Carbon,nitrogen and phosphorus stoichiometry of Myrica nana in Yunnan,China

Aims Carbon (C), nitrogen (N) and phosphorus (P) play important roles in plant growth and physiological functions. We aimed at exploring the intrinsic relationships of C, N and P in Myrica nana—a common shrub in Yunnan Province—as well as their relationships with pant biomass and soil nutrients.
Methods We measured the concentration of C, N and P of M. nana from 29 sites for their magnitudes and correlations with soil nutrients.
Important findings 1) The arithmetic mean value of C, N and P concentration in the roots, stems and leaves of M. nana was 45.94%, 0.54%, 0.03%, and 46.32%, 0.58%, 0.03%, and 49.05%, 1.70%, 0.06%, respectively. C, N and P concentrations in the leaves were significantly higher than those in the roots and the stems. The C:N:P in roots, stems and leaves was 1531:18:1, 1544:19:1, and 818:10:1, respectively. 2) The C concentration and N:P in leaves of M. nana decreased with the increase of biomass of M. nana; the leaf C concentration was significantly correlated with biomass (p < 0.01), while the correlation between N:P and biomass was not significant (p > 0.05). The leaf N increased with the increase of plant biomass, the P was significantly correlated with biomass (p < 0.05), but the correlation between N concentration and biomass was not significant (p > 0.05). N:P in leaves was 34.2, suggesting that plant growth was limited by P. 3) C, N and P concentration in the roots were significantly correlated with soil P (p < 0.05), with N, P concentrations correlated with soil P positively (p < 0.01) and C negatively (p < 0.05). C concentration in the stems was significantly and negatively correlated with soil C, N, with significant correlation with C, N, and P concentration (p < 0.01). P concentration in the stems was significantly and positively correlated with soil P concentration (p < 0.01), while leaf P significantly and positively correlated with soil C, N and P (p < 0.01); leaf C concentration was significantly and negatively correlated with soil P (p < 0.01).     

Physiological responses and photo-protective mechanisms of two Rhododendron plants to natural sunlight after long term shading

AimsResponses of plants to increased irradiance are governed by two strategies: an increase in the utilization of absorbed light and photo-protective mechanisms. Varied physiological responses to increased irradiance were observed in plant species with differing adaptabilities to light regimes. This research aims to explore the physiological responses and photo-protective mechanisms of two Rhododendron plants to changes in light regimes. MethodsChlorophyll fluorescence parameters and rapid light curves were measured for leaves of R. hybrida (a shade-tolerant species) and R. simsii (a light-loving and shade-tolerant species) following exposure to sunlight for five days after growing in the shade for one year.Important findings Natural sunlight decreased the efficiency of photochemical reaction by reducing the fraction of incident light in photochemical energy utilization and decreased thermal dissipation through regulating energy dissipation in photosystem II (PSII) in the leaves of R. hybrida. As a result, natural sunlight induced the accumulation of excess excitation energy in PSII, and caused photo-inhibition and even photodamage in the leaves of R. hybrida, which was suddenly transferred from long-term shading to sun exposures. The acclimation capacity to changes of growth light regimes was stronger in R. simsii than in R. hybrida, due to a higher capability for photochemical reaction, thermal dissipation and cyclic electron flows around photosystem I in the leaves of R. simsii. Rhododendron simsii could utilize a high fraction of incident light in photochemistry and regulate energy dissipation in PSII to protect the photosynthetic apparatus under both shading and natural sunlight condition. Therefore, high light intensity under natural sunlight did not cause photo-inhibition in R. simsii.     

泥炭地特征性环境因子促进泥炭藓持久孢子库的形成

研究泥炭地特征性环境因子——淹水、少氧和化感物质对泥炭藓孢子持久性的影响, 可深入理解泥炭地泥炭藓持久孢子库的形成机制, 为退化泥炭地泥炭藓地被恢复研究提供参考。该研究以藓丘种和丘间种两种泥炭藓的孢子为试验材料, 通过室内模拟控制实验的方法, 研究泥炭藓孢子在空气、超纯水、泥炭地地表水和泥炭藓沥出液中, 及3种速率充气下, 孢子萌发力持久性的变化。经充气处理后, 泥炭藓孢子持久性显著低于不充气处理。不充气时, 泥炭藓孢子在含有化感物质的泥炭地地表水和泥炭藓沥出液中保存, 持久性显著高于在超纯水中保存。通径分析结果显示, 溶解氧是影响泥炭地泥炭藓孢子持久性的主要因子和限制因子, 养分元素氮(TN)和磷(TP)的浓度为孢子持久性的负作用因子。研究结果表明, 泥炭藓孢子散布于苔藓地被基质或淹水的丘间生境中, 比暴露于空气或在无化感物质的水中, 能更好地维持萌发力。泥炭地中, 泥炭藓孢子和其他植物的繁殖体的超长寿命可能归因于少氧、养分贫乏和丰富的化感物质等泥炭地特征性环境因子。     

