Causal effects of shelter forests and water factors on desertification control during 2000–2010 at the Horqin Sandy Land region, China

The Horqin Sandy Land（HSL）, the largest sandy land in the semi-arid agro-pastoral ecotone of Northeast China, has been subject to desertification during the past century. In response, and to control the desertification,government implemented the Three-North Shelter/Protective Forest Program, world＇s largest ecological reforestation/afforestation restoration program. The program began in1978 and will continue for 75 years until 2050. Understanding the dynamics of desertification and its driving forces is a precondition for controlling desertification.However, there is little evidence to directly link causal effects with desertification process（i.e., on the changing area of sandy land） because desertification is a complex process,that can be affected by vegetation（including vegetation cover and extent of shelter forests） and water factors such as precipitation, surface soil moisture, and evapotranspiration.The objectives of this study were to identify how influencing factors, especially shelter forests, affected desertification in HSL over a recent decade. We used Landsat TM imagery analysis and path analysis to identify the effects of spatiotemporal changes in water and vegetation parameters during2000–2010. Desertification was controlled during the study period, as indicated by a decrease in desert area at a rate of163.3 km2year-1and an increase in the area with reduced intensity or extent of desertification. Total vegetation cover in HSL increased by 10.6 % during the study period and this factor exerted the greatest direct and indirect effects on slowing desertification. The contribution of total vegetation cover to controlling desertification increased with the intensity of desertification. On slightly and extremely severe desertified areas, vegetation cover contributed 5 and 42 % of the desertification reduction, respectively. There were significant correlations between total vegetation cover and water conditions（i.e., evapotranspiration and precipitation）and the area of shelter forests（P ／ 0.0001）, in which water conditions and the existence of shelter forests contributed49.7 and 12.8 % to total vegetation cover, respectively. The area of shelter forests increased sharply due to program efforts, but only shrub forests had significant direct effects on reducing the area of desertification categorized as slightly desertified. The reason for the lack of direct effect of increased arbor forests（accounting for 95.3 % of the total increase in shelter forests） on reducing desertification might be that the selected arbor species were not suited to water conditions（low precipitation, high evapotranspiration） prevailing at HSL. The establishment of shelter forests aided control of desertification in the HSL region, but the effect was less than expected. Effective control of desertification in the HSL region or other similar sandy areas will require greater improvements in vegetation cover. In particular,shrub species should be selected for plantation with reference to their potential to survive and reproduce in the harsh climatic and weather conditions typical of desertified areas.

Formation mechanisms and remediation techniques for low-efficiency artificial shelter forests on the Chinese Loess Plateau

The construction of artificial shelter forests(ASFs)has resulted in substantial ecological,economic,and societal benefits to the Chinese Loess Plateau(CLP).However,the health and benefits of ASFs are being increasingly threatened by the formation of low-efficiency artificial shelter forests(LEASFs).In this study,LEASFs are systematically analyzed in terms of their status,formation mechanisms,and developmental obstacles.The key restoration techniques and schemes were summarized to improve the quality and efficiency of LEASFs.LEASFs are formed by relatively complex mechanisms,but they arise mainly due to poor habitat conditions,improper tree species selections,mismatch between stands and habitat,extensive forest management measures,and human interferences.The restoration and improvement of LEASFs are hindered by water deficits,mismatch between stands and habitat,single management purpose,and low efficiency.LEASFs are becoming more complex due to their wide range,the challenges associated with their restoration,and insufficient technological measures for their restoration.The key techniques of the quality and efficiency improvement of LEASFs include basic forest tending methods,near-natural restoration,multifunction-oriented improvement,and systematic restoration.An understanding on the formation mechanisms of LEASFs and a scientific approach toward their restoration are urgently needed and critical for the ecological protection and high-quality development of LEASFs on the CLP.Based on these analyses,we recommend strengthening the monitoring and supervision of LEASFs,considering the bearing capacity of regional water resources,implementing multiple restoration techniques,promoting multifunction-oriented ecological development,and exploring new management concepts to achieve the sustainable development of ASFs on the CLP.

