年表还是高频、低频年表相似性均较差。树轮气候响应分析显示,低海拔STD年表与5月最低温负相关最为显著,STD和低频年表均与5、6月份土壤温度显著负相关,说明生境暖干,树木主要受生长季的干旱胁迫;中海拔STD年表与当年5月最高温正相关最为显著,STD和低频年表与土壤温度相关均不显著,说明生境逐渐变得冷湿,生长季的低温成为树木生长的限制因子;高海拔STD年表与气象要素相关不显著,低频年表与当年4月土壤温度正相关,说明高海拔最为冷湿,并有季节性冻土分布,生长季的土壤低温成为树木生长的限制因子。因此,全球变暖的趋势将更有利于高海拔树木的生长,而低海拔树木的干旱胁迫进一步加剧。     

温带森林不同海拔土壤有机碳及相关胞外酶活性特征

研究测定了老秃顶子温带森林生态系统7个海拔土壤不同形态碳和相关水解酶、氧化还原酶活性,分析了土壤有机碳及相关酶活性沿海拔梯度的影响因素.结果表明: 随海拔升高,土壤有机碳(SOC)、颗粒有机碳(POC)和可溶性有机碳(DOC)含量显著增加,而在海拔825～1233 m之间没有显著变化,DOC/SOC则显著下降;土壤α葡萄糖苷酶、β葡萄糖苷酶、木糖苷酶和纤维二糖水解酶活性显著增加;土壤SOC、POC、DOC、全氮(TN)含量及土壤含水量(SMC)与土壤水解酶活性呈显著正相关;过氧化物酶(POD)活性在低海拔(675 m)落叶松人工林显著低于其他海拔,POD活性与土壤碳氮(SOC、TN、POC、DOC)含量及SMC呈显著正相关,而土壤多酚氧化酶(PPO)活性在海拔947 m落叶阔叶林带和海拔825 m红松林中较高,且仅与土壤pH呈显著正相关,表明土壤酸度是驱动PPO酶活性的主要因素.在温带森林生态系统中,土壤养分含量和含水量是影响土壤水解酶海拔分布的重要因素.     

UV-B对不同发育时期离体蓝莓主要果实品质及相关酶活性的影响

该研究以幼果期、白果期、转色期的离体‘北陆’蓝莓果实为试材,设置0(CK)、5、10、15min紫外光辐照处理,24h后取样分析蓝莓果实中可溶性糖、总酚、类黄酮和花青苷含量,以及苯丙氨酸裂解酶(PAL)和查尔酮异构酶(CHI)活性的变化,探究UV-B紫外照射处理对不同发育时期蓝莓主要果实品质及相关酶活的影响。结果显示:(1)对于幼果期蓝莓,5min UV-B处理可显著增加果实内可溶性糖含量;10min UV-B处理果实PAL活性增加效果最为显著;15min UV-B处理对果实总酚和花青苷积累的促进作用最大,但显著降低了类黄酮含量和CHI活性。(2)对于白果期蓝莓,5min UV-B处理显著增加了果实类黄酮含量和CHI活性,10min处理使果实可溶性糖和总酚含量较对照分别增加25%和18%;15min处理对果实花青苷含量和PAL活性影响作用最大。(3)对于转色期蓝莓,各处理除果实可溶性糖及类黄酮含量降低外,其余物质含量均显著增加。(4)UV-B处理并未改变果实发育过程中可溶性糖、总酚、类黄酮和花青苷含量及PAL、CHI酶活性的积累规律。(5)蓝莓果内PAL活性与其可溶性糖、总酚和类黄酮的积累呈极显著正相关关系,而CHI活性仅与其可溶性糖呈极显著正相关。研究表明,UV-B辐照处理促进了幼果期和白果期可溶性糖的积累,也能促进不同发育时期蓝莓果实总酚和花青苷及白果期类黄酮的积累,对蓝莓果实主要品质能够产生积极的影响。     

Altitudinal differences in the contents of phenolics in flowering heads of three members of the tribe Lactuceae (Asteraceae) occurring as introduced species in New Zealand

