黄土高原先锋种猪毛蒿叶片形态解剖与生理特征对立地的适应性

为了揭示黄土丘陵沟壑区撂荒地植被演替前期优势种猪毛蒿(Artemisia scoparia)对该区立地环境的适应性,探讨猪毛蒿演替生态位的变化,研究了陕北黄土丘陵沟壑区3种立地环境下(阳峁坡、峁顶、阴峁坡)猪毛蒿叶片形态解剖和生理特征的变化,以及这些变化与生态因子之间的相互关系。结果表明:(1)猪毛蒿叶片具有适应该区半干旱环境的形态及解剖结构:叶片针形化、具表皮毛、环栅型叶肉组织、海绵组织特化为贮水组织、维管束退化、具裂生分泌腔,C3植物呈现类似CAM植物的叶片特性;(2)在土壤、空气湿度相对干燥和强光生境的阳峁坡与峁顶,猪毛蒿具有较小的叶面积、发达的栅栏组织、致密的表皮毛和紧密的细胞间隙,而在生境条件较好的阴峁坡则呈相反趋势;(3)阳峁坡猪毛蒿叶片相对含水量和叶绿素含量较小,超氧阴离子自由基增加,但植物体内超氧化物歧化酶和抗坏血酸含量增加以清除植物体内产生的活性氧;(4)冗余及相关性分析表明,猪毛蒿叶片形态、解剖和生理指标的可塑性对立地光照强度、土壤水分和有机质含量较为敏感,同时其形态解剖与生理可塑性可共同调节来适应生境。综合分析,猪毛蒿对陕北黄土丘陵沟壑区撂荒初期光照强度大、土壤贫瘠但土层干化现象尚未出现的立地环境有较好的适应性,使其成为黄土高原植被自然演替过程中的先锋物种。

Adaptability of foliar morphological, anatomical, and physiological characteristics of the pioneer species Artemisia scoparia growing in a hilly-gully Loess Region at different slope sites

Soil erosion by water is considered to be a dominant erosion process in a hilly-gully Loess Plateau, and leads to land degradation and desertification. Although many researchers have investigated the dynamics of plant community traits and soil properties caused by erosion, the effects of soil property variation on vegetation succession, especially in terms of ecophysiology, on abandoned cultivated land in a hilly-gully Loess Plateau region have received little attention to date. This study investigated Artemisia scoparia, which is one of the dominant species in early abandoned field communities in hilly-gully Loess Plateau. We tried to find the environmental acclimation and succession niche changes for this species. The foliar morphological, anatomical, and physiological characteristics of A. scoparia at three different sites (namely sunny hilly slope, SH; hilltop, HT; shady hilly slope, HH) were investigated. Relationships between foliar plasticity and environmental factors were also examined. The results demonstrate that (1) A. scoparia has special morphological and anatomical characteristics, such as needle-shaped leaves, trichomes, a ring palisade, water storage parenchyma specialized from spongy tissue, and a secretory cavity, that enable it to adapt to semi-arid environments. When the ability of vascular tissue to transport water decreased, C₃ plant leaves exhibit characteristics similar to CAM plants. (2) On the SH and HT sites, which are characterized by dry soil, low air humidity, and strong light intensity, A. scoparia had a smaller leaf area, thicker palisade, denser trichomes, and tighter intercellular air spaces than of those growing on the HH site. Furthermore, obvious differences among site conditions can be observed. However, the redundancy analysis (RDA) results revealed that vascular tissue traits, main vascular bundles, and area ratio of xylem to phloem, have a weak correlation with environmental factors. (3) A. scoparia had a low relative water content (RWC), less chlorophyll, and a high superoxide anion radical content on the SH and HT sites. In contrast, superoxide dismutase (SOD) and ascorbic acid (AsA) increased at these sites to clear the reactive oxygen produced by plants. Soluble protein, which shows the osmotic adjustment ability of a plant, had a weaker relationship with environmental factors. (4) Foliar plasticity had a strong relationship with environmental factors, especially with light intensity, soil moisture, and soil organic matter content. These results implied that A. scoparia had strong adaptability to early abandoned sites in a hilly-gully Loess Region that is subject to high light intensities and soil impoverishment without desiccation. (5) Based on the correlations among foliar morphological, anatomical, and physiological characteristics of A. scoparia, the studied parameters, except for vascular tissue traits and soluble protein, were found to be closely related to each other, especially epidermal hair density, stomatal index, and intercellular air spaces. All the above results suggest that A. scoparia is able to adapt to the microclimate and soil conditions present in early abandoned fields due to its foliar anatomical and physiological characteristics. These properties allow A. scoparia to improve its ability to use limited nutrient resources in poor soil environments and to reduce abiotic stresses (including water, light, nutrient, and erosion interference stresses). This means that A. scoparia is able to attain and dominate an extremely wide ecological distribution on early abandoned cultivated land in hilly-gully Loess Plateau regions.