森林类型的最优化选择与经营设计          下载免费PDF全文

刘安兴  杜群 《浙江大学学报(农业与生命科学版)》2005,31(5):545-549

根据现代林业和浙江省木材资源缺乏的实际要求,选择一类生态和经济效益俱优的森林类型进行持续经营.应用景观生态学的原理,对浙江最优化的森林类型--马尾松阔叶树混交林的经营进行了研究,提出了该类型的经营模型,同时对浙江林农对马尾松林的习惯经营状况进行了分析.本文的研究可为浙江森林现实经营提供选择和经营方法.  相似文献   

玉米制种结实率低的原因及防止对策   总被引：4，自引：0，他引：4  

孙尚平  张利成 《山西农业科学》2002,30(3):14-16

花期干旱、高温是降低玉米制种结实率 ,造成花期不遇、花粉活力不强和授粉不好的主要原因 ;基地不稳定、亲本及花期管理混乱和档案不健全是造成结实率低的人为因素。进而针对性地提出了有效防止结实率降低的措施和对策  相似文献   

黑龙江省东部森林中雪的水文效益的初步研究   总被引：4，自引：0，他引：4  

任青山  魏晓华 《东北林业大学学报》1994,22(2):11-16

为了定量研究雪的水文过程，采用冬季野外直接观测法，研究森林对降雪，截雪，积雪，融雪的航森林融雪径流的特点。结果表明，森林的截雪率与林冠郁闭度关系密切，针叶林的截雪率是落叶林的２－３倍；人工红松林内积雪厚度最小，融雪持续的时间最长，而落叶杂木林内积雪厚度最大，融雪持续的时间较短，针混产林则介于二者之间；天然次生林的融雪径流占年径流量的２１．７％，河道径流主要以降雨径流补给为主，占年径流量的７０％以上  相似文献   

马尾松种源区内林分遗传变异及其阶段选择的研究   总被引：3，自引：2，他引：3  

江瑞荣 《福建林学院学报》1995,15(4):364-369

在福建马尾松优良种源区内，密集布点，选择林分，进行林分的遗传测定和分析。结果表明：马尾松优良种源区内林分间在树高、胸径、材积等调查性状上有着极显著的差异。树高、胸径、材积等生长性状的平均遗传方差分量为２６％，轮盘数具有较高的分量（７３．０６％）。１３个参试的初选林分，绝大多数比当地商品种长得快，在优良种源中再进行优良林分选择的材积、胸径、树高平均遗传增益分别为：４２．４７％、２０．４２％和１３．２１％。  相似文献   

Organic Farming Affects C and N in Soils Under Olive Groves in Mediterranean Areas     

Luis Parras‐Alcntara  Luisa Díaz‐Jaimes  Beatriz Lozano‐García 《Land Degradation \u0026amp; Development》2015,26(8):800-806

Under semiarid climatic conditions, intensive tillage increases soil organic matter losses, reduces soil quality, and contributes to climate change due to increased CO₂ emissions. There is a need for an agricultural management increasing soil organic matter. This paper presents the organic carbon (OC) and nitrogen (N) stocks, C:N ratio and stratification ratios (SRs) of these properties for olive groves soils under long‐term organic farming (OF), and conventional tillage (CT) in Los Pedroches valley, southern Spain. The results show that OF increased C and N stocks. The soil organic carbon (SOC) stock was 73·6 Mg ha⁻¹ in OF and 54·4 Mg ha⁻¹ in CT; and the total nitrogen (TN) stock was 7·1 Mg ha⁻¹ and 5·8 Mg ha⁻¹ for OF and CT, respectively. In the surface horizon (A: 0–16·9 cm in OF and Ap: 0–21·8 cm in CT) and Bw horizon (16·9–49·6 cm in OF and 21·8–56 cm in CT), SOC and TN concentrations and C:N ratios were higher in OF than in CT. Soil properties stratification in depth, expressed as a ratio, indicates the soil quality under different soil management systems. The SR of SOC ranged from 2·2 to 3·1 in OF and from 2·1 to 2·2 in CT. However, only SR2 (defined by Ap‐A/C) showed significant differences between CT and OF. The SR of TN showed similar trends to that of the SR of SOC. Organic farming contributes to a better soil quality and to increased carbon sequestration. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

岷江上游中山区次生灌丛与人工油松林土壤理化性质比较研究   总被引：4，自引：2，他引：4       下载免费PDF全文

鲍文  包维楷 《水土保持通报》2004,24(5):10-13

对岷江上游次生灌丛与人工油松林0-60cm深土壤理化性质对比测定，结果表明，人工油松林土壤容重为1．40g／m^3，比次生灌丛(1．01g／m^3)高0．39g／m^3；人工油松林自然含水量略高于次生灌丛，而人工油松林饱和含水量、毛管含水量和非毛管含水量依次为：29．1％，20．9％，11．1％，它们分别比次生灌丛低23．8％，19．1％，1．9％；次生灌丛的土壤孔隙度是53．0％，高出人工油松林21％；土壤养分所测6项指标中，人工油松林土壤养分含量普遍低于次生灌丛，K表现尤为突出，是油松林的1．81倍；人工油松林和次生灌丛pH值分别为6．23和8．39。说明在人为干扰严重的环境下，人工油松林可能有恶化土壤物理性质、降低林地肥力的趋势。  相似文献   

Methane uptake in soils from Pinus radiata plantations, a reverting shrubland and adjacent pastures: Effects of land-use change, and soil texture, water and mineral nitrogen     

