BackgroundChinese pine (Pinus tabuliformis Carr.) is one of the major afforestation species in northern China and plays a key role in restoring forest ecosystems and preserving soil and water. However, most Chinese pine plantations are experiencing ecological problems such as the low diversity of understory plants and difficulty in natural regeneration. Thinning has been widely used to maintain and improve a variety of forest ecosystem services from plantations. To date, however, few studies have been conducted to systematically determine the effects of thinning on understory plant diversity and the regeneration of Chinese pine in plantations.MethodsWe conducted a literature search, and selected 22 publications covering a total of 83 treatments related to thinning effects on the species richness of understory plants and 15 publications covering a total of 43 treatments related to thinning effects on the regeneration of Chinese pine, in tree plantations of northern China. The data from the literature were synthesized and evaluated with meta-analysis approach to determine the treatment effects.ResultsCompared with the control stands, thinning increased the species richness of shrubs and herbs by an average of 25.3% and 26.5%, respectively. While the varying thinning intensities all had significantly positive effects on the species richness of understory plants, only moderate thinning (30%–50%) had a positive effect on the density of regenerating seedlings and saplings of Chinese pine (60.2%). The species richness of understory plants was greatest after 14 years of thinning with an increase of 36.3%, whereas the density of regenerating Chinese pine seedlings and saplings reached a maximum after ≥11 years of thinning with an increase of 76.5%, compared to that of the unthinned stands. Thinning in the half-mature plantations had the greatest effects on the understory shrub richness (44.1%) and the density of regenerating Chinese pine seedlings and saplings (86.5%). Both single and multiple thinning were found to significantly promote the species richness of understory plants and the density of regenerating Chinese pine seedlings and saplings, and the positive effects of thinning were greater in areas with a humidity index (HI) ​< ​30 than in areas with an HI ​≥ ​30. In general, age group, planting density and recovery time were prominent factors affecting the species richness of understory plants, whereas the slope, HI and recovery time were the dominant controls of the density of regenerating Chinese pine seedlings and saplings, indicating differential effects of thinning on the species richness of understory plants and the regeneration capacity of Chinese pine in plantations.ConclusionThinning appears to be a feasible management measure to improve the understory plant diversity and regeneration capacity of Chinese pine in plantations. We postulate that moderate thinning in half-mature forest stands with an HI ​< ​30 can help effectively promote the species diversity of understory plants and the natural regeneration of Chinese pine, thereby maintaining a more resilient stand structure and the development of Chinese pine plantations.

Black locust ( Robinia pseudoacacia L.) plantations have contributed significantly to soil and water conservation and ecological reconstruction on China’s Loess Plateau. Understanding the impact of stand and environment on species composition of understory woody plants will improve the stability of existing black locust plantations. Ten stands were selected in second-generation black locust plantations in tableland and gully areas of the Loess Plateau. The number of understory tree species in the tablelands was significantly lower than in the gully stands. Regenerated black locust (19.76%) and Rubus corchorifolius L.f. (64.85%) were the most abundant understory tree and shrub species, respectively, in the tableland stands; Broussonetia papyrifera (L.) L'Hér. ex Vent. (6.77%) and Acanthopanax senticosus (Rupr. Maxim.) Harms. (37.22%) were most abundant in the gully stands. Species richness ( S ), Shannon diversity ( H ), and evenness index ( J ) of the understory plants were significantly lower in the tableland stands than in the gully stands. More diverse understory species and community structures occurred in the gully stands. Differences in species diversity among landform positions may be attributed to differences in soil moisture. In addition, 77.57% of the variation in understory species composition was explained, among which shrub and herb coverage, stand age, leaf area index, slope and total soil phosphorus in the 10–20 cm layer were the main factors. Soil organic carbon and total potassium significantly impacted S , H and J . Considering the environmental conditions and the biological characteristics of the plants investigated, R. corchorifolius should be given priority in the development of tableland stands, while B. papyrifera and Celtis sinensis Pers. should form mixed forests with black locust in gully stands. This management could promote biodiversity and stability of the existing black locust plantations but also optimize regional landscape patterns.

Taking 17-year-old Acer truncatum stand as reserch object, effects of exogenous kinetin 50 mg/L and 0.5 mg/L 2, 4−epibrassinolide on phenotypic traits, seed yield and quality of A. truncatum were analyzed. The results indicated that the seed width and thickness increased significantly after foliar application of 2, 4−epibrassinolide, concentrations of soluble sugar, protein, oil and nervonic acid were significantly higher than CK; spraying kinetin induced significant increase in contents of soluble sugar, protein, oil and nervonic acid and hundred-grain weight and single branch yield were significantly higher than CK. According to analysis of various indicators, promoting effect of 2, 4−epibrassinolide on A. truncatum was slightly better than kinetin.

