Page 1 of 1
Fertility in Urban and Rural Landscapes
Posted: Wed Apr 22, 2009 10:37 am
A continual message throughout the books is that the old landscape and new landscape have a disparity in fertility levels in the landscape. That is to say that the old landscape that was vegetated, sustained fertility and water cycles adequate for plant life to proliferate as opposed to the relatively barren current landscape that leaches both fertility and water. As a result the new landscape has created harsh conditions that are only suited to the pioneer ‘weed’ species that will add fertility to the soil to recondition it, enabling other phases of plants to grow thereafter such as grasses and trees etc. I live in urban Sydney and as an observer of the landscape I have obviously been looking more at urban landscapes and adjoining areas rather than those of a rural location. The particular area that I live in is blessed in having quite a substantial urban forest and also adjoins a national park and other nature reserves with typical sandstone dry sclerophyll forest types. As you may guess weeds have certainly grown in these nature areas amongst the native forest and particularly in two areas, the margin areas adjoining urban lots and roads as well as the creek lines. I have always learnt in both these instances it was the run off of high nutrient leveled stormwater and other drainage channels (stormwater pipes that contain illegal sewerage connections in the case of the creek lines) that created a different soil condition to the naturally occurring infertile sandy soils derived from the sandstone parent material or bedrock. In this case, lowering the fertility of the high nitrogen and phosphorus content run off would lesson the proliferation of the weeds and make way for other species. This seems to contradict Peter’s observations described in the books. I will say that I don’t think that my example is a counter argument. I suspect there is a link between the two and I offer two suggested explanations. Firstly I thought it could be simply a swing in a different direction to create an imbalance. In your observations fertility was lowered below a desired threshold for ‘non-weed’ species and in my observations the fertility has risen above the threshold for ‘non-weed’ species. My second idea involves a more complex relationship between plant species and their capability of processing nutrients depending on how they are presented chemically. Perhaps the disruption of natural fertility levels due to runoff and/or by soil leaching after ploughing, changes the way nutrients are available for exchange as well as their quantity. Of course it could be a combination of the two or quite possibly both ideas of mine are erroneous. Either way I would be interested to hear thoughts on the comparison I raise, as one thing is for certain, the old landscape did not distinguish from rural and urban landscapes. I am also interested as to how this comparison may affect the potential management of either landscape situation.
fertility, nutrients and phosphorus
Posted: Wed May 06, 2009 9:57 am
The reason weeds grow more in the edges of urban forests and roadsides is because these sites are most disturbed. The disturbance, aeration, moisture and other factors create an opportunity for weed seeds to set and grow. There are also areas disturbed within these more pristine environments due to natural conditions and the introduced problems such as rabbits that our native bushland also has to contend with. The native seeds are used to harsh conditions and often have a hard seed coat that needs to break down before germinating but all that is a subject in itself. The weed seeds germinate quickly and commence a repair process, creating fertility and a succession of conditions. The native seeds germinate when the conditions are right for them and the changed conditions are not right for many of them; but that is not to say that there are not opportunistic natives as well.
High nitrogen is not really a problem for the native forest because there are many native plants such as Fabacea, mimosaceae and native grasses plus others that may or may not have disappeared completely over the last couple of hundred years that would drink up that nitrogen and flourish but the high phosphorus is a key threatening process to the parks and bushland for sure.
The high nitrogen in the water ways creates the very conditions that the wetland require to change and function as it should. The water grows heaps of plants the plants slow the water and when they are washed through by torrents of rain they break down in the water creating a soup that permeates even more fertility through the soil. The grasses take that up well plus the many wetland plants that like those conditions clogging and slowing the water so it can be taken up by the soil and plants. The overflows created by the clogging plant material send the water up over the top of it creating more waterways and flood plains( If there are no flood plains the bogs and swamps). Even in the sandstone regions there are plants that love boggy wet conditions. Epacridaceae, Blandfordia, Rainforest plants, Gahnia and all the other rushes and sedge species.
The problem with the high phosphorus is that the only way to remove it from the environment is through plants. Phosphorous remains in the environment for along time and natives species (especially of the sandstone) as you probably know use very little of it, in fact too much will kill some natives. The creek lines are often full of Privet because Privet likes those conditions and will grow vigourously while doing the job of removing the phosphorous from the waterways. They are in fact doing the job well, so when we remove them, we are removing the repair process.
(Either way I would be interested to hear thoughts on the comparison I raise, as one thing is for certain, the old landscape did not distinguish from rural and urban landscapes.)
The above sentence that you wrote IS the LINK between the two.
I too live in an urban area of Sydney and am familiar with the forest, woodlands and weeds of the area. There are so many beautiful sandstone species and there is always going to be the right place for them.
Australia is no longer the old landscape it used to be. It can never be that again because of rural industries and the population that now lives here. It seems that the population is only going to increase. Australia is expected to not only provide food for it’s country but the rest of the world as well.
The country is full of animals that change the environment with their hard hooves and eating habits. That too is not going to change as I cannot see sheep, cattle, horses, goats, camels and deer (plus the many more feral and introduced species) ever being removed from the country. There is a push for these rural industries to grow and grow and grow. So we a need a link between the two if we are to sustain the country and hang onto and care for what little forest is left while surviving and finding a balance.
The nutrient rich diversity did exist before our settlement here and the historical records speak of the rich farmland which existed. The farmers went on to clear everything that created that fertility and depleted the soils and now they have to pay for fertiliser and water.
