青藏高原东缘林线交错带糙皮桦幼苗光合特性对模拟增温的短期响应

采用开顶式生长室(OTC)模拟增温对植被影响的研究方法,研究了青藏高原东缘林线交错带糙皮桦(Betula utilis)光合特性对模拟增温的响应。结果表明:与对照样地相比,OTC内日平均气温(1.2m)在植物生长季中增加2.9℃,5cm土壤温度增加0.4℃。增温使糙皮桦幼苗叶片的净光合速率(Pn)、蒸腾速率(Tr)和气孔导度(Gs)分别增加17.4%、21.4%和33.9%,但对糙皮桦幼苗叶片的水分利用率(WUE)却没有明显影响,而对糙皮桦的叶氮浓度却表现为显著的负效应。同时,增温能显著增加糙皮桦幼苗的最大同化速率(Pnmax)(+19.6%)、暗呼吸速率(Rd)(+14.3%)、表观量子效率(AQY)(+7.9%),但对其光补偿点(LCP)和光饱和点(LSP)却没有明显的影响。此外,增温使糙皮桦幼苗叶片的最大羧化速率(Vcmax)和电子传递速率(J)分别增加了12.3%和11.7%,而磷酸丙糖利用率(TPU)和CO2补偿点(CCP)对增温却并不敏感。该研究表明,模拟增温对林线糙皮桦光合生理总体上表现为正效应,这有可能帮助该物种对未来气候变化更快更好地适应。     

模拟增温引发的早春冻害：以岷江冷杉为例

以全球变暖为主要特征的全球气候变化已经并正在改变着陆地生态系统的结构和功能.现存植被与环境间的关系是经过漫长自然选择而形成的,因此植物物候变化可能会影响物种与环境间的相互关系.采用开顶式生长室(Open-top chamber,OTC)和移地试验(transposing of surface soil with vegetation,TSSV)模拟增温的方法,研究了川西亚高山岷江冷杉幼苗物候和冻害对模拟增温的短期响应.结果表明,生长季中OTC内日平均气温较对照增加2.2 ℃,高海拔(3 200 m)比低海拔(2 600 m)日平均温度低2.5 ℃.在两种研究方法下,温度升高都使岷江冷杉芽开放提前,休眠期推迟,生长季延长.温度升高使岷江冷杉幼苗新生芽遭受严重的冻害.结果表明,在未来全球气候变化的背景下,高海拔物种遭受早春冻害的可能性大.     

增温对川西亚高山针叶林内不同光环境下红桦和岷江冷杉幼苗生长和生理的影响

 川西亚高山针叶林是青藏高原东部高寒林区的重要组成部分, 也是研究全球变化对森林生态系统影响的重要森林类型。开展亚高山针叶林不同树种对气候变暖响应差异的研究, 可为预测未来气候变暖背景下亚高山针叶林植被组成和森林动态提供科学依据。我们以川西亚高山针叶林两种主要树种——红桦(Betula albo-sinensis)和岷江冷杉(Abies faxoniana)为研究材料, 采用开顶式增温法(Open-top chamber, OTC)模拟气候变暖, 研究了增温对全光条件和林下低光环境中(约为全光的10%)生长的红桦和岷江冷杉幼苗生长和生理的影响。在人工林环境下, OTC使增温框内平均气温和地表温度分别升高了0.51和0.33 ℃; 而在林外空地处, OTC使二者分别升高了0.69和0.41 ℃。研究结果显示, 增温总体上促进了两种幼苗的生长和生理过程, 并促使幼苗将更多的生物量投入到其同化部位——叶, 使幼苗的根冠比(R/S)显著降低。增温通过增加叶片的光合色素含量和表观量子效率等光合参数, 促进了幼苗的光合过程和生长。然而, 增温对两种幼苗生长和生理的影响效果与植物种类及其所处的光环境有关。增温仅在林外全光条件下显著影响红桦幼苗的生长和生理过程。岷江冷杉幼苗对增温的响应与红桦相反, 即增温仅在林下低光环境下对岷江冷杉幼苗的生长和生理过程有明显促进作用。这种响应差异可能赋予这两种植物在未来气候变暖背景下面对外界环境变化时具有不同的适应能力和竞争优势, 从而对亚高山针叶林生态系统物种组成和森林动态产生潜在影响。     

