A comparative analysis of forest cover and catchment water yield relationships in northern China

During the past few decades, China has implemented several large-scale forestation programs that have increased forest cover from 16.0% in the 1980s to 20.4% in 2009. In northern China, water is the most sensitive and limiting ecological factor. Understanding the dynamic interactions between forest ecosystems and water in different regions is essential for maximizing forest ecosystem services. We examined forest cover and runoff relationships in northern China using published data from a variety of sources. In the Loess Plateau region, forest cover is not correlated with annual precipitation (r = 0.08, p > 0.05) at micro (<50 km²) and meso scales (50-1000 km²), while they are positively correlated at macro (>1000 km²) scale (r = 0.77, p < 0.05). Moreover, forest cover is negatively correlated with the runoff coefficient (r = −0.64, p < 0.05). In Northwest China, natural forest distribution is highly correlated with annual precipitation (r = 0.48, p < 0.05) but not with the runoff coefficient (r = −0.09, p > 0.05). In Northeast China, we found a positive relationship between forest cover and the runoff coefficient (r = 0.77, p < 0.05), but the correlation between forest cover and precipitation was not significant (r = 0.28, p > 0.05). The multiple stepwise regression analysis indicated that runoff was influenced by altitude, annual precipitation, forest cover, and PET (potential evapotranspiration) in Northeast China. We concluded that geographic differences could mask the true role of forests in the partitioning of rainfall into runoff and evapotranspiration (ET) in a catchment. In determining the forest-water relationship, one must consider climatic controls on ET in addition to forest cover. Forests could potentially enhance the complementary relationship between ET and PET. Therefore, a greater amount of ET in forested areas may decrease the PET on a regional scale.     

陕西森林病虫害发生现状、原因分析及防控对策

本文根据陕西森林主要病虫害发生现状,从自然因素、人为因素、其他因素分析了陕西主要森林病虫害发生原因,并提出了加强森防检疫设施和队伍建设、加大森防工作的宣传力度、抓好监测预警、严把检疫关、树立健康的森林理念、明确目标责任,建立和完善管理体系、建立应对林业灾害快速反应机制等综合防治对策。     

Assessing drought risk and irrigation need in northern Ethiopia

Long-term climate data of four stations in the northern Ethiopia were analyzed in combination with information from local farmers and documented materials. From this analysis, a suitable drought-assessing technique was developed and site-specific needs for supplementary irrigation were explored. Results showed that our technique for assessing drought and crop failure corresponded well with farmer observations. The three major causes of crop failure (dry spells, short growing period and “total lack of rain”) which were explicitly listed and ranked by the local farmers were found to match the analyzed data well. The agro-meteorological variables with the most severe consequences were “short growing period” and “total lack of rain”. To prolong the growing period, supplementary irrigation is recommended in the month of September for three of the stations (Maychew, Mekelle and Adigudom) because: (1) rain frequently stops in early September or late August and crops have no other source of water for the rest of the growing period; (2) sufficient surface runoff can be harvested in July and August to be stored in farm ponds and used in September; (3) more cultivable land can be irrigated if supplementary irrigation is scheduled only for the month of September; and (4) giving supplementary irrigation in September can cut yield reduction by over 80% and crop failure by over 50%, except at Alamata. At Alamata, supplementary irrigation must be scheduled for July. The conditions experienced during the famine years of the early 1980s were primarily caused by the continued total rain failure over multiple years. Giving supplementary irrigation in July or September would probably not have mitigated the effects of these droughts, especially at Alamata and Maychew stations.     

基于生态足迹模型的喀斯特高原山地生态系统健康评价研究

黄土高原土地不合理利用是土壤侵蚀和水土流失的根本原因。以安塞县马家沟流域为例,采用1990年第一次全国土地利用调查图件,经过实地考查,获取2008年土地利用数据,分析了近20a来流域土地利用的变化趋势及类型间的转化情况。结果表明,马家沟流域1990—2008年农耕地类面积呈显著减少趋势,变化面积占流域面积比例为11.88%,同时草地类面积也减少了1.58%。林地类面积呈显著增加趋势,增加面积比例为11.61%,园地、居民地及工矿用地类面积也增加了1.73%和0.01%。流域农林草结构由1990年的3∶1∶6变为2008年的2∶2∶6。变化流向以草地变为林地,坡耕地类变为草地,坡耕地类变为林地,农耕地变为园地为主要特征。近20a间变化速率最快的地类主要是林地类、园地类和农耕地类,分别是8.06%,2.41%,-2.43%。近20a来流域林地类面积虽有增加,但人工生态系统的特征十分突出,良好自然生态系统的稳定性和持续性比较欠缺。1999年以来国家退耕还林还草政策的实施,以及农民经营方式的转变是林地和园地面积增加的主要原因。     

