IDE ADD-ON PROTOCOL: INCLUDING GRAZING EFFECTS

ADD-ON PROTOCOL TO THE INTERNATIONAL DROUGHT EXPERIMENT (IDE): STUDYING COMBINED EFFECTS OF DROUGHT & GRAZING (‘DROUGHTACT’)

Version 1.2 (November 23rd 2015)

Idea and concept: Anja Linstädter1 & Jan C. Ruppert1,2

1 Range Ecology and Management Group, Botanical Institute, University of Cologne, Zülpicher Str. 47b, D-50674 Cologne, Germany

2 Plant Ecology Group, University of Tübingen, Institute of Ecology and Evolution, Auf der Morgenstelle 5, D-72076 Tübingen

Email Anja: anja.linstaedter@uni-koeln.de Email Jan: jan.ruppert@uni-tuebingen.de

1. What is DroughtAct?

DroughtAct is a facultative extension (Add-On) of the International Drought Experiment (IDE), an

activity of the Drought-Net consortium. It seeks to study combined effects of drought and grazing. In

this way, it aids to better understand their potentially interactive (Ruppert et al. 2015), yet partially

convergent effects (Linstädter et al. 2014) on ecosystems functioning and ecosystem service provision.

DroughtAct also allows transferring the IDE approach (that requires undisturbed/pristine sites) to

ecosystems which are subject to herbivory by wild or domestic herbivores. The sampling procedures of

DroughtAct are fully compatible with the core IDE protocol. It simply adds a grazing treatment (clipped

vs. unclipped, or grazed vs. ungrazed), doubling the number of treatments to four (see Table 1).

To join our network adding grazing to the IDE, you thus need to double the number of rainout shelters.

If small rainout shelters of 3 x3 m are feasible in your case (see section 2), you will need at least eight

shelters instead of four (n ≤ 4), if you go for large rainout shelters (6 x 6 m) you will need at least six

shelters instead of three (n ≤ 3).

Treatment Explanation of factorial combination

G D

G- D- Ambient precipitation without grazing / clipping G- D+ Extreme drought without grazing / clipping G+ D- Ambient precipitation under grazing / clipping G+ D+ Extreme drought under grazing / clipping

Table 1: Treatments (G = grazing/clipping, D = drought; absent and present: - + respectively) and their

factorial combinations in DroughtAct. We use the term ‘grazing’ to describe any form of herbivory here.

2. Grazing or clipping – which option to choose?

When joining the DroughtAct consortium, you need to decide whether you will go for a ‘Simplified

DroughtAct’ (clipping) or for the ‘Full DroughtAct’ (actual grazing). Please consider six main criteria.

2.1 Presence of vertebrate herbivores

The most important point to consider when choosing between these two options is whether domestic

herbivores (e.g. goats, sheep, cattle, camels) or wild/ semi-domestic herbivores (e.g. kangaroos,

antelopes, rabbits, reindeers) are actually present in sufficient numbers and densities in your intended

study area. Game reserves, rangelands or pastures are thus ideal for the Full DroughtAct.

IDE ADD-ON PROTOCOL: INCLUDING GRAZING EFFECTS

2.2. Vegetation properties

The suggested plot size of the Simplified DroughtAct complies with the minimal dimensions of sampling

plots in the IDE protocol (2 x 2 m). These dimensions are appropriate for homogeneous herbaceous

vegetation (e.g. grasslands dominated by stoloniferous grasses). For sites with non-herbaceous and/or

patchy vegetation (e.g. grasslands dominated by tuft grasses, and most shrublands), we recommended

the Full DroughtAct, which is scaled up (and corresponds to the 4 x 4 m sampling plots of IDE). You

should also consider if your vegetation might become patchy after grazing is excluded for several years

(G-); for example, homogeneous ‘grazing lawns’ characteristic for African savanna grasslands (Cromsigt &

Olff 2008) may quickly develop into a grass layer dominated by isolated tuft grass individuals (Linstädter

2009). It is thus advisable to check vegetation structure under lightly grazed or ungrazed conditions. Only

if you have very homogenous vegetation AND solely smallstock (sheep, goats) present, you might opt

for ‘real’ grazing using the small rainout shelters (3 x 3 m). In this case, make shelters higher (≥ 1.4 m)

to ensure that cages can be placed underneath, and that grazing animals could enter from all sides.

