放牧对草地土壤微生物的影响

土壤质量是草地生态系统生产力可持续发展的关键所在。健康的土壤必定拥有丰富的物种多样性、活跃的生命体、高效的内部养分循环及较好的抗干扰能力。土壤微生物作为土壤系统中各种生物进程的主要推动者,其作用不可小觑。因此,我们可以利用土壤微生物的数量、群落结构和多样性等特征监测土壤质量。本文综述了放牧对草地土壤微生物数量、生物量、群落结构和多样性的影响。指出通过了解土壤微生物与放牧行为间的关系,如何评估土壤质量,选取适宜的放牧梯度,完善草地管理模式,并介绍了土壤微生物群落结构和多样性研究方法的利弊。解决两个关键问题：1）土壤微生物的各种特征是如何响应放牧行为的。2）如何通过这些指标评价土壤质量,然后提出合理的放牧模式,改善和维护草地的生产力。     

Factors affecting a sheep vegetation management system in British Columbia, Canada

A silvopastoral agroforestry system involving sheep is an important silvicultural issue. We examined the factors that affect the continuation or discontinuation of sheep vegetation management (SVM) in British Columbia. A questionnaire was used to conduct interviews with a randomly selected sample of contractors and farmers who were involved in SVM in British Columbia (BC). Based on a stepwise discriminant analysis, we found that the profitability of SVM, and the practitioners' commitment (number of ewes owned by the farmer or contractor), experience (number of years the farmer or contractor has practiced SVM on public lands in BC) and trust or confidence (number of years the farmer or contractor has consistently worked for the landlord) contributed to the farmer's or contractor's continuation or discontinuation of SVM practice. The factors we defined seemed to be validated (corroborated) by a complex of determinants voiced by various experts concerning the relationship between SVM and the forestry economy in BC, the scale of sheep farming in BC, the relative absence of an agricultural infrastructure to support sheep farming in BC, and the continuity of SVM from year to year. Further investigation into these factors and others is required to advance our understanding of SVM in British Columbia. This revised version was published online in June 2006 with corrections to the Cover Date.     

生态．植被．泉水

作者对济南泉水由６０年代常年昼夜喷涌到８０年代百泉干涸的变化过程，作了简要回顾，用对比分析方法着重探讨了生态、植被和泉水的内在联系。认为森林植被状况是影响济南市地下水位和泉水涌量的根本原因，提出了以大规模生态工程建设，增加地面植被，丰富地下水源，作为保泉基本措施的建议。     

Seasonal changes of understorey herbage yield in relation to light intensity and soil moisture content in a Pinus pinaster plantation

The relationship of understorey herbage yield with light intensity and soil moisture content was investigated in a 20-year-old Pinus pinaster plantation in Kilkis of Macedonia, northern Greece, in three seasons (fall, winter and spring). The plantation was thinned at three density levels, high, medium and low (2500, 1750 and 1000 trees/ha respectively) and it was seeded with Dactylis glomerata. In addition, two fertilization levels (0 and 110 N+150 P₂O₅ kg/ha) and grazing intensity levels (0 and 0.8 sheep/ha/yr) were applied in a split-split plot experimental design. It was found that herbage yield was highest in the ungrazed and fertilized low tree density stands in all seasons. In the medium tree density stand, although light was lacking, fertilized plots produced higher herbage yield as compared to unfertilized low tree density stands while fertilization is of no use in close stands if herbage production is the goal. Animals seemed to prefer fertilized and medium density stands. Third degree polynomial equations were the best to explain herbage variation through the seasons both in fertilized and unfertilized plots.     

Establishment and early growth characteristics of six Paulownia genotypes for goat browse in Raleigh, NC, USA

Meat goat production in the eastern USA is increasing as a result of growing demand from various ethnic groups. Because goats naturally prefer a high proportion of browse in their diets, research was initiated to investigate various silvopastoral production systems. The genus Paulownia contains several species which exhibit rapid juvenile growth and other characteristics that justify research into their potential use in meat goat feeding systems. In May 1997, six Paulownia genotypes were planted in a randomized complete block experiment with six replications. Trees were between 6 and 12 cm in height at planting. Genotypes included: P. fortunei seedlings, P. tomentosa seedlings, P. elongata seedlings and three P. elongata clones. Each 4-m wide plot contained a single row of 12 trees with an intra-row spacing of 1 m. Plant measurements included height, root collar diameter (RCD) at 3 cm above soil surface, and the number of main branches. Leaf samples were collected from all six replications for estimates of herbage quality. During 1998, trees were browsed with goats on two occasions to assess palatability of the herbage and to determine any preference for specific genotypes by the animals. Compared with seedling trees of all three species, the three P. elongata clones were taller (clones: 79.7 cm, seedlings: 55.9 cm; P < 0.01), had larger RCDs (clones: 18.4 mm, seedlings: 13.9 mm; P < 0.01) and had a higher branching frequency (clones: 4.9, seedlings: 1.5; P < 0.01) by the end of the first growing season. Mortality averaged 4.8% across all treatments and ranged between 0 and 8%. Early in the 1998 growing season before trees were browsed, P. elongata clones grew more rapidly than seedlings (clones: 116.4 cm, seedlings: 84.1 cm; P < 0.01). Estimates of herbage quality indicated favorable concentrations of energy and protein for lamina. In vitro true dry matter disappearance ranged from 85.4 (blades) to 71.5% (petioles) and crude protein from 25.1 (blades) to 4.9% (petioles). Animals readily browsed the lamina during two separate sessions, but no clear preference trends were observed among the different Paulownia genotypes.This revised version was published online in November 2005 with corrections to the Cover Date.     

