At numerous times naturalists, botanical explorers, foresters and trained observers have noted and decried the absence of forests on the mountains and hills of (entral and Northern China. Norman Shaw (7) has clearly indicated the lamentable shortage of forests. Several of the Jesuit priests early noted the destruction of the forests, among whom were Armand David (2) and E. Huc (4). The latter more specifically describes the processes of soil degradation which was at work in Inner Mongolia previous to the year 1844. Sowerby (9) and Wilder (11) have described the same processes at work in the Tung Ling. Numerous writers of travel have noticed the thin soiled slopes and barren hills and mountains.

Shansi was chosen for the studies upon which this paper is based, because of the existence there of remnants of the former extensive forest cover. Adjacent to the forests were found denuded areas. The processes of converting a forest cover into denuded slopes could thus be studied in the very act. The region at the head waters of the Fen River was first selected as the site of these studies for the summer of 1924. During the summer of 1925, similar studies, in addition to special run-off studies, which will form the basis of another paper, were carried out in the three remnant forest areas of Shansi, namely, Ning-wu, at the head waters of the Fen River, also previously studied, Fan Shan, West Central Shansi, and Tsing-yuan Hsien, in which is located the Mien Shan forests, including some very interesting communal forests.

The writer was ably assisted in these studies in the summer of 1924 by Professor C. 0. Lee, associates in Forest Research, Messrs. T. I. Li and C. T. Ren, and by Mr. Tsiang Ying, a senior student in forestry; and in the summer of 1925 by Messrs. T. I. Li, C. T. Ren and H. L. Shen, associates in Forest Research, and by Mr. Chang Wen Tah, a senior student in forestry. During the latter part of the last summer, Mr. T. S. Tseh, Dfrector of the First Forest Experiment Station of Shansi, visited our work at Fan Shan.

Governor Yen Hsi Shan, of Shansi, most cordially gave our party each summer valuable assistance and greatly expedited our work in many ways.

The Tai-yuan plain was suffering from a long drought when we reached Tai-yuan-Fu in 1924. The crops were dying for want of rain, even the wild grass had not started (July 3) and a famine was feared.

The rain clouds broke shortly after our arrival. The moisture which had been accumulating in the atmosphere, superheated by the roasting hills, came down in torrential volumes. The streams were suddenly overcharged with raging waters, heavily laden with mud and silt. The water supply so sorely needed for agricultural crops quickly ran off the steep barren slopes and brought floods and destruction in the place of the desired benefits of rain after drought. Despite the efforts made by the farmers to catch the flood waters for irrigation, most of them soon passed by and were gone. Dry weather in the fall months again made the conditions of the people serious and again threatened them with famine.

In the summer of 1925 the rains were more copious; likewise they were at times gentler than in 1924. Nevertheless the same phenomena of floods occurred as in the former year. The Fen River while in flood washed out the bridge in August on the motor road between Tai.yuan and Fen-chon. In many sections crops were drowned out, or the soil washed away.

From the evidences in stream beds such torrential run-off and destructive flooding are annual occurrences. The questions naturally arise as to whether this run-off has always been thus, and if there is any remedy for the present deplorable situation; for it renders food production over wide areas in the plain quite precarious. It is worth while, therefore, to examine the factors which contribute to the present regimen of run-off of the Shansi streams, as a preliminary to any scheme of flood control.

The stage is set in Shansi for the rapid development of torrents under certain conditions. The topography is steep and mountainous. The provincial surveys place the area of the plain land at 9 per cent. and the mountain land at 91 per cent. of the entire province (1). The slopes are generally steep. It is very probable that the most of the slope area has a gradient of over 25 per cent.

Likewise the rainfall is mostly convectional in character (3). That is, the clouds develop the cumulus form, due to ascending drafts of heated air whose moisture is condensed as the rising current reaches the altitude marking the dew point. The rains, therefore, usualy come

as thunder storm down-pours and occur most often in the latter half of the day, and rarely at night. Exceptions occur, but the precipitation is generally of the convectional type, such as is characteristic of inland mountain regions.