通过对不同林龄不同间伐强度的刺槐人工林进行对比研究,确定出能有效提高刺槐人工林健康状况的间伐强度,为刺槐人工林健康经营提供科学理论依据.基于科学性、系统性和可操作性的原则,在永寿县槐坪林场36块样地中,通过活力、结构和抗逆性3个方面选出9个评价指标.采用层次分析与聚类分析法,构建刺槐人工林评价模型,计算各样地的健康指数,根据健康指数,将处于不同龄级的刺槐林划分为健康、亚健康和不健康3个等级,进而对样地进行健康评价.结果表明在不同间伐强度的林分中,进行了25％ 间伐强度的刺槐人工林最好,未经过间伐的林分状态最差,幼龄林要比中龄林和近熟林的健康状况要好.总体看来,在永寿县槐坪林场的刺槐人工林总体处于亚健康状态,健康林分占其中的25％,亚健康林分占55.6％,不健康林分占19.4％.25％ 强度间伐能有效的提高刺槐人工林的健康状况,当地林业部门应及时进行适当的间伐.

以陕西省永寿县底角沟流域刺槐人工林为对象,通过样地调查选取更新潜力、群落生物量、群落组成及结构、生物多样性和土壤肥力5类19个因子为评价指标,运用主成分分析综合评价法,分析评价刺槐人工林稳定性.结果表明,底角沟流域刺槐纯林稳定性较差,杨树与刺槐混交林的稳定性远好于纯林,影响刺槐林稳定性较大的因素有更新潜力、乔木蓄积量、灌木生物量、生物多样性和土壤有机碳含量.239 hm2人工林刺槐中,稳定的杨树刺槐人工林占2.3％;较稳定的刺槐人工林占83.6％;不稳定的刺槐人工林占14.1％,流域内85.9％刺槐人工林处于较稳定状态.对于不稳定的林分逐步抚育改造或营建混交林,增加流域内混交林的比列,提高流域内人工林整体的稳定性.

油松立地质量的划分与评价可以为其人工林的速生丰产培育及可持续经营提供科学依据.根据不同的林龄、海拔、坡向、坡度、坡位等因子,在洛南古城林场设置了63块20 m×30 m的油松人工林样地,调查了样地内的油松树高、胸径、冠幅等生长指标.通过数量化理论Ⅰ,对洛南地区油松人工林进行立地质量评价,并通过数量化理论II建立了陕西洛南油松人工林立地质量类型判别模型.结果表明:1)洛南地区油松人工林树高、胸径随着林龄的增长有着明显的增加,其中油松在第10～20年时生长迅速,随后在第20～40年时生长速度较快.2)以海拔、坡向、坡位、坡度为主要立地因子将油松人工林划分为36个立地类型区.建立油松人工林立地质量评价表,研究区范围内有71.43％的油松人工林样地立地质量评价在中等及以上,结果说明在洛南地区阴坡、高海拔(≥970 m)且平缓坡度下较适宜油松的生长;洛南地区油松人工林种植区域内油松生长情况较好.3)以51组不同立地样本数据进行数量化理论Ⅱ判别分析,得到相应的判别系数矩阵,确定不同立地类型的样本中心点.用12组样本数据对该判别模型进行检验,正确率达91.67％,表明该模型具有良好的判别能力,可以用来判别预测洛南油松人工林的立地质量.

为研究有机肥施用量对残塬沟壑区苹果园土壤优先流特征的影响,以残塬沟壑区苹果园为研究对象,采用室外染色示踪法结合形态学和统计学方法,对永寿县苹果园土壤垂直染色剖面进行定量分析,使用均方差决策法综合各优先流特征指标对0 kg/hm2(CK)、6000 kg/hm2(T1)、9000 kg/hm2(T2)、12000 kg/hm2(T3)四种不同有机肥施用量苹果园土壤优先流特征进行研究.结果表明:①不同有机肥施用量样地土壤染色面积比随土壤深度的变化状况均与Logistic曲线拟合程度较好,决定系数R2均大于0.986.②选用的优先流特征指标中基质流入渗深度、优先流分数、变异系数和分形维数与均方差决策法计算出的优先流发育程度结果一致,优先流发展程度表现为T3>T2>T1>CK.但平均最大入渗深度、优先流区染色面积比和长度指数在评价优先流程度中结果有些偏差,表现为T3>T2>CK>T1.③利用均方差决策法得到的优先流指数由大到小为:T3(0.75)、T2(0.59)、T1(0.27)、CK(0.25),随着有机肥施肥量的增加,优先流程度也随之增加.本研究可为土壤优先流特征综合评价提供参考,并为残塬沟壑区果园合理施肥提供依据.

