The long-term monoculture of Eucalyptus plantations in southern China has raised ecological concerns, prompting a shift towards mixed-species plantations as a sustainable alternative. This study investigates the mechanisms by which companion tree species enhance soil functionality in subtropical red soil regions. A field experiment compared a pure Eucalyptus (CK) plantation with three mixed-species plantations: Eucalyptus x Mytilaria laosensis (A x M), Eucalyptus x Magnolia hypolampra (A x H), and Eucalyptus x Michelia gioii (A x X). Comprehensive soil analyses were conducted at three soil depths (0-20 cm, 20-40 cm, and 40-60 cm) to assess chemical properties, enzyme activities, and humus components, and soil organic carbon (SOC) molecular structure was characterized by Fourier-Transform Infrared Spectroscopy (FTIR), with the relationships quantified using structural equation modeling (SEM) to test predefined causal hypotheses. The results showed that A x H significantly boosted topsoil fertility (e.g., OM: 46.61 g/kg), while A x M enhanced the recalcitrant organic carbon (ROC: 35.29 g/kg), indicating superior carbon sequestration potential. The FTIR analysis revealed species-specific alterations in SOC chemistry, such as increased aromatic compounds in A x H/A x X. The SEM analysis demonstrated that the latent variable "Humus" (reflected by LOC and ROC) directly and positively influenced the latent variable "Soil Fertility" (reflected by pH, OM, and AP; path coefficient: 0.62). In contrast, the latent variable "Organic Components" (reflected by specific FTIR functional groups) exhibited a significant direct negative effect on "Soil Fertility" (-0.41). The significant pathway from "Organic Components" to "Enzymatic Activity" (0.55*) underscored the role of microbial mediation. The study concludes that mixed plantations, particularly with Mytilaria laosensis (A x M), improve soil health through an "organic input-microbial enzyme response-humus formation" pathway, offering a scientific basis for sustainable forestry practices that balance productivity and ecological resilience.

Eucalyptus as a fast-growing timber tree plays a crucial role in maintaining wood supplication and ecosystem balance worldwide. Nonetheless, the management practices of Eucalyptus plantation in southern China have resulted in productivity decline and soil degradation due to high-intensity successive cultivation. Soil bacteria is a sensitive indicator of soil quality, how does the successive planting of Eucalyptus regulate the soil bacterial community structure for instance the abundance of oligotrophic bacteria, network complexity, and soil bacteria assembly remain ambiguity. To explicate the underlying influencing mechanisms of successive cultivation of Eucalyptus plantations on soil bacterial community structure. Four harvests of Eucalyptus plantations that underwent 0, 1, 2, and 3 times of harvesting were conducted to examine variations in the bacterial community between rhizosphere and bulk soils after successive planting of Eucalyptus. An adjacent evergreen broadleaf forest was employed as control. The present study revealed that successive planting of Eucalyptus increased and reduced the relative abundance of Chloroflexi (oligotrophic bacteria) and Proteobacteria (copiotrophic bacteria), respectively. Continuous planting of Eucalyptus did not modify the assembly pattern of soil bacterial communities, which was governed by stochastic processes. Successive planting of Eucalyptus decreased co-occurrence network complexity, and elevated the proportion of rare microorganisms in the keystone bacterial taxa. Soil particle size composition (clay, silt, sand) indirectly influenced the structure of soil bacterial communities by directly affecting pH, carbon, nutrients, and their stoichiometric ratios. Improving soil physical structure, increasing the input of soil carbon, nitrogen, and other nutrient resources, and maintaining a balanced resource allocation may be effective strategies for ensuring enhanced productivity and sustainable utilization of soil in successive Eucalyptus plantations.