THE STRUCTURE AND DYNAMICS OF THE LAND RESOURCES SYSTEM IN THE FARMLAND SHELTER FOREST REGION IN THE NORTHEAST PLAIN

（张柏）ＴＨＥＳＴＲＵＣＴＵＲＥＡＮＤＤＹＮＡＭＩＣＳＯＦＴＨＥＬＡＮＤＲＥＳＯＵＲＣＥＳＳＹＳＴＥＭＩＮＴＨＥＦＡＲＭＬＡＮＤＳＨＥＬＴＥＲＦＯＲＥＳＴＲＥＧＩＯＮＩＮＴＨＥＮＯＲＴＨＥＡＳＴＰＬＡＩＮ￥ＺｈａｎｇＢａｉ（ＣｈａｎｇｃｈｕｎＩｎｓｔ...

Path Analysis on Environmental Factors Controlling Runoff and Sediment Yields in Shelter Forests in Three Gorges Reservoir Region

Effects of environmental factors such as climate,topography,vegetation and soil in shelter forests in Three Gorges Reservoir Region on runoff and sediment yields were monitored to identify dominant environmental factors controlling runoff and sediment yields in 15 runoff plots in study area by soil sampling,laboratory analysis,stepwise regression analysis and path analysis,and to establish the main control environmental factors that affect runoff and sediment yields. The results showed that soil bulk density,herbaceous cover,slope,and canopy density were the significant factors controlling runoff,and the direct path coefficient of each factor was ranked as canopy closure(-0. 628) > litter thickness(-0. 547) > bulk density( 0. 509) > altitude( 0. 289). The indirect path coefficient was ranked as soil bulk density( 0. 354) >litter thickness(-0. 169) > altitude( 0. 126) > canopy closure(-0. 104). Therefore,canopy closure and litter thickness mainly had direct effects on runoff,while soil bulk density mainly had indirect effects through their contributions to other factors. Herbaceous cover,litter thickness,slope,canopy density,and altitude were the significant factors controlling sediment yields. The direct path coefficient of each factor was ranked as herbaceous cover(-0. 815) > litter thickness(-0. 777) > canopy closure(-0. 624) > slope( 0. 620). The indirect path coefficient was ranked as slope( 0. 272) > litter thickness(-0. 131) > canopy closure(-0. 097) > herbaceous cover(-0. 084). Therefore,herbaceous cover and litter thickness mainly had direct effects on sediment yields,while slope mainly had indirect effects through their contributions to other factors. All the selected environmental factors jointly explained 85. 5% and 78. 3% of runoff and sediment yield variability,respectively. However,there were large values of remaining path coefficients of other factors influencing runoff and sediment yields,which indicated that some important factors are not included and should be taken into account.

LAND RESOURCE CHARACTERISTICS AND RATIONAL LAND-USE ARRANGEMENT FOR FARMING,FORESTRY AND ANIMAL HUSBANDRY IN “THREE NORTHS” SHELTER FOREST AREA

The "Three Norths" (Northeastern China, Northern China, and Northwestern China)Shelter forest area is located in the north part of china. The area of this region occupies41% of the total area of China. This region is eager for being managed because of its fragileecological conditions. Therefore, the basic approach to realize the harmonious developmentof ecological and economic benefits is the rational arrangement of farming, forestry and pas-ure land according to the characteristics of land resources of this region.

