Larreguy C, Carrera A L, Bertiller M B
Instituto Patagónico para el Estudio de los Ecosistemas Continentales - CCT CENPAT- CONICET, Boulevard Brown 2915, Puerto Madryn, 9120, Chubut, Argentina.
Instituto Patagónico para el Estudio de los Ecosistemas Continentales - CCT CENPAT- CONICET, Boulevard Brown 2915, Puerto Madryn, 9120, Chubut, Argentina; Facultad de Ciencias Naturales - UNPSJB, Boulevard Brown 3000, Puerto Madryn, 9120, Chubut, Argentina.
J Environ Manage. 2017 Sep 1;199:139-147. doi: 10.1016/j.jenvman.2017.04.086. Epub 2017 May 18.
The objective of this study was to estimate the size and chemical quality of the total organic C stock and its partition between above-belowground plant parts and soil at sites with different plant cover induced by sheep grazing in the arid Patagonian Monte. This study was conducted at six representative sites with increasing signs of canopy disturbance attributed to grazing pressure. We used faeces density as a proxy of grazing pressure at each site. We assessed the total plant cover, shrub and perennial grass cover, total standing aboveground biomass (AGB), litter mass and belowground biomass (BGB) at each site. We further estimated the content of organic C, lignin and soluble phenols in plant compartments and the content of organic C, organic C in humic substances (recalcitrant C) and water soluble C (labile C) in soil at each site. Total plant cover was significantly related to grazing pressure. Standing AGB and litter mass decreased with increasing canopy disturbance while BGB did not vary across sites. Total organic C stock and the organic C stock in standing AGB increased with increasing total plant, shrub, and perennial grass cover. The organic C stock in litter mass increased with increasing total plant and shrub cover, while the organic C stock in BGB did not vary across sites. Lignin content in plant compartments increased with increasing total and shrub cover, while soluble phenols content did not change across sites. The organic C stock and the water soluble C content in soil were positively associated with perennial grass cover. Changes in total plant cover induced by grazing pressure negatively affected the size of the total organic C stock, having minor impact on the size of belowground than aboveground components. The reduction of perennial grass cover was reflected in decreasing chemical quality of the organic C stock in soil. Accordingly, plant managerial strategies should not only be focused on the amount of organic C sequestered but also on the chemical quality of organic C stocks since C chemistry could have an important impact on ecosystem functioning.
本研究的目的是估算干旱巴塔哥尼亚蒙特地区因绵羊放牧导致植物覆盖不同的地点的总有机碳储量的大小和化学质量，以及地上和地下植物部分与土壤之间的分配情况。本研究在六个具有代表性的地点进行，这些地点因放牧压力导致冠层干扰迹象增加。我们使用粪便密度作为每个地点放牧压力的指标。我们评估了每个地点的总植物覆盖度、灌木和多年生草本植物覆盖度、地上总生物量（AGB）、凋落物质量和地下生物量（BGB）。我们还估算了每个地点植物各部分的有机碳、木质素和可溶性酚含量，以及土壤中的有机碳、腐殖质中的有机碳（难分解碳）和水溶性碳（易分解碳）含量。总植物覆盖度与放牧压力显著相关。随着冠层干扰增加，地上生物量和凋落物质量下降，而地下生物量在各地点之间没有变化。总有机碳储量和地上生物量中的有机碳储量随着总植物、灌木和多年生草本植物覆盖度的增加而增加。凋落物质量中的有机碳储量随着总植物和灌木覆盖度的增加而增加，而地下生物量中的有机碳储量在各地点之间没有变化。植物各部分的木质素含量随着总覆盖度和灌木覆盖度的增加而增加，而可溶性酚含量在各地点之间没有变化。土壤中的有机碳储量和水溶性碳含量与多年生草本植物覆盖度呈正相关。放牧压力引起的总植物覆盖度变化对总有机碳储量大小产生负面影响，对地下部分大小的影响小于地上部分。多年生草本植物覆盖度的降低反映在土壤中有机碳储量化学质量的下降。因此，植物管理策略不仅应关注有机碳的固存数量，还应关注有机碳储量的化学质量，因为碳化学可能对生态系统功能产生重要影响。
