Ecological disturbances due to high cutback in the green infrastructure of Karachi: Analyses of public perception about associated health problems

This paper evaluates the changes to the green infrastructure of the megacity of Karachi, Pakistan, occurring during a period of rapid development, involving extensive loss of trees and green spaces since 2000, occurring as a consequence of road widening and improvements to the city's transport infrastructure, aggravated by a series of cyclones, involving further tree loss and which has led to numerous ecological problems in the city, assessing how the effect of the reduction of Karachi's green infrastructure has impacted both the reality and the perception of human health conditions. It uses medium-resolution satellite images classified for land use and land cover (LULC) data extraction and detailed field surveys to map the extent of change; structured questionnaires are used to identify the perception of selected, targeted groups regarding the state of Karachi's urban green infrastructure and perceived human health conditions. Findings indicate that the public perception of green space functionality or presence does not equate with the remote sensing and field mapping results, which show a dramatic loss. The need to develop a comprehensive urban greening strategy, which considers the needs and priorities of the population, is identified. The impact of such a strategy in terms of increased frequency of visits to green sites and associated increase in the physical activity of the people to improve overall physical health is discussed in relation to the general development of Karachi.     

Vertical farming: a summary of approaches to growing skywards

Pressure on agricultural land from a rising global population is necessitating the maximisation of food production per unit area of cultivation. Attention is increasingly turning to Vertical Farming (VF) approaches in an attempt to provide a greater crop yield per square meter of land. However, this term has been used to cover a broad range of approaches, from personal- or community-scale vegetable and herb growing to vast skyscrapers for commercial production of a wide range of crops. This article summarises the main categories of VF in order to help clarify this emerging but sometimes confusing area of agriculture and discusses how scientific investigation of the potential of VF is currently lacking and will be required to help determine its feasibility as a method to assist meaningfully in global food production.     

Quantifying the agricultural landscape and assessing spatio-temporal patterns of precipitation and groundwater use

Quantitative agricultural landscape indices are useful to describe functional relationships among climatic conditions, groundwater dynamics, soil properties and agricultural land use for mathematical models. We applied methods of regression statistics, variance component estimation and a Geographical Information System (GIS) to construct indices describing crops and soils and to establish functional relationships among these variables. This paper describes the development of indices and the partitioning of the spatial and temporal variation in groundwater models using the data from Tulare County, California, which was selected as the study area. Indices of ground surface elevation, total crop water demand, soil water infiltration rate, and soil production index explain 91% of the variation in average spring groundwater level. After relating spatial patterns of groundwater use to indices of crop and soil properties, we found that mean groundwater use is positively related to total crop water demand and soil water infiltration rate while the variation in groundwater use was negatively correlated with the crop water demand and soil water infiltration rate and positively related to soil water holding capacity. The spatial variation in groundwater use was largely influenced by crops and soil types while the temporal variation was not. We also found that groundwater use increased exponentially with decreasing annual precipitation for most townships. Based on these associations, groundwater use in each township can be forecast from relative precipitation under current methods of agricultural production. Although groundwater table depth is strongly affected by topography, the statistically significant indices observed in the model clearly show that agricultural land use influences groundwater table depth. These simple relationships can be used by agronomists to make water management decisions and to design alternative cropping systems to sustain agricultural production during periods of surface water shortages.     

The effects of land tenure and land use on the urban forest structure and composition of Melbourne

