中国经济增长与耕地资源变化计量分析

经济发展与耕地保护一直是决策者两难的选择,其传统假说大都建立在发展与保护矛盾不断激化的基础之上,该文基于国内外耕地变化轨迹的判断,提出新的研究假说:经济增长与耕地变化存在Logistic曲线关系,并选择全国数据进行实证检验。结果表明:国外(区域)经济发展在工业化、城市化由初级阶段过渡到高级阶段过程中,对建设占用耕地需求的强烈程度先增强后减弱,整个过程类似于Logistic曲线假说。中国不同阶段对比发现,1988-2003年间中国人均经济增长与耕地资源变化具有较为一致波动特征致,2003年以后两者波动出现明显脱钩或分歧。1988-2008年间的全国各省实证结果显示,除上海、广西等8省份无法通过F检验外,其余省份均能验证研究假说,在2002年全国人均国内生产总值8759.2元,是耕地变化加速减少向减速减少的拐点,2009年后数年耕地规模总量不应小于121.7万km2,不同区域耕地变化拐点和规模下限差别较大。研究结论能够为中国耕地保护和公共政策调整提供科学依据和直接参考。     

安徽省城镇化与耕地利用集约化的动态响应关系

为分析城镇化与耕地利用集约化的动态关系,促进新型城镇化与农业现代化协调发展,该文在构建城镇化与耕地利用集约化动态响应关系理论框架的基础上,基于传统农区安徽省1998—2014年相关数据,建立向量自回归(vector autoregression VAR)模型,检验两者之间的协整关系,并在此基础上运用脉冲响应分析和方差分解分析城镇化与耕地利用集约化的互馈关系。结果表明,复种指数对城镇人口比例冲击的响应先为负向后为正向,贡献率为14.4%;对二三产业比例和土地城镇化则均产生负向响应,并呈先增加后减少的趋势,贡献率分别为10.4%、15.6%。化肥投入对城镇人口比例的冲击产生正向的响应,贡献率为12.1%;对二三产业比例有正向和负向响应,反应强度先增加后减少,解释水平为1.2%;对土地城镇化产生先增加后趋于平稳的负向响应,贡献率为22.3%。农业机械总动力对城镇人口比例的反应为正向的先增加后趋于平稳,贡献率为20.3%;对二三产业比例的负向响应的解释水平为2.4%;对土地城镇化的冲击呈现负向增加的响应,且贡献率高达66.3%。总体来看,城镇化水平的提高对耕地利用集约化有正向推动作用,但集约化需要适度发展,过快的城镇化不利于可持续集约化的实现;耕地利用集约化对城镇化的影响程度相对较低,说明耕地集约利用水平的提高仅可在一定程度上支持城镇化的发展。     

山地村域耕地压力与农村贫困耦合协调性分析

探索耕地压力与农村贫困的内在关系,对于基于耕地资源视角下的农村贫困治理具有重要的意义。该研究在实地调研数据的基础上,以云南省镇沅县109个行政村为研究单元,运用加权求和法、耦合度协调度模型等研究方法,对耕地压力与农村贫困的耦合关系进行研究。结果表明：1）镇沅县村域尺度耕地压力指数与农村贫困指数均较高,利用ArcGIS10.2平台对空间分布进行刻画,呈现\     

Solute adjustment to salinity and calcium supply in cultivated and wild barley

Ion relations, water content, leaf water potential, and osmotic adjustment were determined for cultivated barley (cv Harrington) and wild barley grown under mixed sulphate (SO₄) salts with varied calcium (Ca) supply using a hydroponic system. Salinity induced significant increases of leaf, stem and root sodium (Na) concentrations in both species. Salt‐stressed wild barley roots accumulated more Na than shoots, and transport of Na from roots to shoots was low compared to Harrington. Cultivated barley had lower Ca concentrations than wild barley, especially in the low Ca salt treatment. Although potassium (K/Na) and Ca/Na ratios were higher in control wild barley plants than in Harrington, they declined under salt stress, irrespective of Ca supply. Major osmotica in wild barley leaves were K, sugars, organic acids, and quaternary ammonium compounds, while in Harrington they were cations, including Na, K and Mg, and anions such as phosphate (PO₄) and SO₄. Wild barley maintained better water status than Harrington under low Ca salt treatment. Supplemental Ca improved water status more in Harrington than in wild barley. Lack of osmotic adjustment to salinity in wild barley apparently resulted from its ion exclusion. Low Ca salt treatment caused Ca deficiency, Na toxicity, and loss of turgor in Harrington. In the high Ca salt treatment, Harrington had improved water and ion relations, as well as positive turgor.     

