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81.
喀斯特山地主要适生树种幼苗耗水量季节变化及对土壤干旱的响应 总被引:1,自引:0,他引:1
本文通过对柳杉等24个喀斯特山地主要适生树种一年生幼苗不同季节的耗水量进行比较研究、各树种幼苗在不同土壤干旱水平(A:无干旱胁迫;B:轻度胁迫;C:中度胁迫;D:重度胁迫)下的耗水量比较研究,结果表明:各树种幼苗耗水量的季节变化为:常绿树种幼苗耗水量为春季>夏季>秋季>冬季,落叶树种幼苗耗水量为夏季>春季>秋季>冬季。不同土壤干旱水平下,各树种幼苗耗水量均表现为:A>B>C>D。 相似文献
82.
雷公藤和昆明山海棠形态变异的研究 总被引:8,自引:3,他引:8
对雷公藤种质资源进行调查,建立种质资源收集库,定期观察雷公藤表型性状,研究形态标记的遗传变异,结果表明,雷公藤与昆明山海棠的叶片大小、叶背白粉、花序大小等主要分类特征存在显著的差异,但其变异是连续的,而且地理分布也是连续的;昆明山海棠、雷公藤均能适应长江流域的气候条件,但不同种源生长情况及主要活性成分含量存在明显的差异.雷公藤与昆明山海棠现行分类问题值得商榷,两者应属同一种植物,雷公藤与昆明山海棠的遗传多样性预示着遗传改良具有巨大的潜力. 相似文献
83.
根据临淄区2008年、2012年和2018年三期土地利用数据,利用地理信息软件对2008-2018年这10年间临淄区的土地利用变化和生态环境效应进行了计算分析。结果表明:研究区2008~2018年主要土地利用类型为耕地和建设用地。10年间,草地和建设用地的面积增加,耕地、林地、水域和其他用地的面积减小,耕地减少的面积最大,建设用地增加的面积最多。草地增加的面积主要来自耕地和林地,建设用地主要来自耕地;耕地和水域为生态高敏感类型,林地为中敏感,草地低敏感,建设用地和其他用地不敏感。2008~2018年期间的土地利用类型变化导致临淄区中高风险、较高风险和低风险区域的面积不断增加,而中风险和低风险的面积不断减少,临淄区区域总体生态风险增加;10年间,生态环境质量指数逐年下降,2008~2012年,耕地转换为建设用地是生态环境质量恶化的主要因子,耕地转换为草地是生态环境质量改善的主要因子;2012~2018年,草地转换为建设用地是生态环境质量恶化的主要因子,建设用地转换为耕地是生态环境质量改善的主要因子。 相似文献
84.
85.
Walter Seidling 《European Journal of Forest Research》2007,126(4):529-544
Crown transparency estimates of Scots pine, Norway spruce, common beech, pedunculate and sessile oak, annually surveyed between
1990 and 2004 within a grid over Germany, provide a suitable response variable to study drought effects on forest trees. Major
climatic factors, available on a monthly basis as plot-specifically interpolated values and parameters of site and stand conditions,
biotic and other relevant factors were used as predictors in different cross- and length-sectional, and longitudinal models.
Stand age is a considerable and most constant driver of crown transparency in all species. Pine, spruce and beech responded—mainly
with a delay of 1 year—with some foliar loss in areas where there was a surplus of temperature after the generally hot and
dry summer of 2003. Parallel time-series analyses delivered species-specific geographic large-scale patterns with delayed
or recent precipitation deficits or temperature surpluses. Even if beech is partly responding in current years with leaf loss
towards precipitation surpluses, defoliation is especially high 1 year after hot summers, partly a result of high seed sets
after such summers. Crown condition of oak responds in dry and warm areas according to the drought stress hypothesis, however,
in cool and wet mountainous ranges oak responds after wet summers with higher defoliation. Longitudinal approaches revealed
for all 4-tree species significant relationships between crown condition and deviations from the long-term means of temperature,
precipitation but also global radiation and wind speed. Results do not always match the drought stress hypothesis, however,
this is not to expect considering the heterogeneous site, stand and climatic conditions across Germany. Complex interactions
of climatic and biotic factors also impede simple relationships. Soil-related clusters reveal higher sensitivity of spruce
and beech towards climatic drought factors on more acid soils with thin humus layers. Also clusters constructed from plot-specific
courses of defoliation reveal groups with rather closer relationships like a group of pine plots in the Oberpfalz, which seems
to be especially sensitive to summer drought. 相似文献
86.
