补充光照对欧洲云杉苗木生长的影响

光周期具有抑制苗木早期休眠,延长其生长期的作用,具有促进欧洲云杉苗木生长的作用,其在形态指标和生物量上表现得极显著.欧洲云杉大棚育苗补充光照的完整技术可采用整夜补光,随着光强度的增加,苗木生长形状各指标呈渐增的趋势.光质以白光较好.     

Refugee impact on collective management of forest resources: a case study of Bhutanese refugees in Nepal's Eastern Terai region

This article analyzes the relationship between forest resources, refugees, and the host population. The findings of the research suggest that the host population are heavily dependent on the local forest for their daily needs such as fuelwood, timber, grazing area, fodder for domestic animals, foods, and medicine in addition to cultural and esthetic needs. The forest has also been relied upon for agricultural needs such as manufacture of agricultural tools, maintenance of irrigation water systems, erosion control, and fertilizer needs. The forest was under a sustained demand as any other Terai forest of Nepal. After the arrival of refugees in 1992, the demand for forest resources increased substantially. Initially, the construction of the refugee camps decreased the total forest area and also required some felling of trees. More significantly, the refugees themselves became active users of the forest resource, which generated extra pressure on the forest and created scarcity of forest resources. Before the arrival of the refugees, forest management and monitoring of illegal use of the forest resources were carried out by the government through its local forester office. The local residents were active users of the forest resources, but were passive in managing and maintaining the forest resource. However, competition from the refugees instilled a desire in the local population to safeguard and protect the dwindling resource against the external threat by creating the Humse Dumse Community Forest.     

压实技术在公路改建工程中的应用

本文介绍了冲击压实机的冲击压实原理,结合工程实际讲述了冲击压实技术在改建工程施工中的运用情况及效果分析。     

Assessing raindrop impact energy at the forest floor in a mature Japanese cypress plantation using continuous raindrop-sizing instruments

The raindrop size distribution of throughfall and open rainfall was monitored continuously during a rainfall event using laser raindrop-sizing instruments (LD gauges), in order to calculate the raindrop impact energy in a plantation of mature Japanese cypress (Chamaecyparis obtusa), where surface erosion at the forest floor had been a problem. Data from two rainfall events were analyzed. The LD gauges recorded qualitative raindrop size distribution, and the capture rate during each rainfall event was used to manipulate raindrop data quantitatively. Throughfall and open rainfall comparisons revealed several important differences. First, throughfall raindrops were fewer in number and larger in size than open rainfall drops. In one rainfall event, for example, throughfall raindrops were less than one-fifth as frequent as open rainfall raindrops; in addition, the maximum throughfall raindrop diameter was 6.35mm compared to 3.31mm for open rainfall raindrops. Second, throughfall raindrops that were larger than the largest open rainfall raindrops comprised 63.8% of the throughfall precipitation by volume. Third, total raindrop impact energy from throughfall was over twice that of open rainfall. Moreover, comparison of throughfall events implied that throughfall raindrops did not always have a uniform distribution between different events or among different periods of time in one rainfall event, in contrast to findings in previous studies which showed that throughfall raindrops had a uniform size distribution independent of rainfall intensity. It is possible that an abrupt transition of throughfall intensity from low to high changes the distribution of throughfall raindrops.     

土壤水分动态对林地地表径流的影响概况

指出了土壤水分是影响地表径流产生重要因素之一 ,研究土壤水分在土壤中的分布、土壤水分动态变化规律以及影响土壤水分变化的因子 ,对林地的生态环境保护具有重要意义.土壤水分的分布受空间和时间的影响 ,不仅如此 ,土壤水分动态变化和分布规律还受到诸如气象因子、地形因子、地形利用因子、人为活动等因子的影响.这些影响因素都导致了土壤水分动态变化在空间和时间上的差异 ,从而导致了林地降雨-产流的差异.因此 ,深入研究影响土壤水分变化的各种因素 ,以及研究各种因素对土壤水分动态变化的作用规律 ,一方面能够为降雨-地表径流的发生规律提供参考 ,另一方面为保护林地植被生长提供了重要的条件.     

