Invertebrate diversity associated with a shallow rhodolith bed in the Mediterranean Sea (Mar Piccolo of Taranto,south-east Italy)

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A field study of the impact of different irrigation practices on herbicide leaching

Agricultural practices, such as subsurface drainage, irrigation and tillage, may significantly affect pesticide leaching and, consequently, the risk of groundwater contamination. The aim of the present study was to investigate the impact of different irrigation systems on herbicide leaching to shallow groundwater through direct monitoring at the field scale in northern Italy over a 3-year period. Concentrations of the herbicide terbuthylazine (TBA) and its metabolite desethylterbuthylazine (DES) were monitored on 10 farms cropped with maize and irrigated by sprinkler, basin and border systems. Considering the results grouped according to the different irrigation systems, the mean TBA and DES concentrations was lower than the arbitrary non-health based legal limit of 0.1 μg/L using sprinkler and border systems, while it was 0.19 and 0.30 μg/L respectively for TBA and DES using basin systems.However, since many factors other than the irrigation systems can contribute to pesticide leaching and in a field study it is impossible to discriminate between all the different variables, the concentrations of both compounds were simulated with and without irrigation using the model MACRO 5.1 in order to gain a deeper understanding of the role of irrigation on leaching. First, the groundwater table depth, which was measured daily in all fields, was used to calibrate the model and thus achieve a good soil hydrology calibration. To assess the performance of the model the root mean squared error (RMSE) was used. RMSE ranged from 0.2 to 0.5 m, showing that a satisfactory hydrology calibration was obtained. Afterward, the solutes were modelled and the results showed that under non-irrigated conditions, concentrations of both compounds would be very low. These findings validate the hypothesis that careful selection of agricultural practices, such as the type of irrigation, can reduce pesticide leaching.     

基于方格网法的树冠体积测算方法

提出了一种基于方格网法测算树冠体积的方法。研究利用免棱镜全站仪获取树冠点云数据,建立树冠表面特征点的坐标方格网,根据方格网法计算土方量的原理来求算树冠体积,通过传统经典模型人工方法、三维激光量测法与本文算法,分别计算实验区域研究对象的体积,将结果进行对比分析,本研究提出的算法平均相对误差为4.13%,平均准确度为95.97%,且在置信度0.05下树冠体积的计算值与实测值之间的差异性为不显著,结果完全满足计算精度,其计算耗时只有传统人工量测法的1/3,成本为三维激光扫描的2%,降低了成本且提高了效率。     

Will all the trees fall? Variable resistance to an introduced forest disease in a highly susceptible host

Although tanoak (Notholithocarpus densiflorus syn. Lithocarpus densiflorus) is the species most affected by the introduced pathogen Phytophthora ramorum, with demonstrable risk of extirpation, little is known about the origin, range or structuring of the tree's susceptibility. We examined variation in resistance to P. ramorum using a wound inoculation assay of detached leaves from trees at five geographically separated sites, and a non-wound inoculation assay on twigs from trees at two sites. The structure of variation in resistance was compared to the structure at nine nuclear microsatellite markers.Resistance varied quantitatively, with 23% and 12% of the variation among individuals and populations, respectively. There was a significant correlation between resistance in detached leaves and lesion size in non-wounding twig inoculations. Among-population genetic diversity at nine microsatellite loci was weakly structured but significantly non-zero, with 9.5% of variation among populations. Within-population neutral genetic diversity was a poor predictor of resistance, and estimates of phenotypic distances for resistance were no greater than neutral genetic distances.The limited phenotypic and genetic structure we found indicates that tanoaks at all study sites are susceptible, and there is no evidence of prior selection for disease resistance. We conclude that tanoak populations across the species’ range are at risk, but local disease dynamics will depend on both host genetics and environmental conditions.     

Tree-ring Δ13C reveals the impact of past forest management on water-use efficiency in a Mediterranean oak coppice in Tuscany (Italy)

? The effects of thinning and heavy stand density reduction was investigated in Turkey oak (Quercus cerris L.) forests of central Italy, to evaluate the physiological responses and the growth status of trees that survived a past coppice cut and thinning to convert the stand to high-forest.

