内蒙古扎兰屯市典型森林枯落物、土壤水源涵养功能研究

对扎兰屯林区3种典型(天然兴安落叶松、天然白桦、人工兴安落叶松)林分不同郁闭度等级林下枯落物及土壤水文特性进行了研究。结果表明:1)森林枯落物储量为24.81~82.32t/hm2,天然林枯落物的储量明显高于人工林。天然白桦林枯落物持水量最大(270.25t/hm2),人工落叶松纯林最小(88.25t/hm2)。枯落物对水分的有效拦蓄量为天然落叶松林(122.36t/hm2)天然白桦林(94.49t/hm2)人工落叶松林(67.99t/hm2)。2)土壤最大持水量为2958.51~3723.39t/hm2,其总孔隙度、最大持水量均表现为天然落叶松林天然白桦林人工落叶松林。土壤有效持水量天然白桦林(1033.23t/hm2)天然落叶松林(946.37t/hm2)人工落叶松林(833.34t/hm2)。3)天然落叶松林和人工落叶松林当郁闭度处于85%以上,天然白桦林郁闭度处于55%以下时,其枯落物量和最大持水量最大;天然落叶松林在郁闭度65.2~67%,天然白桦林郁闭度40.07~54.52%,人工落叶松林郁闭度85.66~100%时,枯落物对水分有效拦蓄量最大。4)天然落叶松林郁闭度73.49~96%,天然白桦林郁闭度为56.07~65.37%,人工落叶松林郁闭度为46.72~67.29%时,其土壤有效持水量最大。     

六盘山四种典型森林生态水文功能的综合评价

为合理评价水源涵养林垂直结构改变对其水文功能的影响,在对宁夏六盘山香水河小流域内4种典型结构林分(华北落叶松+灌木复层林、华北落叶松纯林、稀植乔木的天然灌丛林、天然灌丛林)林冠层、枯落物层、土壤层的结构指标和功能指标测定的基础上,采用层次分析法建立了林分生态水文功能的层次结构模型,并用综合评分法对4种典型林分进行了评价。结果表明:林冠层生态水文功能以华北落叶松人工纯林最优,枯落物层以华北落叶松+灌木复层林最优,土壤层以稀植乔木的天然灌丛林最优。不同林分生态水文功能整体表现为华北落叶松+灌木复层林(0.902)>稀植乔木的天然灌丛林(0.893)>华北落叶松人工纯林(0.782)>天然灌丛(0.708),说明复层林的综合生态水文功能要好于单层林,表明在六盘山营林区对华北落叶松人工纯林进行林下补植灌木和对退化的天然灌丛稀植乔木等措施有助于林分生态水文功能的发挥。     

华北土石山区不同造林密度的油松林结构与功能研究

对北京八达岭林场32年生5种造林密度(2000株/hm2、1500株/hm2、1200株/hm2、1000株/hm2、800株/hm2)阴坡油松林生物多样性、碳密度、水源涵养等功能进行调查与实验,结果表明:随着林分密度的减小,林木生长状况良好,林下植被层各种生物多样性指数较其它林分高,并伴随着出现辽东栎等其它栎类更树种的生长;800株/hm2的阴坡油松林蓄积为108.19m3/hm2,是2000株/hm2油松林蓄积的1.22倍;不同密度油松林生态系统碳密度范围为107.43 t/hm2-174.30 t/hm2,平均碳密度为135.99 t/hm2,且随着密度增大而减小。油松林碳密度主要有三个部分组成:植被层、枯落物层和土壤层,其空间部分为土壤层>植被层>枯落物层,林地土壤的碳密度是相当可观大的,碳密度平均为90.34 t/hm2以上,地上部分碳密度与地下(包括土壤、树根和死地被物)碳密度之比平均为1?3.173;油松林地的稳渗速率、产流量随林分密度的增大而减小,这对增加该地区的径流水量、涵养水源能力具有重大意义。产沙量也随密度的增加而减少,这对选择油松800株/hm2作为最优林分密度是不利因素,但从北京的多年降雨来看,这种影响对我们选取油松在800株/hm2作为首选经营密度还是较小的。     

