次生马尾松林下植被恢复措施的水土保持效益

通过采集江西省赣县花岗岩区次生马尾松纯林地不同植被恢复措施坡面径流小区2010—2011年的降雨产流产沙资料,分析不同模式的水土保持功能及其植被恢复的水土保持效益。结果表明:1)次生马尾松稀疏纯林地水土流失严重,年产流系数为0.50～0.60,侵蚀模数在2 700～6 000 t/(km2.a)之间。2)植被恢复可以降低林地土壤侵蚀强度,但植被恢复的水土保持效益与林冠结构和地表覆盖度密切相关,当形成乔草或乔灌复合层时,可以起到50%～60%的年蓄水效益和65%～70%的年固土效益。3)植被恢复的水土保持效益亦受植被和降雨类型的影响,百喜草蓄水效益随降雨量先增后减,暴雨是蓄水效益变化的转折点,而胡枝子蓄水效益变化规律不一;植被恢复措施固土效益随降雨量的增加而降低,特别是在大暴雨情景时急剧下降。     

Causes and Effects of Gully Erosion on Agricultural Lands and the Environment

This study was aimed at assessing the causes of the gully erosion and its effects on the agricultural lands in the arid region of southeastern Iran. In this study, we have used geologic maps in scales of 1:50,000 and 1:250,000, aerial photographs on a scale of 1:20,000, field observation, and GPS (global positioning system). Three soil samples were taken from 25, 50, and 75% of the gully length at each location and analyzed for pH, electrical conductivity (EC), exchangeable sodium percentage (ESP), sodium absorption ratio (SAR), cation exchange capacity (CEC), calcium (Ca), and soil texture. The causes of gully erosion, its effects on agricultural lands, characteristics of the gullies, soil depth, and vegetation of each area were evaluated. The results show that several parameters, including poor rangeland vegetation cover, overgrazing, human activities, intensive and short-period rainfall, improper land use, improper irrigation design, improper discharge of water in the channels, and soil characteristics influence the gully erosion. Gully erosion causes severe damage to agricultural lands, including soil loss, increase in surface runoff, lower soil water-holding capacity, lower quality and quantity of water, lower groundwater table, and lower agricultural production. It increased migration from villages to cities and increased socioeconomic problems and poverty. It also caused substantial damages to construction sites such as bridges, roads, and settlements as well as rivers and reservoirs and increased sediment concentration in rivers.     

Estimation of Water Content in Winter Wheat (Triticum aestivum L.) and Soil Based on Remote Sensing Data–Vegetation Index

In this study, a suitable and near-real-time water status monitoring approach for winter wheat before harvest was developed with remotely sensed satellite data. Seven vegetation indices were extracted as remote-sensing parameters by making full use of the land surface reflection and land surface temperature transmitted by moderate resolution imaging spectroradiometer (MODIS) data. The correlation of each vegetation index and measured values of winter wheat and soil water contents in different crop growth periods was established. The simulation models, combining vegetation index, soil water content (SWC), and plant water content (PWC) in different winter wheat growth periods, were constructed to predict water content by using remote-sensing data. We found that the correlations between the difference vegetation index (DVI) and the perpendicular vegetation index (PVI) in the beginning of the stem elongation period with SWC were highly significant (P < 0.01); the correlation between the global environmental monitoring index (GEMI) in the ear emergency period and SWC was highly significant (P < 0.01). Furthermore, the correlation between the PVI in maturing period and SWC was highly significant (P < 0.01). Data of different coefficients of vegetation indices and PWC in different winter wheat growth periods illustrated that correlation between the DVI in the beginning of stem elongation period and PWC was highly significant (P < 0.01), while the correlation between the PVI in the maturing period and PWC was highly significant. Our results indicated that spatial and temporal vegetation indices were closely related to soil moisture and winter wheat water content in Wenxi County, Shanxi Province (P. R. China). The vegetation index is conceptually and computationally straightforward and may be used in prediction of environmental hydrological status.     

天津地区湿地土壤种子库及其在受限空间中的植被演替研究

湿地土壤种子库运用对植被恢复的研究具有重要意义。从植被演替的角度出发,设置相对封闭的受限空间,持续监测土壤种子库萌发及其后续植物群落的演替情况,记录物种组成、群落多样性指数和群落覆盖度等参数的变化规律,评估了采用湿地土壤种子库进行植被恢复的效果。并对地面植被、土壤种子库及其演替植被的群落相似性指数进行了对比分析。结果发现:(1)土壤种子库恢复后期的植被与地面植被相似度较低(小于0.25);(2)植被恢复过程中,群落多样性指数呈现先降低后升高的趋势,而恢复3a后的植被群落多样性指数均接近于地面植被;(3)生长期的群落覆盖度高于90%,能够满足天津地区滨海盐碱型湿地植被恢复的要求。     