2.3. Size of your study site

The Simplified DroughtAct uses the minimum shelter size for the IDE (3 x 3 m), and can be performed on

a comparatively small area (ca. 20 x 20 m). In contrast, the Full DroughtAct uses large shelters (6 x 6 m),

and thus requires a study site of min. 50 x 50 m. Rainout shelters in grazed areas need to be large for

two reasons: (1) To allow large herbivores to freely roam and graze underneath; (2) To account for a

grazing-induced patchy vegetation (although it might also homogenize vegetation; see section 2.2).

Hence we need nested replications, and these also require larger sizes of the sheltered area. Within our

DroughtAct pilot study installed 2014 in a South African savanna rangeland, the shelter size of 6 x 6 m

(> 1.7 m height on the lower side) and a plot size of 4 x 4 m has proven sufficient for grazing treatments.

2.4. Size of your budget

We estimate material and construction costs for the Full DroughtAct of ~8,000 €, and thus 2-3 times

more than for the Simplified DroughtAct. These estimations are mainly based on experiences from our

(full) DroughtAct pilot study; local differences in material and construction costs may occur.

2.5. Compatibility with NutNet and the IDE Snow Removal Add-On

The suggested plot size & sampling procedures of the Simplified DroughtAct (building on the minimal

dimensions of an IDE plot) are compatible with those for a 2 x 2 m subplot in the Nutrient Network

(NutNet), with the small exceptions that the DroughtAct plot is surrounded by a 0.5 m buffer (0.25 m in

case of NutNet), and that the area for annual biomass sampling slightly differs (0.25 m² vs. 0.20 m²). This

makes it quite easy to integrate NutNet and DroughtAct via a full factorial treatment combination.

Moreover, the IDE Snow Removal Add-On is also compatible via a split-plot design (contact Hugh Henry,

its initiator, or us if more information is required). For the Full DroughtAct approach, slight modifications

of the spatial design are required to integrate herbivore caging treatments of NutNet (treatments 9 &

10); contact us if you are interested.

2.6. Feasibility of repeated (monthly) clipping during the vegetation period

The clipping treatment in the Simplified DroughtAct requires elaborate manual work (with monthly

visits in the growth period) to simulate selective herbivory. This might be considerably more time-

consuming than biomass sampling under the grazed conditions of the Full DroughtAct (where a singular

biomass harvest at the time of peak standing crop could be sufficient).

Given the qualitative difference between (unselective) clipping and selective herbivory (Arnold 1964; Li

et al. 2015), we strongly recommend adopting the Full DroughtAct (actual grazing) whenever possible.

IDE ADD-ON PROTOCOL: INCLUDING GRAZING EFFECTS

General recommendations for replications and biomass sampling 3.1. Treatment replications

In accordance with the IDE protocol for small and large plots, you should replicate your treatments at

least three times (n = 4) in the Simplified DroughtAct, and two times (n = 3) in a Full DroughtAct

experiment. Plots may be organized randomly or in a blocked design; we recommend the latter.

3.2. Selection of biomass sampling procedures

For biomass sampling, we suggest destructive methods (and give detailed instructions for them), as

these methods tend to be more accurate compared to non-destructive sampling (allometry). Moreover,

researchers tend to underestimate efforts and caveats of producing robust allometric models. In

accordance to the IDE protocol, our plot layout offers sufficient destructive sampling area to avoid

biomass harvests on the same area. Also note that biomass sampling to be used for an estimation of

aboveground net primary production (ANPP) has to be attuned (1) to vegetation characteristics

(herbaceous vs. non-herbaceous; patchy vs. non-patchy), and (2) to the seasonality of the ecosystem

(sequential biomass sampling vs. peak standing biomass sampling). Please refer to relevant literature for

the selection of a biomass sampling procedure (Scurlock et al. 2002; Fahey & Knapp 2007; Ruppert &

Linstädter 2014), refer to the NutNet protocol and/or contact us.

