Correction: Mackay-Smith et al. A Framework for Reviewing Silvopastoralism: A New Zealand Hill Country Case Study. Land 2021, 10, 1386

The authors would like to make the following correction to the published article [1].

Error in Figure/Table

There was a miscommunication with the journal editors regarding the formatting of the table. Individual points within table boxes were removed for the final manuscript so there were duplicate references in each table box.

1.

The following changes were made to the references in Table 2:

“McIvor et al. [42]” was removed from Page 8; “Charlton et al. [25]” was removed from Page 10; “Marden and Phillips [49]”, “Charlton et al. [25]” and “Boffa Miskell Limited [50]” × 2 were removed from Page 11 and from Page 10.

Additionally, colons were added between references where necessary.

Other changes include the following: “survivial” was changed to “survival” on Page 11; “Quantatiative” was changed to “quantitative” on Page 11; to was removed on Page 11; “precence” was changed to “presence” on Page 13; “11.5 year old” was changed to “11.5-year-old” on Page 8; “16 year-old” was changed to “16-year-old” on Page 8; “32.0-year-old” was changed to “32-year-old” on Page 8; and “5.0, 7.0 and 9.5 year old” changed to “5, 7, and 9.5 years old”.

Finally, “≥25 m” was changed to “>30 m” and “10–20 m” was changed to 8–20 m” on Page 7 due to ongoing research refining the sizes of the tree.

The corrected Table 2 appears below.

Table 2. Tree attributes for poplar (Populus spp.) and kānuka (Kunzea spp.) in a New Zealand hill country silvopastoral system. Tree attributes have been adapted from Wood [15]. The photographs were taken by the lead author.

