Interacting effects of grass height and herbivores on the establishment of an encroaching savanna shrub

Shrub encroachment is a widely observed problem in Southern African savannas. Although the effects of herbivory and grass height on woody species recruitment have been studied individually, little information exists about how these factors interact. In this study seeds and seedlings of the encroaching shrub Dichrostachys cinerea were planted in clipped and unclipped grass plots, with and without large herbivores present. Seed germination, seedling survival and seedling predation were monitored for 8 months. Germination started earlier in plots where herbivores were excluded. Overall, the earlier the seeds germinated, the longer the seedlings survived. Clipping positively affected the number of germinated seeds, seedling growth and survival but effects varied among herbivore exclusion treatments and sites. Invertebrates caused the majority of the seedling damage. We conclude the recruitment of D. cinerea is influenced by the interplay of grass height and herbivory. In this study, the presence of large herbivores early in the wet season, and the absence of simulated grazing later on, affected the regeneration of D. cinerea negatively. However, differences in effects among sites suggest that the mechanisms found here may work differently in other habitats.      

Human Body-mass Index (Weight in kg/stature in m2) as a Useful Proxy to Assess the Relation between Income and Wildlife Consumption in Poor Rural Societies

There is growing interest in assessing how income influences the consumption of wildlife in poor rural areas of developing nations. The interest stems from the possibility of using income to contribute to the conservation of wildlife. Though promising, efforts have been hampered by the difficulty of obtaining accurate measures of income. We propose using human body-mass index (BMI: weight in kilograms/physical stature in m²), an indicator of short-term nutritional status, as a proxy variable for monetary income to estimate income elasticities of wildlife consumption (income elasticity: percent change in wildlife consumption/one-percent change income). The advantages of BMI over monetary income include a positive association with monetary income, ease of measurement, and absence of zero values. The assessment procedure was tested among Tsimane’ Amerindians, a society of foragers and farmers in the Bolivian Amazon. The population over 15 years of age (350 men and 322 women) in 13 villages was surveyed for five consecutive quarters (August 2002–November 2003). Income elasticities of wildlife consumption using BMI as a proxy for income ranged from −0.84 to −1.20. The estimates suggest that wildlife is a food item whose consumption declines with increasing income. Estimates of income elasticity of wildlife consumption using conventional indices of monetary income are negative, but lower and indistinguishable from zero owing to classical measurement errors of monetary income. The use of BMI to estimate income elasticities of wildlife consumption is promising, but requires further validation in different settings.     

Structure and biomass along an Acacia zanzibarica woodland–savanna gradient in a former ranching area in coastal Tanzania

Questions: What factors influence the density, size and growth form of trees in secondary Acacia zanzibarica woodlands on a former humid savanna rangeland? How does tree density relate to variation in tree foliage and spines, and woody and grass biomass? Location: Tropical coastal Tanzania (former Mkwaja Ranch, now in Saadani National Park). Methods: We surveyed 97 circular plots (4‐m radius) representing a gradient from open savanna to dense woodland. Within each plot, we measured all trees and estimated the biomass of spines. Foliage biomass of tree and grass layers was estimated on three occasions, twice during the wet season and once in the dry season. Soil samples were taken from each plot and analysed for texture and nutrient content. Interrelationships among various variables were investigated using linear multiple regression and mixed effects models. Results: Tree densities were highest on more nutrient‐rich, heavy soils. Spinescence was highest on trees in open savanna. Biomass of tree foliage in the wet season was best explained by numbers of ant nests and tree live‐wood ratio. Foliage biomass in the dry season was less than half that in the wet season and best predicted by grass biomass. Variables related to biomass of the grass layer were strongly influenced by fire; living grass biomass also decreased with increasing tree density. Conclusions: A. zanzibarica is a tree with a high water demand, and the association with heavy soils is probably due to greater availability of water on these sites. Establishment of A. zanzibarica woodlands significantly reduced grazing resources at Mkwaja Ranch. Under post‐ranching conditions, however, fires and soil conditions predominate. The woodlands may, therefore, represent a transient state of woody density in a still resilient humid savanna.     

