Division of Earth and Ecosystem Sciences, Desert Research Institute, 2215 Raggio Parkway, Reno, NV 89512, USA.
Glob Chang Biol. 2013 Mar;19(3):948-56. doi: 10.1111/gcb.12082. Epub 2012 Dec 21.
Climate change is expected to impact the amount and distribution of precipitation in the arid southwestern United States. In addition, nitrogen (N) deposition is increasing in these regions due to increased urbanization. Responses of belowground plant activity to increases in soil water content and N have shown inconsistent patterns between biomes. In arid lands, plant productivity is limited by water and N availability so it is expected that changes in these factors will affect fine root dynamics. The objectives of this study were to quantify the effects of increased summer precipitation and N deposition on fine root dynamics in a Mojave Desert ecosystem during a 2-year field experiment using minirhizotron measurements. Root length density, production, and mortality were measured in field plots in the Mojave Desert receiving three 25 mm summer rain events and/or 40 kg N ha(-1) yr(-1) . Increased summer precipitation and N additions did not have an overall significant effect on any of the measured root parameters. However, differences in winter precipitation resulting from interannual variability in rainfall appeared to affect root parameters with root production and turnover increasing following a wet winter most likely due to stimulation of annual grasses. In addition, roots were distributed more deeply in the soil following the wet winter. Root length density was initially higher under canopies compared to canopy interspaces, but converged toward the end of the study. In addition, roots tended to be distributed more deeply into the soil in canopy interspace areas. Results from this study indicated that increased summer precipitation and N deposition in response to climate change and urbanization are not likely to affect fine root dynamics in these Mojave Desert ecosystems, despite studies showing aboveground plant physiological responses to these environmental perturbations. However, changes in the amount and possibly distribution of winter precipitation may affect fine root dynamics.
预计气候变化将影响美国西南部干旱地区的降水量和分布。此外，由于城市化的增加，这些地区的氮（N）沉积也在增加。在不同生物群落中，土壤水分和 N 增加对地下植物活动的响应模式不一致。在干旱地区，植物生产力受到水和 N 供应的限制，因此预计这些因素的变化将影响细根动态。本研究的目的是在一项为期 2 年的野外实验中，使用迷你根管测量来量化夏季降水和 N 沉积增加对莫哈韦沙漠生态系统细根动态的影响。在莫哈韦沙漠的野外试验场中，测量了根长密度、生产和死亡率，这些试验场接收了 3 次 25 毫米的夏季降雨事件和/或 40 千克 N ha(-1) 年(-1) 。夏季降水和 N 添加的增加并没有对任何测量的根系参数产生总体显著影响。然而，由于降雨量的年际变化导致冬季降水的差异似乎影响了根系参数，在湿冬之后，根系的生产和周转率增加，这很可能是由于一年生草本植物的刺激。此外，湿冬过后，根系在土壤中的分布更深。根长密度在树冠下最初高于树冠之间，但在研究结束时趋于收敛。此外，根系在树冠之间的区域往往分布得更深。本研究结果表明，尽管研究表明这些环境干扰对地上植物生理有响应，但气候变化和城市化导致的夏季降水和 N 沉积增加不太可能影响这些莫哈韦沙漠生态系统的细根动态。然而，冬季降水的数量和可能的分布变化可能会影响细根动态。