They did not know better but now we do. Well some of us do. I guarantee there are many that do but don’t care anyway as long as there is a buck in it. Hope you keep writing on the forum as it was great to hear your perspective and thoughts. Hope to get more input from you. Shirley
Posted: Wed Jun 03, 2009 4:34 pm
Thank you for your reply Shirley. I certainly take your points on board especially those regarding the affects of nitrogen and phosphorus and how they have different consequences. However I feel that I intended my query to head in a slightly different direction. This whole thought process started for me when reading Peter’s consistent references to weeds growing in rural areas where there is low fertility. In the urban context we spoke of, I agree with everything you said regarding disturbance and weeds, but how does this fit with Peter’s link between weeds and low fertility? That is the comparison I was trying to point out. In the disturbance I have observed in the urban interface with bushland, low fertility doesn’t seem to be a part of it, in fact quite the opposite. Thus I suggested a change in balance of either high or low fertility will trigger weed dominance. I feel the answer to this may have a great bearing on my perception of bushcare and the role it plays in our urban environments. My point is that nature or ecology doesn’t distinguish between urban and rural land and therefore the differences of our observations must have a common explaination.
Posted: Mon Jun 22, 2009 12:40 pm
The LINK between the two is WATER.
On the dry farms that Peter speaks of the land is low in nutrient and needs to have fertility added by way of purchased fertiliser or naturally created fertility. Clearing has taken it’s toll. There are weeds that grow in these conditions and by slashing and mulching of those weeds a natural process of recovery can be started plus the many other natural sequences that occur there after.
The areas you speak of have too much fertility, there are weeds that can grow in those nutrient rich wetlands, creeks and gullies but how can this affect the sandstone species?
1. The weeds grow where there is moisture.
2. The weeds can grow in nitrogen and phosphorous rich soils.
3. Land surrounding the waterways needs vegetation to retain a small water cycle.
4. No nutrients can be taken up by plants unless it is dissolved in water first.
5. The water must be dispersing nutrients through the soil to affect sandstone species with high nutrient or phosphorous levels.
6. Peter’s suggestion of trees and shrub land and added natural fertility to highlands and hilltops would create fertility moving down hill with rains, taking fertility to crops on farmland.
7. This must be happening in the sandstone and sclerophyll forests.
8. The natives that have low nutrient requirements can be affected fatally such as hakeas?
9. There are natives and weeds that tolerate high levels and can indicate the high nutrients.
10. There are plenty of weeds that will grow in those conditions but they would need water flowing through the soil.
11. I believe that is the difference. The water cycle is still present in the areas you speak of where it has been removed from farmland.
12. When a healthy balance is restored not just by way of nutrients but by way of living microbes and organisms in the soil including fungi, a natural balance will be achieved.
13. Returning the small water cycle to farmland is the first step.
14. In the situation you speak of reducing nitrogen and phosphorous run off from storm water and farm land is probably the best step forward.
15. Forget weed removal.
Posted: Mon Jun 22, 2009 2:20 pm
I think that you have added the missing ingredient to my analysis ie. the influence of the water cycle in my comparison. I dare say it is a different imbalance between rural and urban examples but it is the water cycle that drives differing results. As you say the water allows the nutrients to be taken in by plants. I suspect that you would prioritise addressing the deposition of nutrients and high water velocity into a system above removing the odd weed as a way of bush regeneration or maintenance of natural integrity? Having been involved in a bit of bush regeneration that is simply pulling weeds out continuously, I couldn't help think there were better tactics to the problem. Unfortunately addressing issues within the one catchment can cross the boundaries of private/public ownership, political jurisdiction and other interest groups. But never the less should we see weeds as not the enemy to bushland but rather the indication of a hydrological imbalance that requires our attention?
Posted: Mon Jun 22, 2009 3:15 pm
I have come to believe that all forms of Bush Regeneration is an excellent educational resource. It is also useful for retaining native species and communities as we believe they were or should be. It’s all a bit like gardening though. Removing weeds in a situation where monitoring and maintenance can be kept up is ok when looked at as an ongoing commitment and good records are kept for learning purposes. What really does not make good sense and is terribly expensive is the removal of vegetation in areas where it is not followed up and ordering others to clear their vegetation. This creates havoc with the soil, the water cycle, the land reparation process, displaces wildlife and creates unnecessary disturbance. Pristine untouched bush land does not have weed problems. It takes care of itself. Farmers need every bit of green they can grow be it exotic or native.
Imagine if we had creeks instead of drains and the farmers used natural fertility instead of bagged fertiliser, bores, irrigation and herbicide. What kind of difference could that make?
Posted: Mon Jun 22, 2009 4:48 pm
well that is the difference we are all interested in looking at and strive towards. In Beyond the Brink a phrase along the lines of 'you cant do it better than nature' tells me I am very interested in how nature would repair itself (or more appropriately termed - restore a balance) and thus how we can facilitate that rather than relying on maintenance programs as an ongoing legacy. Of course bush regeneration is a fabulous way for people to interact with plant life in their own context and the educational experience it brings needs to be more widespread.
Posted: Mon Jun 22, 2009 5:37 pm
Going back to your earlier statement “never the less should we see weeds as not the enemy to bushland but rather the indication of a hydrological imbalance that requires our attention?”
We need to work with hydrology in a way that creates a healthy eco system . Yes, weeds and all vegetation indicate the condition of the soil and the water. It’s what we put into our land and waterways either directly or indirectly that is polluting our soil and water.
When water permeates the soil it filters it to a degree. Healthy organic matter is broken down and cleaned but detergents, excess fertiliser and chemical pollutants are another story. The wetland plants also continue the filtration system but law has it that waterways must be cleared so that the water flows fast and easy to catchments such as dams. There it is sold back to us after being chemically treated. Maybe fluoride is necessary now because of bacteria but healthy waterways could be obtained through healthy use of land and healthy waterways functioning naturally.