During the two summers of 1924 and 1925 the rainfall was most often experienced as sudden down-pours. The latter summer, however, was marked by a few typical cyclonic rains, beginning with general sheet over-clouding and fine gentle rain, which lasted sometimes for several hours. Such rains were due to the occasional carrying over into Shansi of moisture-bearing cyclonic winds originating in the Pacific. The bulk of the rainfall, however, comes in the form of thunder showers and cloud bursts of high intensity.

Such is the stage setting in which man has been playing an important, and, perhaps, a somewhat villainous r6le for many centuries. (4) It is reasonable to conjecture that in early times the inhabitants of Shansi first began to clear away the forests from the level alluvial plains where the tilling of the soil for food crops was comparitively easy. As the population increased and the demands on the productivity of the soil grew, lands higher and higher up the slopes were cleared for cultivation. Whether this early clearing of the forest was done primarily for wood or for food production i not known. However, it is certain that as the needs of the increasing population approached the maximum productivity of the land, this clearing was done expressly to grow food crops. This went on until the forest and vegetative covers were cleared up to the mountain tops. Evidence of abandoned fields is found as far as the summit of Mien Shan and other high mountains. (Also see Smith, 8) Now only small remnants of the original vegetative cover can be found in the remotest and loftiest sections of the province, except where it is preserved by temple enclosures. Although timber is now increasing in value, it may be said that the dominant motive in removing the forests and clearing the land has been and in many sections still is to grow crops. The writer found logs rotting in the mountains of Shansi because of lack of transportation or profit in their removal. The land from which the logs were cut had been cleared and sown with oats.

The blind yielding to this demand for crop land has worked immeasurable misfortune to the people of Shansi. The studies in Shansi during the two summers, warrant the conclusion that this clearing of the slope lands for food production has set in motion certain processes which are inimical to the continued welfare of the commonwealth.

Man has no control over topography and little over the type of rainfall which descends on the land. He can, however, control the soil layer, and can, in mountainous areas, determine quite definitely what will become of it. This is not true to the same degree in level areas, for the controlling difference is the gradient of slope. Level lands may be cleared and cultivated for food production. In fact, this is the highest use to which such land may be put, except, perhaps, for residence. On slopes, however, where, according to measurements made in Shansi, the gradient exceeds 25 per cent., cultivated land is subjected to excessive wash and erosion during the sudden down-pours of summer rain. The deep fertile soil layers may be entirely removed in this way after a few years .3 to 10 according to experience in North Shansi and not exceeding 15 years on the more gentle slopes within this limit. The texture of the soil as well as the slope gradient are controlling factors in soil wash after the soils are prepared for crops, and therefore determine only the rapidity of the denudation. Cultivation of slopes makes denudation inevitable

The complete story of the cutting of forests-the transport of some of the more valuable material, the clearing of the forest soil of stumps, roots, shrubs and other binding agencies, the planting with oats and potatoes, and the subsequent erosion, gullying, and development of torrents-was studied in the various stages in the highlands of Shansi during the summers of 1924 and 1925. These processes may be found at work at the present time in the highlands at the head waters of the Fen River, in Ning Wu Hsien. The ancient military camp of Tung Tsai (East Camp) is now the center of the timber trade, which depends upon the logs, boards and poles which are packed out of the mountain valleys on mule back. In the vicinity of Tung Tsai are striking examples of various stages in the development of torrents. The torrent debouching into the main valley opposite Tung Tsai is a very typical example It has come into being in the past 40 years due to the cultivation of the tributary watershed. The same processes and consequences are to be found around Lu Yah Shan on both sides of the divide between the Fen and Yellow River watersheds, and at many other points in these highlands. The unmistakable evidence of the onward march of this type of destruction may be found from Tsing Lo to Tung Tsai, a distance of 120 ii, and throughout the mountains of Shansi.

The Fan Shan area of West Central Shansi presents two phases of these processes. Evidence is plentiful, in the form of abandoned fields on slopes, to show that the cultivation of the high slopes took place several decades age. Few freshly denuded slopes exist now. But the remaining forest stands are now being rapidly cut. Particularly is this true of the holdings of a prominent family of Shansi. Plans are being made to rent as much as possible of this cut-over land to mountain farmers The rocky nature of the soil may fortunately prevent its cultivation and favour the return of the forest, though more slowly than careful treatment would render possible. The timber of the Kuan Ti Shan area, a splendid forest cover of about 150 square ii, has been sold to a match company which expects to use the poplar (Populns sp.) for match sticks and the birch (Betula japonica Sieb.) which occurs in splendid development as both red and white varieties, for match boxes. The spruce (Picea meyeri R. & W. Wilsonji Mast.) and larch (Larix dahurica var. principis rupprechtii R. & W.) are sold as timber, being either floated in summer freshets or transported by camels during the winter to Kai-ssu at the edge of the Tai-yuan plain.