4. Sampling protocol for the Simplified DroughtAct: Simulated grazing via clipping

4.1. General layout

Sampling areas should be selected carefully. Plots should have representative vegetation and should

not show signs of severe disturbances such as recent fire or digging by large ground-dwelling animals;

signs of grazing (including trampling) are unproblematic. Each sampling plot, irrespective of treatment,

has a quadratic shape (see Fig. 1a for a general layout of treatments, plots and subplots). A plot’s

recommended [minimal] dimensions are 2 x 2 m with a 0.5 m buffer strip around (total size plot plus

buffer: 3 x 3 m). Small rainout shelters (3 x 3 m; > 0.8 m high) will be installed above D+ plots (& buffer

strips). Trenching is strongly recommended (see IDE protocol). All plots will be subdivided into four

subplots of 1 x 1 m (see Fig. 2 for details). One subplot is selected for permanent sampling. It will serve

for community composition sampling and for functional trait sampling. The permanent subplots in

grazed (or actually clipped!) treatments (G+D- and G+D+) are named GRA (for grazed); those in non-

grazed treatments (G-D- and G-D+) are named LTE (for ungrazed long-term exclosures treatments). The

other three subplots per plot will serve as biomass sampling subplots (BM for biomass) and for soil

sampling. For estimations of plant cover, and for soil and trait sampling, please refer to the IDE protocol.

At sites where wild or domestic herbivores occur nearby, clipping activities will mimic defoliation

patterns of the grazed area. For doing so, a ‘paired pattern plot’ of the same size as the permanent

subplot (1 x 1 m) should be selected (Fig. 2), more than 5 m away from any sampling plot to omit

confounding effects of treatments. The intensity and selectivity of grazing on this plot will be mimicked

by clipping plots which are subject to herbivory (G+D- and G+D+). The other plots (G-D- and G-D+) should

NOT be clipped at any time and even have to be protected from grazing (via cages or fences) if

herbivores are present. The paired pattern plot should be as similar (in vegetation composition &

structure) to clipped plots as possible. Researchers may choose to select a paired pattern plot for each

clipped plot, but a single pattern plot per replication set or site will be sufficient. To ensure similar

vegetation, the paired pattern plot should be identified prior to first growing season with treatments

(at the end of the pre-treatment growing season, as it is difficult to see similarities in the dry season).

IDE ADD-ON PROTOCOL: INCLUDING GRAZING EFFECTS

4.2. Clipping procedures on G+ plots

All four subplots of the grazing-treatment plots (G+D- and G+D+, see Fig. 2a, c) are meant to be

clipped; this includes the permanent subplot (GRA), as well as the three biomass sampling subplots

(BM). Hence, you need to clip the whole plot area of 2 x 2 m (4 m²).

Plots with non-grazing treatments (G-D- and G-D+, see Fig. 2b & d) are NOT to be clipped.

Clipping is meant to mimic the observed grazing pattern on paired pattern plots. It should be

performed in an as similar as possible way with regard to preferential patterns of defoliation

(selectivity) as well as the amount of removed biomass (intensity).

Where wild or domestic herbivores are absent, clipping should impose a realistic grazing intensity.

Sites under near-natural and unmanaged conditions can be assumed to be under light utilization by

wild herbivores only, whereas regions characterized by livestock production usually exhibit moderate

to heavy utilization. A total seasonal removal of 30% of the peak standing biomass at a site

resembles light, 50% removal a moderate and 65% removal a heavy utilization (Smart et al. 2010).

Repeat clipping monthly throughout the growing season; remove clipped biomass from subplots.

