Mineral concentrations of forages grazed by small ruminants in the wet season in benue state,Nigeria. II. Trace minerals and forage crude protein

Abstract

A total of 71 forage samples were analyzed for trace mineral and crude protein concentrations in three Agricultural zones of Benue State, Nigeria. The zones consisted of the Northern, Eastern, and Central zones, each of which was made up of four Local Government Areas. In each Local Government Area, grazing animals were followed and forages corresponding to those consumed were collected during the peak of the wet season (June) and analyzed for the nutrient composition. Deficiencies were observed in copper (Cu) and cobalt (Co) concentrations in all classes of forage, and in forage Cu and zinc (Zn) in all Local Government Areas in the Northern zone. A higher (P<0.05) forage Cu concentration was observed in legumes compared to other classes of forage in the Eastern zone. Concentrations of iron (Fe) and manganese (Mn) were considered adequate and their contents were not affected (P>0.05) by class of forage or Local Government Areas. In the Eastern zone, the contents of selenium (Se) in grass and tree leaf hay were higher compared to leguminous forage, which in turn was higher compared to Se concentrations in crop wastes. Only about 18% of total forage samples showed protein concentrations below the critical value of 7%. Supplementation of Cu, Zn, and Co would seem to be necessary in the Northern zone, and to a lesser extent in the Eastern zone for optimum productivity of grazing animals.     

Mineral concentrations of forages and soils in Benue State,Nigeria. I. Macrominerals and forage in vitro organic matter digestibility and crude protein concentrations

Abstract

Macromineral composition of different forage species and soils and forage in vitro organic matter digestibility (IVOMD) and crude protein concentrations in three agricultural zones of Benue State were studied. The zones consisted of Tiv zone (Zone A), Igala zone (Zone B), and Idoma zone (Zone C), each of which was made up of three sites. Site I was Fulani cattle migration routes across the state, site II represented grazing sites within home proximity, and site III were grazing reserves. Grazing animals were followed and forages corresponding to that consumed by them, and the corresponding soil samples were collected during the peak of the dry season (December‐January) and analyzed for nutrient composition. Forage IVOMD ranged from 21% to 79%, with values obtained in grass being lowest due to pronounced overmaturity. Only 10% of forage samples (exclusively from grasses), showed protein levels below the critical value of 7%. Most forage samples, as well as their corresponding soil samples were sufficient in calcium (Ca), magnesium (Mg), and potassium (K) concentrations. Soil concentrations of Ca, Mg, and K were particularly high compared to critical requirements in all the zones studied. Approximately 94% and 76% of forages were deficient in phosphorus (P) and sodium (Na), respectively, and the deficiencies were similar in all classes of forage and sites of study for each of the zones investigated. Results of forage‐soil relationships indicated low and nonexisting correlations; therefore soil analyzes are not of great importance in the assessment of available macromineral supplies to grazing livestock. The macrominerals most needed for supplementation of grazing livestock during the dry season are P, Na, and K.     

Mineral Concentrations of Cool Season Pasture Forages in North Florida During Winter-Spring Grazing Season. I. Macrominerals and Forage Organic Constituents