The urban forest provides valuable ecosystem services for enhancing human well-being. Its structure and composition determine the quantity and quality of these services. There has been little research on the heterogeneity in structure and composition of urban forests in the Australasian region, especially in the centre of a highly dynamic and rapidly urbanizing city. This paper quantifies the structure and the composition of the urban forest of Melbourne, Australia's city centre. The effects of land tenure and land use on the heterogeneity of canopy cover, tree density and canopy size were explored. Species and family composition by land use, land ownership and street type were also analysed using the Shannon–Wiener and Jaccard similarity indices. Most of the canopy cover in the city centre is located on public land and is unevenly distributed across the municipality. The mean canopy cover (12.3%) is similar to that found for whole city studies around the world, which often include peri-urban forests. Similarly to other cities, structure varied across different land uses, and tree size, density and cover varied with land tenure and street type. The diversity index shows that the urban forest is rich in species (H′ = 2.9) and is dominated by native species. Improving the distribution, and increasing tree cover and variety of species will result in a more resilient urban centre, able to provide multiple ecosystem services to their residents and its large population of visitors and workers. The study of the urban centre provides further understanding of compact city morphologies, and allows inter-city comparison independent of the size.     

Agricultural expansion: land use shell game in the U.S. Northern Plains

Land area planted to row crops has expanded globally with increased demand for food and biofuels. Agricultural expansion in the Dakota Prairie Pothole Region (DPPR), USA affects a variety of agricultural and non-agricultural land-use types, including grasslands and wetlands that provide critical wildlife habitat and other ecosystem services. The purpose of this study was to quantify recent changes in rural land cover/land use, analyze trends, and interpret results in relation to climate, agronomic practice, and ethanol production. The primary data sources were 1980–2012 statewide cropland data from the U.S. Department of Agriculture (USDA) National Agricultural Statistics Service, and the USDA Cropland Data Layer, produced annually for the DPPR from 2006 through 2012. Area planted to corn or soybean row crops increased, and small grain (e.g., wheat, barley) area decreased significantly over the analysis period. Corn and soybean expanded by 27 % in the DPPR between 2010 and 2012 alone, an areal increase (+15,400 km²) larger than the U.S. state of Connecticut. This expansion displaced primarily small grains and grassland (e.g., pastures, haylands, remnant prairies). Grassland regularly exchanged land with corn and soybean, small grains, and wetlands and water. Corn and soybean had high inter-annual self-replacement values (68–80 %), and continuous corn/soy row cropping was the second most common combination over a three-year period, ranking after continuous grassland. Small grain self-replacement values were only 22–35 %, indicating frequent relocation in the landscape. Temporary gains in wetland and grassland area were attributed to unusually wet climatic conditions and late snowfalls that prevented crop planting. Nearly all of the region’s ethanol refineries were located where corn and soybean crops constituted 50 % or more of the land area. Quantification of grassland losses in the U.S. Northern Plains requires evaluation of all land uses that interact with grasslands, and a longer term perspective that incorporates grassland as part of a normal land-use rotation.     

The impact of pruning and mortality on urban tree canopy volume

Urban trees provide a wide range of ecosystem services for city residents, with tall, mature trees with wide crowns generally regarded as preferable. The tree biomass which is responsible for shading, pollution removal, rain runoff retention etc. gets periodically reduced by the municipal tree management practice of pruning. This is a necessary activity, which reduces the risk of infrastructure damage and falling branches, but many estimates of ecosystem service provision in cities do not consider its impact explicitly. Tree mortality is also higher in cities, preventing trees from attaining and remaining at large sizes. This study used extensive field measurements of tree structure to estimate the impact of pruning on 8 tree species in two Italian cities: Taranto and Florence. Crown widths were reduced by 1.6 m on average, however there is large variation between species variation with branches more often being removed for thinning crowns resulting in larger gap fractions, which increased by 15% on average. No significant differences were observed for crown widths or gap fraction between trees pruned 3 and 4 years previously, suggesting that tree crowns structurally recover from pruning after 3 years. A deterministic model revealed that current urban forest pruning rates (every 6 years) and mortality (1%) may create a situation in which a city dominated by the species studied benefits from 93.5% of the maximum ecosystem services possible. This work will allow more nuanced estimates of urban forest services to be calculated.     

