Age Of Fallows Research Articles

What drives clearing of old-growth forest over secondary forests in tropical shifting cultivation systems? Evidence from the Peruvian Amazon

A key issue in understanding tropical forest disturbance is what drives farmers practicing customary shifting cultivation to clear crop fields in old-growth forest over secondary forest fallows. These farmers typically hold a stock of secondary forest fallows that can be used for cropping in rotation, built up over time in part through initial clearing of old-growth forest. In this paper we examine the most recent field cleared by 2046 indigenous and folk peasant households in 138 communities along three major rivers of the Peruvian Amazon to identify the factors that influence their choice of field location (upland or lowland forests) and type of forest cleared (old-growth or secondary). Data are drawn from a large-scale household and community surveys and remote sensing analysis of Landsat and ArcGIS Worldview imagery. We find that rates of old-growth forest clearing are low and that such land quickly returns to secondary forest cover: about 31% of households cleared forest on the upland (terra firme) but only 8% of households cleared upland old-growth forest. Regression modeling results identify the contextual, historical and household factors that influence the choice to clear upland forest (old-growth or secondary). Access to lowland for floodplain agriculture is associated with lower rates of old-growth forest clearing and higher educational attainment of household heads with increased clearing. Analysis of household land portfolios points to the importance of the size of land holdings, the degree of upland orientation, and the number and age of fallows held at the time of the forest clearing decision in clearing old-growth forest on the upland. Measures to reduce old-growth forest loss around Amazonian communities are discussed.

Carbon Stock as Related to Fallow Age in the Sudano-Guinea Savannahs of Ngaoundere, Adamawa, Cameroon

Aim/Objectives: In order to assess the fallow contribution on the carbon cycle and soil organic matter restoration, a study of the carbon dynamics was undertaken in fallow systems of 1, 2, 5 and 20 years old in the Ngaoundere savannahs of Cameroon.
 Methodology: Carbon stock was estimated in 100 m2 plot for shrubs, in 1 m2 plot for understorey, litter and earthworm casts, and 0.0625m2 plot for fine roots and soil. The experimental design was randomised complete block with three replicates. The age of fallows was the mean treatment whereas the plots were the replicates.
 Results: The results showed that the phytomass increased with fallow age, except that of shrubs. Soils and earthworm casts were the mean carbon sinks in the four fallows, with more than 55.61% and 26.24% of the total carbon stock respectively in the soil and earthworm casts. The total carbon stock increased with fallow age, from 34.54 in the young fallows to 154.52 tC.ha-1 in the old fallows. In the same way, vegetation and soil carbon increased with fallow age except that of shrub. The results showed that the carbon stock was influenced by floristic composition and spatial distribution of the vegetation, which related to fallow age.
 Conclusion: These preliminary results will contribute to the understanding of the impact of fallow age on the global carbon cycle and awareness in the conservation of fallows for the environment protection.

Dynamique De La Végétation De Bamo Et Stocks De Carbone Dans La Mosaïque De Végétation

This study was conducted in Agboville, Ivory Coast. The objective was (1) to characterize the floristic composition, dynamics, and structure of tree diversity of postcultural fallows; and (2) establish the relationship between the diversity and storage of carbon in timber biomass. The study relied on a network of 50 temporary plots. There were 31 postcultural fallows and 19 plots of primary forest. This study has identified 417 plant species distributed in 306 genera and 83 families. Tree density within postcultural fallows varied between 1025 to 5975 stems / ha, and the analysis showed that the density increases with the age of the postcultural fallows. Tree sampling was non-destructive and to estimate C storage, an allomectric models for above and belowground biomasses was used. Mean estimate of carbon (C) stocks in biomass were 80.25 tC / ha for groupe A (fallows from 4 to 8 years) and 256.5 tC / ha for group D (fallows from 14 to 24 years). These values remain far below those seen in the groups of primary forests with lateritic soil (1335.25 tC / ha). Results showed the ability of some postcultural fallows to store much C. It demonstrated that storage depends mainly on age and conserved species. This supports the idea of employing REDD+ processes in enhancing the ecological value associated with carbon.

