Occurrence of arbuscular mycorrhizal fungi in leaf litter and roots of shaded coffee plantations under organic and conventional management

Díaz-Ariza, Lucía Ana; Rivera, Emma Lucía; Sánchez, Natalia

doi:10.36783/18069657rbcs20200110

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Division – Soil Processes and Properties, Commission – Soil Biology • Rev. Bras. Ciênc. Solo 45 • 2021 • https://doi.org/10.36783/18069657rbcs20200110 copy

Occurrence of arbuscular mycorrhizal fungi in leaf litter and roots of shaded coffee plantations under organic and conventional management

Authorship SCIMAGO INSTITUTIONS RANKINGS

ABSTRACT

Evidence of arbuscular mycorrhizal fungal colonization of mat litter in various ecosystems plus previous reports of external mycelium of those fungi and mycorrhizal roots in litter from coffee plants and shade trees on coffee plantations suggest that they have a relationship with closed direct nutrient cycling between organic matter and living roots. This relationship was first proposed more than 50 years ago. Mycorrhizal symbiosis in tropical crops is affected by agricultural management practices. This study aimed to assess the occurrence of arbuscular mycorrhizal fungi in leaf litter from three shaded Colombian coffee agroecosystems under organic and conventional management. One is managed chemically, one organically, and one with a combined use of organic and chemical inputs. Leaf litter and roots were collected from the three coffee plots at three decomposition stages. Each plot represented a distinct fertilization and tree dominance pattern different from the other two plots. Arbuscular mycorrhizal fungi were found in decomposing leaves. The chemically managed plot showed statistical differences (p<0.05) with respect to the other plots, it had the greatest amounts of arbuscular mycorrhizal fungal root colonization (48.76–70.51 %), litter colonization (36.2–69.91 %), external mycelium length (28.66–48.33 m g^-1), and spore number (451.27–681.2 spores in 20 g of dry soil). In contrast, conditions on the combined management coffee plot results in smaller means of the variables evaluated. Arbuscular mycorrhizal fungal root colonization and nitrogen content of leaf litter varied among the decomposition stages (p<0.05). Litter quality of different tree species may have influenced colonization of plant matter within each plot. We found evidence of typical structures of arbuscular mycorrhizal fungi within and among decomposing leaf litter and roots growing into the mat litter in tropical agroecosystems. This supports the thought that these fungi have a role in carbon and nutrient recycling, which are influenced by agricultural management practices and plant population composition.

nutrient cycling; Coffea arabica; organic agriculture; agroforestry

Stage	Description	Leaf area			Decomposition layers reported in literature

		OR	CH	ORCH
		------- cm² -------
1	Upper litter layer composed mainly of not-yet decomposed plant matter and already fragmented leaves	1.0	2.2	2.3	L: composed of recognizable plant remains
2	Fragmented leaves with the greatest proportion of roots and soil. Leaves between topmost layer and soil layer	0.7	0.8	1.0	LF: mixture of organic matter in different stages of 3 decomposition
3	Highly fragmented leaves in contact with roots and incorporated into the upper layer of soil	0.3	0.4	0.3	LF: mixture of organic matter in different stages of 3 decomposition

Tree	Family	Plot

		OR	CH	ORCH
Vernonia sp.	Asteraceae	0.023	0.094	0.000
Protium sp.	Burseraceae	0.012	0.000	0.000
Carica pubescens	Caricaceae	0.012	0.000	0.000
Clethra sp.	Clethraceae	0.000	0.031	0.000
Cupressus lusitanica	Cupressaceae	0.035	0.000	0.000
Macleania rupestris	Ericaceae	0.000	0.031	0.000
Escallonia sp.	Escalloniaceae	0.000	0.031	0.000
Leucaena leucocephala	Fabaceae	0.046	0.000	0.000
Erythrina edulis	Fabaceae	0.035	0.000	0.043
Erythrina rubrinervia	Fabaceae	0.012	0.000	0.000
Inga sp.	Fabaceae	0.035	0.094	0.000
Persea americana	Lauraceae	0.070	0.062	0.000
Ocotea sp.	Lauraceae	0.012	0.000	0.000
Nectandra sp.	Lauraceae	0.012	0.031	0.087
Tibouchina sp.	Melastomataceae	0.012	0.062	0.000
Ficus sp.	Moraceae	0.012	0.125	0.000
Clarisia biflora	Moraceae	0.000	0.031	0.000
Morus insignis	Moraceae	0.000	0.031	0.000
Musa paradisiaca	Musaceae	0.337	0.000	0.740
Eucalyptus globulus	Myrtaceae	0.105	0.031	0.000
Fraxinus sp.	Oleaceae	0.012	0.156	0.000
Retrophyllum rospigliosii	Podocarpaceae	0.035	0.000	0.043
Roupala sp.	Proteaceae	0.012	0.031	0.000
Prunus integrifolia	Rosaceae	0.023	0.031	0.000
Citrus sp.	Rutaceae	0.139	0.094	0.087
Cyphomandra sp.	Solanaceae	0.023	0.000	0.000
Solanum inopinum	Solanaceae	0.000	0.031	0.000

