Grasses cope with high‐contrast ecosystem conditions in the large outflow of the Banhine wetlands,Mozambique

Ecosystems with highly pulsed water supply must be better understood as climate change may increase frequency and severity of intense storms, droughts and floods. Here we collected data over 3 years (2016–2018) in the episodic wetland outflow channel (Aluize), Banhine National Park, in which the system state changed from dry to wet to dry. Field sampling included vegetation records, small‐scale vegetation zoning, the seed bank and water and soil quality. The same main plant species were found in both dry and wet conditions across the riverbed of the outflow channel. We found only very few diaspores of plants in the soil after prolonged drought. In the subsequent flooded state, we examined very dense vegetation on the water surface, which was dominated by the gramineous species Paspalidium obtusifolium. This species formed a compact floating mat that was rooted to the riverbed. The Cyperaceae Bolboschoenus glaucus showed high clonal growth in the form of root tubers, which likely serve as important food reservoir during drought. Soil and water analyses do not indicate a limitation by nutrients. We outline how resident people may change the plant community structure with an increasing practice of setting fire to the meadows in the dried‐up riverbed to facilitate plant regrowth as food for their livestock.     

不同种植年限有机土基质的变化及其对温室黄瓜生长的影响

研究了不同种植年限有机土基质的理化性质变化及其对黄瓜生长的影响.结果表明：随着种植年限的增加,有机土栽培基质的理化性质变差,表现为容重增大、总孔隙度减小、土壤酸碱度降低、有效养分含量下降;有机土微生物区系中细菌、放线菌数量下降,真菌数量增多.随有机土种植年限的增加,黄瓜的生长受到一定影响,表现为株高、叶面积减小,光合功能衰退,黄瓜产量和品质下降,有必要对连续种植3年的有机土基质进行地力恢复.
     

Growth of the tropical Pinus kesiya as influenced by climate and nutrient availability along an elevational gradient

与温带地区相比,人们对在热带山脉中,尤其是热带针叶林中,沿海拔梯度的个体树种生长减少的原因知之甚少。我们的研究目的是检验气候或土壤条件是否会导致在高海拔分布的卡西亚松(Pinus kesiya,一种在南亚和东南亚广泛分布的松树)的生长减少。我们对越南中南部山脉中沿海拔梯度约在900~2000米之间的卡西亚松的树干直径增量和其年轮中13C(△13C)的同位素判别进行分析。同时确定其生长与△13C、气候和土壤变量的关系。研究发现,树木的断面积生长量(BAI)与温度或降水之间没有一致的相关关系。相反,沿海拔梯度,我们发现BAI与△13C以及与上层矿质土壤的C/N比和δ15N特征呈显著负相关。BAI与土壤中有效磷(Pa)和“碱性”阳离子(钙、镁、钾)的浓度呈正相关。我们的结论是,较高海拔下的较低温度会对树木生长产生间接影响,主要通过产生较高的C/N比并降低氮(N)和P矿化率而产生作用,而这些影响因其他负面反馈而进一步受到阻碍。主要包括：降水增加的淋溶作用而导致较低浓度的“碱性”阳离子以及较高海拔土壤矿化的N和P的有效性降低。本研究结果可以进一步解释卡西亚松的最高生长极限以及该物种在其他山区出现的情况     

The only elements required by plants that are deficient in seawater are nitrogen,phosphorous and iron

It has been known for some time that mangroves grow in the intertidal areas of desert countries where fresh water flows into the sea, but this phenomenon has not been understood. In Eritrea we observed that mangroves grow where infrequent rains flow into the Red Sea. We theorized that the fresh water must bring elements needed for plant growth that are absent in seawater. We compared the composition of seawater to that of Zarrouk’s algae medium. All the elements in algae medium are in sufficient quantity in seawater except for nitrogen, phosphorous and iron. If we supply these elements we can grow any plant that can grow in seawater. We have also begun planting plants that can grow in sea water in the Sahara desert with sea water irrigation and fertilization with nitrogen, phosphorus and iron. We believe this will be major step in reducing hunger and poverty in the world.     