Tree Attribute	Poplar (Populus spp.) Attribute		Priority Research Area	Kānuka (Kunzea spp.) Attribute		Priority Research Area
Above ground tree habit and phenology	Current cultivars planted in the 1960s and 1970s are > 30 m in height. Crowns are large and uncompact. Older cultivars often have large branches extended; some are multistemmed. Newer cultivars have been developed which grow as a single, straighter stem. Deciduous.		Yes—an understanding of the form of newer poplar cultivars when they are fully-grown would be informative.	When growing isolated in hill country, kānuka are 8—20 m in height. Compact crowns. Stems can be multi- or single-stemmed. Many branches when unmanaged. The form of kānuka varies with tree density, growing taller and thinning in higher densities. Evergreen.		No
Below ground tree habit	For three 11.5-year-old poplar trees on a 17° hill country site at densities of 156 tree ha−1, maximal lateral root extension ranged from 8.0–12.0 m. Mean tensile strength of 44.0 (minimum: 11.1 MPa; maximum: 114.3 MPa). The total root length of a 9.5-year-old poplar tree was found to be 663.5 m with a root biomass of 17.9 kg. The lateral root extension, root biomass and total root length of ‘fully-grown’ poplar trees on hill country > 25.0° would be valuable.	McIvor et al. [42,43]; Watson et al. [44]	No	Only kānuka growing in high density forest stands (~3000–16,000 stems ha−1) have been studied. Fifteen 16-year-old trees growing at 12,800 stems ha−1 had a maximum root length of 4.5 m. Fifteen 32-year-old trees growing at 3900 stems ha−1 had a maximum root length of 6.1 m Mean tensile strength of 34.1 MPa (minimum: 18.2 MPa; maximum: 75.8 MPa). In another high-density stand (3000 stems ha−1), the total root length of one fully-grown kānuka tree 9.5 m in height was shown to be 123.2 m, have a root biomass without the stump of 11. 8 kg and a lateral root spread of 2.8 m.	Watson et al. [45,46]; Watson and Marden [47]; Watson and O’Loughlin [48]	Yes—research on the root distribution of kānuka growing at typical hill country silvopastoral densities (20–200 tree ha−1) is required.
Growth rate	On a 21–35° slope, the mean height of 268 poplar poles was just under 3.0 m after 12 months, ~3.5 m after 24 months and ~5.3 m after 45.0 months. Start heights were not given by the authors so yearly growth rates could not be calculated. 5, 7 and 9.5 years old trees had heights of 7.0, 9.5 and 13.3 m, respectively, on a 17° hill country site. This equates to a ~1.3 m year−1 growth rate (accounting for the 1.4 m start height of the poles).	Marden and Phillips [49]; McIvor et al. [42]	No	Initial growth rates are often 0.7–0.8 m year−1 in sheltered and high fertility sites, and 0.4–0.5 m year−1 in poorer sites. This data was collected from interviews, and was not stated to be quantitatively studied in the report.	Boffa Miskell Limited [50]	Yes—quantitative information on growth rates in contrasting conditions, as well as at 20–200 tree ha−1 densities, is required.
Water use	Four trees were shown to have an average water use of 180.1 L day−1 during spring, which equated to 1.2 mm day−1. One of these trees had a water use of 417.0 L day−1.	Guevara-Escobar et al. [51]	No			Yes—the water use of kānuka is unknown.
Response to pruning and cutting management practices	Responds well to pruning when the trees are young, as well as coppicing and pollarding.	Charlton et al. [25]	No			Yes—the response to management is unknown.
Tree by-products	Wood—poplars can be pruned and harvested for timber. Fodder—leaves are excellent fodder for animals. Emissions trading scheme (ETS)—there is the potential for farmers to receive carbon credits (1 NZU = 1 tonne of sequestered CO2) if the tree crown canopy is > 30% in each hectare.	Charlton et al. [25]; Kemp at al. [2]; MPI [52]	Yes—research required to understand the density required to achieve a 30.0% canopy cover with poplar.	Wood—reported to be good firewood. Fodder—kānuka leaves are 0.5–2.5 cm, the tree doesn’t have summer leaf flush as they are evergreen and the leaves are potentially bitter, so we tentatively suggest that the trees would be poor fodder quality. Honey—shown to have anit-bacterial, anti-viral, immunostimulatory and anti-inflammatory properties. Essential oil—kānuka essential oil has been shown to be an effective eco-friendly pesticide. Emissions trading scheme—potential exists for farmers to receive carbon credits (1 NZU = 1 tonne of sequestered CO2) if the tree crown canopy is > 30% in each hectare.	Boffa Miskell Limited [50]; Bloor [53]; Gannabathula et al. [54]; Lu [55]; Tomblin et al. [56]; Kassimi et al. [57]; Park [58]; MPI [52]	Yes—research required to understand the density required to achieve a 30.0% canopy cover with kānuka.
Site suitability (ecological range, hardiness, pests/diseases)	Exotic to hill country, although poplar in certain conditions can have a high survival rate when established in hill country. For 300 hill country poplar poles deaths after 45 months, site factors (site conditions, socketing etc.) contributed to 28% deaths, and animal damage contributed to 12% of deaths. After 6 years, survivability on six hill country farms ranged from 0% to 80% (slopes varied from 0% to 32% in the study). Although the reasons for death were not quantitively measured by the authors, reasons given include animal damage, poor planting, continued erosion, winter weather fronts and poor local site conditions. Fungus and rust can be issues, with more resistant clones the main mitigation strategy. As branch breaking is common due to high winds in hill country, and fungus and rust can be issues, best management practice suggests felling and replanting the trees after 40 years. An understanding of the survival rate of poplars on different slope classes (especially the steepest hill country slopes) and in different environmental conditions would be informative, as well as more detailed quantitative information on the reasons for the low survival rates.	Marden and Phillips [49]; McIvor et al. [59]; Charlton et al. [25]	Yes—an understanding of the survival rates of poplar poles on the steepest, most erosion prone, hill country slopes would be helpful.	Native to hill country and already grows readily throughout hill country. Kānuka is reported to potentially grow up to at least 160 years and possibly as old as 300–400 years. Kānuka can grow in unfertile and moisture limited areas of hill country. Kānuka are susceptible to myrtle rust as they are in the myrtle family, Myrtaceae. Data on the survival percentages of kānuka in varying soil conditions is required, as well as how susceptible a kānuka silvopastoral system would be to myrtle rust.	Spiekermann et al. [13]; Boffa Miskell Limited [50]	Yes—quantitative data is lacking on the age to which kānuka grow at 20–200 tree ha−1 densities in hill country, establishment survival rates and the system’s susceptible to myrtle rust.
Establishment method (seedling, cutting, pole)	Can be established as unrooted 1.0–3.0 m poles or stakes (0.5 m cuttings) which are sharpened and rammed into the ground. Sheep and small cattle can be grazed immediately. Large cattle can knock over and break poplar poles, so exclusion until the poles have established is recommended. Regular poplar poles that are planted in hill country normally take 2–3 years to produce, depending on the region, occupy a lot of land in their production and demand for them regularly outstrips supply. Understanding the establishment methods and survival rates of quicker to produce planting material (younger unrooted material or rooted material) that can be grown in a smaller amount of land with less water and lower costs would be helpful.	Marden and Phillips [49]; Phillips et al. [14]; Ian McIvor (personal communication, 26th October 2021) [60]	Yes—understanding the establishment of different planting material (younger unrooted material or rooted material) would be helpful.	With current planting technology and knowledge kānuka would need to be planted as seedlings and protected from animal browsing. Large cattle may require exclusion depending on the protection method. Protection with current technology would need to be strong 1.7 m plastic netting or a wire cage, supported by 2 Y posts for cattle, or by a Y post and a fibreglass rod for sheep. It is unknown at what age seedling protection can be removed.		Yes—little is known on the establishment of kānuka in hill country.
Special qualities (e.g., nitrogen fixation, thorniness, bitter leaves)	No special qualities of note.		No	A key difficulty when establishing trees in hill country is livestock browsing or damaging the tree. Livestock exclusion from paddocks is often not possible. Some land managers state kānuka leaves are bitter, which may reduce or stop browsing by sheep and cattle during establishment. Evidence for this is kānuka is already found growing readily in many parts of unproductive hill country in the presence of animals. Fresh shoots or young seedlings from commercial nurseries are likely to be browsed.		Yes—more information on the relationship between kānuka leaves and livestock is required.

Table 2. Tree attributes for poplar (Populus spp.) and kānuka (Kunzea spp.) in a New Zealand hill country silvopastoral system. Tree attributes have been adapted from Wood [15]. The photographs were taken by the lead author.