探究黄土丘陵区景观格局的时空演变规律和驱动力,对该区土地资源的合理利用和生态环境的优化建设提供指导意义.以陕西省永寿县1998、2008、2018年遥感影像数据为基础,借助ArcGIS和FRAGSTATS等软件,运用景观转移矩阵、景观格局指数对其进行了分析,并运用主成分分析法讨论景观变化驱动力.结果表明:1)从土地利用景观格局变化状况来看,研究区的主导景观由耕地变为林地,主要变化为林地、园地面积的增加.林地面积增加了177.88 km2,园地面积增加了128.66 km2,主要是由耕地转换而来.2)从斑块水平来看,林地在各景观类型中占据主导地位;建设用地、林地、未利用地受到人为干预,斑块形状趋于简单;林地、园地、草地的景观异质性在逐渐增强.3)从景观水平来看,整体景观连通性变差,各斑块类型面积比重趋向平衡,景观的破碎化程度逐渐增大,各景观类型逐步分化为更小的斑块.4)从景观格局变化的驱动因素来看,气温和降水等自然因素对景观格局的演变具有一定的影响,而社会经济因素及政策导向是永寿县景观格局变化的主要因素.

以17年生元宝枫人工林为试验材料,研究叶面喷施激动素和2,4表油菜素内酯对其叶绿素含量、叶片和翅果中糖含量(可溶性糖、蔗糖、淀粉)、蔗糖代谢酶(蔗糖磷酸合成酶、蔗糖合成酶分解方向、蔗糖合成酶合成方向)活性的影响,分析外源激素调控元宝枫叶片和翅果碳水化合物代谢的作用机理,为元宝枫的丰产稳产提供理论指导.结果 表明,元宝枫叶面喷施激动素和2,4-表油菜素内酯可以提高叶绿素含量,增强光合作用,促进光合产物的积累,叶片中可溶性糖含量和蔗糖含量升高,蔗糖磷酸合成酶活性显著增强,叶片源强提高,促进光合产物向翅果运输;翅果中可溶性糖含量、蔗糖含量与淀粉含量均得到提高,蔗糖合成酶分解活性增强,蔗糖磷酸合成酶活性和蔗糖合成酶合成活性减弱,促进翅果中蔗糖的分解转化,有利于翅果的生长发育以及品质产量的提高.

苹果园作为一种农林耦合特殊生态系统,不仅提供农产品,还具有维持自然环境条件与效应的生态服务功能.该研究选取黄土高原残塬沟壑区永寿县苹果果园为评价区,构建评价体系.采用市场价格法、价值替代法等评价方法,评估苹果园生产农副产品、负效应等9项生态服务价值.结果表明:永寿县苹果园生态系统在2019年生态系统综合服务价值为41 495.66万元,其中正效益为45 096.33万元,负效益为-3 600.67万元.在选取的9项苹果果园生态系统服务指标中,生产的价值最大,为21 793.71万元,远大于其他生态服务价值.生物多样性保护(8 247.49万元)＞保育土壤(8 066.69万元)＞负效益(-3 600.67万元)＞涵养水源(2 779.32万元)＞文化娱乐(1814.83万元)＞固碳释氧(1440.45万元)＞净化调节(708.22万元)＞林木养分固持(245.62万元).黄土高原残塬沟壑区为中国水土流失重点治理区,苹果园为该地区林木重要组成部分,对其服务价值的研究,可以为该地区推动经济林建设、发展和可持续利用提供数据支持.