为明确广西人工林土壤肥力指标环境驱动因子,综合评价土壤肥力水平,本文通过系统收集人工林土壤现状数据,分析主要土壤肥力指标的空间分布规律,并制作全区人工林土壤肥力指数空间分布图.利用典范对应分析方法对土壤肥力指标和环境因子进行分析,获取广西主要土壤类型人工林土壤肥力指标的环境驱动因子.结果显示:全区90％以上人工林的土壤肥力指数处于0.20～0.50,不同土壤类型人工林土壤肥力指数由大到小依次为黄棕壤、黄红壤、黄壤、红壤、石灰岩土、赤红壤、砖红壤.赤红壤人工林土壤碱解氮与有机质和年均气温相关性高,土壤有效磷与有机质和pH相关性高,土壤速效钾与环境因子坡度、海拔、降水量、积温和坡向相关性高.红壤人工林土壤碱解氮与坡度和海拔相关性高,土壤有效磷与积温和降水量相关性高,土壤速效钾与pH相关性高.石灰岩土人工林土壤碱解氮与坡度和有机质相关性高,土壤有效磷与积温和降水量相关性高,土壤速效钾与pH相关性高.综合来看,广西人工林土壤肥力整体偏低,不同土壤类型人工林土壤肥力指标的环境驱动因子各有区别.

林下植被抚育是桉树人工林经营中的关键环节.采用调查问卷的方式,在广西区直林场开展桉树林下植被抚育现状的调查,对林下草灌保留、除草方式、除草剂使用等情况进行汇总分析.结果显示,各林场通常采取人工和除草剂两种方式相结合进行桉树林下植被抚育;第一年抚育 1～3次,第二年至第四年抚育0～1 次,采伐前抚育1 次;林下植被抚育时草灌保留高度在 10～20 cm以下,部分林场林下灌木保留10%～30%;抚育成本675～1275 元/hm2;使用的除草剂主要是草甘膦、草舒、草乙疏等,均含有草甘膦成分,施用量为7.5～18.75 kg/hm2.采取多样化的桉树林下植被抚育方式,以平衡桉树生长和林下植被多样性的关系,促进桉树人工林可持续经营.

为了解桉树混交林研究现状和发展趋势,以CNKI数据库为文献来源,采用文献计量法对1978-2022年桉树混交林相关文献进行分析.结果表明:桉树混交林领域研究可分为缓慢起步、平稳增长和急剧上升3个阶段;前沿主题包括土壤养分、林分生长;研究趋势主要集中在桉树树种、伴生树种、生物量、混交造林等;农林类高校及科研院所、林场、林业局等单位是文献产出的主要机构,总体表现为省(自治区)内部合作较多、跨省(自治区)之间合作较少;作者主要来自科研机构或者高校,不同机构间交流和合作较少.

This paper aims to reveal the effects of multi-generational succession of eucalyptus on soil fertility, organic structure and biological properties. Soil samples were collected from eucalyptus plantations of different stand ages (5, 11, 17 and 21 years old) in a typical area in south Asia, soil organic fraction structure and content characteristics were investigated using Fourier transform infrared (FTIR), and structural equation modelling (SEM) was used to explore influences of soil fertility, enzyme activity and organic fraction on stand biomass. FTIR analysis showed that 11 infrared absorption peaks existed in the soils of this study area, attributed to silicates, aromatics, carbonate ions, sugars, esters, polysaccharides, aliphatic hydrocarbons and phenolic alcohols. Combined with the results of peak area integration, the content of esters, aromatics and phenolic alcohols was significantly higher in 17- and 21-year-old stand soils than in control soils. The results of SEM showed that organic components were negatively related (p < 0.01) to enzyme activity and biomass, with standardized coefficients of 0.53 and 0.49, respectively. In summary, multi-generation succession of eucalyptus trees can change the structure of soil organic functional group composition and promote the enrichment of aromatic and phenolic alcohol functional groups. Such changes can directly inhibit the increase in eucalyptus biomass and indirectly negatively affect biomass by inhibiting enzyme activity.

