Central Amazon Floodplain Forests: Root Adaptations to Prolonged Flooding

The floodplains of Central Amazonia represent a complex system of inundated river valleys and shallow lakes along the Solimões–Amazonas river, which is subjected to an annual flood-pulse lasting up to 10 months. Such flooding reaching an amplitude of about ten meters causes dramatic changes in the bioavailability of nutrients and oxygen levels and poses extreme constraints for plant survival and reproductivity. Tree species of inundation forests in Central Amazonia had to evolve adaptive mechanisms to both desiccation of soils and partial or full submergence. To adapt to flooded conditions, some trees overcome the flood period by dormancy accompanied by defoliation and formation of annual rings in the wood. Other species maintain metabolism and retain the foliage during the flooding, representing another adaptive mechanism to low oxygen availability. This investigation focused on the root physiology and morphology of six species typical of white-water inundation areas (várzea) led to a preliminary classification of adaptive strategies of trees inhabiting forest communities in floodplains of the Amazon basin.     

Effects of willow nutrition and morphology on calving success of moose

Across much of North America, populations of moose (Alces alces) are declining because of disease, predation, climate change, and anthropogenic-driven habitat loss. Contrary to this trend, populations of moose in Colorado, USA, have continued to grow. Studying successful (i.e., persistent or growing) populations of moose can facilitate continued conservation by identifying habitat features critical to persistence of moose. We hypothesized that moose using habitat with higher quality willow (Salix spp.) would have a higher probability of having a calf-at-heel (i.e., calving success). We evaluated moose calving success using repeated ground observations of collared individuals with calves in an occupancy model framework to account for detection probability. We then evaluated the impact of willow habitat quality and nutrition on moose calving success by studying 2 spatially segregated populations of moose in Colorado. Last, we evaluated correlations between willow characteristics (browse intensity, height, cover, leaf length, and species) and willow nutrition (dry matter digestibility [DMD]) to assess the utility of using those characteristics to assess willow nutrition. We found willow height and cover had a high probability of being positively associated with higher individual-level calving success. Willow DMD, browse intensity, and leaf length were not predictive of individual moose calving success; however, the site with higher mean DMD consistently had higher mean estimates of calving success for the same year. Our results suggest surveying DMD is likely not a useful metric for assessing differences in calving success of individual moose but may be of use at population levels. Further, the assessment of willow morphology and density may be used to identify areas that support higher levels of moose calving success.     

新疆柳属一新记录种——粉枝柳

在研究新疆阿勒泰地区柳属(SalixL.)植物时发现了新疆杨柳科(Salicaceae)柳属植物新记录组粉枝柳组(Sect.Daphnella Seringe ex Duby)及新疆新记录种粉枝柳(Salix rorida Laksch.)。该种雌花苞片长圆形、倒卵状长圆形、倒卵状椭圆形和倒卵形,先端锐尖,苞片基部两侧各具3~4个腺点;雄花苞片倒卵形和倒卵状长圆形,先端锐尖,稀凹陷,在个别苞片基部一侧会有不明显的2~3个腺点,与其他分布区的粉枝柳稍有差异。主要分布在哈巴河中、上游及其2个支流,生于河岸及人工渠道岸边,海拔900~1 500m之处。     

Leaf beetle grazing does not induce willow trichome defence in the coppicing willow Salix viminalis

Abstract 1 Willows are frequently attacked and defoliated by adult leaf beetles (Phratora vulgatissima L.) early in the season and the plants are then attacked again when new larvae emerge. The native willow Salix cinerea has previously been shown to respond to adult grazing by producing new leaves with an increased trichome density. Subsequent larval feeding was reduced on new leaves. This type of induced plant response may reduce insect damage and could potentially be utilized for plant protection in agricultural systems. 2 Here, we investigated if the willow species most commonly used for biomass production in short rotation coppice, Salix viminalis, also responds to adult beetle grazing by increasing trichome density. Larval performance and feeding behaviour on plants previously exposed to adult beetles was compared with that on undefoliated control plants in a greenhouse. 3 We found an overall decrease in trichome density within all the plants (i.e. trichome density was lower on new leaves compared to that for older basal leaves on S. viminalis). However, leaves of beetle defoliated plants had a higher trichome density compared to control plants. Larval growth and feeding was not affected by this difference between treatments. Larvae appeared to remove trichomes when feeding on S. viminalis, a behaviour that might explain the lack of difference between treatments.     