The south-eastern section of Shansi is an elevated and incised massif which drains southward directly into the Yellow River through its main stream, Tsin Shui. This region is carefully described by Smith, 1925. (8) This section represents a much older stage in the processes of clearing and cultivation. No large single area of forest is to be found, for cultivation has etched the entire landscape. A large part of the slope areas are thin, solid and rocky dry sites on which meagre and scattered pines have established themselves naturally. The restoration of the former cover through slow stages of plant succession are at work, and, if unmolested by sheep, goats and wood cutters, would in time build up a fertile vegetable soil in which trees and shrubs might thrive. Little hope of this exists, however, without an intelligent and energetic conservation policy.

Small forests are found at many points in this region and show the result of communal and temple effort at protecting trees for a continuous crop of material for temple and village house repairs. The Lin Kuen Shan communal forest is the most noteworthy. A most interesting stone tablet was found in the little temple of Tsong Tse Yu in Tsing-yuan Hsien. The inscribed record of 1887 recounts how the beautiful little pine forest on the opposite slope, with its heavy undergrowth of shrubs, had been protected since 1857, to supply the repairs for the temple and the village houses. This stone may be considered the charter stone of communal forests in Shansi. There are also the interesting clan forests which are managed by eleven villages. The white bark pine (Pinus bungeana) of Mien Shan, protected by the temple of Sun Lin Miao (8) is also a noteworthy remnant of forest.

The outstanding impression, after making a reconnaissance through most of the highlands of Shansi, and particularly in the three forest regions of the province, is that cultivation has at one time or another been applied to practically all the slopes of the land area.

Terracing has been resorted to as a safeguard against rapid erosion of the agricultural soils where the loess deposits exceed a thickness of ten or more feet. In a few areas of no great significance terraces are built up with stones to hold the soil wash of the thin rocky limestone slopes. But the area covered by terraces is deceptive to the traveller who follows the roads and trails of the valleys. From such routes the entire landscape appears to be terraced. In fact only the faces of the main slopes are terraced. The back country, comprising a much larger proportion of the land surface, is meagerly terraced or not at all. Perhaps not so much as 10 per cent. of the slopes is terraced. Terracing is a useful treatment of the slope lands if they are cultivated, otherwise the soils are soon washed away leaving the areas unproductive, or, as in the case of loess deposits, are so cut up with gullies as to render cultivation impossible.

Terracing in the loess appears to have originated as a result of the division of the slopes into narrow fields along the contours. Repeated plowing has, through soil-creep, lowered the upper edge and filled up the lower edge of the narrow fields one above the other. The net result has been to establish marked differences in elevation between two fields and the reduction of their gradients. The former slopes have thus been converted into terrace formation.

The process of denudation is considered for convenience in description in three different stages. The cutting of the forest is the first. The methods of cutting in the highlands of Shansi were a great surprise to the writer ; for the waste in high stumps and the careless utilization of timber, which has such high value in the plains and which is so vital to the economy of the province, is practically criminal. Sowerby and Wilder make a similar observation for the Tung Ling (9) (11). The wasteful methods resemble those of America, where the diminishing supply of what was once considered unlimited timber is only beginning to be seriously felt. The costly method of transporting the logs from the mountains on mule back must be considered the primary contributing cause. This is necessitated by the absence of adequate roads. The owner of timber land generally considers that renting his mountain slopes to a farmer for growing oats is more profitable than retaining his land for growing trees. Thus, the forests are frequently cut off more rapidly than transportation can deliver the timber to the plains. Rotting logs and trees are common in the Ning Wu and Fan Shan regions. Thousands of cubic feet of fine timber lie rotting in these regions.

The succeeding stage of cultivation follows immediately upon the cutting of the trees. The forest Soil contains the accumulated fertility of many decades; it is deep, black with humic material and is highly productive. Accordingly, it is eagerly sought for in order to grow food crops. The general experience, however, is that the first year's crop yield is not as high as the second, due to the incomplete decomposition of the raw humus material at first.