The changes in physiological and biochemical traits of Tibetan wild and cultivated barley in response to low phosphorus stress

Low phosphorus (LP) limits crop growth and productivity in the majority of arable lands worldwide. Here, we investigated the changes in physiological and biochemical traits of Tibetan wild barleys (Hordeum vulgare L. ssp. spontaneum) XZ99 (LP tolerant), XZ100 (LP sensitive), and cultivated barley ZD9 (moderately LP tolerant) under two phosphorus (P) levels during vegetative stage. These genotypes showed considerable differences in the change of biomass accumulation, root/shoot dry weight ratio, root morphology, organic acid secretion, carbohydrate metabolism, ATPase (Adenosine triphosphatase) activity, P concentration and accumulation under LP in comparison with CK (control) condition. The higher LP tolerance of XZ99 is associated with more developed roots, enhanced sucrose biosynthesis and hydrolysis of carbohydrate metabolism pathway, higher APase (Acid phosphatase) and ATPase activity, and more secretion of citrate and succinate in roots when plants are exposed to LP stress. The results prove the potential of Tibetan wild barley in developing barley cultivars with high tolerance to LP stress and understanding the mechanisms of LP tolerance in plants.     

Analysis of volatile compounds from various types of barley cultivars

We identified volatile compounds of barley flour and determined the variation in volatile compound profiles among different types and varieties of barley. Volatile compounds of 12 barley and two wheat cultivars were analyzed using solid phase microextraction (SPME) and gas chromatography. Twenty-six volatiles comprising aldehydes, ketones, alcohols, and a furan were identified in barley. 1-Octen-3-ol, 3-methylbutanal, 2-methylbutanal, hexanal, 2-hexenal, 2-heptenal, 2-nonenal, and decanal were identified as key odorants in barley as their concentration exceeded their odor detection threshold in water. Hexanal (46-1269 microg/L) and 1-pentanol (798-1811 microg/L) were the major volatile compounds in barley cultivars. In wheat, 1-pentanol (723-748 microg/L) was a major volatile. Hulled barley had higher total volatile, aldehyde, ketone, alcohol, and furan contents than hulless barley, highlighting the importance of the husk in barley grain aroma. The proanthocyanidin-free varieties generally showed higher total volatile and aldehyde contents than wild-type varieties, potentially due to decreased antioxidant activity by the absence of proanthocyanidins.     

Growth and physiological characterization of low nitrogen responses in Tibetan wild barley (Hordeum spontaneum) and cultivated barley (Hordeum vulgare)

Development of crop cultivars with high yield under low nitrogen (N) supply is a basic approach for the enhancement of agricultural sustainability. The previous studies showed that Tibetan wild barley shows wider genetic diversity in abiotic stress and poor fertility tolerance. In this study, four barley genotypes (two Tibetan wild and two cultivated), differing in N use efficiency (NUE), were characterized for their growth and physiological responses to low N stress. The genotypes ZD9 (cultivated) and XZ149 (wild) with high NUE performed better in terms of shoot dry weight (DW) and photosynthetic parameters under both low and normal N levels and had higher antioxidative enzyme activities, N concentration, and accumulation in both shoots and roots under low N stress. The current results showed the substantial difference among barley genotypes in low N tolerance and verified the significance of Tibetan wild barley in the genetic improvement of cultivated barley in NUE.     