长期模拟增温对岷江冷杉幼苗生长与生物量分配的影响

川西亚高山针叶林是青藏高原东部高寒林区的重要组成部分,也是研究全球变化对森林生态系统影响的重要组成。长期模拟增温对川西亚高山森林树木的生长、物质积累及其分配格局的影响至今鲜有报道。以川西亚高山针叶林优势种岷江冷杉(Abies faxoniana)幼苗为研究对象,采用控制环境生长室模拟增温的方法,研究了模拟增温对岷江冷杉幼苗生长、物质积累及其分配格局的影响。结果表明,模拟增温(2.2±0.2)℃处理65个月后,岷江冷杉幼苗基径、株高、单株叶面积和比叶面积(SLA)均显著增加,比叶重(LMA)显著下降。增温对岷江冷杉幼苗的茎、侧枝、叶和总生物量具有显著的促进作用,对根生物量没有显著影响。岷江冷杉幼苗的叶重比(LMR)下降、枝重比(SMR)增加、根重比(RMR)无显著变化。长期增温能显著促进岷江冷杉幼苗的生长和物质积累,改变生物量分配格局,促使叶片物质向茎转移,降低光合物质投入。     

川西林线交错带岷江冷杉幼苗异龄叶形态对长期模拟增温的响应

全球气候变暖对高纬度、高海拔地区的植物形态产生强烈影响。川西林线交错带是青藏高原东部高寒生态系统的重要组成部分,对全球变化极度敏感。以川西林线交错带岷江冷杉(Abies faxoniana)幼苗异龄叶为对象,采用原位开顶式生长室(Open-top chamber,OTCs)模拟增温,研究了长期模拟增温下岷江冷杉幼苗异龄叶片叶长、叶厚等叶形态的响应,采用表型可塑性指数和变异系数对叶形态的可塑性进行分析。结果表明:增温限制岷江冷杉幼苗叶片的增长、增宽和叶面积、体积的扩大,使叶长、叶宽、叶面积、叶体积分别较对照减小12.77%、11.86%、17.76%、11.49%;增温促进叶片厚度的增加,较对照增加7.27%;除叶长宽比外,增温对其余叶形态均产生显著影响(P0.05)。叶形态对模拟增温的响应具有显著的年龄差异(P0.05)。温度、叶龄的交互效应对叶长和叶面积影响显著(P0.05),对叶宽和叶厚影响不显著(P0.05)。两种表型可塑性分析结果表明,除1 a叶叶长外,增温不同程度增大各叶形态可塑性。长期增温使冷杉幼苗叶片有旱生倾向且形态值更发散。研究提供了岷江冷杉幼苗叶片对长期增温的差异性响应证据,为评估青藏高原东缘优势植物对响应气候变暖提供了基础数据和理论参考。     

川西米亚罗亚高山暗针叶林岷江冷杉和糙皮桦空间格局及其关联性分析

基于2019年9月完成的川西米亚罗亚高山暗针叶林9.6 hm~2动态样地的调查数据，分析了主要优势种岷江冷杉(Abies fargesii var.faxoniana)与糙皮桦(Betula utilis)的径级结构，并运用O-ring统计中的成对相关函数g(r)和g₁₂(r),研究了两个优势种的空间格局及其种内、种间的关联性。结果表明：岷江冷杉与糙皮桦径级分布连续，均呈倒“J”型。岷江冷杉与糙皮桦的不同径级个体主要呈现由聚集分布向随机分布发展的趋势。岷江冷杉的小树对幼树、中树对幼树、中树对小树以及大树对中树的种内相关性在所有空间尺度上均为显著正相关(P<0.05),而相同径级糙皮桦的种内相关性则表现为由显著正相关(P<0.05)逐渐向无显著相关(P>0.05)变化。随着空间尺度的增大，岷江冷杉的大树对幼树、大树和小树由无显著相关(P>0.05)逐渐向显著正相关(P<0.05)变化，糙皮桦的大树对幼树由显著负相关(P<0.05)逐渐向无显著相关(P>0.05)变化。岷江冷杉大树对糙皮桦所有径级个体的种间相关性主要呈现由为显...     

