USDA-Agricultural Research Service, Grassland, Soil & Water Research Laboratory, Temple, Texas, 76502, USA
USDA-Agricultural Research Service, High Plains Grasslands Research Station, Cheyenne, Wyoming, 82009, USA.
J Exp Bot. 2014 Jul;65(13):3415-24. doi: 10.1093/jxb/eru009. Epub 2014 Feb 5.
Climate change drivers affect plant community productivity via three pathways: (i) direct effects of drivers on plants; (ii) the response of species abundances to drivers (community response); and (iii) the feedback effect of community change on productivity (community effect). The contribution of each pathway to driver-productivity relationships depends on functional traits of dominant species. We used data from three experiments in Texas, USA, to assess the role of community dynamics in the aboveground net primary productivity (ANPP) response of C4 grasslands to two climate drivers applied singly: atmospheric CO2 enrichment and augmented summer precipitation. The ANPP-driver response differed among experiments because community responses and effects differed. ANPP increased by 80-120g m(-2) per 100 μl l(-1) rise in CO2 in separate experiments with pasture and tallgrass prairie assemblages. Augmenting ambient precipitation by 128mm during one summer month each year increased ANPP more in native than in exotic communities in a third experiment. The community effect accounted for 21-38% of the ANPP CO2 response in the prairie experiment but little of the response in the pasture experiment. The community response to CO2 was linked to species traits associated with greater soil water from reduced transpiration (e.g. greater height). Community effects on the ANPP CO2 response and the greater ANPP response of native than exotic communities to augmented precipitation depended on species differences in transpiration efficiency. These results indicate that feedbacks from community change influenced ANPP-driver responses. However, the species traits that regulated community effects on ANPP differed from the traits that determined how communities responded to drivers.
（i）驱动因素对植物的直接影响；（ii）物种丰度对驱动因素的响应（群落响应）；以及（iii）群落变化对生产力的反馈效应（群落效应）。每种途径对驱动因素与生产力关系的贡献取决于优势物种的功能特征。我们使用了来自美国德克萨斯州的三个实验的数据，评估了群落动态在 C4 草原对两种气候驱动因素（大气 CO2 富集和夏季增雨）的地上净初级生产力（ANPP）响应中的作用。由于群落响应和效应不同，实验之间的 ANPP-驱动因素响应也不同。在分别进行的牧场和高草草原组合实验中，CO2 每升高 100 μl l(-1)，ANPP 增加了 80-120g m(-2)。在第三个实验中，每年夏季一个月增加 128mm 的环境降水，使原生群落的 ANPP 增加幅度大于外来群落。在草原实验中，群落效应占 ANPP 对 CO2 响应的 21-38%，而在牧场实验中则几乎没有响应。群落对 CO2 的响应与减少蒸腾作用带来更多土壤水分的物种特征（例如更高的高度）有关。群落对 ANPP CO2 响应的影响以及增雨对原生群落而非外来群落的 ANPP 响应更大，取决于蒸腾效率的物种差异。这些结果表明，群落变化的反馈影响了 ANPP-驱动因素的响应。然而，调节群落对 ANPP 影响的物种特征与决定群落对驱动因素响应的特征不同。