Evaluation of cultivated and wild barley for resistance to pathotypes ofPuccinia hordei with wide virulence

An isolate ofPuccinia hordei (ND89-3) originally collected in Morocco is virulent on most barley genotypes reported to possess resistance, except cultivar Estate (CI 3410), which possesses theRph3 gene and exhibits a low to intermediate level of resistance (infection type 12). Isolate ND89-3 possesses one of the widest virulence spectrums reported forP. hordei. Accessions ofHordeum vulgare (1,997 in total) andH. spontaneum (885 in total), mostly originating from the Mediterranean region and parts of North Africa, were evaluated with isolate ND89-3 at the seedling stage to identify new sources of leaf rust resistance. Fifty-eight accessions ofH. vulgare, and 222 accessions ofH. spontaneum exhibited low infection types to this isolate. Further evaluations of these resistant accessions with isolates ofP. hordei virulent forRph3,Rph7, andRph12 suggested that most of the resistantH. vulgare accessions possess theRph3 gene. Data suggested additional sources of effective resistance inH. vulgare are rather limited. FiveH. vulgare accessions and 167H. spontaneum accessions were identified as possible sources of new genes for leaf rust resistance. These accessions likely possess resistance genes that are different fromRph1 toRph12, or gene combinations thereof based on their reaction to four leaf rust isolates. Utilization of these accessions in barley breeding will broaden the germplasm resources available for genetic control ofP. hordei. North Dakota Agricultural Experiment Station Journal Series No. 2123. The U.S. Government right to retain a non-exclusive, royalty free licence in and to any copyright is acknowledged.     

Deconstructing molecular phylogenetic relationship among cultivated and wild Brassica species

Genetic Resources and Crop Evolution - Brassica represents an agriculturally important and diverse group of oilseed crops with a long evolutionary history. Molecular markers played an important...     

耕地不同利用方式下的土壤养分状况分析

以山东青州市为例,在对耕地土壤养分状况进行全面的调查分析,获取大量土壤养分数据的基础上,以数理统计方法对5种耕地利用方式下17种土壤养分状况的差异性进行分析,进而系统地探讨了耕地不同利用方式对土壤养分状况的影响。研究结果表明：耕地不同利用方式对土壤有机质及大量元素、交换性钙、镁、有效硅、锌、硼、土壤pH值和全盐含量有显著影响。由于菜地高施肥量及高产出的影响,大部分菜地土壤养分的含量明显高于粮田,但有效硅含量粮田则远高于菜地。粮田土壤pH值高于菜地,全盐含量菜地高于粮田。在旱地、水浇地粮田和露天菜地中有效磷含量变异最大,但设施菜地中全氮、有效硫含量的变异最大。研究结果对于探明耕地利用对土壤的养分状况的影响,对研究区耕地资源的合理利用与保护将具有积极意义。     

基于耦合协调度模型量化耕地自然质量与立地条件协同关系

耕地自然质量条件与立地系统共同决定了耕地可持续的生产能力,测算二者之间的协同比例关系可为耕地资源的保护分区提供理论和方法借鉴。该文以辽宁省不同地貌区为例,通过构建不同地貌区耕地自然质量评价系统与耕地立地条件评价系统,运用耦合协调度模型量化分析二者之间的协同关系,最后依据二者之间协同关系特征建立耕地资源保护分区。研究结果表明:在辽宁省西部的丘陵地貌区、中部的平原地貌区以及东部的山地地貌区,耕地资源保护优势条件特征存在区域差异,3个地貌区耕地自然质量条件与立地条件协同关系比值分别为4:6、6:4和5:5,应遵循耕地资源条件的地域差异特征实行协同保护。在此基础上,依据耕地资源优势条件特征将辽宁省耕地区域划分为核心保护区、优势整治区以及重点调控区,并提出不同区域耕地资源差异化的利用和保护措施。该研究结果体现了不同地貌区耕地资源优势保护条件特征的差异性与规律性,可为省域尺度耕地资源的永续利用提供参考借鉴。     

Genetic relationships among cultivated types of Perilla frutescens and their weedy types in East Asia revealed by AFLP markers

