Projections of vegetation change in response to future global change conditions are challenged by the lack of long-term, empirical data on how vegetation responds to the variability in climatic conditions. This is particularly true for biodiverse systems that are threatened by climate change such as the winter-rainfall Succulent Karoo biome of southern Africa. In this study we analyse long-term data (2002–2019) of two biodiversity observatories from the Kamiesberg Mountains in the Succulent Karoo. We employed the R package GLMMtmb to analyse counts of abundance and estimated cover values of vegetation as response variables and seasonal Standardised Precipitation-Evapotranspiration Index (SPEI), annual livestock density, topography and soil surface structure as predictors for the interannual change of life forms under low and high land use intensity. We compared the life form composition at the two contrasting land use types and found the cover and abundance of leaf succulents to be higher under low grazing intensity and that of stem succulents to be higher under high grazing intensity. The cover and abundance of herbaceous life forms varied over the years depending on the seasonal weather conditions. Our GLMM results reveal counts of abundance to be a sensitive predictor for population dynamics in various herbaceous and shrub life form types. Estimated cover values showed less of a response to interannual differences in the environmental drivers. All life forms responded strongly to high humid and cool conditions in the second half of the winter rainfall period, when the temperatures increase again. The abundance of leaf-succulent and non-succulent shrubs also responded positively to moderate conditions towards the end of the dry season. The extensive and hot dry summer season in turn had a significant negative effect on the survival of particularly young plants with low cover. Cover values showed no response to the conditions of the late dry season and were generally less sensitive to the variance in seasonal climatic conditions. Our results suggest that future changes in interannual patterns in climatic conditions will affect life form composition of the vegetation.

由于缺乏关于植被如何应对气候条件变化的长期经验数据，针对未来全球变化条件的植被变化预测受到了挑战。对于受到气候变化威胁的生物多样性系统尤其如此，例如南部非洲冬季降雨多肉的卡鲁生物群落。在这项研究中，我们分析了多汁卡鲁卡米斯伯格山脉两个生物多样性观测站的长期数据（2002-2019）。我们使用 R 包 GLMMtmb 来分析植被丰度计数和估计覆盖值作为响应变量，并分析季节标准化降水蒸散指数 (SPEI)、年度牲畜密度、地形和土壤表面结构作为生命形式年际变化的预测因子。土地利用强度低和高。我们比较了两种不同土地利用类型的生命形式组成，发现低放牧强度下叶类多肉植物的覆盖度和丰度较高，而高放牧强度下茎类多肉植物的覆盖度和丰度较高。多年来，草本生命形式的覆盖范围和丰度随季节天气条件的不同而变化。我们的 GLMM 结果表明，丰度计数是各种草本和灌木生命形式类型种群动态的敏感预测因子。估计覆盖值对环境驱动因素的年际差异反应较小。在冬季降雨期的后半段，当气温再次升高时，所有生命形式都对高湿和凉爽的条件做出了强烈的反应。丰富的叶肉质和非肉质灌木也对旱季结束时的温和条件做出了积极的反应。夏季的广泛而炎热干燥的季节反过来对低覆盖度的幼苗植物的生存产生了显着的负面影响。覆盖值对旱季后期的条件没有反应，并且通常对季节性气候条件的变化不太敏感。我们的结果表明，未来气候条件年际模式的变化将影响植被的生命形式组成。