The Value of Long‐Term Assessment of Restoration: Support from a Seagrass Investigation

The importance of judging success of restoration studies over extended time periods has been repeatedly voiced but convincing information to justify increased monitoring is generally unavailable. Building on Bell et al. (2008), we investigated the development of areal coverage of the seagrass, Halodule wrightii, as a metric for assessing the outcome of a restoration effort conducted near Tampa Bay, Florida, U.S.A., over 7 years, thereby expanding the timescale over which a subtropical seagrass restoration project was evaluated for success. In each of 12 plots, 500 planting units of H. wrightii were introduced in 2002, and the seagrass cover level documented annually through 2009. Although only low‐moderate levels of H. wrightii cover were recorded after 3 years, a rapid increase to high coverage levels was evident in many plots after 2006 and sustained through 2009. Plots that supported only low levels of seagrass cover initially remained poor performers, 4–7 years post‐planting. By 2008, substantial seagrass spillover, contiguous with over 75% of plots, was recorded. When both within‐plot coverage and spillover were considered, seagrass restoration success was attained 6 years after initiation. Our findings provide an example of comparatively longer‐term monitoring of a restoration effort leading to reversal of an earlier evaluation of project success. Moreover, unique information on H. wrightii temporal dynamics emerged from the 7 year study, further illustrating the value of long‐term assessment of restoration. Extending the duration of post‐planting surveys of seagrass coverage may address multiple needs as it advances the field of seagrass restoration .     

Water homeostasis by wild larvae of Manduca sexta

Modulation of faecal water loss is the principal mechanism by which larval Lepidoptera maintain water homeostasis in the laboratory. Is this also true of larvae in nature? We observed 12 fifth‐instar larvae of Manduca sexta feeding on Datura wrightii in the Sonoran Desert, U.S.A. The two main sources of water stress were: evaporative water loss across the cuticle, which appeared to be promoted by increasing body temperatures and decreasing relative humidities during daytime observation periods; and attacks by tachinid flies, which prompted caterpillars to defaecate large quantities of water and to regurgitate digestive fluid onto themselves. In both cases, caterpillars responded by producing drier faecal pellets. A subset of caterpillars consumed water‐rich flower buds of D. wrightii, which led to the production of comparatively wet faecal pellets. These data demonstrate that larval water balance in nature is affected by a variety of biotic and abiotic factors and that larvae respond to these perturbations by modulating the loss of water in the faeces.     

悬铃木方翅网蝽在我国的潜在分布分析

运用生态位模型MaxEnt和GARP对悬铃木方翅网蝽Corythucha ciliate(Say)在我国的潜在分布进行了模拟,并结合其寄主植物悬铃木在我国的分布进行了分析。实验采用悬铃木方翅网蝽在我国的分布数据,结合6种气候变量和海拔数据构建模型,并将MaxEnt和GARP的输出结果进行合意。研究显示MaxEnt和GARP的模拟结果基本一致,均能较好的模拟悬铃木方翅网蝽在我国的分布,二者均显示山东西南部和中部、四川中部和东部、重庆、陕西中部、河南中部和东部、安徽、江苏、上海、贵州、湖南、江西、浙江、福建中部和北部、云南中部等地区为悬铃木方翅网蝽的适宜分布区,此外,河北中部和南部、山东东部,广东和广西的北部亦具潜在分布的可能性。与MaxEnt输出结果相比,GARP相对较为保守。MaxEnt输出结果显示年平均气温和极端低温对悬铃木方翅网蝽地理分布的限制作用最大。考虑到该虫对高低温度的耐受性,我国二球悬铃木栽培的南界(南宁和广州)和北界(大连、北京、石家庄、太原)需要重视和监控起来。     