为探讨配方施肥对马尾松Pinus massoniana人工林生长、叶片和土壤肥力的影响,以8年生马尾松人工林为研究对象,设置5个施肥处理,对不同处理后马尾松的树高、胸径、叶片营养、土壤养分等进行了比较分析,并运用灰色关联度法对马尾松人工林叶片营养和土壤肥力状况进行综合评价.结果表明:林地配方施肥具有促进8年生马尾松人工林树高和胸径生长的效果.施肥2年后,最佳的施肥处理T2(N∶P2O5∶ K2O=8∶10∶12)的树高、胸径年均增长量达1.25 m、1.29 cm,分别比不施肥处理CK高61.54％和35.79％.而不同施肥处理对土壤肥力和叶片营养含量的促进效果大小顺序分别 为:T2(N∶P2O5∶K2O=8∶10∶12)＞T4(N∶P2O5∶K2O=10∶10∶10)＞T3(N∶P2O5∶K2O=12∶8∶10)＞T1(N∶P2O5∶K2O=7∶14∶9)＞CK、T2＞T3＞T4＞T1＞CK.不同施肥处理中处理T2对8年生马尾松人工林生长指标、叶片营养和土壤肥力的促进效果最佳,而CK(不施肥)处理的生长表现最差,其土壤肥力严重退化,叶片营养缺素明显.

为维持桉树(Eucalyptus spp.)人工林长期生产力,设置林下间种山毛豆(Tephrosia candida)(T1)、林下间种田菁(Sesbania cannabina)(T2)、有机肥全替代(T3)和单施化肥(CK)4个模式,综合评价不同模式对桉树人工林的营养物质积累、土壤保育功能和价值及经济效益的影响.结果表明,T1和T2模式能提高人工林营养物质积累量和营养物质积累价值;T1、T2和T3模式土壤固土价值增量分别为18.31、21.80和14.08 元/hm2,土壤保肥价值增量分别是CK的3.12、2.18和2.22倍,土壤保育功能价值增量分别比CK高出223.99％、130.23％和131.18％,均可有效提升土壤固土、保肥功能和价值.T3和T1模式的利润分别比CK高出2279.15和1425.06元,T3和T1模式经济效益显著.

通过调查除草剂(T1)、人工带状去除(T2)和人工全去除(T3)三种措施下桉树人工林林下植被多样性、生物量和养分含量等指标,探讨林下植被多样性和养分现存量对抚育措施的响应,为桉树人工林林下植被的科学管理提供技术指导.结果表明:桉树人工林林下植被Margalef丰富度指数(M)、Simpson优势度指数(D)、Shannon-Wiener多样性指数(H)和Pielou均匀度指数(Jsw)的变化范围分别为1.67～4.67、0.46～0.53、0.69～1.03和0.77～0.94;T2的M、D、H指数最高;林下植被生物量的变化范围为241.74～1 046.02 kg·hm-2,以T2最大;不同抚育措施对林下植被N、Ca、Zn、Fe、Mn产生显著影响,而对其他元素无显著影响;林下植被养分现存量的变化范围为79.2～509.80 kg·hm-2,其变化规律与生物量相似,以T2最大;林下植被养分现存量仅与生物量呈显著正相关(0.740),林下植被生物量与多样性指数H呈显著相关(0.564),林下植被多样性主要通过影响生物量间接影响林下植被养分现存量.结合研究结果,维持桉树人工林林下植被多样性的措施以人工带状抚育为佳.

[目的]为揭示猫儿山自然保护区不同林分下的土壤有机碳(C)、全氮(N)、全磷(P)、全钾(K)含量与化学计量比之间的相关性及其变化特点.[方法]采用野外调查采样与室内实验分析相结合的方法,测定水青冈林、毛竹林、杉木林3种林分类型的不同深度土层土壤有机C、全N、全P、全K养分含量,计算其化学计量比,并用多重比较和相关性分析方法综合评价土壤生态化学计量特征.[结果]不同林分类型土壤养分含量与生态化学计量比都存在显著差异(P<0.05).土壤有机C、全N含量在林分和土层间差异显著(P<0.05),在同一林分下随土层深度增加而降低.土壤有机C、全N含量在3种林分间表现为水青冈>毛竹>杉木,即以水青冈林分最大,其平均值分别达55.91 g kg—1和4.20 g kg—1;全P、全K含量在林分间、土层间存在差异,但未达显著水平;而不同养分含量比C/N、C/P、C/K、N/P、N/K、P/K整体变化相似,在林分间排列顺序为水青冈>毛竹>杉木.相关分析结果表明,土壤有机C与全N、全P与全K间分别呈极显著(P<0.01)和显著正相关关系(P<0.05),而全P与有机C、全N均无显著相关性,全K与有机C、全N呈显著负相关关系.[结论]水青冈天然次生林分土壤有机C、全N高于毛竹人工林、杉木人工林两林分,有较好的养分归还及地力维持效果.