Effects of parents and Brown‐headed Cowbirds (Molothrus ater) on nest predation risk for a songbird

Nest predation limits avian fitness, so ornithologists study nest predation, but they often only document patterns of predation rates without substantively investigating underlying mechanisms. Parental behavior and predator ecology are two fundamental drivers of predation rates and patterns, but the role of parents is less certain, particularly for songbirds. Previous work reproduced microhabitat‐predation patterns experienced by Yellow Warblers (Setophaga petechia) in the Mono Lake basin at experimental nests without parents, suggesting that these patterns were driven by predator ecology rather than predator interactions with parents. In this study, we further explored effects of post‐initiation parental behavior (nest defense and attendance) on predation risk by comparing natural versus experimental patterns related to territory density, seasonal timing of nest initiation, and nest age. Rates of parasitism by Brown‐headed Cowbirds (Molothrus ater) were high in this system (49% nests parasitized), so we also examined parasitism‐predation relationships. Natural nest predation rates (NPR) correlated negatively with breeding territory density and nonlinearly (U‐shaped relationship) with nest‐initiation timing, but experimental nests recorded no such patterns. After adjusting natural‐nest data to control for these differences from experimental nests other than the presence of parents (e.g., defining nest failure similarly and excluding nestling‐period data), we obtained similar results. Thus, parents were necessary to produce observed patterns. Lower natural NPR compared with experimental NPR suggested that parents reduced predation rates via nest defense, so this parental behavior or its consequences were likely correlated with density or seasonal timing. In contrast, daily predation rates decreased with nest age for both nest types, indicating this pattern did not involve parents. Parasitized nests suffered higher rates of partial predation but lower rates of complete predation, suggesting direct predation by cowbirds. Explicit behavioral research on parents, predators (including cowbirds), and their interactions would further illuminate mechanisms underlying the density, seasonal, and nest age patterns we observed.     

The Invasive <Emphasis Type="Italic">Buddleja davidii</Emphasis> (Butterfly Bush)

Buddleja davidii Franchet (Synonym. Buddleia davidii; common name butterfly bush) is a perennial, semi-deciduous, multi-stemmed shrub that is resident in gardens and disturbed areas. Since its introduction to the United Kingdom from China in the late 1800s, B. davidii has become an important component in horticulture and human culture. Despite its popularity as a landscape plant, B. davidii is considered problematic because of its ability to naturalize outside of gardens and rapidly invade and dominate disturbed natural areas across a wide range of physical conditions. The primary goal of this paper is to synthesize what is known about B. davidii in order to understand the impacts caused by the continued presence of B. davidii in gardens and natural landscapes. We also address management of B. davidii and discuss the repercussions of management strategies and policies currently implemented to protect or remove B. davidii from natural ecosystems.

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Zusammenfassung   Buddleja davidii Franchet (Synonym Buddleia davidii, umgangsprachlich “Schmetterlingsflieder”) ist ein ausdauernder, halb-immergruener, mehrstaemmiger Busch welcher in Gaerten und auf Umbruchflaechen gedeiht. Seit seiner Einfuehrung in die UK aus China im spaeten 19. Jahrhundert hat B. davidii in Pflanzenzucht und Kultivierung stark an Bedeutung gewonnen. Unabhaengig von seiner Beliebtheit in der Landschaftsgestaltung stellt B. davidii wegen seiner Faehigkeit, sich ueber Gartengrenzen hinaus unter einer Vielzahl von Wachstumsbedingungen in gestoerten Naturgebieten schnell auszubreiten und dort die einheimische Flora zu dominieren, ein grosses Problem dar. Das Ziel der vorliegenden Rezension ist es eine Synopsis zu erstellen, welche die Auswirkungen und Gefahren der konstanten Praesenz von B. davidii in Gaerten und der Naturlandschaft verdeutlicht. Management Optionen und -Fehlschlaege sowie aktuelle Regulationen zu dem Zwecke B. davidii aus natuerlichen Ecosystemen zu entfernen oder sein vordringen zu verhindern, werden ebenfalls diskutiert.