悬铃木方翅网蝽与红带网纹蓟马的竞争关系研究

【背景】悬铃木方翅网蝽是仅危害悬铃木的外来入侵物种,而红带网纹蓟马寄主广泛,可吸食悬铃木叶片汁液,2个物种客观上发生了竞争关系。【方法】以悬铃木方翅网蝽与红带网纹蓟马共同发生的悬铃木种植街区为研究地点,每10d调查15根悬铃木枝条,记录各枝条各叶片上2个物种的数量,进而评价悬铃木方翅网蝽入侵对红带网纹蓟马的竞争排斥能力。【结果】悬铃木方翅网蝽在整个调查期间的种群数量明显高于红带网纹蓟马;悬铃木方翅网蝽在悬铃木上的时间生态位宽度和重叠指数均大于红带网纹蓟马,两者的时间生态位竞争系数达0.7022,明显高于对悬铃木枝条和叶片的竞争强度;悬铃木方翅网蝽和红带网纹蓟马对悬铃木枝条和叶片的竞争强度较低,且具有阶段性,空间竞争主要发生在6月中旬至7月下旬的2个种群发生高峰期;悬铃木方翅网蝽与红带网纹蓟马在悬铃木上的繁殖生态位出现了明显的时间分化,红带网纹蓟马仅秋季世代产卵于悬铃木叶片上,而悬铃木方翅网蝽所有世代均产卵于悬铃木叶上,但2个物种在悬铃木上共同繁殖期间,红带网纹蓟马选择产卵的枝条和叶片均有悬铃木方翅网蝽产卵,表明2个物种对产卵枝条和叶片具有相似的空间需求。【结论与意义】悬铃木方翅网蝽与红带网纹蓟马在悬铃木上整体的时空生态位竞争强度较弱,且2个物种的营养生态位差异较大;悬铃木方翅网蝽的入侵对红带网纹蓟马的生存和种群发展无明显影响。     

Importance of adventitious roots to growth of floodedPlatanus occidentalis seedlings

Summary Flooding of soil with standing water for 50 or 110 days drastically reduced growth of 178-day-oldPlatanus occidentalis seedlings, with growth inhibited more as the duration of flooding was increased. Flooding reduced the rate of height and diameter growth, leaf initiation and expansion, and dry weight increment and relative growth rates of leaves, stems, and roots. Flooding also induced leaf epinasty, leaf necrosis, and formation of hypertrophied lenticels and many adventitious roots on submerged portions of stems. Severing of adventitious roots after 50 and 95 days from the submerged portions of stems of continuously flooded seedlings reduced several growth parameters including height and stem diameter growth and relative growth rates of leaves and roots. Evidence for the physiological importance of flood induced adventitious roots is discussed.Research supported by College of Agricultural and Life Sciences, University of Wisconsin, Madison and by Yamagata University, Tsuruoka, Japan. The technical assistance of John Shanklin is appreciated.     

Influence of stream flow regime and temperature on growth rate of the riparian tree, Platanus wrightii, in Arizona

1. The growth of riparian trees in semi‐arid regions is influenced by stream flow regime, but the relative importance of base flow and seasonal floods on growth has not been explored. I examined abiotic influences on the growth of Platanus wrightii in four stream reaches in Arizona. All reaches had a bimodal pattern of discharge, but only two had continuous flow throughout the growing season.
2. In two reaches of Sycamore Creek without perennial flow, a large percentage of the annual variation in radial growth rate of P. wrightii was explained by annual and growing season flow rate. Growth was related to these same variables in a perennial reach of Sycamore Creek, but trees maintained higher growth during drought years than they did in the temporary reaches. At Oak Creek, a larger perennial stream, P. wrightii growth showed a bell‐shaped relationship with flow. These data suggest that growth rate is frequently limited by water availability at Sycamore Creek, but not at Oak Creek.
3. At both rivers, much of the annual surface flow occurs as winter floods. Oak Creek, however, maintains a high summer base flow even during years with no floods. Platanus wrightii growth was significantly related to winter flood frequency only at Sycamore Creek. The positive relationship of growth with stream flow and winter flood frequency at Sycamore Creek presumably occurs because the P. wrightii trees are dependent on the winter flows to recharge the shallow alluvial aquifer and to raise the level of ground water within the root zone.
4. Frequent summer floods increased the growth of trees in perennial and non‐perennial reaches alike. At perennial Oak Creek, summer flood frequency was the only variable linearly related to growth of P. wrightii. Summer flood frequency was a significant, but secondary, component of multiple‐regression growth models for trees in the perennial and non‐perennial reaches of Sycamore Creek. Summer floods may stimulate growth, in part, by replenishing limiting nutrients.
5. High temperature was negatively associated with the growth of P. wrightii at Sycamore Creek. The combination of drought and high temperature resulted in very low growth rate.
6. These results have implications for the management of flood and base flow regimes on regulated, diverted and pumped rivers.     