连栽障碍是制约中国南方地区桉树Eucalyptus(桉属植物)人工林发展的重要因素之一,由此带来的生态环境问题也让桉树人工林经营备受争议.根际土壤是植物与环境交互最为频繁的区域,正确评估多代连栽对该区域土壤有机环境特征及演变趋势的影响,对于解决桉树人工林连栽问题具有重要意义.以南亚热带新造林(T0)、萌芽1(T1)、萌芽2(T2)、萌芽3(T3)代尾叶桉(Eucalyptus urophylla)人工林根际土壤为研究对象,采用傅里叶变换红外光谱(FTIR)表征各代次桉树人工林根际土壤有机组分结构及含量特征,同时对有机官能团进行半定量分析,探讨多代连栽对土壤有机环境演变趋势的影响.结果表明:不同代次桉树人工林根际土壤有机组分大致相同,酯、芳香族以及酚醇类物质占比较大,醛、多糖类物质及碳酸根离子占比较小.但不同代次桉树人工林根际土壤有机组分含量具有显著差异(P<0.05),其中高代次(T2、T3)林分土壤的红外吸收谱图2929、3423、3620 cm?1处,峰面积积分显著高于T0、T1处理(P<0.05),这主要是由于酚、醇类以及脂肪烃类物质的含量差异而引起的.主成分分析结果2轴(PC1、PC2)共解释了77.59％的方差,表明上述官能团能反映土壤有机官能团分布特征.T3处理中,主效官能团为2929、3423、1631、3620、469 cm?1,官能团分布相对T0、T1、T3处理更集中.综上,多代连栽促进了土壤中酚、醇类物质及脂肪烃类物质的增加,同时高代次桉树人工林土壤有机组分主效官能团逐渐由饱和态向不饱和态(C=C、C=O)演变,有机官能团结构趋于单一.该结果可为进一步阐明根际土壤有机组分结构演变对微生物群落结构的影响以及与植物根系交互作用提供前期理论基础.

为系统评价连栽对桉树人工林土壤有机碳含量的影响,检索了CNKI、万方数据库,搜集相关研究,以土壤有机碳含量的加权均数差为效应量,对纳入研究的文献进行Meta分析.结果表明:随着连栽代次的增加,桉树人工林土壤有机碳含量总体上呈逐渐减少的趋势;随着土层深度的增加,桉树人工林土壤有机碳含量与对照林分的差异逐渐减小,多代连栽对桉树土壤有机碳含量的影响主要体现在表土层.今后在桉树人工林营林实践中应注重对一代、二代和三代桉树人工林的表层土壤的有机质补充,以维持桉树人工林地力和桉树产业健康可持续发展.

为了解微生物液体肥对植物生长的作用,利用香花油茶(Camellia osmantha)果壳和柑橘(Citrus reticulata)落果配合微生物EM菌剂分别制备液体肥,设置3个浓度(1:300、1:650和1:1000)淋施,探究不同微生物液体肥对香花油茶幼苗生长及叶片氮(N)、磷(P)和钾(K)含量的影响.结果表明,两种液体肥处理的幼苗存活率均为96.7％,分别比清水和复合肥水溶液高出30％和10％.液体肥A和液体肥B的苗高、叶芽数和叶片数增量均显著高于复合肥水溶液处理和清水处理;除浓度1:300的柑橘落果+EM菌液外,其他处理的地径增量均大于复合肥水溶液处理和清水处理.浓度1:300的柑橘落果+EM菌液有利于N和K积累,浓度1:1000的香花油茶果壳+EM菌液有利于P积累.