AFLP markers were employed to detect genetic diversity in two cultivated Perilla frutescens (i.e. var. frutescens and var. crispa) and their weedy types and to assess their genetic relationships. Analysis of 60 Perilla accessions from China, Korea and Japan by seven AFLP primer combinations identified a total of 125 fragments, of which 80 (64%) were polymorphic at the species level. The phenotypic diversity meassured by Shannon's index of information for the cultivated type of var. frutescens, the weedy type of var. frutescens, the cultivated type of var. crispa and the weedy type of var. crispa were on average 1.07, 2.23, 1.24 and 1.75, respectively. The weedy types exhibited high within-type variation in spite of a small number of samples. In the neighbor joining tree, two major clusters were recognized: (1) cultivated type of var. frutescens, (2) weedy type of var. frutescens, and cultivated and weedy types of var. crispa. The cultivated types of var. frutescens and of var. crispa were sharply separated by AFLPs. However, there remained ambiguities in regard to the intraspecific relaltionships, due to the clustering of the weedy types which occured in each of the clusters of the cultivated types. Two cultivated types of P. frutescens and their weedy types should be taxonomically considered as a P. frutescens complex. The present AFLP data are consistent with the hypothesis that China is the original place of cultivation of var. frutescens and Korea is a secondary center of diffusion of var. frutescens.     

Could early gene flow have created similar allozyme-gene frequencies in cultivated and wild barley?

The possible role of early gene flow between wild and cultivated barley in their similar esterase gene frequencies was tested in a simulation study. The hypothetical population consisted of 99.9% wild forms possessing three alleles of an esterase gene and 0.01% domesticated forms possessing one of these esterase alleles. Various rates of inbreeding, selection coefficients against the wild form and shifting cultivation methods were tested for their effect on the establishment of the domesticated form and the esterase gene flow between the two barley types. Of these factors, inbreeding rates, in the range of 90–99%, had the smallest effect on the establishment of the domesticated form under primitive cultivation. Via gene flow, the esterase allelic frequency in the domesticated form could be similar to that of the wild form under 90% outcrossing in the domesticated form for 115–230 years, an unrealistic situation for barley which normally exhibits about 1% outcrossing. It seems, therefore, that the similar esterase allelic frequencies in wild and cultivated barley is only partly due to gene flow, and it is more plausibly accounted for by multiple domestications.     

The RAPD evidence for the phylogenetic relationship of the closely related species of cultivated apple

The phylogenetic relationship of cultivated apple and its closely related species is still not clear in the taxonomy of genus Malus. To try to find new evidence for the origin and evolution of the cultivated apple, random amplified polymorphic DNA (RAPD) markers of 14 taxa of Malus, among which a reference species (M. toringoides) and six presumably ancestral species of cultivated apple in the genus were investigated. The RAPD data obtained were used to construct both unrooted and rooted trees using TREECON software package. The result showed in our rooted tree that M. sieversii from the Xinjiang Autonomous Region of China is the species which is most closely related to the cultivated apple, M. domesticacv. `Golden Delicious'. The phylogenetic relationships among the species studied are discussed.     

Invertebrate communities (Annelida and epigeic fauna) in three types of Estonian cultivated soils

The abundance and diversity of invertebrate communities (annelids and epigeic fauna) in three types of cultivated soils were studied. Soil biota communities in the three most widespread soil types in Estonia (Calcaric Regosols, Calcaric Cambisols and Stagnic Luvisols) are influenced by environmental conditions, the factors connected to soil texture including moisture, organic matter content and pH being the most essential, and by the intensity of agricultural practice. Potentially high biological activity and low intensity of agricultural human activity of Calcaric Regosols occurs in parameters of communities of organisms not sensitive to soil which dries off, i.e. epigeic fauna living on the soil surface and preferring dry and warm habitat; temporarily dried off soil is not a suitable habitat for Oligochaeta. Both groups of Oligochaeta (earthworms, enchytraeids) appear to prefer Calcaric Cambisols where soil moisture conditions are more stable. The abundance of invertebrate communities is the highest and the diversity is the lowest in Stagnic Luvisols. Some trends occurred in community characteristics along the soil surface following a hypothetical gradient; the number of carabids per trap and diversity of spiders decreased from the edge to the centre of the field. The results presented here on spatial variability in distribution of soil organisms are preliminary.     