Seasonal growth and year class strength variations of perch near the northern limits of its distribution range

The effects of temperature on seasonal growth and year class strength of perch Perca fluviatilis were studied in a subarctic lake in northern Finland. Two growth models, power and von Bertalanffy, were used to estimate the growth of perch during the growing season from 1988 to 1990. Air temperature, estimated as degree-days >10° C, significantly improved both model fits. The sum of degree-days also correlated positively with the year class strength of perch. The strongest year class was born in a warm summer 1988, while the 1987 year class was totally absent, which was due to the very cold summer of that year. The backcalculation of lengths of fish caught in 1990 showed that the overall growth of perch was slow in the cold summer of 1987 and relatively rapid in the warm summer of 1988. The subsequent growth of the abundant 1988 year class was rapid, even though the summers of 1991 and 1992 were relatively cool. The improved growth could be due to the lack of competition with previous weak year classes of 1986 and 1987. This observation suggests that density-dependent factors might affect growth even near the northern limits of the distribution range of perch.     

Interannual variability in abundance and length of young coastal cod in the subtidal zone

The year‐to‐year variability of total length and abundance of young cod Gadus morhua in the littoral zone of the Norwegian Skagerrak coast was dominant over spatial variability. The 0 year group cod was slightly larger in exposed areas than in protected areas. Contrary to expectations, the 0 year group cod was less abundant in the protected inner parts of the fjords. Although the natural variability was very large, exposed areas (the skerries) seemed to be the better area for the 0 year group cod, while for the 1 year group cod, no differences in abundance or growth could be identified indicating that they had adopted a mature pattern of movement, utilizing the entire fjord for feeding. Available habitat data indicated that the availability of shelter was a potential cause for the distributional pattern.     

乌兰布和沙漠东北部不同耕作年限农田土壤有机碳密度及其影响因素

明确干旱区农田开垦过程中土壤有机碳变化及其影响因素对评估其固存特征具有重要意义。本研究以乌兰布和沙漠东北部不同开垦年限(2～5、12～15、25～30、40～50年)农田为对象,以未开垦的自然土壤为对照,采用空间代替时间的研究方法,探究农田开垦过程中0～2 m土层内土壤有机碳密度变化特征及其影响因素。结果表明: 随开垦年限的增加,浅层(0～0.4 m)土壤有机碳密度呈持续增加趋势,但农田土壤有机碳密度均处于较低水平(0.990～1.983 kg·m^-2)。深层(1.2～2 m)土壤有机碳密度在开垦年限较长(25～30和40～50年)的农田中有所增加,而在开垦年限较短(2～5和12～15年)的农田中无增加趋势。未开垦土壤和各耕作年限农田深层土壤有机碳密度在0～2 m土层中占比较大(28.9%～38.6%)。不同耕作年限农田中土壤有机碳密度随土层深度的增加均呈先减小后增大的二次函数关系,且拟合度较高(R²为0.757～0.972)。土壤黏粒和粉粒含量是影响0～2 m土层有机碳密度的关键因素,且耕作年限对浅层(0～0.4 m)土壤有机碳的积累具有重要促进作用。     

Burden of Chagas disease in Brazil, 1990–2016: findings from the Global Burden of Disease Study 2016

Chagas disease continues to be an important cause of morbidity, mortality and disability in several Latin American countries, including Brazil. Using findings from the Global Burden of Disease Study 2016 (GBD, 2016), we present years of life lost, years lived with disability, and disability-adjusted life years due to Chagas disease in Brazil, by sex, age group, and Brazilian states, from 1990 to 2016. Results are reported in absolute numbers and age-standardized rates (per 100,000 population) with 95% uncertainty intervals. In 2016, 141,640 disability-adjusted life years (95% uncertainty intervals: 129,065–155,941) due to Chagas disease were estimated in Brazil, with a relative reduction of 36.7% compared with 1990 (223,879 disability-adjusted life years (95% uncertainty intervals: 209,372–238,591)). Age-standardized disability-adjusted life year rates declined at the national level (?69.7%) and in all Brazilian states between 1990 and 2016, but with different regional patterns. The decrease in the disability-adjusted life year rates was driven primarily by a consistent reduction in the years of life lost rates, the main component of total disability-adjusted life years for Chagas disease. The highest fatal and non-fatal burden due to Chagas disease was observed among males, the elderly, and in those Brazilian states encompassing important endemic areas for vector transmission in the past. Despite the consistent reduction in its burden during the period, Chagas disease is still an important and neglected cause of health lost due to premature mortality and disability in Brazil. Efforts should be made to maintain the political interest and sustainability of surveillance and control actions for Chagas disease, prevent the risk of re-emergence of vector transmission in endemic areas, and provide health care to chronically infected individuals, including early diagnosis and treatment interventions.     