Abstract Eucalyptus is a short-rotation tree species widely used in tropical and subtropical regions around the world. However, the high-intensity management mode of multi-generational succession has also made eucalyptus planting controversial due to ecological and environmental problems, including soil degradation and declines in stand biomass. This paper aims to reveal the effects of multi-generational succession of eucalyptus on soil fertility, organic structure, and biological properties. Soil samples were collected from eucalyptus plantations of different stand ages (5, 11, 17, and 21 years old) in a typical area in south Asia; soil organic fraction structure and content characteristics were investigated using Fourier transform infrared (FTIR); and structural equation modeling was used to explore the direct and indirect influences of soil fertility, enzyme activity, and organic fraction on stand biomass. The results showed that the soil fertility and enzymatic activity indexes were significantly different (p < 0.05) in different stand age soils, with the exception of total potassium and cellulase. FTIR analysis showed that 11 infrared absorption peaks existed in the soils of this study area, attributed to silicates, aromatics, carbonate ions, sugars, esters and polysaccharides, aliphatic hydrocarbons, and phenolic alcohols. Combined with the results of peak area integration, the content of esters (1088, 1165 cm1), aromatics (1631 cm1), and phenolic alcohols (3423 cm1) was significantly higher in 17- and 21-year-old stand soils than in control soils. The results of the structural equation model showed that organic components were negatively related (p < 0.01) to enzyme activity and biomass fertility, with standardized coefficients of 0.53 and 0.49, respectively. In summary, we concluded that multi-generation succession of eucalyptus trees can change the structure of soil organic functional group composition and promote the enrichment of aromatic and phenolic alcohol functional groups. The results of the structural equation modeling established the relationships between stand age and soil fertility, organic fraction, enzyme activity, and biomass. The increase in aromatic and phenolic alcohol functional groups was the main change in the organic fraction of the soil. Such changes can directly inhibit the increase in eucalyptus biomass and indirectly negatively affect biomass by inhibiting enzyme activity, and the combination of these two inhibitory pathways could be the main reason for the decline in stand biomass after successive plantings of eucalyptus.

为科学评价新型肥料对幼龄期马尾松人工林生长的影响,本研究以广西国有派阳山林场鸿鸪分场造林点的幼龄期马尾松人工林为研究对象,采用随机区组试验设计,设置袋控缓释肥、生物质炭基肥、 非袋控肥和不施肥4种处理方式,跟踪测定林木生长状况.结果表明:对于广西国有派阳山林场鸿鸪分场的幼龄期马尾松人工林而言,施用新型肥料的效果均优于非袋控肥.与非袋控肥相比,施肥19个月后,施用0.5 kg袋控缓释肥和0.5 kg生物质炭基肥处理平均立木蓄积增长率分别提高了2.67％和16.36％.因此,施用新型肥料对幼龄期马尾松人工林的生长有明显促进作用.

为给广西人工林土壤管理和施肥策略制定提供理论依据,保证林业产业高效和可持续发展,基于土壤类型、广西森林气候分区及土壤养分特征等林地土壤环境数据,对广西人工林土壤进行分区及区域化肥力评价.首次将广西人工林地分为7个区,分别为北热带季雨林赤红壤西区、北热带季雨林赤红壤东区、南亚热带常绿阔叶林赤红壤区、半湿润南亚热带常绿阔叶林红壤区、中亚热带常绿阔叶林红壤西区、中亚热带常绿阔叶林红壤东区和南亚热带常绿阔叶林石灰(岩)土区.区域化肥力评价结果显示,各区域土壤pH均值比历史均值均有不同程度下降,其中红壤东区下降幅度最大(17.14％);各区土壤有机质含量均值均比历史均值高,其中南亚热带赤红壤区上升幅度最大(59.63％);各分区土壤碱解氮和有效磷含量均值均比历史均值高,其中南亚热带赤红壤区碱解氮含量上升幅度最大(103.89％),半湿润红壤区和赤红壤西区有效磷含量上升幅度较大,分别为160.29％和155.41％;大部分区域土壤速效钾含量均值比历史均值高,高纬度两个分区(红壤东区和红壤西区)上升幅度较大,分别为106.89％和121.68％.

