首页分享黄土高原生物结皮对地表粗糙度和灌草植物种子二次扩散的影响

黄土高原生物结皮对地表粗糙度和灌草植物种子二次扩散的影响

来源：花匠小妙招时间：2024-12-29 10:43

摘要：

生物结皮是黄土高原常见的地表覆被物, 在灌草群落下方及植被间空地上广泛发育, 深刻影响着灌草植物种子的二次扩散和定居, 但目前针对生物结皮对种子二次扩散影响的研究较少, 且种子二次扩散的主导因素尚不明确。该研究以风沙土和黄绵土上的生物结皮(藻结皮和藓结皮)为对象, 以无结皮为对照, 利用倾斜摄影测量法测定了地表粗糙度, 并通过风力扩散实验测定地表粗糙度对6种不同形态灌草植物种子的移位率、损失率和扩散距离的影响, 继而结合Spearman相关性分析, 研究灌草种子在生物结皮表面扩散的主导因素。研究结果表明: (1)与无结皮相比, 风沙土藻结皮和藓结皮的地表粗糙度分别增加了6.69倍和6.13倍, 黄绵土上分别增加了2.52倍和1.45倍。(2)风沙土上, 干燥条件下的地表粗糙度比湿润条件下增加了26.56%, 而在黄绵土上则降低了9.42%。(3)在干燥条件下, 风沙土生物结皮的地表粗糙度比黄绵土上增加了16.84%, 湿润条件下则降低了16.38%。(4)风沙土上, 种子在生物结皮表面的移位率、损失率和扩散距离分别比无结皮降低了77.1%、95.4%和72.2%, 在黄绵土上则分别降低了76.5%、93.8%和66.8%。土壤类型和干湿条件对生物结皮上种子扩散特征的影响不显著。(5)种子移位率、损失率和扩散距离与地表粗糙度极显著负相关, 种子移位率和损失率与土壤含水量显著负相关, 种子损失率和扩散距离均与种子密度显著负相关。综上, 黄土高原生物结皮主要通过增加地表粗糙度阻碍种子扩散, 增强种子聚集, 进而影响黄土高原灌草植被的空间分布特征与群落动态。

关键词: 种子扩散, 维管束植物, 地表粗糙度, 藻结皮, 藓结皮, 黄土高原

Abstract:

Aims In order to determine whether biocrusts enhance or impede the secondary dispersal of shrub and grass seeds and identify the key factors that influence seed dispersal, we simulated the process of seed secondary dispersal and measured relevant indicators such as the surface roughness of biocrusts.
Methods On the Loess Plateau, we established experimental plots on biocrusts (cyanobacteria- and moss- dominated crusts) and bare soils from aeolian sand and loess soil. For each selected plot, we utilized oblique photogrammetry to measure the surface roughness in both dry and wet conditions. All the treatments were studied in three replicates. Six species seeds of shrubs and grasses (Caragana korshinskii, Hedysarum scoparium, Artemisia ordosica, Setaria viridis, Xanthium sibiricum, and Bidens pilosa) with different morphological characteristics were selected for secondary dispersal experiments, and their seed displacement ratio (SDR), seed loss ratio (SLR), as well as seed displacement distance (SDD), were calculated following the experiments. The Spearman correlation analysis was then performed to identify the dominant factors.
Important findings (1) When compared with bare soils, the surface roughness of cyanobacteria- and moss-dominated crusts on aeolian sand soil increased by 6.69 and 6.13 times and by 2.52 and 1.45 times on loess soil, respectively. (2) Within contrast to wet conditions, the surface roughness of biocrusts increased by 26.56% on dry aeolian sand soil, whereas it reduced by 9.42% on dry loess soil. (3) The surface roughness of biocrusts of the aeolian sand soil rose by 16.84% under dry conditions and decreased by 16.38% under wet conditions compared with that on loess soil. (4) In comparison to bare soils, the SDR, SLR, and SDD of biocrusts dropped by 77.1%, 95.4%, and 72.2% on aeolian sand soil and by 76.5%, 93.8%, and 66.8% on loess soil, respectively. The characteristics of seed dispersal were not significantly affected by soil types or soil water conditions. (5) The SDR, SLR, and SDD were all significantly and negatively correlated with the surface roughness of biocrusts. However, only the SDR and SLR were significantly negatively linked to soil water content, and only the SLR and SDD were significantly negatively correlated with seed density. To summarize, biocrusts obstruct dispersal and enhance aggregation of seeds by increasing land surface roughness, thereby impacting the spatial structures and community dynamics of shrubs and grasses.

Key words: seed dispersal, vascular plant, surface roughness, cyanobacteria crust, moss crust, Loess Plateau