Woody plant encroachment allocated more photosynthetic carbon belowground through soil pores in grasslands

IF 5.4 1区农林科学 Q1 GEOSCIENCES, MULTIDISCIPLINARY

Catena Pub Date : 2025-07-20 DOI:10.1016/j.catena.2025.109303

Ling Gan, Xia Hu

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引用次数: 0

Abstract

Shrub encroachment is a significant ecological challenge for grassland ecosystems worldwide. However, few studies have investigated the allocation of photosynthetic C to soils, and the role of soil pore structure in regulating root-derived C input in shrub-encroached grasslands remains unclear. Therefore, we aimed to investigate the characteristics of the allocation of photosynthetic, root-derived C and the role of soil pore structure in C allocation. To this end, we conducted an in situ ¹³C labeling experiment in typical shrub-encroached grasslands, using native grasslands as the controls, and performed X-ray computed tomography (CT) scanning to determine the soil pore structure. The results showed that a substantially higher proportion of ¹³C was allocated belowground (32.60 % in roots and 19.46 % in soil) in shrub-encroached grasslands than that in native grasslands (5.21 % in roots and 9.46 % in soil) 14 days after labeling. Shrubs allocated more photosynthetic C belowground compared with that allocated by herbs. Additionally, photosynthetic C transport from shrubs to rhizosphere soils was slower than that from herbs. Photosynthetic C was allocated to rhizosphere soils first through macropores (>150 μm Ø) and then through smaller pores (<150 μm Ø). In summary, shrub encroachment enhanced the stability of newly assimilated carbon by increasing photosynthetic carbon input and slowing soil carbon turnover. However, long-term carbon pool measurements revealed that soil C stocks of grasslands were twice as high as those in shrub-encroached soils. Therefore, compared with native grasslands, shrubs may be more suitable for short-term soil C sequestration in shrub-encroached grasslands. However, in the long term, the greater abundance of bacteria and Gram-negative bacteria in shrub-encroached grasslands will enhance mineralization and lead to infertile soils.

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木本植物的入侵通过土壤孔隙向地下分配了更多的光合碳

灌木入侵是全球草地生态系统面临的重大生态挑战。然而，很少有研究研究光合碳在土壤中的分配，土壤孔隙结构在调节灌木侵蚀草地根系碳输入中的作用尚不清楚。因此，我们旨在研究光合、根源碳的分配特征以及土壤孔隙结构在碳分配中的作用。为此，我们在典型灌丛草地上进行了原位13C标记实验，以原生草地为对照，并进行了x射线计算机断层扫描（CT），确定了土壤孔隙结构。结果表明：标记14 d后，灌丛草地13C在地下的分配比例（根系占32.60%，土壤占19.46%）显著高于原生草地（根系占5.21%，土壤占9.46%）；与草本植物相比，灌木在地下分配更多的光合C。此外，灌木向根际土壤的光合碳转运比草本植物慢。光合C首先通过大孔（>150 μm Ø）分配到根际土壤，然后再通过小孔（<150 μm Ø）分配到根际土壤。综上所述，灌木入侵通过增加光合碳输入和减缓土壤碳周转来增强新同化碳的稳定性。然而，长期碳库测量显示，草原土壤C储量是灌木侵占土壤的两倍。因此，与天然草地相比，灌丛可能更适合于短期固碳。然而，从长远来看，细菌和革兰氏阴性菌在灌木侵占草原上的丰度增加将增强土壤的矿化，导致土壤贫瘠。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

Catena 环境科学-地球科学综合

CiteScore

10.50

自引率

9.70%

发文量

816

审稿时长

54 days

期刊介绍： Catena publishes papers describing original field and laboratory investigations and reviews on geoecology and landscape evolution with emphasis on interdisciplinary aspects of soil science, hydrology and geomorphology. It aims to disseminate new knowledge and foster better understanding of the physical environment, of evolutionary sequences that have resulted in past and current landscapes, and of the natural processes that are likely to determine the fate of our terrestrial environment. Papers within any one of the above topics are welcome provided they are of sufficiently wide interest and relevance.