为研究残塬沟壑区苹果园不同果农复合种植模式下土壤入渗能力及其影响因素,采用野外双环入渗法测定了永寿县果-荒(CK)果-草(M1)果-蔬(M2)果-粮(M3)复合种植模式下苹果园的土壤水分入渗参数,使用相关性分析和线性冗余分析研究了土壤入渗特征参数的影响因素.利用3种常用的土壤入渗模型对4种果园入渗过程进行拟合.结果表明:4种果农复合种植模式下果园土壤初始入渗速率在7.18～13.57 mm·min1;稳定入渗速率在1.87～2.94 mm·min-;平均入渗速率在3.36～5.65 mm·min-1;累计入渗量在260.51～423.65 mm,各果农复合种植模式苹果园初始入渗速率和平均入渗速率表现为M1＞M3＞M2＞CK;稳定入渗速率和累计入渗量表现为M1＞M2＞M3＞CK,M1样地各入渗指标显著大于其他管理模式样地,CK样地各入渗特征指标最小.相关性分析发现,土壤入渗特征指标与土壤容重、黏粒含量和粉粒含量呈负相关;与最大持水、最小持水量、毛管持水量、毛管孔隙度、非毛管孔隙度、总孔隙沙粒含量呈正相关.线性冗余分析结果表明,土壤粉粒含量、土壤孔隙度、土壤持水量、土壤容重是影响土壤入渗能力的主要的因素.主成分分析评价的土壤入渗能力排序为M1(2.75)＞M2(0.04)＞M3(-0.63)＞CK(-2.17),苹果园林下种植作物能够有效的增加土壤入渗能力.比较3种模型发现,蒋定生模型对残塬沟壑区4种果农复合种植模式果园土壤入渗过程的拟合精度较高(R2=0.97),适用于描述该地区土壤入渗的实际情况.

为研究残塬沟壑区苹果园不同果农复合模式下土壤理化性质和水源涵养功能并筛选出水源涵养功能主导因素.以陕西省马坊塬果-荒(M0)、果-草(M1)、果-蔬(M2)、果-粮(M3)4种果农复合经营模式苹果园为研究对象,对比4种果农复合模式土壤理化特征差异性,并评估果农复合模式对土壤水源涵养功能指数的影响.使用逐步回归分析和通径分析探讨影响土壤水源涵养功能的主导因素.结果 表明:生草处理 、果蔬间作 、果农间作下果园土壤容重 、孔隙度 、持水能力 、养分含量等理化性质优于人工除草样地.其中生草处理 、果蔬间作 、果农间作土壤容重分比人工除草别降低了15.13％,11.84％,11.18％;有机质含量增加了143.76％,7.14％,120.46％.各果农复合模式下土壤水源涵养功能指数大小依次为M1(0.64)>M3(0.59)>M2(0.51)>M0(0.38).逐步回归分析表明,总孔隙度 、容重和有机质含量是影响土壤水源涵养功能的主要因子,3个土壤因子可解释土壤水源涵养功能指数变异量的95％.通径分析表明,总孔隙度是影响土壤水源涵养功能的主要决策因素,容重是影响土壤水源涵养功能的主要限制因子.研究结果可为残塬沟壑区苹果园可持续土壤管理的选择提供科学依据.

为了解苹果复合种植即果-蔬[MB]、果-草[MH]、果-荒[MW]、果-粮[MZ]模式下土壤动物群落结构特征,采用手拣法和改良干、湿生漏斗法,对黄土残塬沟壑区苹果园4种复合种植模式下的土壤动物群落组成及特征进行调查研究.4种模式下共分离得到土壤动物57.33百只/m2,隶属4门11纲23目42个类群.4种复合种植模式下土壤动物个体密度和类群数的垂直分布特征表现出明显的表聚特征,水平分布特征表现为果-草[MH]＞果-蔬[MB]＞果-荒[MW]≥果-粮[MZ].果-草[MH]复合种植模式下土壤动物的多样性指数、均匀度指数及丰富度指数最高,优势度指数最低,表明4种复合种植模式对果园土壤动物类群多样性的影响呈现不同的特征.研究结果可为黄土残塬沟壑区苹果果园生物多样性保护提供土壤动物生态学依据.

[目的]研究经营方式对残塬沟壑区苹果园土壤动物群落的影响,为果园生物多样性保护和合理利用土地资源提供依据.[方法]2018年夏在陕西省永寿县调查了果-蔬(Malus-Brassica)、果-草(Malus-Trifolium)、果-荒(Malus-Wild)和果-粮(Malus-Zea)等4种经营方式下苹果园土壤动物群落的变化,结合Shannon多样性指数、Pielou均匀度指数、Margalef丰富度指数、Simpson优势度指数、冗余度分析(RDA)等方法,研究4种不同经营方式下残塬沟壑区苹果园土壤动物群落的结构特征、多样性及其与土壤环境因子的关系.[结果]调查区土壤动物为23 811只/m2,隶属4门11纲23目42科,其中优势类群有等节(虫兆)科、小杆科、厉螨科和美绥螨科,常见类群有10类,占采集总量的91.26％.较其他3种经营方式而言,果-草经营方式显著增加了土壤动物个体密度和类群数(P＜0.05).在垂直分布上,土壤动物具有明显的表聚性特征,随着土层的加深其个体密度和类群数显著下降(P＜0.05).果-草经营方式下各土层土壤动物多样性最丰富,且分布最均匀.冗余度分析(RDA)结果表明,速效磷(AP)、速效钾(AK)、酸碱度(pH)、含水率(WC)是影响残塬沟壑区土壤动物分布的主要土壤环境因子.[结论]土壤动物群落生态分布特征与果园经营方式有关,果-草经营方式为土壤动物生存提供了适宜的环境,有利于维持其群落结构的稳定,对果园表层(0～10 cm)土壤动物群落有明显促进作用.