Responses of nonstructural carbohydrates to shoot removal and soil moisture treatments in <Emphasis Type="Italic">Salix nigra</Emphasis>

Aboveground disturbances are common in dynamic riparian environments, and Salix nigra is well adapted with a vigorous resprouting response. Soil moisture stresses are also common, and S. nigra is flood tolerant and drought sensitive. The objective of this study was to quantify nonstructural carbohydrate (NSC) reserves in S. nigra following shoot removal and soil moisture treatments. NSC reserves provide energy for regeneration of shoot tissue until new functional leaves are developed. Three soil moisture treatments: well-watered (W), periodic flooding (F) and drought (D); and three shoot removal treatments: no shoots removed (R0), partial shoot removal (R1), and complete shoot removal (R2) were applied. Plants were harvested when new shoot development was observed (day 13). Statistical significance in the 3 × 3-factorial design was determined in two-factor ANOVA at P < 0.05. Both roots and cuttings were important reservoirs for NSC during resprouting response, with decreases in root (31%) and cutting (14%) biomass in R2 compared to R0. Rapid recovery of photosynthetic surface area (from 15 to 37% of R0) was found in R1. A clear pattern of starch mobilization was found in roots in R0, R1 and R2, with lowest root starch concentration in W, F higher than W, and D higher than F. Shoot starch concentration was lower in F and D compared to W in R0, however, in R1 shoot starch was reduced in W compared to F and D, possibly indicating reduced rates of translocation during soil moisture stress. Evidence of osmotic adjustment was found in roots and shoots with higher total ethanol-soluble carbohydrates (TESC) during soil moisture stress in F and D treatments. Total plant NSC pool was greater in F and D treatments compared to W, and progressively reduced from R0 to R1 to R2. Results indicated negative effects of drought, and to a lesser extent periodic flooding on resprouting response in S. nigra, with implications for reduced survival when exposed to combined stresses of aboveground disturbance and soil moisture.     

The influence of soil moisture and flooding on formation of VA-endo- and ectomycorrhizae in Populus and Salix

Native mixtures of extomycorrhizal fungi were found to infect Populus and Salix roots primarily in very moist but well drained soils in both the field and in controlled experiments (0 to –0.2 MPa), whereas native mixtures of VA-endomycorrhizal fungi infected roots over a much wider range of soil moisture (flooded to –3.4 MPa). Although a moisture gradient experiment showed endomycorrhizal formation was greater in moist soil than in very dry or flooded soils, this pattern was reversed in field transects along drainage gradients. Infection by VA-endomycorrhizal fungi in the field was the lowest where infection by ectomycorrhizal fungi was high, which suggests possible antagonism among the fungal symbionts. The narrow moisture range for ectomycorrhizal formation, and antagonism among endo- and ectomycorrhizal fungi, apparently combine to produce the mycorrhizal distributions found in nature.     

Time‐dependent climate impact and energy efficiency of combined heat and power production from short‐rotation coppice willow using pyrolysis or direct combustion

A life cycle assessment of a Swedish short‐rotation coppice willow bioenergy system generating electricity and heat was performed to investigate how the energy efficiency and time‐dependent climate impact were affected when the feedstock was converted into bio‐oil and char before generating electricity and heat, compared with being combusted directly. The study also investigated how the climate impact was affected when part of the char was applied to soil as biochar to act as a carbon sequestration agent and potential soil improver. The energy efficiencies were calculated separately for electricity and heat as the energy ratios between the amount of energy service delivered by the system compared to the amount of external energy inputs used in each scenario after having allocated the primary energy related to the inputs between the two energy services. The energy in the feedstock was not included in the external energy inputs. Direct combustion had the highest energy efficiency. It had energy ratios of 10 and 36 for electricity and heat, respectively. The least energy‐efficient scenario was the pyrolysis scenario where biochar was applied to soils. It had energy ratios of 4 and 12 for electricity and heat, respectively. The results showed that pyrolysis with carbon sequestration might be an option to counteract the current trend in global warming. The pyrolysis system with soil application of the biochar removed the largest amount of from the atmosphere. However, compared with the direct combustion scenario, the climate change mitigation potential depended on the energy system to which the bioenergy system delivered its energy services. A system expansion showed that direct combustion had the highest climate change mitigation potential when coal or natural gas were used as external energy sources to compensate for the lower energy efficiency of the pyrolysis scenario.     

