Multiyear periods (≥4 years) of extreme rainfall are increasing in frequency as climate continues to change, yet there is little understanding of how rainfall amount and heterogeneity in biophysical properties affect state changes in a sequence of wet and dry periods. Our objective was to examine the importance of rainfall periods, their legacies, and vegetation and soil properties to either the persistence of woody plants or a shift toward perennial grass dominance and a state reversal. We examined a 28-year record of rainfall consisting of a sequence of multiyear periods (average, dry, wet, dry, average) for four ecosystem types in the Jornada Basin. We analyzed relationships between above ground net primary production (ANPP) and rainfall for three plant functional groups that characterize alternative states (perennial grasses, other herbaceous plants, dominant shrubs). A multimodel comparison was used to determine the relative importance of rainfall, soil, and vegetation properties. For perennial grasses, the greatest mean ANPP in mesquite- and tarbush-dominated shrublands occurred in the wet period and in the dry period following the wet period in grasslands. Legacy effects in grasslands were asymmetric, where the lowest production was found in a dry period following an average period, and the greatest production occurred in a dry period following a wet period. For other herbaceous plants, in contrast, the greatest ANPP occurred in the wet period. Mesquite was the only dominant shrub species with a significant positive response in the wet period. Rainfall amount was a poor predictor of ANPP for each functional group when data from all periods were combined. Initial herbaceous biomass at the plant scale, patch-scale biomass, and soil texture at the landscape scale improved the predictive relationships of ANPP compared with rainfall alone. Under future climate, perennial grass production is expected to benefit the most from wet periods compared with other functional groups with continued high grass production in subsequent dry periods that can shift (desertified) shrublands toward grasslands. The continued dominance by shrubs will depend on the effects that rainfall has on perennial grasses and the sequence of high- and low-rainfall periods rather than the direct effects of rainfall on shrub production.

中文翻译：

---

一系列的多年湿润期和干旱期为草地恢复和状态变化逆转提供了机会

随着气候的持续变化，多年期（≥4年）极端降雨的频率不断增加，但人们对降雨量和生物物理特性的异质性如何影响一系列潮湿和干燥时期的状态变化知之甚少。我们的目标是研究降雨期、其影响以及植被和土壤特性对于木本植物的持续存在或向多年生草本优势的转变以及状态逆转的重要性。我们研究了乔纳达盆地四种生态系统类型的 28 年降雨记录，其中包括一系列多年周期（平均、干燥、潮湿、干燥、平均）。我们分析了代表替代状态的三种植物功能群（多年生草本植物、其他草本植物、优势灌木）的地上净初级生产力（ANPP）与降雨量之间的关系。使用多模型比较来确定降雨、土壤和植被特性的相对重要性。对于多年生草本植物，以豆科灌木和塔灌木为主的灌木丛中的最大平均ANPP出现在湿期和草地湿期之后的干旱期。草原的遗留效应是不对称的，最低产量出现在平均时期之后的干旱时期，而最高产量出现在湿润时期之后的干旱时期。相比之下，其他草本植物的 ANPP 最大出现在湿润期。豆科灌木是唯一在湿润期具有显着正响应的优势灌木物种。当合并所有时期的数据时，对于每个功能组来说，降雨量对于 ANPP 的预测效果很差。与单独降雨相比，植物尺度的初始草本生物量、斑块尺度的生物量和景观尺度的土壤质地改善了 ANPP 的预测关系。在未来的气候下，与其他功能组相比，多年生草的生产预计将从湿润期获益最多，在随后的干旱期持续高草产量，可以将（荒漠化）灌木丛转变为草原。灌木的持续主导地位将取决于降雨对多年生草本植物的影响以及高降雨期和低降雨期的顺序，而不是降雨对灌木生产的直接影响。