Marginal effects of silvicultural treatments on soil nutrients following harvest in a Chinese fir plantation

Despite the widespread recognition that silvicultural treatments (prescribed harvest residue burning, site preparation and replanting) applied following clearcutting may cause soil erosion and nutrient loss in Chinese fir ( Cunninghamia Lanceolata (Lamb.) Hook) plantations, it is unclear which specific treatment leads to nutrient loss and whether an appropriate implementation of the treatments during the dry season could avert nutrient loss altogether. To address these two questions, nutrient changes in Alliti-Udic Ferrosols soils within a Chinese fir plantation located in Huitong County, Hunan Province, were investigated through the analysis of soil samples sequentially collected at depths of 0–15 cm and 15–30 cm before and after harvest with the residue material kept in place, a prescribed residue burning operation, site preparation and tree replanting initiative took place. Individual treatments significantly affected the soil pH value, organic matter and C and available N at depths of 0–15 cm, but did not significantly influence soil bulk density, total N and P contents and available P contents. The soil pH value decreased with successive application of the treatments. Soil organic C increased by way of the remaining residue after clearcutting, but declined after prescribed residue burning and ultimately returned to pre-harvest values after site preparation as a result of soil displacement and burning ash. Available N contents decreased significantly after clearcutting and residue burning, but the reduction was more or less offset after site preparation took place. Results after all silvicultural treatments were applied showed that no significant reduction in soil organic matter, C and N and P occurred to date in the Chinese fir plantation studied, suggesting that nutrient loss could be averted if the treatments were implemented during the dry season.     

秸秆全面禁烧后的病虫害防控

介绍了宿迁市的一些农作物病虫害随着秸秆的全面禁烧呈加重趋势,如灰飞虱虫量高,玉米粗缩病大面积发生,地下害虫加重,部分稻田僵苗严重等,这给农作物生长带来了安全隐患,增加了防治难度。提出了一些综合治理策略。     

运动式治理向长效治理的范式转变——以山东和东北地区秸秆禁烧运动为例

在推进国家治理体系和治理能力现代化的大背景下,推动运动式治理转向长效治理,是实现社会治理目标的必要举措。基于此,以山东和东北两地秸秆禁烧运动为例,采用定性研究方法,从政策目标制定、政策执行机制和治理效果评价三大维度阐述两地在秸秆禁烧治理中的运动式治理过程,并提出以用促禁,推动运动式治理向长效治理进行范式转换,以实现治理效果的长期化、稳定化。     

Fire Return Interval and Season of Fire Alter Bud Banks

Despite the importance of vegetative reproduction in annual tiller replacement, little is known about the patterns and timing of tiller recruitment from the bud bank, especially regarding fire return intervals and seasons of fire. We examined aboveground plant density, temporal patterns of tiller production, and belowground bud bank dynamics for Bouteloua gracilis (Willd ex. Kunth) Lag. ex Griffiths), Pascopyrum smithii (Rydb.) A. Löve, and Hesperostipa comata (Trin. & Rupr.) Barkworth following summer, fall, and spring prescribed fires at 2-yr, 3-yr, and 6-yr fire return intervals, and their interactions. Fire treatments were initiated in 2006, and buds were assessed July 2011 through July 2013. Density and number of reproductive B. gracilis tillers increased in 2013 following drought during 2012, unlike H. comata, which decreased reproductive tiller production. Irrespective of fire treatments, B. gracilis produced the most buds (8 ? 10 buds ? tiller^? 1) and H. comata produced the least (2 ? 3 buds ? tiller^? 1), with P. smithii producing an intermediate amount (6 ? 8 buds ? tiller^? 1). Immediate B. gracilis and P. smithii bud mortality did not occur for all season and fire return interval treatments. However, H. comata bud mortality increased immediately following summer and fall prescribed fires. Three-yr fire return intervals increased active buds throughout the 2013 winter and growing season for B. gracilis and P. smithii relative to control plots and 2- and 6-yr fire return intervals. Fire stimulated bud activity of B. gracilis and P. smithii relative to nonburned plots. The aboveground and belowground response of H. comata indicated meristem limitations following fire treatments, illustrating greater vulnerability to fire for that species than B. gracilis and P. smithii.     