     

四川成都发现布氏苇莺和中国鸟类新纪录栗尾姬鹟

2016年4月20日和2017年2月15日先后在成都市区分别记录到了栗尾姬鹟(Ficedula ruficauda)和布氏苇莺(Acrocephalus dumetorum)两种鸟类。经查阅相关文献,确定上述两种鸟类均为四川省鸟类新纪录,其中栗尾姬鹟还是中国鸟类新纪录。     

Micropropagation of Ceratopetalum gummiferum, an important Australian cut flower corp

Summary Ceratopetalum gummiferum Sm. ‘Albery's Red’ (NSW Christmas Bush), a native to eastern Australia, has become an important commercial plant in both the export and domestic markets. A protocol for in vitro culture was investigated for rapid clonal propagation of selected cultivars. Murashige and Skoog medium, supplemented with various concentrations of 6-benzylaminopurine, kinetin, 6(γ,γ-dimethylallylamino)-purine or zeatin were examined for their effects on multiplication. The most successful treatments were 2.2 μM 6-benzylaminopurine and 11.6 μM kinetin which increased shoot number and explant weight. Although zeatin and 6(γ,γ-dimethylallylamino)-purine increased shoot length, both failed to increase multiplication rates. However, hyperhydricity was found to be a serious physiological disorder in tissue culture of C. gummiferum ‘Albery's Red’. Rooting in vitro was also examined with indole-3-butyric acid and naphthalene acetic acid, the most successful being 4.9 mM indole-3-butyric acid. The development of an in vivo rooting protocol, however, may prove to be essential for the commercial production of this plant.     

Plasticity of the Rufous-winged Sparrow, Aimophila carpalis, song control regions during the monsoon-associated summer breeding period

In most temperate zone songbirds, exposure to increasing photoperiod in the spring stimulates the reproductive system and induces reproductive behaviors. Additionally, the brain regions that control singing (song control regions; SCRs) are larger during the breeding season, thus paralleling changes in the activity of the reproductive system. However, in some birds, environmental factors other than photoperiod initiate breeding. For example, free-living male Rufous-winged Sparrows develop their testes in March due to increasing photoperiod, but have relatively low plasma T until after they begin to breed, usually in July, during the monsoon period when day length is declining. We tested the hypothesis that SCRs grow and singing behavior increases after the monsoon rains begin. We captured adult male Rufous-winged Sparrows in July 2002, 7 days before and 20 days after the monsoon rains began, euthanized birds in the field, collected their brains, and measured SCR volumes from sections immunostained for the neuronal marker NeuN. In June and July 2006, we measured song rates in the field before and after the monsoon rains. SCR volumes were larger and singing behavior increased after the onset of the monsoon rains, coinciding with the initiation of breeding. Unlike in other species studied so far, SCR volumes grew as day length was decreasing. Comparative studies utilizing species that do not breed when day length is increasing may provide information on the relative contributions of various environmental factors to SCR neuroplasticity.     

四川瓦屋山金色林鸲的巢址选择和繁殖记录

2010~2011年4~7月,在四川省瓦屋山自然保护区对金色林鸲(Tarsiger chrysaeus)的繁殖生态和巢址选择进行了研究。共发现26巢,金色林鸲2010年和2011年的繁殖成功率分别为43.8%和44.4%,孵化率分别为52.5%和60.0%;育雏成功率分别为85.7%和100.0%。主成分分析表明,影响金色林鸲巢址选择的主要因子包括巢位因素、苔藓盖度因素和乔木郁闭度因素。步道两侧的土坎为金色林鸲巢址选择提供了适宜条件。在瓦屋山,人类活动是影响金色林鸲繁殖、巢址选择、巢的分布和数量的重要因素,并存在两面性;人行步道的修建为金色林鸲提供了更多适宜的巢址,而游客的频繁活动限制了金色林鸲的繁殖活动。