For annual biomass sampling units, i.e. the subplot area dedicated for biomass sampling of the

respective year (proposed size 0.5 x 0.5 m; Fig. 2a & c), the clipped biomass is collected. It is sorted

by biomass class (living green & current year’s dead, and previous year’s dead material); life biomass

is sorted into growth form (grass, legume, non-leguminous forb, and woody). Samples are packed in

appropriate bags (paper bags or plastic bags with air holes), labeled (date, treatment, replication,

biomass class, growth form), dried (at least 48hrs at 60°C) and weighed to the nearest 0.01 g.

4.3. Suggested procedures for ANPP estimation (via destructive biomass sampling)

Please see our general recommendations (section 3) for biomass sampling. Also note that the

procedure below is tailored for herbaceous-dominated vegetation with a marked seasonality.

Aboveground biomass should be assessed at the time that coincides with peak standing crop.

All (!) annual biomass sampling units (0.5 x 0.5 m) dedicated for biomass sampling of the respective

year (including those in G- treatments) are harvested. Cut all herbaceous plants rooted within the

sampling unit to stubble height (ca. 5 cm). For shrubs and subshrubs rooted within the sampling

unit (growth form ‘woody’), harvest leaves and young twigs (current year’s woody growth).

Following the IDE protocol, harvested biomass will be separated into live and dead biomass. Dead

biomass will be further separated into current and previous year’s when appropriate. Live biomass

will be further separated by growth form (grasses, legumes, non-leguminous forbs, and woody).

Note that non-destructive methods might be more feasible for the woody growth form (section 3).

If possible, separate biomass into the following six categories (according to the NutNet protocol):

1. previous year’s dead, 2. current year’s bryophytes, 3. current year’s graminoids (grasses, sedges,

rushes), 4. current year’s legumes, 5. current year’s non-leguminous forbs, and 6. woody.

An additional separation of categories 3-5 into ‘perennials’ and ‘annuals’ would be highly desirable.

Proceed with biomass samples as with clipped biomass (see 4.2).

For G+ treatments, biomass data from clippings and from the final harvest are used for ANPP

estimation, using an appropriate estimation algorithm (Scurlock et al. 2002; Fahey & Knapp 2007;

Ruppert & Linstädter 2014). For G- treatments, the harvest at peak standing crop equals ANPP.

4.4. Grazing offtake

Grazing offtake, the proportion of ANPP consumed per season, will be quantified by summing the

clipped biomass from G+ treatments and representing it as a fraction of ANPP.

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5. Sampling protocol for the Full DroughtAct: Grazing by wild or domestic herbivores

5.1. General layout

Sampling plots should be selected thoroughly. Plots should have representative vegetation and should

not show signs of severe disturbances such as recent fire or digging by large ground-dwelling

vertebrates; signs of grazing (including trampling) are unproblematic. Each sampling plot, irrespective of

treatment, has a quadratic shape (see Fig. 1b for a general layout of treatments, plots and subplots). A

plot’s recommended [minimal] dimensions are 4 x 4 m, with a 1 m buffer strip around (total size plot plus

buffer: 6 x 6 m). Large rainout shelters (6 x 6 m, > 1.7m high) will be installed above D+ plots (& buffer

strips); see Figs. 4 & 5 for a photo and a construction drawing of shelters, as used in our DroughtAct

pilot study. Trenching is strongly recommended (see IDE protocol). Each plot will be subdivided into 16

quadrats of 1 x 1 m (see Fig. 3). The quadrats will be grouped into three subplots of an irregular shape

(à 5 quadrats), and a grazing-offtake subplot. In each subplot, 1 quadrat is selected for permanent

sampling. This permanent subplot (or rather sub-subplot; we skip the second ‘sub’ here) will serve for

community composition sampling and for functional trait sampling. Permanent subplots in grazed

treatments (G+D- and G+D+) are named GRA (for grazed); those in non-grazed treatments (G-D- and G-

D+) are named LTE (for ungrazed long-term exclosures treatments). The remaining four quadrats per

subplot will serve as biomass sampling subplots (named BM for biomass), and for soil sampling. For

community composition assessment, as well as soil and trait sampling, please refer to the IDE protocol.

