Impact of grassland contract policy on soil organic carbon losses from alpine grassland on the Qinghai–Tibetan Plateau

Carbon storage in the soils on the Qinghai–Tibetan Plateau plays a very important role in the global carbon budget. In the 1990s, a policy of contracting collective grasslands to smaller units was implemented, resulting in a change from the traditional collective grassland management to two new management patterns: a multi‐household management pattern (MMP: grassland shared by several households without enclosures) and a single‐household management pattern (SMP: grassland enclosed and used by only one household). In 2016, 50 MMP and 54 SMP winter pastures on the Qinghai–Tibetan Plateau were sampled to assess the differences in soil organic carbon (SOC) between the two management patterns. Results showed that average SOC was significantly greater under MMP than under SMP, with an estimated 0.41 Mg C/ha/yr lost due to SMP following the new grassland contract. Based on the government's grassland policy, four grassland utilization scenarios were developed for both summer and winter pastures. We found that if the grassland were managed under SMP, likely C losses ranged between 0.31 × 10⁷ and 6.15 × 10⁷ Mg C/yr across the Qinghai–Tibetan Plateau relative to MMP, which more closely resembles pre‐1990s grassland management. Previous estimates of C losses have only considered land use change (with cover change) and ignored the impacts driven by land management pattern changes (without cover change). The new data suggest that C losses from the Qinghai–Tibetan Plateau are greater than previously estimated, and therefore that the grassland contract policy should be reviewed and SMP households should be encouraged to reunite into the MMP. These findings have potential implications for land management strategies not only on the Qinghai–Tibetan Plateau but also other grazing regions globally where such practices may exist.     

The importance of native valley oaks (Quercus lobata) as stopover habitat for migratory songbirds in urban Sacramento,California, USA

Urban development occupies over 375,000 ha (6%) of California's Central Valley, and expansion continues to displace natural and agricultural landscapes. The value of urban areas as habitat for native wildlife and the characteristics that determine its value, however, remain little studied. Many Neotropical migrant passerine bird species are declining due to changes in breeding, migratory, and wintering habitats and climatic conditions. During 2010–2013, we evaluated the importance of native valley oak (Quercus lobata) as stopover foraging habitat used by Neotropical migrant birds in urban areas of the Sacramento region in California, USA. Over 3 years, we surveyed spring and late summer-early fall migrant songbirds and measured tree canopy cover within 31 c.0.91 ha transects in Curtis Park, an older residential neighborhood. We detected 607 individuals from 20 migrant species, but four wood warblers comprised the bulk of observations: black-throated gray (Setophaga nigrescens), Wilson's (Cardellina pusilla), orange-crowned (Oreothlypis celata), and yellow warblers (Setophaga petechia). Migrant abundance was closely correlated with valley oak canopy abundance and increased linearly with oak canopy especially during fall migration. Migrants were nearly absent from areas lacking oak canopy. Migrant bird species as a group also foraged in valley oak substantially more often (74%) than would be expected based on its 15% relative canopy cover (χ²_1d.f. = 924, p < 0.0001), as did all species whose selectivity could be tested. These results are important in demonstrating previously undocumented migrant use of urban areas with remnant valley oak canopy and suggest that protecting existing valley oaks and increasing their use in future urban forestry and landscape plantings in the Central Valley could provide substantial habitat benefits for native migratory birds.     

The ecosystem services concept: a new Esperanto to facilitate participatory planning processes?

Landscape Ecology - Several case studies investigated the role of ecosystem services in participatory planning processes. However, no systematic study exists that cuts across a large number of...     

The routes to fruit: Governance of urban food trees in Canada

Interest in planting urban food trees (UFTs) in public spaces is growing in popularity as a form of urban greening and a potential food source. Currently there is minimal research on the governance and policy aspects of integrating food trees into cities. To fill this gap, we investigated the characteristics of UFT site governance and how it compares to current urban forest governance. Semi-structured interviews were conducted with relevant municipal officials in Calgary, Edmonton, Toronto and Victoria about their perspectives and involvement with UFT sites in their city. A scan of policy documents was completed to supplement the interviews. The interviews were analyzed using a deductive coding framework based on the Policy Arrangement Approach. We found that key actors at the UFT sites were local organizations and site champions, with minimal municipal engagement. Most site resources provided by municipalities were in-kind. There are also basic knowledge gaps about how to care for UFTs. Currently municipal by-laws prohibit the harvesting and removal of plant material, and are at odds with the purpose of UFT sites, with few municipalities fully integrating UFTs in policies. The primary discussion around UFTs centre concerns for public health and safety, management, and use of public space with limited discussions of benefits. This research demonstrates the value of co-governance models to support UFTs, while a shift in focus from risks to benefits could encourage additional resources and policy integration. Further, including UFTs into policy would also support foraging and food tree maintenance in public spaces, and more fully reflect the plurality of urban forest engagement.     