Floristic variation in communities of fallow lands of the Podlaski Przełom Bugu mesoregion depending on the time of removal of fields from cultivation

<p>A study of fallow lands in the Podlaski Przełom Bugu (Podlasie Bug River Gorge) mesoregion was conducted over the period 2001–2004 in 77 villages belonging to 20 municipalities located in the Bug River valley along the stretch of the river from Terespol to Małkinia Górna. The aim of this study was to carry out a survey of vascular plants in fallow lands and to perform their multifaceted analysis. The study investigated quantitative and qualitative changes taking place in fallow vegetation with the passage of time from the abandonment of purposeful cultivation. Plant patches in 1–2-year, 3–6-year, 7–10-year and more than 10-year fallows were studied. Vascular plants of fallow lands within the study area comprise 442 species. 3–6-year fallows were richest in species (355). With increasing fallow age, the number of species decreased to 205 species in fallows older than 10 years. Hemicryptophytes dominated in plant communities of fallow lands. Therophytes were the co-dominant biological type in the youngest fallows. Chamaephytes and geophytes in all fellow age groups accounted for about 5%. Among vascular plants of fallow lands, native species dominated and their percentage increased with increasing fallow age, while at the same time the proportion of archeophytes decreased. With the increasing age of fallows, the proportion of species characteristic of forest communities also increased, whereas the percentage of segetal species simultaneously decreased. With the passage of time from the abandonment of cultivation, one can observe the evolution of plant cover of fallow fields from segetal communities towards less synanthropic communities.</p>

Dynamics of carbon balance components in fallow arable lands on the Valdai Upland

The dynamics of carbon pools in the live phytomass, necromass, and soil reservoirs have been analyzed in fallow arable lands of Novgorod oblast. The results show that the amounts of above- and belowground necromass increase with the age of fallows, while the dynamics of live phytomass have no distinct trend. Comparisons with archival data show that the stocks of soil organic carbon in the studied ecosystems have decreased by 1.39 t C/ha since 1983, which is equivalent to an annual loss of 0.03 t C/ha. The main factors accounting for changes in the carbon stocks of fallow soils are the initial organic carbon contents in topsoil, the intensity of agromeliorative measures taken during the period of agricultural land use, and carbon contents in soils of meadow communities typical for a given region (zone).

Assessment of the Nutrient Status of Soil under <em>Chromolaena odorata</em> L. (Siam Weed) Fallow in Moniya, Oyo State Southwestern Nigeria

In Nigeria, soil fertility restoration for improved agricultural production is a recurrent issue of immense importance mostly with her ever increasing population currently above 150 million. Therefore, identifying sustainable ecological practice to improve soil fertility is one of the surest ways to enhance food security. The study examined the trend in soil nutrient under the canopy of Chromolaena odorata of zero, 6 months, 1 yr and 2 yr fallows. The grid system of sampling was employed to collect soil samples from ten quadrats of 5m x 5m in each of the Chromolaena fallows. Result showed that C. odorata, a plant of secondary succession had significant effect on the buildup of nutrients in the soil, as the contents of soil properties under the canopy of C. odorata progressively increased with the age of fallows, which perhaps was affected by the increase in Chromolaena plant and cover. The pH level of soils under the canopy of C. odorata especially in the 2nd year fallow considerably favoured the increase in the contents of essential elements in the soil. However, to improve soil fertility, the study suggested that C. plantshould be planted along with staple crops to help minimize nutrient loss, and also, fallows with C. plantsshould be allowed for a reasonable number of years to facilitate nutrient accretion before cultivation.Keywords: Chromolaena Density, Nutrient Status, Physical and Chemical Properties, Nutrient Accretion

Woody Plants Recovery in Abandoned Farms of Different Ages in the Mount Cameroon Region

Twenty-seven abandoned farms of 400 m2 each, grouped into five different age classes (0- 2, 3-5, 6-10, 11-30 and >30 years) were assessed in 1995 in the Mount Cameroon area, along with three 400 m2 of primary forest plots, in order to assess primary forest biodiversity recovery after shifting cultivation. Three distinct groups of woody species characterised agricultural fallows: pioneers, mid-successional species and shade-tolerant species. Harungana madagascariensis, Solanum torvum and Vernonia conferta were the common pioneer species in fallows less than 10 years; Cecropia peltata, Macaranga occidentalis, Musanga cecropioides and Polyscias fulva were the abundant mid-successional species in fallows between 11-30 years, and Cyathea maniniana, Dicranolepis sp., Dracaena sp., Homalium sp., Uvariodendron sp. were the most common shade-tolerant species in fallows over 30 years. Species richness increased slowly with age of fallows but remained below that of primary forest even after 30 years.

Decomposition of bamboo (Dendrocalamus hamiltonii Nees.) leaflitter in relation to age of jhum fallows in Northeast India

Litter bags, containing bamboo (Dendrocalamus hamiltonii Nees.) leaf litter was used to compare the decomposition rates and microbial populations in litter under fallows of different ages. The age of the fallows were 0,5 and 10 years. All were developed after Jhum (shifting) cultivation.