Initiating Autogenic Restoration on Shallow Semiarid Sites

Abstract

Our objectives were to evaluate the use of microcatchments in the establishment of Leucaena retusa (little‐leaf leadtree) and Atriplex canescens (four‐wing saltbush) and their role in the initiation of autogenic landscape restoration processes on a shallow semiarid site. Three six‐month‐old seedlings of either Leucaena retusa or Atriplex canescens were planted in 1.5‐m2 microcatchments. An equal number of seedlings was planted in control plots (unmodified soil surface). The water collection effects on shrub survival, standing biomass, and the natural immigration of herbaceous vegetation were determined over 42 months. Planting in microcatchment basins doubled Leucaena seedling survival and resulted in a five‐fold increase in standing biomass, compared to the control, during the first growing season. There was a significant increase in soil organic matter in the microcatchment basins within 32 months. At the same time, microcatchments planted with Atriplex canescens seedlings had a ten‐fold increase in seedling standing biomass compared to the control. Forty‐two months after transplanting, the herbaceous standing crop was significantly greater near Atriplex canescens or in microcatchment basins than in plots with unmodified surface soil. Basins containing Atriplex produced significantly more herbaceous vegetation than basins containing Leucaena, and empty basins produced the least herbaceous vegetation of three basin treatments. These data suggest that landscape‐scale procedures that concentrate scarce resources (water, organic matter, nutrients, and propagules), establish keystone species, and ameliorate microenvironmental conditions can initiate autogenic restoration of degraded semiarid ecosystems.

Ecological Succession in Agrarian Impacted Site in Parts of Amafor Rainforest in Ngor-Akpala Local Government Area (LGA) of Imo State, Nigeria: Phytodiversity and Species Composition Assessments

“…On such impacted site, spontaneous colonization is slow and the natural vegetation succession is often inefficient to ensure proper protection against other post impact environmental influences. This also corroborates the assertions of Whisenant et al and Bradshaw [41][42][43] . It has been lamented that over 11,300 ha of forest are been cleared annually in Nigeria forest for the establishment of monoculture plantation of indigenous and exotic trees 44 .…”

Effects of artificial shading and weed mowing in reforestation of Mediterranean abandoned cropland with contrasting Quercus species

“…Additionally, large areas of cropland have been abandoned in the last years due to productivity loss, social changes and set-aside programs (Bot et al, 2000;FAO, 2004). These deforested areas can be left to undergo secondary succession or passive restoration (Debussche et al, 1996); or they can be actively restored by planting and managing native shrubs and trees to reduce soil erosion, increase biological diversity and create carbon sinks (Vieira et al, 1994;Whisenant et al, 1995;Maestre et al, 2001). The environmental conditions of these areas usually differ from those where natural regeneration of shrubs and trees occurs, and different abiotic and biotic factors hinder the establishment of introduced woody seedlings ( Gordon et al, 1989;Brown et al, 1998;Holl, 1998;Hooper et al, 2002).…”

Facilitative effects of Aloe secundiflora shrubs in degraded semi-arid rangelands in Kenya

“…Maerua shrubs also retained soil in their immediate vicinity, but pedestals were only about 3 cm high, and soil retention was not related to any aboveground plant measurements. It is therefore plausible that soil retention was affected by below-ground dynamics; root structure and active soil biota associated with roots can retard erosion by enhancing soil stability and by increasing water infiltration rates (Whisenant et al, 1995;Wilcox and Newman, 2005).…”