在中国温带、暖温带地区，由于木材生产的需求，大面积的次生林被人工用材林取代，从而形成次生林与人工林镶嵌分布的空间格局。然而，作为气候变化响应的敏感区，温带森林连片的次生林与斑块状人工林的镶嵌分布格局对该区域生态系统多功能性的影响及其维持机制仍不清楚。该问题的解决有利于深刻了解人工林和次生林生态系统功能，促进人工林和次生林生态系统的可持续发展及生态系统管理。为此，本研究以北京东灵山地区为研究区，以白桦（Betula platyphylla）、棘皮桦（Betula dahurica）、胡桃楸（Juglans mandshurica）、蒙古栎（Quercus mongolica）、山杨（Populus davidiana）为优势种的次生林，及以油松（Pinus tabulaeformis）和华北落叶松（Larix principisrupprechtii）为优势种的人工林为研究对象，探讨不同次生林之间、不同人工林之间以及两者之间植物多样性和生态系统多功能性的差异特征。运用多项式回归解析物种、功能和系统发育多样性与生态系统多功能性的关系，采用多元回归模型探讨土壤、植物多样性对生态系统多功能性的影响效应，采用结构方程模型探究森林类型对生态系统多功能性变异的作用路径和影响机制。主要研究结论如下：

（1）不同次生林的植物多样性及生态系统多功能性

不同次生林间具有相似的植物多样性，但物种组成、功能属性及系统发育关系发生了显著变化。不同次生林间植物生长功能、凋落物持水能力、凋落物养分归还、土壤酶活性等多个功能指数差异显著。不同林分植物生长功能指数由高到低依次为山杨林、胡桃楸林、白桦林、棘皮桦林、蒙古栎林，其中山杨林的植物生长功能指数显著大于蒙古栎林；棘皮桦林、白桦林和山杨林的凋落物持水功能指数无显著差异，但3者显著低于胡桃楸林，显著高于蒙古栎林；山杨林、棘皮桦林、胡桃楸林、白桦林的凋落物养分归还功能指数依次降低，显著高于蒙古栎林；不同群落土壤酶功能指数从高到低依次为胡桃楸林、白桦林、棘皮桦林、山杨林、蒙古栎林，其中胡桃楸林和白桦林的土壤酶功能指数显著高于蒙古栎林。总体而言，胡桃楸林（0.292）和山杨林（0.192）的生态系统多功能性指数显著高于棘皮桦林（-0.031）和白桦林（-0.062），蒙古栎林的多功能性指数（-0.391）最低。这意味着胡桃楸林和山杨林是北京东灵山地区有利于生态系统多功能性和多服务性维持的林分类型。

（2）不同人工林的植物多样性及生态系统多功能性

人工种植的华北落叶松林在维持群落内植物多样性以及物种组成、功能属性和系统发育关系上均优于人工油松林。对于α多样性，华北落叶松林植物群落的物种丰富度、Shannon-Wiener多样性、Simpson多样性、功能丰富度、功能均匀度、功能分散度、功能离散度和谱系多样性PD指数均明显高于油松林。同样，华北落叶松林群落内物种、功能和谱系的β多样性指数均高于油松林。对生态系统功能而言，华北落叶松植物生长、凋落物持水能力、土壤持水能力、土壤养分含量、土壤酶活性和群落稳定性等多个功能指数均显著高于油松林，其生态系统多功能性指数（0.526）也极显著大于油松林（-0.528）。因此，与油松人工林相比，华北落叶松人工林具备更好的同时提供和维持多个生态系统功能和服务的能力，这对北京东灵山地区人工树种的选择提供了一定的科学依据。

（3）次生林和人工林之间植物多样性及生态系统多功能性差异

自然更新的天然次生林的植物多样性、物种组成、功能属性和系统发育关系均高于人工林。对α多样性而言，人工林的种植导致群落水平的物种、功能和谱系α多样性指数下降，尤其是人工林的物种丰富度、Shannon-Wiener多样性、Simpson多样性、Pielou均匀度、功能丰富度、功能离散度和谱系多样性PD指数均显著低于次生林。同样，人工林群落的物种、功能和谱系β多样性指数也显著低于次生林。此外，与次生林相比，人工林的种植显著降低了植物生长、凋落物持水能力、土壤持水能力、凋落物养分归还、土壤养分含量和土壤酶活性等功能指数，降低了其生态系统多功能性指数（由0.468至-0.466）。这说明对北京东灵山地区而言，连片的次生林与斑块状人工林的镶嵌分布格局降低了该地区森林群落的生态系统多功能性，不利于生态系统多功能性的维持。