Two experimental late fall-winter-spring grazing studies, each lasting two years, were conducted at the North Florida Research and Education Center (NFREC), Marianna, Florida to evaluate the organic constituents and macromineral concentrations of annual cool season pasture forages grazed by growing beef cattle. Eight 1.32 ha fenced pastures or paddocks were divided into two pasture land preparation/planting methods, four pastures for the sod seeding treatments and four for the prepared seedbed treatments. These pastures were planted with two different forage combinations: rye/oats mix with or without ryegrass for the first two years (Study 1), and oats with ryegrass or ryegrass only for the last two years (Study 2). Each of the four forage/land preparation combination treatments was assigned to two pastures each year, thereby giving two replicates per year. Forage samples were collected at the start of grazing and twice monthly thereafter until the end of grazing season for each year, pooled by month, and were analyzed for calcium (Ca), phosphorus (P), sodium (Na), potassium (K), magnesium (Mg), dry matter (DM) yield, crude protein (CP), and in vitro organic matter digestibility (IVOMD). Blood plasma samples were also collected from the tester cattle during the spring season of year 2 of Study 2 and were analyzed for Ca, P, and Mg. Month differences were observed in forage concentrations of P and K (P < 0.0001), and Mg (P < 0.05) in both studies, Ca (P < 0.01) in Study 1 only, and Na (P < 0.05) only in Study 2. Year affected P, K, and Mg concentrations in Study 1 and Ca, P, and Na concentrations in Study 2. In Study 2, forage type by month interactions on Ca, K, and Mg concentrations were noticed (P < 0.01). Forage Ca was lower (P < 0.05) than the critical level for all months from the oat plus ryegrass pastures, and for early winter months and late spring months from ryegrass only pasture. Forage Na concentrations were consistently low throughout the grazing season and unaffected by forage type or land cultivation methods used in both studies. Low Mg concentrations of both forage types in Study 2 (also with high K concentrations) were indicative of a potential risk of grass tetany (hypomagnesemia) for grazing ruminants. Forage DM yields were highly variable with fluctuations among the experimental months and were found to be highest in the spring months, with decreasing yields towards the end of the grazing season in both studies (P < 0.0001). The CP concentrations were greater than the required levels and both CP and IVOMD decreased gradually by month in both studies (P < 0.0001). Normal blood plasma concentrations of Ca and P obtained were indicative of a good overall status of these minerals in the animal's body. Plasma Mg concentrations were slightly above the critical level for cattle from both forage types. In summary, the macrominerals most likely to be deficient in North Florida during the cool season would be Ca, Na, and Mg. Special attention should be given to supplementation of Mg since forages reflected a marginal deficiency of this mineral and high K concentrations were found.     

Monthly variation of forage and soil minerals in central Florida. I. macro‐minerals

Abstract

A two‐year study was conducted to determine the macromineral status of cattle grazed forages, mostly bahiagrass, and soils in central Florida. Soil and forage samples were collected every month for two years. Month differences (P < 0.01) were observed in all forage macrominerals and in crude protein (CP) for both years. No month effect (P > 0.05) was observed in IVOMD level during year 1. Year effects (P < 0.05) were observed in calcium (Ca), sodium (Na) and CP. Concentrations below the critical level were observed in all macrominerals studied. Higher forage macro‐mineral concentrations were found during spring‐summer months. In general, higher (P < 0.05) soil aluminum (Al), Ca, magnesium (Mg), phosphorus (P), and organic matter (OM) were observed during fall‐winter months, while Na was higher in winter. Soil Ca and Mg were adequate and potassium (K), Na and P were deficient. Year 2 showed higher (P < 0.05) soil macromineral concentrations. Correlation coefficients (r >|0.5|, P < 0.05) were present between forage K and forage CP (r = 0.557) and between forage P and forage CP (r = 0.554). Low correlations were found between soil and forage macrominerals. Percentages of total forage samples with macromineral and CP concentrations below critical levels (in parentheses) and suggestive of deficiency were as follow: in forage, Ca (0.30 ppm), 21%; Mg (0.18 ppm), 34%; K (0.60 ppm), 47%; Na (0.06 ppm), 89%; P (0.25 ppm), 85%; and CP (7%), 18%.     

Variation of forage and extractable soil minerals over two grazing seasons in North Florida

Abstract

A two‐year experiment was conducted at a north Florida farm to evaluate the mineral status of bahiagrass forages and soils. Forage samples were collected every 28 d throughout the grazing season, and soils evaluated twice yearly. The minerals calcium (Ca), sodium (Na), copper (Cu), cobalt (Co), selenium (Se), and zinc (Zn) were uniformly below the dietary requirements for growing beef cattle in both years. Forage magnesium (Mg), phosphorus (P), potassium (K), crude protein (CP), and manganese (Mn) were generally adequate throughout the grazing season, with the exception of low P concentration at the end of the growing season for both years. Extractable soil concentrations of Ca, P, K, Mg and Zn were adequate but low in Cu. Although CP was adequate (>7.0%) throughout the grazing season, IVOMD values were relatively low. There was a general trend for forage P, K, and IVOMD to decrease (P<0.05) with time.     