The influence of climate changes in Platanus spp. pollination in Spain and Italy

There is evidence of a significant increase in air temperature in the northern hemisphere over recent decades, with consequent changes for anemophilous pollen. In this work we present the effects of climatic change on Platanus spp. pollination in different areas of Italy and Spain, characterized by different climates. In particular, the historical series of pollen monitoring and meteorological data of two Italian stations, Perugia (1982 – 2003) and Torino (1985 – 2003), and two Spanish stations, Santiago de Compostela (1992 – 2003) and Vigo (1994 – 2003), were analysed. The changes recorded in all stations included the timing and behaviour of pollen release. However, no or minimal influence on the total pollen emission was found. Research has linked the changes in phenological events to an increase in temperature, moreover in this study temperature changes are believed to be mainly responsible for the variations recorded in the pollen season of Platanus. A previous start of pollination (?0.66; ?1.21; days/year) is reported in both Italian stations where the temperatures have significantly increased and a delay of 0.2 – 0.8 days/year in Spanish stations where a different trend of temperature is recorded. Other important data is given regarding the type of discharge of pollen grains during the pollen season. Pollination curves are examined by two statistical shape parameters (kurtosis and skewness) which show that pollen release is more gradual with higher temperatures or faster under colder conditions. A regression analysis links the atmospheric pollen presence to mean air temperature.     

Forecasting airborne Platanus pollen in the Madrid region

This study analyses the atmospheric concentration of Platanus pollen in four stations in the Madrid region over a period of 10 years (1994–2003). Various statistical analyses (regression analysis and decision tree) were used to prepare a forecasting model for possible application as a preventive measure in pollinosis. The data comes from the PALINOCAM network and the samplers used were Hirst type (Burkard pollen trap). Platanus pollen is present in the atmosphere during a short period of time in spring, and the maximum concentrations are detected during the last two weeks of March and the first week of April. Regression analysis shows that the pollen concentration of the two previous days is the best predictive variable. The models obtained for the four stations analysed account for between 37 and 61% of the variation in pollen levels in the air. The decision trees show how the introduction of meteorological variables improves prediction for this pollen type.     

Evidence for light-independent and steeply decreasing PSII efficiency along twig depth in four tree species

Recent reports have indicated a considerably inactivated PSII in twig cortices, in spite of the low light transmittance of overlying periderms. Corresponding information for more deeply located and less illuminated tissues like xylem rays and pith are lacking. In this investigation we aimed to characterize the efficiency of PSII and its light sensitivity along twig depth, in conjunction with the prevailing light quantity and quality. To that aim, optical methods (spectral reflectance and transmittance, chlorophyll fluorescence imaging, low temperature fluorescence spectra) and photoinhibitory treatments were applied in cut twig sections of four tree species, while corresponding leaves served as controls. Compared to leaves, twig tissues displayed lower chlorophyll (Chl) levels and dark-adapted PSII efficiency, with strong decreasing gradients towards the twig center. The low PSII efficiencies in the inner stem were not an artifact due to an actinic effect of measuring beam or to an enhanced contribution of PSI fluorescence. In fact, the PSII/PSI ratios in cortices were higher and those in the xylem rays similar to that of leaves. Inner twig tissues were quite resistant to photoinhibitory treatments, tolerating irradiation levels several-fold higher than those encountered in their microenvironment. Moreover, the extent of high light tolerance was similar in naturally exposed and shaded twig sides. The results indicate an increasing, inherent and light-independent inactivation of PSII along twig depth. The findings are discussed on the basis of a recently proposed model for photosynthetic electron flow in twigs, taking into account the specific atmospheric and light microenvironment as well as the possible metabolic needs of such bulky organs.