小流域防护林适宜覆盖率与植被盖度的理论分析

从防止水土流失和土壤水分容量两个方面出发,分析了以森林植被为主体的植物系统的覆盖率、植被盖度与形成良好的健康的森林水分生态环境和水土保持功能的关系。分析了小流域森林覆盖率与水蚀的关系,地块尺度上植被盖度与水蚀的关系。提出根据最大土壤侵蚀量、年允许土壤流失量和小流域的水分供应关系来确定区域宜林地林分面积与适宜森林覆盖率。根据水分、树种、林龄和立地条件对森林密度做具体分析。研究表明:在黄土区小流域尺度,合理的森林分布是防治水蚀的关键;适宜植被盖度是保证水土保持功能持续的关键,乔木成林林分郁闭度达到40%,草本植物的盖度达到90%就具有较好的防蚀功能,植被盖度与生物量同时处于适宜状态时,林分的水土保持功能最佳。研究认为水土保持有效植被盖度不应低于有效盖度(群落下土壤流失量等于允许流失量),最大为临界盖度(群落下土壤流失量为自然侵蚀量),群落灌层下死被物应具有一定厚度为1.0～2.0cm。研究表明在山西省吉县,阳坡刺槐造林密度小于2250株/hm2,以1111株/hm2为最佳;成林密度为300～1800株/hm2,以小于1500株/hm2为佳。     

甘肃河西绿洲边缘积沙带所表征的气候环境信息

绿洲边缘积沙带的研究是一个新的科学问题。甘肃河西地区经过半个多世纪的防沙治沙,在绿洲边缘形成了一条积沙带。为了研究积沙带的形成和发育与气候环境因子之间的关系,对河西走廊东端至走廊中西部绿洲边缘的积沙带进行了调查。结果表明：① 年降水量是决定积沙带高度和宽度的关键因子;② 降水量是决定植被盖度的关键因子,降水对天然植被盖度的影响大于对包括人工植被在内的植被总盖度的影响,随着降水增加,背风坡植被盖度增加幅度大于迎风坡;③ 积沙带不同样点之间植被盖度的差异主要是由植株个体大小引起的,亦即降水对植株个体大小的影响大于对植株密度的影响。     

胡杨融雪漏斗现象及生态作用

杜加依林春季积雪融化时,存在以胡杨根部为中心的融雪漏斗。通过调查比较胡杨林冠和融雪漏斗的形状相关性,测定漏斗区与林隙地表区温度的不同,分析漏斗区与林隙区表层土壤有机质和总盐的差异。结果表明：胡杨林冠下由于主干的存在,使林冠下土壤能得到较多的太阳辐射能量,并且林冠下枯落物的富集作用和胡杨的＂肥岛＂效应,使林冠下土壤的有机...     

子午岭主要森林类型土壤种子库研究

对子午岭天然油松林、人工油松林、人工落叶松林、人工刺槐林四种林分的土壤种子库特征初步研究结果表明 :人工油松林种子库储量平均为 675 .9粒 /m2 ,人工刺槐林为648.8粒 /m2 ,人工落叶松林为 839.4粒 /m2 ,天然油松林为 45 5粒 /m2 ,各林分土壤种子库储量属中等水平 ;本次调查的天然油松林种子库种子活力为零 ,人工油松林种子库活力种子占 0 .5 % ,人工落叶松林种子库活力种子占 4.2 % ,刺槐林种子库活力种子占 74.4%。除人工刺槐林种子库种子质量较高外 ,针叶林各林分种子库种子质量都较差 ;人工油松林林下油松幼苗的分布密度平均为 1～ 3株 /m2 ,人工刺槐林林下多见灌木幼苗 ,另两种林分林下幼苗较少 ,表明不同林分土壤种子库种子都具有一定的萌发能力 ;从各林分土壤种子库的组成看 ,主要树种的种子在种子库中所占比例都在 85 %以上 ,人工油松林土壤种子库物种多样性指数较高 ,而其它林分土壤种子库物种多样性指数均较小 ;土壤种子库中 80 %左右的种子集中分布在枯枝落叶层和 0 - 2 cm土壤层中 ,下层种子数量很少 ;方差分析表明 ,枯枝落叶层厚度、树高、郁闭度、胸径等因子变化对土壤种子库储量影响显著。综合分析认为 ,子午岭主要森林类型土壤种子库能够为林分的天然更新提供基本条件。     