筑牢北方重要生态安全屏障之认知六人谈

为了治理北方生态环境,我国改革开放之初实施了“三北”防护林工程,实施的手段主要是植树造林,用以防沙固沙,业已取得重大成果。北方生态环境明显好转,沙漠治理工作取得显著成效。生态人类学立足“三北”生态环境的特殊性,从生态治理与区域可持续发展的视角,指出该工程下一步应重视草与树的比例,确保固沙植物水资源分配达到平衡状态。同时,要利用当地形成的地方性知识,在保护生态环境的同时,带动当地经济的增长,筑牢北方重要生态安全屏障的同时,实现当地乡村振兴的目标。

朔州市小叶杨防护林带间植被多样性与土壤理化性质的相关性分析

以朔州市作为试验研究地点,分析小叶杨防护林带间植被多样性和土壤理化性质相关性。方法于小叶杨防护林划分3组不同带间距,分别为5 m、10 m和15 m带间距,测定其不同带间距植被多样性和其土壤理化性质,分析二者相关性。结果:①植被多样性:带间距大小对小叶杨防护林植被多样性有显著影响,植被天然状态下,植被多样性、群落稳定性表现为15 m带间距>10 m>5 m(P<0.05);②土壤理化性质:随着带间距的增加,土壤理化性质(有机碳、全氮、速效磷和速效钾)表现为15 m>10 m>5 m(P<0.05),而土壤容重与其相反,表现为15 m<10 m<5 m(P<0.05);③相关性:植被多样性与土壤理化性质为相辅相成的关系,其中土壤容重与物种多样性指数呈显著负相关,有机碳、全氮、速效磷土壤理化性质与物种多样性指数呈显著正相关,速效磷相关性不显著。经试验研究结果表明,在小叶杨防护林中,适当增加防护林带间距有助于提升植被多样性,增强群落稳定性,改良土壤理化性质,以15 m效果最佳。

林分郁闭度对林下天然构树生长的制约性

通过对鲁西南砂石山构树胁迫防护林生长的调查研究,平茬2 a后构树灌木平均株数、分枝数分别比对照株增加了132.95%、-24.50%,证明构树灌木平茬能够刺激伐桩萌蘖,短期内会加剧对目标林分的生长胁迫。林分郁闭度≥0.75时,林下构树覆盖度≤5%,林下构树种籽或平茬构树失去必须的生存环境;林分郁闭度≤0.3时,林下构树覆盖度≥95%,会对目标林分造成严重的生长胁迫。研究表明,郁闭度低于临界值(郁闭度≤0.3)的目标林分或存在林中空地的林分,有目的选择原生灌木枝条进行人工促进天然更新或补植造林的方式提高林分郁闭度能够使低质低效林达到快速林相改造的目的。

塔克拉玛干西南缘风沙前沿防护林对条田的防护作用

[目的]研究不同疏透度防护林对塔克拉玛干沙漠绿洲边缘条田的防风效能,为当地网格条田可持续发展提供理论指导。[方法]选取塔克拉玛干南缘县城——新疆叶城县恰其库木管理区城郊防护林为研究对象,通过野外实地观测,对比研究不同疏透度防护林对塔克拉玛干沙漠绿洲边缘条田的防风效能。[结果]①叶城县恰其库区防护林内条田里离防护林10—15 m范围是防风效果最佳区域,可种植防风能力较差农作物。②3种结构防护林总体而言,防护林1.5 m高处防风效能最佳,2 m处防风效能最低。本研究区条田内,种植生长期总株高小于1.5 m以下的农作物,可有效避免风害导致的损失。③疏透结构林带固沙效率最佳,通风结构次之,紧密结构林带固沙效率最差,其固沙效率排列顺序为:58.39%>57.99%>36.29%。[结论]要发挥防护林的固沙作用,林带疏透度应控制在疏透结构为宜,可以使其达到较好的防风效果。疏透结构防护林周围的条田内可种植抗沙能力较弱农作物。