Species association and correlation between vertical layers in the Liquidambar formosana community in Tiantong region,Zhejiang Province

Aims Interspecific relationship is one of the most important properties in plant communities. Analyzing species association and correlation between vertical layers in plant communities is ecologically crucial for understanding community structure, dynamics and classification. The objective of this study was to test how plant species in contrasting vertical layers of plant communities associate and correlate. Methods The study sites are located in Tiantong region in Zhejiang Province. Community structure and species composition were measured in an early successional community of Liquidambar formosana. Interspecific relationships were examined between 3 tree species and 3 sub-tree species, between 3 tree species and 28 shrub species, and between 3 sub-tree species and 28 shrub species. Interspecific relationships were analyzed by using χ²-test for 2 × 2 contingency table, variance ratio (VR) test and spearman rank correlation test.Important findings With respect to tree and sub-tree layers, positive significant association was not observed for overall species. Species were independent with each other for most species pairs. Few species pairs showed significant association or correlation. Regarding tree and shrub layers, there were significant positive associations between overall species. Species between tree and shrub layers were more dependent on each other, with the most species showing significant association or correlation. Similarly, positive significant association existed for overall species between sub-tree and shrub layers, displaying a close interspecific relationship. These results suggest that the convergences of species behavior and habitat acclimatization, and complementary differences in habitat requirement over species between vertical layers might be the main driver affecting patterns of species association and correlation in the early successional community.     

鄂西南亚高山湿地泥炭藓的生长与分解

泥炭藓(Sphagnum)是湿地土壤碳的重要来源, 在土壤碳累积过程中发挥着关键作用, 但有关亚热带湿地泥炭藓生长与分解的研究鲜有报道。该研究选择鄂西南亚高山泥炭藓湿地为研究区域, 原位开展不同微生境泥炭藓的生长及其凋落物的分解实验, 室内测试凋落物的化学成分, 探讨亚热带亚高山湿地泥炭藓的生长与分解规律。结果表明: 泥炭藓在自然状态生长12个月后, 丘上和丘间两种微生境下泥炭藓的平均高度增长量分别为2.9和2.7 cm, 对应的净生产量分别为270.94和370.88 g·m ^-2, 生长时间与微生境对泥炭藓的高度增长量及净生产量均有显著影响, 且两者之间存在交互作用, 但是两种微生境下泥炭藓的生长变化过程不同; 两种微生境下泥炭藓的平均生长速率(2017年7-10月)为0.33 mm·d ^-1, 其生长速率高于寒温带地区。另外, 分解时间对泥炭藓的分解量有显著影响, 其残留率随时间增加表现为先减少后增加的趋势。12个月后, 丘间、丘上和水坑3种微生境下最终残留率分别为100.67%、90.54%和85.63%。凋落物中碳含量、碳氮比和多酚含量相比初始值均有所下降, 氮含量则为增加。同时, 微生境对凋落物分解的影响取决于分解时间。分解3个月时, 微生境之间凋落物的分解量差异显著, 其他时间段差异不明显。     

Senescence mechanisms induced by phloem girdling in Karelinia caspia

AimsSenescence constitutes the final stage of a plant’s organ and tissue development, and is subject to gene control and strict regulation. Plant senescence is largely influenced by carbohydrate content and phloem girdling can induce leaf senescence. Our general objective is to study the effect of stem girdling on physiological conditions in Karelinia caspia. Specifically, we want to know the senescence processes after phloem girdling. In addition, we also want to know the possible mechanisms for the senescence processes. MethodsThree different types of girdling treatments, normal branch, semi-girdling, and full-girdling were performed on K. caspia. Twenty days after girdling, photosynthetic pigments content, photosynthetic rate, soluble sugar content, starch content, abscisic acid (ABA) content, and leaf water potential were measured.Important findings Phloem girdling can largely induce leaf senescence in K. caspia, and the reasons for leaf senescence may be as follows: girdling resulted in carbohydrate accumulation in leaf which subsequently led to “carbon feast” induced leaf senescence; girdling caused ABA accumulation in leaf and then resulted in senescence; girdling decreased water status, which may be another reason for leaf senescence. Compared with natural senescence, girdling induced senescence was a disorder and disorganized process, only a limited physiological process can be controlled by senescence related gene in the girdling induced senescence process. The most important role for carotenoids in the senescence process is to protect the photosynthetic apparatus from being damaged by excess light and reactive oxygen species. Many physiological indicators declined in the semi-girdled K. caspia leaves just like full-girdled leaves, indicating that portion (e.g. half) of the phloem cannot undertake the transport flux which was done by the whole phloem sieve.     