Crepis capillaris, Hieracium pilosella, and Hypochaeris radicata were investigated for the influence of the altitude of the collection site on the content of phenolics within the flowering heads. These three taxa from the Lactuceae tribe of the Asteraceae family originate from Europe and are now widespread within New Zealand. Flowering heads collected from different altitudes ranging from 180 m to 1060 m (C. capillaris), from 190 to 1290 m (H. pilosella), and from 20 m to 1290 m (H. radicata), respectively, were extracted and analysed by high performance liquid chromatography. Results showed a positive correlation between the altitude of the growing site and the contents of flavonoids and phenolic acids for all investigated taxa. The altitudinal effect was, however, partially concealed by geographic differences between coastal and inland collection sites, with the inland collections containing higher concentrations of flavonoids and phenolic acids than plants collected from the coast. The results are discussed in the light of a putative UV-B protective function of the quantified compounds and of the immigration histories of the three species at hand.     

Climate sensitivity of purple cone spruce (Picea purpurea) across an altitudinal gradient on the eastern Tibetan Plateau

Picea purpurea (Purple cone spruce) is a dominant and widely distributed tree species in the subalpine area of the Wanglang Nature Reserve. We investigated variations in radial growth and its response to climate in P. purpurea along an altitudinal gradient. In this study, P. purpurea chronologies were developed from three altitudinal sites ranging from 2850 to 3250 m above sea level. Correlation analysis and principal component analysis were used for all the chronologies to detect the growth patterns at different altitudes. Correlation analysis was used to assess the relationships between chronologies and climatic factors. Tree-ring widths among the three elevations were all positively correlated with June maximum temperature in the current year. Radial growth at the higher altitude was more sensitive to temperature than those of the two lower altitudes. Ring-widths at the low and middle sites were mainly negatively affected by temperatures in the previous growing season (June and August). Spruce growth at the upper site was strongly positively affected by temperatures in the previous winter, the current spring and current growing season. Climatological analysis revealed that elevation-dependent and elevation-independent signals were present in this semi-humid subalpine area. Precipitation was not the main factor affecting the tree growth in the growing season throughout the study area. The noteworthy findings were that the lag effects of temperatures to spruce growth was more significant at the low and middle altitude sites, and spruce growth at the high altitude site clearly benefited from the warmer climate before and during the growing season. This study will provide a basis for better predicting forest dynamics and carrying out vegetation restoration in the future.     

不同海拔‘凤丹'牡丹籽粒油脂品质形成及代谢相关基因差异表达

通过对洛阳地区海拔100、650和1010 m‘凤丹'牡丹籽粒发育过程中形态指标、营养成分和关键基因的表达分析,研究了不同海拔条件下‘凤丹'牡丹籽粒产量性状变化和可溶性糖、淀粉、可溶性蛋白质与脂肪酸间的转化规律,以及相关酶活性和油脂代谢关键基因差异表达。结果表明: ‘凤丹'牡丹单果籽粒产量性状随海拔的升高而升高,且高海拔‘凤丹'籽粒生长期长于低、中海拔。成熟籽粒中可溶性糖和淀粉含量随海拔的升高而增加,可溶性蛋白质和粗脂肪含量差异不显著。籽粒发育过程中蔗糖合成酶(SS)和蔗糖磷酸合成酶(SPS)活性呈现先降后升的趋势,花后90 d活性最低;丙酮酸脱氢酶(PDH)、谷丙转氨酶(GPT)和谷草转氨酶(GOT)活性均在花后50～90 d快速增加,花后90 d达到最大值。牡丹籽粒中乙酰CoA羧化酶基因(ACCase)和硬脂酰ACP脱氢酶基因(SAD)相对表达量在花后50 d达到最大值,而ω-6脂肪酸去饱和酶2(FAD2)相对表达量在花后90 d达到最大值。籽粒发育过程中可溶性糖和淀粉与蛋白质和粗脂肪的积累呈负相关;SPS活性与可溶性糖和淀粉呈正相关,与可溶性蛋白质和粗脂肪呈极显著负相关;GPT、GOT与可溶性糖呈负相关,与淀粉呈极显著负相关,与可溶性蛋白质和粗脂肪呈极显著正相关;PDH与可溶性蛋白质、GPT、GOT呈正相关,与可溶性糖呈负相关,与淀粉呈极显著负相关。表明牡丹籽粒发育过程中养分积累是由糖类向粗脂肪和蛋白质的方向转化,SPS、PDH、GPT、GOT等在此过程中起重要作用。籽油中的棕榈酸、硬脂酸和亚油酸与亚麻酸相对增量呈负相关,说明牡丹籽油中脂肪酸去饱和过程是向亚麻酸合成的方向进行。ACCase、SAD和FAD2相对表达量与亚麻酸的相对增量呈正相关,均在亚麻酸合成过程中起重要作用。不同海拔条件下牡丹籽粒油脂品质相对稳定,籽粒生产性能随海拔的升高而升高,故在洛阳中高海拔地区种植油用牡丹是边际土地高效利用的重要策略。     

