Tree Cover Improved the Species Diversity of Understory Spontaneous Herbs in a Small City

Abstract

A large number of trees have been planted in built-up areas to improve the urban environment, but the effects of tree cover on spontaneous understory herbs are not yet well understood. This study surveyed spontaneous herbs in two kinds of habitats (habitats with and without tree cover) in the built-up area of the small city Junlian in Sichuan Province, China. A total of 222 species of spontaneous herbaceous plants in 180 genera of 71 families were recorded, including a vulnerable species and six species endemic to China. Although the overall species richness values were similar in the two kinds of habitat, the average species richness per quadrat of all plants, perennials, plants with the dwarf growth form, and animal-dispersed plants was significantly higher in the habitats with tree cover than in those without tree cover. The overall species association was significantly positive in the habitats with tree cover (VR = 1.51, p < 0.05) and neural (VR = 0.86) in the habitats without tree cover. Among the top 25 frequently recorded species in each kind of habitat, the species association of plants with the same trait combination type differed greatly in the two kinds of habitats. For the species association between annuals, only 13.33% of species pairs were significantly associated in the habitats with tree cover, while 22.22% of the species pairs were significantly negatively associated in the habitats without tree cover. For the species association between plants with tall growth forms, the proportion of significant positive associations in the habitats with tree cover was approximately twice than in the habitats without tree cover. For the species association between plants with the dwarf growth form, the proportion of negative associations in the habitats without tree cover was approximately twice that in the habitats with tree cover. Species with the same dispersal mode generally had a very low proportion of negative interspecific associations or a high proportion of positive interspecific associations in habitats unfavorable to their establishment. Our findings suggest that tree cover can improve the species richness of the spontaneous herbaceous species beneath them and profoundly influence interspecific coexistence relationships in a built-up area.

Diversity and Distribution Characteristics of Spontaneous Plants in Urban Industrial Wasteland in Harbin

“…和Pielou均匀度指数(J，Pielou evenness index) 植物占46.09%) [30,39] ，低于哈尔滨中心城区的 研究结果(一年生植物占57.7%) [40] 。研究区 木本自生植物达到15种，占8.9%，高于北京 东北部二环至六环区域的调查结果(11种， 占6.08%) ， 略 低 于 北 京 城 市 公 园 调 查 结 果 (23种，占9.5%) [41][42] 。总体来看，长期闲置 的废弃地可能比其他城市用地更有利于保存 多年生及木本自生植物。这可能是由于一年 生植物较多年生植物的稳定性差，废弃地较 少受到高强度的人为管理，具备相对稳定的 生境，更有可能完成从一二年生到多年生阶 段的演替，而城市中其他绿色空间受到较多 外来因素干扰，自生植物很难演替到多年生 稳定阶段 [43] 。此外，原有厂区绿化提供了种子 库，速生的木本植物幼苗，如榆树、旱柳、 等，在废弃场地粗放管理环境中能迅速长成 大苗和成株。 从物种来源看，研究区域内自生植物主 要以乡土植物为主，占67.9%，接近于上海废 弃 地( 不 少 于 70%) [30] 和 北 京 城 市 公 园 (76.56%)的调查结果，表明城市闲置地对乡 土植物多样性的保护具有积极作用。研究中 发现入侵物种13种，占7.7%，与北京城市公 园比例接近(17种，占7.02%) [42] ，远低于青 岛湿地公园自生植物调查结果中入侵物种的 比例(18.6%) [44] 。研究区个别入侵物种竞争 有显著差异，与北京奥林匹克森林公园研究 结论一致 [14] 。然而有研究表明有林荫覆盖的生 境总体物种数显著大于无林荫覆盖生境 [46] ，原 因可能是上述研究样地处于人工管理强度较 高的城市开放空间中，相较于林地生境，草 地生境中草坪草生长优势明显，形成具有高 生态优势的植物群落，生物多样性较低，而 本研究样地处于城市废弃地中，草地和林地 生境的人工管理强度均较低且相差不大。若 将工业废弃地再开发作为游憩空间，草地生 境自生植物更容易受到人为干扰，在规划和 管理中应更多关注草地生境的生物多样性保护。 比较不同演替阶段自生植物多样性结果， 中间阶段的物种多样性较高，这与前人研究 结果一致 [47] ，原因是该阶段能够同时为先锋阶 段和中间阶段植被提供适宜的环境 [4] 。由于中 间阶段可以兼顾生物多样性保护和审美价值 [29] ， 30,48] 。 然 而 ， Fischer等在柏林的研究表明人类活动干扰对 荒地植物丰富度和没有显著影响 [49] ，原因可能 whereas high-intensity disturbances may lead to the reduction of diversity. There is no significant difference in diversity indices across various land surface types.…”

Role of Tree Vegetation and Associated Environmental Factors on the Understory Herb-Layer Composition in a Reforested Area: A Study from “Kulon Progo Community Forestry”

“…According to Böhnert et al [13], Barbier et al [16], and Pilon et al [17], the tree stand commonly alters the availability of many resources for understory herb-layer species, such as light, soil, nutrients, water, and temperature. Accordingly, trees facilitate understory vegetation [16,18] and might accelerate forest succession [19] by improving these resources [16,20,21]. Therefore, the colonization of understory species often reflects the quality of the overstory (tree stand), where the abundance, diversity, and composition of understory vegetation are possible to change temporally with stand development [14,22].…”

The Impact of Urbanization on the Distribution of Spontaneous Herbaceous Plants in an Ancient City: A Pilot Case Study in Jingzhou, China

“…With the concept of ecological cities and urban wilderness being increasingly accepted, urban SHPs are receiving increased attention. For example, Zhang et al (2023) [20] studied the impact of landscape structure in urban ecological corridors on the diversity of SHPs, and Ren et al (2022) [21] showed that tree cover can improve species richness of SHPs underneath and have a large impact on the interspecific coexistence relationship in a built-up area. In previous studies, the diverse personality patterns and driving factors of SHPs have been explored at the urban or regional scale [14,22,23].…”