林龄对马尾松人工林水源涵养能力的影响研究

通过对广西大化县带林村不同林龄段马尾松人工林凋落物层和土壤层的水源涵养能力进行研究,探讨了林龄对马尾松人工林水源涵养能力的影响。结果表明:马尾松人工林幼龄林阶段凋落物层最大持水系数年增长率最大,中龄林阶段最大持水量年增长率最大,到近熟林阶段凋落物层最大持水系数、最大持水量均达到最大值;研究期内各样地土壤有机质、全氮、全磷、全钾、速效氮、速效磷、速效钾含量变化表现为幼龄林阶段下降幅度较小、中龄林阶段下降幅度最大、近熟林阶段下降幅度又变小,其中近熟林阶段土壤速效氮、速效钾的含量甚至呈现增加的趋势;马尾松人工林近熟林阶段的土壤涵养水源能力明显高于幼龄林和中龄林阶段。     

吉林省东部低山丘陵区4种林分类型林地的土壤肥力分析

根据吉林省东部低山丘陵区汪清林业局金仓林场中4种主要林分类型(长白落叶松天然林、长白落叶松人工林、天然针阔混交林和天然阔叶混交林)的土壤肥力调查数据,分析和比较了4种林分类型林地的土壤物理和化学性质,并采用主成分分析评价了其土壤肥力状况。(1)随土壤深度增加,土壤容重和土壤pH值增大,而土壤含水量、阳离子交换量和养分含量减少,但其在不同林分下的变化程度不同;(2)林分类型对部分土壤化学性质(如土壤CEC、有机质、全氮和速效钾)影响显著。其中,天然针阔混交林的土壤含水量、土壤pH值、阳离子交换量、有机质含量及全氮、磷、钾含量均为最高;(3)采用主成分分析法对不同林分类型的林地土壤肥力状况进行了评价,结果发现土壤肥力状况为:天然针阔混交林>长白落叶松天然林>长白落叶松人工林>天然阔叶混交林。建议在经营现有的林分时,考虑近自然育林,及时进行林下补植更新,并营造针阔混交林,以改善该区林地土壤的肥力状况。     

大青山不同林地类型土壤特性及其水源涵养功能

对内蒙古大青山4种林地类型的土壤特性、凋落物持水量及林地土壤贮水性能进行了研究。结果表明:①林地间土壤容重和孔隙度差异较大,容重大小依次为油松人工林>虎榛子灌丛林>落叶松人工林>白桦山杨天然次生林;总孔隙大小依次为白桦山杨天然次生林>落叶松人工林>虎榛子灌丛林>油松人工林;②林地间凋落物蓄积量和最大持水率差异较大,蓄积量大小依次为落叶松人工林>白桦山杨天然次生林>虎榛子灌丛林>油松人工林;最大持水率大小依次为落叶松人工林>白桦山杨天然次生林>虎榛子灌丛林>油松人工林;③依据林地总贮水量的大小,4种林地水源涵养功能大小依次为白桦山杨天然次生林(3 687.172 t/hm2)>落叶松人工林(3 553.229 t/hm2)>虎榛子灌丛林(3 035.698 t/hm2)>油松人工林(2 796.279 t/hm2)。     

冀北山区华北落叶松人工林对土壤化学性质的影响

为了研究冀北山区华北落叶松人工林土壤化学性质的变化,采用空间替代时间的研究方法,分析比较了不同林龄华北落叶松人工林林下土壤的酸碱度、阳离子交换量、盐基饱和度、土壤有机质及速效养分含量。结果表明,随着林龄的增长,土壤pH值、速效钾含量有逐渐下降的趋势,土壤速效磷含量有所增加,一代林碱解氮含量呈上升趋势,而土壤盐基饱和度没有明显的变化。同时,与华北落叶松一代人工林相比,二代林土壤pH值下降0.23个单位,土壤阳离子交换量、盐基饱和度、有机质含量、碱解氮含量与速效钾含量分别下降44.43%,9.59%,24.01%,20.27%和28.88%,土壤速效磷含量上升8.09%。该地区华北落叶松人工林土壤有轻微酸化的趋势,二代林土壤肥力有下降的趋势,因此在森林经营管理过程中应采取相应措施加以防范。     