两种品质类型花生品质形成与子叶细胞超微结构的关系

在大田条件下研究了两种品质类型花生(Arachis hypogaea)品质形成的动态差异及其子叶细胞超微结构的差异。结果表明, 高蛋白品种‘XB023’的蛋白质含量在籽仁发育前期较高油品种‘鲁花9号’低, 后期显著高于‘鲁花9号’, 且成熟期籽仁8种必需氨基酸组分含量均高于‘鲁花9号’, 其中谷氨酸、赖氨酸和亮氨酸含量差异极显著; ‘XB023’脂肪含量在籽仁发育期一直低于‘鲁花9号’。‘XB023’各时期的籽仁可溶性糖含量和油酸/亚油酸(O/L)值均显著低于‘鲁花9号’。两品种在果针入土10天时子叶细胞即形成淀粉粒、脂体和蛋白体, 随后脂体、蛋白体的数量不断增加, 淀粉粒先增大后逐渐缩小解体。‘XB023’的脂体达到最大的时间早于‘鲁花9号’, 而‘鲁花9号’的脂体快速积累的时间比‘XB023’长。两品种蛋白体大小都在果针入土40天时达到最大值, ‘XB023’的蛋白体在籽仁发育后期数量增加较快。高蛋白品种较高的蛋白质含量由其子叶细胞中较大蛋白体的大小和较多的蛋白体数量决定, 而高油品种较高的脂肪含量是由其较多的脂体数量决定。     

Associations between litterfall dynamics and micro-climate in forests of Putuoshan Island,Zhejiang, China

Aims Seasonal litterfall production plays an important role in the carbon and nutrient cycling in forest ecosystems. This study examines the effects of micro-environmental factors on seasonal litterfall dynamics in the forests of Putuoshan Island, Zhejiang Province of eastern China.
Methods The study covers five forest types, including Liquidambar formosana forest, Cinnamomum japonicum and Machilus thunbergii forest, Pinus massoniana forest, Cyclobalanopsis glauca forest, and Distylium gracile forest, in Putuoshan Island. We collected micro-meteorological data, and measured monthly litterfall in stands of the five forest types over one year. Redundancy analysis (RDA) was performed to determine the effects of micro-climatic factors on litterfall production．
Important findings The average annual litterfall production ranged from 3.45 to 5.36 t·hm^-2·a^-1 across five types of forests, albeit no effect of forest types on the litterfall production. The partitioning of litterfall components differed among the five forest types. The seasonal litterfall production exhibited two contrasting patterns, i.e. double climax curve and triple peaks, and varied significantly among the five forest types. Moreover, the peak in the litterfall production mostly occurred in the windy months of the year, such as in April, July and December, which was consistent with the dynamics of wind speed. RDA results showed that components of litterfall production in different months were controlled by different micro-climatic factors. The total, leaves, fruits, and miscellaneous litterfall productions were directly and positively affected by air temperature. Twig litterfall production was positively affected by the overstory wind velocity. Flower litterfall production was negatively affected by air humidity. In summary, forest types had no effects on litterfall production. However, variations in litterfall productions were explained by air temperature, air humidity, and overstory wind velocity in the forests studied.     