In contrast to the Simplified DroughtAct with only one permanent (LTE or GRA) subplot per plot, there

will thus be three of them here, serving as nested replications within a plot (see section 2.3 for our

motivation). Each permanent (GRA or LTE) subplot has four adjacent BM subplots, which will be

sequentially used as annual biomass sampling units in the course of the four treatment years, to avoid

double harvesting (cf. IDE protocol). In grazing treatments (G+D- and G+D+, Fig. 3a, c), the fourth (small

quadratic) subplot is used for grazing offtake estimation, it is a spare subplot in G- treatments.

5.2. Ungrazed treatments (G-): Permanent grazing exclusion on whole plot area via fences

The plots with grazing exclusion treatments (G-D- and G-D+, Fig. 3b, d) have to be protected from grazing

throughout the course of the whole experiment, and hence should best be fenced-off. Fences should

have the same size as rainout shelters (minimal dimensions 6 x 6 m) to allow for a 1 m buffer around the

plot. Build quality and number of fencing wires has to be adapted to the type of herbivores present.

For cattle, fences of 1.4 m height with 5 lines of (barbed) wire are sufficient, whereas fences should have

6-8 lines of barbed wire where sheep or goats are present. Where wild bovidae are present, fences

should have an increased height of 2 m or 2.4 m, ideally. Refer to the Fence Protocol of NutNet for

helpful suggestions on proper fence installation, as well as guess-timated prices and weights.

5.3. Grazed treatments (G+): One-year protection of BM subplots from grazing via cages/ small fences

To provide meaningful biomass data for ANPP estimation in grazed treatments (G+D- and G+D+), the BM

subplots to be harvested in the current season have to be protected from grazing throughout the season.

In herbaceous vegetation, season-long protection from grazing can best be realized via moveable cages,

in non-herbaceous vegetation (dominated by shrubs and/or subshrubs), small fences can be

recommended. Cages and fences can be of different design (Fig. 6). Sturdy constructions (Fig. 6a, c) are

better for sites grazed by cattle or other bovidae (as these animals often use the cages to rub their skin).

Cages and fences should have a minimum height of 1.2 m; in areas grazed by goats, a lid is compulsory.

IDE ADD-ON PROTOCOL: INCLUDING GRAZING EFFECTS

At ground level, they should have a minimum size of 1.2 x 1.2 m to allow a buffer zone of 0.1 m around

the biomass sampling area (1.0 x 1.0 m).

5.4. Suggested procedures for ANPP estimation (via destructive biomass sampling)

Please see our general recommendations (section 3) for biomass sampling. Also note that the

procedure below is tailored for herbaceous-dominated vegetation with a marked seasonality.

Biomass is only sampled in the designated BM subplots (Fig. 3). Four BM subplots are allocated to

each of a plot’s three permanent subplots (GRA1-3 or LTE1-3). In the first year, the BM subplots

labeled as ‘year 1’ are meant to be harvested, those labeled with ‘year 2’ in the second year, etc.

Hence, in each year 3 BM subplots per plot are harvested. Given three BM subplots per treatment,

four treatments replicated (at least) 2 times, we have 3 x 4 x 3 = 36 BM subplots harvested annually.

During the dry season – preferably just before the growing season starts – place a moveable cage or fence around the BM subplots in grazed treatments (G+D- and G+D+), leaving a buffer zone of 0.1 m around the sampling area. Anchor cages thoroughly using metal anchors (U-bended metal-rods).

At the time of peak standing biomass, remove cages/ fences (in G+ treatments).

All BM subplots dedicated for biomass sampling of the respective year (= annual biomass sampling

units) are harvested; this includes BM subplots in G- treatments.

