Influence of prior land use on wood quality of Pinus radiata in New South Wales,Australia

Wood quality data from 33 sites aged between 15 and 18 years old were analysed to determine the effect of prior land use (pasture, cleared grazing land or timber) on wood density, wood stiffness, fibre length and kraft pulp yield. Sampling sites covered 6 different forest areas within the estate. Prior land use (PLU) significantly affected wood stiffness, density and fibre length but not the kraft pulping traits. In contrast, differences were found between different forest areas for the kraft pulping traits plus fibre length but not for stiffness or density.     

西北牧区退牧还草工程生态补偿依据与标准

针对西北牧区退牧还草补偿标准的不合理性,依据草地承载力理论和草畜动态平衡原理,采用西北牧区草地资源数据,结合草地生态经济系统中单位草地的净初级生产量和载畜量,确定退牧区不同草地类型禁（休）牧饲料粮、围栏、补播的补偿标准．     

Soil Phosphorus Remediation by Bahia Grass,Common Bermuda Grass,Crab Grass,and Switch Grass

Soil phosphorus (P) removal by harvest may be a practical remediation strategy. Small plots of bahia grass (BG) (Paspalum notatum Flügge), common bermuda grass (CB) (Cynodon dactylon (L.) Pers.), crab grass (CG) (Digitaria ciliaris (Retz.) Koel.), and switch grass (SG) (Panicum virgatum L.) were established on a coastal plain soil (Mehlich 3P, 100–500+ mg kg^?1) . Yield, tissue P concentration, and uptake P were determined in 2002–2005, and surface (0–15 cm) soil P were determined in 2002 and 2005. The uptake decreased, SG > CG > BG = CB (range 230–90 kg ha^?1), paralleling the decrease in surface soil P. Uptake depended on soil P (P < 0.01–0.10), with uptake > surface soil P decrease at low soil P due to uptake from subsoil but decrease > uptake at high soil P due to leaching. Soil P concentration did not affect SG tissue P nor did multiple harvests decrease its relative productivity.     

Soil carbon dynamics under young tropical secondary forests on former pastures—A case study from Panama

Secondary forests are gaining increased importance in tropical landscapes and have recently been reported to act as potential belowground carbon sinks. While economic interest in the management of secondary forests to mitigate carbon emissions is rising, the dynamics of soil carbon stocks under these ecosystems remain poorly understood. Recent studies report conflicting results concerning soil carbon trends as well as multiple confounding factors (e.g. soil type, topography and land-use history) affecting these trends. In this study, organic carbon stocks were measured in the mineral soil up to 20 cm depth of at 24 active pastures, 5-8-year-old, and 12-15-year-old secondary forest sites on former pastures. Additionally, we estimated carbon stocks under a 100-year-old secondary forest and compared them to those of nearby mature forests. Abiotic conditions in the study area were homogenous, enabling us to isolate the effect of land-use change on soil organic carbon stocks. Contrary to our expectations, soil carbon stocks in the top 10 cm did not change with young secondary forest development. Pasture soils stored 24.8 ± 2.9 Mg ha⁻¹ carbon (mean ± standard error) in the top 10 cm, and no accumulation of soil carbon was apparent during the first 15 years of secondary succession. Soil carbon stocks under 100-year-old secondary forests, averaging 43.0 ± 7.9 Mg ha⁻¹ (mean ± standard error), were clearly higher than those recorded at younger sites and approached levels of soil carbon stocks under mature forests. These data indicate that soil carbon stocks in this region of Panama are not affected by the land-use transition from pasture to young secondary regrowth. However, an increase of soil carbon storage might be possible over a longer period of time. Our results support trends observed in other tropical areas and highlight the importance of environmental conditions such as soil properties rather than land-use transitions on soil carbon dynamics. While our understanding of organic carbon dynamics in tropical soils remains limited, these results underscore the challenges of undertaking short-term reforestation projects with the expectation of increasing soil carbon sequestration.     

牧草图像快速分割方法及比较分析

针对北方典型牧草植物-苜蓿图像,采用多种常用的灰度化方法,并对其中的超绿法和Cr色彩法进行了改进,结合灰度图的特点,选用了单阀值分割和基于欧式距离的聚类分割方法将图像二值化,实现了苜蓿与背景的分离提取.利用大量的图像样本,对图像的分割准确率进行了统计分析和比较研究,得到了常用算法的定量评价和分割效果,得到了针对苜蓿图像的有效分割方法,为进一步实现牧草自动识别提供了依据.     