Ontogeny of critical and prolonged swimming performance for the larvae of six Australian freshwater fish species

Critical (<30 min) and prolonged (>60 min) swimming speeds in laboratory chambers were determined for larvae of six species of Australian freshwater fishes: trout cod Maccullochella macquariensis, Murray cod Maccullochella peelii, golden perch Macquaria ambigua, silver perch Bidyanus bidyanus, carp gudgeon Hypseleotris spp. and Murray River rainbowfish Melanotaenia fluviatilis. Developmental stage (preflexion, flexion, postflexion and metalarva) better explained swimming ability than did length, size or age (days after hatch). Critical speed increased with larval development, and metalarvae were the fastest swimmers for all species. Maccullochella macquariensis larvae had the highest critical [maximum absolute 46·4 cm s^?1 and 44·6 relative body lengths (L_B) s^?1] and prolonged (maximum 15·4 cm s^?1, 15·6 L_B s^?1) swimming speeds and B. bidyanus larvae the lowest critical (minimum 0·1 cm s^?1, 0·3 L_B s^?1) and prolonged swimming speeds (minimum 1·1 cm s^?1, 1·0 L_B s^?1). Prolonged swimming trials determined that the larvae of some species could not swim for 60 min at any speed, whereas the larvae of the best swimming species, M. macquariensis, could swim for 60 min at 44% of the critical speed. The swimming performance of species with precocial life‐history strategies, with well‐developed larvae at hatch, was comparatively better and potentially had greater ability to influence their dispersal by actively swimming than species with altricial life‐history strategies, with poorly developed larvae at hatch.     

温度对西花蓟马生长发育、 繁殖和种群增长的影响

西花蓟马Frankliniella occidentalis (Pergande)是一种入侵我国的重要害虫, 温度是决定蓟马能否建立稳定种群的最基本因素。为明确温度对西花蓟马种群增长的影响, 本研究在室内观察了西花蓟马在15℃, 20℃, 25℃, 30℃和35℃温度条件下的生长发育、 存活与繁殖能力, 并计算各温度条件下的种群增长参数。结果表明： 在35℃条件下, 西花蓟马不能完成发育, 其他温度条件下西花蓟马从卵孵化至蛹羽化成成虫, 以20℃条件下的存活率最高, 为62.8%。西花蓟马发育速率随温度升高明显加快, 在15℃下, 完成发育需要近30 d; 而在30℃下, 西花蓟马完成发育仅需10 d 左右。西花蓟马成虫寿命随温度的升高而明显缩短, 在15℃下, 平均寿命为36 d, 最长寿命达60 d; 在30℃下, 西花蓟马的平均寿命为10 d。西花蓟马在 15℃, 20℃和25℃条件下的平均繁殖力差异不显著, 分别为37.70, 32.56, 37.80头1龄若虫/雌, 但显著高于30℃条件下的平均繁殖力（9.36头1龄若虫/雌）。西花蓟马的种群增长参数净生殖率(R0)、 内禀增长率(rm), 在25℃时达最高值, 分别为20.10和0.178 d-1, 而在15℃下分别仅为18.67和0.096 d-1。据此得出, 20~25℃是最适宜西花蓟马生长发育和繁殖温度范围, 温度过高或过低都不利于西花蓟马种群增长。西花蓟马的发育起点温度为7.4℃, 充分完成发育所需的有效积温为208.0日·度。不考虑其他阻碍生长发育因素的情况下, 华南、 华中、 华北和东北地区的年发生代数分别为24~26, 16~18, 13~14和1~4代, 西南地区昆明与丽江分别为13~15和8~10代。