六盘山北侧叠叠沟小流域几种典型植被群落的水文功能研究

在宁夏六盘山北侧的半干旱区,研究了华北落叶松林、沙棘灌丛、虎榛子灌丛、草地植被类型的冠层截留与再分配、枯落物持水及土壤蓄水等水文功能。结果表明,不同植被类型的冠层截留能力相差较大,其中,沙棘灌丛的截留率最高（24.80%）,华北落叶松林略低（21.40%）,虎榛子灌丛最低（9.25%）;与此相反,树干茎流率以虎榛子灌丛为最高（33.18%）,超出大多数干旱半干旱区灌木树干茎流范围（2%～10%）。从季节变化上看,不同植被群落的截留率均为6月份最大,7—9月份持续下降,10月份出现回升;但截留量均为7月份最大。枯落物持水性能以华北落叶松林样地为最高,其次为虎榛子灌丛、沙棘灌丛和草地,这与各植被类型枯落物层贮存量的大小排序一致。1 m土 层的土壤容重以虎榛子样地为最小(1.03 g·cm^-3),然后依华北落叶松(1.07 g·cm^-3)、草地(1.08 g·cm^-3)、沙棘(1.16 g·cm^-3)的顺序增大。土壤总孔隙度、最大持水量以华北落叶松林样地为最高,毛管孔隙度、毛管持水量以虎榛子样地为最高,非毛管孔隙度以草地为最高;这几项指标均以沙棘样地为最低。综上所述,从林冠截持、枯落物持水性、土壤物理性质等总体来看,华北落叶松人工林的土壤存蓄水、调水能力最强,其次为虎榛子灌丛和草地,沙棘灌丛最差。     

呼伦贝尔沙质草地植被的沙漠化演变规律及其机制

为了了解呼伦贝尔沙地植被的沙漠化演变规律及其机制,于2009年在呼伦贝尔沙地陈巴尔虎旗设置样地,调查不同类型沙地植被差异和变化特征,分析植被变化与土壤理化特性的关系,得到如下结果：①随着沙漠化的发展,草地的植被盖度、高度、地上地下生物量和凋落物量急剧下降,物种丰富度、多样性指数、均匀度指数和植物密度呈波动式下降;②沙漠...     

祁连山区沙棘人工林生态经济效益分析

通过对沙棘人工造林效果的调查,分析总结出了沙棘人工林的生长规律;沙棘地上生物量随年龄增长之间有Y=0. 0002X5 -0. 0658X4 +0. 686X3 -2. 5659X2 +2. 2501X+3.3027(R=0. 96)的规律;沙棘产果量与地上生物量之间有Y=-0. 0819+0. 2299X-0. 0018X2(R=0. 99)的规律;沙棘结实和经济系数有随着树龄的增大而增大,石砾河滩至生长10年以后开始逐渐下降的规律;进一步分析了沙棘人工林对改善土壤物理性质的作用和生态水文功能。结果表明:沙棘林可降低土壤容重,增加土壤含水量; 10年生沙棘林枯落物厚度平均在1~3cm,枯落物重22t/hm2,水容量为绝干重的2. 12 ~4. 25倍;蓄水量达13. 65 ~23. 37t/hm2;林冠郁闭度在0. 7~0. 8时,林冠对降雨的截留量为39. 3%;林地0 ~20cm土壤的初渗率为16. 165#/min是对照区的8. 7倍;稳渗率为2. 4#/min是对照区的2. 53倍。     

