Technical Report of theRestoration of a section of the Witteklip River as part

of the Pilot Project for Rehabilitation of the Kouga

River

Master Oficial en Restauración de Ecosistemas

José David Díaz González

Problem description Objectives Site description

Characterization of study site

General diagnose

Review of activities Experiments performed

Conclusions

Problem: ◦ Riparian areas invaded

effects on water yield biodiversity loss soil degradative processes

◦ Situation of special concern for the Nelson Mandela Metropolitan Municipality

Problem description

Cause of the problem: ◦ Initial degradation derived from overgrazing◦ Current degradation caused by Black Wattle

(Acacia mearnsii, Fabaceae) Invasive alien plant for South Africa: Transformer

status Well documented effects on reducing water yield and

in altering indigenous plant structure. Persistent long-lived seeds favored by fire

Problem description

Objectives

Of the Kouga Riparian Rehabilitation Project

Defining the most efficient protocol to clear and restore areas invaded with Black Wattle (Acacia mearnsii)

Of the Practicum

Description of restoration activities in a section of the Witteklip River

Evaluate the possibilities of using fire or transformation of wood to chips, as methods for the disposal of the Black Wattle residues

Objectives

Site description: General location

Feature Description

Climate Annual average rainfall average: 540 mmMaximum temperature: 23.7ºC (warmest month: March)Minimum temperature: 11.74ºC (coldest month: July)Relative Humidity: Maximum: 80%; Minimum: 55%

Geology Southern Folded Mountains.

Soil description

Minimal developmentUsually shallow, on hard or weathering rockIntermittent diverse soils Rock with limited soils (association of Leptosols, Regosols, Durisols and Calcisols). Lime is rare in the landscapeSoil loss for the area, as predicted by the RUSLE model, describes it as Very Low to Low

Site description: Physical Environment

Feature Description

Fauna Different species of antelope e.g. duiker (Sylvicapra grimmia), springbok (Antidorcas marsupialis); Snakes e.g. Cape cobra (Naja nivea), Puff adder (Bitis arietans); Birds e.g. Black Eagle (Aquila verreauxii), Stanley Bustard (Neotis denhami)

Vegetation Humansdorp Grassy Fynbos: with these and other families represented: Trees: Anacardiaceae, Apiaceae, ProteaceaeForbs: Asteraceae, Brassicaceae, EuphorbiaceaeGeophytes: Iridaceae, PteridaceaeSedges: CyperaceaeRestios: RestionaceaeGrasses: PoaceaeShrubs: Asteraceae, Ebenaceae, MyricaceaeWoody herbs: Crassulaceae, Rutaceae, Papilionoideae

Socioeconomic environment

120,000 years ago: San, followed by the Khoikhoi and later by the Koisan. Mid 18th century: European settlement: Main productive model: agrarian and pastoral farming.

Site description: Physical Environment

The Lower Witteklip Restoration Area:◦ Witteklip River, which in turn is tributary of the

Kouga river. ◦ The Kouga River Catchment, represents a key

water source for the Nelson Mandela Bay Metropolitan Municipality,

Site description: Description of the river

Characterization of study site:Longitudingal profile of the Witteklip

River

General dyagnose for the study site

Protocol for the Evaluation of the Ecological Status of Mediterranean rivers (RBP)

QBR index: evaluate riparian quality

IHF index: physical habitat

Feature Characteristic Punctuation

Percentage of riparian zone

cover

< 10% of vegetation cover of the riparian zone

0

Cover structure Less than 10% of cover composed of trees or shrubs

0

Quality of the cover

No indigenous trees 0

Nature of the fluvial channel

The river channel has not been modified

25

TOTAL 25

Rating extremely degraded

site very low quality

Blocks Punctuation

Inclusion of rapids and ponds

Ponds: Sedimentation 0-30% 10

Rapids frequency

Constant laminar flow or shallow rapids 4 Substrate composition

% of blocks and stones 1 - 10% 2 % of gravel > 10% 5

% of sand > 10% 5

% of stilt and clay 1 - 10% 2 Speed/depth regimes No water found 0 Percentage of shade to the channel Exposed 3 Heterogeneous elements

Litter >10% or <75% 4

Presence of logs or stems 2 Exposed roots 2

Percentage of aquatic vegetation

% of Phanerogams and Charales

< 10% or > 50% 5

Total Punctuation 44

extremely degraded site with a very low quality

Site can have a partial success in holding aquatic biota with the initial situation observed

