Linking intra-seasonal variations in climate and tree-ring δC: A functional modelling approach

Stable carbon isotopic composition (δ¹³C) in tree rings is a widely recognized tool for climate reconstruction, and several works suggest that seasonal information can be extracted from intra-ring δ¹³C variations. In this study, we explored the link between climate and intra-seasonal oak ring δ¹³C using a process-based modelling approach. The ISOCASTANEA model was developed to compute the seasonal dynamics of tree-ring δ¹³C for deciduous species from half-hourly climatic data by accounting for photosynthetic discrimination and carbon translocation and allocation at the tree scale and in tree rings.The model was applied from March 2005 to December 2007 in a 150-year-old deciduous oak forest. Canopy photosynthesis and stomatal conductance were calibrated using H₂O and CO₂ fluxes measured by the eddy flux technique, and simulated δ¹³C values were compared to seasonal patterns of total organic matter δ¹³C measured in tree rings for 2006 and 2007 at the same site. With the inclusion of carbon translocation and with regard to ¹³C enrichment of starch compared to soluble sugars, the model can reasonably simulate the intra-seasonal and inter-annual variability of tree-ring δ¹³C using the same parameter values for 2006 and 2007. The amplitude of the seasonal carbon isotope pattern in tree rings was influenced by both photosynthetic and post-photosynthetic processes (starch enrichment and reserve use). The δ¹³C variations in the early part of the ring, i.e., mainly in the earlywood, were related mostly to carbohydrate metabolism, although diluted information about environmental conditions during the previous year could also be found. The last part of the ring, consisting mainly of latewood, was found to be a good recorder of current-year environmental conditions, in particular relative humidity, at a fine temporal resolution when the growth rate was high. The sensitivity of the δ¹³C in the early part of the ring to carbohydrate metabolism suggests that intra-ring δ¹³C could be used to explore the relationship between tree decline or mortality and carbohydrate deficiency.     

THE IMPACT OF GEOTHERMAL POWER PLANTS ON FOREST VEGETATION. A CASE STUDY AT TRAVALE (TUSCANY, CENTRAL ITALY)

A survey of the crown status of Turkey oak Quercus cerris L.) trees in the boron-rich area atTravale (Southern Tuscany, Italy) was carried outin order to evaluate the impact ofgeothermal power plants. Crown thinness was assessed andmorphological and chemical tests werecarried out on leaf samples. Leaf area and dry weight weredetermined as morphological parameters;while the chemical measurements performed included nitrogenand potassium (among the nutrients),and sulphur, boron, arsenic and mercury (among the elements ofgeothermal origin). Acute damagewas found only in the area immediately adjacent to the outletsand is the result of the action of boron;crown thinness, on the other hand, is affected by the natureof the geological substrate. High quantitiesof sulphur were found in leaves throughout the survey area,due both to the availability of this elementin the geopedological substrate and to the atmospheric inputof geothermal H2S. The leafcontent of this element correlates negatively with thedistance from the power plants. Boron andarsenic are the other geothermal origin elements most commonlyfound in plant matrices. The presenceof these two elements is associated with leaf area reductionand/or an increase of specific dry weight.The most significant impact on the environment appears to beexerted by the southernmost powerplant, where there is an unfavourable ratio between quantityof emissions and height of the chimneys.     

大气中O3、CO2浓度升高对蒙古栎叶片生长的影响

以4年生蒙古栎(Quercus mongolica) 幼树为实验材料,分别于2007,2008年6~9月采用开顶箱法,研究了高浓度CO2和O3及复合作用对蒙古栎叶片光合量变化和生长的影响.结果表明,高浓度O3处理下蒙古栎叶片日光合总量降低, 单叶鲜重、干重和单叶面积均有所下降,对蒙古栎叶片生长产生抑制.高浓度CO2处理下,蒙古栎叶片干、鲜重和单叶面积均高于对照,其中2007年差异显著,日光合总量总体高于对照.2种气体复合作用处理下,蒙古栎日光合总量、单叶鲜重、单叶干重、单叶面积均低于对照,且高于O3单独处理,说明高浓度CO2可以通过减缓O3对植物光合的抑制,进而减少O3伤害,缓解生长抑制.     

Anthropogenic NOx emissions alter the intrinsic water-use efficiency (WUEi) for Quercus cerris stands under Mediterranean climate conditions

We investigated the effect of N deposition (Ndep) on intrinsic water-use efficiency (WUE_i), the ratio of photosynthesis (A) to stomatal conductance (g_s), for two Quercus cerris stands at different distances to an oil refinery in Southern Italy. We used δ¹³C in tree rings for assessing changes in WUE_i; while the influence of climate and NO_x emission was explored through δ¹⁸O and δ¹⁵N, respectively. Differences in WUE_i between the two sites were significant, with trees exposed to different degrees of NO_x emissions showing an abrupt increase with the onset of pollution. Assuming similar g_s at the two sites, as inferred through δ¹⁸O, the higher N availability at the polluted site caused the shift of the A/g_s ratio in favour of A. Overall, our result suggests that an increase of Ndep may enhance tree WUE under a scenario of reduction of precipitation predicted for Mediterranean area.     