Effects of vegetation near-soil-surface factors on runoff and sediment reduction in typical grasslands on the Loess Plateau,China

Vegetation near-soil-surface factors can protect topsoil from erosion,however,their contributions to the reduction of soil erosion,especially under natural rainfall events,have not been systematically recognized.This study was performed to quantify the effects of near-soil-surface factors on runoff and sediment under natural rainfall events on grasslands dominated by Bothriochloa ischaemum(Linn.)Keng(BI grassland)and Artemisia gmelinii Thunb.(AG grassland)in two typical watersheds on the Loess Plateau,China in 2018.By successive removal of the plant canopy,litter,biological soil crusts(BSCs)and plant roots,we established five treatments including plant roots,plant roots+BSCs,plant roots+BSCs+litter,intact grassland and bare land in each grassland type.In total,twenty runoff plots(5 m×3 m)with similar slopes and aspects were constructed in the two types of grasslands.Results showed that plant canopy,litter and roots reduced runoff,while BSCs,which swelled in the presence of water,increased runoff.In contrast,all of these factors reduced sediment yield.In addition,the reductions in runoff and sediment yield increased with I30(maximum 30-min rainfall intensity)for each vegetation near-soil-surface factor except for BSCs.Among these factors,plant canopy had the largest contribution to runoff reduction,accounting for 48.8% and 39.9% in the BI and AG grasslands,respectively.The contributions of these vegetation near-soil-surface factors to sediment yield reduction were similar(21.3%-29.9%)in the two types of grasslands except for BSCs in the AG grassland(10.3%).The total reduction in runoff in the BI grassland(70.8%)was greater than that in the AG grassland(53.1%),while the reduction in sediment yield was almost the same in both grasslands(97.4%and 96.7%).In conclusion,according to the effects of different vegetation near-soil-surface factors on runoff and sediment production,our results may provide more complete insight and scientific basis into the effects of various vegetation related factors in controlling soil erosion.     

Impacts of land disturbance and restoration on runoff production and sediment yield in the Chinese Loess Plateau

Land disturbance and land restoration are important factors influencing runoff production and sediment yield in the semi-arid loess regions of China. This study compared the runoff production and sediment yield during the early stage after land disturbance(ESLD) with those during restoring stage after land disturbance(RSLD). Grey relational analysis was used to analyse the importance of each one of the influencing factors(vegetation, rainfall, soil and topography) in affecting the runoff production and sediment yield. Our results showed that during ESLD, topography was the most critical factor controlling the runoff production, while soil was the most important factor controlling the sediment yield. During RSLD, vegetation was more important in affecting runoff production, while rainfall was more important in affecting sediment yield. In additional, this study demonstrated that both the runoff production and the sediment yield can be effectively reduced by restoring vegetation on severely-disturbed lands, thus providing an important theoretical basis for better implementations of the Grain for Green Program. Our results revealed that the vegetation types of Hippophae rhamnoides+Pinus tabulaeformis and H. rhamnoides are better plant selections for land restoration in this area, especially for relatively gentle slopes(i.e., less than 20 degrees).     

