典型草原封育过程中植物凋落物的变化动态

以内蒙古巴林右旗退化草原为研究对象,采用直接收集的方法,研究各种围封条件下,退化草原在自然演替过程中土壤凋落物的变化动态。结果表明：典型草原在封育演替过程中,凋落物呈增加的趋势,以封育10年的凋落物量最高;凋落物的养分,不同年限之间均存在显著差异,其中碳素含量以封育1年的最高,封育10年的最低,氮素则是以封育4年的含量...     

Evaluation of genetic trends and determination of the optimal number of cumulative records of parity required in reproductive traits in a Large White pig population

Genetic improvement of the reproductive performance of pigs is important for pig breeding despite their low heritabilities. The objectives of this study were to investigate the effectiveness of selection concerning reproductive traits and to determine the optimal number of parity records required for accurate estimation of breeding values (BVs) in the open population of a commercial pig breeding company. The study used records of 2220 purebred Large White pigs (9845 litters) farrowed between 1998 and 2009 in the two herds of the Pacific Ocean Breeding Co. Ltd. The traits studied included farrowing interval (FI), total number of piglets at birth (TNB), average weaning weight per litter (AWW), and raising rate (RR). A statistical model was applied to the 4‐trait repeatability animal model. The heritabilities of FI, TNB, AWW and RR were low. The genetic trends in TNB (h² = 0.09) showed approximately 1.0 increase in 6 years from 2003 to 2008. The predicted error variances indicated that up to fourth parity records are necessary for accurate genetic evaluation. The present study results indicated that even reproductive traits with low heritability can be improved.     

大尾寒羊产羔数对胎次的回归分析

该研究利用SPSS软件分析了大尾寒羊产羔数对胎次的回归,大尾寒羊产羔数对胎次的二次方回归和三次方回归的拟合度(R2)分别为0.9246和0.9269,可见两种模型下的回归方程的拟合度都比较高。产羔数对胎次的二次方回归方程中的所有回归参数均达到极显著水平(P<0.01),说明大尾寒羊产羔数对胎次用二次方回归方程具有一定的应用价值。     

初配日龄对母猪产仔性能的影响

根据某猪场淘汰的203头母猪的生产记录,对不同初配日龄母猪的头胎产仔数、产仔胎数及产仔总数进行统计分析。结果表明,240～269日龄的初配母猪头胎产活仔数最少,270～299日龄的初配母猪平均产仔胎数最少,300～329日龄的初配母猪平均产仔胎数和产活仔总数最高,210～239日龄的初配母猪平均产仔胎数最低。从最佳经济效益来看,母猪的最佳初配日龄为210～239日龄。     

4种地被竹枯落物的水文特征及其截持降雨过程研究

运用浸水法和人工模拟降雨法,分析了4种地被竹(铺地竹、菲白竹、鹅毛竹、黄条金刚竹)枯落物的持水能力与截持降雨过程。结果表明,铺地竹、菲白竹、鹅毛竹、黄条金刚竹现存蓄积量分别为4.51,4.33,6.32和6.67 t/hm2,枯落物的持水量介于12.77～16.66 t/hm2之间。4种地被竹枯落物的截留量与枯落物厚度、含水量密切相关,4种地被竹枯落物厚度分别为1和3 cm厚度时截留量差异均达到显著水平,在枯落物含水量达到饱和(50.81%～66.27%)的情况下,随着厚度的增加枯落物的截流量增大,铺地竹枯落物厚度3 cm比1 cm截流量提高了126%,鹅毛竹、菲白竹、黄条金刚竹截流量依次提高了51.4%,114.3%和56%。     

不同生态修复措施下桃林口水库水源涵养区枯落物的蓄水保水效益

以桃林口水库水源涵养区不同生态修复措施下枯落物为研究对象,通过野外调查与室内测试相结合、"空间代替时间"的方法,研究了不同措施及措施实施前后枯落物的蓄积量、吸水速率、持水量和有效拦蓄量等蓄水保水效益。结果表明:生态修复措施的实施增加了林内枯落物的蓄积量,枯落物蓄积量天然(次生)林封育型(26.88t/hm2)>疏林补植型(25.83t/hm2)>人工林封育型(25.11t/hm2)>荒坡造林型(24.10t/hm2)>陡坡梯田退耕型(12.22t/hm2)>荒坡封育型(9.57t/hm2),且生态措施实施前后的差异显著;枯落物持水量与浸泡时间之间存在对数关系,枯落物吸水速率与浸泡时间间存在乘幂函数关系;不同修复措施间枯落物的拦蓄量差异显著,天然(次生)林封育型枯落物有效拦蓄深最大(8.51mm),荒坡封育型的有效拦蓄深最小(2.85mm),其他依次为荒坡造林型(5.22mm)、疏林补植型(5.13mm)、人工林封育型(4.51mm)、陡坡梯田封育型(3.92mm),生态修复措施的实施增加了枯落物拦蓄量,增幅为20.41%～98.63%。研究结果为评价水库水源涵养区不同生态修复措施蓄水保水效益提供了基础。     