Variation in UV sensitivity among common frog Rana temporaria populations along an altitudinal gradient

Solar ultraviolet-B (UV-B) radiation can be harmful for developing amphibians. As the UV-B dose increases with altitude, it has been suggested that high-altitude populations may have an increased tolerance to high levels of UV-B radiation as compared to lowland populations. We tested this hypothesis with the common frog (Rana temporaria) by comparing populations from nine altitudes (from 333 to 2450m above sea level). Eggs collected in the field were used for laboratory experiments, i.e., exposed to high levels of artificial UV-B radiation. Eggs were reared at 14+/-2 degrees C and exposed to UV treatments until hatching. Embryonic developmental rates increased strongly and linearly with increasing altitude, suggesting a genetic capacity for faster development in highland than lowland eggs. Body length at hatching varied significantly with UV-B treatments, being lower when eggs developed under direct UV-B exposure. Body length at hatching also increased as the altitude of populations increased, but UV-B exposure times were shorter as altitude of population increased. However, the body length difference between exposed and non-exposed individuals in each population decreased as altitude of populations increased, suggesting a costly effect of UV exposure on growth. Type of UV exposure did not influence the mean rates of embryonic mortality and deformity, but both mortality and deformity rates increased as the altitude of populations increased (while UV-B exposure duration decreased). The effect of UV-B on body length at hatching, mortality, and deformities suggests that the sensitivity to UV-B varied among populations along the altitudinal gradient. These results are discussed in evolutionary terms, specifically the potential of R. temporaria high-altitude populations to develop local genetic adaptation to high levels of UV-B.     

Altitudinal variation of secondary metabolites in flowering heads of the Asteraceae: trends and causes

Plants in alpine habitats are exposed to severe environmental stresses including temperature and radiation extremes. The observation that flowering heads from high altitude populations of Scorzoneroides helvetica (Mérat) J.Holub (synonym: Leontodon helveticus Mérat) contained higher amounts of luteolin derivatives than conspecific populations in lower altitudes prompted further investigations. An elevational increase of phenolics was confirmed in flowering heads of neophytic populations of three additional taxa of the Cichorieae tribe in New Zealand. A solely genetic basis of the altitudinal trends of flavonoids and phenolic acids was eliminated by field experiments with cultivars of the medicinal herbs Arnica montana L. and Matricaria chamomilla L. planted at nine different altitudes ranging from 600 to 2,200 m in the Tyrolean Alps. Parallel experiments on potted plants excluded soil characteristics as the factor causing the observed variation. The initial hypotheses that enhanced UV-B radiation in higher altitudes was triggering an increase in the ratio of B-ring-ortho-diphenolic versus B-ring-monophenolic flavonols in flowering heads of Arnica was disproved by climate chamber experiments resulting in no significant difference between plants grown in ambient and threefold ambient UV-B radiation regimes. In contrast, an increase of this ratio similar to the changes observed in higher altitudes resulted from a decrease in temperature by 5°C in a second climate chamber experiment. Conclusively, enhanced UV-B radiation is probably not the key factor inducing shifts in the phenolic composition in Asteraceae growing at higher altitudes but it is rather the temperature which decreases with altitude.     