冀北山地天然次生林与人工林地上植被层的水文调控功能

[目的]比较冀北山地天然次生杨桦林(13,18和28a)和人工落叶松林(9,13,15和30a)地上植被层(林冠层、凋落物)的水文调控功能,为评估两种森林类型的转化对该地区水文过程的影响提供科学依据。[方法]采用标准样地和测定分析法对林分的生物量、凋落物及其持水量的进行测算。[结果](1)不同林龄的人工落叶松林地上植被层的降水截留量均大于天然次生杨桦林,且差异显著。(2)两种林分类型不同地上植被层的截留量均表现为:凋落物林冠层灌木层。(3)幼、中龄人工落叶松林的林冠截流量明显大于同龄的天然次生杨桦林,而近熟林,由抚育间伐导致的林分密度下降使得人工落叶松林低于天然次生杨桦林。(4)在各个林龄上,人工落叶松林的凋落物持水量均显著大于天然次生杨桦林,其中13a落叶松为35.36±6.50t/hm2,13a杨桦林为15.79±4.85t/hm2。[结论]冀北山地大面积的人工落叶松林地上植被层具有良好的水文调控功能,其水文调控功能不低于甚至高于当地的天然次生杨桦林,对人工林的抚育间伐在一定程度上会使地上植被层的水文调控功能出现一定程度的下降。     

杉木凋落物源有机酸对土壤磷有效性的影响

以不同林龄(10 a、22 a、34 a)杉木人工林为研究对象,测定其凋落物及土壤中有机酸的组成,比较不同林龄杉木林土壤酸度及不同形态磷的含量,分析杉木凋落物源有机酸对土壤磷有效性的影响。结果表明,在杉木凋落物中检测到草酸、丙二酸、苹果酸、反丁烯二酸、丁二酸及柠檬酸等6种低分子有机酸。其中,草酸含量最大,且凋落叶的有机酸含量最高。不同林龄杉木凋落物的有机酸含量表现为:34 a>22 a>10 a。在土壤中,仅检测到草酸这一凋落物源有机酸的优势有机酸,而不同林龄杉木林的土壤有机酸含量与凋落物一致,也随着林龄的增加而增加,并随着土层加深而减少。因土壤有机酸的存在,不同林龄杉木林土壤存在明显的酸化现象,且林龄越大pH值越低。土壤有效磷与有机酸变化规律一致,表现为:34 a>22 a>10 a,且随土层加深逐渐减少。O-P、Fe-P、Al-P与Ca-P等无机磷则反之,呈现10 a>22 a>34 a的变化规律。可见,不同林龄杉木林中土壤有机酸(主要是草酸)能降低土壤pH值,且有效促进土壤磷的活化,致使土壤有效磷含量的增加,而凋落物源有机酸是土壤有机酸的重要来源之一,对土壤磷有效性的提高起着重要作用。     

不同林龄华北落叶松人工林枯落物储量及持水特性研究

对3种不同林龄阶段的华北落叶松人工林林下枯落物储量及其持水特性进行分析的结果表明:枯落物储量幼龄林、中龄林、近熟林分别为42.23、57.11、65.00t/hm2;各林龄林下枯落物最大持水量均是未分解层小于半分解层,未分解层最大持水量是其风干重的280%～374%,半分解层最大持水量是其风干重的408%～466%;3种林龄按林下枯落物未分解层持水量大小排序为近熟林>幼龄林>中龄林,按半分解层持水量大小排序为近熟林>中龄林>幼龄林。各林龄各层枯落物持水量与浸水时间之间的最佳拟合关系式为W=alnt+b;各林龄各层次枯落物吸水速率与浸水时间之间的关系式为S=ktn,在0—1h内吸水速率急剧下降,1h以后下降平缓,吸水作用逐渐减小。     

