Data from: Nutrient foraging behaviour of four co-occuring perennial grassland plant species alone does not predict behaviour with neighbours

The spatial arrangement of nutrients and neighbours in soil influences plant growth and reproduction. Plants often respond to such stimuli through plasticity in root proliferation (root mass per soil volume), or the breadth of their root system. Here, we asked how plants adjust nutrient foraging strategies when grown alone or with neighbours. We asked (i) Does root proliferation into nutrient-rich patches when plants are grown alone predict root proliferation when plants are grown with neighbours? (ii) What factors (nutrients or neighbours) best predict the probability of root placement at different soil locations? (iii) How does the spatial distribution of nutrients alter the degree to which neighbours suppress plant growth? To answer these questions, we grew four grassland species either as individual plants or in competition, in patchy or patch-free soil, in a factorial design. We used genomic DNA to identify the spatial distribution of roots of each species when plants were grown in mixtures. The root foraging behaviour of individuals grown alone did not consistently predict behaviour in mixture. Specifically, (i) the behaviour of individually grown plants predicted behaviour of competing plants inside patches, but not in background soil. We observed over-proliferation of roots in background soil relative to what was expected from plants grown alone. (ii) Neighbours were consistently the most important variable for predicting the placement of roots in soil and caused either an increase in root system breadth, or no change relative to alone. (iii) If a species experienced growth suppression when grown in competition, individuals experienced this more severely in patchy soil compared to patch-free soil. Synthesis. Game theoretic models have predicted that under interspecific competition, over-proliferation of roots in the presence of neighbours might occur for some species but not others. Our data are consistent with these predictions but more work is needed. Nutrient foraging studies have primarily focused on plants grown alone or assumed that plants do not respond separately to neighbours and nutrients. Our data call these practices into question and contribute to a growing understanding that plants integrate information about both nutrients and neighbours when placing roots in soil.土壤中养分与邻株的空间分布格局，会影响植物的生长与繁殖。植物通常会通过根系增殖（root proliferation，单位土壤体积内的根系质量）或根系系统广度的表型可塑性，响应这类环境刺激。本研究旨在探究植物在单株种植或与邻株共存时，会如何调整其养分觅取（nutrient foraging）策略，并提出三个科学问题：（1）单株种植时植物向富养斑块的根系增殖能力，能否预测其与邻株共存时的根系增殖表现？（2）何种因子（养分或邻株）最能预测根系在不同土壤位置的定植概率？（3）养分的空间分布格局，会如何改变邻株对植物生长的抑制程度？为解答上述问题，本研究采用析因设计，设置四种草原植物的单株种植与种间竞争两种种植模式，以及斑块化土壤与无斑块土壤两种基质类型。当植物以混合群落方式种植时，我们通过基因组DNA技术鉴定各物种根系的空间分布格局。 单株种植个体的根系觅取行为，无法稳定预测其在混合群落中的表现。具体而言：（1）单株种植植物的行为可预测其在斑块内部竞争状态下的表现，但无法预测其在背景土壤中的表现。相较于单株种植的植物，我们观察到混合群落中植物在背景土壤内的根系出现过度增殖现象。（2）邻株始终是预测根系在土壤中定植位置的最重要变量，其作用要么会使根系系统广度增加，要么与单株种植时相比无显著变化。（3）若某物种在种间竞争中出现生长抑制，则相较于无斑块土壤，其在斑块化土壤中的生长抑制程度会更为严重。综合讨论：博弈论模型曾预测，在种间竞争条件下，部分物种在邻株存在时会出现根系过度增殖现象，而另一部分物种则不会。本研究数据与该预测相符，但仍需开展更多相关研究。现有养分觅取研究多以单株种植植物为对象，或默认植物无法分别响应养分与邻株信号。本研究数据对上述研究范式提出了质疑，并助力学界逐步形成共识：植物在确定根系定植位置时，会整合养分与邻株的双重环境信息。