Effects of inoculation with arbuscular mycorrhizal fungi on photosynthetic physiology in females and males of Populus deltoides exposed to cadmium pollution

Aims Populus deltoides is an important plantation tree species in the middle and lower reaches of the Yangtze River and in Huai River Plain. The extensively cultivated varieties are consisted of both females and males of P. deltoides. The objective of this paper was to characterize the difference in cadmium (Cd) tolerance between the sexes and the effects of symbiosis with Rhizophagus intraradices on their Cd tolerance.
Methods The experiment was carried out under semi-controlled conditions in a natural light greenhouse, protected from rain. Rhizophagus intraradices was inoculated on roots of both females and males when transplanting to a sand culture substrate. After one month, half of cuttings were exposed to Cd pollution (10 mg·kg^-1). All cuttings were irrigated with sterile water to avoid infection by other microorganism. About three months later, the gas exchange rate, net photosynthesis rate (P_n)-intercellular CO₂ concentration (C_i) curve, chlorophyll fluorescence, osmotic adjustment and phytohormone content of both females and males of P. deltoides were measured.
Important findings Our main results are as follows: (1) when compared to the controls, decreases in P_n, stomatal conductance, C_i, transpiration rate, maximum photochemical efficiency of photosystem II (PSII), effective quantum yield of PSII, photo-chemical quenching coefficient, maximum rate of carboxylation of Rubisco, photosynthetically active radiation-saturated rate of electron transport and rate of triose phosphate utilization to a different degree in both sexes of P. deltoides under Cd pollution were found, and females exhibited a greater decrease in such parameters than males. Rhizophagus intraradices inoculation mitigated the toxic effect of Cd on such parameters to a different degree in females, not in males. (2) Under Cd pollution, there was an increase in proline content in both sexes when compared to the controls. A further increase in proline content occurred in females, not in males, when inoculated with R. intraradices. (3) When compared to the controls, there was a decrease in indoleacetic acid, but an increase in abscisic acid in leaves of both sexes when exposed to Cd pollution. The amplitude changed in both phytohormones in females was greater than that in males. Rhizophagus intraradices inoculation was helpful for recovery of phytohormone balance in females, which was not observed in males. Therefore, our results indicated that (1) there were a greater negative effect exerted by Cd pollution on gas exchange rate, carbon fixation capacity and phytohormone balance and a more impairment of photosynthetic apparatus in females when compared to males, showing a less tolerance to stress conditions in females; (2) Rhizophagus intraradices inoculation could enhance the osmotic adjustment capacity in females, thus mitigate the negative effect of Cd stress on ability of carbon fixation and phytohormone balance in females. However, such positive effects derived from R. intraradices symbiosis were not observed in males.     

Effects of wind erosion and sand burial on water relations and photosynthesis in Alhagi sparsifolia in the southern edge of the Taklimakan Desert

塔克拉玛干沙漠南缘风沙活动十分频繁, 风蚀和沙埋是该地区自然植被生长发育的重要影响因子。该文以塔克拉玛干沙漠南缘策勒绿洲-沙漠过渡带为研究区, 以该区域主要建群种植物骆驼刺(Alhagi sparsifolia)为研究对象, 对一次强沙尘天气过后沙丘表面5种不同风蚀沙埋状况的骆驼刺植物进行标定(包括10 cm风蚀、5 cm风蚀、不蚀不积、10 cm沙埋、30 cm沙埋), 天晴后测定其叶水势、叶片含水量、光合参数和叶绿素荧光等参数, 分析研究自然环境条件下风蚀和沙埋对骆驼刺水分和光合作用的影响。结果表明: (1)风蚀显著降低了骆驼刺叶水势和叶片含水量, 进而导致植物气孔导度降低, 并引起植物光合速率和蒸腾速率的下降。风蚀的植物水分利用效率低于沙埋, 特别是在10 cm风蚀深度明显降低。 (2)沙埋增加了骆驼刺的叶水势、叶片含水量和气孔导度, 并引起植物光合速率和蒸腾速率的上升, 水分利用效率也得到提升。(3)风蚀条件下骆驼刺所受胁迫增加, 但可以通过增加活性反应中心的数量和光化学效率来抵消胁迫造成的不利影响。沙埋条件下骆驼刺受胁迫减轻, 反应中心吸收的光能和用于光化学反应的能量随着沙埋程度增加而减小, 这是骆驼刺适应风沙环境的一种生存策略。(4)与5 cm风蚀以及10 cm沙埋相比, 10 cm风蚀显著抑制骆驼刺的生长, 30 cm沙埋则会显著促进骆驼刺的生长。     

Effects of shading on photosynthetic characteristics and chlorophyll fluorescence parameters in leaves of Hydrangea macrophylla