宁夏河东沙区刺槐和丝绵木水分利用策略

刺槐和丝绵木混交林是宁夏河东沙区防护林建设的主要模式,了解刺槐和丝绵木的水分利用策略,能为区域植被恢复和防护林林分结构调整提供科学依据。以宁夏河东沙区刺槐(Robinia pseudoacacia)和丝绵木(Euonymus bungeanus)混交林为研究对象,通过监测微气象、树干液流和土壤质量含水量,结合大气降水、土壤水、植物木质部水同位素组成,采用Granier及其校正公式,运用贝叶斯混合模型(MixSIAR)和相似性比例指数(PS)研究2个树种的蒸腾耗水、水分来源和水分利用关系。结果表明:刺槐和丝绵木的蒸腾耗水量在生长季中期较高,前期和后期较小,刺槐的蒸腾耗水量是丝绵木的1.55倍;影响刺槐蒸腾耗水的主要环境因子为饱和水汽压差、太阳辐射、0—40 cm土壤质量含水量和40—120 cm土壤质量含水量;影响丝绵木蒸腾耗水的主要环境因子为饱和水汽压差、太阳辐射、平均气温、0—40 cm土壤质量含水量和40—120 cm土壤质量含水量;蒸腾耗水较高时,刺槐主要吸收利用中层土壤水,丝绵木主要吸收利用浅层土壤水,蒸腾耗水较低时,刺槐主要吸收利用浅层土壤水,丝绵木主要吸收利用中层土壤水;在土壤水分含量较小的月份,刺槐和丝绵木主要通过水分利用空间上的差异来应对干旱,维持自身的蒸腾耗水;土壤水分含量较高的月份,刺槐和丝绵木的相似性比例指数最大,存在较强的水分竞争关系;浅层土壤水分含量较高可能反映了沙区植物根系对土壤水分再分配作用下植物在水分和养分需求之间的平衡。

格库铁路生态防护林区咸水滴灌风沙土盐分运移特征研究

土壤的盐分含量是影响植物生长的重要因素,盐分分布和累积状况关系植物的持续生长。梭梭(Haloxylon ammodendron)是荒漠地区极为抗旱耐盐的荒漠植物种,可以忍耐较高矿化度的咸水灌溉,为干旱区生态建设的重要植物种。开展了室外种植器种植梭梭苗的模拟实验,分别用淡水(CK)和矿化度20、30、40、50 g/L咸水进行灌溉。结果表明:(1)高矿化度水滴灌造成风沙土盐分含量和离子组成的显著变化,由非盐渍土逐渐转变为轻度盐渍土;表层盐结皮盐分含量远高于下层,且土层越深,土壤盐分含量越高,兼有表层集聚性与深层累积性特点;灌溉水矿化度越大,土壤积盐程度越大;土层越深,土壤pH值越低。(2)土壤中盐分以Cl^(-)、Na^(+)为主,也含有较多SO_(4)^(2-)离子;从表层至底部,Cl^(-)、Na^(+)、Ca^(2+)、K^(+)、Mg^(2+)和SO_(4)^(2-)6种离子含量先突降,而后随着土层加深,离子含量不同程度增加;CO32-和HCO3-具有明显的表层集聚特性。(3)当灌溉水矿化度在20~30 g/L时,梭梭仍然能较好生长,但矿化度30~50 g/L时,梭梭仍能够存活,但生长受到了明显抑制。研究结果对干旱荒漠地区地下咸水资源的开发利用和生态建设实践具有一定的参考价值。

基于MLR和人工神经网络的新疆杨日蒸腾量估算

为解决当前旱区防护林主要树种新疆杨日蒸腾量(Tr)估算值的精确度低、估算模型泛化能力差等问题,采用7种气象因子(日照时长、风速、相对湿度、饱和水蒸气压差、最低温、最高温和日均温)的8种组合作为模型输入,构建了传统多元线性回归模型(MLR)和人工神经网络模型(BP和Elman),估算2020年生长季新疆杨Tr值,并对3种模型不同输入组合的估算结果进行比较与评价;同时基于Garson算法量化各气象因子对Tr估算值的相对贡献率。结果显示,BP和Elman模型对Tr估算值的精确度超过73.66%,在不同输入组合下人工神经网络模型估算精确度比MLR模型提高了8.45%~31.33%,其中拓扑结构为6-4-4-1的Elman模型估算值的精确度最高;气象因子饱和水蒸气压差对Tr估算值的相对贡献率最大,相对湿度次之,不同温度变量对Tr估算值的相对贡献率依次为:日均温>最低温>最高温。结果表明,所构建的新疆杨日蒸腾量的估算神经网络模型可提高对干旱地区防护林蒸腾量的估算精确度。