Predicting Carbon Stocks Following Reforestation of Pastures: A Sampling Scenario‐Based Approach for Testing the Utility of Field‐Measured and Remotely Derived Variables

Reforestation of agricultural lands is an important means of restoring land and sequestering carbon (C). At large scales, the labour and costs of direct measurement of ecosystem responses can be prohibitive, making the development of models valuable. Here, we develop a new sampling scenario‐based modelling approach coupled with Bayesian model averaging to build predictive models for absolute values in mixed‐species woody plantings and differences from their adjacent pasture, for litter stocks, soil C stocks and soil C:N ratios. Modelling scenarios of increasing data availability and effort were tested. These included variables that could be derived without a site visit (e.g. location, climate and management) that were sampled in the adjacent pasture (e.g. soil C and nutrients) or were sampled in the environmental planting (e.g. vegetation, litter properties, soil C and nutrients). The predictive power of models varied considerably among C variables (litter stocks, soil C stocks and soil C:N ratios in tree plantings and their differences to their adjacent pastures) and the model scenarios used. The use of a sampling scenario‐based approach to building predictive models shows promise for monitoring changes in tree plantings, following reforestation. The approach could also be readily adapted to other contexts where sampling effort for predictor variables in models is a major potential limitation to model utilization. This study demonstrates the benefit of exploring scenarios of data availability during modelling and will be especially valuable where the sampling effort differs greatly among variables. Copyright © 2016 John Wiley & Sons, Ltd.     

Instrumentation for Evaluating Differences in Ammonia Volatilization from Broiler Litter and Cake

Greater understanding of the mechanisms affecting NH₃ volatilization from reused broiler bedding is needed to determine pathways for mitigating NH₃ emissions. A chamber acid trap (CAT) system was developed to provide an improved laboratory method for determining NH₃ volatilization from litter or cake samples and for assessing treatment technologies to decrease NH₃ losses from poultry litter. The CAT system offers precision control of air flow rate through sample chambers as well as straightforward, precise determination of the amount of N volatilized. This article outlines the basic setup of the CAT system. The system can be utilized and modified for researching specific mechanisms involving physical, chemical, or biological treatments affecting NH₃ volatilization from litter or cake.     

滇中高原区主要森林类型枯枝落叶层对降雨的截留功能

枯枝落叶层是森林植被对降雨再分配的第２作用层，也是对土壤发育具有重要影响的层次。在实测本区主要森林类型枯枝落叶量及其持水能力的基础上，采用１００ｍ２最大截留能力、１００ｇ枯枝落叶最大持水能力及最大持水率等指标对不同森林类型枯枝落叶量、组成及其发育情况进行了综合评价。     

蛋壳粉少量替代石粉对蛋鸭产蛋性能、蛋品质及钙代谢的影响

【目的】研究蛋壳粉少量替代石粉对蛋鸭产蛋性能、蛋品质和钙代谢的影响。【方法】试验选择80只180日龄的健康山麻鸭蛋鸭,随机分为两组,每组5个重复,每个重复8只蛋鸭。对照组饲喂基础饲粮,试验组在基础饲粮基础上,用2 g蛋壳粉取代饲料中等量的钙添加量。试验为期56 d,试验期间检测蛋鸭产蛋性能、蛋品质、钙沉积量、血液中钙磷含量和钙代谢相关激素水平等指标。【结果】试验组平均蛋重、蛋壳强度和蛋白高度均显著高于对照组,表明添加蛋壳粉能明显提高蛋品质量。试验组蛋壳钙沉积量、血磷含量和血浆甲状旁腺素水平显著高于对照组,试验组血钙含量为4.74(±1.17)μmol/mL,极显著高于对照组的2.79(±1.00)μmol/mL,表明蛋壳粉更有利于钙沉积,能明显提高血液中钙磷含量和甲状旁腺素水平。【结论】蛋壳粉少量替代石粉可促进蛋鸭钙吸收代谢和蛋壳钙沉积,提高平均蛋重,改善蛋品质。