Cunliffe Andrew M, McIntire Cameron D, Boschetti Fabio, Sauer Katherine J, Litvak Marcy, Anderson Karen, Brazier Richard E
Department of Geography, University of Exeter, Exeter, United Kingdom.
Department of Biology, University of New Mexico, Albuquerque, NM, United States.
Front Plant Sci. 2020 Feb 26;11:94. doi: 10.3389/fpls.2020.00094. eCollection 2020.
Across the semiarid ecosystems of the southwestern USA, there has been widespread encroachment of woody shrubs and trees including species into former grasslands. Quantifying vegetation biomass in such ecosystems is important because semiarid ecosystems are thought to play an important role in the global land carbon (C) sink, and changes in plant biomass also have implications for primary consumers and potential bioenergy feedstock. Oneseed juniper () is common in desert grasslands and pinyon-juniper rangelands across the intermountain region of southwestern North America; however, there is limited information about the aboveground biomass (AGB) and sapwood area (SWA) for this species, causing uncertainties in estimates of C stock and transpiration fluxes. In this study, we report on canopy area (CA), stem diameter, maximum height, and biomass measurements from trees sampled from central New Mexico. Dry biomass ranged between 0.4 kg and 625 kg, and cross-sectional SWA was measured on n = 200 stems using image analysis. We found a strong linear relationship between CA and AGB (r = 0.96), with a similar slope to that observed in other juniper species, suggesting that this readily measured attribute is well suited for upscaling studies. There was a 9% bias between different approaches to measuring CA, indicating care should be taken to account for these differences to avoid systematic biases. We found equivalent stem diameter (ESD) was a strong predictor of biomass, but that existing allometric models underpredicted biomass in larger trees. We found SWA could be predicted from individual stem diameter with a power relationship, and that tree-level SWA should be estimated by summing the SWA predictions from individual stems rather than ESD. Our improved allometric models for support more accurate and robust measurements of C storage and transpiration fluxes in -dominated ecosystems.
在美国西南部的半干旱生态系统中，包括 物种在内的木本灌木和树木广泛侵入了以前的草原。量化此类生态系统中的植被生物量很重要，因为半干旱生态系统被认为在全球陆地碳（C）汇中发挥着重要作用，而且植物生物量的变化也对初级消费者和潜在生物能源原料有影响。单籽杜松（）在北美西南部山间地区的荒漠草原和松-杜松林牧场很常见；然而，关于该物种地上生物量（AGB）和边材面积（SWA）的信息有限，这导致碳储量和蒸腾通量估计存在不确定性。在本研究中，我们报告了从新墨西哥州中部采集的 棵树的冠层面积（CA）、茎直径、最大高度和生物量测量结果。干生物量在0.4千克至625千克之间，使用图像分析在n = 200个茎上测量了横截面SWA。我们发现CA和AGB之间存在很强的线性关系（r = 0.96），其斜率与在其他杜松物种中观察到的相似，这表明这个易于测量的属性非常适合用于尺度放大研究。测量CA的不同方法之间存在9%的偏差，这表明应注意考虑这些差异以避免系统偏差。我们发现等效茎直径（ESD）是生物量的一个强预测指标，但现有的异速生长模型低估了大树的生物量。我们发现SWA可以通过个体茎直径的幂关系来预测，并且树木水平的SWA应该通过将各个茎的SWA预测值相加而不是ESD来估计。我们改进的 异速生长模型有助于更准确、可靠地测量以 为主的生态系统中的碳储存和蒸腾通量。