Agronomic comparison of six bermudagrasses from Southern United States with five tropical grasses in central Puerto Rico

The dry matter yield (DMY), in vitro organic matter digestibility (IVOMD) and crude protein (CP) content of eleven grasses were studied during the years 1992 to 1994 under mob grazing conditions. Offered and consumed dry forage do not differ significantly (P<0.05) among the highest yielding accessions Cynodon nlenfuensis PRPI 2341, Cynodon plectostachium PRPI 11487, and Cynodon dactylon cv. Tifton 85. However, the commercial Cynodon nlenfuensis PRPI 2341 was consistently the highest yielding accession both years. Among the other grasses, Digitaria eriantha showed the lowest levels of refused dry forage, thus presenting the best forage acceptability by grazing animals. Digitaria eriantha also showed the highest levels of IVOMD in both the short and the long day seasons. It is concluded that none of the evaluated Cynodon dactylon accessions from southern United Sates, nor the digitaria and brachiaria species adapted better than the commercial accession Cynodon nlenfuensis PRPI 2341. Warm‐season perennial grasses are grown extensively in the southeastern United States. Among the grasses, one of the most widely grown is from the species Cynodon dactylon, commonly named bermudagrass (Eichhorn, 1984). The choice of a bermudagrass cultivar for establishment of pastures is an important decision for cattlemen seeking high weight gains of stocker steers throughout the warm grazing season of the southern United States (Greene et al., 1989). Selection of improved bermudagrass hybrids has dramatically increased forage yield over that of common bermudagrass. Improved forage quality has also resulted in improved performance of grazing animals fed harvested hybrid bermudagrass forage (Gates et al., 1989). Reports on average daily weight gains (ADG) of yearling steers grazing different bermudagrass hybrids varied between 0.68 to 0.79 kg animal^‐1 day^‐1 during the summer season of southern Louisiana (Faw et al., 1986). Hill et al. (1993) in Tifton, GA, found yearling ADG of 0.67 and 0.65 kg animal^‐1 day^‐1 for the recent bermudagrass releases Tifton 85 and Tifton 78, respectively. Forage quality dry matter yield and grazing performance support the hypothesis that Tifton 85 will likely become an important hay and grazing forage for the southern United States. In Puerto Rico, Cynodon nlenfuensis PRPI 2341 (stargrass) is at present the grass cultivar most frequently grown on dairy farms (Ramos‐Santana and Randel, 1996). Yearly ADG of 0.59 kg animal^‐1 day^‐1 has been reported for young steers grazing stargrass in the humid tropical zone of Puerto Rico (Vicente‐Chandler et al., 1983). At Ona, FL, lower ADG of 0.54 kg has also been obtained with stargrass (Mislevy, 1989). The objective of this paper is to compare the agronomic performance (dry matter yield and quality) of six of the most outstanding bermudagrass hybrids from the southern United States, with five tropical grasses from the cynodon, brachiaria, and digitaria genera under the tropical conditions of central Puerto Rico.     

Soil,forage, and serum nutrient changes as affected by deposition of volcanic sediments in northwestern nicaragua