Thinning apples via shading: an appraisal under field conditions

Summary

Fruit development and the fate of fruits was followed on ‘Imperial Gala’ apple (Malus × domestica Borkh.) trees thinned chemically or using shading. The percentage fruit drop, fruit growth rates using callipers and electronic gauges, and whole tree gas exchange rates were measured before, during, and after covering with a shading cloth that blocked 90% of solar radiation, applied for 1 week starting 30 d after full bloom (DAFB). While fruits were thinned to similar crop loads and all reached a similar size at harvest, their growth patterns reflected the treatments applied, with fruit growth slowing down and fruit dropping sooner in chemically-thinned trees which were treated earlier, than in the shading treatment, which took place later. Daily fruit growth patterns changed and were greatly reduced under shading, as were the net carbon exchange rates (NCER), both in total per tree and per unit of light intercepted by the trees. Regression analysis of the NCER per unit of light intercepted revealed no difference between the two treatments before and after shading, but a significantly lower relationship during shading. This work supports the hypothesis that C-starvation may induce fruit abscission at approx. 30 DAFB. Fruit growth patterns, and their changes during shading, were consistent with this hypothesis. This method of thinning, may be of interest to reduce the use of chemicals, and in organic fruit growing. However, before it can be adopted, a method to estimate the length of the period of shading is required.     

填闲作物阻控设施菜田土壤功能衰退研究进展

土地集约化经营的设施农业是我国农业的重要组成部分。然而,集约化种植体系中传统的连作和简单轮作更多地依赖农药和化肥,由此引发了温室土壤质量的下降和作物生长障碍,从而使得作物产量下降。如何阻控土壤功能衰退,修复并保持土壤健康,实现设施蔬菜产业可持续发展是设施蔬菜生产上亟待解决的问题。填闲作物是维持集约化种植体系土壤功能的生物途径,随着填闲作物改善土壤养分循环研究的深入,人们对填闲作物生态效应及其机制的认识也越来越深入。本文阐述了国内外填闲作物阻控土壤功能衰退研究进展,并在此基础上分析了填闲作物阻控设施菜田土壤功能衰退的可行性。     

北京创意农业主题公园实践总结——以北京房山粮经作物大观园为例

创意农业是把农业生产消费活动与文化创意活动相融合的一种新型农业产业类型。2010年,北京市农业技术推广站利用北方常见的67种粮经作物,共203个品种,建设集合观光休闲农园、教育农园、科技农园、市民农园特色的＂粮经作物大观园＂。从文化创意、意识创意、功能创意及宣传创意4个方面阐述粮经作物大观园设计理念和特点,即把农作物的科普活动、市民的食品保健宣传、以及现实版开心农场作为园区特色,使园区不仅具备农园的产品生产功能,还具备旅游区的艺术性和休闲观赏性,同时兼具游乐性,满足人们的视觉亲历和心灵感受。还通过参与式调查,研究粮经作物大观园的建设成效,以期为北京市创意性农业主题公园的建设提供新的经验和思路。     

Rhamnus alaternus growth under four simulated shade environments: Morphological,anatomical and physiological responses

Light management and species light plasticity are critical factors for proper crop production in nurseries. So, to assess the light necessities of Rhamnus alaternus, which is a promising native evergreen Mediterranean shrub of ornamental and ecological interest, it was exposed to five shade levels (0%, 32%, 48%, 84% and 93%) for one year (0% of shade received annual mean maximum photosynthetic photon flux density [PPFD] of 1293 ± 415 μmol m⁻² s⁻¹ with a summer mean maximum PPFD of 1541 ± 225 μmol m⁻² s⁻¹ [mean ± s.d.]). The treatments providing 84% and 94% shading produced less compact plants, with greater height and less stem diameter, greater specific leaf area and higher shoot/root index. In general, the shading produced dark green leaves except the 94% treatment, in which the leaves were lighter because the relative chlorophyll content was reduced. Leaf thickness was reduced in all the shading treatments compared with the control. The stomatal density and pore area were reduced with the 84% and 93% shading treatments, as was photosystem II (PSII) efficiency and the leaf soluble sugar content (falling to 60% of the control level); in contrast, non-photochemical quenching increased. The 93% treatment caused irreversible damages in PSII because dark-adapted PSII efficiency was reduced. The results show that solar radiation can be used as a tool to improve plant quality during the nursery period. We conclude that shading screens providing more than 84% shade are not recommendable in terms of photochemical activity, soluble sugar content and overall plant quality. Shading screens of 32% and 48% improve R. alaternus quality in spring and summer, respectively. As regards its interest as an understory species for reforestation programs, we also conclude that this shrub can be adapted to a wide range of shade intensities, although its proper development would be compromised in very strong shading conditions.     

