Impact of enclosure management on soil properties and microbial biomass in a restored semi-arid rangeland, Kenya

Abstract

Rangeland degradation is a serious problem throughout sub-Saharan Africa and its restoration is a challenge for the management of arid and semi-arid areas. In Lake Baringo Basin of Kenya, communities and individual farmers are restoring indigenous vegetation inside enclosures in an effort to combat severe land degradation and address their livelihood problems. This study evaluated the impact of enclosure management on soil properties and microbial biomass, being key indicators of soil ecosystem health. Six reseeded communal enclosures using soil embankments as water-harvesting structures and strictly regulated access were selected, varying in age from 13 to 23 years. In six private enclosures, ranging from 3 to 17 years in age, individual farmers emulated the communal enclosure strategy and restored areas for their exclusive use. Significant decreases in bulk density, and increases in the soil organic carbon, total nitrogen and microbial biomass contents and stocks were found in the enclosures as compared with the degraded open rangeland. In the private enclosures, the impact of rehabilitation on the soil quality was variable, and soil quality was in general lower than that obtained under communal management. The significant increase of absolute stocks of carbon, nitrogen and microbial biomass compared to the degraded open rangeland indicates the potential for the restoration of soil quality through range rehabilitation. Over-sowing with indigenous legume fodder species could improve total nitrogen content in the soil and nutritional value of the pastures as well

Enclosures in West Pokot, Kenya: Transforming land, livestock and livelihoods in drylands

“…Although we did not measure erosion as such, we did measure some reciprocal parameters; the increases in vegetation cover and soil C inside enclosures, which were found by for example Damene et al (2013) in Ethiopia and Mureithi et al (2014) in another area of Kenya, as well as the increasing populations, and the extent of enclosure use in Chepareria, indicate that the title of Tiffen et al's book (1994) might be true also in this area.…”

Exclosures backed up with community-based soil and water conservation practices increased soil organic carbon stock and microbial biomass carbon distribution, in the northern highlands of Ethiopia

“…Means followed by the same letter across each row do not differ significantly at P ≤ 0.05 [32] found that, on average, exclosures lowered the BD of top soil from 1.48 to 1.19 g cm −3 in range lands of Kenya. Mean value for BD varied from 1.12 g cm −3 (in exclosure) to 1.34 g cm −3 (in grazing land) in nearby site [4].…”

“…High MBC can also be used as bio-indicator for the recovery of degraded soils [27]. Thus, high MBC in exclosures indicate that they had the potential for the restoration of soil quality [32].…”

“…Restoration and management of degraded lands significantly contribute to enhanced SOC [30] and MBC [31] which are considered as soil health indicators during restoration process [32]. They vary spatially under different management and plant cover [21], though studies that examine the distribution of these soil properties are limited in the area [33].…”

Experimental Manipulation of Precipitation Affects Soil Nitrogen Availability in Semiarid Mongolian Pine (Pinus sylvestris var. mongolica) Plantation

“…As a sink, the microbial biomass is a mechanism for immobilizing N, effectively reducing N losses through leaching or associated denitrification [41,42]. In other words, the MBN is an indicator of the immobilization of N by microbes, and is considered a regulator of N dynamics in arid and semiarid regions [41,43]. Fisher et al [15] reported that levels of extractable N (NH 4 + -N and NO 3 − -N) in the Jornada Basin directly decreased after rainfall, which they attributed to increased N immobilization in the microbial biomass, as well as to increased leaching of N. Reynolds et al [9] concluded that extractable N (NH 4 + -N and NO 3 − -N) accumulation during the summer drought in the Jornada Basin could result from the effects of drought upon N immobilization in the microbial biomass and plant access to soil moisture and nutrients.…”