黄土高原3～6月土壤含水率与刺槐造林成活率预测模型的建立

选择1年生刺槐为造林树种,通过对造林地3～6月土壤平均含水率与当年刺槐造林成活率的回归分析,建立了二者间的线性回归方程,该方程相关系数R=0.988。同时应用该方程建立了刺槐造林成活率平均值(Y-)的预测模型,模型验证结果表明,该模型具有较强的预测能力,预测准确性较高,可应用于林业生产实践,为春季刺槐造林提供参考依据。     

大白猪基因组选择在不同应用策略下的比较研究

目前,基因组选择（genomic selection,GS）技术已经在种猪育种中开展,但为获得较高的收益,还需研究一些应用策略,如确定仔猪基因分型个体比例和早期仔猪留种比例。本试验选择温氏集团出生于2011—2016年的大白种猪作为研究对象,共有超过4.5万条的生长测定记录,超过7万条繁殖记录,和2 090个个体的简化基因组测序（GBS）数据,其中,出生于2016年7~12月的440个体作为候选群体。研究性状包括两个生长性状（校正100 kg日龄和校正100 kg背膘厚）和一个繁殖性状（总产仔数）。为对比预测效果,在候选群体进行育种值预测时,按照是否利用其基因型或表型信息分为4种预测方案,比较不同方案的预测可靠性和个体选择指数的排名情况。结果显示,在预测候选群育种值时,利用其表型或基因型信息均比不利用时的预测结果更加可靠。对生长性状终测前、后进行基因组选择指数计算,发现,终测后指数排名前30%的个体都位于终测前指数排名前60%内。若仔猪出生后仅选择常规BLUP预测指数排名前60%的个体,会导致有接近15%的具有优秀潜力的个体被遗漏。本研究建议,对所有新生健康仔猪都进行基因分型并计算基因组选择指数,然后对指数排名靠前60%的个体进行性能测定。     

甘肃省草地蝗虫测报系统优化研究

在现有的研究基础上,利用原有的数据进行大量计算机的拟合试验,并对甘肃省草地蝗虫进行实地调查研究,建立了一个具有准确预测预报草地蝗虫发生动态的系统模型。同时,利用所建立的模型,结合有关草地蝗虫的专家知识,在DET平台和网络系统上构建了“甘肃省草地蝗虫预测预报专家系统”软件,以便甘肃省草地防蝗工作有目的、有计划、有重点地进行。     

Drivers of soil respiration and nitrogen mineralization change after litter management at a subtropical Chinese sweetgum tree plantation

Leaf litter decomposition transfers elements from litter to soils that are essential for regulating nutrient cycles in plantation ecosystems, especially carbon and nitrogen. However, soil carbon and nitrogen dynamics in response to tree litter management remains insufficiently researched. We conducted a one-year field experiment at a fast-growing sweetgum tree plantation to evaluate the effects of leaf litter management on soil available nutrients, respiration rate and nitrogen mineralization rate. Three leaf litter treatments were applied, which were: (1) natural input (control); (2) double input and (3) non-input. It was found that the double input treatment increased soil inorganic nitrogen and microbial biomass nitrogen, but had little effect on microbial biomass carbon, dissolved organic carbon or dissolved organic nitrogen compared with natural input. The non-input treatment caused dissolved organic carbon to decrease compared with natural input. The respiration rate increased in the double input treatment, with a positive priming effect observed. Soil net ammonification, nitrification and mineralization rates also increased in the double input treatment in specific seasons. Meanwhile, positive linear relationships between respiration rate and all nitrogen transformation rates were observed for all treatments. Soil temperature was found to be an important prediction factor for predicting the respiration rate and mineralization as seasonal variations, but not for litter-induced fluctuations. Soil water content and mineral nitrogen were the primary drivers of litter-induced change to the respiration rate, whereas mineral nitrogen and microbial biomass were primary drivers of mineralization change. These results suggest that changes in soil nitrogen mineralization rate are strongly associated with the soil respiratory process, resulting in a potentially strong plant–soil feedback mechanism.     

