Establishment of the biological control agent Hypocosmia pyrochroma for Dolichandra unguis-cati (Bignoniaceae) is limited by microclimate

Cat's claw creeper, Dolichandra unguis-cati (Bignoniaceae), a perennial woody vine native to tropical America, is a target for biological control in Australia and South Africa. The cat's claw creeper leaf-tying moth Hypocosmia pyrochroma (Lepidoptera: Pyralidae) from tropical South America was released as a biological control agent for cat's claw creeper in Australia from 2007 to 2010. A total of 2,277 adults, 837 pupae and 77,250 larvae were released at 40 sites in Queensland and New South Wales. Releases were made mostly in open fields (85%), and at limited sites (15%) in insect-proof cages erected over naturally occurring cat's claw creeper infestations in the field. Sampling was conducted annually in spring and autumn to monitor the establishment and dispersal of H. pyrochroma. Establishment of H. pyrochroma was first noticed in 2012 at three release sites and since then the number of established sites has increased to 80 in 2020. Establishment was evident on both ‘short-pod’ and ‘long-pod’ forms of cat's claw creeper and was more widespread in sites where releases were made within insect-proof field cages (50%) than in sites with open field releases (9%). The moth was active from late spring to late autumn with peak larval activity in late summer. To date, all field establishments have been in areas predicted by a CLIMEX model as climatically suitable but restricted mostly to riparian environment (93% of establishment), where the moth has continued to spread from 1.5 to 23 km from release sites. In contrast, there is the only limited establishment and spread in non-riparian corridors, highlighting the role of microclimate (riparian) as a limiting factor for establishment and spread. Future efforts will focus on redistribution of the agent to river/creek systems where the moth is currently not present.     

Water sources of Populus euphratica and Tamarix ramosissima in Ejina Delta,the lower reaches of the Heihe River,China

Aims We aim to evaluate the water sources of typical riparian arbor species (Populus euphratica) and shrub species (Tamarix ramosissima), and analyze the spatial and temporal dynamics of plant water source in Ejina Delta, the lower reaches of the Heihe River, China.Methods Eight sampling sites were selected in the riparian zones along the East River and West River in Ejina. The plant xylem water, soil moisture, rainwater, stream water and groundwater were taken and pretreated during the growing season in 2015-2016, and the stable oxygen isotope ratio (δ¹⁸O) for each water sample was measured. The δ¹⁸O of plant xylem water and soil moisture were compared to estimate the dominant depth of root water uptake, and the linear-mixed model called “IsoSource” were applied to determine plant water sources and quantify their proportions.Important findings This study indicated that the main recharge sources for P. euphratica and T. ramosissima were stream water and groundwater. The contributions of rain water to them was negligible due to the limited amount and the shallow infiltration depth of local rainfall. As affected by groundwater level fluctuation, soil physical properties, as well as lateral and vertical recharge of stream water on soil moisture, the dominant depth of root water uptake spatially varied. However, the relative contributions of stream water or groundwater to plant water sources did not change significantly across space. Populus euphratica used more stream water (68%), while T. ramosissima used more groundwater (65%). Plant water sources were sensitive to environmental flow controls. The contributions of stream water to the water sources of the two species went up to 84% and 48% for P. euphratica and T. ramosissima respectively during the discharge period, but dropped to 63% and 30% during the non-discharge period. On the other hand, the contributions of groundwater decreased to 16% and 52% during the discharge period, but increased to 37% and 70% during non-discharge period. It is noteworthy that the high similarity of δ¹⁸O between stream water and groundwater due to extensive water exchange in the riparian zone made increase the uncertain in quantifying plant water sources.     

Restoration and management of riparian ecosystems: a catchment perspective

1. We propose that strategies for the management of riparian ecosystems should incorporate concepts of landscape ecology and contemporary principles of restoration and conservation. A detailed understanding of the temporal and spatial dynamics of the catchment landscape (e.g. changes in the connectivity and functions of channel, riparian and terrestrial components) is critical. 2. This perspective is based upon previous definitions of riparian ecosystems, consideration of functional attributes at different spatial scales and retrospective analyses of anthropogenic influences on river catchments. 3. Restoration strategies must derive from a concise definition of the processes to be restored and conserved, recognition of social values and commitments, quantification of ecological circumstances and the quality of background information and determination of alternatives. 4. The basic components of an effective restoration project include: clear objectives (ecological and physical), baseline data and historical information (e.g. the hydrogeomorphic setting and the disturbance regime), a project design that recognizes functional attributes of biotic refugia, a comparison of plans and outcomes with reference ecosystems; a commitment to long-term planning, implementation and monitoring and, finally, a willingness to learn from both successes and failures. 5. Particularly important is a thorough understanding of past natural disturbances and human-induced changes on riparian functions and attributes, obtained by a historical reconstruction of the catchment.     

