Forms of Nitrogen Alter Plant Phosphorus Uptake and Pathways in Rehabilitated Highly Alkaline Bauxite Processing Residue Sand

Understanding plant phosphorus (P) uptake and pathways is critical in the rehabilitation of degraded landscapes. This study investigated whether the uptake of P by Lolium rigidum was influenced by forms (inorganic and organic) of nitrogen (N) and whether the forms of N affected P loss by leaching in bauxite‐processing residue sand (BRS). Gypsum amended BRS was grown with L. rigidum and fertilized with P [calcium di‐hydrogen phosphate, Ca (H₂PO₄)₂], plus different forms of N [e.g. control (CK without N addition, glycine (P‐GL), ammonium (P‐AS) and nitrate (P‐KN))]. The experimental treatments were arranged in a complete randomized design. Aboveground biomass P under P‐KN accounted for 47.4% of applied P, but only 26.0% and 25.0% under P‐AS and P‐GL, respectively. However, root P contents showed a different trend where P‐AS (31.9%) was highest followed by P‐GLY (23.0%) and P‐KN (17.1%). Meanwhile, loss of P via leaching was minimal (<5% of applied P) regardless of treatment, which could be because of the high affinity of residue sand for P via specific adsorption sites. This was supported by high percentage recovery of applied P in BRS growth media under P‐GLY (48.1%), P‐AS (37.2%) and P‐KN (32.0%). It is concluded that loss of P via leaching may not be a problem in BRS; however, limited plant P availability may be of more concern. Further, uptake of P by L. rigidum in alkaline BRS was found to be more efficient under nitrate‐N fertilization. Understanding, however, the specific or associated mechanisms involved warrants further investigation. Copyright © 2016 John Wiley & Sons, Ltd.     

Runoff Development and Soil Erosion in a Wet Tropical Montane Setting under Coffee Cultivation

The western interior portions of Puerto Rico offer optimal climatic conditions for coffee cultivation. However, land and water degradation result when abrupt topographic relief and high annual rainfall combine with forest conversion for coffee farming. Small‐scale rainfall simulation experiments were conducted to quantify runoff and erosion from four land surface types (i.e., mulched, weed‐covered, and bare soils under active cultivation, and unpaved roads) representative of coffee farms in Puerto Rico. Results show that mulch‐covered soils had runoff coefficients similar to those from undisturbed forested conditions (~4%), and that they eroded at rates about a quarter of those for bare cultivated soils. Weed‐covered soils had surprisingly high runoff coefficients (~70%), yet their erosion rates were only three‐fourths of those for bare soils. Annualized erosion rates from unpaved roads were 65 Mg ha⁻¹ y⁻¹, or ten times greater than bare soils and about a hundred times higher than weed‐ or mulch‐covered surfaces. Farm‐scale sediment production estimates amount to ~11 Mg ha⁻¹ y⁻¹, about two‐orders of magnitude higher than under forested conditions. At the farm‐scale, only 2 – 8% of the total sediment is potentially attributable to cultivated hillslopes. In contrast, unpaved roads may account for over 90% of the sediment budget, even though they comprise only 15% of the farm surface area. Therefore, while providing mulch or a vegetative cover to bare cultivated soils should be part of effective soil management, mitigating the effects of coffee cultivation on downstream water resources must focus on the unpaved road network as the primary sediment source. Copyright © 2016 John Wiley & Sons, Ltd.     

Light and Temperature Requirements during Germination of Potential Perennial Grasses for Rehabilitation of Degraded Sandy Arabian Deserts

Few plants can tolerate the loose sandy‐soils of the arid deserts. Selection of native plants that could be used in rehabilitation of degraded deserts necessitates information about their seed dormancy and germination requirements. This study assessed the effects of light and temperature requirements during germination for eight common perennial grasses that have the potential to rehabilitate the arid Arabian deserts. The selected grasses vary considerably in seed mass. Germination of clonally propagated grasses (six species) was significantly greater, but slower, than that of two non‐clonal grasses. Four of these six species (Lasiurus scindicus , Panicum turgidum , Aeluropus lagopoides and Halopyrum mucronatum ) produce larger seeds and attained greater germination in both light and darkness at a wide range of temperatures. However, the other two (Centropodia forsskaolii and Coelachyrum piercei ) produce medium‐sized seeds with higher dormancy. Smaller seeds of Sporobolus arabicus were positively photoblastic at all temperatures, but those of Sporobolus spicatus were neutrally photoblastic at lower temperatures and positively photoblastic at higher temperatures. There was a significant negative relationship between seed mass and relative light germination, indicating that small seeds require more light during germination. It is recommended to use seeds of the six clonal grasses for restoration of degraded arid deserts. The ability of these grasses to germinate in different light and temperature regimes indicates their ability to germinate at any time of the year, even when seeds are buried. The light and temperature requirements of the different grasses are explained in the light of their adaptation and distribution in natural habitats. Copyright © 2017 John Wiley & Sons, Ltd.     