Effects of plant interspecific interaction and warming on soil microbial community in root zone soil of two dominant tree species in the subalpine coniferous forest in southwestern China

温度与植物种类是生态系统土壤微生物群落组成与结构的重要影响因子。气候变暖背景下, 不同树种及树种互作对土壤微生物群落产生的影响仍不清楚。该文以西南亚高山针叶林主要建群种粗枝云杉(Picea asperata)和岷江冷杉(Abies faxoniana)为研究对象, 采用红外加热器模拟增温, 通过不同种植方式(云杉、冷杉单种和二者混种, 以及裸地对照), 研究不同物种及增温对土壤微生物磷脂脂肪酸(PLFAs)含量与群落结构的影响。结果表明: (1)无论增温与否, 与裸地相比, 云杉与冷杉单种均显著增加了土壤微生物群落主要类群及总PLFAs含量, 而混种仅在非增温条件下增加了微生物群落PLFAs含量; 另一方面, 增温显著促进了裸地真菌(F)和云杉根区革兰氏阴性菌(GN)的生长, 但对冷杉与冷杉-云杉混种小区微生物群落具有显著的抑制作用。(2)主成分分析(PCA)表明, 非增温条件下, 植物种植对土壤微生物群落组成的影响更为明显。非增温情况下云杉、冷杉单种和混种均对微生物群落结构有显著影响, 显著降低了土壤革兰氏阳性菌/阴性菌(GP/GN), 增加了土壤真菌细菌比(F/B)(64.29%-35.71%), 而增温时, 仅冷杉单种对GP/GN和F/B有显著影响。(3) PLFAs含量与土壤碳含量显著正相关, 微生物群落结构(F/B)则与土壤pH及无机氮含量有显著相关关系。以上结果说明, 在非增温情况下, 无论单种还是混种均有利于土壤微生物生长, 但在增温情况下混种对微生物群落PLFAs含量无显著影响, 两个物种对微生物群落结构的影响在增温条件下也有减弱的趋势。     

Experimental warming changed plants’ phenological sequences of two dominant species in an alpine meadow,western of Sichuan

以西南横断山区高山草甸优势植物种珠芽拳参(Polygonum viviparum)和银叶委陵菜(Potentilla leuconota)为研究对象, 将其物候分为花芽期、开花期、凋谢期和种子成熟期4个阶段, 每个阶段又分为开始、峰值和结束3个状态。采用开顶式增温箱进行模拟增温, 连续增温4年后, 于增温第5年的2016年生长季跟踪调查了模拟增温对珠芽拳参和银叶委陵菜的繁殖物候序列的影响, 以探讨高山植物群落对气候变化的响应过程。结果显示, 模拟增温后: 1)珠芽拳参各物候阶段的持续时间缩短; 除凋谢阶段起始、结束期延迟外, 其他状态均有不同程度的提前; 各阶段的过渡期有不同程度的缩短, 繁殖周期缩短; 2)银叶委陵菜各物候阶段的持续时间延长; 凋谢期结束前各状态(除开花峰值外)表现为不同程度的提前; 各阶段过渡期对增温的响应不一致, 繁殖周期延长。结果表明: 完整的繁殖物候序列能更准确地反映植物物候对气候变暖的响应; 植物对环境变化的响应和应对策略存在种间差异, 这种差异可能会进一步改变植物群落组成和结构。     

模拟增温和功能群去除对岷江冷杉幼苗存活和生长的影响

通过模拟增温和功能群去除试验,研究不同功能群的草本植物在岷江冷杉幼苗更新定植过程的作用,分析其在温度升高条件下生理指标的变化.结果表明:增温提高了岷江冷杉幼苗的存活率和植物体内非结构性碳水化合物含量,但抑制了幼苗的生长和根冠比.岷江冷杉幼苗的非结构性碳水化合物含量,尤其是可溶性糖含量与存活率呈显著正相关.不增温处理中,草本植物降低了幼苗的存活率,促进幼苗的株高生长和地上生物量积累,禾本科植物和杂类草抑制了幼苗根系生长和地下生物量的积累;增温处理中,杂类草的存在提高了幼苗的存活率,莎草科则显著抑制了幼苗根系生长和地下生物量的积累,禾本科植物和杂类草抑制了幼苗的高生长和地上生物量积累.模拟增温提高了林线树种岷江冷杉幼苗的存活率,但使其面临来自草本植物更剧烈的竞争,抑制其生长.     

