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Journal of Arid Land  2022, Vol. 14 Issue (5): 550-560    DOI: 10.1007/s40333-022-0015-y
Research article     
Seed rain and soil seed bank compensatory roles on Nassella tenuis (Phil.) Barkworth seedling recruitment in ungrazed and grazed sites
Cintia Vanesa LEDER1, Dianela Alejandra CALVO2, Guadalupe PETER2,*()
1Universidad Nacional de Río Negro, Sede Atlántica, Centro de Estudios Ambientales desde la NorPatagonia (Center of Environmental Studies from North Patagonia (CEANPa), National University of Río Negro), Viedma 8504, Argentina
2Universidad Nacional de Río Negro, Sede Atlántica, Centro de Estudios Ambientales desde la NorPatagonia-National Council of Scientific and Technical Research (CONICET) (Center of Environmental Studies from North Patagonia (CEANPa), National University of Río Negro), Viedma 8504, Argentina
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In semi-arid lands, vegetation is distributed in shrub patches immersed in a less vegetated interpatch matrix. Grazing affects perennial grass seed bank through a decrease in seed rain and an increase in seed predation and soil compaction. Nevertheless, some species with anchorage mechanisms in their seeds might overcome this, such as Nassella tenuis (Phil.) Barkworth. This is an important species in grazing paddocks because it has an intermediate palatability and its relatively tolerant to grazing. These characteristics allow N. tenuis to increase its abundance in grazed sites. Our objective was to assess how grazing affects the key palatable species from seeds to seedlings: i.e., seed rain, soil seed bank, and seedling recruitment in different microsites along a windward-leeward transect across shrub canopy. We hypothesized that: (1) the negative effects of grazing on N. tenuis fructification are reflected in its seed rain, soil seed bank, and seedling recruitment, especially in interpatches; (2) Nassella tenuis seed rain reduction, soil compaction by cattle in grazed sites, and removal of seeds by wind decrease its soil seed bank, especially in microsites exposed to the predominant wind; and (3) the decrease in N. tenuis soil seed bank and cover increase in annual species in grazed sites have negative effects on its seedling recruitment, especially in microsites exposed to predominant wind. We placed seed traps, collected soil samples, and monitored seedling recruitment in different locations around shrub canopy to address our hypotheses. Also, we established a manipulative experiment in which we sow N. tenuis seeds and followed its recruitment in different microsites. We compared the seed rain, soil seed bank, natural seedling recruitment, and sown seeds recruitment of N. tenuis between grazed and ungrazed sites. We analyzed differences between microsites along a windward-leeward transect across shrubs patches. Seed rain and soil seed bank had the same density in patches and interpatches both in ungrazed and grazed sites. But seed rain was higher, and soil seed bank was lower in ungrazed sites than in grazed sites. Almost all under-canopy microsites showed greater soil seed bank abundance and natural seedling recruitment in ungrazed sites. Sown seeds recruitment was the same between grazed and ungrazed sites, but it showed protective effects of shrubs in leeward microsites under grazed sites. As a conclusion, seed rain and soil seed bank are complementary under grazed sites.

Key wordsseed rain      soil seed bank      seedling recruitment      microsites      grazing     
Received: 27 December 2021      Published: 31 May 2022
Corresponding Authors: Guadalupe PETER     E-mail:
Cite this article:

Cintia Vanesa LEDER, Dianela Alejandra CALVO, Guadalupe PETER. Seed rain and soil seed bank compensatory roles on Nassella tenuis (Phil.) Barkworth seedling recruitment in ungrazed and grazed sites. Journal of Arid Land, 2022, 14(5): 550-560.

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Fig.1 Mean monthly precipitation and temperature during the sampling period
Fig. 2 Wind velocity (a) and vegetation cover (b and c) among six microsites between grazed and ungrazed sites. Stars mean significant differences (P<0.05) between ungrazed and grazed sites, and different lowercase letters indicate significant differences (P<0.05) in vegetation cover between microsites (b) or functional groups (c). IW, windward interpatch; BW, windward border; MW, windward mid patch; ML, leeward mid patch; BL, leeward border; IL, leeward interpatch.
Fig. 3 Nassella tenuis seed rain, soil seed bank, and natural seedling recruitment between grazed and ungrazed sites, and between patches and interpatches. Different letters show statistically significant differences (P<0.05) between the combinations of treatment (grazed and ungrazed) and position (patch and interpatch). Lowercase letters: seed rain; capital normal letters: soil seed bank, capital italic letters: seedling recruitment.
Index Site Windward interpatch Windward border Windward mid patch Leeward mid patch Leeward border Leeward interpatch
SSB U 518.1±211.9 390.7±119.0a 424.6±150.6a 925.7±283.0a 424.6±177.0 229.0±82.7
G 135.9±85.7 17.0±11.6b 127.4±68.1b 178.3±80.4b 144.4±69.1 119.0±75.1
NSR U 37.04±14.85 51.85±14.60 71.11±19.30 34.81±7.96 59.26±15.85 76.30±31.70
G 37.04±19.78 49.63±26.00 22.22±10.34 8.89±4.75 21.48±10.37 44.40±13.40
SSR U 4.44±2.37A 8.88±3.63A 5.93±5.19AB 13.33±4.63B 21.47±8.36AB 4.44±1.81A
G 2.96±1.31AB 2.96±1.31AB 15.55±9.50A 19.99±5.34B 11.10±4.60B 8.14±3.98AB
Table 1 Soil seed bank (SSB), natural seedling recruitment (NSR), and sown seeds recruitment (SSR) of N. tenuis under different microsites and treatments
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