Tree Attribute	Poplar (Populus spp.) Attribute		Priority Research Area	Kānuka (Kunzea spp.) Attribute		Priority Research Area
Above ground tree habit and phenology	Current cultivars planted in the 1960s and 1970s are > 30 m in height. Crowns are large and uncompact. Older cultivars often have large branches extended; some are multistemmed. Newer cultivars have been developed which grow as a single, straighter stem. Deciduous.		Yes—an understanding of the form of newer poplar cultivars when they are fully-grown would be informative.	When growing isolated in hill country, kānuka are 8—20 m in height. Compact crowns. Stems can be multi- or single-stemmed. Many branches when unmanaged. The form of kānuka varies with tree density, growing taller and thinning in higher densities. Evergreen.		No
Below ground tree habit	For three 11.5-year-old poplar trees on a 17° hill country site at densities of 156 tree ha−1, maximal lateral root extension ranged from 8.0–12.0 m. Mean tensile strength of 44.0 (minimum: 11.1 MPa; maximum: 114.3 MPa). The total root length of a 9.5-year-old poplar tree was found to be 663.5 m with a root biomass of 17.9 kg. The lateral root extension, root biomass and total root length of ‘fully-grown’ poplar trees on hill country > 25.0° would be valuable.	McIvor et al. [42,43]; Watson et al. [44]	No	Only kānuka growing in high density forest stands (~3000–16,000 stems ha−1) have been studied. Fifteen 16-year-old trees growing at 12,800 stems ha−1 had a maximum root length of 4.5 m. Fifteen 32-year-old trees growing at 3900 stems ha−1 had a maximum root length of 6.1 m Mean tensile strength of 34.1 MPa (minimum: 18.2 MPa; maximum: 75.8 MPa). In another high-density stand (3000 stems ha−1), the total root length of one fully-grown kānuka tree 9.5 m in height was shown to be 123.2 m, have a root biomass without the stump of 11. 8 kg and a lateral root spread of 2.8 m.	Watson et al. [45,46]; Watson and Marden [47]; Watson and O’Loughlin [48]	Yes—research on the root distribution of kānuka growing at typical hill country silvopastoral densities (20–200 tree ha−1) is required.
Growth rate	On a 21–35° slope, the mean height of 268 poplar poles was just under 3.0 m after 12 months, ~3.5 m after 24 months and ~5.3 m after 45.0 months. Start heights were not given by the authors so yearly growth rates could not be calculated. 5, 7 and 9.5 years old trees had heights of 7.0, 9.5 and 13.3 m, respectively, on a 17° hill country site. This equates to a ~1.3 m year−1 growth rate (accounting for the 1.4 m start height of the poles).	Marden and Phillips [49]; McIvor et al. [42]	No	Initial growth rates are often 0.7–0.8 m year−1 in sheltered and high fertility sites, and 0.4–0.5 m year−1 in poorer sites. This data was collected from interviews, and was not stated to be quantitatively studied in the report.	Boffa Miskell Limited [50]	Yes—quantitative information on growth rates in contrasting conditions, as well as at 20–200 tree ha−1 densities, is required.
Water use	Four trees were shown to have an average water use of 180.1 L day−1 during spring, which equated to 1.2 mm day−1. One of these trees had a water use of 417.0 L day−1.	Guevara-Escobar et al. [51]	No			Yes—the water use of kānuka is unknown.
Response to pruning and cutting management practices	Responds well to pruning when the trees are young, as well as coppicing and pollarding.	Charlton et al. [25]	No			Yes—the response to management is unknown.
Tree by-products	Wood—poplars can be pruned and harvested for timber. Fodder—leaves are excellent fodder for animals. Emissions trading scheme (ETS)—there is the potential for farmers to receive carbon credits (1 NZU = 1 tonne of sequestered CO2) if the tree crown canopy is > 30% in each hectare.	Charlton et al. [25]; Kemp at al. [2]; MPI [52]	Yes—research required to understand the density required to achieve a 30.0% canopy cover with poplar.	Wood—reported to be good firewood. Fodder—kānuka leaves are 0.5–2.5 cm, the tree doesn’t have summer leaf flush as they are evergreen and the leaves are potentially bitter, so we tentatively suggest that the trees would be poor fodder quality. Honey—shown to have anit-bacterial, anti-viral, immunostimulatory and anti-inflammatory properties. Essential oil—kānuka essential oil has been shown to be an effective eco-friendly pesticide. Emissions trading scheme—potential exists for farmers to receive carbon credits (1 NZU = 1 tonne of sequestered CO2) if the tree crown canopy is > 30% in each hectare.	Boffa Miskell Limited [50]; Bloor [53]; Gannabathula et al. [54]; Lu [55]; Tomblin et al. [56]; Kassimi et al. [57]; Park [58]; MPI [52]	Yes—research required to understand the density required to achieve a 30.0% canopy cover with kānuka.
Site suitability (ecological range, hardiness, pests/diseases)	Exotic to hill country, although poplar in certain conditions can have a high survival rate when established in hill country. For 300 hill country poplar poles deaths after 45 months, site factors (site conditions, socketing etc.) contributed to 28% deaths, and animal damage contributed to 12% of deaths. After 6 years, survivability on six hill country farms ranged from 0% to 80% (slopes varied from 0% to 32% in the study). Although the reasons for death were not quantitively measured by the authors, reasons given include animal damage, poor planting, continued erosion, winter weather fronts and poor local site conditions. Fungus and rust can be issues, with more resistant clones the main mitigation strategy. As branch breaking is common due to high winds in hill country, and fungus and rust can be issues, best management practice suggests felling and replanting the trees after 40 years. An understanding of the survival rate of poplars on different slope classes (especially the steepest hill country slopes) and in different environmental conditions would be informative, as well as more detailed quantitative information on the reasons for the low survival rates.	Marden and Phillips [49]; McIvor et al. [59]; Charlton et al. [25]	Yes—an understanding of the survival rates of poplar poles on the steepest, most erosion prone, hill country slopes would be helpful.	Native to hill country and already grows readily throughout hill country. Kānuka is reported to potentially grow up to at least 160 years and possibly as old as 300–400 years. Kānuka can grow in unfertile and moisture limited areas of hill country. Kānuka are susceptible to myrtle rust as they are in the myrtle family, Myrtaceae. Data on the survival percentages of kānuka in varying soil conditions is required, as well as how susceptible a kānuka silvopastoral system would be to myrtle rust.	Spiekermann et al. [13]; Boffa Miskell Limited [50]	Yes—quantitative data is lacking on the age to which kānuka grow at 20–200 tree ha−1 densities in hill country, establishment survival rates and the system’s susceptible to myrtle rust.
Establishment method (seedling, cutting, pole)	Can be established as unrooted 1.0–3.0 m poles or stakes (0.5 m cuttings) which are sharpened and rammed into the ground. Sheep and small cattle can be grazed immediately. Large cattle can knock over and break poplar poles, so exclusion until the poles have established is recommended. Regular poplar poles that are planted in hill country normally take 2–3 years to produce, depending on the region, occupy a lot of land in their production and demand for them regularly outstrips supply. Understanding the establishment methods and survival rates of quicker to produce planting material (younger unrooted material or rooted material) that can be grown in a smaller amount of land with less water and lower costs would be helpful.	Marden and Phillips [49]; Phillips et al. [14]; Ian McIvor (personal communication, 26th October 2021) [60]	Yes—understanding the establishment of different planting material (younger unrooted material or rooted material) would be helpful.	With current planting technology and knowledge kānuka would need to be planted as seedlings and protected from animal browsing. Large cattle may require exclusion depending on the protection method. Protection with current technology would need to be strong 1.7 m plastic netting or a wire cage, supported by 2 Y posts for cattle, or by a Y post and a fibreglass rod for sheep. It is unknown at what age seedling protection can be removed.		Yes—little is known on the establishment of kānuka in hill country.
Special qualities (e.g., nitrogen fixation, thorniness, bitter leaves)	No special qualities of note.		No	A key difficulty when establishing trees in hill country is livestock browsing or damaging the tree. Livestock exclusion from paddocks is often not possible. Some land managers state kānuka leaves are bitter, which may reduce or stop browsing by sheep and cattle during establishment. Evidence for this is kānuka is already found growing readily in many parts of unproductive hill country in the presence of animals. Fresh shoots or young seedlings from commercial nurseries are likely to be browsed.		Yes—more information on the relationship between kānuka leaves and livestock is required.