夜间增温和施肥对川西亚高山针叶林两种树苗根际效应的影响

开展植物根际效应对全球变化响应的研究是深入认识根际微生态系统中植物根系与土壤微生物相互作用过程及机制的关键。以川西亚高山针叶林两种主要树种幼苗--云杉(Picea asperata)和岷江冷杉(Abies faxoniana)为研究材料,采用红外辐射模拟增温和外施NH₄NO₃氮肥的方法,研究了夜间增温和施肥对两种幼苗根际效应的影响。结果表明:红外辐射增温导致气温增加了1.62 ℃,土壤5 cm和10 cm层月均温度显著增加了2.89 ℃和3.10℃。增温和施肥处理对两种幼苗不同参数根际效应的影响各不相同,表现为不同程度的正根际效应、负根际效应或者无影响。增温使云杉幼苗根际与非根际土SMB-C含量均显著增加(分别为42.28%和31.02%),非根际土有机碳含量降低了7.03%;而增温对两种幼苗土壤肥力因素根际效应的影响总体并不显著,增温仅对云杉全氮有显著的负根际效应(79.43%),而岷江冷杉通过根际土全氮和SMB-N含量的增加,其根际效应大小在增温处理下显著增强。施肥处理和两因子的联合作用显著提高了两种幼苗的NO^-₃-N、NH⁺₄-N和云杉非根际土SMB-N含量,并使岷江冷杉NH⁺₄-N表现出正根际效应,而云杉SMB-N表现出明显的负根际效应(120.80%和253.06%)。这种响应差异可能与不同植物种类地下碳分配及其植物根系所吸收的养分有关,从而赋予了不同植物种类在未来全球变化背景下可能具有不同的适应力和竞争优势,并进一步对亚高山针叶林地下过程及其早期更新产生潜在影响。     

Short-term effects of simulated environmental change on phenology, leaf traits, and shoot growth of alpine plants on a temperate mountain, northern Japan

In order to assess the responses of circumpolar and semicircumpolar plants growing around their southern distribution margins to artificial warming, we set up 11 open-top chambers (OTCs) on a fell-field (1680 m a.s.l.) in the Taisetsu Mountains, northern Japan. The OTCs increased mean air temperature by 1.3°C through the growing season (June–September) and extended the length of the growing season. We examined phenology and leaf traits of plants in the OTCs and control plots during the first season under artificial warming treatment using two deciduous and three evergreen species. Ledum palustre (evergreen shrub), Vaccinium uliginosum , and Arctous alpinus (deciduous shrubs) showed earlier leaf emergence and/or flowering in the OTCs. Deciduous shrubs had longer individual leaf longevity and an extended foliage period in the OTCs than in the control plots. There were no significant differences in specific leaf area and leaf size for many species between the OTCs and the control plots. Vaccinium vitis-idaea (evergreen shrub), L. palustre, A. alpinus , and Empetrum nigrum (evergreen shrub) had lower leaf nitrogen concentration in the OTCs than in the control plots, whereas it was higher in V. uliginosum . Only E. nigrum showed larger annual shoot growth in the OTCs. No clear differences in response to the warming effect were detected between evergreen and deciduous species in the first season. Circumpolar plants growing in temperate alpine regions may be more affected by season length rather than temperature itself.     

Responses of alpine shrubs to simulated environmental change during three years in the mid-latitude mountain, northern Japan

Effects of artificial warming on phenology, individual leaf traits, vegetative growth, and reproduction of five alpine species (two deciduous and three evergreen shrubs) were investigated during three years in the mid-latitude alpine, northern Japan. Eleven open-top chambers (OTCs) were set up on a fellfield (1680 m a. s. l.) in the Taisetsu Mountains by which air temperature at plant height was increased by ca 2°C. Vaccinium uliginosum (deciduous shrub) showed earlier leaf emergence in every season and earlier flowering only in the first season in the OTCs. By contrast, acceleration of leaf emergence in the OTCs was not clear for other species, i.e. Arctous alpinus (deciduous shrub). Ledum palustre. V. vitis-idaea , and Empetrum nigrum (evergreen shrub). Both deciduous species showed longer leaf life-span in the OTCs every season. All evergreen species had higher leaf survival rates in the OTCs. indicating extension of leaf life-span. Leaf nitrogen concentration and leaf mass per unit leaf area (mg cm ⁻²) generally tended to decrease in the OTCs. Relationships between the individual leaf traits and cumulative air temperature during the leaf developing period were not clear. Total leaf production during the three seasons increased in the OTCs in A. alpinus. L. palustre. V. vitis-idaea , and E. nigrum. All evergreen shrubs showed larger shoot growth in the OTCs but both deciduous shrubs did not show significant changes. In contrast to the vegetative growth, deciduous shrubs produced more flowers in the OTCs. Fruit production was not influenced by the OTCs for all species. The extension of photosynthetic period in the OTCs may contribute to the larger vegetative growth or flower production.     