秦岭北麓不同林龄华北落叶松土壤速效钾动态变化规律研究

【目的】土壤养分对华北落叶松的生长具有重要作用,钾素是植物所必需的大量营养元素之一, 土壤中钾素对植物最有效的形态为速效钾,其能够直观地反映土壤可供植物利用的钾素水平。华北落叶松是北方人工林栽植的主要树种,具有生长快、木材优质、耐寒性好、水土保持效果好等优点。研究表明华北落叶松人工林种植初期长势良好,而近年来长势明显不良,因此有必要对秦岭北麓不同林龄华北落叶松林地土壤的养分特别是速效钾的变化规律进行研究。【方法】本研究选择土壤性质与林分基本特征相似的幼龄林（5a,10a）,中龄林（20a）,近熟林（30a）及成熟林（40a）等5种不同林龄华北落叶松人工林地。5a、10a、20a华北落叶松试验样地位于陕西省宝鸡市太白县太白林业局南滩实验苗圃林场,30a、40a试验样地位于西北农林科技大学火地塘教学试验林场。从5月开始,每月中旬采集各个样地的土壤样品,直到10月中旬落叶为止。每个林龄林地选5个不同的20 m 20 m样点,用土钻取剖面020 cm、2040 cm、4060 cm土层土壤, 5个点混合均匀成一个土样,分析土壤速效钾含量。【结果】在不同月份,不同林龄的华北落叶松土壤的速效钾含量随土壤深度的增加有下降趋势。020 cm土层的速效钾含量相对于其他土层含量较高,其中,近熟林（30a）及成熟林（40a）土壤速效钾含量明显高于其他林龄的土壤;不同月份不同林龄华北落叶松土壤的速效钾含量差异显著（P001）。研究区域不同林龄华北落叶松土壤速效钾含量达到中等及高水平。在不同华北落叶松生长季节020 cm土层速效钾含量呈先增加后降低的抛物线形变化。土壤速效钾含量与有机质含量有极显著的正相关关系（P001）,与土壤含水量达显著相关（P005）,与土壤pH呈显著负相关关系（P005）。【结论】随林龄的增加,华北落叶松人工林土壤速效钾的含量不会降低。土壤有机质含量,土壤含水量与土壤pH会对土壤速效钾的含量产生影响。秦岭北麓华北落叶松人工林林地土壤速效钾含量丰富,供钾充足。     

植被变化对人工林地蓄水功能的影响

为探讨混交林改为桉树人工林后土壤层和凋落物层水量调蓄功能的变化规律,采用室内试验与野外监测相结合的方法,研究了尾巨桉林和马尾松×杉木混交林0—30 cm土壤层和凋落物层的蓄水功能。结果表明,3年生尾巨桉林0—15和15—30 cm土层土壤容重分别比马尾松×杉木混交林的低8.8%和4.6%,尾巨桉林土壤饱和持水率显著大于混交林;混交林改为尾巨桉林后,0—30 cm土壤层最大蓄水量没有发生显著变化,但土壤水分蒸发速率加快,非降雨天气下尾巨桉林土壤蓄水量显著低于混交林;改为尾巨桉林后林地凋落物现存量和潜在蓄水量显著减少,但随着林龄增加,尾巨桉林地凋落物现存量和潜在蓄水量逐渐回升,凋落物最大持水率逐渐降低;降雨条件下人工林凋落物层比土壤层易于达到其理论最大蓄水量。     

黄土高原中西部人工针叶林浅层土壤有机碳积累及影响因素

林地浅层土壤是凋落物有机质向土壤碳库输移的关键层,对于土壤有机碳积累具有表征作用。为了探究黄土高原中西部3种人工针叶林土壤固碳功能,基于野外调查获取的样地信息和对凋落物、土壤的采样分析,研究了林分条件、凋落物成分以及环境因子对浅层土壤有机碳积累的影响。结果表明:在研究区域内,林龄与浅层土壤碳密度呈现极显著相关关系;年平均温度对于浅层土壤碳密度无明显影响;在海拔高于2 000 m的各样地之间,海拔高度与浅层土壤碳密度呈现极显著正相关关系,而低于2 000 m时不存在这种相关关系;各样地年平均降雨量与浅层土壤碳密度呈现正相关关系,凋落物碳氮比与浅层土壤碳密度呈极显著的负相关关系。运用随机森林法对各影响因子的重要性进行分析排序可知,凋落物成分、气候因子、海拔以及林龄对于全部样地浅层土壤碳密度变异的总解释率为66.2%,其中凋落物碳氮比是影响黄土高原中西部人工针叶林浅层土壤碳积累的主导因子。     

落叶松人工林土壤酸度变化与无机磷形态的关系

 为了科学地经营落叶松人工林,持续改善其土壤质量和提高林分生产力,研究东北东部山地不同发育阶段落叶松人工林土壤酸度变化,以及活性酸(pH值)、交换性酸和水解性酸与无机磷形态的关系。结果表明:1)随林龄的增大,根际土壤活性酸(pH值)持续降低,根际土壤的交换性酸、交换性铝明显增加,根际土壤Ca-P和O-P与水解性总酸度的相关系数减小,Fe-P与交换性酸、交换性铝的相关系数增大。2)根际土壤活性酸、水解性总酸度变化对根际土壤Al-P含量的变化影响较大,尤其是在幼龄林、近熟林和成熟林二者之间达到了极显著或显著水平;根际土壤Ca-P含量的变化主要受根际土壤活性酸的影响;各年龄阶段根际土壤Fe-P含量与水解性总酸度关系密切;根际土壤O-P含量随着土壤交换性酸、水解性总酸度的增高而降低。3)非根际土壤酸度与非根际土壤无机磷形态的相关性不明显。     