奈曼旗土地退化遥感监测研究

奈曼旗是土地退化比较严重的旗县,为查清该旗的土地退化类型、分布及程度,监测其土地退化的发展趋势,该文选取土地利用/覆被方式、复合植被指数、风蚀土地占像元面积百分比和土壤含水率作为土地退化评价体系的4个指标,利用TM数据获取4个指标的反演数据。采用层次分析法构造4个指标的判断矩阵,通过判断矩阵特征向量的计算得到土地退化指标的权重,构建土地退化综合评价公式。结合综合评价公式,计算出奈曼旗的土地退化结果,并将土地退化分为未退化、轻度退化、中度退化、重度退化和严重退化5个等级。1987年、1991年、1996年、1999年、2002年和2007年的土地退化评价结果表明,奈曼旗的土地退化在1987-1999年期间处于"局部好转、整体恶化"的局面,2000年以后土地退化扩展趋势得到遏制,土地退化治理取得了一定的效果。该研究对奈曼旗的土地退化防治和生态建设具有一定的指导意义。     

基于3CCD摄像机的水稻农学参数估算

水稻农学参数的估算是调控水稻生长、预测水稻产量的重要基础和根据。该文以广东省农业科学研究院大丰农场水稻研究所的稻田为研究对象,根据植物反射光谱的特性,研究3CCD摄像机水稻叶面积指数、生物量、叶绿素含量、叶长、叶宽、株高、产量等农学参数的估算,结果表明:分蘖期农学参数不适于用3CCD摄像机估算;叶面积指数在分化期估算最准确;生物量、叶绿素含量、产量均在抽穗期估算较好;3CCD摄像机不适用于大面积水稻株高、剑叶长、剑叶宽等外部特征的估算。该文为CCD摄像机的水稻估产打下基础。     

基于时间序列影像的中观尺度农作物长势监测采样方法

地面采样调查是遥感应用中一个重要的手段。采样点的空间位置和数量决定了监测点的代表性,并受到监测成本限制。高效和经济地设计采样方案是推进地面采样数据更好地服务于遥感应用的重要问题。该文以遥感在农业方面的应用为切入点,在对现有农作物监测现状研究的基础上,通过对时间序列的遥感影像进行农作物长势分布的分析,运用概率比例规模抽样(PPS)的思想提取采样点。通过对2007的农作物长势分布区进行农情参数监测点采样,并与2009年的农作物长势分布对比,发现采样点达到较好的一致性。基本满足中观尺度农作物长势监测中采样点具有代表性、典型性和稳定性的要求。     

黄土坡面不同植被冠层降雨截留模型模拟效果及适用性评价

为探明植被冠层降雨截留水文生态效应,该文通过对黄土区坡面柠条林和杏树林冠层截留量的动态监测与模型模拟,分析了不同类型植被冠层降雨截留规律及其模型模拟的适用性。结果表明:2种不同类型植被冠层降雨截留的特征差异显著。柠条林冠层截留量随大气降雨量的增加而逐渐增加,稳定截留率约为15%。杏树林冠层截留率相对较低,特别是在降雨量小于5mm的量级,冠层"漏斗"效应明显。杏树林冠层截留率与降雨量之间未表现出明显的趋势关系,稳定截留率约为10%。对于柠条林冠层截留规律的模拟,以降雨量和冠层郁闭度为变量的崔启武模型的决定系数为0.74,以降雨量为变量的王彦辉模型的决定系数为0.68;但对于"漏斗"状结构的杏树林冠层,2个模型均未能得到较好的模拟结果。     

黄土区坡面尺度不同植被类型下土壤干层的空间分布

为掌握坡面尺度不同植被类型土壤干层特征,对一典型坡面干层空间分布进行了研究。结果表明:13a杏树地和25a柠条地干层厚度分别在0～400和280～400cm之间,杏树地不同坡位处干层分布有明显差异;在坡面垂直方向上,25a柠条地较13a杏树地土壤水分亏缺严重。而水平方向,13a杏树地干层分布表现为明显的片状和斑块状分布特征,同时呈现出从北至南沿坡面逐渐递减,干层分布受植被,降水、坡位、微地形等因素共同作用。相比之下,25a柠条地干层分布结构性较为单一,干层厚度在381～400cm的面积分布较广且连在一起,表现出由植被控制的分布格局。相关结果可为黄土区土壤干层调控提供参考。     

间伐对华北土石山区油松林生长及其林下植被发育的影响

间伐是森林经营的主要措施之一,研究间伐对森林生态系统的影响对其可持续发展具有深远意义。对河北省木兰围场国有林场管理局北沟林场4块油松人工林样地分别进行46.6%,56.2%,67.1%的3个强度间伐以及对照处理,通过植被群落调查,研究不同间伐强度后油松林生长及其林下植被发育。结果表明:油松林分经不同强度抚育间伐后单木胸径、树高、冠幅和生物量均显著高于对照,且随间伐强度增大而增加,但单位面积蓄积量随间伐强度增大而减小;弱度、中度间伐能够增加林下植物种类,提高林下植物丰富度、多样性和均匀度指数,但是强度间伐后林下植物种类并不会增多,此现象符合"中度干扰假说";林分经不同强度间伐后,林下植被优势种各异;随着间伐强度的增大,林下植被生物量增加。综上,合理的间伐能够促进林分生长及其林下植被发育,研究区选择56.2%左右的间伐强度最优。