电围栏在岩溶地区灌丛草地的放牧试验

岩溶地区喀斯特灌丛草地是贵州省的主要草地类型之一 ,采取何种放牧管理措施 ,来有效地控制山羊放牧密度 ,达到充分利用灌丛资源发展山羊生产 ,使广大农户脱贫致富的同时 ,并保持灌丛草地的良性生态循环 ,达到可持续发展的目的。根据岩溶地区灌丛草地地形非常复杂的特点 ,采用电围栏来进行山羊放牧试验 ,并与生物围栏和简易篱笆比较 ,结果电围栏较经济适用     

Central-place analysis and modeling of landscape-scale resource use in an East African agropastoral system

Most spatial models of grazing assume a global search; that is, the entire paddock or landscape is available to grazers. These `unconstrained' models characterize landscape patches based on absolute properties (i.e., without regard for how individual grazers are situated within them). In most of East Africa cattle are herded and must start and end each day's grazing at their enclosure. Thus, global search is not a realistic assumption. This implies that the relative location of a patch may be more important than its absolute properties because its quality depends not only on the properties of the patch itself, but also on its location relative to home and to water. Using data from 73 full-day herd follows among a group of agropastoralists in western Tanzania, I build and test an unconstrained model and compare its analytical utility and predictive power to a `central-place' model that defines the landscape relative to herders' homes (the central place) and dry season water. The central-place model provides analytical insights into the grazing system that are not apparent when using an unconstrained model, and it explains more of the variance in grazing intensity. Because many types of resources are collected around a focal point, central-place models should have wide applicability for analyzing and modeling many kinds of resource use, particularly in the developing world.     

中国东南部红壤旱地种植系统的生物学及其应用研究——Ⅴ红壤荒坡种草养畜的综合规划研究

本文根据南方红壤荒坡种草养畜试验研究资料,按照建立生态草场的原则和合理利用水土资源,发展人工草地,划区轮牧,饲养绵羊、鹅、兔食草动物的要求,针对丘陵岗地的地形特点,论述了草场规划,养畜规划,以及丘陵水库养鱼规划的原则和方法.     

Nitrous oxide emissions from artificial urine patches applied to different N-fertilized swards and estimated annual N2O emissions for differently fertilized pastures in an upland location in Germany

Abstract. Artificial urine containing 20.2 g N per patch of 0.2 m² was applied in May and September to permanent grassland swards of a long‐term experiment in the western uplands of Germany (location Rengen/Eifel), which were fertilized with 0, 120, 240, 360 kg N ha^?1 yr^?1 given as calcium ammonium nitrate. The effect on N₂O fluxes measured regularly during a 357‐day period with the closed‐chamber technique were as follows. (1) N₂O emission varied widely among the fertilized control areas without urine, and when a threshold water‐filled pore space >60% was exceeded, the greater the topsoil nitrate content the greater the flux from the individual urine patches on the fertilized swards. (2) After urine application in May, 1.4–4.2% of the applied urine‐N was lost as N₂O from the fertilized swards; and after urine application in September, 0.3–0.9% of the applied urine‐N was lost. The primary influence on N₂O flux from urine patches was the date of simulated grazing, N‐fertilization rate being a secondary influence. (3) The large differences in N₂O emissions between unfertilized and fertilized swards after May‐applied urine contrasted with only small differences after urine applied in September, indicating an interaction between time of urine application and N‐fertilizer rate. (4) The estimated annual N₂O emissions were in the range 0.6–1.6 kg N₂O‐N per livestock unit, or 1.4, 3.6, 4.1 and 5.1 kg N₂O‐N ha^?1 from the 0–360 kg ha^?1 of fertilizer‐N. The study demonstrated that date of grazing and N‐fertilizer application could influence the N₂O emission from urine patches to such an extent that both factors should be considered in detailed large‐scale estimations of N₂O fluxes from grazed grassland.     

草地早熟禾宜牧性状的研究

草地早熟禾是我国东北地区很有发展前途的人工栽培牧草,特别是用作放牧地草种。通过对草地早熟禾的产量、草层结构及根系结构进行分析,表明了几乎在所有观测宜牧性状中,草地早熟禾均表现为良好的适宜特征。     

Developing a canopy closure model to predict overstorey/understorey relationships in Pinus radiata silvopastoral systems

Silvopastoral models require the development of the relationship between understorey pasture production, and the overstorey tree production. The Tikitere agroforestry trial, located near Rotorua in the Bay of Plenty, was established in Pinus radiata at a range of stockings in 1973, and monitored for stand parameters, understorey pasture production, and livestock carrying capacity between 1976 and 1992. A canopy closure model, developed for radiata pine plantations in the Bay of Plenty, shows a strong relationship (R2 ≈ 0.92) between canopy closure and the stand parameters of basal area and the ratio of green crown length to mean top height. Canopy closure was predicted for the Tikitere stands using the canopy closure model. A strong linear relationship (R2 ≈ 0.89) was shown to exist between the measured pasture production, and the predicted canopy closure. This indicates that direct assessment of canopy closure combined with a measurement of understorey pasture production, may be a simpler and more cost effective research technique than relying entirely on the continuous measurement of understorey pasture in the development of understorey/overstorey relationships. This revised version was published online in June 2006 with corrections to the Cover Date.     

Grass defoliation affecting survival and growth of seedlings of Acacia karroo,an encroaching species in southwestern Zimbabwe

Abstract

Two experiments were conducted, one in the field and the other in the greenhouse, to investigate the effects of the intensity and frequency of grass defoliation on the survival and growth of Acacia karroo seedlings. In the greenhouse, seedlings growing with heavily clipped grasses had higher biomass production than those competing with moderately clipped grasses. Root/shoot ratios were higher in treatments with undipped grasses. There was a negative relationship between grass root production and A. karroo biomass production. The field experiment was carried out in two paddocks, one previously heavily‐grazed and the other lightly‐grazed. Grazing in both paddocks was simulated by artificial defoliation. Generally more A. karroo seedlings emerged under lightly defoliated treatments. Clipping frequency had a strong effect (P=0.066) on the survival of emerged seedlings during the wet season. There were no differences in survival rate at the end of the dry season. Though grass defoliation was shown to enhance seedling growth under controlled conditions, no evidence was found to suggest that seedling establishment during the first year is influenced by the intensity of grass defoliation.     

天山山地草原适宜放牧率评价体系初探——以新疆新源县为例

在新疆新源县山地草原上，按照当地典型的放牧模式以及单位时间单位面积上放牧的羊单位将研究区划分为极重度放牧区（E）、重度放牧区（H）、中度放牧区（M）、轻度放牧区（L）和无牧区（U）5个放牧梯度，放牧强度E 、H 、M 、L 和U的放牧率分别为0.51、0.43、0.32、0.26和0羊单位/hm2。采用德尔菲法和层次分析法，对不同放牧率下山地草原的植被指数、土壤指数、植被营养指数和经济指数进行综合评价。结果表明，放牧率为0.32羊单位/hm2 时，新源县山地草原从草地生态系统和草地畜牧业两方面考虑为最佳选择。     

The task of forestry in the mountains of the western and southern cape province

Soil fertility with special reference to nitrogen can have an overriding influence on secondary succession.