Differences in growth and physiological traits of Populus cathayana populations as affected by enhanced UV-B radiation and exogenous ABA

During one growing season, the effects of enhanced ultraviolet-B (UV-B) radiation, exogenous abscisic acid (ABA) and their combination on biomass accumulation, gas exchange, endogenous ABA, the concentration of UV-absorbing compounds, antioxidant system and on the carbon (C) and nitrogen (N) content and C/N ratio were investigated in two contrasting Populus cathayana Rehd. populations, originating from high and low altitudes in south-west China. Exogenous ABA was sprayed to the leaves, and enhanced UV-B treatments were applied using a square-wave system to expose the seedlings to ambient (1×) or twice ambient (2×) doses of biologically effective UV-B radiation (UV-B_BE). Enhanced UV-B radiation significantly decreased height, basal diameter, total leaf area, total biomass, net CO₂ assimilation rate (A), stomatal conductance (g_s), transpiration rate (E) and carbon (C) content in leaves, and significantly increased the activities of superoxide dismutase (SOD) and guaiacol peroxidase (GPx), and the contents of hydrogen peroxide (H₂O₂) and malonaldehyde (MDA), as well as the accumulation of UV-absorbing compounds and endogenous ABA concentrations among different organs in both populations. In contrast, exogenous ABA induced a significant decrease in A and significant increases in the activities of SOD and GPx, in the content of H₂O₂ and MDA, and in the endogenous ABA concentrations. Compared with the low altitude population, the high altitude population was more tolerant to enhanced UV-B and exogenous ABA. Significant interactions between UV-B and ABA were observed in A, E, and in the activities of SOD and GPx, as well as in endogenous ABA in the leaves and roots of both populations. Across all treatments, the C and N contents of leaves were strongly correlated with their contents in stems and roots. Additionally, the N content of leaves and stems were significantly correlated with the C content of stems.     

Temperature is the key to altitudinal variation of phenolics in Arnica montana L. cv. ARBO

Plants in alpine habitats are exposed to many environmental stresses, in particular temperature and radiation extremes. Recent field experiments on Arnica montana L. cv. ARBO indicated pronounced altitudinal variation in plant phenolics. Ortho-diphenolics increased with altitude compared to other phenolic compounds, resulting in an increase in antioxidative capacity of the tissues involved. Factors causing these variations were investigated by climate chamber (CC) experiments focusing on temperature and ultraviolet (UV)-B radiation. Plants of A. montana L. cv. ARBO were grown in CCs under realistic climatic and radiation regimes. Key factors temperature and UV-B radiation were altered between different groups of plants. Subsequently, flowering heads were analyzed by HPLC for their contents of flavonoids and caffeic acid derivatives. Surprisingly, increased UV-B radiation did not trigger any change in phenolic metabolites in Arnica. In contrast, a pronounced increase in the ratio of B-ring ortho-diphenolic (quercetin) compared to B-ring monophenolic (kaempferol) flavonols resulted from a decrease in temperature by 5°C in the applied climate regime. In conclusion, enhanced UV-B radiation is probably not the key factor triggering shifts in the phenolic composition in Arnica grown at higher altitudes but rather temperature, which decreases with altitude.     

Altitudinal differences in UV absorbance,UV reflectance and related morphological traits of Quercus ilex and Rhododendron ferrugineum in the Mediterranean region