Aims The objectives were to investigate the effects of different light intensities on photosynthetic characteristics and chlorophyll fluorescence parameters, to clarify the physiological responses and photo-protective mechanisms of Hydrangea macrophylla to changes in light regimes in view of the distribution of energy absorbed and photosynthetic characteristics.Methods Three light regimes including natural and shade (shading rate 50% and 75% of natural light) were applied to plants for 60 days. After the treatment, the gas-exchange, chlorophyll a fluorescence and photosynthesis-light curves were measured by a portable leaf gas exchange system (LI-6400).Important findings The results showed that the weak light intensity treatment reduced dark respiration rate, light compensation point and light saturation point of plant, but increased apparent quantum yield, suggesting that plants had the physiological strategy to utilize the weakening light by reducing respiration. The net photosynthetic rate, intercellular CO₂ concentration, transpiration rate and water use efficiency of plants grown below 50% of natural light showed significant difference compared with natural and shading rate 75% of natural light. There were significant difference between natural and shade treatments in the maximal quantum efficiency of PSII (F_v/F_m), as indicated that it was significantly less at full light than that at 50% of natural light. Initial fluorescence intensity (F_o) of plants was higher at full light than that at 50% of natural light, suggesting that photoinhibition occurred in natural light. The non-photochemical quenching (NQP) decreased with the aggravation of shade stress, indicating that shading decreased the efficiency of photochemical reaction by reducing the fraction of incident light in photochemical energy utilization and decreased thermal dissipation through regulating energy distribution in photosystem II (PSII) in the leaves of Hydrangea macrophylla. In general, the 70% of incident light in photochemical energy utilization was distributed to thermal dissipation, 20% was distributed to non-regulated energy dissipation and 4% was distributed to effective photochemical reaction. In conclusion, responses of plants to increased irradiance are governed by strategy: to utilize a high fraction of incident light in photochemistry and regulate energy dissipation in PSII and weaken the accumulation of excess excitation energy in PSII to protect the photosynthetic apparatus in the leaves of H. macrophylla under saturated radiation.     

Kin recognition in Setaria italica under the condition of root segregation

Aims Kin recognition may play an important part in the performance and productivity of crop plants. However, so far, little is known about whether crop plants can recognize their kin neighbors. The aim of this study was to explore kin recognition in Setaria italica, and its responses to changes in environmental and biological conditions.Methods A field experiment was conducted in the suburb of Shanghai. Setaria italica grew with different neighbors (kin, non-kin and strangers), under the condition of root segregation and different plant densities (high and low) and soil nutrient levels (high and low), respectively. We investigated how neighbor identity and its interactions with plant density and soil nutrient level affected the morphology and biomass allocation of S. italica.Important findings Under the condition of root segregation, 1) Leaf biomass allocation and stem diameter of plants in the kin groups significantly decreased and increased, respectively, suggesting that plants of S. italica in the kin groups reduced inter-individual competition, and adapted to the local windy climate. 2) Compared with the non-kin groups, plants in the stranger groups significantly increased the biomass allocation to seeds, while plant height decreased significantly, suggesting that the plants of S. italica in the stranger groups may reduce the growth of their neighbors due to asymmetric competition (S. italica significantly increased height compared with the neighboring plants, Panicum miliaceum). Therefore, the S. italic plants in the stranger groups allocated more biomass to reproduction and increased fitness than those in non-kin groups. 3) Under the condition of high plant density, no significant differences were found in stem biomass and leaf biomass allocation of plants among different neighbor identity treatments. While under the condition of low plant density, compared with the non-kin groups, biomass allocation to stem and leaf in the kin groups significantly increased and decreased, respectively. As the plant density decreased, plants in the kin groups decreased leaf biomass allocation significantly, while plants in the non-kin and stranger groups did not show such a response. 4) Under the condition of low soil nutrient level, no significant difference was found in leaf biomass allocation between the kin and non-kin groups, while the ear length of plants in the kin groups decreased significantly. Under the condition of high soil nutrient level, the biomass allocated to leaves in the kin groups decreased significantly, while ear length increased significantly compared with the non-kin groups. Therefore, under the condition of root segregation, plants of S. italica showed the ability to recognize their kin neighbors, and the aboveground competitive cues may play important roles in the course of kin recognition in S. italica. Lower plant density and higher soil nutrient level may facilitate the ability of kin recognition in S. italica.     