Micro-scale heterogeneity in urban forest soils affects fine root foraging by ornamental seedlings of Buddhist pine and Northeast yew

Urban soils are frequently characterized by a strong heterogeneity caused by intense anthropogenic activity and land use changes. Soil heterogeneity is commonly known to affect tree root development, but little has been detected concerning root foraging by ornamental trees in heterogeneous urban soils at micro-scale. In this study, Buddhist pine [Podocarpus macrophyllus (Thunb.) D. Don] and Northeast yew (Taxus cuspidata S. et Z.) were selected as ornamental tree species for a two-year study. In the first-year, seedlings were cultured under contrasting photoperiods to generate different morphologies. In the second year, seedlings were transplanted to pots filled with soils collected from an urban forest. Controlled-release fertilizers (N-P₂O₅-K₂O, 14-13-13) were evenly broadcasted to a half patch of the pot (heterogeneity) or to both halves (homogeneity) on the surface 5 cm beneath the pot-top at the rate of 0.135 g N seedling⁻¹. In the fertilized heterogeneous patch, larger Buddhist pine seedlings had greater dry weight, length, surface area, volume, number of tips, and morphological foraging-precision in fine roots. Compared to Northeast yew seedlings under natural photoperiod in the first year, those under the extended photoperiod had larger size, greater fine root biomass, and length but lower foraging-precision in the second year. N and P concentrations in second-year fine roots mainly increased with the availability of patches generated by fertilization for both species. In conclusion, the ability to forage for nutrients by ornamental tree seedlings in heterogeneous urban forest soils was species-specific. Buddhist pine seedlings had higher foraging precision in heterogeneous urban soils than Northeast yew seedlings due to their response to the extended photoperiod during culture.     

Allergenic pollen of ornamental plane trees in a Mediterranean environment and urban planning as a prevention tool

Green spaces and urban green infrastructure are new concepts in urban planning, and lately, the influence of green spaces in cities and how this presence affects local climate change have been taken into account. Moreover, some of the ornamental trees most used in cities provoke allergic symptoms in sensitized people. Due to the importance the plane trees in our parks and cities have as ornamental trees, this article assesses the urban Platanus airborne pollen concentration in the air of five cities of the SW Iberian Peninsula and tries to determine the differential factors that its distribution has by means of combining continuous monitoring of the air using volumetric spore traps and the geolocation of plane trees. They were counted separately according to the direction (Q1 NE, Q2 SE, Q3 SW, Q4 NW) around the spore trap location in circles of 100, 200, 300, 400, 500, 1000, 1500, 2000 and 2500 m in diameter. Pollen sums were distributed according to the predominant wind direction for each day. The highest concentrations for Platanus pollen were recorded in Don Benito. Differences amongst pollen stations were found and were mainly related to their degree of maturity and their proximity to spore traps, and finally, with the number of plane trees. Furthermore, other factors, as the pruning, which is different in each city and even in a more local way, affects pollination and is frequently unknown to aerobiological studies. The geolocation of ornamental trees can be a useful tool for providing summarized information about their behavioral differences amongst cities, which can be used to create healthy itineraries, minimizing the natural hazards in human health (allergic diseases) and could be implemented into a model to help policy-makers to create measures to improve green urban development.     

Community structure of arbuscular mycorrhizal fungi associated with Robinia pseudoacacia in uncontaminated and heavy metal contaminated soils

The significance of arbuscular mycorrhizal fungi (AMF) in soil remediation has been widely recognized because of their ability to promote plant growth and increase phytoremediation efficiency in heavy metal (HM) polluted soils by improving plant nutrient absorption and by influencing the fate of the metals in the plant and soil. However, the symbiotic functions of AMF in remediation of polluted soils depend on plant–fungus–soil combinations and are greatly influenced by environmental conditions. To better understand the adaptation of plants and the related mycorrhizae to extreme environmental conditions, AMF colonization, spore density and community structure were analyzed in roots or rhizosphere soils of Robinia pseudoacacia. Mycorrhization was compared between uncontaminated soil and heavy metal contaminated soil from a lead–zinc mining region of northwest China. Samples were analyzed by restriction fragment length polymorphism (RFLP) screening with AMF-specific primers (NS31 and AM1), and sequencing of rRNA small subunit (SSU). The phylogenetic analysis revealed 28 AMF group types, including six AMF families: Glomeraceae, Claroideoglomeraceae, Diversisporaceae, Acaulosporaceae, Pacisporaceae, and Gigasporaceae. Of all AMF group types, six (21%) were detected based on spore samples alone, four (14%) based on root samples alone, and five (18%) based on samples from root, soil and spore. Glo9 (Rhizophagus intraradices), Glo17 (Funneliformis mosseae) and Acau3 (Acaulospora sp.) were the three most abundant AMF group types in the current study. Soil Pb and Zn concentrations, pH, organic matter content, and phosphorus levels all showed significant correlations with the AMF species compositions in root and soil samples. Overall, the uncontaminated sites had higher species diversity than sites with heavy metal contamination. The study highlights the effects of different soil chemical parameters on AMF colonization, spore density and community structure in contaminated and uncontaminated sites. The tolerant AMF species isolated and identified from this study have potential for application in phytoremediation of heavy metal contaminated areas.