General diagnose for study site: Digital image of site, 2001

Review of the clearing and rehabilitation

activities in the study site• Clear-cutting all Acacia

mearnsii trees

• Application of herbicides to suppress resprouting

• Wood stacks piling and drying for 3 months

• Biomass burning

• Restoration of plant cover

• Restoration

• Management of seedbank

Experiments performed:Biomass burning

Assessment of temperature in first 5 cm of soil:◦ Soil-stored seed banks

in fynbos tend to be concentrated in the upper 3–5 cm of the soil

◦ What temperatures are reached under different conditions of biomass loads?

Labels with temperature sensitive paint.

Color changes permanently when exposed to heat for more than ten minutes

Sets placed at: Surface, 2 cm, 5 cm

Results: Biomass burning

Fuel load - temperature

Influence of depth Highest temperature

peaks High temperatures

more likely to happen in the surface.

Discussion: Biomass burning

Experiments assisted:Revegetation

Identify species or guilds and densities which would effectively restore the ecological functions for invaded areas

◦ 98 planting plots divided into two sub-plots: Burned and not burned

◦ Treatments:

◦ Control

◦ High density planting

◦ 9 plants/m²

◦ Low density planting

◦ 4 plants/m²

◦ Seeding and planting

◦ Eragostis tef sowing

Revegetation:Distribution of paired plots

Revegetation with a mixture of native species selected by the R3G researchers under several considerations: ◦ Species from surrounding, uninvaded reference

sites◦ Species whose seeds could be collected,

propagated and established well with relative ease:◦ Species that would grow quickly: this would

potentially suppress alien recruitment.◦ Species that will provide good ground cover: This

selection criteria considers the risk having bare ground exposed to erosion.

Revegetation:Criteria for species selection

Revegetation:Conditions recommended for planting

riparian vegetation in alien invaded fynbos

Condition Situation in study site 1.   Indigenous vegetation present, possible propagules

Long term and dense invasion from the Black Wattle. Seedbank is assumed to be poor.

2.   Severe fire has gone through the area, seed banks will have been severely depleted.

Evidence of previous fires is seen in the study site. Erosion is not evident. Active restoration is considered the main strategy for intervention.

3.   If pockets of indigenous scrub persist along the river, these species will recolonize over time.

There are no pockets of remaining scrub in the catchment, and active planting will be applied.

4.   Riparian scrub species may be established from rooted cuttings or seedlings transplanted in the field.

-

5.   Sowing should be done directly onto bare ground with the seed lightly raked into the soil or covered by light wood chip mulch

6.   Planting is best done under similar conditions to the sowing treatment although

Planting and sowing were done without wood chip mulch during early spring.

Experiments performed:Management of seedbank

Comparison of two methods to eliminate unwanted biomass left after large scale Black Wattle clearing: ◦ Burning◦ transformation to wood

chips, What happens to the

seedbank?◦ From Black Wattle?◦ From the other species?

Results: Management of seedbank

Results: Effects of soil preparation methods on soil seedbank

Results: Management of seedbank

Estimated germination means for Black Wattle and the other species group, separated by temperature range.

Germination of Black Wattle increased with the burned treatment ◦ Control and wood chips treatment: almost no germination

Other species group, germination was observed but low in wood chips and control. ◦ Not possible to define if germination in the controls section

(sand control, wood chips control) was a result of the presence of seeds in the sand control or in the wood chips

Results dependant on:◦ the treatments

◦ low seed rain

◦ depletion of surface seedbank

◦ not enough time for germination

Similar experiments: final results in 12 months

Discussion: Management of seedbank

Black Wattle: ◦ Reduced presence of indigenous species in the

study site◦ Decreased the quality of the riparian vegetation

which was almost absent

Fell and Burn method, ◦ Possible outbreak of Black Wattle with few

indigenous species present

Conclusions

Soil temperature: ◦ Surface temperature◦ Large logs on wood stacks

Soil seedbank◦ Germination of Acacia mearnsii◦ Germination of other species

No separation between other species, did not allow to define groups of species, families or plant growth forms

Unclear which treatments influenced on the results obtained.

Time for experiments, was not enough

Conclusions

¡Muchas gracias!