We studied the variations in different physiological parameters associated with UV-B radiation defense: UV-B radiation absorbance, UV-visible spectral reflectance, carotenoids concentration, leaf thickness, SLW (specific leaf weigth) and trichome density in Quercus ilex growing at 200 and 1200 m and Rhododendron ferrugineum growing at 2200 m. We examined the role of these parameters as protection mechanisms in an altitudinal gradient of increasing UV radiation in northern Catalonia and in sun and shade leaves. The concentration of UV-B radiation absorbing pigments was 15% higher in sun leaves of Q. ilex at 1200 m than in those from 200 m altitude. Sun leaves of R. ferrugineum presented concentrations three times higher than those of Q. ilex. Reflectance ranged between 5% (in the region 300–400 nm) and 12% (in the region 280–300 nm). The variation of reflectance with altitude followed an inverse trend respect to absorbance in the 280–300 nm region, with higher values the lower the altitude, but in the 300–400 nm region, reflectance of the lower site was the lowest. In both species and altitudes sun leaves presented higher concentrations of UV-B radiation absorbing pigments and UV reflectance than shade leaves. Quercus ilex trees of the higher location presented higher NDPI (Normalized Difference Pigment Reflectance Index) values, indicating higher carotenoids/chlorophyll a ratio. Actual measurements of carotenoid/chlorophyll a ratio confirmed this pattern. The photochemical reflectance index (PRI) presented higher values the higher the location indicating lower photosynthetic radiation-use efficiency. Specific leaf weight (SLW) and leaf thickness were larger in Q. ilex trees of higher location than in those of lower location. In both sites, sun leaves also presented larger SLW values than shade leaves. Adaxial leaf hair density in sun leaves was significantlly higher in the lower location. UV absorption and linked morphological traits (SLW, leaf thickness measured in Q. ilex) presented the larger differences among studied plants at different altitudes and seem to be the dominant UV protecting mechanisms.     

增强UV-B辐射和氮对谷子叶光合色素及非酶促保护物质的影响

以谷子(Setaria italica(L)Beauv.)为对象,从拔节期开始持续给予低氮(1.875 mmol/L)和高氮(15 mmol/L)两种氮供应条件并从抽穗期开始进行26 d两种强度(4.29、7.12 kJ·m-2·d-1)的增强UV-B辐射处理,研究了谷子叶中光合色素含量、类黄酮含量和苯丙氨酸解氨酶(PAL)活性的变化.结果表明:与高氮供应条件相比,低氮供应条件明显降低了谷子叶中光合色素含量但提高了类胡萝卜素/叶绿素含量比值;在开花期中段和灌浆期中段,高氮供应条件下谷子叶中光合色素含量对增强UV-B辐射比低氮供应条件下的谷子更敏感.从灌浆期开始到处理结束,两种影响因子对谷子叶中类黄酮含量均有显著影响,增强UV-B辐射导致谷子叶中类黄酮含量逐渐升高,且相同增强UV-B辐射强度下低氮供应条件下的谷子叶中类黄酮含量明显高于高氮供应条件下的谷子.谷子叶中PAL活性对两种影响因子的响应较类黄酮含量更加敏感,低氮供应条件使谷子叶中PAL活性明显提高.结合上述指标的相关性分析结果可知,低氮供应条件加强了处于繁殖期主要阶段的谷子叶中类黄酮的积累,并使谷子叶中的类胡萝卜素/叶绿素含量比值明显提高,进而有助于维持谷子叶中光合色素含量在增强UV-B辐射条件下的相对稳定性,对植株抵抗UV-B辐射伤害有利.     

Effects of an enhanced ultraviolet-B irradiation on photosynthetic apparatus of several forest coniferous tree species from different locations

The effect of UV-B on the photosynthetic apparatus of coniferous trees: Picea abies (L.) Karst., Picea pungens (Engelm.), Pinus sylvestris (L.), Pinus cembra (L.) and Abies alba (Mill.) was investigated. Three and four-year-old plantlets coming from different latitudes, longitudes and altitudes were used. The experiment was carried out in greenhouse. Two doses of ultraviolet-B irradiation were applied: control=0, low dose=11.32 and high dose=22.64 kJ·m⁻²·d⁻¹ UV-B_BE (biologically effective irradiance of UV-B). Measurements of chlorophyll fluorescence, gas exchange, chlorophyll and flavonoids content were carried out. Response of forest trees to an increased UV-B radiation depends on species, location of place of pantalets collecting and UV-B dose. Pinus cembra, Picea abies and Pinus sylvestris from high altitude (1000 m a.s.l.) were less sensitive to UV-B than these from plain location. The altitude determined adaptation of forest coniferous trees to an enhanced UV-B radiation much more than the latitudinal gradient. Permanent discoloration was observed only on the young needles of the fir plantlets that were grown in light limiting conditions. Photosynthetic parameters were affected by the UV-B radiation. Both maximal and the steady state fluorescence of chlorophyll were reduced as a consequence of elevated UV-B in case of some species. The chlorophyll content was enhanced, increased or was not affected according to species and to locations. The flavonoids content in the needles increased with chlorophyll content at both UV-B treatments. An opposite trend was found in the control. The increased content of screening pigments in the needles of all the tested coniferous trees was detected. Picea abies and Picea pungens photosynthesis response curves to the light and to the intercellular CO₂ concentration did not change significantly under increased UV-B because of higher concentration in screening pigments in leaves. The increased concentration of flavonoids in forest litter may lead to changes in the biogeochemical cycle in the forest ecosystem.     