Short-term responses of phenology, shoot growth and leaf traits of four alpine shrubs in a timberline ecotone to simulated global warming, Eastern Tibetan Plateau, China

The short-term effects of artificial warming on phenology, growth and leaf traits were investigated in four alpine shrubs using the open-top chamber (OTC) method in a timberline ecotone (3240 m a.s.l.) on the Eastern Tibetan Plateau. The OTC enhanced the mean air temperature by 2.9°C throughout the growing season. In contrast, only a slight difference (0.4°C) in the mean soil temperature was observed in the OTC compared with the control plots (CP). Spiraea mongolica , Potentilla fruticosa , Conicera hispida (deciduous shrubs) and Daphne retusa (evergreen shrub) showed earlier bud break, flowering and fruit coloring as well as longer flower longevity in the OTC than in the CP. All deciduous shrubs in the OTC had a longer leaf lifespan. Daphne retusa had higher leaf survival rates in the OTC. No significant differences in the total number of flowers and fruits were noticed for most species between the two treatments. Warming stimulated the shoot and leaf growth for most species. The specific leaf area tended to increase for many species in the OTC. However, the leaf nitrogen concentration tended to decrease in P. fruticosa and S. mongolica. The results obtained in the present study indicate that warming conditions can have strong impacts on alpine shrubs in a timberline ecotone.     

Variation in evergreen and deciduous species leaf phenology in Assam, India

In the present study phenological activities such as leaf and shoot growth, leaf pool size and leaf fall were observed for 3 years (March 2007–March 2010) in 19 tree species (13 evergreen and 6 deciduous species) in a wet tropical forest in Assam, India. The study area receives total annual average rainfall of 2,318 mm of which most rain fall (>70 %) occurs during June–September. Both the plant groups varied significantly on most of the shoot and leaf phenology parameters. In general, growth in deciduous species initiated before the evergreen species and showed a rapid shoot growth, leaf recruitment and leaf expansion compared to evergreen species. Leaf recruitment period was significantly different between evergreen (4.2 months) and deciduous species (6.8 months). Shoot elongation rate was also significantly different for evergreen and deciduous species (0.09 vs. 0.14 cm day^?1 shoot^?1). Leaf number per shoot was greater for deciduous species than for evergreen species (34 vs. 16 leaves). The average leaf life span of evergreen species (328 ± 32 days) was significantly greater than that of deciduous species (205 ± 16 days). The leaf fall in deciduous species was concentrated during the winter season (Nov–Feb), whereas evergreens retained their leaves until the next growing season. Although the climate of the study area supports evergreen forests, the strategies of the deciduous species such as faster leaf recruitment rate, longer leaf recruitment time, faster shoot elongation rate during favorable growing season and short leaf life span perhaps allows them to coexist with evergreen species that have the liberty to photosynthesize round the year. Variations in phenological strategies perhaps help to reduce the competition among evergreen and deciduous species for resources in these forests and enable the coexistence of both the groups.     

Plant phenological responses to a long‐term experimental extension of growing season and soil warming in the tussock tundra of Alaska

Climate warming is strongly altering the timing of season initiation and season length in the Arctic. Phenological activities are among the most sensitive plant responses to climate change and have important effects at all levels within the ecosystem. We tested the effects of two experimental treatments, extended growing season via snow removal and extended growing season combined with soil warming, on plant phenology in tussock tundra in Alaska from 1995 through 2003. We specifically monitored the responses of eight species, representing four growth forms: (i) graminoids (Carex bigellowii and Eriophorum vaginatum); (ii) evergreen shrubs (Ledum palustre, Cassiope tetragona, and Vaccinium vitis‐idaea); (iii) deciduous shrubs (Betula nana and Salix pulchra); and (iv) forbs (Polygonum bistorta). Our study answered three questions: (i) Do experimental treatments affect the timing of leaf bud break, flowering, and leaf senescence? (ii) Are responses to treatments species‐specific and growth form‐specific? and (iii) Which environmental factors best predict timing of phenophases? Treatment significantly affected the timing of all three phenophases, although the two experimental treatments did not differ from each other. While phenological events began earlier in the experimental plots relative to the controls, duration of phenophases did not increase. The evergreen shrub, Cassiope tetragona, did not respond to either experimental treatment. While the other species did respond to experimental treatments, the total active period for these species did not increase relative to the control. Air temperature was consistently the best predictor of phenology. Our results imply that some evergreen shrubs (i.e., C. tetragona) will not capitalize on earlier favorable growing conditions, putting them at a competitive disadvantage relative to phenotypically plastic deciduous shrubs. Our findings also suggest that an early onset of the growing season as a result of decreased snow cover will not necessarily result in greater tundra productivity.     