Abstract

A study was carried out to determine the mineral status of grazing cattle as affected by the eruption of the Cerro Negro Volcano in northwestern Nicaragua. A total of 14 composite soil and forage samples and 30 blood samples were collected at each collection period, before (August 1991) and after (August 1992) the volcanic eruption. Higher soil levels of calcium (Ca), sodium (Na), manganese (Mn) (P<0.01), zinc (Zn) (P<0.05), and lower organic matter (OM) (P<0.01) were found after the volcanic eruption. Phosphorus (P) was the only macromineral found deficient with 93 and 71% of the samples below a critical level before and after volcanic eruption, respectively. Forage Ca, potassium (K), magnesium (Mg), P, Zn, copper (Cu), and selenium (Se) concentrations did not vary between collections. Forage crude protein (CP), in vitro organic matter digestibility [(IVOMD) P<0.05], cobalt (Co), Mn, and Na (P<0.01) were lower after the eruption. Iron (Fe) was the only mineral in forages that increased (P<0.01) after the volcanic eruption. Of the six minerals evaluated in serum only Ca and Mg concentrations were higher (P<0.05) after the volcanic eruption. The macrominerals more likely to be deficient in this area are P and Mg. Trace elements most likely to limit cattle productivity are Zn, Mn, Cu, Se, and Co. Special attention should be given to supplementation of Cu, since both plant and animal tissue samples reflected a deficiency of this mineral.     

Mineral concentrations in leaves and stems of various forages of the Colombian paramo

Abstract

A study was conducted to determine the elemental composition of two plant fractions (leaves and stems) of several forage species in three sheep farms of the paramo in Colombia. The elemental composition of the forage species, and the relationship between soil chemistry and the elemental composition of the forages were also determined. Sampling periods corresponded to the end of the rainy season (May‐June 1987), and the middle end of the dry season (February 1988). Leaves were higher (P<0.05) than stems in the following: calcium, phosphorus, magnesium, potassium, iron, molybdenum, crude protein, and IVOMD. Overall percentage of deficiencies were related to the requirements for sheep as follows: calcium (88%, 13%), phosphorus (50%, 27%), magnesium (85%, 41%), potassium (13%,3%), sodium (94%, 96%), iron (10%, 4%), copper (82%, 65%), manganese (7%, 0%), zinc (46%, 42%), cobalt (92%, 85%), selenium (77%, 65%), crude protein (45%, 8%) for stems and leaves, respectively.

Based on analyses, elemental, crude protein and IVOMD concentrations of forage species, tended to differ. Soil‐forage correlation coefficients of the same mineral for the rainy season were calcium (r = 0.81), magnesium (r = 0.89), potassium (r = 0.71), zinc (r = 0. 69). For the dry season, correlations were calcium (r = 0.61) and magnesium ( r = 0.58). Results indicated low correlation coefficients between most soil and forage elements, and that they are not of great value in assessing the elemental status of grazing sheep in the paramo.     

Effects of pasture‐applied biosolids on forage and soil concentrations over a grazing season in north Florida. I. macrominerals,crude protein,and in vitro digestibility

Abstract

The rationale for this experiment was to determine forage nutrient concentrations as affected by biosolids fertilization. We studied the effects of single applications of two exceptional quality biosolids to bahiagrass (Paspalum notatum) pasture with regard to satisfying beef cattle nutrient requirements. Twenty‐five 0.8‐ha pastures were divided into five blocks. Two biosolids were applied as normal and double agronomic rates. The control plot received NH₄NO₃. Forages were analyzed for calcium (Ca), phosphorus (P), magnesium (Mg), potassium (K), sodium (Na), crude protein (CP), and in vitro organic matter digestibility (IVOMD), and soils were analyzed for Mehlich I extractable Ca, P, Mg, and K. Single (agronomic or twice this) applications of biosolids to pastures had little effect on Ca, P, Na, and K forage concentrations, but forage Mg was elevated in several treatments late in the season. Crude protein concentrations were elevated above the control for all biosolids treatments late in the season, whereas only small differences were observed at early sampling times. Trends were similar for IVOMD. In general, all treatments were associated with soils with adequate Ca, P, and Mg concentrations, while soil K was uniformly low. In relation to grazing beef cattle requirements, all treatments resulted in generally adequate forage levels of Ca, P, Mg, K, CP, and IVOMD, however, Na (<0.06%) was deficient.     