辽东栎叶片气孔特征参数的时空变异

利用数码图像显微镜处理系统 ,对 2 0世纪 30年代至 80年代不同植被区域内辽东栎叶片气孔特征参数进行了较为系统的观测 ,明确了辽东栎叶片气孔特征参数的变化范围 ,并对其时空变异规律进行研究 .结果表明 ,从时间分布角度 ,由 30年代至 80年代 ,暖温带落叶阔叶林区域中气孔长度、面积变化呈上升趋势 ,而气孔宽度、密度呈下降趋势 ;亚热带常绿阔叶林区域中 4个气孔特征参数均逐年递增 ;青藏高原高寒植被区域中除气孔长度下降外 ,其它 3个气孔特征参数均逐年递增 .从空间分布角度 ,在由北部至南部再到西南部分布的暖温带落叶阔叶林、亚热带常绿阔叶林至青藏高原高寒植被区域 ,30年代中 ,气孔长度、面积呈上升趋势 ,而气孔宽度、密度呈下降趋势 ;5 0年代中 ,不同植被类型区之间 ,除气孔密度差异较大外 ,其它 3个气孔特征参数差异均不明显 .图 1表 1参 9     

Organochlorine compounds in a three-step terrestrial food chain

The concentrations of 15 organochlorine chemicals (PCBs and pesticides) were studied in a Central European oak wood food chain system: Great tit (Parus major), caterpillars (Tortrix viridana, Operophtera brumata, Erannis defoliaria), and oak-leaves (Quercus robur). Juvenile tits receive organochlorines from the mother via egg transfer and, eventually to a greater extent, from the caterpillar food source during nestling period. The concentrations of PCB 153 (2,2′,4,4′,5,5′-hexachlorobiphenyl, the most abundant in this study) was found in leaf material at ca. 1 ng/g, in caterpillars 10 ng/g, and in bird eggs 170 ng/g on an average and on a dry mass basis.     

生境异质性对金沙江干热河谷锥连栎天然更新幼苗早期生长的影响

锥连栎林是金沙江干热河谷仅有的几种重要天然植被之一,由于恶劣的气候环境以及长期严重的人为干扰作用,林地生境破碎化程度较高,幼苗天然更新极为困难.分析了锥连栎林更新幼苗主要生长的落叶堆积洼地、落叶堆积平地、菁沟冲积台地和缓坡草丛等4种微生境特点,并比较研究了不同微生境下天然更新幼苗生长的形态特征、生物量分配以及幼苗生存状...     

Trace element accumulation in woody plants of the Guadiamar Valley, SW Spain: a large-scale phytomanagement case study

Phytomanagement employs vegetation and soil amendments to reduce the environmental risk posed by contaminated sites. We investigated the distribution of trace elements in soils and woody plants from a large phytomanaged site, the Guadiamar Valley (SW Spain), 7 years after a mine spill, which contaminated the area in 1998. At spill-affected sites, topsoils (0-25 cm) had elevated concentrations of As (129 mg kg(-1)), Bi (1.64 mg kg(-1)), Cd (1.44 mg kg(-1)), Cu (115 mg kg(-1)), Pb (210 mg kg(-1)), Sb (13.8 mg kg(-1)), Tl (1.17 mg kg(-1)) and Zn (457 mg kg(-1)). Trace element concentrations in the studied species were, on average, within the normal ranges for higher plants. An exception was white poplar (Populus alba), which accumulated Cd and Zn in leaves up to 3 and 410 mg kg(-1) respectively. We discuss the results with regard to the phytomanagement of trace element contaminated sites.     

The effect of nitrogen additions on oak foliage and herbivore communities at sites with high and low atmospheric pollution

To evaluate plant and herbivore responses to nitrogen we conducted a fertilization study at a low and high pollution site in the mixed conifer forests surrounding Los Angeles, California. Contrary to expectations, discriminant function analysis of oak herbivore communities showed significant response to N fertilization when atmospheric deposition was high, but not when atmospheric deposition was low. We hypothesize that longer-term fertilization treatments are needed at the low pollution site before foliar N nutrition increases sufficiently to affect herbivore communities. At the high pollution site, fertilization was also associated with increased catkin production and higher densities of a byturid beetle that feeds on the catkins of oak. Leaf nitrogen and nitrate were significantly higher at the high pollution site compared to the low pollution site. Foliar nitrate concentrations were positively correlated with abundance of sucking insects, leafrollers and plutellids in all three years of the study.