陕北农牧交错带50年来土地沙漠化的自然和人为成因定量分析

荒漠化的发生发展受自然及人为因素的共同作用,为了对自然及人为因素的贡献进行定量化分析,以陕北农牧交错带为研究对象,选择该区1949—2000年7个自然和人为因子,运用主成分分析方法,对土地荒漠化过程中的自然与人为要素作用强度进行量化分析。结果表明:1)陕北农牧交错带自1949年以来气候呈现暖干、冷湿交替过程,而未来气候将逐渐趋于暖干,但平均风速则呈现逐渐降低的趋势;人口和牲畜数量及工业总产值持续增长,人均耕地面积则持续下降,这些对荒漠化防治均是不利因素。2)在陕北农牧交错带荒漠化的发展过程中,自然因素的贡献率为13.06%,人为因素与自然因素综合作用的贡献率为73.51%。3)尽管自然及人为因素50年来的变化促进了荒漠化的发生发展,但自20世纪50年代开始的"三北防护林建设"和"退耕还林(草)工程"对阻止荒漠化的发展起到了关键作用。     

陕北丘陵沟壑区退耕还林(草)中土地的合理利用与管理

退耕还林(草)是陕北丘陵沟壑区土地资源利用、生态环境建设中植被恢复的重要措施,而合理利用和科学管理土地资源是实施退耕还林(草)战略的重要保证。分析了区域自然及土地利用特点,指出应遵循综合性、区域性、生态优先和土地的可持续利用等原则加强土地管理,增加投入,完善经营机制,才能实现土地生产力的提高和生态环境的改善。     

陕西猕猴桃主产区眉县果园土壤养分分析

【目的】全面了解陕西眉县猕猴桃果园土壤的管理水平,为生产提供合理的施肥依据。【方法】2008年冬季,对眉县422个果园土壤0～60cm土层样品采用十字交叉法取样,风干处理后对养分进行分析。【结果】全县猕猴桃园土壤速效氮含量最大值为169.5mg/kg,最小值6.07mg/kg,平均为23.08mg/kg,不及猕猴桃要求最低水平的20%;速效磷含量最大值205.4mg/kg,最小值4.5mg/kg,多数果园为中等水平,平均50.3mg/kg;速效钾含量最大值953.0mg/kg,最小值86.9mg/kg,平均389.5mg/kg,全部超过了最适范围;速效铁含量为0.351～26.251mg/kg,平均5.483mg/kg,普遍较低;有机质含量为8.18～34.34g/kg,普遍较高,平均水平接近17g/kg。【结论】建议在今后的施肥过程中增加氮肥的施用量,控制钾肥的施用量,维持或适量增加磷肥的施用量;结合具体果园的叶片症状,对有黄化现象的果园,应追施铁肥,继续加大对有机肥的投入,改善土壤环境;村与村及户与户果园之间土壤养分差异较大,土壤总体营养水平以上第二坡村和下第二坡村较高,青化村最低。     

The Empidemiology of Wheat Rosette Stunt in Hulunbeir District of Inner—Mongolia

The virus disease threatening wheat production in Hulunbeir District of Inner-Mongolia was identified as NCMV(Northern Cereal Mosaic Virus)or WRSV(Wheat Rosette Stunt Virus)by test of host range,transmission,virus particle and serology.The main vector for spreading the virus is planthopper,Laodelphax striatellus(Fallen),Which overwinters in the stubbles of wheat underground.The overwintered viruliferous nymphs emerged in late Pril is responsible for the early infection of the disease.Agropyron repens,an important perennial weed in cultivated regions,is also an important wild host of the virus and its vector.Severe loss is induced when wheat is infected before 3-leaf stage.The disease incidence could be predicted by a model with the population and viruliferous rate of overwintered vectors as independent variables.     

关中地区小麦品种株型变化的研究

对陕西关中地区５０年代以来大面积栽培及近期育成的２２个小麦品种品系株型性状进行因子分析、聚类分析和逐步回归分析，结果表明，５０年代以来小麦品种的株高构成指数、叶层重心相对高度、比叶重上升，株高、叶层重心绝对高度、叶片基角、叶片披角减小；增大穗长、叶层重心相对高度和比叶重，减小叶片的基角和披角对品种产量的提高具有正效应；冠层内的透光性主要受叶片基角、叶片披角和穗数的影响     

几种我国北方绿化树种滞尘能力的研究

[目的]随着城市环境污染问题的日益严重,树种的滞尘能力成为城市绿化树种选择的一个因子。[方法]对中国北方10种主要绿化树种的滞尘能力进行了研究。[结果]不同树种间滞尘能力存在很大差异,阔叶乔木树种中白玉兰、槐树的滞尘能力强,毛白杨和白蜡的滞尘能力弱;阔叶灌木树种中水木旬子、金银木和紫叶小檗滞尘能力强,连翘和女贞的滞尘能力弱。[结论]在北方城市绿化树种的选择上,应优先考虑乔木树种白玉兰、槐树,灌木树种水木旬子、金银木和紫叶小檗。