植被对小流域汇流及侵蚀产沙影响研究

本文从物理概念出发对小流域产汇流及侵蚀产沙过程进行研究,并结合实例分析了流域内森林植被对产汇流和侵蚀产沙的影响。森林植被的调节径流、防治侵蚀的功能体现在各个层面,林冠及下部枯落层可削减雨滴动能;树干及下部枯落层可削减地表径流流速;林地可改善土壤的渗透性,减少地表径流流量;根系可固持土壤,增加抗蚀力。     

Comparative Analysis of Runo and Sediment Yield with a Rainfall Simulator After Experimental Fire

Changes produced in runoff and sediment levels before and after fire and during the revegetation process were examined using a rainfall simulator. The area was burned in an experimental fire, reaching temperatures from 35° to 563° C. Then it was revegetated using different species combinations. Fifteen permanent plots were established in the burnt area (4 treatments and a control replicated three times). Simulated rainfall of 15 mm per 5 min was applied in each treatment. No significant differences were found in sediment yield and runoff between treatments, but greatest runoff was observed to occur immediately after the fire. A significant relationship was found between runoff and woody cover, and a decrease in runoff can be observed as cover increases. The relationship between sediment yields and runoff rates was also positive. The low rates observed during rainfall simulation are due to the effect of natural vegetation rather than revegetation treatments. The high organic matter content also had an influence on the low rates of runoff and sediment.     

黄河中游小流域侵蚀产沙机理研究

本文研究的典型流域指基本上具有单一的下垫面物质组成的流域。本文选取黄河中游河段上的支流；皇甫川、窟野河、无定河上一些小流域作为典型流域进行分析研究。根据下垫面差异，将产沙区分为黄土区、基岩区、风沙区；通过各产沙因子对侵蚀产沙影响作用的分析，对三种产沙区进行定性到定量分析，全面研究了黄河中游产沙机理，并进一步提出了治理对策。     

晋北黄土丘陵区不同林草措施的蓄水保土和土壤水分效应研究

以设在山西省阳高县的大型径流观测场为依托,以2005-2009年的野外实测数据为依据,研究了晋北黄土丘陵区人工植被与鱼鳞坑配合的蓄水保土及土壤水分效应,并与荒坡、苜蓿地进行了对比。结果表明:在观测的5年内,柠条、沙棘、油松的蓄水保土能力随种植年限延长无明显增加趋势,但鱼鳞坑的蓄水能力和保土能力分别高达84.7%～96.0%和95.2%～99.7%;荒坡和苜蓿(Medicago sativa)第一年和第二年的蓄水保土能力较差,第三年和第四年随植被盖度增加能力急剧增强,第四年蓄水能力分别达82.8%和91.2%,保土能力达97.0%和98.0%;土壤水份分析结果表明:不同小区4～9月土壤水分变异系数为7.0%～19.1%,油松区变异系数最大,其次为沙棘、苜蓿和柠条区,荒坡区和裸坡区变异较小,不同小区土壤水分亏缺率为23.98%～52.66%,亏缺顺序为柠条区>苜蓿区>油松区>沙棘区>荒坡区>裸坡区;林草植被有效地减少了水土流失,亦增加了土壤水分的变异及亏缺程度,应注意林草植被的合理选择和配置。     

Effects of Alternaria macrospora on the yield components of Pima cotton in Israel

Effects of Alternaria leaf spot (caused by Alternaria macrospora ) on the yield components of Pima cotton ( Gossypium barbadense ) were examined in four field trials, for the lower (< 30–50 cm), middle (30–50 to 70–90 cm) and upper (>70–90 cm) layers of the canopy. The influence of the disease on yield was determined by comparing measurements taken in fungicide-treated plots with those taken in untreated plots. Alternaria -induced defoliation was most severe in the lower canopy layer and gradually decreased towards the upper canopy layers. Significantly fewer bolls (26·0%) were picked in untreated plots than in fungicide-treated plots, but differences in average boll size (reduction of 1·07%) among the treatments were non-significant. The relationship between disease intensity and the loss of bolls was linear. Of the differences in yield between fungicide-treated and untreated plots, 43·5% was observed in the lower canopy layer, 37·6% in the middle canopy layer and only 18·9% in the upper canopy layer.     

