植物养分捕获策略随成土年龄的变化及生态学意义

自然成土过程中土壤养分的变化与植被原生演替常同时发生。随成土年龄变化的植物养分捕获策略(NASs)对植物竞争能力和演替过程具有重要影响。该文将植物NASs划分为细根、微生物、特殊根系、食虫和寄生策略等5个类型; 发现植物NASs的多样性随成土年龄的增加呈哑铃型变化模式; 特殊根系策略对植物捕获养分的作用在成土中期最小、后期最大, 细根和微生物策略的作用随成土年龄的增加逐渐降低; 分析了成土过程中NASs对植物种间关系影响的变化, 发现NASs对成土早期植物的促进作用和中期的竞争关系具有重要影响, 而成土后期多样和互补的NASs对植被群落的稳定共存及多样性的形成具有影响; 提出应进一步探究成土过程中土壤养分与植物NASs变化之间的定量关系, 开展更多研究以阐明NASs对植被原生演替、物种多样性形成和成土过程的贡献与机理。

Temporal trends of plant nutrient-acquisition strategies with soil age and their ecological significance

Changes in soil nutrient availability and primary succession of vegetation often co-occur during the processes of natural soil development. A low availability of nitrogen (N) and phosphorus (P) resources is common in the very early and late stage of soil development, respectively. Plants have evolved different nutrient-acquisition strategies (NASs) in response to low nutrient availability. Although the changes and responses of plant NASs to soil nutrients may affect primary succession and species diversity, the temporal trends and underlying mechanisms of plant NASs with soil development remain unknown. We reviewed 104 studies mainly carried out on soil chronosequences to clarify changes in plant NASs with soil age and its ecological significance. We classify plant NASs into Fine root, Microbial, Specialized root, Carnivorous and Parasitic strategies. We argue that the diversity of plant NASs changes with increasing soil age following a dumbbell-pattern, while reaching the maximum in the late stage of soil development. The role of Microbial and Fine root strategies in plants acquiring nutrients gradually decreases with increasing soil age, while the minimum and maximum role of Specialized root strategies in plants acquiring P is in the intermediate and late stages of soil development, respectively. The effects of NASs on interspecific relationships of plants vary with soil age. Specifically, pioneer plants with biological N fixation and specialized root strategies usually increase available soil N and regolith-derived nutrients to facilitate the colonization of subsequent plants in the early stage of soil development. During the early-intermediate stage, NASs mainly affect plant competitiveness in acquiring relatively abundantly available nutrients from soil. The facilitation and competition affected by NASs contribute to plant species turnover in the first two stages. In the late stage, diverse NASs enable plants to acquire distinct forms of nutrients from different soil spaces and complementary NASs enable plants to take up soil nutrients mobilized by their neighbors. Together with the interactions between NASs and soil pathogens, these processes contribute the coexistence and diversity of plant species in this stage when most soil nutrients have a very low availability. We propose that it is necessary to quantify the relationships between changes in soil nutrient availability (including concentrations and fractions) and plant NASs with soil age. More studies are also needed to quantify contributions of NASs to primary succession, diversity of plant species and soil development.