Chinese pine is one of the major afforestation species in North China, and plantations of this species are of great significance for improving the ecological environment and for conserving soil and water. However, most of the Chinese pine plantations established by the government in the 1970s are mature or nearly mature. Therefore, how to successfully promote natural regeneration has become a major issue in plantation management. We established four types of gaps with different diameters in a plantation in northern China based on the average canopy height (H), i.e., L-I (0.75 H), L-II (1.00 H), L-III (1.25 H), and L-IV (1.50 H). Seven years after gap creation, each gap was divided into four aspects by vertical lines along the main direction of the gap center. Additionally, three sections were partitioned in each gap according to the mean crown radius of the border trees; these sections were the central area of the gap (section B), the inner edge of the gap (section C) and the outer edge of the gap (section D). The results showed that there were no differences in density among gap size classes and gap aspects, but a positive response was observed for regeneration growth. The maximum growth in L-III implied that this gap was the optimal size for promoting the establishment, survival and development of regenerated trees. The highest density and greatest growth occurred mostly along the gap edge. Spatial patterns of abundance were generally concurrent with patterns of regeneration stature (e.g., height) in all tested gaps. However, the spatial distributions of regeneration density and growth exhibited obvious differences in different gap size classes, which likely resulted from heterogeneity in the micro-environment within the gap and the differences in the regeneration responses to these variations. The mark correlation function indicated that spatial autocorrelation characteristics of regeneration growth within gaps and gap sections were mainly independent. Collectively, our findings suggested that the expansion of gaps with continuous monitoring will likely be necessary to promote further canopy recruitment. Additionally, regenerating trees exhibited different spatial distributions and could be more resilient to various interferences. Factors influencing the differences in spatial distribution need to be further studied in light of the relationship between variations in the micro-environment and regeneration responses after gap creation. Moreover, whether large-scale vegetation displacement and reorganization will result from clear cutting these plantations warrants further investigation.

以陕北晋枣为材料,研究果实发育过程中叶片、细根和果实中可溶性蛋白、可溶性糖含量的动态变化及其相关性,为枣树营养调控提供理论依据.采用蒽酮比色法和考马斯亮蓝法分别测定晋枣开花坐果期、果实膨大期、果实成熟期3个发育阶段细根、叶片和果实中可溶性糖和可溶性蛋白的含量,并进行相关性分析.结果表明,3个发育阶段可溶性糖含量表现为果实＞叶片＞细根,可溶性蛋白含量表现为细根＞叶片＞果实,细根和叶片中可溶性糖及可溶性蛋白含量的最大值均分别出现在果实膨大期、开花坐果期,果实中可溶性糖含量的最大值出现在果实成熟期,可溶性蛋白含量最大值出现在开花坐果期.果实与叶片之间可溶性蛋白含量具有极显著正相关性,可溶性糖含量具有负相关性,果实与细根间相关性不显著.与细根相比,叶片中可溶性糖和可溶性蛋白含量与果实具有更大的相关性.

细根形态反映细根功能,以黄土高原陕西省永寿县15年生刺槐人工林为研究对象,采集刺槐完整根段,依据根序分成1～5级根,对其细根形态结构和生物量进行测定分析,为深入认识刺槐人工林细根形态特征提供参考.结果表明:1)1～2、2～3、3～4、4～5级根的平均分支比分别为4.52、2.06、4.03和4.17.其中,只有2～3级根的分支比与其他分支水平之间具有显著差异(P＜0.05).2)从1级根到5级根,随序级的升高,刺槐细根直径、根长呈升高趋势,而比根长呈降低趋势.各根序之间的细根直径、根长、比根长都具有显著差异(P＜0.05).3)刺槐1～5级细根生物量的排序为1级＜2级＜3级＜5级＜4级,且前4级之间的细根生物量具有显著差异(P＜0.05).1～5级细根总生物量为240.95 g· m-2,4～5级根生物量之和占总生物量的75.88％,对总生物量有较大的贡献.1～5级细根各分支水平高级根与低级根的细根生物量之间具有显著的线性关系.