区域农用地土壤重金属超标评价与种植适宜分区

农用地是最宝贵的农业资源、最重要的生产资料,是人类最宝贵的财富。本文以江苏省某镇为例,采用单因子指数评价法、内梅罗综合指数评价法和潜在生态风险评价法对区域农用地土壤进行重金属超标评价,综合三种评价结果提出区域农用地安全利用等级和安全利用综合分区划分方案。基于安全利用综合分区和原有农业区划进行叠置分析后,以精细化管控用地为出发点,提出区域农业种植适宜区划分方案。结果表明:文章针对安全利用区、基本安全利用区、低风险监控区、中风险预警区和高风险限制区这5种安全利用综合分区,定性的提出了分区内涵、主要特征、安全水平提出相应的利用对策。(2)划分出4种区域农业种植适宜区:稻-茶-竹-栗-果适种区、林-竹-茶-果-栗适种区、稻-油-麦-豆-桑-瓜适种区、稻-麦-油-豆-百合、芦苇经济作物适种区。乡镇尺度区域农用地土壤重金属超标评价和种植适宜分区研究可为区域土地资源的合理、高效安全利用提供一定的科学依据。     

Identification of nutritional status,emphasizing minerals,in northwestern zaire

Abstract

A study was conducted in northwestern Zaire during the beginning of the dry season (December 1994) at a specific ranch to determine the crude protein (CP), in vitro organic matter digestibility (IVOMD), and mineral content of the principal pasture forages. This region is located in Zaire at 4°36'N latitude and 20°28'E longitude. Average rainfall is 1695 mm a year and mean monthly temperature is 25.5°C. Soils are red lateritic clays. Thirty forage samples were collected at 2‐, 3‐, and 4‐week regrowths of Imperata cylindrica and Savanna Stylosanthes (excluding 2‐week age) from low and high elevation grazing areas. Eighteen soil samples and a mineral supplement fed to cattle (primarily N'dama breeding) were collected for analysis. There were decreases (PO.05) in IVOMD as plants matured and deficiencies of protein, sodium (Na), phosphorus (P), magnesium (Mg), and copper (Cu) at 4 weeks of regrowth. The mineral mixture fed to cattle provided less than 1% of the requirements for the deficient minerals. This study suggests the need for provision of a suitable free‐choice mineral supplement.     

Yield,in vitro digestibility,crude protein,and mineral concentration of eight Digitaria introductions in Puerto rico

Abstract

Dry matter (DM) yield, in vitro organic matter digestibility (IVOMD), crude protein (CP) and mineral composition of eight Digitaria accessions were compared between long‐ and short‐day seasons in the semiarid southern region of Puerto Rico and evaluated in relation to grazing ruminant requirements. Digitaria milanjiana 6416 was consistently among the highest DM yielding accessions in both seasons. The mean IVOMD was similar in both seasons for most accessions. Concentrations of CP, magnesium (Mg), copper (Cu), zinc (Zn), cobalt (Co), and selenium (Se) were below the recommended levels for grazing ruminants in both seasons. This study suggests the need for livestock mineral supplementation, even under conditions of high pasture fertilization (NPK) and forage‐growing conditions in the semiarid southern region of Puerto Rico.     

Mineral Concentrations of Cool Season Pasture Forages in North Florida During the Winter-Spring Grazing Season: II. Trace Minerals

