TY - JOUR

T1 - Livestock grazing and rainfall manipulation alter the patterning of CO2 fluxes and biomass development of the herbaceous community in a humid savanna

AU - Okach, Daniel O.

AU - Ondier, Joseph O.

AU - Kumar, Amit

AU - Rambold, Gerhard

AU - Tenhunen, John

AU - Huwe, Bernd

AU - Otieno, Dennis

PY - 2019/11/1

Y1 - 2019/11/1

N2 - Overgrazing by livestock and the changing patterns of rainfall, characterized by severe drought and floods during dry and wet seasons, respectively, threaten the sustainable productivity of the savannas. To understand the implications of such changes in Lambwe Valley—Kenya, we simulated 50% decrease (50%) and increase (150%) in ambient rainfall (100%), respectively, in grazed (G) and ungrazed (U) sites during dry and wet months. CO2 exchange and biomass production were quantified using chamber method and direct biomass sampling technique, respectively. Plots were named by combining the first letters of the sites followed by rainfall amount, i.e., U150%. Soil moisture (VWC) increased along a rainfall gradient of 50–150%. Grazing reduced the VWC, net ecosystem exchange (NEE), and total biomass by 19.07%, 57.14%, and 37.03%, respectively, with severe effects during the dry months. 50% rainfall strongly influenced the VWC, NEE (negative and positive signs indicate CO2 uptake and net carbon loss, respectively), and biomass compared to 150% rainfall. The U150% plot reported the highest mean NEE (– 8.80 ± 2.26 µmol m−2 s−1), AGB (1208.41 g m−2), and total biomass (1589.06 g m−2) during the wet months. Lower VWC in the G50% plot triggered a net carbon loss of 3.68 ± 0.81 µmol m−2 s−1 (NEE). Our results show that livestock grazing during the dry months hinders herbaceous CO2 uptake and standing biomass. Proper understanding of the interaction between livestock grazing and rainfall variability in humid savannas is essential for sustainable management strategies to regulate the herbaceous productivity.

AB - Overgrazing by livestock and the changing patterns of rainfall, characterized by severe drought and floods during dry and wet seasons, respectively, threaten the sustainable productivity of the savannas. To understand the implications of such changes in Lambwe Valley—Kenya, we simulated 50% decrease (50%) and increase (150%) in ambient rainfall (100%), respectively, in grazed (G) and ungrazed (U) sites during dry and wet months. CO2 exchange and biomass production were quantified using chamber method and direct biomass sampling technique, respectively. Plots were named by combining the first letters of the sites followed by rainfall amount, i.e., U150%. Soil moisture (VWC) increased along a rainfall gradient of 50–150%. Grazing reduced the VWC, net ecosystem exchange (NEE), and total biomass by 19.07%, 57.14%, and 37.03%, respectively, with severe effects during the dry months. 50% rainfall strongly influenced the VWC, NEE (negative and positive signs indicate CO2 uptake and net carbon loss, respectively), and biomass compared to 150% rainfall. The U150% plot reported the highest mean NEE (– 8.80 ± 2.26 µmol m−2 s−1), AGB (1208.41 g m−2), and total biomass (1589.06 g m−2) during the wet months. Lower VWC in the G50% plot triggered a net carbon loss of 3.68 ± 0.81 µmol m−2 s−1 (NEE). Our results show that livestock grazing during the dry months hinders herbaceous CO2 uptake and standing biomass. Proper understanding of the interaction between livestock grazing and rainfall variability in humid savannas is essential for sustainable management strategies to regulate the herbaceous productivity.

KW - Ecosystems Research

KW - Defoliation

KW - Rainfall variability

KW - Environmental planning

KW - Productivity

KW - Soil volumetric water content

KW - Respiration

UR - http://www.scopus.com/inward/record.url?scp=85074369621&partnerID=8YFLogxK

U2 - 10.1007/s11258-019-00977-2

DO - 10.1007/s11258-019-00977-2

M3 - Journal articles

AN - SCOPUS:85074369621

VL - 220

SP - 1085

EP - 1100

JO - Plant Ecology

JF - Plant Ecology

SN - 1385-0237

IS - 11

ER -