Return of Salmon-Derived Nutrients from the Riparian Zone to the Stream during a Storm in Southeastern Alaska

Spawning salmon deliver nutrients (salmon-derived nutrients, SDN) to natal watersheds that can be incorporated into terrestrial and aquatic food webs, potentially increasing ecosystem productivity. Peterson Creek, a coastal watershed in southeast Alaska that supports several species of anadromous fish, was sampled over the course of a storm during September 2006 to test the hypothesis that stormflows re-introduce stored SDN into the stream. We used stable isotopes and PARAFAC modeling of fluorescence excitation–emission spectroscopy to detect flushing of DOM from salmon carcasses in the riparian zone back into a spawning stream. During the early storm hydrograph, streamwater concentrations of NH₄–N and total dissolved phosphorus (TDP), the fluorescent protein tyrosine and the δ¹⁵N content of DOM peaked, followed by a rapid decrease during maximum stormflow. Although δ¹⁵N has previously been used to track SDN in riparian zones, the use of fluorescence spectroscopy provides an independent indicator that SDN are being returned from the riparian zone to the stream after a period of intermediate storage outside the stream channel. Our findings further demonstrate the utility of using both δ¹⁵N of streamwater DOM and fluorescence spectroscopy with PARAFAC modeling to monitor how the pool of streamwater DOM changes in spawning salmon streams.     

基于生态系统服务重要性和生态敏感性的广东省生态安全格局构建

生态空间结构合理有序是区域赖以生存和发展的基础和保障,构建省域生态安全格局,优化生态空间结构,有利于提高生态环境的承载力并促进社会经济与生态环境的协同互惠关系,实现可持续发展。以广东省为例,通过重要性-敏感性的生态评估方法识别广东省重要的生态源地,使用最小阻力模型识别重要生态廊道,构建生态安全格局,并对生态空间结构的调整和管控提出策略。结果表明：（1）重要的生态源地面积为54636.77 km²,占广东省国土面积的25.04%;（2）研究所识别的生态源地与广东省生态红线和自然保护地的重合程度较高,在自然保护地和生态源地的基础上共选出87处重要生态源地;（3）广东省生态廊道的总长度为7400 km,廊道周边的主要以林地为主;（4）广东省的生态空间主要以环珠三角生态屏障和外围生态屏障为主,其中环珠三角生态屏障的面积、生态重要性略高于北部生态屏障。所构建的生态安全格局可以为广东省的生态安全保护和可持续发展提供参考,也可以为完整生态保护体系的构建提供政策导向。     

Plant distribution and dispersal mechanisms at the Hassayampa River Preserve, Arizona, USA

This study focuses on the relationships between plant dispersal syndromes and plant distributions at the community scale. Species composition and cover are reported from 29 10 × 20-m vegetation plots along five topographic cross-sections in the riparian zone of the Hassayampa River Preserve, Arizona. We find that spatial patterns of dispersal guilds vary within the flood plain of this semiarid region river. Our main results are: (1) wind-dispersed species are fairly evenly distributed at all elevations and distances from the river, whereas cover of animal-dispersed species increases with elevation above, and at greater distances from, the river; (2) wind-dispersed species are proportionally more abundant in the pioneer Populus–Salix community, whereas plants in the late-seral Prosopis community are predominantly animal-dispersed; (3) most of the species classified as obligate-wetland and facultative-wetland are wind-dispersed, whereas facultative-upland and obligate-upland species are mostly animal-dispersed; and (4) there are significantly fewer wind-dispersed species in areas of high total vegetation cover. These results may reflect successional patterns resulting from periodic flooding. Low areas close to the river flood more frequently and with greater intensity than areas farther from the river. Many pioneer species that establish in disturbed areas are wind-dispersed. Over successional time, pioneer species cede to more drought tolerant species that are predominantly animal-dispersed.     