Trace mineral concentrations of annual cool season pasture forages grazed by growing beef cattle during late fall-winter-spring grazing season were evaluated during two experimental cool season grazing studies, each lasting two years at the North Florida Research and Education Center (NFREC), Marianna, Florida. Eight 1.32 ha fenced pastures or paddocks were divided into two groups of pasture land preparation/planting methods, four pastures for the sod seeding treatments (SS) and four for the prepared seedbed treatments (PS). Two different pasture forages, small grains, (rye/oats mix) with or without ryegrass for the first two years (Study 1); and oats with ryegrass or ryegrass only for the last two years (Study 2) were planted in these pasture lands. Each of the four forage, type, and cultivation combination treatments was assigned to two pastures each year, thereby giving two replicates per pasture treatment per year. Forage samples were collected at the start of pasture grazing and twice monthly thereafter until the end of grazing season, pooled by month, and analyzed for copper (Cu), iron (Fe), zinc (Zn), manganese (Mn), cobalt (Co), molybdenum (Mo), and selenium (Se). Liver biopsies and blood plasma samples were collected from the tester cattle only during the spring of year two of Study 2. Liver was analyzed for Cu, Fe, Mn, Co, Mo, and Se and plasma for Cu, Fe, Zn, and Se. Forage trace mineral concentrations were found to differ by month in Cu (P < 0.01), Fe and Zn (P < 0.0001) in both studies, and with Mn (P < 0.0001) in Study 2 only. Pasture forage type effects on Cu (P < 0.05), Fe and Zn (P < 0.01), and Se (P < 0.05) and forage type by month interactions on Cu and Mn (P < 0.0001), and Zn (P < 0.05) were observed in Study 2. Forage concentrations of Cu, Zn, Mn, and Mo in Study 1 and Mn, Mo, and Se in Study 2 were affected (P < 0.05) by pasture land preparation/planting methods in that these minerals were found to be lower from forages of sod-seeded treatments than from those of prepared seedbed treatments. Forage Cu concentrations were lower than the minimum requirements (10 ppm, DM) for beef cattle among months in both studies. Oats-ryegrass pastures of Study 2 had surprisingly low Fe concentrations (P < 0.01) in all months of the winter-spring grazing season. Cobalt, Mn, Mo, and Se did not vary much month to month during the winter-spring grazing months. All mean forage Se concentrations were lower than the requirements (0.10 ppm, DM) for grazing beef cattle. There were no differences (P > 0.05) in mean Se values between the two studies. Liver Cu, Fe, Co, and Se concentrations were sufficient to indicate adequate status of these minerals in tester animals from both forage types. Liver concentrations of Mn and Mo were slightly low, indicating a low status or these minerals. Plasma concentrations of Cu, Fe, Se, and Zn were all above the recommended concentrations for beef cattle. In conclusion, trace minerals deficient in North Florida during the cool season were Cu, Co, and Se, and a special consideration should be given to include adequate amounts while supplementing the mineral mixtures to growing beef cattle since forage samples reflected deficient concentrations of these minerals.     

Crofting and bumblebee conservation: The impact of land management practices on bumblebee populations in northwest Scotland

The northwest of Scotland is a stronghold for two of the UK’s rarest bumblebee species, Bombus distinguendus and Bombus muscorum. The predominant form of agricultural land management in this region is crofting, a system specific to Scotland in which small agricultural units (crofts) operate rotational cropping and grazing regimes. Crofting is considered to be beneficial to a wide range of flora and fauna. However, currently there is a lack of quantitative evidence to support this view with regard to bumblebee populations. In this study we assessed the effect of land management on the abundance of foraging bumblebees and the availability of bumblebee forage plants across crofts in northwest Scotland. The results of our study show that current crofting practices do not support high densities of foraging bumblebees. Traditional crofting practice was to move livestock to uplands in the summer, but this has been largely abandoned. Summer sheep grazing of lowland pasture had a strong negative impact on bumblebee abundance and forage plant availability throughout the survey period. The use of specific ‘bird and bee’ conservation seed mixes appears to improve forage availability within the crofted landscape, although the number of bees observed remained low. Of the forage plants available, the three most frequently visited species were from the Fabaceae. We therefore conclude that the creation of agri-environment schemes which promote the use of Fabaceae-rich seed mixes and encourage the removal of sheep grazing on lowland areas throughout the summer are essential in order to conserve bumblebee populations within crofted areas.     