Warming effects on growth,production, and vegetation structure of alpine shrubs: a five-year experiment in northern Japan

Warming effects on shoot growth, production, reproductive activity, and vegetation structure of alpine shrubs were measured over 5 years in a mid-latitude alpine fellfield in northern Japan. Open-top chambers (OTC) increased the daily mean air-temperature by 1.5-2.3 degrees C throughout the growing season but the effect on soil temperature was small. Two evergreen species, Ledum palustre and Empetrum nigrum, tended to increase their annual shoot production and aboveground-mass accumulation in the OTCs, whereas flower production did not differ. Two deciduous species, Vaccinium uliginosum and Arctous alpinus, increased their flower production in the OTCs, whereas the vegetative growth and mass accumulation did not change. No significant differences in vegetative and flower production were detected in Vaccinium vitis-idaea between the OTCs and control plots. The shoot survival and growth in terms of height of most species increased in the OTCs relative to the control treatment, and the growth rate was significantly different among species. As a result, interspecific competition seemed to be accelerated in the OTCs, and the less competitive V. vitis-idaea was suppressed by other plant species. The response to the warming observed in this study was rather different from that seen in arctic and subarctic plants even within the same species, indicating that the warming effect may cause different responses between arctic and mid-latitude alpine ecosystems. We concluded that the artificial warming over 5 years accelerated the growth of a few restricted species and lead to the change in vegetation structure in the mid-latitude alpine ecosystem.     

The use of open-top chambers in forests for evaluating warming effects on herbaceous understorey plants

Open-top chambers (OTCs) are widely used experimental warming devices in open-field ecosystems such as tundra and alpine heath. However, knowledge of their performance in temperate deciduous forest ecosystems is largely lacking. The application of OTCs in forests might become important in the future since the effects of climate warming on growth, reproduction, and future distribution of understorey forest herbs have rarely been investigated. Therefore, polycarbonate OTCs covered with (OTCs+GF) and without permeable polypropylene GardenFleece (OTCs−GF) were installed in a temperate deciduous forest to create an experimental warming gradient. Short-term responses in phenology, growth, and reproduction of a model understorey forest herb (Anemone nemorosa L.) to OTC installation were determined. In a second growing season, an in-depth study of multiple abiotic conditions inside OTCs−GF was performed. Both OTCs+GF and OTCs−GF raised air and soil temperature in a realistic manner (ca. +0.4°C to +1.15°C), but OTCs−GF only in the leafless period (up to +1.5°C monthly average soil temperature). The early flowering forest herb A. nemorosa also showed a clear phenotypic response to OTC installation. Based on these facts and the large ecological drawbacks associated with OTCs+GF (mostly in connection with a higher relative air humidity and a lower light quantity) and very modest abiotic changes in OTCs−GF, we encourage the use of OTCs−GF in deciduous forest ecosystems for evaluating climate-warming effects on early flowering understorey forest herbs. There is also a potential to use this warming method on later flowering species, but this needs further research.     

Aphid–willow interactions in a high Arctic ecosystem: responses to raised temperature and goose disturbance

Recently, there have been several studies using open top chambers (OTCs) or cloches to examine the response of Arctic plant communities to artificially elevated temperatures. Few, however, have investigated multitrophic systems, or the effects of both temperature and vertebrate grazing treatments on invertebrates. This study investigated trophic interactions between an herbivorous insect (Sitobion calvulum, Aphididae), a woody perennial host plant (Salix polaris) and a selective vertebrate grazer (barnacle geese, Branta leucopsis). In a factorial experiment, the responses of the insect and its host to elevated temperatures using open top chambers (OTCs) and to three levels of goose grazing pressure were assessed over two summer growing seasons (2004 and 2005). OTCs significantly enhanced the leaf phenology of Salix in both years and there was a significant OTC by goose presence interaction in 2004. Salix leaf number was unaffected by treatments in both years, but OTCs increased leaf size and mass in 2005. Salix reproduction and the phenology of flowers were unaffected by both treatments. Aphid densities were increased by OTCs but unaffected by goose presence in both years. While goose presence had little effect on aphid density or host plant phenology in this system, the OTC effects provide interesting insights into the possibility of phenological synchrony disruption. The advanced phenology of Salix effectively lengthens the growing season for the plant, but despite a close association with leaf maturity, the population dynamics of the aphid appeared to lack a similar phenological response, except for the increased population observed.