Community characteristics and population structure of Ferrocalamus strictus,a rare species in Mojiang,Yunnan, China

铁竹(Ferrocalamus strictus)分布在云南南部局部区域, 其数量少, 分布范围狭窄, 为云南省极小种群物种。对铁竹野生种群结构及其所在群落特征进行研究可以为了解其濒危机制提供科学依据, 也可为其保护提供前期研究基础。该研究通过对墨江铁竹野生资源的调查, 从物种组成、种群密度、种群存活曲线和死亡因素等方面, 分析铁竹的种群结构及其所在群落特征。结果表明: (1)墨江铁竹种群所在群落的外貌、物种组成均具有山地雨林的特征; (2)墨江铁竹种群密度为2.04株·m ^-2; 铁竹种群的存活曲线介于Deevey-I型和Deevey-II型之间; 铁竹种群的净增殖率(R₀)为1.10, 表明铁竹种群处于增长阶段; (3)导致铁竹死亡的原因有人为砍伐、自然枯立、退笋及昆虫啃食, 其中人为砍伐所占比例最大; (4)铁竹为南亚热带森林竹种, 属中型竹类, 节间长度从基部3-4节起突然伸长, 最长超过1 m, 在竹类植物中居于前列, 这与其适应热带山地雨林环境密切相关。     

Effects of drought stress on the osmotic adjustment and active oxygen metabolism of Phoebe zhennan seedlings and its alleviation by nitrogen application

以二年生桢楠(Phoebe zhennan)幼树为研究对象, 采用盆栽控水的方法, 探讨了桢楠幼树在干旱胁迫下渗透调节和活性氧代谢的变化, 以及施氮对桢楠幼树应对干旱胁迫能力的影响。试验先将土壤含水量调整到4个梯度(田间持水量的80% (80% FC)、50% FC、30% FC和15% FC), 1周后测定受胁迫植株的相关生理指标, 之后进行3个水平的施氮处理(对照N0, 中氮MN, 高氮HN, 各施氮量分4次(即干旱梯度形成后第7、14、21和28天)分别施入)。在施氮结束后30天(即开始施肥处理后51天)再次测定各项生理指标。结果表明: 1)干旱处理7天后, 桢楠叶片中游离脯氨酸(Pro)和可溶性糖(SS)含量均随胁迫强度增大而显著增加, 重度干旱(15% FC)下的Pro含量增加尤为明显, 可溶性蛋白(SP)含量则呈先增加后降低的趋势。施氮后, 各种土壤水分状态下的Pro含量进一步增加。水分充足和轻度干旱MN水平下, SS含量也增加, 而在中度和重度干旱下的SS含量显著降低, HN水平各干旱状态下SS含量变化均不显著。施氮结束后30天时, 80% FC和50% FC下的SP含量表现为施氮组低于对照组, 而30% FC和15% FC下则相反。2)施氮前随着干旱胁迫的增强, 桢楠幼树叶片中过氧化氢(H₂O₂)含量、超氧化物歧化酶(SOD)活性、过氧化氢酶(CAT)活性显著上升, 而过氧化物酶(POD)活性呈先上升后下降的趋势。施氮后, H₂O₂含量总体上表现为减少趋势, 且MN水平下降幅度最大, HN水平反而不利于降低H₂O₂的含量。3种酶活性的变化则因干旱程度和施氮水平的不同而呈现出不同的变化趋势。3)施氮前随着干旱胁迫的增强, 叶片丙二醛(MDA)含量呈显著上升趋势, 相对电导率(REC)先显著下降后显著上升; 施氮后, 除重度干旱胁迫外, 其他各干旱处理植株的MDA含量都表现为在MN水平下有所下降, 而在HN水平下有所回升, 但在重度干旱时, 无论是MN或HN处理, MDA含量均呈上升趋势, 表明在重度干旱胁迫下, 难以通过施氮的方式缓解干旱胁迫产生的伤害。4)双因素方差分析显示, 施氮与干旱胁迫间具有极显著的交互效应。以上结果表明: 施一定量的氮肥有利于缓解桢楠幼树受到的干旱胁迫, 以年施氮量计, 施中氮(N元素质量为1.35 g·株 ^-1)对除重度干旱外的干旱胁迫具有一定的缓解作用, 但施高氮(N元素质量为2.70 g·株 ^-1)时反而会对植株造成不利影响。     