A river runs through it: Land-use and the composition of vegetation along a riparian corridor in the Cape Floristic Region, South Africa

Riparian zones are important for the many ecosystem services they supply. In settled areas, the vegetation of such zones is shaped by human land-use; this often creates conditions under which alien plant species thrive. Alien plants have been shown to induce large-scale changes in riparian habitats, and they pose a major threat to the continued provision of key ecosystem services. We used direct gradient analysis to assess correlations between land-use and the composition of vegetation along a riparian river corridor in the highly transformed landscape surrounding Stellenbosch in South Africa’s Western Cape Province. Vegetation plots were sampled along the entire length of the river from headwaters to estuary (ca. 40 km). Plant community composition was analyzed in relation to land-use data collected in the field, and additional land-use variables computed from digital land-cover data. Patterns of plant community structure were found to be directly related to land-use, with measures of cover, richness, and diversity differing significantly among land-use types. Portions of the riparian zone adjacent to agricultural land had the greatest level of alien plant cover, while areas bordered by urban land maintained the highest alien species richness. Areas adjacent to grazing and natural lands showed intermediate and low levels of invasion, respectively. Several native species were found to persist in areas with high abundance and diversity of invasive alien plants, suggesting that they will be valuable focal species for future restoration attempts. Due to the level of human-mediated change in many areas of the riparian zone, restoration to historic conditions over most of the river is not considered feasible. These areas should be recognized as examples of novel ecosystems, and management efforts should focus on restoring or creating desirable ecosystem functions, rather than on achieving assemblages comprising only native species.     

Land use changes and raptor conservation in steppe habitats of Eastern Kazakhstan

Steppe habitats in central Asia have suffered important land use changes during this century which are similar to those that have been pointed out as the causes of the decline of steppe birds in western Europe. During June 1999 we conducted road surveys of raptors in Eastern Kazakhstan to detect specific and community responses to land use changes. We detected 11 species of raptors. Kestrels (Falco naumanni and tinnunculus) were the most common species in grasslands and agricultural landscapes, harriers (Circus pygargus and macrourus) were dominant in saline steppes and steppe eagles (Aquila nipalensis) were dominant in dry steppes. There were fewer species in agricultural habitats than in grassland and steppe habitats. Ground-nesting raptors were negatively affected by land use changes and four species were never detected in agricultural zones. Raptor abundance patterns differed between natural steppe habitats and human-transformed habitats, where a patchy distribution was detected. The future of raptor communities in Kazakhstan seems uncertain although the progressive abandonment of intensive agriculture may benefit species sensitive to human presence. The long-term conservation of vertebrate communities may depend upon the maintenance of ecologically and socially sustainable grazing systems.     

生态约束下的乡村旅游用地空间布局规划研究 ——以福建省晋江市紫星村为例

为避免乡村旅游开发引起乡村特色消失和生态风险加剧等负面影响,该文采用最小累积阻力模型构建福建省晋江市紫星村"自然?文化"综合生态安全格局,以此为约束条件对旅游用地进行空间布局规划,将综合生态安全格局划分为核心保护区、生态缓冲区、生态过渡区和人类活动区4类生态功能区,各区空间分布和土地利用现状决定了其差异化的用地特征。自然旅游用地规划以维持原有景观不变为主,对景观进行修复为辅的原则布局在生态缓冲区、生态过渡区和人类活动区内,采用GIS空间叠加分析法将金溪北部片区规划为农事活动体验区,农科所片区规划为农业生态观光区,紫溪水库、金溪规划为水域观光游览区。文化观光旅游用地和休闲旅游用地规划以景观不变和景观修复为原则,主要布局在核心保护区和生态缓冲区内;而农业科教旅游用地布局规划在人类活动区内,结合实地调研选址在下溪园北侧新建生态农业展览馆。服务设施用地规划以景观发生变化为原则,主要布局在生态过渡区和人类活动区,采用GIS核密度和空间叠加分析法划定顶溪园西北部为游客中心,金星村为民宿、餐饮集中布局区。其他旅游用地规划以景观不发生变化为原则布局在人类活动区内。生态约束下的乡村旅游用地空间布局有利于协调人与自然之间关系,对乡村旅游用地规划具有较强的理论与现实意义。     