The soil is first broken with a long pick or mattock; since the network of shrub and tree roots makes turning with a plough impracticable. In succeeding years the land is ploughed with bullocks, unless the slope is too steep, in which case the long bladed m4tock is used as long as the crops justify cultivation. The chief crop is oats, particularly with freshly cleared lands. Peas and potatoes are sown to lesser extent at the higher elevations, whereas millet, maize and flax constitute the crops at the lower elevations of the mountain areas.

The third stage is erosion, or soil wash, to a disastrous extent. As soon as the slope soils are deprived of the protecting layers of leaves and twigs, and the binding net-work of roots of shrubs and trees, dashing rain storms pack the outer soil surface and start tiny rivulets of flowing slime. (5) These accumulate and develop into rills which join together to form gullies. The run-off attains accelerated velocities as it accumulates and increases its transporting power by 6+ times the increase in velocity. The annual cultivation of the fields levels out the rills and fills up the small gullies and tends temporarily to cheek the development of larger gullies. Only a few years are needed so to remove the soil layer that the farmer can no longer afford to cultivate the slope fields. He, therefore, moves on to freshly cleared forest or shrub, and sets in motion the same processes of destructive erosion over an ever widening area. When the field is abandoned, the development of the gully is unhindered and goes on apace. The loss of the soil layer exposes residual rock fragments, which accumulate to form a rocky surface, whereby the rain waters are so much the more quickly converted into rills. The rills and gullies swell the run-off to proportions of powerful erosive force. Rocks are torn from the hillside, soil and rock debris are carried along in a raging torrent receiving accretions from all sides until great boulders are rushed along in the mad flood. It requires the contemplation of a torrent in full flood to appreciate the destructive power which is released in raging run-off waters of the steep valleys within the mountain areas.

These torrents carry and roll boulders and rocky debris along to cover and make sterile the agricultural fields in the valley of debouchment, and transport soil material in astonishing quantities, choking up the stream channels in the plains with troublesome silt. The slower currents of the streams in the plains are unable to keep in suspension these large quantities of silt, amounting to 22 per cent. by weight of the water in stream velocities of nearly 10 feet per second, and which the torrents in the steeper portions of the watershed tear off the mountain slopes. In consequence, the extra load is dropped, only to cause the disastrous flooding which is such a persistent occurence in the plains of Shansi.

The result of these processes is the denudation of the soil layers from extensive areas of the slope region. The character of run-off is changed from perennial or prolonged flows to sudden floods, which leave the stream beds dry until the next heavy rain storm or the next rainy season. This marked alteration of stream flow has been going on within the memory of prominent inhabitants of the regions where the processes of denudation are now at work. A few perennial streams were found flowing out of untouched remnants of the forest cover, and some are in process of being changed to summer torrents. (Lu Yah Shan, Kwan Ti Shan).

If the denuded areas, however, should be left entirely to themselves, natural reclamation would in time heal the wounds so inconsiderately made by eager man. For a succession of hardy herbs and shrubs take possession of the denuded slopes as soon as cultivation ceases. In time a soil is built up and seeds from chance trees find lodgement, germinate, and in time will restore the forest in wide areas above an altitude estimated at between 5,000 and 5,500 feet. Below this level artificial reclamation may be required to assist the return of vegetation due to reduced supplies of soil moisture. But another agency is at work on the abandoned fields, preventing the working of natural forces in revegetation over extensive areas. Sheep and goats are driven almost daily over these areas ; and both by their feeding and trampling, effectively prevent or at least hinder the return of the former shrub and forest cover.

If some eventuality causes the migration of the population from a mountain region, or if the population is heavily reduced in numbers, as was the case in Shansi during the great famine of 1877-9, opportunities are created for the natural restoration of the soil layers through the revegetation of the mountains. Apparently, this happened after the great famine in parts of the Fen Ho, Wen-shui and Tsin-shui watersheds. There is now a general movement of farmers back into the mountains of Shansi to clear and cultivate shrub and forest lands. Numerous evidences of this tendency are to be found in the rebuilding of partially ruined villages, in the formation of mountain land companies, and in the rapid buying up of mountain lands. Our party encountered several villages peopled with former inhabitants of the Tai-yuan plain who had within the past ten years established themselves in the mountains near Fan Shan.