Isozyme relationships between cultivated artichoke and the wild relatives

Summary The genetic affinities between the cultivated artichoke Cynara cardunculus L. var. scolym (L.) Fiori [= C. scolymus L.] and its wild relatives were assessed by tests of 20 enzyme systems (28 loci). Six representative cultivars and the following wild taxa were examined: (i) wild cardoon C.cardunculus L. var. sylvestris (Lamk) Fiori, (ii) C. syriaca Boiss., (iii) C. cornigera (Lindley) [=C. sibthorpiana Boiss.], (iv) C. algarbiensis Cosson, (v) C. baetica (Spreng.) Pau [=C. alba Boiss.], and (vi) C. humilis L. Twenty one out of the 28 loci tested were polymorphic (mainly between species). The genetic identity between the cultivars and the wild cardoon forms ranged from 0.92 to 0.96; while that between these two taxa and the five other wild Cynara species ranged between 0.67 and 0.79. This implicates wild C. cardunculus in the wild ancestry of the cultivated artichoke.     

中国粮食安全与耕地资源变化的相关分析

科学评估耕地细碎化治理的适宜性与必要性,并进行合理的整治分区有利于耕地资源的高效利用与空间布局,促进三生空间协调发展。该研究以典型山区县及资源型城市江西省德兴市为例,基于村域尺度,从生产适宜性、空间集聚性、管控约束性3个视角构建评价体系,采用多因素综合叠加评价法对耕地细碎化进行评价,借助三维魔方空间分类法开展整治分区研究。结果表明：1）各村耕地资源生产适宜性良好,均值为0.558;空间集聚性一般,均值为0.350;管控约束性标准差大于均值,各村差异较大;耕地细碎化治理适宜性较高,均值为0.711。2）统筹评价结果将德兴市划分为高质保障区、综合整治区、设施优化区、集约整合区以及现状维持区5区,基于各区生产适宜性、空间集聚性与管控约束性差异制定差别化整治措施与治理策略。研究结果可为耕地细碎化整治提供有益的参考借鉴。

     

Hybrids between wild and cultivated carrots in Danish carrotfields

It is well known that wild carrots may pollute the seed cropsof cultivated carrots, but whether cultivated carrots can alsodisperse pollen and seed, and thereby introduce genes into wildcarrot populations, is only little described. In Denmark, there is nocommercial seed production of carrots, and as biennials they shouldnormally not flower before harvest of the roots. Still, floweringindividuals can be found in most Danish fields, and sometimes in veryhigh numbers. At least 75% of the flowering plants are malefertile, with ca. 83% of the pollen being viable. More thanhalf of the plants produce seeds. Pollen and seed dispersal fromfields into wild carrot populations is probably rather frequent inDenmark. A closer inspection of the morphology of flowering plantsindicate that some of these (2–60%) arebolters of pure cultivar origin, as indicated primarily by orangeroot colour. The remainder is probably first or advanced generationhybrids between wild and cultivated plants, as indicated by theirwhite roots and combinations of morphological characters from eitherplant type. Some of these hybrids are imported to Denmark togetherwith the sowing seed, as indicated by significantly differentfrequencies of bolters with white roots in different carrot cultivarstested in the field.     

The relationship between structure and the hydraulic conductivity of soil

A random fractal matrix comprising a hierarchical aggregation of primary structural elements is used to capture the characteristics of a heterogeneous soil structure with a tortuous pore space. The influence of heterogeneity of both the solid matrix and the pore space, as well as the shape of the pore boundary, on the saturated and unsaturated hydraulic conductivity is studied. For such random structures, the fractal (Hausdorff) dimension alone is not enough to characterize the structure from the point of view of fluid flow and additional characterizations are introduced. The porosity, ρ_p, of the primary elements has a critical value, ρ_c. With probability 1, both the saturated and unsaturated conductivities are found to be dependent as a power law on the length scale, L, at which the measurement is made when ρ_p>ρ_c. When ρ_p<ρ_c, only the unsaturated conductivity is scaling in length scale, while the saturated conductivity becomes dominated, with probability close to 1, by the conductivity of the largest connecting pores in the structure, i.e. preferential pathways. The relationships between the parameters of the power laws and structure are derived and are found to depend on the fractal (Hausdorff) and spectral dimensions of the solid matrix, denoted d_m and respectively. A discussion of the importance of these results for the interpretation and extrapolation of measurements is presented, and the implications for variability and predictability of the hydraulic properties of soil is discussed.