Resultado descriptivo de la investigación

China减缓单一橡胶种植的负面环境影响：关于橡胶与当地树种混种并结合杂草管理的生态种植研究

The technology combines the integration of native tree species into rubber monocultures with changed weed management to mitigate negative environmental impacts and to provide alternative income options for farmers.

Natural rubber is a crucial renewable resource produced from the tree Hevea brasiliensis. Production is largely based on monoculture, often associated with chemical-based clean-weeding. This causes environmental problems such as loss of biodiversity, pesticide pollution and erosion of topsoil. The SLM-technology aims at mitigating negative impacts by interplanting the rubber with native tree species which have economic potential of their own. Changes in weed management are part of the package also.

Native (indigenous) tree species are integrated into mature rubber plantations. Criteria for species selection are: a) adapted to environmental conditions; b) shade tolerant; c) vertical growth not affected by light; d) conservation value; e) economic potential; f) easy to manage. Rubber trees are usually planted in rows at a spacing of 6-8 m, and an intra-row distance of 2.5 to 3 m. The native trees are planted between the rubber rows. The plantation should be mature as the canopy will have reached its highest density, and weed competition is naturally suppressed. The spacing of the native trees needs to be adapted to their growth potential and intended usage. After planting, regular monitoring is necessary to identify pests or diseases. The following species were selected for demonstration sites: 1) Parashorea chinensis, a valuable timber tree, 2) Taxus mairei, a multi-purpose tree, providing good timber but also an anti-cancer drug, taxol, and 3) Nyssa yunnanensis, selected for its conservation value. At the end of the economic life span of the rubber trees (about 30 years) there will be several options, but there are three main ones. First the rubber plantation can be replanted, although the harvest of the Parashorea chinensis trees would be premature. The Taxus mairei trees could be maintained through a new plantation cycle. Second, both, the rubber and the intercropped trees could be maintained for future timber and taxol production. Third, the plantation could be transformed into a sustainable forest managed scheme where the rubber trees are extracted step by step and the intercropped trees maintained for their intrinsic value.

Procedures for the selection and planting of the indigenous tree species are crucial.

Identification should be based on suitability for the climate and soil as well as economic potential. The raising of tree seedlings requires experience and nursery propagation by experts might be required. Only healthy seedlings should be used.

Planting should take place during rainy periods. Potted seedlings are better than bare-rooted seedlings since they establish better. Generally, weed management (if necessary) should shift from herbicide application to mechanical weeding. Grass competition needs to be avoided in any case! Controlled cover of natural undergrowth will reduce erosion and promote water infiltration.

The implementation site for the trials is located in Xishuangbanna Prefecture, Yunnan Province, SW China. The original vegetation was tropical rain and monsoon forest, but now there is a rich mosaic of different land-use and vegetation types. The whole region is exceptionally species rich and part of the Indo-Burma-Biodiversity Hotspot.

left:Rubber plantation with thriving undergrowth – no herbicides are used for maintenance (Hainan Island, China). (Gerhard Langenberger) right: Taking care of an underplanted Taxus mairei seedling in a rubber plantation in the Naban River Watershed National Nature Reserve, Xishuangbanna, China. (Gerhard Langenberger)

Location: Xishuangbanna Dai Autonomous Prefecture, Yunnan Province, PR China Region: Naban River Watershed National Nature Reserve

Technology area: 0.03 km² Conservation measure: vegetative, management

Stage of intervention: mitigation / reduction of land degradation

Origin: developed through experiments / research, recent (<10 years ago); review on available knowledge on rubber management and history (10-50 years ago)

Land use type: cropland: tree and shrub cropping (monocultures) (current); forests / natural vegetation (before), agroforestry (after) Climate: subhumid, subtropics

WOCAT database reference: T_CHN056en Related approach: A_CHN054en (Scientist-practitioner communication for sustainable rubber cultivation in China)

Compiled by: Gerhard Langenberger, University of Hohenheim, Institute of Agricultural Sciences in the Tropics, 70593 Stuttgart, Germany. [email protected] Date: 12^thFebruary 2012, updated June 2016

SLM Technologies – Integrating native trees in rubber monocultures, China

Soil depth (cm) 20-500-20 50-80 80-120

>120

Growing season(s): 270 days(April - December) Soil texture: medium (loam), fine / heavy (clay) Soil fertility: medium

