Sanou Lassina, Zida Didier, Savadogo Patrice, Thiombiano Adjima
Département Environnement et Forêts, Centre National de la Recherche Scientifique et Technologique, INERA, BP 7047, Ouagadougou 03, Burkina Faso.
Unité de Formation et de Recherche en Sciences de la Vie et de la Terre/Laboratoire de Biologie et Ecologie Végétales (UFR/SVT), Université Ouaga I Pr Joseph Ki-Zerbo, Ouagadougou, Burkina Faso.
J Plant Res. 2018 Sep;131(5):773-788. doi: 10.1007/s10265-018-1048-3. Epub 2018 Jun 11.
Grazing removes a plant's aboveground vegetative and reproductive tissues and can modify the soil seed bank, potentially impacting the restoration of preferred species. Knowledge about aboveground vegetation and species composition of soil seed bank and the processes that contribute to vegetation recovery on and surrounding watering points subjected to grazing is lacking. Successful restoration strategies hinge on addressing these knowledge gaps. We assessed the effects of livestock grazing on aboveground vegetation and soil seed bank characteristics along a river bank and surrounding areas subject to different grazing intensities and draw implications for restoration. Plots (50 × 50 m) were established along five transects representing differing levels of grazing intensity. Soil samples were taken from three layers within each plot to determine soil properties and species composition of soil seed bank using the seedling emergence method. Heavy grazing resulted in the disappearance of perennial grasses, a reduction in species diversity and a decrease in soil nutrients with increased soil depth. Overall, the similarity between the extant aboveground vegetation and flora within the soil seed bank was low. The soil seed bank was dominated by herbaceous species and two woody species, suggesting that many woody species are not accumulating in the soil. With increasing soil depth, the seed density and richness declined. Canonical correspondence analyses (CCAs) showed that emerged seedlings from the soil seed bank were significantly influenced by soil carbon, organic matter, total nitrogen, total potassium and soil cation exchange capacity. This finding suggests that current grazing practices have a negative impact on the vegetation surrounding watering points; hence there is a need for improved grazing management strategies and vegetation restoration in these areas. The soil seed bank alone cannot restore degraded river banks; active transfer of propagules from adjacent undisturbed forest areas is essential.
放牧会去除植物的地上营养组织和生殖组织，并可能改变土壤种子库，从而潜在地影响优势物种的恢复。目前缺乏关于受放牧影响的取水点及其周边地区地上植被、土壤种子库的物种组成以及有助于植被恢复的过程的相关知识。成功的恢复策略取决于填补这些知识空白。我们评估了牲畜放牧对河岸及周边地区不同放牧强度下地上植被和土壤种子库特征的影响，并得出恢复的相关启示。沿着代表不同放牧强度水平的五条样带设置了样地（50×50米）。从每个样地的三层土壤中取样，采用幼苗出土法测定土壤性质和土壤种子库的物种组成。重度放牧导致多年生草本植物消失，物种多样性降低，土壤养分随土壤深度增加而减少。总体而言，现存地上植被与土壤种子库内植物区系之间的相似度较低。土壤种子库以草本物种和两种木本物种为主，这表明许多木本物种并未在土壤中积累。随着土壤深度增加，种子密度和丰富度下降。典范对应分析（CCA）表明，土壤种子库中出土的幼苗受土壤碳、有机质、全氮、全钾和土壤阳离子交换容量的显著影响。这一发现表明，当前的放牧方式对取水点周边的植被有负面影响；因此，需要改进这些地区的放牧管理策略和植被恢复措施。仅靠土壤种子库无法恢复退化的河岸；从相邻未受干扰的森林地区积极转移繁殖体至关重要。