Average height of surrounding buildings and district age are the main predictors of tree failure on the streets of São Paulo/Brazil

Tree failure is an increasingly frequent issue in cities worldwide leading to the risk of property damage, financial loss, citizen injury, and death. Assessing tree failure is a challenging task since early signs are often not visible and require a detailed evaluation of each tree, which is limiting considering the management of trees across the whole city. We used Regression Trees and Bagging to assess tree failure on the streets of São Paulo / Brazil using parameters from the gray and green infrastructure that could be easily estimated in the field to support the proper preventive maintenance of street trees. We characterized the districts’ age, average building height, tree height, canopy cover, sidewalk width, sidewalk slope, and terrain slope of 26,616 fallen trees. The Regression Tree shows 82% accuracy and reveals that building height is the main predictor of tree failure, followed by district age, sidewalk width, and tree height. The proportion of tree failure in the most verticalized areas, with on average five stories buildings or taller, is twice that observed in the entire city. Tree failure also increases in districts older than 42 years. The proportion of tree failure is 37% lower than the city’s average in relatively newer districts with low building height, where trees taller than 9.58 m are more prone to failure. These results point to possible roles of wind tunneling, shading, pollution, canopy conflicts with service cables in the urban canyons, and the natural senescence of trees in the oldest districts. The present study establishes comprehensive guidelines for effective preventive maintenance of the street trees in São Paulo.     

Adapting agricultural land management to climate change: a regional multi-objective optimization approach

In several regions of the world, climate change is expected to have severe impacts on agricultural systems. Changes in land management are one way to adapt to future climatic conditions, including land-use changes and local adjustments of agricultural practices. In previous studies, options for adaptation have mostly been explored by testing alternative scenarios. Systematic explorations of land management possibilities using optimization approaches were so far mainly restricted to studies of land and resource management under constant climatic conditions. In this study, we bridge this gap and exploit the benefits of multi-objective regional optimization for identifying optimum land management adaptations to climate change. We design a multi-objective optimization routine that integrates a generic crop model and considers two climate scenarios for 2050 in a meso-scale catchment on the Swiss Central Plateau with already limited water resources. The results indicate that adaptation will be necessary in the study area to cope with a decrease in productivity by 0–10 %, an increase in soil loss by 25–35 %, and an increase in N-leaching by 30–45 %. Adaptation options identified here exhibit conflicts between productivity and environmental goals, but compromises are possible. Necessary management changes include (i) adjustments of crop shares, i.e. increasing the proportion of early harvested winter cereals at the expense of irrigated spring crops, (ii) widespread use of reduced tillage, (iii) allocation of irrigated areas to soils with low water-retention capacity at lower elevations, and (iv) conversion of some pre-alpine grasslands to croplands.     

Land cover and climate changes drive regionally heterogeneous increases in US insecticide use

Context

Global environmental change is expected to dramatically affect agricultural crop production through a myriad of pathways. One important and thus far poorly understood impact is the effect of land cover and climate change on agricultural insect pests and insecticides.

Objectives

Here we address the following three questions: (1) how do landscape complexity and weather influence present-day insecticide use, (2) how will changing landscape characteristics and changing climate influence future insecticide use, and how do these effects manifest for different climate and land cover projections? and (3) what are the most important drivers of changing insecticide use?

