Sevilleta plant phenology predicts stability of primary production from 2002 to 2020.

The temporal stability of plant productivity affects species’ access to resources, exposure to stressors, and strength of interactions with other species in the community, including support to the food web. The magnitude of temporal stability may depend on how a species allocates resources across phenological stages, such as vegetative growth versus reproduction. Understanding whether and how plant phenological traits correlate with the long-term stability of plant biomass is particularly important in highly variable environments, such as drylands. We evaluated whether phenological traits predict the temporal stability of plant species productivity by correlating 18 years of monthly phenology observations with biannual estimates of aboveground plant biomass for 98 plant species from semi-arid grasslands and shrublands. We then paired these phenological traits with potential climate drivers to identify abiotic contexts that favor specific phenological strategies among plant species. Phenological traits strongly predicted the stability of plant species biomass. Plant species with longer annual vegetative phenophases had more stable production over time but also failed to fruit in a greater proportion of years, indicating a growth-reproduction trade-off. Earlier leaf- out dates, longer fruiting duration, and longer time lags between leaf and fruit production also predicted greater temporal stability. Species with stability-promoting traits began growing in drier conditions than their counterparts and experienced greater exposure to stress, evaluated by the wider range of temperatures and precipitation during biologically active periods. Our results suggest that bet-hedging strategies which spread resource acquisition and reproduction over longer time periods help to stabilize plant species productivity in variable environments.

植物生产力的时间稳定性影响物种对资源的获取、对胁迫因子的暴露程度，以及与群落中其他物种（包括对食物网的支撑）的相互作用强度。时间稳定性的大小可能取决于物种如何在不同物候阶段（如营养生长与繁殖）分配资源。在干旱区等高度可变环境中，理解植物物候性状（phenological traits）是否以及如何与植物生物量的长期稳定性相关尤为重要。我们通过将半干旱草原和灌丛中98种植物的18年月度物候观测数据与半年一次的地上生物量估算值相关联，评估了物候性状是否能预测植物物种生产力的时间稳定性。随后，我们将这些物候性状与潜在气候驱动因子配对，以识别有利于植物物种采取特定物候策略的非生物环境。物候性状能强烈预测植物物种生物量的稳定性。年营养物候期（vegetative phenophases）较长的植物物种，其生产力随时间更稳定，但未能结果的年份比例也更高，这表明存在生长-繁殖权衡。更早的展叶期、更长的结果持续时间以及展叶与结果之间更长的时间差，也能预测更高的时间稳定性。具有促进稳定性性状的物种，其生长起始条件比对应物种更干旱，且面临更强的胁迫暴露（通过生物活跃期（biologically active periods）内更广泛的温度和降水范围评估）。我们的结果表明，将资源获取和繁殖分散到更长时间段的风险规避策略（bet-hedging strategies）有助于在可变环境中稳定植物物种的生产力。