蒙古莸叶片解剖结构的地理种源变异及其对环境变化响应的意义

长期受到生长环境影响而形成的遗传变异对植物生长发育有着显著的影响。叶片是植物对环境变化最敏感的器官, 了解叶片解剖结构在不同环境中产生的适应性变异是探索植物对环境适应的基础。同质园试验是研究遗传与环境因素对植物生长代谢等影响的一种有效方法, 该研究利用同质园试验排除了环境梯度的影响, 通过常规石蜡切片、多重比较、相关性分析、一般线性模型分析等方法, 对7个不同种源地的蒙古莸(Caryopteris mongholica)叶片解剖结构及其影响因素进行了定量比较。结果表明, 7个种源地的蒙古莸叶片均为等面叶, 无海绵组织分化, 其上表皮细胞较下表皮细胞厚, 上栅栏组织较下栅栏组织厚; 叶片各解剖结构参数间存在显著的自相关性, 不同种源叶片解剖结构存在显著差异: 随种源地年平均气温升高, 叶厚度、栅栏组织厚度呈增大趋势, 其中, 最西南部的阿左旗种源蒙古莸叶片的上下栅栏组织、叶厚度及叶片结构紧密度值均最大, 表现出明显的抗旱特征。种源地经纬度、气温、降水等对解剖结构指标有显著的影响, 其解释程度为34.09%-81.43%。同质园试验说明, 种源地气候差异驱动的遗传变异是引起不同种源叶片解剖结构差异的重要因素。     

Predicting phenology shifts of herbaceous plants on the Qinghai-Xizang Plateau under climate warming with the space-for-time method

气候变暖背景下的植物物候变化广受关注, 然而常用的植物物候变化预测模型未充分考虑植物对环境的适应性, 给预测结果带来了较大的不确定性。该文基于2002-2011年青藏高原10个站点的地面物候观测资料以及年平均气温数据, 对空间换时间模型预测车前(Plantago asiatica)和蒲公英(Taraxacum mongolicum)各主要物候事件(展叶始期、开花始期和黄枯普遍期)变化的可行性及其在升温背景下的变化规律进行了分析。首先利用不同海拔高度的气温和物候事件分别与地理因子(经度、纬度和海拔)建立多元线性回归模型, 然后在此基础上剔除经度和纬度的影响, 单独考察海拔变化所引起的气温与植物物候变化, 最后以海拔高度作为桥梁来考察物候变化与温度变化的关系。结果表明, 采用各站点对应的海拔高度来模拟年平均气温空间差异的R²均大于0.89, 表明海拔梯度可以用来反映时间尺度下的年际温度变化; 车前和蒲公英各物候事件发生日期拟合值均与海拔高度变化关系显著, R²均大于0.70, 表明海拔变化是影响它们各物候事件变化的主要地理因子; 在物候事件发生日期拟合值和年平均气温拟合值的回归方程中, R²均大于0.93, 说明基于不同海拔高度模拟得到的年平均气温变化可以对时间尺度上车前和蒲公英的物候事件变化进行预测。空间换时间预测表明, 温度每升高1 ℃, 车前展叶始期和开花始期分别提前5.1和5.4 d, 而黄枯普遍期推迟4.8 d; 蒲公英展叶始期和开花始期分别提前6.5和7.8 d, 而黄枯普遍期推迟6.7 d。     

Dynamic characteristics of metal element content and return of Casuarina equisetifolia litter at different distances to the coastline

精确估算生态系统内部环境梯度引起的养分循环差异, 对评估其生态功能十分重要。为探讨不同距海生境对木麻黄(Casuarina equisetifolia)凋落叶金属元素含量及养分归还动态的影响, 以福建省惠安赤湖国有防护林场木麻黄凋落叶为研究对象, 按照离海由近及远的顺序设置5个距离(T₁到T₅), 收集凋落叶测定金属元素含量。结果表明: 1)海岸梯度环境对木麻黄凋落叶各元素含量及归还量具有显著影响, 由基干林带向林内元素含量、归还量呈线性规律, 总体上近海高于远海, 按照离海由近及远元素含量逐渐降低, 铁(Fe)、铜(Cu)、锌(Zn)和锰(Mn)在T₄后上升, 归还量变化趋势与含量相似。2)凋落叶元素含量在不同月份存在显著差异, Na、Fe、Cu、Zn具有相似性, 6月、11月存在明显低谷; Mn在2至4月下降后波动上升。归还量总体表现为钠(Na)、Cu相似, 5、8、次年1月出现峰值;Mn、Fe、Zn相似, 5、8、11、次年1月出现峰值。3)土壤Na含量按照离海由近及远逐渐降低, 其他元素波动变化, 各距离之间差异不明显。4)凋落叶Na-Fe含量存在显著正相关关系, Na-Zn、Fe-Cu、Fe-Zn含量存在极显著正相关关系; 土壤与凋落叶相同元素含量间存在正相关关系, Na和Cu达到显著水平。究其原因, 叶片元素含量差异受叶凋落时间差异造成的重吸收差异影响大; 月间差异因植物生命活动对元素需求量存在差异; 归还量差异与凋落叶量及元素含量有关。     