Topsoil organic matter: medium (1-3%) Soil drainage/infiltration: medium

Soil water storage capacity: medium Ground water table: n/a

Availability of surface water: good Water quality: poor drinking water Biodiversity: high

Classification

Land use problems: Large-scale expansion of rubber monocultures results in the loss of topsoil and siltation of streams with respective consequences for CO2emissions (increased), soil degradation, water quality and stream ecology. The excessive application of

agrochemicals adds to these problems. The monoculture practice combined with clean weeding results in plant biodiversity loss. The related simplification of habitat structures also leads to a considerable decline in animal biodiversity (expert's point of view ). The focus of land users is primarily on sustainable income, and their environmental concerns mainly relate to water provisioning (land user's point of view). In the farmers view: “The biggest environmental problem is water quantity. Rubber sucks out a lot of water, therefore we do have a water scarcity problem”. Farmers are aware of the contamination of drinking water due to the use of pesticides and herbicides in the rubber plantations.

Land use Climate Degradation Conservation measure

tree and shrub cropping (current);

forests / natural vegetation (before) agroforestry (after)

Stage of intervention Origin Level of technical knowledge

Prevention

Mitigation / Reduction Rehabilitation

Land user's initiative

Experiments / research:recent (<10 years ago) Externally introduced

Review on available knowledge on rubber management and history: 10-50 years ago

Agricultural advisor Land user

Main causes of land degradation:

Direct causes - Human induced: deforestation / removal of natural vegetation (incl. forest fires) Indirect causes: poverty / wealth, inputs and infrastructure, governance / institutional

Main technical functions:

− control of dispersed runoff: retain / trap

− stabilisation of soil (eg by tree roots against landslides)

− increase in organic matter

− increase of infiltration

− promotion of vegetation species and varieties (quality, eg palatable fodder)

Secondary technical functions:

− improvement of surface structure (crusting, sealing)

− improvement of topsoil structure (compaction)

− increase / maintain water stored in soil

− increase of groundwater level / recharge of groundwater

Environment Natural Environment Average annual rainfall

(mm) Altitude (m a.s.l.) Landform Slope (%)

SLM Technologies – Integrating native trees in rubber monocultures, China 193

Tolerant of climatic gradual change and extremes: temperature increase, seasonal rainfall increase, heavy rainfall events (intensities and amount)

Sensitive to climatic gradual change and extremes: seasonal rainfall decrease, droughts / dry spells, decreasing length of growing period, cold spells

If sensitive, what modifications were made / are possible: the above assessment is based on the fact that the native tree species are adapted to tropical conditions. Therefore, the species should be less affected by high temperatures and increasing rainfall, but might still be sensitive to droughts. Nevertheless, there is no experience or data as yet.

Human Environment Cropland per household (ha)

<0.5 0.5-1 1-2 2-5 5-15 15-50 50-100 100-500 500-1,000 1,000-10,000 >10,000

Land user:individual / household, small-scale land users, leaders / privileged, mainly men Population density: 10-50 persons/km² Annual population growth:< 0.5%

Land ownership: state

Water use rights: complex depending if water is on village land or not

Land use rights: mainly individual

Relative level of wealth: farmers have been well off in the past, currently they are under pressure due to the very low rubber prices

Importance of off-farm income: 30%

Access to service and infrastructure: moderate:

technical assistance, employment (e.g. off-farm), drinking water and sanitation; high: health, education, market, energy, roads & transport Market orientation: commercial / market Mechanization: manual labour

Livestock grazing on cropland: no

Technical drawing

The concept is based on rubber planted in rows of ca. 7 m and within rows of ca. 2.5 to 3 m.

Intercropping takes place between the rows.

However farmers often plant at a higher density which requires an assessment of the light / shade conditions. At too high a density the light conditions can be too poor for intercropping even for shade tolerant forest trees. In this case study, the distance within a row of the intercropped trees was set at 6 m, due to the ecological characteristics of the selected tree species. Thus, in this case, the choice was for a higher density of Taxus (bold circles) which is well known for its slow growth and the two other tree species were integrated at a wider distance (dotted circles) (G. Langenberger).