2.

The following changes were made to the references in Table 3:

“Guevara-Escobar et al. [26]” and “Wall [27]” were removed from Page 14, and “Guevara-Escobar et al. [26]” was removed from Page 16. Additionally, the Table 3 header was moved to the left and the font size of Table 3 was adjusted to size 8. The corrected Table 3 appears below.

Table 3. Silvopastoral outcomes for poplar (Populus spp.) and kānuka (Kunzea spp.) in a New Zealand hill country silvopastoral system. Tree outcomes have been adapted from Wood [15].

Silvopastoral Outcome	Poplar (Populus spp.) Outcome		Priority Area for Research	Kānuka (Kunzea spp.) Outcome		Priority Area for Research
Influence of the tree on the pasture and soil	Evidence against Pasture reduction beneath the canopy between 12% and 65% for poplar greater than 15 years old. A relationship has been found between increased canopy closure and decreased pasture production. Leaf smother has been shown to depress autumn grass growth beneath poplar canopies. Poplars do not fix nitrogen. One study found 33.0% less soil moisture beneath poplars when compared with open pasture in summer and autumn. Another study found slightly more water in the top 15 cm in pasture away from poplar throughout the year, with the difference most pronounced in summer and autumn. As pasture production and soil moisture has been shown to reduce under poplar, there is no evidence that wind-run reductions caused by poplar facilitate water conservation in the soil. Found no evidence that poplar facilitate the build-up of organic matter, nitrogen, phosphorus or sulphate beneath their canopies between 0.0 and 7.5 cm at three sites with poplar trees > 28 years old. Found varied results of soil organic matter, phosphorus and sulphate beneath fully developed poplar canopies between 0.0 and 15.0 cm compared to open pasture at two sites. There is evidence that poplar increase exchangeable cations (calcium, potassium, magnesium, sodium) beneath their canopies, most likely because of the chemical composition of their leaves. Along with light interception and autumn pasture smother, the water use of poplar could be contributing to the reduced pasture production beneath their canopies.	Reviewed by Benavides et al. [9]; Wall et al. [61]; Douglas et al. [62]; Kemp et al. [2]; Douglas et al. [63]; Guevara-Escobar et al. [64]; Guevara-Escobar et al. [26]; Wall [27]	No—there is a good understanding of how poplar influences the pasture and soil.	No evidence Likely outcome There has been no research on pasture production, and the constraints to pasture production, beneath kānuka in hill country. More research is required to produce any likely outcome predictions for the influence of kānuka on pasture, livestock and soil. Kānuka are evergreen, so this may have varying influences on the system when compared to poplar. Kānuka do not fix nitrogen.		Yes
Livestock shelter	No evidence Likely outcome Trees will most likely provide less shelter to animals in winter than summer (poplars are deciduous). The summer shelter will most likely be positive for animal grazing time in summer, and may reduce heat stress resulting in greater live weight growth of livestock. The influence of poplar stem and branches on wind-run in winter may have positive influences in terms of reduced deaths and increased livestock live weight growth by reducing wind chill.		Yes	No evidence Likely outcome As kānuka are evergreen it is expected the trees will provide good shade and shelter to animals in summer and winter. The summer and winter shelter will most likely be positive for animal grazing time throughout the year. The influence of kānuka on wind-run in winter may have positive influences in terms of reduced livestock deaths and increased livestock live weight growth by reducing wind chill.		Yes
Water and nutrient gains or losses	No evidence Hill country 20–200 tree ha−1 densities have not been studied.		Yes	No evidence It is unknown how kānuka impacts these system dynamics.		Yes
Biodiversity interactions (excluding livestock and the forage crop)	Evidence against Poplar were found to either reduce or maintain earthworm populations compared to equivalent open pasture positions. The three most abundant earthworms found beneath poplars were all exotic (Aporrectodea caliginosa, A. longa, Lumbricus rubellus). No evidence As far as we are aware, nothing is known on how poplar influence bird, insect and fungi populations. Likely outcome Biodiversity value to native fauna is predicted to be small as poplar are exotic. As poplar are deciduous, predicted to have less value to biodiversity than an evergreen tree.	Guevara-Escobar et al. [26]	Yes	Evidence for 16 native and exotic bird species documented in high density (no density was given but the canopy was stated to be dense) native forest stands of kānuka. Higher density forest stands host diverse invertebrate populations. No evidence As far as we are aware, nothing is known about how kānuka influences fungi, bird or insect populations in a silvopastoral system. Likely outcome Although only high density kānuka stands (> 1000 trees ha−1) have been studied, a kānuka silvopastoral system is predicted to have a high biodiversity value to native fauna as the genus is native.	Williams and Karl [39]; Boffa Miskell Limited [50]	Yes
Greenhouse gas implications	Evidence for The above and below ground carbon pool of a poplar silvopastoral system was estimated to be 18.1 tonnes ha−1. Nevertheless, the amount of carbon sequestered (above ground biomass) would reduce after the tree is felled. Evidence against No clear evidence poplars increase soil organic matter beneath their canopies. No evidence It is unknown how a poplar silvopastoral system may influence methane and nitrous oxide emissions.	Guevara-Escobar et al. [26]; Wall [27]	Yes	No evidence It is unknown how kānuka impacts soil conditions and the carbon pool of a kānuka silvopastoral system has not been estimated. Is unknown how a kānuka silvopastoral system may influence methane and nitrous oxide emissions. Likely outcome If kānuka can grow for > 100 years in hill country, it would be a long-term carbon sink in terms of above and below ground biomass when compared to hill country without trees.		Yes
Soil conservation effectiveness	Evidence for Highly effective as soil conservation trees due to their large total root length, lateral root spread (even when not fully-grown), as well as their high root tensile strength. One study found poplar to have an average maximum effective distance of 20 m for landslide mitigation.	Hawley and Dymond [65]; Douglas et al. [66]; McIvor [12]; Spiekermann et al. [13]	No—the soil conservation effectiveness of poplar is well understood.	Evidence for Even though root systems of 20–200 trees ha−1 have not been studied, one study found kānuka to have an average maximum effective distance of 17.0 m for landslide mitigation. More research is required on the root distribution of kānuka growing at low densities (20–200 tree ha−1) to gain a better understanding of the soil conservation value of a kānuka silvopastoral system.	Spiekermann et al. [13]	Yes