Microhabitat Characteristics of Preble's Meadow Jumping Mouse High-Use Areas

ABSTRACT Riparian wetlands are complex ecosystems containing species diversity that may easily be affected by anthropogenic disturbances. Preble's meadow jumping mouse (Zapus hudsonius preblei) is a federally threatened subspecies dependent upon riparian wetlands along the Front Range of Colorado and southeastern Wyoming, USA. Although habitat improvements for Preble's meadow jumping mouse are designed at multiple spatial scales, most knowledge about its habitat requirements has been described at a landscape scale. Our objective was to improve our understanding of Preble's meadow jumping mouse microhabitat characteristics within high-use areas (hotspots), which are essential for the development of effective management and conservation strategies. We evaluated Preble's meadow jumping mouse habitat by describing areas of high use and no use as determined from monitoring radiocollared individuals. A comparison of microhabitat characteristics from random samples of high-use and no-use areas indicated that mice use areas closer to the center of the creek bed and positively associated with shrub, grass, and woody debris cover. Distance to center of the creek bed, and percent of shrub and grass cover also had the greatest relative importance of habitat variables modeled when describing high-use areas. High-use areas contained 3 times more grass cover than forb cover, and overall had a greater proportion of wetland shrub and grass cover. However, proportion of cover type (shrub or grass) did not vary greatly between high-use and no-use areas. Our results suggest that management and conservation efforts should continue to focus on establishment of native wetland vegetation near streams and creeks. For example, vegetation should include shrubs such as willow (Salix spp.), narrowleaf cottonwood (Populus angustifolia), alder (Alnus incana), grasses such as fescue (Fescue spp.), sedges (Carex spp.), and rush (Juncus spp).     

Comparing transect survey and WSR‐88D radar methods for monitoring daily changes in stopover migrant communities

ABSTRACT For decades, researchers have successfully used ground‐based surveys to understand localized spatial and temporal patterns in stopover habitat use by migratory birds. Recent technological advances with WSR‐88D radar now allow such investigations on much broader spatial scales. Both methods are assumed to accurately quantify patterns in migrant bird communities, yet information is lacking regarding relationships between radar estimates of migration and different ground‐based monitoring methods. From 2005 to 2007, we monitored migrant communities on or near two Department of Defense installations in the spring (Ft. Polk Military Complex, LA; U.S. Army Test and Evaluation Command, Yuma Proving Ground, AZ) and on two installations in the fall (Ft. Polk Military Complex, LA; Eglin Air Force Base, FL) using both ground‐based transect surveys and radar imagery of birds aloft. We modeled daily changes in migrant abundance and positive and negative species turnover measured on the ground as a function of radar estimates of migrant exodus and input densities. Radar data were not significant predictors of any response variable in any season either in the southeastern or southwestern United States, indicating a disparity between the results obtained using different methods. Multiple unique sources of error associated with each technique likely contributed to the conflicting outcomes, and researchers should take great care when selecting monitoring methods appropriate to address research questions, effects of management practices, or when comparing the results of migration studies using different survey techniques.     

文峪河上游河岸林群落类型及其生态适应性

以文峪河上游河岸林为研究对象,采用TWINSPAN法对研究地区河岸林进行群落分类,对各群落类型特征进行分析.在提出河岸林群落生态功能适应性指标的基础上,对研究地区河岸林群落进行生态功能适应性分组.通过研究,文峪河上游河岸林可划分为阔叶混交林、华北落叶松阔叶混交林、云杉落叶松混交林、云杉阔叶混交林、阔针混交林、油松阔叶混交林、青杨林、沙棘灌丛和柳树灌丛等9个群落类型,但群落类型之间的分异性总体表现不高,且表现出突出的多样性特征;群落乔木层和灌木层的物种组成复杂,草本层多为一些耐干扰种和耐水湿种,总体上越远离河岸,高地群落中的物种比例越高,表现出高地森林与河流之间生态过渡带的典型特点和河岸带生态环境的高度异质性;根据本文构建的群落的生态功能适应性指标,研究地区9个河岸林群落类型可以划分为强入侵性功能组、中等入侵性功能组、弱入侵性功能组和高逃避性功能组等4个生态适应性功能组,不同生态适应性功能组的群落中,乔木层和灌木层的主要物种具有明显不同的生态对策,而草本层物种的差异不明显.