榆林沙地防护林退化原因分析

通过查阅文献和野外调查相结合的方法,分析了榆林风沙区飞播灌木林的现状及其退化原因。结果表明:榆林沙区防护林的退化原因与立地条件、气候条件、经营管理有关。通过分析不同立地类型同种植物的生长势,同种立地类型不同植物的生长量以及防护林退化和演替方向,发现杨柴(Hedysarum mongolicum Turez)和蒙古虫实(Corispermum mongolicum)更适宜生长在迎风坡,沙蒿和狗娃花更适合生长在丘间地和坡底。丘间地灌木生长适宜性从高到低依次为沙打旺、沙蒿、柠条,缓坡依次为柠条、沙蒿、沙打旺,平沙地依次为沙打旺、柠条、沙蒿。

阿拉尔垦区新疆杨农田防护林防风效果研究

以阿拉尔市新疆杨农田防护林为研究对象,通过林业调查和野外风速测定,依据疏透度将新疆杨防护林的林带结构划分为通风型、疏透型、稀疏型3种结构类型,并采用隶属函数法对比分析各林带防风效果。结果表明:1)水平方向上,防风效能随防护距离的增加呈下降趋势。3种结构类型防护林的防风效能表现为稀疏型>疏透型>通风型。2)防风效能与树高、胸径、林带行数、冠幅呈正相关,与密度、疏透度呈负相关。3)8条林带综合隶属函数值在0.097~0.770之间,依次表现为林带Ⅲ>林带Ⅴ>林带Ⅳ>林带Ⅶ>林带Ⅷ>林带Ⅱ>林带Ⅵ>林带Ⅰ。其中,林带Ⅲ、林带Ⅴ为稀疏型,隶属函数值在0.50以上,综合防护效益表现较好。

Nutrient retranslocation strategies associated with dieback of Pinus species in a semiarid sandy region of Northeast China

In the semiarid sandy region of Northeast China,Mongolian pine(Pinus sylvestris var.mongolica)suffers dieback after the age of 35,while Japanese red pine(Pinus densiflora)and Chinese pine(Pinus tabuliformis)stay healthy.Foliar nutrient retranslocation reflects the nutrient conservation and utilization mechanism of plants in response to their habitats.However,the nutrient retranslocation strategies employed by three Pinus tree species to cope with nutrient limitations remain largely unknown.For this study,we investigated the seasonal variations in nitrogen(N)and phosphorus(P)concentrations of Mongolian pine,Japanese red pine,and Chinese pine plantations in terms of the green needles of all ages,senesced needles,and soil.Further,the N retranslocation efficiency(NRE),and P retranslocation efficiency(PRE),and correlations between the N:P ratios of needles and soil were analyzed.The results showed that,except for the spring NRE in 1-year-old needles of Mongolian pine,the spring NRE and PRE in 1-and 2-year-old needles of the three tree species were greater than zero.The autumn PRE was higher than zero for Mongolian pine,but lower than zero for Japanese red pine and Chinese pine.Among the three Pinus species,Mongolian pine showed greater spring PRE in 2-year-old needles,and PRE from 1-to 2-yearold needles,and from 2-year-old needles to litter.However,Japanese red pine had higher P concentrations and lower N:P ratios in senesced needles,while greater PRE was found in Chinese pine litter.Significant relationships between the N:P ratios were found in the current year and 1-year-old needles and soil in the Mongolian pine plantation,while there was an insignificant relationship between the N:P ratios of the needles and soil in the Chinese pine plantation.Thus,for Mongolian pine,the removal of P from needles in autumn,and higher P translocation from older needles under P-deficient soil may have contributed to the tree dieback.In contrast,Japanese red pine and Chinese pine stored P in their needles during autumn.Japanese red pine returned more P to the soil via litter,while Chinese pine maintained N:P homeostasis and increased P withdrawal prior to needle abscission.