Responses of the flavonoid pathway to UV-B radiation stress and the correlation with the lipid antioxidant characteristics in the desert plant Caryopteris mongolica

Caryopteris mongolica is a dwarf shrub mainly found in grassland and desert areas of north-west China, and which can survive severe environmental stress. This study aimed to assess the responses of the flavonoid pathway to UV-B radiation treatments and its correlation to the lipid peroxide and antioxidant systems in C. mongolica. In UV-B radiation experiments, plants were exposed to UV-B radiation treatments with a intensity of 30 J/s for 1, 4 and 24 h, respectively. A control group without UV-B radiation treatment was also used. The chlorophyll fluorescence parameters, contents of chlorophyll and carotenoid, levels of lipid peroxidation, activities of antioxidant system enzymes, accumulations of total flavonoids and anthocyanins, and activities of phenylalanine ammonialyase (PAL) and chalcone isomerase (CHI) under different UV-B radiation treatments were investigated. The correlations between products and key enzymes in the flavonoid pathway and the lipid peroxide and antioxidant systems were also analyzed. The results showed that chlorophyll fluorescence parameters decreased within 24 h of treatment. The chlorophyll contents decreased within 4 h and remained stable after 24 h. Carotenoid content significantly increased. The level of MDA, the activities of superoxide dismutase (SOD), ascorbate peroxidase (APX) and peroxidase (POD) and the contents of total flavonoids and anthocyanidins increased, while catalase (CAT) activity decreased under UV-B stress. The activities of PAL and CHI also increased with the increased content of total flavonoids. The flavonoid products anthocyanidins had a significant positive correlation with MDA level, as well as the activities of antioxidant enzyme SOD. In conclusion, UV-B radiation induced the degradation of photosynthetic pigments and decreased photochemical efficiency of Photosystem II; increased the contents of MDA, total flavonoids and anthocyanidins; and also enhanced activities of antioxidant enzymes (SOD, APX and POD) and key enzymes (PAL and CHI) in the flavonoid pathway in C. mongolica. Thus, we speculate that the flavonoid pathway were involved in the regulation of stress resistance in C. mongolica.     

青藏高原东缘过路黄在资源交互斑块性生境中的克隆内资源共享

在青藏高原和四川盆地过渡带,分别于618m和1800m两个海拔高度上研究匍匐茎克隆植物过路黄(Lysimachia christinae)在资源交互斑块性生境中的克隆内资源共享及其对生长的影响.结果显示, 在海拔1800m处,与资源的空间同质性处理(Ⅰ) 和(Ⅱ)相比, 资源的空间异质性处理(Ⅲ)和(Ⅳ)下过路黄整个克隆片段的生物量和分株数均获得显著增加;在海拔618m处,与资源的空间同质性处理(Ⅰ) 和(Ⅱ)相比,资源的空间异质性处理(Ⅲ)和(Ⅳ)下过路黄整个克隆片段生物量显著增加.在海拔618m和1800m处,生长在低光高养条件下的远端分株, 若与高光低养的近端分株相连, 相比连接到低光高养的近端分株, 它们分配更多的生物量到地下部分;在海拔1800m处,生长在高光低养条件下的远端分株, 若与低光高养的近端分株相连, 相比连接到高光低养的近端分株, 它们分配更多的生物量到地上部分.在海拔618m和1800m处,生长在高光低养条件下的近端分株, 若与低光高养的远端分株相连, 相比连接到高光低养的远端分株, 它们分配更多的生物量到地上部分.处于资源交互斑块性生境中的过路黄发生了克隆内分工,依靠相连分株间的功能分化, 克隆植物能有效的利用异质性分布的资源, 缓解资源交互斑块性分布对克隆植物生长的不利影响.通过间隔子(匍匐茎或根状茎),相连分株间能够相互传递和共享由不同分株获得的资源,这种资源共享能够提高克隆植物在异质性生境中的存活与生长.同时,方差分析显示环境异质性和海拔的交互作用显著影响克隆片段的生物量和分株数.相比于海拔618m,在海拔1800m处克隆内资源共享对克隆植物生长表现的影响更大.     