京津水源区坡耕地土壤侵蚀特征分析

坡耕地是保障粮食安全与经济发展的重要资源.本文利用承德市南山径流场资料对不同坡长下径流深、含沙量及侵蚀量进行对比分析,结果显示:坡长和降雨强度都对土壤侵蚀有影响,随着坡长变化,导致土壤侵蚀量变化的两个主导因素不断变换.雨强小于0.25 mm/min时,坡面土壤侵蚀模数随坡长的增加而增大;雨强大于0.25mm/min时,随坡长的增加先增大后减小,最大侵蚀量总是出现在22 m坡长范围内.径流深均值与侵蚀量增量随坡长变化趋势一致,含沙量均值变化与雨强关系密切.所以治理京津水源区坡耕地水土流失,应在22 m坡长以内采取等高植物篱等措施,既可降低工程投入,又减少坡面土壤流失,提高土地生产力.     

黄土区小流域水沙对降雨及土地利用变化响应研究

降雨和土地利用/覆被变化是流域径流、泥沙的两个主要影响因子。本研究采用SWAT模型,用固定其中一个影响因子而改变另一个影响因子的方法,对研究区降雨变化与土地利用/覆被变化对径流泥沙影响进行估算,目的在于从年月不同时间尺度上确定黄土高原小流域水沙对降雨和土地利用变化的响应状况。结果表明,在年尺度上降雨变化对径流影响的贡献率为84.20%,土地利用变化对径流影响的贡献率为28.63%;在月尺度上,降雨对径流贡献率也大于土地利用对径流的贡献率,尤其在雨季降雨对径流的影响程度和土地利用对径流影响程度的比值最大可以达到4.5。因此,不论在年尺度还是月尺度上,降雨对径流的贡献率都远远大于土地利用对径流的贡献率。此外,研究结果也表明流域年降水量和流域森林植被盖度均与流域径流模数或输沙模数呈指数关系。     

The relationship between soil,climate and forest development in the mid-mountain zone of the Sangong River watershed in the northern Tianshan Mountains,China

The mountainous forests in arid regions, being sensitive to climate change, are one of the key research topics related to the mechanism of interaction between climate and the terrestrial ecosystem. In this study, the spatial distribution of a mid-mountain forest and its environmental factors were investigated by using a combination of remote sensing technology, field survey, climate indices and soil nutrient analysis in the Sangong River watershed of the northern Tianshan Mountains. The forest(Picea schrenkiana) was distributed between 1,510 and 2,720 m asl. Tree height and diameter at breast height(DBH) exhibited a bi-modal pattern with increasing elevation, and rested at 2,450 and 2,250 m asl, respectively. The two maxima of DBH appeared at 2,000 and 2,550 m asl, and the taller trees were observed at 2,100 and 2,600 m asl. For the annual mean temperature, the difference was approximately 5.8°C between the lowest and the highest limits of the forest, and the average decreasing rates per hundred meters were 0.49°C and 0.55°C with increasing altitude between 1,500 and 2,000 m asl and above 2,000 m asl, respectively. The annual precipitation in the forest zone first increased and then decreased with the increase of altitude, and the maximum value was at 2,000 m asl. For per hundred meters, the annual precipitation increased with the rate of 31 mm between 1,500 and 2,000 m asl and decreased by 7.8 mm above 2,000 m asl. The SOM, TN and TP were high between 2,000 and 2,700 m asl and low at the lower and upper forest limits. The minimum Ca CO3 concentration, p H value and EC coincided with the maximum precipitation belt at 2,000 m asl. The SOM, TN and TP were high in the topsoil(0–10 cm) and differed significantly from the values observed in the deep soil layers(10 cm). The soil nutrients exhibited spatial heterogeneity and higher aggregation in the topsoil. In conclusion, soil and climate are closely related to each other, working synergistically to determine the development and spatial distribution of the mid-mountain forest in the study area. The order of the importance of environmental factors to forest development in this study is as follows: soil nutrientsprecipitationelevationtemperature.