Time until the provision of a silvopastoral outcome	Evidence for Quick as poplar are fast growing.	McIvor et al. [42]	No	No evidence There is no quantitative information on the growth rate of kānuka or kānuka roots growing at low densities (20–200 trees ha−1). Likely outcome Slower than poplar, as poplar are a fast-growing tree, and one qualitative study provides evidence that kānuka grows more slowly than poplar.	Boffa Miskell Limited [50]	Yes
The ability of farmers to receive extra income streams from tree plantings	Evidence for Fodder—feeding poplar fodder to livestock is a practice undertaken by some farmers in summer drought conditions. Emissions trading scheme—poplars at 30% canopy are eligible for carbon credits. Evidence against Wood—although poplars can be pruned and harvested for timber, as of 2021, this isn’t a regular practice in New Zealand.	Charlton et al. [25]; Kemp et al. [2]	No	Evidence for Emissions trading scheme—kānuka at 30% canopy are eligible for carbon credits. No evidence Timber—the commercial value of kānuka wood (for firewood and timber) is unknown. It is suggested that harvesting kānuka for timber is not a suitable practice for a kānuka hill country silvopastoral system because the tree density will be low (< 200 trees ha−1) compared to a typical plantation density, plus when the trees are felled this would stop each tree’s impact on other silvopastoral outcomes. Honey—high density stands of trees > 40 ha are generally required to harvest high purity kānuka honey so it is unknown if honey can be harvested from a low density (20–200 trees ha−1) kānuka silvopastoral system. Further research is required. Essential oil—it is unlikely that a kānuka silvopastoral system would provide enough foliage for essential oil production because of the low density (20–200 trees ha−1), although further research is required to confirm this.	Boffa Miskell Limited [50]	Yes—more information on the commercial potential of kānuka wood, honey and essential oil production is required.
Ease of pruning, management and harvesting tree products	Evidence against Tall height and multi-branching habit mean management is difficult and often dangerous.	Charlton et al. [25]	No—there are other outcomes which have a higher priority.	No evidence Likely outcome The smaller and compact habit of kānuka compared to poplar suggests management would be easier.		No—there are other outcomes which have a higher priority.
Cultural values	No evidence As far as we are aware, there has been no research on the cultural value of poplar, despite there being a lot of research on the functional value of poplar. Likely outcome Poplar is an exotic genus so it is predicted to have less value than a native genus.		Yes	Evidence for Kānuka is a native and so has cultural significance. Nevertheless, more work is required to understand the cultural significance of kānuka compared to other genera (native or exotic) in New Zealand.		Yes
Aesthetics	Evidence against One study has shown that when people are informed that shelterbelts are exotic, they are preferred less than native shelterbelts. No evidence As far as we are aware, there have been no studies on how the preference of poplar compares to other genera.	Brown et al. [67]	No—despite little research, there are more important research priorities for poplar.	Evidence for One study has shown that when people are informed that shelterbelts contain native trees, they are preferred over exotic shelterbelts. No evidence As far as we are aware, there have been no studies on the visual qualities of specific trees within a native tree category, or on kānuka specifically.	Brown et al. [67]	No—despite little research, there are more important research priorities for kānuka.
Longevity of the trees	Evidence against Tall height and multi-branching habit mean they are not very resistant against wind damage Best management practice suggests felling and replanting trees after 40 years (due to impact of wind on branches, and wood rot or leaf fungus). Above ground silvopastoral benefits are lost when the trees are felled. It is unknown how resistant new straighter cultivars are against wind as they have only recently been planted.	Charlton et al. [25]	Yes—an understanding of the resistance of new cultivars to wind damage is important.	No evidence Likely outcome The small and compact habit of kānuka compared to poplar, that they are native to windy hill country conditions, and are already found on many parts of hill country, suggests kānuka are highly resistant against wind damage. If kānuka can grow up to 400 years in hill country, even if only over 100 years, this means silvopastoral benefits will be lasting compared to poplar.	Boffa Miskell Limited [50]	Yes—confirming the longevity of kānuka is important.
Costs and ease of establishment	Evidence for Planting as unrooted poles is an efficient way of planting trees. Recommended practice is excluding large cattle for 2 years, but sheep can still be grazed. Survival rate is normally high for poplar. Costs $20–25 NZD to plant a pole as of 2021 (not including labour and transport costs). Evidence against The survival of poplar can be low, and more detailed quantitative information is required to understand the instances when survival rates can be low. No evidence More work is required to understand the establishment of poplar on the steepest hill country slopes.	Marden and Phillips [49]; McIvor [59]	Yes—more research is required on the establishment of poplar on steeper, more erosion prone slopes.	Evidence against The time required to plant seedlings and protect them is longer than when planting poplar poles. Cost of planting and protecting a commercially bought 50 cm kānuka seedling with protection is $20–30 NZD as of 2021 (not including labour and transport costs). No evidence Nevertheless, there is limited understanding into the methods of establishing kānuka in hill country, and more work is required to better understand kānuka establishment.		Yes—comparing the establishment ease of kānuka with poplar is a priority as it is an important outcome in hill country.
Special qualities reducing animal interactions with the tree (thorniness, bitter leaves, etc.)	Evidence for Poplar can be established as unrooted poles which reduces the chance of grazing by livestock, as when leaves grow on the poles, they are normally above the reach of grazing livestock.	Marden and Phillips [49]	No	No evidence Likely outcome If kānuka are browsed less than other genera due to their leaves being bitter, establishing the seedlings or young trees may require protection for a shorter period of time than other more desirable browse genera.		Yes—understanding the interaction between kānuka and livestock will be useful information when attempted to establish kānuka.
Ability to refine the tree form for improved silvopastoral outcomes	No evidence Likely outcome Even though pruning, coppicing, and pollarding is possible that will reduce management in later life, this is only done sparingly by farms.		No—there are other outcomes which have a higher priority.	No evidence It is unknown how a refined form will impact hill county silvopastoral outcomes, or if tree management would be taken up by landowners.		No—there are other outcomes which have a higher priority.