Morphological, genetic, and chromosomal variation at a small spatial scale within a mosaic hybrid zone of the grasshopper Dichroplus pratensis Bruner (Acrididae)

Hybrid zones are regions where genetically different populations meet and mate, resulting in offspring of mixed characteristics. In organisms with limited dispersal, such as melanopline grasshoppers, hybrid zones can occur at small spatial scales (i.e., <500 m). We assessed levels of morphological, chromosomal, and molecular variability in adult males of the grasshopper Dichroplus pratensis Bruner (N = 137 males, 188 females) collected at 12 sites within a mosaic hybrid zone in a heterogeneous environment in Sierra de la Ventana, Argentina. In this hybrid zone, 2 Robertsonian chromosomal races, polymorphic for different centric fusions, meet (the "Northern race" at low altitudes and the "Southern race" at higher altitudes), forming hybrids that show monobrachial homologies during meiosis. High morphometric variation in 6 traits was revealed among grasshoppers of both sexes, with male body size positively and significantly correlated with increasing altitude. Frequency of Robertsonian fusions characteristic of the Southern race increased significantly with altitude. Moreover, fusion frequencies covaried between samples. Considerable genetic variation was revealed by random amplification of polymorphic DNA markers, with heterozygosity ranging from 0.3477 to 0.3745. Insects from low-altitude and high-altitude populations showed significant genetic differentiation, as indicated by F(ST) values. The proposed model for D. pratensis, involving the generation and maintenance by chromosomal fusions, of gene complexes adaptive in different environments, could explain the observed clinal patterns within the contact zone.     

海拔对青藏高原东部毛茛科植物繁殖特征和资源分配的影响

通过野外采样对青藏高原东部高寒草甸上两个海拔间3种常见毛茛科植物条裂银莲花(Anemone trullifo-liavar.linearis)、粗距翠雀花(Delphinium pachycentrumHemsl.)和钝裂银莲花(Anemone obtusiloba)的繁殖性状和资源分配进行了研究,并对植物在极端环境下采取的繁殖策略及繁殖模式进行了探讨.结果显示:(1)3个物种的株高都随着海拔的升高而降低;同一物种的花大小在不同海拔间均无显著差异;条裂银莲花单个种子重随海拔的升高而增加,但虫食数/株、结籽率和种子数/株均随着海拔的升高而减少;钝裂银莲花的繁殖分配、虫食数/株、种子数/株和单个种子重均随着海拔的升高而减小.(2)不同海拔条裂银莲花的个体大小与单花重、雄蕊重、虫食数/株均呈显著正相关,且回归斜率在海拔间有显著差异.粗距翠雀花花期的雄蕊重与个体大小呈显著正相关,但这种异速关系不受海拔和个体大小的影响;钝裂银莲花的个体大小与花期的所有繁殖特征以及果期的种子重/果实均呈显著正相关,不同海拔间个体大小与种子重/果实的斜率差异显著,且与花期各繁殖性状异速关系的截距差异显著.研究表明海拔对植物的个体大小以及种群间的繁殖对策和繁殖成功率有着重要的影响.     

