One idea would be to measure nearest-neighbor distances and compare this to an expected random result. If it is a plantation sort of stand, the trees might be over-dispersed (more regularly spaced than expected). However, a "plantation-like", regular spacing might be present only if these are the original, planted trees you are looking at. Also, age structure of the stand might be helpful--is there a variety of ages suggesting reproduction, or is it an even-aged stand?--I don't think this would be definitive, but it might be suggestive.

Best,

Hi Hamed

the distance to the nearest natural patch of the Pterocarya (1000 km) is indeed very far. Therefore I would suggest two ways of checking the naturality of this forest:

1. DNA studies may give you some idea about origin of the trees in your forest; if it is a remnant of natural population then it suppose to be closely related to some nearest forest of the same species; you would need samples of trees from wide geographical range;  that is an expensive solution;

2. much cheapper is to check if there are any specific insect or fungi species "monofagous" on the Pterocarya present in the forest in question; their presence will not proove naturalness of the forest but it would be a strong argument for its natural origin; if those trees were planted then chance for presence of any specialized parazites or herbivores in so remote localisation is very small;

Bogdan

This is a difficult question to answer as many factors may either show or hide evidence of the past. Normally, there is not 'one answer' but frequently each case may need to be examined separately. Moreover, ancient planted forests may have reached levels of biodiversity and structural differentiation that may make it difficult to understand their original 'artificiality' especially where the forested landscape has been used or cultivated over centuries. Of course, any document, photo, painting, or other annotations can help to understand the origin of a forest. In some cases, a strongly limited genetic variability of the specimens may contribute useful information especially when compared to the variability of forests in similar environments where the same species has not been planted (or re-planted). In other cases, the planted species is followed by a different vegetation pattern growing as understorey and natural regeneration of the planted species is poor or absent. The planted species may also show health problems especially - but not only - in the rooting system while the species that have grown by seeds are much less affected.   All these approaches may work together, and other tools can also be used.