Table 3. Silvopastoral outcomes for poplar (Populus spp.) and kānuka (Kunzea spp.) in a New Zealand hill country silvopastoral system. Tree outcomes have been adapted from Wood [15].

Silvopastoral Outcome	Poplar (Populus spp.) Outcome		Priority Area for Research	Kānuka (Kunzea spp.) Outcome		Priority Area for Research
Influence of the tree on the pasture and soil	Evidence against Pasture reduction beneath the canopy between 12% and 65% for poplar greater than 15 years old. A relationship has been found between increased canopy closure and decreased pasture production. Leaf smother has been shown to depress autumn grass growth beneath poplar canopies. Poplars do not fix nitrogen. One study found 33.0% less soil moisture beneath poplars when compared with open pasture in summer and autumn. Another study found slightly more water in the top 15 cm in pasture away from poplar throughout the year, with the difference most pronounced in summer and autumn. As pasture production and soil moisture has been shown to reduce under poplar, there is no evidence that wind-run reductions caused by poplar facilitate water conservation in the soil. Found no evidence that poplar facilitate the build-up of organic matter, nitrogen, phosphorus or sulphate beneath their canopies between 0.0 and 7.5 cm at three sites with poplar trees > 28 years old. Found varied results of soil organic matter, phosphorus and sulphate beneath fully developed poplar canopies between 0.0 and 15.0 cm compared to open pasture at two sites. There is evidence that poplar increase exchangeable cations (calcium, potassium, magnesium, sodium) beneath their canopies, most likely because of the chemical composition of their leaves. Along with light interception and autumn pasture smother, the water use of poplar could be contributing to the reduced pasture production beneath their canopies.	Reviewed by Benavides et al. [9]; Wall et al. [61]; Douglas et al. [62]; Kemp et al. [2]; Douglas et al. [63]; Guevara-Escobar et al. [64]; Guevara-Escobar et al. [26]; Wall [27]	No—there is a good understanding of how poplar influences the pasture and soil.	No evidence Likely outcome There has been no research on pasture production, and the constraints to pasture production, beneath kānuka in hill country. More research is required to produce any likely outcome predictions for the influence of kānuka on pasture, livestock and soil. Kānuka are evergreen, so this may have varying influences on the system when compared to poplar. Kānuka do not fix nitrogen.		Yes
Livestock shelter	No evidence Likely outcome Trees will most likely provide less shelter to animals in winter than summer (poplars are deciduous). The summer shelter will most likely be positive for animal grazing time in summer, and may reduce heat stress resulting in greater live weight growth of livestock. The influence of poplar stem and branches on wind-run in winter may have positive influences in terms of reduced deaths and increased livestock live weight growth by reducing wind chill.		Yes	No evidence Likely outcome As kānuka are evergreen it is expected the trees will provide good shade and shelter to animals in summer and winter. The summer and winter shelter will most likely be positive for animal grazing time throughout the year. The influence of kānuka on wind-run in winter may have positive influences in terms of reduced livestock deaths and increased livestock live weight growth by reducing wind chill.		Yes
Water and nutrient gains or losses	No evidence Hill country 20–200 tree ha−1 densities have not been studied.		Yes	No evidence It is unknown how kānuka impacts these system dynamics.		Yes
Biodiversity interactions (excluding livestock and the forage crop)	Evidence against Poplar were found to either reduce or maintain earthworm populations compared to equivalent open pasture positions. The three most abundant earthworms found beneath poplars were all exotic (Aporrectodea caliginosa, A. longa, Lumbricus rubellus). No evidence As far as we are aware, nothing is known on how poplar influence bird, insect and fungi populations. Likely outcome Biodiversity value to native fauna is predicted to be small as poplar are exotic. As poplar are deciduous, predicted to have less value to biodiversity than an evergreen tree.	Guevara-Escobar et al. [26]	Yes	Evidence for 16 native and exotic bird species documented in high density (no density was given but the canopy was stated to be dense) native forest stands of kānuka. Higher density forest stands host diverse invertebrate populations. No evidence As far as we are aware, nothing is known about how kānuka influences fungi, bird or insect populations in a silvopastoral system. Likely outcome Although only high density kānuka stands (> 1000 trees ha−1) have been studied, a kānuka silvopastoral system is predicted to have a high biodiversity value to native fauna as the genus is native.	Williams and Karl [39]; Boffa Miskell Limited [50]	Yes
Greenhouse gas implications	Evidence for The above and below ground carbon pool of a poplar silvopastoral system was estimated to be 18.1 tonnes ha−1. Nevertheless, the amount of carbon sequestered (above ground biomass) would reduce after the tree is felled. Evidence against No clear evidence poplars increase soil organic matter beneath their canopies. No evidence It is unknown how a poplar silvopastoral system may influence methane and nitrous oxide emissions.	Guevara-Escobar et al. [26]; Wall [27]	Yes	No evidence It is unknown how kānuka impacts soil conditions and the carbon pool of a kānuka silvopastoral system has not been estimated. Is unknown how a kānuka silvopastoral system may influence methane and nitrous oxide emissions. Likely outcome If kānuka can grow for > 100 years in hill country, it would be a long-term carbon sink in terms of above and below ground biomass when compared to hill country without trees.		Yes
Soil conservation effectiveness	Evidence for Highly effective as soil conservation trees due to their large total root length, lateral root spread (even when not fully-grown), as well as their high root tensile strength. One study found poplar to have an average maximum effective distance of 20 m for landslide mitigation.	Hawley and Dymond [65]; Douglas et al. [66]; McIvor [12]; Spiekermann et al. [13]	No—the soil conservation effectiveness of poplar is well understood.	Evidence for Even though root systems of 20–200 trees ha−1 have not been studied, one study found kānuka to have an average maximum effective distance of 17.0 m for landslide mitigation. More research is required on the root distribution of kānuka growing at low densities (20–200 tree ha−1) to gain a better understanding of the soil conservation value of a kānuka silvopastoral system.	Spiekermann et al. [13]	Yes
Time until the provision of a silvopastoral outcome	Evidence for Quick as poplar are fast growing.	McIvor et al. [42]	No	No evidence There is no quantitative information on the growth rate of kānuka or kānuka roots growing at low densities (20–200 trees ha−1). Likely outcome Slower than poplar, as poplar are a fast-growing tree, and one qualitative study provides evidence that kānuka grows more slowly than poplar.	Boffa Miskell Limited [50]	Yes