Modelling the effects of landscape pattern and grazing regimes on the persistence of plant species with high conservation value in grasslands in south-eastern Sweden

Semi-natural grasslands in Sweden are threatened by land-use change and lack of management with attendant risk to their biodiversity. We present a model to explore the effects of grazing frequency and intensity on plant species persistence, and the relative effects of grassland size and pattern. We used a landscape modelling platform, LAMOS (LAndscape MOdelling Shell), to design a landscape model of vegetation dynamics incorporating the effects of local succession, dispersal and grazing disturbance. Five plant functional groups (PFG), representing various combinations of persistence and dispersal character, light requirements and disturbance responses, were defined to model species dynamics. Based on old cadastral maps three different landscapes were designed representing specific time-layers, i.e., a historical (17th to 18th century), a pre-modern (1940s) and a present-day landscape. Simulations showed that a threshold was crossed when grasslands decreased in area to about 10–30% of the modelled area, and as a consequence the biomass of grassland-specific PFGs was strongly reduced. These competition sensitive groups did not persist in the model even with intense grazing in the present-day landscape, where grasslands occupy 11% of the total area. However, all grassland species would have been able to persist in the historical landscape, where grasslands occupied 59% of the total area, even without grazing. Our results suggest that continuous but low-intensity grazing is more positive for grassland PFGs than discontinuous but highly intensive grazing. This effect was particularly strong when the frequency and/or intensity of grazing dropped below a threshold of 20%. Simulations using three landscape maps designed to explore effects of further fragmentation and habitat loss showed that the spatial pattern of remaining grasslands is important for the persistence of grassland-specific PFG. The model presented here is an advance towards more realistic grazing models to explore the effects of prescribed grazing and landscape fragmentation on the persistence species or plant functional groups.This revised version was published online in May 2005 with corrections to the Cover Date.     

Simulation studies of Senegalese Grasshopper ecosystem interactions II: the role of egg pod predators and birds

We present a simulation study of the role of birds and egg pod predators in the population dynamics of the Senegalese grasshopper. The model was an energetics-driven ecosystem model that included a natural Sahelian grass, millet, grasshoppers, the egg pod predators bombyliidae and Tenebrionidae, and 24 species of birds that prey on grasshopper nymphs and adults. The model simulated the rain-dependent dynamics and migration along a five-location south–north transect in Niger and Senegal, and the main outputs were the grasshopper pressure on the transect, measured as accumulated transect grasshopper days, and the density of eggs ready to emerge the following rainy season. The model was calibrated using observations from transects in Niger (2003, 2004) and Senegal (2004).

When input data from Niger 2003 and 2004 were applied, simulated reductions in grasshopper pressure during the rainy season from egg pod predators and birds, respectively, were within a range of 18–25%, but taken together the overall reduction in grasshopper pressure ranged between 35 and 37%. Using input from Senegal (2004) the birds accounted for reductions of around 25%.

When the impact of the natural enemies was measured in terms of reduction in the density of eggs hatching the following year, the simulated impact of the egg pod predators ranged between 45 and 83% and that of the birds between 33 and 39%, and the two groups combined caused reductions between 60 and 75%.

Analyses of the sensitivity to the bird species, added one by one, showed ‘predator saturation’ along the Niger transects (with low grasshopper density) but not along the Senegal transect.

For Niger, the sensitivity analyses revealed Cattle Egret, Grey-headed Sparrow, Chestnut-bellied Starling, Buffalo Weaver, Sudan Golden Sparrow, Grey Hornbill, Red-billed Hornbill and Abyssinian Roller to be the most important individual species. For Senegal the top-five individual bird species were Village Weaver, Buffalo Weaver, Savile's Bustard, Grey-headed Sparrow and Abyssinian Roller.     

Plant Protection in India: Problems and Prospects

Abstract

Agricultural productivity in India has hardly increased in the past 25 years. Inefficient plant protection services are held responsible to some extent by the author. Suggestions for improvements in surveillance and diagnosis and emphasis on cultural control and safe storage are made with an example from the Saharanpur District.     

