Birds as Suppliers of Seed Dispersal in Temperate Ecosystems: Conservation Guidelines from Real‐World Landscapes

Abstract: Seed dispersal by animals is considered a pivotal ecosystem function that drives plant‐community dynamics in natural habitats and vegetation recovery in human‐altered landscapes. Nevertheless, there is a lack of suitable ecological knowledge to develop basic conservation and management guidelines for this ecosystem service. Essential questions, such as how well the abundance of frugivorous animals predicts seeding function in different ecosystems and how anthropogenic landscape heterogeneity conditions the role of dispersers, remain poorly answered. In three temperate ecosystems, we studied seed dispersal by frugivorous birds in landscape mosaics shaped by human disturbance. By applying a standardized design across systems, we related the frequency of occurrence of bird‐dispersed seeds throughout the landscape to the abundance of birds, the habitat features, and the abundance of fleshy fruits. Abundance of frugivorous birds in itself predicted the occurrence of dispersed seeds throughout the landscape in all ecosystems studied. Even those landscape patches impoverished due to anthropogenic disturbance received some dispersed seeds when visited intensively by birds. Nonetheless, human‐caused landscape degradation largely affected seed‐deposition patterns by decreasing cover of woody vegetation or availability of fruit resources that attracted birds and promoted seed dispersal. The relative role of woody cover and fruit availability in seed dispersal by birds differed among ecosystems. Our results suggest that to manage seed dispersal for temperate ecosystem preservation or restoration one should consider abundance of frugivorous birds as a surrogate of landscape‐scale seed dispersal and an indicator of patch quality for the dispersal function; woody cover and fruit resource availability as key landscape features that drive seedfall patterns; and birds as mobile links that connect landscape patches of different degrees of degradation and habitat quality via seed deposition.     

Urban Plants as Genetic Reservoirs or Threats to the Integrity of Bushland Plant Populations

Abstract:  Remnant plants in urban fringes and native plants in gardens have the potential to contribute to the conservation of threatened plants by increasing genetic diversity, effective size of populations, and levels of genetic connectedness. But they also pose a threat through the disruption of locally adapted gene pools. At Hyams Beach, New South Wales, Australia, four bushland stands of the rare shrub, Grevillea macleayana McGillivray, surround an urban area containing remnant and cultivated specimens of this species. Numbers of inflorescences per plant, fruits per plant, and visits by pollinators were similar for plants in urban gardens and bushland. Urban plants represented a substantial but complex genetic resource, displaying more genetic diversity than bushland plants judged by H_e , numbers of alleles per locus, and number of private alleles. Of 27 private alleles in urban plants, 17 occurred in a set of 19 exotic plants. Excluding the exotic plants, all five stands displayed a moderate differentiation ( F_ST = 0.14 ± 0.02), although the urban remnants clustered with two of the bushland stands. These patterns may be explained by high levels of selfing and inbreeding in this species and by long-distance dispersal (several seeds in the urban stand were fathered by plants in other stands). Genetic leakage (gene flow) from exotic plants to 321 seeds on surrounding remnant or bushland plants has not occurred. Our results demonstrate the conservation value of this group of urban plants, which are viable, productive, genetically diverse, and interconnected with bushland plants. Gene flow has apparently not yet led to genetic contamination of bushland populations, but high levels of inbreeding would make this a rare event and difficult to detect. Remnant plants in urban gardens could successfully contribute to recovery plans for endangered and vulnerable species.     

Predicting the Range of Chinese Mitten Crabs in Europe

Abstract:  Ecological niche modeling provides a means for predicting the potential future distribution of a nonindigenous species based on environmental characteristics of the species' native range. We applied this method to the Chinese mitten crab (Eriocheir sinensis) , a catadromous crustacean with a long history of invasion in Europe. We used genetic algorithm for rule-set prediction to predict the potential European distribution of mitten crab based on its distribution in 42 locations in its native Asia. The climatic variables, air temperature, number of days, amount of precipitation, and wetness index, contributed significantly to predictions of native distribution limits. Although the genetic algorithm for rule-set prediction model was developed for the native range, the species' extensive distribution in Europe ( n = 434) allowed independent validation of the predictions. Application of the model to Europe was successful, with 84% of occurrences in regions predicted to be suitable by >80% of the models and <4% of occurrences in areas predicted suitable by <50% of the models (mainly along the northern range). At the watershed scale, areas with established mitten crab populations had significantly higher habitat matching than sites that were not invaded. The independent validation of the Asian-based model by the European distribution revealed that predictions were highly accurate. The model also identified large areas of Europe, particularly along the Mediterranean coast, as vulnerable to future invasion. These predictions can be used to develop strategies to control the spread of mitten crab by preventing introductions into vulnerable areas.     