Herbicide risk assessment during the Wheat Self-sufficiency Project in Iran

BACKGROUND: The present study describes the quantitative changes in herbicide use during the specific observation periods in the Wheat Self-sufficiency Project in Iran from 1994 to 2004 and the associated changes in herbicide risk, area and yield in this context. A risk index, the environmental impact quotient (EIQ), was used to estimate the environmental impacts (EIs) of herbicides applied to wheat agroecosystems. RESULTS: The results suggest that, during this period, the overall risk posed by the herbicides applied to wheat agroecosystems increased substantially, as evidenced by a 71% increase in herbicide usage (weight of pesticide applied) and a 62.2% increase in EI rating, in spite of an 8.2% decrease in overall EIQ rating and an 89.2% decrease in mean application rate. Furthermore, a 0.57% increase in the area and a 23.6% and 22.7% increase in irrigated and rainfed yields, respectively, were observed. The results also indicate that the EIQ(FUR) of two herbicides, dichlorprop-P/mecoprop-P/MCPA and difenzoquat, is much higher than that of other herbicides, and they could be qualified as high-risk herbicides. CONCLUSION: As a whole, an increase in herbicide usage (weight of pesticide applied) was an important factor on herbicide environmental impact boost. However, this increase has not led to a similar increase in wheat yield, which could be attributed in part to the negative impact of high herbicide consumption in wheat fields and subsequent threat to the long-term sustainability of these agroecosystems.     

The potential environmental impact of pesticides removed from sprayers during cleaning

BACKGROUND: There is concern that pesticide residues on the external surfaces of sprayers could have an adverse impact on the environment if they are washed off, yet there is a need to remove these residues for health reasons. The aim of this study was to quantify pesticide residues contained in washings from cleaning discrete parts of a sprayer and to assess their likely environmental impact. RESULTS: The boom/rear of the sprayer and the spray tank accounted for 80% of the total pesticide load in the washings. Predicted environmental pesticide concentrations from sprayer washings were lower than predictions from the FOCUS surface water model for pesticides used under normal agricultural conditions, although for tebuconazole this difference was smaller than for the other compounds investigated. The field area over which the residues may need to be uniformly deposited to avoid overdosing during infield cleaning was typically less than 0.5 m(2), with a maximum value of 4 m(2). CONCLUSIONS: It is unlikely that infield cleaning will lead to overdosing. External residues are not insignificant, so any adverse impact on the environment must be mitigated. Appropriate measures include cleaning in the field away from surface waters and other sensitive areas, and cleaning machines over bunded areas or similar.     

不同土地利用类型氨挥发氮同位素自然丰度特征

为了探讨不同土地利用类型下氨（NH3）挥发氮同位素自然丰度特征,采集3种土地利用类型（果园、菜地和林地）土壤,在可控条件下采用海绵吸收法开展了为期15d的室内培养试验,测定了不同土地利用类型下土壤NH3挥发全过程δ15N值及其变化规律。培养期间,3种土地利用类型下的土壤NH+4-N浓度均呈现先上升后下降的趋势;果园和菜...     

皖南茶叶生长季气候资源变化特征及其影响分析

【目的】通过分析气候变暖背景下皖南地区茶叶生长气候资源变化特征,为皖南地区茶叶生产合理利用气候资源、应对气候变化提供科学依据。【方法】利用安徽省皖南山区19个气象观测站1971—2019年的逐日平均气温、日照时数、降水量、相对湿度等资料,分析气候变暖背景下皖南山区茶叶生长热量、光照、降水等气候资源及开采期变化特征。【结果】近50年安徽省皖南山区茶叶生长热量资源呈极显著增加,其中年平均气温、≥10 ℃活动积温和适宜生长日数增幅分别为0.29 ℃/10年、111.7 ℃/10年和2.7 d/10年;光照资源极显著减少,年均日照时数降幅为57.5 h/10年;降水资源变化不一,其中降水量呈增加趋势、增幅为13.7 mm/10年,相对湿度极显著降低,降幅为0.5%/10年。【结论】气候变暖造成皖南山区早生种和中晚生种茶叶开采期极显著提前,提前幅度分别为4.2、3.6 d/10年,气候变暖带来的气温和降水的变化对皖南山区茶叶产量影响较大。     

土地整理对水土体系的环境影响及减缓措施

近年来,土地整理项目在全国范围内广泛开展,在发挥巨大经济效益的同时,对环境的影响也日益受到专家学者的重视。因水环境和土壤环境是农业活动中最重要的2个环境要素且密不可分,该文将水土作为一个体系,综述了土地整理对其产生的影响,并提出了相应的减缓措施以减缓不利影响,使得其经济、社会和生态效应达到最大化。