Data from: Local root growth and death are mediated by contrasts in nutrient availability and root quantity between soil patches

Plants are thought to be able to regulate local root growth according to its overall nutrient status as well as nutrient contents in a local substrate patch. Therefore, root plastic responses to environmental changes are likely co-determined by local responses of root modules and systematic control of the whole plant. Recent studies showed that the contrast in nutrient availability between different patches could significantly influence the growth and death of local roots. In this study, we further explored beside nutrient contrast, whether root growth and death in a local patch are also affected by relative root quantity in the patch. We conducted a split-root experiment with different splitting ratios of roots of Canada goldenrod (Solidago canadensis) individuals, as well as high (5× Hoagland solution vs water) or low (1× Hoagland solution vs water) contrast nutrient conditions for the split roots. The results showed that root growth decreased in nutrient-rich patches but increased in nutrient-poor patches when more roots co-occurred in the same patches, irrespective of nutrient contrast condition. Root mortality depended on contrasts in both root quantity and nutrients: in the high nutrient contrast condition, it increased in nutrient-rich patches but decreased in nutrient-poor patches with increasing root proportion; while in the low nutrient contrast condition it showed the opposite trend. These results demonstrated that root growth and death dynamics were affected by the contrast in both nutrient availability and root quantity between patches. Our study provided ecological evidence that local root growth and death are mediated by both the responses of root modules to a nutrient patch and the whole plant nutrient status, suggesting that future work investigating root production and turnover should take into account the degree of heterogeneity in nutrient and root distribution.学界普遍认为，植物可依据自身整体营养状况与局部基质斑块内的养分含量，调控根系的局部生长。因此，植物根系对环境变化的塑性响应，大概率由根模块的局部响应与整株植株的系统调控共同决定。已有研究证实，不同斑块间的养分可用性差异，可显著影响局部根系的生长与死亡。本研究进一步探究：除养分差异外，局部斑块内的相对根系数量是否同样会对该区域的根系生长与死亡产生影响。我们以加拿大一枝黄花（Solidago canadensis）个体的根系为材料开展分根试验（split-root experiment），设置了不同的根系分割比例，并为分根根系设置高养分对比（5×霍格兰德溶液（Hoagland solution） vs 去离子水）与低养分对比（1×霍格兰德溶液 vs 去离子水）两种处理条件。结果表明：当同一斑块内共存的根系数量更多时，无论养分对比条件如何，养分富集斑块内的根系生长均受到抑制，而养分匮乏斑块内的根系生长则会提升。根系死亡率同时受根系数量与养分差异的共同调控：在高养分对比处理下，随着斑块内根系占比升高，养分富集斑块的根系死亡率上升，养分匮乏斑块的死亡率则下降；而在低养分对比处理下，该趋势恰好相反。上述结果证实，根系生长与死亡动态同时受斑块间养分可用性差异与根系数量差异的共同影响。本研究为“局部根系的生长与死亡同时受根模块对养分斑块的响应以及整株植株营养状况的调控”这一论点提供了生态学证据，同时提示未来有关根系生产与周转的研究，应将养分与根系分布的异质性程度纳入考量范畴。