Cut all herbaceous plants rooted within the sampling unit to stubble height (ca. 5 cm). For shrubs

and subshrubs rooted within the sampling unit (growth form ‘woody’), harvest leaves and young

twigs (current year’s woody growth). Following the IDE protocol, harvested biomass will be

separated into live and dead biomass. Dead biomass will be further separated into current and

previous year’s when appropriate. Live biomass will be further separated by growth form (grasses,

legumes, non-leguminous forbs, and woody).

Note that non-destructive methods might be more feasible for the woody growth form (section 3).

If possible, separate biomass into the following six categories (according to the NutNet protocol):

1. previous year’s dead, 2. current year’s bryophytes, 3. current year’s graminoids (grasses, sedges,

rushes), 4. current year’s legumes, 5. current year’s non-leguminous forbs, and 6. woody.

An additional separation of categories 3-5 into ‘perennials’ and ‘annuals’ would be highly desirable.

Pack samples in appropriate bags (paper, or plastic with air holes), label (date, treatment,

replication, subplot, growth form/biomass class), dry (48 hrs at 60°C) and weigh to nearest 0.01 g.

Use collected biomass data for estimation of ANPP, applying an appropriate estimation algorithm

for the ecosystem (Scurlock et al. 2002; Fahey & Knapp 2007; Ruppert & Linstädter 2014).

For G+ treatments, either put cages/ fences back in place or (preferably) store them in a safe place.

Directly before the next growth period starts, re-install cages/fences on BM subplots (G+

treatments) designated for biomass sampling in the respective growth period (see Fig. 3).

5.5. Grazing offtake

Grazing offtake, the proportion of ANPP consumed per season, will be determined in the grazed

treatments (G+D- and G+D+) using the grazing offtake subplot (Fig. 3). This subplot is subject to grazing

and, hence, should not be protected by a cage or fence. In each of the four years, one fourth of the

grazing offtake subplot (0.5 x 0.5 m) will be sampled in the same way as the BM subplots. The absolute

grazing offtake is then estimated as the difference between (a) the mean aboveground net primary

production across BM subplots and (b) the estimate of biomass on the grazing offtake subplot. The

relative grazing offtake should be expressed as proportion of consumed biomass to ANPP.

IDE ADD-ON PROTOCOL: INCLUDING GRAZING EFFECTS

General layout of treatments, plots and subplots

Figure 1: (a) and (b) provide an overview on the layout of the Simplified and Full DroughtAct experiment, respectively, as well as on the general nomenclature used throughout the protocol.

IDE ADD-ON PROTOCOL: INCLUDING GRAZING EFFECTS

Simplified DroughtAct – Simulated grazing via clipping

Figure 2: Sampling layout for the Simplified DroughtAct experiment, where grazing is simulated via clipping (see Fig. 1a for an overview on the general layout of treatments, plots and subplots). Plot and subplot sizes are recommended (minimal) dimensions (see IDE protocol and section 2.2). DroughtAct combines two treatment-layers (Grazing and Drought) with dichotomous factors (absent and present: - + respectively), resulting in four treatments: (a) grazed and ambient precipitation (G+D-), (b) ungrazed and ambient precipitation (G-D-), (c) grazed and drought (G+D+) and (d) ungrazed and drought (G-D+). Subplots labeled GRA and LTE are permanent subplots, reserved for community composition and functional trait sampling. BM subplots serve biomass sampling for ANPP estimation; they are further divided into annual biomass sampling units (year 1-year 4). Ungrazed exclosure treatments (G-) have to be fenced if herbivores are present. Paired pattern plots serve to monitor grazing patterns where herbivores are present. Observed patterns (intensity and selectivity of grazing) will be mimicked on all BM and GRA subplots of G+ treatments via clipping.