Implementation activities, inputs and costs

Establishment activities Establishment inputs and costs per ha

1. Seedling acquisition and transport 2. Planting of seedlings in rainy season 3. Weed management with brush cutters.

Inputs Costs (US$) % met by

land user

Labour 80.00 100%

Equipment

− machine use 80.00 0%

− tools 8.00 100%

Agricultural

− seedlings 2400.00 0%

TOTAL 2568.00 3.5%

Maintenance/recurrent activities Maintenance/recurrent inputs and costs per ha per year

1. Control of pests and diseases Inputs Costs (US$) % met by

land user

Labour 96.00 100%

TOTAL 96.00 100%

Remarks: Seedling costs are the major cost factor. Since the selected species are unusual and are not readily available they are very expensive. Because Taxus is also a medicinal plant, this might also have influenced the price. All other costs are practically negligible. In this case the establishment of a nursery might considerably reduce the costs, since propagation (at least of Taxus and Parashorea) is easy if the seeds can be acquired. The costs are based on the establishment of 3 demonstration plots of ca. 1 ha each. It should be possible to considerably reduce the costs by producing seedlings on site.

Assessment

Impacts of the Technology

Production and socio-economic benefits Production and socio-economic disadvantages increased labour constraints

Socio-cultural benefits Socio-cultural disadvantages

improved conservation / erosion knowledge

Ecological benefits Ecological disadvantages

reduced surface runoff improved soil cover increased water quality

increased biomass and above ground carbon Off-site benefits

reduced downstream siltation

improved buffering / filtering capacity (by soil, vegetation, wetlands)

reduced groundwater / river pollution

reduced erosion and pesticide inputs contribute to water security and maintain stream ecology

Off-site disadvantages

Contribution to human well-being/livelihoods

Since we are still at an experimental level there isn't yet any experience.

Benefits/costs according to land user Benefits compared with costs short-term: long-term:

Establishment negative positive

Maintenance/recurrent positive very positive The establishment costs for the demo-sites have been very high, but could be considerably reduced if adopted by more farmers.

The assessment above therefore needs verification in the course of time.

Acceptance/adoption: Three families have been approached for testing in different areas of the Xishuangbanna prefecture. They have been supported by external material support. There is little trend towards (growing) spontaneous adoption of the technology, although there is an increasing interest. But due to the lack of experience and the lack of affordable and accessible seedlings farmers were hesitant.

Concluding statements

Strengths and ^how to sustain/improve Weaknesses and ^how to overcome The technology offers considerable long-term advantages to

farmers. After establishment it doesn't require much labour  A proper and sustainable extension service is required to accompany the development of the technology. Government subsidies for establishment of seedlings would certainly increase the number of farmers adopting the concept.

Additional income options  It diversifies the product portfolio with good options for additional income in the future.

The technology is based on a long-term perspective and thus favours farmers who have a such an outlook. But farmers with little land usually think short-term  The current trend of rural-urban migration will support the technology since it can be easily combined with farm work. According to SURUMER findings off-farm income already contributes about one third of the overall household income in the rubber growing areas.

Current establishment costs are very high due to the lack of a seedling market  If the technology becomes known and popular, more nurseries will produce seedlings which will reduce costs.

Alternatively, farmers might establish their individual (or community) nurseries.

The technology requires considerable knowledge about tree ecology and tree breeding  There should be extension officers at the local agricultural or forestry bureaus supporting farmers.

High investment costs  Government subsidies

Time until first returns can be expected. 5-10 years for taxol production)

Key reference(s): Ahrends, A. et al. (2015) Current trends of rubber plantation expansion may threaten biodiversity and livelihoods. Global Environ Change, 34, 48-58. • Langenberger, G. et al. (2016) Rubber intercropping: a viable concept for the 21st century? Agrofor Syst, 1-20. • Liu, H. et al. (2016) Impact of herbicide application on soil erosion and induced carbon loss in a rubber plantation of Southwest China. CATENA, 145, 180-192.

Contact person(s): Gerhard Langenberger, University of Hohenheim, Institute of Agricultural Sciences in the Tropics, 70593 Stuttgart, Germany, [email protected] • Feng Liu, Naban River Watershed National Nature Reserve Bureau, Jinghong, China, [email protected]

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Scientist-practitioner communication