柳属的叶表皮微形态特征及其分类学意义

研究了29种柳属( Salix )植物在扫描电镜下的叶表皮微形态特征.结果表明:柳属的角质层蜡质纹饰可以划分为:痂状蜡质层,壳状平滑蜡质层,具凸起颗粒的蜡质层,具颗粒的蜡质层,锥形纤维体和鳞片状纤维体6种类型.其中锥形纤维体和鳞片状纤维体均为柳属所特有的蜡质类型,后者为前者的变型,这两种蜡质纹饰类型多见于较为进化的皱纹柳亚属和黄花柳亚属,故推测其可能为柳属中较为进化的性状.研究还发现气孔有外拱盖扁平和隆起呈脊状2种类型.而气孔外拱盖内缘为浅波状的类型仅见于高山和北极的类群中,因而推测该类型可能同高山和极地的低温等环境有关.气孔外拱盖的形态及其角化的情况以及蜡质类型是稳定的鉴别特征,对于柳属植物,尤其是一些表型相似的种类有很好的鉴别作用,但对于组、亚属的界定作用不大.     

Willow water uptake and shoot extension growth in response to nutrient and moisture on a clay landfill cap soil

Extension growth of willow (Salix viminalis L.) and changes in soil water were measured in lysimeters containing clay and sandy loam soils with different amendment and watering treatments. No water uptake was found below 0.3 m in the nutritionally poor unamended clay; amendment with organic matter to 0.4 m depth resulted in water extraction down to 0.5 m depth whereas in the sandy loam, there was greater extraction from all depths down to 0.6 m. With water stress, wilting of plants occurred when the volumetric soil water content at 0.1 m was about 31% in the clay and 22% in the sandy loam. Compared with shoots on plants in the amended clay, those in the unamended treatment showed reduced extension growth, little increase in stem basal area (SBA) and a small shoot leaf area, resulting from a reduced number of leaves shoot⁻¹ and a small average area leaf⁻¹. Water stress also reduced shoot extension growth, SBA gain and the leaf area on extension growth. Shoot growth rates were significantly correlated with air temperature and base temperatures between 2.0 and 7.6 °C were indicated for the different treatments. These studies have helped to explain some of the large treatment effects described previously on biomass production and plant leaf area.     

HCO−3 uptake through the roots and its effect on the productivity of willow cuttings

Abstract Young willow plants (Salix‘aquatica gigantea’) were grown in hydroponic culture media, and ¹⁴C–labelled sodium bicarbonate was fed to the roots. Uptake of ¹⁴C-label in the leaves and shoots was assayed after two different feeding periods (6 h, 48 h). Even during the shortest feeding period, ¹⁴C-label had been transferred to the leaves and shoots. Compared with the longer feeding period, after the 6 h feeding period more label was in the form of acid-labile products, whereas after the 48 h feeding period most of the label was in acid-stable products. A second experiment was designed to test whether carbon uptake by roots affects the growth of young willow plants. Uniform rooted cuttings were grown in hydroponic cultures at five different levels of bicarbonate: 0, 0.015, 0.147 0.737, and 1.473 mol m^?3 NaHCO₃. After a 4-week growing period we determined the biomass of leaves, shoots, roots and cuttings. Production of total dry matter (shoots, leaves and roots) increased with increasing bicarbonate concentration. Saturation of dry matter production was reached at 0.737 mol m^?3 NaHCO₃, but a higher concentration of NaHCO₃ (1.470 mol m^?3) caused a slight decrease in the dry matter production. At 0.737 mol m^?3 NaHCO₃ the total dry weight increased by 31.1%, which suggests that uptake of dissolved carbon dioxide through the roots might affect carbon budgeting in young willow plants.