K.R. Tate  D.J. Ross  C.B. Hedley  B.K. Singh 《Soil biology & biochemistry》2007,39(7):1437-1449

Afforestation and reforestation of pastures are key land-use changes in New Zealand that help sequester carbon (C) to offset its carbon dioxide (CO₂) emissions under the Kyoto Protocol. However, relatively little attention has been given so far to associated changes in trace gas fluxes. Here, we measure methane (CH₄) fluxes and CO₂ production, as well as microbial C, nitrogen (N) and mineral-N, in intact, gradually dried (ca. 2 months at 20 °C) cores of a volcanic soil and a heavier textured, non-volcanic soil collected within plantations of Pinus radiata D. Don (pine) and adjacent permanent pastures. CH₄ fluxes and CO₂ production were also measured in cores of another volcanic soil under reverting shrubland (mainly Kunzea var. ericoides (A. Rich) J. Thompson) and an adjacent pasture. CH₄ uptake in the pine and shrubland cores of the volcanic soils at field capacity averaged about 35 and 14 μg CH₄-C m⁻² h⁻¹, respectively, and was significantly higher than in the pasture cores (about 21 and 6 μg CH₄-C m⁻² h⁻¹, respectively). In the non-volcanic soil, however, CH₄-C uptake was similar in most cores of the pine and pasture soils, averaging about 7-9 μg m⁻² h⁻¹, except in very wet samples. In contrast, rates of CO₂ production and microbial C and N concentrations were significantly lower under pine than under pasture. In the air-dry cores, microbial C and N had declined in the volcanic soil, but not in the non-volcanic soil; ammonium-N, and especially nitrate-N, had increased significantly in all samples. CH₄ uptake was, with few exceptions, not significantly influenced by initial concentrations of ammonium-N or nitrate-N, nor by their changes on air-drying. A combination of phospholipid fatty acid (PLFA) and stable isotope probing (SIP) analyses of only the pine and pasture soils showed that different methanotrophic communities were probably active in soils under the different vegetations. The C18 PLFAs (type II methanotrophs) predominated under pine and C16 PLFAs (type I methanotrophs) predominated under pasture. Overall, vegetation, soil texture, and water-filled pore space influenced CH₄-C uptake more than did soil mineral-N concentrations.  相似文献   

黄河上游退耕地植被组成、结构及水保功能评价          下载免费PDF全文

胡建忠  郑佳丽  张春霞 《中国水土保持科学》2005,3(2):42-50

 面对黄河上游地区生态失衡的严重现实,作为植被恢复重建重要手段的退耕还林还草工程,其水保功能研究不仅具有理论价值,而且有十分迫切的实践需要。退耕地人工植被的建立,是一种仿拟自然植被的过程,植物种数越多,垂直层次性越复杂,植被的水保功能也越高。在黄河上游脑山区,物种丰富度指数最高的阶段,往往为植物群落演替的中间阶段,此时植物层次较多,一般可达3～5层,种类繁杂,生物基因保存多;同时,多层次的植物群落结构,对降水的截留作用明显,水保功能突出,以青海云杉为主的针阔混交类型,就是其典型代表之一。退耕地植被随着林分年龄增加,其水保功能逐步提高。一些退耕20多年的人工植被类型,生物多样性高,垂直层次结构复杂,水保功能甚至超过一些天然植被类型,直逼水保功能表现最好的50多年生天然青海云杉针阔混交林。在退耕还林还草工作中,通过仿拟自然植被结构,建造复层、混交的植被类型,来实现稳定的退耕地人工植被水保功能的整体思路,是切实可行的。  相似文献   

北方农牧交错带(武川县)土壤微生物数量分布及层化比率研究   总被引：12，自引：0，他引：12  

李涛  潘志华  安萍莉  妥德宝  赵沛义 《水土保持学报》2006,20(1):99-102

采用田间采样及室内培养方法，对内蒙古武川县耕地、退耕还灌地和放牧草原3种类型土地土壤微生物各类群的数量分布和层化比率进行了研究。结果表明：在土壤耕作层（0～30cm）土壤微生物数量呈逐层下降趋势，3种类型土地的土壤微生物总数相差不大，3种类型土地土壤微生物层化比率存在明显差异。同时提出了土壤微生物层化比率的概念，并认为土壤微生物层化比率可能是一个比较好的指示动态土壤质量（土壤演替方向）的指标，当一个区域土壤微生物层化比率大于2时，土地一般不会发生退化现象。在研究的3块实验区域中，耕地存在较高的退化风险．退耕还灌地正处于逐步恢复的阶段，放牧草原依然存在逐步退化的趋势。  相似文献   

Effects of Long-Term Aerial Pollution on Soil Seed Banks in Drained Pine Mires in Southern Finland     

Mia Huopalainen  Eeva-Stiina Tuittila  Ilkka Vanha-Majamaa  Hannu Nousiainen  Jukka Laine  Harri Vasander 《Water, air, and soil pollution》2001,125(1):69-79

The effects of pollution on thecomposition of soil seed banks in four drained pinemires located along a pollution gradient in southernFinland were studied using the emergence method. Thespecies composition of the seed bank was compared withthe above ground vegetation. Dominant species in theseed banks were Calluna vulgaris, Betulaspp. and Ledum palustre. Seeds seemed to beviable despite a heavy pollution load. Especially inthe vicinity of the pollution source, seed bank andabove ground vegetation were weakly correlated.  相似文献