? The working hypothesis was that a strong decrease in stand density would cause a decreasing in canopy-intrinsic water-use efficiency (measured as the ratio of CO₂ assimilation to stomatal conductance, A/g), thus an increase in tree-ring carbon isotopic discrimination (Δ¹³C).

? The tree-ring Δ¹³C of the remaining trees (“survivors”) was found to have significantly (P < 0.05) raised between year two and year seven since the coppice stand was thinned (high-forest conversion thinnings). This effect was mostly caused by a large decrease in tree-rings Δ¹³C at control site which was characterized by high density and competition by trees. An increase in survivors tree-rings Δ¹³C probably indicates an improved water availability, possibly induced by a decrease in competition and in stand density or a decrease in the precipitation intercepted by the canopy (i.e., a stronger increase in g over A since a decrease in A is highly unlikely). A change in foliar nitrogen, foliar Δ¹³C and content in chlorophylls was also recorded seven years after thinning.

? Thinnings carried out to convert old abandoned coppices into high-forest stands induce short-term stimulation of Turkey oak growth by increasing light and water availability. We were able to make a detailed reconstruction of the impact of past silvicultural treatment on the stand using a tree-ring wood Δ¹³C time-series.

     

Multiple functions of buffer strips in farming areas

Buffer strips (BSs) are strips interposed between fields and streams that intercept and treat the waters leaving cropland, and so are a useful tool for reducing agricultural diffuse pollution in lowland areas. If properly vegetated and managed, they can also produce wood for burning, act as sinks for atmospheric CO₂ and enhance the landscape beauty.The paper presents an analysis of the different functions of BS and reviews the more important data from research programmes conducted over the last decade in Veneto Region (North-East Italy). Over a period of 3–5 years, in two experimental sites, young BS reduced total runoff by 33%, losses of N by 44% and P by 50% compared to no-BS. A mature BS was able to abate both NO₃–N and dissolved phosphorus concentrations by almost 100%, in most cases having exiting water that satisfied the limit for avoiding eutrophication. The BS also proved to be a useful barrier for herbicides, with concentrations abated by 60% and 90%, depending on the chemical and the time elapsed since application. Considering the CO₂ immobilized in the wood and soil together, the different BS monitored stored up to 80 t ha^?1 year^?1.The BS caused negligible disturbance to maize, soybean and sugarbeet yields. The hedgerows, particularly if composed of trees taller than 6 m, positively influenced the aesthetic value of the territory, improving its perceived naturalness and screening the man-made elements.Lastly, through a multi-objective analysis, opportunity costs were estimated to support the public decision-maker in determining the subsidies to be paid to encourage farmers to plant BS.     

Changes in foliar carbon isotope composition and seasonal stomatal conductance reveal adaptive traits in Mediterranean coppices affected by drought

We estimated water-use efficiency and potential photosynthetic assimilation of Holm oak(Quercus ilex L.) on slopes of NW and SW aspects in a replicated field test examining the effects of intensifying drought in two Mediterranean coppice forests. We used standard techniques for quantifying gas exchange and carbon isotopes in leaves and analyzed total chlorophyll, carotenoids and nitrogen in leaves collected from Mediterranean forests managed under the coppice system. We postulated that responses to drought of coppiced trees would lead to differential responses in physiological traits and that these traits could be used by foresters to adapt to predicted warming and drying in the Mediterranean area. We observed physiological responses of the coppiced trees that suggested acclimation in photosynthetic potential and water-use efficiency:(1) a significant reduction in stomatal conductance(p0.01) wasrecorded as the drought increased at the SW site;(2) foliar δ13C increased as drought increased at the SW site(p0.01);(3) variations in levels of carotenoids and foliar nitrogen, and differences in foliar morphology were recorded, and were tentatively attributed to variation in photosynthetic assimilation between sites. These findings increase knowledge of the capacity for acclimation of managed forests in the Mediterranean region of Europe.