（4）植物多样性与生态系统多功能性的关系

在局域范围内，土壤理化性质相较于植物多样性对生态系统多功能性变异的影响效应更大，其中土壤pH和土壤氮磷比显著提高了生态系统多功能性，土壤容重和土壤碳磷比显著抑制了生态系统多功能性。在植物多样性中，功能均匀度、功能丰富度、物种和系统发育β多样性均促进了生态系统多功能性指数。基于不同尺度多样性而言，相比于β尺度的多样性，α多样性的增加更有利于维持生态系统多功能性；基于不同维度多样性而言，功能、系统发育和物种多样性对生态系统多功能性的影响效应依次减弱。同时，结构方程模型显示，在次生林与人工林镶嵌分布的生态系统中，人工林种植对生态系统多功能性存在直接和间接抑制作用。人工林种植的间接作用是通过影响土壤pH值、土壤容重、植物多样性和土壤养分含量比进而实现的。其中，土壤pH值、植物多样性和土壤养分含量比通过直接或间接作用促进了生态系统多功能性提高，而土壤容重通过直接和间接作用显著降低了多功能性。这说明北京东灵山地区森林生态系统中土壤和多样性的变化可以中介人工林种植对生态系统多功能性的影响。

综上，局域环境中人工林镶嵌在次生林中的分布不利于生态系统多功能性的提高。因此，从促进养分循环、提高群落稳定性等角度出发，维持或扩大次生林在北京东灵山地区的覆盖面积十分重要。对于人工林而言，应该采取一些森林抚育措施引导人工林成为混交林，提高植物群落的α和β多样性，这不仅可以直接提高生态系统多功能性，还会缓解由于人工林的种植所带来的不利影响。

In temperate and warm temperate regions of China, a large area of secondary forest is replaced by artificial timber forest due to the demand of wood production, thus forming a Mosaic distribution pattern of secondary forest and artificial forest. However, the Mosaic distribution pattern of contiguous secondary forest and patch plantation in temperate forests, which is sensitive to climate change response, is still unclear on the effects and maintenance mechanisms of ecosystem multifunctionality in this region. The solution of this problem is conducive to the deep understanding of the ecosystem function of plantation forest and secondary forest, and promote the sustainable development and ecosystem management of plantation forest and secondary forest ecosystem. In this study, the Dongling Mountain area of Beijing was selected as the research area, and the secondary forest with Quercus mongolica, Betula platyphylla, Betula dahurica, Juglans mandshurica and Populus davidiana as dominant species, and plantations with Larix principisrupprechtii and Pinus tabulaeformis as the dominant species were selected as the research object, to explore the differences in plant diversity and ecosystem multifunctionality among different secondary forests, between different plantations and between them. Polynomial regression was used to analyze the relationship between species, function and phylogenetic diversity and ecosystem multifunctionality. Multiple regression models were used to explore the effects of soil and plant diversity on ecosystem multifunctionality. Structural equation model was used to explore the pathways and mechanisms of forest types on ecosystem multifunctionality variation. The main research conclusions are as follows:

(1) Plant diversity and ecosystem multifunctionality in different secondary forests

Different secondary forests had similar plant diversity, but species composition, functional attributes and phylogenetic relationships changed significantly. There were significant differences in plant growth function, litter water holding capacity, litter nutrient return and soil enzyme activity among different secondary forests. The plant growth function index of different stands from high to low was aspen Populus davidiana forest, Juglans mandshurica forest, Betula platyphylla forest, Betula dahurica forest, Quercus mongolica forest. The plant growth function index of Populus davidiana forest was significantly higher than that of Quercus mongolica forest. There was no significant difference in the litter water holding function index of Betula dahurica, Betula platyphylla and Populus davidiana forest, but the litter holding function index of Betula platyphylla, Betula dahurica and Populus davidiana forest was significantly lower than that of Juglans mandshurica forest and significantly higher than that of Quercus mongolica forest. The nutrient return function index of litters in Populus davidiana forest, Betula dahurica forest, Juglans mandshurica forest and Betula platyphylla forest decreased successively, and was significantly higher than that in Quercus mongolica forest. The soil enzyme function index of different communities from high to low was in order of Juglans mandshurica forest, Betula platyphylla forest, Betula dahurica forest, Populus davidiana forest, Quercus mongolica forest. The soil enzyme function index of Juglans mandshurica forest and Betula platyphylla forest was significantly higher than that of Quercus mongolica forest. In general, the ecosystem multifunctionality index of the Juglans mandshurica forest (0.292) and Populus davidiana forest (0.192) was significantly higher than that of the Betula dahurica forest (-0.031) and the Betula platyphylla forest (-0.062), and that of the Quercus mongolica forest (-0.391) was the lowest. This means that the Juglans mandshurica forest and Populus davidiana forest are the forest types most conducive to ecosystem multifunctionality and multi-service maintenance in Dongling Mountain area of Beijing.