YU Da-pao GU Hui-yan WANG Jian-dong WANG Qing-li DAI Li-min 《林业研究》2005,16(3):187-192
Based on the tree-ring growth characteristics of Erman's birch (Betula ermanii charm.) and the relationships between it and climatic )'actors at elevation of 1950m, the sensitivity of tree lines in Changbai Mountain to climatic factors was assessed. The results indicated tree line forest in Changbai Mountain had an obvious sensitivity to climate factors. However, difference from other study sits is that the main climatic control factor on tree-ring growth was not current growth season temperatures, as might be expected, but previous winter and current March temperature. Although the precipitation in the region was quite abundant, the tree-ring growth was still significantly correlated with the precipitation during previous winter and current spring. Additionally, climatic factors which influenced the Erman's birch growth were not the yearly variables, but seasonal and monthly variables. Therefore, the reported increase in yearly mean temperature and total yearly precipitation since 1980s was not responded by sustained increase in ring widths in recent decades. 相似文献
87.
Eugene L. Chia Didier Hubert Kevin Enongene Yitagesu T. Tegegne 《Journal of Sustainable Forestry》2020,39(4):379-391
ABSTRACTAs the role of forests in climate change mitigation is explicitly recognized in the Paris Agreement, the need to enhance the adoption of Sustainable Forest Management (SFM) practices is crucial. Therefore, this paper aims at identifying and evaluating barriers in adopting SFM practices in the context of forest carbon emission reductions. A total of 15 barriers in adopting SFM practices are listed through literature and expert inputs. Using Cameroon as a case study, the listed barriers are then evaluated by experts to determine their relative importance using the Analytical Hierarchy Process (AHP) method. According to our findings, the ‘Regulatory and Legislative frameworks’ barrier category was attributed to the highest importance among other categories, in adopting SFM practices in the forestry sector. ‘Inadequate political will and incentive to enforce regulations’ appears to be the major obstacle in adopting SFM practices in Cameroon. As carbon emission reduction initiatives are being developed, there is need to move from broad to concrete suggestions that will overcome these barriers. However, proper diagnosis is necessary in order to target barriers with the right incentives and enabling conditions that will support carbon programs and projects to deliver effective emission reductions. 相似文献
88.
通过换冠改良技术,板栗幼树生长很快,丰产稳产且性能很好。大部分植株第2年挂果,第3年便能丰产,且产量稳定,其经济效益是非常显著的。 相似文献
89.
华山松针叶中矿质元素含量的地理变异 总被引:1,自引:1,他引:1
以12年生的种源林为取材对象,在1991年4月30日、7月30日、10月30日及1992年1月30日同时采当年和1年生针叶,测定N、P、K、Ca和Mg浓度。结果表明,除K外,其它矿质元素浓度种源间存在极显著差异。地理变异呈纬向渐变型。极端温度与元素地理差异有密切关系,并构成主导自然选择压。元素浓度的季节动态与针叶生长节律循环相伴。南、北华山松已分化成两个营养能力显著不同的地理种群,但动态模式基本相似。 相似文献
90.
IntroductionItissurethatpresentelevatiollsofCO2a11dotllergrcc11-housegasesinducedbyhumanactivitiesaren1akli1gglobalclimategothroughinexperielICedcl1anges(Scl1le-subgerl987).Thecurrentquasi-equilibriulllstatesofbio-sphereecosystCm,esPeciallyterrestrialecosystems,wouldbebrokenbecausetl1estructure,fu11ction,distributio11andtlledynamicsofanyexistedecosystemsareIberesultsoflongtermadaptationofbio-systemtocurrentclin1ate.Theec()systemsdistributedinhighlatitlldeareawouldhavemuchbiggerchai1ge(Bona… 相似文献