农用地土壤重金属超标评价与安全利用分区

土地资源是大自然馈赠给人类的独特珍品,承载万物。开展区域农用地土壤重金属超标评价与安全利用分区、分类利用管控,促进区域土地资源合理、高效利用是新常态下耕地保护的基本要求。该文分不同p H值区间、8种不同地类,基于现行土壤环境质量评价和食品安全评价的众多标准集成土壤环境质量现状评价标准,以江苏省某市为例,运用单因子指数法、内梅罗综合指数法和潜在生态危害指数法开展土壤重金属超标评价,进而提出了安全利用等级划分方案和分区、分类利用与管理的管控策略。结果表明:将研究区农用地分为安全、基本安全、低风险、中风险和高风险5种综合分区,分别采取优先保护、综合监控、预警防控和限制利用等措施,以精细化管理思想为出发点,从源头控制、农艺措施调控、种植作物调整、地类转换以及土壤修复、综合整治等方面提出了各综合分区的安全利用管控策略。因此,开展区域农用地土壤重金属超标评价与安全利用分区研究为确保土地资源合理利用保护耕地提供了重要思路。     

Using Landsat Images and Spectral Mixture Analysis to Assess Drivers of 21‐Year LULC Changes in Sudan

Landsat images acquired in 1987, 1999 and 2008 were selected to evaluate land use and land cover changes in three different ecological zones in the Republic of the Sudan: savannah (North Kordofan), semi‐desert (River Nile) and desert (Northern State). Maps of soil, vegetation and non‐photosynthetic material were built by spectral mixture analysis using endmembers spectra derived from images. Multitemporal comparison techniques were then applied to vegetation and soil maps to estimate the long‐term land degradation/re‐growth dynamics and to emphasize land cover variation over time and in space. Multitemporal comparisons have shown that site‐specific interactions between natural processes, climate variation and human activity played a pivotal role in land use and land cover change. In savannah, human activities strongly affected degradation phenomena. Expansion of villages triggered a change in land use and mismanagement of the natural resources, mainly caused by deforestation to supply wood for domestic uses. The degradation then promoted sand encroachment and dune migration. On average, 48% of the total area was subjected to medium (25–50%) and high (50–75%) land degradation. Differently, climatic constraints drove increasing degradation processes in semi‐desert and desert zones. The phenomenon was particularly severe in the desert zone. In each site, an inversion of the general trend was due to a land use change where forestry or agricultural projects were established, partly sustained in savannah by the positive rainfall trend of the last two decades. Site‐specific strategies that take into account the interactions of the driving factors at local scale are thus necessary to combat land degradation. Copyright © 2016 John Wiley & Sons, Ltd.     

In vitro digestibility and crude protein and mineral concentrations of guinea grass accessions in a humid tropical region of Puerto rico

Abstract

The in vitro organic matter digestibility (IVOMD), crude protein (CP) content and mineral composition of ten Panicum maximum accessions were compared between seasons in Puerto Rico and evaluated in relation to grazing ruminants requirements. On short days, PRPI 13605 was superior (P<0.05) in IVOMD to all the other accessions. In terms of the CP content, accession PRPI 3634 was above 11% in both seasons, however, without differing (P>0.05) from most accessions. The mean macroelement content of the accessions was generally adequate in relation to grazing ruminant requirements with the exception of Na and Mg. Phosphorus was less than the critical concentration (0.25%) for one‐half of the accessions in the short day season and 2 of 10 for the long day season. For all samples, Mn was high and Fe was generally adequate in relation to ruminant requirements. Most all samples contained deficient concentrations of Co, Cu, Se, and Zn. Forage Mo concentrations, therefore, did not result in conditioned Cu deficiencies. In this context, it is probable that Na, Se, Cu, Co, Zn, and perhaps Mg, will be needed even if intensive fertilization is practiced in the humid tropical region of Puerto Rico.