川西亚高山针叶林植物群落演替对生物学特性的影响

通过对川西亚高山针叶林人工重建过程中土壤微生物数量、酶活性及其与土壤养分性状的关系研究表明,云杉人工成熟林土壤微生物数量、酶活性明显低于云杉人工幼林地,也低于同龄的次生阔叶林地,人工云杉林随着林龄的增加土壤肥力严重退化。土壤微生物数量、酶活性与土壤有机质、全N、全P和碱解N等养分指标呈显著相关关系,土壤生物学指标能较好地反映土壤肥力状况。解决当前人工成熟云杉林土壤退化的主要措施应因地制宜地进行抚育间伐,改善林地的微生态条件,尽量避免营造针叶纯林,建议营造针阔混交林。     

川南地区不同退耕地对土壤抗蚀性的影响

对川南坡地退耕5年后的慈竹林地、杂交竹林地、桤木+慈竹混交林地和弃耕地土壤抗蚀性变化进行了研究,探讨了土壤抗蚀性指标间的关系。结果表明:退耕后土壤水稳性团聚体平均质量直径、结构性颗粒指数、团聚状况、团聚度、物理稳定性指数和有机质增加,土壤结构体破坏率、不稳定团粒指数、分散率、侵蚀系数和受蚀性指数降低;各退耕地土壤抗蚀性综合主成分值为-4.466~3.436,呈现出慈竹林地杂交竹林地桤木+慈竹混交林地弃耕地对照的特点;土壤有机质与大多数抗蚀性指标具有显著相关性,且与抗蚀性综合主成分值呈极显著正相关,说明坡地退耕后土壤有机质增加是土壤抗蚀性增强的关键,坡地退耕成慈竹林地更有利于增强研究区土壤抗蚀性。     

Decomposition rates of forest residues and soil fertility after clear‐cutting of Eucalyptus grandis stands in response to site management and fertilizer application

Forest residues (i.e. harvest residues and litter) are important nutrient sources for trees because soils of poor fertility are used for eucalypt plantations in Brazil. Understanding the dynamics of decomposition for these residues and their effects on soil fertility are relevant for the management of forest plantations. The objectives with this study were to assess the effects of forest residue management and fertilizer, both applied in the establishment of a Eucalyptus grandis Hill ex Maiden stand, on the decomposition rate (k), nutrient release and soil fertility after harvest of this stand. The treatments were applied to a plantation (R1). After 8 yr, R1 was clear‐cut and all of the treatments were reapplied to a new planting (R2). At the end of R1 (age of 8 yr), there was a reduction of 10% in the wood volume in the treatment with the forest residues removed and 36% reduction with no fertilizer application. At the end of 1 yr for plantation R2, these reductions were 30 and 57%, respectively. Residue decomposition under R2 was assessed by a new approach that involved collecting samples directly on the site without using litter bags. The k of forest residues was 3.6 for leaves, 1.2 for bark and 0.8 for branches. The application of small rates of N and P fertilizer did not influence the k of forest residues. In the first 300 days after clear‐cutting, approximately 50% of N, P, Ca, Mg and S and 80% of K in the forest residues were released. Even so, this did not result in significant changes in soil fertility levels. Only small reductions in soil N and P contents over time and changes in topsoil pH resulted from forest residue removal.     

雷州半岛桉树人工林土壤肥力特征及其成因

对雷州林业局桉树人工林地进行了土壤普查,结果表明,桉树人工林土壤肥力很低;其现状肥力特征的形成与桉树人工林生态系统水土流失严重,人为因素对土壤养分生物积累过程的干扰,桉树全树利用方式,耕垦和采后剩余物处理不适当有关。因此,增加桉树人工林生物多样性、回归林地凋落物于土壤,应用适当地采伐利用方式和采伐剩余物的处理方式,是改善桉树人工林土壤肥力必须采取的措施。     

The effects of mixed broad-leaved trees on the collembolan community in larch plantations of central Japan

The effects of broad-leaved trees on the collembolan community in larch plantations were investigated at the foot of Mt. Yatsugatake (1200–1400 m a.s.l.) in Japan. The study sites comprised five pure larch plantation plots (larch dominated more than 95% of the area at breast height) and five mixed forest plots (larch dominated between 50% and 80% of the area at breast height). We compared the collembolan community structures between stand types and related them to the plant community composition and soil properties at each plot. Density and species richness of Collembola were not significantly different between pure larch and mixed plots. Using partial redundancy analysis (pRDA), the variance of collembolan species data in the litter layer was explained by the biomass of grass on the forest floor, and the variance in the soil layer was explained by the biomass of total forest floor plants. These results suggest that the biomass or the composition of forest floor plants influence the collembolan community more than the crown trees in this area.     