The ability of farmers to receive extra income streams from tree plantings	Evidence for Fodder—feeding poplar fodder to livestock is a practice undertaken by some farmers in summer drought conditions. Emissions trading scheme—poplars at 30% canopy are eligible for carbon credits. Evidence against Wood—although poplars can be pruned and harvested for timber, as of 2021, this isn’t a regular practice in New Zealand.	Charlton et al. [25]; Kemp et al. [2]	No	Evidence for Emissions trading scheme—kānuka at 30% canopy are eligible for carbon credits. No evidence Timber—the commercial value of kānuka wood (for firewood and timber) is unknown. It is suggested that harvesting kānuka for timber is not a suitable practice for a kānuka hill country silvopastoral system because the tree density will be low (< 200 trees ha−1) compared to a typical plantation density, plus when the trees are felled this would stop each tree’s impact on other silvopastoral outcomes. Honey—high density stands of trees > 40 ha are generally required to harvest high purity kānuka honey so it is unknown if honey can be harvested from a low density (20–200 trees ha−1) kānuka silvopastoral system. Further research is required. Essential oil—it is unlikely that a kānuka silvopastoral system would provide enough foliage for essential oil production because of the low density (20–200 trees ha−1), although further research is required to confirm this.	Boffa Miskell Limited [50]	Yes—more information on the commercial potential of kānuka wood, honey and essential oil production is required.
Ease of pruning, management and harvesting tree products	Evidence against Tall height and multi-branching habit mean management is difficult and often dangerous.	Charlton et al. [25]	No—there are other outcomes which have a higher priority.	No evidence Likely outcome The smaller and compact habit of kānuka compared to poplar suggests management would be easier.		No—there are other outcomes which have a higher priority.
Cultural values	No evidence As far as we are aware, there has been no research on the cultural value of poplar, despite there being a lot of research on the functional value of poplar. Likely outcome Poplar is an exotic genus so it is predicted to have less value than a native genus.		Yes	Evidence for Kānuka is a native and so has cultural significance. Nevertheless, more work is required to understand the cultural significance of kānuka compared to other genera (native or exotic) in New Zealand.		Yes
Aesthetics	Evidence against One study has shown that when people are informed that shelterbelts are exotic, they are preferred less than native shelterbelts. No evidence As far as we are aware, there have been no studies on how the preference of poplar compares to other genera.	Brown et al. [67]	No—despite little research, there are more important research priorities for poplar.	Evidence for One study has shown that when people are informed that shelterbelts contain native trees, they are preferred over exotic shelterbelts. No evidence As far as we are aware, there have been no studies on the visual qualities of specific trees within a native tree category, or on kānuka specifically.	Brown et al. [67]	No—despite little research, there are more important research priorities for kānuka.
Longevity of the trees	Evidence against Tall height and multi-branching habit mean they are not very resistant against wind damage Best management practice suggests felling and replanting trees after 40 years (due to impact of wind on branches, and wood rot or leaf fungus). Above ground silvopastoral benefits are lost when the trees are felled. It is unknown how resistant new straighter cultivars are against wind as they have only recently been planted.	Charlton et al. [25]	Yes—an understanding of the resistance of new cultivars to wind damage is important.	No evidence Likely outcome The small and compact habit of kānuka compared to poplar, that they are native to windy hill country conditions, and are already found on many parts of hill country, suggests kānuka are highly resistant against wind damage. If kānuka can grow up to 400 years in hill country, even if only over 100 years, this means silvopastoral benefits will be lasting compared to poplar.	Boffa Miskell Limited [50]	Yes—confirming the longevity of kānuka is important.
Costs and ease of establishment	Evidence for Planting as unrooted poles is an efficient way of planting trees. Recommended practice is excluding large cattle for 2 years, but sheep can still be grazed. Survival rate is normally high for poplar. Costs $20–25 NZD to plant a pole as of 2021 (not including labour and transport costs). Evidence against The survival of poplar can be low, and more detailed quantitative information is required to understand the instances when survival rates can be low. No evidence More work is required to understand the establishment of poplar on the steepest hill country slopes.	Marden and Phillips [49]; McIvor [59]	Yes—more research is required on the establishment of poplar on steeper, more erosion prone slopes.	Evidence against The time required to plant seedlings and protect them is longer than when planting poplar poles. Cost of planting and protecting a commercially bought 50 cm kānuka seedling with protection is $20–30 NZD as of 2021 (not including labour and transport costs). No evidence Nevertheless, there is limited understanding into the methods of establishing kānuka in hill country, and more work is required to better understand kānuka establishment.		Yes—comparing the establishment ease of kānuka with poplar is a priority as it is an important outcome in hill country.
Special qualities reducing animal interactions with the tree (thorniness, bitter leaves, etc.)	Evidence for Poplar can be established as unrooted poles which reduces the chance of grazing by livestock, as when leaves grow on the poles, they are normally above the reach of grazing livestock.	Marden and Phillips [49]	No	No evidence Likely outcome If kānuka are browsed less than other genera due to their leaves being bitter, establishing the seedlings or young trees may require protection for a shorter period of time than other more desirable browse genera.		Yes—understanding the interaction between kānuka and livestock will be useful information when attempted to establish kānuka.
Ability to refine the tree form for improved silvopastoral outcomes	No evidence Likely outcome Even though pruning, coppicing, and pollarding is possible that will reduce management in later life, this is only done sparingly by farms.		No—there are other outcomes which have a higher priority.	No evidence It is unknown how a refined form will impact hill county silvopastoral outcomes, or if tree management would be taken up by landowners.		No—there are other outcomes which have a higher priority.