Variability of hormetic dose responses of the antiauxin PCIB on Lactuca sativa in a plant bioassay

Some herbicidal agents that damage plants at high doses stimulate their growth at low doses. This phenomenon of hormesis constitutes an alternative possible use of herbicidal agents that is, however, compromised by the apparent variability of the phenomenon. However, studies demonstrating and quantifying this apparent variability are lacking. The auxin‐inhibitor PCIB [2‐(p‐chlorophenoxy)‐2‐methylpropionic acid] was therefore investigated to determine whether interassay variability of stimulatory effects exceeds those of inhibitory effects and which hormetic quantity is most variable. Reparameterisation of the dose–response model used to estimate the hormetic dose range allowed including this feature as an explicit parameter. In bioassays with lettuce and root length as response variable, the variability of PCIB effects was evaluated in 33 complete dose–response assays. In a meta‐analysis, the occurrence of PCIB hormesis proved highly reproducible. However, the variability of effects was dose‐dependent and increased with decreasing dose. The response before the maximum stimulatory response and the absolute magnitude of hormesis proved most variable. Comparing the frequency distribution of effective doses demonstrated there was a risk of a previously hormetic dose causing a loss of hormesis or inhibitory effects in a subsequent experiment. Therefore, selecting a hormetic dose that will induce hormesis under any circumstances will be a major challenge.     

Land application of crushed gypsum wallboard waste for alfalfa

Abstract

Three seasons of research that evaluated the effect of the land application of crushed gypsum wallboard waste (CW) for alfalfa were conducted at four Wisconsin locations having differing soil types and climatic conditions. Material was applied at rates up to 36.0 Mg ha^‐1 preplant and 2.2 Mg ha^‐1 topdress. The highest application of CW pre‐plant showed a positive trend for increased yield of alfalfa at three of the four locations, although this response was not statistically significant. Stand density was not affected with the exception of one year at one location for which the stand was lower where the highest rate Of CW was applied. The soil pH decreased slightly where high rates of CW were applied, presumably caused by an increase in soil solution hydrogen ions which were displaced from exchange sites. Soil calcium (Ca) and sulfur (S) usually increased, and soil test magnesium (Mg) usually decreased where the highest rate of CW was applied. There was no consistent effect of CW application on the soil test levels of other nutrients. Application of CW generally increased the Ca and S, and reduced the Mg concentrations in the harvested forage. Crushed wallboard appears to be as effective as commercial gypsum fertilizer, although this study did not compare equivalent rates of the two materials. No phytotoxic effects from the direct application of CW were noted. The land application of wallboard was found to have no substantial positive or negative agronomic effect on alfalfa production. This practice provides a reasonable alternative to land filling.     

基于 MaxEnt 模拟三叶海棠的地理分布

【目的】用已有的采集标本分布记录,模拟三叶海棠的地理分布。【方法】从中国4个标本馆获取三叶海棠的291个分布数据,从WorldClim网站下载1950-2000年生物气候数据,用最大熵模型(MaxEnt)模拟其地理分布。【结果】①三叶海棠的潜在分布地区有:巴基斯坦东北部;不丹中部、东北部;印度东北部;中国西藏东南部、河北省东北部和北京西部山区。②依据模拟分布值0.5～0.7标定的三叶海棠分布区域,排除其潜在分布区域,再结合这些区域的地理间隔性,从宏观景观上将三叶海棠的地理分布格局划分为4个区块:中国四川、甘肃、陕西三省交界地区;中国重庆大部分地区,贵州大部分地区,湖北西南部,湖南大部分地区,广西与贵州、湖南交界地区,江西,广东与湖南、江西交界地区,福建东北部,浙江大部分地区,安徽南部;韩国南部沿海地区;日本岛大部分地区。③刀切法检测表明,温暖季节平均降雨量对三叶海棠的分布增益贡献最大,三叶海棠喜生于温暖季节平均降雨量在450～800mm的地区。【结论】用MaxEnt模拟三叶海棠的地理分布有一定的准确性,反映出了三叶海棠基本的地理分布格局和潜在分布区域,并阐明了主导其地理分布的生物气候因子。