沿海防护林体系建设工程区生态系统服务权衡/协同及驱动力

探究沿海地区的生态系统服务、权衡协同关系及其驱动机制是区域自然资源科学管理及生态合理规划的基础,对有效提升地区生态、经济、社会效益和人类福祉具有重要理论意义。以海防林工程区为研究区,多角度探究区域内固碳、土壤保持、产水量的生态系统服务、关系特征、驱动机制,从而为沿海地区制定合理生态建设规划提供参考。研究结果表明:(1)沿海防护林体系建设工程区在2000—2020年期间生态系统服务水平整体提升,生态建设效果第二期最佳。(2)2000—2020年区域内各生态系统服务间以协同关系为主,土壤保持和产水量协同显著。(3)建设分区、建设分亚区生态系统服务间关系尺度效应主要存在于土壤保持和产水量。(4)权衡协同关系北方主要受气象因子影响,南方受植被、地形地貌因子影响,人类活动对权衡协同关系的影响以负效应为主,驱动因子存在空间异质性。

三北防护林工程科学绿化策略研究

科学绿化是我国多年开展国土绿化的实践总结,也是新时期我国进行生态建设的根本遵循。三北工程区作为我国开展国土绿化、深入推进国家生态安全屏障的主战场,贯彻落实科学绿化理念,对提高三北地区生态系统的多样性、稳定性和可持续性,促进国土绿化高质量发展具有重要意义。以新时期科学绿化总体要求为主线,对三北防护林工程存在的主要问题进行了剖析,并从贯彻新发展理念、树立近自然林业、科学划定绿化空间、以水定林草、强化科技支撑等方面提出建议,以期为三北防护林工程建设提供参考。

林分密度和种植点配置对梭梭人工林防风效应的影响

研究不同密度和种植点配置对梭梭人工林防风效应的影响,为优化干旱区防风固沙林结构提供科学依据。以梭梭为原型,利用仿真植物设计了3种密度、4种种植点配置的品字形林带,编号与对应植株的株行距分别为A:17 cm×17 cm,B_(1):34 cm×17 cm,B_(2):17 cm×34 cm,C:34 cm×34 cm,通过风洞模拟试验,对林带在密度和种植点位发生变化时的流场和防风效应进行了测定分析。结果表明:(1)A、B_(1)、B_(2)、C林带的风速减速区(U/U0<1)的面积分别占流场总面积的78.06%、70.41%、74.36%和82.80%;弱风区(U/U0<0.4)的面积分别占流场总面积的22.46%、0.73%、5.91%和0;(2)林分密度越大,冠下平均风速越小,但林带后近地层风速恢复越快,A、B_(1)、B_(2)、C林带的最小风速点分别在带后的11H、15H、15H和20H处(H为树高);(3)4个林带防风效应从大到小的排序为A>B_(2)>B_(1)>C,林带防风效应与林分密度间为非线性关系,林带在带后近地层风速降幅的比例关系为A:B:C≈6:3:2。具体造林时,应根据土壤水分承载力确定造林密度,在此基础上,优先选用“小株距,大行距”的种植点配置方式。

山丹县退化防护林分布特征及土壤状况分析

山丹县防护林建设对县域发展做出了积极贡献,但受多种因素影响,近年来防护林出现大面积退化。以山丹县2022年森林资源和国土资源调查结果为依据,对县域内退化防护林进行全面调查,统计退化面积、林种类型、退化程度、分布特征等。结果表明:全县退化防护林面积达到4384.77 hm^(2),其中农田牧场防护林占80.59%,防风固沙林占19.41%;轻度退化8.28%,中度退化63.55%,重度退化28.17%;重度退化林地土壤有机质含量和养分指标含量显著低于中度和轻度退化林地(P<0.05),极显著低于未退化林地(P<0.01)。综合来看,山丹县退化防护林以中度退化为主,多为农田牧场灌木防护林,且退化程度越高,土壤状况越差,应结合调查结果及时开展精准修复。