Methods

We use panel models applied to county-level agriculture, land cover, and weather data in the US to understand how landscape composition and configuration, weather, and farm characteristics impact present-day insecticide use. We then leverage forecasted changes in land cover and climate under different future scenarios to predict insecticide use in 2050.

Results

We find different future scenarios—through modifications in both landscape and climate conditions—increase the amount of area treated by ~ 4–20% relative to 2017, with regionally heterogeneous impacts. Of note, we report large farms are more influential than large crop patches and increased winter minimum temperature is more influential than increased summer maximum temperature. However, our results suggest the most important determinants of future insecticide use are crop composition and farm size, variables for which future forecasts are sparse.

Conclusions

Both landscape and climate change are expected to increase future insecticide use. Yet, crop composition and farm size are highly influential, data-poor variables. Better understanding of future crop composition and farm economics is necessary to effectively predict and mitigate increases in pesticide use.

     

Some Experiments to Investigate the Control of Apple Sawfly,Hoplocampa Testudinea (Klug), by Concentrate Sprays

Eight-year-old trees of Laxton’s Superb apple on M.II rootstock growing on loamy fine sand of low moisture retention were used to study growth and crop responses to different soil moisture conditions from 1953 to i960 inclusive. Water was applied when soil moisture tensiometers set at 1 ft. depth indicated tensions of : A, 10 cm. Hg ; B, 20 cm. Hg ; C, 50 cm. Hg. Treatment D was unwatered.

Water was applied to an area 12 ft. in diameter around each tree, which was about one-third of the ground area available to each tree. The average amount of water required by each treatment during a season was equivalent to : A, 4-1 ; B, 3-5 ; C, 2-1 inches over its whole area.

Comparison of soil moisture deficits in the unwatered plots in the very dry season of 1959 with amounts of water applied to the other trees suggested that the rate of water loss throughout the experiment was not seriously affected by the treatments applied.

The water treatments stimulated trunk and shoot growth ; growth differences between differently treated trees could be adequately explained in terms of soil moisture tension and root-occupied soil volume. Evidence was found of serious leaching under the wettest treatment, and this may have caused a lower growth and crop response to treatment A than to B in the later years of the trial.

Crop increases were directly related to growth increases. Despite the marked effects of water treatments on shoot numbers and on crop increase the growth and crop relationship was virtually unchanged.

Treatments A, B and C increased total crops by 40%, 46% and 25% respectively, and marketable crops by 44%, 55% and 42% respectively. There was no marked effect of treatment on fruit size, though the increased proportion of fruit of a commercial size from the watered trees was of importance. Treatment B provided the largest total and marketable crops, but treatment C provided the greatest increase in marketable crop for each inch of water applied.     

Amenity trees and green space structure in urban settlements of Kigali,Rwanda

According to the national policy, overall forest and agroforestry cover in Rwanda is to increase up to 30% land cover by 2020. On the other hand, demographic data reveal that Rwanda's urban areas are among the fastest-growing on the continent. Unfortunately, there is only little information of the effects of such a rapid urbanization on tree cover and green space structure, knowing that data on urban plant assemblages in the country are rather rare. The paper discusses developments in Kigali's green spaces with regard to its rapid rate of expansion. An integrated approach of research, combining results from interview sessions, desk-based investigations, walk-over and vegetation surveys, and photogrammetric analyses of remotely acquired imagery was applied. The findings suggest that the city green space network consists of plant assemblages largely dominated by alien species (75%). Tree cover fraction averaged at around 10–35%. No significant difference was observed between field-drawn and photogrammetric-based fraction of tree cover estimates; making the later a quick but cheap tool for rapid tree cover evaluation. Cultivated forests, urban woodlots and domestic garden tree stands are far the most dominant types of green spaces in terms of coverage of city surface area. Street tree communities and institutional gardens appear to be the most intensively designed green space layouts. Both distribution and species composition in domestic gardens were socioeconomic-driven. For instance, palm trees were characteristic of fortunate quarters while fruitbearing ornamental such as Psidium guajava and Persea americana were common within scattered and informal settlements. Markhamia lutea, Erythina abyssinica, Euphorbia candelabrum, Phoenix reclinata and Acacia sieberiana are among native taxa that thrive to keep a place in the city. Euphorbia tirucalli, a native tree that is widespread in home compound fences within informal settlements, is significantly declining as modern housing expands and concrete-based fences replace live enclosures.     