按照“激励相容”原理启动热带次生林和退化林地的可持续经营

中国热带天然次生林和退化林地约有1000万hm2,约占热带国土总面积的1/3。在这里,涉及森林资源可持续经营和经济社会可持续发展的基本课题尚未解决。文中建议利用“激励相容”的原理,针对中国的3种次生林和退化林地大类型,选择典型地区,按照尽可能接近当地社区及居民的原则,建立一个由分散化、微型化和多样化示范的小区组成的示范体系,高效率地推进热带次生林和退化林地的可持续经营,增强热带经济社会发展的弱可持续性并进一步向强可持续性转化。     

Emerging forests on abandoned land: Puerto Rico’s new forests

The species composition of forests change continuously as the earth’s biota evolves and adjusts to environmental change. Humans are accelerating the rate of species turnover by moving species around the planet and dramatically changing environmental conditions. Our focus is on new forests in Puerto Rico that emerge naturally on abandoned lands previously converted to agriculture and degraded. These forest stands have combinations of species that are new to the island’s landscapes. New forests exhibit high species dominance during forest establishment, which includes dominance by alien tree species. These alien tree species establish and maintain forest cover, which may facilitate regeneration of native tree species. Landscape analysis and literature review revealed that these emerging stands are highly fragmented (60% were <1 ha in 1991), function as refugia for native organisms, and at 60–80 years old have similar species richness and structural features as native stands of similar age. However, the island’s new forests exhibit important differences from mature native forests on unconverted forestlands. New forests have fewer endemic species and fewer large trees (≥55 cm dbh) than mature native forests; they have higher soil bulk density and lower soil carbon and litter stocks; and they accumulate aboveground biomass, basal area, and soil carbon more slowly than native forests of similar age. We suggest that new forests will become increasingly prevalent in the biosphere in response to novel environmental conditions introduced to the planet by humans.     

退化土壤竹子栽培模式研究

采用正交试验设计,在退化土壤上安排3个竹种、3种种植密度、3种抚育管理措施搭配的栽培试验,研究各因素对竹林产量的影响。结果表明:抚育管理措施之间、竹种之间均存在显著差异;施肥后的粉单竹林新竹产量最高,造林后第4年达到35.28 t/hm2;3个因素对竹林产量的影响力是抚育管理措施>竹种>种植密度。种植竹子后,林地未发生雨水冲刷的现象,竹林下的土壤的理化性质较种植前得到改善。     

Tenure reform in British Columbia? Model,trust and charter forests

By retaining 91% of the forests in public ownership, British Columbia (BC) holds one of the world’s highest proportion of forest land under a publicsector model for the development and management of the province’s increasingly valuable forest resource. Public ownership implies that critical linkages between the natural forest resource endowment, public-sector management policies and the standard of living of the people of the province are to be forged. Yet, the emerging changes in fundamental public perception of the appropriate use of forests suggests that some of these policies, especially as they relate to forest tenure, are failing to respond to the needs of people in the 21^st century. Some of those linkages require retooling. Although somewhat constrained by past forest activities and policies, the provincial government possesses broad authority across the entire public and private forest system to regulate forest practices and determine rate of cut, stumpage, royalties and rents. It can change the way it does business. It can also devolve responsibility and decision-making to local institutions and create innovative ways of moving toward sustainable forestry. This paper argues that a tenure option developing in the United States — charter forests — may have application in BC and explores briefly how five types of pilots could be tested in the province.     

The role of saltbushes (Atriplex spp.) in arid land rehabilitation in the Mediterranean Basin: a review

Arid lands in the Mediterranean Basin harbour populations of saltbushes over substantial areas. These have been grazed for centuries and often cleared. There are also some 100,000 hectares of artificially established saltbushes, both native and exotic; they include no more than half a dozen species, when large scale plantations are concerned. Another dozen of exotic species, introduced from Australia, Southern and Northern America, have successfully undergone field trials and could be used on a large scale in a near future. The present paper attempts to review the current state of knowledge on Atriplex spp. in the Mediterranean Basin as a means of Arid Land rehabilitation at a time where huge areas in the region have undergone processes of severe degradation or have been subjected to desertization, particularly over the past four decades. In spite of a number of constraints in their establishment, management and utilization, the plantation of Atriplex spp. appears as one of the best way, if not the best one, to rehabilitate desertized areas and restore them to production, under the present state of knowledge on arid land rehabilitation. They, in particular, are amenable to inclusion into new, man-made agro-sylvo-pastoral systems of production well adapted to arid lands and to the needs of their populations.     

Effects of adding water on seasonal variation of soil nitrogen availability under sandy grasslands in semi-arid region

Water is usally thought of a limiting factor for the restoration of semi-arid ecosystem. In the growing season of 2006, a study was conducted to determine the effects of modeling precipitation on seasonal patterns in concentrations of soil-available nitrogen and to describe the seasonal patterns in soil nitrogen availability and seasonal variation in the rates of net nitrogen mineralization of topsoil at Daqinggou ecological station in Keerqin sand lands, Inner Mongolia Autonomous Region, China. Manipulation of water （80 mm） was designed to be added to experiment plots of sandy grasslands in dry season. Water addition （W） treatment and control （CK） treatment were separately taken in six replications and randomly assigned in 12 plots （4 m×4 m for each） with 2-m buffers betweens. Results showed that the content of soil inorganic nitrogen and net nitrogen mineralization rate were not affected by adding water in sandy grassland of Keerqin sand lands. Net ni- trogen mineralization rates ranged from 0.5μg·g^-1,month^-1 to 4 μg.g^-1.month^-1. The highest values of soil inorganic nitrogen and net nitrogen mineralization occurred on October 15 in control plots. The seasonal changes of soil inorganic nitrogen contents exhibited ＂V＂ shape pattern that was related to seasonal patterns of soil ammonium-N （ascending trend） and nitrate-N transformation （descending trend）.     

日本林地施肥技术

本文介绍日本林地的施肥技术和施肥效果,并对中国林地施肥技术进行了探讨。