Sustainable use of Miombo woodlands

July 23, 2014

When is the use of fuel wood and poles from Miombo woodland sustainable – when we move people out to protect the woodlands, or when we apply simple silvicultural practices to sustain resource use for rural livelihoods? Can we talk about degradation and deforestation when clearing of Miombo woodland is essential to maintain plant diversity and productivity in healthy systems? In plantation forestry, we apply intensive silvicultural management to provide for productive and sustainable timber resources of good quality. Why can we not apply silvicultural management for productive replacement of harvested trees from the woodlands for subsistence or commercial benefits? Do we really conserve diversity and productivity through protecting woodlands?

by Dr Coert J Geldenhuys

Closed woodland during rainy season in Malawi.
Miombo poles of various sizes used in diverse constructions on a typical farm.

 
Introduction

Rural small-scale farmers in the Miombo woodlands are marginalised when governments issue concessions for large-scale commercial enterprises (commercial timber concessions, plantation forestry, agricultural crops, and protected areas) over large areas. Financial incentives to farmers for not clearing land or cutting trees for fuel wood and poles through REDD+ (reduced emissions from degradation and deforestation) often do not benefit the rural farmers. The outgrower scheme for tobacco production through >300 000 small-scale farmers, provide direct financial benefits to the farmers but has been criticised as contributing to deforestation through clearing land for growing tobacco and using large amounts of poles and fuel wood for tobacco curing. Will growing of eucalypts and other crops of introduced tree species really provide cost-effective alternative sources of fuel wood and poles? What are the options to ensure sustainable, integrated multiple-use rural development in Miombo woodlands?

What is Miombo woodland?
It is the dominant vegetation type in the Zambezian woodlands, the largest vegetation formation in southern Africa, and is dominated by Brachystegia species, with or without Julbernardia and/or Isoberlinia species. It is a tropical summer-rainfall zone with 500-1 400mm/annum falling during November to April, followed by a severe, six-month dry season. Woodland structure varies from closed to open stands, to wooded grassland to scrub woodland, depending on climate and soil conditions, but probably more importantly, on disturbance factors such as fire, drought, frost, browsing by wildlife and livestock, and resource use (including crop cultivation). Most Miombo species are light-demanding and have developed vegetative regrowth (sprouting) from thick rootstocks and/or stems in response to browsing (including fire as a non-selective browser), similar to the Australian eucalypts. They do not establish under low light conditions under the canopy. Sprouting enables rapid recovery of plant diversity and productivity; even when mature, often moribund, stands are degraded or cleared. Most stands, therefore, have trees of similar age and size. Healthy Miombo woodlands should have stands in different stages of recovery, from young regrowth, to advanced re-growth, to mature woodland, with some old-growth stands, and provide the basis for sustainable resource use. Extensive areas of secondary woodland in southern Africa have developed in this manner.

Rural resource use
Woodlands provide a wide range of potential timber, non-timber and non-wood products to different users (local households, formal local and regional businesses), and crop cultivation. Clearing for cropping and collection of poles of different sizes (houses, storage facilities, sheds, barns, fences, etc.) and fuel wood (firewood and possibly charcoal) are the main reasons for the observed change from closed to open mature stands, and then to scrub where most tree species occur in short stands with coppicing stems. There are always potential conflicts in the harvesting and use of woodland products, which often leads to excessive use and great wastage of resources. For example, the small-scale tobacco farmer has to ensure an ongoing source of fuel wood and poles in a way that would maintain the environment (plant and animal species, and their natural processes of regeneration and growth) and local livelihoods (food, medicines, cultural activities, etc.), within the laws, regulations and customs of the country. Commercial ventures increase such conflicts.

Sustainable woodland management
Woodland management, like management of any other natural woody system, is the process of matching resource use needs with resource availability in different vegetation and landscape units, considering the ecological constraints of regeneration and productive growth of the species. If this can be done in Miombo woodlands, then the direction of change can be reversed. Integrated multiple use should reduce conflict and wastage (see SA Forestry Magazine’s August 2013 issue, pages 36-37) and is essential in the sustainable management of Miombo woodland. It requires consideration of the different users in a village and the broader range of stakeholders, and the different woodland development stages in the resource area.

Silvicultural management should aim for regeneration and establishment of the desired species (commercially useful and ecologically important): the main criterion of a successful silvicultural system.

A multiple silvicultural system for Miombo woodland should include:

• controlled group felling of trees (with gap diameter ±three times stand height) in mature woodland to allow regeneration and fast growth of the light-demanding species;

• coppice management in secondary woodland through selective pruning of branches for straighter stems and reduced dead stem knots, selective stem thinning to remove stems of poor form, retain stems of good form and

• productive growth, and to create growing space (stand hygiene) for better height and diameter growth; and

• fire management in the broader landscape to reduce fuel loads and competing grass cover to ensure regeneration of some species and survival of others.

Five woodland development stages have been identified, and provide the basis for selective pruning and thinning in silvicultural management:

• Stage 0 is woodland that had been cleared for cyclic crop production. Main action is to not remove rootstocks of cut trees.

• Stage 1 is an early development stage with short multi-stem plants (<2m height), but with productive and most diverse regrowth. The main action is selective branch pruning and limited stem thinning.

• Stage 2 is an intermediate development stage with many young pole-sized stems (<5cm stem diameter, 2-5m height). The main action is more focused, selective stem thinning and branch pruning to retain trees of good stem form and productive growth.

• Stage 3 is advanced secondary woodland with young trees (>5cm stem diameter, 5-15m height). The main action is selective thinning of less good stems and a last effort towards branch pruning (thick branches have poor recovery of pruning scars).

• Stage 4 is mature to old-growth stands with most trees in mature stage. The main action is group felling of trees if canopy tree species do not regenerate, to restart the cycle.

Such silvicultural management is in tune with the ecology of targeted tree species. It will provide a regular supply of firewood, and periodic supply of poles; initially laths, then poles for various uses, and then trees for house and fence construction (and other uses). It does not increase costs for the farmer but rebuilds diverse and productive Miombo woodland for the future, through the free supply of sunlight, carbon dioxide from the air, and moisture and nutrients from the soil. |

Mosaic of scrub woodland within wooded grassland in dry season in northern Mozambique.
Rootstock of Afzelia quanzensis (Chamfuta), the typical system for vegetative regrowth of many Miombo tree species.
Selective pruning and thinning during normal harvesting of firewood and poles can improve the productive growth of quality poles for the future and improve stand condition and recovery of the woodlands.
 
Stand development stages in the recovery of Miombo woodland after clearing for crop cultivation
Stage 0, with early diverse and productive sprouting
Stage 1, with young regrowth.
Stage 4 or old-growth Miombo woodland (moribund) with large trees of a few species and very few to no regeneration. This stage requires clearing to rejuvenate the system.

 

* Dr Geldenhuys is a Forest Ecologist/Associate Professor in Forest Science, Department of Forest & Wood Science, University of Stellenbosch
Tel: +2782 776-1593; cgelden@mweb.co.za

**Published in April 2014

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