Development, dilemma and potential strategies for the application of nanocatalysts in wastewater catalytic ozonation: A review

With the continuous development of nanomaterials in recent years, the application of nanocatalysts in catalytic ozone oxidation has attracted more and more researchers' attention due to their excellent catalytic properties. In this review, we systematically summarized the current research status of nanocatalysts mainly involving material categories, mechanisms and catalytic efficiency. Based on summary and analysis, we found most of the reported nanocatalysts were in the stage of laboratory research, which was caused by the nanocatalysts defects such as easy aggregation, difficult separation, and easy leakage. These defects might result in severe resource waste, economic loss and potentially adverse effects imposed on the ecosystem and human health. Aiming at solving these defects, we further analyzed the reasons and the existing reports, and revealed that coupling nano-catalyst and membrane, supported nanocatalysts and magnetic nanocatalysts had promising potential in solving these problems and promoting the actual application of nanocatalysts in wastewater treatment. Furthermore, the advantages, shortages and our perspectives of these methods are summarized and discussed.     

洞庭湖浮游植物增长的限制性营养元素研究

近20年水质监测资料表明,洞庭湖水体富营养化日趋严重。洞庭湖水体主要污染物为氮和磷,而营养盐赋存形态及其含量对浮游植物生长的影响在洞庭湖尚未见报道。2011年9月至2012年8月对洞庭湖浮游植物生物量及主要营养盐赋存形态与含量进行监测,同时利用藻类增长的生物学（NEB）评价方法对限制浮游植物增长的营养盐进行了研究,并分析了浮游植物生物量与各营养元素之间的相关性。结果表明：洞庭湖主要污染物总氮（TN）和总磷（TP）的年平均值分别为1.90 mg·L-1和0.093 mg·L-1,溶解态无机氮（DIN）平均占ρ（TN）比例为87%,溶解态总磷（DTP）平均占ρ（TP）比例为70%。洞庭湖水体中,DIN是TN的主要贡献者,且不同形态DIN的贡献大小依次为ρ（NO3--N）〉ρ（NH4＋-N）〉ρ（NO2--N）;磷形态组成中,TP主要以溶解反应性磷（SRP）存在。春季洞庭湖水体中ρ（TN）、ρ（TP）较高,这一结果可能源于春季面源污染。洞庭湖水体中ρ（Chla）与氮显著正相关,与磷显著负相关。NEB 实验结果表明氮对洞庭湖浮游植物生长有明显的促进作用,其幅度随氮浓度的增加而加强,而磷对浮游植物的生长影响不大,有时出现抑制作用,硝态氮与磷之间不存在交互作用。因此,氮可能是洞庭湖浮游植物增长的主要限制性营养因子,这一研究暗示在洞庭湖富营养化控制过程中应特别注重氮的控制。     

Coccolithophorids,Nutrients and the Greenhouse Effect

Despite the fact that coccolithophorids such as Emiliania huxleyi are suspected to play an important role in carbon-cycling, there are few data from which to deduce how these organisms may respond to CO₂-induced global warming. the nitrogen and phosphorus nutrient physiology of these organisms, together with its interaction with photosynthesis, needs to be studied especially in connection with the selection for coccolith forming individuals and the quantity and quality of the CaCO₃ deposited in the coccoliths. Without such data, it will not be possible to model the contributions that these microalgae may play in arresting the increase in levels of atmospheric CO₂.     

岷江干旱河谷灌木幼苗的土壤养分适应性研究

岷江上游干旱河谷地区的植被恢复是目前急需解决的问题,小马鞍羊蹄甲（Bauhinia faberi var. microphylla）是干旱河谷地区的优势乡土灌木,并作为当地植被恢复过程中的重要备选物种,因而进行小马鞍羊蹄甲种群在土壤贫瘠的干旱河谷的养分限制研究十分必要。针对性地进行施肥将影响到小马鞍羊蹄甲幼苗存活、生长和定殖,而如何有效提高该物种的存活和生长速率对于干旱河谷植被恢复将具有重要的意义。采用野外调查与模拟实验相结合的方法,分别研究了干旱河谷地区3个典型群落（干旱河谷的核心区——飞虹,干旱河谷灌丛与亚高山森林的过渡区——北部的石大关、干旱河谷灌丛与温性森林的过渡区——南部的蓝新镇）中小马鞍羊蹄甲幼苗叶片的化学计量特征,和施肥试验[w（有效氮）分别为100、280、460 mg·kg–1、w（有效磷）分别为12、24、48 mg·kg–1、w（氮）分别为40、70、100 mg·kg–1、w（磷）分别为12和24 mg·kg–1]中叶片化学计量特征及幼苗生长参数（叶片数、基径和株高）和各器官（根茎叶）生物量。结果表明：在野外各演替阶段的小马鞍羊蹄甲幼苗生物量和营养元素质量分数都随着磷肥的增加而增加,表明磷素是植物生长的限制因子,同时N∶P比均大于16,也暗示其受到P养分的限制;在室内施肥试验中,施加N肥没有促进小马鞍羊蹄甲生物量的积累,反而抑制了幼苗生长;施加P肥促进了幼苗生物量的积累,表明幼苗缺乏P元素,养分限制类型为P限制。     