The significance of these processes must rest on the extent of the original forest and shrub cover of Shansi. Evidence of a former extensive cover of forest and shrubs is patent. Sowerby suggests a strip of forests from the Tung Ling across the highlands in a southwesterly direction to the great central highland forests of Asia (10). Hue, even as late as 1844, describes forest stands in Inner Mongolia which no longer exist (4). Hsien histories of Ning Wu and others include references to more extensive forest areas. Perhaps the most trust worthy indications are the existing temple forests. To include all areas of similar altitude, or higher, with the existing temple forests would in itself indicate an extensive forest cover for Shansi (8).

The clearing of the natural vegetation and the cultivation of the slopes of Shansi have been going on at an increasing rate until only remnants and spots of the former vegetation are now left. These are found in the quite well distributed temple forests and in the remnant - forests in the higher and more inacessible parts of the mountains. In some of these areas ideal forest conditions exist. It would seem that such areas should now be made into provincial forests and carefully preserved as specimens of true forest conditions. The eager -- search for land to produce food has, however, taken precedence in the past and continues to do so. It appears that the cultivation of the slope lands has, in the last analysis, effectively reduced rather than increased the total food production.

The problem of forest restoration on the slopes of Shansi involves many factors. Watershed protection in its broad sense is the most urgent. For the need of a regular water supply supercedes an additional wood supply in Shansi. Watershed protection comprises the preservation of forest conditions, where they now exist, by controlled cutting, the regulation of slope farming and the management of the ranges for grazing. Range management is perhaps one of the most urgent requirements as well as difficult. Many seriously over-grazed areas were encountered in quite extensive travels into the back country Tree planting is badly needed in some sections, but the most effective method of restoring a cover sufficient to prevent erosion and to check the development of torrents is to give the native hardy vegetation an opportunity to develop and to render this artificial assistance at altitudes below 5,500 feet. Works of torrent correction and erosion prevention are needed in the gullies and torrents where conditions have developed to serious proportions.

SUMMARY:

With steep topography and a convectional type of rainfall, Shansi is a stage admirably set for the play of processes of excessive erosion and denudation. The condition of the soil layer is the only factor within the effective control of the inhabitants. Exposing the soils on the slopes to the wash of torrential rains has brought about immeasurable ills to the inhabitants through loss of productive soil resources, in the irregular regimen of run-off and in the reduction of the aggregate food supply. Forest destruction appears in Shansi to have been only a preliminary stage of a more disasterous process of slope cultivation, which is considered essentially responsible for the unfortunate conditions of the mountain lands and river plains.

REFERENCES:

1. Anonymous. Shansi Provincial Surveys.
   
2. David, Armand. Journal de mon Troisieme Voyage danse 1 Empire Chinois, Tome I.
   
3. Fritsche, H. "The Climate of Eastern Asia," Journ. N. C.
   B. R. A. Soc. New Series No. XII, 1878.
   
4. Huc, E. Souvenirs d'un Voyage dans la Tartarie et Thibet.
   1844-45-46, Nouvelle Edition, Peking, 1924.
5. McGee, W. J. "Soil Erosion," Bulletin 71. U.S.D.A. Bureau of 50i18. 1911.
   
6. Nystrom, E. T. "Some Shansi Waters Chemically Examined":
   China Jour. Sc. and Arts, Vol.11, No.2 and 3, 1924.
   
7. Shaw, Norman. "Chinese Trees and Timber Supply, 1914."
   
8. Smith H., "A Preliminary Report on Botanical Investigations in South and Central Shansi": China Jour. Sc. and Arts, Vol. III, No.8 and 9, 1925.
   
9. Sowerby, Arthur de C., "Forestry in China," China Jour. of Sc. and Arts, Vol.11, No.4, 1924.
   
10. Sowerby, Arthur de C., "Approaching Desert Conditions in North China" ; China Jour. Sc. and Arts, Vol.11, No.3, 1924.
    
11. Wilder, G. D. "Wild Life To-day in the Eastern Tombs Forest"; China Jour. Sc. and Arts, Vol.111, No.5, 1925.
    

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