(2) Plant diversity and ecosystem multifunctionality of different plantations

In terms of plant diversity, species composition, functional attributes and phylogenetic relationships, the Larix principisrupprechtii forest was superior to that of the Pinus tabulaeformis forest. In terms of α diversity, species richness, Shannon-Wiener diversity, Simpson diversity, function richness, function evenness, function dispersion, function dispersion and pedigree diversity of plant community in Larix principisrupprechtii forest were significantly higher than those in Pinus tabulaeformis forest. Similarly, β diversity index of species, function and lineage in Larix principisrupprechtii forest community was higher than that in Pinus tabulaeformis forest. In terms of ecosystem function, plant growth, litter water holding capacity, soil water holding capacity, soil nutrient content, soil enzyme activity and community stability were significantly higher than those of Pinus tabulaeformis forest, and the ecosystem multifunctionality index (0.526) was significantly higher than that of Pinus tabulaeformis forest (-0.528). Therefore, compared with Pinus tabulaeformis plantation, the Larix principisrupprechtii forest has a better ability to provide and maintain multiple ecosystem functions and services at the same time, which provides a certain scientific basis for the selection of artificial tree species in Dongling Mountain area of Beijing.

(3) Differences in plant diversity and ecosystem multifunctionality between secondary forest and plantation

The plant diversity, species composition, functional attributes and phylogenetic relationships of natural secondary forests were higher than those of plantation forests. In terms of α diversity, the species, function and pedigree α diversity indices of plantation decreased at the community level, especially the species richness, Shannon-Wiener diversity, Simpson diversity, Pielou evenness, function richness, function dispersion and pedigree diversity PD indices of plantation were significantly lower than those of secondary forest. Similarly, the species, function and lineage β diversity index of plantation community was significantly lower than that of secondary forest. In addition, compared with secondary forest, plantation significantly decreased plant growth, litter water holding capacity, soil water holding capacity, litter nutrient return, soil nutrient content, soil enzyme activity and other functional indexes, and decreased the ecosystem multifunctionality index (from 0.468 to -0.466). This indicates that the Mosaic distribution pattern of contiguous secondary forest and patch plantation reduces the ecosystem multifunctionality of forest communities in Dongling Mountain, Beijing, and is not conducive to the maintenance of ecosystem multifunctionality.

(4) The relationship between plant diversity and ecosystem multifunctionality

At the local scale, soil physical and chemical properties had a greater effect on ecosystem multifunctionality than plant diversity. Soil pH and soil N/P ratio significantly improved ecosystem multifunctionality, while soil bulk density and soil C/P ratio significantly inhibited ecosystem multifunctionality. In plant diversity, functional evenness, functional richness, species and phylogenetic β diversity all contributed to ecosystem multifunctionality index. Compared with β-scale diversity, the increase of α-scale diversity is more beneficial to maintain ecosystem multifunctionality. Based on the diversity of different dimensions, the effects of functional, phylogenetic, and species diversity on ecosystem multifunctionality declined successively. Meanwhile, the structural equation model showed that plantations had direct and indirect inhibition on ecosystem multifunctionality in the Mosaic distribution of secondary forest and plantation. The indirect effects of plantations were achieved by affecting soil pH value, soil bulk density, plant diversity and soil nutrient ratio. Among them, soil pH, plant diversity and soil nutrient ratio contributed to the improvement of ecosystem multifunctionality through direct and indirect effects, while soil bulk density significantly reduced the versatility through direct and indirect effects. These results indicate that the changes of soil and diversity in the forest ecosystem in Dongling Mountain can mediate the effects of plantation on ecosystem multifunctionality.

In summary, the distribution of plantation forests embedded in secondary forests in local environments is not conducive to the improvement of ecosystem functionality. Therefore, from the perspective of promoting nutrient cycling and improving community stability, it is crucial to maintain or expand the coverage area of secondary forests in the Dongling Mountain area of Beijing. For plantation forests, some forest tending measures should be taken to guide the plantation to become a mixed forest and improve the α and β diversity not only directly enhances the versatility of ecosystems, but also alleviates the adverse effects caused by the planting of plantations.