IDE ADD-ON PROTOCOL: INCLUDING GRAZING EFFECTS

Full DroughtAct – Actual grazing by wild or domestic herbivores

Figure 3: Treatment and plot layout for the Full DroughtAct experiment. Plot and subplot sizes are comparatively large, and thus appropriate for actually grazed vegetation (see IDE protocol and section 2.2). DroughtAct combines two treatment-layers (Grazing and Drought) with dichotomous factors (absent and present: - + respectively), resulting in four treatments: (a) grazed and ambient precipitation (G+D-), (b) ungrazed and ambient precipitation (G-D-), (c) grazed and drought (G+D+) and (d) ungrazed and drought (G-D+). Subplots GRA1-3/ LTE1-3 are three permanent subplots (nested replications) per plot, serving community composition and functional trait sampling. BM subplots serve biomass sampling for ANPP estimation. In grazed (G+) treatments, current year’s BM subplots are protected from grazing via moveable cages or small fences (Fig. 6). Exclosure treatments (G-) are fenced.

IDE ADD-ON PROTOCOL: INCLUDING GRAZING EFFECTS

Figure 4: Rainout shelter with dimension appropriate for large herbivore grazing, used in the Full DroughtAct experiment. The construction is built from rectangular steel pipes (3mm walls). For transportation reasons, each shelter is built from two parts that are joint along the middle axis. Please note, that pillars of the shelter are actually 200 cm and 300 cm, but are buried 30 cm in concrete fundaments. This is required as the large roof area is prone to strong winds. Given the 100 cm difference between higher and lower side, the lower side should be facing the main wind/weather direction to avoid unwanted drifting of precipitation below the sheltered area. Photograph from the DroughtAct pilot study, situated in South Africa’s Limpopo province.

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Figure 5: Construction drawing of large rainout shelters for the Full DroughtAct (with actual grazing by wild or domestic herbivores). Construction developed for the DroughtAct pilot study in South Africa’s Limpopo province; drawing courtesy of Connie de Lange, Great North Structure, Polokwane, South Africa.

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Figure 6: Examples of moveable cages and small fences built from widely available materials, to be used in the Full DroughtAct experiment. (a) Cage built from metal panels (normally used for reinforced concrete construction). This cage type is inexpensive, sufficiently sturdy for large herbivores, but somewhat dangerous for domestic animals if edges are not blunt. (b) Light, fence-like cage built from metal rods and chicken wire. This cage type is inexpensive and sufficiently sturdy for small herbivores such as goats and sheep; it should have a lid if goats are present. (c) Cage built from steel profiles and reinforcement metal panels. This cage type was developed for the DroughtAct pilot study in South Africa’s Limpopo province; it is an extremely sturdy construction (reusable for many years), and has a good transportability (stackable).

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Linstädter, A., Schellberg, J., Brüser, K., Oomen, R.J., Du Preez, C.C., Ruppert, J.C. & Ewert, F. 2014. Are there consistent grazing indicators in drylands? Testing plant functional types of various complexity in South Africa’s grassland and savanna biomes. PLoS ONE 9: e104672.

Ruppert, J.C., Harmoney, K., Henkin, Z., Snyman, H.A., Sternberg, M., Willms, W. & Linstädter, A. 2015. Quantifying drylands’ drought resistance and recovery: The importance of drought intensity, dominant life history and grazing regime. Global Change Biology 21: 258–1270.

Ruppert, J.C. & Linstädter, A. 2014. Convergence between ANPP estimation methods in grasslands — A practical solution to the comparability dilemma. Ecological Indicators 36: 524-531.

Scurlock, J.M.O., Johnson, K. & Olson, R.J. 2002. Estimating net primary productivity from grassland biomass dynamics measurements. Global Change Biology 8: 736-753.

Smart, A.J., Derner, J.D., Hendrickson, J.R., Gillen, R.L., Dunn, B.H., Mousel, E.M., Johnson, P.S., Gates, R.N., Sedivec, K.K., Harmoney, K.R., Volesky, J.D. & Olson, K.C. 2010. Effects of Grazing Pressure on Efficiency of Grazing on North American Great Plains Rangelands. Rangeland Ecology & Management 63: 397-406.