内蒙古西鄂尔多斯地区半日花荒漠群落特征及其分类

半日花(Helianthemum songaricum)为亚洲中部特有种和古地中海残遗植物, 其群落为内蒙古西鄂尔多斯地区的特有荒漠植物群落。该文以2016-2017年野外调查数据为基础, 结合相关文献资料, 对半日花荒漠群落的分布、群落特征及其分类进行了总结。结果表明: (1)半日花荒漠群落集中分布于黄河以东内蒙古西鄂尔多斯的阿尔巴斯山麓南北部、千里沟; 少量分布于黄河以西贺兰山北端内蒙古乌海市与阿拉善盟交界处及贺兰山最南端的内蒙古阿拉善盟与宁夏交界处明长城沿线的石质残丘。(2)根据样地调查, 半日花荒漠群落记录到种子植物58种, 隶属于17科39属, 其中灌木、半灌木18种, 多年生草本27种, 一年生草本植物13种; 水分生态类型中强旱生植物(15种)和旱生植物(29种)占绝对优势; 区系地理成分以中亚东部成分为主, 其次为古地中海成分和戈壁成分。(3)根据生活型和优势度, 半日花荒漠群落可分为半日花-草本荒漠群丛组、半日花-灌木-草本荒漠群丛组和半日花-半灌木荒漠群丛组, 进一步分为10个群丛。     

内蒙古典型草原优势种冷蒿和克氏针茅对土壤低磷环境适应策略的比较

为探究典型草原植物长期共存的生理生态机制, 以典型草原的优势物种克氏针茅(Stipa krylovii)和冷蒿(Artemisia frigida)为材料, 采用基质培养方法, 通过比较不同供磷浓度对二者生物量、根系形态、质子分泌、酸性磷酸酶和有机酸分泌以及磷吸收利用效率的影响, 探讨克氏针茅和冷蒿对土壤磷缺乏的适应策略。研究结果表明: 冷蒿主要通过根系分泌酸性磷酸酶和酸化根际来适应低磷环境; 而克氏针茅主要是通过根系分泌有机酸(主要是苹果酸)来适应土壤磷缺乏。在低磷条件下, 克氏针茅和冷蒿的磷吸收效率没有显著差异, 但克氏针茅的磷利用效率显著高于冷蒿。随着供磷浓度增加, 二者的磷吸收速率增加, 磷利用效率降低。在生物量、地上部分性状以及根系生长方面, 克氏针茅和冷蒿对磷供给的响应都表现先增长后降低的趋势; 克氏针茅的生物量在外源供0.25 mmol·L^-1磷时达到最大, 而冷蒿的生物量在外源供0.50 mmol·L^-1磷时达到最大, 表明冷蒿对磷的生理需求高于克氏针茅。因此, 克氏针茅和冷蒿具备各自不同的适应土壤有效磷缺乏的生理策略, 这可能是它们在土壤贫瘠的温带典型草原长期共存的重要机制。     

不同林龄、树种落叶松人工林径向生长与气候变化的关系

研究人工林径向生长与气候变化的关系对全球气候变暖背景下人工林合理经营有着重要的意义。该文对在辽东山区广泛栽培的黄花落叶松(Larix olgensis)和日本落叶松(Larix kaempferi)人工林, 运用树木年轮气候学方法建立了辽宁草河口和湾甸子林场落叶松人工林年表, 分析了落叶松径向生长对气候变化的响应以及气候条件、树种、立地条件和林分因子(林龄、密度、蓄积量等)的相对影响程度。结果发现在影响年轮-气候关系的因素中, 气象因子的潜在蒸发散(PET)的影响力最大; 林龄、密度和蓄积量同时也具有重要的影响作用。中龄落叶松人工林径向生长主要与气温呈正相关关系, 成熟落叶松人工林径向生长主要与气温呈负相关关系; 而其他因素, 如树种、立地条件等的影响作用不大。这表明在气候变暖背景下随着林龄增加, 林分会逐渐受到气温升高导致的水分亏缺的限制, 导致明显的生长下降趋势, 因而气候变暖对成熟落叶松人工林威胁更为严重, 所以要注重对成熟林的优先保护, 同时可以预测, 随着东北地区今后气候进一步变暖, 可能将逐步影响到林龄更小的林分的生长, 因此需要进一步研究如何在落叶松人工林经营中采取科学的措施来更好地应对未来气候变化。