黄土丘陵区撂荒农田土壤酶活性及酶化学计量变化特征

明确土壤胞外酶活性及酶化学计量比在农田撂荒过程中的变化特征及驱动因素,对揭示土壤养分可利用性随植被恢复的变化规律和阐明生态系统养分循环机制有重要意义.本文以黄土丘陵区不同撂荒年限坡耕地（0、10、20和30 a）为研究对象,通过测定土壤酶活性及酶计量比、土壤理化性质、植物多样性和科组成,探讨农田撂荒后土壤微生物养分限制状况及酶活性和酶计量比的主控因子.结果表明,β-1,4-N-乙酰氨基葡萄糖苷酶（NAG）、亮氨酸氨基肽酶（LAP）和碱性磷酸酶（ALP）的活性均随撂荒年限增加而显著增加,而β-1,4-葡萄糖苷酶（BG）活性则相反.土壤BG：（NAG+LAP）和BG：ALP呈现出与土壤BG活性相同的随撂荒年限增加而减小的趋势;而（NAG+LAP）：ALP呈先升后降趋势,在撂荒20 a时达到最高值.酶化学计量的向量长度随撂荒年限增加而显著减小,表明撂荒过程中土壤微生物受碳（C）限制程度的减弱.撂荒前10 a酶化学计量的向量角度小于45°,后20 a大于45°,说明撂荒前期微生物受氮（N）限制,后期受磷（P）限制.冗余分析结果揭示土壤有机碳含量、总氮含量、C：N、C：P、pH以及植被多样性是调控酶活性和酶计量比变化的主要因子.分类变异分析表明,土壤和植物因素可解释不同撂荒年限下土壤酶活性及酶计量比差异的62.0%,植被特征与土壤理化特性之间的交互作用是土壤酶活性及酶计量比变化的主控因子,解释度为37.1%.综上所述,黄土丘陵区农田撂荒过程中应考虑外源P的投入以缓解生态系统中有效P的不足,研究结果可为理解脆弱生境恢复生态系统中微生物介导的生物地球化学循环机制以及指导土壤养分管理和生态可持续发展提供理论依据.     

Modeling individual and population dynamics in a consumer–resource system: Behavior under food limitation and crowding and the effect on population cycling in Daphnia

In population modeling, a considerable level of complexity is often required to provide trustworthy results, comparable with field observations. By assuring sufficient detail at the individual level while preserving the potential to explore the consequences at higher levels, individual-based modeling may thus provide a useful tool to investigate dynamics at different levels of organization. Still, population dynamics resulting from such models are often at odds with observations from the field. This may be partly caused by a lack of focus on the individual dynamics under conditions of food stress and starvation. I developed a physiologically structured, individual-based simulation model to investigate life history of Daphnia and its effect on population dynamics in response to the productivity of the system. In verifying model behavior with available literature data on life history and physiology, I paid special attention to the dynamics of food intake and the verification of individual level results under conditions of food limitation and starvation. I show that the maximum filtering rates under low food levels used in the current model are much closer to measured filtering rates than the ones used in other models. Being consistent with results on physiology and life history from experiments at a wide range of food availability (including starvation), the model generates low amplitude or high amplitude population density cycles depending on the productivity of the system, as observed in field and experimental populations of Daphnia and with the minimum population densities being one to two orders of magnitude lower in the high amplitude than in the low amplitude cycles. To generate results which are not only qualitatively but also quantitatively comparable to experimental and field observations, however, a crowding effect on the filtering response has to be incorporated in the model.     

Use of trace element analysis of feathers as a tool to track fine-scale dispersal in birds

Tracking dispersal and migratory movements of animals over small and large spatial scales is a challenge. In birds, a promising yet underutilized tool is the trace elemental composition of feathers. The elemental profile of a feather may reveal information about the geographic origin of a bird provided that molting occurs on the breeding grounds and that elemental differences exist between breeding areas. Here, we explore the use of trace elemental composition in body feathers of the Puget Sound white-crowned sparrow Zonotrichia leucophrys pugetensis as a tool (1) to discriminate among birds collected in four different song dialect populations along a 400-km stretch of the Pacific Northwest coast and (2) to assign males singing nonlocal dialects in one population to potential natal populations. Inductively coupled plasma mass spectrometry detected 34 trace elements in sampled feathers and in a discriminant function analysis seven of these elements differed among the four source populations. Half of the six nonlocal dialect singers, who were likely to have immigrated into the focal population, were assigned to a population that matched their song dialect. Our study suggests that feather microchemistry is a promising tool for identifying geographic origins of dispersing birds over small geographic scales and in combination with other markers, such as song, may give insight into ecological and evolutionary processes.