Effective soil spectral band selection and modeling methods can improve modeling accuracy. To establish a hyperspectral prediction model of soil organic matter (SOM) content, this study investigated a forested Eucalyptus plantation in Huangmian Forest Farm, Guangxi, China. The Ranger and Lasso algorithms were used to screen spectral bands. Subsequently, models were established using four algorithms: partial least squares regression, random forest (RF), a support vector machine, and an artificial neural network (ANN). The optimal model was then selected. The results showed that the modeling accuracy was higher when band selection was based on the Ranger algorithm than when it was based on the Lasso algorithm. ANN modeling had the best goodness of fit, and the model established by RF had the most stable modeling results. Based on the above results, a new method is proposed in this study for band selection in the early phase of soil hyperspectral modeling. The Ranger algorithm can be applied to screen the spectral bands, and ANN or RF can then be selected to construct the prediction model based on different datasets, which is applicable to establish the prediction model of SOM content in red soil plantations. This study provides a reference for the remote sensing of soil fertility in forests of different soil types and a theoretical basis for developing portable equipment for the hyperspectral measurement of SOM content in forest habitats.

2017-2018年,对广西不同区域、不同林龄的马尾松采脂林土壤的主要肥力指标进行测定,并采用灰色关联分析方法对其土壤肥力进行综合评价.结果 表明:6个马尾松采脂林样地的根际土和非根际土均呈酸性至强酸性,有机质、全N、碱解N含量处于中等水平,土壤全P、有效P、全K和速效K含量均处于极贫乏水平;土壤中量元素:交换性Ca、交换性Mg含量大部分处于极低水平;土壤微量元素:有效Cu和有效Zn含量处于中等水平,有效Fe含量处于极丰富水平,有效B和有效Mn含量大部分处于极贫乏水平.各马尾松采脂林根际土和非限际土的土壤肥力综合指标值关联度主要分布在0.379 ～0.647,其中乐里林场15年生的马尾松采脂林土壤综合肥力最高,派阳山林场13年生的马尾松采脂林土壤综合肥力最低.不同区域、不同林龄马尾松采脂林的土壤综合肥力普遍较低.

本文以广西钦州市林湖森林公园植物科普园为例展开分析,介绍了科普园的概况,阐述植物科普园的规划、设计及建设技术,并以专类植物分类为主,致力建设科普、观赏、游憩等功能于一体,具有南国景观特色的科普型植物园.以期为同类型的植物园规划建设提供借鉴.

为解决桂南地区桉树高代次纯林投入产出比逐年提高及土壤酸化严重、有机质含量和土壤肥力下降等问题,采用林下套种山毛豆(Tephrosia candida)和田菁(Sesbania cannabina)(T1和T2)、剩余物还林(T3)、施用有机肥(T4)、测土配方施肥(T5)和常规施肥(CK)6种不同处理,研究不同处理下桉树人工林产量和土壤肥力的变化,综合评价各处理对桉树人工林的影响.结果表明,T1～T5处理下,除T5处理的平均树高增量外,桉树的平均胸径、树高和蓄积增量较CK处理均有一定程度的提升.T1处理的桉树平均蓄积增量最大,其次为T5处理.T1、T2、T3和T5处理均能提高人工林土壤有机质含量和土壤肥力,T4处理对土壤有机质含量和肥力的短期促进效应不显著.在实际生产过程中,林下套种绿肥和剩余物还林处理在可操作性和适用性上欠佳,施用有机肥和测土配方施肥处理是广西桉树人工林林地生产力提升和土壤提质增效的较好选择.