Chinese pine (Pinus tabulaeformis Carr.) is a widely distributed moderately shade-tolerant tree species with important economic and ecological value in northern China. The productivity of the plantations established by the government in the 1970s has apparently begun to decline. Therefore, the identification of silviculture measures that can feasibly and reasonably balance timber production and sustainable forest management is of interest to many operators and researchers. The main purpose of our study was to understand whether the height growth of trees regenerating under the canopy would positively respond to thinning and provide sufficient high-quality regenerating trees for the successful transformation to uneven-aged forests. Four different thinning intensity treatments were implemented in a 40-year-old plantation based on the number of trees that were cut down using the thinning-from-below approach: 0.0% (unmanaged), 20.0-21.0% (weak thinning), 30.0-31.0% (moderate thinning), and 40.0-41.0% (strong thinning). After five years of thinning, the differences in growth among the different thinning intensities were compared using nonparametric statistical methods. Additionally, the height growth rates of regenerating trees over the past five years were predicted using a linear mixed-effects model that included variables related to stand characteristics, soil physiochemical properties and measurements of individual regenerating trees. The results showed that thinning could significantly promote the height growth of regenerating trees in comparison to the growth in unmanaged plots. Significant differences were found among thinning intensities in terms of growth, excluding ground diameter, with the maximum and minimum values in the strong thinning and unmanaged plots, respectively. However, the models never explained more than 50% of the variation regardless of whether the plot level or the individual level was considered, although they included the majority of the evaluated variables. In conclusion, strong thinning is a potentially feasible silvicultural method for uneven-aged Chinese pine plantations in northern China. Some factors that are important in terms of the growth of regenerating trees but were not tested in our study, such as competition, light intensity and distribution, and microsite environment, are recommended to be considered in future research to improve the explanatory power of the model. Moreover, based on our results and to supplement thinning, the gap expansion harvesting system should be carried out in gaps opened by thinning to not only maintain stand stability but also facilitate the growth of regenerating trees into the canopy for canopy recruitment.

The objective of this study was to examine the morphological variations of the fine roots of "Qiyuexian",a cultivar of jujube growing in Northern Shaanxi,China,in different developmental stages (bud leaf,early-and middle-period of leaf expansion,full leaf,fruit ripening,and leaf falling stage).The complete fine roots were collected by excavating soil blocks and ranked by root order.The fine root samples were scanned by the Espon scanner,Win-RHIZO system was used to obtain root parameters such as total length,surface area,volume and average diameter.The results showed that 1) in different developmental stages,the ratios of the first order roots to the second ones (ranged from 5.2 to 6.2) were higher than those of the second ones to the third ones (2.7 to 3.3).Differences in branching ratios of the first and second roots,as well as the second and the third roots were not significant (P＞0.05).2) Root diameters and tissue densities of the roots with different orders increased with the increase of the root order (1st＜2nd＜3rd),which were lower in bud leaf stage and higher in leaf falling stage to accumulate nutrients for the root growth in the next year.3) The maximum values of specific root length and specific surface area appeared in bud leaf stage,while peak values were also observed in fruit ripening stage.These results suggested that the seasonal variations of the fine root morphology of Qiyuexian had obvious changes in different phenological periods,which could be considered as a theoretical basis for the underground management of jujube trees.

以黄土高原刺槐人工林为研究对象,采用手工挖掘法,配合完整土块法获取根系样品,分析幼龄（11a）,中龄（22a）,成熟（34a）刺槐人工林细根活力、可溶性糖含量、可溶性蛋白含量和细胞膜透性等细根衰老生理指标的差异,为深入了解刺槐细根的生长和衰老机制提供参考。结果表明:（1）在生长季节,刺槐细根活力表现为,幼龄林＞成熟林＞中龄林,可溶性糖含量、可溶性蛋白含量随着林龄增大而增加,而细胞膜透性则随林龄的增加而减小。（2）随着根序增加,根活力和可溶性糖含量增加,而可溶性蛋白含量和细胞膜透性则呈波动式降低。这表明,在生长季节幼龄林细根较中龄林和成熟林更容易出现衰老,刺槐不同根序衰老具有顺序性,衰老先从1级根开始,然后是2级根和3级根。