Text Correction

• There was an error in the original publication. “Forst.” should be “(G. Forst.) Oerst.”
  A correction has been made to Section 1. Introduction, paragraph 1: Page 1.
• There was an error in the original publication. “>15” has been changed to “> 15”.
  A correction has been made to Section 1. Introduction, paragraph 3: Page 1.
• There was an error in the original publication. “(Populus spp.)” and “(Salix spp.)” have been removed.
  A correction has been made to Section 3.1. Poplar and Willow, paragraph 1: Page 5.
• There was an error in the original publication. “40 year” has been changed to “40-year”.
  A correction has been made to Section 3.1. Poplar and Willow, paragraph 2: Page 5.
• There was an error in the original publication. “serotine” should be “serotina”.
  A correction has been made to Section 3.2. Kānuka, paragraph 1: Page 6.
• There was an error in the original publication. “(Leptospermum scoparium)” has been removed.
  A correction has been made to Section 3.2. Kānuka, paragraph 2: Page 6.
• There was an error in the original publication. The reference “[23,24,25]” should be “[25]”.
  A correction has been made to Section 4.1. The interaction of Poplar and Kānuka with the Pasture and Soil, paragraph 5: Page 21.
• There was an error in the original publication. “400-years-old” should be “400 years old”.
  A correction has been made to Section 4.2. Longevity, paragraph 1: Page 21.
• There was an error in the original publication. Reference [80] should be removed after kiwi-fruit orchards.
  A correction has been made to Section 4.6. Bird biodiversity, paragraph 2: Page 22.
• There was an error in the original publication. “2 year” should be “2-year”.
  A correction has been made to Section 4.6. Bird biodiversity, paragraph 2: Page 22.
• There was an error in the original publication. “(Leptospermum scoparium)” has been removed.
  A correction has been made to Section 4.7. Additional Income, paragraph 1: Page 23.
• There was an error in the original publication. “7-years-old” should be “7 years old”.
  A correction has been made to Section 4.7. Additional Income, paragraph 3: Page 23.
• There was an error in the original publication. Reference [46] has been changed to [52].
  A correction has been made to Section 4.7. Additional Income, paragraph 4: Page 23.
• There was an error in the original publication. reference [52] should be “Ministry for Primary Industries. Forest land in the ETS. Available online: https://www.mpi.govt.nz/forestry/forestry-in-the-emissions-trading-scheme/forest-land-in-the-ets/ (accessed on 8 May 2020)”.
  A correction has been made to References section: Page 27.
  The authors apologize for any inconvenience caused and state that the scientific conclusions are unaffected. The original publication has also been updated.