Home gardening in Singapore: A feasibility study on the utilization of the vertical space of retrofitted high-rise public housing apartment buildings to increase urban vegetable self-sufficiency

In land-scarce cities, high-rise apartment buildings may provide vertical spaces for natural-light home gardening along corridors, rooftops, balconies as well as façades. The vertical space can improve not only urban environmental sustainability but also food security. Using an experimental approach, we investigated the food production potential of a high-rise public housing apartment building based on different gardening systems, food crops, and sunlight availability. A gardening prototype system for building corridors was shown to increase the unit area yield of corridor gardening by fivefold compared to a commercial trough planter system. Additionally, this commercial trough planter system was mainly for leafy vegetable production, whereas the gardening prototype system for corridors is also suitable for climbing crops, such as legumes and cucurbits. Nevertheless, because of the limited space along corridors of the apartment building and the relatively low-light levels on average, corridor gardening was estimated to meet only 0.5 % of the demand for vegetables of the residents living in the apartment building. Rooftop gardening with shallow growing medium (depth < 15 cm) was estimated to meet 3 % of demand, and façade gardening 43 %, given the larger space available. Although the vegetable production potential in this study was estimated based on a particular typology of public housing apartment buildings in Singapore, our results showed that vegetable production in public housing apartment buildings is feasible, and home gardening can produce a substantial amount of vegetables for consumption if well deployed. Governments of highly urbanized cities may wish to invest in better home garden designs for high-rise public housing apartment buildings and encourage residents’ participation in home gardening, which would increase high-rise greenery coverage and improve urban food system resilience. Future studies should also investigate the environmental sustainability and food safety aspects of home gardening in highly urbanized cities.     

Tree mortality rates and tree population projections in Baltimore, Maryland, USA

Based on re-measurements (1999 and 2001) of randomly-distributed permanent plots within the city boundaries of Baltimore, Maryland, trees are estimated to have an annual mortality rate of 6.6% with an overall annual net change in the number of live trees of –4.2%. Tree mortality rates were significantly different based on tree size, condition, species, and land use. Morus alba, Ailanthus altissima, and trees in small diameter classes, poor condition, or in transportation or commercial – industrial land uses exhibited relatively high mortality rates. Trees in medium- to low-density residential areas exhibited low mortality rates. The high mortality rate for A. altissima is an artifact of this species distribution among land use types (24% were in the transportation land use). Based on a new tree population projection model that incorporates Baltimore's existing tree population and annual mortality estimates, along with estimates of annual tree growth, Baltimore's urban forest is projected to decline in both number of trees and canopy area over the next century. Factors affecting urban tree mortality are discussed.     

我国瓜菜遮阳网覆盖栽培研究进展

遮阳网覆盖栽培已应用到农业生产的各方面，对农业生产的防虫、遮阳、节水、提高产量等方面起到了很大的促进作用。本文从遮阳网在节水灌溉、遮光降温、气体交换、延迟采收、防虫及对作物产量和品质的影响等方面，综述了其在农业生产方面的应用状况和相关研究，为遮阳网的合理科学利用提供参考。     

果树单倍体和加倍单倍体（DH）技术研究与应用进展

果树具有生殖周期长、基因高度杂合、树体高大、通常自交不亲和的特点,导致其无法通过传统育种方法获得纯系。单倍体和加倍单倍体（DH）的产生为解决这一问题提供了一种强有力的生物技术工具。与传统育种方法相比,单倍体和加倍单倍体（DH）可缩短从杂合亲本中获得纯系的时间,这一特点使其被广泛应用于植物育种和遗传研究。果树单倍体的获得...