长白山东部4种林分类型土壤有机碳及养分特征研究

以长白山东部长白落叶松天然林、长白落叶松人工林、天然阔叶混交林、天然针阔混交林4种林分类型为研究对象,对比分析了土壤有机碳(SOC)的垂直分布特征,以及与土壤理化性质的相关性.结果表明,4种林分下土壤有机碳含量及其差异程度随土壤深度增加均呈现逐渐减小的趋势.0-60 cm土层土壤有机碳含量大小依次为天然针阔混交林(33.64士17.48 g/kg)＞长白落叶松天然林(25.30±15.09 g/kg)＞天然阔叶混交林(22.13±13.74 g/kg)＞长白落叶松人工林(19.23±12.35 g/kg);天然针阔混交林0-60 cm土壤有机碳密度为21.44±8.31 kg/m2,显著高于其他3种林分类型,长白落叶松人工林最小,为14.29±1.59 kg/m2.对不同土层土壤有机碳和土壤理化性质进行相关分析,结果表明,整个土壤剖面有机碳含量与自然含水率、全N、全P、全K、速效K均呈极显著或显著正相关,与土壤密度呈极显著负相关;不同林分类型土壤有机碳含量和碳密度与全N均呈显著或极显著正相关,与土壤理化性质相关性存在较大差异.     

冰雪灾害后林窗对杉木林土壤性质的影响

During January–February 2008, a severe ice storm caused significant damages to forests in southern China, creating canopy gaps and changing soil nutrient availability and enzyme activity. To understand the relationships between gap size, changes in the soil environment and the effects that these changes have on soil processes, we investigated the effects of gap size on soil chemical and biological properties in the forest gaps in a Cunninghamia lanceolata stand in northern Guangdong Province, southern China. Ten naturally created gaps, five large(80–100 m~2) and five small(30–40 m~2), were selected in the stand of C.lanceolata. The large gaps showed a significant increase in light transmission ratio and air and soil temperatures and a decline in soil moisture, organic matter,N and P compared with the small gaps and the adjacent canopy-covered plots in the 0–10 cm soil. The differences in organic matter and nutrient levels found between the large and small gaps and the canopy-covered plots may be related to changes in environmental conditions. This indicated rapid litter decomposition and increased nutrient leaching in the large gaps. Moreover, the lowest levels of catalase, acid phosphatase and urease activities occurred in large gaps because of the decline in their soil fertility. Large forest gaps may have a region of poor fertility, reducing soil nutrient availability and enzyme activity within the C.lanceolata stand.     

Effect of fire on solute release from organic horizons under larch forest in Central Siberian permafrost terrain

To evaluate the effects of forest fire and post-fire stand recovery on the organic layer chemistry and solute release within mound and trough microrelief elements (termed earth hummock microtopography) that mainly distribute permafrost affected area, we chose five fire plots (larch forests burned in 1951, 1981, 1990, 1994 and 2005) paired with adjacent control plots in mature larch forests in Central Siberian permafrost terrain. We determined total carbon, nitrogen and ash content in solid organic soils, and analyzed total carbon, nitrogen, bases and major anions in water extracts. There was a significant correlation between water-extracted organic carbon (WEOC) and total carbon (kg m⁻²) in area basis, implying that the quantity of total carbon was a major factor in WEOC production. WEOC correlated negatively with pH, indicating strong control by organic horizons (organic solute leaching) on soil acidity and base cation dynamics. The sum of water extractable base cations was also correlated significantly to total carbon, indicating that cations can be released through organic matter decomposition. Organic horizons in troughs in burned plots released greater amounts of Ca, Mg and K than those in mounds, probably due to greater content of organic matter as a cation source. Anions including nitrate and phosphate and WEOC also accumulated in trough depressions, due probably to organic matter degradation. The contrasting distribution of solutes between mounds and troughs in burned plots seems to be controlled by organic horizon development via changes in microtopography after forest fires.