冬季火烧对青藏高原亚高山草甸草地地上生产力和植物群落的影响

以2010年1月21日发生于青藏高原亚高山草甸草地火灾的过火草地为对象,通过对比2010年生长季火烧与未火烧草地生产力及植物群落的变化,发现火烧后第1年草地生产力有不同程度提高,以高寒灌丛草甸线叶嵩草+发草+苔草草地增产影响最大(P0.05)。火烧对植物群落中的种类成分没有明显影响,但在各火烧草地牧草经济类群中,以占优势的莎草科植物呈现出明显的增产效果(P0.05),说明火烧对根茎型莎草科植物起着刺激生长的作用。群落中禾本科植物产草量均有较大幅度下降(P0.05),表明火烧对根茎型禾本科高草的叶层高度有明显的抑制。火烧对各类草地植物生长期产生不同的影响,牧草返青期提前15~25d,生长期延长。     

Determinants of the occurrence of a native encroacher species,Pechuelloeschea leubnitziae (wild sage), in the eastern Okavango Delta,Botswana

Although indigenous to southern Africa, Pechuel-loeschea leubnitziae is considered a problematic weed as it forms dense monotypic stands in the grasslands and woodlands of the Okavango Delta, Botswana, and is associated with veld degradation and a dominance of shade-tolerant, poor-quality grass species. Generalised linear modelling was used to determine the effect of the following environmental conditions on the likelihood of occurrence of P. leubnitziae: type of land use, vegetation type, burning history, total woody species density, soil pH and soil texture. There was no difference in P. leubnitziae presence under wildlife, large livestock and small livestock land use (p = 0.227). Only vegetation type (p<0.001) and total woody species density (p<0.001) significantly affected P. leubnitziae occurrence, with the species being rare in dense mopane woodlands and most likely to occur in mixed thornveld and mixed broadleaf woodland, although this likelihood decreased with increasing total woody species density. A single burn had no effect on P. leubnitziae occurrence, but repeated burning should be investigated as a means to reduce the vigour and recoppicing success of P. leubnitziae.     

茶园化学除草试验效果

比较了８种除草剂的灭草效果,证明该８种除草剂均有除草效果,但除草剂之间具有显著差异。同时发现,除草剂对茶树具有一定的药害。     

焚烧枯草对三色堇幼苗及其根际微生物的影响

利用选择性培养基,对焚烧和未焚烧土壤中的三色堇幼苗根际微生物进行分离,分析其数量变化;用简单装置测定2种土壤中三色堇幼苗的生理指标;用钾稀蓝吸附法测定2种土壤中的三色堇幼苗的根系活力。结果表明:相比于未经焚烧过的土壤,经焚烧过的土壤中的三色堇幼苗根际单位根菌量真菌、细菌、放线菌、磷细菌、钾细菌都减少了。在同样生长时间内,经枯草焚烧过的土壤中的三色堇幼苗在苗体积、根湿重、根干重、根体积等方面均明显低于未焚烧的土壤,而苗高、苗湿重、苗干重3方面变化不大。而枯草焚烧土壤比未焚烧土壤中的三色堇幼苗根的总比表面和活跃比表面均减少。     

秸秆焚烧土壤提取液对小麦种子萌发和幼苗生长的影响

采用水培法研究了秸秆焚烧土壤提取液对小麦种子萌发和幼苗生长的影响。结果表明,种子发芽势较秸秆焚烧前土壤提取液培养的种子明显提高,但种子发芽指数、发芽率和活力指数与焚烧前处理无差异;幼苗芽长、胚根长和须根数与秸秆焚烧前处理差异均不显著,但苗鲜重和苗干重均明显减少;种子萌发期α-淀粉酶活性较秸秆焚烧前处理明显下降,胚乳储藏物质转化率明显降低;幼苗叶片叶绿素和可溶性蛋白含量与秸秆焚烧前处理无显著差异,但净光合速率明显降低。这些结果揭示秸秆焚烧土壤对小麦种子萌发影响不大,但不利于小麦幼苗生长。     

农作物秸秆资源化利用技术与发展方向探讨

农业秸秆作为一种可再生能源资源,充分开发利用可促进当地经济发展和能源结构调整,其经济效益是十分可观的。大力发展农作物秸秆利用产业,对于充分利用作物再生资源,增加农民收入,推进科技创新,建立循环经济发展模式和环境友好型社会,具有重要的经济意义和深远的社会意义。