Understanding factors driving soil multifunctionality can help with terrestrial ecosystem restoration. Soil microbial diversity and network complexity are two important factors influencing ecosystem multifunctionality. However, their effects on soil multifunctionality are still unclear. Based on high-throughput sequencing, we analyzed soil microbial alpha diversity and network complexity and their relative impacts on soil multifunctionality during the aerial seeding restoration process from 1983 to 2017 in Mu Us sandy land, China, a region threatened by desertification. Our results showed soil bacterial and fungal alpha diversity and multifunctionality increased with aerial seeding restoration. We found the community composition of soil bacteria and fungi changed with restoration periods. The keystone species of the soil bacterial network changed during restoration, while those of the soil fungal network remained unchanged. Soil bacterial and fungal species mainly maintained positive associations throughout the restoration periods. Soil bacterial network complexity initially decreased before increasing with restoration, while soil fungal network complexity increased continuously. Soil multifunctionality was found to have significantly positive correlations with soil fungal network complexity and soil bacterial alpha diversity. Compared with soil fungal alpha diversity and soil microbial network complexity, soil bacterial alpha diversity significantly promoted soil multifunctionality. Our research highlights the critical impact that soil bacterial alpha diversity plays in soil multifunctionality in restored ecosystems threatened by desertification.

Thinning is an important silvicultural practice for improving the productivity and wood production in plantation forest. Different intensities of thinning management can affect tree growth and alter soil nutrient effectiveness, thus affecting soil fungal community structure and diversity. Our objective is to determine the soil factors and their regulatory mechanisms that influence stand growth by thinning, and to provide data to support the establishment of large diameter timber cultivation technology for Picea koraiensis. In this study, we conducted medium- and high-intensity thinning in 43a P. koraiensis plantation middle-aged forests and investigated the growth indexes, soil physicochemical properties, and fungal community diversity in rhizosphere and non-rhizosphere soils of the stands after thinning at different densities (904 plants/ha for control, 644 plants/ha for 30% thinning intensity, and 477 plants/ha for 50% thinning intensity). The results showed that all growth indicators (annual growth of tree height, diameter at breast height, height under live branches and crown width) of the plantation after high-intensity thinning (477 plants/ha) were higher than those of the control (no thinning, significant) and medium-intensity thinning (644 plants/ha). Mycorrhizal infection rate was higher at the beginning of the growing season than at the end of the growing season, and increased slightly with decreasing stand density. Compared to the control, all medium- and high-intensity thinning treatments significantly improved soil nutrient content (P < 0.05), including total carbon, total nitrogen, total phosphorus, total potassium, Available phosphorus and Available potassium. Fungal diversity was higher but lower in abundance than the control in both rhizosphere and non-rhizosphere soils after thinning. The number of OTUs and fungal richness and diversity indices of non-rhizosphere soil fungi were higher than those of rhizosphere soil fungi. In conclusion, this study provides new evidence that reasonable intercalation can increase the radial and vertical growth of P. koraiensis plantation forests and promote the diversity of subsurface soil fungal communities. It is shown that thinning intensity regulates biogeochemical cycles in P. koraiensis plantation ecosystems by affecting soil nutrients and fungal community structure. Therefore, 50% thinning intensity can be used to increase timber production in plantation forests during large diameter timber cultivation of P. koraiensis and improve predictions associated with achieving long-term forest management strategies.

The restoration of degraded ecosystems is an important issue in applied ecology. Understanding community assembly during restoration can help facilitate ecological restoration. Aerial seeding is a widely used method to restore degraded ecosystems threatened by desertification. However, there is limited understanding of how aerial seeding affects community assembly processes and the driving factors of plants, soil bacteria, and fungi during ecosystem restoration. This study analyzed the community composition, β-diversity (community difference degree), community assembly processes, and influencing factors of plants, soil bacteria, and fungi using aerial seeding restoration chronosequences from 1983 to 2017 in Mu Us sandy land, China. Our results showed that plant biomass and relative abundances of beneficial flora in soil bacterial and fungal communities all increased since restoration commenced. β-Diversity of plant communities first decreased and then increased with increasing restoration time. Community assembly was dominated by stochastic processes in early stages of restoration, deterministic processes in middle stages, and stochastic processes in later stages. Dispersal limitation and environmental filtering (soil total nitrogen, soil total organic carbon, and mean annual precipitation) influenced stochastic and deterministic processes in plant communities, respectively. The β-diversity of soil bacteria continuously decreased, and community assembly was almost entirely driven by stochastic processes in the entire chronosequences. Homogenizing dispersal was the key factor driving community assembly. We found no significant changes in soil fungal β-diversity. Deterministic and stochastic processes simultaneously drove soil fungal community assembly. Both environmental filtering (soil total organic carbon and mean annual precipitation) and dispersal limitation affected the community assembly. We confirmed the effectiveness of aerial seeding restoration by studying the community composition of plants, soil bacteria, and fungi. Our study highlights that the community assembly processes and driving factors varied for plants, soil bacteria, and fungi during restoration chronosequences. It is necessary to carry out research simultaneously on the community assembly of aboveground plants and underground soil microorganisms.