Traditional agroforestry practices in Zimbabwe

Traditional agroforestry systems in the communal areas of Zimbabwe are described. There are systems centered on main fields, on home gardens, on homesites and on grazing areas. In the main fields, the major tree-related management practice is the conservation of preferred indigenous fruit trees. Fruit trees are also the focus of forestry activities around the gardens and the homesite; but here it is the planting of exotic species. In a localized area of Zimbabwe Acacia albida is important in fields. There is almost no use of tree fallows in Zimbabwe. Trees in grazing areas have numerous roles, but at present there is little knowledge about traditional management practices in these areas. In the development of agroforestry systems in Zimbabwe it is suggested that those systems designed to improve fodder production will make a significant contribution to farm productivity because of the importance of cattle in the farming system and the present fodder shortage. Interventions involving the planting of fruit trees are likely to be very successful, as there is much interest in such planting. Another area that needs to be developed is that of tree plantings to improve soil fertility.     

Agroforestry systems in North America

Agroforestry systems in North America vary widely in terms of components (tree, forb, graminoid, and shrub species) and outputs. Most of the agroforestry systems used in North America have emphasized wood and livestock production. The objective of each system has been to produce annual and long term economic returns and sustainable yields. Inputs such as fossil fuels, fertilizers, herbicides and pesticides are relatively low compared to those used in conventional agriculture.Major agroforestry system types in each of eight North American regions are described. The major species used as vegetational components in each system are enumerated by region. The numerous variations in how these components are mixed have created an almost endless number of actual systems. Management problems and solutions, economic concerns, and system comparisons have also been addressed for each region.     

Effects of Land Use and Wildfires on the Habitat Selection of Great Bustard (Otis tarda l.)—Implications for Species Conservation

Increasing agricultural activities have been shown to affect soil and vegetation changes leading to serious biodiversity declines throughout the world. These effects are amplified in dry grassland areas, where resulting changes in habitat structure affect threatened animals on long temporal scales. Great bustards (Otis tarda) inhabit open landscapes where fire and grazing have been a part of the natural disturbance regime since historical times. Even fire and grazing are hypothesized to be important factors in the lifecycle of the species, studies are still missing on disturbance‐related lekking distribution patterns of great bustards. We analyzed the importance of fires and grazing on the spatial distribution of lekking bustards controlling for habitat types, habitat diversity, distance from roads and social effects. Our standardized dataset spanned 31 years, being one of the largest datasets on bustard lekking. During the 31 years we observed 10 118 individuals at 639 observation points in Hortobágy National Park, East‐Hungary. One of the most important predictors for total number of birds and number of males was the area burnt in previous years. We found that increased habitat diversity had a positive effect on female numbers. Models fit on second‐ and third‐year burn data detected no substantial role of burning on lekking distribution. Our results suggest that introduction of a patch‐burning management system in lekking areas could increase the availability of optimal lek sites for bustards. As an effective management tool, we suggest applying patch‐burning annually in a spatially mosaic structure inside the area occupied by each sub‐population unit. Copyright © 2016 John Wiley & Sons, Ltd.     

祁连山坡地草场水土流失回归模型的建立

通过对祁连山坡地草场过度、中度和轻度放牧类型产生水土流失的数据分析，运用回归分析及方差显著性检验对径流量和土壤流失量、降水强度对水土流失量的影响情况进行了分析，结果表明，过度放牧观测小区水土流失量（E）与径流量（F）、径流系数（C）及降水量（P）之间呈现E=68.4831 3.9532F-0.8586C-11.1243P的拟合关系（r=0.9091），中度放牧地呈现E=2.8184 0.8692F-0.3325C-0.6627P的拟合关系（r=0.9734），轻度放牧呈现E=-0.0019-0.0781F-0.0009C-0.0005P的拟合关系（r=0.8986）。同时指出当降水强度一定时，坡地草场由于放牧强度不同，其径流系数差异显著，过度放牧草地在雨季有较大降水量是流域内产生水土流失的主要来源。