略论经济开发与生态环境的再适应——以黔西北畜牧业的衰落为例

黔西北位处长江、珠江的中上游,就自然背景而言,其主体为典型的疏林草坡生态区,生态系统十分脆弱,一旦开发不当,就会出现土地石漠化、沙化等生态灾变。历史上,生息在这一地区的氐羌系统各民族一直实施农牧混合生计模式,这样的生计模式不仅繁荣了当地的经济,维护了生态系统的稳定,而且还为长江、珠江中下游水资源的稳定做出过重要贡献。康熙＂改土归流＂后的300余年间,随着垦殖面积的扩大,无序的矿业开发,不但没有出现经济的大繁荣,反而诱发了诸种生态灾变,成了当前贵州省结构性贫困和经济性贫穷的重灾区。因此认真总结历史时期黔西北畜牧业衰落的经验教训,对于当前贵州省的经济建设、生态建设大有裨益。     

Cool-season annual pastures with clovers to supplement wintering beef cows nursing calves

ABSTRACT: In December of 3 years, 87 beef cows with nursing calves (594 +/- 9.8 kg; calving season, September to November) at side were stratified by body condition score, body weight, cow age, and calf gender and divided randomly into 6 groups assigned to 1 of 6 cool-season annual pastures (0.45 ha/cow) that had been interseeded into a dormant common bermudagrass (Cynodon dactylon [L.] Pers.)/bahiagrass (Paspalum notatum Flugge) sod. Pastures contained 1 of the following 3 seeding mixtures (2 pastures/mixture): 1) wheat (Triticum aestivum L.) and ryegrass (Lolium multiflorum Lam., WRG), 2) wheat and ryegrass plus red clover (Trifolium pretense L., WRR), or 3) wheat and ryegrass plus white (Trifolium repens L.) and crimson clovers (Trifolium incarnatum L., WRW). All groups had ad libitum access to grass hay (12% crude protein; 58% total digestible nutrients). The second week in December, cow estrous cycles were synchronized and artificially inseminated. In late December, a bull was placed with each group for 60-d. Data were analyzed with an analysis of variance using a mixed model containing treatment as the fixed effect and year as the random effect. Body weight and condition scores did not differ (P > 0.27) among cows between February and June. Calf birth weights or average daily gain did not differ (P [greater than or equal to] 0.17) among treatments; however, calves grazing pastures with clovers did tend (P = 0.06) to weigh more than calves grazing grass only. Weaning weight per cow exposed to a bull was greater (P = 0.02) for WRR and WRW than WRG. Cows grazing winter-annual pastures containing clovers tended to wean more calf body weight per cow exposed to a bull than cows grazing the grass only pastures.     

硫肥对内蒙古典型草原牧草产量和品质及绵羊生产的影响

该试验于１９９５－１９９６年内蒙古草原生态系统定位研究站进行。土壤类型为沙质栗钙土，０－３０ｃｍ土层有机质含量１．５０％左右，有效硫含量８ｐｐｍ分别设在三块１ｈｍ＾２的围栏样地，１９９５年５月－一次性施入０，３０和６０ｋｇ硫肥（ＣａＳＯ４．２Ｈ２Ｏ），分别定期测试草原群落生产力，主要草种地上生物量以及１．５岁内蒙古细毛羊的体重和羊毛等生产性能。     

Human land use and patterns of parasitism in tropical amphibian hosts

Landscape alterations by humans can change patterns of parasite transmission. Depending on the type alteration and the life histories of parasites and hosts, parasitism may increase or decrease. To investigate whether parasitism in tropical amphibians was associated with land use change, I studied three species of amphibians, Rana vaillanti, Eleutherodactylus fitzingeri, and Smilisca puma from the Province of Heredia, Costa Rica, in the Atlantic lowlands. Frogs were collected and examined for parasites during the rainy seasons of 2001-2003 from sites in forest or clear-cut cattle pastures. The abundances of five species of parasites and parasite species richness of R. vaillanti were significantly higher in pasture habitat. A single parasite species shared by E. fitzingeri and S. puma showed a trend of increased abundance in pasture habitats. Overall, the abundances of six parasite species (three trematodes, an intestinal nematode, an encysted nematode, and a filarial nematode) were higher in pastures, while two species (trematodes) were higher in forest. This study suggests that land use activities in tropical regions affects the abundance and richness of amphibian parasites. Converting forest to pasture may impact the abundance of amphibian parasites because subsequent water quality changes (e.g. eutrophication, higher pH) often enhance habitat and resources for intermediate hosts (e.g. snails, mosquitoes) involved in parasite life cycles. Aquatic amphibians (e.g. R. vaillanti) may be particularly prone to experiencing increases in parasitism in agricultural habitats due to the positive relationship between many aquatic intermediate hosts and water quality changes associated with agricultural land use.     

重庆喀斯特地貌型优良牧草引种筛选试验

通过3年对29个牧草品种物候期、适应性能、产量、主要营养成分、再生性能等进行的试验研究,在酉阳县3个不同海拔高度共筛选出20个优良牧草品种,其中豆科6个、禾本科11个、其他科3个。这些牧草产量高、适应性强、营养价值高,可作为喀斯特地貌型区域人工草地建植、天然草地改良的主打草种,可进行大面积推广。