Plot	C	N	C:N ratio
	------- % -------
OR	41.67 a	1.9 a	22.29 a
CH	36.36 a	2.04 a	17.72 a
ORCH	31.3 a	1.64 a	19.04 a
Stage
1	44.1 a	2.13 a	21.02 a
2	37.6 a	1.77 ab	21.57 a
3	29.34 a	1.56 b	18.65 a

Plot	Stage	Arbuscular mycorrhizal fungi												Non-arbuscular mycorrhizal fungi

		Spore number			External mycelium length			Leaf litter colonization			Root colonization			Leaf litter colonization			Root colonization
		spores per 20 g of dry soil		%	------- m g⁻¹ -------		%	------- % -------
		Mean	SD	CV	Mean	SD	CV	Mean	SD	CV	Mean	SD	CV	Mean	SD	CV	Mean	SD	CV
OR	1	51.61	39.21	93.04	23.18	2.94	15.52	22.55	22.55	141.42	18.83	9.07	59.01	12.29	8.29	95.37	7.15	9.10	155.86
	2	39.24	9.68	30.22	27.54	7.23	32.17	54.44	13.34	34.64	35.68	9.01	30.92	11.73	8.28	99.81	4.51	1.78	48.35
	3	27.35	11.92	53.36	19.25	8.26	52.55	56.12	43.88	110.58	31.84	6.59	25.36	8.33	1.88	31.85	5.63	1.18	25.60
CH	1	681.20	493.53	88.73	28.66	20.52	87.69	36.20	17.56	59.41	70.51	5.69	9.88	12.06	9.30	94.46	7.22	4.72	80.09
	2	483.41	276.03	69.93	36.24	27.37	92.50	42.32	24.29	70.30	67.38	9.53	17.33	5.21	3.52	82.70	3.44	1.48	52.66
	3	451.27	260.39	70.67	48.33	26.17	66.33	69.91	29.96	52.50	48.76	21.18	53.21	14.23	10.12	87.05	0.87	0.99	139.70
ORCH	1	45.74	29.94	80.18	7.31	4.28	71.73	6.86	9.70	173.21	29.55	11.81	48.93	6.60	9.33	173.21	2.42	2.17	109.71
	2	40.76	10.20	30.66	9.69	9.28	117.24	9.55	2.95	43.69	18.85	4.83	31.36	11.38	11.38	141.42	3.31	4.68	173.21
	3	41.78	18.91	55.44	5.48	2.81	62.91	14.80	0.00	0.00	7.56	6.21	116.18	ND	ND	ND	1.04	1.04	141.42
ANOVA p-value
Plot		1.23e^-05			0.00543			0.0352			2.29e^-06			0.437			0.199
Stage		0.935			0.66184			0.2172			0.0457			0.977			0.328

	Spore number	External mycelium length	AMF in litter	AMF in roots	Non-AMF in litter
External mycelium length	0.567 (0.121)
AMF litter colonization	0.000 (>0.999)	0.733 (0.031)
AMF root colonization	0.517 (0.162)	0.817 (0.011)	0.567 (0.121)
NAMF litter colonization	0.250 (0.521)	0.583 (0.108)	0.417 (0.270)	0.283 (0.463)
NAMF root colonization	0.083 (0.843)	0.183 (0.644)	0.100 (0.810)	0.267 (0.493)	0.267 (0.493)

	C	N	C:N ratio
Spore number	0.117 (0.776)	0.633 (0.076)	_0.517 (0.162)
External mycelium length	0.117 (0.776)	0.417 (0.270)	0.000 (>0.999)
AMF litter colonization	-0.100 (0,810)	-0.050 (0.912)	0.100 (0.810)
AMF root colonization	0.233 (0.552)	0.467 (0.213)	0.100 (0.810)
NAMF litter colonization	0.450 (0.230)	0.400 (0.291)	0.383 (0.312)
NAMF root colonization	0.833 (0.008)	0.600 (0.097)	-0.517 (0.162)

	OR	CH	ORCH
Sand (g kg^-1)	660	340	500
Loam (g kg^-1)	220	260	180
Clay (g kg^-1)	120	400	320
pH(H₂O)	5.1	5.7	4.6
Al (cmol_c kg^-1)	0.3	ND	6.1
AlS (g kg^-1)	0.09	ND	0.43
OC (g kg^-1)	0.83	0.50	0.50
EP (ppm)	174.5	118.2	155.2
BS (%)	62.3	55.2	25.2
Exchangeable complex (cmol_c kg^-1)
CEC	50.6	35.4	32.7
Ca²⁺	24.01	17.47	7.22
Mg²⁺	6.11	1.73	0.64
K⁺	1.16	0.31	0.34
Na⁺	0.27	0.03	0.05
TB	31.55	19.54	8.25
Cation ratios
Ca/Mg	3.93	10.29	12.03
Mg/K	5.08	5.60	2.00
Ca/K	20.00	58.30	24.06
(Ca + Mg)/K	25.08	64.00	26.06

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[1] * Corresponding author: E-mail: luciaana@javeriana.edu.co