Studies on a climosequence of soils in tussock grasslands

Nematodes were extracted and identified from tussocks growing on eight soil types (Conroy, Cluden, Tawhiti, Lammerlaw, Carrick, McKerrow, Obelisk, Harihari) from altitudes of 80–1550 m. Most soils were from schist parent material in Otago. Samples from the bottom 5 cm of the leaves and the 0–5‐cm and 8–12‐cm soil strata were analysed separately. Altogether 4455 specimens of nematodes were identified, and the percentage composition in each stratum was calculated. Seventy species were found; only 1 occurred at all sites, 22 were found at only 1 site; 28 occurred in all 3 strata, 18 in only 1 stratum. A strong site factor was noted in species distribution, and there was distinct stratification. Correlation coefficients were calculated for nematode abundance and diversity with altitude, rainfall, and chemical factors (pH, organic C, and soil N); calculations were also made for only six sites by omitting Lammerlaw and Harihari, which did not reflect stages in the climosequence. Considering the six sites, total numbers of nematodes decline with altitude, but numbers of species do not; numbers in 0–5‐cm soil are significantly positively correlated with pH, and negatively with organic C. The correlation with pH is not causal, but reflects a negative association of pH with both precipitation and altitude which tends to obscure relationships between nematodes and environmental factors. Paratylenchus sp. was dominant at the two driest sites; at the next site it was mixed with Macroposthonia, which occurred at the subsequent wetter sites; this distribution apparently reflects the resistant preadult stage of Paratylenchus. Most Dorylai‐moidea had a wide distribution, but Belondiroidea and Mononchoidea showed a preference for the wetter sites. Of the 70 species found, 30 were named and 18 were previously known from New Zealand, 6 appear cosmopolitan in distribution, 2 have Australian relationships, and 1 has Southern Hemisphere relationships.     

Phenology of Festuca pallescens in relation to topography in north-western Patagonia

Abstract. The phenological changes in populations of Festuca pallescens (St. Yves) Parodi at different topographic positions and exposure along an altitudinal gradient (600 - 1100 m) were investigated during two growing seasons in northwestern Patagonia. Stepwise multiple regression analysis was used to describe the relationship between phenology and environment during the entire growing season. Analysis of variance was also performed at each sample date to detect significant environmental factors influencing phenology at different sites. The sum of maximum air temperatures was identified as the environmental variable best correlated with the seasonal variation of phenological events of Festuca pallescens over the period of two growing seasons, explaining 93.2 % of the total variance. Significant differences between sites were observed at each sample date. Main effects of altitude and topographic position and two-way interactions between altitude and topographic position, and topographic position and exposure were also detected as significant. Phenology was delayed at increased altitude. Differences in phenology between topographic sites at the same altitude were not detected during the entire growing season and were only observed in the reproductive phase. At this time, the phenology was significantly delayed at high topographic positions on the slopes as compared with low and mid positions. At high altitudes in the valley (950 m a. s. 1.), where steep slopes and humid conditions prevail, phenology was delayed on western exposures and low positions. The results adequately summarize and quantify the effect of spatial and temporal environmental variation on the phenological development of Festuca pallescens in northwestern Patagonia.     

小兴安岭红皮云杉年轮-气候关系及其衰退原因

运用树木年轮学方法,建立了小兴安岭丰林自然保护区不同海拔2个红皮云杉树轮宽度年表,研究其与局地温度、降水、帕默尔干旱指数(PDSI)及大尺度气候因子的关系,探讨红皮云杉径向生长的主要限制因子,分析其近几十年衰退的原因.结果表明： 小兴安岭红皮云杉径向生长受温度限制作用强于降水,且生长季最低温度限制最强.不同海拔红皮云杉径向生长对气候响应存在明显差异：低海拔红皮云杉径向生长与生长季(6—9月)年降水量呈显著正相关;与不同深度土壤温度呈显著负相关,80 cm土层土温在生长季阶段限制作用最强;与PDSI在生长季呈显著正相关.高海拔红皮云杉与空气温度、降水、土壤温度及PDSI的关系没有低海拔显著.小兴安岭红皮云杉衰退可能与北大西洋多年代际振荡(AMO)、太平洋年代际振荡(PDO)的相位转变以及1980年后的显著升温有一定关联,上述因素的耦合作用使该区土壤蒸发量加大,暖干化现象加剧,进而导致低海拔红皮云杉生长衰退.