Habitat fragmentation is a primary cause of biodiversity loss. As an essential part of the ecosystem, soil microorganisms participate in a series of ecosystem processes. However, the role of landscape factors on soil microorganisms is not well understood. Based on high-throughput sequencing of soil samples at three depths (0-10 cm, 10-20 cm, 20-30 cm) from 30 landscape sites along a habitat fragmentation gradient, we calculated soil bacterial and fungal diversity in the agm-pastoral ecotone of northern China. We then investigated the impact of climatic factors, soil characteristics, and landscape context (patch density, edge density, mean patch size, and mean nearest-neighbor distance) on soil bacterial and fungal diversity. We found that soil fungal richness increased with habitat fragmentation (patch density and edge density), although soil bacterial richness did not change significantly. Soil bacterial and fungal community composition both changed with habitat fragmentation. Soil characteristics were key factors determining soil bacterial diversity, especially in the 10-20 cm soil depth. Soil fungal diversity was closely related to landscape context, showing a significant positive correlation with patch density and edge density, and a significant negative correlation with mean patch size. Structural equation modeling showed that landscape factors directly affected soil fungal diversity but indirectly affected soil bacterial diversity by changing soil characteristics. We highlight that soil fungal diversity shows an increasing trend with increased habitat fragmentation. Landscape context plays a stronger role in maintaining soil fungal diversity than soil characteristics and climatic factors.

为探究毛乌素沙地不同飞播造林年限对土壤真菌群落结构的影响,以O、6、16、26和36年共5个飞播造林年限的土壤为对象,采用高通量测序技术检测土壤真菌,分析了其群落结构及多样性,并探讨了土壤因子的影响.结果 表明:随着飞播年限的增加土壤真菌群落结构发生变化,除Simpson指数无明显变化外,真菌Alpha多样性指数、菌门和菌属种类以及特有的OTU数量均呈现先降低后增加的趋势;PCoA分析显示,不同年限的土壤真菌群落组成具有差异性,且飞播后期差异增大;Pearson相关性分析结果表明,影响土壤真菌Alpha多样性的主要土壤因子有硝态氮和有效磷.飞播造林有利于毛乌素沙地土壤真菌群落结构的改变和多样性的增加,也有利于优势菌群出现,研究结果对毛乌素沙地飞播造林植被恢复效果提供了一定的理论支持.

以黑龙江省佳木斯市孟家岗林场43 a红皮云杉人工林为研究对象,测定不同坡位红皮云杉的生长状况和林下土壤理化性质,分析不同坡位红皮云杉人工林林木生长状况和土壤肥沃程度的差异,为建立红皮云杉大径材培育技术提供参考依据.分别在人工林南坡的上、中、下3个坡位上设置样地,调查红皮云杉的树高、胸径、冠幅、活枝下高、单株材积、单位面积蓄积量和单位面积胸高断面积,五点法收集样地不同土层的土壤样品,测定土壤pH和土壤养分(全碳、全氮、全磷、全钾、铵态氮、硝态氮、有效磷和速效钾)含量.对林木生长状况调查发现:不同坡位之间,下坡位的林木生长状况最佳,其树高、胸径、冠幅、活枝下高和单株材积均最大.不同坡位之间,树高、冠幅、活枝下高和单株材积的比较由小到大排序为上坡位、中坡位、下坡位;胸径和单株材积的比较由小到大排序为:中坡位、上坡位、下坡位;单位面积蓄积量和单位面积胸高断面积的比较由小到大排列为:上坡位、下坡位、中坡位.对土壤理化性质分析结果表明,土壤pH随着坡位下降呈增加趋势.不同坡位之间,下坡位的土壤养分含量最高.除了全钾和速效钾的养分含量变化趋势由小到大为:中坡位、上坡位、下坡位外,其余养分含量依次由小到大排列为:上坡位、中坡位、下坡位.对相同坡位土壤养分空间分布的比较发现,林下表层(0～20 cm)土壤养分含量高于较深处(＞20 ～40 cm)土壤.下坡位更有利于红皮云杉林木生长和土壤养分积累,是适合红皮云杉大径材林木培育的有利坡位条件.

揭示落叶松凋落叶覆盖影响土壤理化性质的机理,为阐明落叶松凋落叶覆盖促进种子萌发和幼苗初期生长的机理提供科学依据.本文以不同浓度(0.2、2.0、20.0 g/L)长白落叶松凋落叶鲜提液或腐解液处理苗床表层土壤,测定处理前后土壤pH、土壤含水量、土壤养分(全氮、全碳、全磷、全钾、有效磷、碱解氮和速效钾)、微生物(细菌、真菌、放线菌)数量和土壤酶(水解酶类和氧化还原酶类)活性的变化.结果表明,不同浓度长白落叶松凋落叶的水提液(鲜提液或腐解液)处理均提高了土壤中全磷、全钾、速效钾和碱解氮的含量(P<0.05),其中,0.2 g/L鲜提液处理的碱解氮含量最高(比对照增加了75.13％).水提液(鲜提液或腐解液)处理增加了微生物(真菌、细菌、放线菌)数量,促进了有机质的分解.与对照相比,腐解液对微生物数量的响应效应由大到小排序为:真菌、放线菌、细菌,其中2.0 g/L腐解液真菌增加率最高为526.90％,有机质分解速率增加了34.7％和36.83％.不同处理中,20 g/L鲜提液和腐解液的有机质分解速率最高.水提液(鲜提液或腐解液)处理提高了土壤中除碱性磷酸酶外的其他全部土壤酶的活性.酸性和氧化还原酶(过氧化氢酶、多酚氧化酶、过氧化物酶)均在水提液(鲜提液或腐解液)浓度为20 g/L时达到最高,而此时中性磷酸酶则最低.从而得到结论:落叶松凋落叶覆盖可增加土壤微生物的数量,且对真菌数量的增加最显著、落叶松凋落叶水提液可提高土壤酶活性、增加有机质分解速率、增强土壤中相关营养元素的转化效率.